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Sample records for dry afromontane tropical

  1. Seed ecology and regeneration in dry Afromontane forests of Ethiopia

    Energy Technology Data Exchange (ETDEWEB)

    Teketay, D. [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Vegetation Ecology

    1996-12-31

    Various aspects of seed and regeneration ecology: germination requirements of seeds, seed longevity in the soil, soil seed banks in forests, gaps and arable land as well as density, survival and growth of seedlings were investigated within the dry Afromontane region in Ethiopia. In laboratory germination tests, 60% of the species studied exhibited some degree of initial dormancy and the optimum constant temperature for germination was between 20 and 25 deg C in the majority of the species. A few species showed a requirement for fluctuating temperatures and germination was suppressed or completely inhibited in several, mainly small-seeded, species when they were incubated in darkness or in light filtered through green leaves. Hard-seeded species required scarification treatments to improve germination, indicating seed-coat imposed dormancy. Dry storage reduced the germinability of seeds in a few species, suggesting a recalcitrant behaviour, while seeds of many species remained unaffected. During four years of storage in forest soils, seeds of 2 out of 8 species germinated in the soil almost completely within a year, 2 of the species maintained nearly full viability, while 4 were intermediate. The generally high levels of dormancy and somewhat extended viability of seeds in the soil may have been selected for under a climate of seasonal drought and unreliable rainfall that characterizes the dry Afromontane region. Dry Afromontane forests have a potential to recover in relatively short time after natural and man-made disturbances, e.g. after carefully managed selective cutting. However, the common practice of clearing forests and converting them into permanent arable land destroys the sources of regrowth thereby preventing regeneration of the forest vegetation. Therefore, the fate of dry Afromontane forests depends on the protection, careful management and conservation of the remaining patches. 102 refs, 4 figs, 1 tab

  2. Plant diversity and regeneration in a disturbed isolated dry Afromontane forest in northern Ethiopia

    DEFF Research Database (Denmark)

    Aynekulu, Ermias; Aerts, Raf; Denich, Manfred

    2016-01-01

    We studied the diversity, community composition and natural regeneration of woody species in an isolated but relatively large (> 1,000 ha) dry Afromontane forest in northern Ethiopia to assess its importance for regional forest biodiversity conservation. The principal human-induced disturbance...... in biodiversity through local extinction of indigenous tree species. Despite the problems associated with conserving plant species diversity in small and isolated populations, this relic forest is of particular importance for regional conservation of forest biodiversity, as species with high conservation value...

  3. Carbon stocks and dynamics at different successional stages in an Afromontane tropical forest

    Science.gov (United States)

    Nyirambangutse, Brigitte; Zibera, Etienne; Uwizeye, Félicien K.; Nsabimana, Donat; Bizuru, Elias; Pleijel, Håkan; Uddling, Johan; Wallin, Göran

    2017-03-01

    As a result of different types of disturbance, forests are a mixture of stands at different stages of ecological succession. Successional stage is likely to influence forest productivity and carbon storage, linking the degree of forest disturbance to the global carbon cycle and climate. Although tropical montane forests are an important part of tropical forest ecosystems (ca. 8 %, elevation > 1000 m a.s.l.), there are still significant knowledge gaps regarding the carbon dynamics and stocks of these forests, and how these differ between early (ES) and late successional (LS) stages. This study examines the carbon (C) stock, relative growth rate (RGR) and net primary production (NPP) of ES and LS forest stands in an Afromontane tropical rainforest using data from inventories of quantitatively important ecosystem compartments in fifteen 0.5 ha plots in Nyungwe National Park in Rwanda. The total C stock was 35 % larger in LS compared to ES plots due to significantly larger above-ground biomass (AGB; 185 and 76 Mg C ha-1 in LS and ES plots), while the soil and root C stock (down to 45 cm depth in the mineral soil) did not significantly differ between the two successional stages (178 and 204 Mg C ha-1 in LS and ES plots). The main reasons for the difference in AGB were that ES trees had significantly lower stature and wood density compared to LS trees. However, ES and LS stands had similar total NPP (canopy, wood and roots of all plots ˜ 9.4 Mg C ha-1) due to counterbalancing effects of differences in AGB (higher in LS stands) and RGR (higher in ES stands). The AGB in the LS plots was considerably higher than the average value reported for old-growth tropical montane forest of south-east Asia and Central and South America at similar elevations and temperatures, and of the same magnitude as in tropical lowland forest of these regions. The results of this study highlight the importance of accounting for disturbance regimes and differences in wood density and allometry of

  4. Dry and Semi-Dry Tropical Cyclones

    Science.gov (United States)

    Cronin, T.; Chavas, D. R.

    2017-12-01

    Our understanding of dynamics in our real moist atmosphere is strongly informed by idealized dry models. It is widely believed that tropical cyclones (TCs) are an intrinsically moist phenomenon - relying fundamentally on evaporation and latent heat release - yet recent numerical modeling work has found formation of dry axisymmetric tropical cyclones from a state of dry radiative-convective equilibrium. What can such "dry hurricanes" teach us about intensity, structure, and size of real moist tropical cyclones in nature? Are dry TCs even stable in 3D? What about surfaces that are nearly dry but have some latent heat flux - can they also support TCs? To address these questions, we use the SAM cloud-system resolving model to simulate radiative-convective equilibrium on a rapidly rotating f-plane, subject to constant tropospheric radiative cooling. We use a homogeneous surface with fixed temperature and with surface saturation vapor pressure scaled by a factor 0-1 relative to that over pure water - allowing for continuous variation between moist and dry limits. We also explore cases with surface enthalpy fluxes that are uniform in space and time, where partitioning between latent and sensible heat fluxes is specified directly. We find that a completely moist surface yields a TC-world where multiple vortices form spontaneously and persist for tens of days. A completely dry surface can also yield a parallel dry TC-world with many vortices that are even more stable and persistent. Spontaneous cyclogenesis, however, is impeded for a range of low to intermediate surface wetness values, and by the combination of large rotation rates and a dry surface. We discuss whether these constraints on spontaneous cyclogenesis might arise from: 1) rain evaporation in the subcloud layer limiting the range of viable surface wetness values, and 2) a natural convective Rossby number limiting the range of viable rotation rates. Finally, we discuss simulations with uniform surface enthalpy

  5. Climate change and early human land-use in a biodiversity hotspot, the Afromontane region

    Science.gov (United States)

    Ivory, S.; Russell, J. M.; Sax, D. F.; Early, R.

    2015-12-01

    African ecosystems are at great risk due to climate and land-use change. Paleo-records illustrate that changes in precipitation and temperature have led to dramatic alterations of African vegetation distribution over the Quaternary; however, despite the fact that the link between mankind and the environment has a longer history in the African tropics than anywhere else on earth, very little is known about pre-colonial land-use. Disentangling the influence of each is particularly critical in areas of exceptional biodiversity and endemism, such as the Afromontane forest region. This region is generally considered to be highly sensitive to temperature and thus at risk to future climate change. However, new evidence suggests that some high elevation species may have occupied warmer areas in the past and thus are not strongly limited by temperature and may be at greater risk from intensifying land-use. First, we use species distribution models constructed from modern and paleo-distributions of high elevation forests in order to evaluate differences in the climatic space occupied today compared to the past. We find that although modern Afromontane species ranges occupy very narrow climate conditions, and in particular that most species occur only in cold areas, in the past most species have tolerated warmer conditions. This suggests that many montane tree species are not currently limited by warm temperatures, and that the region has already seen significant reduction in the climate space occupied, possibly from Holocene land-use. Second, to evaluate human impacts on montane populations, we examine paleoecological records from lakes throughout sub-Saharan Africa that capture ecological processes at difference time scales to reconstruct Afromontane forest range changes. Over long time scales, we observe phases of forest expansion in the lowlands associated with climate variability alone where composition varies little from phase to phase but include both modern low and

  6. Floristic diversity in fragmented Afromontane rainforests

    DEFF Research Database (Denmark)

    Schmitt, Christine B.; Denich, Manfred; Demissew, Sebsebe

    2010-01-01

    Ordination and indicator species analyses showed gradual variations in floristic diversity along the altitudinal gradient with a pronounced shift in species composition at ca. 1830 m. Upper montane forest is characterized by high fern diversity and indicator species that are Afromontane endemics...

  7. Floristics and biogeography of vegetation in seasonally dry tropical regions

    DEFF Research Database (Denmark)

    Dexter, K.G.; Smart, B.; Baldauf, C.

    2015-01-01

    To provide an inter-continental overview of the floristics and biogeography of drought-adapted tropical vegetation formations, we compiled a dataset of inventory plots in South America (n=93), Africa (n=84), and Asia (n=92) from savannas (subject to fire), seasonally dry tropical forests (not...... similar vegetation formations (e.g. savannas) are floristically highly dissimilar. Neotropical moist forest, savanna and seasonally dry tropical forest are floristically distinct, but elsewhere there is no clear floristic division of savanna and seasonally dry tropical forest, though moist and dry...... of the ecology, biology and conservation of savannas and seasonally dry tropical forests may be difficult....

  8. Abiotic factors influencing tropical dry forests regeneration

    Directory of Open Access Journals (Sweden)

    Ceccon Eliane

    2006-01-01

    Full Text Available Tropical dry forests represent nearly half the tropical forests in the world and are the ecosystems registering the greatest deterioration from the anthropogenic exploitation of the land. This paper presents a review on the dynamics of tropical dry forests regeneration and the main abiotic factors influencing this regeneration, such as seasonal nature, soil fertility and humidity, and natural and anthropic disturbances. The main purpose is to clearly understand an important part of TDF succession dynamics.

  9. The Afromontane Research Unit—Growing as a Hub of Transdisciplinary Research

    Directory of Open Access Journals (Sweden)

    Aliza le Roux

    2018-02-01

    Full Text Available The Afromontane Research Unit (ARU at the University of the Free State's Qwaqwa campus in South Africa has a steadily growing reputation as a leading research unit on sustainable development in Afromontane regions. Learning from international experts, researchers in this unit have focused on multi- and transdisciplinary scientific approaches to the challenges faced by montane communities. The ARU is therefore strongly attuned to the global research focus on complex systems approaches, as it acknowledges that the Sustainable Development Goals cannot be reached by a “business as usual” approach.

  10. Tropical savannas and dry forests.

    Science.gov (United States)

    Pennington, R Toby; Lehmann, Caroline E R; Rowland, Lucy M

    2018-05-07

    In the tropics, research, conservation and public attention focus on rain forests, but this neglects that half of the global tropics have a seasonally dry climate. These regions are home to dry forests and savannas (Figures 1 and 2), and are the focus of this Primer. The attention given to rain forests is understandable. Their high species diversity, sheer stature and luxuriance thrill biologists today as much as they did the first explorers in the Age of Discovery. Although dry forest and savanna may make less of a first impression, they support a fascinating diversity of plant strategies to cope with stress and disturbance including fire, drought and herbivory. Savannas played a fundamental role in human evolution, and across Africa and India they support iconic megafauna. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Preliminary inventory and classification of indigenous afromontane forests on the Blyde River Canyon Nature Reserve, Mpumalanga, South Africa

    Directory of Open Access Journals (Sweden)

    Beck Hans T

    2004-08-01

    Full Text Available Abstract Background Mixed evergreen forests form the smallest, most widely distributed and fragmented biome in southern Africa. Within South Africa, 44% of this vegetation type has been transformed. Afromontane forest only covers 0.56 % of South Africa, yet it contains 5.35% of South Africa's plant species. Prior to this investigation of the indigenous forests on the Blyde River Canyon Nature Reserve (BRCNR, very little was known about the size, floristic composition and conservation status of the forest biome conserved within the reserve. We report here an inventory of the forest size, fragmentation, species composition and the basic floristic communities along environmental gradients. Results A total of 2111 ha of forest occurs on Blyde River Canyon Nature Reserve. The forest is fragmented, with a total of 60 forest patches recorded, varying from 0.21 ha to 567 ha in size. On average, patch size was 23 ha. Two forest communities – high altitude moist afromontane forest and low altitude dry afromontane forest – are identified. Sub-communities are recognized based on canopy development and slope, respectively. An altitudinal gradient accounts for most of the variation within the forest communities. Conclusion BRCNR has a fragmented network of small forest patches that together make up 7.3% of the reserve's surface area. These forest patches host a variety of forest-dependent trees, including some species considered rare, insufficiently known, or listed under the Red Data List of South African Plants. The fragmented nature of the relatively small forest patches accentuates the need for careful fire management and stringent alien plant control.

  12. Diversity of arbuscular mycorrhizal fungi in the rhizosphere of Coffea ...

    African Journals Online (AJOL)

    SARAH

    2013-04-25

    Apr 25, 2013 ... approximately 125 million people in Latin America,. Africa, and Asia are dependent on coffee for their livelihoods (Osorio 2002 ; Lewin ..... 2009), dry Afromontane forests of Ethiopia (Tesfaye et al., 2004), the tropical rain forest.

  13. Dendrochronology in the dry tropics: the Ethiopian case

    NARCIS (Netherlands)

    Wils, T.; Sass-Klaassen, U.; Eshetu, Z.; Bräuning, A.; Gebrenirstos, A.; Couralet, C.; Robertson, I.; Touchan, R.; Koprowski, M.; Conway, D.; Briffa, K.R.; Beeckman, H.

    2011-01-01

    Dendrochronology is developing outside temperate and boreal regions. Over the past decade substantial progress has been made in Mediterranean and wet tropical regions. However, research in dry tropical regions, notably those of sub-Saharan Africa, has remained fragmentary. Here, we try to identify

  14. Emergence of nutrient limitation in tropical dry forests: hypotheses from simulation models

    Science.gov (United States)

    Medvigy, D.; Waring, B. G.; Xu, X.; Trierweiler, A.; Werden, L. K.; Wang, G.; Zhu, Q.; Powers, J. S.

    2017-12-01

    It is unclear to what extent tropical dry forest productivity may be limited by nutrients. Direct assessment of nutrient limitation through fertilization experiments has been rare, and paradigms pertaining to other ecosystems may not extend to tropical dry forests. For example, because dry tropical forests have a lower water supply than moist tropical forests, dry forests can have lower decomposition rates, higher soil carbon and nitrogen concentrations, and a more open nitrogen cycle than moist forests. We used a mechanistic, numerical model to generate hypotheses about nutrient limitation in tropical dry forests. The model dynamically couples ED2 (vegetation dynamics), MEND (biogeochemistry), and N-COM (plant-microbe competition for nutrients). Here, the MEND-component of the model has been extended to include nitrogen (N) and phosphorus (P) cycles. We focus on simulation of sixteen 25m x 25m plots in Costa Rica where a fertilization experiment has been underway since 2015. Baseline simulations are characterized by both nitrogen and phosphorus limitation of vegetation. Fertilization with N and P increased vegetation biomass, with N fertilization having a somewhat stronger effect. Nutrient limitation was also sensitive to climate and was more pronounced during drought periods. Overflow respiration was identified as a key process that mitigated nutrient limitation. These results suggest that, despite often having richer soils than tropical moist forests, tropical dry forests can also become nutrient-limited. If the climate becomes drier in the next century, as is expected for Central America, drier soils may decrease microbial activity and exacerbate nutrient limitation. The importance of overflow respiration underscores the need for appropriate treatment of microbial dynamics in ecosystem models. Ongoing and new nutrient fertilization experiments will present opportunities for testing whether, and how, nutrient limitation may indeed be emerging in tropical dry

  15. Towards restoration of Hawaiian tropical dry forests: the Kaupulehu outplanting programme

    Science.gov (United States)

    Susan Cordell; Moana McClellan; Yvonne Yarber Carter; Lisa J. Hadway

    2008-01-01

    Hawaiian tropical dry forests contain diverse assemblages of woody canopy species, including many endemic and endangered species that warrant conservation attention before completely disappearing. Today, tropical dry forests in Hawaii are not viable ecosystems. Poor land use practices, fragmentation, non-native plant invasions, and inadequate native vegetation...

  16. Dry season aerosol iron solubility in tropical northern Australia

    Directory of Open Access Journals (Sweden)

    V. H. L. Winton

    2016-10-01

    Full Text Available Marine nitrogen fixation is co-limited by the supply of iron (Fe and phosphorus in large regions of the global ocean. The deposition of soluble aerosol Fe can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. We present dry season soluble Fe data from the Savannah Fires in the Early Dry Season (SAFIRED campaign in northern Australia that reflects coincident dust and biomass burning sources of soluble aerosol Fe. The mean soluble and total aerosol Fe concentrations were 40 and 500 ng m−3 respectively. Our results show that while biomass burning species may not be a direct source of soluble Fe, biomass burning may substantially enhance the solubility of mineral dust. We observed fractional Fe solubility up to 12 % in mixed aerosols. Thus, Fe in dust may be more soluble in the tropics compared to higher latitudes due to higher concentrations of biomass-burning-derived reactive organic species in the atmosphere. In addition, biomass-burning-derived particles can act as a surface for aerosol Fe to bind during atmospheric transport and subsequently be released to the ocean upon deposition. As the aerosol loading is dominated by biomass burning emissions over the tropical waters in the dry season, additions of biomass-burning-derived soluble Fe could have harmful consequences for initiating nitrogen-fixing toxic algal blooms. Future research is required to quantify biomass-burning-derived particle sources of soluble Fe over tropical waters.

  17. Utilization of geothermal heat in tropical fruit-drying process

    Energy Technology Data Exchange (ETDEWEB)

    Chen, B.H.; Lopez, L.P.; King, R.; Fujii, J.; Tanaka, M.

    1982-10-01

    The power plant utilizes only the steam portion of the HGP-A well production. There are approximately 50,000 pounds per hour of 360/sup 0/F water produced (approximately 10 million Btu per hour) and the water is currently not used and is considered a waste. This tremendous resource could very well be used in applications such as food processing, food dehydration and other industrial processing that requires low-grade heat. One of the applications is examined, namely the drying of tropical fruits particularly the papaya. The papaya was chosen for the obvious reason that it is the biggest crop of all fruits produced on the Big Island. A conceptual design of a pilot plant facility capable of processing 1000 pounds of raw papaya per day is included. This facility is designed to provide a geothermally heated dryer to dehydrate papayas or other tropical fruits available on an experimental basis to obtain data such as drying time, optimum drying temperature, etc.

  18. [Diversity, structure and regeneration of the seasonally dry tropical forest of Yucatán Peninsula, Mexico].

    Science.gov (United States)

    Hernández-Ramírez, Angélica María; García-Méndez, Socorro

    2015-09-01

    Seasonally dry tropical forests are considered as the most endangered ecosystem in lowland tropics. The aim of this study was to characterize the floristic composition, richness, diversity, structure and regeneration of a seasonally dry tropical forest landscape constituted by mature forest, secondary forest and seasonally inundated forest located in the Northeastern part of the Yucatán Peninsula, Mexico. We used the Gentry's standard inventory plot methodology (0.1 ha per forest type in 2007) for facilitating comparison with other Mesoamerican seasonally dry tropical forests. A total of 77 species belonging to 32 families were observed in the study area. Fabaceae and Euphorbiaceae were the families with the largest taxonomic richness in the three forest types. Low levels of β diversity were observed among forest types (0.19-0.40), suggesting a high turnover of species at landscape level. The non-regenerative species were dominant (50-51 %), followed by regenerative species (30- 28 %), and colonizer species (14-21 %) in the three forest types. Zoochory was the most common dispersal type in the study area. The 88 % of the observed species in the study area were distributed in Central America. Some floristic attributes of the seasonally dry tropical forest of the Yucatán Peninsula, fall into the values reported for Mesoamerican seasonally dry tropical forests. Natural disturbances contributed to explain the high number of individuals, the low number of liana species, as well as the low values of basal area observed in this study. Our results suggested that the seasonally dry tropical forest of Yucatán Peninsula seems to be resilient to natural disturbances (hurricane) in terms of the observed number of species and families, when compared with the reported values in Mesoamerican seasonally dry tropical forests. Nonetheless, the recovery and regeneration of vegetation in long-term depends on animal-dispersed species. This study highlights the importance of

  19. Tropical dry forest recovery : processes and causes of change

    NARCIS (Netherlands)

    Lebrija Trejos, E.E.

    2009-01-01

    Seasonally dry areas are one of the preferred zones for human inhabitance in the tropics. Large forest areas are converted to other land uses and many are covered by secondary forests that grow naturally after cessation of disturbance. Surprisingly, secondary succession in these strongly seasonal

  20. Propagation of dry tropical forest trees in Mexico

    Science.gov (United States)

    Martha A. Cervantes Sanchez

    2002-01-01

    There is a distinct lack of technical information on the propagation of native tree species from the dry tropical forest ecosystem in Mexico. This ecosystem has come under heavy human pressures to obtain several products such as specialty woods for fuel, posts for fences and construction, forage, edible fruits, stakes for horticulture crops, and medicinal products. The...

  1. SRTM-DEM and Landsat ETM+ data for mapping tropical dry forest cover and biodiversity assessment in Nicaragua

    Science.gov (United States)

    S.E. Sesnie; S.E. Hagell; S.M. Otterstrom; C.L. Chambers; B.G. Dickson

    2008-01-01

    Tropical dry and deciduous forest comprises as much as 42% of the world’s tropical forests, but has received far less attention than forest in wet tropical areas. Land use change threatens to greatly reduce the extent of dry forest that is known to contain high levels of plant and animal diversity. Forest fragmentation may further endanger arboreal mammals that play...

  2. Pan tropical biomass equations for Mexico's dry forests

    Directory of Open Access Journals (Sweden)

    José Návar

    2014-12-01

    Full Text Available This study reports a set of robust regional M-tree allometric equations for Mexico's tropical dry forests and their application to a forest inventory dataset for the States of Durango and Sinaloa, Mexico. Calculated M data from 15 reported equations were fitted, applied and validated for regional and global models. Proposed theoretical models, empirically derived equations, as well as global and local reported equations were fitted and applied to calculated M-tree data using wood specific gravity, diameter at breast height, and top height as exogenous variables. Empirically-derived, computer-based equations assessed the M-tree evaluations slightly better than the theoretical, the global and the local models. However, the theoretical models projected compatible M-tree values and deserve further attention once wood specific gravity data are collected in the field. Using the best fit equation, mean M plot density values of 30, 41 and 35 Mg ha-1 were estimated from 57 plots (1,600 m² each, 217 plots (1,000 m² each and 166 plots (1,000 m² each in the tropical dry forests of the States of Durango, Tiniaquis and Vado Hondo (Sinaloa, respectively. The large sample size, the richness of the tested allometric models, the economic and ecological importance of this data-source, and the spatial coverage of these equations made this dataset uniquely useful for biomass, charcoal, and other bio-energy estimations, as well as for understanding the inherent heterogeneity of the stand-structure in dynamic tropical forest environments.

  3. Arthropod pests of dried fish and fish by product in a tropical urban ...

    African Journals Online (AJOL)

    A four months research survey of arthropod pests infesting dried fish sold in a tropical urban community market (Ogige), Nsukka, Ngeria showed that 10 genera o dried freshwater fish (Synodontis, Hemisynodontis, Oreochromis, Hepsetus, Gymnarchus, Labeo, Protopterus, Heterobranchus, Alestes, Heterotis) and two ...

  4. Soil water storage, rainfall and runoff relationships in a tropical dry forest catchment

    Science.gov (United States)

    Farrick, Kegan K.; Branfireun, Brian A.

    2014-12-01

    In forested catchments, the exceedance of rainfall and antecedent water storage thresholds is often required for runoff generation, yet to our knowledge these threshold relationships remain undescribed in tropical dry forest catchments. We, therefore, identified the controls of streamflow activation and the timing and magnitude of runoff in a tropical dry forest catchment near the Pacific coast of central Mexico. During a 52 day transition phase from the dry to wet season, soil water movement was dominated by vertical flow which continued until a threshold soil moisture content of 26% was reached at 100 cm below the surface. This satisfied a 162 mm storage deficit and activated streamflow, likely through lateral subsurface flow pathways. High antecedent soil water conditions were maintained during the wet phase but had a weak influence on stormflow. We identified a threshold value of 289 mm of summed rainfall and antecedent soil water needed to generate >4 mm of stormflow per event. Above this threshold, stormflow response and magnitude was almost entirely governed by rainfall event characteristics and not antecedent soil moisture conditions. Our results show that over the course of the wet season in tropical dry forests the dominant controls on runoff generation changed from antecedent soil water and storage to the depth of rainfall.

  5. Recovery of Biomass Following Shifting Cultivation in Dry Tropical Forests of the Yucatan

    OpenAIRE

    Read, L; Lawrence, Deborah; Foster, David Russell

    2003-01-01

    Land-use change in the tropics is creating secondary forest at an unprecedented rate. In the tropical Americas, mature dry tropical forest is rapidly being converted to secondary forest during the fallow period of shifting cultivation. This study addresses changes in forest biomass during forest recovery following shifting cultivation of maize (corn) in the Southern Yucatan Peninsular Region (SYPR), Mexico. We sampled stems .1 cm diameter at breast height at 36 study sites in t...

  6. SRTM-DEM AND LANDSAT ETM+ DATA FOR MAPPING TROPICAL DRY FOREST COVER AND BIODIVERSITY ASSESSMENT IN NICARAGUA

    OpenAIRE

    Brett G. Dickson; Carol L. Chambers; Sarah M. Otterstrom; Suzanne E. Hagell; Steven E. Sesnie

    2008-01-01

    Tropical dry and deciduous forest comprises as much as 42% of the world’s tropical forests, but hasreceived far less attention than forest in wet tropical areas. Land use change threatens to greatly reducethe extent of dry forest that is known to contain high levels of plant and animal diversity. Forest fragmentationmay further endanger arboreal mammals that play principal role in the dispersal of large seeded fruits, plantcommunity assembly and diversity in these systems. Data on the spatial...

  7. FLORULA URBAN FRAGMENT OF TROPICAL DRY FOREST

    Directory of Open Access Journals (Sweden)

    Willington Barranco-Pérez

    2016-01-01

    Full Text Available The aim of this study was to record the composition of plant species in an urban fragment of tropical dry forest of secondary regeneration (bs-T to generate information that can be used in the planning and management of green spaces in the city of Santa Marta. Transects of 2 x 50 m were established equivalent to 0.1 ha and all species were counted >1.0 cm DBH (Diameter at Breast Height: 1.3m. 100 species of angiosperms were recorded of which 47% have herbaceous habit. The number of species recorded in this study represents 39.6% of the species reported for the hills of Santa Marta and 3.8% for the dry forests of Colombia. It is suggested to isolate this type of secondary formations of any intervention and contemplate the reintroduction of individuals and conservation strategies.

  8. Water flow and energy balance for a tropical dry semideciduous forest

    Science.gov (United States)

    Andrade, J. L.; Garruña-Hernandez, R.; Leon-Palomo, M.; Us-Santamaria, R.; Sima, J. L.

    2013-05-01

    Tropical forests cool down locally because increase water evaporation from the soil to the atmosphere, reduce albedo and help forming clouds that reflect solar radiation back to the atmosphere; this, aligned to the carbon catchment, increase forests value. We will present an estimation of the sap flow and energy balance for the tropical dry semideciduous forest at Kiuic, Yucatan, Mexico during a year. We use a meteorological tower equipped with a rain gauge, temperature and relative humidity, heat flow plates, thermocouples and volumetric soil water content. We recorded net radiation and soil heat flux and estimated sensible heat and latent heat. Besides, we estimated latent heat by measuring sap flow directly in tres using disispation constant heat probes during the rainy season. Results show the influence of the seasonality on net radiation, air temperatura and vapor pressure deficit, because during the dry season his variables were higher and with more duation than during the rainy and early dry season. Sap flow was different for trees belonging to the family Fabaceae compared to trees from other families.

  9. Succesional change and resilience of a very dry tropical deciduous forest following shifting agriculture

    NARCIS (Netherlands)

    Lebrija Trejos, E.E.; Bongers, F.J.J.M.; Pérez-García, E.; Meave, J.

    2008-01-01

    We analyzed successional patterns in a very dry tropical deciduous forest by using 15 plots differing in age after abandonment and contrasted them to secondary successions elsewhere in the tropics. We used multivariate ordination and nonlinear models to examine changes in composition and structure

  10. A molecular phylogeny of Afromontane dwarf geckos (Lygodactylus) reveals a single radiation and increased species diversity in a South African montane center of endemism.

    Science.gov (United States)

    Travers, Scott L; Jackman, Todd R; Bauer, Aaron M

    2014-11-01

    Afromontane habitats throughout eastern sub-Saharan Africa support remarkable levels of microendemism. However, despite being the subject of decades of research interest, biogeographical patterns of diversification throughout this disjunct montane system still remain largely unknown. We examined the evolutionary relationships of diurnal dwarf geckos (Lygodactylus) from several Afromontane regions throughout southeastern Africa, focusing primarily on two species groups (rex and bonsi groups). Using both mitochondrial and nuclear markers, we generate a molecular phylogeny containing all members of the rex and bonsi groups, to evaluate the monophyly of these groups along with previous biogeographic hypotheses suggesting independent southward invasions into the greater Drakensberg Afromontane center of endemism in northeastern South Africa by each group. Our results provide no support for these taxonomic and biogeographic hypotheses, and instead reveal geographically circumscribed patterns of diversification. One clade is restricted to the highlands of southern Malawi and northern Mozambique and the other to the greater Drakensberg region of northeastern South Africa and Swaziland. Interestingly, L. bernardi from the Nyanga Highlands of eastern Zimbabwe is nested within the primarily savanna-dwelling capensis group. We use Bayesian species delimitation methods to evaluate species limits within the greater Drakensberg clade, which support the elevation of the subspecies of L. ocellatus and L. nigropunctatus, thus bringing the total to eight species within a relatively confined geographic area. These results further highlight the greater Drakensberg Afromontane region as both an important center of endemism, as well as a center of diversification contributing to the accumulation of southern Africa's rich species diversity. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Multi-Temporal Monitoring Of Ecological Succession In Tropical Dry Forests Using Angular - Hyperspectral Data (Chris/Proba)

    Science.gov (United States)

    Garcia Millan, V. E.

    2015-12-01

    The tropical dry forest is the largest and most threatened ecosystem in Latin America. Remote sensing can effectively contribute to the surveillance of conservation measurements and laws through the monitoring of natural protected areas, at the required temporal and spatial scales. CHRIS/PROBA is the only satellite that presents quasi-simultaneous multi-angular pointing and hyperspectral spectroscopy. These two characteristics permit the study of structural and compositional traces of successional stages within the tropical dry forest. The current study presents the results of mapping the succession of tropical dry forest in the Parque Estadual de la Mata-Seca, in Minas Gerais, Brazil, using a temporal analysis of CHRIS/PROBA images in a time frame of 7 years, between 2008 and 2014. For the purpose the -55° angle of observation has been used, which enhances spectral differences between successional stages. Spectral Angle Mapper has been used for mapping succession of tropical dry forest and afterwards Change Detection Analysis has been performed. Based on our observations, the tropical dry forest in the Parque Estadual de la Mataseca recovers at a fast rate, for the observed period (2008-2014). More than the 50% of the early and intermediate forests has been recovered to a mature forest. Significantly, around a 12% of old pastures have been converted into forest. The spatial analysis also reveals that the areas that recover most rapidly are located in the east of the Park, close to mature forests. The provision of seeds from these forests might be the cause for the fast recovery.

  12. A warming tropical central Pacific dries the lower stratosphere

    Science.gov (United States)

    Ding, Qinghua; Fu, Qiang

    2018-04-01

    The amount of water vapor in the tropical lower stratosphere (TLS), which has an important influence on the radiative energy budget of the climate system, is modulated by the temperature variability of the tropical tropopause layer (TTL). The TTL temperature variability is caused by a complex combination of the stratospheric quasi-biennial oscillation (QBO), tropospheric convective processes in the tropics, and the Brewer-Dobson circulation (BDC) driven by mid-latitude and subtropical atmospheric waves. In 2000, the TLS water vapor amount exhibited a stepwise transition to a dry phase, apparently caused by a change in the BDC. In this study, we present observational and modeling evidence that the epochal change of water vapor between the periods of 1992-2000 and 2001-2005 was also partly caused by a concurrent sea surface temperature (SST) warming in the tropical central Pacific. This SST warming cools the TTL above by enhancing the equatorial wave-induced upward motion near the tropopause, which consequently reduces the amount of water vapor entering the stratosphere. The QBO affects the TLS water vapor primarily on inter-annual timescales, whereas a classical El Niño southern oscillation (ENSO) event has small effect on tropical mean TLS water vapor because its responses are longitudinally out of phase. This study suggests that the tropical central Pacific SST is another driver of TLS water vapor variability on inter-decadal timescales and the tropical SST changes could contribute to about 30% of the step-wise drop of the lower stratospheric water vapor from 1992-2000 to 2001-2005.

  13. Desorption isotherms, drying characteristics and qualities of glace tropical fruits undergoing forced convection solar drying

    Energy Technology Data Exchange (ETDEWEB)

    Jamradloedluk, Jindaporn; Wiriyaumpaiwong, Songchai [Mahasarakham Univ. Khamriang, Kantarawichai, Mahasarakham (Thailand)

    2008-07-01

    Solar energy, a form of sustainable energy, has a great potential for a wide variety of applications because it is abundant and accessible, especially for countries located in the tropical region. Drying process is one of the prominent techniques for utilization of solar energy. This research work proposes a forced convection solar drying of osmotically pretreated fruits viz. mango, guava, and pineapple. The fruit cubes with a dimension of 1cm x 1cm x 1cm were immersed in 35% w./w. sucrose solution prior to the drying process. Drying kinetics, color and hardness of the final products obtained from solar drying were investigated and compared with those obtained from open air-sun drying. Desorption isotherms of the osmosed fruits were also examined and five mathematical models were used to fit the desorption curves. Experimental results revealed that solar drying provided higher drying rate than natural sun drying. Color of glace fruit processed by solar drying was more intense, indicated by lower value of lightness and higher value of yellowness, than that processed by sun drying. Hardness of the products dehydrated by both drying methods, however, was not significantly different (p>0.05). Validation of the mathematical models developed showed that the GAB model was most effective for describing desorption isotherms of osmotically pretreated mango and pineapple whereas Peleg's model was most effective for describing desorption isotherms of osmotically pretreated guava. (orig.)

  14. Short dry spells in the wet season increase mortality of tropical pioneer seedlings.

    Science.gov (United States)

    Engelbrecht, Bettina M J; Dalling, James W; Pearson, Timothy R H; Wolf, Robert L; Gálvez, David A; Koehler, Tobias; Tyree, Melvin T; Kursar, Thomas A

    2006-06-01

    Variation in plant species performance in response to water availability offers a potential axis for temporal and spatial habitat partitioning and may therefore affect community composition in tropical forests. We hypothesized that short dry spells during the wet season are a significant source of mortality for the newly emerging seedlings of pioneer species that recruit in treefall gaps in tropical forests. An analysis of a 49-year rainfall record for three forests across a rainfall gradient in central Panama confirmed that dry spells of > or = 10 days during the wet season occur on average once a year in a deciduous forest, and once every other year in a semi-deciduous moist and an evergreen wet forest. The effect of wet season dry spells on the recruitment of pioneers was investigated by comparing seedling survival in rain-protected dry plots and irrigated control plots in four large artificially created treefall gaps in a semi-deciduous tropical forest. In rain-protected plots surface soil layers dried rapidly, leading to a strong gradient in water potential within the upper 10 cm of soil. Seedling survival for six pioneer species was significantly lower in rain-protected than in irrigated control plots after only 4 days. The strength of the irrigation effect differed among species, and first became apparent 3-10 days after treatments started. Root allocation patterns were significantly, or marginally significantly, different between species and between two groups of larger and smaller seeded species. However, they were not correlated with seedling drought sensitivity, suggesting allocation is not a key trait for drought sensitivity in pioneer seedlings. Our data provide strong evidence that short dry spells in the wet season differentially affect seedling survivorship of pioneer species, and may therefore have important implications to seedling demography and community dynamics.

  15. [Regenerative morphological traits in a woody species community in Tumbesian tropical dry forest].

    Science.gov (United States)

    Romero-Saritama, José Miguel; Pérez-Rúuz, César

    2016-06-01

    The study of functional morphological traits enables us to know fundamental aspects of the dynamics of plant communities in local and global habitats. Regenerative morphological traits play an important role in defining plant history and ecological behavior. Seed and fruit characteristics determine to a large extent the patterns for dispersal, germination, establishment and seedling recruitment a given species exhibits on its natural habitat. Despite their prominent role, seed and fruit traits have been poorly studied at the community level of woody plant species in neo-tropical dry forests. In the present study we aimed at i) evaluate the functional role of morphological traits of seeds, fruits and embryo in woody plant species; ii) determine which are the morphological patterns present in seeds collected from the community of woody species that occur in neo-tropical dry forests; and iii) compare woody plant species seed mass values comparatively between neo-tropical dry and tropical forests. To do so, mature seeds were collected from 79 plant species that occur in the Tumbesian forest of Southwest Ecuador. The studied species included the 42 and 37 most representative tree and shrubbery species of the Tumbesian forest respectively. A total of 18 morphological traits (seven quantitative and 11 qualitative) were measured and evaluated in the seeds, fruits and embryos of the selected species, and we compared the seeds mass with other forest types. Our results showed a huge heterogeneity among traits values in the studied species. Seed mass, volume and number were the traits that vary the most at the community level, i.e. seed length ranged from 1.3 to 39 mm, and seed width from 0.6 to 25 mm. Only six embryo types were found among the 79 plant species. In 40 % of the cases, fully developed inverted embryos with large and thick cotyledons to store considerable amount of nutrients were recorded. We concluded that highly variable and functionally complementary

  16. Effect of Tropical Climatic Conditions on the Stability of Cefaclor Dry ...

    African Journals Online (AJOL)

    Purpose: Two critical factors that govern the stability of pharmaceutical formulations in the tropics are humidity and temperature. This study was carried out to investigate the effect of moisture sorption at two different storage conditions on Cefaclor dry powder for oral suspension and predict the effect of moisture interaction on ...

  17. Extending the baseline of tropical dry forest loss in Ghana (1984–2015) reveals drivers of major deforestation inside a protected area

    OpenAIRE

    Janssen, T; Ametsisi, G; Collins, M; Adu-Bredu, S; Oliveras-Menor, I; Mitchard, ETA; Veenendaal, EM

    2017-01-01

    Abstract Tropical dry forests experience the highest deforestation rates on Earth, with major implications for the biodiversity of these ecosystems, as well as for its human occupants. Global remote sensing based forest cover data (2000 − 2012) point to the rapid loss of tropical dry forest in South America and Africa, also, if not foremost, inside formally protected areas. Here, we significantly extend the baseline of tropical dry forest loss inside a protected area in Ghana using a generali...

  18. Dry season distribution of hydroids in a small tropical estuary, Pernambuco, Brazil

    NARCIS (Netherlands)

    Calder, D.R.; Maÿal, E.M.

    1998-01-01

    Hydroid distribution patterns along a horizontal ecocline in the Rio Formoso/Rio Ariquindá/Rio Porto Alegre system, a small and seasonally poikilohaline estuary on the tropical northeast coast of Brazil, were investigated. Collecting was undertaken during the dry season, in November 1993, by diving

  19. Selective logging and fire as drivers of alien grass invasion in a Bolivian tropical dry forest

    NARCIS (Netherlands)

    Veldman, J.W.; Mostacedo, B.; Peña-Claros, M.; Putz, F.E.

    2009-01-01

    Logging is an integral component of most conceptual models that relate human land-use and climate change to tropical deforestation via positive-feedbacks involving fire. Given that grass invasions can substantially alter fire regimes, we studied grass distributions in a tropical dry forest 1-5 yr

  20. Persistent Soil Seed Banks for Natural Rehabilitation of Dry Tropical Forests in Northern Ethiopia

    OpenAIRE

    Gebrehiwot, K.; Heyn, M.; Reubens, B.; Hermy, M.; Muys, B.

    2007-01-01

    Dry tropical forests are threatened world-wide by conversion to grazing land, secondary forest, savannah or arable land. In Ethiopia, natural dry forest cover has been decreasing at an alarming rate over the last decennia and has reached a critical level. Efforts like the rehabilitation of dry forests to curb this ecological degradation, need a stronger scientific basis than currently available. The aim of the present research was to test the hypothesis whether soil seed banks can contribute ...

  1. Forest structure in low diversity tropical forests: a study of Hawaiian wet and dry forests

    Science.gov (United States)

    R. Ostertag; F. Inman-Narahari; S. Cordell; C.P. Giardina; L. Sack

    2014-01-01

    The potential influence of diversity on ecosystem structure and function remains a topic of significant debate, especially for tropical forests where diversity can range widely. We used Center for Tropical Forest Science (CTFS) methodology to establish forest dynamics plots in montane wet forest and lowland dry forest on Hawai‘i Island. We compared the species...

  2. Diameter distribution in a Brazilian tropical dry forest domain: predictions for the stand and species.

    Science.gov (United States)

    Lima, Robson B DE; Bufalino, Lina; Alves, Francisco T; Silva, José A A DA; Ferreira, Rinaldo L C

    2017-01-01

    Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.

  3. The Predictability of Dry-Season Precipitation in Tropical West Africa

    Science.gov (United States)

    Knippertz, P.; Davis, J.; Fink, A. H.

    2012-04-01

    Precipitation during the boreal winter dry season in tropical West Africa is rare but occasionally connected to high-impacts for the local population. Previous work has shown that these events are usually connected to a trough over northwestern Africa, an extensive cloud plume on its eastern side, unusual precipitation at the northern and western fringes of the Sahara, and reduced surface pressure over the southern Sahara and Sahel, which allows an inflow of moist southerlies from the Gulf of Guinea to feed the unusual dry-season rainfalls. These results also suggest that the extratropical influence enhances the predictability of these events on the synoptic timescale. Here we further investigate this question for the 11 dry seasons (November-March) 1998/99-2008/09 using rainfall estimates from TRMM (Tropical Rainfall Measuring Mission) and GPCP (Global Precipitation Climatology Project), and operational ensemble predictions from the European Centre for Medium-Range Forecasts (ECMWF). All fields are averaged over the study area 7.5-15°N, 10°W-10°E that spans most of southern West Africa. For each 0000 UTC analysis time, the daily precipitation estimates are accumulated to pentads and compared with 120-hour predictions starting at the same time. Compared to TRMM, the ensemble mean shows a weak positive bias, whereas there is a substantial negative bias with regard to GPCP. Temporal correlations reach a high value of 0.8 for both datasets, showing similar synoptic variability despite the differences in total amount. Standard probabilistic evaluation methods such as relative operating characteristic (ROC) diagrams indicate remarkably good reliability, resolution and skill, particularly for lower precipitation thresholds. Not surprisingly, forecasts cluster at low probabilities for higher thresholds, but the reliability and ROC score are still reasonably high. The results show that global ensemble prediction systems are capable to predict dry-season rainfall events

  4. Pasture research in the wet and dry tropics of Nigeria with particular reference to isotope applications

    International Nuclear Information System (INIS)

    Adegbola, A.A.; Adepoju, A.

    1983-01-01

    Pasture research in western Nigeria, which typifies the wet and dry tropics of Nigeria, is discussed fully. Interest in pasture research in the area was kindled in 1930 with the introduction of Cynodon nlemfuensis var. robusta, but systematic work did not start until the 1950s. Early agronomic studies centred on easy means of establishing the adapted species from cuttings, sprigs or seeds. The most important species in the dry tropics is Andropogon gayanus, while in the wet tropics it is Panicum maximum. Later, investigations on yield of dry matter, intervals and height of cutting and response to fertilizer applications were carried out. Radioactive fertilizer 32 P- and 15 N-urea were also used to study the yield response of pasture to fertilizer application and to determine the percentage uptake of nutrients by plants. The results of such trials in different locations in the area are discussed extensively. Also, 32 P was used to determine the depth of active absorption of the root system of Andropogon gayanus and Panicum maximum, thus establishing their rooting pattern. (author)

  5. Light Diffusion in the Tropical Dry Forest of Costa Rica

    Science.gov (United States)

    Calvo-Rodriguez, S.; Sanchez-Azofeifa, G. A.

    2016-06-01

    Leaf Area Index (LAI) has been defined as the total leaf area (one-sided) in relation to the ground. LAI has an impact on tree growth and recruitment through the interception of light, which in turn affects primary productivity. Even though many instruments exist for estimating LAI from ground, they are often laborious and costly to run continuously. Measurements of LAI from the field using traditional sensors (e.g., LAI-2000) require multiple visits to the field under very specific sky conditions, making them unsuitable to operate in inaccessible areas and forests with dense vegetation, as well as areas where persistent sunny conditions are the norm like tropical dry forests. With this context, we proposed a methodology to characterize light diffusion based on NDVI and LAI measurements taken from the field in two successional stages in the tropical dry forest of Santa Rosa National Park in Costa Rica. We estimate a "K" coefficient to characterize light diffusion by the canopy, based on field NDVI measurements derived from optical phenology instruments and MODIS NDVI. From the coefficients determined, we estimated LAI values and compared them with ground measurements of LAI. In both successional stages ground measurements of LAI had no significant difference to the tower-derived LAI and the estimated LAI from MODIS NDVI.

  6. Light-dependent leaf trait variation in 43 tropical dry forest tree species

    NARCIS (Netherlands)

    Markesteijn, L.; Poorter, L.; Bongers, F.J.J.M.

    2007-01-01

    Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun¿shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small

  7. Former land-use and tree species affect nitrogen oxide emissions from a tropical dry forest.

    Science.gov (United States)

    Heather Erickson; Eric A. Davidson; Michael Keller

    2002-01-01

    Species composition in successional dry forests in the tropics varies widely, but the effect of this variation on biogeochemical processes is not well known. We examined fluxes of N oxides (nitrous and nitric oxide), soil N cycling, and litter chemistry (C/N ratio) in four successional dry forests on similar soils in western Puerto Rico with differing species...

  8. Analyzing the edge effects in a Brazilian seasonally dry tropical forest.

    Science.gov (United States)

    Arruda, D M; Eisenlohr, P V

    2016-02-01

    Due to the deciduous nature of dry forests (widely known as seasonally dry tropical forests) they are subject to microclimatic conditions not experienced in other forest formations. Close examinations of the theory of edge effects in dry forests are still rare and a number of questions arise in terms of this topic. In light of this situation we examined a fragment of the dry forest to respond to the following questions: (I) Are there differences in canopy cover along the edge-interior gradient during the dry season? (II) How does the microclimate (air temperature, soil temperature, and relative humidity) vary along that gradient? (III) How does the microclimate influence tree species richness, evenness and abundance along that gradient? (IV) Are certain tree species more dominant closer to the forest edges? Regressions were performed to address these questions. Their coefficients did not significantly vary from zero. Apparently, the uniform openness of the forest canopy caused a homogeneous internal microclimate, without significant differentiation in habitats that would allow modifications in biotic variables tested. We conclude that the processes of edge effect commonly seen in humid forests, not was shared with the dry forest assessed.

  9. Insect herbivores associated with an evergreen tree Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) in a tropical dry forest.

    Science.gov (United States)

    Silva, J O; Neves, F S

    2014-08-01

    Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) is a tree species found in Brazilian tropical dry forests that retain their leaves during the dry season. That being, we addressed the following question: i) How do insect diversity (sap-sucking and chewing), leaf herbivory and defensive traits (tannin and leaf sclerophylly) vary on the evergreen tree species G. marginata between seasons? The abundance of sap-sucking insects was higher in the dry season than in the rainy season. However, we did not verify any difference in the species richness and abundance of chewing insects between seasons. Leaf herbivory was higher in the rainy season, whereas leaf sclerophylly was higher in the dry season. However, herbivory was not related to sclerophylly. Insect herbivores likely decrease their folivory activity during the dry season due to life history patterns or changes in behaviour, possibly entering diapause or inactivity during this period. Therefore, G. marginata acts as a likely keystone species, serving as a moist refuge for the insect fauna during the dry season in tropical dry forest, and the presence of this evergreen species is crucial to conservation strategies of this threatened ecosystem.

  10. Diurnal thermoregulatory responses in pregnant Yankasa ewes to the dry season in a tropical Savannah.

    Science.gov (United States)

    Yaqub, Lukuman Surakat; Ayo, Joseph Olusegun; Kawu, Muhammad Umar; Rekwot, Peter Ibrahim

    2017-08-01

    The study investigated concomitant effect of gestation and high ambient temperature under a tropical environment on rectal temperature (RT), respiratory rate (RR) and heart rate (HR) responses in Yankasa ewes. Twenty Yankasa ewes, consisting of ten pregnant and ten non-pregnant ewes, were used for the study. Ewes were synchronised and bred, such that each gestation phase coincided with different periods of the dry-seasons, early-gestation (cold/harmattan), mid-gestation (peak hot-dry) and late-gestation (late hot-dry). The RT, RR and HR were recorded thrice, 2 days apart at middle of each gestation period at 06:00, 14:00 and 18:00 h, concurrently with dry- (DBT) and wet-bulb temperatures of the experimental pen. The DBT was positively correlated with RT, RR during the different gestation stages. The RT significantly (P ewes, with peak at 14:00 h. Values of RT and RR were higher (P ewes at mid- and late-gestation, respectively. Mean RT was lower (P ewes at early-gestation (cold-dry). The HR was (P ewes during the different gestation phases. In conclusion, ambient temperature and gestation concomitantly modulate diurnal thermoregulatory responses of the ewes to hot-dry season. Adequate measures should be adopted to mitigate adverse impact of prolonged high RR on the dam and the foetus during the peak of ambient temperature prevailing in the tropical Savannah environment.

  11. Extending the baseline of tropical dry forest loss in Ghana (1984–2015) reveals drivers of major deforestation inside a protected area

    NARCIS (Netherlands)

    Janssen, Thomas A.J.; Ametsitsi, George K.D.; Collins, Murray; Adu-Bredu, Stephen; Oliveras, Imma; Mitchard, Edward T.A.; Veenendaal, Elmar M.

    2018-01-01

    Tropical dry forests experience the highest deforestation rates on Earth, with major implications for the biodiversity of these ecosystems, as well as for its human occupants. Global remote sensing based forest cover data (2000 − 2012) point to the rapid loss of tropical dry forest in South America

  12. Extending the baseline of tropical dry forest loss in Ghana (1984–2015) reveals drivers of major deforestation inside a protected area

    NARCIS (Netherlands)

    Janssen, Thomas A.J.; Ametsitsi, George K.D.; Collins, Murray; Adu-Bredu, Stephen; Oliveras, Imma; Mitchard, Edward T.A.; Veenendaal, Elmar M.

    2018-01-01

    Abstract Tropical dry forests experience the highest deforestation rates on Earth, with major implications for the biodiversity of these ecosystems, as well as for its human occupants. Global remote sensing based forest cover data (2000 − 2012) point to the rapid loss of tropical dry forest in South

  13. Microhabitat partitioning between leiuperidae and bufonidae species (amphibia: anura) in tropical dry forest areas in Colombian Caribbean

    International Nuclear Information System (INIS)

    Blanco Torres, Argelina; Bonilla Gomez, Maria Argenis

    2010-01-01

    We analyzed partitioning of microhabitats by five species of frogs in the families, Bufonidae (Rhinella marina, r. granulosa), and Leiuperidae (Engystomops pustulosus, Pleurodema brachyops and Pseudopaludicola pusilla) in six different localities of the Colombian Caribbean with tropical dry forest fragments and different land uses. We identified 29 types of microhabitats; permanent ponds in pastures with trees (CPPA) and flooded pastures without trees (PISA) were the most important environmental used. Engystomops pustulosus used the must microhabitats, and none are used by specialist species. Thus, differences in the use of resource on regional and local scales appeared. Dynamics of microhabitat uses was influenced by the climatic variations of the tropical dry forest. Microhabitats distribution as a mechanism of coexistence in these species is implemented for dry season but in rainfall season this mechanism not exists.

  14. Dry eye syndrome: A rising occupational hazard in tropical countries

    Directory of Open Access Journals (Sweden)

    Kavita R Bhatnagar

    2014-01-01

    Full Text Available Aim : The aim of this study was to find out the prevalence of dry eye and evaluate personal and environmental risk factors attributable to dry eye in a hospital-based population. Materials and Methods : In this cross-sectional study, 1890 patients above 15 years of age were screened randomly for dry eye. McMonnies Dry Eye Questionnaire, Schirmer′s test, tear film breakup time (TBUT, presence of conjunctival injection, punctate epithelial erosions (PEE, and meibomian gland dysfunction (MGD were used to diagnose dry eye. Patient demographics including age, sex, smoking, and occupation and working environment were also recorded. Correlation of dry eye signs with symptoms and TFBUT and Schirmer′s tests was also assessed. Results : The prevalence of dry eye was 10.58%. The prevalence was higher in outdoor workers (17.77%. The male: female ratio was 2.33:1. The number of males was highest in the 56-60 (13% and 60-65 (14% years age groups while that of females was highest in the 46-50 (16.67% years age group. A total of 10% of the patients were smokers, while 8% were tobacco chewers. A 2.15-fold increase was found in the odds for dry eye in those exposed to excessive wind, 1.91-fold to sunlight exposure, and 2.04 for air pollution. Abnormally low TBUT and Schirmer′s tests were significantly associated with dry eye signs (P=0.009 and 0.014, respectively. Conclusion : Dry eye is a leading cause of ocular discomfort in OPD patients. Excessive exposure to wind, sunlight, high temperature, and air pollution was significantly related to dry eyes. There was a significant correlation between patient′s history, symptoms, dry eye signs and objective tests for tear film. The rural people and those with outdoor occupation are more exposed to extraneous influences of environmental factors in tropical climate. These factors affect the tear film and ocular surface causing the dry eye syndrome.

  15. Impact of livestock on a mosquito community (Diptera: Culicidae) in a Brazilian tropical dry forest

    OpenAIRE

    Santos,Cleandson Ferreira; Borges,Magno

    2015-01-01

    AbstractINTRODUCTION: This study evaluated the effects of cattle removal on the Culicidae mosquito community structure in a tropical dry forest in Brazil.METHODS: Culicidae were collected during dry and wet seasons in cattle presence and absence between August 2008 and October 2010 and assessed using multivariate statistical models.RESULTS: Cattle removal did not significantly alter Culicidae species richness and abundance. However, alterations were noted in Culicidae community composition.CO...

  16. Tropical anurans mature early and die young: Evidence from eight Afromontane Hyperolius species and a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Ulrich Sinsch

    Full Text Available Age- and size-related life-history traits of anuran amphibians are thought to vary systematically with latitude and altitude. Because the available data base is strongly biased towards temperate-zone species, we provide new estimates on eight afrotropical Reed Frog species. A meta-analysis of the demographic traits in 44 tropical anuran species aims to test for the predicted clinal variation and to contrast results with variation detected in temperate-zone species. The small-sized reed frogs reach sexual maturity during the first or second year of life, but longevity does not exceed three to four years. Latitudinal effects on demographic life-history traits are not detectable in tropical anurans, and altitudinal effects are limited to a slight size reduction at higher elevations. Common features of anuran life-history in the tropics are early sexual maturation at small size and low longevity resulting in low lifetime fecundity. This pattern contrasts with that found in temperate-zone anurans which mature later at larger size and grow considerably older yielding greater lifetime fecundity than in the tropics. Latitudinal and altitudinal contraction of the yearly activity period shape the evolution of life-history traits in the temperate region, while trait variation in the tropics seems to be driven by distinct, not yet identified selective forces.

  17. Stated preferences for tropical wildlife conservation amongst distant beneficiaries

    DEFF Research Database (Denmark)

    Morse-Jones, Sian; Bateman, Ian J.; Kontoleon, Andreas

    2012-01-01

    Despite heightened awareness of the need to find additional resources for tropical biodiversity conservation, and recognition that the benefits to populations in developed countries may be significant, very few empirical studies have been conducted to estimate these values. In this article, we...... report the results of a choice experiment survey that investigated the preferences of UK residents for the conservation of threatened wildlife in the Eastern Arc Mountains in Tanzania, part of the Eastern Afromontane “biodiversity hotspot”. We examine the sensitivity of values to species types......, the number of species, the number of conservation sites and, more unusually, to potential substitutes/complements. Critically we find some evidence of coherency in preferences. Respondents are willing to pay significant, positive amounts to conserve charismatic and/or endemic species and are scope sensitive...

  18. Dispersal, isolation and diversification with continued gene flow in an Andean tropical dry forest.

    Science.gov (United States)

    Toby Pennington, R; Lavin, Matt

    2017-07-01

    The Andes are the world's longest mountain chain, and the tropical Andes are the world's richest biodiversity hot spot. The origin of the tropical Andean cordillera is relatively recent because the elevation of the mountains was relatively low (400-2500 m palaeoelevations) only 10 MYA with final uplift being rapid. These final phases of the Andean orogeny are thought to have had a fundamental role in shaping processes of biotic diversification and biogeography, with these effects reaching far from the mountains themselves by changing the course of rivers and deposition of mineral-rich Andean sediments across the massive Amazon basin. In a recent issue of Molecular Ecology, Oswald, Overcast, Mauck, Andersen, and Smith (2017) investigate the biogeography and diversification of bird species in the Andes of Peru and Ecuador. Their study is novel in its focus on tropical dry forests (Figure 1) rather than more mesic biomes such as rain forests, cloud forests and paramos, which tend to be the focus of science and conservation in the Andean hot spot. It is also able to draw powerful conclusions via the first deployment of genomic approaches to a biogeographic question in the threatened dry forests of the New World. © 2017 John Wiley & Sons Ltd.

  19. Phytogeography of the tropical north-east African mountains

    Directory of Open Access Journals (Sweden)

    I. Friis

    1983-11-01

    Full Text Available The tropical north-east African mountains are tentatively divided into four phytochoria, the formal rank of which is not defined. The division is based on patterns of distribution and endemism in the region. The recognition of a distinct Afromontane phytochorion is now well established (Chapman & White, 1970; Werger, 1978; White, 1978. However, there is still very little information on the phytogeography of the individual mountains or mountain systems. This study hopes to fill a little of the gap by analysing distribution patterns and patterns of endemism in the flora of the tropical north-east African mountains. The north-east African mountain system is the largest in tropical Africa (see e.g. map in White, 1978. At the core of this system is the large Ethiopian massif, around which are located various mountains and mountain chains. These include the Red Sea Hills in the Sudan, the mountain chain in northern Somalia, the south-west Arabian mountains, and the Imatong mountains of south-east Sudan. The latter are often referred to the East African mountain system (White, 1978 but. as I will point out later, they also have a close connection with the south-west highlands of Ethiopia. The paper presents some results of my study of the mountain flora of tropical north-east Africa, particularly the forest species. Where no source is indicated, the data are from my own unpublished studies.

  20. Resource partitioning by evergreen and deciduous species in a tropical dry forest.

    Science.gov (United States)

    Álvarez-Yépiz, Juan C; Búrquez, Alberto; Martínez-Yrízar, Angelina; Teece, Mark; Yépez, Enrico A; Dovciak, Martin

    2017-02-01

    Niche differentiation can lead to coexistence of plant species by partitioning limiting resources. Light partitioning promotes niche differentiation in tropical humid forests, but it is unclear how niche partitioning occurs in tropical dry forests where both light and soil resources can be limiting. We studied the adult niche of four dominant evergreen (cycad, palm) and drought-deciduous (legume, oak) species co-occurring along environmental gradients. We analyzed light intensity and soil fertility effects on key functional traits related to plant carbon and water economy, how these traits determine species' functional strategies, and how these strategies relate to relative species abundance and spatial patterns. Light intensity was negatively associated with a key trait linked to plant water economy (leaf δ 13 C, a proxy for long-term water-use efficiency-WUE), while soil fertility was negatively associated with a key trait for plant carbon economy (LNC, leaf nitrogen content). Evergreens were highly sclerophyllous and displayed an efficient water economy but poor carbon economy, in agreement with a conservative resource-use strategy (i.e., high WUE but low LNC, photosynthetic rates and stature). Conversely, deciduous species, with an efficient carbon economy but poor water economy, exhibited an exploitative resource-use strategy (i.e., high LNC, photosynthetic rates and stature, but low WUE). Evergreen and deciduous species segregated spatially, particularly at fine-scales, as expected for species with different resource-use strategies. The efficient water economy of evergreens was related to their higher relative abundance, suggesting a functional advantage against drought-deciduous species in water-limited environments within seasonally dry tropical forests.

  1. Effect of freeze-drying on the antioxidant compounds and antioxidant activity of selected tropical fruits.

    Science.gov (United States)

    Shofian, Norshahida Mohamad; Hamid, Azizah Abdul; Osman, Azizah; Saari, Nazamid; Anwar, Farooq; Dek, Mohd Sabri Pak; Hairuddin, Muhammad Redzuan

    2011-01-01

    The effects of freeze-drying on antioxidant compounds and antioxidant activity of five tropical fruits, namely starfruit (Averrhoa carambola L.), mango (Mangifera indica L.), papaya (Carica papaya L.), muskmelon (Cucumis melo L.), and watermelon Citruluss lanatus (Thunb.) were investigated. Significant (p dried fruit samples, except muskmelon. There was no significant (p > 0.05) change, however, observed in the ascorbic acid content of the fresh and freeze-dried fruits. Similarly, freeze-drying did not exert any considerable effect on β-carotene concentration of fruits, except for mango and watermelon, where significantly (p dried fruits. Overall, in comparison to β-carotene and ascorbic acid, a good correlation was established between the result of TPC and antioxidant assays, indicating that phenolics might have been the dominant compounds contributing towards the antioxidant activity of the fruits tested.

  2. Intermediate tree cover can maximize groundwater recharge in the seasonally dry tropics

    Science.gov (United States)

    Ilstedt, U.; Bargués Tobella, A.; Bazié, H. R.; Bayala, J.; Verbeeten, E.; Nyberg, G.; Sanou, J.; Benegas, L.; Murdiyarso, D.; Laudon, H.; Sheil, D.; Malmer, A.

    2016-01-01

    Water scarcity contributes to the poverty of around one-third of the world’s people. Despite many benefits, tree planting in dry regions is often discouraged by concerns that trees reduce water availability. Yet relevant studies from the tropics are scarce, and the impacts of intermediate tree cover remain unexplored. We developed and tested an optimum tree cover theory in which groundwater recharge is maximized at an intermediate tree density. Below this optimal tree density the benefits from any additional trees on water percolation exceed their extra water use, leading to increased groundwater recharge, while above the optimum the opposite occurs. Our results, based on groundwater budgets calibrated with measurements of drainage and transpiration in a cultivated woodland in West Africa, demonstrate that groundwater recharge was maximised at intermediate tree densities. In contrast to the prevailing view, we therefore find that moderate tree cover can increase groundwater recharge, and that tree planting and various tree management options can improve groundwater resources. We evaluate the necessary conditions for these results to hold and suggest that they are likely to be common in the seasonally dry tropics, offering potential for widespread tree establishment and increased benefits for hundreds of millions of people. PMID:26908158

  3. Forest structure in low-diversity tropical forests: a study of Hawaiian wet and dry forests.

    Science.gov (United States)

    Ostertag, Rebecca; Inman-Narahari, Faith; Cordell, Susan; Giardina, Christian P; Sack, Lawren

    2014-01-01

    The potential influence of diversity on ecosystem structure and function remains a topic of significant debate, especially for tropical forests where diversity can range widely. We used Center for Tropical Forest Science (CTFS) methodology to establish forest dynamics plots in montane wet forest and lowland dry forest on Hawai'i Island. We compared the species diversity, tree density, basal area, biomass, and size class distributions between the two forest types. We then examined these variables across tropical forests within the CTFS network. Consistent with other island forests, the Hawai'i forests were characterized by low species richness and very high relative dominance. The two Hawai'i forests were floristically distinct, yet similar in species richness (15 vs. 21 species) and stem density (3078 vs. 3486/ha). While these forests were selected for their low invasive species cover relative to surrounding forests, both forests averaged 5->50% invasive species cover; ongoing removal will be necessary to reduce or prevent competitive impacts, especially from woody species. The montane wet forest had much larger trees, resulting in eightfold higher basal area and above-ground biomass. Across the CTFS network, the Hawaiian montane wet forest was similar to other tropical forests with respect to diameter distributions, density, and aboveground biomass, while the Hawai'i lowland dry forest was similar in density to tropical forests with much higher diversity. These findings suggest that forest structural variables can be similar across tropical forests independently of species richness. The inclusion of low-diversity Pacific Island forests in the CTFS network provides an ∼80-fold range in species richness (15-1182 species), six-fold variation in mean annual rainfall (835-5272 mm yr(-1)) and 1.8-fold variation in mean annual temperature (16.0-28.4°C). Thus, the Hawaiian forest plots expand the global forest plot network to enable testing of ecological theory for

  4. Forest structure in low-diversity tropical forests: a study of Hawaiian wet and dry forests.

    Directory of Open Access Journals (Sweden)

    Rebecca Ostertag

    Full Text Available The potential influence of diversity on ecosystem structure and function remains a topic of significant debate, especially for tropical forests where diversity can range widely. We used Center for Tropical Forest Science (CTFS methodology to establish forest dynamics plots in montane wet forest and lowland dry forest on Hawai'i Island. We compared the species diversity, tree density, basal area, biomass, and size class distributions between the two forest types. We then examined these variables across tropical forests within the CTFS network. Consistent with other island forests, the Hawai'i forests were characterized by low species richness and very high relative dominance. The two Hawai'i forests were floristically distinct, yet similar in species richness (15 vs. 21 species and stem density (3078 vs. 3486/ha. While these forests were selected for their low invasive species cover relative to surrounding forests, both forests averaged 5->50% invasive species cover; ongoing removal will be necessary to reduce or prevent competitive impacts, especially from woody species. The montane wet forest had much larger trees, resulting in eightfold higher basal area and above-ground biomass. Across the CTFS network, the Hawaiian montane wet forest was similar to other tropical forests with respect to diameter distributions, density, and aboveground biomass, while the Hawai'i lowland dry forest was similar in density to tropical forests with much higher diversity. These findings suggest that forest structural variables can be similar across tropical forests independently of species richness. The inclusion of low-diversity Pacific Island forests in the CTFS network provides an ∼80-fold range in species richness (15-1182 species, six-fold variation in mean annual rainfall (835-5272 mm yr(-1 and 1.8-fold variation in mean annual temperature (16.0-28.4°C. Thus, the Hawaiian forest plots expand the global forest plot network to enable testing of ecological

  5. Modeling carbon stocks in a secondary tropical dry forest in the Yucatan Peninsula, Mexico

    Science.gov (United States)

    Zhaohua Dai; Richard A. Birdsey; Kristofer D. Johnson; Juan Manuel Dupuy; Jose Luis Hernandez-Stefanoni; Karen. Richardson

    2014-01-01

    The carbon balance of secondary dry tropical forests of Mexico’s Yucatan Peninsula is sensitive to human and natural disturbances and climate change. The spatially explicit process model Forest-DeNitrification-DeComposition (DNDC) was used to estimate forest carbon dynamics in this region, including the effects of disturbance on carbon stocks. Model evaluation using...

  6. Soil Effects on Forest Structure and Diversity in a Moist and a Dry Tropical Forest

    NARCIS (Netherlands)

    Peña-Claros, M.; Poorter, L.; Alarcon, A.; Blate, G.; Choque, U.; Fredericksen, T.S.; Justiniano, J.; Leaño, C.; Licona, J.C.; Pariona, W.; Putz, F.E.; Quevedo, L.; Toledo, M.

    2012-01-01

    Soil characteristics are important drivers of variation in wet tropical forest structure and diversity, but few studies have evaluated these relationships in drier forest types. Using tree and soil data from 48 and 32 1 ha plots, respectively, in a Bolivian moist and dry forest, we asked how soil

  7. Estimation of some comfort parameters for sleeping environments in dry-tropical sub-Saharan Africa region

    International Nuclear Information System (INIS)

    Djongyang, Noël; Tchinda, René; Njomo, Donatien

    2012-01-01

    Highlights: ► Thermal comfort in sleeping environments in the sub-Saharan Africa is presented. ► Comfort charts for the dry-tropical regions were established. ► Total insulation values for bedding systems range between 0.81 clo and 0.94 clo. ► Thermoneutral operative temperature ranges between 29.5 °C and 31.7 °C. ► Thermoneutral air temperature ranges between 27.1 °C and 29.6 °C. - Abstract: A human being spends approximately one-third of his/her life in sleep. For an efficient and peaceful rest, he/she therefore needs some level of comfort. This includes acceptable environmental parameters as well as suitable bedding systems. While the theories of thermal comfort in workplaces at daytime are currently well established, research on thermal comfort for sleeping environment at night is limited. Further studies in relation with sleep are needed. This paper presents an investigation on thermal comfort in sleeping environments in the sub-Saharan Africa region. The comfort equation used is based on the energy balance of the human body derived from Fanger’s comfort model. Comfort charts for the dry-tropical sub-Saharan Africa region were established using indoor climatic conditions collected over five years in Ouagadougou (12°22′N, 1°32′W). Results obtained show that the suitable monthly total insulation values for bedding systems in the dry-tropical regions range between 0.81 clo and 0.94 clo. The thermoneutral operative temperature range between 29 °C and 32 °C, while the thermoneutral air temperature range between 27 °C and 30 °C.

  8. Diversity and Phenology of Wild Bees in a Highly Disturbed Tropical Dry Forest "Desierto de la Tatacoa", Huila-Colombia.

    Science.gov (United States)

    Poveda-Coronel, C A; Riaño-Jiménez, D; Cure, J R

    2018-01-12

    Colombian tropical dry forest is considered the most endangered tropical biome due to anthropic activities. Desierto de la Tatacoa (DsT) is an example of high disturbed tropical dry forest which still maintains a high biodiversity. The objective of the study was to record the diversity and phenology of wild bees in this place by monthly sampling between December 2014 and December 2016 in a 9-km 2 area. During the study, there was a prolonged El Niño-Southern Oscillation period. Bees were collected by entomological nets, malaise traps, eugenol scent trapping, and nest traps. Shannon index was calculated to estimate diversity and Simpson index to determine dominance of a species. The effect of environmental conditions (wet and dry season) in richness and abundance was analyzed by paired T tests. A total of 3004 bee specimens were collected, belonging to 80 species from Apidae, Megachilidae, Halictidae, and Colletidae. Apidae was the most diverse. Shannon index value was 2.973 (discarding Apis mellifera Linnaeus 1758 data); thus, DsT can be considered as a zone of high wild bee diversity. Dry and rainy season showed differences in diversity (p < 0.05). Rainy season showed larger blooming periods and higher bee diversity than dry season. In both seasons, social species were dominant (e.g., A. mellifera or Trigona fulviventris Guérin 1844). Although DsT is a highly disturbed ecosystem, this study found it has the second highest number of genera and the fourth highest number of species reported in Colombia.

  9. Deforestation trends of tropical dry forests in central Brazil

    Science.gov (United States)

    Bianchi, Carlos A.; Haig, Susan M.

    2013-01-01

    Tropical dry forests are the most threatened forest type in the world yet a paucity of research about them stymies development of appropriate conservation actions. The Paranã River Basin has the most significant dry forest formations in the Cerrado biome of central Brazil and is threatened by intense land conversion to pastures and agriculture. We examined changes in Paranã River Basin deforestation rates and fragmentation across three time intervals that covered 31 yr using Landsat imagery. Our results indicated a 66.3 percent decrease in forest extent between 1977 and 2008, with an annual rate of forest cover change of 3.5 percent. Landscape metrics further indicated severe forest loss and fragmentation, resulting in an increase in the number of fragments and reduction in patch sizes. Forest fragments in flatlands have virtually disappeared and the only significant forest remnants are mostly found over limestone outcrops in the eastern part of the basin. If current patterns persist, we project that these forests will likely disappear within 25 yr. These patterns may be reversed with creation of protected areas and involvement of local people to preserve small fragments that can be managed for restoration.

  10. Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest.

    Science.gov (United States)

    Schilling, Erik M; Waring, Bonnie G; Schilling, Jonathan S; Powers, Jennifer S

    2016-09-01

    We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.

  11. Evolutionary trade-offs between drought resistance mechanisms across a precipitation gradient in a seasonally dry tropical oak (Quercus oleoides).

    Science.gov (United States)

    Ramírez-Valiente, Jose A; Cavender-Bares, Jeannine

    2017-07-01

    In seasonally dry tropical forest regions, drought avoidance during the dry season coupled with high assimilation rates in the wet season is hypothesized to be an advantageous strategy for forest trees in regions with severe and long dry seasons. In contrast, where dry seasons are milder, drought tolerance coupled with a conservative resource-use strategy is expected to maximize carbon assimilation throughout the year. Tests of this hypothesis, particularly at the intraspecific level, have been seldom conducted. In this study, we tested the extent to which drought resistance mechanisms and rates of carbon assimilation have evolved under climates with varying dry season length and severity within Quercus oleoidesCham. and Schlect., a tropical dry forest species that is widely distributed in Central America. For this purpose, we conducted a greenhouse experiment where seedlings originating from five populations that vary in rainfall patterns were grown under different watering treatments. Our results revealed that populations from xeric climates with more severe dry seasons exhibited large mesophyllous leaves (with high specific leaf area, SLA), and leaf abscission in response to drought, consistent with a drought-avoidance strategy. In contrast, populations from more mesic climates with less severe dry seasons had small and thick sclerophyllous leaves with low SLA and reduced water potential at the turgor loss point (πtlp), consistent with a drought-tolerance strategy. Mesic populations also showed high plasticity in πtlp in response to water availability, indicating that osmotic adjustment to drought is an important component of this strategy. However, populations with mesophyllous leaves did not have higher maximum carbon assimilation rates under well-watered conditions. Furthermore, SLA was negatively associated with mass-based photosynthetic rates, contrary to expectations of the leaf economics spectrum, indicating that drought-resistance strategies are not

  12. Spatio-Temporal Distribution of Bark and Ambrosia Beetles in a Brazilian Tropical Dry Forest.

    Science.gov (United States)

    Macedo-Reis, Luiz Eduardo; Novais, Samuel Matos Antunes de; Monteiro, Graziela França; Flechtmann, Carlos Alberto Hector; Faria, Maurício Lopes de; Neves, Frederico de Siqueira

    2016-01-01

    Bark and the ambrosia beetles dig into host plants and live most of their lives in concealed tunnels. We assessed beetle community dynamics in tropical dry forest sites in early, intermediate, and late successional stages, evaluating the influence of resource availability and seasonal variations in guild structure. We collected a total of 763 beetles from 23 species, including 14 bark beetle species, and 9 ambrosia beetle species. Local richness of bark and ambrosia beetles was estimated at 31 species. Bark and ambrosia composition was similar over the successional stages gradient, and beta diversity among sites was primarily determined by species turnover, mainly in the bark beetle community. Bark beetle richness and abundance were higher at intermediate stages; availability of wood was the main spatial mechanism. Climate factors were effectively non-seasonal. Ambrosia beetles were not influenced by successional stages, however the increase in wood resulted in increased abundance. We found higher richness at the end of the dry and wet seasons, and abundance increased with air moisture and decreased with higher temperatures and greater rainfall. In summary, bark beetle species accumulation was higher at sites with better wood production, while the needs of fungi (host and air moisture), resulted in a favorable conditions for species accumulation of ambrosia. The overall biological pattern among guilds differed from tropical rain forests, showing patterns similar to dry forest areas. © The Author 2016. Published by Oxford University Press on behalf of the Entomological Society of America.

  13. Water uptake and transport in lianas and co-occurring trees of a seasonally dry tropical forest.

    Science.gov (United States)

    José Luis Andrade; Frederick C. Meinzer; Guillermo Goldstein; Stefan A. Schnitzer

    2005-01-01

    Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island, Panama. Stable hydrogen isotope composition (δD) of xylem and soil water, soil volumetric water content (θv), and basal sap flow were measured during the 1997 and...

  14. Impact of livestock on a mosquito community (Diptera: Culicidae) in a Brazilian tropical dry forest.

    Science.gov (United States)

    Santos, Cleandson Ferreira; Borges, Magno

    2015-01-01

    This study evaluated the effects of cattle removal on the Culicidae mosquito community structure in a tropical dry forest in Brazil. Culicidae were collected during dry and wet seasons in cattle presence and absence between August 2008 and October 2010 and assessed using multivariate statistical models. Cattle removal did not significantly alter Culicidae species richness and abundance. However, alterations were noted in Culicidae community composition. This is the first study to evaluate the impact of cattle removal on Culicidae community structure in Brazil and demonstrates the importance of assessing ecological parameters such as community species composition.

  15. Bali cattle peBali cattle performance in the dry tropics of Sumbawarformance in the dry tropics of Sumbawa

    Directory of Open Access Journals (Sweden)

    Tanda Panjaitan

    2004-10-01

    Full Text Available Preliminary data on Bali cattle reproduction and growth presented is based on monitoring between August 2001 and August 2003 in the Sumbawa and Dompu Districts of Sumbawa Island, NTB. Sixty two % of calves were born between May and July inclusively. Inter-calving interval averaged 11.9 ±1.9 months; though recognized as an under-estimate, it still indicated of high fertility. Post-natal calf mortality was 5.3%. Birth, 6-, and 18-month weights of 14.2 ± 2.4 kg, 90 ± 20 kg, 172 ± 40 kg, respectively, were recorded. Average daily gains between birth to 6 months and from 6 to 18 months were 0.41 ± 0.11 and 0.23 ± 0.11 kg/d, respectively. Females reached mature size at 2.5-3.0 years at a mean weight of 237 kg and height of 1147 mm. Weight could be accurately predicted from chest girth: Weight (kg = 7e0.0023 Chest girth (mm (R2=0.9656. At the sites monitored, reproduction was high, and growth was typical for Bali cattle, indicating that these animals are well suited to the dry tropical environment of Sumbawa.

  16. Estimating the opportunity costs of activities that cause degradation in tropical dry forest: Implications for REDD +

    NARCIS (Netherlands)

    Borrego, Armonia; Skutsch, Margaret

    2014-01-01

    The viability of national REDD + programs will depend in part on whether funds generated from sales of carbon credits are sufficient to cover the opportunity costs (OC) of forgone uses of the forest. We present the results of a study in which OC were estimated in dry tropical forest, in western

  17. Exploiting water versus tolerating drought: water-use strategies of trees in a secondary successional tropical dry forest.

    Science.gov (United States)

    Pineda-García, Fernando; Paz, Horacio; Meinzer, Frederick C; Angeles, Guillermo

    2016-02-01

    In seasonal plant communities where water availability changes dramatically both between and within seasons, understanding the mechanisms that enable plants to exploit water pulses and to survive drought periods is crucial. By measuring rates of physiological processes, we examined the trade-off between water exploitation and drought tolerance among seedlings of trees of a tropical dry forest, and identified biophysical traits most closely associated with plant water-use strategies. We also explored whether early and late secondary successional species occupy different portions of trade-off axes. As predicted, species that maintained carbon capture, hydraulic function and leaf area at higher plant water deficits during drought had low photosynthetic rates, xylem hydraulic conductivity and growth rate under non-limiting water supply. Drought tolerance was associated with more dense leaf, stem and root tissues, whereas rapid resource acquisition was associated with greater stem water storage, larger vessel diameter and larger leaf area per mass invested. We offer evidence that the water exploitation versus drought tolerance trade-off drives species differentiation in the ability of tropical dry forest trees to deal with alternating water-drought pulses. However, we detected no evidence of strong functional differentiation between early and late successional species along the proposed trade-off axes, suggesting that the environmental gradient of water availability across secondary successional habitats in the dry tropics does not filter out physiological strategies of water use among species, at least at the seedling stage. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. Modeling seasonal surface temperature variations in secondary tropical dry forests

    Science.gov (United States)

    Cao, Sen; Sanchez-Azofeifa, Arturo

    2017-10-01

    Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15-20 K higher than in the wet season at SRNP. We found that the early successional stages were about 6-8 K warmer than the intermediate successional stages and were 9-10 K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0-1 K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

  19. Seasonal variation in soil and plant water potentials in a Bolivian tropical moist and dry forest

    NARCIS (Netherlands)

    Markesteijn, L.; Iraipi, J.; Bongers, F.; Poorter, L.

    2010-01-01

    We determined seasonal variation in soil matric potentials (¿soil) along a topographical gradient and with soil depth in a Bolivian tropical dry (1160 mm y-1 rain) and moist forest (1580 mm y-1). In each forest we analysed the effect of drought on predawn leaf water potentials (¿pd) and drought

  20. Bioquality Hotspots in the Tropical African Flora.

    Science.gov (United States)

    Marshall, Cicely A M; Wieringa, Jan J; Hawthorne, William D

    2016-12-05

    Identifying areas of high biodiversity is an established way to prioritize areas for conservation [1-3], but global approaches have been criticized for failing to render global biodiversity value at a scale suitable for local management [4-6]. We assembled 3.1 million species distribution records for 40,401 vascular plant species of tropical Africa from sources including plot data, herbarium databases, checklists, and the Global Biodiversity Information Facility (GBIF) and cleaned the records for geographic accuracy and taxonomic consistency. We summarized the global ranges of tropical African plant species into four weighted categories of global rarity called Stars. We applied the Star weights to summaries of species distribution data at fine resolutions to map the bioquality (range-restricted global endemism) of areas [7]. We generated confidence intervals around bioquality scores to account for the remaining uncertainty in the species inventory. We confirm the broad significance of the Horn of Africa, Guinean forests, coastal forests of East Africa, and Afromontane regions for plant biodiversity but also reveal the variation in bioquality within these broad regions and others, particularly at local scales. Our framework offers practitioners a quantitative, scalable, and replicable approach for measuring the irreplaceability of particular local areas for global biodiversity conservation and comparing those areas within their global and regional context. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. High density of tree-cavities and snags in tropical dry forest of western Mexico raises questions for a latitudinal gradient.

    Directory of Open Access Journals (Sweden)

    Leopoldo Vázquez

    Full Text Available It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha, though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters.

  2. High density of tree-cavities and snags in tropical dry forest of western Mexico raises questions for a latitudinal gradient.

    Science.gov (United States)

    Vázquez, Leopoldo; Renton, Katherine

    2015-01-01

    It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha), though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters.

  3. Vulnerable Habitats Alter African Meliponine Bee’s (Hymenoptera: Apidae Assemblages in an Eastern Afromontane Biodiversity Hotspot

    Directory of Open Access Journals (Sweden)

    Bridget O Bobadoye

    2017-05-01

    Full Text Available Habitat degradation has over time formed synergy with other factors to contribute to dwindling populations of both fauna and flora by altering their habitats. The disturbance of natural habitats affects the diversity of both vertebrates and invertebrates by altering both feeding and nesting sites for which organisms are known to depend on for survival. Little is known of the extent to which vulnerable habitats could shape the diversity of most indigent pollinators such as African meliponine bee species in tropical ecosystems. This study was conducted to determine how disturbance could shape the natural occurrence of African meliponine bee species in different ecological habitats of Taita Hills, leading to changes in their diversity. A total of four species depicted by the Renyi diversity profile was recorded in five of the six main habitat types surveyed, and a further extrapolation with Shannon index ( E H also predicted the highest species richness of 4.24 in a deciduous habitat type. These meliponine bee species ( Hypotrigona gribodoi , Hypotrigona ruspolii , Meliponula ferruginea (black, and Plebeina hildebrandti were observed to be unevenly distributed across all habitats, further indicating that mixed deciduous habitat was more diverse than acacia-dominated bush lands, grasslands, and exotic forest patches. Geometric morphometrics categorized all four meliponine bee species into two major clusters—cluster 1 ( H gribodoi , H ruspolii , M ferruginea (black and cluster 2 ( P hildebrandti —and further discriminated populations against the 4 potential habitats they are likely to persist or survive in. Each habitat appeared to consist of a cluster of subpopulations and may possibly reveal ecotypes within the four meliponine populations. This has revealed that unprecedented conversions of natural habitats to agroecosystems are a key driving factor causing increased habitat isolation and vulnerability in this Afromontane region which may

  4. Predicting of biomass in Brazilian tropical dry forest: a statistical evaluation of generic equations

    Directory of Open Access Journals (Sweden)

    ROBSON B. DE LIMA

    2017-08-01

    Full Text Available ABSTRACT Dry tropical forests are a key component in the global carbon cycle and their biomass estimates depend almost exclusively of fitted equations for multi-species or individual species data. Therefore, a systematic evaluation of statistical models through validation of estimates of aboveground biomass stocks is justifiable. In this study was analyzed the capacity of generic and specific equations obtained from different locations in Mexico and Brazil, to estimate aboveground biomass at multi-species levels and for four different species. Generic equations developed in Mexico and Brazil performed better in estimating tree biomass for multi-species data. For Poincianella bracteosa and Mimosa ophthalmocentra, only the Sampaio and Silva (2005 generic equation was the most recommended. These equations indicate lower tendency and lower bias, and biomass estimates for these equations are similar. For the species Mimosa tenuiflora, Aspidosperma pyrifolium and for the genus Croton the specific regional equations are more recommended, although the generic equation of Sampaio and Silva (2005 is not discarded for biomass estimates. Models considering gender, families, successional groups, climatic variables and wood specific gravity should be adjusted, tested and the resulting equations should be validated at both local and regional levels as well as on the scales of tropics with dry forest dominance.

  5. Predicting of biomass in Brazilian tropical dry forest: a statistical evaluation of generic equations.

    Science.gov (United States)

    Lima, Robson B DE; Alves, Francisco T; Oliveira, Cinthia P DE; Silva, José A A DA; Ferreira, Rinaldo L C

    2017-01-01

    Dry tropical forests are a key component in the global carbon cycle and their biomass estimates depend almost exclusively of fitted equations for multi-species or individual species data. Therefore, a systematic evaluation of statistical models through validation of estimates of aboveground biomass stocks is justifiable. In this study was analyzed the capacity of generic and specific equations obtained from different locations in Mexico and Brazil, to estimate aboveground biomass at multi-species levels and for four different species. Generic equations developed in Mexico and Brazil performed better in estimating tree biomass for multi-species data. For Poincianella bracteosa and Mimosa ophthalmocentra, only the Sampaio and Silva (2005) generic equation was the most recommended. These equations indicate lower tendency and lower bias, and biomass estimates for these equations are similar. For the species Mimosa tenuiflora, Aspidosperma pyrifolium and for the genus Croton the specific regional equations are more recommended, although the generic equation of Sampaio and Silva (2005) is not discarded for biomass estimates. Models considering gender, families, successional groups, climatic variables and wood specific gravity should be adjusted, tested and the resulting equations should be validated at both local and regional levels as well as on the scales of tropics with dry forest dominance.

  6. Impact of livestock on a mosquito community (Diptera: Culicidae in a Brazilian tropical dry forest

    Directory of Open Access Journals (Sweden)

    Cleandson Ferreira Santos

    2015-08-01

    Full Text Available AbstractINTRODUCTION: This study evaluated the effects of cattle removal on the Culicidae mosquito community structure in a tropical dry forest in Brazil.METHODS: Culicidae were collected during dry and wet seasons in cattle presence and absence between August 2008 and October 2010 and assessed using multivariate statistical models.RESULTS: Cattle removal did not significantly alter Culicidae species richness and abundance. However, alterations were noted in Culicidae community composition.CONCLUSIONS: This is the first study to evaluate the impact of cattle removal on Culicidae community structure in Brazil and demonstrates the importance of assessing ecological parameters such as community species composition.

  7. Species biogeography predicts drought responses in a seasonally dry tropical forest

    Science.gov (United States)

    Schwartz, N.; Powers, J. S.; Vargas, G.; Xu, X.; Smith, C. M.; Brodribb, T.; Werden, L. K.; Becknell, J.; Medvigy, D.

    2017-12-01

    The timing, distribution, and amount of rainfall in the seasonal tropics have shifted in recent years, with consequences for seasonally dry tropical forests (SDTF). SDTF are sensitive to changing rainfall regimes and drought conditions, but sensitivity to drought varies substantially across species. One potential explanation of species differences is that species that experience dry conditions more frequently throughout their range will be better able to cope with drought than species from wetter climates, because species from drier climates will be better adapted to drought. An El-Niño induced drought in 2015 presented an opportunity to assess species-level differences in mortality in SDTF, and to ask whether the ranges of rainfall conditions species experience and the average rainfall regimes in species' ranges predict differences in mortality rates in Costa Rican SDTF. We used field plot data from northwest Costa Rica to determine species' level mortality rates. Mortality rates ranged substantially across species, with some species having no dead individuals to as high as 50% mortality. To quantify rainfall conditions across species' ranges, we used species occurrence data from the Global Biodiversity Information Facility, and rainfall data from the Chelsa climate dataset. We found that while the average and range of mean annual rainfall across species ranges did not predict drought-induced mortality in the field plots, across-range averages of the seasonality index, a measure of rainfall seasonality, was strongly correlated with species-level drought mortality (r = -0.62, p < 0.05), with species from more strongly seasonal climates experiencing less severe drought mortality. Furthermore, we found that the seasonality index was a stronger predictor of mortality than any individual functional trait we considered. This result shows that species' biogeography may be an important factor for how species will respond to future drought, and may be a more integrative

  8. Nitrogen, phosphorus, and cation use efficiency in stands of regenerating tropical dry forest.

    Science.gov (United States)

    Waring, Bonnie G; Becknell, Justin M; Powers, Jennifer S

    2015-07-01

    Plants on infertile soils exhibit physiological and morphological traits that support conservative internal nutrient cycling. However, potential trade-offs among use efficiencies for N, P, and cations are not well explored in species-rich habitats where multiple elements may limit plant production. We examined uptake efficiency and use efficiency of N, P, K, Ca, Mg, Al, and Na in plots of regenerating tropical dry forests spanning a gradient of soil fertility. Our aim was to determine whether plant responses to multiple elements are correlated, or whether there are trade-offs among exploitation strategies across stands varying in community composition, soil quality, and successional stage. For all elements, both uptake efficiency and use efficiency decreased as availability of the corresponding element increased. Plant responses to N, Na, and Al were uncoupled from uptake and use efficiencies for P and essential base cations, which were tightly correlated. N and P use efficiencies were associated with shifts in plant species composition along the soil fertility gradient, and there was also a trend towards increasing N use efficiency with stand age. N uptake efficiency was positively correlated with the abundance of tree species that associate with ectomycorrhizal fungi. Taken together, our results suggest that successional processes and local species composition interact to regulate plant responses to availability of multiple resources. Successional tropical dry forests appear to employ different strategies to maximize response to N vs. P and K.

  9. SENSITIVITY ANALYSIS OF BIOME-BGC MODEL FOR DRY TROPICAL FORESTS OF VINDHYAN HIGHLANDS, INDIA

    OpenAIRE

    M. Kumar; A. S. Raghubanshi

    2012-01-01

    A process-based model BIOME-BGC was run for sensitivity analysis to see the effect of ecophysiological parameters on net primary production (NPP) of dry tropical forest of India. The sensitivity test reveals that the forest NPP was highly sensitive to the following ecophysiological parameters: Canopy light extinction coefficient (k), Canopy average specific leaf area (SLA), New stem C : New leaf C (SC:LC), Maximum stomatal conductance (gs,max), C:N of fine roots (C:Nfr), All-sided to...

  10. Diverse patterns of stored water use among saplings in seasonally dry tropical forests.

    Science.gov (United States)

    Wolfe, Brett T; Kursar, Thomas A

    2015-12-01

    Tree species in seasonally dry tropical forests likely vary in their drought-survival mechanisms. Drought-deciduousness, which reduces water loss, and low wood density, which may permit dependence on stored water, are considered key traits. For saplings of six species at two distinct sites, we studied these and two associated traits: the seasonal amount of water released per stem volume ("water released") and the hydraulic capacitance of the stem (C). Two deciduous species with low stem density, Cavanillesia platanifolia and Bursera simaruba, had high C and high dry-season stem water potential (Ψ(stem)), but differed in dry-season water released. C. platanifolia did not use stored water during the dry season whereas B. simaruba, in a drier forest, released stored water. In both, water released was highest while flushing leaves, suggesting that stored water supports leaf flushing. In contrast, two deciduous species with intermediate stem density, Annona hayesii and Genipa americana, had intermediate C, low dry-season Ψ(stem), and high seasonal change in water released. Meanwhile, two evergreen species with intermediate stem density, Cojoba rufescens and Astronium graveolens, had relatively low C, low dry-season Ψ(stem), and intermediate seasonal change in water released. Thus, at least three, distinct stored-water-use strategies were observed. Additionally, bark relative water content (RWC) decreased along with Ψ(stem) during the dry season while xylem RWC did not change, suggesting that bark-stored water buffers Ψ(stem) seasonally. Together these results suggest that seasonal use of stored water and change in Ψ(stem) are associated with functional groups that are characterized by combinations of deciduousness and stem density.

  11. Tropical Drosophila ananassae of wet-dry seasons show cross resistance to heat, drought and starvation

    Directory of Open Access Journals (Sweden)

    Chanderkala Lambhod

    2017-11-01

    Full Text Available Plastic responses to multiple environmental stressors in wet or dry seasonal populations of tropical Drosophila species have received less attention. We tested plastic effects of heat hardening, acclimation to drought or starvation, and changes in trehalose, proline and body lipids in Drosophila ananassae flies reared under wet or dry season-specific conditions. Wet season flies revealed significant increase in heat knockdown, starvation resistance and body lipids after heat hardening. However, accumulation of proline was observed only after desiccation acclimation of dry season flies while wet season flies elicited no proline but trehalose only. Therefore, drought-induced proline can be a marker metabolite for dry-season flies. Further, partial utilization of proline and trehalose under heat hardening reflects their possible thermoprotective effects. Heat hardening elicited cross-protection to starvation stress. Stressor-specific accumulation or utilization as well as rates of metabolic change for each energy metabolite were significantly higher in wet-season flies than dry-season flies. Energy metabolite changes due to inter-related stressors (heat versus desiccation or starvation resulted in possible maintenance of energetic homeostasis in wet- or dry-season flies. Thus, low or high humidity-induced plastic changes in energy metabolites can provide cross-protection to seasonally varying climatic stressors.

  12. Solar drying and organoleptic characteristics of two tropical African fish species using improved low-cost solar driers.

    Science.gov (United States)

    Mustapha, Moshood K; Ajibola, Taiye B; Salako, Abdulbashir F; Ademola, Sunmola K

    2014-05-01

    This study was done to evaluate the drying performance, efficiency, and effectiveness of five different types of improved low-cost solar driers in terms of moisture loss from two tropical African fish species Clarias gariepinus (African sharp tooth catfish) and Oreochromis niloticus (Nile tilapia) and testing the organoleptic characteristics of the dried samples. The driers used were made from plastic, aluminum, glass, glass with black igneous stone, and mosquito net, with traditional direct open-sun drying as a control. A significant (P < 0.05) decrease in weight resulting from moisture loss in the two fish species was observed in all the driers, with the highest reduction occurring in the glass drier containing black stone. The rate of weight loss was faster in the first 4 days of drying with black stone-inserted glass drier showing the fastest drying rate with a constant weight in C. gariepinus attained on the 11th day and in O. niloticus on the eighth day. The slowest drier was plastic where a constant weight of the species were recorded on and 13th day and 11th day, respectively. Volunteers were used to assess the organoleptic characteristics of the dried samples and they showed lowest acceptability for the open-sun drying, while samples from the glass drier containing black stone had the highest acceptability in terms of the taste, flavor, appearance, texture, odor, palatability, and shelf-life. The low-cost solar driers were effective found in removing water from the fish resulting in significant loss of weight and moisture. The highest drying time, efficient performance, drying effectiveness, and high acceptability of the organoleptic parameters of the dried products from the black stone-inserted glass drier were due to the ability of the glass and the black stone to retain, transmit, and radiate heat to the fish sample all the time (day and night). These low-cost driers are simple to construct, materials for its construction readily available, easy to

  13. Mapping tropical dry forest habitats integrating landsat NDVI, Ikonos imagery, and topographic information in the Caribbean island of Mona.

    Science.gov (United States)

    Martinuzzi, Sebastiáin; Gould, William A; Ramos Gonzalez, Olga M; Martinez Robles, Alma; Calle Maldonado, Paulina; Pérez-Buitrago, Néstor; Fumero Caban, José J

    2008-06-01

    Assessing the status of tropical dry forest habitats using remote sensing technologies is one of the research priorities for Neotropical forests. We developed a simple method for mapping vegetation and habitats in a tropical dry forest reserve, Mona Island, Puerto Rico, by integrating the Normalized Difference Vegetation Index (NDVI) from Landsat, topographic information, and high-resolution Ikonos imagery. The method was practical for identifying vegetation types in areas with a great variety of plant communities and complex relief, and can be adapted to other dry forest habitats of the Caribbean Islands. NDVI was useful for identifying the distribution of forests, woodlands, and shrubland, providing a natural representation of the vegetation patterns on the island. The use of Ikonos imagery allowed increasing the number of land cover classes. As a result, sixteen land-cover types were mapped over the 5500 ha area, with a kappa coefficient of accuracy equal to 79%. This map is a central piece for modeling vertebrate species distribution and biodiversity patterns by the Puerto Rico Gap Analysis Project, and it is of great value for assisting research and management actions in the island.

  14. Chronic human disturbance affects plant trait distribution in a seasonally dry tropical forest

    Science.gov (United States)

    Sfair, Julia C.; de Bello, Francesco; de França, Thaysa Q.; Baldauf, Cristina; Tabarelli, Marcelo

    2018-02-01

    The effects of human disturbance on biodiversity can be mediated by environmental conditions, such as water availability, climate and nutrients. In general, disturbed, dry or nutrient-depleted soils areas tend to have lower taxonomic diversity. However, little is known about how these environmental conditions affect functional composition and intraspecific variability in tropical dry forests. We studied a seasonally dry tropical forest (SDTF) under chronic anthropogenic disturbance (CAD) along rainfall and soil nutrient gradients to understand how these factors influence the taxonomic and functional composition. Specifically we evaluated two aspects of CAD, wood extraction and livestock pressure (goat and cattle grazing), along soil fertility and rainfall gradients on shrub and tree traits, considering species turnover and intraspecific variability. In addition, we also tested how the traits of eight populations of the most frequent species are affected by wood extraction, livestock pressure, rainfall and soil fertility. In general, although CAD and environmental gradients affected each trait of the most widespread species differently, the most abundant species also had a greater variation of traits. Considering species turnover, wood extraction is associated with species with a smaller leaf area and lower investment in leaf mass, probably due to the indirect effects of this disturbance type on the vegetation, i.e. the removal of branches and woody debris clears the vegetation, favouring species that minimize water loss. Livestock pressure, on the other hand, affected intraspecific variation: the herbivory caused by goats and cattle promoted individuals which invest more in wood density and leaf mass. In this case, the change of functional composition observed is a direct effect of the disturbance, such as the decrease of palatable plant abundance by goat and cattle herbivory. In synthesis, CAD, rainfall and soil fertility can affect trait distribution at community

  15. Effect of Freeze-Drying on the Antioxidant Compounds and Antioxidant Activity of Selected Tropical Fruits

    Directory of Open Access Journals (Sweden)

    Muhammad Redzuan Hairuddin

    2011-07-01

    Full Text Available The effects of freeze-drying on antioxidant compounds and antioxidant activity of five tropical fruits, namely starfruit (Averrhoa carambola L., mango (Mangifera indica L., papaya (Carica papaya L., muskmelon (Cucumis melo L., and watermelon Citruluss lanatus (Thunb. were investigated. Significant (p < 0.05 differences, for the amounts of total phenolic compounds (TPC, were found between the fresh and freeze-dried fruit samples, except muskmelon. There was no significant (p > 0.05 change, however, observed in the ascorbic acid content of the fresh and freeze-dried fruits. Similarly, freeze-drying did not exert any considerable effect on β-carotene concentration of fruits, except for mango and watermelon, where significantly (p < 0.05 higher levels were detected in the fresh samples. The results of DPPH (2,2-diphenyl-1-picrylhydrazyl radical scavenging and reducing power assays revealed that fresh samples of starfruit and mango had relatively higher antioxidant activity. In case of linoleic acid peroxidation inhibition measurement, a significant (p < 0.05 but random variation was recorded between the fresh and freeze-dried fruits. Overall, in comparison to β-carotene and ascorbic acid, a good correlation was established between the result of TPC and antioxidant assays, indicating that phenolics might have been the dominant compounds contributing towards the antioxidant activity of the fruits tested.

  16. Seasonality in the dung beetle community in a Brazilian tropical dry forest: Do small changes make a difference?

    Science.gov (United States)

    Medina, Anderson Matos; Lopes, Priscila Paixão

    2014-01-01

    Dung beetle (Coleoptera: Scarabaeoidea: Scarabaeinae) activity is influenced by rainfall seasonality. We hypothesized that rainfall might also play a major role in regulating the community structure of this group. In this study, we describe seasonal changes in the richness, composition, and structure of the Scarabaeinae community in a Brazilian tropical dry forest. A fragment of arboreal Caatinga was sampled using baited pitfall traps during the early dry season (EDS), late dry season (LDS), early wet season (EWS), and middle wet season (MWS). We compared the dung beetle community in each season in relationship to species richness, rank-dominance, curves, and composition. We collected 1352 Scarabaeinae individuals , belonging to 15 species. Dichotomius aff. laevicollis Felsche (Coleoptera: Scarabaeidae) was the dominant species, representing 73.89% of the individuals. There were no seasonal changes in the rank dominance curves; all had a single dominant species and a few species with low abundance, typical for arid areas. Estimated richness was highest in MWS, followed by EWS. Dry-season samples (EDS and LDS) had lower richness, with no significant difference between the dry seasons. Although species richness increased as the habitat became wetter, the difference between the wet and dry seasons was small, which differs completely from the findings of other studies in Neotropical dry forests, where almost all species cease activities in the dry season. Species composition changes were found in non-metric multidimensional scaling and sustained by analysis of similarity. All the seasons had pairwise differences in composition, with the exception of EDS and MWS, which indicates that the dung beetle community in this fragment requires more than three months of drought to trigger changes in species composition; this is probably due to small changes in the forest canopy. There was no difference in composition between EDS and MWS. As in other tropical dry forests, although

  17. Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape

    Science.gov (United States)

    Mark W. Chynoweth; Christopher A. Lepczyk; Creighton M. Litton; Steven C. Hess; James R. Kellner; Susan Cordell; Lalit Kumar

    2015-01-01

    Advances in wildlife telemetry and remote sensing technology facilitate studies of broad-scale movements of ungulates in relation to phenological shifts in vegetation. In tropical island dry landscapes, home range use and movements of non-native feral goats (Capra hircus) are largely unknown, yet this information is important to help guide the...

  18. Effect of Freeze-Drying on the Antioxidant Compounds and Antioxidant Activity of Selected Tropical Fruits

    Science.gov (United States)

    Shofian, Norshahida Mohamad; Hamid, Azizah Abdul; Osman, Azizah; Saari, Nazamid; Anwar, Farooq; Dek, Mohd Sabri Pak; Hairuddin, Muhammad Redzuan

    2011-01-01

    The effects of freeze-drying on antioxidant compounds and antioxidant activity of five tropical fruits, namely starfruit (Averrhoa carambola L.), mango (Mangifera indica L.), papaya (Carica papaya L.), muskmelon (Cucumis melo L.), and watermelon Citruluss lanatus (Thunb.) were investigated. Significant (p 0.05) change, however, observed in the ascorbic acid content of the fresh and freeze-dried fruits. Similarly, freeze-drying did not exert any considerable effect on β-carotene concentration of fruits, except for mango and watermelon, where significantly (p < 0.05) higher levels were detected in the fresh samples. The results of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and reducing power assays revealed that fresh samples of starfruit and mango had relatively higher antioxidant activity. In case of linoleic acid peroxidation inhibition measurement, a significant (p < 0.05) but random variation was recorded between the fresh and freeze-dried fruits. Overall, in comparison to β-carotene and ascorbic acid, a good correlation was established between the result of TPC and antioxidant assays, indicating that phenolics might have been the dominant compounds contributing towards the antioxidant activity of the fruits tested. PMID:21845104

  19. The impact of an invasive African bunchgrass (Pennisetum setaceum) on water availability and productivity of canopy trees within a tropical dry forest in Hawaii

    Science.gov (United States)

    Susan Cordell; D. R. Sandquist

    2008-01-01

    Tropical dry forests are among the Earth's most threatened ecosystems. On the Island of Hawaii the African bunchgrass Pennisetum setaceum (fountain grass) dominates the understorey of the few remaining fragments of native dry forests and is contributing to the degradation of this once diverse ecosystem. In this study, we...

  20. Functional strategies of tropical dry forest plants in relation to growth form and isotopic composition

    Science.gov (United States)

    Santiago, L. S.; Silvera, K.; Andrade, J. L.; Dawson, T. E.

    2017-11-01

    Tropical dry forests (TDFs) undergo a substantial dry season in which plant species must endure several months of drought. Although TDFs support a diverse array of plant growth forms, it is not clear how they vary in mechanisms for coping with seasonal drought. We measured organic tissue stable isotopic composition of carbon (δ13C) and nitrogen (δ15N) across six plant growth forms including epiphytes, terrestrial succulents, trees, shrubs, herbs, and vines, and oxygen (δ18O) of four growth forms, to distinguish among patterns of resource acquisition and evaluate mechanisms for surviving annual drought in a lowland tropical dry forest in Yucatan, Mexico. Terrestrial succulent and epiphyte δ13C was around -14‰, indicating photosynthesis through the Crassulacean acid metabolism pathway, and along with one C4 herb were distinct from mean values of all other growth forms, which were between -26 and -29‰ indicating C3 photosynthesis. Mean tissue δ15N across epiphytes was -4.95‰ and was significantly lower than all other growth forms, which had values around +3‰. Tissue N concentration varied significantly among growth forms with epiphytes and terrestrial succulents having significantly lower values of about 1% compared to trees, shrubs, herbs and vines, which were around 3%. Tissue C concentration was highest in trees, shrubs and vines, intermediate in herbs and epiphytes and lowest in terrestrial succulents. δ18O did not vary among growth forms. Overall, our results suggest several water-saving aspects of resource acquisition, including the absolute occurrence of CAM photosynthesis in terrestrial succulents and epiphytes, high concentrations of leaf N in some species, which may facilitate CO2 drawdown by photosynthetic enzymes for a given stomatal conductance, and potentially diverse N sources ranging from atmospheric N in epiphytes with extremely depleted δ15N values, and a large range of δ15N values among trees, many of which are legumes and dry season

  1. Climate change effects on the geographic distribution of specialist tree species of the Brazilian tropical dry forests.

    Science.gov (United States)

    Rodrigues, P M S; Silva, J O; Eisenlohr, P V; Schaefer, C E G R

    2015-08-01

    The aim of this study was to evaluate the ecological niche models (ENMs) for three specialist trees (Anadenanthera colubrina, Aspidosperma pyrifolium and Myracrodruon urundeuva) in seasonally dry tropical forests (SDTFs) in Brazil, considering present and future pessimist scenarios (2080) of climate change. These three species exhibit typical deciduousness and are widely distributed by SDTF in South America, being important in studies of the historical and evolutionary processes experienced by this ecosystem. The modeling of the potential geographic distribution of species was done by the method of maximum entropy (Maxent).We verified a general expansion of suitable areas for occurrence of the three species in future (c.a., 18%), although there was reduction of areas with high environmental suitability in Caatinga region. Precipitation of wettest quarter and temperature seasonality were the predictor variables that most contributed to our models. Climatic changes can provide more severe and longer dry season with increasing temperature and tree mortality in tropics. On this scenario, areas currently occupied by rainforest and savannas could become more suitable for occurrence of the SDTF specialist trees, whereas regions occupied by Caatinga could not support the future level of unsustainable (e.g., aridity). Long-term multidisciplinary studies are necessary to make reliable predictions of the plant's adaptation strategies and responses to climate changes in dry forest at community level. Based on the high deforestation rate, endemism and threat, public policies to minimize the effects of climate change on the biodiversity found within SDTFs must be undertaken rapidly.

  2. Litter decomposition, N2-fixer abundance, and microbial dynamics govern tropical dry forest recovery to land use change

    Science.gov (United States)

    Trierweiler, A.; Powers, J. S.; Xu, X.; Gei, M. G.; Medvigy, D.

    2017-12-01

    As one of the most threatened tropical biomes, Seasonal Dry Tropical Forests (TDF) have undergone extensive land-use change. However, some areas are undergoing recovery into secondary forests. Despite their broad distribution (42% of tropical forests), they are under-studied compared to wet tropical forests and our understanding of their biogeochemical cycling and belowground processes are limited. Here, we use models along with field measurements to improve our understanding of nutrient cycling and limitation in secondary TDFs. We ask (1) Is there modeling evidence that tropical dry forests can become nutrient limited? (2) What are the most important mechanisms employed to avoid nutrient limitation? (3) How might climate change alter biogeochemical cycling and nutrient limitation in recovering TDF? We use a new version of the Ecosystem Demography (ED2) model that has been recently parameterized for TDFs and incorporates a range of plant functional groups (including deciduousness and N2-fixation) and multiple resource constraints (carbon, nitrogen, phosphorus, and water). In the model, plants then can dynamically adjust their carbon allocation and nutrient acquisition strategies using N2-fixing bacteria and mycorrhizal fungi according to the nutrient limitation status. We ran the model for a nutrient gradient of field sites in Costa Rica and explored the sensitivity of nutrient limitation to key mechanisms including litter respiration, N resorption, N2-fixation, and overflow respiration. Future runs will evaluate how CO2 and climate change affect recovering TDFs. We found increasing nutrient limitation across the nutrient gradient of sites. Nitrogen limitation dominated the nutrient limitation signal. In the model, forest litter accumulation was negatively correlated with site fertility in Costa Rican forests. Our sensitivity analyses indicate that N2-fixer abundance, decomposition rates, and adding more explicit microbial dynamics are key factors in overcoming

  3. Carbon dioxide and water vapour exchange in a tropical dry forest as influenced by the North American Monsoon System (NAMS)

    Science.gov (United States)

    To better understand the effects and relationship between precipitation, net ecosystem carbon dioxide (NEE) and water vapor exchange (ET), we report a study conducted in the tropical dry forest (TDF) in the northwest of Mexico. Ecosystem gas exchange was measured using the eddy correlation technique...

  4. Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape.

    Science.gov (United States)

    Chynoweth, Mark W; Lepczyk, Christopher A; Litton, Creighton M; Hess, Steven C; Kellner, James R; Cordell, Susan

    2015-01-01

    Advances in wildlife telemetry and remote sensing technology facilitate studies of broad-scale movements of ungulates in relation to phenological shifts in vegetation. In tropical island dry landscapes, home range use and movements of non-native feral goats (Capra hircus) are largely unknown, yet this information is important to help guide the conservation and restoration of some of the world's most critically endangered ecosystems. We hypothesized that feral goats would respond to resource pulses in vegetation by traveling to areas of recent green-up. To address this hypothesis, we fitted six male and seven female feral goats with Global Positioning System (GPS) collars equipped with an Argos satellite upload link to examine goat movements in relation to the plant phenology using the Normalized Difference Vegetation Index (NDVI). Movement patterns of 50% of males and 40% of females suggested conditional movement between non-overlapping home ranges throughout the year. A shift in NDVI values corresponded with movement between primary and secondary ranges of goats that exhibited long-distance movement, suggesting that vegetation phenology as captured by NDVI is a good indicator of the habitat and movement patterns of feral goats in tropical island dry landscapes. In the context of conservation and restoration of tropical island landscapes, the results of our study identify how non-native feral goats use resources across a broad landscape to sustain their populations and facilitate invasion of native plant communities.

  5. Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape

    Science.gov (United States)

    Chynoweth, Mark W.; Lepczyk, Christopher A.; Litton, Creighton M.; Hess, Steve; Kellner, James; Cordell, Susan

    2015-01-01

    Advances in wildlife telemetry and remote sensing technology facilitate studies of broad-scale movements of ungulates in relation to phenological shifts in vegetation. In tropical island dry landscapes, home range use and movements of non-native feral goats (Capra hircus) are largely unknown, yet this information is important to help guide the conservation and restoration of some of the world’s most critically endangered ecosystems. We hypothesized that feral goats would respond to resource pulses in vegetation by traveling to areas of recent green-up. To address this hypothesis, we fitted six male and seven female feral goats with Global Positioning System (GPS) collars equipped with an Argos satellite upload link to examine goat movements in relation to the plant phenology using the Normalized Difference Vegetation Index (NDVI). Movement patterns of 50% of males and 40% of females suggested conditional movement between non-overlapping home ranges throughout the year. A shift in NDVI values corresponded with movement between primary and secondary ranges of goats that exhibited long-distance movement, suggesting that vegetation phenology as captured by NDVI is a good indicator of the habitat and movement patterns of feral goats in tropical island dry landscapes. In the context of conservation and restoration of tropical island landscapes, the results of our study identify how non-native feral goats use resources across a broad landscape to sustain their populations and facilitate invasion of native plant communities.

  6. Tree species effects on pathogen-suppressive capacities of soil bacteria across two tropical dry forests in Costa Rica.

    Science.gov (United States)

    Becklund, Kristen; Powers, Jennifer; Kinkel, Linda

    2016-11-01

    Antibiotic-producing bacteria in the genus Streptomyces can inhibit soil-borne plant pathogens, and have the potential to mediate the impacts of disease on plant communities. Little is known about how antibiotic production varies among soil communities in tropical forests, despite a long history of interest in the role of soil-borne pathogens in these ecosystems. Our objective was to determine how tree species and soils influence variation in antibiotic-mediated pathogen suppression among Streptomyces communities in two tropical dry forest sites (Santa Rosa and Palo Verde). We targeted tree species that co-occur in both sites and used a culture-based functional assay to quantify pathogen-suppressive capacities of Streptomyces communities beneath 50 focal trees. We also measured host-associated litter and soil element concentrations as potential mechanisms by which trees may influence soil microbes. Pathogen-suppressive capacities of Streptomyces communities varied within and among tree species, and inhibitory phenotypes were significantly related to soil and litter element concentrations. Average proportions of inhibitory Streptomyces in soils from the same tree species varied between 1.6 and 3.3-fold between sites. Densities and proportions of pathogen-suppressive bacteria were always higher in Santa Rosa than Palo Verde. Our results suggest that spatial heterogeneity in the potential for antibiotic-mediated disease suppression is shaped by tree species, site, and soil characteristics, which could have significant implications for understanding plant community composition and diversity in tropical dry forests.

  7. Large-scale carbon stock assessment of woody vegetation in tropical dry deciduous forest of Sathanur reserve forest, Eastern Ghats, India.

    Science.gov (United States)

    Gandhi, Durai Sanjay; Sundarapandian, Somaiah

    2017-04-01

    Tropical dry forests are one of the most widely distributed ecosystems in tropics, which remain neglected in research, especially in the Eastern Ghats. Therefore, the present study was aimed to quantify the carbon storage in woody vegetation (trees and lianas) on large scale (30, 1 ha plots) in the dry deciduous forest of Sathanur reserve forest of Eastern Ghats. Biomass of adult (≥10 cm DBH) trees was estimated by species-specific allometric equations using diameter and wood density of species whereas in juvenile tree population and lianas, their respective general allometric equations were used to estimate the biomass. The fractional value 0.4453 was used to convert dry biomass into carbon in woody vegetation of tropical dry forest. The mean aboveground biomass value of juvenile tree population was 1.86 Mg/ha. The aboveground biomass of adult trees ranged from 64.81 to 624.96 Mg/ha with a mean of 245.90 Mg/ha. The mean aboveground biomass value of lianas was 7.98 Mg/ha. The total biomass of woody vegetation (adult trees + juvenile population of trees + lianas) ranged from 85.02 to 723.46 Mg/ha, with a mean value of 295.04 Mg/ha. Total carbon accumulated in woody vegetation in tropical dry deciduous forest ranged from 37.86 to 322.16 Mg/ha with a mean value of 131.38 Mg/ha. Adult trees accumulated 94.81% of woody biomass carbon followed by lianas (3.99%) and juvenile population of trees (1.20%). Albizia amara has the greatest biomass and carbon stock (58.31%) among trees except for two plots (24 and 25) where Chloroxylon swietenia contributed more to biomass and carbon stock. Similarly, Albizia amara (52.4%) showed greater carbon storage in juvenile population of trees followed by Chloroxylon swietenia (21.9%). Pterolobium hexapetalum (38.86%) showed a greater accumulation of carbon in liana species followed by Combretum albidum (33.04%). Even though, all the study plots are located within 10 km radius, they show a significant spatial variation among

  8. Disentangling the environmental heterogeneity, floristic distinctiveness and current threats of tropical dry forests in Colombia

    Science.gov (United States)

    González-M, Roy; García, Hernando; Isaacs, Paola; Cuadros, Hermes; López-Camacho, René; Rodríguez, Nelly; Pérez, Karen; Mijares, Francisco; Castaño-Naranjo, Alejandro; Jurado, Rubén; Idárraga-Piedrahíta, Álvaro; Rojas, Alicia; Vergara, Hernando; Pizano, Camila

    2018-04-01

    Tropical dry forests (TDFs) have been defined as a single biome occurring mostly in the lowlands where there is a marked period of drought during the year. In the Neotropics, dry forests occur across contrasting biogeographical regions that contain high beta diversity and endemism, but also strong anthropogenic pressures that threaten their biodiversity and ecological integrity. In Colombia, TDFs occur across six regions with contrasting soils, climate, and anthropogenic pressures, therefore being ideal for studying how these variables relate to dry forest species composition, successional stage and conservation status. Here, we explore the variation in climate and soil conditions, floristic composition, forest fragment size and shape, successional stage and anthropogenic pressures in 571 dry forest fragments across Colombia. We found that TDFs should not be classified solely on rainfall seasonality, as high variation in precipitation and temperature were correlated with soil characteristics. In fact, based on environmental factors and floristic composition, the dry forests of Colombia are clustered in three distinctive groups, with high species turnover across and within regions, as reported for other TDF regions of the Neotropics. Widely distributed TDF species were found to be generalists favored by forest disturbance and the early successional stages of dry forests. On the other hand, TDF fragments were not only small in size, but highly irregular in shape in all regions, and comprising mostly early and intermediate successional stages, with very little mature forest left at the national level. At all sites, we detected at least seven anthropogenic disturbances with agriculture, cattle ranching and human infrastructure being the most pressing disturbances throughout the country. Thus, although environmental factors and floristic composition of dry forests vary across regions at the national level, dry forests are equally threatened by deforestation, degradation

  9. Diurnal flight behavior of Ichneumonoidea (Insecta: Hymenoptera) related to environmental factors in a tropical dry forest.

    Science.gov (United States)

    González-Moreno, A; Bordera, S; Leirana-Alcocer, J; Delfín-González, H

    2012-06-01

    The biology and behavior of insects are strongly influenced by environmental conditions such as temperature and precipitation. Because some of these factors present a within day variation, they may be causing variations on insect diurnal flight activity, but scant information exists on the issue. The aim of this work was to describe the patterns on diurnal variation of the abundance of Ichneumonoidea and their relation with relative humidity, temperature, light intensity, and wind speed. The study site was a tropical dry forest at Ría Lagartos Biosphere Reserve, Mexico; where correlations between environmental factors (relative humidity, temperature, light, and wind speed) and abundance of Ichneumonidae and Braconidae (Hymenoptera: Ichneumonoidea) were estimated. The best regression model for explaining abundance variation was selected using the second order Akaike Information Criterion. The optimum values of temperature, humidity, and light for flight activity of both families were also estimated. Ichneumonid and braconid abundances were significantly correlated to relative humidity, temperature, and light intensity; ichneumonid also showed significant correlations to wind speed. The second order Akaike Information Criterion suggests that in tropical dry conditions, relative humidity is more important that temperature for Ichneumonoidea diurnal activity. Ichneumonid wasps selected toward intermediate values of relative humidity, temperature and the lowest wind speeds; while Braconidae selected for low values of relative humidity. For light intensity, braconids presented a positive selection for moderately high values.

  10. Forest structure, diversity and soil properties in a dry tropical forest in Rajasthan, Western India

    OpenAIRE

    J. I. Nirmal Kumar,; Kanti Patel,; Rohit Bhoi Kumar

    2011-01-01

    Structure, species composition, and soil properties of a dry tropical forest in Rajasthan Western India, were examined by establishment of 25 plots. The forest was characterized by a relatively low canopy and a large number of small-diameter trees. Mean canopy height for this forest was 10 m and stands contained an average of 995 stems ha-1 (≥ 3.0 cm DBH); 52% of those stems were smaller than 10 cm DBH. The total basal area was 46.35 m2ha-1, of which Tectona grandis L. contributed 48%. The fo...

  11. Sensitivity Analysis of Biome-Bgc Model for Dry Tropical Forests of Vindhyan Highlands, India

    Science.gov (United States)

    Kumar, M.; Raghubanshi, A. S.

    2011-08-01

    A process-based model BIOME-BGC was run for sensitivity analysis to see the effect of ecophysiological parameters on net primary production (NPP) of dry tropical forest of India. The sensitivity test reveals that the forest NPP was highly sensitive to the following ecophysiological parameters: Canopy light extinction coefficient (k), Canopy average specific leaf area (SLA), New stem C : New leaf C (SC:LC), Maximum stomatal conductance (gs,max), C:N of fine roots (C:Nfr), All-sided to projected leaf area ratio and Canopy water interception coefficient (Wint). Therefore, these parameters need more precision and attention during estimation and observation in the field studies.

  12. The geomorphology of the wet and dry tropics and problems associated with the storage of uranium tailings in Northern Australia

    International Nuclear Information System (INIS)

    Warner, R.F.; Pickup, G.

    1982-01-01

    This paper describes the principal landforms of the Alligator Rivers Region Uranium Province of Northern Australia, reviews work on landforms and processes in this wet and dry tropical environment, and discusses the kinds of geomorphological hazards which might be encountered in disposing of uranium tailings at the Nabarlek, Ranger, Koongarra and Jabiluka Uranium Project Sites

  13. Morphological, sediment and soil chemical characteristics of dry tropical shallow reservoirs in the Southern Mexican Highlands

    Directory of Open Access Journals (Sweden)

    José Luis ARREDONDO-FIGUEROA

    2011-02-01

    Full Text Available The morphometry, sediment and soil chemical characteristics of eleven dry tropical shallow reservoirs situated in Southern Mexican Highlands were studied. The reservoirs are located at 1104 to 1183 meters above sea level in a sedimentary area. Seventeen morphometric and eight sediment and soil chemical parameters were measured. The results of the morphometric parameters showed that these reservoirs presented a soft and roughness bottom, with an ellipsoid form and a concave depression that permit the mix up of water and sediments, causing turbidity and broken thermal gradients; their slight slopes allowed the colonization of submerged macrophyte and halophyte plants and improved the incidence of sunlight on water surface increasing evaporation and primary productivity. Dry tropical shallow reservoirs have fluctuations in area, and volume according to the amount of rainfall, the effect of evaporation, temperature, lost volume for irrigation, and other causes. The sand-clay was the most important sediment texture and their values fluctuated with the flooded periods. The concentration-dilution cycle showed a direct relationship in the percentage of organic matter in the soil as well as with pH, soil nitrogen and phosphorus. El Tilzate, El Candelero and El Movil were related by the shore development and high concentrations of organic matter and nitrogen in the soil. Finally, we emphasize the importance of this study, in relation to possible future changes in morphometrical parameters as a consequence of human impact.

  14. Variations in soil carbon sequestration and their determinants along a precipitation gradient in seasonally dry tropical forest ecosystems.

    Science.gov (United States)

    Campo, Julio; Merino, Agustín

    2016-05-01

    The effect of precipitation regime on the C cycle of tropical forests is poorly understood, despite the existence of models that suggest a drier climate may substantially alter the source-sink function of these ecosystems. Along a precipitation regime gradient containing 12 mature seasonally dry tropical forests growing under otherwise similar conditions (similar annual temperature, rainfall seasonality, and geological substrate), we analyzed the influence of variation in annual precipitation (1240 to 642 mm) and duration of seasonal drought on soil C. We investigated litterfall, decomposition in the forest floor, and C storage in the mineral soil, and analyzed the dependence of these processes and pools on precipitation. Litterfall decreased slightly - about 10% - from stands with 1240 mm yr(-1) to those with 642 mm yr(-1), while the decomposition decreased by 56%. Reduced precipitation strongly affected C storage and basal respiration in the mineral soil. Higher soil C storage at the drier sites was also related to the higher chemical recalcitrance of litter (fine roots and forest floor) and the presence of charcoal across sites, suggesting an important indirect influence of climate on C sequestration. Basal respiration was controlled by the amount of recalcitrant organic matter in the mineral soil. We conclude that in these forest ecosystems, the long-term consequences of decreased precipitation would be an increase in organic layer and mineral soil C storage, mainly due to lower decomposition and higher chemical recalcitrance of organic matter, resulting from changes in litter composition and, likely also, wildfire patterns. This could turn these seasonally dry tropical forests into significant soil C sinks under the predicted longer drought periods if primary productivity is maintained. © 2016 John Wiley & Sons Ltd.

  15. Wildfires, Ecosystem Services, and Biodiversity in Tropical Dry Forest in India

    Science.gov (United States)

    Schmerbeck, Joachim; Fiener, Peter

    2015-08-01

    This review is intended to contribute to the understanding of the interlinkage between wildfire in India's tropical dry forest (TDF) and selected ecosystem services (ES), namely forest provisioning and water regulating services, as well as biodiversity. TDF covers approximately 146,000 km2 (4.4 %) of India, whereas according to the MODIS fire product about 2200 km2 (1.4 %) burns per year. As studies on wildfire effects upon ESs and biodiversity in Indian TDFs are rare we partly transferred findings from other (dry) forest areas to the environmental situation in India. In India (intentionally lit) wildfires have a very important connection to local livelihoods and the availability of non-wood forest products. Very important adverse long-term effects are the deterioration of forest ecosystems and soil degradation. The potential for TDF to regulate hydrological cycles is expected to be greater in the absence of fire than with it. A general judgment on the effect of fire on biodiversity is difficult as it depends on the community and species involved but a loss of biodiversity under regular burnings is apparent. Consequently, forest managers need sound knowledge regarding the interplay of wildfires and ecosystem behavior in general and more specific knowledge regarding the effects on taxa being considered for conservation efforts. Generally, much more research is needed to understand the trade-offs between the short-term benefits gained from forest provisioning services and long-term adverse effects.

  16. Wildfires, Ecosystem Services, and Biodiversity in Tropical Dry Forest in India.

    Science.gov (United States)

    Schmerbeck, Joachim; Fiener, Peter

    2015-08-01

    This review is intended to contribute to the understanding of the interlinkage between wildfire in India's tropical dry forest (TDF) and selected ecosystem services (ES), namely forest provisioning and water regulating services, as well as biodiversity. TDF covers approximately 146,000 km(2) (4.4%) of India, whereas according to the MODIS fire product about 2200 km(2) (1.4%) burns per year. As studies on wildfire effects upon ESs and biodiversity in Indian TDFs are rare we partly transferred findings from other (dry) forest areas to the environmental situation in India. In India (intentionally lit) wildfires have a very important connection to local livelihoods and the availability of non-wood forest products. Very important adverse long-term effects are the deterioration of forest ecosystems and soil degradation. The potential for TDF to regulate hydrological cycles is expected to be greater in the absence of fire than with it. A general judgment on the effect of fire on biodiversity is difficult as it depends on the community and species involved but a loss of biodiversity under regular burnings is apparent. Consequently, forest managers need sound knowledge regarding the interplay of wildfires and ecosystem behavior in general and more specific knowledge regarding the effects on taxa being considered for conservation efforts. Generally, much more research is needed to understand the trade-offs between the short-term benefits gained from forest provisioning services and long-term adverse effects.

  17. Floristic composition of the dry tropical forest in biological reserve (sanctuary "Los Besotes" and phenology of the dominant arboreal species (Valledupar, Cesar, Colombia

    Directory of Open Access Journals (Sweden)

    Mary Lee Berdugo Lattke

    2015-01-01

    Full Text Available Based on the floristic composition and structural aspects, the formation tropical dry forest of the reserve "Los Besotes" (Valledupar, Cesar; 248 y 1046m of altitude was characterized. In 35 individuals from nine dominant tree species in two forest types, the phenological characteristics were assessed. Seven monitoring were performed along one year according to the scheme of distribution of rainfall. The leaf fall in the forests of Myrcianthes aff. fragrans and Brosimum alicastrum did not exceed 20% regardless of the climatic period (drought or rainy seasons. In others dominant understory species the leaf fall was less than 40%, thus species of the canopy are classified as evergreen while those of the understory as semideciduous. Blooming peaked during the dry season while fruit production peaked during the two rainy seasons. In the forest ofBursera simaruba and Pterocarpus acapulcensis the leaf fall exceeded 60% in the dry season, while in the rainy season was only 30%. The leaf fall increased to 60% in others dominant understory species. Both canopy as well as understory species are deciduous. Blooming was observed during the dry season (December to March, and July, but it is also likely to occur in October; fruit production was observed at the end of the rainy season. In the tropical dry forest formation evergreen plant communities with low values of leaf fall (40% and deciduous communities with values greater than 60% are recognized.

  18. Leaf traits show different relationships with shade tolerance in moist versus dry tropical forests.

    Science.gov (United States)

    Poorter, Lourens

    2009-03-01

    Shade tolerance is the central paradigm for understanding forest succession and dynamics, but there is considerable debate as to what the salient features of shade tolerance are, whether adult leaves show similar shade adaptations to seedling leaves, and whether the same leaf adaptations are found in forests under different climatic control. Here, adult leaf and metamer traits were measured for 39 tree species from a tropical moist semi-evergreen forest (1580 mm rain yr(-1)) and 41 species from a dry deciduous forest (1160 mm yr(-1)) in Bolivia. Twenty-six functional traits were measured and related to species regeneration light requirements.Adult leaf traits were clearly associated with shade tolerance. Different, rather than stronger, shade adaptations were found for moist compared with dry forest species. Shade adaptations exclusively found in the evergreen moist forest were related to tough and persistent leaves, and shade adaptations in the dry deciduous forest were related to high light interception and water use.These results suggest that, for forests differing in rainfall seasonality, there is a shift in the relative importance of functional leaf traits and performance trade-offs that control light partitioning. In the moist evergreen forest leaf traits underlying the growth-survival trade-off are important, whereas in the seasonally deciduous forest leaf traits underlying the growth trade-off between low and high light might become important.

  19. Caribbean dry forest networking: an opportunity for conservation

    Science.gov (United States)

    K. Banda-Rodriguez; J. Weintritt; R.T. Pennington

    2016-01-01

    Seasonally dry tropical forest is the most threatened tropical forest in the world. Though its overall plant species diversity is lower than in neighboring biomes such as rain forest, species endemism can be high, and its conservation has often been neglected. Caribbean dry forests face diverse threats including tourism, agriculture, and climate change. The Latin...

  20. Forest structure, diversity and soil properties in a dry tropical forest in Rajasthan, Western India

    Directory of Open Access Journals (Sweden)

    J. I. Nirmal Kumar

    2011-06-01

    Full Text Available Structure, species composition, and soil properties of a dry tropical forest in Rajasthan Western India, were examined by establishment of 25 plots. The forest was characterized by a relatively low canopy and a large number of small-diameter trees. Mean canopy height for this forest was 10 m and stands contained an average of 995 stems ha-1 (= 3.0 cm DBH; 52% of those stems were smaller than 10 cm DBH. The total basal area was 46.35 m2ha-1, of which Tectona grandis L. contributed 48%. The forest showed high species diversity of trees. 50 tree species (= 3.0 cm DBH from 29 families were identified in the 25 sampling plots. T. grandis (20.81% and Butea monosperma (9% were the dominant and subdominant species in terms of importance value. The mean tree species diversity indices for the plots were 1.08 for Shannon diversity index (H´, 0.71 for equitability index (J´ and 5.57 for species richness index (S´, all of which strongly declined with the increase of importance value of the dominant, T. grandis. Measures of soil nutrients indicated low fertility, extreme heterogeneity. Regression analysis showed that stem density and the dominant tree height were significantly correlated with soil pH. There was a significant positive relationship between species diversity index and soil available P, exchangeable K+, Ca2+ (all p values < 0.001 and a negative relationship with N, C, C:N and C:P ratio. The results suggest that soil properties are major factors influencing forest composition and structure within the dry tropical forest in Rajasthan.

  1. Vegetation and Lepidoptera in Seasonally Dry Tropical Forests. Community structure along climate zones, forest succession and seasonality in the Southern Yucatán, Mexico

    NARCIS (Netherlands)

    Essens, T.; Leyequien, E.; Pozo, C.

    2010-01-01

    Seasonally dry tropical forests are worldwide recognized as important ecosystems for biodiversity conservation. Increasing agricultural activities (e.g., slash-and-burn agriculture) leads to a heterogeneous landscape matrix; and as ecological succession takes over in abandoned fields, plant and

  2. Diametric structure in a tropical dry forest fragment in the Cerrado Eco-Museum region, Brazil

    International Nuclear Information System (INIS)

    Imana Encinas Jose, Antunes Santana Otacilio; Rainier Imana Christian

    2011-01-01

    In a tropical dry forest area of the Brazilian central region, the DBH distribution of 742 trees ≥ 5 cm was analyzed in a 4000 m 2 area. Eighty three tree species were found, of which 25 species with more than 10 individuals were analyzed for this study. The frequency histograms were obtained through the Meyer and Gaussian equations. The DBH distribution of the population showed a negative exponential inverse J curve. Of the 25 species selected, 14 exhibited the same pattern. Eight species presented a tendency near the normal distribution while three species had an abnormal pattern. We concluded that the observed fragment is in a natural auto regenerative status.

  3. Carbon emission as a function of energy generation in hydroelectric reservoirs in Brazilian dry tropical biome

    International Nuclear Information System (INIS)

    Ometto, Jean P.; Cimbleris, André C.P.; Santos, Marco A. dos; Rosa, Luiz P.; Abe, Donato; Tundisi, José G.; Stech, José L.; Barros, Nathan; Roland, Fábio

    2013-01-01

    Most energy generation globally is fueled by coal and oil, raising concerns about greenhouse gas emissions. Hydroelectric reservoirs are anthropogenic aquatic systems that occur across a wide geographical extent, and, in addition to their importance for energy production, they have the potential to release two important greenhouse gases (GHGs), carbon dioxide and methane. We report results from an extensive study of eight hydroelectric reservoirs located in central and southeastern tropical Brazil. In the Brazilian dry tropical biome reservoirs, emissions (in tons of CO 2 Eq. per MW h) varied from 0.01 to 0.55, and decreased with reservoir age. Total emissions were higher in the reservoir lake when compared to the river downstream the dam; however, emissions per unit area, in the first kilometer of the river after the dam, were higher than that in the reservoir. The results showed, despite higher carbon emissions per energy production in the youngest reservoirs, lower emission from hydroelectric reservoirs from the studied region in relation to thermo electrical supply, fueled by coal or fossil fuel. The ratio emission of GHG per MWh produced is an important parameter in evaluating the service provided by hydroelectric reservoir and for energy planning policies. - Highlights: ► Hydroelectric reservoirs construction is growing worldwide. ► The effect of hydropower reservoir in the carbon cycle is dependent on environment characteristics. ► Carbon emissions per energy production are higher in the youngest tropical savannah reservoirs. ► Methane emissions decrease with reservoir age in tropical savannah reservoirs. ► In general, the effect of hydropower in the carbon cycle is lower than other energy sources

  4. Landscape genetics of leaf-toed geckos in the tropical dry forest of northern Mexico.

    Directory of Open Access Journals (Sweden)

    Christopher Blair

    Full Text Available Habitat fragmentation due to both natural and anthropogenic forces continues to threaten the evolution and maintenance of biological diversity. This is of particular concern in tropical regions that are experiencing elevated rates of habitat loss. Although less well-studied than tropical rain forests, tropical dry forests (TDF contain an enormous diversity of species and continue to be threatened by anthropogenic activities including grazing and agriculture. However, little is known about the processes that shape genetic connectivity in species inhabiting TDF ecosystems. We adopt a landscape genetic approach to understanding functional connectivity for leaf-toed geckos (Phyllodactylus tuberculosus at multiple sites near the northernmost limit of this ecosystem at Alamos, Sonora, Mexico. Traditional analyses of population genetics are combined with multivariate GIS-based landscape analyses to test hypotheses on the potential drivers of spatial genetic variation. Moderate levels of within-population diversity and substantial levels of population differentiation are revealed by FST and Dest. Analyses using structure suggest the occurrence of from 2 to 9 genetic clusters depending on the model used. Landscape genetic analysis suggests that forest cover, stream connectivity, undisturbed habitat, slope, and minimum temperature of the coldest period explain more genetic variation than do simple Euclidean distances. Additional landscape genetic studies throughout TDF habitat are required to understand species-specific responses to landscape and climate change and to identify common drivers. We urge researchers interested in using multivariate distance methods to test for, and report, significant correlations among predictor matrices that can impact results, particularly when adopting least-cost path approaches. Further investigation into the use of information theoretic approaches for model selection is also warranted.

  5. Landscape genetics of leaf-toed geckos in the tropical dry forest of northern Mexico.

    Science.gov (United States)

    Blair, Christopher; Jiménez Arcos, Victor H; Mendez de la Cruz, Fausto R; Murphy, Robert W

    2013-01-01

    Habitat fragmentation due to both natural and anthropogenic forces continues to threaten the evolution and maintenance of biological diversity. This is of particular concern in tropical regions that are experiencing elevated rates of habitat loss. Although less well-studied than tropical rain forests, tropical dry forests (TDF) contain an enormous diversity of species and continue to be threatened by anthropogenic activities including grazing and agriculture. However, little is known about the processes that shape genetic connectivity in species inhabiting TDF ecosystems. We adopt a landscape genetic approach to understanding functional connectivity for leaf-toed geckos (Phyllodactylus tuberculosus) at multiple sites near the northernmost limit of this ecosystem at Alamos, Sonora, Mexico. Traditional analyses of population genetics are combined with multivariate GIS-based landscape analyses to test hypotheses on the potential drivers of spatial genetic variation. Moderate levels of within-population diversity and substantial levels of population differentiation are revealed by FST and Dest. Analyses using structure suggest the occurrence of from 2 to 9 genetic clusters depending on the model used. Landscape genetic analysis suggests that forest cover, stream connectivity, undisturbed habitat, slope, and minimum temperature of the coldest period explain more genetic variation than do simple Euclidean distances. Additional landscape genetic studies throughout TDF habitat are required to understand species-specific responses to landscape and climate change and to identify common drivers. We urge researchers interested in using multivariate distance methods to test for, and report, significant correlations among predictor matrices that can impact results, particularly when adopting least-cost path approaches. Further investigation into the use of information theoretic approaches for model selection is also warranted.

  6. Landscape Genetics of Leaf-Toed Geckos in the Tropical Dry Forest of Northern Mexico

    Science.gov (United States)

    Blair, Christopher; Jiménez Arcos, Victor H.; Mendez de la Cruz, Fausto R.; Murphy, Robert W.

    2013-01-01

    Habitat fragmentation due to both natural and anthropogenic forces continues to threaten the evolution and maintenance of biological diversity. This is of particular concern in tropical regions that are experiencing elevated rates of habitat loss. Although less well-studied than tropical rain forests, tropical dry forests (TDF) contain an enormous diversity of species and continue to be threatened by anthropogenic activities including grazing and agriculture. However, little is known about the processes that shape genetic connectivity in species inhabiting TDF ecosystems. We adopt a landscape genetic approach to understanding functional connectivity for leaf-toed geckos (Phyllodactylus tuberculosus) at multiple sites near the northernmost limit of this ecosystem at Alamos, Sonora, Mexico. Traditional analyses of population genetics are combined with multivariate GIS-based landscape analyses to test hypotheses on the potential drivers of spatial genetic variation. Moderate levels of within-population diversity and substantial levels of population differentiation are revealed by F ST and D est. Analyses using structure suggest the occurrence of from 2 to 9 genetic clusters depending on the model used. Landscape genetic analysis suggests that forest cover, stream connectivity, undisturbed habitat, slope, and minimum temperature of the coldest period explain more genetic variation than do simple Euclidean distances. Additional landscape genetic studies throughout TDF habitat are required to understand species-specific responses to landscape and climate change and to identify common drivers. We urge researchers interested in using multivariate distance methods to test for, and report, significant correlations among predictor matrices that can impact results, particularly when adopting least-cost path approaches. Further investigation into the use of information theoretic approaches for model selection is also warranted. PMID:23451230

  7. Vegetation geographical patterns as a key to the past, with emphasis on the dry vegetation types of South Africa

    Directory of Open Access Journals (Sweden)

    M. J. A. Werger

    1983-11-01

    Full Text Available Southern Africa is characterized by a highly diversified vegetational cover with extremes as contrasting as desert, tropical forest, alpine grassland, or mediterranean type scrub, and many other types in between. This vegetational pattern is strongly correlated to the climatological pattern. It is therefore likely that past changes in climate can still be partly traced in the vegetational pattern, particularly in geographical anomalies, and that study of these patterns provides complementary evidence to palynological research. The following anomalies in the vegetational pattern are briefly discussed: 1. island-wise occurrence of Afro-montane vegetation on mesic, sheltered sites in the southern Sudano- Zambezian Region, in particular in the Highveld grassland/False Karoo transition area; 2. similar westward occurrence of Sudano-Zambezian scrub patches in the Karoo-Namib Region near the Orange/Vaal confluence; 3. scattered occurrence of Sudano-Zambezian woody species in a matrix of Karoo-Namib vegetation in the marginal Karoo-Namib Region; 4. island-wise occurrence of frost-tolerant, dry, karroid dwarf shrub vegetation of predominantly C,-plants on isolated peaks in the winter rainfall area of Namaqualand; 5. peculiar patchy distribution of some succulents in wide areas of climatically rather homogeneous, succulent dwarf shrub vegetation of predominantly CAM-plants in the escarpment area of Namaqualand. a pattern reminiscent of that in many Cape fynbos species. Interpretation of these patterns logically leads to the conclusion that these result from a previously wetter, a previously cooler, or a previously wetter and cooler climate, respectively, over the parts of southern Africa under discussion. This conclusion is compared with published palynological views.

  8. Wet-to-dry shift over Southwest China in 1994 tied to the warming of tropical warm pool

    Science.gov (United States)

    Wang, Lin; Huang, Gang; Chen, Wen; Zhou, Wen; Wang, Weiqiang

    2018-01-01

    The autumn climate in Southwest China (SWC) experienced a notable wet-to-dry shift in 1994. Associated with this change in precipitation, decadal signatures of large-scale atmospheric circulation and SST identify a likely dynamical origin: the tropical warm pool (TWP) consisting of tropical northwest Pacific (TNWP, 3°S-12°N and 110°E-150°E) sector and tropical east Indian Ocean (TEI, 10°S-3°N and 80°E-110°E) sector. A cold-to-warm phase switch of TWP SST occurred in 1994, coinciding exactly with the timing of the regime transition of SWC precipitation. During post-1994 period, warm states in the TNWP and TEI sectors plays in a synergistic fashion to invoke dry decades in SWC. On the one side, warm SST over the TNWP sector excites an anomalous cyclone centered on the South China Sea directed opposite to the climatological moisture transport and strengthened zonal wind to its west accompanied by a weakening of the poleward flux; on the other side, warm SST over the TEI sector acts to intensify inflow into TEI with less concurrent transfer of moisture to SWC and to steer moisture to the northern Arabic Sea and away from the SWC-oriented track. Meanwhile, the troposphere over SWC is capped by subsidence, which is jointly contributed by TNWP and TEI. It then follows a reduced moisture supply, suppressed convective activity, and anomalous divergence in SWC, bringing a precipitation deficit there. In contrast, cold TWP SST during 1961-1994 favors wet conditions in SWC, given a perfectly symmetrical circulation pattern. Further, the dominant role of TWP is confirmed, because the modeled response to TWP SST forcing alone bears a great resemblance to the observed evidence. Finally, it is also found that the teleconnected influence induced by TWP is stronger in southern SWC than in northern SWC, which explains the south-north gradient of interdecadal signal of SWC precipitation.

  9. Natural and near natural tropical forest values

    Science.gov (United States)

    Daniel H. Henning

    2011-01-01

    This paper identifies and describes some of the values associated with tropical rain forests in their natural and near-natural conditions. Tropical rain forests are moist forests in the humid tropics where temperature and rainfall are high and the dry season is short. These closed (non-logged) and broad-leaved forests are a global resource. Located almost entirely in...

  10. Dry mass estimation of tropical aquatic insects using different short-term preservation methods

    Directory of Open Access Journals (Sweden)

    Claudia Cressa

    1999-06-01

    Full Text Available Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes sp. (Ephemeroptera, Leptonema sp. and Nectopsyche sp. (Trichoptera, and Anacroneuria sp. (Plecoptera using different preservatives (Freezing, Formaldehyde 4% and Kahle. The organisms were collected monthly during a year on the Orituco river, Venezuela with a Surber net (0. 1296 m² and 0.286 mm mesh size. The data presented here are representative of the organism conditions year around. No attempt was made to quantify intersample variation. Regression analysis indicated that all relationships were highly correlated for any of the fixatives used. Changes in dry mass per unit change of head capsule width, vary among species and preservatives with no clear relationship among them. Changes in dry mass calculated as the difference between dry mass of preserved samples to those of unpreserved ones, indicate that all fixatives underestimate dry mass by as much as 85.4%, except for Nectopsyche sp. whose dry mass was always overestimated. These results provide further evidence on the effect of preservatives on dry mass losses. Even when working with tropical species, any study in which biomass is going to be determined should consider the effect of preservatives on dry mass.Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera, Leptonema sp., Nectopsyche sp. (Trichoptera y Anacroneuria sp. (Plecoptera usando diferentes preservativos (Congelamiento, Formol 4% and Kahle. El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa

  11. Sensitivity of South American tropical climate to Last Glacial Maximum boundary conditions: focus on teleconnections with tropics and extratropics (Invited)

    Science.gov (United States)

    Khodri, M.; Kageyama, M.; Roche, D. M.

    2009-12-01

    Proxy data over tropical latitudes for the Last Glacial Maximum (LGM) has been interpreted as a southward shift of the Inter Tropical Convergence Zone (ITCZ) and so far linked to a mechanism analogous to the modern day “meridional-mode” in the Atlantic Ocean. Here we have explored alternative mechanisms, related to the direct impact of the LGM global changes in the dry static stability on tropical moist deep convection. We have used a coupled ocean-atmosphere model capable of capturing the thermodynamical structure of the atmosphere and the tropical component of the Hadley and Walker circulations. In each experiment, we have applied either all the LGM forcings, or the individual contributions of greenhouse gases (GHG) concentrations, ice sheet topography and/or albedo to explore the hydrological response over tropical latitudes with a focus on South America. The dominant forcing for the LGM tropical temperature and precipitation changes is found to be due to the reduced GHG, through the direct effect of reduced radiative heating (Clausius-Clapeyron relationship). The LGM GHG is also responsible for increased extra-tropical static stability which strengthens the Hadley Cell. Stronger subsidence over northern tropics then produces an amplification of the northern tropics drying initially due to the direct cooling effect. The land ice sheet is also able to promote the Hadley cell feedback mostly via the topographic effect on the extra-tropical dry static stability and on the position of the subtropical jets. Our results therefore suggest that the communication between the extratropics and the tropics is tighter during LGM and does not necessarily rely on the “meridional-mode” mechanism. The Hadley cell response is constrained by the requirement that diabatic heating in the tropics balances cooling in subtropics. We show that such extratropics-tropics dependence is stronger at the LGM because of the stronger perturbation of northern extra tropical thermal and

  12. Influence of matrix type on tree community assemblages along tropical dry forest edges.

    Science.gov (United States)

    Benítez-Malvido, Julieta; Gallardo-Vásquez, Julio César; Alvarez-Añorve, Mariana Y; Avila-Cabadilla, Luis Daniel

    2014-05-01

    • Anthropogenic habitat edges have strong negative consequences for the functioning of tropical ecosystems. However, edge effects on tropical dry forest tree communities have been barely documented.• In Chamela, Mexico, we investigated the phylogenetic composition and structure of tree assemblages (≥5 cm dbh) along edges abutting different matrices: (1) disturbed vegetation with cattle, (2) pastures with cattle and, (3) pastures without cattle. Additionally, we sampled preserved forest interiors.• All edge types exhibited similar tree density, basal area and diversity to interior forests, but differed in species composition. A nonmetric multidimensional scaling ordination showed that the presence of cattle influenced species composition more strongly than the vegetation structure of the matrix; tree assemblages abutting matrices with cattle had lower scores in the ordination. The phylogenetic composition of tree assemblages followed the same pattern. The principal plant families and genera were associated according to disturbance regimes as follows: pastures and disturbed vegetation (1) with cattle and (2) without cattle, and (3) pastures without cattle and interior forests. All habitats showed random phylogenetic structures, suggesting that tree communities are assembled mainly by stochastic processes. Long-lived species persisting after edge creation could have important implications in the phylogenetic structure of tree assemblages.• Edge creation exerts a stronger influence on TDF vegetation pathways than previously documented, leading to new ecological communities. Phylogenetic analysis may, however, be needed to detect such changes. © 2014 Botanical Society of America, Inc.

  13. Occurrence of termites (Isoptera on living and standing dead trees in a tropical dry forest in Mexico

    Directory of Open Access Journals (Sweden)

    Nancy Calderón-Cortés

    2018-05-01

    Full Text Available Termites play a key role as ecosystem engineers in numerous ecological processes though their role in the dynamics of wood degradation in tropical dry forests, particularly at the level of the crown canopy, has been little studied. In this study, we analysed the occurrence of termites in the forest canopy by evaluating the density and proportion of living and standing dead trees associated with termites in deciduous and riparian habitats of the tropical dry forest in Chamela, Mexico. The results indicated that 60–98% of standing dead trees and 23–59% of living trees in Chamela were associated with termites. In particular, we found that the density of standing dead trees was higher in deciduous forests (0.057–0.066 trees/m2 than in riparian forests (0.022 and 0.027 trees/m2, even though the proportion of trees was not significantly different among habitats. Additionally, we found a higher density of trees associated with termites in trees of smaller size classes (0.01–0.09 trees/m2 than in larger class sizes (0–0.02 trees/m2. Interestingly, 72% of variation in the density of trees associated with termites is explained by the density of standing dead trees. Overall, these results indicate that standing dead tree availability might be the main factor regulating termite populations in Chamela forest and suggest that termites could play a key role in the decomposition of above-ground dead wood, mediating the incorporation of suspended and standing dead wood into the soil.

  14. Occurrence of termites (Isoptera) on living and standing dead trees in a tropical dry forest in Mexico.

    Science.gov (United States)

    Calderón-Cortés, Nancy; Escalera-Vázquez, Luis H; Oyama, Ken

    2018-01-01

    Termites play a key role as ecosystem engineers in numerous ecological processes though their role in the dynamics of wood degradation in tropical dry forests, particularly at the level of the crown canopy, has been little studied. In this study, we analysed the occurrence of termites in the forest canopy by evaluating the density and proportion of living and standing dead trees associated with termites in deciduous and riparian habitats of the tropical dry forest in Chamela, Mexico. The results indicated that 60-98% of standing dead trees and 23-59% of living trees in Chamela were associated with termites. In particular, we found that the density of standing dead trees was higher in deciduous forests (0.057-0.066 trees/m 2 ) than in riparian forests (0.022 and 0.027 trees/m 2 ), even though the proportion of trees was not significantly different among habitats. Additionally, we found a higher density of trees associated with termites in trees of smaller size classes (0.01-0.09 trees/m 2 ) than in larger class sizes (0-0.02 trees/m 2 ). Interestingly, 72% of variation in the density of trees associated with termites is explained by the density of standing dead trees. Overall, these results indicate that standing dead tree availability might be the main factor regulating termite populations in Chamela forest and suggest that termites could play a key role in the decomposition of above-ground dead wood, mediating the incorporation of suspended and standing dead wood into the soil.

  15. Local deforestation patterns and their driving forces of tropical dry forest in two municipalities in Southern Oaxaca, Mexico (1985-2006

    Directory of Open Access Journals (Sweden)

    L. Galicia

    2016-11-01

    Full Text Available The tropical dry forest is an ecosystem that is undergoing rapid changes. Although global driving forces behind these changes have been addressed at a local scale, spatio-temporal dynamics are still largely unknown. The main objective of this study was to identify the causes governing the dynamics of changes in land use and land cover in the tropical dry forest in two municipalities in Southern México. Satellite imagery and air photographs were used in a GIS context to produce maps of land use and land cover for 1985, 1995 and 2006. A number of statistical methods (Markov chains, general lineal models and regression tree analysis were applied to identify the proximate and the underlying causes of deforestation, agriculture being the most important one. When agriculture is mainly for self consumption, topographic factors determine its location. Increasing job opportunities in the tourism sector has resulted in the abandonment of agricultural land; consequently, the forest has recovered. Different studies have examined the dynamics of local deforestation and its driving forces in México; however, this study considered both spatial and temporal elements in order to identify the most important underlying driving forces of deforestation and its dynamics at local scale, and also compared two neighboring municipalities.

  16. Spatial patterns and recent trends in the climate of tropical rainforest regions.

    Science.gov (United States)

    Malhi, Yadvinder; Wright, James

    2004-03-29

    We present an analysis of the mean climate and climatic trends of tropical rainforest regions over the period 1960-1998, with the aid of explicit maps of forest cover and climatological databases. Until the mid-1970s most regions showed little trend in temperature, and the western Amazon experienced a net cooling probably associated with an interdecadal oscillation. Since the mid-1970s, all tropical rainforest regions have experienced a strong warming at a mean rate of 0.26 +/- 0.05 degrees C per decade, in synchrony with a global rise in temperature that has been attributed to the anthropogenic greenhouse effect. Over the study period, precipitation appears to have declined in tropical rainforest regions at a rate of 1.0 +/- 0.8% per decade (p Africa (at 3-4% per decade), declining marginally in tropical Asia and showing no significant trend in Amazonia. There is no evidence so far of a decline in precipitation in eastern Amazonia, a region thought vulnerable to climate-change-induced drying. The strong drying trend in Africa suggests that this should be a priority study region for understanding the impact of drought on tropical rainforests. We develop and use a dry-season index to study variations in the length and intensity of the dry season. Only African and Indian tropical rainforests appear to have seen a significant increase in dry-season intensity. In terms of interannual variability, the El Niño-Southern Oscillation (ENSO) is the primary driver of temperature variations across the tropics and of precipitation fluctuations for large areas of the Americas and southeast Asia. The relation between ENSO and tropical African precipitation appears less direct.

  17. Photoprotection related to xanthophyll cycle pigments in epiphytic orchids acclimated at different light microenvironments in two tropical dry forests of the Yucatan Peninsula, Mexico.

    Science.gov (United States)

    de la Rosa-Manzano, Edilia; Andrade, José Luis; García-Mendoza, Ernesto; Zotz, Gerhard; Reyes-García, Casandra

    2015-12-01

    Epiphytic orchids from dry forests of Yucatán show considerable photoprotective plasticity during the dry season, which depends on leaf morphology and host tree deciduousness. Nocturnal retention of antheraxanthin and zeaxanthin was detected for the first time in epiphytic orchids. In tropical dry forests, epiphytes experience dramatic changes in light intensity: photosynthetic photon flux density may be up to an order of magnitude higher in the dry season compared to the wet season. To address the seasonal changes of xanthophyll cycle (XC) pigments and photosynthesis that occur throughout the year, leaves of five epiphytic orchid species were studied during the early dry, dry and wet seasons in a deciduous and a semi-deciduous tropical forests at two vertical strata on the host trees (3.5 and 1.5 m height). Differences in XC pigment concentrations and photosynthesis (maximum quantum efficiency of photosystem II; F v/F m) were larger among seasons than between vertical strata in both forests. Antheraxanthin and zeaxanthin retention reflected the stressful conditions of the epiphytic microhabitat, and it is described here in epiphytes for the first time. During the dry season, both XC pigment concentrations and photosystem II heat dissipation of absorbed energy increased in orchids in the deciduous forest, while F v/F m and nocturnal acidification (ΔH(+)) decreased, clearly as a response to excessive light and drought. Concentrations of XC pigments were higher than those in orchids with similar leaf shape in semi-deciduous forest. There, only Encyclia nematocaulon and Lophiaris oerstedii showed somewhat reduced F v/F m. No changes in ΔH(+) and F v/F m were detected in Cohniella ascendens throughout the year. This species, which commonly grows in forests with less open canopies, showed leaf tilting that diminished light interception. Light conditions in the uppermost parts of the canopy probably limit the distribution of epiphytic orchids and the retention of

  18. Associations between soil variables and vegetation structure and composition of Caribbean dry forests

    Science.gov (United States)

    Elvia M. Melendez-Ackerman; Julissa Rojas-Sandoval; Danny S. Fernandez; Grizelle Gonzalez; Hana Lopez; Jose Sustache; Mariely Morales; Miguel Garcia-Bermudez; Susan Aragon

    2016-01-01

    Soil–vegetation associations have been understudied in tropical dry forests when compared to the amount of extant research on this issue in tropical wet forests. Recent studies assert that vegetation in tropical dry forests is highly heterogeneous and that soil variability may be a contributing factor. In this study, we evaluated the relationship between soil variables...

  19. Light habitat, structure, diversity and dynamic of the tropical dry forest

    Directory of Open Access Journals (Sweden)

    Omar Melo-Cruz

    2017-01-01

    Full Text Available Tropical dry forests are complex and fragile ecosystems with high anthropic intervention and restricted reproductive cycles. These have unique richness, structural diversity, physiological and phenological . This research was executed  in the Upper Magdalena Valley, in four forest fragments with different successional stages. In each fragment four permanent plots of 0.25 ha were established and lighting habitat associated with richness, relative abundance and rarity of species. The forest dynamics included the mortality, recruitment and diameter growth for a period of 5.25 years. The species rischness found in the mature riparian forestis higher than that reported in other studies of similar areas in Valle del Cauca and the Atlantic coast.  The values of richness, diversity and rarity species are more evidenced  than the magnitudes found in  drier areas of Tolima. The structure, diversity and dynamics of forests were correlated with the lighting habitat, showing differences in canopy architecture and its role in the capture and absorption of radiation. Forests with dense canopy have limited availability of photosynthetically active radiation in understory related low species richness, while illuminated undergrowth are richer and heterogeneous.

  20. Distribution of tropical tropospheric water vapor

    Science.gov (United States)

    Sun, De-Zheng; Lindzen, Richard S.

    1993-01-01

    Utilizing a conceptual model for tropical convection and observational data for water vapor, the maintenance of the vertical distribution of the tropical tropospheric water vapor is discussed. While deep convection induces large-scale subsidence that constrains the turbulent downgradient mixing to within the convective boundary layer and effectively dries the troposphere through downward advection, it also pumps hydrometeors into the upper troposphere, whose subsequent evaporation appears to be the major source of moisture for the large-scale subsiding motion. The development of upper-level clouds and precipitation from these clouds may also act to dry the outflow, thus explaining the low relative humidity near the tropopause. A one-dimensional model is developed to simulate the mean vertical structure of water vapor in the tropical troposphere. It is also shown that the horizontal variation of water vapor in the tropical troposphere above the trade-wind boundary layer can be explained by the variation of a moisture source that is proportional to the amount of upper-level clouds. Implications for the nature of water vapor feedback in global warming are discussed.

  1. Foggy days and dry nights determine crown-level water balance in a seasonal tropical Montane cloud forest.

    Science.gov (United States)

    Gotsch, Sybil G; Asbjornsen, Heidi; Holwerda, Friso; Goldsmith, Gregory R; Weintraub, Alexis E; Dawson, Todd E

    2014-01-01

    The ecophysiology of tropical montane cloud forest (TMCF) trees is influenced by crown-level microclimate factors including regular mist/fog water inputs, and large variations in evaporative demand, which in turn can significantly impact water balance. We investigated the effect of such microclimatic factors on canopy ecophysiology and branch-level water balance in the dry season of a seasonal TMCF in Veracruz, Mexico, by quantifying both water inputs (via foliar uptake, FU) and outputs (day- and night-time transpiration, NT). Measurements of sap flow, stomatal conductance, leaf water potential and pressure-volume relations were obtained in Quercus lanceifolia, a canopy-dominant tree species. Our results indicate that FU occurred 34% of the time and led to the recovery of 9% (24 ± 9.1 L) of all the dry-season water transpired from individual branches. Capacity for FU was independently verified for seven additional common tree species. NT accounted for approximately 17% (46 L) of dry-season water loss. There was a strong correlation between FU and the duration of leaf wetness events (fog and/or rain), as well as between NT and the night-time vapour pressure deficit. Our results show the clear importance of fog and NT for the canopy water relations of Q. lanceifolia. © 2013 John Wiley & Sons Ltd.

  2. Post-fire regeneration in seasonally dry tropical forest fragments in southeastern Brazil.

    Science.gov (United States)

    Costa, Mayke B; Menezes, Luis Fernando T DE; Nascimento, Marcelo T

    2017-01-01

    Seasonally dry tropical forest is one of the highly threatened biome. However, studies on the effect of fire on these tree communities are still scarce. In this context, a floristic and structural survey in three forest areas in the southeast of Brazil that were affected by fire between 14 and 25 years ago was performed with the objective of evaluating post-fire regeneration. In each site, five systematically placed plots (25 m x 25 m each) were established. The more recently burnt site had significantly lower values of richness and diversity than the other two sites. However, the sites did not differ in density and basal area. Annona dolabripetala, Astronium concinnum, Joannesia princeps and Polyandrococos caudescens were within the 10 most important species for the three sites. Comparing these data with adjacent mature forests, the results indicated differences both in structural and floristic aspects, suggesting that the time after fire was not sufficient for recuperation of these areas. The recovery process indicate at least 190 years for areas return to basal area values close to those observed in mature forests nearby.

  3. Ethiopian church forests : opportunities and challenges for restoration

    NARCIS (Netherlands)

    Wassie Eshete, A.

    2007-01-01

    In Northern Ethiopia almost all dry Afromontane forests have been converted to open agricultural lands. Only small isolated fragments remain around churches ("church forests"), but these are many. This study analyses forest community structure and composition of the church forests, investigates

  4. Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest.

    Science.gov (United States)

    Power, M J; Whitney, B S; Mayle, F E; Neves, D M; de Boer, E J; Maclean, K S

    2016-06-05

    South American seasonally dry tropical forests (SDTFs) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12 000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the Early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8000 and 7000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined but severe regional droughts persisted through the Middle Holocene, SDTFs, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTFs are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime.This article is part of the themed issue 'The interaction of fire and mankind'. © 2016 The Author(s).

  5. Terrestrial Macrofungal Diversity from the Tropical Dry Evergreen Biome of Southern India and Its Potential Role in Aerobiology.

    Science.gov (United States)

    Priyamvada, Hema; Akila, M; Singh, Raj Kamal; Ravikrishna, R; Verma, R S; Philip, Ligy; Marathe, R R; Sahu, L K; Sudheer, K P; Gunthe, S S

    2017-01-01

    Macrofungi have long been investigated for various scientific purposes including their food and medicinal characteristics. Their role in aerobiology as a fraction of the primary biological aerosol particles (PBAPs), however, has been poorly studied. In this study, we present a source of macrofungi with two different but interdependent objectives: (i) to characterize the macrofungi from a tropical dry evergreen biome in southern India using advanced molecular techniques to enrich the database from this region, and (ii) to assess whether identified species of macrofungi are a potential source of atmospheric PBAPs. From the DNA analysis, we report the diversity of the terrestrial macrofungi from a tropical dry evergreen biome robustly supported by the statistical analyses for diversity conclusions. A total of 113 macrofungal species belonging to 54 genera and 23 families were recorded, with Basidiomycota and Ascomycota constituting 96% and 4% of the species, respectively. The highest species richness was found in the family Agaricaceae (25.3%) followed by Polyporaceae (15.3%) and Marasmiaceae (10.8%). The difference in the distribution of commonly observed macrofungal families over this location was compared with other locations in India (Karnataka, Kerala, Maharashtra, and West Bengal) using two statistical tests. The distributions of the terrestrial macrofungi were distinctly different in each ecosystem. We further attempted to demonstrate the potential role of terrestrial macrofungi as a source of PBAPs in ambient air. In our opinion, the findings from this ecosystem of India will enhance our understanding of the distribution, diversity, ecology, and biological prospects of terrestrial macrofungi as well as their potential to contribute to airborne fungal aerosols.

  6. Postdispersal seed predation and seed viability in forest soils: implications for the regeneration of tree species in Ethiopian church forests

    NARCIS (Netherlands)

    Wassie Eshete, A.; Bekele, T.; Sterck, F.J.; Teketay, D.; Bongers, F.

    2010-01-01

    Almost all dry Afromontane forests of Northern Ethiopia have been converted to agricultural, grazing or scrub lands except for small fragments left around churches ('Church forests'). Species regeneration in these forests is limited. We investigated (i) how intense postdispersal seed predation was

  7. Effect of drought on productivity in a Costa Rican tropical dry forest

    Science.gov (United States)

    Castro, S. M.; Sanchez-Azofeifa, G. A.; Sato, H.

    2018-04-01

    Climate models predict that precipitation patterns in tropical dry forests (TDFs) will change, with an overall reduction in rainfall amount and intensification of dry intervals, leading to greater susceptibility to drought. In this paper, we explore the effect of drought on phenology and carbon dynamics of a secondary TDF located in the Santa Rosa National Park (SRNP), Costa Rica. Through the use of optical sensors and an eddy covariance flux tower, seasonal phenology and carbon fluxes were monitored over a four-year period (2013-2016). Over this time frame, annual precipitation varied considerably. Total precipitation amounts for the 2013-2016 seasons equaled 1591.8 mm (+14.4 mm SD), 1112.9 mm (+9.9 mm SD), 600.8 mm (+7.6 mm SD), and 1762.2 mm (+13.9 mm SD), respectively. The 2014 and 2015 (ENSO) seasonal precipitation amounts represent a 30% and 63% reduction in precipitation, respectively, and were designated as drought seasons. Phenology was affected by precipitation patterns and availability. The onset of green-up was closely associated with pre-seasonal rains. Drought events lead to seasonal NDVI minimums and changes in phenologic cycle length. Carbon fluxes, assimilation, and photosynthetic light use efficiency were negatively affected by drought. Seasonal minimums in photosynthetic rates and light use efficiency were observed during drought events, and gross primary productivity was reduced by 13% and 42% during drought seasons 2014 and 2015, respectively. However, all four growth seasons were net carbon sinks. Results from this study contribute towards a deeper understanding of the impact of drought on TDF phenology and carbon dynamics.

  8. Trade-offs between ecosystem services and alternative pathways toward sustainability in a tropical dry forest region

    Directory of Open Access Journals (Sweden)

    Francisco Mora

    2016-12-01

    Full Text Available The design of strategies aimed at sustainable resource management requires an understanding of the trade-offs between the ecosystem services at stake, to determine appropriate ways in which to navigate them. We assess trade-offs between forage production for cattle ranching and the maintenance of carbon stocks or tree diversity in a Mexican tropical dry forest. Trade-offs between pairs of services were assessed by identifying their efficiency frontiers at both site and landscape scales. We also estimated service outcomes under current and hypothetical land-management conditions. We found stark trade-offs between fodder and carbon stocks and between fodder and tree species richness at the site scale. At the landscape scale, the efficiency frontier was concave, with a much less pronounced trade-off in the fodder-species richness case. Our estimates of current service supply levels showed a reduction of 18-21% for C stock and 41-43% for fodder biomass, relative to the maximum feasible values along the efficiency frontier. Choice of the optimum management strategy to reduce such inefficiency depended on deforestation level: secondary forest regeneration was most suitable when deforestation is low, whereas increased fodder productivity in the pastures is best when deforestation is high. Pasture enrichment with forage trees and secondary forest growth are potential management alternatives for achieving sustainability given the range of enabling ecological factors and to balance ecological and social sustainability given the requirements and preferences of local stakeholders. Given that analogous trade-offs are found across the tropics, this work contributes to reconciling tropical forest maintenance and its use for sustainable rural livelihoods.

  9. Attaining the canopy in dry and moist tropical forests: strong differences in tree growth trajectories reflect variation in growing conditions.

    Science.gov (United States)

    Brienen, Roel J W; Zuidema, Pieter A; Martínez-Ramos, Miguel

    2010-06-01

    Availability of light and water differs between tropical moist and dry forests, with typically higher understorey light levels and lower water availability in the latter. Therefore, growth trajectories of juvenile trees--those that have not attained the canopy--are likely governed by temporal fluctuations in light availability in moist forests (suppressions and releases), and by spatial heterogeneity in water availability in dry forests. In this study, we compared juvenile growth trajectories of Cedrela odorata in a dry (Mexico) and a moist forest (Bolivia) using tree rings. We tested the following specific hypotheses: (1) moist forest juveniles show more and longer suppressions, and more and stronger releases; (2) moist forest juveniles exhibit wider variation in canopy accession pattern, i.e. the typical growth trajectory to the canopy; (3) growth variation among dry forest juveniles persists over longer time due to spatial heterogeneity in water availability. As expected, the proportion of suppressed juveniles was higher in moist than in dry forest (72 vs. 17%). Moist forest suppressions also lasted longer (9 vs. 5 years). The proportion of juveniles that experienced releases in moist forest (76%) was higher than in dry forest (41%), and releases in moist forests were much stronger. Trees in the moist forest also had a wider variation in canopy accession patterns compared to the dry forest. Our results also showed that growth variation among juvenile trees persisted over substantially longer periods of time in dry forest (>64 years) compared to moist forest (12 years), most probably because of larger persistent spatial variation in water availability. Our results suggest that periodic increases in light availability are more important for attaining the canopy in moist forests, and that spatial heterogeneity in water availability governs long-term tree growth in dry forests.

  10. Tree diversity in the tropical dry forest of Bannerghatta National Park in Eastern Ghats, Southern India

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    Gopalakrishna S. Puttakame

    2015-12-01

    Full Text Available Tree species inventories, particularly of poorly known dry deciduous forests, are needed to protect and restore forests in degraded landscapes. A study of forest stand structure, and species diversity and density of trees with girth at breast height (GBH ≥10 cm was conducted in four management zones of Bannerghatta National Park (BNP in the Eastern Ghats of Southern India. We identified 128 tree species belonging to 45 families in 7.9 hectares. However, 44 species were represented by ≤ 2 individuals. Mean diversity values per site for the dry forest of BNP were: tree composition (23.8 ±7.6, plant density (100.69 ± 40.02, species diversity (2.56 ± 0.44 and species richness (10.48 ± 4.05. Tree diversity was not significantly different (P>0.05 across the four management zones in the park. However, the number of tree species identified significantly (P<0.05 increased with increasing number of sampling sites, but majority of the species were captured. Similarly, there were significant variations (p<0.05 between tree diameter class distributions. Juveniles accounted for 87% of the tree population. The structure of the forest was not homogeneous, with sections ranging from poorly structured to highly stratified configurations. The study suggests that there was moderate tree diversity in the tropical dry thorn forest of Bannerghatta National Park, but the forest was relatively young.

  11. Root depth and morphology in response to soil drought: comparing ecological groups along the secondary succession in a tropical dry forest.

    Science.gov (United States)

    Paz, Horacio; Pineda-García, Fernando; Pinzón-Pérez, Luisa F

    2015-10-01

    Root growth and morphology may play a core role in species-niche partitioning in highly diverse communities, especially along gradients of drought risk, such as that created along the secondary succession of tropical dry forests. We experimentally tested whether root foraging capacity, especially at depth, decreases from early successional species to old-growth forest species. We also tested for a trade-off between two mechanisms for delaying desiccation, the capacity to forage deeper in the soil and the capacity to store water in tissues, and explored whether successional groups separate along such a trade-off. We examined the growth and morphology of roots in response to a controlled-vertical gradient of soil water, among seedlings of 23 woody species dominant along the secondary succession in a tropical dry forest of Mexico. As predicted, successional species developed deeper and longer root systems than old-growth forest species in response to soil drought. In addition, shallow root systems were associated with high plant water storage and high water content per unit of tissue in stems and roots, while deep roots exhibited the opposite traits, suggesting a trade-off between the capacities for vertical foraging and water storage. Our results suggest that an increased capacity of roots to forage deeper for water is a trait that enables successional species to establish under the warm-dry conditions of the secondary succession, while shallow roots, associated with a higher water storage capacity, are restricted to the old-growth forest. Overall, we found evidence that the root depth-water storage trade-off may constrain tree species distribution along secondary succession.

  12. Novelty and its ecological implications to dry forest functioning and conservation

    Science.gov (United States)

    Ariel Lugo; Heather. Erickson

    2017-01-01

    Tropical and subtropical dry forest life zones support forests with lower stature and species richness than do tropical and subtropical life zones with greater water availability. The number of naturalized species that can thrive and mix with native species to form novel forests in dry forest conditions in Puerto Rico and the US Virgin Islands is lower than in other...

  13. Effects of Habitat Structure, Plant Cover, and Successional Stage on the Bat Assemblage of a Tropical Dry Forest at Different Spatial Scales

    Directory of Open Access Journals (Sweden)

    Luiz A. D. Falcão

    2018-05-01

    Full Text Available Bats play a fundamental role in ecosystem functioning since they are responsible for several ecological services such as seed dispersal and pollination. Therefore, assessing the effects of habitat structure at different scales on the bat assemblage is extremely important for supporting conservation strategies. The objective of the present study was to investigate the effects of habitat structure at multiple spatial scales on the bat assemblages and their variation along a gradient of secondary succession in a Brazilian tropical dry forest. Our results suggest that bat abundance is higher in areas close to mature forests, which shows the important role of those habitats as refuges for the regional bat fauna (in a fragmented landscape and for the maintenance of ecosystem services provided by this group in tropical dry forests in a landscape context. In addition, bat abundance was lower in protected areas whose surroundings were better preserved (greater forest extension. This unexpected finding could result from an altered behavior in areas under a strong influence of a fruit crop matrix. Finally, we showed that the effects of the surroundings depend on the successional stage of the area under analysis. Late forests are more susceptible to variations in the forest cover in their surroundings, which show the higher fragility of these environments.

  14. Comparing MODIS and near-surface vegetation indexes for monitoring tropical dry forest phenology along a successional gradient using optical phenology towers

    Science.gov (United States)

    Rankine, C.; Sánchez-Azofeifa, G. A.; Guzmán, J. Antonio; Espirito-Santo, M. M.; Sharp, Iain

    2017-10-01

    Tropical dry forests (TDFs) present strong seasonal greenness signals ideal for tracking phenology and primary productivity using remote sensing techniques. The tightly synchronized relationship these ecosystems have with water availability offer a valuable natural experiment for observing the complex interactions between the atmosphere and the biosphere in the tropics. To investigate how well the MODIS vegetation indices (normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI)) represented the phenology of different successional stages of naturally regenerating TDFs, within a widely conserved forest fragment in the semi-arid southeast of Brazil, we installed several canopy towers with radiometric sensors to produce high temporal resolution near-surface vegetation greenness indices. Direct comparison of several years of ground measurements with a combined Aqua/Terra 8 day satellite product showed similar broad temporal trends, but MODIS often suffered from cloud contamination during the onset of the growing season and occasionally during the peak growing season. The strength of the in-situ and MODIS linear relationship was greater for NDVI than for EVI across sites but varied with forest stand age. Furthermore, we describe the onset dates and duration of canopy development phases for three years of in-situ monitoring. A seasonality analysis revealed significant discrepancies between tower and MODIS phenology transitions dates, with up to five weeks differences in growing season length estimation. Our results indicate that 8 and 16 day MODIS satellite vegetation monitoring products are suitable for tracking general patterns of tropical dry forest phenology in this region but are not temporally sufficient to characterize inter-annual differences in phenology phase onset dates or changes in productivity due to mid-season droughts. Such rapid transitions in canopy greenness are important indicators of climate change sensitivity of these

  15. Seasonal variability in physiological and anatomical traits contributes to invasion success of Prosopis juliflora in tropical dry forest.

    Science.gov (United States)

    Oliveira, Marciel T; Souza, Gustavo M; Pereira, Silvia; Oliveira, Deborah A S; Figueiredo-Lima, Karla V; Arruda, Emília; Santos, Mauro G

    2017-03-01

    We investigated whether there were consistent differences in the physiological and anatomical traits and phenotypic variability of an invasive (Prosopis juliflora (Sw.) DC.) and native species (Anadenanthera colubrina (Vell.) Brenan) in response to seasonality in a tropical dry forest. The water potential, organic solutes, gas exchange, enzymes of the antioxidant system, products of oxidative stress and anatomical parameters were evaluated in both species in response to seasonality. An analysis of physiological responses indicated that the invasive P. juliflora exhibited higher response in net photosynthetic rate to that of the native species between seasons. Higher values of water potential of the invasive species than those of the native species in the dry season indicate a more efficient mechanism for water regulation in the invasive species. The invasive species exhibits a thicker cuticle and trichomes, which can reduce transpiration. In combination, the increased epidermal thickness and the decreased thickness of the parenchyma in the dry season may contribute to water saving. Our data suggest a higher variability in anatomical traits in the invasive species as a response to seasonality, whereas physiological traits did not present a clear pattern of response. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Functional trait strategies of trees in dry and wet tropical forests are similar but differ in their consequences for succession.

    Science.gov (United States)

    Lohbeck, Madelon; Lebrija-Trejos, Edwin; Martínez-Ramos, Miguel; Meave, Jorge A; Poorter, Lourens; Bongers, Frans

    2014-01-01

    Global plant trait studies have revealed fundamental trade-offs in plant resource economics. We evaluated such trait trade-offs during secondary succession in two species-rich tropical ecosystems that contrast in precipitation: dry deciduous and wet evergreen forests of Mexico. Species turnover with succession in dry forest largely relates to increasing water availability and in wet forest to decreasing light availability. We hypothesized that while functional trait trade-offs are similar in the two forest systems, the successful plant strategies in these communities will be different, as contrasting filters affect species turnover. Research was carried out in 15 dry secondary forest sites (5-63 years after abandonment) and in 17 wet secondary forest sites (dry and wet forest and compare trait trade-offs. We evaluated whether multivariate plant strategies changed during succession, by calculating a 'Community-Weighted Mean' plant strategy, based on species scores on the first two PCA-axes. Trait spectra reflected two main trade-off axes that were similar for dry and wet forest species: acquisitive versus conservative species, and drought avoiding species versus evergreen species with large animal-dispersed seeds. These trait associations were consistent when accounting for evolutionary history. Successional changes in the most successful plant strategies reflected different functional trait spectra depending on the forest type. In dry forest the community changed from having drought avoiding strategies early in succession to increased abundance of evergreen strategies with larger seeds late in succession. In wet forest the community changed from species having mainly acquisitive strategies to those with more conservative strategies during succession. These strategy changes were explained by increasing water availability during dry forest succession and increasing light scarcity during wet forest succession. Although similar trait spectra were observed among dry and

  17. Controls of Soil Spatial Variability in a Dry Tropical Forest.

    Directory of Open Access Journals (Sweden)

    Sandeep Pulla

    Full Text Available We examined the roles of lithology, topography, vegetation and fire in generating local-scale (<1 km2 soil spatial variability in a seasonally dry tropical forest (SDTF in southern India. For this, we mapped soil (available nutrients, Al, total C, pH, moisture and texture in the top 10 cm, rock outcrops, topography, all native woody plants ≥1 cm diameter at breast height (DBH, and spatial variation in fire frequency (times burnt during the 17 years preceding soil sampling in a permanent 50-ha plot. Unlike classic catenas, lower elevation soils had lesser moisture, plant-available Ca, Cu, Mn, Mg, Zn, B, clay and total C. The distribution of plant-available Ca, Cu, Mn and Mg appeared to largely be determined by the whole-rock chemical composition differences between amphibolites and hornblende-biotite gneisses. Amphibolites were associated with summit positions, while gneisses dominated lower elevations, an observation that concurs with other studies in the region which suggest that hillslope-scale topography has been shaped by differential weathering of lithologies. Neither NO3(--N nor NH4(+-N was explained by the basal area of trees belonging to Fabaceae, a family associated with N-fixing species, and no long-term effects of fire on soil parameters were detected. Local-scale lithological variation is an important first-order control over soil variability at the hillslope scale in this SDTF, by both direct influence on nutrient stocks and indirect influence via control of local relief.

  18. Above Canopy Emissions of Isoprene and Monoterpenes from a Southeast Asian Tropical Forest

    Science.gov (United States)

    Baker, B.; Johnson, C.; Cai, Z.; Guenther, A.; Greenberg, J.; Bai, J.; Li, Q.

    2003-12-01

    Fluxes of isoprene were measured using the eddy covariance technique and an ozone chemiluminescence isoprene sensor above a secondary tropical forest/rubber tree plantation located in the Xishuangbanna region of southern China during the wet and dry seasons. Fluxes of monoterpenes were inferred from ambient boundary layer concentrations (wet season) and from relaxed eddy accumulation measurements (dry season). Isoprene emissions were comparable to what has been observed from other tropical forests in Africa and South America. In this forest, monoterpene emissions were much higher during the wet season due to the senescence of the rubber trees during the dry season. These flux measurements represent the first ecosystem level flux measurements reported from Southeast Asian tropical forests.

  19. Sources and sinks of diversification and conservation priorities for the Mexican tropical dry forest.

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    Judith X Becerra

    Full Text Available Elucidating the geographical history of diversification is critical for inferring where future diversification may occur and thus could be a valuable aid in determining conservation priorities. However, it has been difficult to recognize areas with a higher likelihood of promoting diversification. We reconstructed centres of origin of lineages and identified areas in the Mexican tropical dry forest that have been important centres of diversification (sources and areas where species are maintained but where diversification is less likely to occur (diversity sinks. We used a molecular phylogeny of the genus Bursera, a dominant member of the forest, along with information on current species distributions. Results indicate that vast areas of the forest have historically functioned as diversity sinks, generating few or no extant Bursera lineages. Only a few areas have functioned as major engines of diversification. Long-term preservation of biodiversity may be promoted by incorporation of such knowledge in decision-making.

  20. Diptera of Medico-Legal Importance Associated With Pig Carrion in a Tropical Dry Forest.

    Science.gov (United States)

    Vasconcelos, S D; Salgado, R L; Barbosa, T M; Souza, J R B

    2016-06-20

    The diversity of necrophagous Diptera is largely unknown in seasonally dry tropical forests, despite their medical, veterinary, and forensic relevance. We performed a study in the dry Caatinga forest exclusive to Brazil in order to assess the diversity and temporal pattern of Diptera species using pig carcasses as substrates. Adults were collected daily until complete skeletonization. We collected 17,142 adults from 18 families, 10 of which comprise species with known necrophagous habits. The most abundant families were Calliphoridae (47.3% of specimens), Sarcophagidae (20.8%), and Muscidae (15.5%), whereas Sarcophagidae stood out in terms of richness with 21 species. The native Cochliomyia macellaria (F.) (Diptera: Calliphoridae) and the invasive Chrysomya albiceps (Wiedmann) (Calliphoridae) were the dominant species. A total of 18 species reached the carcass during the first 48 h postdeath. The bloated and active decay stages had the highest richness and abundance of dipterans. From a forensic standpoint, C. macellaria and C. albiceps are likely to aid in establishing postmortem interval due to their early arrival and high abundance on the carcass. Despite harsh environmental conditions, the Caatinga harbors a rich assemblage of dipterans that play a key role in carrion decomposition. Their medico-veterinary importance is strengthened by the poor local sanitary conditions. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. The intermediate disturbance hypothesis applies to tropical forests, but disturbance contributes little to tree diversity.

    Science.gov (United States)

    Bongers, Frans; Poorter, Lourens; Hawthorne, William D; Sheil, Douglas

    2009-08-01

    The intermediate disturbance hypothesis (IDH) predicts local species diversity to be maximal at an intermediate level of disturbance. Developed to explain species maintenance and diversity patterns in species-rich ecosystems such as tropical forests, tests of IDH in tropical forest remain scarce, small-scale and contentious. We use an unprecedented large-scale dataset (2504 one-hectare plots and 331,567 trees) to examine whether IDH explains tree diversity variation within wet, moist and dry tropical forests, and we analyse the underlying mechanism by determining responses within functional species groups. We find that disturbance explains more variation in diversity of dry than wet tropical forests. Pioneer species numbers increase with disturbance, shade-tolerant species decrease and intermediate species are indifferent. While diversity indeed peaks at intermediate disturbance levels little variation is explained outside dry forests, and disturbance is less important for species richness patterns in wet tropical rain forests than previously thought.

  2. Soil carbon and nitrogen losses following deforestation in Ethiopia

    Science.gov (United States)

    Dry Afromontane forests of Ethiopia have faced vast exploitation and almost all these forests have been converted to agricultural lands. The disappearance of the forests has been most drastic during the past 100 years and has affected the functionality and stability of agroecosystem. The dynamics in...

  3. Stress tolerance and ecophysiological ability of an invader and a native species in a seasonally dry tropical forest.

    Science.gov (United States)

    Oliveira, Marciel Teixeira; Matzek, Virginia; Dias Medeiros, Camila; Rivas, Rebeca; Falcão, Hiram Marinho; Santos, Mauro Guida

    2014-01-01

    Ecophysiological traits of Prosopis juliflora (Sw.) DC. and a phylogenetically and ecologically similar native species, Anadenanthera colubrina (Vell.) Brenan, were studied to understand the invasive species' success in caatinga, a seasonally dry tropical forest ecosystem of the Brazilian Northeast. To determine if the invader exhibited a superior resource-capture or a resource-conservative strategy, we measured biophysical and biochemical parameters in both species during dry and wet months over the course of two years. The results show that P. juliflora benefits from a flexible strategy in which it frequently outperforms the native species in resource capture traits under favorable conditions (e.g., photosynthesis), while also showing better stress tolerance (e.g., antioxidant activity) and water-use efficiency in unfavorable conditions. In addition, across both seasons the invasive has the advantage over the native with higher chlorophyll/carotenoids and chlorophyll a/b ratios, percent N, and leaf protein. We conclude that Prosopis juliflora utilizes light, water and nutrients more efficiently than Anadenanthera colubrina, and suffers lower intensity oxidative stress in environments with reduced water availability and high light radiation.

  4. How to restore dry forest ecosystems

    OpenAIRE

    Nalvarte, Jaime

    2012-01-01

    AIDER is a Peruvian non-governmental organization working since 1992 on forest management activities, watershed management and urban forest management on tropical humid and dry forest at a national level. AIDER and the José Ignacio Távara Pasapera rural community have been working on dry forest management and recovery since 1992. This paper summarizes the activity of AIDER in the dry forests for the purpose of recovering degraded forest areas and conserve existing forests by developing sustai...

  5. Drought resistance in early and late secondary successional species from a tropical dry forest: the interplay between xylem resistance to embolism, sapwood water storage and leaf shedding

    Science.gov (United States)

    Fernando Pineda-Garcia; Horacio Paz; Frederick C. Meinzer

    2013-01-01

    The mechanisms of drought resistance that allow plants to successfully establish at different stages of secondary succession in tropical dry forests are not well understood. We characterized mechanisms of drought resistance in early and late-successional species and tested whether risk of drought differs across sites at different successional stages, and whether early...

  6. Functional trait strategies of trees in dry and wet tropical forests are similar but differ in their consequences for succession.

    Directory of Open Access Journals (Sweden)

    Madelon Lohbeck

    Full Text Available Global plant trait studies have revealed fundamental trade-offs in plant resource economics. We evaluated such trait trade-offs during secondary succession in two species-rich tropical ecosystems that contrast in precipitation: dry deciduous and wet evergreen forests of Mexico. Species turnover with succession in dry forest largely relates to increasing water availability and in wet forest to decreasing light availability. We hypothesized that while functional trait trade-offs are similar in the two forest systems, the successful plant strategies in these communities will be different, as contrasting filters affect species turnover. Research was carried out in 15 dry secondary forest sites (5-63 years after abandonment and in 17 wet secondary forest sites (<1-25 years after abandonment. We used 11 functional traits measured on 132 species to make species-trait PCA biplots for dry and wet forest and compare trait trade-offs. We evaluated whether multivariate plant strategies changed during succession, by calculating a 'Community-Weighted Mean' plant strategy, based on species scores on the first two PCA-axes. Trait spectra reflected two main trade-off axes that were similar for dry and wet forest species: acquisitive versus conservative species, and drought avoiding species versus evergreen species with large animal-dispersed seeds. These trait associations were consistent when accounting for evolutionary history. Successional changes in the most successful plant strategies reflected different functional trait spectra depending on the forest type. In dry forest the community changed from having drought avoiding strategies early in succession to increased abundance of evergreen strategies with larger seeds late in succession. In wet forest the community changed from species having mainly acquisitive strategies to those with more conservative strategies during succession. These strategy changes were explained by increasing water availability during

  7. Does the edge effect influence plant community structure in a tropical dry forest?

    Directory of Open Access Journals (Sweden)

    Diogo Gallo Oliveira

    2013-04-01

    Full Text Available Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.

  8. INVENTORY OF MOSQUITOES (DIPTERA: CULICIDAE IN CONSERVATION UNITS IN BRAZILIAN TROPICAL DRY FORESTS

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    Cleandson Ferreira SANTOS

    2015-06-01

    Full Text Available In Brazil, most studies of the Culicidae family are concentrated in rainforest regions. As such, there is a lack of knowledge regarding the diversity of Culicidae in regions with different climatic and vegetational characteristics. The aim of this study was to compile an inventory of Culicidae in protected areas of the semi-arid region of the state of Minas Gerais, Brazil, in order to better understand the diversity of the family within this region. The study was conducted across four protected areas in the northern region of the state, in tropical dry forest (TDF fragments. Sampling methods included Shannon trap and CDC light trap, as well as active collection. A total of 11,219 mosquito specimens were collected between August 2008 and July 2012, belonging to 11 genera and 45 species; 15 new records for the state of Minas Gerais were registered, as well as 26 new records for semi-arid regions within the state. The high number of new Culicidae records in this region demonstrates the importance of inventory studies for increasing the knowledge of culicid biodiversity in Minas Gerais, and in particular within semi-arid regions of the state.

  9. INVENTORY OF MOSQUITOES (DIPTERA: CULICIDAE) IN CONSERVATION UNITS IN BRAZILIAN TROPICAL DRY FORESTS.

    Science.gov (United States)

    Santos, Cleandson Ferreira; Silva, Alex Chavier; Rodrigues, Raquel Andrade; de Jesus, Jamilli Sanndy Ramos; Borges, Magno Augusto Zazá

    2015-01-01

    In Brazil, most studies of the Culicidae family are concentrated in rainforest regions. As such, there is a lack of knowledge regarding the diversity of Culicidae in regions with different climatic and vegetational characteristics. The aim of this study was to compile an inventory of Culicidae in protected areas of the semi-arid region of the state of Minas Gerais, Brazil, in order to better understand the diversity of the family within this region. The study was conducted across four protected areas in the northern region of the state, in tropical dry forest (TDF) fragments. Sampling methods included Shannon trap and CDC light trap, as well as active collection. A total of 11,219 mosquito specimens were collected between August 2008 and July 2012, belonging to 11 genera and 45 species; 15 new records for the state of Minas Gerais were registered, as well as 26 new records for semi-arid regions within the state. The high number of new Culicidae records in this region demonstrates the importance of inventory studies for increasing the knowledge of culicid biodiversity in Minas Gerais, and in particular within semi-arid regions of the state.

  10. Contribution á l’étude des lichens du Kivu (Zaire, du Rwanda et du Burundi. VII. Approche écogéographique de la flore et de la végétation lichéniques dans Pest de P Afrique centrale

    Directory of Open Access Journals (Sweden)

    J. Lambinon

    1983-11-01

    Full Text Available A short historical record of the lichenological exploration of tropical Africa, especially Kivu (Zaire, Rwanda and Burundi is given, including an account of the material collected and of the present state of taxonomic knowledge of the lichens. Several phytogeographical categories can be recognized in this area; they are (some with significant variants: subcosmopolitan, temperate-tropical, pantropical, paleotropical, afro-neotropical, guineo-congolian, sudano-zambezian, zambezian-afrooriental and zambezian, central African lakes endemic, afromontane and afroalpine. The distributional types of the lichens within the studied area are briefly described, as well as their importance in the main vegetation types.

  11. Ability of crassulacean acid metabolism plants to overcome interacting stresses in tropical environments.

    Science.gov (United States)

    Lüttge, Ulrich

    2010-01-01

    Single stressors such as scarcity of water and extreme temperatures dominate the struggle for life in severely dry desert ecosystems or cold polar regions and at high elevations. In contrast, stress in the tropics typically arises from a dynamic network of interacting stressors, such as availability of water, CO(2), light and nutrients, temperature and salinity. This requires more plastic spatio-temporal responsiveness and versatility in the acquisition and defence of ecological niches. The mode of photosynthesis of crassulacean acid metabolism (CAM) is described and its flexible expression endows plants with powerful strategies for both acclimation and adaptation. Thus, CAM plants are able to inhabit many diverse habitats in the tropics and are not, as commonly thought, successful predominantly in dry, high-insolation habitats. Typical tropical CAM habitats or ecosystems include exposed lava fields, rock outcrops of inselbergs, salinas, savannas, restingas, high-altitude páramos, dry forests and moist forests. Morphotypical and physiotypical plasticity of CAM phenotypes allow a wide ecophysiological amplitude of niche occupation in the tropics. Physiological and biochemical plasticity appear more responsive by having more readily reversible variations in performance than do morphological adaptations. This makes CAM plants particularly fit for the multi-factor stressor networks of tropical forests. Thus, while the physiognomy of semi-deserts outside the tropics is often determined by tall succulent CAM plants, tropical forests house many more CAM plants in terms of quantity (biomass) and quality (species diversity).

  12. Molecular phylogenetics and species delimitation of leaf-toed geckos (Phyllodactylidae: Phyllodactylus) throughout the Mexican tropical dry forest.

    Science.gov (United States)

    Blair, Christopher; Méndez de la Cruz, Fausto R; Law, Christopher; Murphy, Robert W

    2015-03-01

    Methods and approaches for accurate species delimitation continue to be a highly controversial subject in the systematics community. Inaccurate assessment of species' limits precludes accurate inference of historical evolutionary processes. Recent evidence suggests that multilocus coalescent methods show promise in delimiting species in cryptic clades. We combine multilocus sequence data with coalescence-based phylogenetics in a hypothesis-testing framework to assess species limits and elucidate the timing of diversification in leaf-toed geckos (Phyllodactylus) of Mexico's dry forests. Tropical deciduous forests (TDF) of the Neotropics are among the planet's most diverse ecosystems. However, in comparison to moist tropical forests, little is known about the mode and tempo of biotic evolution throughout this threatened biome. We find increased speciation and substantial, cryptic molecular diversity originating following the formation of Mexican TDF 30-20million years ago due to orogenesis of the Sierra Madre Occidental and Mexican Volcanic Belt. Phylogenetic results suggest that the Mexican Volcanic Belt, the Rio Fuerte, and Isthmus of Tehuantepec may be important biogeographic barriers. Single- and multilocus coalescent analyses suggest that nearly every sampling locality may be a distinct species. These results suggest unprecedented levels of diversity, a complex evolutionary history, and that the formation and expansion of TDF vegetation in the Miocene may have influenced subsequent cladogenesis of leaf-toed geckos throughout western Mexico. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. A Preliminary Assessment of Ethiopian Sacred Grove Status at the Landscape and Ecosystem Scales.

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    Alemaheyu Wassie Eshete

    2013-04-01

    Full Text Available The northern Ethiopian landscape is dotted with small patches of church forests that are religious centers for the Ethiopian Orthodox Tewahido Church (EOTC. These sacred groves are what remain of the once vast tropical Afromontane dry forest. Herein we review the landscape pattern of sacred groves in the Amhara region of Ethiopia, and their local scale nutrient status at two sites, Zahara and Debresena. A total of 1,488 sacred groves were inventoried within the study area, yielding an overall density of one sacred grove for every twenty square kilometers. Sacred groves averaged a little over five hectares and were separated from one another by more than two kilometers. At the local scale we found that soil carbon and nitrogen stocks have decreased significantly between the forest interior and the clearing indicating decreased soil fertility. Together our data indicate that these sacred groves are vulnerable to loss because of their small average size, isolation from seed sources, and decreasing soil status.

  14. Geomorphological evidence of warm-humid and cold-dry glaciations in the dry western Cordillera of the tropical Peruvian Andes

    Science.gov (United States)

    Mächtle, B.; Hein, A. S.; Dunai, T.; Eitel, B.

    2012-04-01

    The western Cordillera of the Andes (14°30'S, 74°W) is characterized by high altitudes, strong radiation and semi-arid conditions. Therefore, glacial processes and resulting landforms differ markedly from these of the outer-tropics. However, under sub-arctic conditions similar glacial landforms occur. This congruence can be explained by comparable environmental conditions, which determine the dynamics of ice flow, glacial erosion, debris production as well as moraine deposition. Outside the higher latitudes, typical sub-arctic glacial landforms as controlled moraines and trimline moraines (Evans 2009, Ó Cofaigh et al. 2005) remained undescribed until now. These landforms result from polythermal or cold-basal ice flow, respectively, which is typical for polar conditions. Beside this, we also found steep lateral moraines, which give evidence of increased ice thickness, debris production and deposition and warm-basal ice flow, which is conceivable only for alpine-type valley glaciers. Striations of the bedrock give evidence of accompanied basal erosion. Coexisting trimline moraines and steep lateral moraines rule out the influence of topography on ice thickness and the resulting thermal regime. Therefore, we match the different moraine types to changes in ice thickness, which was controlled by considerable precipitation changes during the last glaciation. An erroneous classification of the observed boulder associations as trimline moraine due to selective erosion after deposition can be excluded due to general arid conditions, slow weathering and the chronological proximity of only a few millennia between both landforms, determined from cosmogenic nuclides. Therefore, the occurrence of different thermal regimes gives evidence of considerable changes in precipitation during the last glaciation - but furthermore requires an associated change in the thermal conditions to explain the very close spatial position of both ice margins. Changes in ice volume must have

  15. Seed rain dynamics following disturbance exclusion in a secondary tropical dry forest in Morelos, Mexico.

    Science.gov (United States)

    Ceccon, Eliane; Hernández, Patricia

    2009-01-01

    In most of the legally protected areas in Mexico local inhabitants use natural resources, such as fire wood or cattle grazing. These frequent but low-intensity disturbances have consequences at various levels of the tropical ecosystems and strongly impact forest structure and its regeneration capacity. Despite their importance, the effects of these perturbations in many aspects of tropical forest ecology and in the forest's capacity to recover after disturbance exclusion remain poorly understood. Understanding the impact of these processes on tropical forests is necessary for rehabilitating these forests and enhancing their productivity. In this study, we evaluate the impact of twelve years of exclusion (E) of cattle grazing and fire wood extraction in the composition and dynamics of seed rain, and compare this assessment to a similar analysis in an area where these perturbations continued (without exclusion, WE). We found a strong seasonality in seed rain (96% of seeds fell in the dry season) in both areas. There were no significant differences between E and WE sites in relation to overall seed density, species richness and diversity. However, the distribution along the year of seed species density was significantly different among the E and WE sites. The Jaccard's similarity index between E and WE sites was relatively low (0.57). Barochory was the most common dispersal mode observed among the 23 species in terms of seed species density (48%), followed by anemochory (39%) and zoochory (13%). In relation to seed density, anemochory was the most frequent dispersal mode (88%). Most species in the zone were categorized as small seeds (92%), and there were no significant differences in the distribution of seed size between E and WE. The spatial pattern of dispersal of the four species with the highest relative importance value index, in both areas, was aggregated. Twelve years of disturbance exclusion were not enough to fully restore the seed rain of the area; some

  16. Seasonal Precipitation Variability Effects on Carbon Exchange in a Tropical Dry Forest of Northwest Mexico

    Science.gov (United States)

    Verduzco, V.; Garatuza-Payan, J.; Yépez, E. A.; Watts, C. J.; Rodriguez, J. C.; Robles-Morua, A.; Vivoni, E. R.

    2015-12-01

    The Tropical Dry Forest (TDF) cover a large area in tropical and subtropical regions in the Americas and its productivity is thought to have an important contribution to the atmospheric carbon fluxes. However, due to this ecosystem complex dynamics, our understanding about the mechanisms controlling net ecosystem exchange is limited. In this study, five years of continue water and carbon fluxes measurements from eddy covariance complemented with remotely sensed vegetation greenness were used to investigate the ecosystem carbon balance of a TDF in the North American Monsoon region under different hydro climatic conditions. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer a predominant heterotrophic control owed to high decomposition of accumulated labile soil organic matter from prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production over the year, but can be overwhelmed by the strength of the primary productivity during the monsoon season. Precipitation characteristics during the monsoon have significant controls on sustaining carbon fixation in the TDF ecosystem into the fall season. A threshold of ~350 to 400 mm of summer precipitation was identify to switch the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This research points at the needs for understanding the potential effects of changing seasonal precipitation patterns on ecosystem dynamics and carbon sequestration in subtropical regions.

  17. Plant diversity patterns in neotropical dry forests and their conservation implications.

    Science.gov (United States)

    Banda-R, Karina; Delgado-Salinas, Alfonso; Dexter, Kyle G; Linares-Palomino, Reynaldo; Oliveira-Filho, Ary; Prado, Darién; Pullan, Martin; Quintana, Catalina; Riina, Ricarda; Rodríguez M, Gina M; Weintritt, Julia; Acevedo-Rodríguez, Pedro; Adarve, Juan; Álvarez, Esteban; Aranguren B, Anairamiz; Arteaga, Julián Camilo; Aymard, Gerardo; Castaño, Alejandro; Ceballos-Mago, Natalia; Cogollo, Álvaro; Cuadros, Hermes; Delgado, Freddy; Devia, Wilson; Dueñas, Hilda; Fajardo, Laurie; Fernández, Ángel; Fernández, Miller Ángel; Franklin, Janet; Freid, Ethan H; Galetti, Luciano A; Gonto, Reina; González-M, Roy; Graveson, Roger; Helmer, Eileen H; Idárraga, Álvaro; López, René; Marcano-Vega, Humfredo; Martínez, Olga G; Maturo, Hernán M; McDonald, Morag; McLaren, Kurt; Melo, Omar; Mijares, Francisco; Mogni, Virginia; Molina, Diego; Moreno, Natalia Del Pilar; Nassar, Jafet M; Neves, Danilo M; Oakley, Luis J; Oatham, Michael; Olvera-Luna, Alma Rosa; Pezzini, Flávia F; Dominguez, Orlando Joel Reyes; Ríos, María Elvira; Rivera, Orlando; Rodríguez, Nelly; Rojas, Alicia; Särkinen, Tiina; Sánchez, Roberto; Smith, Melvin; Vargas, Carlos; Villanueva, Boris; Pennington, R Toby

    2016-09-23

    Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextualize the floristic significance of their dry forest at a regional and continental scale. Copyright © 2016, American Association for the Advancement of Science.

  18. Temperature and rainfall strongly drive temporal growth variation in Asian tropical forest trees.

    Science.gov (United States)

    Vlam, Mart; Baker, Patrick J; Bunyavejchewin, Sarayudh; Zuidema, Pieter A

    2014-04-01

    Climate change effects on growth rates of tropical trees may lead to alterations in carbon cycling of carbon-rich tropical forests. However, climate sensitivity of broad-leaved lowland tropical trees is poorly understood. Dendrochronology (tree-ring analysis) provides a powerful tool to study the relationship between tropical tree growth and annual climate variability. We aimed to establish climate-growth relationships for five annual-ring forming tree species, using ring-width data from 459 canopy and understory trees from a seasonal tropical forest in western Thailand. Based on 183/459 trees, chronologies with total lengths between 29 and 62 years were produced for four out of five species. Bootstrapped correlation analysis revealed that climate-growth responses were similar among these four species. Growth was significantly negatively correlated with current-year maximum and minimum temperatures, and positively correlated with dry-season precipitation levels. Negative correlations between growth and temperature may be attributed to a positive relationship between temperature and autotrophic respiration rates. The positive relationship between growth and dry-season precipitation levels likely reflects the strong water demand during leaf flush. Mixed-effect models yielded results that were consistent across species: a negative effect of current wet-season maximum temperatures on growth, but also additive positive effects of, for example, prior dry-season maximum temperatures. Our analyses showed that annual growth variability in tropical trees is determined by a combination of both temperature and precipitation variability. With rising temperature, the predominantly negative relationship between temperature and growth may imply decreasing growth rates of tropical trees as a result of global warming.

  19. Chemical composition of the fruit of two species of tropical dry forest in the coastal region of Ecuador as food source for ruminants

    Directory of Open Access Journals (Sweden)

    Henrry Othón Intriago Mendoza

    2015-04-01

    Full Text Available Fodder species of trees in the coastal region of Manabí are an alternative food to cattle, especia-lly between the months of september and december when the pasture gets scarce. To evaluate their nutritional potential was made a compositional analysis of nutritional parameters to the fruits of Prosopis juliflora (Sw. DC. (Algarrobo and Guazuma ulmifolia Lam. (Guasmo. Botanical characters of these trees and compositional analysis results are described. Furthermore, a comparison of these results with those obtained by other authors by con-sidering the values of protein, fat, fiber, ash and moisture is performed. For the environmental conditions of tropical dry forest, the guasmo presents higher contents of protein, fat, ash and fiber carob, although both species are important in the diet of herbivores, especially in dry seasons as providers of usable nutrients favoring animal nutrition

  20. Observed and simulated precipitation responses in wet and dry regions 1850–2100

    International Nuclear Information System (INIS)

    Liu Chunlei; Allan, Richard P

    2013-01-01

    Global warming is expected to enhance fluxes of fresh water between the surface and atmosphere, causing wet regions to become wetter and dry regions drier, with serious implications for water resource management. Defining the wet and dry regions as the upper 30% and lower 70% of the precipitation totals across the tropics (30° S–30° N) each month we combine observations and climate model simulations to understand changes in the wet and dry regions over the period 1850–2100. Observed decreases in precipitation over dry tropical land (1950–2010) are also simulated by coupled atmosphere–ocean climate models (−0.3%/decade) with trends projected to continue into the 21st century. Discrepancies between observations and simulations over wet land regions since 1950 exist, relating to decadal fluctuations in El Niño southern oscillation, the timing of which is not represented by the coupled simulations. When atmosphere-only simulations are instead driven by observed sea surface temperature they are able to adequately represent this variability over land. Global distributions of precipitation trends are dominated by spatial changes in atmospheric circulation. However, the tendency for already wet regions to become wetter (precipitation increases with warming by 3% K −1 over wet tropical oceans) and the driest regions drier (precipitation decreases of −2% K −1 over dry tropical land regions) emerges over the 21st century in response to the substantial surface warming. (letter)

  1. Changes in composition and structure of a tropical dry forest following intermittent Cattle grazing

    Directory of Open Access Journals (Sweden)

    Margaret Stern

    2002-12-01

    Full Text Available In northwestern Costa Rica, cattle are being used as a "management tool" to reduce the amount of combustible material, mainly dominated by Hyparrhenia rufa, an African grass. This project is being developed within Parque Nacional Palo Verde and Reserva Biológica Lomas Barbudal, both of which fonn part of the only remaining tropical dry forests in Mesoamerica. To determine the short-term effects of cattle grazing on the natural vegetation, we compared the floristic composition within Palo Verde in an area under intermittent cattle grazing with an area that has not been grazed. There were significantly fewer plant species in the area with intermittent cattle grazing compared to the area with no grazing. Floristic composition of these two habitats was different as reflected by both Fisher's alpha values and the Shannon index of diversity, both of which were significantly higher in the ungrazed site. The ungrazed area contained more plant species and was more similar to mature forest. The structure of the vegetation was significantly different between the intermittently grazed and ungrazed sites with more small stems (1-5 cm dbh and fewer large stems (>5 cm dbh in the intermittently grazed habitat. These results indicate that cattle grazing has an impact on the dry forest by reducing the relative abundance and density of larger tree species and by changing the species composition and structure of the community. The current management plan implemented in Palo Verde and Lomas Barbudal is not appropriate because of the impact that cattle have on the structure of the natural vegetation and should not be considered a viable alternative in other protected areas of dry forest in the Neotropics. We suggest that alternative fire prevention measures be evaluated including hand-cutting H. rufa, the creation of more frequent and larger fire breaks, and the development of green breaks.En el noroeste de Costa Rica se utiliza ganado como una "herramienta de

  2. Land application of mine water causes minimal uranium loss offsite in the wet-dry tropics: Ranger Uranium Mine, Northern Territory, Australia.

    Science.gov (United States)

    Mumtaz, Saqib; Streten, Claire; Parry, David L; McGuinness, Keith A; Lu, Ping; Gibb, Karen S

    2015-11-01

    Ranger Uranium Mine (RUM) is situated in the wet-dry tropics of Northern Australia. Land application (irrigation) of stockpile (ore and waste) runoff water to natural woodland on the mine lease is a key part of water management at the mine. Consequently, the soil in these Land Application Areas (LAAs) presents a range of uranium (U) and other metals concentrations. Knowledge of seasonal and temporal changes in soil U and physicochemical parameters at RUM LAAs is important to develop suitable management and rehabilitation strategies. Therefore, soil samples were collected from low, medium, high and very high U sites at RUM LAAs for two consecutive years and the effect of time and season on soil physicochemical parameters particularly U and other major solutes applied in irrigation water was measured. Concentrations of some of the solutes applied in the irrigation water such as sulphur (S), iron (Fe) and calcium (Ca) showed significant seasonal and temporal changes. Soil S, Fe and Ca concentration decreased from year 1 to year 2 and from dry to wet seasons during both years. Soil U followed the same pattern except that we recorded an increase in soil U concentrations at most of the RUM LAAs after year 2 wet season compared to year 2 dry season. Thus, these sites did not show a considerable decrease in soil U concentration from year 1 to year 2. Sites which contained elevated U after wet season 2 also had higher moisture content which suggests that pooling of U containing rainwater at these sites may be responsible for elevated U. Thus, U may be redistributed within RUM LAAs due to surface water movement. The study also suggested that a decrease in U concentrations in LAA soils at very high U (>900 mg kg(-1)) sites is most likely due to transport of particulate matter bound U by surface runoff and U may not be lost from the surface soil due to vertical movement through the soil profile. Uranium attached to particulate matter may reduce its potential for environmental

  3. Understanding spatial heterogeneity in soil carbon and nitrogen cycling in regenerating tropical dry forests

    Science.gov (United States)

    Waring, B. G.; Powers, J. S.; Branco, S.; Adams, R.; Schilling, E.

    2015-12-01

    Tropical dry forests (TDFs) currently store significant amounts of carbon in their biomass and soils, but these highly seasonal ecosystems may be uniquely sensitive to altered climates. The ability to quantitatively predict C cycling in TDFs under global change is constrained by tremendous spatial heterogeneity in soil parent material, land-use history, and plant community composition. To explore this variation, we examined soil carbon and nitrogen dynamics in 18 permanent plots spanning orthogonal gradients of stand age and soil fertility. Soil C and N pools, microbial biomass, and microbial extracellular enzyme activities were most variable at small (m2) spatial scales. However, the ratio of organic vs. inorganic N cycling was consistently higher in forest stands dominated by slow-growing, evergreen trees that associate with ectomycorrhizal fungi. Similarly, although bulk litter stocks and turnover rates varied greatly among plots, litter decomposition tended to be slower in ectomycorrhizae-dominated stands. Soil N cycling tended to be more conservative in older plots, although the relationship between stand age and element cycling was weak. Our results emphasize that microscale processes, particularly interactions between mycorrhizal fungi and free-living decomposers, are important controls on ecosystem-scale element cycling.

  4. Tropical Hydroclimate Change during Heinrich Stadial 1: An Integrative Proxy-Model Synthesis

    Science.gov (United States)

    Lawman, A. E.; Sun, T.; Shanahan, T. M.; Di Nezio, P. N.; Gomez, K.; Piatrunia, N.; Sun, C.; Wu, X.; Kageyama, M.; Merkel, U.; Otto-Bliesner, B. L.; Abe-Ouchi, A.; Lohmann, G.; Singarayer, J. S.

    2017-12-01

    We explore the response of tropical climate to abrupt cooling of the North Atlantic (NA) during Heinrich Stadial 1 (HS1) combining paleoclimate proxies with model simulations. A total of 146 published paleoclimate records from tropical locations are used to categorize whether HS1 was wetter, drier, or unchanged relative to a deglacial baseline state. Only records with sufficient resolution to resolve HS1 and sufficient length to characterize the deglacial trend are considered. This synthesis reveals large-scale patterns of hydroclimate change relative to glacial conditions, confirming previously reported weaker Indian summer monsoon, a wetter southern Africa, and drying over the Caribbean. Our synthesis also reveals large-scale drying over the Maritime continent as well as wetter conditions in northern Australia and southern tropical South America. Our reinterpretation of the available proxy data reveals far more complexity and uncertainties for equatorial East Africa, a region that appears to straddle a pattern of dryer conditions to the north and wetter conditions to the south. Overall, these patterns of hydroclimate change depart from a southward shift of the Inter Tropical Convergence Zone (ITCZ), particularly outside the tropical Atlantic. We explore mechanisms driving these changes using a multi-model ensemble of "hosing" simulations performed relative to glacial conditions. The models show robust weakening of the Afro-Asian Monsoon, which we attribute to ventilation of colder mid-latitude air. Not all models simulate the remaining patterns inferred from the proxy data. The best-agreeing models indicate that cooling over the tropical NA and the Caribbean may be essential to communicate the response to the global tropics. This response can induce warming over the tropical South Atlantic via the wind-evaporation-SST feedback, driving wetter conditions in South Africa and tropical South America. Cooling over the Caribbean is communicated to the Pacific over the

  5. Botanical and ecological basis for the resilience of Antillean dry forests

    Science.gov (United States)

    A.E. Lugo; E. Medina; J. Carlos Trejo Torres; E. Helmer

    2006-01-01

    Dry forest environments limit the number of species that can survive there. Antillean dry forests have low floristic diversity and stature, high density of small and medium-sized trees, and are among the least conserved of the tropical forests. Their canopies are smooth with no emergent trees and have high species dominance. Antillean dry forests occur mostly on...

  6. Tropical dry forest status and relative importance of woody flora, islands of Old Providence and Santa Catalina, Colombia, Southwestern Caribbean

    International Nuclear Information System (INIS)

    Linares, Jorge Ruiz; Fandino Orozco, Maria Claudia

    2009-01-01

    The purpose of this paper is to present evidence on the condition of the Dry Tropical Forest (DtF) in Old Providence. A chronological study was carried out in order to assess the land cover change in DtF between 1944 and 2005. Additionally, we established 109 plots 2 x 50 m, following the protocol by Gentry (1982); and species abundance models were fitted to the data. It is concluded that up to 2000 the forest recovered, yet, in 2005 it retreated to 1990 levels. The lognormal distribution suggests that the forest is indeed in good condition. Anacardiaceae is the family with the highest Importance Value Index (IVI) while Acacia collinsii is the species with the highest IVI.

  7. Phytogeography and conservation of neotropical dry forest with emphasis on Columbia

    OpenAIRE

    Banda Rodriguez, Karina Paola

    2017-01-01

    Dry forest is one of the most threatened tropical forests in the world. Human impact has caused its massive transformation but conservation of dry forest has often been neglected across Latin America. In Colombia, less than 10% of the original extension of dry forest remains. This thesis studies the phytogeography of neotropical dry forest and its relevance for conservation using data from 1602 tree species inventories made in dry forests across Latin America and the Caribbean ...

  8. Tropical Indian Ocean Variability Driving Southeast Australian Droughts

    Science.gov (United States)

    Ummenhofer, C. C.; England, M. H.; McIntosh, P. C.; Meyers, G. A.; Pook, M. J.; Risbey, J. S.; Sen Gupta, A.; Taschetto, A. S.

    2009-04-01

    Variability in the tropical Indian Ocean has widespread effects on rainfall in surrounding countries, including East Africa, India and Indonesia. The leading mode of tropical Indian Ocean variability, the Indian Ocean Dipole (IOD), is a coupled ocean-atmosphere mode characterized by sea surface temperature (SST) anomalies of opposite sign in the east and west of the basin with an associated large-scale atmospheric re-organisation. Earlier work has often focused on the positive phase of the IOD. However, we show here that the negative IOD phase is an important driver of regional rainfall variability and multi-year droughts. For southeastern Australia, we show that it is actually a lack of the negative IOD phase, rather than the positive IOD phase or Pacific variability, that provides the most robust explanation for recent drought conditions. Since 1995, a large region of Australia has been gripped by the most severe drought in living memory, the so-called "Big Dry". The ramifications for affected regions are dire, with acute water shortages for rural and metropolitan areas, record agricultural losses, the drying-out of two of Australia's major river systems and far-reaching ecosystem damage. Yet the drought's origins have remained elusive. For Southeast Australia, we show that the "Big Dry" and other iconic 20th Century droughts, including the Federation Drought (1895-1902) and World War II drought (1937-1945), are driven by tropical Indian Ocean variability, not Pacific Ocean conditions as traditionally assumed. Specifically, a conspicuous absence of characteristic Indian Ocean temperature conditions that are conducive to enhanced tropical moisture transport has deprived southeastern Australia of its normal rainfall quota. In the case of the "Big Dry", its unprecedented intensity is also related to recent above-average temperatures. Implications of recent non-uniform warming trends in the Indian Ocean and how that might affect ocean characteristics and climate in

  9. New recommendations for building in tropical climates

    Energy Technology Data Exchange (ETDEWEB)

    Waal, H.B. de (ISOVER BV, Cappelle a/d IJssel (Netherlands))

    1993-07-01

    Traditional recommendations for building a thermally efficient or comfortable building in a tropical climate are briefly summarized. They suffer from three main drawbacks; they are not quantitative, partly incorrect and only for two climates; the hot dry and the warm humid. A new climate classification, made up of forty tropical climates is presented. Eight building elements, which affect the thermal system of a building, are distinguished. The method by which the new recommendations are derived, is discussed. The new recommendations are briefly presented. (Author)

  10. Diversified Native Species Restoration for Recovery of Multiple Ecosystem Services in a Highly Disturbed Tropical Dry Forest Landscape of Southwestern Nicaragua

    Science.gov (United States)

    Williams-Guillen, K.; Otterstrom, S.; Perla, C.

    2015-12-01

    Tropical dry forests have been reduced to a fraction of their original extent in the Neotropics due to conversion to agriculture and cattle pasture. While TDF can recover via natural regeneration, resulting forests are dominated by wind-dispersed pioneer species of limited value for frugivorous wildlife. Additionally, passive restoration can be perceived as "abandonment" resulting in neighbors casually invading property to rear livestock and extract timber. In 2007, the NGO Paso Pacífico initiated restoration in a highly degraded tropical dry forest landscape of southwestern Nicaragua; funded by an ex-ante carbon purchase, the project was designed to integrate multiple native tree species known to provide resources used by local wildlife. We restored roughly 400 hectares spanning a rainfall gradient from dry to transitional moist forest, using reforestation (planting 70 species of tree seedlings in degraded pastures on a 4x4 m grid, leaving occurring saplings) and assisted regeneration (clearing vines and competing vegetation from saplings in natural regeneration and strategically managing canopy cover). In just over seven years, mean carbon increased nearly threefold, from to 21.5±5.0 to 57.9±9.6 SE tonnes/ha. Current carbon stocks match those of 20-year-old forests in the area, accumulated in less than a decade. Stem density per 15-m radius plot decreased from 16.3±2.3 to 12.5±0.9 SE, while species richness increased from 3.9±0.4 to 18.4±1.4 SE. Alpha richness of woody stems across plots increased from 36 to 94 species, and over 20 tree species established as a result of natural dispersal and recruitment. We have observed sensitive species such as spider monkeys and parrots foraging in restoration areas. Managed reforestation is a highly effective method for rapidly restoring the functionality of multiple ecosystem services in degraded TDF, particularly when social and political realities force restoration to coexist with human productive activities

  11. The Microclimate of a Tropical Evergreen Forest.

    Science.gov (United States)

    1980-08-01

    of Human Bioclimate - A Review. World Meteorological Organization Bulletin, Geneva, 56 pp. REFERENCES (con’t) Lee, R., 1978. Forest Micrometeorology...Geophysics, and Bioclimatology , Ser. B 24, 243-251. Pinker, R. (1980): The Microclimate of a dry tropical forest. (Accepted for publication in

  12. Asynchronous response of tropical forest leaf phenology to seasonal and el Niño-driven drought.

    Directory of Open Access Journals (Sweden)

    Stephanie Pau

    2010-06-01

    Full Text Available The Hawaiian Islands are an ideal location to study the response of tropical forests to climate variability because of their extreme isolation in the middle of the Pacific, which makes them especially sensitive to El Niño-Southern Oscillation (ENSO. Most research examining the response of tropical forests to drought or El Niño have focused on rainforests, however, tropical dry forests cover a large area of the tropics and may respond very differently than rainforests. We use satellite-derived Normalized Difference Vegetation Index (NDVI from February 2000-February 2009 to show that rainforests and dry forests in the Hawaiian Islands exhibit asynchronous responses in leaf phenology to seasonal and El Niño-driven drought. Dry forest NDVI was more tightly coupled with precipitation compared to rainforest NDVI. Rainforest cloud frequency was negatively correlated with the degree of asynchronicity (Delta(NDVI between forest types, most strongly at a 1-month lag. Rainforest green-up and dry forest brown-down was particularly apparent during the 2002-003 El Niño. The spatial pattern of NDVI response to the NINO 3.4 Sea Surface Temperature (SST index during 2002-2003 showed that the leeward side exhibited significant negative correlations to increased SSTs, whereas the windward side exhibited significant positive correlations to increased SSTs, most evident at an 8 to 9-month lag. This study demonstrates that different tropical forest types exhibit asynchronous responses to seasonal and El Niño-driven drought, and suggests that mechanisms controlling dry forest leaf phenology are related to water-limitation, whereas rainforests are more light-limited.

  13. Land application of mine water causes minimal uranium loss offsite in the wet-dry tropics: Ranger Uranium Mine, Northern Territory, Australia

    International Nuclear Information System (INIS)

    Mumtaz, Saqib; Streten, Claire; Parry, David L.; McGuinness, Keith A.; Lu, Ping; Gibb, Karen S.

    2015-01-01

    Ranger Uranium Mine (RUM) is situated in the wet-dry tropics of Northern Australia. Land application (irrigation) of stockpile (ore and waste) runoff water to natural woodland on the mine lease is a key part of water management at the mine. Consequently, the soil in these Land Application Areas (LAAs) presents a range of uranium (U) and other metals concentrations. Knowledge of seasonal and temporal changes in soil U and physicochemical parameters at RUM LAAs is important to develop suitable management and rehabilitation strategies. Therefore, soil samples were collected from low, medium, high and very high U sites at RUM LAAs for two consecutive years and the effect of time and season on soil physicochemical parameters particularly U and other major solutes applied in irrigation water was measured. Concentrations of some of the solutes applied in the irrigation water such as sulphur (S), iron (Fe) and calcium (Ca) showed significant seasonal and temporal changes. Soil S, Fe and Ca concentration decreased from year 1 to year 2 and from dry to wet seasons during both years. Soil U followed the same pattern except that we recorded an increase in soil U concentrations at most of the RUM LAAs after year 2 wet season compared to year 2 dry season. Thus, these sites did not show a considerable decrease in soil U concentration from year 1 to year 2. Sites which contained elevated U after wet season 2 also had higher moisture content which suggests that pooling of U containing rainwater at these sites may be responsible for elevated U. Thus, U may be redistributed within RUM LAAs due to surface water movement. The study also suggested that a decrease in U concentrations in LAA soils at very high U (>900 mg kg"−"1) sites is most likely due to transport of particulate matter bound U by surface runoff and U may not be lost from the surface soil due to vertical movement through the soil profile. Uranium attached to particulate matter may reduce its potential for

  14. Identifying tropical dry forests extent and succession via the use of machine learning techniques

    Science.gov (United States)

    Li, Wei; Cao, Sen; Campos-Vargas, Carlos; Sanchez-Azofeifa, Arturo

    2017-12-01

    Information on ecosystem services as a function of the successional stage for secondary tropical dry forests (TDFs) is scarce and limited. Secondary TDFs succession is defined as regrowth following a complete forest clearance for cattle growth or agriculture activities. In the context of large conservation initiatives, the identification of the extent, structure and composition of secondary TDFs can serve as key elements to estimate the effectiveness of such activities. As such, in this study we evaluate the use of a Hyperspectral MAPper (HyMap) dataset and a waveform LIDAR dataset for characterization of different levels of intra-secondary forests stages at the Santa Rosa National Park (SRNP) Environmental Monitoring Super Site located in Costa Rica. Specifically, a multi-task learning based machine learning classifier (MLC-MTL) is employed on the first shortwave infrared (SWIR1) of HyMap in order to identify the variability of aboveground biomass of secondary TDFs along a successional gradient. Our paper recognizes that the process of ecological succession is not deterministic but a combination of transitional forests types along a stochastic path that depends on ecological, edaphic, land use, and micro-meteorological conditions, and our results provide a new way to obtain the spatial distribution of three main types of TDFs successional stages.

  15. Flowering phenology, growth forms, and pollination syndromes in tropical dry forest species: Influence of phylogeny and abiotic factors.

    Science.gov (United States)

    Cortés-Flores, Jorge; Hernández-Esquivel, Karen Beatriz; González-Rodríguez, Antonio; Ibarra-Manríquez, Guillermo

    2017-01-01

    Analyses of the influence of temporal variation in abiotic factors on flowering phenology of tropical dry forest species have not considered the possible response of species with different growth forms and pollination syndromes, while controlling for phylogenetic relationships among species. Here, we investigated the relationship between flowering phenology, abiotic factors, and plant functional attributes, while controlling for phylogenetic relationship among species, in a dry forest community in Mexico. We characterized flowering phenology (time and duration) and pollination syndromes of 55 tree species, 49 herbs, 24 shrubs, 15 lianas, and 11 vines. We tested the influence of pollination syndrome, growth form, and abiotic factors on flowering phenology using phylogenetic generalized least squares. We found a relationship between flowering duration and time. Growth form was related to flowering time, and the pollination syndrome had a more significant relationship with flowering duration. Flowering time variation in the community was explained mainly by abiotic variables, without an important phylogenetic effect. Flowering time in lianas and trees was negatively and positively correlated with daylength, respectively. Functional attributes, environmental cues, and phylogeny interact with each other to shape the diversity of flowering patterns. Phenological differentiation among species groups revealed multiples strategies associated with growth form and pollination syndromes that can be important for understanding species coexistence in this highly diverse plant community. © 2017 Botanical Society of America.

  16. Spatial and temporal distribution of tropical biomass burning

    Science.gov (United States)

    Hao, Wei Min; Liu, Mei-Huey

    1994-12-01

    A database for the spatial and temporal distribution of the amount of biomass burned in tropical America, Africa, and Asia during the late 1970s is presented with a resolution of 5° latitude × 5° longitude. The sources of burning in each grid cell have been quantified. Savanna fires, shifting cultivation, deforestation, fuel wood use, and burning of agricultural residues contribute about 50, 24, 10, 11, and 5%, respectively, of total biomass burned in the tropics. Savanna fires dominate in tropical Africa, and forest fires dominate in tropical Asia. A similar amount of biomass is burned from forest and savanna fires in tropical America. The distribution of biomass burned monthly during the dry season has been derived for each grid cell using the seasonal cycles of surface ozone concentrations. Land use changes during the last decade could have a profound impact on the amount of biomass burned and the amount of trace gases and aerosol particles emitted.

  17. Organismal responses to habitat change: herbivore performance, climate and leaf traits in regenerating tropical dry forests.

    Science.gov (United States)

    Agosta, Salvatore J; Hulshof, Catherine M; Staats, Ethan G

    2017-05-01

    The ecological effects of large-scale climate change have received much attention, but the effects of the more acute form of climate change that results from local habitat alteration have been less explored. When forest is fragmented, cut, thinned, cleared or otherwise altered in structure, local climates and microclimates change. Such changes can affect herbivores both directly (e.g. through changes in body temperature) and indirectly (e.g. through changes in host plant traits). We advance an eco-physiological framework to understand the effects of changing forests on herbivorous insects. We hypothesize that if tropical forest caterpillars are climate and resource specialists, then they should have reduced performance outside of mature forest conditions. We tested this hypothesis with a field experiment contrasting the performance of Rothschildia lebeau (Saturniidae) caterpillars feeding on the host plant Casearia nitida (Salicaceae) in two different aged and structured tropical dry forests in Area de Conservación Guanacaste, Costa Rica. Compared to more mature closed-canopy forest, in younger secondary forest we found that: (1) ambient conditions were hotter, drier and more variable; (2) caterpillar growth and development were reduced; and (3) leaves were tougher, thicker and drier. Furthermore, caterpillar growth and survival were negatively correlated with these leaf traits, suggesting indirect host-mediated effects of climate on herbivores. Based on the available evidence, and relative to mature forest, we conclude that reduced herbivore performance in young secondary forest could have been driven by changes in climate, leaf traits (which were likely climate induced) or both. However, additional studies will be needed to provide more direct evidence of cause-and-effect and to disentangle the relative influence of these factors on herbivore performance in this system. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

  18. No evidence that elevated CO2 gives tropical lianas an advantage over tropical trees.

    Science.gov (United States)

    Marvin, David C; Winter, Klaus; Burnham, Robyn J; Schnitzer, Stefan A

    2015-05-01

    Recent studies indicate that lianas are increasing in size and abundance relative to trees in neotropical forests. As a result, forest dynamics and carbon balance may be altered through liana-induced suppression of tree growth and increases in tree mortality. Increasing atmospheric CO2 is hypothesized to be responsible for the increase in neotropical lianas, yet no study has directly compared the relative response of tropical lianas and trees to elevated CO2 . We explicitly tested whether tropical lianas had a larger response to elevated CO2 than co-occurring tropical trees and whether seasonal drought alters the response of either growth form. In two experiments conducted in central Panama, one spanning both wet and dry seasons and one restricted to the dry season, we grew liana (n = 12) and tree (n = 10) species in open-top growth chambers maintained at ambient or twice-ambient CO2 levels. Seedlings of eight individuals (four lianas, four trees) were grown in the ground in each chamber for at least 3 months during each season. We found that both liana and tree seedlings had a significant and positive response to elevated CO2 (in biomass, leaf area, leaf mass per area, and photosynthesis), but that the relative response to elevated CO2 for all variables was not significantly greater for lianas than trees regardless of the season. The lack of differences in the relative response between growth forms does not support the hypothesis that elevated CO2 is responsible for increasing liana size and abundance across the neotropics. © 2014 John Wiley & Sons Ltd.

  19. Cultural significance of the flora of a tropical dry forest in the Doche vereda (Villavieja, Huila, Colombia).

    Science.gov (United States)

    Rosero-Toro, Jeison Herley; Romero-Duque, Luz Piedad; Santos-Fita, Dídac; Ruan-Soto, Felipe

    2018-03-22

    In Colombia, ethnobotanical studies regarding plant cultural significance (CS) in tropical dry forests are scarce and mainly focused on the Caribbean region. Different authors have indicated that the plants with the most uses are those of greater cultural importance. Additionally, gender differences in knowledge and interest in natural resources has been widely recorded. This study evaluated the cultural significance of plants in the Doche community, in the Department of Huila. Furthermore, it evaluates the richness of plant knowledge among local inhabitants, looking for testing the hypothesis that the CS of plants positively correlates to the number of uses people inform about, and that there are significant differences on the richness of ethnobotanical knowledge between men and women in this community. The ethnobotanical categories: "food," "condiment," "economy," "fodder," "firewood," "timber", "medicine," and "others" were established to carry out semi-structured interviews, social cartography, and ethnobotanical walks. The frequency of mention was calculated as a measure of CS. The richness of knowledge of each collaborator was obtained. Non-parametric tests were performed to determine whether differences between the numbers of mentioned species existed between genders and ethnobotanical categories. Finally, Pearson correlation tests determined the relationship between CS and the number of ethnobotanical categories. A hundred useful species were registered in crops and forests. The most abundant categories were medicinal (45 species), firewood (30), and fodder (28). The most culturally significant species according to frequency of mention were Pseudosamanea guachapele, Guazuma ulmifolia, Manihot esculenta, and Musa balbisiana. The species with the most registered uses (five) were Guazuma ulmifolia and Gliricidia sepium. We found a correlation between CS and the number of uses per ethnobotanical category, but no significant difference between genders regarding

  20. Environmental determinants of tropical forest and savanna distribution: A quantitative model evaluation and its implication

    Science.gov (United States)

    Zeng, Zhenzhong; Chen, Anping; Piao, Shilong; Rabin, Sam; Shen, Zehao

    2014-07-01

    The distributions of tropical ecosystems are rapidly being altered by climate change and anthropogenic activities. One possible trend—the loss of tropical forests and replacement by savannas—could result in significant shifts in ecosystem services and biodiversity loss. However, the influence and the relative importance of environmental factors in regulating the distribution of tropical forest and savanna biomes are still poorly understood, which makes it difficult to predict future tropical forest and savanna distributions in the context of climate change. Here we use boosted regression trees to quantitatively evaluate the importance of environmental predictors—mainly climatic, edaphic, and fire factors—for the tropical forest-savanna distribution at a mesoscale across the tropics (between 15°N and 35°S). Our results demonstrate that climate alone can explain most of the distribution of tropical forest and savanna at the scale considered; dry season average precipitation is the single most important determinant across tropical Asia-Australia, Africa, and South America. Given the strong tendency of increased seasonality and decreased dry season precipitation predicted by global climate models, we estimate that about 28% of what is now tropical forest would likely be lost to savanna by the late 21st century under the future scenario considered. This study highlights the importance of climate seasonality and interannual variability in predicting the distribution of tropical forest and savanna, supporting the climate as the primary driver in the savanna biogeography.

  1. Large rainfall changes consistently projected over substantial areas of tropical land

    Science.gov (United States)

    Chadwick, Robin; Good, Peter; Martin, Gill; Rowell, David P.

    2016-02-01

    Many tropical countries are exceptionally vulnerable to changes in rainfall patterns, with floods or droughts often severely affecting human life and health, food and water supplies, ecosystems and infrastructure. There is widespread disagreement among climate model projections of how and where rainfall will change over tropical land at the regional scales relevant to impacts, with different models predicting the position of current tropical wet and dry regions to shift in different ways. Here we show that despite uncertainty in the location of future rainfall shifts, climate models consistently project that large rainfall changes will occur for a considerable proportion of tropical land over the twenty-first century. The area of semi-arid land affected by large changes under a higher emissions scenario is likely to be greater than during even the most extreme regional wet or dry periods of the twentieth century, such as the Sahel drought of the late 1960s to 1990s. Substantial changes are projected to occur by mid-century--earlier than previously expected--and to intensify in line with global temperature rise. Therefore, current climate projections contain quantitative, decision-relevant information on future regional rainfall changes, particularly with regard to climate change mitigation policy.

  2. Effect of different drying techniques on the volatile compounds ...

    African Journals Online (AJOL)

    Tropical Journal of Pharmaceutical Research June 2017; 16 (6): 1399-1406 ... Original Research Article ... and compact while the sun- and oven dried particles resembled angular bricks. ... better preserve the quality of medicinal plants.

  3. Fires in Seasonally Dry Tropical Forest: Testing the Varying Constraints Hypothesis across a Regional Rainfall Gradient.

    Science.gov (United States)

    Mondal, Nandita; Sukumar, Raman

    2016-01-01

    The "varying constraints hypothesis" of fire in natural ecosystems postulates that the extent of fire in an ecosystem would differ according to the relative contribution of fuel load and fuel moisture available, factors that vary globally along a spatial gradient of climatic conditions. We examined if the globally widespread seasonally dry tropical forests (SDTFs) can be placed as a single entity in this framework by analyzing environmental influences on fire extent in a structurally diverse SDTF landscape in the Western Ghats of southern India, representative of similar forests in monsoonal south and southeast Asia. We used logistic regression to model fire extent with factors that represent fuel load and fuel moisture at two levels-the overall landscape and within four defined moisture regimes (between 700 and1700 mm yr-1)-using a dataset of area burnt and seasonal rainfall from 1990 to 2010. The landscape scale model showed that the extent of fire in a given year within this SDTF is dependent on the combined interaction of seasonal rainfall and extent burnt the previous year. Within individual moisture regimes the relative contribution of these factors to the annual extent burnt varied-early dry season rainfall (i.e., fuel moisture) was the predominant factor in the wettest regime, while wet season rainfall (i.e., fuel load) had a large influence on fire extent in the driest regime. Thus, the diverse structural vegetation types associated with SDTFs across a wide range of rainfall regimes would have to be examined at finer regional or local scales to understand the specific environmental drivers of fire. Our results could be extended to investigating fire-climate relationships in STDFs of monsoonal Asia.

  4. Ground Monitoring Neotropical Dry Forests: A Sensor Network for Forest and Microclimate Dynamics in Semi-Arid Environments (Enviro-Net°)

    Science.gov (United States)

    Rankine, C. J.; Sánchez-Azofeifa, G.

    2011-12-01

    In the face of unprecedented global change driven by anthropogenic pressure on natural systems it has become imperative to monitor and better understand potential shifts in ecosystem functioning and services from local to global scales. The utilization of automated sensors technologies offers numerous advantages over traditional on-site ecosystem surveying techniques and, as a result, sensor networks are becoming a powerful tool in environmental monitoring programs. Tropical forests, renowned for their biodiversity, are important regulators of land-atmosphere fluxes yet the seasonally dry tropical forests, which account for 40% of forested ecosystems in the American tropics, have been severely degraded over the past several decades and not much is known of their capacity to recover. With less than 1% of these forests protected, our ability to monitor the dynamics and quantify changes in the remaining primary and recovering secondary tropical dry forests is vital to understanding mechanisms of ecosystem stress responses and climate feedback with respect to annual productivity and desertification processes in the tropics. The remote sensing component of the Tropi-Dry: Human and Biophysical Dimensions of Tropical Dry Forests in the Americas research network supports a network of long-term tropical ecosystem monitoring platforms which focus on the dynamics of seasonally dry tropical forests in the Americas. With over 25 sensor station deployments operating across a latitudinal gradient in Mexico, Costa Rica, Brazil, and Argentina continuously collecting hyper-temporal sensory input based on standardized deployment parameters, this monitoring system is unique among tropical environments. Technologies used in the network include optical canopy phenology towers, understory wireless sensing networks, above and below ground microclimate stations, and digital cameras. Sensory data streams are uploaded to a cyber-infrastructure initiative, denominated Enviro-Net°, for data

  5. Ecological and evolutionary variation in community nitrogen use traits during tropical dry forest secondary succession.

    Science.gov (United States)

    Bhaskar, Radika; Porder, Stephen; Balvanera, Patricia; Edwards, Erika J

    2016-05-01

    We assessed the role of ecological and evolutionary processes in driving variation in leaf and litter traits related to nitrogen (N) use among tropical dry forest trees in old-growth and secondary stands in western Mexico. Our expectation was that legumes (Fabaceae), a dominant component of the regional flora, would have consistently high leaf N and therefore structure phylogenetic variation in N-related traits. We also expected ecological selection during succession for differences in nitrogen use strategies, and corresponding shifts in legume abundance. We used phylogenetic analyses to test for trait conservatism in foliar and litter N, C:N, and N resorption. We also evaluated differences in N-related traits between old-growth and secondary forests. We found a weak phylogenetic signal for all traits, partly explained by wide variation within legumes. Across taxa we observed a positive relationship between leaf and litter N, but no shift in resorption strategies along the successional gradient. Despite species turnover, N-resorption, and N-related traits showed little change across succession, suggesting that, at least for these traits, secondary forests rapidly recover ecosystem function. Collectively, our results also suggest that legumes should not be considered a single functional group from a biogeochemical perspective.

  6. Effects of land use change and seasonality of precipitation on soil nitrogen in a dry tropical forest area in the Western Llanos of Venezuela.

    Science.gov (United States)

    González-Pedraza, Ana Francisca; Dezzeo, Nelda

    2014-01-01

    We evaluated changes of different soil nitrogen forms (total N, available ammonium and nitrate, total N in microbial biomass, and soil N mineralization) after conversion of semideciduous dry tropical forest in 5- and 18-year-old pastures (YP and OP, resp.) in the western Llanos of Venezuela. This evaluation was made at early rainy season, at end rainy season, and during dry season. With few exceptions, no significant differences were detected in the total N in the three study sites. Compared to forest soils, YP showed ammonium losses from 4.2 to 62.9% and nitrate losses from 20.0 to 77.8%, depending on the season of the year. In OP, the ammonium content increased from 50.0 to 69.0% at the end of the rainy season and decreased during the dry season between 25.0 and 55.5%, whereas the nitrate content increased significantly at early rainy season. The net mineralization and the potentially mineralizable N were significantly higher (P forest and YP, which would indicate a better quality of the substrate in OP for mineralization. The mineralization rate constant was higher in YP than in forest and OP. This could be associated with a reduced capacity of these soils to preserve the available nitrogen.

  7. Accumulation and distribution of dry matter in relation to root yield of ...

    African Journals Online (AJOL)

    Cassava an important staple food is grown both in upland and inland valley in the tropics. A trial to assess dry matter production and partitioning in relation to root yield was conducted in 3 positions along inland valley toposequence using 4 x 4 Latin square design. Dry matter partitioning differed among cultivars, ...

  8. Characterization of Wet and Dry Deposition in the Downwind of Industrial Sources in a Dry Tropical Area

    Directory of Open Access Journals (Sweden)

    Raj K. Singh

    2001-01-01

    Full Text Available An atmospheric deposition study was conducted in the downwind of Shaktinagar Thermal Power Plant (STPP, Renusagar Thermal Power Plant (RTPP, and Anpara Thermal Power Plant (ATPP, at Singrauli region, Uttar Pradesh (UP, India to characterize dry and wet deposition in relation to different pollution loading. During the study period, dry and wet depositions and levels of gaseous pollutants (SO2 and NO2 were estimated across the sites. Dry deposition was collected on a monthly basis and wet deposition on an event basis. Depositions were analyzed for pH, nitrate (NO3�, ammonium (NH4+, and sulphate (SO42� contents. Dry deposition rate both collected as clearfall and throughfall varied between 0.15 to 2.28 and 0.33 to 3.48 g m�2 day�1, respectively, at control and maximally polluted sites. The pH of dry deposition varied from 5.81 to 6.89 during winter and 6.09 to 7.02 during summer across the sites. During the rainy season, the mean pH of clear wet deposition varied from 6.56 to 7.04 and throughfall varied from 6.81 to 7.22. The concentrations of NO2 and SO2 pollutants were highest during the winter season. Mean SO2 concentrations varied from 18 to 75 �g m�3 at control and differently polluted sites during the winter season. The variation in NO2 concentrations did not show a pattern similar to that of SO2. The highest NO2 concentration during the winter season was 50 �g m�3, observed near RTPP. NO2 concentration did not show much variation among different sites, suggesting that the sources of NO2 emission are evenly distributed along the sites. The concentrations of NH4+, NO3�, and SO42� ions in dry deposition were found to be higher in summer as compared to the winter season. In dry deposition (clearfall the concentrations of NH4+, NO3�, and SO42� varied from 0.13 to 1.0, 0.81 to 1.95, and 0.82 to 3.27 mg l�1, respectively, during winter. In wet deposition (clearfall, the above varied from 0.14 to 0.74, 0.81 to 1.82, and 0

  9. Characterization of wet and dry deposition in the downwind of industrial sources in a dry tropical area.

    Science.gov (United States)

    Singh, R K; Agrawal, M

    2001-12-19

    An atmospheric deposition study was conducted in the downwind of Shaktinagar Thermal Power Plant (STPP), Renusagar Thermal Power Plant (RTPP), and Anpara Thermal Power Plant (ATPP), at Singrauli region, Uttar Pradesh (UP), India to characterize dry and wet deposition in relation to different pollution loading. During the study period, dry and wet depositions and levels of gaseous pollutants (SO2 and NO2) were estimated across the sites. Dry deposition was collected on a monthly basis and wet deposition on an event basis. Depositions were analyzed for pH, nitrate (NO3-), ammonium (NH4+), and sulphate (SO4(2-)) contents. Dry deposition rate both collected as clearfall and throughfall varied between 0.15 to 2.28 and 0.33 to 3.48 g m(-2) day(-1), respectively, at control and maximally polluted sites. The pH of dry deposition varied from 5.81 to 6.89 during winter and 6.09 to 7.02 during summer across the sites. During the rainy season, the mean pH of clear wet deposition varied from 6.56 to 7.04 and throughfall varied from 6.81 to 7.22. The concentrations of NO2 and SO2 pollutants were highest during the winter season. Mean SO2 concentrations varied from 18 to 75 g m(-3) at control and differently polluted sites during the winter season. The variation in NO2 concentrations did not show a pattern similar to that of SO2. The highest NO2 concentration during the winter season was 50 g m(-3), observed near RTPP. NO2 concentration did not show much variation among different sites, suggesting that the sources of NO2 emission are evenly distributed along the sites. The concentrations of NH4+, NO3-, and SO4(2-) ions in dry deposition were found to be higher in summer as compared to the winter season. In dry deposition (clearfall) the concentrations of NH4+, NO3-, and SO4(2-) varied from 0.13 to 1.0, 0.81 to 1.95, and 0.82 to 3.27 mg l(-1), respectively, during winter. In wet deposition (clearfall), the above varied from 0.14 to 0.74, 0.81 to 1.82, and 0.67 to 2.70 mg l(-1

  10. Morphotype-based characterization of arbuscular mycorrhizal fungal communities in a restored tropical dry forest, Margarita island-Venezuela

    Directory of Open Access Journals (Sweden)

    Laurie Fajardo

    2015-09-01

    Full Text Available The mycorrhizal component of revegetated areas after ecological restoration or rehabilitation in arid and semiarid tropical areas has been scarcely assessed, particularly those made after mining disturbance. We evaluated and compared the presence of arbuscular mycorrhizal fungi of a small area of restored tropical dry for est destroyed by sand extraction, with a non-restored area of similar age, at the peninsula of Macanao, Margarita Island (Venezuela. Our study was undertaken in 2009, four years after planting, and the mycorrhizal status was evaluated in four restored plots (8 x 12.5 m (two were previously treated with hydrogel (R2 and R2', and two were left untreated (R1 and R1', and four non-restored plots of similar size (NR1 and NR1' with graminoid physiognomy with some scattered shrubs; and NR2 and NR2', with a more species rich plant community. Apparently the restoration management promoted higher arbuscular mycorrhizal fungi (AMF species richness and diversity, particularly in restored soils where the hydrogel was added (R2 treatment. Soil of the NR1 treat ment (with a higher herbaceous component showed the highest spore density, compared to samples of soils under the other treatments. Considering species composition, Claroideoglomus etunicatumand Rhizophagus intraradiceswere found in all treatments; besides, Diversispora spurcaand Funneliformis geosporumwere only found in non-restored plots, while members of the Gigasporaceae (a family associated with little disturbed sites were commonly observed in the plots with restored soils. Mycorrhizal colonization was similar in the restored and non-restored areas, being a less sensitive indicator of the ecosystem recovery. The trend of higher richness and diversity of AMF in the restored plot with hydrogel suggests that this management strategy contributes to accelerate the natural regeneration in those ecosystems where water plays an essential role.

  11. Do Reductions in Dry Season Transpiration Allow Shallow Soil Water Uptake to Persist in a Tropical Lower Montane Cloud Forest?

    Science.gov (United States)

    Munoz Villers, L. E.; Holwerda, F.; Alvarado-Barrientos, M. S.; Goldsmith, G. R.; Geissert Kientz, D. R.; González Martínez, T. M.; Dawson, T. E.

    2016-12-01

    Tropical montane cloud forests (TMCF) are ecosystems particularly sensitive to climate change; however, the effects of warmer and drier conditions on TMCF water cycling remain poorly understood. To investigate the plant functional response to reduced water availability, we conducted a study during the mid to late dry season (2014) in the lower limit (1,325 m asl) of the TMCF belt (1200-2500 m asl) in central Veracruz, Mexico. The temporal variation of transpiration rates of dominant upper canopy and mid-story tree species, depth of water uptake, as well as tree water sources were examined using micrometeorological, sapflow and soil moisture measurements, in combination with data on stable isotope (δ18O and δ2H) composition of rain, tree xylem, soil (bulk and low suction-lysimeter) and stream water. The sapflow data suggest that crown conductances decreased as temperature and vapor pressure deficit increased, and soil moisture decreased from the mid to late dry season. Across all samplings (January 21, April 12 and 26), upper canopy species (Quercus spp.) showed more depleted (negative) isotope values compared to mid-story trees (Carpinus tropicalis). Overall, we found that the evaporated soil water pool was the main source for the trees. Furthermore, our MixSIAR Bayesian mixing model results showed that the depth of tree water uptake changed over the course of the dry season. Unexpectedly, a shift in water uptake from deeper (60-120 cm depth) to shallower soil water (0-30 cm) sources was observed, coinciding with the decreases in transpiration rates towards the end of the dry season. A larger reduction in deep soil water contributions was observed for upper canopy trees (from 70±14 to 22±15%) than for mid-story species (from 10±13 to 7±10%). The use of shallow soil water by trees during the dry season seems consistent with the greater root biomass and higher macronutrient concentrations found in the first 10 cm of the soil profiles. These findings are an

  12. Phylogenetic classification of the world's tropical forests.

    Science.gov (United States)

    Slik, J W Ferry; Franklin, Janet; Arroyo-Rodríguez, Víctor; Field, Richard; Aguilar, Salomon; Aguirre, Nikolay; Ahumada, Jorge; Aiba, Shin-Ichiro; Alves, Luciana F; K, Anitha; Avella, Andres; Mora, Francisco; Aymard C, Gerardo A; Báez, Selene; Balvanera, Patricia; Bastian, Meredith L; Bastin, Jean-François; Bellingham, Peter J; van den Berg, Eduardo; da Conceição Bispo, Polyanna; Boeckx, Pascal; Boehning-Gaese, Katrin; Bongers, Frans; Boyle, Brad; Brambach, Fabian; Brearley, Francis Q; Brown, Sandra; Chai, Shauna-Lee; Chazdon, Robin L; Chen, Shengbin; Chhang, Phourin; Chuyong, George; Ewango, Corneille; Coronado, Indiana M; Cristóbal-Azkarate, Jurgi; Culmsee, Heike; Damas, Kipiro; Dattaraja, H S; Davidar, Priya; DeWalt, Saara J; Din, Hazimah; Drake, Donald R; Duque, Alvaro; Durigan, Giselda; Eichhorn, Karl; Eler, Eduardo Schmidt; Enoki, Tsutomu; Ensslin, Andreas; Fandohan, Adandé Belarmain; Farwig, Nina; Feeley, Kenneth J; Fischer, Markus; Forshed, Olle; Garcia, Queila Souza; Garkoti, Satish Chandra; Gillespie, Thomas W; Gillet, Jean-Francois; Gonmadje, Christelle; Granzow-de la Cerda, Iñigo; Griffith, Daniel M; Grogan, James; Hakeem, Khalid Rehman; Harris, David J; Harrison, Rhett D; Hector, Andy; Hemp, Andreas; Homeier, Jürgen; Hussain, M Shah; Ibarra-Manríquez, Guillermo; Hanum, I Faridah; Imai, Nobuo; Jansen, Patrick A; Joly, Carlos Alfredo; Joseph, Shijo; Kartawinata, Kuswata; Kearsley, Elizabeth; Kelly, Daniel L; Kessler, Michael; Killeen, Timothy J; Kooyman, Robert M; Laumonier, Yves; Laurance, Susan G; Laurance, William F; Lawes, Michael J; Letcher, Susan G; Lindsell, Jeremy; Lovett, Jon; Lozada, Jose; Lu, Xinghui; Lykke, Anne Mette; Mahmud, Khairil Bin; Mahayani, Ni Putu Diana; Mansor, Asyraf; Marshall, Andrew R; Martin, Emanuel H; Calderado Leal Matos, Darley; Meave, Jorge A; Melo, Felipe P L; Mendoza, Zhofre Huberto Aguirre; Metali, Faizah; Medjibe, Vincent P; Metzger, Jean Paul; Metzker, Thiago; Mohandass, D; Munguía-Rosas, Miguel A; Muñoz, Rodrigo; Nurtjahy, Eddy; de Oliveira, Eddie Lenza; Onrizal; Parolin, Pia; Parren, Marc; Parthasarathy, N; Paudel, Ekananda; Perez, Rolando; Pérez-García, Eduardo A; Pommer, Ulf; Poorter, Lourens; Qie, Lan; Piedade, Maria Teresa F; Pinto, José Roberto Rodrigues; Poulsen, Axel Dalberg; Poulsen, John R; Powers, Jennifer S; Prasad, Rama Chandra; Puyravaud, Jean-Philippe; Rangel, Orlando; Reitsma, Jan; Rocha, Diogo S B; Rolim, Samir; Rovero, Francesco; Rozak, Andes; Ruokolainen, Kalle; Rutishauser, Ervan; Rutten, Gemma; Mohd Said, Mohd Nizam; Saiter, Felipe Z; Saner, Philippe; Santos, Braulio; Dos Santos, João Roberto; Sarker, Swapan Kumar; Schmitt, Christine B; Schoengart, Jochen; Schulze, Mark; Sheil, Douglas; Sist, Plinio; Souza, Alexandre F; Spironello, Wilson Roberto; Sposito, Tereza; Steinmetz, Robert; Stevart, Tariq; Suganuma, Marcio Seiji; Sukri, Rahayu; Sultana, Aisha; Sukumar, Raman; Sunderland, Terry; Supriyadi; Suresh, H S; Suzuki, Eizi; Tabarelli, Marcelo; Tang, Jianwei; Tanner, Ed V J; Targhetta, Natalia; Theilade, Ida; Thomas, Duncan; Timberlake, Jonathan; de Morisson Valeriano, Márcio; van Valkenburg, Johan; Van Do, Tran; Van Sam, Hoang; Vandermeer, John H; Verbeeck, Hans; Vetaas, Ole Reidar; Adekunle, Victor; Vieira, Simone A; Webb, Campbell O; Webb, Edward L; Whitfeld, Timothy; Wich, Serge; Williams, John; Wiser, Susan; Wittmann, Florian; Yang, Xiaobo; Adou Yao, C Yves; Yap, Sandra L; Zahawi, Rakan A; Zakaria, Rahmad; Zang, Runguo

    2018-02-20

    Knowledge about the biogeographic affinities of the world's tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world's tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: ( i ) Indo-Pacific, ( ii ) Subtropical, ( iii ) African, ( iv ) American, and ( v ) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests. Copyright © 2018 the Author(s). Published by PNAS.

  13. Mapping tropical dry forest habitats integrating Landsat NDVI, Ikonos imagery, and topographic information in the Caribbean Island of Mona

    Directory of Open Access Journals (Sweden)

    Sebastián Martinuzzi

    2008-06-01

    Full Text Available Assessing the status of tropical dry forest habitats using remote sensing technologies is one of the research priorities for Neotropical forests. We developed a simple method for mapping vegetation and habitats in a tropical dry forest reserve, Mona Island, Puerto Rico, by integrating the Normalized Difference vegetation Index (NDvI from Landsat, topographic information, and high-resolution Ikonos imagery. The method was practical for identifying vegetation types in areas with a great variety of plant communities and complex relief, and can be adapted to other dry forest habitats of the Caribbean Islands. NDvI was useful for identifying the distribution of forests, woodlands, and shrubland, providing a natural representation of the vegetation patterns on the island. The use of Ikonos imagery allowed increasing the number of land cover classes. As a result, sixteen land-cover types were mapped over the 5 500 ha area, with a kappa coefficient of accuracy equal to 79 %. This map is a central piece for modeling vertebrate species distribution and biodiversity patterns by the Puerto Rico Gap Analysis Project, and it is of great value for assisting research and management actions in the island. Rev. Biol. Trop. 56 (2: 625-639. Epub 2008 June 30.El estudio y evaluación de los bosques tropicales secos mediante herramientas de teledetección es una de las prioridades de investigación en los ambientes neotropicales. Desarrollamos una metodología simple para mapear la vegetación de la isla de Mona, Puerto Rico, mediante el uso del índice de vegetación normalizado (NDVI por sus siglas en inglés de Landsat, información topográfica, e imágenes auxiliares de alta resolución Ikonos. La metodología fue útil para identificar las clases de vegetación en un área de gran variedad de comunidades vegetales y relieve complejo, y puede ser adaptada a otras regiones de bosque seco de las islas del Caribe. El NDVI permitió identificar la distribución de

  14. Variations of net ecosystem production due to seasonal precipitation differences in a tropical dry forest of northwest Mexico

    Science.gov (United States)

    Verduzco, Vivian S.; Garatuza-Payán, Jaime; Yépez, Enrico A.; Watts, Christopher J.; Rodríguez, Julio C.; Robles-Morua, Agustin; Vivoni, Enrique R.

    2015-10-01

    Due to their large extent and high primary productivity, tropical dry forests (TDF) are important contributors to atmospheric carbon exchanges in subtropical and tropical regions. In northwest Mexico, a bimodal precipitation regime that includes winter precipitation derived from Pacific storms and summer precipitation from the North American monsoon (NAM) couples water availability with ecosystem processes. We investigated the net ecosystem production of a TDF ecosystem using a 4.5 year record of water and carbon fluxes obtained from the eddy covariance method complemented with remotely sensed data. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer that respiration is mainly due to decomposition of soil organic matter accumulated from the prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production but can be overwhelmed by the strength of the primary productivity during the NAM. Precipitation characteristics during NAM have significant controls on sustaining carbon fixation in the TDF into the fall season. We identified that a threshold of ~350 to 400 mm of monsoon precipitation leads to a switch in the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This monsoonal precipitation threshold is typically exceeded one out of every 2 years. The close coupling of winter and summer periods with respect to carbon fluxes suggests that the annual carbon balance is dependent on precipitation amounts in both seasons in TDF ecosystems.

  15. Runoff thresholds and land-to-marine ecosystem connectivity in a dry tropical setting: St. John, US Virgin Islands

    Science.gov (United States)

    Ramos-Scharron, C. E.; LaFevor, M. C.; Roy, J.

    2017-12-01

    Developing a conceptually sound yet practical understanding of runoff and sediment delivery from human occupied lands to tropical ocean waters still represents a pivotal need of coral reef management worldwide. In the dry tropical and ephemeral streamflow setting that typifies the small watersheds ( 1s km2) draining the US Virgin Islands, changes in hydrologic and sediment delivery dynamics provoked by unsurfaced road networks represent a major threat to coral reefs and other sensitive marine ecosystems. Through a combined empirical and modeling approach, this study evaluates how road building and associated stormflow restoration strategies affect rainfall thresholds for runoff generation at varying spatial scales and their impact on land-to-sea connectivity. Rainfall thresholds and runoff coefficients for precipitation excess on unpaved roads are 2-3 mm and 22-30% (respectively) or a full order of magnitude different from those for undisturbed hillslopes and watersheds. Here we discuss the use of a `volume-to-breakthrough' inspired index to predict the potential of road runoff to reach downslope portions of the watershed and the coastline as runon. The index integrates the effects of storm-by-storm runoff accumulation for every road drainage point with its flow distance to specific locations along the stream network. While large runoff volumes and short flow distances imply a relatively high connectivity potential, small volumes and long distances are associated to low delivery potential. The index has proven able to discern observed runoff responses under a variety of road-stream network scenarios and rainfall conditions. These results enhance our understanding of ephemeral stream hydrology and are serving to improve coral reef management strategies throughout the Northeastern Caribbean.

  16. Design and operation of a solarheated dry kiln for tropical latitudes

    Science.gov (United States)

    Brian Bond; Omar Espinoza; Philip Araman

    2011-01-01

    Lumber is usually dried to a specific moisture content prior to further manufacturing or use. While lumber can be air-dried, the ambient humidity in most localities prevents the lumber from reaching the moisture content necessary for dimensional stability and use, especially for interior use. Solar kilns are an inexpensive alternative to conventional steam-heated kilns...

  17. Monitoring coastal wetlands in a highly dynamic tropical environment

    International Nuclear Information System (INIS)

    Saynor, M.J.; Finlayson, C.M.; Spiers, A.; Eliot, I.

    2001-01-01

    The Alligator Rivers Region in the wet-dry tropics of northern Australia has been selected by government and collaborating agencies as a key study area for the monitoring of natural and human-induced coastal change. The Region contains the floodplain wetlands of Kakadu National Park which have been recognised internationally for their natural and cultural heritage value. A coastal monitoring program for assessing and monitoring environmental change in the Alligator Rivers Region has been established at the Environmental Research Institute of the Supervising Scientist. This program has developed a regional capacity to measure and assess change on the wetlands, floodplains and coastline within the region. Field assessment and monitoring procedures have been developed for the program. The assessment procedures require use of georeferencing and data handling techniques to facilitate comparison and relational overlay of a wide variety of information. Monitoring includes regular survey of biophysical and cultural processes on the floodplains; such as the extension of tidal creeks and mangroves, shoreline movement, dieback in Melaleuca wetlands, and weed invasion of freshwater wetlands. A differential Global Positioning System is used to accurately georeference spatial data and a Geographic Information System is then used to store and assess information. The assessment and monitoring procedures can be applied to the wet-dry tropics in general. These studies are all particularly pertinent with the possibility of greenhouse gases causing global warming and potential sea-level rise, a major possible threat to the valued wetlands of Kakadu National Park, and across the wet-dry tropics in general

  18. floristic composition and structure of the dry afromontane forest at ...

    African Journals Online (AJOL)

    ADMIN

    Key words/phrases: Bale Mountains, floristic composition, plant community, vegetation structure. INTRODUCTION .... from ground was estimated for each tree and shrub species by ...... and environmental factors characterizing coffee forests in ...

  19. Performance of tropical legumes grown as understory of a eucalypt plantation in a seasonally dry area of the Brazilian Cerrado

    Directory of Open Access Journals (Sweden)

    Maria Luiza F. Nicodemo

    2015-09-01

    Full Text Available Nine tropical legumes were grown outside the canopy and in the understory of an 8-year-old Eucalyptus grandis stand in order to assess their seasonal production and forage quality for 4 evaluation periods. Incident photosynthetically active radiation in the understory was 18% of that outside the canopy. In the understory, production of Lablab purpureus, Centrosema schiedeanum, Clitoria ternatea, Pueraria phaseoloides, Alysicarpus vaginalis, Aeschynomene villosa, Estilosantes Campo Grande (Stylosanthes capitata + S. macrocephala, Calopogonium mucunoides and Arachis pintoi was <1 kg/ha/d for most samples. Even considering this low production, the large area available for animal production in forest plantations might justify the interest in legumes because of their high nutritive value. Lablab purpureus produced the greatest amount of dry matter in the understory in the establishment phase (12.1 kg/ha/d, but did not persist. It could be a suitable candidate for a cover legume species mixture to provide early growth. Centrosema schiedeanum developed rapidly and showed a high capacity for ground cover (>70% and persistence, and had high nitrogen concentration, thus demonstrating good potential for protecting soils and promoting nutrient cycling in forest plantations. Another species with potential is A. pintoi, which established slowly but towards the end of the experiment showed moderate to high understory ground cover.Keywords: Dry matter production, forage quality, shade, silvopastoral system.DOI: 10.17138/TGFT(3151-160

  20. Symbiosis with AMF and leaf Pi supply increases water deficit tolerance of woody species from seasonal dry tropical forest.

    Science.gov (United States)

    Frosi, Gabriella; Barros, Vanessa A; Oliveira, Marciel T; Santos, Mariana; Ramos, Diego G; Maia, Leonor C; Santos, Mauro G

    2016-12-01

    In seasonal dry tropical forests, plants are subjected to severe water deficit, and the arbuscular mycorrhizal fungi (AMF) or inorganic phosphorus supply (P i ) can mitigate the effects of water deficit. This study aimed to assess the physiological performance of Poincianella pyramidalis subjected to water deficit in combination with arbuscular mycorrhizal fungi (AMF) and leaf inorganic phosphorus (P i ) supply. The experiment was conducted in a factorial arrangement of 2 water levels (+H 2 O and -H 2 O), 2 AMF levels (+AMF and -AMF) and 2P i levels (+P i and -P i ). Leaf primary metabolism, dry shoot biomass and leaf mineral nutrients were evaluated. Inoculated AMF plants under well-watered and drought conditions had higher photosynthesis and higher shoot biomass. Under drought, AMF, P i or AMF+P i plants showed metabolic improvements in photosynthesis, leaf biochemistry and higher biomass compared to the plants under water deficit without AMF or P i . After rehydration, those plants submitted to drought with AMF, P i or AMF+P i showed a faster recovery of photosynthesis compared to treatment under water deficit without AMF or P i . However, plants under the drought condition with AMF showed a higher net photosynthesis rate. These findings suggest that AMF, P i or AMF+P i increase the drought tolerance in P. pyramidalis, and AMF associations under well-watered conditions increase shoot biomass and, under drought, promoted faster recovery of photosynthesis. Copyright © 2016 Elsevier GmbH. All rights reserved.

  1. Four new species, DNA barcode library and pre-Pliocene speciation of the euedaphic Afromontane Clivinini genera Trilophidius and Antireicheia (Coleoptera: Carabidae, Scaritinae

    Directory of Open Access Journals (Sweden)

    Vasily V. Grebennikov

    2017-06-01

    Full Text Available We describe and extensively illustrate four new species of euedaphic (= dwelling in the soil Clivinini ground beetles: Trilophidius acastus sp. nov. and T. argus sp. nov. (both from Bioko, Equatorial Guinea, as well as Antireicheia calais sp. nov. and A. zetes sp. nov. (both from the South Pare Mountains, Tanzania. We generate and report all currently available DNA barcode (= cytochrome oxidase subunit I data for euedaphic Afromontane Clivinini of the genera Trilophidius (2 species, four records and Antireicheia (13 species, 43 records. We infer a phylogeny for these beetles using a Maximum Likelihood approach based upon a matrix of 53 sequenced specimens (dx.doi.org/10.5883/DS-ANTIREI with 658 aligned positions. All nominative species represented by two or more sequences are recovered as monophyletic. Both new species of Trilophidius form a weakly supported clade, while all seven species of South African Antireicheia form a moderately supported clade. The genus Antireicheia and the geographical assemblage of its six Tanzanian species are not monophyletic. We perform divergence time estimation in Afrotropical Antireicheia, and our analysis indicates that these lineages diverged predominantly in the middle or late Miocene. We highlight the notable lack of phylogenetic hypothesis linked with the vaguely and variably defined taxon “subfamily Scaritinae” and its subordinated taxa.

  2. Impact of habitat degradation on phlebotominae (Diptera: Psychodidae) of tropical dry forests in Northern Colombia.

    Science.gov (United States)

    Travi, Bruno L; Adler, Gregory H; Lozano, Margarita; Cadena, Horacio; Montoya-Lerma, James

    2002-05-01

    We examined changes in the phlebotomine fauna resulting from human intervention in a tropical dry forest of Northern Colombia where visceral and cutaneous leishmaniases are endemic. A natural forest reserve (Colosó) and a highly degraded area (San Andrés de Sotavento [SAS]) were sampled monthly for 8 mo using Shannon traps, sticky traps, and resting-site collections. Overall abundances were higher in Colosó (15,988) than in SAS (2,324). and species richness of phlebotomines was greater in the forest reserve (11 species) than in the degraded habitat (seven species). Fisher alpha, a measure of diversity, reinforced this trend. Both sand fly communities were dominated by Lutzomyia evansi (Nuòez-Tovar), vector of Leishmania chagasi (Cunha & Chagas), representing 92 and 81% of all captures in Colosó and SAS, respectively. Lutzomyia longipalpis (Lutz & Neiva), the common vector of visceral leishmaniasis, accounted for 4-7% of the sand fly community. Lutzornyia panamensis (Shannon) and Lutzomya gomezi (Nitzulescu), putative vectors of Leishmania braziliensis (Vianna), had low abundances at both study sites. The zoophilic species Lutzomyia cayennensis (Floch & Abonneuc) and Lutzomyia trinidadensis (Newstead) were present in variable numbers according to trapping methods and site. Habitat degradation negatively affected sand fly communities, but medically important species were able to exploit modified environments, thereby contributing to Lishmania endemicity.

  3. Variability in core areas of spider monkeys (Ateles geoffroyi) in a tropical dry forest in Costa Rica.

    Science.gov (United States)

    Asensio, Norberto; Schaffner, Colleen M; Aureli, Filippo

    2012-04-01

    Core areas are highly used parts of the home range on which the survival of solitary or group-living animals depends. We investigated the home range and core area size and area fidelity of a spider monkey community in a tropical dry forest over a 4-year period. Home ranges overlapped extensively across years, subgroup sizes, and seasons. In contrast, spider monkeys used core areas that varied in size and location across the study years, subgroup sizes, and seasons. These shifts in core areas suggest that the understanding of core areas, and thus the spatial requirements, of a species in a particular habitat may be limited if based on short-term studies. In this respect, our findings emphasize the importance of long-term studies of the spatial ecology of any species in a particular habitat. Our study also shows that the yearly home range basically includes all the core areas from different years, seasons, and subgroup sizes (i.e., the super-core area). This is conceptually important for territorial species, such as spider monkeys, which defend a stable home range as it contains not only the current, but also the future core areas.

  4. Population dynamics of Rodents and Insectivores in lowland tropical ...

    African Journals Online (AJOL)

    The community structure of rodents and insectivores in the lowland tropical rainforest of Okomu National Park, Edo State, Nigeria was assessed using a combination of live-trapping and sighting techniques during the dry and wet seasons. Seventeen species (14 species of rodent, 3 species of insectivores) were captured, ...

  5. Drying hot red pepper using solar tunnel drier

    International Nuclear Information System (INIS)

    Hossain, M.A; Bala, B.K.

    2006-01-01

    A solar tunnel drier was used to dry red hot pepper under the tropical weather conditions of Bangladesh in order to investigate its performance and the quality of the drier product. The drier comprises a plastic sheet-covered flat plate collector and a drying tunnel. The drier is arranged to supply hot air to the drying tunnel using two small fans powered by a 40 watt PV module. Fresh red pepper was water blanched before drying. In each drying batch in the solar tunnel drier, 20 kg of dried red pepper with 4 to 6% moisture content (wb) was obtained from 80 kg of fresh red pepper with initial moisture content of 73 to 75% (wb) in 20 to 22 hours of drying while it took 32 to 34 hours to bring down the moisture content of similar sample to 8 to 10% (wb) in sun drying methods. The pepper dried in the solar tunnel drier was completely protected from dust, dirt, rain, insects, birds, rodents and microorganisms and it was a quality-dried product in term of colour and pungency. The solar tunnel drier is recommended for drying of pepper as well as vegetables and fruits in developing countries especially in Bangladesh

  6. Phylogenetic classification of the world’s tropical forests

    Science.gov (United States)

    Franklin, Janet; Arroyo-Rodríguez, Víctor; Field, Richard; Aguilar, Salomon; Aguirre, Nikolay; Ahumada, Jorge; Aiba, Shin-Ichiro; K, Anitha; Avella, Andres; Mora, Francisco; Aymard C., Gerardo A.; Báez, Selene; Balvanera, Patricia; Bastian, Meredith L.; Bastin, Jean-François; Bellingham, Peter J.; van den Berg, Eduardo; da Conceição Bispo, Polyanna; Boeckx, Pascal; Boehning-Gaese, Katrin; Bongers, Frans; Boyle, Brad; Brearley, Francis Q.; Brown, Sandra; Chai, Shauna-Lee; Chazdon, Robin L.; Chen, Shengbin; Chhang, Phourin; Chuyong, George; Ewango, Corneille; Coronado, Indiana M.; Cristóbal-Azkarate, Jurgi; Culmsee, Heike; Damas, Kipiro; Dattaraja, H. S.; Davidar, Priya; DeWalt, Saara J.; Din, Hazimah; Drake, Donald R.; Durigan, Giselda; Eichhorn, Karl; Eler, Eduardo Schmidt; Enoki, Tsutomu; Ensslin, Andreas; Fandohan, Adandé Belarmain; Farwig, Nina; Feeley, Kenneth J.; Fischer, Markus; Forshed, Olle; Garcia, Queila Souza; Garkoti, Satish Chandra; Gillespie, Thomas W.; Gillet, Jean-Francois; Gonmadje, Christelle; Granzow-de la Cerda, Iñigo; Griffith, Daniel M.; Grogan, James; Hakeem, Khalid Rehman; Harris, David J.; Harrison, Rhett D.; Hector, Andy; Hemp, Andreas; Hussain, M. Shah; Ibarra-Manríquez, Guillermo; Hanum, I. Faridah; Imai, Nobuo; Jansen, Patrick A.; Joly, Carlos Alfredo; Joseph, Shijo; Kartawinata, Kuswata; Kearsley, Elizabeth; Kelly, Daniel L.; Kessler, Michael; Killeen, Timothy J.; Kooyman, Robert M.; Laumonier, Yves; Laurance, William F.; Lawes, Michael J.; Letcher, Susan G.; Lovett, Jon; Lozada, Jose; Lu, Xinghui; Lykke, Anne Mette; Mahmud, Khairil Bin; Mahayani, Ni Putu Diana; Mansor, Asyraf; Marshall, Andrew R.; Martin, Emanuel H.; Calderado Leal Matos, Darley; Meave, Jorge A.; Melo, Felipe P. L.; Mendoza, Zhofre Huberto Aguirre; Metali, Faizah; Medjibe, Vincent P.; Metzger, Jean Paul; Metzker, Thiago; Mohandass, D.; Munguía-Rosas, Miguel A.; Muñoz, Rodrigo; Nurtjahy, Eddy; de Oliveira, Eddie Lenza; Onrizal; Parolin, Pia; Parren, Marc; Parthasarathy, N.; Paudel, Ekananda; Perez, Rolando; Pérez-García, Eduardo A.; Pommer, Ulf; Poorter, Lourens; Qie, Lan; Piedade, Maria Teresa F.; Pinto, José Roberto Rodrigues; Poulsen, Axel Dalberg; Poulsen, John R.; Powers, Jennifer S.; Prasad, Rama Chandra; Puyravaud, Jean-Philippe; Rangel, Orlando; Reitsma, Jan; Rocha, Diogo S. B.; Rolim, Samir; Rovero, Francesco; Ruokolainen, Kalle; Rutishauser, Ervan; Rutten, Gemma; Mohd. Said, Mohd. Nizam; Saiter, Felipe Z.; Saner, Philippe; Santos, Braulio; dos Santos, João Roberto; Sarker, Swapan Kumar; Schoengart, Jochen; Schulze, Mark; Sheil, Douglas; Sist, Plinio; Souza, Alexandre F.; Spironello, Wilson Roberto; Sposito, Tereza; Steinmetz, Robert; Stevart, Tariq; Suganuma, Marcio Seiji; Sukri, Rahayu; Sukumar, Raman; Sunderland, Terry; Supriyadi; Suresh, H. S.; Suzuki, Eizi; Tabarelli, Marcelo; Tang, Jianwei; Tanner, Ed V. J.; Targhetta, Natalia; Theilade, Ida; Thomas, Duncan; Timberlake, Jonathan; de Morisson Valeriano, Márcio; van Valkenburg, Johan; Van Do, Tran; Van Sam, Hoang; Vandermeer, John H.; Verbeeck, Hans; Vetaas, Ole Reidar; Adekunle, Victor; Vieira, Simone A.; Webb, Campbell O.; Webb, Edward L.; Whitfeld, Timothy; Wich, Serge; Williams, John; Wiser, Susan; Wittmann, Florian; Yang, Xiaobo; Adou Yao, C. Yves; Yap, Sandra L.; Zahawi, Rakan A.; Zakaria, Rahmad; Zang, Runguo

    2018-01-01

    Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests. PMID:29432167

  7. Crotalaria trifoliolata (Leguminosae: Papilionoideae), a previously incompletely known Ethiopian endemic rediscovered after 120 years

    DEFF Research Database (Denmark)

    Friis, Ib; Weber, Odile

    2014-01-01

    . rhynchocarpa Polhill, C. saltiana Andrews, C. thomasii Harms) in having the inside of the pod densely packed with long, white hairs. C. trifoliolata was observed at the edge of and in glades inside dry Juniperus-Olea forest, in which the canopy is dominated by J. procera Endl. and the undergrowth by Barbeya...... oleoides Schweinf. and other species characteristic of dry Afromontane forest and bushland. The species is found only in a limited area near the eastern Ethiopian escarpment at Sheik Hussein. It is documented with images and maps, its potential distribution is modelled and a conservation assessment...

  8. Non-native grass removal and shade increase soil moisture and seedling performance during Hawaiian dry forest restoration

    Science.gov (United States)

    Jared M. Thaxton; Susan Cordell; Robert J. Cabin; Darren R. Sandquist

    2012-01-01

    Invasive non-native species can create especially problematic restoration barriers in subtropical and tropical dry forests. Native dry forests in Hawaii presently cover less than 10% of their original area. Many sites that historically supported dry forest are now completely dominated by non-native species, particularly grasses. Within a grass-dominated site in leeward...

  9. Pathways, mechanisms and predictability of vegetation change during tropical dry forest succession

    NARCIS (Netherlands)

    Lebrija Trejos, E.E.; Meave, J.; Poorter, L.; Pérez- García, E.A.; Bongers, F.

    2010-01-01

    The development of forest succession theory has been based on studies in temperate and tropical wet forests. As rates and pathways of succession vary with the environment, advances in successional theory and study approaches are challenged by controversies derived from such variation and by the

  10. Application of digital field photographs as documents for tropical plant inventory.

    Science.gov (United States)

    LaFrankie, James V; Chua, Anna I

    2015-05-01

    We tested the credibility and significance of digital field photographs as supplements or substitutes for conventional herbarium specimens with particular relevance to exploration of the tropics. We made 113 collections in triplicate at a species-rich mountain in the Philippines while we took 1238 digital photographs of the same plants. We then identified the plants from the photographs alone, categorized the confidence of the identification and the reason for failure to identify, and compared the results to identifications based on the dried specimens. We identified 72.6% of the photographic sets with high confidence and 27.4% with low confidence or only to genus. In no case was a confident identification altered by subsequent examination of the dried specimen. The failure to identify photographic sets to species was due to the lack of a key feature in 67.8% of the cases and due to a poorly understood taxonomy in 32.2%. We conclude that digital photographs cannot replace traditional herbarium specimens as the primary elements that document tropical plant diversity. However, photographs represent a new and important artifact that aids an expedient survey of tropical plant diversity while encouraging broad public participation.

  11. Are Mixed Tropical Tree Plantations More Resistant to Drought than Monocultures?

    Directory of Open Access Journals (Sweden)

    Norbert Kunert

    2015-06-01

    Full Text Available Tropical tree plantations usually consist of a single exotic fast growing species, but recent research describes positive effects on ecosystem functions from mixed tropical tree plantations. In this review, we present the current knowledge of drought resistance of tropical mixed species plantations and summarize preliminary evidence from a tree biodiversity experiment in Panama. Converting mono-specific stands into mixed ones may improve stand stability and might reduce increasing abiotic and biotic disturbances due to climate change. However, little is known about the extent to which tropical tree species or tropical tree communities can resist increasing disturbances in the short term, e.g., water limitations due to increasing dry season intensity or length, or about their resilience after such disturbances and their capacity to adapt to changing conditions in the long term. Studies relating drought resistance and resilience to community diversity are missing. Further, we highlight the urgent need for a multifactorial manipulative throughfall reduction experiment in tropical environments. The outcome of such studies would greatly assist the forestry sector in tropical regions to maintain highly productive and ecologically sound forest plantations in a changing climate.

  12. Fog Water Is Important in Maintaining the Water Budgets of Vascular Epiphytes in an Asian Tropical Karst Forests during the Dry Season

    Directory of Open Access Journals (Sweden)

    Yi Wu

    2018-05-01

    Full Text Available Fog may be an important source of water for forest vascular epiphytes on trees, because they lack direct access to sources of soil water, but little is known about the water use proportions from various sources and potential water uptake pathways in epiphytes. Here, we analyzed leaf carbon isotope ratios as a measure of water use efficiency (WUE, proportions of fog, rain, and soil water use, and foliar water uptake (FWU in species of epiphyte and their host trees in a tropical karst dwarf forest in China during the dry season. We found that the WUE, as represented by leaf δ13C, was generally enriched in the epiphyte species compared to their host trees. Epiphytes used substantial proportions of fog water, whereas water use in the host trees was dominated by soil water. The leaves of epiphytes and host trees absorbed water following immersion in water for 3 h and FWU possibly related to foliar epicuticular structures, such as fungal endophytes. Our results show a divergence of water use strategies between epiphytes and their hosts and highlight the importance of fog water for epiphytes during the dry season and under a climate change scenario with a reduced occurrence of fog events.

  13. Effect of fragmentation on the Costa Rican dry forest avifauna

    OpenAIRE

    Barrantes, Gilbert; Ocampo, Diego; Ram?rez-Fern?ndez, Jos? D.; Fuchs, Eric J.

    2016-01-01

    Deforestation and changes in land use have reduced the tropical dry forest to isolated forest patches in northwestern Costa Rica. We examined the effect of patch area and length of the dry season on nestedness of the entire avian community, forest fragment assemblages, and species occupancy across fragments for the entire native avifauna, and for a subset of forest dependent species. Species richness was independent of both fragment area and distance between fragments. Similarity in bird comm...

  14. Broadcast seeding as a potential tool to reestablish native species in degraded dry forest ecosystems in Hawaii

    Science.gov (United States)

    S. Brooks; S. Cordell; L. Perry

    2009-01-01

    Hawaiian dry forests currently occupy a small fraction of their former range, and worldwide tropical dry forests are one of the most human-altered systems. Many small-scale projects have been successful in restoring native dry forests in abandoned pastures and degraded woodlands by outplanting after invasive species removal, but this is a costly approach. In this...

  15. Regeneration of tropical maize lines ( Zea mays l .) from mature ...

    African Journals Online (AJOL)

    The use of immature zygotic embryos as an explant for maize regeneration has been hampered by the strictly limited suitable duration of immature embryos for culture. In contrast, mature zygotic embryos harvested from dry seeds are ubiquitous. However, generally mature embryos and especially tropical maize genotypes ...

  16. Seasonal differences in leaf-level physiology give lianas a competitive advantage over trees in a tropical seasonal forest.

    Science.gov (United States)

    Cai, Zhi-Quan; Schnitzer, Stefan A; Bongers, Frans

    2009-08-01

    Lianas are an important component of most tropical forests, where they vary in abundance from high in seasonal forests to low in seasonal forests. We tested the hypothesis that the physiological ability of lianas to fix carbon (and thus grow) during seasonal drought may confer a distinct advantage in seasonal tropical forests, which may explain pan-tropical liana distributions. We compared a range of leaf-level physiological attributes of 18 co-occurring liana and 16 tree species during the wet and dry seasons in a tropical seasonal forest in Xishuangbanna, China. We found that, during the wet season, lianas had significantly higher CO(2) assimilation per unit mass (A(mass)), nitrogen concentration (N(mass)), and delta(13)C values, and lower leaf mass per unit area (LMA) than trees, indicating that lianas have higher assimilation rates per unit leaf mass and higher integrated water-use efficiency (WUE), but lower leaf structural investments. Seasonal variation in CO(2) assimilation per unit area (A(area)), phosphorus concentration per unit mass (P(mass)), and photosynthetic N-use efficiency (PNUE), however, was significantly lower in lianas than in trees. For instance, mean tree A(area) decreased by 30.1% from wet to dry season, compared with only 12.8% for lianas. In contrast, from the wet to dry season mean liana delta(13)C increased four times more than tree delta(13)C, with no reduction in PNUE, whereas trees had a significant reduction in PNUE. Lianas had higher A(mass) than trees throughout the year, regardless of season. Collectively, our findings indicate that lianas fix more carbon and use water and nitrogen more efficiently than trees, particularly during seasonal drought, which may confer a competitive advantage to lianas during the dry season, and thus may explain their high relative abundance in seasonal tropical forests.

  17. Phylogenetic classification of the world's tropical forests

    DEFF Research Database (Denmark)

    Slik, J. W. Ferry; Franklin, Janet; Arroyo-Rodriguez, Victor

    2018-01-01

    -Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between......Knowledge about the biogeographic affinities of the world's tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern...... phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world's tropical forests based on their phylogenetic similarity. We identify five principal...

  18. Biomass burning in the tropics: Impact on atmospheric chemistry and biogeochemical cycles

    International Nuclear Information System (INIS)

    Crutzen, P.J.; Andreae, M.O.

    1990-01-01

    Biomass burning is widespread, especially in the tropics. It serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses. Furthermore, much agricultural waste and fuel wood is being combusted, particularly in developing countries. Biomass containing 2 to 5 petagrams of carbon is burned annually (1 petagram = 10 15 grams), producing large amounts of trace gases and aerosol particles that play important roles in atmospheric chemistry and climate. Emissions of carbon monoxide and methane by biomass burning affect the oxidation efficiency of the atmosphere by reacting with hydroxyl radicals, and emissions of nitric oxide and hydrocarbons lead to high ozone concentrations in the tropics during the dry season. Large quantities of smoke particles are produced as well, and these can serve as cloud condensation nuclei. These particles may thus substantially influence cloud microphysical and optical properties, an effect that could have repercussions for the radiation budget and the hydrological cycle in the tropics. Widespread burning may also disturb biogeochemical cycles, especially that of nitrogen. About 50% of the nitrogen in the biomass fuel can be released as molecular nitrogen. This pyrodenitrification process causes a sizable loss of fixed nitrogen in tropical ecosystems, in the range of 10 to 20 teragrams per year (1 teragram = 10 12 grams)

  19. Effect of water stress on seedling growth in two species with different abundances: the importance of Stress Resistance Syndrome in seasonally dry tropical forest

    Directory of Open Access Journals (Sweden)

    Wanessa Nepomuceno Ferreira

    2015-09-01

    Full Text Available ABSTRACTIn seasonally dry tropical forests, species carrying attributes of Stress Resistance Syndrome (SRS may have ecological advantages over species demanding high quantities of resources. In such forests, Poincianella bracteosa is abundant, while Libidibia ferrea has low abundance; therefore, we hypothesized that P. bracteosa has characteristics of low-resource species, while L. ferrea has characteristics of high-resource species. To test this hypothesis, we assessed morphological and physiological traits of seedlings of these species under different water regimes (100%, 70%, 40%, and 10% field capacity over 85 days. For most of the studied variables we observed significant decreases with increasing water stress, and these reductions were greater in L. ferrea. As expected, L. ferreamaximized their growth with increased water supply, while P. bracteosa maintained slower growth and had minor adjustments in biomass allocation, characteristics representative of low-resource species that are less sensitive to stress. We observed that specific leaf area, biomass allocation to roots, and root/shoot ratio were higher in L. ferrea, while biomass allocation to leaves and photosynthesis were higher in P. bracteosa. Results suggest that the attributes of SRS can facilitate high abundance of P. bracteosa in dry forest.

  20. Vegetation controls on weathering intensity during the last deglacial transition in southeast Africa

    Science.gov (United States)

    Ivory, Sarah J.; McGlue, Michael M.; Ellis, Geoffrey S.; Lézine, Anne-Marie; Cohen, Andrew S.; Vincens, Annie

    2015-01-01

    Tropical climate is rapidly changing, but the effects of these changes on the geosphere are unknown, despite a likelihood of climatically-induced changes on weathering and erosion. The lack of long, continuous paleo-records prevents an examination of terrestrial responses to climate change with sufficient detail to answer questions about how systems behaved in the past and may alter in the future. We use high-resolution records of pollen, clay mineralogy, and particle size from a drill core from Lake Malawi, southeast Africa, to examine atmosphere-biosphere-geosphere interactions during the last deglaciation (~18–9 ka), a period of dramatic temperature and hydrologic changes. The results demonstrate that climatic controls on Lake Malawi vegetation are critically important to weathering processes and erosion patterns during the deglaciation. At 18 ka, afromontane forests dominated but were progressively replaced by tropical seasonal forest, as summer rainfall increased. Despite indication of decreased rainfall, drought-intolerant forest persisted through the Younger Dryas (YD) resulting from a shorter dry season. Following the YD, an intensified summer monsoon and increased rainfall seasonality were coeval with forest decline and expansion of drought-tolerant miombo woodland. Clay minerals closely track the vegetation record, with high ratios of kaolinite to smectite (K/S) indicating heavy leaching when forest predominates, despite variable rainfall. In the early Holocene, when rainfall and temperature increased (effective moisture remained low), open woodlands expansion resulted in decreased K/S, suggesting a reduction in chemical weathering intensity. Terrigenous sediment mass accumulation rates also increased, suggesting critical linkages among open vegetation and erosion during intervals of enhanced summer rainfall. This study shows a strong, direct influence of vegetation composition on weathering intensity in the tropics. As climate change will likely impact

  1. Effects of soil type and light on height growth, biomass partitioning, and nitrogen dynamics on 22 species of tropical dry forest tree seedlings: Comparisons between legumes and nonlegumes.

    Science.gov (United States)

    Smith-Martin, Christina M; Gei, Maria G; Bergstrom, Ellie; Becklund, Kristen K; Becknell, Justin M; Waring, Bonnie G; Werden, Leland K; Powers, Jennifer S

    2017-03-01

    The seedling stage is particularly vulnerable to resource limitation, with potential consequences for community composition. We investigated how light and soil variation affected early growth, biomass partitioning, morphology, and physiology of 22 tree species common in tropical dry forest, including eight legumes. Our hypothesis was that legume seedlings are better at taking advantage of increased resource availability, which contributes to their successful regeneration in tropical dry forests. We grew seedlings in a full-factorial design under two light levels in two soil types that differed in nutrient concentrations and soil moisture. We measured height biweekly and, at final harvest, biomass partitioning, internode segments, leaf carbon, nitrogen, δ 13 C, and δ 15 N. Legumes initially grew taller and maintained that height advantage over time under all experimental conditions. Legumes also had the highest final total biomass and water-use efficiency in the high-light and high-resource soil. For nitrogen-fixing legumes, the amount of nitrogen derived from fixation was highest in the richer soil. Although seed mass tended to be larger in legumes, seed size alone did not account for all the differences between legumes and nonlegumes. Both belowground and aboveground resources were limiting to early seedling growth and function. Legumes may have a different regeneration niche, in that they germinate rapidly and grow taller than other species immediately after germination, maximizing their performance when light and belowground resources are readily available, and potentially permitting them to take advantage of high light, nutrient, and water availability at the beginning of the wet season. © 2017 Botanical Society of America.

  2. Coexistence of Dunes and Humid Conditions at Titan's Tropics

    Science.gov (United States)

    Radebaugh, Jani; Lorenz, R. D.; Lunine, J. I.; Kirk, R. L.; Ori, G. G.; Farr, T. G.; Malaska, M.; Le Gall, A.; Liu, Z. Y. C.; Encrenaz, P. J.; Paillou, P.; Hayes, A.; Lopes, R. M. C.; Turtle, E. P.; Wall, S. D.; Stofan, E. R.; Wood, C. A.; Cassini RADAR Team

    2012-10-01

    At Titan's equatorial latitudes there are tens of thousands of dunes, a landform typical of desert environments where sand does not become anchored by vegetation or fluids. Model climate simulations predict generally dry conditions at the equator and humid conditions near the poles of Titan, where lakes of methane/ethane are found. However, moderate relative methane humidity was observed at the Huygens landing site, recent rainfall was seen by Cassini ISS near the Belet Sand Sea, and a putative transient lake in Shangri-La was observed by Cassini VIMS, all of which indicate abundant fluids may be present, at least periodically, at Titan's equatorial latitudes. Terrestrial observations and studies demonstrate dunes can exist and migrate in conditions of high humidity. Active dunes are found in humid climates, indicating the movement of sand is not always prohibited by the presence of fluids. Sand mobility is related to precipitation, evaporation and wind speed and direction. If dune surfaces become wetted by rainfall or rising subsurface fluids, they can become immobilized. However, winds can act to dry the uppermost layers, freeing sands for saltation and enabling dune migration in wet conditions. Active dunes are found in tropical NE Brazil and NE Australia, where there are alternating dry and wet periods, a condition possible for Titan's tropics. Rising and falling water levels lead to the alteration of dune forms, mainly from being anchored by vegetation, but also from cementation by carbonates or clays. Studies of Titan's dunes, which could undergo anchoring of organic sediments by hydrocarbon fluids, could inform the relative strength of vegetation vs. cementation at humid dune regions on Earth. Furthermore, a comprehensive survey of dune morphologies near regions deemed low by SARTopo and stereo, where liquids may collect in wet conditions, could reveal if bodies of liquid have recently existed at Titan's tropics.

  3. Emerging deforestation trends in tropical dry forests ecoregions of Mexico and Central America

    Science.gov (United States)

    Portillo, C. A.; Cao, G.; Smith, V.

    2015-12-01

    Neotropical dry forests (TDF) have experienced an unprecedented deforestation that is leading to the loss of tropical biodiversity at a rapid pace, but information on deforestation dynamics in TDF is scarce. In this study, we present a sub-continental and national level assessment of TDF loss patterns in Mexico and Central America at high spatial and temporal resolution using remote sensing and GIS technologies. We used the Global Forest Change (GFC) dataset published by Hansen et al. (2013) which shows results from time-series analysis of Landsat images in characterizing global forest extent and change from 2000 through 2013. We analyzed forest loss within and around mapped TDF cover mapped by Portillo-Quintero et al. 2010. In order to minimize errors in source data, we overlaid a 25 x 25 km grid on top of the regional dataset and conducted a cell by cell and country by country inspection at multiple scales using high resolution ancillary data. We identified trends in the clustering of space-time TDF deforestation data using ArcGIS, categorizing trends in: new, consecutive, intensifying, persistent, diminishing, sporadic, oscillating and historical hotspots (high frequency of deforestation events) and cold spots (low frequency of deforestation). In general, the region is experiencing less frequent deforestation events with a higher number of intensifying and new cold spots across TDF landscapes. However, an important number of intensifying and persistent hotspots exist so no general trend in forest loss was detected for the period 2001-2013, except for El Salvador which shows a significant decreasing trend in forest loss. Mexico, Nicaragua, Honduras and Guatemala are the major sources of intensifying, persistent and new deforestation hot spots. These were identified in the southern pacific coast and the Yucatan Peninsula in Mexico, northwestern Guatemala, both western and eastern Honduras and around Lake Nicaragua in Nicaragua.

  4. Radiation preservation of dry fruits and nuts

    International Nuclear Information System (INIS)

    Wahid, M.; Sattar, A.; Jan, M.; Ahmad, A.; Khan, I.

    1988-01-01

    Dried fruits are considered a major source of income and foreign exchange in many countries. The spoilage of dried fruits and nuts by insect infestation, colour deterioration and chemical changes during storage are the serious problems especially under humid tropical conditions. The present work was undertaken to study the effect of irradiation in combination with different modified storage environments on insect infestation as well as chemical and sensory quality indices. The affect of gamma radiation dose of 1 KGy and storage environments such as air vacuum and carbon dioxide on insect infestation of dry fruits and nuts. In the case of un-irradiated samples, insect infestation progressed throughout the storage period especially in those kept under air. The vacuum storage was found better in checking infestation followed by CO/sub/2 and air. (orig./A.B.)

  5. Biogenic VOC Emissions from Tropical Landscapes

    Science.gov (United States)

    Guenther, A.; Greenberg, J.; Harley, P.; Otter, L.; Vanni Gatti, L.; Baker, B.

    2003-04-01

    Biogenic VOC have an important role in determining the chemical composition of atmosphere. As a result, these compounds are important for visibility, biogeochemical cycling, climate and radiative forcing, and the health of the biosphere. Tropical landscapes are estimated to release about 80% of total global biogenic VOC emissions but have been investigated to lesser extent than temperate regions. Tropical VOC emissions are particularly important due to the strong vertical transport and the rapid landuse change that is occurring there. This presentation will provide an overview of field measurements of biogenic VOC emissions from tropical landscapes in Amazonia (Large-scale Biosphere-atmosphere experiment in Amazonia, LBA) Central (EXPRESSO) and Southern (SAFARI 2000) Africa, Asia and Central America. Flux measurement methods include leaf-scale (enclosure measurements), canopy-scale (above canopy tower measurements), landscape-scale (tethered balloon), and regional-scale (aircraft measurements) observations. Typical midday isoprene emission rates for different landscapes vary by more than a factor of 20 with the lowest emissions observed from degraded forests. Emissions of alpha-pinene vary by a similar amount with the highest emissions associated with landscapes dominated by light dependent monoterpene emitting plants. Isoprene emissions tend to be higher for neotropical forests (Amazon and Costa Rica) in comparison to Africa and Asian tropical forests but considerable differences are observed within regions. Strong seasonal variations were observed in both the Congo and the Amazon rainforests with peak emissions during the dry seasons. Substantial emissions of light dependent monoterpenes, methanol and acetone are characteristic of at least some tropical landscapes.

  6. Contrasting patterns of leaf trait variation among and within species during tropical dry forest succession in Costa Rica.

    Science.gov (United States)

    Derroire, Géraldine; Powers, Jennifer S; Hulshof, Catherine M; Cárdenas Varela, Luis E; Healey, John R

    2018-01-10

    A coordinated response to environmental drivers amongst individual functional traits is central to the plant strategy concept. However, whether the trait co-ordination observed at the global scale occurs at other ecological scales (especially within species) remains an open question. Here, for sapling communities of two tropical dry forest types in Costa Rica, we show large differences amongst traits in the relative contribution of species turnover and intraspecific variation to their directional changes in response to environmental changes along a successional gradient. We studied the response of functional traits associated with the leaf economics spectrum and drought tolerance using intensive sampling to analyse inter- and intra-specific responses to environmental changes and ontogeny. Although the overall functional composition of the sapling communities changed during succession more through species turnover than through intraspecific trait variation, their relative contributions differed greatly amongst traits. For instance, community mean specific leaf area changed mostly due to intraspecific variation. Traits of the leaf economics spectrum showed decoupled responses to environmental drivers and ontogeny. These findings emphasise how divergent ecological mechanisms combine to cause great differences in changes of individual functional traits over environmental gradients and ecological scales.

  7. Tropical rainforest methane consumption during the El Niño of 2015-16

    Science.gov (United States)

    Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Allen, M. F.

    2016-12-01

    Tropical forests sequester up to 40% of the anthropogenic and natural carbon exchanged with the atmosphere. Even though soils are the largest pool of terrestrial carbon, relatively little is known about the methane consumption capacity of tropical forest soils. Under high water, low oxygen (anaerobic) conditions, carbon decomposed is respired as methane (CH4) by methanogen microorganisms. During dry seasons, deeper rainforest soils remain wet, but dry at the surface. Since molecule for molecule the global warming potential of CH4 is two orders of magnitude greater than CO2, the relative production and sequestration of CO2 versus CH4 in tropical rainforests has a large impact on global climate trends. In 2015-16, the globe experienced an unusually strong ENSO event, which impacted the tropics. Atypical ENSO climatic events such as this include drought in tropical forests of Central America. We hypothesized that ENSO controls much of the year-to-year variability in the global CH4 cycle, primarily by turning the tropical forest from a strong annual source for CH4 during the La Niña or normal rainy season, to a year-round sink for CH4 during El Niño events. Further, we hypothesized that during a strong El Niño event, the unusually dry conditions of the tropical rainy season lead to the methanotrophs in these soils consuming large amounts of CH4. In order to investigate these predictions, CH4 flux was measured in three campaigns in March, during peak ENSO impact, as well as May and July 2016, at the La Selva Biological Station, Costa Rica. Fluxes were measured in eight paired plots, each with four collars. The collars measure 20 cm diameter by 12 cm in length, inserted into the soil, with a collar height of around 8 cm, in February 2016, a month before the first field campaign. Air samples were injected into pre-evacuated exetainers, and analyzed by gas chromatograph within 72 h. We found an average CH4 sink of -0.018 mg m-2 h-1. This flux is roughly four times lower

  8. Plant cover and hydrological response in a seasonally dry tropical forest (SDTF = Cobertura vegetal e as respostas hidrológicas em floresta tropical sazonalmente seca (FTSS

    Directory of Open Access Journals (Sweden)

    Eunice Maia de Andrade

    2017-10-01

    Full Text Available The scarcity of information on the processes of rainfall-flow limits understanding of the hydrology of dry regions of the world. In order to minimise the problem, this study was developed to investigate the influence of the characteristics of rainfall events and plant cover on the effective precipitation (Pe in a seasonally dry tropical forest (SDTF in the Northeast of Brazil. The study was carried out in two paired watersheds, one with SDTF under regeneration for 35 years (CR35 and the other under thinned SDTF for 5 years (TC. A historical series of five years (2009-2013 was analysed, with a total of 203 rainfall events, where only those rainfall events that generated a Pe > 1.0 mm were considered. CR35 had a greater number of Pe events (47 than TC (35. Rainfall depth and intensity were the factors that best explained the effective precipitation under both types of vegetation cover. The influence of herbaceous vegetation on the reduction of surface runoff was demonstrated by the smaller runoff depth and the greater potential for soil water storage in the watershed under thinned Caatinga. This fact leads to the conclusion that the technique of thinning is suitable management for Caatinga vegetation, and is capable of promoting the retention of soil water. = A escassez de informações sobre os processos chuva-deflúvio é uma limitação no entendimento da hidrologia das regiões secas do globo terrestre. Buscando minimizar esta problemática, desenvolveuse este estudo objetivando investigar as influências das características dos eventos pluviométricos e da cobertura vegetal na precipitação efetiva (Pe em floresta tropical sazonalmente seca (FTSS, no nordeste do Brasil. O estudo foi realizado em duas microbacias emparelhadas, uma com FTSS em regeneração há 35 anos (CR35 e outra com FTSS raleada há 5 anos (CR. Foi analisada uma série histórica de cinco anos (2009-2013, com um total de 203 eventos pluviométricos, sendo considerados

  9. Effects of precipitation regime and soil nitrogen on leaf traits in seasonally dry tropical forests of the Yucatan Peninsula, Mexico.

    Science.gov (United States)

    Roa-Fuentes, Lilia L; Templer, Pamela H; Campo, Julio

    2015-10-01

    Leaf traits are closely associated with nutrient use by plants and can be utilized as a proxy for nutrient cycling processes. However, open questions remain, in particular regarding the variability of leaf traits within and across seasonally dry tropical forests. To address this, we considered six leaf traits (specific area, thickness, dry matter content, N content, P content and natural abundance (15)N) of four co-occurring tree species (two that are not associated with N2-fixing bacteria and two that are associated with N2-fixing bacteria) and net N mineralization rates and inorganic N concentrations along a precipitation gradient (537-1036 mm per year) in the Yucatan Peninsula, Mexico. Specifically we sought to test the hypothesis that leaf traits of dominant plant species shift along a precipitation gradient, but are affected by soil N cycling. Although variation among different species within each site explains some leaf trait variation, there is also a high level of variability across sites, suggesting that factors other than precipitation regime more strongly influence leaf traits. Principal component analyses indicated that across sites and tree species, covariation in leaf traits is an indicator of soil N availability. Patterns of natural abundance (15)N in foliage and foliage minus soil suggest that variation in precipitation regime drives a shift in plant N acquisition and the openness of the N cycle. Overall, our study shows that both plant species and site are important determinants of leaf traits, and that the leaf trait spectrum is correlated with soil N cycling.

  10. Antioxidant content in two CAM bromeliad species as a response to seasonal light changes in a tropical dry deciduous forest.

    Science.gov (United States)

    González-Salvatierra, Claudia; Luis Andrade, José; Escalante-Erosa, Fabiola; García-Sosa, Karlina; Manuel Peña-Rodríguez, Luis

    2010-07-01

    Plants have evolved photoprotective mechanisms to limit photodamage; one of these mechanisms involves the biosynthesis of antioxidant metabolites to neutralize reactive oxygen species generated when plants are exposed to excess light. However, it is known that exposure of plants to conditions of extreme water stress and high light intensity results in their enhanced susceptibility to over-excitation of photosystem II and to photooxidative stress. In this investigation we used the 2,2-diphenyl-1-picrylhydrazyl reduction assay to conduct a broad survey of the effect of water availability and light exposure conditions on the antioxidant activity of the leaf extracts of two bromeliad species showing crassulacean acid metabolism. One of these was an epiphyte, Tillandsia brachycaulos, and the other a terrestrial species, Bromelia karatas. Both species were found growing wild in the tropical dry deciduous forest of Dzibilchaltún National Park, México. The microenvironment of T. brachycaulos and B. karatas experiences significant diurnal and seasonal light variations as well as changes in temperature and water availability. The results obtained showed that, for both bromeliads, increases in antioxidant activity occurred during the dry season, as a consequence of water stress and higher light conditions. Additionally, in T. brachycaulos there was a clear correlation between high light intensity conditions and the content of anthocyanins which accumulated below the leaf epidermis. This result suggests that the role of these pigments is as photoprotective screens in the leaves. The red coloration below the leaf epidermis of B. karatas was not due to anthocyanins but to other unidentified pigments. 2010 Elsevier GmbH. All rights reserved.

  11. Accumulation and distribution of dry matter in relation to root yield of ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-10-05

    Oct 5, 2009 ... Cassava an important staple food is grown both in upland and inland valley in the tropics. A trial to ... high dry matter also produce high leaf area index and root yield ..... Proportion (%) of DM accumulated in root stock.

  12. Regional variation in Caribbean dry forest tree species composition

    Science.gov (United States)

    Janet Franklin; Julie Ripplinger; Ethan H. Freid; Humfredo Marcano-Vega; David W. Steadman

    2015-01-01

    How does tree species composition vary in relation to geographical and environmental gradients in a globally rare tropical/subtropical broadleaf dry forest community in the Caribbean? We analyzed data from 153 Forest Inventory and Analysis (FIA) plots from Puerto Rico and the U.S. Virgin Islands (USVI), along with 42 plots that we sampled in the Bahamian Archipelago (...

  13. Explosive Radiation of Malpighiales Supports a Mid-Cretaceous Origin of Modern Tropical Rain Forests

    OpenAIRE

    Wurdack, Kenneth J.; Jaramillo, Carlos A.; Davis, Charles; Webb, Campbell O.; Donoghue, Michael J.

    2005-01-01

    Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, p...

  14. Evaporation from Pinus caribaea plantations on former grassland soils under maritime tropical conditions.

    NARCIS (Netherlands)

    Waterloo, M.J.; Bruijnzeel, L.A.; Vugts, H.F.; Rawaqa, T.T.

    1999-01-01

    Wet canopy and dry canopy evaporation from young and mature plantations of Pinus caribaea on former grassland soils under maritime tropical conditions in southwestern Viti Levu, Fiji, were determined using micrometeorological and hydrological techniques. Modeled annual evaporation totals (ET) of

  15. Evaporation from Pinus caribaea plantations on former grassland soils under maritime tropical conditions

    NARCIS (Netherlands)

    Waterloo, M.J.; Bruijnzeel, L.A.; Vugts, H.F.; Rawaqa, T.T.

    1999-01-01

    Wet canopy and dry canopy evaporation from young and mature plantations of Pinus caribaea on former grassland soils under maritime tropical conditions in southwestern Viti Levu, Fiji, were determined using micrometeorological and hydrological techniques. Modeled annual evaporation totals (ET) of

  16. FUEL CONDITIONS ASSOCIATED WITH NATIVE AND EXOTIC GRASSES IN A SUBTROPICAL DRY FOREST IN PUERTO RICO

    Science.gov (United States)

    Jarrod M. Thaxton; Skip J. Van Bloem; Stefanie Whitmire

    2012-01-01

    Exotic grasses capable of increasing frequency and intensity of anthropogenic fire have invaded subtropical and tropical dry forests worldwide. Since many dry forest trees are susceptible to fire, this can result in decline of native species and loss of forest cover. While the contribution of exotic grasses to altered fire regimes has been well documented, the role of...

  17. Timber drying kilns using solar energy

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-15

    The objective of this project was to research the potential for solar kilns for drying timber in tropical countries (Guyana, Honduras and Belize) and produce a manual which will provide the knowledge necessary to build and operate a solar kiln. The main output of the project is the manual Solar Heated Timber Drying Kilns - a Manual on their Design and Operation. The manual covers:- background information; selection of construction materials; methods of kiln construction; kiln operation and maintenance procedure. The manual has been designed to provide the necessary knowledge and confidence to build and operate a solar kiln, and ultimately benefit from an improved product. Specifically, the manual will benefit small building construction units, furniture and joinery manufacturers and sawmill operators in developing and developed countries worldwide. (author)

  18. Application of digital field photographs as documents for tropical plant inventory1

    Science.gov (United States)

    LaFrankie, James V.; Chua, Anna I.

    2015-01-01

    Premise of the study: We tested the credibility and significance of digital field photographs as supplements or substitutes for conventional herbarium specimens with particular relevance to exploration of the tropics. Methods: We made 113 collections in triplicate at a species-rich mountain in the Philippines while we took 1238 digital photographs of the same plants. We then identified the plants from the photographs alone, categorized the confidence of the identification and the reason for failure to identify, and compared the results to identifications based on the dried specimens. Results: We identified 72.6% of the photographic sets with high confidence and 27.4% with low confidence or only to genus. In no case was a confident identification altered by subsequent examination of the dried specimen. The failure to identify photographic sets to species was due to the lack of a key feature in 67.8% of the cases and due to a poorly understood taxonomy in 32.2%. Discussion: We conclude that digital photographs cannot replace traditional herbarium specimens as the primary elements that document tropical plant diversity. However, photographs represent a new and important artifact that aids an expedient survey of tropical plant diversity while encouraging broad public participation. PMID:25995976

  19. Insights into the historical construction of species-rich Mesoamerican seasonally dry tropical forests: the diversification of Bursera (Burseraceae, Sapindales).

    Science.gov (United States)

    De-Nova, J Arturo; Medina, Rosalinda; Montero, Juan Carlos; Weeks, Andrea; Rosell, Julieta A; Olson, Mark E; Eguiarte, Luis E; Magallón, Susana

    2012-01-01

    • Mesoamerican arid biomes epitomize neotropical rich and complex biodiversity. To document some of the macroevolutionary processes underlying the vast species richness of Mesoamerican seasonally dry tropical forests (SDTFs), and to evaluate specific predictions about the age, geographical structure and niche conservatism of SDTF-centered woody plant lineages, the diversification of Bursera is reconstructed. • Using a nearly complete Bursera species-level phylogeny from nuclear and plastid genomic markers, we estimate divergence times, test for phylogenetic and temporal diversification heterogeneity, test for geographical structure, and reconstruct habitat shifts. • Bursera became differentiated in the earliest Eocene, but diversified during independent early Miocene consecutive radiations that took place in SDTFs. The late Miocene average age of Bursera species, the presence of phylogenetic geographical structure, and its strong conservatism to SDTFs conform to expectations derived from South American SDTF-centered lineages. • The diversification of Bursera suggests that Mesoamerican SDTF richness derives from high speciation from the Miocene onwards uncoupled from habitat shifts, during a period of enhanced aridity resulting mainly from global cooling and regional rain shadows. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  20. FITTING AND TESTING ALLOMETRIC EQUATIONS FOR MEXICO’S SINALOAN TROPICAL DRY TREES AND FOREST INVENTORY PLOTS

    Directory of Open Access Journals (Sweden)

    Jose de Jesus Navar Chaidez

    2016-05-01

    Full Text Available Aboveground tree biomass (bole, branches and foliage, M, plays a key role in the conventional and sustainable management of forest communities. The standard approach to assess tree or plot M is harvesting trees, developing and fitting allometric equations to trees or forest inventory plot data. In the absence of local tree allometry, it is usually recommended to fit off site allometric equations to evaluate tree or plot M. This research aims: (a to develop an updated on site allometric equation (b to fit available off site allometric equations to destructively harvested trees and (c to fit available allometric equations to plot M of Mexico’s Sinaloan tropical dry forests to understand sources of inherent tree and plot M variability. Results showed that: (a the improved on site allometric equation increases precision in contrast to the conventional biomass equation previously reported as well as to off site tree M equations, (b off site allometry projects tree and plot M deviates by close to one order of magnitude. Two tested and recommended approaches to increase tree and plot M precision when fitting off site equations are: (i to use all available tree allometric functions to come up with a mean equation or (ii to calibrate off site equations by fitting new, local parameters that can be calculated using statistical programs.These options would eventually increase tree and plot M precision in regional evaluations.

  1. Restoring lepidopteran diversity in a tropical dry forest: relative importance of restoration treatment, tree identity and predator pressure

    Directory of Open Access Journals (Sweden)

    Lizet Solis-Gabriel

    2017-05-01

    Full Text Available Tropical dry forests (TDFs have been widely transformed by human activities worldwide and the ecosystem services they provide are diminishing. There has been an urgent call for conservation and restoration of the degraded lands previously occupied by TDFs. Restoration experiences aim to recover species diversity and ecological functions. Different restoration strategies have been used to maximize plant performance including weeding, planting or using artificial mulching. In this investigation, we evaluated whether different restoration practices influence animal arrival and the reestablishment of biotic interactions. We particularly evaluated lepidopteran larvae diversity and caterpillar predation on plants established under different restoration treatments (mulching, weeding and control in the Pacific West Coast of México. This study corroborated the importance of plant host identity for lepidopteran presence in a particular area. Lepidopteran diversity and herbivory rates were not affected by the restoration treatment but they were related to tree species. In contrast, caterpillar predation marks were affected by restoration treatment, with a greater number of predation marks in control plots, while caterpillar predation marks among plant species were not significantly different. This study highlights the importance of considering the introduction of high plant species diversity when planning TDF restoration to maximize lepidopteran diversity and ecosystem functioning.

  2. Restoring lepidopteran diversity in a tropical dry forest: relative importance of restoration treatment, tree identity and predator pressure.

    Science.gov (United States)

    Solis-Gabriel, Lizet; Mendoza-Arroyo, Wendy; Boege, Karina; Del-Val, Ek

    2017-01-01

    Tropical dry forests (TDFs) have been widely transformed by human activities worldwide and the ecosystem services they provide are diminishing. There has been an urgent call for conservation and restoration of the degraded lands previously occupied by TDFs. Restoration experiences aim to recover species diversity and ecological functions. Different restoration strategies have been used to maximize plant performance including weeding, planting or using artificial mulching. In this investigation, we evaluated whether different restoration practices influence animal arrival and the reestablishment of biotic interactions. We particularly evaluated lepidopteran larvae diversity and caterpillar predation on plants established under different restoration treatments (mulching, weeding and control) in the Pacific West Coast of México. This study corroborated the importance of plant host identity for lepidopteran presence in a particular area. Lepidopteran diversity and herbivory rates were not affected by the restoration treatment but they were related to tree species. In contrast, caterpillar predation marks were affected by restoration treatment, with a greater number of predation marks in control plots, while caterpillar predation marks among plant species were not significantly different. This study highlights the importance of considering the introduction of high plant species diversity when planning TDF restoration to maximize lepidopteran diversity and ecosystem functioning.

  3. Ethnobotanical value of dry, fallen ovaries of Bombax ceiba L. (Bombacaceae: Malvales

    Directory of Open Access Journals (Sweden)

    S. Gopakumar

    2012-12-01

    Full Text Available In the tropics, the traditional ecological knowledge regarding utilization of diverse Non Timber Forest Products (NTFPs available with different human communities remains under-explored. Though not on an organized scale, the collection and sale of various NTFPs, help the members of tropical rural communities to sustain themselves. Bombax ceiba, a tropical moist deciduous tree has various ethnobotanical values. Semul gum is edible and possesses medicinal value. Immature fruits of this tree have value as an expectorant, stimulant and diuretic. Extracts of young roots are used for treating dysentery. Now the dry, fallen ovaries of this tree species have a new commercial value, and are being widely collected and traded by some local herbalists in Thrissur District of Kerala.

  4. WET AND DRY SEASON ECOSYSTEM LEVEL FLUXES OF ISOPRENE AND MONOTERPENES FROM A SOUTHEAST ASIAN SECONDARY FOREST AND RUBBER TREE PLANTATION

    Science.gov (United States)

    Canopy scale fluxes of isoprene and monoterpenes were investigated in both wet and dry seasons above a rubber tree (Hevea brasiliensis)/secondary tropical forest in the Yunnan province of southwestern China. Drought conditions were unusually high during the dry season experiment....

  5. Prospects and Challenges in tropical isotope dendroclimatology

    Science.gov (United States)

    Evans, M. N.; Anchukaitis, K. J.; White, S. R.; Ektvedt, T. M.; Penniston, R. C.; Rheaume, M. M.; Bowman, D. M.

    2008-12-01

    We review a stable isotope-based approach to the development, modeling, interpretation, and analysis of hydrometeorological estimates from tropical trees. The strategy overcomes the common problem of missing, intermittent or non-annual ring structure in tropical trees by relying instead on the observation of the annual wet-dry seasonality typical to tropical environments as mirrored in the oxygen isotopic composition of wood-derived α-cellulose. We explore regions for which forward modeling of the proxy system would expect us to resolve hydrometeorological variations associated with the El Niño-Southern Oscillation (ENSO) phenomenon, rather than being limited to regions with tree species or environments producing verifiable annual ring chronologies. A modified protocol allows for rapid, simple and non-toxic micro-extraction of pure α-cellulose, which is isotopically indistinguishable from that produced by more classical means. We describe a new reactor for the pyrolysis of α-cellulose in an induction heater, which permits isotopic analysis of α-cellulose samples as small as 30μg, and as many as 100 automated sample analyses per day. A forward model adapted for tropical environments can be used to test and refine the interpretation of the isotopic data, and to predict locales for which we should be able to maximize the paleoclimatic potential of future sample collections. We have found the modeled isotopic chronometer and raingage in agreement with independent chronological controls in a variety of environments and tree species in Costa Rica, Indonesia, Brazil, Peru and Australia. Development of long hydrometeorological records from the terrestrial tropics is underway not only by our group, but by a growing number of collaborators and colleagues. Together we should be able to build a network of paleoprecipitation records and better understand the linkages between tropical surface ocean temperatures and large-scale drought.

  6. Land use policies and deforestation in Brazilian tropical dry forests between 2000 and 2015

    Science.gov (United States)

    Dupin, Mariana G. V.; Espírito-Santo, Mário M.; Leite, Marcos E.; Silva, Jhonathan O.; Rocha, André M.; Barbosa, Rômulo S.; Anaya, Felisa C.

    2018-03-01

    Tropical Dry Forests (TDFs) have been broadly converted into pastures and crops, with direct consequences to biodiversity, ecosystem services, and social welfare. Such land use and cover changes (LUCC) usually are strongly influenced by government environmental and development policies. The present study aimed at analyzing LUCC in Brazilian TDFs between 2000 and 2015, using the north of Minas Gerais state (128 000 km2) as a case study. We evaluated the potential biophysical and social-economic drivers of TDF loss, natural regeneration and net area change at the county level. Further, we determined the effects of these LUCC variables on socioeconomic indicators. We identified a considerable change in TDF cover, expressed as 9825 km2 of deforestation and 6523 km2 of regeneration, which resulted in a net loss of 3302 km2. The annual rate of TDF cover change was -1.2%, which is extremely high for a vegetation type that is protected as part of the Atlantic Rain Forest biome since 1993. TDF deforestation was directly affected by county area and by the increase in cattle density, and inversely affected by terrain declivity, indicating that land conversion is mostly driven by cattle ranching in flat regions. TDF regeneration was directly affected by county area and inversely affected by the increase in population density and terrain declivity. LUCC variables did not affect welfare indicators, undermining claims from rural sectors that TDF protection would cause a socioeconomic burden for northern Minas Gerais. Our results highlight the importance of naturally regenerating secondary forests to the maintenance of ecosystem integrity and its services, which are frequently neglected in conservation strategies. Hegemonic macroeconomic policies affecting TDFs have been deeply rooted in deforestation for commodities production, and need urgent review because they cause long-term environmental impacts without evidence of welfare gains.

  7. Effect of Tropical Climatic Conditions on the Stability of Cefaclor Dry ...

    African Journals Online (AJOL)

    Erah

    This study was carried out to investigate the effect of moisture sorption at two different storage conditions ... Keywords: Dry powder for suspension; Moisture content; Colour; Stability; Moisture migration;. Interaction. ..... condensation. Sorption of ...

  8. Anfibios de un bosque seco tropical: Reserva Ecológica Arenillas, Ecuador

    OpenAIRE

    Szekely, József Paul

    2016-01-01

    Arenillas Ecological Reserve (Reserva Ecológica Arenillas - REA) is located in southwestern Ecuador, close to the Peruvian border, and belongs to the Tumbesian Endemism Region and is one of the last remnants of tropical dry forests at altitudes below 100 m a.s.l. Climate is characterized by a rainy season extending from January to May and a dry season extending from June to December. Few studies on the amphibians from the reserve have been made so far. Over a period of twelve months, from 201...

  9. Plant diversity patterns in neotropical dry forests and their conservation implications

    Science.gov (United States)

    K. Banda-R; A. Delgado-Salinas; K. G. Dexter; R. Linares-Palomino; A. Oliveira-Filho; D. Prado; M. Pullan; C. Quintana; R. Riina; G. M. Rodriguez M.; J. Weintritt; P. Acevedo-Rodriguez; J. Adarve; E. Alvarez; A. Aranguren B.; J. C. Arteaga; G. Aymard; A. Castano; N. Ceballos-Mago; A. Cogollo; H. Cuadros; F. Delgado; W. Devia; H. Duenas; L. Fajardo; A. Fernandez; M. A. Fernandez; J. Franklin; E. H. Freid; L. A. Galetti; R. Gonto; R. Gonzalez-M.; R. Graveson; E. H. Helmer; A. Idarraga; R. Lopez; H. Marcano-Vega; O. G. Martinez; H. M. Maturo; M. McDonald; K. McLaren; O. Melo; F. Mijares; V. Mogni; D. Molina; N. d. P. Moreno; J. M. Nassar; D. M. Neves; L. J. Oakley; M. Oatham; A. R. Olvera-Luna; F. F. Pezzini; O. J. R. Dominguez; M. E. Rios; O. Rivera; N. Rodriguez; A. Rojas; T. Sarkinen; R. Sanchez; M. Smith; C. Vargas; B. Villanueva; R. T. Pennington

    2016-01-01

    Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than...

  10. Heavy metals pollution influence the community structure of Cyanobacteria in nutrient rich tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Anas, A.; Jasmin, C.; Sheeba V.A.; Gireeshkumar, T.R; Nair, S.

    , Mn, Fe, Ni, Cu and Zn) on community structure of cyanobacteria in a nutrient rich tropical estuary, Cochin Estuary (CE), across the southwest coast of India. Dissolved heavy metals were higher in CE during dry season, with Zn as major pollutant...

  11. Response of cultivars of malanga (Xanthosoma sagittifolium (L. Schott to dry rot

    Directory of Open Access Journals (Sweden)

    Ernesto Espinosa Cuéllar

    2017-01-01

    Full Text Available Malanga (Xanthosoma sagittifolium (L. Schott is an important food crop for over 400 million people in the tropics and subtropics. In order to determine the response of different varieties of malanga Xanthosoma to dry rot, a series of experiments were conducted in the period between 2012 and 2014. The experiments were performed on loamy Soil at the National Research Institute in Tropical Crops and Roots (INIVIT. We determined the incidence and severity of damage, yields and percent of losses at harvest. The lowest values of incidence and the highest total return was achieved in clons ‘INIVIT MX-95-2’, ‘INIVIT MX-95-1’ and ‘INIVIT MX-2007’. Clones of malanga Xanthosoma belonging to the group purple, showed lower incidence that of white and yellow groups. These results will allow selecting cultivars of malanga with greater resistance to the dry rot and with this to diminish the losses in the harvest.

  12. Large scale atmospheric tropical circulation changes and consequences during global warming

    International Nuclear Information System (INIS)

    Gastineau, G.

    2008-01-01

    The changes of the tropical large scale circulation during climate change can have large impacts on human activities. In a first part, the meridional atmospheric tropical circulation was studied in the different coupled models. During climate change, we find, on the one hand, that the Hadley meridional circulation and the subtropical jet are significantly shifted poleward, and on the other hand, that the intensity of the tropical circulation weakens. The slow down of the atmospheric circulation results from the dry static stability changes affecting the tropical troposphere. Secondly, idealized simulations are used to explain the tropical circulation changes. Ensemble simulation using the model LMDZ4 are set up to study the results from the coupled model IPSLCM4. The weakening of the large scale tropical circulation and the poleward shift of the Hadley cells are explained by both the uniform change and the meridional gradient change of the sea surface temperature. Then, we used the atmospheric model LMDZ4 in an aqua-planet configuration. The Hadley circulation changes are explained in a simple framework by the required poleward energy transport. In a last part, we focus on the water vapor distribution and feedback in the climate models. The Hadley circulation changes were shown to have a significant impact on the water vapour feedback during climate change. (author)

  13. Four new bat species (Rhinolophus hildebrandtii complex) reflect Plio-Pleistocene divergence of dwarfs and giants across an Afromontane archipelago.

    Science.gov (United States)

    Taylor, Peter J; Stoffberg, Samantha; Monadjem, Ara; Schoeman, Martinus Corrie; Bayliss, Julian; Cotterill, Fenton P D

    2012-01-01

    Gigantism and dwarfism evolve in vertebrates restricted to islands. We describe four new species in the Rhinolophus hildebrandtii species-complex of horseshoe bats, whose evolution has entailed adaptive shifts in body size. We postulate that vicissitudes of palaeoenvironments resulted in gigantism and dwarfism in habitat islands fragmented across eastern and southern Africa. Mitochondrial and nuclear DNA sequences recovered two clades of R. hildebrandtii senso lato which are paraphyletic with respect to a third lineage (R. eloquens). Lineages differ by 7.7 to 9.0% in cytochrome b sequences. Clade 1 includes R. hildebrandtii sensu stricto from the east African highlands and three additional vicariants that speciated across an Afromontane archipelago through the Plio-Pleistocene, extending from the Kenyan Highlands through the Eastern Arc, northern Mozambique and the Zambezi Escarpment to the eastern Great Escarpment of South Africa. Clade 2 comprises one species confined to lowland savanna habitats (Mozambique and Zimbabwe). A third clade comprises R. eloquens from East Africa. Speciation within Clade 1 is associated with fixed differences in echolocation call frequency, and cranial shape and size in populations isolated since the late Pliocene (ca 3.74 Mya). Relative to the intermediate-sized savanna population (Clade 2), these island-populations within Clade 1 are characterised by either gigantism (South African eastern Great Escarpment and Mts Mabu and Inago in Mozambique) or dwarfism (Lutope-Ngolangola Gorge, Zimbabwe and Soutpansberg Mountains, South Africa). Sympatry between divergent clades (Clade 1 and Clade 2) at Lutope-Ngolangola Gorge (NW Zimbabwe) is attributed to recent range expansions. We propose an "Allometric Speciation Hypothesis", which attributes the evolution of this species complex of bats to divergence in constant frequency (CF) sonar calls. The origin of species-specific peak frequencies (overall range = 32 to 46 kHz) represents the

  14. Climate change, allergy and asthma, and the role of tropical forests.

    Science.gov (United States)

    D'Amato, Gennaro; Vitale, Carolina; Rosario, Nelson; Neto, Herberto Josè Chong; Chong-Silva, Deborah Carla; Mendonça, Francisco; Perini, Josè; Landgraf, Loraine; Solé, Dirceu; Sánchez-Borges, Mario; Ansotegui, Ignacio; D'Amato, Maria

    2017-01-01

    Tropical forests cover less than 10 per cent of all land area (1.8 × 107 km 2 ) and over half of the tropical-forest area (1.1 × 107 Km 2 ) is represented by humid tropical forests (also called tropical rainforests). The Amazon basin contains the largest rainforest on Earth, almost 5.8 million km 2 , and occupies about 40% of South America; more than 60% of the basin is located in Brazil and the rest in Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname and Venezuela. Over the past decade the positive role of tropical rainforests in capturing large amounts of atmospheric carbon dioxide (CO 2 ) has been demonstrated. In response to the increase in atmospheric CO 2 concentration, tropical forests act as a global carbon sink. Accumulation of carbon in the tropical terrestrial biosphere strongly contributes to slowing the rate of increase of CO 2 into the atmosphere, thus resulting in the reduction of greenhouse gas effect. Tropical rainforests have been estimated to account for 32-36% of terrestrial Net Primary Productivity (NPP) that is the difference between total forest photosynthesis and plant respiration. Tropical rainforests have been acting as a strong carbon sink in this way for decades. However, over the past years, increased concentrations of greenhouse gases, and especially CO 2 , in the atmosphere have significantly affected the net carbon balance of tropical rainforests, and have warmed the planet substantially driving climate changes through more severe and prolonged heat waves, variability in temperature, increased air pollution, forest fires, droughts, and floods. The role of tropical forests in mitigating climate change is therefore critical. Over the past 30 years almost 600,000 km 2 have been deforested in Brazil alone due to the rapid development of Amazonia, this is the reason why currently the region is one of the 'hotspots' of global environmental change on the planet. Deforestation represents the second largest

  15. Silvicultural treatments enhance growth rates of future crop trees in a tropical dry forest

    NARCIS (Netherlands)

    Villegas, Z.; Peña-Claros, M.; Mostacedo, B.; Alarcón, A.; Licona, J.C.; Leaño, C.; Pariona, W.; Choque, U.

    2009-01-01

    Silvicultural treatments are often needed in selectively logged tropical forest to enhance the growth rates of many commercial tree species and, consequently, for recovering a larger proportion of the initial volume harvested over the next cutting cycle. The available data in the literature suggest,

  16. Frequency and distribution of forest, savanna, and crop fires over tropical regions during PEM-Tropics A

    Science.gov (United States)

    Olson, Jennifer R.; Baum, Bryan A.; Cahoon, Donald R.; Crawford, James H.

    1999-03-01

    Advanced very high resolution radiometer 1.1 km resolution satellite radiance data were used to locate active fires throughout much of the tropical region during NASA's Global Tropospheric Experiment (GTE) Pacific Exploratory Mission-Tropics (PEM-Tropics A) aircraft campaign, held in September and October 1996. The spatial and temporal distributions of the fires in Australia, southern Africa, and South America are presented here. The number of fires over northern Australia, central Africa, and South America appeared to decrease toward the end of the mission period. Fire over eastern Australia was widespread, and temporal patterns showed a somewhat consistent amount of burning with periodic episodes of enhanced fire counts observed. At least one episode of enhanced fire counts corresponded to the passage of a frontal system which brought conditions conducive to fire to the region, with strong westerlies originating over the hot, dry interior continent. Regions that were affected by lower than normal rainfall during the previous wet season (e.g., northern Australia and southwestern Africa) showed relatively few fires during this period. This is consistent with a drought-induced decrease in vegetation and therefore a decreased availability of fuel for burning. Alternatively, a heavier than normal previous wet season along the southeastern coast of South Africa may have contributed to high fuel loading and an associated relatively heavy amount of burning compared to data from previous years.

  17. [Dynamics of Amomum villosum growth and its fruit yield cultivated under tropical forests].

    Science.gov (United States)

    Zheng, Zheng; Gan, Jianmin; Feng, Zhili; Meng, Ying

    2004-01-01

    Investigations on the dynamics of Amomum villosum growth and its fruit yield cultivated under tropical ravine rainforest and secondary forest at different elevations in Xishuangbanna showed that the yield of A. villosum was influenced by the site age, sun light level of understorey, and water stress in dry season. The fruit yield and mature plant density decreased with increasing age of the A. villosum site. The fruit yield increased with sun light level when the light level in understorey was under 35% of full sun light (P forest was not significant. Planned cultivation of A. villosum in the secondary forest of the shifting cultivation land by ravine from 800-1000 m elevation instead of customary cultivation in the ravine rainforest, could not only resolve the problem of the effect of light deficiency in understorey and water stress in the dry season on A. villosum fruit yield, but also be useful to protect the tropical ravine rain forest.

  18. Leaf gas exchange in the frankincense tree (Boswellia papyrifera) of African dry woodlands

    NARCIS (Netherlands)

    Mengistu, T.; Sterck, F.J.; Fetene, M.; Tadesse, W.; Bongers, F.

    2011-01-01

    A conceptual model was tested for explaining environmental and physiological effects on leaf gas exchange in the deciduous dry tropical woodland tree Boswellia papyrifera (Del.) Hochst. For this species we aimed at (i) understanding diurnal patterns in leaf gas exchange, (ii) exploring cause–effect

  19. The roles of convection, extratropical mixing, and in-situ freeze-drying in the Tropical Tropopause Layer

    Directory of Open Access Journals (Sweden)

    W. G. Read

    2008-10-01

    Full Text Available Mechanisms for transporting and dehydrating air across the tropical tropopause layer (TTL are investigated with a conceptual two dimensional (2-D model. The 2-D TTL model combines the Holton and Gettelman cold trap dehydration mechanism (Holton and Gettelman, 2001 with the two column convection model of Folkins and Martin (2005. We investigate 3 possible transport scenarios through the TTL: 1 slow uniform ascent across the level of zero radiative heating without direct convective mixing, 2 convective mixing of H2O vapor at 100% relative humidity with respect to ice (RHi with no ice retention, and 3 convective mixing of extremely subsaturated air (100% RHi following the moist adiabatic temperature above the level of neutral buoyancy with sufficient ice retention such that total H2O is 100%RHi. The three mechanisms produce similar seasonal cycles for H2O that are in good quantitative agreement with the Aura Microwave Limb Sounder (MLS measurements. We use Aura MLS measurement of CO and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer measurement of HDO to distinguish among the transport mechanisms. Model comparisons with the observations support the view that H2O is predominantly controlled by regions having the lowest cold point tropopause temperature but the trace species CO and HDO support the convective mixing of dry air and lofted ice. The model provides some insight into the processes affecting the long term trends observed in stratospheric H2O.

  20. Estimating tropical vertical motion profile shapes from satellite observations

    Science.gov (United States)

    Back, L. E.; Handlos, Z.

    2013-12-01

    The vertical structure of tropical deep convection strongly influences interactions with larger scale circulations and climate. This research focuses on investigating this vertical structure and its relationship with mesoscale tropical weather states. We test the hypothesis that vertical motion shape varies in association with weather state type. We estimate mean state vertical motion profile shapes for six tropical weather states defined using cloud top pressure and optical depth properties from the International Satellite Cloud Climatology Project. The relationship between vertical motion and the dry static energy budget are utilized to set up a regression analysis that empirically determines two modes of variability in vertical motion from reanalysis data. We use these empirically determined modes, this relationship and surface convergence to estimate vertical motion profile shape from observations of satellite retrievals of rainfall and surface convergence. We find that vertical motion profile shapes vary systematically between different tropical weather states. The "isolated systems" regime exhibits a more ''bottom-heavy'' profile shape compared to the convective/thick cirrus and vigorous deep convective regimes, with maximum upward vertical motion occurring in the lower troposphere rather than the middle to upper troposphere. The variability we observe with our method does not coincide with that expected based on conventional ideas about how stratiform rain fraction and vertical motion are related.

  1. Growing tropical forage legumes in full sun and silvopastoral systems

    Directory of Open Access Journals (Sweden)

    Saulo Alberto do Carmo Araújo

    2017-02-01

    Full Text Available Growth was evaluated three tropical forage legumes in two cropping systems: silvopastoral system (SSP and full sun. A completely randomized design was adopted in factorial three legumes (estilosanthes cv. Campo Grande (Stylozanthes macrocephala x Stylozanthes capitata, tropical kudzu (Pueraria phaseoloides (Roxb. Benth and macrotiloma (Macrotyloma axillare cv. Java x two farming systems, with 4 repetitions. A eucalyptus SSP already deployed, with spatial arrangement of 12 x 2 m between trees was used. Legumes were planted in January 2014 a uniform cut being made in May 2014. The court assessment was carried out 125 days after the uniformity cut. There was difference for mass production of dry legumes (PMMSL between cultivation systems, evidencing increased productivity in the farming full sun. The macrotiloma showed higher PMSL (5.29 kg DM ha-1 cut-1, while the kudzu obtained the lowest yield (3.42 kg DM ha-1 cut-1 in the sun growing full. The cultivation of legumes in SSP increased the levels of mineral matter, crude protein and neutral detergent fiber. The shade provided by the SSP caused a reduction in the mass of dry matter production, but also altered the chemical composition of the studied legumes.

  2. Correlations of Mean Process Parameters for Agricultural Products Drying in Thin Bed in Solar Direct Dryers

    Directory of Open Access Journals (Sweden)

    MSc. Ciro César Bergues-Ricardo

    2015-11-01

    Full Text Available A group of correlations is given between mean parameters of drying process drying velocity, energy losses, useful energy, and thermal efficiency. Those are suitable for conditions of thin bed drying, in direct solar dryers, and may help for developing of an integral approach of solar drying in those conditions. Correlations are reliable for drying processes of diverse crop products specified, suchas roots, seeds, vegetables, fruits, wood, etc, with natural or forced convection. Correlations were validated in Cuba for usual ranges of efficiency and products in solar dryers of cover, cabinet and house types, in tropical conditions. These correlations are useful for design and exploitation ofdryers and for theoretical and practical comprehension of solar drying like a system.

  3. Environmental constraints on the compositional and phylogenetic beta-diversity of tropical forest snake assemblages.

    Science.gov (United States)

    Moura, Mario R; Costa, Henrique C; Argôlo, Antônio J S; Jetz, Walter

    2017-09-01

    The ongoing biodiversity crisis increases the importance and urgency of studies addressing the role of environmental variation on the composition and evolutionary history of species assemblages, but especially the tropics and ectotherms remain understudied. In regions with rainy summers, coexistence of tropical ectothermic species may be determined by the partitioning of the climatic niche, as ectotherms can rely on water availability and thermoregulatory behaviour to buffer constraints along their climatic niche. Conversely, tropical ectotherms facing dry summers would have fewer opportunities to climatic niche partitioning and other processes rather than environmental filtering would mediate species coexistence. We used 218 snake assemblages to quantify the compositional (CBD) and phylogenetic (PBD) beta-diversity of snakes in the Atlantic Forest (AF) hotspot, South America. We identify two AF regions with distinct climatological regimes: dry summers in the northern-AF and rainy summers in the southern-AF. While accounting for the influence of multiscale spatial processes, we disentangle the relative contribution of thermal, water-related and topographic conditions in structuring the CBD and PBD of snake assemblages, and determine the extent in which snake assemblages under distinct climatological regimes are affected by environmental filtering. Thermal conditions best explain CBD and PBD of snakes for the whole AF, whereas water-related factors best explain the structure of snake assemblages within a same climatological regime. CBD and PBD patterns are similarly explained by spatial factors but snake assemblages facing dry summers are more affected by spatial processes operating at fine to intermediate spatial scale, whereas those assemblages in regions with rainy summers have a stronger signature of coarse-scale processes. As expected, environmental filtering plays a stronger role in southern-AF than northern-AF, and the synergism between thermal and water

  4. Tropical cyanobacterial blooms: a review of prevalence, problem taxa, toxins and influencing environmental factors

    Directory of Open Access Journals (Sweden)

    Maxine A.D. Mowe

    2014-12-01

    Full Text Available Toxic cyanobacterial blooms are a major issue in freshwater systems in many countries. The potentially toxic species and their ecological causes are likely to be different in tropical zones from those in temperate water bodies; however, studies on tropical toxic cyanobacterial blooms are sporadic and currently there is no global synthesis. In this review, we examined published information on tropical cyanobacterial bloom occurrence and toxin production to investigate patterns in their growth and distribution. Microcystis was the most frequently occurring bloom genus throughout tropical Asia, Africa and Central America, while Cylindrospermopsis and Anabaena blooms occurred in various locations in tropical Australia, America and Africa. Microcystis blooms were more prevalent during the wet season while Cylindrospermopsis blooms were more prevalent during the dry period. Microcystin was the most encountered toxin throughout the tropics. A meta-analysis of tropical cyanobacterial blooms showed that Microcystis blooms were more associated with higher total nitrogen concentrations, while Cylindrospermopsis blooms were more associated with higher maximum temperatures. Meta-analysis also showed a positive linear relationship between levels of microcystin and N:P (nitrate:phosphate ratio. Tropical African Microcystis blooms were found to have the lowest microcystin levels in relation to biomass and N:P (nitrate:phosphate compared to tropical Asian, Australian and American blooms. There was also no significant correlation between microcystin concentration and cell concentration for tropical African blooms as opposed to tropical Asian and American blooms. Our review illustrates that some cyanobacteria and toxins are more prevalent in tropical areas. While some tropical countries have considerable information regarding toxic blooms, others have few or no reported studies. 

  5. Demise and rise : the biogeography and taxonomy of the Odonata of tropical Africa

    NARCIS (Netherlands)

    Dijkstra, Klaas-Douwe Benediktus

    2007-01-01

    Africa has a large and almost uninterrupted land surface that is isolated from surrounding continents. In the last 20 million years Africa had a variable and increasingly dry climate. As a result the Afrotropics have only half as many odonate species as tropical America or Asia. ‘Relict’ families

  6. Collective Action in the Management of a Tropical Dry Forest Ecosystem: Effects of Mexico's Property Rights Regime

    Science.gov (United States)

    Schroeder, Natalia Mariel; Castillo, Alicia

    2013-04-01

    Dilemmas of natural resources governance have been a central concern for scholars, policy makers, and users. Major debates occur over the implications of property rights for common resources management. After the Mexican Revolution (1910-1917), land was distributed mainly as ejidos conceived as a hereditary but unalienable collective form of property. In 1992, a new Agrarian Law was decreed that allows individual ownership by removing various restrictions over the transfer of land. Scholars have examined the reform mainly focusing on land-tenure changes and environmental fragmentation. This study examines how the new ownership regime is affecting collective decision-making in ejidos located in a tropical dry forest (TDF) ecosystem. Information on decision-making processes before and after the 1992 reform was gathered through 52 interviews conducted in four ejidos selected along a gradient including agricultural, cattle-raising, and TDF use. The new individualized land property system reduced collective action in ejidos but did not trigger it. Collective action responses to the 1992 reform were buffered by self-organization each ejido already had. Heterogeneous users who shared a short history and showed little understanding of TDF and low dependence on its resources seemed to explain why ejidos have not been able to share a sense of community that would shape the construction of institutions for the collective management of forest resources. However, when a resource is scarce and highly valuable such as water the same users showed capacities for undertaking costly co-operative activities.

  7. Spoil characteristics and vegetation development of an age series of mine spoils in a dry tropical environment

    Energy Technology Data Exchange (ETDEWEB)

    Jha, A K; Singh, J S [Banaras Hindu University, Varanasi (India). Dept. of Botany

    1991-12-01

    A series of coal mine spoils (5,10,12,16 and 20-yr old) in a dry tropical environment was sampled to assess the changes with time in spoil characteristics, species composition and plant biomass. Coarse fragments ({gt} 2 mm) decreased with age of mine spoil while the proportion of 0.2-0.1 mm particles increased. Total soil N, mineral N, NaHCO{sub 3}-extractable P, and exchangeable K increased with age of mine spoil and these parameters were lower in mine spoils than native forest soil even after 20 years of succession. Exchangeable Na decreased with age of mine spoil and in 20-yr old spoil it was higher than native forest soil. Plant community composition changed with age. Only a few species participated in community formation. Species richness increased with age, while evenness and species diversity declined from 5-yr old to 16-yr old community with an increase in the 20-yr old community. A reverse trend occurred for concentration of dominance. Area-weighted shoot and root biomass of other species increased with the age of the mine spoil while that of Xanthium strumarium patches declined with age. Data collection on spoil features, microbial C, N and P,and shoot and root biomass when subjected to Discriminant Analysis indicated a continued profound effect of age. 10 and 12-yr old mine spoils were closer to each other and 5 and 20-yr old spoils were farthest apart.

  8. Spoil characteristics and vegetation development of an age series of mine spoils in a dry tropical environment

    International Nuclear Information System (INIS)

    Jha, A.K.; Singh, J.S.

    1991-01-01

    A series of coal mine spoils (5,10,12,16 and 20-yr old) in a dry tropical environment was sampled to assess the changes with time in spoil characteristics, species composition and plant biomass. Coarse fragments (> 2 mm) decreased with age of mine spoil while the proportion of 0.2-0.1 mm particles increased. Total soil N, mineral N, NaHCO 3 -extractable P, and exchangeable K increased with age of mine spoil and these parameters were lower in mine spoils than native forest soil even after 20 years of succession. Exchangeable Na decreased with age of mine spoil and in 20-yr old spoil it was higher than native forest soil. Plant community composition changed with age. Only a few species participated in community formation. Species richness increased with age, while evenness and species diversity declined from 5-yr old to 16-yr old community with an increase in the 20-yr old community. A reverse trend occurred for concentration of dominance. Area-weighted shoot and root biomass of other species increased with the age of the mine spoil while that of Xanthium strumarium patches declined with age. Data collection on spoil features, microbial C, N and P,and shoot and root biomass when subjected to Discriminant Analysis indicated a continued profound effect of age. 10 and 12-yr old mine spoils were closer to each other and 5 and 20-yr old spoils were farthest apart

  9. Vegetation structure and composition of a tropical dry forest in regeneration in Bataclán (Cali, Colombia

    Directory of Open Access Journals (Sweden)

    Viviana Londoño Lemos

    2015-01-01

    Full Text Available Characterization of long-term vegetation in a tropical dry forest (TDF that is in the process of regeneration permits establishment of patterns of composition, structure and dynamics of plant communities and sheds light on the different stages of plant succession. In this study, the plant community of ecoparque Bataclán, Cali, Colombia was evaluated by determining its structure and composition in two regeneration strategies. One strategy consisted of natural regeneration with bamboo barriers and the other of natural regeneration without bamboo barriers. Three permanent plots of 500 m2 were established in each regeneration strategy (six plots in total. Composition and structure was determined, taking into account all the growth habits, with different sampling methods. We found no significant differences between vegetation structure and composition of the two strategies for forest regeneration. forty-one species belonging to 27 families were recorded (trees and shrubs 58.5 %, herbs 24.4 %, climbers or scandents 14.6 %, epiphytes 2.4 %. The dominant family was Melastomataceae and the dominant species was Miconia prasina. The orchidCatasetum ochraceum and the grass Thrasya petrosa were indicator species for high luminosity. We conclude that the plant community is in an early successional stage, where there is a mixture of planted and naturally regenerated species in the zone, characterized by pioneer species from TDF and other nearby life zones.

  10. Desorption isotherms of heavy (AZOBE, EBONY) and light heavyweight tropical woods (IROKO, SAPELLI) of Cameroon

    Science.gov (United States)

    Nsouandélé, J. L.; Tamba, J. G.; Bonoma, B.

    2018-04-01

    This work is centered on the study of the desorption isotherms of heavy (Azobe, Ebony) and heavyweight (Iroko, Sapelli) tropical woods, which contribute in the determination of drying and storage of tropical plank woods. Desorption isotherms of tropical woods were experimentally determined under different temperatures in this study using the gravimetric method. The determination of Henderson's model isotherms parameters of desorption were obtained for temperatures of 20 °C, 30 °C, 40 °C, and 50 °C. The mean relative deviation between theoretical and experimental moisture contents was calculated and fitted well with the desorption models of tropical woods. We noticed that Henderson models fitted much better with experimental ones for 95% of relative humidity. The sigmoid shapes of results are satisfactory. Hysteresis phenomenon was observed for desorption isotherms of heavy (Azobe, Ebony) and heavyweight (Iroko, Sapelli) tropical woods. Results showed the difference between the stability and use of heavy and heavyweight tropical wood. These results help in the estimation of water content at equilibrium of tropical woods in relative humidity from experimented ones. Hygroscopic equilibrium humidity of heavy tropical woods varied between 0% and 50% while those of heavyweight varied between 0% and 25%. Therefore, these woods can be used in an opened environment; woodwork and decoration.

  11. Water vapor stable isotope observations from tropical Australia

    KAUST Repository

    Parkes, Stephen

    2015-04-01

    The response of the tropical hydrological cycle to anthropogenically induced changes in radiative forcing is one of the largest discrepancies between climate models. Paleoclimate archives of the stable isotopic composition of precipitation in the tropics indicate a relationship with precipitation amount that could be exploited to study past hydroclimate and improve our knowledge of how this region responds to changes in climate forcing. Recently modelling studies of convective parameterizations fitted with water isotopes and remote sensing of water vapor isotopes in the tropics have illustrated uncertainty in the assumed relationship with rainfall amount. Therefore there is a need to collect water isotope data in the tropics that can be used to evaluate these models and help identify the relationships between the isotopic composition of meteoric waters and rainfall intensity. However, data in this region is almost non-existent. Here we present in-situ water vapor isotopic measurements and the HDO retrievals from the co-located Total Column Carbon Observing Network (TCCON) site at Darwin in Tropical Australia. The Darwin site is interestingly placed within the tropical western pacific region and is impacted upon by a clear monsoonal climate, and key climate cycles including ENSO and Madden Julian Oscillations. The analysis of the data illustrated relationships between water vapor isotopes and humidity which demonstrated the role of precipitation processes in the wet season and air mass mixing during the dry season. Further the wet season observations show complex relationships between humidity and isotopes. A simple Rayleigh distillation model was not obeyed, instead the importance of rainfall re-evaporation in generating the highly depleted signatures was demonstrated. These data potentially provide a useful tool for evaluating model parameterizations in monsoonal regions as they demonstrate relationships with precipitation processes that cannot be observed with

  12. Scavenger removal: Bird and bat carcass persistence in a tropical wind farm

    Science.gov (United States)

    Villegas-Patraca, Rafael; Macías-Sánchez, Samuel; MacGregor-Fors, Ian; Muñoz-Robles, Carlos

    2012-08-01

    Energy produced by wind farms has diverse positive environmental effects, but can also be related to negative impacts, including wildlife mortality through collisions with wind turbines. Bird and bat mortality caused by collisions with wind turbines can be estimated indirectly by counting carcasses within wind farms. However, carcass removal by scavengers often biases such measurements. In this study, we identified the main scavengers removing bird and bat carcasses in a tropical wind farm. A known fate analysis was done to assess the effect of carcass type (i.e., small bird, large bird, bat), vegetation type (i.e., secondary vegetation, croplands) and season (dry and rainy seasons of 2009) on carcass persistence rates. We identified three main scavenger groups, with mammals being the most abundant group. Our results show high rates of carcass removal relative to previous studies, especially for bats; there were fewer remaining carcasses after 20 days in our tropical site than in non-tropical environments reported elsewhere. We found a higher carcass persistence rate during the rainy season than in the dry season, possibly due to a greater abundance of food resources for scavenger organisms in the rainy season. Although we found some evidence for higher persistence rates for large bird carcasses than for small bird and bat carcasses during the rainy season, overall carcass type was not a strong predictor of persistence rates. Similarly, we did not find a strong effect of vegetation type on carcass persistence rates. Results suggest that in order to estimate accurate bird and bat mortality in tropical wind farm areas, seasonality should be incorporated to correction factors of carcass removal rates.

  13. Extremely low prevalence of Batrachochytrium dendrobatidis in frog populations from neotropical dry forest of Costa Rica supports the existence of a climatic refuge from disease.

    Science.gov (United States)

    Zumbado-Ulate, Héctor; Bolaños, Federico; Gutiérrez-Espeleta, Gustavo; Puschendorf, Robert

    2014-12-01

    Population declines and extinctions of numerous species of amphibians, especially stream-breeding frogs, have been linked to the emerging infectious disease chytridiomycosis, caused by the chytrid fungus, Batrachochytrium dendrobatidis. In Central America, most of the 34 species of the Craugastor punctariolus species group have disappeared in recent years in high- and low-elevation rainforests. Distribution models for B. dendrobatidis and the continuous presence of the extirpated stream-dwelling species, Craugastor ranoides, in the driest site of Costa Rica (Santa Elena Peninsula), suggest that environmental conditions might restrict the growth and development of B. dendrobatidis, existing as a refuge from chytridiomycosis-driven extinction. We conducted field surveys to detect and quantify the pathogen using Real-time PCR in samples from 15 species of frogs in two locations of tropical dry forest. In Santa Elena Peninsula, we swabbed 310 frogs, and only one sample of the species, C. ranoides, tested positive for B. dendrobatidis (prevalence dry and hot environments of tropical dry forest. This study supports the existence of climatic refuges from chytridiomycosis and highlights the importance of tropical dry forest conservation for amphibians in the face of epidemic disease.

  14. Moringa oleifera: un árbol multiusos para las zonas tropicales secas Moringa oleifera: a multipurpose tree for the dry tropics

    Directory of Open Access Journals (Sweden)

    Mark E. Olson

    2011-12-01

    Full Text Available En zonas tropicales secas, el árbol de la moringa (Moringa oleifera Lam. es objeto de gran atención por parte de los productores, en tanto que crece el número de proveedores que promueven la planta como panacea. Ante esta situación, es necesario separar los usos que están identificados y fundamentados por el conocimiento científico de aquellos que no lo están. Con base en el presente estudio y en la literatura, se presenta un resumen de las bases científicas que sustentan algunos de los beneficios de la moringa, en la medida de lo que hasta hoy se conoce. Los análisis comprueban que la harina de hoja de la moringa se compara favorablemente con la leche en polvo en cuanto a sus componentes de proteína y de calcio y tiene, adicionalmente, un alto contenido de vitamina A. Además de su valor nutritivo, las hojas son ricas en antioxidantes, entre los cuales destacan los isotiocianatos, los cuales parecen presentar propiedades anticancerígenas, hipotensoras, hipoglucemiantes y antibióticas. Las concentraciones de factores antinutritivos en las hojas, tales como inhibidores de proteasas, taninos, saponinas y lectinas, son insignificantes. La mayoría de los estudios sobre las cualidades benéficas de la moringa se han llevado a cabo in vitro o en animales; por lo tanto, se desconocen las dosis necesarias para producir algún efecto benéfico en humanos. Sin embargo, dado que los beneficios potenciales son muchos y los niveles de sustancias antinutricionales bajísimos, no encontramos argumentos en contra del consumo de la planta. En resumen, Moringa oleifera es un alimento nutritivo y benéfico que ofrece características muy atractivas para establecer su cultivo en comunidades sostenibles en el trópico seco de México y otros países de Latinoamérica.Farmers in the dry tropics are increasingly turning their attention to the moringa tree (Moringa oleifera Lam., while the plant is increasingly touted as a cure-all for ailments from cancer

  15. Tropical convection regimes in climate models: evaluation with satellite observations

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    A. K. Steiner

    2018-04-01

    Full Text Available High-quality observations are powerful tools for the evaluation of climate models towards improvement and reduction of uncertainty. Particularly at low latitudes, the most uncertain aspect lies in the representation of moist convection and interaction with dynamics, where rising motion is tied to deep convection and sinking motion to dry regimes. Since humidity is closely coupled with temperature feedbacks in the tropical troposphere, a proper representation of this region is essential. Here we demonstrate the evaluation of atmospheric climate models with satellite-based observations from Global Positioning System (GPS radio occultation (RO, which feature high vertical resolution and accuracy in the troposphere to lower stratosphere. We focus on the representation of the vertical atmospheric structure in tropical convection regimes, defined by high updraft velocity over warm surfaces, and investigate atmospheric temperature and humidity profiles. Results reveal that some models do not fully capture convection regions, particularly over land, and only partly represent strong vertical wind classes. Models show large biases in tropical mean temperature of more than 4 K in the tropopause region and the lower stratosphere. Reasonable agreement with observations is given in mean specific humidity in the lower to mid-troposphere. In moist convection regions, models tend to underestimate moisture by 10 to 40 % over oceans, whereas in dry downdraft regions they overestimate moisture by 100 %. Our findings provide evidence that RO observations are a unique source of information, with a range of further atmospheric variables to be exploited, for the evaluation and advancement of next-generation climate models.

  16. Tropical convection regimes in climate models: evaluation with satellite observations

    Science.gov (United States)

    Steiner, Andrea K.; Lackner, Bettina C.; Ringer, Mark A.

    2018-04-01

    High-quality observations are powerful tools for the evaluation of climate models towards improvement and reduction of uncertainty. Particularly at low latitudes, the most uncertain aspect lies in the representation of moist convection and interaction with dynamics, where rising motion is tied to deep convection and sinking motion to dry regimes. Since humidity is closely coupled with temperature feedbacks in the tropical troposphere, a proper representation of this region is essential. Here we demonstrate the evaluation of atmospheric climate models with satellite-based observations from Global Positioning System (GPS) radio occultation (RO), which feature high vertical resolution and accuracy in the troposphere to lower stratosphere. We focus on the representation of the vertical atmospheric structure in tropical convection regimes, defined by high updraft velocity over warm surfaces, and investigate atmospheric temperature and humidity profiles. Results reveal that some models do not fully capture convection regions, particularly over land, and only partly represent strong vertical wind classes. Models show large biases in tropical mean temperature of more than 4 K in the tropopause region and the lower stratosphere. Reasonable agreement with observations is given in mean specific humidity in the lower to mid-troposphere. In moist convection regions, models tend to underestimate moisture by 10 to 40 % over oceans, whereas in dry downdraft regions they overestimate moisture by 100 %. Our findings provide evidence that RO observations are a unique source of information, with a range of further atmospheric variables to be exploited, for the evaluation and advancement of next-generation climate models.

  17. Wood Decomposition of Cyrilla racemiflora (Cyrillaceae) in Puerto Rican Dry and Wet Forests: A 13-year Case Study.

    Science.gov (United States)

    Juan A. Torres; Grizelle Gonzalez

    2005-01-01

    We studied the decomposition of Cyrilla racemiflora logs over a 13-yr period in tropical dry and wet forests in Puerto Rico. The mean mass loss, ratio of soft to hard wood, nutrient concentrations, and the diversity of wood-inhabiting organisms were greater in logs decomposing in the dry forest than in the wet forest. Termites were also more abundant in the logs...

  18. Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

    Science.gov (United States)

    Tang Che Ing, A.; Stoy, P. C.; Melling, L.

    2014-12-01

    Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

  19. Storms in the tropics of Titan.

    Science.gov (United States)

    Schaller, E L; Roe, H G; Schneider, T; Brown, M E

    2009-08-13

    Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe at latitudes thought incapable of supporting convection (and thus strong rain) has been suggested to be due to geological seepage or other mechanisms not related to precipitation. Here we report the presence of bright, transient, tropospheric clouds in tropical latitudes. We find that the initial pulse of cloud activity generated planetary waves that instigated cloud activity at other latitudes across Titan that had been cloud-free for at least several years. These observations show that convective pulses at one latitude can trigger short-term convection at other latitudes, even those not generally considered capable of supporting convection, and may also explain the presence of methane-carved rivers and channels near the Huygens landing site.

  20. Tropical forest cover change in the 1990s and options for future monitoring.

    Science.gov (United States)

    Mayaux, Philippe; Holmgren, Peter; Achard, Frédéric; Eva, Hugh; Stibig, Hans-Jürgen; Branthomme, Anne

    2005-02-28

    Despite the importance of the world's humid tropical forests, our knowledge concerning their rates of change remains limited. Two recent programmes (FAO 2000 Forest Resources Assessment and TREES II), exploiting the global imaging capabilities of Earth observing satellites, have recently been completed to provide information on the dynamics of tropical forest cover. The results from these independent studies show a high degree of conformity and provide a good understanding of trends at the pan-tropical level. In 1990 there were some 1150 million ha of tropical rain forest with the area of the humid tropics deforested annually estimated at 5.8 million ha (approximately twice the size of Belgium). A further 2.3 million ha of humid forest is apparently degraded annually through fragmentation, logging and/or fires. In the sub-humid and dry tropics, annual deforestation of tropical moist deciduous and tropical dry forests comes to 2.2 and 0.7 million ha, respectively. Southeast Asia is the region where forests are under the highest pressure with an annual change rate of -0.8 to -0.9%. The annual area deforested in Latin America is large, but the relative rate (-0.4 to -0.5%) is lower, owing to the vast area covered by the remaining Amazonian forests. The humid forests of Africa are being converted at a similar rate to those of Latin America (-0.4 to -0.5% per year). During this period, secondary forests have also been established, through re-growth on abandoned land and forest plantations, but with different ecological, biophysical and economic characteristics compared with primary forests. These trends are significant in all regions, but the extent of new forest cover has proven difficult to establish. These results, as well as the lack of more detailed knowledge, clearly demonstrate the need to improve sound scientific evidence to support policy. The two projects provide useful guidance for future monitoring efforts in the context of multilateral environmental

  1. Determining the K coefficient to leaf area index estimations in a tropical dry forest

    Science.gov (United States)

    Magalhães, Sarah Freitas; Calvo-Rodriguez, Sofia; do Espírito Santo, Mário Marcos; Sánchez Azofeifa, Gerardo Arturo

    2018-03-01

    Vegetation indices are useful tools to remotely estimate several important parameters related to ecosystem functioning. However, improving and validating estimations for a wide range of vegetation types are necessary. In this study, we provide a methodology for the estimation of the leaf area index (LAI) in a tropical dry forest (TDF) using the light diffusion through the canopy as a function of the successional stage. For this purpose, we estimated the K coefficient, a parameter that relates the normalized difference vegetation index (NDVI) to LAI, based on photosynthetically active radiation (PAR) and solar radiation. The study was conducted in the Mata Seca State Park, in southeastern Brazil, from 2012 to 2013. We defined four successional stages (very early, early, intermediate, and late) and established one optical phenology tower at one plot of 20 × 20 m per stage. Towers measured the incoming and reflected solar radiation and PAR for NDVI calculation. For each plot, we established 24 points for LAI sampling through hemispherical photographs. Because leaf cover is highly seasonal in TDFs, we determined ΔK (leaf growth phase) and K max (leaf maturity phase). We detected a strong correlation between NDVI and LAI, which is necessary for a reliable determination of the K coefficient. Both NDVI and LAI varied significantly between successional stages, indicating sensitivity to structural changes in forest regeneration. Furthermore, the K values differed between successional stages and correlated significantly with other environmental variables such as air temperature and humidity, fraction of absorbed PAR, and soil moisture. Thus, we established a model based on spectral properties of the vegetation coupled with biophysical characteristics in a TDF that makes possible to estimate LAI from NDVI values. The application of the K coefficient can improve remote estimations of forest primary productivity and gases and energy exchanges between vegetation and atmosphere

  2. Recovering more than tree cover: herbivores and herbivory in a restored tropical dry forest.

    Directory of Open Access Journals (Sweden)

    Iris Juan-Baeza

    Full Text Available Intense and chronic disturbance may arrest natural succession, reduce environmental quality and lead to ecological interaction losses. Where natural succession does not occur, ecological restoration aims to accelerate this process. While plant establishment and diversity is promoted by restoration, few studies have evaluated the effect of restoration activities on ecological processes and animal diversity. This study assessed herbivory and lepidopteran diversity associated with two pioneer tree species growing in 4-year-old experimental restoration plots in a tropical dry forest at Sierra de Huautla, in Morelos, Mexico. The study was carried out during the rainy season of 2010 (July-October in eleven 50 x 50 m plots in three different habitats: cattle-excluded, cattle-excluded with restoration plantings, and cattle grazing plots. At the beginning of the rainy season, 10 juveniles of Heliocarpus pallidus (Malvaceae and Ipomoea pauciflora (Convolvulaceae were selected in each plot (N = 110 trees. Herbivory was measured in 10 leaves per plant at the end of the rainy season. To evaluate richness and abundance of lepidopteran larvae, all plants were surveyed monthly. Herbivory was similar among habitats and I. pauciflora showed a higher percentage of herbivory. A total of 868 lepidopteran larvae from 65 morphospecies were recorded. The family with the highest number of morphospecies (9 sp. was Geometridae, while the most abundant family was Saturnidae, with 427 individuals. Lepidopteran richness and abundance were significantly higher in H. pallidus than in I. pauciflora. Lepidopteran richness was significantly higher in the cattle-excluded plots, while abundance was significantly higher in the non-excluded plots. After four years of cattle exclusion and the establishment of plantings, lepidopteran richness increased 20 -fold in the excluded plots compared to the disturbed areas, whereas herbivory levels were equally high in both restored and

  3. Effects of soil water depletion on the water relations in tropical kudzu

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    Adaucto Bellarmino de Pereira-Netto

    1999-07-01

    Full Text Available Tropical kudzu (Pueraria phaseoloides (Roxb. Benth., Leguminosae: Faboideae is native to the humid Southeastern Asia. Tropical kudzu has potential as a cover crop in regions subjected to dryness. The objective of this paper was to evaluate the effect of soil water depletion on leaflet relative water content (RWC, stomatal conductance (g and temperature (T L in tropical kudzu. RWC of waterstressed plants dropped from 96 to 78%, following a reduction in SWC from 0.25 to 0.17 g (H2O.g (dry soil-1.Stomatal conductance of stressed plants decreased from 221 to 98 mmol.m-2.s-1, following the reduction in soil water content (SWC. The day after re-irrigation, g of water stressed plants was 15% lower than g of unstressed plants. Differences in T L between waterstressed and unstressed plants (deltaT L rose linearly from 0.1 to 2.2ºC following progressive water deficit. RWC and T L of waterstressed plants paralled RWC and T L of unstressed plants the day after reirrigation. The strong decrease in SWC found in this study only induced moderate water stress in tropical kudzu. In addition, tropical kudzu recover rapidly from the induced water stress after the re-irrigation.

  4. Tropical Glaciers

    Science.gov (United States)

    Fountain, Andrew

    The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.

  5. Heavy metal concentrations in redeveloping soil of mine spoil under plantations of certain native woody species in dry tropical environment, India

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.N.; Zeng, D.H.; Chen, F.S. [Chinese Academy of Science, Shenyang (China). Inst. of Applied Ecology

    2005-07-01

    Total concentration of heavy metals (Cd, Cr, Cu, Fe, Pb, Ni, Mn and Zn) was estimated in the redeveloping soil of mine spoil under 5-yr old plantations of four woody species namely: Albizia lebbeck, Albizia procera, Tectona grandis and Dendrocalamus strictus. The data recorded in the present study were compared with other unplanted coal mine spoil colliery, which was around to the study site and adjoining area of dry tropical forest. Among all the heavy metals, the maximum concentration was found for Fe and minimum for Cd. However, among all four species, total concentrations of these heavy metals were recorded maximally in the plantation plots of T. grandis except for Fe, while minimally in A. lebbeck except for Zn, whereas, the maximum concentration of Fe and Zn was in the plantation plots of D. strictus and A. procera. Statistical analysis revealed significant differences due to species for all the heavy metals except Cu. Among four species, A. lebbeck, A. procera and D. strictus showed more efficient for reducing heavy metal concentrations whereas T. grandis was not more effective to reduce heavy metal concentrations in redeveloping soil of mine spoil.

  6. Heavy metal concentrations in redeveloping soil of mine spoil under plantations of certain native woody species in dry tropical environment, India.

    Science.gov (United States)

    Singh, Anand N; Zeng, De-hui; Chen, Fu-sheng

    2005-01-01

    Total concentration of heavy metals (Cd, Cr, Cu, Fe, Pb, Ni, Mn and Zn) was estimated in the redeveloping soil of mine spoil under 5-yr old plantations of four woody species namely: Albizia lebbeck, Albizia procera, Tectona grandis and Dendrocalamus strictus. The data recorded in the present study were compared with other unplanted coal mine spoil colliery, which was around to the study site and adjoining area of dry tropical forest. Among all the heavy metals, the maximum concentration was found for Fe and minimum for Cd. However, among all four species, total concentrations of these heavy metals were recorded maximally in the plantation plots of T. grandis except for Fe, while minimally in A. lebbeck except for Zn, whereas, the maximum concentration of Fe and Zn was in the plantation plots of D. strictus and A. procera. Statistical analysis revealed significant differences due to species for all the heavy metals except Cu. Among four species, A. lebbeck, A. procera and D. strictus showed more efficient for reducing heavy metal concentrations whereas T. grandis was not more effective to reduce heavy metal concentrations in redeveloping soil of mine spoil.

  7. Height-related changes in leaf photosynthetic traits in diverse Bornean tropical rain forest trees.

    Science.gov (United States)

    Kenzo, Tanaka; Inoue, Yuta; Yoshimura, Mitsunori; Yamashita, Megumi; Tanaka-Oda, Ayumi; Ichie, Tomoaki

    2015-01-01

    Knowledge of variations in morphophysiological leaf traits with forest height is essential for quantifying carbon and water fluxes from forest ecosystems. Here, we examined changes in leaf traits with forest height in diverse tree species and their role in environmental acclimation in a tropical rain forest in Borneo that does not experience dry spells. Height-related changes in leaf physiological and morphological traits [e.g., maximum photosynthetic rate (Amax), stomatal conductance (gs), dark respiration rate (Rd), carbon isotope ratio (δ(13)C), nitrogen (N) content, and leaf mass per area (LMA)] from understory to emergent trees were investigated in 104 species in 29 families. We found that many leaf area-based physiological traits (e.g., A(max-area), Rd, gs), N, δ(13)C, and LMA increased linearly with tree height, while leaf mass-based physiological traits (e.g., A(max-mass)) only increased slightly. These patterns differed from other biomes such as temperate and tropical dry forests, where trees usually show decreased photosynthetic capacity (e.g., A(max-area), A(max-mass)) with height. Increases in photosynthetic capacity, LMA, and δ(13)C are favored under bright and dry upper canopy conditions with higher photosynthetic productivity and drought tolerance, whereas lower R d and LMA may improve shade tolerance in lower canopy trees. Rapid recovery of leaf midday water potential to theoretical gravity potential during the night supports the idea that the majority of trees do not suffer from strong drought stress. Overall, leaf area-based photosynthetic traits were associated with tree height and the degree of leaf drought stress, even in diverse tropical rain forest trees.

  8. The Neutral Detergent Fiber Digestibility of Some Tropical Grasses at Different Stage of Maturity

    Directory of Open Access Journals (Sweden)

    P Mahyuddin

    2009-09-01

    Full Text Available The digestibility of neutral detergent fiber (IVNDFD was determined by Telly and Terry methods in vitro on 5 tropical grasses species, Sorghum, Themeda, Iseilema, Brachyacne and Dicanthium. Stem and leaf samples were harvested at different maturity stages, started from early flowering stage to the stage when the grasses were dried. In general, IVNDFD ranged from 22% to 41%. Stages of maturity affected IVNDFD in 4 species; IVNDFD was higher in the stems than in the leaves for 2 species out of 5 species of grasses; the rest was similar. There was no correlation between NDF and IVNDFD, showing that NDF degradability in the rumen was vary. Digestibility potential of NDF (PDNDF varied from 21% to 44% and has negative correlation with IVNDFD (r=0.75. Growth affected PDNDF in 2 species; and 3 out 5 species observed showed PDNDF in the leaves was higher than that in the stems. Negative correlation was exist between dry matter digestibility (IVDMD, water soluble extract (WSE and protein with PDNDF. Grasses with stated PDNDF values have relatively high NDF retention in the rumen, which will cause low NDF or dry matter consumption. (Animal Production 11(3: 189-195 (2009Key Words: NDF digestibility, tropical grasses, stem, leaves, maturity stage

  9. Drought resistance in early and late secondary successional species from a tropical dry forest: the interplay between xylem resistance to embolism, sapwood water storage and leaf shedding.

    Science.gov (United States)

    Pineda-García, Fernando; Paz, Horacio; Meinzer, Frederick C

    2013-02-01

    The mechanisms of drought resistance that allow plants to successfully establish at different stages of secondary succession in tropical dry forests are not well understood. We characterized mechanisms of drought resistance in early and late-successional species and tested whether risk of drought differs across sites at different successional stages, and whether early and late-successional species differ in resistance to experimentally imposed soil drought. The microenvironment in early successional sites was warmer and drier than in mature forest. Nevertheless, successional groups did not differ in resistance to soil drought. Late-successional species resisted drought through two independent mechanisms: high resistance of xylem to embolism, or reliance on high stem water storage capacity. High sapwood water reserves delayed the effects of soil drying by transiently decoupling plant and soil water status. Resistance to soil drought resulted from the interplay between variations in xylem vulnerability to embolism, reliance on sapwood water reserves and leaf area reduction, leading to a tradeoff of avoidance against tolerance of soil drought, along which successional groups were not differentiated. Overall, our data suggest that ranking species' performance under soil drought based solely on xylem resistance to embolism may be misleading, especially for species with high sapwood water storage capacity. © 2012 Blackwell Publishing Ltd.

  10. Spatial and Temporal Microbial Patterns in a Tropical Macrotidal Estuary Subject to Urbanization

    Directory of Open Access Journals (Sweden)

    Mirjam Kaestli

    2017-07-01

    Full Text Available Darwin Harbour in northern Australia is an estuary in the wet-dry tropics subject to increasing urbanization with localized water quality degradation due to increased nutrient loads from urban runoff and treated sewage effluent. Tropical estuaries are poorly studied compared to temperate systems and little is known about the microbial community-level response to nutrients. We aimed to examine the spatial and temporal patterns of the bacterial community and its association with abiotic factors. Since Darwin Harbour is macrotidal with strong seasonal patterns and mixing, we sought to determine if a human impact signal was discernible in the microbiota despite the strong hydrodynamic forces. Adopting a single impact–double reference design, we investigated the bacterial community using next-generation sequencing of the 16S rRNA gene from water and sediment from reference creeks and creeks affected by effluent and urban runoff. Samples were collected over two years during neap and spring tides, in the dry and wet seasons. Temporal drivers, namely seasons and tides had the strongest relationship to the water microbiota, reflecting the macrotidal nature of the estuary and its location in the wet-dry tropics. The neap-tide water microbiota provided the clearest spatial resolution while the sediment microbiota reflected current and past water conditions. Differences in patterns of the microbiota between different parts of the harbor reflected the harbor's complex hydrodynamics and bathymetry. Despite these variations, a microbial signature was discernible relating to specific effluent sources and urban runoff, and the composite of nutrient levels accounted for the major part of the explained variation in the microbiota followed by salinity. Our results confirm an overall good water quality but they also reflect the extent of some hypereutrophic areas. Our results show that the microbiota is a sensitive indicator to assess ecosystem health even in this

  11. Ecophysiological and phenological strategies in seasonally-dry ecosystems: an ecohydrological approach

    Science.gov (United States)

    Vico, Giulia; Manzoni, Stefano; Thompson, Sally; Molini, Annalisa; Porporato, Amilcare

    2015-04-01

    Seasonally-dry climates are particularly challenging for vegetation, as they are characterized by prolonged dry periods and often marked inter-annual variability. During the dry season plants face predictable physiological stress due to lack of water, whereas the inter-annual variability in rainfall timing and amounts requires plants to develop flexible adaptation strategies. The variety of strategies observed across seasonally-dry (Mediterranean and tropical) ecosystems is indeed wide - ranging from near-isohydric species that adjust stomatal conductance to avoid drought, to anisohydric species that maintain gas exchange during the dry season. A suite of phenological strategies are hypothesized to be associated to ecophysiological strategies. Here we synthetize current knowledge on ecophysiological and phenological adaptations through a comprehensive ecohydrological model linking a soil water balance to a vegetation carbon balance. Climatic regimes are found to select for different phenological strategies that maximize the long-term plant carbon uptake. Inter-annual variability of the duration of the wet season allows coexistence of different drought-deciduous strategies. In contrast, short dry seasons or access to groundwater favour evergreen species. Climatic changes causing more intermittent rainfall and/or shorter wet seasons are predicted to favour drought-deciduous species with opportunistic water use.

  12. Ocean-atmosphere forcing of South American tropical paleoclimate, LGM to present

    Science.gov (United States)

    Baker, P. A.; Fritz, S. C.; Dwyer, G. S.; Rigsby, C. A.; Silva, C. G.; Burns, S. J.

    2012-12-01

    Because of many recent terrestrial paleoclimatic and marine paleoceanographic records, late Quaternary South American tropical paleoclimate is as well understood as that anywhere in the world. While lessons learned from the recent instrumental record of climate are informative, this record is too short to capture much of the lower frequency variability encountered in the paleoclimate records and much of the observed paleoclimate is without modern analogue. This paleoclimate is known to be regionally variable with significant differences both north and south of the equator and between the western high Andes and eastern lowlands of the Amazon and Nordeste Brazil. Various extrinsic forcing mechanisms affected climate throughout the period, including global concentrations of GHGs, Northern Hemisphere ice sheet forcing, seasonal insolation forcing of the South American summer monsoon (SASM), millennial-scale Atlantic forcing, and Pacific forcing of the large-scale Walker circulation. The magnitude of the climate response to these forcings varied temporally, largely because of the varying amplitude of the forcing itself. For example, during the last glacial, large-amplitude north Atlantic forcing during Heinrich 1 and the LGM itself, led to wet (dry) conditions south (north) of the equator. During the Holocene, Atlantic forcing was lower amplitude, thus seasonal insolation forcing generally predominated with a weaker-than-normal SASM during the early Holocene resulting in dry conditions in the south-western tropics and wet conditions in the eastern lowlands and Nordeste; in the late Holocene seasonal insolation reached a maximum in the southern tropics and climate conditions reversed.

  13. Assessing the effects of multiple stressors on the recruitment of fruit harvested trees in a tropical dry forest, Western Ghats, India.

    Directory of Open Access Journals (Sweden)

    Anita Varghese

    Full Text Available The harvest of non-timber forest products (NTFPs, together with other sources of anthropogenic disturbance, impact plant populations greatly. Despite this, conservation research on NTFPs typically focuses on harvest alone, ignoring possible confounding effects of other anthropogenic and ecological factors. Disentangling anthropogenic disturbances is critical in regions such as India's Western Ghats, a biodiversity hotspot with high human density. Identifying strategies that permit both use and conservation of resources is essential to preserving biodiversity while meeting local needs. We assessed the effects of NTFP harvesting (fruit harvest from canopy and lopping of branches for fruit in combination with other common anthropogenic disturbances (cattle grazing, fire frequency and distance from village, in order to identify which stressors have greater effects on recruitment of three tropical dry forest fruit tree species. Specifically, we assessed the structure of 54 populations of Phyllanthus emblica, P. indofischeri and Terminalia chebula spread across the Nilgiri Biosphere Reserve, Western Ghats to ask: (1 How are populations recruiting? and (2 What anthropogenic disturbance and environmental factors, specifically forest type and elevation, are the most important predictors of recruitment status? We combined participatory research with an information-theoretic model-averaging approach to determine which factors most affect population structure and recruitment status. Our models illustrate that for T. chebula, high fire frequency and high fruit harvest intensity decreased the proportion of saplings, while lopping branches or stems to obtain fruit increased it. For Phyllanthus spp, recruitment was significantly lower in plots with more frequent fire. Indices of recruitment of both species were significantly higher for plots in more open-canopy environments of savanna woodlands than in dry forests. Our research illustrates an approach for

  14. Assessing the effects of multiple stressors on the recruitment of fruit harvested trees in a tropical dry forest, Western Ghats, India.

    Science.gov (United States)

    Varghese, Anita; Ticktin, Tamara; Mandle, Lisa; Nath, Snehlata

    2015-01-01

    The harvest of non-timber forest products (NTFPs), together with other sources of anthropogenic disturbance, impact plant populations greatly. Despite this, conservation research on NTFPs typically focuses on harvest alone, ignoring possible confounding effects of other anthropogenic and ecological factors. Disentangling anthropogenic disturbances is critical in regions such as India's Western Ghats, a biodiversity hotspot with high human density. Identifying strategies that permit both use and conservation of resources is essential to preserving biodiversity while meeting local needs. We assessed the effects of NTFP harvesting (fruit harvest from canopy and lopping of branches for fruit) in combination with other common anthropogenic disturbances (cattle grazing, fire frequency and distance from village), in order to identify which stressors have greater effects on recruitment of three tropical dry forest fruit tree species. Specifically, we assessed the structure of 54 populations of Phyllanthus emblica, P. indofischeri and Terminalia chebula spread across the Nilgiri Biosphere Reserve, Western Ghats to ask: (1) How are populations recruiting? and (2) What anthropogenic disturbance and environmental factors, specifically forest type and elevation, are the most important predictors of recruitment status? We combined participatory research with an information-theoretic model-averaging approach to determine which factors most affect population structure and recruitment status. Our models illustrate that for T. chebula, high fire frequency and high fruit harvest intensity decreased the proportion of saplings, while lopping branches or stems to obtain fruit increased it. For Phyllanthus spp, recruitment was significantly lower in plots with more frequent fire. Indices of recruitment of both species were significantly higher for plots in more open-canopy environments of savanna woodlands than in dry forests. Our research illustrates an approach for identifying which

  15. Termites as ecological indicators of mine-land rehabilitation in tropical Australia

    International Nuclear Information System (INIS)

    Hinz, D.A.

    2001-01-01

    This paper presents examples from field research of termites as indicators of rehabilitation success in the wet-dry tropics at Nabalco's bauxite mine, Gove, Australia and in Sierra Leone, West Africa. Field studies indicate that soil-plant-animal interactions are crucial in determining the recovery of disturbed land and that termites play an over-riding role in the process. Termites are seen as ecological indicators for successful soil and vegetation development in humid tropical environments. In land rehabilitation, termites help to create healthy, self-regulated vegetation systems that integrate with the surrounding landscapes and build structures and functions equal to those of the pre-disturbed system. They are reliable in signaling the health and stress factors of a system and provide a predictable response

  16. Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae)

    NARCIS (Netherlands)

    Born, M.; Bongers, F.; Poelman, E.H.; Sterck, F.J.

    2010-01-01

    Dry-season retreat and dietary shift of the dart-poison frog Delldrobates tillCtOrillS (Anura: Dendrobatidae). Seasonal rainfall affects tropical forest dynamics and behavior of species that are part of these ecosystems. TIle positive correlation between amphibian ac tivity pattems and rainfall has

  17. How competitive is drought deciduousness in tropical forests? A combined eco-hydrological and eco-evolutionary approach

    Science.gov (United States)

    Vico, Giulia; Dralle, David; Feng, Xue; Thompson, Sally; Manzoni, Stefano

    2017-06-01

    Drought-deciduous and evergreen species are both common in tropical forests, where there is the need to cope with water shortages during periodic dry spells and over the course of the dry season. Which phenological strategy is favored depends on the long-term balance of carbon costs and gains that leaf phenology imposes as a result of the alternation of wet and dry seasons and the unpredictability of rainfall events. This study integrates a stochastic eco-hydrological framework with key plant economy traits to derive the long-term average annual net carbon gain of trees exhibiting different phenological strategies in tropical forests. The average net carbon gain is used as a measure of fitness to assess which phenological strategies are more productive and more evolutionarily stable (i.e. not prone to invasion by species with a different strategy). The evergreen strategy results in a higher net carbon gain and more evolutionarily stable communities with increasing wet season lengths. Reductions in the length of the wet season or the total rainfall, as predicted under climate change scenarios, should promote a shift towards more drought-deciduous communities, with ensuing implications for ecosystem functioning.

  18. Dispersal limitation of Tillandsia species correlates with rain and host structure in a central Mexican tropical dry forest.

    Science.gov (United States)

    Victoriano-Romero, Elizabeth; Valencia-Díaz, Susana; Toledo-Hernández, Víctor Hugo; Flores-Palacios, Alejandro

    2017-01-01

    Seed dispersal permits the colonization of favorable habitats and generation of new populations, facilitating escape from habitats that are in decline. There is little experimental evidence of the factors that limit epiphyte dispersion towards their hosts. In a tropical dry forest in central Mexico, we monitored the phenology of dispersion of epiphyte species of the genus Tillandsia; we tested experimentally whether precipitation could cause failures in seed dispersal and whether seed capture differs among vertical strata and between host species with high (Bursera copallifera) and low (Conzattia multiflora) epiphyte loads. With the exception of one species that presents late dispersion and low abundance, all of the species disperse prior to the onset of the rainy season. However, early rains immobilize the seeds, affecting up to 24% of the fruits in species with late dispersion. We observed that Tillandsia seeds reach both Bursera and Conzattia hosts, but found that adherence to the host is 4-5 times higher in Bursera. Furthermore, seeds liberated from Bursera travel shorter distances and up to half may remain within the same crown, while the highest seed capture takes place in the upper strata of the trees. We conclude that dispersion of Tillandsia seeds is limited by early rains and by the capture of seeds within the trees where populations concentrate. This pattern of capture also helps to explain the high concentrations of epiphytes in certain hosts, while trees with few epiphytes can be simultaneously considered deficient receivers and efficient exporters of seeds.

  19. Diversity in plant hydraulic traits explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests.

    Science.gov (United States)

    Xu, Xiangtao; Medvigy, David; Powers, Jennifer S; Becknell, Justin M; Guan, Kaiyu

    2016-10-01

    We assessed whether diversity in plant hydraulic traits can explain the observed diversity in plant responses to water stress in seasonally dry tropical forests (SDTFs). The Ecosystem Demography model 2 (ED2) was updated with a trait-driven mechanistic plant hydraulic module, as well as novel drought-phenology and plant water stress schemes. Four plant functional types were parameterized on the basis of meta-analysis of plant hydraulic traits. Simulations from both the original and the updated ED2 were evaluated against 5 yr of field data from a Costa Rican SDTF site and remote-sensing data over Central America. The updated model generated realistic plant hydraulic dynamics, such as leaf water potential and stem sap flow. Compared with the original ED2, predictions from our novel trait-driven model matched better with observed growth, phenology and their variations among functional groups. Most notably, the original ED2 produced unrealistically small leaf area index (LAI) and underestimated cumulative leaf litter. Both of these biases were corrected by the updated model. The updated model was also better able to simulate spatial patterns of LAI dynamics in Central America. Plant hydraulic traits are intercorrelated in SDTFs. Mechanistic incorporation of plant hydraulic traits is necessary for the simulation of spatiotemporal patterns of vegetation dynamics in SDTFs in vegetation models. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  20. Gall inducing arthropods from a seasonally dry tropical forest in Serra do Cipó, Brazil Artrópodes indutores de galhas em Floresta Sazonal Tropical Seca da Serra do Cipó, Brasil

    Directory of Open Access Journals (Sweden)

    Marcel Serra Coelho

    2009-01-01

    Full Text Available Highly diverse forms of galling arthropods can be identified in much of southeastern Brazil's vegetation. Three fragments of a Seasonally Dry Tropical Forest (SDTF located in the southern range of the Espinhaço Mountains were selected for study in the first survey of galling organisms in such tropical vegetation. Investigators found 92 distinct gall morphotypes on several organs of 51 host plant species of 19 families. Cecidomyiidae (Diptera was the most prolific gall-inducing species, responsible for the largest proportion of galls (77% observed. Leaves were the most frequently galled plant organ (63%, while the most common gall morphotype was of a spherical shape (30%. The two plant species, Baccharis dracunculifolia (Asteraceae and Celtis brasiliensis (Cannabaceae, presented the highest number of gall morphtypes, displaying an average of 5 gall morphotypes each. This is the first study of gall-inducing arthropods and their host plant species ever undertaken in a Brazilian SDTF ecosystem. Given the intense human pressure on SDTFs, the high richness of galling arthropods, and implied floral host diversity found in this study indicates the need for an increased effort to catalogue the corresponding flora and fauna, observe their intricate associations and further understand the implications of such rich diversity in these stressed and vulnerable ecosystems.Artrópodes indutores de galhas são muito ricos em espécies nas formações vegetais no sudeste do Brasil. Três fragmentos de Floresta Sazonal Tropical Seca (FSTS foram selecionados nas montanhas do sudeste da cadeia do Espinhaço para a primeira pesquisa de organismos indutores de galhas nesse tipo de vegetação. Encontramos 92 morfotipos distintos de galhas em vários órgãos de 51 espécies de plantas hospedeiras pertencentes à 19 famílias. A maioria das galhas (77% foi induzida pela família Cecidomyiidae (Diptera. A folha foi o órgão mais atacado (63%, enquanto o morfotipo mais

  1. Pan-Tropical Analysis of Climate Effects on Seasonal Tree Growth

    Science.gov (United States)

    Wagner, Fabien; Rossi, Vivien; Aubry-Kientz, Mélaine; Bonal, Damien; Dalitz, Helmut; Gliniars, Robert; Stahl, Clément; Trabucco, Antonio; Hérault, Bruno

    2014-01-01

    Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent. PMID:24670981

  2. Warming Affects Growth Rates and Microcystin Production in Tropical Bloom-Forming Microcystis Strains

    Directory of Open Access Journals (Sweden)

    Trung Bui

    2018-03-01

    Full Text Available Warming climate is predicted to promote cyanobacterial blooms but the toxicity of cyanobacteria under global warming is less well studied. We tested the hypothesis that raising temperature may lead to increased growth rates but to decreased microcystin (MC production in tropical Microcystis strains. To this end, six Microcystis strains were isolated from different water bodies in Southern Vietnam. They were grown in triplicate at 27 °C (low, 31 °C (medium, 35 °C (high and 37 °C (extreme. Chlorophyll-a-, particle- and MC concentrations as well as dry-weights were determined. All strains yielded higher biomass in terms of chlorophyll-a concentration and dry-weight at 31 °C compared to 27 °C and then either stabilised, slightly increased or declined with higher temperature. Five strains easily grew at 37 °C but one could not survive at 37 °C. When temperature was increased from 27 °C to 37 °C total MC concentration decreased by 35% in strains with MC-LR as the dominant variant and by 94% in strains with MC-RR. MC quota expressed per particle, per unit chlorophyll-a and per unit dry-weight significantly declined with higher temperatures. This study shows that warming can prompt the growth of some tropical Microcystis strains but that these strains become less toxic.

  3. Tropical radioecology

    CERN Document Server

    Baxter, M

    2012-01-01

    Tropical Radioecology is a guide to the wide range of scientific practices and principles of this multidisciplinary field. It brings together past and present studies in the tropical and sub-tropical areas of the planet, highlighting the unique aspects of tropical systems. Until recently, radioecological models for tropical environments have depended upon data derived from temperate environments, despite the differences of these regions in terms of biota and abiotic conditions. Since radioactivity can be used to trace environmental processes in humans and other biota, this book offers examples of studies in which radiotracers have been used to assess biokinetics in tropical biota. Features chapters, co-authored by world experts, that explain the origins, inputs, distribution, behaviour, and consequences of radioactivity in tropical and subtropical systems. Provides comprehensive lists of relevant data and identifies current knowledge gaps to allow for targeted radioecological research in the future. Integrate...

  4. A Late Holocene Record of Human Impact in the Tropical Lowlands of the Mexican Gulf Coast: Lago Verde.

    Science.gov (United States)

    Socorro, L.; Sosa, S.; Caballero, M.; Rodriguez, A.; Ortega, B.

    2005-05-01

    Lago Verde is a maar lake (18 36 43 N; 95 20 52 W) located on the Gulf Coast of Mexico in "Los Tuxtlas" region. The area was cover by tropical rain forest and is part of the core area of the earliest Mesoamerican cultures. A 6 m sediment core was obtained in order to document vegetation and lake level history of this area. Lago Verde is a shallow, eutrophic lake (max. 4 m), the natural vegetation has been removed and grasslands with some tropical trees such Bursera grows around the lake. According with the radiocarbon chronology the sequence covers the last 2500 yr BP. At the base of the sequence low abundance of tropical trees is record, with intermediate lake levels. A sudden change in the pollen stratigraphy occurs at ca. 2000 yr BP, with important presence of Poaceae, Ambrosia and Cheno.-Am. along with Zea mays indicating human activity in the area. This is associated with a change in limnological conditions, recording turbid, shallow environments. This pollen signals correlates with dry phases in Yucatan, suggesting that this dry climatic signal probably had effect on an ample area of Mexico. However, at 1200 yr BP, no more Zea mays pollen is recovered suggesting the abandonment of the area. Lake levels recover as well as the tropical forest. The last 150 yr BP is characterized by the reduction in the pollen of tropical forest trees, presence of Zea mays, increased erosion rates, turbidity and eutrophication in the lake, all related to deforestation.

  5. Relation between century-scale Holocene arid intervals in tropical and temperate zones

    Science.gov (United States)

    Lamb, H. F.; Gasse, F.; Benkaddour, A.; El Hamouti, N.; van der Kaars, S.; Perkins, W. T.; Pearce, N. J.; Roberts, C. N.

    1995-01-01

    CLIMATE records from lake sediments in tropical Africa, Central America and west Asia show several century-scale arid intervals during the Holocene1-10. These may have been caused by temporary weakening of the monsoonal circulation associated with reduced northward heat transport by the oceans7 or by feedback processes stimulated by changes in tropical land-surface conditions10. Here we use a lake-sediment record from the montane Mediterranean zone of Morocco to address the question of whether these events were also felt in temperate continental regions. We find evidence of arid intervals of similar duration, periodicity and possibly timing to those in the tropics. But our pollen data show that the forest vegetation was not substantially affected by these events, indicating that precipitation remained adequate during the summer growing season. Thus, the depletion of the groundwater aquifer that imprinted the dry events in the lake record must have resulted from reduced winter precipitation. We suggest that the occurrence of arid events during the summer in the tropics but during the winter at temperate latitudes can be rationalized if they are both associated with cooler sea surface temperatures in the North Atlantic.

  6. Luminous effectiveness of tubular light-guides in tropics

    Energy Technology Data Exchange (ETDEWEB)

    Darula, Stanislav; Kittler, Richard; Kocifaj, Miroslav [ICA, Slovak Academy of Sciences, 9, Dubravska Road, 845 03 Bratislava (Slovakia)

    2010-11-15

    Novel tubular light-guides with a transparent hemispherical cupola placed on an unobstructed flat roof collect all sunlight and skylight available at ground level year round. This advantage is heightened in the dry and sunny tropical regions where the sun rises to very high altitudes and often the hours of sunshine last throughout the whole day. Hollow light-guides with very high inner specular reflectances can transport sunbeams downward into the windowless building core very effectively. Due to the tube's diameter and length and multiple reflections, complex illuminance patterns are produced on the underside of the tube, i.e. on top of the glazed ceiling aperture that illuminates the interior space or its working plane. This paper discusses several daylight conditions in tropical interiors illuminated by tubular light-guides. The recently published HOLIGILM calculation program and the user-friendly tool HOLIGILM 4.2 have facilitated the production of this paper. (author)

  7. A relação entre a temperatura da superfície dos oceanos tropicais e a duração dos veranicos no Estado da Paraíba Relationship between the surface temperature on the tropical oceans and the duration of dry spells in the Paraíba State

    Directory of Open Access Journals (Sweden)

    Hudson Ellen Alencar Menezes

    2008-06-01

    Full Text Available Este trabalho tem por o objetivo verificar possíveis influências das anomalias de temperatura da superfície do mar (TSM no Pacífico Equatorial e no Atlântico Tropical durante os veranicos mais longos dentro da estação chuvosa das microrregiões do Estado da Paraíba. Foram utilizados dados de precipitação diária de postos pluviométricos distribuídos por toda a Paraíba, no período compreendido de 1º de janeiro de 1963 a 31 de dezembro de 1999, de anomalias mensais de TSM na área dos niños: Niño 1+2, Niño 3, Niño 3.4 e Niño 4, e de índices mensais do Atlântico Tropical Norte e Sul, de outubro de 1962 a dezembro de 1999 da base de dados do Centro Diagnóstico do Clima da NOAA. Foram calculadas e analisadas as correlações obtidas entre as anomalias de TSM e os veranicos e gráficos que mostram a variabilidade interanual dos maiores veranicos do estado da Paraíba. Os resultados obtidos mostraram que os veranicos das microrregiões do Litoral e Brejo são mais influenciados pelas condições de anomalias de TSM sobre o Atlântico Tropical, enquanto os veranicos das microrregiões do Cariri/Curimataú e Sertão, na parte central e oeste do Estado, são influenciados pelas anomalias de TSM do Pacífico Equatorial.This paper has the objective of verifying the possible influences of the anomalies of sea surface temperature (SST in the Equatorial Pacific and in the Tropical Atlantic on the duration of the largest dry spell of the rainy season of the micro-regions of the Paraíba State. Daily precipitation data of the rain gauge stations distributed in the all sectors of Paraíba, for the period from January 1, 1963 to December 31, 1999, the monthly anomalies of SST in the area of the niños: Niño 1+2, Niño 3, Niño 3.4 and Niño 4, and monthly indices of North and South Tropical Atlantic, for the period from October, 1962 to December, 1999, obtained from the Diagnostic Center of Climate of the NOAA were used in this study

  8. Functional traits, drought performance, and the distribution of tree species in tropical forests of Ghana

    NARCIS (Netherlands)

    Amissah, L.

    2014-01-01

    Tropical forests occur along a rainfall gradient where annual amount, the length and intensity of dry season vary and water availability shapes therefore strongly the distribution of tree species. Annual rainfall in West Africa has declined at a rate of 4% per decade, and climate change

  9. Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

    OpenAIRE

    M. D. Mallet; M. J. Desservettaz; B. Miljevic; A. Milic; Z. D. Ristovski; J. Alroe; L. T. Cravigan; E. R. Jayaratne; C. Paton-Walsh; D. W. T. Griffith; S. R. Wilson; G. Kettlewell; M. V. van der Schoot; P. Selleck; F. Reisen

    2017-01-01

    The SAFIRED (Savannah Fires in the Early Dry Season) campaign took place from 29 May until 30 June 2014 at the Australian Tropical Atmospheric Research Station (ATARS) in the Northern Territory, Australia. The purpose of this campaign was to investigate emissions from fires in the early dry season in northern Australia. Measurements were made of biomass burning aerosols, volatile organic compounds, polycyclic aromatic carbons, greenhouse gases, radon, speciated atmospheric ...

  10. Hydrological effects of tropical land use management incentives: Panama Canal Watershed

    Science.gov (United States)

    Fred Ogden; Jefferson S. Hall; Holly Barnard; Robert F. Stallard; Ell Fenichel; Vic Adamowicz; Brent Ewers; Ed Kempema; Julian Zhu

    2016-01-01

    Panama lies in the seasonal tropics and over 85 percent of annual precipitation falls during the May-December wet season. Extreme rainfall events near the end of the wet season can produce flooding that impact Panama Canal operations. During the December-April dry season, occasional water shortages limit the draft of ships passing through the Panama Canal, as well as...

  11. Glacier monitoring and glacier-climate interactions in the tropical Andes: A review

    Science.gov (United States)

    Veettil, Bijeesh Kozhikkodan; Wang, Shanshan; Florêncio de Souza, Sergio; Bremer, Ulisses Franz; Simões, Jefferson Cardia

    2017-08-01

    In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to

  12. Four new bat species (Rhinolophus hildebrandtii complex reflect Plio-Pleistocene divergence of dwarfs and giants across an Afromontane archipelago.

    Directory of Open Access Journals (Sweden)

    Peter J Taylor

    Full Text Available Gigantism and dwarfism evolve in vertebrates restricted to islands. We describe four new species in the Rhinolophus hildebrandtii species-complex of horseshoe bats, whose evolution has entailed adaptive shifts in body size. We postulate that vicissitudes of palaeoenvironments resulted in gigantism and dwarfism in habitat islands fragmented across eastern and southern Africa. Mitochondrial and nuclear DNA sequences recovered two clades of R. hildebrandtii senso lato which are paraphyletic with respect to a third lineage (R. eloquens. Lineages differ by 7.7 to 9.0% in cytochrome b sequences. Clade 1 includes R. hildebrandtii sensu stricto from the east African highlands and three additional vicariants that speciated across an Afromontane archipelago through the Plio-Pleistocene, extending from the Kenyan Highlands through the Eastern Arc, northern Mozambique and the Zambezi Escarpment to the eastern Great Escarpment of South Africa. Clade 2 comprises one species confined to lowland savanna habitats (Mozambique and Zimbabwe. A third clade comprises R. eloquens from East Africa. Speciation within Clade 1 is associated with fixed differences in echolocation call frequency, and cranial shape and size in populations isolated since the late Pliocene (ca 3.74 Mya. Relative to the intermediate-sized savanna population (Clade 2, these island-populations within Clade 1 are characterised by either gigantism (South African eastern Great Escarpment and Mts Mabu and Inago in Mozambique or dwarfism (Lutope-Ngolangola Gorge, Zimbabwe and Soutpansberg Mountains, South Africa. Sympatry between divergent clades (Clade 1 and Clade 2 at Lutope-Ngolangola Gorge (NW Zimbabwe is attributed to recent range expansions. We propose an "Allometric Speciation Hypothesis", which attributes the evolution of this species complex of bats to divergence in constant frequency (CF sonar calls. The origin of species-specific peak frequencies (overall range = 32 to 46 kHz represents the

  13. Diversidad de avispas parasitoides de la familia Encyrtidae (Hymenoptera: Chalcidoidea del bosque tropical caducifolio en San Buenaventura, Jalisco, México Diversity of parasitoid wasps of the family Encyrtidae (Hymenoptera: Chalcidoidea in the tropical dry forest of San Buenaventura, Jalisco, Mexico

    Directory of Open Access Journals (Sweden)

    Beatriz Rodríguez-Velez

    2011-09-01

    Full Text Available Se presentan los resultados del estudio de la fauna de avispas parasitoides de la familia Encyrtidae en el bosque tropical caducifolio de San Buenaventura, Jalisco, México. El estudio se llevó a cabo de noviembre de 1996 a octubre de 1997. La recolección se realizó con trampas Malaise durante 5 días de cada mes. Se registró un total de 61 especies, 30 géneros, 13 tribus y 2 subfamilias. El mayor número de géneros y especies fue de la subfamilia Encyrtinae, con 22 géneros y 44 especies, seguida por Tetracneminae con 8 géneros y 17 especies. El género con mayor número de especies fue Metaphycus con 11. Las especies recolectadas no fueron abundantes, y su riqueza y abundancia varió estacionalmente, registrándose los valores más altos durante la temporada de lluvias. La similitud de la fauna de San Buenaventura, Jalisco con la de Huautla, Morelos fue mayor que la encontrada en otras regiones previamente estudiadas de bosque tropical caducifolio (San Javier, Sonora y Huatulco, Oaxaca.Results of a faunistic study of the parasitoid wasps of the family Encyrtidae of the tropical dry forest of San Buenaventura, Jalisco, Mexico are presented. The study was carried out from November 1996 to October 1997. Collecting technique was Malaise trapping. Collections were carried out during 5 days of every month. A total of 61 species, 30 genera, 13 tribes and 2 subfamilies were recorded. The subfamily with the largest number of species was Encyrtinae with 22 genera and 44 species, followed by Tetracneminae with 8 genera and 17 species. The genus with the largest number of species was Metaphycus with 11. Species had low abundance. Species richness and abundance varied with time, with the highest values recorded in the rainy season. The fauna of San Buenaventura, Jalisco was most similar to that of Huautla, Morelos, than to that of San Javier, Sonora and Huatulco, Oaxaca, all of them previously studied.

  14. Biodiversity and functional regeneration during secondary succession in a tropical dry forest: from microorganisms to mammals

    Science.gov (United States)

    do Espírito Santo, M. M.; Neves, F. S.; Valério, H. M.; Leite, L. O.; Falcão, L. A.; Borges, M.; Beirão, M.; Reis, R., Jr.; Berbara, R.; Nunes, Y. R.; Silva, A.; Silva, L. F.; Siqueira, P. R.

    2015-12-01

    In this study, we aimed to determine the changes on soil traits, forest structure and species richness and composition of multiple groups of organisms along secondary succession in a tropical dry forest (TDF) in southeastern Brazil. We defined three successional stages based in forest vertical and horizontal structure and age: early (18-25 years), intermediate (50-60 years) and late (no records of clearing). Five plots of 50 x 20 m were established per stage, and the following groups were sampled using specific techniques: rhizobacteria, mycorrhiza, trees and lianas, butterflies, ants, dung beetles, mosquitoes (Culicidae), birds and bats. We also determined soil chemical and physical characteristics and forest structure (tree height, density and basal area). Soil fertility increased along the successional gradient, and the same pattern was observed for all the forest structure variables. However, species richness and composition showed mixed results depending on the organism group. Three groups usually considered as good bioindicators of habitat quality did not differ in species richness and composition between stages: butterflies, ants and dung beetles. On the other hand, rizhobacteria and mycorrhiza differed both in species richness and composition between stages and may be more sensitive to changes in environmental conditions in TDFs. The other five groups differed either in species richness or composition between one or two pairs of successional stages. Although changes in abiotic conditions and forest structure match the predictions of classical successional models, the response of each group of organism is idiosyncratic in terms of diversity and ecological function, as a consequence of specific resource requirements and life-history traits. In general, diversity increased and functional groups changed mostly from early to intermediate-late stages, strengthening the importance of secondary forests to the maintenance of ecosystem integrity of TDFs.

  15. Occurrence, distribution, and sources of emerging organic contaminants in tropical coastal sediments of anthropogenically impacted Klang River estuary, Malaysia.

    Science.gov (United States)

    Omar, Tuan Fauzan Tuan; Aris, Ahmad Zaharin; Yusoff, Fatimah Md; Mustafa, Shuhaimi

    2018-06-01

    This baseline assessment reports on the occurrence, distribution, and sources of emerging organic contaminants (EOCs) in tropical coastal sediments of anthropogenically impacted Klang River estuary, Malaysia. Bisphenol A was the highest concentration detected at 16.84 ng g -1 dry weight, followed by diclofenac (13.88 ng g -1 dry weight) and E1 (12.47 ng g -1 dry weight). Five compounds, namely, amoxicillin, progesterone, diazinon, bisphenol A, and E1, were found in all sampling stations assessed, and other compounds such as primidone, diclofenac, testosterone, E2, and EE2 were ubiquitously present in sediment samples, with percentage of detection range from 89.04% to 98.38%. Organic carbon content and pH were the important factors controlling the fate of targeted compounds in the tropical estuarine sediment. On the basis of the literature from other studies, the sources of EOCs are thought to be from wastewater treatment plants, domestic/medical waste discharge, livestock activities, industrial waste discharge, and agricultural activities. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Soil emissions of nitric oxide in a seasonally dry tropical forest of Mexico

    Science.gov (United States)

    Davidson, Eric A.; Vitousek, Peter M.; Riley, Ralph; Matson, Pamela A.; Garcia-Mendez, Georgina; Maass, J. M.

    1991-01-01

    Soil emissions of NO were measured at the Chamela Biological Station, Mexico, using soil covers and a field apparatus of NO detection based on CrO3 conversion of NO to NO2 and detection of NO2 by chemiluminescence with Luminol. Mean NO fluxes from forest soils ranged from 0.14 to 0.52 ng NO-N/sq cm/hr during the dry season and from 0.73 to 1.27 ng NO-N/sq cm/hr during the wet season. A fertilized floodplain pasture exhibited higher fluxes, but an unfertilized upland pasture, which represents the fastest growing land use in the region, had flux rates similar to the forest sites. Wetting experiments at the end of the dry season caused large pulses of NO flux, equaling 10 percent to 20 percent of the estimated annual NO emissions of 0.5-1.0 kg N/ha from the forest sites. Absence of a forest canopy during the dry season and the first wet season rain probably results in substantial NO(x) export from the forest system that may be important to regional atmospheric chemical processes. Wetting experiments during the wet season and a natural rain event had little or no stimulatory effect on NO flux rates.

  17. Seasonal changes in the assembly mechanisms structuring tropical fish communities.

    Science.gov (United States)

    Fitzgerald, Daniel B; Winemiller, Kirk O; Sabaj Pérez, Mark H; Sousa, Leandro M

    2017-01-01

    Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems. © 2016 by the Ecological Society of America.

  18. Patterns of loss and regeneration of tropical dry forest in Madagascar: the social institutional context.

    Science.gov (United States)

    Elmqvist, Thomas; Pyykönen, Markku; Tengö, Maria; Rakotondrasoa, Fanambinantsoa; Rabakonandrianina, Elisabeth; Radimilahy, Chantal

    2007-05-02

    Loss of tropical forests and changes in land-use/land-cover are of growing concern worldwide. Although knowledge exists about the institutional context in which tropical forest loss is embedded, little is known about the role of social institutions in influencing regeneration of tropical forests. In the present study we used Landsat images from southern Madagascar from three different years (1984, 1993 and 2000) and covering 5500 km(2), and made a time-series analysis of three distinct large-scale patterns: 1) loss of forest cover, 2) increased forest cover, and 3) stable forest cover. Institutional characteristics underlying these three patterns were analyzed, testing the hypothesis that forest cover change is a function of strength and enforcement of local social institutions. The results showed a minor decrease of 7% total forest cover in the study area during the whole period 1984-2000, but an overall net increase of 4% during the period 1993-2000. The highest loss of forest cover occurred in a low human population density area with long distances to markets, while a stable forest cover occurred in the area with highest population density and good market access. Analyses of institutions revealed that loss of forest cover occurred mainly in areas characterized by insecure property rights, while areas with well-defined property rights showed either regenerating or stable forest cover. The results thus corroborate our hypothesis. The large-scale spontaneous regeneration dominated by native endemic species appears to be a result of a combination of changes in precipitation, migration and decreased human population and livestock grazing pressure, but under conditions of maintained and well-defined property rights. Our study emphasizes the large capacity of a semi-arid system to spontaneously regenerate, triggered by decreased pressures, but where existing social institutions mitigate other drivers of deforestation and alternative land-use.

  19. Patterns of loss and regeneration of tropical dry forest in Madagascar: the social institutional context.

    Directory of Open Access Journals (Sweden)

    Thomas Elmqvist

    Full Text Available Loss of tropical forests and changes in land-use/land-cover are of growing concern worldwide. Although knowledge exists about the institutional context in which tropical forest loss is embedded, little is known about the role of social institutions in influencing regeneration of tropical forests. In the present study we used Landsat images from southern Madagascar from three different years (1984, 1993 and 2000 and covering 5500 km(2, and made a time-series analysis of three distinct large-scale patterns: 1 loss of forest cover, 2 increased forest cover, and 3 stable forest cover. Institutional characteristics underlying these three patterns were analyzed, testing the hypothesis that forest cover change is a function of strength and enforcement of local social institutions. The results showed a minor decrease of 7% total forest cover in the study area during the whole period 1984-2000, but an overall net increase of 4% during the period 1993-2000. The highest loss of forest cover occurred in a low human population density area with long distances to markets, while a stable forest cover occurred in the area with highest population density and good market access. Analyses of institutions revealed that loss of forest cover occurred mainly in areas characterized by insecure property rights, while areas with well-defined property rights showed either regenerating or stable forest cover. The results thus corroborate our hypothesis. The large-scale spontaneous regeneration dominated by native endemic species appears to be a result of a combination of changes in precipitation, migration and decreased human population and livestock grazing pressure, but under conditions of maintained and well-defined property rights. Our study emphasizes the large capacity of a semi-arid system to spontaneously regenerate, triggered by decreased pressures, but where existing social institutions mitigate other drivers of deforestation and alternative land-use.

  20. Mating system, population growth, and management scenario for Kalanchoe pinnata in an invaded seasonally dry tropical forest.

    Science.gov (United States)

    González de León, Salvador; Herrera, Ileana; Guevara, Roger

    2016-07-01

    Ecological invasions are a major issue worldwide, where successful invasion depends on traits that facilitate dispersion, establishment, and population growth. The nonnative succulent plant Kalanchoe pinnata, reported as invasive in some countries, is widespread in remnants of seasonally dry tropical forest on a volcanic outcrop with high conservation value in east-central Mexico where we assessed its mating system and demographic growth and identified management strategies. To understand its local mating system, we conducted hand-pollination treatments, germination, and survival experiments. Based on the experimental data, we constructed a life-stage population matrix, identified the key traits for population growth, weighted the contributions of vegetative and sexual reproduction, and evaluated management scenarios. Hand-pollination treatments had slight effects on fruit and seed setting, as well as on germination. With natural pollination treatment, the successful germination of seeds from only 2/39 fruit suggests occasional effective natural cross-pollination. The ratios of the metrics for self- and cross-pollinated flowers suggest that K. pinnata is partially self-compatible. Most of the pollinated flowers developed into fruit, but the seed germination and seedling survival rates were low. Thus, vegetative propagation and juvenile survival are the main drivers of population growth. Simulations of a virtual K. pinnata population suggest that an intense and sustained weeding campaign will reduce the population within at least 10 years. Synthesis and applications. The study population is partially self-compatible, but sexual reproduction by K. pinnata is limited at the study site, and population growth is supported by vegetative propagation and juvenile survival. Demographic modeling provides key insights and realistic forecasts on invasion process and therefore is useful to design management strategies.

  1. Proxies of Tropical Cyclone Isotope Spikes in Precipitation: Landfall Site Selection

    Science.gov (United States)

    Lawrence, J. R.; Maddocks, R.

    2011-12-01

    The human experience of climate change is not one of gradual changes in seasonal or yearly changes in temperature or rainfall. Despite that most paleoclimatic reconstructions attempt to provide just such information. Humans experience climate change on much shorter time scales. We remember hurricanes, weeks of drought or overwhelming rainy periods. Tropical cyclones produce very low isotope ratios in both rainfall and in atmospheric water vapor. Thus, climate proxies that potentially record these low isotope ratios offer the most concrete record of climate change to which humans can relate. The oxygen isotopic composition of tropical cyclone rainfall has the potential to be recorded in fresh water carbonate fossil material, cave deposits and corals. The hydrogen isotopic composition of tropical cyclone rainfall has the potential to be recorded in tree ring cellulose and organic matter in fresh water bodies. The Class of carbonate organisms known as Ostracoda form their carapaces very rapidly. Thus fresh water ephemeral ponds in the subtropics are ideal locations for isotopic studies because they commonly are totally dry when tropical cyclones make landfall. The other proxies suffer primarily from a dilution effect. The water from tropical cyclones is mixed with pre-existing water. In cave deposits tropical cyclone rains mix with soil and ground waters. In the near shore coral environment the rain mixes with seawater. For tree rings there are three sources of water: soil water, atmospheric water vapor that exchanges with leaf water and tropical cyclone rain. In lakes because of their large size rainfall runoff mixes with ground water and preexisting water in the lake. A region that shows considerable promise is Texas / Northeast Mexico. In a study of surface waters that developed from the passage of Tropical Storm Allison (2001) in SE Texas both the pond water and Ostracoda that bloomed recorded the low oxygen isotope signal of that storm (Lawrence et al, 2008). In

  2. Carbon budget of leaves of the tropical intertidal seagrass Thalassia hemprichii

    Science.gov (United States)

    Chiu, Shih-Han; Huang, Yen-Hsun; Lin, Hsing-Juh

    2013-07-01

    The question of whether seagrass beds are effective carbon sinks has recently attracted much attention. Leaf production and consumption, and detrital export and decomposition were determined to quantify the carbon budget of leaf production in a southern Taiwan seagrass bed composed of the tropical intertidal seagrass Thalassia hemprichii, which is widely distributed in intertidal zones of the western Pacific. The influence of elevation in the intertidal zone on these processes was also investigated. Leaf production and consumption, and export of leaf detritus showed seasonal variations, with higher rates in the wet season (summer and autumn) and lower rates in the dry season (winter and spring). At the high-elevation site, leaf consumption by fish was significantly higher than that by sea urchins. At the low-elevation site, however, the proportion of leaves consumed by sea urchins was equivalent to that by fish. Leaf detritus decomposed rapidly within the first 9 days, then gradually slowed down, and stabilised after 212 days, at which only 8.7% of dry weight remained in the litterbags. The carbon budget of seagrass leaves demonstrated that 20% of leaf production was grazed by fish and sea urchins and 80% flowed to detritus. This suggests that seagrass leaves are important food sources for inhabiting herbivores. Most of the detritus decomposed (44% of leaf production) or was exported (32% of leaf production), and only 4% of leaf production or 22 g C m-2 yr-1 was stored in this tropical intertidal seagrass bed. Mass balance calculations support this tropical seagrass bed acting as a carbon sink and an outwelling system which exports organic detritus to neighboring coral reefs.

  3. β-Diversity of functional groups of woody plants in a tropical dry forest in Yucatan.

    Directory of Open Access Journals (Sweden)

    Jorge Omar López-Martínez

    Full Text Available Two main theories have attempted to explain variation in plant species composition (β-diversity. Niche theory proposes that most of the variation is related to environment (environmental filtering, whereas neutral theory posits that dispersal limitation is the main driver of β-diversity. In this study, we first explored how α- and β-diversity of plant functional groups defined by growth form (trees, shrubs and lianas, which represent different strategies of resource partitioning, and dispersal syndrome (autochory, anemochory and zoochory, which represent differences in dispersal limitation vary with successional age and topographic position in a tropical dry forest. Second, we examined the effects of environmental, spatial, and spatially-structured environmental factors on β-diversity of functional groups; we used the spatial structure of sampling sites as a proxy for dispersal limitation, and elevation, soil properties and forest stand age as indicators of environmental filtering. We recorded 200 species and 22,245 individuals in 276 plots; 120 species were trees, 41 shrubs and 39 lianas. We found that β-diversity was highest for shrubs, intermediate for lianas and lowest for trees, and was slightly higher for zoochorous than for autochorous and anemochorous species. All three dispersal syndromes, trees and shrubs varied in composition among vegetation classes (successional age and topographic position, whilst lianas did not. β-diversity was influenced mostly by proxies of environmental filtering, except for shrubs, for which the influence of dispersal limitation was more important. Stand age and topography significantly influenced α-diversity across functional groups, but showed a low influence on β-diversity -possibly due to the counterbalancing effect of resprouting on plant distribution and composition. Our results show that considering different plant functional groups reveals important differences in both α- and

  4. Temporal variability in methane fluxes from tropical peatlands within the Peruvian Amazon

    Science.gov (United States)

    Murphy, Wayne; Berrio, Juan Carlos; Boom, Arnoud; Page, Sue; Arn Teh, Yit

    2016-04-01

    Tropical peatlands are one of the largest soil carbon (C) reservoirs globally and play a significant role in modulating fluxes of C between the tropical biosphere and atmosphere. These C fluxes are of global importance because tropical wetlands are the single largest natural source of atmospheric methane (CH4); while land-use change and biomass burning also contribute to the growing global atmospheric carbon dioxide (CO2) burden. Amazonian peatlands play a potentially important role in regional and global atmospheric budgets of C because of their large extent. These ecosystems cover an estimated 150,000km2, which is roughly three-quarters the size of Indonesian peatlands; the world's most extensive and well-studied tropical peatlands. Here we report CH4 fluxes from a lowland tropical peatland in the Pastaza-Maranon foreland basin in Peru, one of the largest peatland complexes in the lowland Amazon Basin. Strong prolonged seasonal rainfall events and the annual Amazon River flood-pulse may lead to pronounced temporal variability in biogeochemical cycling and trace gas fluxes, and this study explored how CH4 fluxes varied among wet and dry season periods in a number of key vegetation types in this region. Sampling was concentrated in 3 of the most numerically-dominant vegetation types: Forested Swamp, Mixed Palm Swamp and Mauritia flexuosa-dominated Palm Swamp, with data collection occurring in both wet and dry seasons over a 2 year period from 2012-2014 (4 field campaigns in total). Overall mean CH4 fluxes from the Forested Swamp, Mixed Palm Swamp and Mauritia flexuosa-dominated Palm Swamp for the entire sampling period were 31.06 ± 3.42 mg CH4 - C m-2 d-1, 52.03 ± 16.05 mg CH4 - C m-2 d-1 and 36.68 ± 4.32 mg CH4 - C m-2 d-1. CH4 emissions, when averaged across the entire dataset, did not differ significantly among habitats. However, when CH4 emissions were aggregated by season, the Mixed Palm Swamp showed a significantly different emissions from all other

  5. Patterns of forest composition and their long term environmental drivers in the tropical dry forest transition zone of southern Africa

    Directory of Open Access Journals (Sweden)

    Vera De Cauwer

    2016-09-01

    Full Text Available Background Tropical dry forests cover less than 13 % of the world’s tropical forests and their area and biodiversity are declining. In southern Africa, the major threat is increasing population pressure, while drought caused by climate change is a potential threat in the drier transition zones to shrub land. Monitoring climate change impacts in these transition zones is difficult as there is inadequate information on forest composition to allow disentanglement from other environmental drivers. Methods This study combined historical and modern forest inventories covering an area of 21,000 km2 in a transition zone in Namibia and Angola to distinguish late succession tree communities, to understand their dependence on site factors, and to detect trends in the forest composition over the last 40 years. Results The woodlands were dominated by six tree species that represented 84 % of the total basal area and can be referred to as Baikiaea - Pterocarpus woodlands. A boosted regression tree analysis revealed that late succession tree communities are primarily determined by climate and topography. The Schinziophyton rautanenii and Baikiaea plurijuga communities are common on slightly inclined dune or valley slopes and had the highest basal area (5.5 – 6.2 m2 ha−1. The Burkea africana - Guibourtia coleosperma and Pterocarpus angolensis – Dialium englerianum communities are typical for the sandy plateaux and have a higher proportion of smaller stems caused by a higher fire frequency. A decrease in overall basal area or a trend of increasing domination by the more drought and cold resilient B. africana community was not confirmed by the historical data, but there were significant decreases in basal area for Ochna pulchra and the valuable fruit tree D. englerianum. Conclusions The slope communities are more sheltered from fire, frost and drought but are more susceptible to human expansion. The community with the important timber tree P

  6. Measured and modelled sublimation on the tropical Glaciar Artesonraju, Perú

    OpenAIRE

    M. Winkler; I. Juen; T. Mölg; G. Kaser

    2008-01-01

    Sublimation plays a decisive role in the surface energy balance of tropical glaciers. During the dry season low specific humidity and high surface roughness favour the direct transition from ice to vapour and drastically reduce the energy available for melting. However, field measurements are scarce and little is known about the performance of sublimation parametrisations in glacier mass balance and runoff models.

    During 15 days in August 2005 sublimation was measured on ...

  7. Measured and modelled sublimation on the tropical Glaciar Artesonraju, Perú

    OpenAIRE

    Winkler , M.; Juen , I.; Mölg , T.; Wagnon , Patrick; Gómez , J.; Kaser , G.

    2009-01-01

    Sublimation plays a decisive role in the surface energy and mass balance of tropical glaciers. During the dry season (May–September) low specific humidity and high surface roughness favour the direct transition from ice to vapour and drastically reduce the energy available for melting. However, field measurements are scarce and little is known about the performance of sublimation parameterisations in glacier mass balance and runoff models.

    During 15 days in August 2005 su...

  8. Monitoring forest cover loss using multiple data streams, a case study of a tropical dry forest in Bolivia

    Science.gov (United States)

    Dutrieux, Loïc Paul; Verbesselt, Jan; Kooistra, Lammert; Herold, Martin

    2015-09-01

    Automatically detecting forest disturbances as they occur can be extremely challenging for certain types of environments, particularly those presenting strong natural variations. Here, we use a generic structural break detection framework (BFAST) to improve the monitoring of forest cover loss by combining multiple data streams. Forest change monitoring is performed using Landsat data in combination with MODIS or rainfall data to further improve the modelling and monitoring. We tested the use of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) with varying spatial aggregation window sizes as well as a rainfall derived index as external regressors. The method was evaluated on a dry tropical forest area in lowland Bolivia where forest cover loss is known to occur, and we validated the results against a set of ground truth samples manually interpreted using the TimeSync environment. We found that the addition of an external regressor allows to take advantage of the difference in spatial extent between human induced and naturally induced variations and only detect the processes of interest. Of all configurations, we found the 13 by 13 km MODIS NDVI window to be the most successful, with an overall accuracy of 87%. Compared with a single pixel approach, the proposed method produced better time-series model fits resulting in increases of overall accuracy (from 82% to 87%), and decrease in omission and commission errors (from 33% to 24% and from 3% to 0% respectively). The presented approach seems particularly relevant for areas with high inter-annual natural variability, such as forests regularly experiencing exceptional drought events.

  9. Dispersal limitation of Tillandsia species correlates with rain and host structure in a central Mexican tropical dry forest.

    Directory of Open Access Journals (Sweden)

    Elizabeth Victoriano-Romero

    Full Text Available Seed dispersal permits the colonization of favorable habitats and generation of new populations, facilitating escape from habitats that are in decline. There is little experimental evidence of the factors that limit epiphyte dispersion towards their hosts. In a tropical dry forest in central Mexico, we monitored the phenology of dispersion of epiphyte species of the genus Tillandsia; we tested experimentally whether precipitation could cause failures in seed dispersal and whether seed capture differs among vertical strata and between host species with high (Bursera copallifera and low (Conzattia multiflora epiphyte loads. With the exception of one species that presents late dispersion and low abundance, all of the species disperse prior to the onset of the rainy season. However, early rains immobilize the seeds, affecting up to 24% of the fruits in species with late dispersion. We observed that Tillandsia seeds reach both Bursera and Conzattia hosts, but found that adherence to the host is 4-5 times higher in Bursera. Furthermore, seeds liberated from Bursera travel shorter distances and up to half may remain within the same crown, while the highest seed capture takes place in the upper strata of the trees. We conclude that dispersion of Tillandsia seeds is limited by early rains and by the capture of seeds within the trees where populations concentrate. This pattern of capture also helps to explain the high concentrations of epiphytes in certain hosts, while trees with few epiphytes can be simultaneously considered deficient receivers and efficient exporters of seeds.

  10. Removal rates of native and exotic dung by dung beetles (Scarabaeidae: Scarabaeinae) in a fragmented tropical rain forest.

    Science.gov (United States)

    Amézquita, Sandra; Favila, Mario E

    2010-04-01

    Many studies have evaluated the effect of forest fragmentation on dung beetle assemblage structure. However, few have analyzed how forest fragmentation affects the processes carried out by these insects in tropical forests where their food sources consist mainly of dung produced by native herbivore mammals. With the conversion of forests to pastures, cattle dung has become an exotic alternative and abundant food for dung beetles. This study compares dung removal rates of native (monkey) and exotic (cow) dung in different-sized fragments of tropical rain forests, during the dry and rainy seasons at the Los Tuxtlas Biosphere Reserve. Dung removal rates were affected by season, dung type, and the interaction between resource type and season. During the dry season, the removal rates of monkey dung were somewhat similar than during the rainy season, whereas the removal rates of cow dung were much higher during the rainy season. Dung beetle biomass and species richness were almost three times greater in monkey dung than in cow dung. Monkey dung attracted species belonging to the dweller, roller, and tunneler guilds; cow dung attracted mostly tunnelers. Therefore, the use of exotic dung may result in a biased misconception of the rates of dung removal in tropical forest and an underestimation of dung beetle diversity. This study highlights the importance of working with natural tropical forest resources when attempting to identify realistic tendencies concerning processes in natural habitats and those modified by fragmentation and by other human activities.

  11. Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands.

    Directory of Open Access Journals (Sweden)

    Carmen Rojo

    Full Text Available The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abundance and composition of planktonic and benthic microalgae was determined. Variation partitioning analysis (as explained by spatial distance or environmental factors was applied to each seasonal dataset by means of partial redundancy analysis. Our results show that microalgal assemblages were structured by spatial and environmental factors depending on the hydrological period of the year. At the onset of hydroperiod and during flooding, neutral effects dominated community dynamics, but niche-based local effects resulted in more structured algal communities at the final periods of desiccating water bodies. Results suggest that climate-mediated effects on hydrology can influence the relative role of spatial and environmental factors on metacommunities of microalgae. Such variability needs to be accounted in order to describe accurately community dynamics in tropical coastal wetlands.

  12. Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands.

    Science.gov (United States)

    Rojo, Carmen; Mesquita-Joanes, Francesc; Monrós, Juan S; Armengol, Javier; Sasa, Mahmood; Bonilla, Fabián; Rueda, Ricardo; Benavent-Corai, José; Piculo, Rubén; Segura, M Matilde

    2016-01-01

    The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abundance and composition of planktonic and benthic microalgae was determined. Variation partitioning analysis (as explained by spatial distance or environmental factors) was applied to each seasonal dataset by means of partial redundancy analysis. Our results show that microalgal assemblages were structured by spatial and environmental factors depending on the hydrological period of the year. At the onset of hydroperiod and during flooding, neutral effects dominated community dynamics, but niche-based local effects resulted in more structured algal communities at the final periods of desiccating water bodies. Results suggest that climate-mediated effects on hydrology can influence the relative role of spatial and environmental factors on metacommunities of microalgae. Such variability needs to be accounted in order to describe accurately community dynamics in tropical coastal wetlands.

  13. Observing Seasonal and Diurnal Hydrometeorological Variability Within a Tropical Alpine Valley: Implications for Evapotranspiration

    Science.gov (United States)

    Hellstrom, R. A.; Mark, B. G.

    2007-12-01

    Conditions of glacier recession in the seasonally dry tropical Peruvian Andes motivate research to better constrain the hydrological balance in alpine valleys. There is an outstanding need to better understand the impact of the pronounced tropical hygric seasonality on energy and water budgets within pro-glacial valleys that channel glacier runoff to stream flow. This paper presents a novel embedded network installed in the glacierized Llanganuco valley of the Cordillera Blanca (9°S) comprising eight low-cost, discrete temperature and humidity microloggers ranging from 3470 to 4740 masl and an automatic weather station at 3850 masl. Data are aggregated into distinct dry and wet periods sampled from two full annual cycles (2004-2006) to explore patterns of diurnal and seasonal variability. The magnitude of diurnal solar radiation varies little within the valley between the dry and wet periods, while wet season near-surface air temperatures are cooler. Seasonally characteristic diurnal fluctuations in lapse rate partially regulate convection and humidity. Steep lapse rates during the wet season afternoon promote up-slope convection of warm, moist air and nocturnal rainfall events. Standardized grass reference evapotranspiration (ET0) was estimated using the FAO-56 algorithm of the United Nations Food and Agriculture Organization and compared with estimates of actual ET from the process-based BROOK90 model that incorporates more realistic vegetation parameters. Comparisons of composite diurnal cycles of ET for the wet and dry periods suggest about twice the daily ET0 during the dry period, attributed primarily to the 500% higher vapor pressure deficit and 20% higher daily total solar irradiance. Conversely, the near absence of rainfall during the dry season diminishes actual ET below that of the wet season by two orders of magnitude. Nearly cloud-free daylight conditions are critical for ET during the wet season. We found significant variability of ET with elevation

  14. Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

    OpenAIRE

    Mallet, Marc D.; Desservettaz, Maximilien J.; Miljevic, Branka; Milic, Andelija; Ristovski, Zoran D.; Alroe, Joel; Cravigan, Luke T.; Jayaratne, E. Rohan; Paton-Walsh, Clare; Griffith, David W. T.; Wilson, Stephen R.; Kettlewell, Graham; Schoot, Marcel V.; Selleck, Paul; Reisen, Fabienne

    2016-01-01

    The SAFIRED (Savannah Fires in the Early Dry Season) campaign took place from 29th of May, 2014 until the 30th June, 2014 at the Australian Tropical Atmospheric Research Station (ATARS) in the Northern Territory, Australia. The purpose of this campaign was to investigate emissions from fires in the early dry season in northern Australia. Measurements were made of biomass burning aerosols, volatile organic compounds, polycyclic aromatic carbons, greenhouse gases, radon, mercury cycle, and trac...

  15. Controls over foliar N:P ratios in tropical rain forests.

    Science.gov (United States)

    Townsend, Alan R; Cleveland, Cory C; Asner, Gregory P; Bustamante, Mercedes M C

    2007-01-01

    Correlations between foliar nutrient concentrations and soil nutrient availability have been found in multiple ecosystems. These relationships have led to the use of foliar nutrients as an index of nutrient status and to the prediction of broadscale patterns in ecosystem processes. More recently, a growing interest in ecological stoichiometry has fueled multiple analyses of foliar nitrogen:phosphorus (N:P) ratios within and across ecosystems. These studies have observed that N:P values are generally elevated in tropical forests when compared to higher latitude ecosystems, adding weight to a common belief that tropical forests are generally N rich and P poor. However, while these broad generalizations may have merit, their simplicity masks the enormous environmental heterogeneity that exists within the tropics; such variation includes large ranges in soil fertility and climate, as well as the highest plant species diversity of any biome. Here we present original data on foliar N and P concentrations from 150 mature canopy tree species in Costa Rica and Brazil, and combine those data with a comprehensive new literature synthesis to explore the major sources of variation in foliar N:P values within the tropics. We found no relationship between N:P ratios and either latitude or mean annual precipitation within the tropics alone. There is, however, evidence of seasonal controls; in our Costa Rica sites, foliar N:P values differed by 25% between wet and dry seasons. The N:P ratios do vary with soil P availability and/or soil order, but there is substantial overlap across coarse divisions in soil type, and perhaps the most striking feature of the data set is variation at the species level. Taken as a whole, our results imply that the dominant influence on foliar N:P ratios in the tropics is species variability and that, unlike marine systems and perhaps many other terrestrial biomes, the N:P stoichiometry of tropical forests is not well constrained. Thus any use of N

  16. Orbital Forcing driving climate variability on Tropical South Atlantic

    Science.gov (United States)

    Oliveira, A. S.; Baker, P. A.; Silva, C. G.; Dwyer, G. S.; Chiessi, C. M.; Rigsby, C. A.; Ferreira, F.

    2017-12-01

    Past research on climate response to orbital forcing in tropical South America has emphasized on high precession cycles influencing low latitude hydrologic cycles, and driving the meridional migration of Intertropical Convergence Zone (ITCZ).However, marine proxy records from the tropical Pacific Ocean showed a strong 41-ka periodicities in Pleistocene seawater temperature and productivity related to fluctuations in Earth's obliquity. It Indicates that the western Pacific ITCZ migration was influenced by combined precession and obliquity changes. To reconstruct different climate regimes over the continent and understand the orbital cycle forcing over Tropical South America climate, hydrological reconstruction have been undertaken on sediment cores located on the Brazilian continental slope, representing the past 1.6 million years. Core CDH 79 site is located on a 2345 m deep seamount on the northern Brazilian continental slope (00° 39.6853' N, 44° 20.7723' W), 320 km from modern coastline of the Maranhão Gulf. High-resolution XRF analyses of Fe, Ti, K and Ca are used to define the changes in precipitation and sedimentary input history of Tropical South America. The response of the hydrology cycle to orbital forcing was studied using spectral analysis.The 1600 ka records of dry/wet conditions presented here indicates that orbital time-scale climate change has been a dominant feature of tropical climate. We conclude that the observed oscillation reflects variability in the ITCZ activity associated with the Earth's tilt. The prevalence of the eccentricity and obliquity signals in continental hydrology proxies (Ti/Ca and Fe/K) as implicated in our precipitation records, highlights that these orbital forcings play an important role in tropics hydrologic cycles. Throughout the Quaternary abrupt shifts of tropical variability are temporally correlated with abrupt climate changes and atmospheric reorganization during Mid-Pleistocene Transition and Mid-Brunhes Events

  17. The effects of the insecticide lambda-Cyhalothrin on the earthworm Eisenia fetida under experimental conditions of tropical and temperate regions.

    Science.gov (United States)

    Garcia, Marcos; Scheffczyk, Adam; Garcia, Terezinha; Römbke, Jörg

    2011-02-01

    Plant Protection Products can affect soil organisms and thus might have negative impacts on soil functions. Little research has been performed on their impact on tropical soils. Therefore, the effects of the insecticide lambda-Cyhalothrin on earthworms were evaluated in acute and chronic laboratory tests modified for tropical conditions, i.e. at selected temperatures (20 and 28°C) and with two strains (temperate and tropical) of the compost worm Eisenia fetida. The insecticide was spiked in two natural soils, in OECD artificial soil and a newly developed tropical artificial soil. The effects of lambda-Cyhalothrin did rarely vary in the same soil at tropical (LC50: 68.5-229 mg a.i./kg dry weight (DW); EC50: 54.2-60.2 mg a.i./kg DW) and temperate (LC50: 99.8-140 mg a.i./kg DW; EC50: 37.4-44.5 mg a.i./kg DW) temperatures. In tests with tropical soils and high temperature, effect values differed by up to a factor of ten. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Observations of increased tropical rainfall preceded by air passage over forests.

    Science.gov (United States)

    Spracklen, D V; Arnold, S R; Taylor, C M

    2012-09-13

    Vegetation affects precipitation patterns by mediating moisture, energy and trace-gas fluxes between the surface and atmosphere. When forests are replaced by pasture or crops, evapotranspiration of moisture from soil and vegetation is often diminished, leading to reduced atmospheric humidity and potentially suppressing precipitation. Climate models predict that large-scale tropical deforestation causes reduced regional precipitation, although the magnitude of the effect is model and resolution dependent. In contrast, observational studies have linked deforestation to increased precipitation locally but have been unable to explore the impact of large-scale deforestation. Here we use satellite remote-sensing data of tropical precipitation and vegetation, combined with simulated atmospheric transport patterns, to assess the pan-tropical effect of forests on tropical rainfall. We find that for more than 60 per cent of the tropical land surface (latitudes 30 degrees south to 30 degrees north), air that has passed over extensive vegetation in the preceding few days produces at least twice as much rain as air that has passed over little vegetation. We demonstrate that this empirical correlation is consistent with evapotranspiration maintaining atmospheric moisture in air that passes over extensive vegetation. We combine these empirical relationships with current trends of Amazonian deforestation to estimate reductions of 12 and 21 per cent in wet-season and dry-season precipitation respectively across the Amazon basin by 2050, due to less-efficient moisture recycling. Our observation-based results complement similar estimates from climate models, in which the physical mechanisms and feedbacks at work could be explored in more detail.

  19. Axial and radial water transport and internal water storage in tropical forest canopy trees.

    Science.gov (United States)

    Shelley A. James; Frederick C. Meinzer; Guillermo Goldstein; David Woodruff; Timothy Jones; Teresa Restom; Monica Mejia; Michael Clearwater; Paula. Campanello

    2003-01-01

    Heat and stable isotope tracers were used to study axial and radial water transport in relation to sapwood anatomical characteristics and internal water storage in four canopy tree species of a seasonally dry tropical forest in Panama. Anatomical characteristics of the wood and radial profiles of sap flow were measured at the base, upper trunk, and crown of a single...

  20. Tropical Estuarine Macrobenthic Communities Are Structured by Turnover Rather than Nestedness.

    Science.gov (United States)

    Medeiros, Carlinda Raílly; Hepp, Luiz Ubiratan; Patrício, Joana; Molozzi, Joseline

    2016-01-01

    Turnover (i.e., species substitution) and nestedness (i.e., subsets of species from more diverse locations), the two main mechanisms used to explain the beta diversity of biological communities, have different implications for biodiversity conservation. To better understand how these mechanisms contribute to beta diversity, we tested the following hypotheses: (i) greater dissimilarity in community composition occurs between estuarine zones than other hierarchical level studied; (ii) beta diversity in these communities develops by turnover in estuaries with a lower degree of anthropogenic impact, but by nestedness in estuaries with a greater degree of anthropogenic impact; and (iii) the structuring mechanism is independent of season. We studied two tropical estuaries (dry and wet seasons) that vary in terms of land-use of the drainage basins. Subtidal benthic macroinvertebrates were sampled along the estuarine gradient in each of the two estuaries. The additive partitioning approach to species diversity was used to determine the hierarchical scale with the greatest dissimilarity in community composition. General beta diversity was measured using the Sorensen dissimilarity index, partitioning the turnover and nestedness components. The greatest dissimilarity in the composition of the communities occurred between the zones along the estuarine gradient in both seasons (dry = 58.6%; wet = 46.3%). In the estuary with a lower degree of anthropogenic influence, benthic macroinvertebrate diversity was generated by turnover regardless of the season. In the estuary with a greater degree of anthropogenic impact, beta diversity was structured by turnover during the dry season and a combination of both mechanisms during the wet season. We conclude that turnover is the principal mechanism responsible for beta diversity in benthic macroinvertebrate communities in tropical estuaries.

  1. Patterns and correlates of plant diversity differ between common and rare species in a neotropical dry forest

    NARCIS (Netherlands)

    Tetetla-Rangel, Erika; Dupuy, Juan Manuel; Hernández-Stefanoni, José Luis; Hoekstra, Paul H.

    2017-01-01

    Determining which factors affect species richness is important for conservation theory and practice. However, richness of common and rare species may be affected by different factors. We use an extensive inventory of woody plants from a tropical dry forest landscape in Yucatan, Mexico to assess the

  2. An integrated pan-tropical biomass map using multiple reference datasets.

    Science.gov (United States)

    Avitabile, Valerio; Herold, Martin; Heuvelink, Gerard B M; Lewis, Simon L; Phillips, Oliver L; Asner, Gregory P; Armston, John; Ashton, Peter S; Banin, Lindsay; Bayol, Nicolas; Berry, Nicholas J; Boeckx, Pascal; de Jong, Bernardus H J; DeVries, Ben; Girardin, Cecile A J; Kearsley, Elizabeth; Lindsell, Jeremy A; Lopez-Gonzalez, Gabriela; Lucas, Richard; Malhi, Yadvinder; Morel, Alexandra; Mitchard, Edward T A; Nagy, Laszlo; Qie, Lan; Quinones, Marcela J; Ryan, Casey M; Ferry, Slik J W; Sunderland, Terry; Laurin, Gaia Vaglio; Gatti, Roberto Cazzolla; Valentini, Riccardo; Verbeeck, Hans; Wijaya, Arief; Willcock, Simon

    2016-04-01

    We combined two existing datasets of vegetation aboveground biomass (AGB) (Proceedings of the National Academy of Sciences of the United States of America, 108, 2011, 9899; Nature Climate Change, 2, 2012, 182) into a pan-tropical AGB map at 1-km resolution using an independent reference dataset of field observations and locally calibrated high-resolution biomass maps, harmonized and upscaled to 14 477 1-km AGB estimates. Our data fusion approach uses bias removal and weighted linear averaging that incorporates and spatializes the biomass patterns indicated by the reference data. The method was applied independently in areas (strata) with homogeneous error patterns of the input (Saatchi and Baccini) maps, which were estimated from the reference data and additional covariates. Based on the fused map, we estimated AGB stock for the tropics (23.4 N-23.4 S) of 375 Pg dry mass, 9-18% lower than the Saatchi and Baccini estimates. The fused map also showed differing spatial patterns of AGB over large areas, with higher AGB density in the dense forest areas in the Congo basin, Eastern Amazon and South-East Asia, and lower values in Central America and in most dry vegetation areas of Africa than either of the input maps. The validation exercise, based on 2118 estimates from the reference dataset not used in the fusion process, showed that the fused map had a RMSE 15-21% lower than that of the input maps and, most importantly, nearly unbiased estimates (mean bias 5 Mg dry mass ha(-1) vs. 21 and 28 Mg ha(-1) for the input maps). The fusion method can be applied at any scale including the policy-relevant national level, where it can provide improved biomass estimates by integrating existing regional biomass maps as input maps and additional, country-specific reference datasets. © 2015 John Wiley & Sons Ltd.

  3. Does the edge effect influence plant community structure in a tropical dry forest? O efeito de borda influencia a estrutura da comunidade vegetal em uma floresta tropical seca?

    Directory of Open Access Journals (Sweden)

    Diogo Gallo Oliveira

    2013-04-01

    Full Text Available Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.Efeitos de borda são considerados fator-chave na regulação da estrutura de comunidades vegetais em diferentes ecossistemas. Entretanto, apesar dos poucos estudos relacionados, o efeito de borda parece não ser determinante em regiões semiáridas, como a floresta tropical seca brasileira, conhecida como Caatinga. Este estudo testou a hipótese nula de que a comunidade vegetal arbustivo-arbórea não sofre alterações em sua estrutura, riqueza e composição devido ao efeito de borda. Foram instaladas 24 parcelas (20 x 20 m em um fragmento de Caatinga arbórea, sendo 12 parcelas na borda do fragmento e 12 parcelas no seu interior. A riqueza, abundância e composição das espécies não diferiram estatisticamente entre as parcelas de borda e interior. Os resultados deste estudo corroboram um possível padr

  4. Recent Biomass Burning in the Tropics and Related Changes in Tropospheric Ozone

    Science.gov (United States)

    Ziemke; Chandra, J. R. S.; Duncan, B. N.; Schoeberl, M. R.; Torres, O.; Damon, M. R.; Bhartia, P. K.

    2009-01-01

    Biomass burning is an important source of chemical precursors of tropospheric ozone. In the tropics, biomass burning produces ozone enhancements over broad regions of Indonesia, Africa, and South America including Brazil. Fires are intentionally set in these regions during the dry season each year to clear cropland and to clear land for human/industrial expansion. In Indonesia enhanced burning occurs during dry El Nino conditions such as in 1997 and 2006. These burning activities cause enhancement in atmospheric particulates and trace gases which are harmful to human health. Measurements from the Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) from October 2004-November 2008 are used to evaluate the effects of biomass burning on tropical tropospheric ozone. These measurements show sizeable decreases approx.15-20% in ozone in Brazil during 2008 compared to 2007 which we attribute to the reduction in biomass burning. Three broad biomass burning regions in the tropics (South America including Brazil, western Africa, and Indonesia) were analyzed in the context of OMI/MLS measurements and the Global Modeling Initiative (GMI) chemical transport model developed at Goddard Space Flight Center. The results indicate that the impact of biomass burning on ozone is significant within and near the burning regions with increases of approx.10-25% in tropospheric column ozone relative to average background concentrations. The model suggests that about half of the increases in ozone from these burning events come from altitudes below 3 km. Globally the model indicates increases of approx.4-5% in ozone, approx.7-9% in NO, (NO+NO2), and approx.30-40% in CO.

  5. How Does Dung Beetle (Coleoptera: Scarabaeidae) Diversity Vary Along a Rainy Season in a Tropical Dry Forest?

    Science.gov (United States)

    Novais, Samuel M A; Evangelista, Lucas A; Reis-Júnior, Ronaldo; Neves, Frederico S

    2016-01-01

    Dung beetle community dynamics are determined by regional rainfall patterns. However, little is known about the temporal dynamics of these communities in tropical dry forests (TDFs). This study was designed to test the following predictions: 1) Peak diversity of dung beetle species occurs early in the wet season, with a decrease in diversity (α and β) and abundance throughout the season; 2) Nestedness is the primary process determining β-diversity, with species sampled in the middle and the end of the wet season representing subsets of the early wet season community. Dung beetles were collected in a TDF in the northern Minas Gerais state, Brazil over three sampling events (December 2009, February and April 2010). We sampled 2,018 dung beetles belonging to 39 species and distributed among 15 genera. Scarabaeinae α-diversity and abundance were highest in December and equivalent between February and April, while β-diversity among plots increased along the wet season. The importance of nestedness and species turnover varies between pairs of sample periods as the main process of temporal β-diversity. Most species collected in the middle and end of the wet season were found in greater abundance in early wet season. Thus, the dung beetle community becomes more homogeneous at the beginning of the wet season, and as the season advances, higher resource scarcity limits population size, which likely results in a smaller foraging range, increasing β-diversity. Our results demonstrate high synchronism between the dung beetle life cycle and seasonality of environmental conditions throughout the wet season in a TDF, where the onset of rains determines adult emergence for most species. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America.

  6. Cyclic changes in Pennsylvanian paleoclimate and effects on floristic dynamics in tropical Pangaea

    Science.gov (United States)

    DiMichele, W.A.; Cecil, C.B.; Montanez, I.P.; Falcon-Lang, H. J.

    2010-01-01

    Wetland floras narrowly define perceptions of Pennsylvanian tropical ecosystems, the so-called Coal Age. Such wetlands reflect humid to perhumid climate, leading to characterizations of Pennsylvanian tropics as everwet, swampy. These views are biased by the high preservation potential of wetlands. Sedimentation patterns, paleosols, and fossil floras indicate the presence of vegetation tolerant of subhumid to dry-subhumid, perhaps semi-arid climate in basins between peat formation times. Understanding the significance of this seasonally-dry vegetation has suffered from conceptual and terminological confusion. A clearer view has emerged as models for framing the data have improved. Basinal floras typical of seasonally-dry conditions, relatively low soil moisture regimes, are well documented but mainly from isolated deposits. Some of the earliest, dominated by primitive pteridosperms ("Fl??zfern" floras), occur in clastic rocks between European Early Pennsylvanian coal beds. Later Early Pennsylvanian, fern-cordaitalean vegetation, different from coal floras, is preserved in marine goniatite bullions. Conifers are first suggested by late Mississippian Potoniesporites pollen. About the same time, in North America, broadleaf foliage, Lesleya and Megalopteris occur in basin-margin settings, on drought-prone limestone substrates. The best known, xeromorphic floras found between coal beds appear in the Middle through Late Pennsylvanian, containing conifers, cordaitaleans, and pteridosperms. The Middle Pennsylvanian appearances of this flora are mainly allochthonous, though parautochthonous occurrences have been reported. Parautochthonous assemblages are mostly Late Pennsylvanian. The conifer flora became dominant in western and central Pangaean equatorial lowlands in earliest Permian. Location of the humid-perhumid wetland flora during periods of relative dryness, though rarely discussed, is as, or more, perplexing than the spatial location of seasonally-dry floras through

  7. ADDITION POLYUNSATURATED FATTY ACIDS IN THE DIET INCREASES THE NUMBER AND SIZE OF FOLLICLES IN COWS FED UNDER TROPICAL GRAZING SYSTEM

    Directory of Open Access Journals (Sweden)

    G. Cansino-Arroyo

    2014-08-01

    Full Text Available The objective was determined the effect of polyunsaturated fatty acids (PUFAS on the number and follicular size in cows fed under tropical grazing during the dry season and rainy season. Using a group of cows PUFAS (GA, dry: n=9 and rain: n=13 maintained under grazing continuo, which received a nutritional supplement, with the addition of 5 % of PUFAS in the supplement. A second control group (GT; dry: n=13 and rain: n=9, kept in the same conditions as the previous group, without PUFAS. The number of follicles was greater during the rainy season than during dry (P=0.0001. Cows GT nutritional supplement did not improve the number of follicles between 2 times (P ≥ 0.7. However, the addition of PUFAS to supplement increases the number of follicles during the rainy season (P=0.002. Otherwise, when the cows were ovulation hormonally stimulated are not noted an increase in the number of follicles in cows with or without PUFAS in the supplement. With these results, we can conclude that the number of follicles is affected by perceived conditions, besides that addition of PUFAS increases the number of follicles during the rainy season in tropical grazing cows.

  8. Long-term changes in above ground biomass after disturbance in a neotropical dry forest, Hellshire Hills, Jamaica

    DEFF Research Database (Denmark)

    Niño, Milena; McLaren, Kurt P.; Meilby, Henrik

    2014-01-01

    We used data from experimental plots (control, partially cut and clear-cut) established in 1998, in a tropical dry forest (TDF) in Jamaica, to assess changes in above ground biomass (AGB) 10 years after disturbance. The treatments reduced AGB significantly in 1999 (partially cut: 37.6 %, clear-cu...

  9. Layout Guide for Burnt and Un-burnt Tropical Forest: The Diversity of Forest Plants and Insetcs for Sustainable Environmental

    Science.gov (United States)

    Watiniasih, N. L.; Tambunan, J.; Merdana, I. M.; Antara, I. N. G.

    2018-04-01

    Forest fire is a common phenomenon in tropical forest likes in Indonesia. Beside the effect of soaring heat and lack of rain during dry season due to the tropical climate, farming system is also reported as one reason of forest fire in Indonesia. People of surrounding areas and neighbouring countries are suffering from the effect of forest fire. Plants and animals are the most suffer from this occurrence that they cannot escape. This study aimed to investigate the effect of previously burnt and un-burnt tropical forest in Borneo Island on the plant and insect diversity of the tropical forest. The result of the study found that the plants in previously burnt forest area was dominated by one species, while higher and more stable plant diversity was found in un-burnt forest. Although the number of individual insects was higher in previously burnt tropical forest, but the insects was more diverse in un-burnt tropical forest. The alteration of environmental conditions in previously burnt and un-burnt forest indicate that the energy held in natural forest support higher number and more stable insects than previously burnt forest.

  10. Floristic structure and biomass distribution of a tropical seasonal rain forest in Xishuangbanna, southwest China

    Energy Technology Data Exchange (ETDEWEB)

    Shanmughavel, P.; Zheng Zheng; Sha Liqing; Cao Min [Chinese Academy of Sciences, Kunming (China). Dept. of Forest Ecology

    2001-07-01

    The aim of this research was to study the forest community structure, tree species diversity and biomass production of a tropical seasonal rain forest in Xishuangbanna, southwest China. The community structure showed a diversified species composition and supported many species of economic significance. This tropical rain forest in closely related to Malaysian forests. The biomass and its distribution were studied using standard regression analysis and the clear-cut method for shrubs and herbs. The total biomass was 360.9 t/ha and its allocation in different layers was: tree layer 352.5 t/ha, shrub layer 4.7 t/ha, liana 3.1 t/ha and herb layer 0.5 t/ha. Most of the biomass was concentrated in the trees: stem 241.2 t/ha, root 69.6 t/ha, branch 37.2 t/ha and leaves 4.3 t/ha. The DBH class allocation of the tree biomass was concentrated in the middle DBH class. The biomass of six DBH classes from 20 to 80 cm was 255.4 t/ha. There are twenty-six species with biomass over 0.5% of the total biomass of the tree layer, and three species with biomass over 5%, i.e., Pometia tomentosa, Barringtonia macrostachya (5.4%) and Terminalia myriocarpa (5.2%). Data on stem, branch, leaves and root of the individual tree species were used to develop regression models. D{sup 2}H was found to be the best estimator of the biomass in this tropical rain forest. However, higher biomass figures have been reported from tropical forests elsewhere e.g., 415-520 t/ha in the tropical forests of Cambodia, the tropical moist mixed dipterocarp forests, and the tropical moist logged moist evergreen-high, medium, and low yield forests of Sri Lanka. In some forests, lower accumulation of biomass was reported, e.g., 10-295 t/ha in the tropical moist forests of Bangladesh, the tropical moist dense forest of Cambodia, the tropical dry forests of India, the tropical moist forests of Peninsular-Malaysia, the tropical moist mixed dipterocarp forests of Sarawak-Malaysia, the tropical evergreen forests of

  11. Plant-pollinator interactions in tropical monsoon forests in Southeast Asia.

    Science.gov (United States)

    Kato, Makoto; Kosaka, Yasuyuki; Kawakita, Atsushi; Okuyama, Yudai; Kobayashi, Chisato; Phimminith, Thavy; Thongphan, Daovorn

    2008-11-01

    Forests with different flora and vegetation types harbor different assemblages of flower visitors, and plant-pollinator interactions vary among forests. In monsoon-dominated East and Southeast Asia, there is a characteristic gradient in climate along latitude, creating a broad spectrum of forest types with potentially diverse pollinator communities. To detect a geographical pattern of plant-pollinator interactions, we investigated flowering phenology and pollinator assemblages in the least-studied forest type, i.e., tropical monsoon forest, in the Vientiane plain in Laos. Throughout the 5-year study, we observed 171 plant species blooming and detected flower visitors on 145 species. Flowering occurred throughout the year, although the number of flowering plant species peaked at the end of dry season. The dominant canopy trees, including Dipterocarpaceae, bloomed annually, in contrast to the supra-annual general flowering that occurs in Southeast Asian tropical rain forests. Among the 134 native plant species, 68 were pollinated by hymenopterans and others by lepidopterans, beetles, flies, or diverse insects. Among the observed bees, Xylocopa, megachilids, and honeybees mainly contributed to the pollination of canopy trees, whereas long-tongued Amegilla bees pollinated diverse perennials with long corolla tubes. This is the first community-level study of plant-pollinator interactions in an Asian tropical monsoon forest ecosystem.

  12. Climate-mediated nitrogen and carbon dynamics in a tropical watershed

    Science.gov (United States)

    Ballantyne, A. P.; Baker, P. A.; Fritz, S. C.; Poulter, B.

    2011-06-01

    Climate variability affects the capacity of the biosphere to assimilate and store important elements, such as nitrogen and carbon. Here we present biogeochemical evidence from the sediments of tropical Lake Titicaca indicating that large hydrologic changes in response to global glacial cycles during the Quaternary were accompanied by major shifts in ecosystem state. During prolonged glacial intervals, lake level was high and the lake was in a stable nitrogen-limited state. In contrast, during warm dry interglacials lake level fell and rates of nitrogen concentrations increased by a factor of 4-12, resulting in a fivefold to 24-fold increase in organic carbon concentrations in the sediments due to increased primary productivity. Observed periods of increased primary productivity were also associated with an apparent increase in denitrification. However, the net accumulation of nitrogen during interglacial intervals indicates that increased nitrogen supply exceeded nitrogen losses due to denitrification, thereby causing increases in primary productivity. Although primary productivity in tropical ecosystems, especially freshwater ecosystems, tends to be nitrogen limited, our results indicate that climate variability may lead to changes in nitrogen availability and thus changes in primary productivity. Therefore some tropical ecosystems may shift between a stable state of nitrogen limitation and a stable state of nitrogen saturation in response to varying climatic conditions.

  13. Traditional and formal ecological knowledge to assess harvesting and conservation of a Mexican Tropical Dry Forest.

    Science.gov (United States)

    Monroy-Ortiz, Columba; García-Moya, Edmundo; Romero-Manzanares, Angélica; Luna-Cavazos, Mario; Monroy, Rafael

    2018-05-15

    This research integrates Traditional and Formal Ecological Knowledge (TEK / FEK) of a Tropical Dry Forest in central Mexico, in order to assess harvesting and conservation of the non-timber forest species. We were interested in: knowing the structure and diversity of the forest community; identifying which are the tree resources of common interest to the users through participatory workshops. A further interest was to identify those resources which are important to local people in terms of preservation; explaining the relationship of the species with some environmental factors; and visualizing which management practices endanger or facilitate the conservation of species. Studied areas were defined and labelled on a map drawn by local informants, where they indicated those plant species of common interest for preservation. Ethnobotanical techniques were used to reveal the TEK and assess harvesting and conservation of the species. With the FEK through community and population ecology, we detected the importance of five environmental factors, obtained various ecological indicators of the vegetation, and studied the population structure of the relevant species. The FEK was analyzed using descriptive and multivariate statistics. As a result, low density and small basal area of trees were registered. Species richness and diversity index were similar to other natural protected areas in Mexico. Tree species harvested shown an asymmetric distribution of diameters. Harvesting, elevation, and accessibility were the most influential factors on tree density. FEK demonstrated that TEK is helpful for the assessment of forest harvesting. Ecological analysis complemented the local knowledge detecting that Lysiloma tergemina is a species non-identified for the people as interesting, although we discover that it is a threatened species by over-harvesting. Haematoxylum brasiletto was identified as important for conservation due to its scarcity and medicinal use. Our results advanced

  14. How Do Tropical Sea Surface Temperatures Influence the Seasonal Distribution of Precipitation in the Equatorial Amazon?.

    Science.gov (United States)

    Fu, Rong; Dickinson, Robert E.; Chen, Mingxuan; Wang, Hui

    2001-10-01

    Although the correlation between precipitation over tropical South America and sea surface temperatures (SSTs) over the Pacific and Atlantic has been documented since the early twentieth century, the impact of each ocean on the timing and intensity of the wet season over tropical South America and the underlying mechanisms have remained unclear. Numerical experiments have been conducted using the National Center for Atmospheric Research Community Climate Model Version 3 to explore these impacts. The results suggest the following.1)Seasonality of SSTs in the tropical Pacific and Atlantic has an important influence on precipitation in the eastern Amazon during the equinox seasons. The eastern side of the Amazon is influenced both by the direct thermal circulation of the Atlantic intertropical convergence zone (ITCZ) and by Rossby waves. These processes are enhanced by the seasonal cycles of SSTs in the tropical Atlantic and Pacific. SSTs affect Amazon precipitation much less during the solstice seasons and in the western Amazon.2)The seasonality of SSTs in the Atlantic more strongly affects Amazon rainfall than does that of the Pacific. Without the former, austral spring in the eastern equatorial Amazon would be a wet season, rather than the observed dry season. As a consequence of the lag at that time of the southward seasonal migration of the Atlantic SSTs behind that of the insolation, the Atlantic ITCZ centers itself near 10°N, instead of at the equator, imposing subsidence and low-level anticyclonic flow over the eastern equatorial Amazon, thus drying the air above the planetary boundary layer and reducing the low-level moisture convergence. Consequently, convection in the eastern Amazon is suppressed despite strong surface heating.3)Seasonality of the SSTs in the tropical Pacific also tends to reduce precipitation in the eastern Amazon during both spring and fall. In spring, subsidence is enhanced not only through a zonal direct circulation, but also through

  15. The Effect of Drying-Wetting Cycle’s Repetition to the Characteristic of Natural and Stabilization Residual Soils Jawa Timur - Indonesia

    Science.gov (United States)

    Muntaha, M.

    2017-11-01

    Indonesia, which located in tropical region, continuously undergoes wetting and drying cycles due to the changeable seasons. An important role in activating the clay minerals on tropical residual soils is the main factor that affects the static and dynamic properties, such as: volume change, soil suction and dynamic modulus. The purpose of this paper is to evaluate the effect of drying-wetting cycles repetition on volume change, soil suction and mechanical characteristics of natural and stabilization of residual soils from Jawa Timur - Indonesia. The natural undisturbed and stabilized residual soil sample was naturally and gradually dried up with air to 25%, 50%, 75%, and 100 % of the initial water content. The wetting processes were carried out with the gradual increment water content of 25 %(wsat - wi), 50 %(wsat - wi), 75 %(wsat - wi), up to 100 %(wsat - wi). The Direct Shear test is used to measure the mechanic properties, and Whatman filter paper No. 42 is used to measure the soil suction. The drying-wetting processes were carried out for 1, 2, 4, and 6 cycles. The laboratory test results showed that, the void ratio decreased, the unit weight, cohesion and the internal friction angle were increasing due to stabilization. Drying-wetting cycle repetition reduces void ratio, negative pore-water pressure, cohesion and internal friction angle of natural and stabilized soils. Briefly, the decreased of mechanical soil properties was proven from the physical properties change observation.

  16. Carbon budget of tropical forests in Southeast Asia and the effects of deforestation: an approach using a process-based model and field measurements

    Directory of Open Access Journals (Sweden)

    M. Adachi

    2011-09-01

    Full Text Available More reliable estimates of the carbon (C stock within forest ecosystems and C emission induced by deforestation are urgently needed to mitigate the effects of emissions on climate change. A process-based terrestrial biogeochemical model (VISIT was applied to tropical primary forests of two types (a seasonal dry forest in Thailand and a rainforest in Malaysia and one agro-forest (an oil palm plantation in Malaysia to estimate the C budget of tropical ecosystems in Southeast Asia, including the impacts of land-use conversion. The observed aboveground biomass in the seasonal dry tropical forest in Thailand (226.3 t C ha−1 and the rainforest in Malaysia (201.5 t C ha−1 indicate that tropical forests of Southeast Asia are among the most C-abundant ecosystems in the world. The model simulation results in rainforests were consistent with field data, except for the NEP, however, the VISIT model tended to underestimate C budget and stock in the seasonal dry tropical forest. The gross primary production (GPP based on field observations ranged from 32.0 to 39.6 t C ha−1 yr−1 in the two primary forests, whereas the model slightly underestimated GPP (26.5–34.5 t C ha−1 yr−1. The VISIT model appropriately captured the impacts of disturbances such as deforestation and land-use conversions on the C budget. Results of sensitivity analysis showed that the proportion of remaining residual debris was a key parameter determining the soil C budget after the deforestation event. According to the model simulation, the total C stock (total biomass and soil C of the oil palm plantation was about 35% of the rainforest's C stock at 30 yr following initiation of the plantation. However, there were few field data of C budget and stock, especially in oil palm plantation. The C budget of each ecosystem must be evaluated over the long term using both the model simulations and observations to

  17. Diverging responses of tropical Andean biomes under future climate conditions.

    Directory of Open Access Journals (Sweden)

    Carolina Tovar

    Full Text Available Observations and projections for mountain regions show a strong tendency towards upslope displacement of their biomes under future climate conditions. Because of their climatic and topographic heterogeneity, a more complex response is expected for biodiversity hotspots such as tropical mountain regions. This study analyzes potential changes in the distribution of biomes in the Tropical Andes and identifies target areas for conservation. Biome distribution models were developed using logistic regressions. These models were then coupled to an ensemble of 8 global climate models to project future distribution of the Andean biomes and their uncertainties. We analysed projected changes in extent and elevational range and identified regions most prone to change. Our results show a heterogeneous response to climate change. Although the wetter biomes exhibit an upslope displacement of both the upper and the lower boundaries as expected, most dry biomes tend to show downslope expansion. Despite important losses being projected for several biomes, projections suggest that between 74.8% and 83.1% of the current total Tropical Andes will remain stable, depending on the emission scenario and time horizon. Between 3.3% and 7.6% of the study area is projected to change, mostly towards an increase in vertical structure. For the remaining area (13.1%-17.4%, there is no agreement between model projections. These results challenge the common believe that climate change will lead to an upslope displacement of biome boundaries in mountain regions. Instead, our models project diverging responses, including downslope expansion and large areas projected to remain stable. Lastly, a significant part of the area expected to change is already affected by land use changes, which has important implications for management. This, and the inclusion of a comprehensive uncertainty analysis, will help to inform conservation strategies in the Tropical Andes, and to guide similar

  18. An Embedded Sensor Network for Measuring Elevation Effects on Temperature, Humidity, and Evapotranspiration Within a Tropical Alpine Valley

    Science.gov (United States)

    Hellstrom, R. A.; Mark, B. G.

    2006-12-01

    Conditions of glacier recession in the seasonally dry tropical Peruvian Andes motivates research to better constrain the hydrological balance in alpine valleys. Studies suggest that glaciers in the tropical Andes are particularly sensitive to seasonal humidity flux due to the migration of the Intertropical Convergence Zone. However, there is an outstanding need to better measure and model the spatiotemporal variability of energy and water budgets within pro-glacial valleys. In this context, we introduce a novel embedded network of low- cost, discrete temperature and humidity microloggers and an automatic weather station installed in the Llanganuco valley of the Cordillera Blanca. This paper presents data recorded over a full annual cycle (2004- 2005) and reports on network design and results during the dry and wet seasons. The transect of sensors ranging from about 3500 to 4700 m reveal seasonally characteristic diurnal fluctuations in up-valley lapse rate. A process-based water balance model (Brook90) examines the influence of meteorological forcing on evapotranspiration (ET) rates in the valley. The model results suggest that cloud-free daylight conditions enhances ET during the wet season. ET was insignificant throughout the dry season. In addition, we report on the effects of elevation on ET.

  19. Camerobiid mites (Acariformes: Raphignathina: Camerobiidae inhabiting epiphytic bromeliads and soil litter of tropical dry forest with analysis of setal homology in the genus Neophyllobius

    Directory of Open Access Journals (Sweden)

    Ricardo Paredes-León

    2016-06-01

    Full Text Available A survey of the camerobiid mites living on epiphytic bromeliads and the forest floor of a Mexican tropical dry forest was carried out. We found three new species of the genus Neophyllobius, which are described in this paper; the first two, namely N. cibyci sp. nov. and N. tepoztlanensis sp. nov., were both found inhabiting bromeliads (Tillandsia spp. and living on two tree species (Quercus obtusata and Sapium macrocarpum; the third, N. tescalicola sp. nov., was found in soil and litter under Q. obtusata. These three new species can be differentiated from other species in the genus by a combination of morphological characters in adult females, mainly those setae on femora and genua I. The idiosoma and leg setal ontogeny of a camerobiid mite is presented for the first time in this paper, illustrating chaetotaxic notations and their relative positions in N. cibyci sp. nov. larva, protonymph and adults (female and male, and establishing setal homologies among instars. Setal homology with other species in the cohort Raphignathina is briefly discussed. Additionally, a compilation and an identification key to all known species of camerobiid mites in Mexico is provided.

  20. Pasture shade and farm management effects on cow productivity in the tropics

    OpenAIRE

    Ainsworth, Justin A.W.; Moe, Stein R.; Skarpe, Christina

    2012-01-01

    This is the postprint version of the article. The published article can be located at the publisher's webpage Shade, provided by trees within pastures, can affect cattle productivity through mitigating heat stress and by altering understorey pasture growth and cattle behaviour. Models for daily milk yield and body condition were used to evaluate the effect of pasture shade on dual purpose cow productivity within a silvopastoral system in a dry tropical province of Nicaragua. Daily milk yie...

  1. Water Use Patterns of Four Tropical Bamboo Species Assessed with Sap Flux Measurements.

    Science.gov (United States)

    Mei, Tingting; Fang, Dongming; Röll, Alexander; Niu, Furong; Hendrayanto; Hölscher, Dirk

    2015-01-01

    Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed.

  2. Bark traits and life-history strategies of tropical dry- and moist forest trees

    NARCIS (Netherlands)

    Poorter, L.; McNeil, A.; Hurtado, V.H.; Prins, H.H.T.; Putz, F.E.

    2014-01-01

    1.Bark is crucial to trees because it protects their stems against fire and other hazards and because of its importance for assimilate transport, water relationships and repair. We evaluate size-dependent changes in bark thickness for 50 woody species from a moist forest and 50 species from a dry

  3. Relating tropical ocean clouds to moist processes using water vapor isotope measurements

    Directory of Open Access Journals (Sweden)

    J. Lee

    2011-01-01

    Full Text Available We examine the co-variations of tropospheric water vapor, its isotopic composition and cloud types and relate these distributions to tropospheric mixing and distillation models using satellite observations from the Aura Tropospheric Emission Spectrometer (TES over the summertime tropical ocean. Interpretation of these process distributions must take into account the sensitivity of the TES isotope and water vapor measurements to variations in cloud, water, and temperature amount. Consequently, comparisons are made between cloud-types based on the International Satellite Cloud Climatology Project (ISSCP classification; these are clear sky, non-precipitating (e.g., cumulus, boundary layer (e.g., stratocumulus, and precipitating clouds (e.g. regions of deep convection. In general, we find that the free tropospheric vapor over tropical oceans does not strictly follow a Rayleigh model in which air parcels become dry and isotopically depleted through condensation. Instead, mixing processes related to convection as well as subsidence, and re-evaporation of rainfall associated with organized deep convection all play significant roles in controlling the water vapor distribution. The relative role of these moisture processes are examined for different tropical oceanic regions.

  4. Tropical vegetation evidence for rapid sea level changes associated with Heinrich Events

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Catalina; Dupont, Lydie M, E-mail: catalina@uni-bremen.d, E-mail: dupont@uni-bremen.d [MARUM - Centre for Marine Environmental Sciences, University of Bremen, Leobener Strasse, D-28359 Germany (Germany)

    2010-03-15

    A Cariaco Basin pollen record shows the development of tropical salt marshes during marine isotope stage 3. Rapid and abrupt expansions of salt marsh vegetation in tropical South America are associated with north Atlantic Heinrich Events stadials (HE-stadials). Intervals of salt marsh expansion have an internal structure, which consists of a recurrent alternation of species that starts with pollen increments of Chenopodiaceae, that are followed by increments of grasses, and subsequently by increments of Cyperaceae. This pattern suggests a successional process that is determined by the close relationship between sea-level and plant community dynamics. The salt tolerant Chenopodiaceae, indicate hypersaline intertidal environments, which were most likely promoted by extremely dry atmospheric conditions. Rapid sea-level rise characterizes the onset of HE-stadials, causing the continued recruitment of pioneer species, which are the only ones tolerating rapid rates of disturbance. Once sea-level rise decelerates, marsh plants are able to trap and stabilize sediments, favouring the establishment of more competitive species. These results add to the scarce knowledge on the dynamics of tropical salt marsh ecosystems, and provide independent paleoclimatic evidence on sea-level changes following Antarctic climate variability.

  5. Amplification of wildfire area burnt by hydrological drought in the humid tropics

    Science.gov (United States)

    Taufik, Muh; Torfs, Paul J. J. F.; Uijlenhoet, Remko; Jones, Philip D.; Murdiyarso, Daniel; van Lanen, Henny A. J.

    2017-06-01

    Borneo's diverse ecosystems, which are typical humid tropical conditions, are deteriorating rapidly, as the area is experiencing recurrent large-scale wildfires, affecting atmospheric composition and influencing regional climate processes. Studies suggest that climate-driven drought regulates wildfires, but these overlook subsurface processes leading to hydrological drought, an important driver. Here, we show that models which include hydrological processes better predict area burnt than those solely based on climate data. We report that the Borneo landscape has experienced a substantial hydrological drying trend since the early twentieth century, leading to progressive tree mortality, more severe than in other tropical regions. This has caused massive wildfires in lowland Borneo during the past two decades, which we show are clustered in years with large areas of hydrological drought coinciding with strong El Niño events. Statistical modelling evidence shows amplifying wildfires and greater area burnt in response to El Niño/Southern Oscillation (ENSO) strength, when hydrology is considered. These results highlight the importance of considering hydrological drought for wildfire prediction, and we recommend that hydrology should be considered in future studies of the impact of projected ENSO strength, including effects on tropical ecosystems, and biodiversity conservation.

  6. Characteristics and development of European cyclones with tropical origin in reanalysis data

    Science.gov (United States)

    Dekker, Mark M.; Haarsma, Reindert J.; Vries, Hylke de; Baatsen, Michiel; Delden, Aarnout J. van

    2018-01-01

    Major storm systems over Europe frequently have a tropical origin. This paper analyses the characteristics and dynamics of such cyclones in the observational record, using MERRA reanalysis data for the period 1979-2013. By stratifying the cyclones along three key phases of their development (tropical phase, extratropical transition and final re-intensification), we identify four radically different life cycles: the tropical cyclone and extratropical cyclone life cycles, the classic extratropical transition and the warm seclusion life cycle. More than 50% of the storms reaching Europe from low latitudes follow the warm seclusion life cycle. It also contains the strongest cyclones. They are characterized by a warm core and a frontal T-bone structure, with a northwestward warm conveyor belt and the effects of dry intrusion. Rapid deepening occurs in the latest phase, around their arrival in Europe. Both baroclinic instability and release of latent heat contribute to the strong intensification. The pressure minimum occurs often a day after entering Europe, which enhances the potential threat of warm seclusion storms for Europe. The impact of a future warmer climate on the development of these storms is discussed.

  7. Three Decades of Remote Sensing Based Tropical Forests Phenological Patterns and Trends

    Science.gov (United States)

    Didan, K.

    2010-12-01

    The faint climatic seasonality of tropical rain forests is believed to be the reason these biomes lack strong and detectable seasonality. Forest seasonality is a critical element of ecosystem functions. It moderates the echo-hydrology, carbon, and nutrient exchange of the area. While deciduous forests exhibit distinct and strong seasonality, tropical forests do not, yet they play a large role in the cycling of energy and mass. Tropical forests represent a large percentage of vegetated land and their importance to the Earth system stems from their biological diversity, their habitat role, their role in regulating global weather, and the role they play in carbon storage. While Tropical forests are well buffered by their sheer size, their vulnerability to climate change is exacerbated by the human pressure. All of this begs the questions of what are the patterns and characteristic of tropical forests phenology and are there any detectable trends over the last three decades of synoptic remote sensing. These three decades comprise different episodes of droughts and an ever increasing level of human encroachment. In so far understanding the function and dynamic of these biomes, field studies continue to play a major role, but synoptic remote sensing is emerging as a viable tool to addressing the spatial and temporal scale associated with this problem. Recent studies of Brazilian rainforest with synoptic remote sensing point to a sizable seasonal signal coincident with the dry season. However, these studies were not extensive in time or space and did not look at other rainforests. Using data from AVHRR and MODIS, we generated a 30 year record of the 2 bands Enhance Vegetation Index (EVI2), and analyzed the patterns and trends of land surface phenology across all tropical forests using the homogeneous phenology cluster approach. We chose EVI because of its superior performance over these dense forests, and we selected the homogeneous phenology cluster approach to abate the

  8. Tropical Soil Chemistry

    DEFF Research Database (Denmark)

    Borggaard, Ole K.

    and environmental protection. Tropical Soil Chemistry by Ole K. Borggaard provides an overview of the composition, occurrence, properties, processes, formation, and environmental vulnerability of various tropical soil types (using American Soil Taxonomy for classification). The processes and the external factors...... soil chemical issues are also presented to assess when, why, and how tropical soils differ from soils in other regions. This knowledge can help agricultural specialists in the tropics establish sustainable crop production. Readers are assumed to be familiar with basic chemistry, physics...

  9. Ant species (Hymenoptera, Formicidae from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records

    Directory of Open Access Journals (Sweden)

    Mônica A. Ulysséa

    2013-06-01

    Full Text Available Ant species (Hymenoptera, Formicidae from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records. The Caatingas occur predominantly in northeastern Brazil and comparatively it is the biome that received less attention than any other ecosystem in Brazil, representing the region where invertebrate groups are less known. We present here the first list of ant species of the Caatingas, compiling information from the literature, from a study of samples preserved in alcohol in the Laboratory of Entomology (Universidade Estadual de Feira de Santana, and from a field survey conducted in Milagres, Bahia, submitting standardized 1-m² samples of the leaf-litter to Winkler extractors. Summing all information, 11 subfamilies, 61 genera and 173 species (plus one subspecies of ants are recognized in the biome. This species number does not consider morphospecies that could not be named due to the lack of reliable recent taxonomic information for some Neotropical ant genera. The list presented here for ant species of the Caatingas is therefore underestimated, but it is relevant because it allows the identification of areas to be sampled in order to improve our knowledge of the diversity of ants in this biome.

  10. Diversity and aboveground biomass of lianas in the tropical seasonal rain forests of Xishuangbanna, SW China.

    Science.gov (United States)

    Lü, Xiao-Tao; Tang, Jian-Wei; Feng, Zhi-Li; Li, Mai-He

    2009-01-01

    Lianas are important components of tropical forests and have significant impacts on the diversity, structure and dynamics of tropical forests. The present study documented the liana flora in a Chinese tropical region. Species richness, abundance, size-class distribution and spatial patterns of lianas were investigated in three 1-ha plots in tropical seasonal rain forests in Xishuangbanna, SW China. All lianas with > or = 2 cm diameter at breast height (dbh) were measured, tagged and identified. A total of 458 liana stems belonging to 95 species (ranging from 38 to 50 species/ha), 59 genera and 32 families were recorded in the three plots. The most well-represented families were Loganiaceae, Annonceae, Papilionaceae, Apocynaceae and Rhamnaceae. Papilionaceae (14 species recorded) was the most important family in the study forests. The population density, basal area and importance value index (IVI) varied greatly across the three plots. Strychnos cathayensis, Byttneria grandifolia and Bousigonia mekongensis were the dominant species in terms of IVI across the three plots. The mean aboveground biomass of lianas (3 396 kg/ha) accounted for 1.4% of the total community above-ground biomass. The abundance, diversity and biomass of lianas in Xishuangbanna tropical seasonal rain forests are lower than those in tropical moist and wet forests, but higher than those in tropical dry forests. This study provides new data on lianas from a geographical region that has been little-studied. Our findings emphasize that other factors beyond the amount and seasonality of precipitation should be included when considering the liana abundance patterns across scales.

  11. Explosive radiation of Malpighiales supports a mid-cretaceous origin of modern tropical rain forests.

    Science.gov (United States)

    Davis, Charles C; Webb, Campbell O; Wurdack, Kenneth J; Jaramillo, Carlos A; Donoghue, Michael J

    2005-03-01

    Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, provide new tests of these hypotheses. We estimate that all 28 major lineages (i.e., traditionally recognized families) within this clade originated in tropical rain forest well before the Tertiary, mostly during the Albian and Cenomanian (112-94 Ma). Their rapid rise in the mid-Cretaceous may have resulted from the origin of adaptations to survive and reproduce under a closed forest canopy. This pattern may also be paralleled by other similarly diverse lineages and supports fossil indications that closed-canopy tropical rain forests existed well before the K/T boundary. This case illustrates that dated phylogenies can provide an important new source of evidence bearing on the timing of major environmental changes, which may be especially useful when fossil evidence is limited or controversial.

  12. Tropical Freshwater Biology

    African Journals Online (AJOL)

    Tropical Freshwater Biology promotes the publication of scientific contributions in the field of freshwater biology in the tropical and subtropical regions of the world. One issue is published annually but this number may be increased. Original research papers and short communications on any aspect of tropical freshwater ...

  13. The energy balance on the surface of a tropical glacier tongue. Investigations on glacier Artesonraju, Cordillera Blanca, Perú.

    Science.gov (United States)

    Juen, I.; Mölg, T.; Wagnon, P.; Cullen, N. J.; Kaser, G.

    2006-12-01

    The Cordillera Blanca in Perú is situated in the Outer Tropics spanning from 8 to 10 ° South. Solar incidence and air temperature show only minor seasonal variations whereas precipitation occurs mainly from October to April. An energy balance station was installed on the tongue of glacier Artesonraju (4850 m a.s.l.) in March 2004. In this study each component of the energy balance on the glacier surface is analysed separately over a full year, covering one dry and one wet season. During the dry season glacier melt at the glacier tongue is app. 0.5 m we per month. In the wet season glacier melt is twice as much with 1 m we per month. This is due to higher energy fluxes and decreased sublimation during the wet season. With an energy balance model that has already been proved under tropical climate conditions (Mölg and Hardy, 2004) each energy flux is changed individually to evaluate the change in the amount of glacier melt. First results indicate that a change in humidity related variables affects glacier melt very differently in the dry and wet season, whereas a change in air temperature changes glacier melt more constantly throughout the year.

  14. Revegetation of mined land in the wet-dry tropics of northern Australia: a review. Supervising Scientist report 150

    International Nuclear Information System (INIS)

    Corbett, M.H.

    1999-01-01

    This review aims to assist the Alligator Rivers Technical Committee (ARRTC) in determining whether current practices and plans for revegetation at Ranger mine and elsewhere in the Alligator Rivers Region (ARR) are appropriate, and to establish research priorities in this region. The majority of information regarding revegetation in the wet-dry tropics (WDT) of northern Australia pertains to Ranger mine. However, there is a dearth of peer-reviewed published papers which is a significant problem that may limit effective communication and application of appropriate revegetation techniques on mines in the WDT. The use of topsoil on hard rock mines in northern Australia is a contentious issue, with topsoil re-spreading being excluded from many rehabilitation programs. However, the experience of many WDT rehabilitation researchers indicates that use of topsoil containing indigenous microbes, valuable nutrients and organic matter increases the probability of achieving a successful, self-sustaining native ecosystem in the long term (eg Bell 1993. Hinz 1996, Tongway et al 1997). This review examines five methodologies that have been used to assess the success of rehabilitation in the WDT. Success criteria based on a single or narrow set of parameters are likely to be inadequate. A study comparing the indicator value of the various monitoring methods would be valuable, with a possible outcome being the development of a 'multi-discipline' monitoring approach. Gaps in the existing knowledge or practices that may limit the success of revegetation at minesites in the Alligator Rivers Region are identified. The most critical issues are identified broadly as: topsoil utilisation and management; fire; management/prediction of successional processes; establishment of symbiotic micro-organisms; native seed collection, storage and germination; development of monitoring methodologies and acceptable success criteria; and technology transfer

  15. A floristic analysis of forest and thicket vegetation of the Marakele National Park

    Directory of Open Access Journals (Sweden)

    P.J. van Staden

    2006-12-01

    Full Text Available One of the major plant communities identified in the Marakele National Park was forest. It became clear that this major forest community contained various forest and thicket communities. Relevés compiled in the forest were classified by TWINSPAN and Braun-Blanquet procedures identified six communities that are hierarchically classified. The forests dominated by Podocarpus latifolius and Widdringtonia nodiflora represent Afromontane Forests, whereas the Buxus macowanii-dominated dry forests and Olea europaea subsp. africana represent Northern Highveld Forests. A further group of communities represent thickets on termitaria with floristic affinities to both savanna and forest. The floristic composition and relationships of the forest and thicket communities are discussed.

  16. Acceleration of tropical cyclogenesis by self-aggregation feedbacks.

    Science.gov (United States)

    Muller, Caroline J; Romps, David M

    2018-03-20

    Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.

  17. Future drying of the southern Amazon and central Brazil

    Science.gov (United States)

    Yoon, J.; Zeng, N.; Cook, B.

    2008-12-01

    Recent climate modeling suggests that the Amazon rainforest could exhibit considerable dieback under future climate change, a prediction that has raised considerable interest as well as controversy. To determine the likelihood and causes of such changes, we analyzed the output of 15 models from the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC/AR4) and a dynamic vegetation model VEGAS driven by these climate output. Our results suggest that the core of the Amazon rainforest should remain largely stable. However, the periphery, notably the southern edge, is in danger of drying out, driven by two main processes. First, a decline in precipitation of 24% in the southern Amazon lengthens the dry season and reduces soil moisture, despite of an increase in precipitation during the wet season, due to the nonlinear response in hydrology and ecosystem dynamics. Two dynamical mechanisms may explain the lower dry season precipitation: (1) a stronger north-south tropical Atlantic sea surface temperature gradient; (2) a general subtropical drying under global warming when the dry season southern Amazon is under the control of the subtropical high pressure. Secondly, evaporation will increase due to the general warming, thus also reducing soil moisture. As a consequence, the median of the models projects a reduction of vegetation by 20%, and enhanced fire carbon flux by 10-15% in the southern Amazon, central Brazil, and parts of the Andean Mountains. Because the southern Amazon is also under intense human influence, the double pressure of deforestation and climate change may subject the region to dramatic changes in the 21st century.

  18. Scale-dependent variation in nitrogen cycling and soil fungal communities along gradients of forest composition and age in regenerating tropical dry forests.

    Science.gov (United States)

    Waring, Bonnie G; Adams, Rachel; Branco, Sara; Powers, Jennifer S

    2016-01-01

    Rates of ecosystem nitrogen (N) cycling may be mediated by the presence of ectomycorrhizal fungi, which compete directly with free-living microbes for N. In the regenerating tropical dry forests of Central America, the distribution of ectomycorrhizal trees is affected by succession and soil parent material, both of which may exert independent influence over soil N fluxes. In order to quantify these interacting controls, we used a scale-explicit sampling strategy to examine soil N cycling at scales ranging from the microsite to ecosystem level. We measured fungal community composition, total and inorganic N pools, gross proteolytic rate, net N mineralization and microbial extracellular enzyme activity at multiple locations within 18 permanent plots that span dramatic gradients of soil N concentration, stand age and forest composition. The ratio of inorganic to organic N cycling was correlated with variation in fungal community structure, consistent with a strong influence of ectomycorrhiza on ecosystem-scale N cycling. However, on average, > 61% of the variation in soil biogeochemistry occurred within plots, and the effects of forest composition were mediated by this local-scale heterogeneity in total soil N concentrations. These cross-scale interactions demonstrate the importance of a spatially explicit approach towards an understanding of controls on element cycling. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  19. Isoprene emission from tropical tree species

    International Nuclear Information System (INIS)

    Padhy, P.K.; Varshney, C.K.

    2005-01-01

    Foliar emission of isoprene was measured in nine commonly growing tree species of Delhi, India. Dynamic flow enclosure technique was used and gas samples were collected onto Tenax-GC/Carboseive cartridges, which were then attached to the sample injection system in the gas chromatograph (GC). Eluting compounds were analysed using a flame ionisation detector (FID). Out of the nine tree species, isoprene emission was found in six species (Eucalyptus sp., Ficus benghalensis, Ficus religiosa, Mangifera indica, Melia azedarach, and Syzygium jambolanum), whereas, in the remaining three tree species (Alstonia scholaris, Azadirachta indica, and Cassia fistula) no isoprene emission was detected or the levels of emission were negligible or below the detection limit (BDL). Among six tree species, the highest hourly emission (10.2±6.8 μg g -1 leaf dry weight, average of five seasons) was observed in Ficus religiosa, while minimum emission was from Melia azedarach (2.2±4.9 μg g -1 leaf dry weight, average of five seasons). Isoprene emission (average of six species), over five seasons, was found to vary between 3.9 and 8.5 μg g -1 leaf dry weight during the rainy season. In addition, significant diurnal variation in isoprene emission was observed in each species. The preliminary estimate made in this study on the annual biogenic VOC emission from India may probably be the first of its kind from this part of the world. - Isoprene flux (diurnal and seasonal) from some tropical tree species was estimated and a regional comparison was made

  20. Isoprene emission from tropical tree species

    Energy Technology Data Exchange (ETDEWEB)

    Padhy, P.K. [School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India)]. E-mail: padhypk2003@yahoo.com; Varshney, C.K. [School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India)

    2005-05-01

    Foliar emission of isoprene was measured in nine commonly growing tree species of Delhi, India. Dynamic flow enclosure technique was used and gas samples were collected onto Tenax-GC/Carboseive cartridges, which were then attached to the sample injection system in the gas chromatograph (GC). Eluting compounds were analysed using a flame ionisation detector (FID). Out of the nine tree species, isoprene emission was found in six species (Eucalyptus sp., Ficus benghalensis, Ficus religiosa, Mangifera indica, Melia azedarach, and Syzygium jambolanum), whereas, in the remaining three tree species (Alstonia scholaris, Azadirachta indica, and Cassia fistula) no isoprene emission was detected or the levels of emission were negligible or below the detection limit (BDL). Among six tree species, the highest hourly emission (10.2{+-}6.8 {mu}g g{sup -1} leaf dry weight, average of five seasons) was observed in Ficus religiosa, while minimum emission was from Melia azedarach (2.2{+-}4.9 {mu}g g{sup -1} leaf dry weight, average of five seasons). Isoprene emission (average of six species), over five seasons, was found to vary between 3.9 and 8.5 {mu}g g{sup -1} leaf dry weight during the rainy season. In addition, significant diurnal variation in isoprene emission was observed in each species. The preliminary estimate made in this study on the annual biogenic VOC emission from India may probably be the first of its kind from this part of the world. - Isoprene flux (diurnal and seasonal) from some tropical tree species was estimated and a regional comparison was made.

  1. Applications of NASA TROPICS Data for Tropical Cyclone Analysis, Nowcasting, and Impacts

    Science.gov (United States)

    Zavodsky, B.; Dunion, J. P.; Blackwell, W. J.; Braun, S. A.; Green, D. S.; Velden, C.; Adler, R. F.; Cossuth, J.; Murray, J. J.; Brennan, M. J.

    2017-12-01

    The National Aeronautics and Space Administration (NASA) Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission is a constellation of state-of-the-science observing platforms that will measure temperature and humidity soundings and precipitation with spatial resolution comparable to current operational passive microwave sounders but with unprecedented temporal resolution. TROPICS is a cost-capped ($30M) Venture-class mission funded by the NASA Earth Science Division. The mission is comprised of a constellation of 3 unit (3U) SmallSats, each hosting a 12-channel passive microwave spectrometer based on the Micro-sized Microwave Atmospheric Satellite 2 (MicroMAS-2) developed at MIT LL. TROPICS will provide imagery near 91 and 205 GHz, temperature sounding near 118 GHz, and moisture sounding near 183 GHz. Spatial resolution at nadir will be around 27 km for temperature and 17 km for moisture and precipitation. The swath width is approximately 2000 km. TROPICS enables temporal resolution similar to geostationary orbit but at a much lower cost, demonstrating a technology that could impact the design of future Earth-observing missions. The TROPICS satellites for the mission are slated for delivery to NASA in 2019 with potential launch opportunities in 2020. The primary mission objective of TROPICS is to relate temperature, humidity, and precipitation structure to the evolution of tropical cyclone (TC) intensity. This abstract summarizes the outcomes of the 1st TROPICS Applications Workshop, held from May 8-10, 2017 at the University of Miami. At this meeting, a series of presentations and breakout discussions in the topical areas of Tropical Cyclone Dynamics, Tropical Cyclone Analysis and Nowcasting, Tropical Cyclone Modeling and Data Assimilation, and Terrestrial Impacts were convened to identify applications of the mission data and to begin to establish a community of end-users who will be able to

  2. [Species composition and diversity of soil mesofauna in the 'Holy Hills' fragmentary tropical rain forest of Xishuangbanna, China].

    Science.gov (United States)

    Yang, X; Sha, L

    2001-04-01

    The species composition and diversity of soil mesofauna were examined in fragmented dry tropical seasonal rainforest of tow 'Holy Hills' of Dai nationality, compared with the continuous moist tropical seasonal rain forest of Nature Reserve in Xishuangbanna area. 5 sample quadrats were selected along the diagonal of 20 m x 20 m sampling plot, and the samples of litterfall and 0-3 cm soil were collected from each 50 cm x 10 cm sample quadrat. Animals in soil sample were collected by using dry-funnel(Tullgren's), were identified to their groups according to the order. The H' index, D.G index and the pattern of relative abundance of species were used to compare the diversity of soil mesofauna. The results showed that the disturbance of vegetation and soil resulted by tropical rainforest fragmentation was the major factor affecting the diversity of soil mesofauna. Because the fragmented forest was intruded by some pioneer tree species and the "dry and warm" effect operated, this forest had more litterfall on the floor and more humus in the soil than the continuous moist rain forest. The soil condition with more soil organic matter, total N and P, higher pH value and lower soil bulk density became more favorable to the soil mesofauna. Therefore, the species richness, abundance and diversity of soil mesofauna in fragmented forests were higher than those in continuous forest, but the similarity of species composition in fragmented forest to the continuous forest was minimal. Soil mesofauna diversity in fragmented forests did not change with decreasing fragmented area, indicating that there was no species-area effect operation in this forest. The pattern of relative abundance of species in these forest soils was logarithmic series distribution.

  3. The role of arbuscular mycorrhizal fungi on the early-stage restoration of seasonally dry tropical forest in Chamela, Mexico

    Directory of Open Access Journals (Sweden)

    Pilar Huante

    2012-04-01

    Full Text Available It was evaluated the effect of two different sources of local inocula from two contrasting sites (mature forest, pasture of arbuscular mycorrhizae fungi (AMF and a non-mycorrhizal control on the plant growth of six woody species differing in functional characteristics (slow-, intermediate- and fast-growth, when introduced in a seasonally tropical dry forest (STDF converted into abandoned pasture. Six plots (12 X 12m were set as AMF inoculum source. Six replicates of six different species arranged in a Latin Square design were set in each plot. Plant height, cover area and the number of leaves produced by individual plant was measured monthly during the first growing season in each treatment. Species differed in their ability to benefit from AMF and the largest responsiveness in plant height and leaf production was exhibited by the slow-growing species Swietenia humilis, Hintonia latiflora and Cordia alliodora. At the end of the growing season (November, the plant height of the fast growing species Tabebuia donnel-smithii, Ceiba pentandra and Guazuma ulmifolia were not influenced by AMF. However, inocula of AMF increased leaf production of all plant species regardless the functional characteristics of the species, suggesting a better exploitation of above-ground space and generating a light limited environment under the canopy, which contributed to pasture suppression. Inoculation of seedlings planted in abandoned pasture areas is recommended for ecological restoration due to the high responsiveness of seedling growth in most of species. Use of forest inoculum with its higher diversity of AMF could accelerate the ecological restoration of the above and below-ground comunities.

  4. Neglected tropical diseases

    Directory of Open Access Journals (Sweden)

    David Molyneux

    2013-08-01

    Full Text Available Seventeen neglected tropical diseases (NTDs have been identified by the World Health Organization (WHO. It is estimated that over 1 billion people are infected with NTDs, with a further 1 billion at risk. The majority of NTDs occur in the tropics and sub-tropics and have particular characteristics in common.

  5. Tropical Rainforests.

    Science.gov (United States)

    Nigh, Ronald B.; Nations, James D.

    1980-01-01

    Presented is a summary of scientific knowledge about the rainforest environment, a tropical ecosystem in danger of extermination. Topics include the current state of tropical rainforests, the causes of rainforest destruction, and alternatives of rainforest destruction. (BT)

  6. Dynamic vegetation modeling of tropical biomes during Heinrich events

    Science.gov (United States)

    Handiani, Dian Noor; Paul, André; Dupont, Lydie M.

    2010-05-01

    changed from warm temperate forest during the last glacial maximum to the grassland and dry shrubland, suggesting a drier climate during Heinrich event 1. In south-western Africa savanna and dry woodland changed into boreal forest and boreal-temperate forest suggesting wetter conditions. The biomes diagnosed from the control-run, were compared to the modern vegetation reconstruction of BIOME 4 (http://www.bridge.bris.ac.uk/resources/Databases/BIOMES_data). Consistent biome patterns were simulated for the tropical forests of western and south-western Africa and the grasslands of northern Africa. On the other hand, in southern Europe, where the BIOME 4 vegetation reconstruction is dominated by warm temperate and temperate forest, our model shows a strong bias towards the grassland.

  7. Evaporation from Pinus caribaea plantations on former grassland soils under maritime tropical conditions.

    OpenAIRE

    Waterloo, M.J.; Bruijnzeel, L.A.; Vugts, H.F.; Rawaqa, T.T.

    1999-01-01

    Wet canopy and dry canopy evaporation from young and mature plantations of Pinus caribaea on former grassland soils under maritime tropical conditions in southwestern Viti Levu, Fiji, were determined using micrometeorological and hydrological techniques. Modeled annual evaporation totals (ET) of 1926 and 1717 mm were derived for the 6- and the 15-year-old stands, respectively. Transpiration made up 72% and 70% of annual ET, and modeled rainfall interception by the trees and litter layer was 2...

  8. Comparison of drying characteristic and uniformity of banana cubes dried by pulse-spouted microwave vacuum drying, freeze drying and microwave freeze drying.

    Science.gov (United States)

    Jiang, Hao; Zhang, Min; Mujumdar, Arun S; Lim, Rui-Xin

    2014-07-01

    To overcome the flaws of high energy consumption of freeze drying (FD) and the non-uniform drying of microwave freeze drying (MFD), pulse-spouted microwave vacuum drying (PSMVD) was developed. The results showed that the drying time can be dramatically shortened if microwave was used as the heating source. In this experiment, both MFD and PSMVD could shorten drying time by 50% as compared to the FD process. Depending on the heating method, MFD and PSMVD dried banana cubes showed trends of expansion while FD dried samples demonstrated trends of shrinkage. Shrinkage also brought intensive structure and highest fracturability of all three samples dried by different methods. The residual ascorbic acid content of PSMVD dried samples can be as high as in FD dried samples, which were superior to MFD dried samples. The tests confirmed that PSMVD could bring about better drying uniformity than MFD. Besides, compared with traditional MFD, PSMVD can provide better extrinsic feature, and can bring about improved nutritional features because of the higher residual ascorbic acid content. © 2013 Society of Chemical Industry.

  9. Trait acclimation mitigates mortality risks of tropical canopy trees under global warming

    Directory of Open Access Journals (Sweden)

    Frank eSterck

    2016-05-01

    Full Text Available There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area to maximize carbon gain. We simulated tree carbon gain for temperatures (25-35ºC and ambient CO2 concentrations (390-800 ppm predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10-20% and the maximum tolerated temperature by up to 2ºC, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change.

  10. Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming

    Science.gov (United States)

    Sterck, Frank; Anten, Niels P. R.; Schieving, Feike; Zuidema, Pieter A.

    2016-01-01

    There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25–35°C) and ambient CO2 concentrations (390–800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10–20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change. PMID:27242814

  11. Improving predictions of tropical forest response to climate change through integration of field studies and ecosystem modeling

    Science.gov (United States)

    Feng, Xiaohui; Uriarte, María; González, Grizelle; Reed, Sasha C.; Thompson, Jill; Zimmerman, Jess K.; Murphy, Lora

    2018-01-01

    Tropical forests play a critical role in carbon and water cycles at a global scale. Rapid climate change is anticipated in tropical regions over the coming decades and, under a warmer and drier climate, tropical forests are likely to be net sources of carbon rather than sinks. However, our understanding of tropical forest response and feedback to climate change is very limited. Efforts to model climate change impacts on carbon fluxes in tropical forests have not reached a consensus. Here we use the Ecosystem Demography model (ED2) to predict carbon fluxes of a Puerto Rican tropical forest under realistic climate change scenarios. We parameterized ED2 with species-specific tree physiological data using the Predictive Ecosystem Analyzer workflow and projected the fate of this ecosystem under five future climate scenarios. The model successfully captured inter-annual variability in the dynamics of this tropical forest. Model predictions closely followed observed values across a wide range of metrics including above-ground biomass, tree diameter growth, tree size class distributions, and leaf area index. Under a future warming and drying climate scenario, the model predicted reductions in carbon storage and tree growth, together with large shifts in forest community composition and structure. Such rapid changes in climate led the forest to transition from a sink to a source of carbon. Growth respiration and root allocation parameters were responsible for the highest fraction of predictive uncertainty in modeled biomass, highlighting the need to target these processes in future data collection. Our study is the first effort to rely on Bayesian model calibration and synthesis to elucidate the key physiological parameters that drive uncertainty in tropical forests responses to climatic change. We propose a new path forward for model-data synthesis that can substantially reduce uncertainty in our ability to model tropical forest responses to future climate.

  12. Tropical Agroecosystems: These habitats are misunderstood by the temperate zones, mismanaged by the tropics.

    Science.gov (United States)

    Janzen, D H

    1973-12-21

    structured around a single export crop such as coffee, sugar, rubber, cotton, cacao, or tea. A major portion of their budgets comes directly or indirectly from the industry concerned. This industry can hardly be expected to wish to see its production integrated with a sustained-yield system that charges real costs for its materials. When an experiment station is centered around a major food crop, such as rice or maize, the goal becomes one of maximizing production per acre rather than per unit of resource spent; this goal may often be translated into one of generating more people. More general experiment stations tend to be established in the most productive regions of the country and, therefore, receive the most funding. Such regions (islands, intermediate elevations, areas with severe dry seasons) need experiment stations the least because they can often be successfully farmed with only slightly modified temperate zone technologies and philosophies. The administrators of tropical experiment stations often regard their job as a hardship post and tend to orient their research toward the hand that feeds them, which is certainly not the farming communities in which they have been placed. The tropics do not need more hard cash for tractors; they need a program that will show when, where, and how hand care should be replaced with draft animals, and draft animals with tractors. The tropics do not need more randomly gathered, esoteric or applied agricultural research: they need a means to integrate what is already known into the process of developing SYTA's. The tropics do not need more food as much as a means of evaluating the resources they have and generating social systems that will maximize the standard of living possible with those resources, whatever the size. The tropics need a realistic set of expectations.

  13. Forgotten forests--issues and prospects in biome mapping using Seasonally Dry Tropical Forests as a case study.

    Science.gov (United States)

    Särkinen, Tiina; Iganci, João R V; Linares-Palomino, Reynaldo; Simon, Marcelo F; Prado, Darién E

    2011-11-24

    South America is one of the most species diverse continents in the world. Within South America diversity is not distributed evenly at both local and continental scales and this has led to the recognition of various areas with unique species assemblages. Several schemes currently exist which divide the continental-level diversity into large species assemblages referred to as biomes. Here we review five currently available biome maps for South America, including the WWF Ecoregions, the Americas basemap, the Land Cover Map of South America, Morrone's Biogeographic regions of Latin America, and the Ecological Systems Map. The comparison is performed through a case study on the Seasonally Dry Tropical Forest (SDTF) biome using herbarium data of habitat specialist species. Current biome maps of South America perform poorly in depicting SDTF distribution. The poor performance of the maps can be attributed to two main factors: (1) poor spatial resolution, and (2) poor biome delimitation. Poor spatial resolution strongly limits the use of some of the maps in GIS applications, especially for areas with heterogeneous landscape such as the Andes. Whilst the Land Cover Map did not suffer from poor spatial resolution, it showed poor delimitation of biomes. The results highlight that delimiting structurally heterogeneous vegetation is difficult based on remote sensed data alone. A new refined working map of South American SDTF biome is proposed, derived using the Biome Distribution Modelling (BDM) approach where georeferenced herbarium data is used in conjunction with bioclimatic data. Georeferenced specimen data play potentially an important role in biome mapping. Our study shows that herbarium data could be used as a way of ground-truthing biome maps in silico. The results also illustrate that herbarium data can be used to model vegetation maps through predictive modelling. The BDM approach is a promising new method in biome mapping, and could be particularly useful for mapping

  14. Tropical dendrochemistry: A novel approach to estimate age and growth from ringless trees

    International Nuclear Information System (INIS)

    Poussart, P.; Myneni, S.; Lanzirotti, A.

    2006-01-01

    Although tropical forests play an active role in the global carbon cycle and climate, their growth history remains poorly characterized compared to other ecosystems on the planet. Trees are prime candidates for the extraction of paleoclimate archives as they can be probed sub-annually, are widely distributed and can live for over 1400 years. However, dendrochronological techniques have found limited applications in the tropics because trees often lack visible growth rings. Alternative methods exist (dendrometry, radio- and stable isotopes), but the derived records are either of short-duration, lack seasonal resolution or are prohibitively labor intensive to produce. Here, we show the first X-ray microprobe synchrotron record of calcium (Ca) from a ringless Miliusa velutina tree from Thailand and use it to estimate the tree's age and growth history. The Ca age model agrees within (le)2 years of bomb-radiocarbon age estimates and confirms that the cycles are seasonal. The amplitude of the Ca annual cycle is correlated significantly with growth and annual Ca maxima correlate with the amount of dry season rainfall. Synchrotron measurements are fast and producing sufficient numbers of replicated multi-century tropical dendrochemical climate records now seems analytically feasible

  15. Forest structure and carbon dynamics in Amazonian tropical rain forests.

    Science.gov (United States)

    Vieira, Simone; de Camargo, Plinio Barbosa; Selhorst, Diogo; da Silva, Roseana; Hutyra, Lucy; Chambers, Jeffrey Q; Brown, I Foster; Higuchi, Niro; dos Santos, Joaquim; Wofsy, Steven C; Trumbore, Susan E; Martinelli, Luiz Antonio

    2004-08-01

    Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha(-1) respectively), less biodiversity (Shannon-Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha(-1)) than the Manaus site (626 trees ha(-1), 180.1 Mg C ha(-1)), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41-45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha(-1) year(-1). At all sites, trees in the 10-30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha(-1) year(-1) in Manaus (40% of annual mean) and 0.9 Mg C ha(-1) year(-1) (33% of

  16. Cyclic changes in Pennsylvanian paleoclimate and effects on floristic dynamics in tropical Pangaea

    Energy Technology Data Exchange (ETDEWEB)

    DiMichele, William A. [National Museum of Natural History MRC-121, Smithsonian Institution, Washington, DC 20560 (United States); Cecil, C. Blaine [National Museum of Natural History MRC-121, Smithsonian Institution, Washington, DC 20560 (United States); U.S. Geological Survey, Reston, VA 20192 (United States); Montanez, Isabel P. [Department of Geology, University of California, Davis, CA 95616 (United States); Falcon-Lang, Howard J. [Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX (United Kingdom)

    2010-08-01

    Wetland floras narrowly define perceptions of Pennsylvanian tropical ecosystems, the so-called Coal Age. Such wetlands reflect humid to perhumid climate, leading to characterizations of Pennsylvanian tropics as everwet, swampy. These views are biased by the high preservation potential of wetlands. Sedimentation patterns, paleosols, and fossil floras indicate the presence of vegetation tolerant of subhumid to dry-subhumid, perhaps semi-arid climate in basins between peat formation times. Understanding the significance of this seasonally-dry vegetation has suffered from conceptual and terminological confusion. A clearer view has emerged as models for framing the data have improved. Basinal floras typical of seasonally-dry conditions, relatively low soil moisture regimes, are well documented but mainly from isolated deposits. Some of the earliest, dominated by primitive pteridosperms (''Floezfern'' floras), occur in clastic rocks between European Early Pennsylvanian coal beds. Later Early Pennsylvanian, fern-cordaitalean vegetation, different from coal floras, is preserved in marine goniatite bullions. Conifers are first suggested by late Mississippian Potoniesporites pollen. About the same time, in North America, broadleaf foliage, Lesleya and Megalopteris occur in basin-margin settings, on drought-prone limestone substrates. The best known, xeromorphic floras found between coal beds appear in the Middle through Late Pennsylvanian, containing conifers, cordaitaleans, and pteridosperms. The Middle Pennsylvanian appearances of this flora are mainly allochthonous, though parautochthonous occurrences have been reported. Parautochthonous assemblages are mostly Late Pennsylvanian. The conifer flora became dominant in western and central Pangaean equatorial lowlands in earliest Permian. Location of the humid-perhumid wetland flora during periods of relative dryness, though rarely discussed, is as, or more, perplexing than the spatial location of

  17. The effects of the insecticide lambda-Cyhalothrin on the earthworm Eisenia fetida under experimental conditions of tropical and temperate regions

    International Nuclear Information System (INIS)

    Garcia, Marcos; Scheffczyk, Adam; Garcia, Terezinha; Roembke, Joerg

    2011-01-01

    Plant Protection Products can affect soil organisms and thus might have negative impacts on soil functions. Little research has been performed on their impact on tropical soils. Therefore, the effects of the insecticide lambda-Cyhalothrin on earthworms were evaluated in acute and chronic laboratory tests modified for tropical conditions, i.e. at selected temperatures (20 and 28 o C) and with two strains (temperate and tropical) of the compost worm Eisenia fetida. The insecticide was spiked in two natural soils, in OECD artificial soil and a newly developed tropical artificial soil. The effects of lambda-Cyhalothrin did rarely vary in the same soil at tropical (LC50: 68.5-229 mg a.i./kg dry weight (DW); EC50: 54.2-60.2 mg a.i./kg DW) and temperate (LC50: 99.8-140 mg a.i./kg DW; EC50: 37.4-44.5 mg a.i./kg DW) temperatures. In tests with tropical soils and high temperature, effect values differed by up to a factor of ten. - Research highlights: → In one soil, effects of lambda-Cyhalothrin did not vary much at two temperatures. → In tropical soils at high temperature, effects differed by up to a factor of ten. → In the tropics, effects of pesticides can be higher or lower as in temperate regions. - The effects of the insecticide lambda-cyhalothrin on earthworms did not differ considerably when performed in the same soil under different temperatures, but LC/EC 50 values varied by a factor of ten between OECD and tropical artificial soil.

  18. The effects of the insecticide lambda-Cyhalothrin on the earthworm Eisenia fetida under experimental conditions of tropical and temperate regions

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Marcos [Embrapa Amazonia Ocidental, Rod. AM-10, Km 28, 69.011-970 Manaus, AM (Brazil); Scheffczyk, Adam [ECT Oekotoxikologie, Boettgerstr. 2-14, D-65439 Floersheim (Germany); Garcia, Terezinha [Embrapa Amazonia Ocidental, Rod. AM-10, Km 28, 69.011-970 Manaus, AM (Brazil); Roembke, Joerg, E-mail: j-roembke@ect.d [ECT Oekotoxikologie, Boettgerstr. 2-14, D-65439 Floersheim (Germany)

    2011-02-15

    Plant Protection Products can affect soil organisms and thus might have negative impacts on soil functions. Little research has been performed on their impact on tropical soils. Therefore, the effects of the insecticide lambda-Cyhalothrin on earthworms were evaluated in acute and chronic laboratory tests modified for tropical conditions, i.e. at selected temperatures (20 and 28 {sup o}C) and with two strains (temperate and tropical) of the compost worm Eisenia fetida. The insecticide was spiked in two natural soils, in OECD artificial soil and a newly developed tropical artificial soil. The effects of lambda-Cyhalothrin did rarely vary in the same soil at tropical (LC50: 68.5-229 mg a.i./kg dry weight (DW); EC50: 54.2-60.2 mg a.i./kg DW) and temperate (LC50: 99.8-140 mg a.i./kg DW; EC50: 37.4-44.5 mg a.i./kg DW) temperatures. In tests with tropical soils and high temperature, effect values differed by up to a factor of ten. - Research highlights: In one soil, effects of lambda-Cyhalothrin did not vary much at two temperatures. In tropical soils at high temperature, effects differed by up to a factor of ten. In the tropics, effects of pesticides can be higher or lower as in temperate regions. - The effects of the insecticide lambda-cyhalothrin on earthworms did not differ considerably when performed in the same soil under different temperatures, but LC/EC{sub 50} values varied by a factor of ten between OECD and tropical artificial soil.

  19. Seasonal changes in water content and turnover in cattle, sheep and goats grazing under humid tropical conditions in Ghana

    International Nuclear Information System (INIS)

    Aggrey, E.K.

    1982-01-01

    The effect of seasonal changes on water content and water turnover of cattle, sheep and goats at pasture under humid tropical conditions was studied. Measurement of total body water and water turnover was based on the tritium dilution technique. Total body water was significantly higher in all three species of animal during the dry season, while water turnover was significantly lower in the dry season than in the wet season. In all seasons water turnover was highest in cattle, followed by sheep and then goat. Changes in body weight, body water, body solids and water turnover were associated with seasonal variations in nutrition. The indication was that the goat would be a more suitable animal for production under dry conditions than cattle and sheep. (author)

  20. Demise and rise: the biogeography and taxonomy of the Odonata of tropical Africa

    OpenAIRE

    Dijkstra, Klaas-Douwe Benediktus

    2007-01-01

    Africa has a large and almost uninterrupted land surface that is isolated from surrounding continents. In the last 20 million years Africa had a variable and increasingly dry climate. As a result the Afrotropics have only half as many odonate species as tropical America or Asia. ‘Relict’ families are scarce and concentrated in five isolated, climatically stable areas: (1) the Cameroon highlands, (2) locally in East Africa, (3) the Cape region, (4) the granitic Seychelles, and especially (5) M...

  1. Tropospheric VHF radiowave propagation measurements in a tropical location in Nigeria

    International Nuclear Information System (INIS)

    Aboaba, O.A.

    2006-04-01

    A major task for the radiocommunication engineer in designing a communication system is to be able to predict the behaviour of the radio signal from the point of transmission to the receiving point. Usually, the radiocommunication engineer would have available propagation data that will enable him to demonstrate that the radiocommunications system will meet both the performance and the availability objectives. The data obtained from a 10-month period of terrestrial over-the-horizon propagation measurements, carried out in southwestern part of Nigeria, have been statistically analyzed in this study. The findings from the analysis show that the measured values of field strength were significantly high during the dry months of November to March, the night time and early morning hours while lower values were obtained during the wet months of April to October. In particular, it is observed that the dry month of March recorded the highest median value of field strength while the wet month of July recorded the lowest. These high values of field strength observed during the dry months are attributed to anomalous propagation effects such as extreme super-refractivity and ducting which are often prevalent in the West African tropical sub-region. (author)

  2. Halogenated organic species over the tropical South American rainforest

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    S. Gebhardt

    2008-06-01

    Full Text Available Airborne measurements of the halogenated trace gases methyl chloride, methyl bromide and chloroform were conducted over the Atlantic Ocean and about 1000 km of pristine tropical rainforest in Suriname and French Guyana (3–6° N, 51–59° W in October 2005. In the boundary layer (0–1.4 km, maritime air masses, advected over the forest by southeasterly trade winds, were measured at various distances from the coast. Since the organohalogens presented here have relatively long atmospheric lifetimes (0.4–1.0 years in comparison to the advection times from the coast (1–2 days, emissions will accumulate in air traversing the rainforest. The distributions of methyl chloride, methyl bromide and chloroform were analyzed as a function of time the air spent over land and the respective relationship used to determine net fluxes from the rainforest for one week within the long dry season.

    Net fluxes from the rainforest ecosystem have been calculated for methyl chloride and chloroform as 9.5 (±3.8 2σ and 0.35 (±0.15 2σμg m-2 h−1, respectively. No significant flux was observed for methyl bromide within the limits of these measurements.

    The global budget of methyl chloride contains large uncertainties, in particular with regard to a possible source from tropical vegetation. Our measurements are used in a large-scale approach to determine the net flux from a tropical ecosystem to the planetary boundary layer. The obtained global net flux of 1.5 (±0.6 2σ Tg yr-1 for methyl chloride is at the lower end of current estimates for tropical vegetation sources, which helps to constrain the range of tropical sources and sinks (0.82 to 8.2 Tg yr-1 from tropical plants, 0.03 to 2.5 Tg yr-1 from senescent/dead leaves and a sink of 0.1 to 1.6 Tg yr-1 by soil uptake. Nevertheless, these results show that the contribution of the rainforest ecosystem is the major source in the

  3. Economic, Socio-Political and Environmental Risks of Road Development in the Tropics.

    Science.gov (United States)

    Alamgir, Mohammed; Campbell, Mason J; Sloan, Sean; Goosem, Miriam; Clements, Gopalasamy Reuben; Mahmoud, Mahmoud I; Laurance, William F

    2017-10-23

    It is projected that 25 million km of new paved roads will be developed globally by 2050 - enough to encircle the planet more than 600 times. Roughly 90% of new roads will be built in developing nations, frequently in tropical and subtropical regions with high biodiversity and environmental values. Many developing nations are borrowing from international lenders or negotiating access to their natural resources in order to expand their transportation infrastructure. Given the unprecedented pace and extent of these initiatives, it is vital to thoroughly assess the potential consequences of large-scale road and highway projects. In appropriate contexts and locales, new roads can promote sizeable economic and social benefits. If poorly planned or implemented, however, new roads can provoke serious cost overruns, corruption and environmental impacts, while generating sparse economic benefits and intense social and political conflict. Using examples from developing nations, we identify risks that can hinder road projects in wet and dry tropical environments. Such risks, we assert, are often inadequately considered by project proponents, evaluators and the general public, creating a systematic tendency to overestimate project benefits while understating project risks. A more precautionary approach is needed to reduce risks while maximizing benefits of new road projects in the tropics. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Characteristics of Timbers Dried Using Kiln Drying and Radio Frequency-Vacuum Drying Systems

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    Rabidin Zairul Amin

    2017-01-01

    Full Text Available Heavy hardwoods are difficult-to-dry timbers as they are prone to checking and internal stresses when dried using a conventional kiln drying system. These timbers are usually dried naturally to reach 15% to 19% moisture content with an acceptable defects. Besides long drying time, timbers at these moisture contents are not suitable for indoor applications since they will further dry and causing, for example, jointing and lamination failures. Drying to a lower moisture content could only be achieved in artificial drying kilns such as conventional kiln, dehumidification kiln, solar kiln, radio frequency-vacuum, etc. The objective of this study was to evaluate the characteristics of 30 mm and 50 mm thick kekatong (Cynometra spp. timber dried using kiln drying (KD and radio frequency-vacuum drying (RFV system. The investigation involved drying time, moisture content (MC variations between and within boards, drying defects, shrinkage, and drying stress. Drying defects include checks (surface, end, and internal checks and warping (bowing, cuping, spring, and twisting. The results showed that RFV drying time was reduced to 50% compared to the KD. RFV dried boards demonstrated a more uniform MC between and within boards. Shrinkage in width and thickness, as well as tangential/radial and volumetric shrinkages were substantially less in RFV boards. The amount of cupping, bowing and spring were very low and negligible in all drying runs. There was no twisting observed in all drying methods. The number of stress-free RFV board was higher than KD. With proper procedure, the RFV technology could be used for drying heavy hardwoods which are difficult to dry in conventional kilns due to excessive drying times and degradation.

  5. Time-dependent effects of climate and drought on tree growth in a Neotropical dry forest: Short-term tolerance vs. long-term sensitivity

    NARCIS (Netherlands)

    Mendivelso, H.A.; Camarero, J.J.; Gutierrez, E.; Zuidema, P.

    2014-01-01

    We analyzed the effects of climate and drought on radial growth using dendrochronology in seven deciduous tree species coexisting in a Bolivian tropical dry forest subjected to seasonal drought. Precipitation, temperature and a multiscalar drought index were related to tree-ring width data at

  6. Seed rain dynamics following disturbance exclusion in a secondary tropical dry forest in Morelos, Mexico

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    Eliane Ceccon

    2009-06-01

    Full Text Available In most of the legally protected areas in Mexico local inhabitants use natural resources, such as fire wood or cattle grazing. These frequent but low-intensity disturbances have consequences at various levels of the tropical ecosystems and strongly impact forest structure and its regeneration capacity. Despite their importance, the effects of these perturbations in many aspects of tropical forest ecology and in the forest’s capacity to recover after disturbance exclusion remain poorly understood. Understanding the impact of these processes on tropical forests is necessary for rehabilitating these forests and enhancing their productivity. In this study, we evaluate the impact of twelve years of exclusion (E of cattle grazing and fire wood extraction in the composition and dynamics of seed rain, and compare this assessment to a similar analysis in an area where these perturbations continued (without exclusion, WE. We found a strong seasonality in seed rain (96% of seeds fell in the dry season in both areas. There were no significant differences between E and WE sites in relation to overall seed density, species richness and diversity. However, the distribution along the year of seed species density was significantly different among the E and WE sites. The Jaccard’s similarity index between E and WE sites was relatively low (0.57. Barochory was the most common dispersal mode observed among the 23 species in terms of seed species density (48%, followed by anemochory (39% and zoochory (13%. In relation to seed density, anemochory was the most frequent dispersal mode (88%. Most species in the zone were categorized as small seeds (92%, and there were no significant differences in the distribution of seed size between E and WE. The spatial pattern of dispersal of the four species with the highest relative importance value index, in both areas, was aggregated. Twelve years of disturbance exclusion were not enough to fully restore the seed rain of the

  7. Tracing the Sources of Atmospheric Phosphorus Deposition to a Tropical Rain Forest in Panama Using Stable Oxygen Isotopes.

    Science.gov (United States)

    Gross, A; Turner, B L; Goren, T; Berry, A; Angert, A

    2016-02-02

    Atmospheric dust deposition can be a significant source of phosphorus (P) in some tropical forests, so information on the origins and solubility of atmospheric P is needed to understand and predict patterns of forest productivity under future climate scenarios. We characterized atmospheric dust P across a seasonal cycle in a tropical lowland rain forest on Barro Colorado Nature Monument (BCNM), Republic of Panama. We traced P sources by combining remote sensing imagery with the first measurements of stable oxygen isotopes in soluble inorganic phosphate (δ(18)OP) in dust. In addition, we measured soluble inorganic and organic P concentrations in fine (1 μm) aerosol fractions and used this data to estimate the contribution of P inputs from dust deposition to the forest P budget. Aerosol dry mass was greater in the dry season (December to April, 5.6-15.7 μg m(-3)) than the wet season (May to November, 3.1-7.1 μg m(-3)). In contrast, soluble P concentrations in the aerosols were lower in the dry season (980-1880 μg P g(-1)) than the wet season (1170-3380 μg P g(-1)). The δ(18)OP of dry-season aerosols resembled that of nearby forest soils (∼19.5‰), suggesting a local origin. In the wet season, when the Trans-Atlantic Saharan dust belt moves north close to Panama, the δ(18)OP of aerosols was considerably lower (∼15.5‰), suggesting a significant contribution of long-distance dust P transport. Using satellite retrieved aerosol optical depth (AOD) and the P concentrations in aerosols we sampled in periods when Saharan dust was evident we estimate that the monthly P input from long distance dust transport during the period with highest Saharan dust deposition is 88 ± 31 g P ha(-1) month(-1), equivalent to between 10 and 29% of the P in monthly litter fall in nearby forests. These findings have important implications for our understanding of modern nutrient budgets and the productivity of tropical forests in the region under future climate scenarios.

  8. Classification of tree species based on longwave hyperspectral data from leaves, a case study for a tropical dry forest

    Science.gov (United States)

    Harrison, D.; Rivard, B.; Sánchez-Azofeifa, A.

    2018-04-01

    Remote sensing of the environment has utilized the visible, near and short-wave infrared (IR) regions of the electromagnetic (EM) spectrum to characterize vegetation health, vigor and distribution. However, relatively little research has focused on the use of the longwave infrared (LWIR, 8.0-12.5 μm) region for studies of vegetation. In this study LWIR leaf reflectance spectra were collected in the wet seasons (May through December) of 2013 and 2014 from twenty-six tree species located in a high species diversity environment, a tropical dry forest in Costa Rica. A continuous wavelet transformation (CWT) was applied to all spectra to minimize noise and broad amplitude variations attributable to non-compositional effects. Species discrimination was then explored with Random Forest classification and accuracy improved was observed with preprocessing of reflectance spectra with continuous wavelet transformation. Species were found to share common spectral features that formed the basis for five spectral types that were corroborated with linear discriminate analysis. The source of most of the observed spectral features is attributed to cell wall or cuticle compounds (cellulose, cutin, matrix glycan, silica and oleanolic acid). Spectral types could be advantageous for the analysis of airborne hyperspectral data because cavity effects will lower the spectral contrast thus increasing the reliance of classification efforts on dominant spectral features. Spectral types specifically derived from leaf level data are expected to support the labeling of spectral classes derived from imagery. The results of this study and that of Ribeiro Da Luz (2006), Ribeiro Da Luz and Crowley (2007, 2010), Ullah et al. (2012) and Rock et al. (2016) have now illustrated success in tree species discrimination across a range of ecosystems using leaf-level spectral observations. With advances in LWIR sensors and concurrent improvements in their signal to noise, applications to large-scale species

  9. Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs.

    Science.gov (United States)

    Ghimire, Chandra Prasad; Bruijnzeel, L Adrian; Lubczynski, Maciek W; Zwartendijk, Bob W; Odongo, Vincent Omondi; Ravelona, Maafaka; van Meerveld, H J Ilja

    2018-04-21

    It has been suggested that vigorous secondary tropical forests can have very high transpiration rates, but sap flow and stomatal conductance dynamics of trees and shrubs in these forests are understudied. In an effort to address this knowledge gap, sap flow (thermal dissipation method, 12 trees) and stomatal conductance (porometry, six trees) were measured for young (5-7 years) Psiadia altissima (DC.) Drake trees, a widely occurring species dominating young regrowth following abandonment of swidden agriculture in upland eastern Madagascar. In addition, stomatal conductance (gs) was determined for three individuals of two locally common invasive shrubs (Lantana camara L. and Rubus moluccanus L.) during three periods with contrasting soil moisture conditions. Values of gs for the three investigated species were significantly higher and more sensitive to climatic conditions during the wet period compared with the dry period. Further, gs of the understorey shrubs was much more sensitive to soil moisture content than that of the trees. Tree transpiration rates (Ec) were relatively stable during the dry season and were only affected somewhat by soil water content at the end of the dry season, suggesting the trees had continued access to soil water despite drying out of the topsoil. The Ec exhibited a plateau-shaped relation with vapour pressure deficit (VPD), which was attributed to stomatal closure at high VPD. Vapour pressure deficit was the major driver of variation in Ec, during both the wet and the dry season. Overall water use of the trees was modest, possibly reflecting low site fertility after three swidden cultivation cycles. The observed contrast in gs response to soil water and climatic conditions for the trees and shrubs underscores the need to take root distributions into account when modelling transpiration from regenerating tropical forests.

  10. Interactions between atmospheric circulation, nutrient deposition, and tropical forest primary production (Invited)

    Science.gov (United States)

    Randerson, J. T.; Chen, Y.; Rogers, B. M.; Morton, D. C.; van der Werf, G.; Mahowald, N. M.

    2010-12-01

    Tropical forests influence regional and global climate by means of several pathways, including by modifying surface energy exchange and by forming clouds. High levels of precipitation, leaching, and soil weathering limit nutrient availability in these ecosystems. Phosphorus (P) is a key element limiting net primary production, and in some areas, including forests recovering from prior disturbance, nitrogen (N) also may limit some components of production. Here we quantified atmospheric P and N inputs to these forests from fires using satellite-derived estimates of emissions and atmospheric models. In Africa and South America, cross-biome transport of fire-emitted aerosols and reactive N gases from savannas and areas near the deforestation frontier increased deposition of P and N in interior forests. Equatorward atmospheric transport during the dry (fire) season in one hemisphere was linked with surface winds moving toward the inter-tropical convergence zone (ITCZ) in the other hemisphere. Deposition levels were higher in tropical forests in Africa than in South America because of large savanna areas with high levels of fire emissions in both southern and northern Africa. We conclude by describing a potential feedback loop by which equatorward transport of fire emissions, dust, and spores sustains the productivity of tropical forests. We specifically assessed evidence that savanna-to-forest atmospheric transport of nutrients increases forest productivity, height, and rates of evapotranspiration (ET). In parallel, we examined the degree to which increases in ET and surface roughness in tropical forests have the potential to strengthen several components of the Hadley circulation, including deep convection, equatorward return flow (near the surface), and the intensity of seasonal drought in the subtropics (thereby increasing fires). These interactions are important for understanding biogeochemical - climate interactions on millennial timescales and for quantifying how

  11. Freezing temperatures as a limit to forest recruitment above tropical Andean treelines.

    Science.gov (United States)

    Rehm, Evan M; Feeley, Kenneth J

    2015-07-01

    The elevation of altitudinal treelines is generally believed to occur where low mean temperatures during the growing season limit growth and prevent trees from establishing at higher elevations. Accordingly, treelines should move upslope with increasing global temperatures. Contrary to this prediction, tropical treelines have remained stable over the past several decades despite increasing mean temperatures. The observed stability of tropical treelines, coupled with the drastically different temperature profiles between temperate and tropical treelines, suggests that using mean measures of temperature to predict tropical treeline movements during climate change may be overly simplistic. We hypothesize that frost events at tropical treelines may slow climate driven treeline movement by preventing tree recruitment beyond the established forest canopy. To assess this hypothesis, we measured freezing resistance of four canopy-forming treeline species (Weinmannia fagaroides, Polylepis pauta, Clethra cuneata, and Gynoxys nitida) at two life stages (juvenile and adult) and during two seasons (warm-wet and cold-dry). Freezing resistances were then compared to microclimatic data to determine if freezing events in the grassland matrix above treeline are too harsh for these forest species. Freezing resistance varied among species and life stages from -5.7 degrees C for juveniles of P. pauta to -11.1 degrees C for juveniles of W. fagaroides. Over a four-year period, the lowest temperatures recorded at 10 cm above ground level in the grasslands above treeline and at treeline itself were -8.9 degrees C and -6.8 degrees C, respectively. Juveniles maintained freezing resistances similar to adults during the coldest parts of the year and ontogenetic differences in freezing resistance were only present during the warm season when temperatures did not represent a significant threat to active plant tissue. These findings support the hypothesis that rare extreme freezing events at and

  12. Prevalence and risk factors associated with dry eye symptoms: a population based study in Indonesia

    Science.gov (United States)

    Lee, A J; Lee, J; Saw, S-M; Gazzard, G; Koh, D; Widjaja, D; Tan, D T H

    2002-01-01

    Aim: To determine the prevalence and identify associated risk factors for dry eye syndrome in a population in Sumatra, Indonesia. Methods: A one stage cluster sampling procedure was conducted to randomly select 100 households in each of the five rural villages and one provincial town of the Riau province, Indonesia, from April to June 2001. Interviewers collected demographic, lifestyle, and medical data from 1058 participants aged 21 years or over. Symptoms of dry eye were assessed using a six item validated questionnaire. Presence of one or more of the six dry eye symptoms often or all the time was analysed. Presence of pterygium was documented. Results: Prevalence of one or more of the six dry eye symptoms often or all the time adjusted for age was 27.5% (95% confidence interval (CI) 24.8 to 30.2). After adjusting for all significant variables, independent risk factors for dry eye were pterygium (p<0.001, multivariate odds ratio (OR) 1.8; 95% CI 1.4 to 2.5) and a history of current cigarette smoking (p=0.05, multivariate OR 1.5; 95% CI 1.0 to 2.2). Conclusions: This population based study provides prevalence rates of dry eye symptoms in a tropical developing nation. From our findings, pterygium is a possible independent risk factor for dry eye symptoms. PMID:12446361

  13. Reducing supplementation frequency for Nellore beef steers grazing tropical pastures

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    Roberta Carrilho Canesin

    2014-04-01

    Full Text Available Reduced supplementation frequency is a broadly applied management practice. Ruminants consuming low quality forages/pastures, supplemented less than once daily are able to maintain body weight gain (BWG, efficiency of use of dry matter, nitrogen and other nutrients, as compared with animals supplemented once daily. We evaluated the feeding behavior, dry matter intake (DMI, dry matter and organic matter digestibility (DMD and OMD, BWG, Longissimus muscle area and backfat depth of Nellore steers raised on Brachiaria brizantha cv. Marandu pastures during the dry season, with different supplementation patterns. Thirty six animals (338 ± 40.7 kg were distributed over nine paddocks according to a completely randomized design. Treatments were based on supplementation frequency: once daily (OD, once daily except Saturdays and Sundays (SS, or on alternate days (AD, at 1.0 %, 1.4 % and 2.0 % BW, respectively. Average total DMI accounted for 1.6 % BW day-1, with no effect of supplementation frequency. Supplementation frequency had no effect on BWG or grazing time during the day. There was no difference in Longissimus muscle area animals supplemented daily, SS and AD. The backfat depth was thinner in animals supplemented AD, but even in this case, it was within the standards considered satisfactory for a finishing steer. Reducing supplementation frequency seems a good option to lower labor costs without affecting feed efficiency or carcass quality in beef cattle grazing tropical pastures.

  14. Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient

    Science.gov (United States)

    Gaviria, Julian; Engelbrecht, Bettina M. J.

    2015-01-01

    Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests

  15. A Drone-based Tropical Forest Experiment to Estimate Vegetation Properties

    Science.gov (United States)

    Henke, D.

    2017-12-01

    In mid-latitudes, remote sensing technology is intensively used to monitor vegetation properties. However, in the tropics, high cloud-cover and saturation effects of vegetation indices (VI) hamper the reliability of vegetation parameters derived from satellite data. A drone experiment over the Barro Colorado Island (BCI), Panama, with high temporal repetition rates was conducted in spring 2017 to investigate the robustness and stability of remotely sensed vegetation parameters in tropical environments. For this purpose, three 10-day flight windows in February, March and April were selected and drone flights were repeated on daily intervals when weather conditions and equipment allowed it. In total, 18 days were recorded with two different optical cameras on sensefly's eBee drone: one red, green, blue (RGB) camera and one camera with near infra-red (NIR), green and blue channels. When possible, the data were acquired at the same time of day. Pix4D and Agisoft software were used to calculate the Normalized Difference VI (NDVI) and forest structure. In addition, leave samples were collected ones per month from 16 different plant species and the relative water content was measured as ground reference. Further data sources for the analysis are phenocam images (RGB & NIR) on BCI and satellite images of MODIS (NDVI; Enhanced VI EVI) and Sentinel-1 (radar backscatter). The attached figure illustrates the main data collected on BCI. Initial results suggest that the coefficient of determination (R2) is relatively high between ground samples and drone data, Sentinel-1 backscatter and MODIS EVI with R2 values ranging from 0.4 to 0.6; on the contrary, R2 values between ground measurements and MODIS NDVI or phenocam images are below 0.2. As the experiment took place mainly during dry season on BCI, cloud-cover rates are less dominate than during wet season. Under these conditions, MODIS EVI, which is less vulnerable to saturation effects, seems to be more reliable than MODIS

  16. The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs.

    Directory of Open Access Journals (Sweden)

    Gabriela Silva Ribeiro Gonçalves

    Full Text Available Understanding the processes that influence species diversity is still a challenge in ecological studies. However, there are two main theories to discuss this topic, the niche theory and the neutral theory. Our objective was to understand the importance of environmental and spatial processes in structuring bird communities within the hydrological seasons in dry forest areas in northeastern Brazil. The study was conducted in two National Parks, the Serra da Capivara and Serra das Confusões National Parks, where 36 areas were sampled in different seasons (dry, dry/rainy transition, rainy, rainy/dry transition, in 2012 and 2013. We found with our results that bird species richness is higher in the rainy season and lower during the dry season, indicating a strong influence of seasonality, a pattern also found for environmental heterogeneity. Richness was explained by local environmental factors, while species composition was explained by environmental and spatial factors. The environmental factors were more important in explaining variations in composition. Climate change predictions have currently pointed out frequent drought events and a rise in global temperature by 2050, which would lead to changes in species behavior and to increasing desertification in some regions, including the Caatinga. In addition, the high deforestation rates and the low level of representativeness of the Caatinga in the conservation units negatively affects bird communities. This scenario has demonstrated how climatic factors affect individuals, and, therefore, should be the starting point for conservation initiatives to be developed in xeric environments.

  17. The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs).

    Science.gov (United States)

    Gonçalves, Gabriela Silva Ribeiro; Cerqueira, Pablo Vieira; Brasil, Leandro Schlemmer; Santos, Marcos Pérsio Dantas

    2017-01-01

    Understanding the processes that influence species diversity is still a challenge in ecological studies. However, there are two main theories to discuss this topic, the niche theory and the neutral theory. Our objective was to understand the importance of environmental and spatial processes in structuring bird communities within the hydrological seasons in dry forest areas in northeastern Brazil. The study was conducted in two National Parks, the Serra da Capivara and Serra das Confusões National Parks, where 36 areas were sampled in different seasons (dry, dry/rainy transition, rainy, rainy/dry transition), in 2012 and 2013. We found with our results that bird species richness is higher in the rainy season and lower during the dry season, indicating a strong influence of seasonality, a pattern also found for environmental heterogeneity. Richness was explained by local environmental factors, while species composition was explained by environmental and spatial factors. The environmental factors were more important in explaining variations in composition. Climate change predictions have currently pointed out frequent drought events and a rise in global temperature by 2050, which would lead to changes in species behavior and to increasing desertification in some regions, including the Caatinga. In addition, the high deforestation rates and the low level of representativeness of the Caatinga in the conservation units negatively affects bird communities. This scenario has demonstrated how climatic factors affect individuals, and, therefore, should be the starting point for conservation initiatives to be developed in xeric environments.

  18. Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere.

    Science.gov (United States)

    Cleveland, Cory C; Townsend, Alan R

    2006-07-05

    Terrestrial biosphere-atmosphere carbon dioxide (CO(2)) exchange is dominated by tropical forests, where photosynthetic carbon (C) uptake is thought to be phosphorus (P)-limited. In P-poor tropical forests, P may also limit organic matter decomposition and soil C losses. We conducted a field-fertilization experiment to show that P fertilization stimulates soil respiration in a lowland tropical rain forest in Costa Rica. In the early wet season, when soluble organic matter inputs to soil are high, P fertilization drove large increases in soil respiration. Although the P-stimulated increase in soil respiration was largely confined to the dry-to-wet season transition, the seasonal increase was sufficient to drive an 18% annual increase in CO(2) efflux from the P-fertilized plots. Nitrogen (N) fertilization caused similar responses, and the net increases in soil respiration in response to the additions of N and P approached annual soil C fluxes in mid-latitude forests. Human activities are altering natural patterns of tropical soil N and P availability by land conversion and enhanced atmospheric deposition. Although our data suggest that the mechanisms driving the observed respiratory responses to increased N and P may be different, the large CO(2) losses stimulated by N and P fertilization suggest that knowledge of such patterns and their effects on soil CO(2) efflux is critical for understanding the role of tropical forests in a rapidly changing global C cycle.

  19. Using a prescribed fire to test custom and standard fuel models for fire behaviour prediction in a non-native, grass-invaded tropical dry shrubland

    Science.gov (United States)

    Andrew D. Pierce; Sierra McDaniel; Mark Wasser; Alison Ainsworth; Creighton M. Litton; Christian P. Giardina; Susan Cordell; Ralf Ohlemuller

    2014-01-01

    Questions: Do fuel models developed for North American fuel types accurately represent fuel beds found in grass-invaded tropical shrublands? Do standard or custom fuel models for firebehavior models with in situ or RAWS measured fuel moistures affect the accuracy of predicted fire behavior in grass-invaded tropical shrublands? Location: Hawai’i Volcanoes National...

  20. Heat and mass transfer coefficients and modeling of infrared drying of banana slices

    Directory of Open Access Journals (Sweden)

    Fernanda Machado Baptestini

    Full Text Available ABSTRACT Banana is one of the most consumed fruits in the world, having a large part of its production performed in tropical countries. This product possesses a wide range of vitamins and minerals, being an important component of the alimentation worldwide. However, the shelf life of bananas is short, thus requiring procedures to prevent the quality loss and increase the shelf life. One of these procedures widely used is drying. This work aimed to study the infrared drying process of banana slices (cv. Prata and determine the heat and mass transfer coefficients of this process. In addition, effective diffusion coefficient and relationship between ripening stages of banana and drying were obtained. Banana slices at four different ripening stages were dried using a dryer with infrared heating source with four different temperatures (65, 75, 85, and 95 ºC. Midilli model was the one that best represented infrared drying of banana slices. Heat and mass transfer coefficients varied, respectively, between 46.84 and 70.54 W m-2 K-1 and 0.040 to 0.0632 m s-1 for temperature range, at the different ripening stages. Effective diffusion coefficient ranged from 1.96 to 3.59 × 10-15 m² s-1. Activation energy encountered were 16.392, 29.531, 23.194, and 25.206 kJ mol-1 for 2nd, 3rd, 5th, and 7th ripening stages, respectively. Ripening stages did not affect the infrared drying of bananas.

  1. Detecting Climate Signals in Precipitation Extremes from TRMM (1998-2013) - Increasing Contrast Between Wet and Dry Extremes During the "Global Warming Hiatus"

    Science.gov (United States)

    Wu, Huey-Tzu Jenny; Lau, William K.-M.

    2016-01-01

    We investigate changes in daily precipitation extremes using Tropical Rainfall Measuring Mission (TRMM) data (1998-2013), which coincides with the "global warming hiatus." Results show a change in probability distribution functions of local precipitation events (LPEs) during this period consistent with previous global warming studies, indicating increasing contrast between wet and dry extremes, with more intense LPE, less moderate LPE, and more dry (no rain) days globally. Analyses for land and ocean separately reveal more complex and nuanced changes over land, characterized by a strong positive trend (+12.0% per decade, 99% confidence level (c.l.)) in frequency of extreme LPEs over the Northern Hemisphere extratropics during the wet season but a negative global trend (-6.6% per decade, 95% c.l.) during the dry season. A significant global drying trend (3.2% per decade, 99% c.l.) over land is also found during the dry season. Regions of pronounced increased dry events include western and central U.S., northeastern Asia, and Southern Europe/Mediterranean.

  2. Parc des ventilateurs et des résistances dans les techniques de séchage adaptées à l'environnement tropical

    Directory of Open Access Journals (Sweden)

    Kapseu, C.

    1999-01-01

    Full Text Available Fans and Resistances Park in Drying Technologies Appropriate for Tropical Environment. To design a dryer, it is necessary to master its elements. Fan and resistance are parts of heated and convective dryer. Catalogues analysis of 33 and 14 french suppliers of fans and resistances respectively showed 773 fans and 226 resistances suitable for drying technologies. Fans are classified as follows in decreasing order : axial (58 %, centrifugal (42 % and tangential (1 %. Specifications of fans used in pilots dryers adapted for developing countries in the literature are presented. Centrifugal fan appeared to be the most used. Optimisation of fan parameters (rating fan, air circulation are presented as a function of drying time.

  3. Assessment of water availability and its relationship with vegetation distribution over a tropical montane system

    Science.gov (United States)

    Streher, A. S.; Sobreiro, J. F. F.; Silva, T. S. F.

    2017-12-01

    Water availability is one of the main drivers of vegetation distribution, but assessing it over mountainous regions is difficult given the effects of rugged topography on hydroclimatic dynamics (orographic rainfall, soil water, and runoff). We assessed how water availability may influence the distribution of vegetation types in the Espinhaço Range, a South American tropical mountain landscape comprised of savannas, grasslands, rock outcrops, cloud forests, and semi-deciduous/deciduous forests. For precipitation, we used CHIRPS monthly and daily products (1981- 2016) and 112 rain gauge ground stations, and assessed potential evapotranspiration (PET) using the MODIS MOD16A3 (2000-2013) product. Vegetation types were classified according to the Global Ecoregions by WWF. We show that rainfall has well-defined rainy and dry seasons with a strong latitudinal pattern, there is evidence for local orographic effects. Dry forests (907 mm/yr; 8% cv) and caatinga vegetation (795 mm/yr; 7% cv) had the lowest average annual precipitation and low variance, whilst Atlantic tropical forest in the southeast (1267 mm/yr; 15% cv), cerrado savanna vegetation in the west (1086 mm/yr; 15% cv) and rupestrian grasslands above 800m (1261 mm/yr; 20% cv) received the highest annual precipitation, with the largest observed variance due to their wide latitudinal distribution. Forests and rupestrian grasslands in the windward side of the mountain had a higher frequency of intense rainfall events (> 20mm), accounting for 6% of the CHIRPS daily time series, suggesting orographic effects on precipitation. Annual average PET was highest for dry forests (2437 mm/yr) and caatinga (2461 mm/yr), intermediate for cerrado (2264 mm/yr) and lowest for Atlantic tropical forest (2083 mm/yr) and rupestrian grasslands (2136 mm/yr). All vegetation types received less rainfall than its PET capacity based on yearly data, emphasizing the need for ecophysiological adaptations to water use. Climate change threatens

  4. Characteristics of Timbers Dried Using Kiln Drying and Radio Frequency-Vacuum Drying Systems

    OpenAIRE

    Rabidin Zairul Amin; Seng Gan Kee; Wahab Mohd Jamil Abdul

    2017-01-01

    Heavy hardwoods are difficult-to-dry timbers as they are prone to checking and internal stresses when dried using a conventional kiln drying system. These timbers are usually dried naturally to reach 15% to 19% moisture content with an acceptable defects. Besides long drying time, timbers at these moisture contents are not suitable for indoor applications since they will further dry and causing, for example, jointing and lamination failures. Drying to a lower moisture content could only be ac...

  5. Effects of intermittent CO2 convection under far-infrared radiation on vacuum drying of pre-osmodehydrated watermelon.

    Science.gov (United States)

    Chakraborty, Rajat; Mondal, Pijus

    2017-08-01

    Watermelon, a tropical seasonal fruit with high nutrient content, requires preservation through drying due to its perishable nature. Nevertheless, drying of watermelon through conventional processes has a negative impact either on the drying time or on the final product quality. In this work, osmotic dehydration of watermelon followed by far-infrared radiation-assisted vacuum drying (FIRRAVD) was optimized to develop dehydrated watermelon with minimum moisture content. Significantly, during FIRRAVD, an attempt was made to further intensify the drying rate by forced convection through intermittent CO 2 injection. Drying kinetics of each operation and physicochemical qualities of dried products were evaluated. FIRRAVD was a viable method of watermelon drying with appreciably high moisture diffusivity (D eff,m ) of 4.97 × 10 -10 to 1.49 × 10 -9 m 2 s -1 compared to conventional tray drying. Moreover, intermittent CO 2 convection during FIRRAVD (ICFIRRAVD) resulted in appreciable intensification of drying rate, with enhanced D eff,m (9.93 × 10 -10 to 1.99 × 10 -9 m 2 s -1 ). Significantly, ICFIRRAVD required less energy and approximately 16% less time compared to FIRRAVD. The quality of the final dehydrated watermelon was superior compared to conventional drying protocols. The novel CO 2 convective drying of watermelon in the presence of far-infrared radiation demonstrated an energy-efficient and time-saving operation rendering a dehydrated watermelon with acceptable quality parameters. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  6. Reduced heat stress in offices in the tropics using solar powered drying of the supply air

    DEFF Research Database (Denmark)

    Gunnarsen, Lars; Santos, A M B

    2002-01-01

    air may facilitate personal cooling by increased evaporation of sweat. Heat acclimatized people with efficient sweating may in particular benefit from this cooling. A prototype solar powered supply system for dried-only air was made. Air from the system was mixed with room air, heated to six different...... content of room air, temperature of supply air and moisture content of supply air was developed based on the experiments. Reduction of moisture content in the supply air by 1.6 g/kg had the same effect as lowering the operative temperature by 1 degree C. The solar-powered system for supplying dry air...... is a low-cost alternative to traditional air conditioning in hot and humid regions....

  7. Tropical Peatland Geomorphology and Hydrology

    Science.gov (United States)

    Cobb, A.; Harvey, C. F.

    2017-12-01

    Tropical peatlands cover many low-lying areas in the tropics. In tropical peatlands, a feedback between hydrology, landscape morphology, and carbon storage causes waterlogged organic matter to accumulate into gently mounded land forms called peat domes over thousands of years. Peat domes have a stable morphology in which peat production is balanced by loss and net precipitation is balanced by lateral flow, creating a link between peatland morphology, rainfall patterns and drainage networks. We show how landscape morphology can be used to make inferences about hydrologic processes in tropical peatlands. In particular, we show that approaches using simple storage-discharge relationships for catchments are especially well suited to tropical peatlands, allowing river forecasting based on peatland morphology in catchments with tropical peatland subcatchments.

  8. Dynamics of sward condition and botanical composition in mixed pastures of marandugrass, forage peanut and tropical kudzu

    Directory of Open Access Journals (Sweden)

    Carlos Mauricio Soares de Andrade

    2012-03-01

    Full Text Available This study was carried out to evaluate the dynamics of sward condition and botanical composition of a mixed pasture of marandugrass (Brachiaria brizantha cv. Marandu, forage peanut (Arachis pintoi cv. Mandobi and tropical kudzu (Pueraria phaseoloides, rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight. Sward condition was characterized in each stocking cycle by measuring pre- and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, forage peanut, tropical kudzu and weeds was evaluated before each stocking period. Swards under smaller forage allowances presented lower height, forage mass and ground cover. This condition favored the growth of forage peanut, which constituted 21.1, 15.2, 8.4 and 3.8% of forage mass in the last quarter of the experimental period, from the lowest to the highest forage allowance, respectively. Tropical kudzu was sensitive to all forage allowance levels and its percentage in the botanical composition was strongly reduced along the experimental period, especially during the dry season (July to September. Forage peanut cv. Mandobi and marandugrass form a more balanced mixture when pre-grazing sward height is maintained shorter than 45 cm. Tropical kudzu is intolerant to intensive grazing management systems when associated to marandugrass.

  9. Terrestrial Ecosystem Science 2017 ECRP Annual Report: Tropical Forest Response to a Drier Future: Turnover Times of Soil Organic Matter, Roots, Respired CO2, and CH4 Across Moisture Gradients in Time and Space

    Energy Technology Data Exchange (ETDEWEB)

    McFarlane, Karis J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-05-30

    The overall goal of my Early Career research is to constrain belowground carbon turnover times for tropical forests across a broad range in moisture regimes. My group is using 14C analysis and modeling to address two major objectives: quantify age and belowground carbon turnover times across tropical forests spanning a moisture gradient from wetlands to dry forest; and identify specific areas for focused model improvement and data needs through site-specific model-data comparison and belowground carbon modeling for tropic forests.

  10. Drought stress and tree size determine stem CO2 efflux in a tropical forest.

    Science.gov (United States)

    Rowland, Lucy; da Costa, Antonio C L; Oliveira, Alex A R; Oliveira, Rafael S; Bittencourt, Paulo L; Costa, Patricia B; Giles, Andre L; Sosa, Azul I; Coughlin, Ingrid; Godlee, John L; Vasconcelos, Steel S; Junior, João A S; Ferreira, Leandro V; Mencuccini, Maurizio; Meir, Patrick

    2018-06-01

    CO 2 efflux from stems (CO 2_stem ) accounts for a substantial fraction of tropical forest gross primary productivity, but the climate sensitivity of this flux remains poorly understood. We present a study of tropical forest CO 2_stem from 215 trees across wet and dry seasons, at the world's longest running tropical forest drought experiment site. We show a 27% increase in wet season CO 2_stem in the droughted forest relative to a control forest. This was driven by increasing CO 2_stem in trees 10-40 cm diameter. Furthermore, we show that drought increases the proportion of maintenance to growth respiration in trees > 20 cm diameter, including large increases in maintenance respiration in the largest droughted trees, > 40 cm diameter. However, we found no clear taxonomic influence on CO 2_stem and were unable to accurately predict how drought sensitivity altered ecosystem scale CO 2_stem , due to substantial uncertainty introduced by contrasting methods previously employed to scale CO 2_stem fluxes. Our findings indicate that under future scenarios of elevated drought, increases in CO 2_stem may augment carbon losses, weakening or potentially reversing the tropical forest carbon sink. However, due to substantial uncertainties in scaling CO 2_stem fluxes, stand-scale future estimates of changes in stem CO 2 emissions remain highly uncertain. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust.

  11. Linking Vital Rates of Landbirds on a Tropical Island to Rainfall and Vegetation Greenness.

    Directory of Open Access Journals (Sweden)

    James F Saracco

    Full Text Available Remote tropical oceanic islands are of high conservation priority, and they are exemplified by range-restricted species with small global populations. Spatial and temporal patterns in rainfall and plant productivity may be important in driving dynamics of these species. Yet, little is known about environmental influences on population dynamics for most islands and species. Here we leveraged avian capture-recapture, rainfall, and remote-sensed habitat data (enhanced vegetation index [EVI] to assess relationships between rainfall, vegetation greenness, and demographic rates (productivity, adult apparent survival of three native bird species on Saipan, Northern Mariana Islands: rufous fantail (Rhipidura rufifrons, bridled white-eye (Zosterops conspicillatus, and golden white-eye (Cleptornis marchei. Rainfall was positively related to vegetation greenness at all but the highest rainfall levels. Temporal variation in greenness affected the productivity of each bird species in unique ways. Predicted productivity of rufous fantail was highest when dry and wet season greenness values were high relative to site-specific 5-year seasonal mean values (i.e., relative greenness; while the white-eye species had highest predicted productivity when relative greenness contrasted between wet and dry seasons. Survival of rufous fantail and bridled white eye was positively related to relative dry-season greenness and negatively related to relative wet-season greenness. Bridled white-eye survival also showed evidence of a positive response to overall greenness. Our results highlight the potentially important role of rainfall regimes in affecting population dynamics of species on oceanic tropical islands. Understanding linkages between rainfall, vegetation, and animal population dynamics will be critical for developing effective conservation strategies in this and other regions where the seasonal timing, extent, and variability of rainfall is expected to change in the

  12. Comments on "Atlantic Tropical Cyclogenetic Processes during SOP-3 NAMMA in the GEOS-5 Global Data Assimilation and Forecast System"

    Science.gov (United States)

    Braun, Scott A.

    2010-01-01

    Considerable attention has been given to the potential negative impacts of the Saharan air layer (SAL) in recent years. Researchers recently raised questions about the negative impacts of Dunion and Velden and other studies in terms of storms that reached at least tropical storm strength and suggested that the SAL was an intrinsic part of the tropical cyclone environment for both storms that weaken after formation and those that intensify. Braun also suggested that several incorrect assumptions underlie many of the studies on the negative impacts of the SAL, including assumptions that most low-to-midlevel dry tropical air is SAL air, that the SAL is dry throughout its depth, and that the proximity of the SAL to storms struggling to intensify implies some role in that struggle. The recent paper by Reale et al.(RL1) is an example of the problems inherent in some of these assumptions. In their paper, RL1 analyze a simulation from the Global Earth Observing System (GEOS-5) global model and describe an extensive tongue of warm, dry air that stretches southward from at least 30 deg N (the northern limit of their plots) and wraps into a low pressure system during the period 26-29 August 2006, suppressing convection and possibly development of the African easterly wave associated with that low pressure system. They attributed the warm, dry tongue to the SAL (i.e., heating of the air mass during passage over the Sahara and radiative warming of the dust layer). Whether it was their intention, the implication is that this entire feature is due solely to the SAL and not to other possible sources of dry air or warmth. In addition, they suggested that a cool tongue of air in the boundary layer located directly beneath the elevated warm, dry tongue (forming a thermal dipole) was possibly the result of reduced solar radiation caused by an overlying dust layer. They stated that "the cool anomaly in the lower levels does not have any plausible explanation relying only on transport

  13. Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

    Directory of Open Access Journals (Sweden)

    M. D. Mallet

    2017-11-01

    Full Text Available The SAFIRED (Savannah Fires in the Early Dry Season campaign took place from 29 May until 30 June 2014 at the Australian Tropical Atmospheric Research Station (ATARS in the Northern Territory, Australia. The purpose of this campaign was to investigate emissions from fires in the early dry season in northern Australia. Measurements were made of biomass burning aerosols, volatile organic compounds, polycyclic aromatic carbons, greenhouse gases, radon, speciated atmospheric mercury and trace metals. Aspects of the biomass burning aerosol emissions investigated included; emission factors of various species, physical and chemical aerosol properties, aerosol aging, micronutrient supply to the ocean, nucleation, and aerosol water uptake. Over the course of the month-long campaign, biomass burning signals were prevalent and emissions from several large single burning events were observed at ATARS.Biomass burning emissions dominated the gas and aerosol concentrations in this region. Dry season fires are extremely frequent and widespread across the northern region of Australia, which suggests that the measured aerosol and gaseous emissions at ATARS are likely representative of signals across the entire region of north Australia. Air mass forward trajectories show that these biomass burning emissions are carried north-west over the Timor Sea and could influence the atmosphere over Indonesia and the tropical atmosphere over the Indian Ocean. Here we present characteristics of the biomass burning observed at the sampling site and provide an overview of the more specific outcomes of the SAFIRED campaign.

  14. Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

    Science.gov (United States)

    Mallet, Marc D.; Desservettaz, Maximilien J.; Miljevic, Branka; Milic, Andelija; Ristovski, Zoran D.; Alroe, Joel; Cravigan, Luke T.; Rohan Jayaratne, E.; Paton-Walsh, Clare; Griffith, David W. T.; Wilson, Stephen R.; Kettlewell, Graham; van der Schoot, Marcel V.; Selleck, Paul; Reisen, Fabienne; Lawson, Sarah J.; Ward, Jason; Harnwell, James; Cheng, Min; Gillett, Rob W.; Molloy, Suzie B.; Howard, Dean; Nelson, Peter F.; Morrison, Anthony L.; Edwards, Grant C.; Williams, Alastair G.; Chambers, Scott D.; Werczynski, Sylvester; Williams, Leah R.; Winton, V. Holly L.; Atkinson, Brad; Wang, Xianyu; Keywood, Melita D.

    2017-11-01

    The SAFIRED (Savannah Fires in the Early Dry Season) campaign took place from 29 May until 30 June 2014 at the Australian Tropical Atmospheric Research Station (ATARS) in the Northern Territory, Australia. The purpose of this campaign was to investigate emissions from fires in the early dry season in northern Australia. Measurements were made of biomass burning aerosols, volatile organic compounds, polycyclic aromatic carbons, greenhouse gases, radon, speciated atmospheric mercury and trace metals. Aspects of the biomass burning aerosol emissions investigated included; emission factors of various species, physical and chemical aerosol properties, aerosol aging, micronutrient supply to the ocean, nucleation, and aerosol water uptake. Over the course of the month-long campaign, biomass burning signals were prevalent and emissions from several large single burning events were observed at ATARS.Biomass burning emissions dominated the gas and aerosol concentrations in this region. Dry season fires are extremely frequent and widespread across the northern region of Australia, which suggests that the measured aerosol and gaseous emissions at ATARS are likely representative of signals across the entire region of north Australia. Air mass forward trajectories show that these biomass burning emissions are carried north-west over the Timor Sea and could influence the atmosphere over Indonesia and the tropical atmosphere over the Indian Ocean. Here we present characteristics of the biomass burning observed at the sampling site and provide an overview of the more specific outcomes of the SAFIRED campaign.

  15. Forgotten forests - issues and prospects in biome mapping using Seasonally Dry Tropical Forests as a case study

    Directory of Open Access Journals (Sweden)

    Särkinen Tiina

    2011-11-01

    Full Text Available Abstract Background South America is one of the most species diverse continents in the world. Within South America diversity is not distributed evenly at both local and continental scales and this has led to the recognition of various areas with unique species assemblages. Several schemes currently exist which divide the continental-level diversity into large species assemblages referred to as biomes. Here we review five currently available biome maps for South America, including the WWF Ecoregions, the Americas basemap, the Land Cover Map of South America, Morrone's Biogeographic regions of Latin America, and the Ecological Systems Map. The comparison is performed through a case study on the Seasonally Dry Tropical Forest (SDTF biome using herbarium data of habitat specialist species. Results Current biome maps of South America perform poorly in depicting SDTF distribution. The poor performance of the maps can be attributed to two main factors: (1 poor spatial resolution, and (2 poor biome delimitation. Poor spatial resolution strongly limits the use of some of the maps in GIS applications, especially for areas with heterogeneous landscape such as the Andes. Whilst the Land Cover Map did not suffer from poor spatial resolution, it showed poor delimitation of biomes. The results highlight that delimiting structurally heterogeneous vegetation is difficult based on remote sensed data alone. A new refined working map of South American SDTF biome is proposed, derived using the Biome Distribution Modelling (BDM approach where georeferenced herbarium data is used in conjunction with bioclimatic data. Conclusions Georeferenced specimen data play potentially an important role in biome mapping. Our study shows that herbarium data could be used as a way of ground-truthing biome maps in silico. The results also illustrate that herbarium data can be used to model vegetation maps through predictive modelling. The BDM approach is a promising new method in

  16. Forgotten forests - issues and prospects in biome mapping using Seasonally Dry Tropical Forests as a case study

    Science.gov (United States)

    2011-01-01

    Background South America is one of the most species diverse continents in the world. Within South America diversity is not distributed evenly at both local and continental scales and this has led to the recognition of various areas with unique species assemblages. Several schemes currently exist which divide the continental-level diversity into large species assemblages referred to as biomes. Here we review five currently available biome maps for South America, including the WWF Ecoregions, the Americas basemap, the Land Cover Map of South America, Morrone's Biogeographic regions of Latin America, and the Ecological Systems Map. The comparison is performed through a case study on the Seasonally Dry Tropical Forest (SDTF) biome using herbarium data of habitat specialist species. Results Current biome maps of South America perform poorly in depicting SDTF distribution. The poor performance of the maps can be attributed to two main factors: (1) poor spatial resolution, and (2) poor biome delimitation. Poor spatial resolution strongly limits the use of some of the maps in GIS applications, especially for areas with heterogeneous landscape such as the Andes. Whilst the Land Cover Map did not suffer from poor spatial resolution, it showed poor delimitation of biomes. The results highlight that delimiting structurally heterogeneous vegetation is difficult based on remote sensed data alone. A new refined working map of South American SDTF biome is proposed, derived using the Biome Distribution Modelling (BDM) approach where georeferenced herbarium data is used in conjunction with bioclimatic data. Conclusions Georeferenced specimen data play potentially an important role in biome mapping. Our study shows that herbarium data could be used as a way of ground-truthing biome maps in silico. The results also illustrate that herbarium data can be used to model vegetation maps through predictive modelling. The BDM approach is a promising new method in biome mapping, and could be

  17. Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae

    Directory of Open Access Journals (Sweden)

    Marga Born

    2010-07-01

    Full Text Available Seasonal rainfall affects tropical forest dynamics and behaviorof species that are part of these ecosystems. The positive correlation between amphibian activity patterns and rainfall has been demonstrated repeatedly. Members of Dendrobatidae, a clade of Neotropical dart-poison frogs, are well known for their habitat use and behavior during the rainy season, but their behavior during the dry season has received little attention. We studied habitat use and diet of the dendrobatid frog Dendrobates tinctorius in French Guiana during the rainy and dry seasons. Unlike many other dendrobatid frogs, D. tinctorius does not maintain territories for the entire rainy season. Both sexes colonize recently formed canopy-gaps and stay in these forest patches for only a few weeks. The frogs inthese patches consume a great diversity of prey, consisting of ants, beetles, wasps, insect larvae, and mites. During the dry season, frogs move to retreat sites in mature forest, such as palm bracts and tree holes. The frogs are less active and consume fewer prey items in the dry season, and they consume fewer wasps and insect larvae, but more termites. Ants are the most common prey items during both the wet and dry seasons. We discuss the effects of shifts in seasonal habitat use on the territorial behavior of dendrobatid frogs.

  18. The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata.

    Science.gov (United States)

    Elahi, Robin

    2005-11-18

    The large predatory ant, Paraponera clavata, exerts measurable top-down effects in wet and moist Neotropical forests, and therefore its distribution has potential ecological implications. To determine how water affects the presence of this important predator, the ground nesting ecology of P. clavata was examined with respect to various habitat characteristics. Four hectares of disturbed Costa Rican lowland rain forest were surveyed for ant colonies to determine nest distribution patterns in wet and dry habitat; significantly more colonies were found in dry habitat. Seventeen of 19 nests built on slopes of > 5 degrees inclination were positioned on the downward side of the tree, possibly using the trunk as a shield against runoff during rain showers. Moisture and pH inside nests were significantly different from adjacent soil. These results suggest that water influences the ground nesting habits of P. clavata, thus ecological differences between comparatively wet and dry portions of tropical forests may arise from the relative abundance of this ant species.

  19. Unique competitive effects of lianas and trees in a tropical forest understory.

    Science.gov (United States)

    Wright, Alexandra; Tobin, Mike; Mangan, Scott; Schnitzer, Stefan A

    2015-02-01

    Lianas are an important component of tropical forests, contributing up to 25% of the woody stems and 35% of woody species diversity. Lianas invest less in structural support but more in leaves compared to trees of similar biomass. These physiological and morphological differences suggest that lianas may interact with neighboring plants in ways that are different from similarly sized trees. However, the vast majority of past liana competition studies have failed to identify the unique competitive effects of lianas by controlling for the amount of biomass removed. We assessed liana competition in the forest understory over the course of 3 years by removing liana biomass and an equal amount of tree biomass in 40 plots at 10 sites in a secondary tropical moist forest in central Panama. We found that growth of understory trees and lianas, as well as planted seedlings, was limited due to competitive effects from both lianas and trees, though the competitive impacts varied by species, season, and size of neighbors. The removal of trees resulted in greater survival of planted seedlings compared to the removal of lianas, apparently related to a greater release from competition for light. In contrast, lianas had a species-specific negative effect on drought-tolerant Dipteryx oleifera seedlings during the dry season, potentially due to competition for water. We conclude that, at local scales, lianas and trees have unique and differential effects on understory dynamics, with lianas potentially competing more strongly during the dry season, and trees competing more strongly for light.

  20. Tropical myeloneuropathies: the hidden endemias.

    Science.gov (United States)