WorldWideScience

Sample records for humid tropic soils

  1. Soil phosphorus dynamics in a humid tropical silvopastoral system

    International Nuclear Information System (INIS)

    Cooperband, L.R.

    1992-01-01

    In developing countries of the humid tropics, timber exploitation and agricultural expansion frequently result in deforestation. Extensive land management, coupled with inherently low soil fertility invariably produce declines in agricultural/livestock productivity which eventually lead to land abandonment and further deforestation. Phosphorus is often the major nutrient limiting plant growth in tropical soils. Agroforestry systems have been considered as viable alternatives to current land use practices. Several hypotheses suggest that combining trees with crops or pasture, especially leguminous species will improve soil nutrient cycling, soil structure and soil organic matter. In this experiment Erythrina berteroana (an arboreous legume) was grown in native grass pastures in Costa Rica to determine the effects of tree pruning and cattle grazing on soil P availability. I measured soil P fluxes as well as changes in pasture biomass over an 18-month period. In a separate field experiment, I determined decomposition rates and P release characteristics of Erythrina leaves, pasture grass clippings and cattle dung. Erythrina leaves decomposed faster than both pasture grass and cattle dung. Erythrina and pasture residues released 4-5 times less P than dung. Phosphorus fluxes after tree pruning and grazing were highly dynamic for all treatments. Tree pruning increased labile soil P over time when coupled with grazing. Pasture biomass production was greatest in the grazed tree treatment. Pasture biomass P production and concentration was greatest in the non-grazed treatment. Trees and grazing together tended to increase nutrient (P) turnover which stimulated biomass production. In contrast, trees without grazing promoted nutrient (P) accumulation in pasture biomass

  2. Soil phosphorus dynamics in a humid tropical silvopastoral system

    Energy Technology Data Exchange (ETDEWEB)

    Cooperband, L.R.

    1992-01-01

    In developing countries of the humid tropics, timber exploitation and agricultural expansion frequently result in deforestation. Extensive land management, coupled with inherently low soil fertility invariably produce declines in agricultural/livestock productivity which eventually lead to land abandonment and further deforestation. Phosphorus is often the major nutrient limiting plant growth in tropical soils. Agroforestry systems have been considered as viable alternatives to current land use practices. Several hypotheses suggest that combining trees with crops or pasture, especially leguminous species will improve soil nutrient cycling, soil structure and soil organic matter. In this experiment Erythrina berteroana (an arboreous legume) was grown in native grass pastures in Costa Rica to determine the effects of tree pruning and cattle grazing on soil P availability. I measured soil P fluxes as well as changes in pasture biomass over an 18-month period. In a separate field experiment, I determined decomposition rates and P release characteristics of Erythrina leaves, pasture grass clippings and cattle dung. Erythrina leaves decomposed faster than both pasture grass and cattle dung. Erythrina and pasture residues released 4-5 times less P than dung. Phosphorus fluxes after tree pruning and grazing were highly dynamic for all treatments. Tree pruning increased labile soil P over time when coupled with grazing. Pasture biomass production was greatest in the grazed tree treatment. Pasture biomass P production and concentration was greatest in the non-grazed treatment. Trees and grazing together tended to increase nutrient (P) turnover which stimulated biomass production. In contrast, trees without grazing promoted nutrient (P) accumulation in pasture biomass.

  3. Anoxic conditions drive phosphorus limitation in humid tropical forest soil microorganisms

    Science.gov (United States)

    Gross, A.; Pett-Ridge, J.; Weber, P. K.; Blazewicz, S.; Silver, W. L.

    2017-12-01

    The elemental stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) of soil microorganisms (C:N:P ratios) regulates transfers of energy and nutrients to higher trophic levels. In humid tropical forests that grow on P-depleted soils, the ability of microbes to concentrate P from their surroundings likely plays a critical role in P-retention and ultimately in forest productivity. Models predict that climate change will cause dramatic changes in rainfall patterns in the humid tropics and field studies have shown these changes can affect the redox state of tropical forest soils, influencing soil respiration and biogeochemical cycling. However, the responses of soil microorganisms to changing environmental conditions are not well known. Here, we incubated humid tropical soils under oxic or anoxic conditions with substrates differing in both C:P stoichiometry and lability, to assess how soil microorganisms respond to different redox regimes. We found that under oxic conditions, microbial C:P ratios were similar to the global optimal ratio (55:1), indicating most microbial cells can adapt to persistent aerated conditions in these soils. However, under anoxic conditions, the ability of soil microbes to acquire soil P declined and their C:P ratios shifted away from the optimal ratio. NanoSIMS elemental imaging of single cells extracted from soil revealed that under anoxic conditions, C:P ratios were above the microbial optimal value in 83% of the cells, in comparison to 41% under oxic conditions. These data suggest microbial growth efficiency switched from being energy limited under oxic conditions to P-limited under anoxic conditions, indicating that, microbial growth in low P humid tropical forests soils may be most constrained by P-limitation when conditions are oxygen-limited. We suggest that differential microbial responses to soil redox states could have important implications for productivity of humid tropical forests under future climate scenarios.

  4. N2O emissions from humid tropical agricultural soils: effects of soil moisture, texture and nitrogen availability

    Science.gov (United States)

    A.M. Weitza; E. Linderb; S. Frolkingc; P.M. Crillc; M. Keller

    2001-01-01

    We studied soil moisture dynamics and nitrous oxide (N2O) ¯uxes from agricultural soils in the humid tropics of Costa Rica. Using a splitplot design on two soils (clay, loam) we compared two crop types (annual, perennial) each unfertilized and fertilized. Both soils are of andic origin. Their properties include relatively low bulk density and high organic matter...

  5. Soil mineralogy and microbes determine forest life history strategy and carbon cycling in humid tropical forests

    Science.gov (United States)

    Soong, J.; Verbruggen, E.; Peñuelas, J.; Janssens, I. A.; Grau, O.

    2017-12-01

    Tropical forests account for over one third of global terrestrial gross primary productivity and cycle more C than any other ecosystem on Earth. However, we still lack a mechanistic understanding of how such high productivity is maintained on the old, highly weathered and phosphorus depleted soils in the tropics. We hypothesized that heterogeneity in soil texture, mineralogy and microbial community composition may be the major drivers of differences in soil C storage and P limitation across tropical forests. We sampled 12 forest sites across a 200 km transect in the humid neo-tropics of French Guiana that varied in soil texture, precipitation and mineralogy. We found that soil texture was a major driver of soil carbon stocks and forest life history strategy, where sandy forests have lower soil C stocks, slower turnover and decomposition and a more closed nutrient cycle while clayey forests have higher soil C stocks, faster turnover and a more leaky nutrient cycle (using natural abundance stable isotope evidence). We found that although the presence of Al and Fe oxides in the clayey soils occludes soil organic matter and P, a greater abundance of arbuscular mycorrhizal fungi help forests to access occluded P in clayey soils fueling higher turnover and faster decomposition rates. Evidence from a laboratory incubation of tropical soils with nutrient additions further demonstrates the de-coupling of microbial P demands from C:N limitations providing further evidence for the need to examine microbial stoichiometry to explain C cycling in the P-limited tropics. We argue that microbial community composition and physiological demands, constrained within the limitations of soil mineralogical reactivity, largely controls nutrient and C cycling in tropical forest soils. Together our observational field study and laboratory incubation provide a unique dataset to shed light on the mineralogical and microbial controls on C and nutrient cycling in tropical soils. By integrating

  6. Biological effects of plant residues with constrasting chemical compositions on plant and soil under humid tropical conditions

    NARCIS (Netherlands)

    Tian, G.

    1992-01-01

    A study on plant residues with contrasting chemical compositions was conducted under laboratory, growth chamber and humid tropical field conditions to understand the function of the soil fauna in the breakdown of plant residues, the cycling of nutrients, in particular nitrogen, and the

  7. Soil crusting regulator characteristics of some allic humid tropical soils from Colombia

    International Nuclear Information System (INIS)

    Arias, Dora M; Madero E E; Amezquita E

    2001-01-01

    It was collected soil samples within 5 cm of the surface from Amazonia soils in Caqueta (Macagual); Orinoquia in Meta (Carimagua), Casanare (Matazul) and Vichada (La Primavera); and in Andean region in Cauca (San Isidro) and Valle (CIAT, Palmira). In each of those sites, the International Center for Tropical Agriculture (CIAT) has many experiments to know the impact of land husbandry, leguminous associations and rotations and mulches on natural system. After evaluating weighed particle size, sand particle size, soil organic matter, iron, aluminum and silicon oxides, and fertility, it could cluster in three groups according to those characteristics and their importance in governing soil hazard crusting: la Primavera and Carimagua (high organic matter, oxides and fine sand but low in clay); Matazul and Macagual (low in organic matter, oxides and clay but variable sand values); and San Isidro (the greatest in Al 2 O 3 concentrations, high in Fe 2 O 3 clay and fine sand but the poorest in soil organic matter). Soil organic matter contents were significantly associated with the kind of management

  8. Minerals Masquerading As Enzymes: Abiotic Oxidation Of Soil Organic Matter In An Iron-Rich Humid Tropical Forest Soil

    Science.gov (United States)

    Hall, S. J.; Silver, W. L.

    2010-12-01

    Oxidative reactions play an important role in decomposing soil organic matter fractions that resist hydrolytic degradation, and fundamentally affect the cycling of recalcitrant soil carbon across ecosystems. Microbial extracellular oxidative enzymes (e.g. lignin peroxidases and laccases) have been assumed to provide a dominant role in catalyzing soil organic matter oxidation, while other potential oxidative mechanisms remain poorly explored. Here, we show that abiotic reactions mediated by the oxidation of ferrous iron (Fe(II)) could explain high potential oxidation rates in humid tropical forest soils, which often contain high concentrations of Fe(II) and experience rapid redox fluctuations between anaerobic and aerobic conditions. These abiotic reactions could provide an additional mechanism to explain high rates of decomposition in these ecosystems, despite frequent oxygen deficits. We sampled humid tropical forest soils in Puerto Rico, USA from various topographic positions, ranging from well-drained ridges to riparian valleys that experience broad fluctuations in redox potential. We measured oxidative activity by adding the model humic compound L-DOPA to soil slurries, followed by colorimetric measurements of the supernatant solution over time. Dilute hydrogen peroxide was added to a subset of slurries to measure peroxidative activity. We found that oxidative and peroxidative activity correlated positively with soil Fe(II) concentrations, counter to prevailing theory that low redox potential should suppress oxidative enzymes. Boiling or autoclaving sub-samples of soil slurries to denature any enzymes present typically increased peroxidative activity and did not eliminate oxidative activity, further suggesting the importance of an abiotic mechanism. We found substantial differences in the oxidation products of the L-DOPA substrate generated by our soil slurries in comparison with oxidation products generated by a purified enzyme (mushroom tyrosinase

  9. Soil bio-engineering for risk mitigation and environmental restoration in a humid tropical area

    Science.gov (United States)

    Petrone, A.; Preti, F.

    2009-07-01

    The use of soil bio-engineering techniques in developing countries is a relevant issue for disaster mitigation, environmental restoration and poverty reduction. Research on authochtonal plants suitable for this kind of works and on economic efficiency is essential for the divulgation of such techniques. The present paper is focused on this two issues related to the realization of various typologies of soil bio-engineering works in the humid tropic of Nicaragua. In the area of Río Blanco, located in the Department of Matagalpa, soil bio-engineering installations were built in several sites. The particular structures built were: drainages with live fascine mattress, a live palisade, a vegetated live crib wall for riverbank protection, a vegetative covering made of a metallic net and biotextile coupled with a live palisade made of bamboo. In order to evaluate the suitability of the various plants used in the works, monitorings were performed, one in the live palisade alongside an unpaved road and the other on the live crib wall along a riverbank, collecting survival rate and morphological parameters data. Concerning the economic efficiency we proceed to a financial analysis of the works and once the unit price was obtained, we converted the amount in EPP Dollars (Equal Purchasing Power) in order to compare the Nicaraguan context with the Italian one. Among the used species we found that Madero negro (Gliricidia sepium) and Roble macuelizo (Tabebuia rosea) are adequate for soil-bioengineering measure on slopes while Helequeme (Erythrina fusca) reported a successful behaviour only in the crib wall for riverbank protection. In the comparison of the costs in Nicaragua and in Italy, the unit price reduction for the Central American country ranges between 1.5 times (for the vegetative covering) and almost 4 times (for the fascine mattress) if it's used the EPP dollar exchange rate. Conclusions are reached with regard to hydrological-risk mitigating actions performed on a

  10. Soil bioengineering for risk mitigation and environmental restoration in a humid tropical area

    Science.gov (United States)

    Petrone, A.; Preti, F.

    2010-02-01

    The use of soil bio-engineering techniques in developing countries is a relevant issue for disaster mitigation, environmental restoration and poverty reduction. Research on the autochthonal plants suitable for these kinds of interventions and on the economic efficiency of the interventions is essential for the dissemination of such techniques. The present paper is focused on these two issues as related to the realization of various typologies of soil bioengineering works in the humid tropics of Nicaragua. In the area of Río Blanco, located in the Department of Matagalpa, soil bioengineering installations were built in several sites. The particular structures built were: drainages with live fascine mattress, a live palisade, a vegetated live crib wall for riverbank protection, a vegetative covering made of a metallic net and biotextile coupled with a live palisade made of bamboo. In order to evaluate the suitability of the various plants used in these works, monitoring was performed, one on the live palisade alongside an unpaved road and the other on the live crib wall along a riverbank, by collecting data on survival rate and morphological parameters. Concerning economic efficiency, we proceeded to a financial analysis of the works. Once the unit price was obtained, we converted the amount into EPP Dollars (Equal Purchasing Power) in order to compare the Nicaraguan context with the European one. Among the species used we found that Gliricidia sepium (local common name: Madero negro) and Tabebuia rosea (local common name: Roble macuelizo) are adequate for soil bioengineering measures on slopes, while Erythrina fusca (local common name: Helequeme) resulted in successful behaviour only in the crib wall for riverbank protection. In comparing costs in Nicaragua and in Italy, the unit price reduction for Nicaragua ranges from 1.5 times (for the vegetative covering) to almost 4 times (for the fascine mattress), using the EPP dollar exchange rate. Our conclusions with

  11. Soil bioengineering for risk mitigation and environmental restoration in a humid tropical area

    Directory of Open Access Journals (Sweden)

    A. Petrone

    2010-02-01

    Full Text Available The use of soil bio-engineering techniques in developing countries is a relevant issue for disaster mitigation, environmental restoration and poverty reduction. Research on the autochthonal plants suitable for these kinds of interventions and on the economic efficiency of the interventions is essential for the dissemination of such techniques. The present paper is focused on these two issues as related to the realization of various typologies of soil bioengineering works in the humid tropics of Nicaragua.

    In the area of Río Blanco, located in the Department of Matagalpa, soil bioengineering installations were built in several sites. The particular structures built were: drainages with live fascine mattress, a live palisade, a vegetated live crib wall for riverbank protection, a vegetative covering made of a metallic net and biotextile coupled with a live palisade made of bamboo. In order to evaluate the suitability of the various plants used in these works, monitoring was performed, one on the live palisade alongside an unpaved road and the other on the live crib wall along a riverbank, by collecting data on survival rate and morphological parameters. Concerning economic efficiency, we proceeded to a financial analysis of the works. Once the unit price was obtained, we converted the amount into EPP Dollars (Equal Purchasing Power in order to compare the Nicaraguan context with the European one.

    Among the species used we found that Gliricidia sepium (local common name: Madero negro and Tabebuia rosea (local common name: Roble macuelizo are adequate for soil bioengineering measures on slopes, while Erythrina fusca (local common name: Helequeme resulted in successful behaviour only in the crib wall for riverbank protection.

    In comparing costs in Nicaragua and in Italy, the unit price reduction for Nicaragua ranges from 1.5 times (for the vegetative covering to almost 4 times (for the fascine mattress

  12. Sensitivity of soil respiration to variability in soil moisture and temperature in a humid tropical forest

    Science.gov (United States)

    Tana Wood; M. Detto; W.L. Silver

    2013-01-01

    Precipitation and temperature are important drivers of soil respiration. The role of moisture and temperature are generally explored at seasonal or inter-annual timescales; however, significant variability also occurs on hourly to daily time-scales. We used small (1.54 m2), throughfall exclusion shelters to evaluate the role soil moisture and temperature as temporal...

  13. Impact of Soil and Water Conservation Interventions on Watershed Runoff Response in a Tropical Humid Highland of Ethiopia.

    Science.gov (United States)

    Sultan, Dagnenet; Tsunekawa, Atsushi; Haregeweyn, Nigussie; Adgo, Enyew; Tsubo, Mitsuru; Meshesha, Derege Tsegaye; Masunaga, Tsugiyuki; Aklog, Dagnachew; Fenta, Ayele Almaw; Ebabu, Kindiye

    2018-05-01

    Various soil and water conservation measures (SWC) have been widely implemented to reduce surface runoff in degraded and drought-prone watersheds. But little quantitative study has been done on to what extent such measures can reduce watershed-scale runoff, particularly from typical humid tropical highlands of Ethiopia. The overall goal of this study is to analyze the impact of SWC interventions on the runoff response by integrating field measurement with a hydrological CN model which gives a quantitative analysis future thought. Firstly, a paired-watershed approach was employed to quantify the relative difference in runoff response for the Kasiry (treated) and Akusty (untreated) watersheds. Secondly, a calibrated curve number hydrological modeling was applied to investigate the effect of various SWC management scenarios for the Kasiry watershed alone. The paired-watershed approach showed a distinct runoff response between the two watersheds however the effect of SWC measures was not clearly discerned being masked by other factors. On the other hand, the model predicts that, under the current SWC coverage at Kasiry, the seasonal runoff yield is being reduced by 5.2%. However, runoff yields from Kasiry watershed could be decreased by as much as 34% if soil bunds were installed on cultivated land and trenches were installed on grazing and plantation lands. In contrast, implementation of SWC measures on bush land and natural forest would have little effect on reducing runoff. The results on the magnitude of runoff reduction under optimal combinations of SWC measures and land use will support decision-makers in selection and promotion of valid management practices that are suited to particular biophysical niches in the tropical humid highlands of Ethiopia.

  14. Characterizing the Suitability of Selected Indigenous Soil Improving Legumes in a Humid Tropical Environment Using Shoot and Root Attributes

    Directory of Open Access Journals (Sweden)

    Anikwe, MAN.

    2003-01-01

    Full Text Available We studied the biomass accumulation, root length, nodulation, and chemical composition of roots and shoot of ten indigenous soil improving legumes in a humid tropical ecosystem with the view to selecting species for soil improvement programmes. Two cultivars of Vigna unguiculata, and one each of Glycine max, Arachis hypogaea, Crotararia ochroleuca, Cajanus cajan, Pueraria phaseoloides, Lablab purpureus, Mucuna pruriens and Vigna subterranea as treatments were planted in 20 kg pots containing soil from an Oxic paleustalf in Nigeria. The pots were arranged in randomized complete block layout with three replications in a greenhouse at IITA Ibadan, Nigeria. Results from the work show that M. pruriens and C. cajan produced the highest quantity of biomass. Root elongation was highest in M. pruriens whereas A. hypogaea produced the most root nodules with native rhizobia. The highest quantity of nodule dry weight was produced by A. hypogaea and P. phaseoloides whereas most of the legumes except G. max and P. phaseoloides had high and statistically comparable N content of between 2.36 and 3.34 mg.kg-1 N. The results show that the legumes have different root and shoot characteristics, which should be taken into consideration when selecting species for soil improvement programmes.

  15. Impact of Restoration of Soil in a Humid Tropical Region on Storage of Organic Carbon in a Recalcitrant Pool

    Science.gov (United States)

    Jyoti Nath, Arun; Brahma, Biplab; Lal, Rattan; Das, Ashesh Kumar

    2017-04-01

    Quantifying soil organic carbon (SOC) changes through restoration of degraded lands is important to assessing the changes in soil properties. However, SOC measures all C fractions and its assessment is not adequate to distinguish between the more dynamic or active C (AC) fractions and the recalcitrant or passive C (PC) form. SOC fractions comprising of the recalcitrant pools have been suggested as a driver for long term soil C sink management. Therefore, the present study was undertaken at a site within the North Eastern India (NEI) region with an objective to explore whether or not SOC fractions change with restoration of degraded lands under humid tropical climate. An age-chronosequence study was established comprising of four different aged rubber plantations (6, 15, 27 and 34 yr. old) planted on Imperata grasslands. The site was selected to study changes in the different fractions of SOC and total SOC stock, and the data were compared with that of a native forest. The data indicated that the SOC stock increased from 106 Mg ha-1 under 6 yr. to 130 Mg ha-1 under 34 yr. old plantations. The SOC stock after 34 yr. of plantation was 20% higher than that under Imperata grassland, but was 34% lower than that under the native forest soil. With respect to lability of C fractions, proportion of AC pool decreased linearly with increase in plantation age from 59 % under 6 yr to 33 % under 34 yr. old plantations. In contrast, proportion of PC pool increased from 41 % of SOC stock under 6 yr. to 67 % of SOC under 34 yr. old plantations, suggesting the significant role of old aged plantation in C sink management.

  16. Soil organic carbon dynamics in pastures established after deforestation in the humid tropics of Costa Rica

    NARCIS (Netherlands)

    Veldkamp, E.

    1993-01-01

    Currently, rates of deforestation in the tropics are probably higher than ever before in the past. As a consequence, changes in the earth's physical and chemical environments are proceeding at unprecedented rates. Increasing atmospheric concentrations of CO

  17. Lignin decomposition is sustained under fluctuating redox conditions in humid tropical forest soils

    Science.gov (United States)

    Steven J. Hall; Whendee L. Silver; Vitaliy I. Timokhin; Kenneth E. Hammel

    2015-01-01

    Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia is thought to suppress lignin decomposition, yet potential effects of oxygen (O2) variability in surface soils have not been explored. Here, we...

  18. Iron Redox Dynamics in Humid Tropical Forest Soils: Carbon Stabilization vs. Degradation?

    Science.gov (United States)

    Hall, S. J.; Silver, W. L.; Hammel, K.

    2015-12-01

    Most terrestrial soils exhibit a patchwork of oxygen (O2) availability that varies over spatial scales of microsites to catenas to landscapes, and over temporal scales of minutes to seasons. Oxygen fluctuations often drive microbial iron (Fe) reduction and abiotic/biotic Fe oxidation at the microsite scale, contributing to anaerobic carbon (C) mineralization and changes in soil physical and chemical characteristics, especially the dissolution and precipitation of short-range ordered Fe phases thought to stabilize C. Thus, O2 fluctuations and Fe redox cycling may have multiple nuanced and opposing impacts on different soil C pools, illustrated by recent findings from Fe-rich Oxisols and Ultisols in the Luquillo Experimental Forest, Puerto Rico. Spatial patterns in surface soil C stocks at the landscape scale correlated strongly (R2 = 0.98) with concentrations of reduced Fe (Fe(II)), reflecting constitutive differences in reducing conditions within and among sites that promote C accumulation in mineral soil horizons. Similarly, turnover times of a decadal-cycling pool of mineral-associated organic matter increased with Fe(II) across a catena, possibly reflecting the role of anaerobic microsites in long-term C stabilization. However, two different indices of short-range order Fe showed highly significant opposing relationships (positive and negative) with spatial variation in soil C concentrations, possibly reflecting a dual role of Fe in driving C stabilization via co-precipitation, and C solubilization and loss following dissimilatory Fe reduction. Consistent with the field data, laboratory incubations demonstrated that redox fluctuations can increase the contribution of biochemically recalcitrant C (lignin) to soil respiration, whereas addition of short-range order Fe dramatically suppressed lignin mineralization but had no impact on bulk soil respiration. Thus, understanding spatial and temporal patterns of Fe redox cycling may provide insight into explaining the

  19. Landscape formation and soil genesis in volcanic parent materials in humid tropical lowlands of Costa Rica

    NARCIS (Netherlands)

    Nieuwenhuyse, A.

    1996-01-01


    The influence of volcanism on landscape genesis, and formation of soils on volcanic parent material was studied in the Atlantic lowland of Costs Rica. This lowland is a subduction basin of tectonic origin, in which thick alluvial and marine sediments are accumulated. At its southwestern

  20. Nutrient stocks of short-term fallows on high base status soils in the humid tropics of Papua New Guinea

    NARCIS (Netherlands)

    Hartemink, A.E.

    2004-01-01

    In order to understand nutrient dynamics in tropical farming systems with fallows, it is necessary to assess changes in nutrient stocks in plants, litter and soils. Nutrient stocks (soil, above ground biomass, litter) were assessed of one-year old fallows with Piper aduncum, Gliricidia sepium and

  1. Establishment of five cover crops and total soil nutrient extraction in a humid tropical soil in the Peruvian Amazon

    Science.gov (United States)

    In order to evaluate the establishment of five cover crops and their potential to increase soil fertility through nutrient extraction, an experiment was installed in the Research Station of Choclino, San Martin, Peru. Five cover crops were planted: Arachis pintoi Krapov. & W.C. Greg, Calopogonium m...

  2. Exclusion of soil macrofauna did not affect soil quality but increases crop yields in a sub-humid tropical maize-based system

    NARCIS (Netherlands)

    Paul, B.K.; Vanlauwe, B.; Hoogmoed, M.; Hurisso, T.T.; Ndabamenye, T.; Terano, Y.; Ayuke, F.O.; Pulleman, M.M.

    2015-01-01

    Soil macrofauna such as earthworms and termites are involved in key ecosystem functions and thus considered important for sustainable intensification of crop production. However, their contribution to tropical soil and crop performance, as well as relations with agricultural management (e.g.

  3. 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...

  4. Stabilization of recent soil carbon in the humid tropics following land use changes: evidence from aggregate fractionation and stable isotope analyses

    OpenAIRE

    Paul, Sonja; Flessa, Heiner; Veldkamp, Edzo; López-Ulloa, Magdalena

    2008-01-01

    Keywords: Carbon sequestration - Ecuador - Mean residence time - Pasture - Secondary forest - Soil type - Texture - Water-stable aggregates Quantitative knowledge of stabilization- and decomposition processes is necessary to understand, assess and predict effects of land use changes on storage and stability of soil organic carbon (soil C) in the tropics. Although it is well documented that different soil types have different soil C stocks, it is presently unknown how different soil types a...

  5. Soil erosion in humid regions: a review

    Science.gov (United States)

    Daniel J. Holz; Karl W.J. Williard; Pamela J. Edwards; Jon E. Schoonover

    2015-01-01

    Soil erosion has significant implications for land productivity and surface water quality, as sediment is the leading water pollutant worldwide. Here, erosion processes are defined. The dominant factors influencing soil erosion in humid areas are reviewed, with an emphasis on the roles of precipitation, soil moisture, soil porosity, slope steepness and length,...

  6. Deformation of high performance concrete plate under humid tropical weather

    Science.gov (United States)

    Niken, C.; Elly, T.; Supartono, FX; Laksmi, I.

    2018-03-01

    This paper presents the relationship between surrounding relative humidity and temperature on deformation behavior of one sample concrete plate with compressive strength of 60MPa. This research was done in Indonesia that is in humid tropical weather. A specimens measuring 3000 mm × 1600 mm × 150 mm were used. The behavior was obtained by using four embedded vibrating wire strain gauges (VWESG). As a result there is a very strong relationship between humidity and deformation at the age range of 7 until 21 days. The largest deformation occurs in the corner and the fluctuation of deformation in side position is larger than in the corner and in the middle. The peaks of surrounding relative humidity were fully followed by the deepest valley of deformation on time in the corner, while in another position the range delay time was 8 - 11 hours. There is a strong relationship between surrounding temperature and deformation at the range of 7 until 14 days. The influenced of surrounding relative humidity to concrete behavior is faster and longer than surrounding temperature. The influence of surrounding temperature in humid tropical weather was shorter than in non-humid tropical weather.

  7. Mycorrhizas and tropical soil fertility

    NARCIS (Netherlands)

    Cardoso, I.M.; Kuyper, T.W.

    2006-01-01

    Major factors that constrain tropical soil fertility and sustainable agriculture are low nutrient capital, moisture stress, erosion, high P fixation, high acidity with aluminium toxicity, and low soil biodiversity. The fragility of many tropical soils limits food production in annual cropping

  8. Influência da temperatura, umidade e profundidade do solo na persistência do diurom e sulfato de endossulfam em um solo tropical Influence of temperature, soil humidity and soil depth on the persistence of diuron and endosulfan sulfate in a tropical soil

    Directory of Open Access Journals (Sweden)

    Flávia de Amorim Silva

    2010-01-01

    Full Text Available The influence of temperature (30 and 40 ºC and soil humidity (20, 50 and 70% of water holding capacity on the degradation of the herbicide diurom and the endosulfan metabolite, endosulfan sulfate was studied under laboratory conditions, in different soil layers (0-30, 30-38 and 38-83 cm of an Oxisol (Yellow Latosol collected in an agricultural area of Mato Grosso State, Brazil. Endosulfan sulfate was rapidly degraded under lower soil humidity, higher temperature and deeper soil layers. For diurom the opposite was observed as a consequence of its higher water solubility and lower soil sorption coefficient.

  9. Small-scale variability in tropical tropopause layer humidity

    Science.gov (United States)

    Jensen, E. J.; Ueyama, R.; Pfister, L.; Karcher, B.; Podglajen, A.; Diskin, G. S.; DiGangi, J. P.; Thornberry, T. D.; Rollins, A. W.; Bui, T. V.; Woods, S.; Lawson, P.

    2016-12-01

    Recent advances in statistical parameterizations of cirrus cloud processes for use in global models are highlighting the need for information about small-scale fluctuations in upper tropospheric humidity and the physical processes that control the humidity variability. To address these issues, we have analyzed high-resolution airborne water vapor measurements obtained in the Airborne Tropical TRopopause EXperiment over the tropical Pacific between 14 and 20 km. Using accurate and precise 1-Hz water vapor measurements along approximately-level aircraft flight legs, we calculate structure functions spanning horizontal scales ranging from about 0.2 to 50 km, and we compare the water vapor variability in the lower (about 14 km) and upper (16-19 km) Tropical Tropopause Layer (TTL). We also compare the magnitudes and scales of variability inside TTL cirrus versus in clear-sky regions. The measurements show that in the upper TTL, water vapor concentration variance is stronger inside cirrus than in clear-sky regions. Using simulations of TTL cirrus formation, we show that small variability in clear-sky humidity is amplified by the strong sensitivity of ice nucleation rate to supersaturation, which results in highly-structured clouds that subsequently drive variability in the water vapor field. In the lower TTL, humidity variability is correlated with recent detrainment from deep convection. The structure functions indicate approximately power-law scaling with spectral slopes ranging from about -5/3 to -2.

  10. Hygroscopical behaviour of basic electrodes in a tropical humid climate

    International Nuclear Information System (INIS)

    Valencia, E.; Galeano, N.J.

    1993-01-01

    The study of the wetting kynetics of basic electrodes in a tropical humid climate is very important since the water contained in them is the main source for the atomic hydrogen absorbed by the fused metal during electric arc welding. It is also the origin of multiple defects in the added metal. A calculating method is established for evaluating the kynetics of wetness incorporation to the coating of basic electrodes exposed to a humid tropical climate. The method is based on the Fick's diffusion equation for both adequate system geometry and boundary conditions, which allows the evaluation of the effective diffusion coefficient and critical times of exposure to the different environments, along with the packing and storage conditions of electrodes. (Author)

  11. 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.

  12. Mechanized farming in the humid tropics with special reference to soil tillage, workability and timeliness of farm operations : a case study for the Zanderij area of Suriname

    NARCIS (Netherlands)

    Goense, D.

    1987-01-01

    The reported investigations concern aspects of mechanized farming for the production of rainfed crops on the loamy soils of the Zanderij formation in Suriname and in particular, the effect of tillage on crop yield and soil properties, workability of field operations and timeliness of field

  13. Estimating the Consequences of Fire Exclusion for Food Crop Production, Soil Fertility, and Fallow Recovery in Shifting Cultivation Landscapes in the Humid Tropics

    Science.gov (United States)

    Norgrove, Lindsey; Hauser, Stefan

    2015-03-01

    In the Congo Basin, smallholder farmers practice slash-and-burn shifting cultivation. Yet, deliberate burning might no longer be sustainable under reduced fallow scenarios. We synthesized data from the Forest Margins Benchmark Area (FMBA), comprising 1.54 million hectares (ha), in southern Cameroon and assessed the impact of fire exclusion on yield, labor inputs, soil fertility, ecosystem carbon stocks, and fallow recovery indicators in two common field types (plantain and maize) under both current and reduced fallow scenarios. While we could not distinguish between impacts of standard farmer burning practice and fire exclusion treatments for the current fallow scenario, we concluded that fire exclusion would lead to higher yields, higher ecosystem carbon stocks as well as potentially faster fallow recovery under the reduced fallow scenario. While its implementation would increase labor requirements, we estimated increased revenues of 421 and 388 US ha-1 for plantain and maize, respectively. Applied to the FMBA, and assuming a 6-year reduced fallow scenario, fire exclusion in plantain fields would potentially retain 240,464 Mg more ecosystem carbon, comprising topsoil carbon plus tree biomass carbon, than standard farmer practice. Results demonstrate a potential "win-win scenario" where yield benefits, albeit modest, and conservation benefits can be obtained simultaneously. This could be considered as a transitional phase towards higher input use and thus higher yielding systems.

  14. Tropical Volcanic Soils From Flores Island, Indonesia

    Directory of Open Access Journals (Sweden)

    Hikmatullah

    2010-01-01

    Full Text Available Soils that are developed intropical region with volcanic parent materials have many unique properties, and high potential for agricultural use.The purpose of this study is to characterize the soils developed on volcanic materials from Flores Island, Indonesia,and to examine if the soils meet the requirements for andic soil properties. Selected five soils profiles developed fromandesitic volcanic materials from Flores Island were studied to determine their properties. They were compared intheir physical, chemical and mineralogical characteristics according to their parent material, and climatic characteristicdifferent. The soils were developed under humid tropical climate with ustic to udic soil moisture regimes withdifferent annual rainfall. The soils developed from volcanic ash parent materials in Flores Island showed differentproperties compared to the soils derived from volcanic tuff, even though they were developed from the sameintermediary volcanic materials. The silica contents, clay mineralogy and sand fractions, were shown as the differences.The different in climatic conditions developed similar properties such as deep solum, dark color, medium texture, andvery friable soil consistency. The soils have high organic materials, slightly acid to acid, low to medium cationexchange capacity (CEC. The soils in western region have higher clay content and showing more developed than ofthe eastern region. All the profiles meet the requirements for andic soil properties, and classified as Andisols order.The composition of sand mineral was dominated by hornblende, augite, and hypersthenes with high weatherablemineral reserves, while the clay fraction was dominated by disordered kaolinite, and hydrated halloysite. The soilswere classified into subgroup as Thaptic Hapludands, Typic Hapludands, and Dystric Haplustands

  15. Lability of soil organic carbon in tropical soils with different clay minerals

    DEFF Research Database (Denmark)

    Bruun, Thilde Bech; Elberling, Bo; Christensen, Bent Tolstrup

    2010-01-01

    Soil organic carbon (SOC) storage and turnover is influenced by interactions between organic matter and the mineral soil fraction. However, the influence of clay content and type on SOC turnover rates remains unclear, particularly in tropical soils under natural vegetation. We examined the lability...... of SOC in tropical soils with contrasting clay mineralogy (kaolinite, smectite, allophane and Al-rich chlorite). Soil was sampled from A horizons at six sites in humid tropical areas of Ghana, Malaysian Borneo and the Solomon Islands and separated into fractions above and below 250 µm by wet sieving....... Basal soil respiration rates were determined from bulk soils and soil fractions. Substrate induced respiration rates were determined from soil fractions. SOC lability was significantly influenced by clay mineralogy, but not by clay content when compared across contrasting clay minerals. The lability...

  16. Impacts of Present and Future Climate Variability On Agriculture and Forestry in the Humid and Sub-Humid Tropics

    International Nuclear Information System (INIS)

    Zhao, Y.; Wang, C.; Wang, S.; Tibig, Lourdes V.

    2005-01-01

    Although there are different results from different studies, most assessments indicate that climate variability would have negative effects on agriculture and forestry in the humid and sub-humid tropics. Cereal crop yields would decrease generally with even minimal increases in temperature. For commercial crops, extreme events such as cyclones, droughts and floods lead to larger damages than only changes of mean climate. Impacts of climate variability on livestock mainly include two aspects; impacts on animals such as increase of heat and disease stress-related death, and impacts on pasture. As to forestry, climate variability would have negative as well as some positive impacts on forests of humid and sub-humid tropics. However, in most tropical regions, the impacts of human activities such as deforestation will be more important than climate variability and climate change in determining natural forest cover

  17. First stages of zinc runoff in humid tropical climate

    International Nuclear Information System (INIS)

    Meraz, E.; Veleva, L.; Acosta, M.

    2007-01-01

    Frequently used metals in building application are Zinc and hot dip galvanized steel. The zinc has a relatively good atmospheric resistance, due to its oxidation in air and formation of protective layer. However, some of the zinc corrosion products can be dissolved by pluvial precipitations and water condensed on the metal surface. This process is called metal runoff. In order to estimate el zinc runoff in humid tropical climate, since its firs stages, samples of pure zinc and hot dip galvanized steel have been exposed during 2 years in outdoor atmosphere (rural and urban). The data reveal high annual values of zinc runoff (8,20-12,40±0.30 g/m''2 ano), being this process 80% of total mass loss of corroded zinc. The runoff and corrosion processes are more accelerated for zinc, than that of galvanized steel. The principal factors that control the runoff process are discussed. (Author) 48 refs

  18. Towards a universal sampling protocol for soil biotas in the humid tropics Em direção a um protocolo universal de amostragem de biotas do solo nos trópicos úmidos

    Directory of Open Access Journals (Sweden)

    David Edward Bignell

    2009-08-01

    Full Text Available This paper reviews the methods for the inventory of below-ground biotas in the humid tropics, to document the (hypothesized loss of soil biodiversity associated with deforestation and agricultural intensification at forest margins. The biotas were grouped into eight categories, each of which corresponded to a major functional group considered important or essential to soil function. An accurate inventory of soil organisms can assist in ecosystem management and help sustain agricultural production. The advantages and disadvantages of transect-based and grid-based sampling methods are discussed, illustrated by published protocols ranging from the original "TSBF transect", through versions developed for the alternatives to Slash-and-Burn Project (ASB to the final schemes (with variants adopted by the Conservation and Sustainable Management of Below-ground Biodiversity Project (CSM-BGBD. Consideration is given to the place and importance of replication in below-ground biological sampling and it is argued that the new sampling protocols are inclusive, i.e. designed to sample all eight biotic groups in the same field exercise; spatially scaled, i.e. provide biodiversity data at site, locality, landscape and regional levels, and link the data to land use and land cover; and statistically robust, as shown by a partial randomization of plot locations for sampling.Este trabalho faz uma revisão dos métodos de inventariado da biota edáfica nos trópicos úmidos para documentar a (hipotética perda de biodiversidade do solo associada ao desmatamento e à intensificação agrícola nas margens de florestas. A biota foi agrupada em oito categorias, cada uma correspondente a um grande grupo funcional considerado importante ou essencial para a função do solo. Um inventário cuidadoso dos organismos do solo pode auxiliar a gestão de ecossistemas e a sustentabilidade da produção agrícola. As vantagens e desvantagens de métodos de amostragem baseados em

  19. Predicting soil properties in the tropics

    NARCIS (Netherlands)

    Minasny, B.; Hartemink, A.E.

    2011-01-01

    It is practically impossible to measure soil properties continuously at each location across the globe. Therefore, it is necessary to have robust systems that can predict soil properties at a given location. That is needed in many tropical countries where the dearth of soil property measurements is

  20. Hydrological drought and wildfire in the humid tropics

    NARCIS (Netherlands)

    Taufik, Muh

    2017-01-01

    Drought is a recurrent hazard, which has happened throughout human history, and it is anticipated to become more severe in multiple regions across the world. Drought occurs in all climate regimes from humid to dry and from hot to cold. Drought is often viewed through its impact on environment and

  1. Soil metagenomics and tropical soil productivity

    OpenAIRE

    Garrett, Karen A.

    2009-01-01

    This presentation summarizes research in the soil metagenomics cross cutting research activity. Soil metagenomics studies soil microbial communities as contributors to soil health.C CCRA-4 (Soil Metagenomics)

  2. Taxonomy and remote sensing of leaf mass per area (LMA) in humid tropical forests

    Science.gov (United States)

    Gregory P. Asner; Roberta E. Martin; Raul Tupayachi; Ruth Emerson; Paola Martinez; Felipe Sinca; George V.N. Powell; S. Joseph Wright; Ariel E. Lugo

    2011-01-01

    Leaf mass per area (LMA) is a trait of central importance to plant physiology and ecosystem function, but LMA patterns in the upper canopies of humid tropical forests have proved elusive due to tall species and high diversity. We collected top-of-canopy leaf samples from 2873 individuals in 57 sites spread across the Neotropics, Australasia, and Caribbean and Pacific...

  3. Soil physical properties affecting soil erosion in tropical soils

    International Nuclear Information System (INIS)

    Lobo Lujan, D.

    2004-01-01

    detachment. Studies on necessary kinetic energy to detach one kilogram of sediments by raindrop impact have shown that the minimum energy is required for particles of 0.125 mm. Particles between 0.063 to 0.250 mm are the most vulnerable to detachment. This means that soils with high content of particles into vulnerable range, for example silty loam, loamy, fine sandy, and sandy loam are the most susceptible soils to detachment. Many aspects of soil behaviour in the field such as hydraulic conductivity water retention, soil crusting, soil compaction, and workability are influenced strongly by the primary particles. In tropical soils also a negative relation between structure stability and particles of silt, fine sand and very fine sand has been found, this is attributed to low cohesiveness of these particles. The ability of a structure to persist is known as its stability. There are two principal types of stability: the ability of the soil to retain its structure under the action of water, and the ability of the soil to retain its structure under the action of external mechanical stresses. (e.g. by wheels). Both types of stability are related with susceptibility to erosion

  4. Diurnal variations of humidity and ice water content in the tropical upper troposphere

    Directory of Open Access Journals (Sweden)

    P. Eriksson

    2010-12-01

    Full Text Available Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these two satellite combinations are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hpa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is ~7 RHi for humidity and ~50% for ice mass. The greatest ice mass for these regions is found during the afternoon, and the humidity maximum is observed to lag this peak by ~6 h. Over tropical ocean regions the variations are smaller and the maxima in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3. Direct measurement-model comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (outside the 1-σ uncertainty. The models also show clear deficiencies when it comes to amplitude and phase of the regional variations, but to varying degrees.

  5. Nitrogen Oxide Fluxes and Nitrogen Cycling during Postagricultural Succession and Forest Fertilization in the Humid Tropics.

    Science.gov (United States)

    Heather Erickson; Michael Keller; Eric Davidson

    2001-01-01

    The effects of changes in tropical land use on soil emissions of nitrous oxide (N2O) and nitric oxide (NO) are not well understood. We examined emissions of N2O and NO and their relationships to land use and forest composition, litterfall, soil nitrogen (N) pools and turnover, soil moisture, and patterns of carbon (C) cycling in a lower montane, subtropical wet region...

  6. Sediment Transport Capacity and Channel Processes in a Humid Tropical Montane River - Rio Pacuare, Costa Rica

    Science.gov (United States)

    Lind, P.; McDowell, P. F.

    2017-12-01

    Investigating sediment transport capacity as well as the spatial and temporal variations of sediment flux are critical component of river research, especially for applications in resource management and conservation, hazards assessment and planning, and riverine ecology. The bedload fraction of sediment transported through montane rivers often defines channel and bed form processes. It is understood that humid tropical montane rivers are capable of producing some of the largest quantities of sediment per unit drainage area. Bedload flux reported on a few Southeast Asian humid tropical montane rivers show that bedload constituted 16-75% of the total sediment load - this is notably higher than the generally accepted 10% of a channel's sediment load. However, to date almost all of the research done on sediment transport in humid tropical systems has focused on suspended load. This study presents annual bedload transport rate estimates for six field sites distributed within 45 river kilometers (Rkm) of the montane portion of the Rio Pacuare, located in the Talamanca Mountains of Costa Rica. This research reveals that flows capable of mobilizing the D84 occur on average at least once but often multiple times a year in this river system. The Rio Pacuare has a sufficient supply of sediment to meet its high transport capacity needs. As a result, large active bars composed of imbricated boulders define channel form at moderate and low flows throughout the study area. Differences in the magnitude, as well as the spatial and temporal variations of sediment flux at each field site are discussed in relation to stream power, and annual/inter-annual precipitation patterns. A unique mix of field and remote sensing techniques were applied to address these questions and to overcome some of the challenges of tropical river research. For example, due to the large grain size and high stream energy, grain mobilization and validation of modeled shear stress requirements for transport

  7. Effects of phosphorus addition on soil microbial biomass and community composition in three forest types in tropical China

    DEFF Research Database (Denmark)

    Liu, Lei; Gundersen, Per; Zhang, Tao

    2012-01-01

    Elevated nitrogen (N) deposition in humid tropical regions may aggravate phosphorus (P) deficiency in forest on old weathered soil found in these regions. From January 2007 to August 2009, we studied the responses of soil microbial biomass and community composition to P addition (in two monthly...

  8. Effect of climate on the seminal characteristics of boars in a region of humid tropical forest

    International Nuclear Information System (INIS)

    Henao Restrepo, Guillermo; Trujillo Aramburo, Luis Emilio; Buritica Henao, Maria Elizabet; Sierra Perez, Carlos Ignacio; Correa Londono, Guillermo; Gonzalez Boto, Oscar Domingo

    2004-01-01

    In a region of humid tropical forest, ten boars of from 12 to 24 months of age were selected to evaluate the effect of climatic variables measured on the day of semen collection and for each of preceding 45 days. On seminal characteristics, the variability of each characteristic was separated into an intra individual component and an interindividual component, using maximum likelihood estimators (PROC VARCOMP of SAS). In order to relate the seminal characteristics with the climatic variables, morphological abnormalities were grouped according to the affected spermatic region, into head. Midsection and main section abnormalities; the other characteristics were evaluated without any modification. Possible correlations between seminal characteristics and climatic variables were evaluated. In a total of 298 ejaculates collected weekly during a period of 30 weeks, except for total volume and morphological abnormalities. The seminal characteristics presented low or moderate intra and interindividual variation and were similar to those found in other latitudes, with a tendency to present greater seminal volumes and concentrations maximum temperature minimum temperature. Range among temperatures. Relative humidity and precipitation of the day of the semen collection and on each of the preceding 45 days had low effects on the seminal characteristics. It is possible that the boars in warm humid tropical areas develop a high level of adaptation that permits an adequate testicular thermoregulation that favors the spermatogenic function of the seminiferous tubules in a way that does not perceptibly affect production the seminal quality

  9. Calibration of a neutron probe for determining the humidity in deep alluvial soils

    International Nuclear Information System (INIS)

    Ferrer, A.; Rivero, H.; Lopez, F.; Cantillo, O.

    1993-01-01

    Preliminary data for the calibration of a neutron probe in deep alluvial soils for determining the humidity are reported. Comparisons of Neutron flow behaviour with the depth of the land are established. A characteristic curve of amount of detected neutrons according to the humidity percentage (from 50 to 100 % of the field humidity) is obtained

  10. Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

    KAUST Repository

    Raddadi, Noura; Giacomucci, Lucia; Marasco, Ramona; Daffonchio, Daniele; Cherif, Ameur; Fava, Fabio

    2018-01-01

    Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

  11. Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil.

    Science.gov (United States)

    Raddadi, Noura; Giacomucci, Lucia; Marasco, Ramona; Daffonchio, Daniele; Cherif, Ameur; Fava, Fabio

    2018-05-31

    Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils. From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls. Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

  12. Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

    KAUST Repository

    Raddadi, Noura

    2018-05-31

    Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

  13. Soil properties related to 60Co bioavailability in tropical soils

    International Nuclear Information System (INIS)

    Bartoly, Flavia; Wasserman, Maria Angelica; Rochedo, Elaine Ruas Rodriguez; Viana, Aline Gonzalez; Souza, Rodrigo Camara; Oliveira, Giselle Rodrigues; Reis, Wagner Goncalves Soares; Perez, Daniel Vidal

    2005-01-01

    This work presents the results of field experiments to obtain soil to plants Transfer factor (TF) for 60 Co in reference plants cultivated in Ferralsol, Acrisol and Nitisol. These soils represent the majority of Brazilian agricultural area. Values of TF varied from 0.001 to 0.05 for corn and from 0.001 to 0.81 for cabbage. Results of 60 Co TF were discussed in relation to the physical and chemical properties of the soils and 60 Co geochemical partition. The sequential chemical extraction showed that more than 40% of the 60 Co present in the soils are associated to manganese oxides. These results will provide regional values for parameters used in the environmental radiological modeling aiming to optimize the planning of emergency interventions or the waste management related to tropical soils. (author)

  14. Degradation of chlorpyrifos in tropical rice soils.

    Science.gov (United States)

    Das, Subhasis; Adhya, Tapan K

    2015-04-01

    Chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridinol) phosphorothioate] is used worldwide as an agricultural insecticide against a broad spectrum of insect pests of economically important crops including rice, and soil application to control termites. The insecticide mostly undergoes hydrolysis to diethyl thiophosphoric acid (DETP) and 3,5,6-trichloro-2-pyridinol (TCP), and negligible amounts of other intermediate products. In a laboratory-cum-greenhouse study, chlorpyrifos, applied at a rate of 10 mg kg(-1) soil to five tropical rice soils of wide physico-chemical variability, degraded with a half-life ranging from 27.07 to 3.82 days. TCP was the major metabolite under both non-flooded and flooded conditions. Chlorpyrifos degradation had significant negative relationship with electrical conductivity (EC), cation exchange capacity (CEC), clay and sand contents of the soils under non-flooded conditions. Results indicate that degradation of chlorpyrifos was accelerated with increase in its application frequency, across the representative rice soils. Management regimes including moisture content and presence or absence of rice plants also influenced the process. Biotic factors also play an important role in the degradation of chlorpyrifos as demonstrated by its convincing degradation in mineral salts medium inoculated with non-sterile soil suspension. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Physiological adaptation to the humid tropics with special reference to the West African Dwarf (WAD) goat.

    Science.gov (United States)

    Daramola, J O; Adeloye, A A

    2009-10-01

    West African Dwarf (WAD) goats are widely distributed in the subhumid and humid zones of Africa but are particularly associated with less favourable environments. Adaptive features such as feeding behaviour, efficiency of feed use and disease tolerance enable WAD goats to thrive on natural resources left untouched by other domestic ruminants. In marginal environments this goat remains the only domestic species that is able to survive. Among its physiological features small body size and low metabolic requirements are important traits that enable the animal to minimize its requirements in area or season where food sources are limited in quality and quantity. Specialized feeding behaviour and an efficient digestive system enable the animal to maximize food intake. Coat colour plays an important role in the evolved adaptation of this goat type. Reproductive fitness as manifested by prolific breeding is a major factor of adaptation. Defence mechanisms against infectious agents enable this type to thrive well in the hot humid tropics. The mechanisms involved in the regulation of these physiological functions of WAD goat are discussed. An understanding of these mechanisms could result in the development of improved techniques for enhancing goat productivity in humid environments.

  16. 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.

  17. National satellite-based humid tropical forest change assessment in Peru in support of REDD+ implementation

    Science.gov (United States)

    Potapov, P. V.; Dempewolf, J.; Talero, Y.; Hansen, M. C.; Stehman, S. V.; Vargas, C.; Rojas, E. J.; Castillo, D.; Mendoza, E.; Calderón, A.; Giudice, R.; Malaga, N.; Zutta, B. R.

    2014-12-01

    Transparent, consistent, and accurate national forest monitoring is required for successful implementation of reducing emissions from deforestation and forest degradation (REDD+) programs. Collecting baseline information on forest extent and rates of forest loss is a first step for national forest monitoring in support of REDD+. Peru, with the second largest extent of Amazon basin rainforest, has made significant progress in advancing its forest monitoring capabilities. We present a national-scale humid tropical forest cover loss map derived by the Ministry of Environment REDD+ team in Peru. The map quantifies forest loss from 2000 to 2011 within the Peruvian portion of the Amazon basin using a rapid, semi-automated approach. The available archive of Landsat imagery (11 654 scenes) was processed and employed for change detection to obtain annual gross forest cover loss maps. A stratified sampling design and a combination of Landsat (30 m) and RapidEye (5 m) imagery as reference data were used to estimate the primary forest cover area, total gross forest cover loss area, proportion of primary forest clearing, and to validate the Landsat-based map. Sample-based estimates showed that 92.63% (SE = 2.16%) of the humid tropical forest biome area within the country was covered by primary forest in the year 2000. Total gross forest cover loss from 2000 to 2011 equaled 2.44% (SE = 0.16%) of the humid tropical forest biome area. Forest loss comprised 1.32% (SE = 0.37%) of primary forest area and 9.08% (SE = 4.04%) of secondary forest area. Validation confirmed a high accuracy of the Landsat-based forest cover loss map, with a producer’s accuracy of 75.4% and user’s accuracy of 92.2%. The majority of forest loss was due to clearing (92%) with the rest attributed to natural processes (flooding, fires, and windstorms). The implemented Landsat data processing and classification system may be used for operational annual forest cover loss updates at the national level for REDD

  18. National satellite-based humid tropical forest change assessment in Peru in support of REDD+ implementation

    International Nuclear Information System (INIS)

    Potapov, P V; Dempewolf, J; Talero, Y; Hansen, M C; Stehman, S V; Vargas, C; Rojas, E J; Calderón, A; Giudice, R; Malaga, N; Zutta, B R; Castillo, D; Mendoza, E

    2014-01-01

    Transparent, consistent, and accurate national forest monitoring is required for successful implementation of reducing emissions from deforestation and forest degradation (REDD+) programs. Collecting baseline information on forest extent and rates of forest loss is a first step for national forest monitoring in support of REDD+. Peru, with the second largest extent of Amazon basin rainforest, has made significant progress in advancing its forest monitoring capabilities. We present a national-scale humid tropical forest cover loss map derived by the Ministry of Environment REDD+ team in Peru. The map quantifies forest loss from 2000 to 2011 within the Peruvian portion of the Amazon basin using a rapid, semi-automated approach. The available archive of Landsat imagery (11 654 scenes) was processed and employed for change detection to obtain annual gross forest cover loss maps. A stratified sampling design and a combination of Landsat (30 m) and RapidEye (5 m) imagery as reference data were used to estimate the primary forest cover area, total gross forest cover loss area, proportion of primary forest clearing, and to validate the Landsat-based map. Sample-based estimates showed that 92.63% (SE = 2.16%) of the humid tropical forest biome area within the country was covered by primary forest in the year 2000. Total gross forest cover loss from 2000 to 2011 equaled 2.44% (SE = 0.16%) of the humid tropical forest biome area. Forest loss comprised 1.32% (SE = 0.37%) of primary forest area and 9.08% (SE = 4.04%) of secondary forest area. Validation confirmed a high accuracy of the Landsat-based forest cover loss map, with a producer’s accuracy of 75.4% and user’s accuracy of 92.2%. The majority of forest loss was due to clearing (92%) with the rest attributed to natural processes (flooding, fires, and windstorms). The implemented Landsat data processing and classification system may be used for operational annual forest cover loss updates at the national level

  19. Management and conservation of tropical acid soils for sustainable crop production. Proceedings of a consultants meeting

    International Nuclear Information System (INIS)

    2000-06-01

    Forests of the tropics are invaluable ecosystems of global, regional and local importance, particularly in terms of protection and conservation of biodiversity and water resources. The indiscriminate conversion of tropical forests into agricultural land as a result of intense human activities - logging and modem shifting cultivation - continues to cause soil erosion and degradation. However, the acid savannahs of the world, such as the cerrado of Brazil, the Llanos in Venezuela and Colombia, the savannahs of Africa, and the largely anthropic savannahs of tropical Asia, encompass vast areas of potentially arable land. The acid soils of the savannahs are mostly considered marginal because of low inherent fertility and susceptibility to rapid degradation. These constraints for agricultural development are exacerbated by the poverty of new settlers who try to cultivate such areas after deforestation. Low- or minimum-input systems are not sustainable on these tropical acid soils but, with sufficient investment and adequate technologies, they can be highly productive. Thus, there is a need to develop management practices for sustainable agricultural production systems on such savannah acid soils. The Soil and Water Management and Crop Nutrition Sub-programme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture strongly supports an integrated approach to soil, water and nutrient management within cropping systems. In this context, nuclear and related techniques can be used to better understand the processes and factors influencing the productivity of agricultural production systems, and improve them through the use of better soil, water and nutrient management practices. A panel of experts actively engaged in field projects on acid soils of savannah agro-ecosystems in the humid and sub-humid tropics convened in March 1999 in Vienna to review and discuss recent research progress, along the following main lines of investigation: (i) utilization of

  20. Effect of Stocking Density on Performance of Growing Rabbits in Semi-Humid Tropics

    Directory of Open Access Journals (Sweden)

    Iyeghe-Erakpotobor Grace, T.

    2005-01-01

    rabbits as stocking density increases in week 1-2 and 3-4. Feed conversion ratio was poorer at higher densities (16.7, 20 rabbits/m2 than at lower densities (6.7, 10, 13.3 rabbits/m2. There was no definite relationship between stocking density and mortality rate of rabbits. Rabbits stocked at 6.7 to 13.3 rabbits/m2 had significantly higher body condition score and fur condition compared with those stocked at 16.7 and 20 rabbits/m2. There were no differences in fighty bites for all the stocking densities. It is concluded from this study that the optimum stocking density for rabbits in the semi-humid tropics is 13.3 rabbits/m2.

  1. Optimizing cloud removal from satellite remotely sensed data for monitoring vegetation dynamics in humid tropical climate

    International Nuclear Information System (INIS)

    Hashim, M; Pour, A B; Onn, C H

    2014-01-01

    Remote sensing technology is an important tool to analyze vegetation dynamics, quantifying vegetation fraction of Earth's agricultural and natural vegetation. In optical remote sensing analysis removing atmospheric interferences, particularly distribution of cloud contaminations, are always a critical task in the tropical climate. This paper suggests a fast and alternative approach to remove cloud and shadow contaminations for Landsat Enhanced Thematic Mapper + (ETM + ) multi temporal datasets. Band 3 and Band 4 from all the Landsat ETM + dataset are two main spectral bands that are very crucial in this study for cloud removal technique. The Normalise difference vegetation index (NDVI) and the normalised difference soil index (NDSI) are two main derivatives derived from the datasets. Change vector analysis is used in this study to seek the vegetation dynamics. The approach developed in this study for cloud optimizing can be broadly applicable for optical remote sensing satellite data, which are seriously obscured with heavy cloud contamination in the tropical climate

  2. A critical assessment of the JULES land surface model hydrology for humid tropical environments

    Science.gov (United States)

    Zulkafli, Z.; Buytaert, W.; Onof, C.; Lavado, W.; Guyot, J. L.

    2013-03-01

    Global land surface models (LSMs) such as the Joint UK Land Environment Simulator (JULES) are originally developed to provide surface boundary conditions for climate models. They are increasingly used for hydrological simulation, for instance to simulate the impacts of land use changes and other perturbations on the water cycle. This study investigates how well such models represent the major hydrological fluxes at the relevant spatial and temporal scales - an important question for reliable model applications in poorly understood, data-scarce environments. The JULES-LSM is implemented in a 360 000 km2 humid tropical mountain basin of the Peruvian Andes-Amazon at 12-km grid resolution, forced with daily satellite and climate reanalysis data. The simulations are evaluated using conventional discharge-based evaluation methods, and by further comparing the magnitude and internal variability of the basin surface fluxes such as evapotranspiration, throughfall, and surface and subsurface runoff of the model with those observed in similar environments elsewhere. We find reasonably positive model efficiencies and high correlations between the simulated and observed streamflows, but high root-mean-square errors affecting the performance in smaller, upper sub-basins. We attribute this to errors in the water balance and JULES-LSM's inability to model baseflow. We also found a tendency to under-represent the high evapotranspiration rates of the region. We conclude that strategies to improve the representation of tropical systems to be (1) addressing errors in the forcing and (2) incorporating local wetland and regional floodplain in the subsurface representation.

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

    Directory of Open Access Journals (Sweden)

    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. Morphological, physico-chemical and geochemical characterization of two weathering profiles developed on limestone from the Mintom Formation in the tropical humid zone of Cameroon

    Science.gov (United States)

    Engon, Thierry Constant; Abane, Monique Abessolo-Angue; Zo'o Zame, Philémon; Ekomane, Emile; Bekoa, Etienne; Mvogo, Kisito; Bitom, Dieudonné

    2017-07-01

    The purpose of this work was to study the morphology, physico-chemistry and geochemistry of two weathering profiles developed on limestone using observations area, basic analysis, and X-ray Fluorescence. The results showed that these soils have three main sets from the bottom to the top: the alteritic set (isalteritic and alloteritic horizons), the glaebular set (exclusively on profile TCR) with a more or less hardened duricrust, and the loose set (loose clayey and humiferous horizons). The soils were acid, with moderate cation exchange capacity, low to moderate sum of bases (0.96-8.24 meq/100 g). The base saturation, organic carbon and C/N ratio (˂15) were low. The geochemical signatures of the bedrock along the whole profile are not preserved, with SiO2 (∼45.26 wt%) being the dominant oxide followed by Al2O3 (∼13.37 wt%) and Fe2O3 (∼09.36 wt%). Also, the Si/Al ratio is always higher than 1 (2.17-4.43). The other major oxides such as MgO, K2O and Na2O show negligible contents in the profiles, while CaO is well represented at the top of the isalteritic horizon reaching 14.25 wt%. Weathering indices show that CaO, MgO, Na2O, and K2O are rapidly lost during chemical weathering and the amount of these elements lost is proportional to the degree of weathering. Humid tropical soils show pedological evolution mainly dominated by the behaviour of silicon and aluminium, with an intensive release of carbonates during the early stage of weathering. However, contrary to soils in temperate climates, in which bisiallitisation is the predominant process, soils of the humid tropical zone, characterized by high evacuation of silica concomitantly to notable accumulations of aluminium, allitisation and monosiallitisation predominate.

  5. The formation of fire residues associated with hunter-gatherers in humid tropical environments: A geo-ethnoarchaeological perspective

    Science.gov (United States)

    Friesem, David E.; Lavi, Noa; Madella, Marco; Boaretto, Elisabetta; Ajithparsad, P.; French, Charles

    2017-09-01

    Tropical forests have been an important human habitat and played a significant role in early human dispersal and evolution. Likewise, the use of fire, besides being one of the exceptional characteristics of humans, serves as a marker for human evolution. While the use of fire by prehistoric hunter-gatherers is relatively well documented in arid and temperate environments, the archaeological evidence in humid tropical environment is to date very limited. We first review the archaeological evidence for hunter-gatherer use of fire in humid tropical environments and suggest that better understanding of formation processes is required. We present a geo-ethnoarchaeological study from South India, involving ethnography, excavations and laboratory-based analyses in order to build a new framework to study fire residues in humid tropical forests associated with hunter-gatherer's use of fire. Ethnographic observations point to a dynamic and ephemeral use of hearths. Hearths location were dictated by the social and ever-changing social dynamics of the site. The hearths deposited small amount of residues which were later swept on a daily basis, re-depositing ash and charcoal in waste areas and leaving only a microscopic signal in the original location. Particular acidic conditions and intensive biological activity within tropical sediments result in the complete dissolution of ash and bones while favouring the preservation of charcoal and phytoliths. Consequently, the identification of fire residues in humid tropical forests and the reconstruction of the human use of fire must involve multi-proxy microscopic analysis to detect its micro-signatures.

  6. Agriculture at the Edge: Landscape Variability of Soil C Stocks and Fluxes in the Tropical Andes

    Science.gov (United States)

    Riveros-Iregui, D. A.; Peña, C.

    2015-12-01

    Paramos, or tropical alpine grasslands occurring right above the forest tree-line (2,800 - 4,700 m), are among the most transformed landscapes in the humid tropics. In the Tropical Andes, Paramos form an archipelago-like pattern from Northern Colombia to Central Peru that effectively captures atmospheric moisture originated in the Amazon-Orinoco basins, while marking the highest altitude capable of sustaining vegetation growth (i.e., 'the edge'). This study investigates the role of land management on mediating soil carbon stocks and fluxes in Paramo ecosystems of the Eastern Cordillera of Colombia. Observations were collected at a Paramo site strongly modified by land use change, including active potato plantations, pasture, tillage, and land abandonment. Results show that undisturbed Paramos soils have high total organic carbon (TOC), high soil water content (SWC), and low soil CO2 efflux (RS) rates. However, Paramo soils that experience human intervention show lower TOC, higher and more variable RS rates, and lower SWC. This study demonstrates that changes in land use in Paramos affect differentially the accumulation and exchange of soil carbon with the atmosphere and offers implications for management and protection strategies of what has been deemed the fastest evolving biodiversity ecosystem in the world.

  7. Comparisons of urban and rural heat stress conditions in a hot–humid tropical city

    Directory of Open Access Journals (Sweden)

    Ahmed A. Balogun

    2010-11-01

    Full Text Available Background: In recent years the developing world, much of which is located in the tropical countries, has seen dramatic growth of its urban population associated with serious degradation of environmental quality. Climate change is producing major impacts including increasing temperatures in these countries that are considered to be most vulnerable to the impact of climate change due to inadequate public health infrastructure and low income status. However, relevant information and data for informed decision making on human health and comfort are lacking in these countries. Objective: The aim of this paper is to study and compare heat stress conditions in an urban (city centre and rural (airport environments in Akure, a medium-sized tropical city in south-western Nigeria during the dry harmattan season (January–March of 2009. Materials and methods: We analysed heat stress conditions in terms of the mean hourly values of the thermohygrometric index (THI, defined by simultaneous in situ air temperature and relative humidity measurements at both sites. Results: The urban heat island (UHI exists in Akure as the city centre is warmer than the rural airport throughout the day. However, the maximum UHI intensity occurs at night between 1900 and 2200 hours local time. Hot conditions were predominant at both sites, comfortable conditions were only experienced in the morning and evenings of January at both sites, but the rural area has more pleasant morning and evenings and less of very hot and torrid conditions. January has the lowest frequency of hot and torrid conditions at both sites, while March and February has the highest at the city centre and the airport, respectively. The higher frequencies of high temperatures in the city centre suggest a significant heat stress and health risk in this hot humid environment of Akure. Conclusions: More research is needed to achieve better understanding of the seasonal variation of indoor and outdoor heat stress

  8. Groundwater circulations within a tropical humid andesitic volcanic watershed using the temperature as a tracer

    Science.gov (United States)

    Selles, Adrien; Violette, Sophie; Hendrayana, Heru

    2014-05-01

    Groundwater flow within volcano-detritic environment, is of prime importance to many human needs and activities, from the supply of clean drinking water to the extraction of hydrocarbons or geothermal energy. However, the heterogeneity of the geological formations makes difficult to quantify the groundwater spatial distribution. Moreover, its temporal variation in tropical humid regions is sometimes poorly known. For instance, the surronding of the Merapi volcano, in Central Java, Indonesia, is an area of high but seasonal rainfall, and extensive crop irrigation. It has a large population and a need to increase food and potable water supplies depending upon exploiting groundwater ressources. The stress on these resources increases with the intensification of the demography, the agricultural practices and the industrial exploitations. In order to implement a sustainable management of the water resources, the description of the groundwater circulations and the quantification of the resources is needed. A mutidisciplinary approach has been performed at the watershed scale, including geology, hydrogeochemistry and long term hydrogeological monitoring. The data synthesis and constisency have been confirm with a numerical model of physical processes. Based on a geological and geomorphological study, the hydrogeological watershed on the Eastern flank of the Merapi volcano is composed by an alternation of aquitards (mainly ashes, tuffs and clay) and aquifers (sand, gravel and boulders). The deep aquifers are agenced in conduit following the burried channel of the paleo-rivers. The eastern flank of Merapi provides excellent example of a volcanic-sedimentary environment. From 20 cold springs of 3 spring zones, sampled on 2 hydrological years (2011 to 2013), the study of the transfer into the saturated zone from upstream to downstream, given the geological context and topography, allows to estimate the role of supply from high and low altitudes to the recharge processes. The

  9. Perceived Thermal Discomfort and Stress Behaviours Affecting Students’ Learning in Lecture Theatres in the Humid Tropics

    Directory of Open Access Journals (Sweden)

    Tamaraukuro Tammy Amasuomo

    2016-04-01

    Full Text Available The study investigated the relationship between students’ perceived thermal discomfort and stress behaviours affecting their learning in lecture theatres in the humid tropics. Two lecture theatres, LTH-2 and 3, at the Niger Delta University, Nigeria, were used for the study. Two groups of students from the Faculties of Agriculture and Engineering and the Department of Technology Education constituted the population. The sample size selected through random sampling for Groups A and B was 210 and 370 students, respectively. Objective and self-report instruments were used for data collection. The objective instrument involved physical measurement of the two lecture theatres and of the indoor temperature, relative humidity and air movement. The self-report instrument was a questionnaire that asked for the students perceived indoor thermal discomfort levels and the effect of indoor thermal comfort level on perceived stress behaviours affecting their learning. The objective indoor environmental data indicated thermal discomfort with an average temperature of 29–32 °C and relative humidity of 78% exceeding the ASHARE [1] and Olgyay [2].The students’ experienced a considerable level of thermal discomfort and also perceived that stress behaviours due to thermal discomfort affected their learning. Further, there were no significant differences in the perceived thermal discomfort levels of the two groups of students in LTH-2 and 3. Furthermore, stress behaviours affecting learning as perceived by the two groups of students did not differ significantly. In addition, no correlation existed between the perceived indoor thermal discomfort levels and stress behaviour levels affecting learning for students in LTH-2, because the arousal level of the students in the thermal environment was likely higher than the arousal level for optimal performance [3,4]. However, a correlation existed in the case of students in LTH-3, which was expected because it only

  10. Urban heat island and bioclimatological conditions in a hot-humid tropical city: the example of Akure, Nigeria

    Directory of Open Access Journals (Sweden)

    Balogun, Ifeoluwa A.

    2014-09-01

    Full Text Available The impact of weather on human health has become an issue of increased significance in recent times, considering the increasing rate of urbanisation and the much associated heat island phenomenon. This study examines the urbanisation influence on human bioclimatic conditions in Akure, a medium sized hot-humid tropical city in Nigeria, utilising data from measurements at urban and rural sites in the city. Differences in the diurnal, monthly and seasonal variation of human bioclimatic characteristics between both environments were evaluated and tested for statistical significance. Higher frequencies of high temperatures observed in the city centre suggest a significant heat stress and health risk in this hot-humid city.

  11. Design of evaporative-cooling roof for decreasing air temperatures in buildings in the humid tropics

    Science.gov (United States)

    Kindangen, Jefrey I.; Umboh, Markus K.

    2017-03-01

    This subject points to assess the benefits of the evaporative-cooling roof, particularly for buildings with corrugated zinc roofs. In Manado, many buildings have roofed with corrugated zinc sheets; because this material is truly practical, easy and economical application. In general, to achieve thermal comfort in buildings in a humid tropical climate, people applying cross ventilation to cool the air in the room and avoid overheating. Cross ventilation is a very popular path to achieve thermal comfort; yet, at that place are other techniques that allow reducing the problem of excessive high temperature in the room in the constructions. This study emphasizes applications of the evaporative-cooling roof. Spraying water on the surface of the ceiling has been executed on the test cell and the reuse of water after being sprayed and cooled once more by applying a heat exchanger. Initial results indicate a reliable design and successfully meet the target as an effective evaporative-cooling roof technique. Application of water spraying automatic and cooling water installations can work optimally and can be an optimal model for the cooling roof as one of the green technologies. The role of heat exchangers can lower the temperature of the water from spraying the surface of the ceiling, which has become a hot, down an average of 0.77° C. The mass flow rate of the cooling water is approximately 1.106 kg/h and the rate of heat flow is around 515 Watt, depend on the site.

  12. Night ventilation at courtyard housing estate in warm humid tropic for sustainable environment

    Science.gov (United States)

    Defiana, Ima; Teddy Badai Samodra, FX; Setyawan, Wahyu

    2018-03-01

    The problem in the night-time for warm humid tropic housing estate is thermal discomfort. Heat gains accumulation from building envelope, internal heat gains and activities of occupants influence indoor thermal comfort. Ventilation is needed for transfer or removes heat gains accumulation to outdoor. This study describes the role of an inner courtyard to promote pressure difference. Pressure difference as a wind driven force to promote wind velocity thereby could transfer indoor heat gains accumulation to outdoor of building. A simulation used as the research method for prediction wind velocity. Purposive sampling used as the method to choose building sample with similar inner courtyards. The field survey was conducted to obtain data of inner courtyard typologies and two housing were used as model simulation. Furthermore, the simulation is running in steady state mode, at 05.00 pm when the occupants usually close window. But the window should be opened in the night-time to transfer indoor heat gain to outdoor. The result shows that the factor influencing physiological cooling as consequences of inner courtyard are height to width ratio, the distance between inner courtyard to windward, window configuration and the inner courtyard design-the proportion between the length, the width, and the height.

  13. Flood moderation by large reservoirs in the humid tropics of Western ghat region of Kerala, India

    Energy Technology Data Exchange (ETDEWEB)

    Abe, George [Centre for Water Resources Development and Management, Sub Centre, Kottayam South P.O, Kottayam-686 039, Kerala (India); James, E.J. [Water Institute and Dean (Research), Karunya University, Coimbatore-641 114, Tamil Nadu (India)

    2013-07-01

    Kerala State located in the humid tropics receives an average rainfall of 2810 mm. On an average 85% of this rainfall is received during the two monsoons spread from June to November. Midland and lowland regions of several of the river basins of Kerala experience severe flood events during the monsoons. Idamalayar hydro-electric project (1987) in Periyar River basin envisages flood control apart from power generation. This paper analyzes the flood moderation by Idamalayar reservoir considering the storage regime (inflow and outflow) which is subjected to a strong inter annual variability. The role of Idamalayar reservoir in controlling the monsoon floods is analyzed using daily data (1987-2010). The results of analysis show that the flood moderation by the reservoir is 92% when water storage is less than 50%. The reduction is 87% when reservoir storage is between 50 to 90% and moderation reduces to 62% when the reservoir storage is above 90%. Non-parametric trend analysis of fifty years of hydrologic data shows a reducing trend in inflow and storage during south-west monsoon which reduced spill and subsequent flood events during north-east monsoon.

  14. Final report of the FAO/IAEA/SIDA co-ordinated research programme on the use of isotope studies on increasing and stabilizing plant productivity in low phosphate and semi-arid and sub-humid soils of the tropics and sub-tropics, October 1989 - October 1994. SIDA annual review 1995

    International Nuclear Information System (INIS)

    Kumarasinghe, Saliya

    1994-11-01

    In developing countries low soil resources and fragile soils are the major limitation to crop production. This project addresses two of the most common and serious soil limitations to agricultural productivity in the developing world, i.e., low soil moisture and low soil nutrients, especially phosphorus and nitrogen. For economic reasons, these problems can rarely be solved in developing countries by expensive soil inputs. A more effective approach would be to identify genotypes (of commonly used species) which are highly effective in the use of the soil resources for plant productivity and to integrate these with minimum inputs of fertilizers where necessary. Relatively simple isotope and nuclear related methods are extremely important in identifying such efficient genotypes. The project focused on Africa (but not necessarily exclusively) and on food crops as well as on fuel wood trees. Many African countries are in a fuel wood crisis which will get worse. Integrating fuelwood trees into agricultural/pastoral practices will not only help alleviate this crisis in the agricultural community but will form a component part in stabilizing fragile soils against erosion and desertification. The project was primarily institution building in nature and provided training, equipment and expert services to participating institutes and through these direct recipients, the project aimed at reaching the target beneficiaries who are basically farmers and other agriculturalists. The final goal was to develop agricultural practices that would contribute to increasing and sustaining crop productivity in soils of low water and low phosphate levels

  15. Hygroscopical behaviour of basic electrodes in a tropical humid climate. Comportamiento microscopico de ciertos electrodos revistidos de caracter basico en clima tropical humedo

    Energy Technology Data Exchange (ETDEWEB)

    Valencia, E.; Galeano, N.J.

    1993-01-01

    The study of the wetting kynetics of basic electrodes in a tropical humid climate is very important since the water contained in them is the main source for the atomic hydrogen absorbed by the fused metal during electric arc welding. It is also the origin of multiple defects in the added metal. A calculating method is established for evaluating the kynetics of wetness incorporation to the coating of basic electrodes exposed to a humid tropical climate. The method is based on the Fick's diffusion equation for both adequate system geometry and boundary conditions, which allows the evaluation of the effective diffusion coefficient and critical times of exposure to the different environments, along with the packing and storage conditions of electrodes. (Author)

  16. Hygroscopical behaviour of basic electrodes in a tropical humid climate. Comportamiento microscopico de ciertos electrodos revistidos de caracter basico en clima tropical humedo

    Energy Technology Data Exchange (ETDEWEB)

    Valencia, E; Galeano, N J

    1993-01-01

    The study of the wetting kynetics of basic electrodes in a tropical humid climate is very important since the water contained in them is the main source for the atomic hydrogen absorbed by the fused metal during electric arc welding. It is also the origin of multiple defects in the added metal. A calculating method is established for evaluating the kynetics of wetness incorporation to the coating of basic electrodes exposed to a humid tropical climate. The method is based on the Fick's diffusion equation for both adequate system geometry and boundary conditions, which allows the evaluation of the effective diffusion coefficient and critical times of exposure to the different environments, along with the packing and storage conditions of electrodes. (Author)

  17. PAIR INFLUENCE OF WIND SPEED AND MEAN RADIANT TEMPERATURE ON OUTDOOR THERMAL COMFORT OF HUMID TROPICAL ENVIRONMENT

    Directory of Open Access Journals (Sweden)

    Sangkertadi Sangkertadi

    2016-01-01

    Full Text Available The purposes of this article is to explore knowledge of outdoor thermal comfort in humid tropical environment for urban activities especially for people in walking activity, and those who stationary/seated with moderate action. It will be characterized the pair influence of wind speed and radiant temperature on the outdoor thermal comfort. Many of researchers stated that those two microclimate variables give significant role on outdoor thermal comfort in tropical humid area. Outdoor Tropical Comfort (OTC model was used for simulation in this study. The model output is comfort scale that refers on ASHRAE definition. The model consists of two regression equations with variables of air temperature, globe temperature, wind speed, humidity and body posture, for two types of activity: walking and seated. From the results it can be stated that there is significant role of wind speed to reduce mean radiant temperature and globe temperature, when the velocity is elevated from 0.5 m/s to 2 m/s. However, the wind has not play significant role when the speed is changed from 2 m/s to 3.5 m/s. The results of the study may inspire us to implement effectiveness of electrical-fan equipment for outdoor space in order to get optimum wind speed, coupled with optimum design of shading devices to minimize radiant temperature for thermal comfort.

  18. Agroecology and healthy food systems in semi-humid tropical Africa: Participatory research with vulnerable farming households in Malawi.

    Science.gov (United States)

    Nyantakyi-Frimpong, Hanson; Kangmennaang, Joseph; Bezner Kerr, Rachel; Luginaah, Isaac; Dakishoni, Laifolo; Lupafya, Esther; Shumba, Lizzie; Katundu, Mangani

    2017-11-01

    This paper assesses the relationship between agroecology, food security, and human health. Specifically, we ask if agroecology can lead to improved food security and human health among vulnerable smallholder farmers in semi-humid tropical Africa. The empirical evidence comes from a cross-sectional household survey (n=1000) in two districts in Malawi, a small country in semi-humid, tropical Africa. The survey consisted of 571 agroecology-adoption and 429 non-agroecology-adoption households. Ordered logistics regression and average treatment effects models were used to determine the effect of agroecology adoption on self-reported health. Our results show that agroecology-adoption households (OR=1.37, p=0.05) were more likely to report optimal health status, and the average treatment effect shows that adopters were 12% more likely to be in optimal health. Furthermore, being moderately food insecure (OR=0.59, p=0.05) and severely food insecure (OR=0.89, p=0.10) were associated with less likelihood of reporting optimal health status. The paper concludes that with the adoption of agroecology in the semi-humid tropics, it is possible for households to diversify their crops and diets, a condition that has strong implications for improved food security, good nutrition and human health. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Viability of microcomputed tomography to study tropical marine worm galleries in humid muddy sediments

    International Nuclear Information System (INIS)

    Pennafirme, Simone F.; Machado, Alessandra S.; Lima, Inaya; Suzuki, Katia N.; Lopes, Ricardo T.

    2013-01-01

    sediment, decreasing the accuracy of the wormholes identification. To sum up, the images show that the investigation of small tropical marine worm's galleries within humid muddy sediments is possible by this X-ray image technique. The final 3D images were performed in two different pixel sizes (23.83 μm and 30.08 μm), which allow the identification/quantification of galleries and, therefore, supporting the improvement of knowledge on bioturbation processes in marine benthic systems. (author)

  20. Viability of microcomputed tomography to study tropical marine worm galleries in humid muddy sediments

    Energy Technology Data Exchange (ETDEWEB)

    Pennafirme, Simone F., E-mail: sipennafirme@gmail.com [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Biologia. Dept. de Biologia Marinha; Machado, Alessandra S.; Lima, Inaya; Suzuki, Katia N.; Lopes, Ricardo T., E-mail: machado@lin.ufrj.br, E-mail: inaya@lin.ufrj.br, E-mail: norisuzuki6@yahoo.com.br, E-mail: ricardo@lin.ufj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), RJ (Brazil). Lab. de Instrumentacao Nuclear

    2013-07-01

    within the sediment, decreasing the accuracy of the wormholes identification. To sum up, the images show that the investigation of small tropical marine worm's galleries within humid muddy sediments is possible by this X-ray image technique. The final 3D images were performed in two different pixel sizes (23.83 μm and 30.08 μm), which allow the identification/quantification of galleries and, therefore, supporting the improvement of knowledge on bioturbation processes in marine benthic systems. (author)

  1. Soil CO2 flux from three ecosystems in tropical peatland of Sarawak, Malaysia

    International Nuclear Information System (INIS)

    Melling, Lulie; Hatano, Ryusuke

    2005-01-01

    Soil CO 2 flux was measured monthly over a year from tropical peatland of Sarawak, Malaysia using a closed-chamber technique. The soil CO 2 flux ranged from 100 to 533 mg C/m 2 /h for the forest ecosystem, 63 to 245 mg C/m 2 /h for the sago and 46 to 335 mg C/m 2 /h for the oil palm. Based on principal component analysis (PCA), the environmental variables over all sites could be classified into three components, namely, climate, soil moisture and soil bulk density, which accounted for 86% of the seasonal variability. A regression tree approach showed that CO 2 flux in each ecosystem was related to different underlying environmental factors. They were relative humidity for forest, soil temperature at 5 cm for sago and water-filled pore space for oil palm. On an annual basis, the soil CO 2 flux was highest in the forest ecosystem with an estimated production of 2.1 kg C/m 2 /yr followed by oil palm at 1.5 kg C/m 2 /yr and sago at 1.1 kg C/m 2 /yr. The different dominant controlling factors in CO 2 flux among the studied ecosystems suggested that land use affected the exchange of CO 2 between tropical peatland and the atmosphere

  2. Dependence of the concentrations of "1"3"7Cs and potassium in extracted soil solutions on soil humidity before centrifugation

    International Nuclear Information System (INIS)

    Prorok, V.V.; Datsenko, O.Yi.; Bulavyin, L.A.; Zlens'kij, S.Je.; Melnichenko, L.Yu.; Rozuvan, S.G.; Poperenko, L.V.; White, P.J.

    2017-01-01

    Concentrations of 137Cs and potassium in solutions extracted by centrifugation from soils selected at some experimental sites in the 10-km Exclusion Zone of Chornobyl Nuclear Plant were determined. The results showed that for the majority of investigated soils, the concentration of 137Cs in soil solution depends on the humidity of the soil before centrifugation. It is possible to explain the dependence of the concentration of 137Cs in the soil solution on soil humidity from the dependence of the concentrations of molecules of different molecular-gravimetric fractions in soil solution on soil humidity. Considerable amount of 137Cs in soil solution is associated with these molecules, that is why the concentration of 137Cs in the extracted soil solution changes with the humidity of soil. These dependences differ between soils. For the majority of investigated soils the concentration of 137Cs in the extracted soil solution increases with increasing humidity of the soil. By contrast, soil humidity had no effect on the potassium concentration in the extracted soil solution for any soil investigated. It is concluded, that potassium is practically not associated with molecules of different molecular-gravimetric fractions in the extracted soil solutions

  3. The Role of Temperature and Humidity on Seasonal Influenza in Tropical Areas: Guatemala, El Salvador and Panama, 2008-2013

    Science.gov (United States)

    Soebiyanto, Radina P.; Clara, Wilfrido; Jara, Jorge; Castillo, Leticia; Sorto, Oscar Rene; Marinero, Sidia; Antinori, Maria E. Barnett de; McCracken, John P.; Widdowson, Marc-Alain; Azziz-Baumgartner, Eduardo; hide

    2014-01-01

    Background: The role of meteorological factors on influenza transmission in the tropics is less defined than in the temperate regions. We assessed the association between influenza activity and temperature, specific humidity and rainfall in 6 study areas that included 11 departments or provinces within 3 tropical Central American countries: Guatemala, El Salvador and Panama. Method/ Findings: Logistic regression was used to model the weekly proportion of laboratory-confirmed influenza positive samples during 2008 to 2013 (excluding pandemic year 2009). Meteorological data was obtained from the Tropical Rainfall Measuring Mission satellite and the Global Land Data Assimilation System. We found that specific humidity was positively associated with influenza activity in El Salvador (Odds Ratio (OR) and 95% Confidence Interval of 1.18 (1.07-1.31) and 1.32 (1.08-1.63)) and Panama (OR = 1.44 (1.08-1.93) and 1.97 (1.34-2.93)), but negatively associated with influenza activity in Guatemala (OR = 0.72 (0.6-0.86) and 0.79 (0.69-0.91)). Temperature was negatively associated with influenza in El Salvador's west-central departments (OR = 0.80 (0.7-0.91)) whilst rainfall was positively associated with influenza in Guatemala's central departments (OR = 1.05 (1.01-1.09)) and Panama province (OR = 1.10 (1.05-1.14)). In 4 out of the 6 locations, specific humidity had the highest contribution to the model as compared to temperature and rainfall. The model performed best in estimating 2013 influenza activity in Panama and west-central El Salvador departments (correlation coefficients: 0.5-0.9). Conclusions/Significance: The findings highlighted the association between influenza activity and specific humidity in these 3 tropical countries. Positive association with humidity was found in El Salvador and Panama. Negative association was found in the more subtropical Guatemala, similar to temperate regions. Of all the study locations, Guatemala had annual mean temperature and specific

  4. Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed

    NARCIS (Netherlands)

    Bayabil, Haimanote K.; Tebebu, Tigist Y.; Stoof, Cathelijne R.; Steenhuis, Tammo S.

    2016-01-01

    Placement and hence performance of many soil and water conservation structures in tropical highlands has proven to be challenging due to uncertainty of the actual location of runoff-generating areas in the landscape. This is the case especially in the (sub-)humid areas of the Ethiopian highlands,

  5. Modelling soil moisture under different land covers in a sub-humid ...

    Indian Academy of Sciences (India)

    in the sub-humid climate within the Western Ghats, Karnataka, India. ... carried out with respect to the water-holding capacity of the soils with the aim of explaining ... changes have taken place in the land-use/cover of ... about 20–25 km inland.

  6. Volumetric humidity timely variation, at different depths, in soils of a toposequence of the Reconcavo Baiano - Brazil

    International Nuclear Information System (INIS)

    Ribeiro, Antonio Carlos; Costa, Liovando Marciano da; Paiva, Arlicelio de Queiroz; Souza, Luciano da Silva; Santana, Marlete Bastos

    1997-01-01

    Aiming the time basis volumetric humidity evaluation, at different depths, the present work has been developed in a Reconcavo Baiano toposequence consisting of three different soils, in accordance with the distances from the toposequence begin. A neutron probe has been used for determination of the soil water contents. The relative counting of the neutron probe has been converted to gravimetric humidity by using regression equation for each type of soil

  7. Transpiration efficiency of a tropical pioneer tree (Ficus insipida) in relation to soil fertility.

    Science.gov (United States)

    Cernusak, Lucas A; Winter, Klaus; Aranda, Jorge; Turner, Benjamin L; Marshall, John D

    2007-01-01

    The response of whole-plant water-use efficiency, termed transpiration efficiency (TE), to variation in soil fertility was assessed in a tropical pioneer tree, Ficus insipida Willd. Measurements of stable isotope ratios (delta(13)C, delta(18)O, delta(15)N), elemental concentrations (C, N, P), plant growth, instantaneous leaf gas exchange, and whole-plant water use were used to analyse the mechanisms controlling TE. Plants were grown individually in 19 l pots with non-limiting soil moisture. Soil fertility was altered by mixing soil with varying proportions of rice husks, and applying a slow release fertilizer. A large variation was observed in leaf photosynthetic rate, mean relative growth rate (RGR), and TE in response to experimental treatments; these traits were well correlated with variation in leaf N concentration. Variation in TE showed a strong dependence on the ratio of intercellular to ambient CO(2) mole fractions (c(i)/c(a)); both for instantaneous measurements of c(i)/c(a) (R(2)=0.69, P <0.0001, n=30), and integrated estimates based on C isotope discrimination (R(2)=0.88, P <0.0001, n=30). On the other hand, variations in the leaf-to-air humidity gradient, unproductive water loss, and respiratory C use probably played only minor roles in modulating TE in the face of variable soil fertility. The pronounced variation in TE resulted from a combination of the strong response of c(i)/c(a) to leaf N, and inherently high values of c(i)/c(a) for this tropical tree species; these two factors conspired to cause a 4-fold variation among treatments in (1-c(i)/c(a)), the term that actually modifies TE. Results suggest that variation in plant N status could have important implications for the coupling between C and water exchange in tropical forest trees.

  8. Tropical forest soil microbial communities couple iron and carbon biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dubinsky, E.A.; Silver, W.L.; Firestone, M.K.

    2009-10-15

    We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500 - 5000 mm yr-1) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 x 10{sup 9} cells per gram soil) indicated that they possess extensive metabolic capacity to catalyze the reduction of iron minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could account for up to 44 % of organic carbon oxidation. Iron reducers appeared to compete with methanogens when labile carbon availability was limited. We found large numbers of bacteria that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron-reducers. the coexistence of large populations of ironreducing and iron-oxidizing bacteria is evidence for rapid iron cycling between its reduced and oxidized states, and suggests that mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and inhibit CH4 production in these upland tropical forests.

  9. Cropping enhances mycorrhizal benefits to maize in a tropical soil

    Czech Academy of Sciences Publication Activity Database

    Jemo, M.; Souleymanou, A.; Frossard, E.; Jansa, Jan

    2014-01-01

    Roč. 79, č. 2014 (2014), s. 117-124 ISSN 0038-0717 R&D Projects: GA MŠk(CZ) LK11224; GA ČR GAP504/12/1665 Institutional support: RVO:61388971 Keywords : tropical soil * mycorrhizal benefits * southern Cameroon Subject RIV: EE - Microbiology, Virology Impact factor: 3.932, year: 2014

  10. Bioremediation of a crude oil polluted tropical rain forest soil ...

    African Journals Online (AJOL)

    These results suggest that Biostimulation with tilling (nutrient enhanced in-situ bioremediation) and or the combination ofBiostimulation and Bioaugumentation with indigenous hydrocarbon utilizers would be effective in the remediation of crude oil polluted tropical soils. Key Words: Bioremediation, Bioaugumentation, ...

  11. How soil scientists help combat podoconiosis, a neglected tropical disease

    NARCIS (Netherlands)

    Visser, Benjamin Jelle

    2014-01-01

    Podoconiosis or "endemic non-filarial elephantiasis" is a tropical disease caused by prolonged exposure of bare feet to irritant alkaline clay soils of volcanic origin [1]. The name of the disease is derived from the Greek words for foot: podos, and dust: konos. Small mineral particles from irritant

  12. Microbial population changes in tropical agricultural soil ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-12-17

    Dec 17, 2008 ... Microbial degradation is known to be an efficient process in the in ..... exhibited a great impact on the ecology of the soil by causing drastic ... city of the soil (Dibble and Bartha, 1979). Hydrocarbon .... Atlas RM (1991). Microbial ...

  13. Microbial population changes in tropical agricultural soil ...

    African Journals Online (AJOL)

    Impacts of crude petroleum pollution on the soil environment and microbial population dynamics as well as recovery rates of an abandoned farmland was monitored for seven months spanning the two major seasons in Nigeria with a ... The physico-chemistry of the control and contaminated soils differed just significantly (P ...

  14. Glutamine and glutamic acid supplementation enhances performance of broiler chickens under the hot and humid tropical condition

    Directory of Open Access Journals (Sweden)

    Joshua O. Olubodun

    2015-02-01

    Full Text Available Day-old (day 1 commercial broiler chickens were fed i basal diet (control, ii basal diet +0.5% AminoGut (AG, or iii basal diet +1% AG from 1 to 42 d of age under the hot and humid tropical environment. AminoGut is a commercial dietary supplement containing a mixture of L-glutamine (Gln and L-glutamic (Glu acid. Weight gain and feed conversion ratio during the starter (1 to 21 d and overall (1 to 42 d periods improved linearly and quadratically with AG supplementation when compared to control. Supplementing birds with AG significantly reduced overall mortality rate. At 21 and 42 d of age, intestinal (duodenum and ileum villi height and crypt depth showed both linear and quadratic positive responses to AG supplementation. Intestinal amylase activity increased linearly and quadratically on d 21, and linearly only on d 42. In conclusion, Gln and Glu supplementation was beneficial in improving the growth performance and survivability of broiler chickens under the hot and humid tropical environment.

  15. 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.

  16. Are tall trees more sensitive to prolonged drought in tropical per-humid forests?

    Science.gov (United States)

    Schuldt, Bernhard; Horna, Viviana; Leuschner, Christoph

    2010-05-01

    Seasonality of water flux was investigated for common tree species of a Central Sulawesi pre-montane perhumid forest located in the Lore Lindu National Park. Trees were exposed to reduced soil water levels under a rainfall exclusion experiment (Sulawesi Throughfall Displacement Experiment, STD), to simulate drought effects and to monitor species-specific short-term responses to extended water stress. Several climate scenarios predict more frequent occurrence of ENSO droughts with increasing severity induced by global warming. Detailed assessments of the ecological consequences of droughts in perhumid forests are scarce and knowledge whether and how these ecosystems are adapted to severe droughts is limited. Key research questions were: (1) how do tall rainforest trees cope with long pathways under low evaporative demand, (2) how sensitive are trees from tropical perhumid forests and how do they acclimate to drought-stress and 3) does wood density determine the drought sensitivity of perhumid forest trees? From June 2007 until October 2009 we monitored 95 trees from 8 common tree species. Half of them were located under the STD Experiment and the other half in control areas. We used the constant heated method to continuously monitor stem xylem flux density and conduct parallel measurements of xylem anatomy and hydraulic conductivity in twigs, stems and roots. After almost 22 months of experimental drought only 25% of xylem flux density reduction was observed in the experimental trees. But the reaction to water stress was species-specific and in some species xylem flux went down to 50 % compared to the individuals located at the control plots. Wood density did not correlate with any hydraulic measurement, but anatomy and hydraulic architecture observations showed a positive correlation between xylem conductivity and vessel size with tree height. These results reveal a well adapted hydraulic system of tall canopy trees allowing for highly efficient water flow under

  17. Germination of tropical forage seeds stored for six years in ambient and controlled temperature and humidity conditions in Thailand

    Directory of Open Access Journals (Sweden)

    Michael D. Hare

    2018-01-01

    Full Text Available The germination performances of fresh seed lots were determined for 5 tropical forage species: Mulato II hybrid brachiaria [Urochloa ruziziensis (syn. Brachiaria ruziziensis x U. decumbens (syn. B. decumbens x U. brizantha (syn. B. brizantha], Mombasa guinea [Megathyrsus maximus (syn. Panicum maximum], Tanzania guinea [M. maximus (syn. P. maximum], Ubon paspalum (Paspalum atratum and Ubon stylo (Stylosanthes guianensis, stored under ambient conditions in Thailand (mean monthly temperatures 23‒34 ºC; mean monthly relative humidity 40‒92% or in a cool room (18‒20 ºC and 50% relative humidity for up to 6 years. The first paper of this study showed all seeds, except unscarified Ubon stylo seed, were dead after a single year of storage in ambient conditions. This second paper shows that cool-room storage extended seed viability, but performance varied considerably between species. Germination percentage under laboratory conditions declined to below 50%, after 3 years storage for Mombasa guinea seed and Tanzania guinea seed, 4 years for Ubon paspalum seed and 4‒5 years for Mulato II seed. Ubon stylo seed maintained high germination for 5 years, in both cool-room storage (96% and ambient-room storage (84%. Apparent embryo dormancy in acid-scarified Mulato II seed steadily increased with time in cool-storage and this seed had to be acid-scarified again each year at the time of germination testing to overcome dormancy. Physical dormancy of Mulato II seeds, imposed by the tightly bound lemma and palea in unscarified seed, was not overcome by length of time in cool-storage and these seeds had to be acid-scarified to induce germination. Hardseeded percentage in Ubon stylo seed remained high throughout the study and could be overcome only by acid-scarification. The difficulties of maintaining acceptable seed germination percentages when storing forage seeds in the humid tropics are discussed.

  18. How Soil Scientists Help Combat Podoconiosis, A Neglected Tropical Disease

    Directory of Open Access Journals (Sweden)

    Benjamin Jelle Visser

    2014-05-01

    Full Text Available Podoconiosis or “endemic non-filarial elephantiasis” is a tropical disease caused by prolonged exposure of bare feet to irritant alkaline clay soils of volcanic origin [1]. The name of the disease is derived from the Greek words for foot: podos, and dust: konos. Small mineral particles from irritant soils penetrate the skin and provoke an inflammatory response leading to fibrosis and blockage of lymphatic vessels, causing lymphoedema [2]. Patients suffer from disabling physical effects, but also stigma [1]. The disease can simply be prevented by avoiding contact with irritant soils (wearing shoes but this is still an unaffordable “luxury” for many people. Podoconiosis is unique because it is a completely preventable non-communicable tropical disease [1]. In the past few years, podoconiosis has received increased advocacy and is now step by step appearing on the agenda of medical researchers as well as politicians.  [...

  19. Proposition of Regression Equations to Determine Outdoor Thermal Comfort in Tropical and Humid Environment

    Directory of Open Access Journals (Sweden)

    Sangkertadi Sangkertadi

    2012-05-01

    Full Text Available This study is about field experimentation in order to construct regression equations of perception of thermalcomfort for outdoor activities under hot and humid environment. Relationships between thermal-comfort perceptions, micro climate variables (temperatures and humidity and body parameters (activity, clothing, body measure have been observed and analyzed. 180 adults, men, and women participated as samples/respondents. This study is limited for situation where wind velocity is about 1 m/s, which touch the body of the respondents/samples. From questionnaires and field measurements, three regression equations have been developed, each for activity of normal walking, brisk walking, and sitting.

  20. Submerged Humid Tropical Karst Landforms Observed By High-Resolution Multibeam Survey in Nagura Bay, Ishigaki Island, Southwestern Japan

    Science.gov (United States)

    Kan, H.; Urata, K.; Nagao, M.; Hori, N.; Fujita, K.; Yokoyama, Y.; Nakashima, Y.; Ohashi, T.; Goto, K.; Suzuki, A.

    2014-12-01

    Submerged tropical karst features were discovered in Nagura Bay on Ishigaki Island in the South Ryukyu Islands, Japan. This is the first description of submerged humid tropical karst using multibeam bathymetry. We conducted a broadband multibeam survey in the central area of Nagura Bay (1.85 × 2.7 km) and visualized the high-resolution bathymetric results with a grid size of 1 m over a depth range of 1.6-58.5 m. Various types of humid tropical karst landforms were found to coexist within the bay, including fluviokarst, doline karst, cockpit karst, polygonal karst, uvalas, and mega-dolines. We assume that Nagura Bay was a large karst basin in which older limestone remained submerged, thus preventing corrosion and the accumulation of reef sediments during periods of submersion, whereas the limestone outcropping on land was corroded during multiple interglacial and glacial periods. Based on our bathymetric result together with aerial photographs of the coastal area, we conclude that the submerged karst landscape has likely developed throughout the whole of Nagura Bay, covering an area of ~6 × 5 km. Accordingly, this area hosts the largest submerged karst in Japan. We also observed abundant coral communities during our SCUBA observations. The present marine conditions of Nagura Bay are characterized by low energy (calm sea) and low irradiance owing to the terrestrial influence. Such conditions have been emphasized by the presence of large undulating landforms, which cause decreases in wave intensity and irradiance with depth. These characteristics have acted to establish unique conditions compared to other coral reef areas in the Ryukyu Islands. It may play an important role in supporting the regional coral reef ecosystem.

  1. Measurement of density and humidity of soils using radioactive techniques and its application in civil work

    International Nuclear Information System (INIS)

    Obando, E.; Torres, J.E.; Moreno, N.J.

    1987-01-01

    The purpose of this article is to inform about the applications of radioactive techniques related with the measurement of humidity and density of soils. After a brief introduction which describes the basic equipment the main advantages and applications in relation with the conventional methods in engineering, agriculture and industry, it gives a description of the theory related with the basis of these techniques, such as transmission and detection

  2. An Integrated Use of Experimental, Modeling and Remote Sensing Techniques to Investigate Carbon and Phosphorus Dynamics in the Humid Tropics

    Science.gov (United States)

    Townsend, Alan R.; Asner, Gregory P.; Bustamante, Mercedes M. C.

    2001-01-01

    Moist tropical forests comprise one of the world's largest and most diverse biomes, and exchange more carbon, water, and energy with the atmosphere than any other ecosystem. In recent decades, tropical forests have also become one of the globe's most threatened biomes, subjected to exceptionally high rates of deforestation and land degradation. Thus, the importance of and threats to tropical forests are undeniable, yet our understanding of basic ecosystem processes in both intact and disturbed portions of the moist tropics remains poorer than for almost any other major biome. Our approach in this project was to take a multi-scale, multi-tool approach to address two different problems. First, we wanted to test if land-use driven changes in the cycles of probable limiting nutrients in forest systems were a key driver in the frequently observed pattern of declining pasture productivity and carbon stocks. Given the enormous complexity of land use change in the tropics, in which one finds a myriad of different land use types and intensities overlain on varying climates and soil types, we also wanted to see if new remote sensing techniques would allow some novel links between parameters which could be sensed remotely, and key biogeochemical variables which cannot. Second, we addressed to general questions about the role of tropical forests in the global carbon cycle. First, we used a new approach for quantifying and minimizing non-biological artifacts in the NOAA/NASA AVHRR Pathfinder time series of surface reflectance data so that we could address potential links between Amazonian forest dynamics and ENSO cycles. Second, we showed that the disequilibrium in C-13 exchanged between land and atmosphere following tropical deforestation probably has a significant impact on the use of 13-CO2 data to predict regional fluxes in the global carbon cycle.

  3. Does the increased air humidity affect soil respiration and carbon stocks?

    Science.gov (United States)

    Kukumägi, Mai; Celi, Luisella; Said-Pullicino, Daniel; Kupper, Priit; Sõber, Jaak; Lõhmus, Krista; Kutti, Sander; Ostonen, Ivika

    2013-04-01

    Climate manipulation experiments at ecosystem-scale enable us to simulate, investigate and predict changes in carbon balance of forest ecosystems. Considering the predicted increase in air humidity and precipitation for northern latitudes, this work aimed at investigating the effect of increased air humidity on soil respiration, distribution of soil organic matter (SOM) among pools having different turnover times, and microbial, fine root and rhizome biomass. The study was carried out in silver birch (Betula pendula Roth.) and hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in a Free Air Humidity Manipulation (FAHM) experimental facility containing three humidified (H; on average 7% above current ambient levels since 2008) and three control (C) plots. Soil respiration rates were measured monthly during the growing season using a closed dynamic chamber method. Density fractionation was adopted to separate SOM into two light fractions (free and aggregate-occluded particulate organic matter, fPOM and oPOM respectively), and one heavy fraction (mineral-associated organic matter, MOM). The fine root and rhizome biomass and microbial data are presented for silver birch stands only. In 2011, after 4 growing seasons of humidity manipulation soil organic carbon contents were significantly higher in C plots than H plot (13.5 and 12.5 g C kg-1, respectively), while soil respiration tended to be higher in the latter. Microbial biomass and basal respiration were 13 and 14% higher in H plots than in the C plots, respectively. Twice more fine roots of trees were estimated in H plots, while the total fine root and rhizome biomass (tree + understory) was similar in C and H plots. Fine root turnover was higher for both silver birch and understory roots in H plots. Labile SOM light fractions (fPOM and oPOM) were significantly smaller in H plots with respect to C plots (silver birch and hybrid aspen stands together), whereas no differences were observed in the

  4. A soil mechanics approach to study soil compaction and traffic effect on the preconsolidation pressure of tropical soils

    International Nuclear Information System (INIS)

    Dias Junior, Moacir de Souza

    2004-01-01

    Several researchers have already demonstrated the causes and the effects of soil compaction. These studies showed that the soil compaction is a limiting factor in the agricultural production. The attributes of the soil conventionally monitored has not been capable to quantify the load support capacity of the soil, not allowing to foresee the levels of pressures that can be applied to the soils at different moisture conditions without additional soil compaction (structure degradation) happens. The researches done in the soil compressive behaviour of some tropical soils indicate that the pre-compression stress may be used as an alternative measure of the load support capacity and as a quantitative indicator of the structure sustainability of the tropical soils

  5. Stability and instability on Maya Lowlands tropical hillslope soils

    Science.gov (United States)

    Beach, Timothy; Luzzadder-Beach, Sheryl; Cook, Duncan; Krause, Samantha; Doyle, Colin; Eshleman, Sara; Wells, Greta; Dunning, Nicholas; Brennan, Michael L.; Brokaw, Nicholas; Cortes-Rincon, Marisol; Hammond, Gail; Terry, Richard; Trein, Debora; Ward, Sheila

    2018-03-01

    Substantial lake core and other evidence shows accelerated soil erosion occurred in the Maya Lowlands of Central America over ancient Maya history from 3000 to 1000 years ago. But we have little evidence of the wider network of the sources and sinks of that eroded sediment cascade. This study begins to solve the mystery of missing soil with new research and a synthesis of existing studies of tropical forest soils along slopes in NW Belize. The research aim is to understand soil formation, long-term human impacts on slopes, and slope stability over time, and explore ecological implications. We studied soils on seven slopes in tropical forest areas that have experienced intensive ancient human impacts and those with little ancient impacts. All of our soil catenas, except for one deforested from old growth two years before, contain evidence for about 1000 years of stable, tropical forest cover since Maya abandonment. We characterized the physical, chemical, and taxonomic characteristics of soils at crest-shoulder, backslopes, footslopes, and depression locations, analyzing typical soil parameters, chemical elements, and carbon isotopes (δ13C) in dated and undated sequences. Four footslopes or depressions in areas of high ancient occupation preserved evidence of buried, clay-textured soils covered by coarser sediment dating from the Maya Classic period. Three footslopes from areas with scant evidence of ancient occupation had little discernable deposition. These findings add to a growing corpus of soil toposequences with similar facies changes in footslopes and depressions that date to the Maya period. Using major elemental concentrations across a range of catenas, we derived a measure (Ca + Mg) / (Al + Fe + Mn) of the relative contributions of autochthonous and allochthonous materials and the relative age of soil catenas. We found very low ratios in clearly older, buried soils in footslopes and depressions and on slopes that had not undergone ancient Maya erosion. We

  6. Strontium-Doped Hematite as a Possible Humidity Sensing Material for Soil Water Content Determination

    Directory of Open Access Journals (Sweden)

    Carlo Grignani

    2013-09-01

    Full Text Available The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prepared powder and subsequent firing in the 800–1,000 °C range. These sensors were first tested in a laboratory apparatus under humid air and then in an homogenized soil and finally in field. The results evidenced that the screen printed film was able to give a response for a soil matric potential from about 570 kPa, that is to say well below the wilting point in the used soil.

  7. Strontium-doped hematite as a possible humidity sensing material for soil water content determination.

    Science.gov (United States)

    Tulliani, Jean-Marc; Baroni, Chiara; Zavattaro, Laura; Grignani, Carlo

    2013-09-10

    The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prepared powder and subsequent firing in the 800-1,000 °C range. These sensors were first tested in a laboratory apparatus under humid air and then in an homogenized soil and finally in field. The results evidenced that the screen printed film was able to give a response for a soil matric potential from about 570 kPa, that is to say well below the wilting point in the used soil.

  8. The behavior of P in tropical soils

    International Nuclear Information System (INIS)

    Bittencourt, V.C.; Zambello Junior, E.

    1975-06-01

    The experimental data showed that the whole P retention process depends on the levels and the reactivities of the iron oxides in the soils. It was established that the retention mechanism occurs in 2 or 3 stages and it is related to both the maximum adsorption and the absorbent capacity of the several soils as determined by the Langmuir and the Freundlich equations respectively. The final step of the P interaction which shows small rate constants is due to a diffusion of the phosphate ions from the oxide surface to the internal layers producing more stable iron-phosphate compounds

  9. Conceptual differences between the bioclimatic urbanism for Europe and for the tropical humid climate

    Energy Technology Data Exchange (ETDEWEB)

    Corbella, O.D.; Magalhaes, M.A.A.A. [Faculdade de Arquitetura e Urbanismo, Universidade Federal do Rio de Janeiro, Rio de Janeiro (Brazil)

    2008-05-15

    This article makes part of a series of conceptual papers to continue the discussion about how architecture and urbanism interact with climate, in tropical regions. Students engaged in normal courses of architecture in tropical regions, particularly in South America, develop their knowledge based on concepts generated in the developed countries - usually related to cold environments. Consequently, these students acquire wrong ideas about urban design of open spaces. Integrating urbanism and climate in tropical countries is still very incipient as an approach and many lecturers reject it, since they prefer to continue with a more formal one, dictated by most of the dominant countries. The herein paper underlines several different concepts and perspectives that separate the two conceptions, leading to a reflection about the subject. (author)

  10. Assessing soil fertility decline in the tropics using soil chemical data

    NARCIS (Netherlands)

    Hartemink, A.E.

    2006-01-01

    Soil fertility decline is perceived to be widespread in the upland soils of the tropics, particularly in sub-Saharan Africa. Most studies have used nutrient balances to assess the degree and extent of nutrient depletion; these have created awareness but suffer methodological problems as several of

  11. Pesticide-Biota Interactions in Tropical Soils

    International Nuclear Information System (INIS)

    Sethunathan, N.; Wahid, P.A.; Rao, T.R.; Adhya, T.K.; Ramakrishna, C.; Ray, R.C.; Pal, S.S.; Chendrayan, K.; Sudhakar-Barik; Venkateswarlu, K.; Nayak, D.N.; Charyulu, P.B.B.N.; Rao, V.R.

    1981-01-01

    Studies using radiotracer techniques and gas-liquid chromatography showed that instantaneous degradation of parathion, methyl parathion and fenitrothion occurred upon their equilibration with soils pre-reduced by flooding with water; amino analogues of the respective insecticides were formed as major degradation products

  12. Pesticide-Biota Interactions in Tropical Soils

    Energy Technology Data Exchange (ETDEWEB)

    Sethunathan, N.; Wahid, P. A.; Rao, T. R.; Adhya, T. K.; Ramakrishna, C.; Ray, R. C.; Pal, S. S.; Chendrayan, K.; Sudhakar-Barik,; Venkateswarlu, K.; Nayak, D. N.; Charyulu, P. B.B.N.; Rao, V. R. [Laboratory of Soil Microbiology, Division of Soil Science and Microbiology, Central Rice Research Institute, Cuttack-753006 (India)

    1981-05-15

    Studies using radiotracer techniques and gas-liquid chromatography showed that instantaneous degradation of parathion, methyl parathion and fenitrothion occurred upon their equilibration with soils pre-reduced by flooding with water; amino analogues of the respective insecticides were formed as major degradation products.

  13. The behavior of P in tropical soils

    International Nuclear Information System (INIS)

    Bittencourt, V.C.; Zambello Junior, E.

    1975-06-01

    The 32 P isotopic exchange between the equilibrium solution and the soil can be described by 2 or 3 first order reactions, which are mainly determined by the iron oxide content of the samples. The first reaction in Terra Roxa Estruturada and in Latosol Roxo soils was found to be independent of the ionic strength of the solution and this may be atributed to a chemical adsorption of the phosphate in the solid phase surface, with an ulterior occlusion of the ion in the internal layers. Since the constant rates of the second and third reactions was found to depend on the ionic strength of the solution and after these interactions a considerable amount of isotopic exchangeable P was observed, it is suggested that 2 phosphate diffusion processes occur: One from the hydratation shell to the solid surface and the other the equilibrium solution to the hydratation shell. The reactions in the Latosol Vermelho Escuro-fase arenosa and in the Podzolizados de Lins e Marilia, variacao Lins, soils were more intense in the liquid phase, and therefore less amounts of phosphate was subject to chemical adsorption

  14. Sorption-desorption of radiocesium interception potential in tropical soils

    International Nuclear Information System (INIS)

    Roque, Mario L.; Boaretto, Rodrigo M.; Boaretto, Antonio E.; Smolders, Erik E.T.

    2000-01-01

    A study of sorption of radiocaesium in soils of tropical climate (Brazil) was carried. The values of definitive fixation of the radiocaesium were determined by analytic methodology of sorption-desorption and the availability to plants were calculated by the determination of radiocesium interception potential (RIP). The values of sorption varied from 1,2 to 74,8% and the fixation varied from 3,2% to 32,2%. The results shown that the radiocaesium did remain adsorbed mainly to the frayed edge site. The low values of interception potential and definitive fixation demonstrated high capacity of the tropical soils in disposal the radionuclide for the solution and, consequently, to plants. (author)

  15. Ground source heat pump performance in case of high humidity soil and yearly balanced heat transfer

    International Nuclear Information System (INIS)

    Schibuola, Luigi; Tambani, Chiara; Zarrella, Angelo; Scarpa, Massimiliano

    2013-01-01

    Highlights: • GSHPs are simulated in case of humid soil and yearly balanced heat transfer. • Humid soil and yearly balanced heat transfer imply higher compactness of GSHPs. • Resulting GSHPs are compared with other traditional and innovative HVAC systems. • GSHPs score best, especially in case of inverter-driven compressors. - Abstract: Ground source heat pump (GSHP) systems are spreading also in Southern Europe, due to their high energy efficiency both in heating and in cooling mode. Moreover, they are particularly suitable in historical cities because of difficulties in the integration of heating/cooling systems into buildings subjected to historical preservation regulations. In these cases, GSHP systems, especially the ones provided with borehole heat exchangers, are a suitable solution instead of gas boilers, air-cooled chillers or cooling towers. In humid soils, GSHP systems are even more interesting because of their enhanced performance due to higher values of soil thermal conductivity and capacity. In this paper, GSHP systems operating under these boundary conditions are analyzed through a specific case study set in Venice and related to the restoration of an historical building. With this analysis the relevant influences of soil thermal conductivity and yearly balanced heat transfer in the design of the borehole field are shown. In particular, the paper shows the possibility to achieve higher compactness of the borehole field footprint area when yearly balanced heat transfer in the borehole field is expected. Then, the second set of results contained in the paper shows how GSHP systems designed for high humidity soils and yearly balanced heat loads at the ground side, even if characterized by a compact footprint area, may still ensure better performance than other available and more common technologies such as boilers, air-cooled chillers, chillers coupled with cooling towers and heat pumps and chillers coupled with lagoon water. As a consequence

  16. 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)

  17. Estimation of exterior vertical daylight for the humid tropic of Kota Kinabalu city in East Malaysia

    Energy Technology Data Exchange (ETDEWEB)

    Djamila, Harimi; Ming, Chu Chi; Kumaresan, Sivakumar [School of Engineering and Information Technology, Universiti Malaysia Sabah, Locked Bag No. 2073, 88999 Kota Kinabalu, Sabah (Malaysia)

    2011-01-15

    In tropical regions natural daylight has been a fundamental factor in building design. It is the most efficient way of lighting a building in the daytime and has a great potential for energy conservation in buildings. In Malaysia there are a limited available data of measured illuminance which is the case of several regions in the tropics. Using established models it is possible to predict the luminous efficacy and then estimate the monthly mean hourly exterior illuminance. In this study two different models were chosen. The Perez and Du Mortier-Perraudeau-Page-Littlefair models were selected for the prediction of hourly exterior horizontal illuminance for the city of Kota Kinabalu in East Malaysia. Comparison between the two models were made. The vertical hourly illuminance was predicted also using Perez approach. The potentiality of daylight in four orientations was discussed. This study highlights the importance of Sunpath diagram on daylight illuminance during the conceptual design stage. The results in this study is hoped to contribute further insight into the potentiality of daylighting of tropical sky. (author)

  18. Remote sensing of soil radionuclide fluxes in a tropical ecosystem

    International Nuclear Information System (INIS)

    Clegg, B.; Koranda, J.; Robinson, W.; Holladay, G.

    1980-01-01

    We are using a transponding geostationary satellite to collect surface environmental data to describe the fate of soil-borne radionuclides. The remote, former atomic testing grounds at the Eniwetok and Bikini Atolls present a difficult environment in which to collect continuous field data. Our land-based, solar-powered microprocessor and environmental data systems remotely acquire measurements of net and total solar radiation, rain, humidity, temperature, and soil-water potentials. For the past year, our water flux model predicts wet season plant transpiration rates nearly equal to the 6 to 7 mm/d evaporation pan rate, which decreases to 2 to 3 mm/d for the dry season. Radioisotopic analysis confirms the microclimate-estimated 1:3 to 1:20 soil to plant 137 Cs dry matter concentration ratio. This ratio exacerbates the dose to man from intake of food plants. Nephelometer measurements of airborne particulates presently indicate a minimum respiratory radiological dose

  19. Maize Storage in Termite Mound Clay, Concrete, and Steel Silos in the Humid Tropics: Comparison and Effect on Bacterial and Fungal Counts

    Science.gov (United States)

    This study investigated the functional suitability of using the readily-available termite mound clay (TMC) for grain silo construction in comparison to conventional reinforced concrete (RC) and galvanized steel (GS) silos for maize storage in the humid tropics. The extent to which temperature and r...

  20. Factors influencing storm-generated suspended-sediment concentrations and loads in four basins of contrasting land use, humid-tropical Puerto Rico

    Science.gov (United States)

    A. C. Gellis; NO-VALUE

    2013-01-01

    The significant characteristics controlling the variability in storm-generated suspended-sediment loads and concentrations were analyzed for four basins of differing land use (forest, pasture, cropland, and urbanizing) in humid-tropical Puerto Rico. Statistical analysis involved stepwise regression on factor scores. The explanatory variables were attributes of flow,...

  1. Corrosion study of steels exposed over five years to the humid tropical atmosphere of Panama

    Energy Technology Data Exchange (ETDEWEB)

    Jaén, Juan A., E-mail: juan.jaen@up.ac.pa [Departamento de Química Física, Edificio de Laboratorios Científicos-VIP (Panama); Iglesias, Josefina [Laboratorio de Análisis Industriales y Ciencias Ambientales (Panama)

    2017-11-15

    The results of assessing five-year corrosion of low-carbon and conventional weathering steels exposed to the Panamanian tropical atmosphere is presented. Two different test sites, one in Panama City: 5 km from the shoreline of the Pacific Ocean, and another in the marine environment of Fort Sherman, Caribbean coast of Panama; namely, Fort Sherman Coastal site: 100 m from coastline. The corrosion products, formed in the skyward and earthward faces in the studied tropical environment, were mainly identified using room temperature and low temperature (15 K) Mössbauer spectroscopy, and ATR-FTIR. In all samples, lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) were the main constituents. Some maghemite (γ-Fe{sub 2}O{sub 3}), was also identified in Tocumen by Mössbauer spectroscopy and traces of feroxyhyte (δ-FeOOH) using ATR-FTIR. The corrosion rate values obtained are discussed in light of the atmospheric exposure conditions and atmospheric pollutants.

  2. Accumulation of heavy metals in a tropical soil type Oxisol

    International Nuclear Information System (INIS)

    Reynaldo, I.M.; Escudey, M.; Utria, E.; Garcia, D.; Cartaya, O.; Morua, A.

    2003-01-01

    In this investigation sewage sludges from Quibu plant, located in City of the Havana, with the objective of evaluating the capacity of accumulation of heavy metals in a tropical soil type Oxisol when in the wheat plants are cultivated (Triticum aestivum L.) , as well as the potential damages in this plants. Rates of 0, 60, 180 and 300 sludges tons/ soil hectare was applied and the plants were growth in recipient of 5 L of capacity. The levels of heavy metals were evaluated before the and after the crop. The extraction one carries out with the mixture HCl:HNO3 and they were determined by spectroscopy inductively coupled to plasma. Presence of Zn, Cu and Pb were detected in sludges and a tendency decrease is observed to heavy metals retention is observed in soil with the increase of the disposition rate together to a differential behavior of the different chemical species

  3. Susceptibility of coarse-textured soils to soil erosion by water in the tropics

    International Nuclear Information System (INIS)

    Salako, F.K.

    2004-01-01

    The application of soil physics for the evaluation of factors of soil erosion in the tropics received considerable attention in the last four decades. In Nigeria, physical characteristics of rainfall such as drop size and drop-size distribution, rainfall intensity at short intervals and kinetic energy of rainfall were evaluated using different methods. Thus, compound erosivity indices were evaluated which showed a similar trend in annual rainfall erosivity with annual rainfall amounts. Attempts have also been made to use geostatistical tools and fractal theory to describe temporal variability in rainfall erosivity. High erosivity aggravates the vulnerability of coarse-textured soils to erosion. These soils, high in sand content were poorly aggregated and structurally weak. Thus, they were easily detached and transported by runoff. Long-term data are needed to describe factors of soil erosion in the tropics but quite often, equipment are not available or poorly maintained where available such that useful data are not collected. A greater cooperation of pure physicists, soil physicists and engineers in the developing nations is needed to improve or design equipment and methods for the characterization of factors of soil erosion in the tropics. (author)

  4. Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere

    OpenAIRE

    Cleveland, Cory C.; Townsend, Alan R.

    2006-01-01

    Terrestrial biosphere–atmosphere carbon dioxide (CO2) 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 hig...

  5. Soil macrofauna community structure along a gradient of land use intensification in the humid forest zone of southern Cameroon.

    NARCIS (Netherlands)

    Madong à Birang,

    2004-01-01

    The impact of land use systems on soil macrofauna community structures is described as well as their relationships with the vegetation and soil parameters in the humid forest zone of southernCameroon

  6. High-coercivity minerals from North African Humid Period soil material deposited in Lake Yoa (Chad)

    Science.gov (United States)

    Just, J.; Kroepelin, S.; Wennrich, V.; Viehberg, F. A.; Wagner, B.; Rethemeyer, J.; Karls, J.; Melles, M.

    2015-12-01

    The Holocene is a period of fundamental climatic change in North Africa. Humid conditions during the so-called African Humid Period (AHP) have favored the formation of big lake systems. Only very few of these lakes persist until today. One of them is Lake Yoa (19°03'N/20°31'E) in the Ounianga Basin, Chad, which maintains its water level by ground water inflow. Here we present the magnetic characteristics together with proxies for lacustrine productivity and biota of a sediment core (Co1240) from Lake Yoa, retrieved in 2010 within the framework of the Collaborative Research Centre 806 - Our Way to Europe (Deutsche Forschungsgemeinschaft). Magnetic properties of AHP sediments show strong indications for reductive diagenesis. An up to ~ 80 m higher lake level is documented by lacustrine deposits in the Ounianga Basin, dating to the early phase of the AHP. The higher lake level and less strong seasonality restricted deep mixing of the lake. Development of anoxic conditions consequently lead to the dissolution of iron oxides. An exception is an interval with high concentration of high-coercivity magnetic minerals, deposited between 7800 - 8120 cal yr BP. This interval post-dates the 8.2 event, which was dry in Northern Africa and probably caused a reduced vegetation cover. We propose that the latter resulted in the destabilization of soils around Lake Yoa. After the re-establishment of humid conditions, these soil materials were eroded and deposited in the lake. Magnetic minerals appear well preserved in the varved Late Holocene sequence, indicating (sub-) oxic conditions in the lake. This is surprising, because the occurrence of varves is often interpreted as an indicator for anoxic conditions of the lake water. However, the salinity of lake water rose strongly after the AHP. We therefore hypothesize that the conservation of varves and absence of benthic organisms rather relates to the high salinity than to anoxic conditions.

  7. Microbial surfactant activities from a petrochemical landfarm in a humid tropical region of Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Maciel, B.M.; Dias, J.C.T.; Santos, A.C.F.; Argolo-Filho, R.C.; Fontana, R.; Loguercio, L.L.; Rezende, R.P. [Univ. Estadual de Santa Cruz, Santa Cruz (Brazil). Dept. de Ciencias Biologicas

    2007-08-15

    Studies have suggested that biosurfactants can enhance the biodegradation of almost insoluble organics by increasing cell uptake availability. In this study, micro-organisms were isolated from a soil sample from a Brazilian petrochemical waste landfarm and grown in petroleum as a carbon source in order to assess their surfactant potential. Isolated colonies were inoculated into tubes, and a drop-collapse method was used to select micro-organisms with surfactant activity. Surfactant activity of the isolates was assessed when the activity was detected for the first time in each culture. The supernatant of each micro-organism was then diluted. The surfactant activity of each dilution was then observed via micelles formation. DNA was then extracted from the samples. A total of 60 microbial strains were selected. Results showed that a variety of petroleum-grown micro-organisms obtained from the landfarm soil showed surfactant activity. Results showed that the micro-organisms were able to use petroleum as a sole carbon source. The production of surfactant compounds occurred during the declining stages of microbial culture curves, which suggested that the nutritional stress achieved on the fourth day of the culture induced the synthesis and secretion of biosurfactants by the isolates. It was concluded that micro-organisms derived from soils polluted with hydrocarbons can be used in bioremediation processes. 21 refs., 1 tab., 3 figs.

  8. Agriculturization in the Argentinean Northern Humid Pampas: the Impact on Soil Structure and Runoff

    Science.gov (United States)

    Sasal, M. C.; Léonard, J.; Andriulo, A.; Wilson, M. G.

    2012-04-01

    Argentina is among the countries with the largest cropped area under no-tillage (NT). No tillage was adopted in the northern Humid Pampas to reduce the widespread soil degradation by water erosion. With the advent of genetically modified soybean varieties, NT has developed exponentially. This evolution, combined with the influence of the international market trend, has resulted in large changes in crop sequence composition toward the disappearance of pastures and the expansion of soybean monoculture. The aim of this work was to evaluate the long-term consequences of these changes on the topsoil structure and the way in which the evolution of soil structure relates to the simplification of the crop sequence and to runoff at a regional scale. We analyzed the topsoil structure of 25 sites with Argiudolls having 4 to 29 consecutive years of NT using the cultural profile approach. An intensification sequence index (ISI) was calculated as the ratio between the length of the growth period and the length of the year. Fifteen natural-rainfall runoff plots (100 m2) with 3.5% slope were used to analyze the relationship between soil structural state, crop sequence and runoff for four years. Four types of soil structures were identified and a general pattern of vertical soil structure organization was revealed. The top centimeters of 72% of the sites were dominated by a granular structure. Platy soil structure development was omnipresent: all sites exhibited a horizontal platy structure (wheat/soybean double crop (ISI=0.83) could limit soil structure degradation and reduce runoff and the associated environmental risks.

  9. Initial stages of indoor atmospheric corrosion of electronics contact metals in humid tropical climate: tin and nickel

    Directory of Open Access Journals (Sweden)

    Veleva, L.

    2007-04-01

    Full Text Available Samples of electrolytic tin and nickel have been exposed for 1 to 12 m in indoor environment, inside a box (rain sheltered cabinet, placed in tropical humid marine-urban climate, as a part of Gulf of Mexico. The corrosion aggressiveness of box has been classified as a very high corrosive, based on the monitored chlorides and SO2 deposition rates, and the Temperature/Relative Humidity air daily complex. The annual mass increasing of nickel is approximately twice higher than its values of mass loss (C. The relation between nickel mass loss or increasing and time of wetness (t of metal surface is linear and does not obey the power equation C = A tn, which has be found for tin. The SEM images reveal a localized corrosion on nickel and tin surfaces. XRD detects the formation of SnCl2.H2O as a corrosion product. Within the time on the tin surface appear black spots, considered as organic material.

    Muestras de estaño y níquel electrolíticos han sido expuestas de 1 a 12 m en ambiente interno (indoor, en una caseta (gabinete protegido de lluvia, colocada en clima tropical húmedo marino-urbano del Golfo de México. La agresividad de la caseta ha sido clasificada como muy altamente corrosiva, basada al registro de la velocidad de deposición de cloruros y SO2, y en el complejo diario de temperatura/humedad relativa del aire. El incremento de masa anual de níquel es, aproximadamente, dos veces mayor que del valor de su pérdida de masa (C. La relación entre la pérdida de masa de Ni o su incremento, y el tiempo de humectación (t de la superficie metálica y lineal y no obedece la ley de potencia C = A tn , que ha sido encontrada para el estaño. Las imágenes del SEM revelan una corrosión localizada en las superficie de níquel y estaño. El análisis de rayos-X detecta la formación de SnCl2.H2O como producto de corrosión. Con el tiempo

  10. Iron Availability in Tropical Soils and Iron Uptake by Plants

    Directory of Open Access Journals (Sweden)

    Guilherme Furlan Mielki

    Full Text Available ABSTRACT Given the increase in crop yields and the expansion of agriculture in low fertility soils, deficiency of micronutrients, such as iron, in plants grown in tropical soils has been observed. The aim of this study was to evaluate Fe availability and Fe uptake by corn (Zea mays L. plants in 13 different soils, at two depths. Iron was extracted by Mehlich-1, Mehlich-3, and CaCl2 (Fe-CC and was fractionated in forms related to low (Feo and high (Fed crystallinity pedogenic oxyhydroxides, and organic matter (Fep using ammonium oxalate, dithionite-citrate, and sodium pyrophosphate, respectively. In order to relate Fe availability to soil properties and plant growth, an experiment was carried out in a semi-hydroponic system in which part of the roots developed in a nutrient solution (without Fe and part in the soil (the only source of Fe. Forty-five days after seeding, we quantified shoot dry matter and leaf Fe concentration and content. Fed levels were high, from 5 to 132 g kg-1, and Feo and Fe-CC levels were low, indicating the predominance of Fe as crystalline oxyhydroxides and a low content of Fe readily available to plants. The extraction solutions showed significant correlations with various soil properties, many common to both, indicating that they act similarly. The correlation between the Mehlich-1 and Mehlich-3 extraction solutions was highly significant. However, these two extraction methods were inefficient in predicting Fe availability to plants. There was a positive correlation between dry matter and Fe levels in plant shoots, even within the ranges considered adequate in the soil and in the plant. Dry matter production and leaf Fe concentration and content were positively correlated with Fep concentration, indicating that the Fe fraction related to soil organic matter most contributes to Fe availability to plants.

  11. Carbazole degradation in the soil microcosm by tropical bacterial strains

    Directory of Open Access Journals (Sweden)

    Lateef B. Salam

    2015-01-01

    Full Text Available In a previous study, three bacterial strains isolated from tropical hydrocarbon-contaminated soils and phylogenetically identified as Achromobacter sp. strain SL1, Pseudomonassp. strain SL4 and Microbacterium esteraromaticum strain SL6 displayed angular dioxygenation and mineralization of carbazole in batch cultures. In this study, the ability of these isolates to survive and enhance carbazole degradation in soil were tested in field-moist microcosms. Strain SL4 had the highest survival rate (1.8 x 107 cfu/g after 30 days of incubation in sterilized soil, while there was a decrease in population density in native (unsterilized soil when compared with the initial population. Gas chromatographic analysis after 30 days of incubation showed that in sterilized soil amended with carbazole (100 mg/kg, 66.96, 82.15 and 68.54% were degraded by strains SL1, SL4 and SL6, respectively, with rates of degradation of 0.093, 0.114 and 0.095 mg kg−1 h−1. The combination of the three isolates as inoculum in sterilized soil degraded 87.13% carbazole at a rate of 0.121 mg kg−1 h−1. In native soil amended with carbazole (100 mg/kg, 91.64, 87.29 and 89.13% were degraded by strains SL1, SL4 and SL6 after 30 days of incubation, with rates of degradation of 0.127, 0.121 and 0.124 mg kg−1h−1, respectively. This study successfully established the survivability (> 106 cfu/g detected after 30 days and carbazole-degrading ability of these bacterial strains in soil, and highlights the potential of these isolates as seed for the bioremediation of carbazole-impacted environments.

  12. An Assessment of some Fertilizer Recommendations under Different Cropping Systems in a Humid Tropical Environment

    Directory of Open Access Journals (Sweden)

    Fondufe, EY.

    2001-01-01

    Full Text Available Studies were carried out to determine the effects of four fertilizer recommendation systems (bianket recommendation, soil test recommendation, recommendation based on nutrient supplementation index and unfertilized control on five cropping systems (sole cassava, maize, melon, cassava + maize and cassava + maize + melon. The experiment was a split-plot in randomised complete block design, with fertilizer recommendation systems in main plots and cropping systems in subplots. Observations were made on plant growth and yield. Plant samples were also analyzed for N, P and K uptake. Cassava and melon gave higher yields in sole cropping than intercropping while maize yield under intercropping exceeded that under sole cropping by 17 %. Cassava root yield was significantly reduced by 24 and 35 % in cassava + maize and cassava + maize + melon plots. Fertilizer recommendation based on nutrient supplementation index (NSI gave the highest crop yield 41, 31, and 27 t/ha of maize in sole maize, maize + cassava and maize + cassava + melon and 0.6 and 0.2 t/ha of sole melon and intercropped melon respectively. Nitrogen uptake by cassava and maize was highest under NSI, but fertilizer recommendation based on soil test gave the highest crop yield and monetary returns per unit of fertilizer used.

  13. Infrared heater system for warming tropical forest understory plants and soils

    Science.gov (United States)

    Bruce A. Kimball; Aura M. Alonso-Rodríguez; Molly A. Cavaleri; Sasha C. Reed; Grizelle González; Tana E. Wood

    2018-01-01

    The response of tropical forests to global warming is one of the largest uncertainties in predicting the future carbon balance of Earth. To determine the likely effects of elevated temperatures on tropical forest understory plants and soils, as well as other ecosystems, an infrared (IR) heater system was developed to provide in situ warming for the Tropical Responses...

  14. Does the Establishment of Sustainable Use Reserves Affect Fire Management in the Humid Tropics?

    Science.gov (United States)

    Carmenta, Rachel; Blackburn, George Alan; Davies, Gemma; de Sassi, Claudio; Lima, André; Parry, Luke; Tych, Wlodek; Barlow, Jos

    2016-01-01

    Tropical forests are experiencing a growing fire problem driven by climatic change, agricultural expansion and forest degradation. Protected areas are an important feature of forest protection strategies, and sustainable use reserves (SURs) may be reducing fire prevalence since they promote sustainable livelihoods and resource management. However, the use of fire in swidden agriculture, and other forms of land management, may be undermining the effectiveness of SURs in meeting their conservation and sustainable development goals. We analyse MODIS derived hot pixels, TRMM rainfall data, Terra-Class land cover data, socio-ecological data from the Brazilian agro-census and the spatial extent of rivers and roads to evaluate whether the designation of SURs reduces fire occurrence in the Brazilian Amazon. Specifically, we ask (1) a. Is SUR location (i.e., de facto) or (1) b. designation (i.e. de jure) the driving factor affecting performance in terms of the spatial density of fires?, and (2), Does SUR creation affect fire management (i.e., the timing of fires in relation to previous rainfall)? We demonstrate that pre-protection baselines are crucial for understanding reserve performance. We show that reserve creation had no discernible impact on fire density, and that fires were less prevalent in SURs due to their characteristics of sparser human settlement and remoteness, rather than their status de jure. In addition, the timing of fires in relation to rainfall, indicative of local fire management and adherence to environmental law, did not improve following SUR creation. These results challenge the notion that SURs promote environmentally sensitive fire-management, and suggest that SURs in Amazonia will require special attention if they are to curtail future accidental wildfires, particularly as plans to expand the road infrastructure throughout the region are realised. Greater investment to support improved fire management by farmers living in reserves, in addition to

  15. Does the Establishment of Sustainable Use Reserves Affect Fire Management in the Humid Tropics?

    Directory of Open Access Journals (Sweden)

    Rachel Carmenta

    Full Text Available Tropical forests are experiencing a growing fire problem driven by climatic change, agricultural expansion and forest degradation. Protected areas are an important feature of forest protection strategies, and sustainable use reserves (SURs may be reducing fire prevalence since they promote sustainable livelihoods and resource management. However, the use of fire in swidden agriculture, and other forms of land management, may be undermining the effectiveness of SURs in meeting their conservation and sustainable development goals. We analyse MODIS derived hot pixels, TRMM rainfall data, Terra-Class land cover data, socio-ecological data from the Brazilian agro-census and the spatial extent of rivers and roads to evaluate whether the designation of SURs reduces fire occurrence in the Brazilian Amazon. Specifically, we ask (1 a. Is SUR location (i.e., de facto or (1 b. designation (i.e. de jure the driving factor affecting performance in terms of the spatial density of fires?, and (2, Does SUR creation affect fire management (i.e., the timing of fires in relation to previous rainfall? We demonstrate that pre-protection baselines are crucial for understanding reserve performance. We show that reserve creation had no discernible impact on fire density, and that fires were less prevalent in SURs due to their characteristics of sparser human settlement and remoteness, rather than their status de jure. In addition, the timing of fires in relation to rainfall, indicative of local fire management and adherence to environmental law, did not improve following SUR creation. These results challenge the notion that SURs promote environmentally sensitive fire-management, and suggest that SURs in Amazonia will require special attention if they are to curtail future accidental wildfires, particularly as plans to expand the road infrastructure throughout the region are realised. Greater investment to support improved fire management by farmers living in reserves

  16. Assessing health impacts in complex eco-epidemiological settings in the humid tropics: Modular baseline health surveys

    Energy Technology Data Exchange (ETDEWEB)

    Winkler, Mirko S., E-mail: mirko.winkler@unibas.ch [Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel (Switzerland); University of Basel, P.O. Box, CH-4003 Basel (Switzerland); Divall, Mark J., E-mail: mdivall@shapeconsulting.org [SHAPE Consulting Ltd., Pretoria 0062 (South Africa); Krieger, Gary R., E-mail: gkrieger@newfields.com [NewFields, LLC, Denver, CO 80202 (United States); Schmidlin, Sandro, E-mail: sandro.schmidlin@gmail.com [Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel (Switzerland); University of Basel, P.O. Box, CH-4003 Basel (Switzerland); Magassouba, Mohamed L., E-mail: laminemagass@yahoo.fr [Clinique Ambroise Pare, P.O. Box, 1042 Conakry (Guinea); Knoblauch, Astrid M., E-mail: astrid.knoblauch@me.com [SHAPE Consulting Ltd., Pretoria 0062 (South Africa); Singer, Burton H., E-mail: bhsinger@epi.ufl.edu [Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610 (United States); Utzinger, Juerg, E-mail: juerg.utzinger@unibas.ch [Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel (Switzerland); University of Basel, P.O. Box, CH-4003 Basel (Switzerland)

    2012-02-15

    The quantitative assessment of health impacts has been identified as a crucial feature for realising the full potential of health impact assessment (HIA). In settings where demographic and health data are notoriously scarce, but there is a broad range of ascertainable ecological, environmental, epidemiological and socioeconomic information, a diverse toolkit of data collection strategies becomes relevant for the mainly small-area impacts of interest. We present a modular, cross-sectional baseline health survey study design, which has been developed for HIA of industrial development projects in the humid tropics. The modular nature of our toolkit allows our methodology to be readily adapted to the prevailing eco-epidemiological characteristics of a given project setting. Central to our design is a broad set of key performance indicators, covering a multiplicity of health outcomes and determinants at different levels and scales. We present experience and key findings from our modular baseline health survey methodology employed in 14 selected sentinel sites within an iron ore mining project in the Republic of Guinea. We argue that our methodology is a generic example of rapid evidence assembly in difficult-to-reach localities, where improvement of the predictive validity of the assessment and establishment of a benchmark for longitudinal monitoring of project impacts and mitigation efforts is needed.

  17. Assessing health impacts in complex eco-epidemiological settings in the humid tropics: Modular baseline health surveys

    International Nuclear Information System (INIS)

    Winkler, Mirko S.; Divall, Mark J.; Krieger, Gary R.; Schmidlin, Sandro; Magassouba, Mohamed L.; Knoblauch, Astrid M.; Singer, Burton H.; Utzinger, Jürg

    2012-01-01

    The quantitative assessment of health impacts has been identified as a crucial feature for realising the full potential of health impact assessment (HIA). In settings where demographic and health data are notoriously scarce, but there is a broad range of ascertainable ecological, environmental, epidemiological and socioeconomic information, a diverse toolkit of data collection strategies becomes relevant for the mainly small-area impacts of interest. We present a modular, cross-sectional baseline health survey study design, which has been developed for HIA of industrial development projects in the humid tropics. The modular nature of our toolkit allows our methodology to be readily adapted to the prevailing eco-epidemiological characteristics of a given project setting. Central to our design is a broad set of key performance indicators, covering a multiplicity of health outcomes and determinants at different levels and scales. We present experience and key findings from our modular baseline health survey methodology employed in 14 selected sentinel sites within an iron ore mining project in the Republic of Guinea. We argue that our methodology is a generic example of rapid evidence assembly in difficult-to-reach localities, where improvement of the predictive validity of the assessment and establishment of a benchmark for longitudinal monitoring of project impacts and mitigation efforts is needed.

  18. Irrigation water consumption modelling of a soilless cucumber crop under specific greenhouse conditions in a humid tropical climate

    Directory of Open Access Journals (Sweden)

    Galo Alberto Salcedo

    Full Text Available ABSTRACT: The irrigation water consumption of a soilless cucumber crop under greenhouse conditions in a humid tropical climate has been evaluated in this paper in order to improve the irrigation water and fertilizers management in these specific conditions. For this purpose, a field experiment was conducted. Two trials were carried out during the years 2011 and 2014 in an experimental farm located in Vinces (Ecuador. In each trial, the complete growing cycle of a cucumber crop grown under a greenhouse was evaluated. Crop development was monitored and a good fit to a sigmoidal Gompertz type growth function was reported. The daily water uptake of the crop was measured and related to the most relevant indoor climate variables. Two different combination methods, namely the Penman-Monteith equation and the Baille equation, were applied. However, the results obtained with these combination methods were not satisfactory due to the poor correlation between the climatic variables, especially the incoming radiation, and the crop's water uptake (WU. On contrary, a good correlation was reported between the crop's water uptake and the leaf area index (LAI, especially in the initial crop stages. However, when the crop is fully developed, the WU stabilizes and becomes independent from the LAI. A preliminary model to simulate the water uptake of the crop was adjusted using the data obtained in the first experiment and then validated with the data of the second experiment.

  19. Breed-Specific Haematologic Reference Values in Adult Turkeys (Meleagris gallopavo in the Humid Tropics of Nigeria

    Directory of Open Access Journals (Sweden)

    Daniel-Igwe G.

    2017-03-01

    Full Text Available One hundred (50 males and 50 females B-not strain indigenous turkeys, Meleagris gallopavo, were used to determine the reference values for their haematological parameters. The turkeys were housed in the poultry unit and jugular venepunctures were used to collect their blood. The haematological parameters were determined using standard procedures. The mean values of: the packed cell volume (PCV; 37.29 ± 0.37 %, red blood cell (RBC counts (2.50 ± 0.44 × 106.µl−1, haemoglobin concentration (Hbc; 10.89 ± 0.34 g.dl−1, mean corpuscular volume (MCV; 150.63 ± 0.73 fl, mean corpuscular haemoglobin (MCH; 44.29 ± 1.78 pg, mean corpuscular haemoglobin concentration (MCHC; 29.10 ± 0.73 g.dl−1, and white blood cell (WBC counts (12.41 ± 0.83 × 103 µl−1 were determined. No significant differences were found between the male and female B-not strain turkeys in this study. The results will help in the interpretation of cases of disease when there are variations in the values and serve as baseline data for B-not strain of turkeys in the humid tropics.

  20. Floristic Diversity of Two Zones of Humid Tropical Forest at Alto Baudó, Chocó, Colombia

    Directory of Open Access Journals (Sweden)

    Luis Javier Mosquera Ramos

    2007-08-01

    Full Text Available Between June and August of 2005 the floristic composition ≥1 cm of DAP was determined in an area of ? 0.2 ha of humid tropical forest at the localities of Pie de >Pató (05º 30' 56" N and 76º 58' 26" W and Nauca (5º 41' 6" N and 77º 00' 36" W, Alto Baudó, Chocó Colombia . En each locality an area of 0.1 ha was sampled which was divided into smaller areas of 2 x 50 cm each. A total of 1618 inidivduals were recorded represented by 257 species, 156 genres and 56 botanical families from which 842 individuals, 161 species, 108 genres and 46 families where found at Pie de Pató, and 776 individuals, 161 species, 98 genres and 45 families at Nauca. At Pie de Pató the families best represented in terms of genres were Rubiaceae (12 genres and 27 species, Arecaceae (eight genres and eight species and Bombacaceae (seven genres and ten species. At Nauca they were Rubiaceae (eleven genres and 25 species, Moraceae (eight genera and 13 species and Arecaceae (eigth genres and eight species. The richness index was of 23,75 and 24,05 for Pie de Pató and Nauca respectively. Diversity change was stimated as 4,43 for both localities. These results indicate high diversity of these forests at Alto Baudó.

  1. Ecology of soil arthropod fauna in tropical forests: A review of studies from Puerto Rico

    Science.gov (United States)

    Grizelle Gonzalez; María F. Barberena

    2017-01-01

    The majority of ecological studies in the tropics deal with organisms participating in grazing food webs, while few deal with the diversity of invertebrates in the soil, leaf litter or dead wood that participate in detrital food webs. For tropical forests, the status of information on soil animal diversity is limited, especially when compared to other ecosystems such...

  2. 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.

  3. Hydrology and human behavior: two key factors of diarrhea incidence in montane tropical humid areas

    Science.gov (United States)

    Boithias, Laurie; Choisy, Marc; Souliyaseng, Noy; Jourdren, Marine; Quet, Fabrice; Buisson, Yves; Thammahacksa, Chanthamousone; Silvera, Norbert; Latsachack, Keooudone; Sengtaheuanghoung, Oloth; Pierret, Alain; Rochelle-Newall, Emma; Becerra, Sylvia; Ribolzi, Olivier

    2017-04-01

    The global burden of diarrhea is a leading cause of morbidity and mortality worldwide. In montane areas of South-East Asia such as northern Laos, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads, and potential pathogen dissemination. In this study we hypothesized that climate factors combined with human behavior control diarrhea incidence, either because higher rainfall, leading to higher stream discharges, suspended sediment loads and Fecal Indicator Bacteria (FIB) counts, are associated with higher numbers of reported diarrhea cases during the rainy season, or because water shortage leads to the use of less safe water sources during the dry season. For this mixed methods approach, we conducted a retrospective time series analysis of meteorological variables (rainfall, air temperature), hydrological variables (discharge, suspended sediments, FIB counts, water temperature) at the outlet of 2 catchments in Northern Lao PDR, and the number of diarrheal disease cases reported in 6 health centers located in the Luang Prabang Province. We also examined the socio-behavioral factors potentially affecting vulnerability to the effect of the climate factors, such as drinking water sources and hygiene habits. We found the FIB Escherichia coli to be present all year long (100-1,000 MPN 100 mL-1) indicating that fecal contamination is ubiquitous and constant. We found that populations switch their water supply from wells to surface water during drought periods, the latter of which appear to be at higher risk of bacterial contamination than municipal water fountains. We thus found that water shortage in the Luang Prabang area triggers diarrhea peaks during the dry and hot season and that rainfall and aquifer refill ends the epidemic during the wet season. We thus found that anthropogenic drivers, such as hygiene practices, were at least as important as environmental drivers in determining the seasonal pattern of a

  4. Microorganisms in Soils of Bovine Production Systems in Tropical Lowlands and Tropical Highlands in the Department of Antioquia, Colombia

    OpenAIRE

    Molina-Guzmán, Licet Paola; Henao-Jaramillo, Paula Andrea; Gutiérrez-Builes, Lina Andrea; Ríos-Osorio, Leonardo Alberto

    2018-01-01

    Studies on the physical and chemical effects of extensive grazing on soils have been performed in Colombia, but the effects of dairy cattle rearing on the biological properties of soils are not well known. The objective of this study was to evaluate microorganisms in 48 soils from livestock farms in the highland and lowland tropics in the Northern and Magdalena Medio subregions of the Department of Antioquia (Colombia). Principal component analysis demonstrated differences in the edaphic comp...

  5. Microorganisms in Soils of Bovine Production Systems in Tropical Lowlands and Tropical Highlands in the Department of Antioquia, Colombia

    Directory of Open Access Journals (Sweden)

    Licet Paola Molina-Guzmán

    2018-01-01

    Full Text Available Studies on the physical and chemical effects of extensive grazing on soils have been performed in Colombia, but the effects of dairy cattle rearing on the biological properties of soils are not well known. The objective of this study was to evaluate microorganisms in 48 soils from livestock farms in the highland and lowland tropics in the Northern and Magdalena Medio subregions of the Department of Antioquia (Colombia. Principal component analysis demonstrated differences in the edaphic compositions of the soils, with increased percentages of root colonization by arbuscular mycorrhizal fungi and the density of microorganisms in farms that have soils with moderate phosphorus and nitrogen contents, low potassium content, and a moderately acidic pH. Agglomerative cluster analysis showed two groups for the highland tropic soils and six groups for the lowland tropic soils based on their population densities and interactions with the studied parameters. These results represent a first attempt to describe the density of microorganisms and the effect of soil physicochemical parameters on colonization by arbuscular mycorrhizal fungi in areas with determinant agroecological conditions, microbial functional diversity, and the presence of mycorrhizal fungi in livestock farm soils in Colombia.

  6. Earthworms in tropical tree plantations: effects of management and relations with soil carbon and nutrient use efficiency

    Science.gov (United States)

    X Zou; Grizelle Gonzalez

    2001-01-01

    With the vast amount of abandoned tropical land due to non- sustainable farming practices, tropical tree-plantations become an effective means in restoring soil productivity and preserving ecosystem biodiversity. Because earthworms are the dominant soil fauna in moist tropical regions and play an important role in improving soil fertility, understanding the mechanisms...

  7. Isolation and characterization of oxalotrophic bacteria from tropical soils.

    Science.gov (United States)

    Bravo, Daniel; Braissant, Olivier; Cailleau, Guillaume; Verrecchia, Eric; Junier, Pilar

    2015-01-01

    The oxalate-carbonate pathway (OCP) is a biogeochemical set of reactions that involves the conversion of atmospheric CO2 fixed by plants into biomass and, after the biological recycling of calcium oxalate by fungi and bacteria, into calcium carbonate in terrestrial environments. Oxalotrophic bacteria are a key element of this process because of their ability to oxidize calcium oxalate. However, the diversity and alternative carbon sources of oxalotrophs participating to this pathway are unknown. Therefore, the aim of this study was to characterize oxalotrophic bacteria in tropical OCP systems from Bolivia, India, and Cameroon. Ninety-five oxalotrophic strains were isolated and identified by sequencing of the 16S rRNA gene. Four genera corresponded to newly reported oxalotrophs (Afipia, Polaromonas, Humihabitans, and Psychrobacillus). Ten strains were selected to perform a more detailed characterization. Kinetic curves and microcalorimetry analyses showed that Variovorax soli C18 has the highest oxalate consumption rate with 0.240 µM h(-1). Moreover, Streptomyces achromogenes A9 displays the highest metabolic plasticity. This study highlights the phylogenetic and physiological diversity of oxalotrophic bacteria in tropical soils under the influence of the oxalate-carbonate pathway.

  8. Tropical forest soil microbes and climate warming: An Andean-Amazon gradient and `SWELTR'

    Science.gov (United States)

    Nottingham, A.; Turner, B. L.; Fierer, N.; Whitaker, J.; Ostle, N. J.; McNamara, N. P.; Bardgett, R.; Silman, M.; Bååth, E.; Salinas, N.; Meir, P.

    2017-12-01

    Climate warming predicted for the tropics in the coming century will result in average temperatures under which no closed canopy forest exists today. There is, therefore, great uncertainty associated with the direction and magnitude of feedbacks between tropical forests and our future climate - especially relating to the response of soil microbes and the third of global soil carbon contained in tropical forests. While warming experiments are yet to be performed in tropical forests, natural temperature gradients are powerful tools to investigate temperature effects on soil microbes. Here we draw on studies from a 3.5 km elevation gradient - and 20oC mean annual temperature gradient - in Peruvian tropical forest, to investigate how temperature affects the structure of microbial communities, microbial metabolism, enzymatic activity and soil organic matter cycling. With decreased elevation, soil microbial diversity increased and community composition shifted, from taxa associated with oligotrophic towards copiotrophic traits. A key role for temperature in shaping these patterns was demonstrated by a soil translocation experiment, where temperature-manipulation altered the relative abundance of specific taxa. Functional implications of these community composition shifts were indicated by changes in enzyme activities, the temperature sensitivity of bacterial and fungal growth rates, and the presence of temperature-adapted iso-enzymes at different elevations. Studies from a Peruvian elevation transect indicated that soil microbial communities are adapted to long-term (differences with elevation) and short-term (translocation responses) temperature changes. These findings indicate the potential for adaptation of soil microbes in tropical soils to future climate warming. However, in order to evaluate the sensitivity of these processes to climate warming in lowland forests, in situ experimentation is required. Finally, we describe SWELTR (Soil Warming Experiment in Lowland

  9. Soil to plant transfer values of 137 Cs in soils of tropical agro-ecological systems

    International Nuclear Information System (INIS)

    Wasserman, Maria Angelica; Ferreira, Ana Cristina Melo; Conti, Claudio Carvalho; Rochedo, Elaine Rua Rodriguez; Bartoly, Flavia; Viana, Aline Gonzalez; Moura, Glaucio Pereira; Poquet, Isabel; Perez, Daniel Vidal

    2002-01-01

    Recent radioecological studies have showed that some ecosystems present more suitable conditions for soil to plant transfer of some radionuclides, while others present lower transfer when compared with average values. Due to the difficulty to generate, experimentally, soil to plant transfer factors enough to cover the totality of existing soil and vegetation types, an alternative way has been the use of soil to reference plant transfer factor determined in various ecosystems. Trough the use of conversion factors, the reference transfer factor can be converted in values of transfer factor specific for a specific type of crop. These values can be used regionally to improve dose calculation and models for radiological risk assessments. This work presents experimental data for 137 Cs for reference crops grown up in Oxisol, Ultisol and Alfisol. These results allow the assessment of sensibility of main Brazilian soils regarding a radiological contamination with 137 Cs and provide regional parameters values. The results obtained in soils of tropical climate validate the international methodology aiming to derive generic transfer factor values for 137 Cs in reference crops based on a few soil properties such as fertility, pH and organic matter content. (author)

  10. The Soil-Water Characteristic Curve of Unsaturated Tropical Residual Soil

    Science.gov (United States)

    Yusof, M. F.; Setapa, A. S.; Tajudin, S. A. A.; Madun, A.; Abidin, M. H. Z.; Marto, A.

    2016-07-01

    This study was conducted to determine the SWCC of unsaturated tropical residual soil in Kuala Lumpur, Malaysia. Undisturbed soil samples at five locations of high-risk slopes area were taken at a depth of 0.5 m using block sampler. In the determination of the SWCC, the pressure plate extractor with the capacity of 1500 kN/m2 has been used. The index properties of the soil such as natural moisture content, Atterberg limits, specific gravity, and soil classification are performed according to BS 1377: Part 2: 1990. The results of index properties show that the natural moisture content of the soil is between 36% to 46%, the plasticity index is between 10% - 26%, the specific gravity is between 2.51 - 2.61 and the soils is classified as silty organic clay of low plasticity. The SWCC data from the pressure plate extractor have been fitted with the Fredlund and Xing equation. The results show that the air entry value and residual matric suction for residual soils are in the range of 17 kN/m2 to 24 kN/m2 and 145 kN/m2 to 225 kN/m2 respectively. From the fitting curve, it is found that the average value of the Fredlund and Xing parameters such as a, n and m are in the range of 0.24-0.299, 1.7-4.8 and 0.142-0.440 respectively.

  11. Soil-Water Repellency and Critical Humidity as Cleanup Criteria for Remediation of a Hydrocarbon Contaminated Mud

    Science.gov (United States)

    Guzmán, Francisco Javier; Adams, Randy H.

    2010-05-01

    The majority of soil remediation programs focus mainly on reducing the hydrocarbon concentration, based on the assumption that the primary impact is toxicity and/or leachates and that these are directly proportional to concentration. None-the-less, interference with natural soil-water interactions are frequently more damaging, especially for sites contaminated with very viscous, weathered hydrocarbons. Therefore, the kind of hydrocarbons present in the soil and their interactions with soil surfaces may be more important than the overall hydrocarbon concentration in terms of soil restoration. One recently patented technology, the Chemical-Biological Stabilization process, focuses specifically on restoring soil fertility as the main objective for remediation of sites with agricultural use. This method was recently validated at an industrial scale by the treatment of 150 cubic meters of bentonitic drilling muds (70,5% fines) from an old sulphur mine, which were contaminated with very weathered oil (4° API), consisting of 31% asphaltenes. This material was treated by adding 4% (w/w, dry) of calcium hydroxide, followed by 4% (w/w, dry) of sugar cane cachasse (a fine fibered agricultural waste), thoroughly mixing between additions using an excavator. After the soil had dried sufficiently and the pH was soil water repellency. MED was measured on air dried soil and WDPT values were calculated from the extrapolation of penetration time vs. ethanol molarity functions (Rx=0,99). Additionally, water penetration times were measured at different humidities to determine critical moisture levels for absorption in soil humic substances while a vigorous vegetative growth was established. During two years of treatment the MED values were reduced 30% from 5,13 to 3,58M, and WDPT values were reduced over 25 times (from 10 exp5,6 s to 10 exp4,2 s). Critical humidity values varied from ~16,9 - 19,5%H for penetration in treated and untreated material. During the driest part of the year

  12. 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

  13. 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

  14. Bioremediation of a tropical clay soil contaminated with diesel oil.

    Science.gov (United States)

    Chagas-Spinelli, Alessandra C O; Kato, Mario T; de Lima, Edmilson S; Gavazza, Savia

    2012-12-30

    The removal of polyaromatic hydrocarbons (PAH) in tropical clay soil contaminated with diesel oil was evaluated. Three bioremediation treatments were used: landfarming (LF), biostimulation (BS) and biostimulation with bioaugmentation (BSBA). The treatment removal efficiency for the total PAHs differed from the efficiencies for the removal of individual PAH compounds. In the case of total PAHs, the removal values obtained at the end of the 129-day experimental period were 87%, 89% and 87% for LF, BS and BSBA, respectively. Thus, the efficiency was not improved by the addition of nutrients and microorganisms. Typically, two distinct phases were observed. A higher removal rate occurred in the first 17 days (P-I) and a lower rate occurred in the last 112 days (P-II). In phase P-I, the zero-order kinetic parameter (μg PAH g(-1) soil d(-1)) values were similar (about 4.6) for all the three treatments. In P-II, values were also similar but much lower (about 0.14). P-I was characterized by a sharp pH decrease to less than 5.0 for the BS and BSBA treatments, while the pH remained near 6.5 for LF. Concerning the 16 individual priority PAH compounds, the results varied depending on the bioremediation treatment used and on the PAH species of interest. In general, compounds with fewer aromatic rings were better removed by BS or BSBA, while those with 4 or more rings were most effectively removed by LF. The biphasic removal behavior was observed only for some compounds. In the case of naphthalene, pyrene, chrysene, benzo[k]fluoranthene and benzo[a]pyrene, removal occurred mostly in the P-I phase. Therefore, the best degradation process for total or individual PAHs should be selected considering the target compounds and the local conditions, such as native microbiota and soil type. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Potential of indirect evaporative passive cooling with embedded tubes in a humid tropical climate : applications in a typical hot humid climate

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Chavez, J.R. [Univ. Autonoma Metropolitana-Azcapotzalco, Mexico City (Mexico). Dept. de Medio Ambiente, Laboratorio de Investigaciones en Arquitectura Bioclimatica; Givoni, B. [California Univ., Los Angeles, CA (United States); BGU, Beer Sheva (Israel); Viveros, O. [Cristobal Colon Univ., Veracruz (Mexico)

    2009-07-01

    The use of passive cooling techniques in buildings in hot and humid regions can reduce energy consumption while increasing thermal comfort for occupants. A study was conducted in the City of Veracruz, Mexico to investigate the performance of tubes embedded in the roof of the Gulf Meteorological Prevision Centre. Two identical insulated experimental cells were used, one serving as the control and the other one as the test unit, where the technique of embedded tubes in the roof was implemented and investigated during a typical overheating season. Results showed that this indirect evaporative cooling system is an effective strategy to reduce indoor temperatures without increasing the indoor humidity in buildings. The indoor maximum temperature was lowered by 2.72 K in the experimental test cell relative to the control unit. In addition, the resulting reduction of radiant temperatures in the test unit improved the thermal comfort of the occupants. It is expected that the implementation of this passive cooling technique will eventually contribute to reduced energy consumption and less use of air-conditioning systems in buildings, and thereby prevent emission of greenhouse gases to the atmosphere. 9 refs., 1 tab., 6 figs.

  16. 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.

  17. Effect of wood ash application on soil solution chemistry of tropical acid soils: incubation study.

    Science.gov (United States)

    Nkana, J C Voundi; Demeyer, A; Verloo, M G

    2002-12-01

    The objective of this study was to determine the effect of wood ash application on soil solution composition of three tropical acid soils. Calcium carbonate was used as a reference amendment. Amended soils and control were incubated for 60 days. To assess soluble nutrients, saturation extracts were analysed at 15 days intervals. Wood ash application affects the soil solution chemistry in two ways, as a liming agent and as a supplier of nutrients. As a liming agent, wood ash application induced increases in soil solution pH, Ca, Mg, inorganic C, SO4 and DOC. As a supplier of elements, the increase in the soil solution pH was partly due to ligand exchange between wood ash SO4 and OH- ions. Large increases in concentrations of inorganic C, SO4, Ca and Mg with wood ash relative to lime and especially increases in K reflected the supply of these elements by wood ash. Wood ash application could represent increased availability of nutrients for the plant. However, large concentrations of basic cations, SO4 and NO3 obtained with higher application rates could be a concern because of potential solute transport to surface waters and groundwater. Wood ash must be applied at reasonable rates to avoid any risk for the environment.

  18. 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

  19. 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

  20. Soil organic matter dynamics during 80 years of reforestation of tropical pastures

    Science.gov (United States)

    Erika Marin-Spiotta; Whendee L. Silver; Christopher W. Swanston; Rebecca. Ostertag

    2009-01-01

    Our research takes advantage of a historical trend in natural reforestation of abandoned tropical pastures to examine changes in soil carbon (C) during 80 years of secondary forest regrowth. We combined a chronosequence...

  1. Soil phosphorus cycling in tropical soils: An ultisol and oxisol perspective

    Science.gov (United States)

    Reed, Sasha C.; Wood, Tana E

    2016-01-01

    Phosphorus (P) is essential for life. It is the backbone of our DNA, provides energy for biological reactions, and is an integral component of cell membranes. As such, it is no surprise that P availability plays a strong role in regulating ecosystem structure and function (Wassen et al. 2005, Elser et al. 2007, Condit et al. 2013), and in determining our capacity to grow food for a burgeoning human population (Sharpley et al. 1997, Sims and Sharpley 2005, Lal 2009). Concerns that P supplies are insufficient to meet our species’ growing demands are on the rise (Richardson and Simpson 2011) and scientific and media outlets increasingly discuss P as an element worthy of our attention and concern (e.g., Cordell et al. 2009, Lougheed 2011, Edixhoven et al. 2013, Ulrich et al. 2013). Indeed, a number of groups are calling for the explicit stewardship of our planet’s P stocks (Schipper 2014, Withers et al. 2015). Yet a focus on P as a vital and limited resource is not new in the tropics, where an abundance of soils characterized by low P has resulted in a substantial, longstanding reliance on P inputs for tropical ecosystem function in both unmanaged and agriculture settings (Table 1, Figure 2; Sanchez 1976, Swap et al. 1992, Chadwick et al. 1999, Okin et al. 2004, Lal 2009). Indeed, there is a long history of cultivation in the tropics, where for thousands of years land management practices have included methods that effectively modify P availability for plant growth (e.g., Giardina et al. 2000, Lawrence and Schlesinger 2001, Vitousek et al. 2004, Lewis et al. 2015). Nevertheless, low soil fertility in tropical systems where fertilizer is scarce has enduringly been recognized as a major source of hunger and starvation (Sanchez and Buol 1975, Sanchez 2002, Sanchez and Swaminathan 2005).

  2. The Vertical Structure of Relative Humidity and Ozone in the Tropical Upper Troposphere: Intercomparisons Among In Situ Observations, A-Train Measurements and Large-Scale Models

    Science.gov (United States)

    Selkirk, Henry B.; Manyin, Michael; Douglass, Anne R.; Oman, Luke; Pawson, Steven; Ott, Lesley; Benson, Craig; Stolarski, Richard

    2010-01-01

    In situ measurements in the tropics have shown that in regions of active convection, relative humidity with respect to ice in the upper troposphere is typically close to saturation on average, and supersaturations greater than 20% are not uncommon. Balloon soundings with the cryogenic frost point hygrometer (CFH) at Costa Rica during northern summer, for example, show this tendency to be strongest between 11 and 15.5 km (345-360 K potential temperature, or approximately 250-120 hPa). this is the altitude range of deep convective detrainment. Additionally, simultaneous ozonesonde measurements show that stratospheric air (O3 greater than 150 ppbv) can be found as low as approximately 14 km (350 K/150 hPa). In contrast, results from northern winter show a much drier upper troposphere and little penetration of stratospheric air below the tropopause at 17.5 km (approximately 383 K). We show that these results are consistent with in situ measurements from the Measurement of Ozone and water vapor by Airbus In-service airCraft (MOZAIC) program which samples a wider, though still limited, range of tropical locations. To generalize to the tropics as a whole, we compare our insitu results to data from two A-Train satellite instruments, the Atmospheric Infrared Sounder (AIRS) and the Microwave Limb Sounder (MLS) on the Aqua and Aura satellites respectively. Finally, we examine the vertical structure of water vapor, relative humidity and ozone in the NASA Goddard MERRA analysis, an assimilation dataset, and a new version of the GEOS CCM, a free-running chemistry-climate model. We demonstrate that conditional probability distributions of relative humidity and ozone are a sensitive diagnostic for assessing the representation of deep convection and upper troposphere/lower stratosphere mixing processes in large-scale analyses and climate models.

  3. Light and soil humidity influencing oak seedling growth and physiology in mixed hardwood gaps

    Directory of Open Access Journals (Sweden)

    Raddi S

    2009-06-01

    Full Text Available In “S. Rossore, Migliarino, Massaciuccoli” Natural Park (Pisa, I six-month-old pedunculate oak seedlings (Quercus robur L. were transplanted within natural gaps of a mixed oak forest. Micro-environmental variability for radiation and water soil content were measured for 145 seedlings during the year. Irradiation relative to the open field (IR ranged from 5% to 57%. Seven classes of IR each with 20 seedlings were selected. Leaf mass per area was strongly influenced by IR. In the first 3 years survival was high (95, 76 and 75%, respectively and seedling reached 14±6 cm, 27±13 cm and 39±19 (sd cm of height. Even if IR and soil water content (SWC were negatively associated, indicating a lower SWC at the centre of the gaps, height and its relative growth rate increased with IR (explored range: 8-40% with a significant interaction with SWC in the 1st year, indicating the positive effect of soil moisture. In the 3rd year dimensional traits were higher in L+W+ (high light and humidity followed by L-W+ (low light and high humidity, L+W- and finally by L-W-. Summer drought typical of the Mediterranean climate was evaluated by chlorophyll fluorescence of PSII on apical leaves of seedlings and mature trees at the beginning (21 June and in mid-summer (20 July. While in June physiological traits did not differ between low and high IR, in mid-summer (at the peak of water-stress seedlings of the two highest light classes showed chronic photoinhibition (Fv/Fm<0.75 and an increase in thermal dissipation (D by constitutive term (Dc=1-Fv/Fm and by regulated mechanisms of dissipation through xanthophyll-cycle term (Dx. Moreover, in July seedling leaf physiology largely differed with IR: leaves acclimated to high IR have higher photosynthetic potentialities, as shown by electron transport rate (ETR and quantum yield (P at saturating light maintained by an increase of the fraction of open reaction centres (qP, counterbalancing the efficiency decrease of the

  4. Implementation monitoring temperature, humidity and mositure soil based on wireless sensor network for e-agriculture technology

    Science.gov (United States)

    Sumarudin, A.; Ghozali, A. L.; Hasyim, A.; Effendi, A.

    2016-04-01

    Indonesian agriculture has great potensial for development. Agriculture a lot yet based on data collection for soil or plant, data soil can use for analys soil fertility. We propose e-agriculture system for monitoring soil. This system can monitoring soil status. Monitoring system based on wireless sensor mote that sensing soil status. Sensor monitoring utilize soil moisture, humidity and temperature. System monitoring design with mote based on microcontroler and xbee connection. Data sensing send to gateway with star topology with one gateway. Gateway utilize with mini personal computer and connect to xbee cordinator mode. On gateway, gateway include apache server for store data based on My-SQL. System web base with YII framework. System done implementation and can show soil status real time. Result the system can connection other mote 40 meters and mote lifetime 7 hours and minimum voltage 7 volt. The system can help famer for monitoring soil and farmer can making decision for treatment soil based on data. It can improve the quality in agricultural production and would decrease the management and farming costs.

  5. Sorption of pesticides in tropical and temperate soils from Australia and the Philippines.

    Science.gov (United States)

    Oliver, Danielle P; Kookana, Rai S; Quintana, Belen

    2005-08-10

    The sorption behavior of diuron, imidacloprid, and thiacloprid was investigated using 22 soils collected in triplicate from temperate environments in Australia and tropical environments in Australia and the Philippines. Within the temperate environment in Australia, the soils were selected from a range of land uses. The average KOC values (L/kg) for imidacloprid were 326, 322, and 336; for thiacloprid, the values were 915, 743, and 842; and for diuron, the values were 579, 536, and 618 for the Ord (tropical), Mt. Lofty (temperate), and Philippines (tropical) soils, respectively. For all soils, the sorption coefficients decreased in the following order: thiacloprid > diuron > imidacloprid. There were no significant differences in sorption behavior between the tropical soils from the Philippines and the temperate soils from Australia. Sorption was also not significantly related with soil characteristics, namely, organic carbon (OC) content, clay content, and pH, for any of the three chemicals studied. When the data were sorted into separate land uses, the sorption of all three chemicals was highly correlated (P soils from the Philippines. Sorption coefficients for all three chemicals were highly correlated with OC in temperate, native soils only when one extreme value was removed. The relationships between sorption of all three chemicals and OC in temperate, pasture soils were best described by a polynomial. Sorption coefficients for imidacloprid and thiacloprid determined in the temperate pasture soils remained fairly consistent as the OC content increased from 3.3 to 5.3%, indicating that, although the total OC in the pasture soils was increasing, the component of OC involved with sorption of these two compounds may have been remaining constant. This study demonstrated that the origin of the soils (i.e., temperate vs tropical) had no significant effect on the sorption behavior, but in some cases, land use significantly affected the sorption behavior of the three

  6. Use of cesium 137 as a radiotracer in the quantification of tropical soil erosion

    International Nuclear Information System (INIS)

    Sibello Hernandez, Rita Y.; Cartas Aguila, Hector; Martin Perez, Jorge

    2005-01-01

    The main objective of this work was to evaluate the applicability of this technique to quantify the soil erosion in the tropical region. With this purpose the technique was applied in the tropical soils belonging to a glide parcel, in Cienfuegos province, in Cuba, in the Caribbean area. This allowed us to compare and to demonstrate the good agreement of the results of the soil loss quantification obtained using the 137 Cs technique: 37.00 + - 0.80 t.ha -1 . year -1 with the obtained using erosion plots in the Soil Experimental Station in Barajagua: 40 t.ha -1 . year -1

  7. Effects of phosphorus and nitrogen additions on tropical soil microbial activity in the context of experimental warming

    Science.gov (United States)

    Foley, M.; Nottingham, A.; Turner, B. L.

    2017-12-01

    Soil warming is generally predicted to increase microbial mineralization rates and accelerate soil C losses which could establish a positive feedback to climatic warming. Tropical rain forests account for a third of global soil C, yet the responseto of tropical soil C a warming climate remains poorly understood. Despite predictions of soil C losses, decomposition of soil organic matter (SOM) in tropical soils may be constrained by several factors including microbial nutrient deficiencies. We performed an incubation experiment in conjunction with an in-situ soil warming experiment in a lowland tropical forest on Barro Colorado Island, Panama, to measure microbial response to two key nutrient additions in shallow (0-10cm) and deep (50-100 cm) soils. We compared the response of lowland tropical soils to montane tropical soils, predicting that lowland soils would display the strongest response to phosphorus additions. Soils were treated with either carbon alone (C), nitrogen (CN), phosphorus (CP) or nitrogen and phosphorus combined (CNP). Carbon dioxide (CO2) production was measured by NaOH capture and titrimetric analysis for 10 days. Cumulative CO2 production in montane soils increased significantly with all additions, suggesting these soils are characterized by a general microbial nutrient deficiency. The cumulative amount of C respired in deep soils from the lowland site increased significantly with CP and CNP additions, suggesting that microbial processes in deep lowland tropical soils are phosphorus-limited. These results support the current understanding that lowland tropical forests are growing on highly weathered, phosphorus-deplete soils, and provide novel insight that deep tropical SOM may be stabilized by a lack of biologically-available phosphorus. Further, this data suggests tropical soil C losses under elevated temperature may be limited by a strong microbial phosphorus deficiency.

  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. Soil C dynamics under intensive oil palm plantations in poor tropical soils

    Science.gov (United States)

    Guillaume, Thomas; Ruegg, Johanna; Quezada, Juan Carlos; Buttler, Alexandre

    2017-04-01

    Oil palm cultivation mainly takes place on heavily-weathered tropical soils where nutrients are limiting factors for plant growth and microbial activity. Intensive fertilization and changes of C input by oil palms strongly affects soil C and nutrient dynamics, challenging long-term soil fertility. Oil palm plantations management offers unique opportunities to study soil C and nutrients interactions in field conditions because 1) they can be considered as long-term litter manipulation experiments since all aboveground C inputs are concentrated in frond pile areas and 2) mineral fertilizers are only applied in specific areas, i.e. weeded circle around the tree and interrows, but not in harvest paths. Here, we determined impacts of mineral fertilizer and organic matter input on soil organic carbon dynamics and microbial activity in mature oil palm plantation established on savanna grasslands. Rates of savanna-derived soil organic carbon (SOC) decomposition and oil palm-derived SOC net stabilization were determined using changes in isotopic signature of in C input following a shift from C4 (savanna) to C3 (oil palm) vegetation. Application of mineral fertilizer alone did not affect savanna-derived SOC decomposition or oil palm-derived SOC stabilization rates, but fertilization associated with higher C input lead to an increase of oil palm-derived SOC stabilization rates, with about 50% of topsoil SOC derived from oil palm after 9 years. High carbon and nutrients inputs did not increase microbial biomass but microorganisms were more active per unit of biomass and SOC. In conclusion, soil organic matter decomposition was limited by C rather than nutrients in the studied heavily-weathered soils. Fresh C and nutrient inputs did not lead to priming of old savanna-derived SOC but increased turnover and stabilization of new oil palm-derived SOC.

  10. Biodegradation of di(2-ethylhexyl)phthalate in a typical tropical soil

    Energy Technology Data Exchange (ETDEWEB)

    Castelo de Moura Carrara, Silvia Marta; Morita, Dione Mari [Polytechnic School, University of Sao Paulo (Brazil); Boscov, Maria Eugenia Gimenez, E-mail: meboscov@usp.br [Polytechnic School, University of Sao Paulo (Brazil)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Scarce literature on contamination of tropical soils by phthalates. Black-Right-Pointing-Pointer Investigation of mobility of DEHP in a tropical soil by infiltration tests showed that DEHP is retained in the upper layer of the soil. Black-Right-Pointing-Pointer Low air and water permeability indicate that in situ bioremediation is not feasible for this soil. Black-Right-Pointing-Pointer Respirometric tests were inadequate to investigate biodegradation because tropical soils are acidic. Black-Right-Pointing-Pointer Slurry-phase reactor with cement mixer provided significant biodegradation (99% in 49 days). - Abstract: The aim of this research was to evaluate the possibility of biodegradation of di(2-ethylhexyl)phthalate (DEHP), widely used as an industrial plasticizer and considered an endocrine-disrupting chemical included in the U.S. Environmental Protection Agency priority list, in a Brazilian tropical soil, which has not been previously reported in the literature, despite the geographic importance of tropical soils. Preliminary laboratory testing comprised respirometric, air and water permeability, and pilot scale infiltration tests. Standard respirometric tests were found inadequate for studying biodegradation in tropical contaminated soils, due to the effect of the addition of significant amounts of calcium carbonate, necessary to adjust soil pH. Pilot scale infiltration tests performed for 5 months indicated that DEHP was retained in the superficial layer of the soil, barely migrating downwards, whereas air and water permeability tests discarded in situ bioremediation. However, ex situ bioremediation was possible, using a slurry-phase reactor with acclimated microorganisms, in pilot scale tests conducted to remediate a total mass of 150 kg of contaminated soil with 100 mg DEHP/kg. The removal of DEHP in the slurry-phase reactor achieved the percentage of 99% in 49 days, with biodegradation following a first

  11. Soil changes induced by rubber and tea plantation establishment: comparison with tropical rain forest soil in Xishuangbanna, SW China.

    Science.gov (United States)

    Li, Hongmei; Ma, Youxin; Liu, Wenjie; Liu, Wenjun

    2012-11-01

    Over the past thirty years, Xishuangbanna in Southwestern China has seen dramatic changes in land use where large areas of tropical forest and fallow land have been converted to rubber and tea plantations. In this study we evaluated the effects of land use and slope on soil properties in seven common disturbed and undisturbed land-types. Results indicated that all soils were acidic, with pH values significantly higher in the 3- and 28-year-old rubber plantations. The tropical forests had the lowest bulk densities, especially significantly lower from the top 10 cm of soil, and highest soil organic matter concentrations. Soil moisture content at topsoil was highest in the mature rubber plantation. Soils in the tropical forests and abandoned cultivated land had inorganic N (IN) concentrations approximately equal in NH(4) (+)-N and NO(3) (-)-N. However, soil IN pools were dominated by NH(4) (+)-N in the rubber and tea plantations. This trend suggests that conversion of tropical forest to rubber and tea plantations increases NH(4) (+)-N concentration and decreases NO(3) (-)-N concentration, with the most pronounced effect in plantations that are more frequently fertilized. Soil moisture content, IN, NH(4) (+)-N and NO(3) (-)-N concentrations within all sites were higher in the rainy season than in the dry season. Significant differences in the soil moisture content, and IN, NH(4) (+)-N and NO(3) (-)-N concentration was detected for both land uses and sampling season effects, as well as interactions. Higher concentrations of NH(4) (+)-N were measured at the upper slopes of all sites, but NO(3) (-)-N concentrations were highest at the lower slope in the rubber plantations and lowest at the lower slopes at all other. Thus, the conversion of tropical forests to rubber and tea plantations can have a profound effect on soil NH(4) (+)-N and NO(3) (-)-N concentrations. Options for improved soil management in plantations are discussed.

  12. Streptomyces solisilvae sp. nov., isolated from tropical forest soil.

    Science.gov (United States)

    Zhou, Shuangqing; Yang, Xiaobo; Huang, Dongyi; Huang, Xiaolong

    2017-09-01

    A novel streptomycete (strain HNM0141T) was isolated from tropical forest soil collected from Bawangling mountain of Hainan island, PR China and its taxonomic position was established in a polyphasic study. The organism had chemical and morphological properties consistent with its classification as a member of the Streptomyces violaceusnigerclade. On the basis of the results of 16S rRNA gene sequence analysis, HNM0141T showed highest similarity to Streptomyces malaysiensisCGMCC4.1900T (99.4 %), Streptomyces samsunensis DSM 42010T (98.9 %), Streptomyces yatensis NBRC 101000T (98.3 %), Streptomyces rhizosphaericus NBRC 100778T (98.0 %) and Streptomyces sporoclivatus NBRC 100767T (97.9 %). The strain formed a well-delineated subclade with S. malaysiensis CGMCC4.1900T and S. samsunensis DSM 42010T. The levels of DNA-DNA relatedness between HNM0141T and S. malaysiensis CGMCC4.1900T and S. samsunensis DSM 42010T were 62 and 44 %, respectively. On the basis of phenotypic and genotypic characteristics, HNM0141T represents a novel species in the S. violaceusnigerclade for which the name Streptomyces solisilvae sp. nov. is proposed. The type strain is HNM0141 T (=CCTCC AA 2016045T=KCTC 39905T).

  13. Dissipation of 2,4-D in soils of the Humid Pampa region, Argentina: a microcosm study.

    Science.gov (United States)

    Merini, Luciano J; Cuadrado, Virginia; Flocco, Cecilia G; Giulietti, Ana M

    2007-06-01

    Phenoxy herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in agricultural practices. Although its half life in soil is 7-14d, the herbicide itself and its first metabolite 2,4-dichlorophenol (2,4-DCP) could remain in the soil for longer periods, as a consequence of its intensive use. Microcosms assays were conducted to study the influence of indigenous microflora and plants (alfalfa) on the dissipation of 2,4-D from soils of the Humid Pampa region, Argentina, with previous history of phenoxy herbicides application. Results showed that 2,4-D was rapidly degraded, and the permanence of 2,4-DCP in soil depended on the presence of plants and soil microorganisms. Regarding soil microbial community, the presence of 2,4-D degrading bacteria was detected even in basal conditions in this soil, possibly due to the adaptation of the microflora to the herbicide. There was an increment of two orders of magnitude in herbicide degraders after 15d from 2,4-D addition, both in planted and unplanted microcosms. Total heterotrophic bacteria numbers were about 1x10(8) CFUg(-1) dry soil and no significant differences were found between different treatments. Overall, the information provided by this work indicates that the soil under study has an important intrinsic degradation capacity, given by a microbial community adapted to the presence of phenoxy herbicides.

  14. Multivariate analysis of effects of diurnal temperature and seasonal humidity variations by tropical savanna climate on the emissions of anthropogenic volatile organic compounds.

    Science.gov (United States)

    Liu, Chih-Chung; Chen, Wei-Hsiang; Yuan, Chung-Shin; Lin, Chitsan

    2014-02-01

    Volatile organic compounds (VOCs), particularly those from anthropogenic sources, have been of substantial concern. In this study, the influences of diurnal temperature and seasonal humidity variations by tropical savanna climate on the distributions of VOCs from stationary industrial sources were investigated by analyzing the concentrations during the daytime and nighttime in the dry and wet seasons and assessing the results by principal component analysis (PCA) and cluster analysis. Kaohsiung City in Southern Taiwan, known for its severe VOC pollution, was chosen as the location to be examined. In the results, the VOC concentrations were lower during the daytime and in the wet season, possibly attributed to the stronger photochemical reactions and increasing inhibition of VOC emissions and transports by elevating humidity levels. Certain compounds became appreciably more important at higher humidity, as these compounds were saturated hydrocarbons with relatively low molecular weights. The influence of diurnal temperature variation on VOC distribution behaviors seemed to be less important than and interacted with that of seasonal humidity variation. Heavier aromatic hydrocarbons with more complex structures and some aliphatic compounds were found to be the main species accounting for the maximum variances of the data observed at high humidity, and the distinct grouping of compounds implied a pronounced inherent characteristic of each cluster in the observed VOC distributions. Under the influence of diurnal temperature variation, selected VOCs that may have stronger photochemical resistances and/or longer lifetimes in the atmosphere were clustered with each other in the cluster analysis, whereas the other groups might consist of compounds with different levels of vulnerability to sunlight or high temperatures. These findings prove the complications in the current knowledge regarding the VOC contaminations and providing insight for managing the adverse impacts of

  15. pH dominates variation in tropical soil archaeal diversity and community structure.

    Science.gov (United States)

    Tripathi, Binu M; Kim, Mincheol; Lai-Hoe, Ang; Shukor, Nor A A; Rahim, Raha A; Go, Rusea; Adams, Jonathan M

    2013-11-01

    Little is known of the factors influencing soil archaeal community diversity and composition in the tropics. We sampled soils across a range of forest and nonforest environments in the equatorial tropics of Malaysia, covering a wide range of pH values. DNA was PCR-amplified for the V1-V3 region of the 16S rRNA gene, and 454-pyrosequenced. Soil pH was the best predictor of diversity and community composition of Archaea, being a stronger predictor than land use. Archaeal OTU richness was highest in the most acidic soils. Overall archaeal abundance in tropical soils (determined by qPCR) also decreased at higher pH. This contrasts with the opposite trend previously found in temperate soils. Thaumarcheota group 1.1b was more abundant in alkaline soils, whereas group 1.1c was only detected in acidic soils. These results parallel those found in previous studies in cooler climates, emphasizing niche conservatism among broad archaeal groups. Among the most abundant operational taxonomic units (OTUs), there was clear evidence of niche partitioning by pH. No individual OTU occurred across the entire range of pH values. Overall, the results of this study show that pH plays a major role in structuring tropical soil archaeal communities. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  16. The ameliorative effect of ascorbic acid on the oxidative status, live weight and recovery rate in road transport stressed goats in a hot humid tropical environment.

    Science.gov (United States)

    Nwunuji, Tanko Polycarp; Mayowa, Opeyemi Onilude; Yusoff, Sabri Mohd; Bejo, Siti-Khairani; Salisi, Shahrom; Mohd, Effendy Abd Wahid

    2014-05-01

    The ameliorative effect of ascorbic acid (AA) on live weight following transportation is vital in animal husbandry. This study investigated the influence of AA on live weight, rectal temperature (rt), and oxidative status of transport stressed goats in a hot humid tropical environment. Twenty-four goats were divided into four groups, A, B, C and D of six animals each. Group A were administered AA 100 mg/kg intramuscularly 30 min prior to 3.5 h transportation. Group B was administered AA following transportation. Group C were transported but not administered AA as positive controls while group D were not transported but were administered normal saline as negative controls. Live weight, rt and blood samples were collected before, immediately post-transport (pt), 24 h, 3 days, 7 days and 10 days pt. Plasma was used for malondialdehyde (MDA) analysis while hemolysates were used for superoxide dismutase (SOD) analysis. There was minimal live weight loss in group A compared to groups B and C. Group A recorded reduced MDA activities and increased SOD activities compared to groups B and C which recorded significantly high MDA activities. This study revealed that AA administration ameliorated the stress responses induced by transportation in animals in hot humid tropical environments. The administration of AA to goats prior to transportation could ameliorate stress and enhance productivity. © 2014 Japanese Society of Animal Science.

  17. Climate Impacts on Soil Carbon Processes along an Elevation Gradient in the Tropical Luquillo Experimental Forest

    Directory of Open Access Journals (Sweden)

    Dingfang Chen

    2017-03-01

    Full Text Available Tropical forests play an important role in regulating the global climate and the carbon cycle. With the changing temperature and moisture along the elevation gradient, the Luquillo Experimental Forest in Northeastern Puerto Rico provides a natural approach to understand tropical forest ecosystems under climate change. In this study, we conducted a soil translocation experiment along an elevation gradient with decreasing temperature but increasing moisture to study the impacts of climate change on soil organic carbon (SOC and soil respiration. As the results showed, both soil carbon and the respiration rate were impacted by microclimate changes. The soils translocated from low elevation to high elevation showed an increased respiration rate with decreased SOC content at the end of the experiment, which indicated that the increased soil moisture and altered soil microbes might affect respiration rates. The soils translocated from high elevation to low elevation also showed an increased respiration rate with reduced SOC at the end of the experiment, indicating that increased temperature at low elevation enhanced decomposition rates. Temperature and initial soil source quality impacted soil respiration significantly. With the predicted warming climate in the Caribbean, these tropical soils at high elevations are at risk of releasing sequestered carbon into the atmosphere.

  18. Advancing the quantification of humid tropical forest cover loss with multi-resolution optical remote sensing data: Sampling & wall-to-wall mapping

    Science.gov (United States)

    Broich, Mark

    Humid tropical forest cover loss is threatening the sustainability of ecosystem goods and services as vast forest areas are rapidly cleared for industrial scale agriculture and tree plantations. Despite the importance of humid tropical forest in the provision of ecosystem services and economic development opportunities, the spatial and temporal distribution of forest cover loss across large areas is not well quantified. Here I improve the quantification of humid tropical forest cover loss using two remote sensing-based methods: sampling and wall-to-wall mapping. In all of the presented studies, the integration of coarse spatial, high temporal resolution data with moderate spatial, low temporal resolution data enable advances in quantifying forest cover loss in the humid tropics. Imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used as the source of coarse spatial resolution, high temporal resolution data and imagery from the Landsat Enhanced Thematic Mapper Plus (ETM+) sensor are used as the source of moderate spatial, low temporal resolution data. In a first study, I compare the precision of different sampling designs for the Brazilian Amazon using the annual deforestation maps derived by the Brazilian Space Agency for reference. I show that sampling designs can provide reliable deforestation estimates; furthermore, sampling designs guided by MODIS data can provide more efficient estimates than the systematic design used for the United Nations Food and Agricultural Organization Forest Resource Assessment 2010. Sampling approaches, such as the one demonstrated, are viable in regions where data limitations, such as cloud contamination, limit exhaustive mapping methods. Cloud-contaminated regions experiencing high rates of change include Insular Southeast Asia, specifically Indonesia and Malaysia. Due to persistent cloud cover, forest cover loss in Indonesia has only been mapped at a 5-10 year interval using photo interpretation of single

  19. FATTY ACID STABLE ISOTOPE INDICATORS OF MICROBIAL CARBON SOURCE IN TROPICAL SOILS

    Science.gov (United States)

    The soil microbial community plays an important role in tropical ecosystem functioning because of its importance in the soil organic matter (SOM) cycle. We have measured the stable carbon isotopic ratio (delta13C) of individual phospholipid fatty acids (PLFAs) in a variety of tr...

  20. Comparing soil organic carbon dynamics in plantation and secondary forest in wet tropics in Puerto Rico

    Science.gov (United States)

    LI YIQING; MING XU; ZOU XIAOMING; PEIJUN SHI§; YAOQI ZHANG

    2005-01-01

    We compared the soil carbon dynamics between a pine plantation and a secondary forest, both of which originated from the same farmland abandoned in 1976 with the same cropping history and soil conditions, in the wet tropics in Puerto Rico from July 1996 to June 1997. We found that the secondary forest accumulated the heavy-fraction organic carbon (HF-OC) measured by...

  1. Rice straw biochar affects water retention and air movement in a sand-textured tropical soil

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Ahmed, Fauziatu

    2017-01-01

    Despite the current global attention on biochar (BC) as a soil amendment, knowledge is limited on how BC impacts the physical properties of coarse-textured soils (sand > 95%), particularly in tropical regions. A two-season field-study was conducted to investigate the effect of rice straw BC (3% w...

  2. Soil-mediated filtering organizes tree assemblages in regenerating tropical forests

    NARCIS (Netherlands)

    Pinho, Bruno Ximenes; Melo, de Felipe Pimentel Lopes; Arroyo-Rodríguez, Víctor; Pierce, Simon; Lohbeck, Madelon; Tabarelli, Marcelo

    2018-01-01

    Secondary forests are increasingly dominant in human-modified tropical landscapes, but the drivers of forest recovery remain poorly understood. Soil conditions influence plant community composition, and are expected to change over a gradient of succession. However, the role of soil conditions as

  3. Soil and water pollution in a banana production region in tropical Mexico

    NARCIS (Netherlands)

    Geissen, V.; Que Ramos, F.; Bastidas-Bastidas, de P.J.; Díaz-González, G.; Bello-Mendoza, R.; Huerta-Lwanga, E.; Ruiz-Suárez, L.E.

    2010-01-01

    The effects of abundant Mancozeb (Mn, Zn— bisdithiocarbamate) applications (2.5 kg ha-1week-1 for 10 years) on soil and surface-, subsurface- and groundwater pollution were monitored in a banana production region of tropical Mexico. In soils, severe manganese accumulation was observed, wheras the

  4. Soil phosphorus heterogeneity promotes tree species diversity and phylogenetic clustering in a tropical seasonal rainforest.

    Science.gov (United States)

    Xu, Wumei; Ci, Xiuqin; Song, Caiyun; He, Tianhua; Zhang, Wenfu; Li, Qiaoming; Li, Jie

    2016-12-01

    The niche theory predicts that environmental heterogeneity and species diversity are positively correlated in tropical forests, whereas the neutral theory suggests that stochastic processes are more important in determining species diversity. This study sought to investigate the effects of soil nutrient (nitrogen and phosphorus) heterogeneity on tree species diversity in the Xishuangbanna tropical seasonal rainforest in southwestern China. Thirty-nine plots of 400 m 2 (20 × 20 m) were randomly located in the Xishuangbanna tropical seasonal rainforest. Within each plot, soil nutrient (nitrogen and phosphorus) availability and heterogeneity, tree species diversity, and community phylogenetic structure were measured. Soil phosphorus heterogeneity and tree species diversity in each plot were positively correlated, while phosphorus availability and tree species diversity were not. The trees in plots with low soil phosphorus heterogeneity were phylogenetically overdispersed, while the phylogenetic structure of trees within the plots became clustered as heterogeneity increased. Neither nitrogen availability nor its heterogeneity was correlated to tree species diversity or the phylogenetic structure of trees within the plots. The interspecific competition in the forest plots with low soil phosphorus heterogeneity could lead to an overdispersed community. However, as heterogeneity increase, more closely related species may be able to coexist together and lead to a clustered community. Our results indicate that soil phosphorus heterogeneity significantly affects tree diversity in the Xishuangbanna tropical seasonal rainforest, suggesting that deterministic processes are dominant in this tropical forest assembly.

  5. Trace metal uptake by tropical vegetables grown on soil amended with urban sewage sludge

    International Nuclear Information System (INIS)

    Nabulo, G.; Black, C.R.; Young, S.D.

    2011-01-01

    Trace metal uptake was measured for tropical and temperate leafy vegetables grown on soil from an urban sewage disposal farm in the UK. Twenty-four leafy vegetables from East Africa and the UK were assessed and the five vegetable types that showed the greatest Cd concentrations were grown on eight soils differing in the severity of contamination, pH and other physico-chemical properties. The range of Cd concentrations in the edible shoots was greater for tropical vegetables than for temperate types. Metal uptake was modelled as a function of (i) total soil metal concentration, (ii) CaCl 2 -soluble metal, (iii) soil solution concentration and (iv) the activity of metal ions in soil pore water. Tropical vegetables were not satisfactorily modelled as a single generic 'green vegetable', suggesting that more sophisticated approaches to risk assessment may be required to assess hazard from peri-urban agriculture in developing countries. - Research highlights: → Cadmium uptake by tropical green vegetables varies greatly between types. → Modelling metal uptake works best for Ni, Cd and Zn but is poor for Cu, Ba and Pb. → Modelling with dilute CaCl 2 extraction is as good as metal ion activity in pore water. - Trace metal uptake by tropical leaf vegetables can be predicted from dilute CaCl 2 extraction of soil but model parameters are genotype-specific.

  6. Trace metal uptake by tropical vegetables grown on soil amended with urban sewage sludge

    Energy Technology Data Exchange (ETDEWEB)

    Nabulo, G.; Black, C.R. [School of Biosciences, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Young, S.D., E-mail: scott.young@nottingham.ac.u [School of Biosciences, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)

    2011-02-15

    Trace metal uptake was measured for tropical and temperate leafy vegetables grown on soil from an urban sewage disposal farm in the UK. Twenty-four leafy vegetables from East Africa and the UK were assessed and the five vegetable types that showed the greatest Cd concentrations were grown on eight soils differing in the severity of contamination, pH and other physico-chemical properties. The range of Cd concentrations in the edible shoots was greater for tropical vegetables than for temperate types. Metal uptake was modelled as a function of (i) total soil metal concentration, (ii) CaCl{sub 2}-soluble metal, (iii) soil solution concentration and (iv) the activity of metal ions in soil pore water. Tropical vegetables were not satisfactorily modelled as a single generic 'green vegetable', suggesting that more sophisticated approaches to risk assessment may be required to assess hazard from peri-urban agriculture in developing countries. - Research highlights: Cadmium uptake by tropical green vegetables varies greatly between types. Modelling metal uptake works best for Ni, Cd and Zn but is poor for Cu, Ba and Pb. Modelling with dilute CaCl{sub 2} extraction is as good as metal ion activity in pore water. - Trace metal uptake by tropical leaf vegetables can be predicted from dilute CaCl{sub 2} extraction of soil but model parameters are genotype-specific.

  7. Changes in bacterial diversity associated with bioremediation of used lubricating oil in tropical soils.

    Science.gov (United States)

    Meeboon, Naruemon; Leewis, Mary-Cathrine; Kaewsuwan, Sireewan; Maneerat, Suppasil; Leigh, Mary Beth

    2017-08-01

    Used lubricating oil (ULO) is a widespread contaminant, particularly throughout tropical regions, and may be a candidate for bioremediation. However, little is known about the biodegradation potential or basic microbial ecology of ULO-contaminated soils. This study aims to determine the effects of used ULO on bacterial community structure and diversity. Using a combination of culture-based (agar plate counts) and molecular techniques (16S rRNA gene sequencing and DGGE), we investigated changes in soil bacterial communities from three different ULO-contaminated soils collected from motorcycle mechanical workshops (soil A, B, and C). We further explored the relationship between bacterial community structure, physiochemical soil parameters, and ULO composition in three ULO-contaminated soils. Results indicated that the three investigated soils had different community structures, which may be a result of the different ULO characteristics and physiochemical soil parameters of each site. Soil C had the highest ULO concentration and also the greatest diversity and richness of bacteria, which may be a result of higher nutrient retention, organic matter and cation exchange capacity, as well as freshness of oil compared to the other soils. In soils A and B, Proteobacteria (esp. Gammaproteobacteria) dominated the bacterial community, and in soil C, Actinobacteria and Firmicutes dominated. The genus Enterobacter, a member of the class Gammaproteobacteria, is known to include ULO-degraders, and this genus was the only one found in all three soils, suggesting that it could play a key role in the in situ degradation of ULO-contaminated tropical Thai soils. This study provides insights into our understanding of soil microbial richness, diversity, composition, and structure in tropical ULO-contaminated soils, and may be useful for the development of strategies to improve bioremediation.

  8. IMPACT OF TROPICAL CONDITIONS ON THIN-LAYER CHROMATOGRAPHY IN ANALYTICAL TOXICOLOGY - HIGH-TEMPERATURES AND MODERATE HUMIDITIES

    NARCIS (Netherlands)

    DEZEEUW, RA; FRANKE, JP; DIK, E; TENDOLLE, W; KAM, BL

    The impact of high temperatures (24 to 39-degrees-C) and low to moderately high humidities (20 to 70%) on the applicability of TLC systems for drug identification was studied during a 6 month climatologic cycle in Burkina Faso (West Africa). In general, the Rf values as observed on the plates were

  9. Overall assessment of soil quality on humid sandy loams: Effects of location, rotation and tillage

    DEFF Research Database (Denmark)

    Abdollahi, Lotfollah; Hansen, Elly Møller; Rickson, J.M.

    2015-01-01

    .e. visual evaluation of soil structure (VESS), overall visual structure (OVS) and overall soil structure (OSS)) were employed to differentiate the effects of these alternative management practices on soil structural quality and relative crop yield (RY). A Pearson correlation was also employed to find...... the correlation between the soil quality indices and relative crop yield. Relevant soil properties for calculating the soil quality indices were measured or obtained from previous publications. Crop rotation affected the soil structure and RY. The winter-dominated crop rotation (R2) resulted in the poorest soil...... correlations were found in most cases between soil quality indices (including M-SQR) and RY. This highlights the influence of soil quality (as measured by the selected indicators) – and soil structure in particular – on crop yield potential....

  10. Available nitrogen is the key factor influencing soil microbial functional gene diversity in tropical rainforest.

    Science.gov (United States)

    Cong, Jing; Liu, Xueduan; Lu, Hui; Xu, Han; Li, Yide; Deng, Ye; Li, Diqiang; Zhang, Yuguang

    2015-08-20

    Tropical rainforests cover over 50% of all known plant and animal species and provide a variety of key resources and ecosystem services to humans, largely mediated by metabolic activities of soil microbial communities. A deep analysis of soil microbial communities and their roles in ecological processes would improve our understanding on biogeochemical elemental cycles. However, soil microbial functional gene diversity in tropical rainforests and causative factors remain unclear. GeoChip, contained almost all of the key functional genes related to biogeochemical cycles, could be used as a specific and sensitive tool for studying microbial gene diversity and metabolic potential. In this study, soil microbial functional gene diversity in tropical rainforest was analyzed by using GeoChip technology. Gene categories detected in the tropical rainforest soils were related to different biogeochemical processes, such as carbon (C), nitrogen (N) and phosphorus (P) cycling. The relative abundance of genes related to C and P cycling detected mostly derived from the cultured bacteria. C degradation gene categories for substrates ranging from labile C to recalcitrant C were all detected, and gene abundances involved in many recalcitrant C degradation gene categories were significantly (P rainforest. Soil available N could be the key factor in shaping the soil microbial functional gene structure and metabolic potential.

  11. Endogeic earthworms shape bacterial functional communities and affect organic matter mineralization in a tropical soil

    Science.gov (United States)

    Bernard, Laetitia; Chapuis-Lardy, Lydie; Razafimbelo, Tantely; Razafindrakoto, Malalatiana; Pablo, Anne-Laure; Legname, Elvire; Poulain, Julie; Brüls, Thomas; O'Donohue, Michael; Brauman, Alain; Chotte, Jean-Luc; Blanchart, Eric

    2012-01-01

    Priming effect (PE) is defined as a stimulation of the mineralization of soil organic matter (SOM) following a supply of fresh organic matter. This process can have important consequences on the fate of SOM and on the management of residues in agricultural soils, especially in tropical regions where soil fertility is essentially based on the management of organic matter. Earthworms are ecosystem engineers known to affect the dynamics of SOM. Endogeic earthworms ingest large amounts of soil and assimilate a part of organic matter it contains. During gut transit, microorganisms are transported to new substrates and their activity is stimulated by (i) the production of readily assimilable organic matter (mucus) and (ii) the possible presence of fresh organic residues in the ingested soil. The objective of our study was to see (i) whether earthworms impact the PE intensity when a fresh residue is added to a tropical soil and (ii) whether this impact is linked to a stimulation/inhibition of bacterial taxa, and which taxa are affected. A tropical soil from Madagascar was incubated in the laboratory, with a 13C wheat straw residue, in the presence or absence of a peregrine endogeic tropical earthworm, Pontoscolex corethrurus. Emissions of 12CO2 and 13CO2 were followed during 16 days. The coupling between DNA-SIP (stable isotope probing) and pyrosequencing showed that stimulation of both the mineralization of wheat residues and the PE can be linked to the stimulation of several groups especially belonging to the Bacteroidetes phylum. PMID:21753801

  12. Filamentous fungi remove weathered hydrocarbons from polluted soil of tropical Mexico

    OpenAIRE

    PÉREZ-ARMENDÁRIZ, Beatriz; MARTÍNEZ-CARRERA, Daniel; CALIXTO-MOSQUEDA, María; ALBA, Joel; RODRÍGUEZ-VÁZQUEZ, Refugio

    2010-01-01

    Weathered hydrocarbons from worldwide petrolic activities become more recalcitrant over time. The removal of petroleum hydrocarbons from a polluted soil [65,000 mg total petroleum hydrocarbons (TPH)/kg soil], which had been exposed to tropical environmental conditions for more than 20 years in southeast Mexico, was studied using filamentous fungi. Experiments were carried out in batch reactors (60 mL) containing a substrate consisting of polluted soil and sugar cane bagasse pith as bulk agent...

  13. Effects of nitrogen and phosphorus additions on soil microbial biomass and community structure in two reforested tropical forests.

    Science.gov (United States)

    Liu, Lei; Gundersen, Per; Zhang, Wei; Zhang, Tao; Chen, Hao; Mo, Jiangming

    2015-09-23

    Elevated nitrogen (N) deposition may aggravate phosphorus (P) deficiency in forests in the warm humid regions of China. To our knowledge, the interactive effects of long-term N deposition and P availability on soil microorganisms in tropical replanted forests remain unclear. We conducted an N and P manipulation experiment with four treatments: control, N addition (15 g N m(-2)·yr(-1)), P addition (15 g P m(-2)·yr(-1)), and N and P addition (15 + 15 g N and P m(-2)·yr(-1), respectively) in disturbed (planted pine forest with recent harvests of understory vegetation and litter) and rehabilitated (planted with pine, but mixed with broadleaf returning by natural succession) forests in southern China. Nitrogen addition did not significantly affect soil microbial biomass, but significantly decreased the abundance of gram-negative bacteria PLFAs in both forest types. Microbial biomass increased significantly after P addition in the disturbed forest but not in the rehabilitated forest. No interactions between N and P additions on soil microorganisms were observed in either forest type. Our results suggest that microbial growth in replanted forests of southern China may be limited by P rather than by N, and this P limitation may be greater in disturbed forests.

  14. Daily changes of radon concentration in soil gas under influence of atmospheric factors: room temperature, soil surface temperature and relative humidity

    Energy Technology Data Exchange (ETDEWEB)

    Lara, Evelise G.; Oliveira, Arno Heeren de, E-mail: evelise.lara@gmail.com, E-mail: heeren@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Rocha, Zildete; Rios, Francisco Javier, E-mail: rochaz@cdtn.br, E-mail: javier@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    This work aims at relating the daily change in the radon concentration in soil gas in a Red Yellow Acrisol (SiBCS) under influence of atmospheric factors: room temperature, soil surface temperature and relative humidity. The {sup 226}Ra, {sup 232}Th, U content and permeability were also performed. The measurements of radon soil gas were carried out by using an AlphaGUARD monitor. The {sup 226}Ra activity concentration was made by Gamma Spectrometry (HPGe); the permeability was carried out using the RADON-JOK permeameter and ICP-MS analysis to {sup 232}Th and U content. The soil permeability is 5.0 x 10{sup -12}, which is considered average. The {sup 226}Ra (22.2 ± 0.3 Bq.m{sup -3}); U content (73.4 ± 3.6 Bq.kg{sup -1}) and {sup 232}Th content (55.3 ± 4.0 Bq.kg{sup -1}) were considered above of average concentrations, according to mean values for soils typical (~ 35.0 Bq.kg{sup -1}) by UNSCEAR. The results showed a difference of 26.0% between the highest and the lowest concentration of radon in soil gas: at midnight (15.5 ± 1.0 kBq.m{sup -3}) and 3:00 pm, the highest mean radon concentration (21.0 ± 1.0 kBq.m{sup -3}). The room temperature and surface soil temperature showed equivalent behavior and the surface soil temperature slightly below room temperature during the entire monitoring time. Nevertheless, the relative humidity showed the highest cyclical behavior, showing a higher relationship with the radon concentration in soil gas. (author)

  15. Daily changes of radon concentration in soil gas under influence of atmospheric factors: room temperature, soil surface temperature and relative humidity

    International Nuclear Information System (INIS)

    Lara, Evelise G.; Oliveira, Arno Heeren de

    2015-01-01

    This work aims at relating the daily change in the radon concentration in soil gas in a Red Yellow Acrisol (SiBCS) under influence of atmospheric factors: room temperature, soil surface temperature and relative humidity. The 226 Ra, 232 Th, U content and permeability were also performed. The measurements of radon soil gas were carried out by using an AlphaGUARD monitor. The 226 Ra activity concentration was made by Gamma Spectrometry (HPGe); the permeability was carried out using the RADON-JOK permeameter and ICP-MS analysis to 232 Th and U content. The soil permeability is 5.0 x 10 -12 , which is considered average. The 226 Ra (22.2 ± 0.3 Bq.m -3 ); U content (73.4 ± 3.6 Bq.kg -1 ) and 232 Th content (55.3 ± 4.0 Bq.kg -1 ) were considered above of average concentrations, according to mean values for soils typical (~ 35.0 Bq.kg -1 ) by UNSCEAR. The results showed a difference of 26.0% between the highest and the lowest concentration of radon in soil gas: at midnight (15.5 ± 1.0 kBq.m -3 ) and 3:00 pm, the highest mean radon concentration (21.0 ± 1.0 kBq.m -3 ). The room temperature and surface soil temperature showed equivalent behavior and the surface soil temperature slightly below room temperature during the entire monitoring time. Nevertheless, the relative humidity showed the highest cyclical behavior, showing a higher relationship with the radon concentration in soil gas. (author)

  16. Assessment of soil water use by grassland by frequency domain reflectometry in the humid area of Spain

    Science.gov (United States)

    Mestas Valero, R. M.; Báez Bernal, D.; García Pomar, M. I.; Paz González, A.

    2009-04-01

    Frequency domain reflectometry (FDR) is becoming increasingly used for indirect water content determination in soils. In Galica, located in NW Spain, the humid region of this country, annual precipitation exceeds evapotranspiration. However, the yearly distribution of rainfall is irregular, so that supplementary irrigation during the dry warm summer is required often. This study aims to evaluate soil water use by grasslands and soil water regime patterns during the warm season from soil moisture measured at successive depths using FDR. The study sity is located at the experimental field of the Centre for Agricultural Research (CIAM) in Mabegondo, latitude 43°14' N and longitude 08°15' W. Soil moisture was monitored at six experimental plots from July to October 2008 two times per week using a portable FDR sensor. Measurements were made from 10 to 160 cm depth at 10 cm intervals. Moreover one of the plots was equipped with a continuous recording FDR-EnviroSCAN probe. Crop potential evapotranspiration (ETc) was estimated according to the of FAO version of the Penman-Monteith equation and the meteorological information required to apply this method was provided by a station located in the place experimental field. Cumulative rainfall along the study period was 195 mm, which is above the long-term mean and cumulative potential evapotranspiration was 264.7 mm. Using the water balance method the total value of actual evapotranspiration was estimated at 205.2 mm. Analysis of soil moisture content profiles allowed a description of soil water regime and main soil water withdrawal patterns under grassland. In general, grassland roots extracted most soil water from the 0-40 cm depth. In contrast, moisture content at the bottom of the profile was close to saturation, even the driest weeks of the study period. Continuous monitoring of soil water content allowed a more detailed characterization of dry and wet periods during the study season. The study data set may be useful

  17. Phosphate-induced cadmium adsorption in a tropical savannah soil ...

    African Journals Online (AJOL)

    The influence of phosphate (P) on cadmium (Cd) adsorption was examined in a savanna soil with long history of different fertilizer amendment. The soil was incubated with P at 0, 250 and 500 mg P kg-1 soil and left to equilibrate for 2 weeks. Cd was added to the P-incubated soil at concentrations ranging from 27, 49 and ...

  18. Soil ecological interactions: comparisons between tropical and subalpine forests

    Science.gov (United States)

    Grizelle Gonzalez; Ruth E. Ley; Steven K. Schmidt; Xiaoming Zou; Timothy R. Seastedt

    2001-01-01

    Soil fauna can influence soil processes through interactions with the microbial community. Due to the complexity of the functional roles of fauna and their effects on microbes, little consensus has been reached on the extent to which soil fauna can regulate microbial activities. We quantified soil microbial biomass and maximum growth rates in control and fauna-excluded...

  19. The effect of biochar and its interaction with the earthworm Pontoscolex corethrurus on soil microbial community structure in tropical soils.

    Directory of Open Access Journals (Sweden)

    Jorge Paz-Ferreiro

    Full Text Available Biochar effects on soil microbial abundance and community structure are keys for understanding the biogeochemical cycling of nutrients and organic matter turnover, but are poorly understood, in particular in tropical areas. We conducted a greenhouse experiment in which we added biochars produced from four different feedstocks [sewage sludge (B1, deinking sewage sludge (B2, Miscanthus (B3 and pine wood (B4] at a rate of 3% (w/w to two tropical soils (an Acrisol and a Ferralsol planted with proso millet (Panicum milliaceum L.. The interactive effect of the addition of earthworms was also addressed. For this purpose we utilized soil samples from pots with or without the earthworm Pontoscolex corethrurus, which is a ubiquitous earthworm in tropical soils. Phospholipid fatty acid (PLFA measurements showed that biochar type, soil type and the presence of earthworms significantly affected soil microbial community size and structure. In general, biochar addition affected fungal but not bacterial populations. Overall, biochars rich in ash (B1 and B2 resulted in a marked increase in the fungi to bacteria ratio, while this ratio was unaltered after addition of biochars with a high fixed carbon content (B3 and B4. Our study remarked the contrasting effect that both, biochar prepared from different materials and macrofauna, can have on soil microbial community. Such changes might end up with ecosystem-level effects.

  20. Digging a Little Deeper: Microbial Communities, Molecular Composition and Soil Organic Matter Turnover along Tropical Forest Soil Depth Profiles

    Science.gov (United States)

    Pett-Ridge, J.; McFarlane, K. J.; Heckman, K. A.; Reed, S.; Green, E. A.; Nico, P. S.; Tfaily, M. M.; Wood, T. E.; Plante, A. F.

    2016-12-01

    Tropical forest soils store more carbon (C) than any other terrestrial ecosystem and exchange vast amounts of CO2, water, and energy with the atmosphere. Much of this C is leached and stored in deep soil layers where we know little about its fate or the microbial communities that drive deep soil biogeochemistry. Organic matter (OM) in tropical soils appears to be associated with mineral particles, suggesting deep soils may provide greater C stabilization. However, few studies have evaluated sub-surface soils in tropical ecosystems, including estimates of the turnover times of deep soil C, the sensitivity of this C to global environmental change, and the microorganisms involved. We quantified bulk C pools, microbial communities, molecular composition of soil organic matter, and soil radiocarbon turnover times from surface soils to 1.5m depths in multiple soil pits across the Luquillo Experimental Forest, Puerto Rico. Soil C, nitrogen, and root and microbial biomass all declined exponentially with depth; total C concentrations dropped from 5.5% at the surface to communities in surface soils (Acidobacteria and Proteobacteria) versus those below the active rooting zone (Verrucomicrobia and Thaumarchaea). High resolution mass spectrometry (FTICR-MS) analyses suggest a shift in the composition of OM with depth (especially in the water soluble fraction), an increase in oxidation, and decreasing H/C with depth (indicating higher aromaticity). Additionally, surface samples were rich in lignin-like compounds of plant origin that were absent with depth. Soil OM 14C and mean turnover times were variable across replicate horizons, ranging from 3-1500 years at the surface, to 5000-40,000 years at depth. In comparison to temperate deciduous forests, these 14C values reflect far older soil C. Particulate organic matter (free light fraction), with a relatively modern 14C was found in low but measureable concentration in even the deepest soil horizons. Our results indicate these

  1. On the comparisons of tropical relative humidity in the lower and middle troposphere among COSMIC radio occultations, MERRA and ECMWF data sets

    Science.gov (United States)

    Vergados, P.; Mannucci, A. J.; Ao, C. O.; Jiang, J. H.; Su, H.

    2015-01-01

    The spatial variability of the tropical tropospheric relative humidity (RH) throughout the vertical extent of the troposphere is examined using Global Positioning System Radio Occultation (GPSRO) observations from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission. These high vertical resolution observations capture the detailed structure and moisture budget of the Hadley Cell circulation. We compare the COSMIC observations with the European Center for Medium-range Weather Forecast (ECMWF) Re-Analysis Interim (ERA-Interim) and the Modern-Era Retrospective analysis for Research and Applications (MERRA) climatologies. Qualitatively, the spatial pattern of RH in all data sets matches up remarkably well, capturing distinct features of the general circulation. However, RH discrepancies exist between ERA-Interim and COSMIC data sets, which are noticeable across the tropical boundary layer. Specifically, ERA-Interim shows a drier Inter Tropical Convergence Zone (ITCZ) by 15-20% compared both to COSMIC and MERRA data sets, but this difference decreases with altitude. Unlike ECMWF, MERRA shows an excellent agreement with the COSMIC observations except above 400 hPa, where GPSRO observations capture drier air by 5-10%. RH climatologies were also used to evaluate intraseasonal variability. The results indicate that the tropical middle troposphere at ±5-25° is most sensitive to seasonal variations. COSMIC and MERRA data sets capture the same magnitude of the seasonal variability, but ERA-Interim shows a weaker seasonal fluctuation up to 10% in the middle troposphere inside the dry air subsidence regions of the Hadley Cell. Over the ITCZ, RH varies by maximum 9% between winter and summer.

  2. Aggregate stability and soil degradation in the tropics

    International Nuclear Information System (INIS)

    Mbagwu, J.S.C.

    2004-01-01

    Aggregate stability is a measure of the structural stability of soils. Factors that influence aggregate stability are important in evaluating the ease with which soils erode by water and/or wind, the potential of soils to crust and/or seal, soil permeability, quasi-steady state infiltration rates and seedling emergence and in predicting the capacity of soils to sustain long-term crop production. Aggregate stability of soils can be measured by the wet-sieving or raindrop techniques. A reduction in soil aggregate stability implies an increase in soil degradation. Hence aggregate stability and soil degradation are interwoven. The measures used can either be preventive or remedial. Preventive practices minimize the chances of soil degradation occurring or the magnitude or severity of the damage when the degradation manifests. These include in Nigeria, (i) manuring and mulching, (ii) planted fallows and cover crops, (iii) sustainable farming systems, (iv) adequate rotations, (v) home gardens or compound farms, (vi) alley cropping and related agro forestry systems, and (vii) chemical fertilizers which are mainly remedial measures. Because of alterations in soil properties that affect particular land uses, soils may degrade for one crop (maize rather sorghum). As long as some land use is possible soil degradation is not always an absolute concept. Decline in agricultural productivity should be evaluated in terms of inputs such as fertilizer use, water management and tillage methods. We can alleviate some types of soil degradation by use of micronutrients, inorganic fertilizers and organic residues. Soil that responds to management practices cannot be said to be degraded. Since crop growth depends on weather, degraded soils may be more sensitive to harsh weather (e.g. drought, temperature) than undegraded soils. A soil is degraded if its productivity falls below the economic threshold even under favourable weather conditions or with judicious inputs. All human

  3. Soil respiration in tropical seasonal rain forest in Xishuangbanna, SW China

    Institute of Scientific and Technical Information of China (English)

    SHA; Liqing; ZHENG; Zheng; TANG; Jianwei; WANG; Yinghong

    2005-01-01

    With the static opaque chamber and gas chromatography technique, from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna, SW China. In this study three treatments were applied, each with three replicates: A (bare soil), B (soil+litter), and C (soil+litter+seedling). The results showed that soil respiration varied seasonally, low from December 2003 to February 2004, and high from June to July 2004. The annual average values of CO2 efflux from soil respiration differed among the treatments at 1% level, with the rank of C (14642 mgCO2· m-2. h-1)>B (12807 mgCO2· m-2. h-1)>A (9532 mgCO2· m-2. h-1). Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna. There was a parabola relationship between soil respiration and soil moisture at 1% level. Soil respiration rates were higher when soil moisture ranged from 35% to 45%. There was an exponential relationship between soil respiration and soil temperature (at a depth of 5cm in mineral soil) at 1% level. The calculated Q1o values in this study,ranging from 2.03 to 2.36, were very near to those of tropical soil reported. The CO2 efflux in 2003was 5.34 kgCO2· m-2. a-1 from soil plus litter plus seedling, of them 3.48 kgCO2· m-2. a-1 from soil (accounting for 62.5%), 1.19 kgCO2· m-2. a-1 from litter (22.3%) and 0.67 kgCO2·m-2. a-1 from seedling (12.5%).

  4. Tropical organic soils ecosystems in relation to regional water resources in southeast Asia

    Energy Technology Data Exchange (ETDEWEB)

    Armentano, T. V.

    1982-01-01

    Tropical organic soils have functioned as natural sinks for carbon, nitrogen, slfur and other nutrients for the past 4000 years or more. Topographic evolution in peat swamp forests towards greater oligotrophy has concentrated storage of the limited nutrient stock in surface soils and biota. Tropical peat systems thus share common ecosystem characteristics with northern peat bogs and certain tropical oligotrophic forests. Organic matter accumulation and high cation-exchange-capacity limit nutrient exports from undisturbed organic soils, although nutrient retention declines with increasing eutrophy and wetland productivity. Peat swamps are subject to irreversible degradation if severely altered because disturbance of vegetation, surface peats and detritus can disrupt nuttrient cycles and reduce forest recovery capacity. Drainage also greatly increases exports of nitrogen, phosphorus and other nutrients and leads to downstream eutrophication and water quality degradation. Regional planning for clean water supplies must recognize the benefits provided by natural peatlands in balancing water supplies and regulating water chemistry.

  5. Retention of available P in acid soils of tropical and subtropical evergreen broad-leaved forests

    Institute of Scientific and Technical Information of China (English)

    CHEN Jianhui; ZOU Xiaoming; YANG Xiaodong

    2007-01-01

    Precipitation of mineral phosphate is often recognized as a factor of limiting the availability of P in acidic soils of tropical and subtropical forests.For this paper,we studied the extractable P pools and their transformation rates in soils of a tropical evergreen forest at Xishuangbanna and a subtropical montane wet forest at the Ailao Mountains in order to understand the biogeochemical processes regulating P availability in acidic soils.The two forests differ in forest humus layer;it is deep in the Ailao forest while little is present in the Xishuangbanna forest.The extractable P pools by resin and sodium-bicarbonate decreased when soil organic carbon content was reduced.The lowest levels of extractable P pools occurred in the surface (0-10 era) mineral soils of the Xishuangbanna forest.However,microbial P in the mineral soil of the Xishuangbauna forest was twice that in the Ailao forest.Potential rates of microbial P immobilization were greater than those of organic P mineralization in mineral soils for both forests.We suggest that microbial P immobilization plays an essential role in avoiding mineral P precipitation and retaining available P of plant in tropical acidic soils,whereas both floor mass accumulation and microbial P immobilization function benefit retaining plant available P in subtropical montane wet forests.

  6. Composition and fate of mine- and smelter-derived particulates in soils from humid subtropical and semiarid areas

    Science.gov (United States)

    Ettler, Vojtech; Kribek, Bohdan; Mihaljevic, Martin; Vanek, Ales; Penizek, Vit; Sracek, Ondra; Mapani, Ben; Kamona, Fred; Nyambe, Imasiku

    2017-04-01

    Soils in the vicinity of non-ferrous metal smelters are often highly polluted by inorganic contaminants released from particulate emissions, which undergo weathering processes and release contaminants when deposited in soils. We studied the heavy mineral fraction, separated from mining- and smelter-affected topsoils, from both a humid subtropical area in the Zambian Copperbelt and a hot semi-arid area in the northern Namibia. High concentrations of metal(loid)s were detected in the studied soils: up to 1450 ppm As, 8980 ppm Cu, 4640 ppm Pb, 2620 ppm Zn. A combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS), and electron probe microanalysis (EPMA) helped to identify the phases forming individual metal(loid)-bearing particles. Whereas spherical particles originate from the smelting and flue gas cleaning processes, angular particles either have geogenic origins or they are windblown from the mining operations and mine waste disposal sites. Sulphides from ores and mine tailings often exhibit weathering rims in contrast to smelter-derived high-temperature sulphides (chalcocite [Cu2S], digenite [Cu9S5], covellite [CuS], non-stoichiometric quenched Cu-Fe-S phases). Soils from humid subtropical areas exhibit higher available concentrations of metal(loids), and higher frequencies of weathering features (especially for copper-bearing oxides such as delafossite [CuFeO2]) are observed. In contrast, metal(loid)s are efficiently retained in semi-arid soils, where a high proportion of non-weathered smelter slag particles and low-solubility Ca-Cu-Pb arsenates occur. Our results indicate that compared to semi-arid areas (where inorganic contaminants were rather immobile in soils despite their high concentrations) a higher potential risk exists for agriculture in mine- and smelter-affected humid subtropical areas (where metal(loid) contaminants can be highly available for the uptake by crops). This study was supported by the Czech Science

  7. Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest.

    Science.gov (United States)

    Vandecar, Karen L; Lawrence, Deborah; Wood, Tana; Oberbauer, Steven F; Das, Rishiraj; Tully, Katherine; Schwendenmann, Luitgard

    2009-09-01

    The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short-term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray-extractable P were investigated in relation to ecosystem carbon flux, soil CO2 efflux, soil moisture, soil temperature, solar radiation, and sap-flow velocity. Spatially averaged bi-hourly (every two hours) labile P ranged from 0.88 to 2.48 microg/g across days. The amplitude in labile P throughout the day was 0.61-0.82 microg/g (41-54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.

  8. Effects of tropical ecosystem engineers on soil quality and crop performance under different tillage and residue management

    Science.gov (United States)

    Pulleman, Mirjam; Paul, Birthe; Fredrick, Ayuke; Hoogmoed, Marianne; Hurisso, Tunsisa; Ndabamenye, Telesphore; Saidou, Koala; Terano, Yusuke; Six, Johan; Vanlauwe, Bernard

    2014-05-01

    Feeding a future global population of 9 billion will require a 70-100% increase in food production, resulting in unprecedented challenges for agriculture and natural resources, especially in Sub-saharan Africa (SSA). Agricultural practices that contribute to sustainable intensification build on beneficial biological interactions and ecosystem services. Termites are the dominant soil ecosystem engineers in arid to sub-humid tropical agro-ecosystems. Various studies have demonstrated the potential benefits of termites for rehabilitation of degraded and crusted soils and plant growth in semi-arid and arid natural ecosystems. However, the contribution of termites to agricultural productivity has hardly been experimentally investigated, and their role in Conservation Agriculture (CA) systems remains especially unclear. Therefore, this study aimed to quantify the effects of termites and ants on soil physical quality and crop productivity under different tillage and residue management systems in the medium term. A randomized block trial was set up in sub-humid Western Kenya in 2003. Treatments included a factorial combination of residue retention and removal (+R/-R) and conventional and reduced tillage (+T/-T) under a maize (Zea mays L.) and soybean (Glyxine max. L.) rotation. A macrofauna exclusion experiment was superimposed in 2005 as a split-plot factor (exclusion +ins; inclusion -ins) by regular applications of pesticides (Dursban and Endosulfan) in half of the plots. Macrofauna abundance and diversity, soil aggregate fractions, soil carbon contents and crop yields were measured between 2005 and 2012 at 0-15 cm and 15-30 cm soil depths. Termites were the most important macrofauna species, constituting between 48-63% of all soil biota, while ants were 13-34%, whereas earthworms were present in very low numbers. Insecticide application was effective in reducing termites (85-56% exclusion efficacy) and earthworms (87%), and less so ants (49-81%) at 0-15 cm soil depth

  9. Genotype-environment interaction of maternal influence characteristics in Nellore cattle bred in the Brazilian humid tropical regions by reaction norm

    Directory of Open Access Journals (Sweden)

    Jorge Luís Ferreira

    2015-08-01

    Full Text Available Reaction Norm (RN is the study of genotype-environment interaction (GxE that complies with alternative ways of genotypes within different environments. This study was carried out to verify GxE by a reaction norm model of weights at 120 (W120 and 210 (W210 days of age in Nellore cattle raised in the Humid Tropical Regions of Brazil. Environmental gradients were obtained by solutions of contemporary groups which were fitted as co-variables in the random regression model via reaction norms. Mean weight at 120 days of age was 127.97 kg, and environmental gradients ranged between -27 and +26 kg. Average was 185.60 kg at 210 days of age and gradients ranged from -54 to +55 kg. Scale changes in the breeding values and heritability estimates occurred along the gradients for the two weights; the genetic correlations between breeding value breeding values were also similar for both weights. These correlations were high between the close gradients, and low to even negative between extreme environments. Slopes representing the environmental sensitivity were high, with changes of scale and changes in classification of ten bulls with a great numbers of calves for the two traits. When regression slopes of the ten bulls with the highest breeding value breeding values were evaluated, these values were different in W120 from those in W210, perhaps due to the greater influence of maternal effect on W120. These results characterize the influence of GxE on the pre-weaning weights of animals in the humid tropical regions of Brazil. Due to this, it is possible to get greater precision on the predictions of the animals breeding values breeding value. A less biased selection and a greater genetic progress occurred.

  10. Effect of land management models on soil erosion in wet tropical cacao plantations in Indonesia

    OpenAIRE

    Suhardi

    2017-01-01

    Indonesia is one of the world???s largest cocoa exporters and is located in a tropical wet region. In tropical regions, surface run off is a major factor behind the occurrence of erosion-driven land degradation. Both land slope and land cover influence the magnitude of surface run off and soil erosion. Cocoa plants are generally cultivated on land that has a steep slope without regard to existing land cover conditions resulting in a susceptibility to soil erosion. The purpose of this resea...

  11. Soil macrofauna and litter nutrients in three tropical tree plantations on a disturbed site in Puerto Rico.

    Science.gov (United States)

    Matthew W. Warren; Xiaoming Zou

    2002-01-01

    Tree plantations are increasingly common in tropical landscapes due to their multiple uses. Plantations vary in structure and composition, and these variations may alter soil fauna communities. Recent studies have demonstrated the important role of soil fauna in the regulation of plant litter decomposition in the tropics. However, little is known about how plantation...

  12. Effects of nitrogen enrichment on soil organic matter in tropical forests with different ambient nutrient status

    Science.gov (United States)

    Vaughan, E.; Cusack, D. F.; McDowell, W. H.; Marin-Spiotta, E.

    2017-12-01

    Nitrogen (N) enrichment is a widespread and increasingly important human influence on ecosystems globally, with implications for net primary production and biogeochemical processes. Previous research has shown that N enrichment can alter soil carbon (C) cycling, although the direction and magnitude of the changes are not consistent across studies, and may change with time. Inconsistent responses to N additions may be due to differences in ambient nutrient status, and/or variable responses of plant C inputs and microbial decomposition. Although plant production in the tropics is not often limited by N, soil processes may respond differently to N enrichment. Our study uses a 15-year N addition experiment at two different tropical forest sites in the Luquillo Long-Term Ecological Research project site in Puerto Rico to address long-term changes in soil C pools due to fertilization. The two forests differ in elevation and ambient nutrient status. Soil sampling three and five years post-fertilization showed increased soil C concentrations under fertilization, driven by increases in mineral-associated C (Cusack et al. 2011). However, the longer-term trends at these sites are unknown. To this end, soil samples were collected following fifteen years of fertilization. Soils were sampled from 0-10 cm and 10-20 cm. Bulk soil C and N concentrations will be measured and compared to samples collected before fertilization (2002) and three years post fertilization (2005). We are using density fractionation to isolate different soil organic matter pools into a free light, occluded light, and dense, mineral associated fraction. These pools represent different mechanisms of soil organic matter stabilization, and provide more detailed insight into changes in bulk soil C. These data will provide insight into the effects of N enrichment on tropical forest soils, and how those effects may change through time with a unique long-term data set.

  13. Responses of soil fungi to logging and oil palm agriculture in Southeast Asian tropical forests.

    Science.gov (United States)

    McGuire, K L; D'Angelo, H; Brearley, F Q; Gedallovich, S M; Babar, N; Yang, N; Gillikin, C M; Gradoville, R; Bateman, C; Turner, B L; Mansor, P; Leff, J W; Fierer, N

    2015-05-01

    Human land use alters soil microbial composition and function in a variety of systems, although few comparable studies have been done in tropical forests and tropical agricultural production areas. Logging and the expansion of oil palm agriculture are two of the most significant drivers of tropical deforestation, and the latter is most prevalent in Southeast Asia. The aim of this study was to compare soil fungal communities from three sites in Malaysia that represent three of the most dominant land-use types in the Southeast Asia tropics: a primary forest, a regenerating forest that had been selectively logged 50 years previously, and a 25-year-old oil palm plantation. Soil cores were collected from three replicate plots at each site, and fungal communities were sequenced using the Illumina platform. Extracellular enzyme assays were assessed as a proxy for soil microbial function. We found that fungal communities were distinct across all sites, although fungal composition in the regenerating forest was more similar to the primary forest than either forest community was to the oil palm site. Ectomycorrhizal fungi, which are important associates of the dominant Dipterocarpaceae tree family in this region, were compositionally distinct across forests, but were nearly absent from oil palm soils. Extracellular enzyme assays indicated that the soil ecosystem in oil palm plantations experienced altered nutrient cycling dynamics, but there were few differences between regenerating and primary forest soils. Together, these results show that logging and the replacement of primary forest with oil palm plantations alter fungal community and function, although forests regenerating from logging had more similarities with primary forests in terms of fungal composition and nutrient cycling potential. Since oil palm agriculture is currently the mostly rapidly expanding equatorial crop and logging is pervasive across tropical ecosystems, these findings may have broad applicability.

  14. Microbial C:P stoichiometry is shaped by redox conditions along an elevation gradient in humid tropical rainforests

    Science.gov (United States)

    Lin, Y.; Gross, A.; Silver, W. L.

    2017-12-01

    Elemental stoichiometry of microorganisms is intimately related to ecosystem carbon and nutrient fluxes and is ultimately controlled by the chemical (plant tissue, soil, redox) and physical (temperature, moisture, aeration) environment. Previous meta-analyses have shown that the C:P ratio of soil microbial biomass exhibits significant variations among and within biomes. Little is known about the underlying causes of this variability. We examined soil microbial C:P ratios along an elevation gradient in the Luquillo Experimental Forest in Puerto Rico. We analyzed soils from mixed forest paired with monodominant palm forest every 100 m from 300 m to 1000 m a.s.l.. Mean annual precipitation increased with increasing elevation, resulting in stronger reducing conditions and accumulation of soil Fe(II) at higher elevations. The mean value and variability of soil microbial C:P ratios generally increased with increasing elevation except at 1000 m. At high elevations (600-900 m), the average value of microbial C:P ratio (108±10:1) was significantly higher than the global average ( 55:1). We also found that soil organic P increased with increasing elevation, suggesting that an inhibition of organic P mineralization, not decreased soil P availability, may cause the high microbial C:P ratio. The soil microbial C:P ratio was positively correlated with soil HCl-extractable Fe(II), suggesting that reducing conditions may be responsible for the elevational changes observed. In a follow-up experiment, soils from mixed forests at four elevation levels (300, 500, 700, and 1000 m) were incubated under aerobic and anaerobic conditions for two weeks. We found that anaerobic incubation consistently increased the soil microbial C:P ratio relative to the aerobic incubation. Overall, our results indicate that redox conditions can shift the elemental composition of microbial biomass. The high microbial C:P ratios induced under anoxic conditions may reflect inhibition of microbial P

  15. A modelling study of the event-based retention performance of green roof under the hot-humid tropical climate in Kuching.

    Science.gov (United States)

    Chai, C T; Putuhena, F J; Selaman, O S

    2017-12-01

    The influences of climate on the retention capability of green roof have been widely discussed in existing literature. However, knowledge on how the retention capability of green roof is affected by the tropical climate is limited. This paper highlights the retention performance of the green roof situated in Kuching under hot-humid tropical climatic conditions. Using the green roof water balance modelling approach, this study simulated the hourly runoff generated from a virtual green roof from November 2012 to October 2013 based on past meteorological data. The result showed that the overall retention performance was satisfactory with a mean retention rate of 72.5% from 380 analysed rainfall events but reduced to 12.0% only for the events that potentially trigger the occurrence of flash flood. By performing the Spearman rank's correlation analysis, it was found that the rainfall depth and mean rainfall intensity, individually, had a strong negative correlation with event retention rate, suggesting that the retention rate increases with decreased rainfall depth. The expected direct relationship between retention rate and antecedent dry weather period was found to be event size dependent.

  16. Quantitative physical and chemical variables used to assess erosion and fertility loss in tropical Dominican and Haitian soils

    Science.gov (United States)

    Pastor, J.; Alexis, S.; Vizcayno, C.; Hernández, A. J.

    2009-04-01

    mines (bauxite and limestone), crops and livestock. The hypothesis that heavy metals liberated by geochemical actions in some of these tropical ecosystems could be related both to productivity and to human and animal health, led us also to assess metal bioavailability in the area's main crops as the primary source of food or fodder. To establish the context of the heavy metal pollution, we characterized the geoedaphic features of the region. The predominant rocks are sedimentary limestones: with limestone colluvial deposits dominant in the tropical conifer forest and rain forest of the Sierra de Bahoruco; crystalline limestones in the tropical latifoliated forest; and Quaternary detritic rocks and reefs (carbonates overlying alterites) in the dry tropical forest. Across the territory, there is a marked predominance of soils that range from surface soils to shallow, poorly developed stony soils of low natural fertility. Most can be classified as entisols. Soils of recent alluvial origin lack pedogenetic horizons and are subjected to diverse humidity and temperature regimens. Slopes are pronounced and relief and altitudes vary. Their profiles include A-R horizons characterised by displaying an ochre epipedon over a fractured rock bed whose depth is shallow and A-C horizons of a sandy to clayey soil and subsoil texture, whose colours range from dark brown to grey and depths from very shallow to deep. Soils occur from the mountains to landscapes including rivers or sandy coasts. The ecosystems examined occur from an altitude of 1300-1200 m to sea level and the cultivated soils have the main food sources for human and animal consumption: bean, corn, sorghum, coffee, Guinea banana, fruit trees and tubers. We present these data for 79 soil samples according to the corresponding landscape units (forests) along with their dominant lithologies (crystalline limestones, carbonated limestones on alterites and coral limestones). Our study describes edaphic processes linked to

  17. Measurements of soil respiration and simple models dependent on moisture and temperature for an Amazonian southwest tropical forest

    NARCIS (Netherlands)

    Zanchi, F.B.; Rocha, Da H.R.; Freitas, De H.C.; Kruijt, B.; Waterloo, M.J.; Manzi, A.O.

    2009-01-01

    Soil respiration plays a significant role in the carbon cycle of Amazonian tropical forests, although in situ measurements have only been poorly reported and the dependence of soil moisture and soil temperature also weakly understood. This work investigates the temporal variability of soil

  18. On the comparisons of tropical relative humidity in the lower and middle troposphere among COSMIC radio occultations and MERRA and ECMWF data sets

    Science.gov (United States)

    Vergados, P.; Mannucci, A. J.; Ao, C. O.; Jiang, J. H.; Su, H.

    2015-04-01

    The spatial variability of the tropical tropospheric relative humidity (RH) throughout the vertical extent of the troposphere is examined using Global Positioning System Radio Occultation (GPSRO) observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission. These high vertical resolution observations capture the detailed structure and moisture budget of the Hadley Cell circulation. We compare the COSMIC observations with the European Center for Medium-range Weather Forecast (ECMWF) Reanalysis Interim (ERA-Interim) and the Modern-Era Retrospective analysis for Research and Applications (MERRA) climatologies. Qualitatively, the spatial pattern of RH in all data sets matches up remarkably well, capturing distinct features of the general circulation. However, RH discrepancies exist between ERA-Interim and COSMIC data sets that are noticeable across the tropical boundary layer. Specifically, ERA-Interim shows a drier Intertropical Convergence Zone (ITCZ) by 15-20% compared to both COSMIC and MERRA data sets, but this difference decreases with altitude. Unlike ECMWF, MERRA shows an excellent agreement with the COSMIC observations except above 400 hPa, where GPSRO observations capture drier air by 5-10%. RH climatologies were also used to evaluate intraseasonal variability. The results indicate that the tropical middle troposphere at ±5-25° is most sensitive to seasonal variations. COSMIC and MERRA data sets capture the same magnitude of the seasonal variability, but ERA-Interim shows a weaker seasonal fluctuation up to 10% in the middle troposphere inside the dry air subsidence regions of the Hadley Cell. Over the ITCZ, RH varies by maximum 9% between winter and summer.

  19. Variation in pH Optima of Hydrolytic Enzyme Activities in Tropical Rain Forest Soils

    OpenAIRE

    Turner, Benjamin L.

    2010-01-01

    Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly am...

  20. Soil and water pollution in a banana production region in tropical Mexico

    OpenAIRE

    Geissen, V.; Que Ramos, F.; Bastidas-Bastidas, de, P.J.; Díaz-González, G.; Bello-Mendoza, R.; Huerta-Lwanga, E.; Ruiz-Suárez, L.E.

    2010-01-01

    The effects of abundant Mancozeb (Mn, Zn— bisdithiocarbamate) applications (2.5 kg ha-1week-1 for 10 years) on soil and surface-, subsurface- and groundwater pollution were monitored in a banana production region of tropical Mexico. In soils, severe manganese accumulation was observed, wheras the main metabolite ethylenethiourea was near the detection limit. Surface and subsurface water was highly polluted with ethylenethiourea, the main metabolite of Mancozeb (22.5 and 4.3 lg L-1, respective...

  1. Spatial variability of physical properties of tropical soil

    International Nuclear Information System (INIS)

    Reichardt, K.; Libardi, P.L.; Queiroz, S.V.; Grohmann, F.

    1976-04-01

    A basic study with objectives of improving the use of soil and water resources under a particular condition and of developing means for controlling the dynamics of soil-water movement are presented. Special emphasis is given to the variability in space of geometric soil properties such as bulk density, particle density and texture in order to make it possible to define representative means which ideed will be usable to describe the movement of water and of salt in the entire field

  2. Behaviour of radioactive and stable isotopes of calcium in the soil-solution-plant system at different soil humidity

    International Nuclear Information System (INIS)

    Karavaeva, E.N.; Molchanova, I.V.

    1976-01-01

    The results of experiments performed to study the behaviour of radioactive and stable isotopes of Ca in soil - solution - plant system at different soil moistening are given. The experiments have been conducted in culture pans with two soils: soddy-meadow and soddy-podzolic differing in a number of physico-chemical properties. The solution of radioactive Ca( 45 CaCl 2 ) has been applied to soddy-meadow soil at the rate of 0.2 μcurie/kg, and to soddy-podzolic soil - at the rate of 0.1 μcurie/kg. The distribution and accumulation coefficients are estimated by the ratio to the total content of stable Ca and 45 Ca in soil. A direct relationship between distribution coefficients and the rate of soil moistening is observed. It has been established that 45 Ca and the natural stable isotopes of Ca applied to the soil differ in the type of distribution in soil - soil solution system and in accumulation by plants. However, a great similarity has been observed in behaviour of radioactive and stable isotopes of Ca depending on soil moistening

  3. Effect of typhoon disturbance on soil respiration dynamic in a tropical broadleaves plantation in southern Taiwan

    Science.gov (United States)

    Chiang, Po-Neng; Yu, Jui-Chu; Lai, Yen-Jen

    2017-04-01

    Global forests contain 69% of total carbon stored in forest soil and litter. But the carbon storage ability and release rate of warming gases of forest soil also affect global climate change. Reforestation is one of the best solutions to mitigate warming gases release and to store in soil. Typhoon is one of the most hazards to disturb forest ecosystem and change carbon cycle. Typhoon disturbance is also affect soil carbon cycle such as soil respiration, carbon storage. Therefore, the objective of this study is to clarify the effect of typhoon disturbance on soil respiration dynamic in a tropical broadleaves plantation in southern Taiwan. Fourteen broadleaved tree species were planted in 2002-2005. Twelves continuous soil respiration chambers was divided two treatments (trench and non-trench) and observed since 2011 to 2014. The soil belongs to Entisol with over 60% of sandstone. The soil pH is 5.5 with low base cations because of high sand percentage. Forest biometric such as tree high, DBH, litterfall was measured in 2011-2014. Data showed that the accumulation amount of litterfall was highest in December to February and lowest in June. Soil respiration was related with season variation in research site. Soil temperature showed significantly exponential related with soil respiration in research site (p<0.001).However, soil respiration showed significantly negative relationship with total amount of litterfall (p<0.001), suggesting that the tree was still young and did not reach crown closure.

  4. Arsenic content and forms in some tropical soils

    Energy Technology Data Exchange (ETDEWEB)

    Fassbender, H W

    1975-01-01

    Some Latin American soils were analyzed for total arsenic and its various forms. For the volcanic ash soils from Colombia and Costa Rica an average of 5.1 and 7.0 ppm As was found. Some oxisols and ultisols from Puerto Rico reached an average of 10.0 ppm As. The distribution of arsenic with soil depth does not show any trend; consequently unlike P, it does not undergo biogenic accumulation on soil surfaces. Two soils of Puerto Rico reached exceptional high As values (over 100 ppm); it is believed that As of sea water precipitates with carbonate in calcareous sediments. In these soils Ca-bound As predominates over Fe - and Al-arsenate. In a Costa Rican soil, where arsenic compounds are used to control coffee diseases, a great accumulation of As in the upper soils depths was registered (for 0 to 5 cm from 10.6 to 49.0 ppm As). In the soil profile represents the most important transformation form applied arsenate.

  5. Soil trace gas fluxes along orthogonal precipitation and soil fertility gradients in tropical lowland forests of Panama

    Directory of Open Access Journals (Sweden)

    A. L. Matson

    2017-07-01

    Full Text Available Tropical lowland forest soils are significant sources and sinks of trace gases. In order to model soil trace gas flux for future climate scenarios, it is necessary to be able to predict changes in soil trace gas fluxes along natural gradients of soil fertility and climatic characteristics. We quantified trace gas fluxes in lowland forest soils at five locations in Panama, which encompassed orthogonal precipitation and soil fertility gradients. Soil trace gas fluxes were measured monthly for 1 (NO or 2 (CO2, CH4, N2O years (2010–2012 using vented dynamic (for NO only or static chambers with permanent bases. Across the five sites, annual fluxes ranged from 8.0 to 10.2 Mg CO2-C, −2.0 to −0.3 kg CH4-C, 0.4 to 1.3 kg N2O-N and −0.82 to −0.03 kg NO-N ha−1 yr−1. Soil CO2 emissions did not differ across sites, but they did exhibit clear seasonal differences and a parabolic pattern with soil moisture across sites. All sites were CH4 sinks; within-site fluxes were largely controlled by soil moisture, whereas fluxes across sites were positively correlated with an integrated index of soil fertility. Soil N2O fluxes were low throughout the measurement years, but the highest emissions occurred at a mid-precipitation site with high soil N availability. Net negative NO fluxes at the soil surface occurred at all sites, with the most negative fluxes at the low-precipitation site closest to Panama City; this was likely due to high ambient NO concentrations from anthropogenic sources. Our study highlights the importance of both short-term (climatic and long-term (soil and site characteristics factors in predicting soil trace gas fluxes.

  6. Hot moments of N2O transformation and emission in tropical soils from the Pantanal and the Amazon (Brazil)

    DEFF Research Database (Denmark)

    Liengaard, Lars; Figueiredo, Viviane; Markfoged, Rikke

    2014-01-01

    Tropical wetland soils emit large amounts of nitrous oxide (N2O), especially following wetting of drained soil. We investigated seasonally drained wetland soils from the Pantanal and the Amazon, both with a natural high nitrate content and low pH. Here we report the effect of wetting on the produ......Tropical wetland soils emit large amounts of nitrous oxide (N2O), especially following wetting of drained soil. We investigated seasonally drained wetland soils from the Pantanal and the Amazon, both with a natural high nitrate content and low pH. Here we report the effect of wetting...

  7. 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.

  8. Ecotoxicological evaluation of swine manure disposal on tropical soils in Brazil.

    Science.gov (United States)

    Segat, Julia Corá; Alves, Paulo Roger Lopes; Baretta, Dilmar; Cardoso, Elke Jurandy Bran Nogueira

    2015-12-01

    Swine production in Brazil results in a great volume of manure that normally is disposed of as agricultural fertilizer. However, this form of soil disposal, generally on small farms, causes the accumulation of large amounts of manure and this results in contaminated soil and water tables. To evaluate the effects of increasing concentrations of swine manure on earthworms, several ecotoxicological tests were performed using Eisenia andrei as test organism in different tropical soils, classified respectively as Ultisol, Oxisol, and Entisol, as well as Tropical Artificial Soil (TAS). The survival, reproduction and behavior of the earthworms were evaluated in experiments using a completely randomized design, with five replications. In the Ultisol, Oxisol and TAS the swine manure showed no lethality, but in the Entisol it caused earthworm mortality (LOEC=45 m(3)ha(-1)). In the Entisol, the waste reduced the reproductive rate and caused avoidance behavior in E. andrei (LOEC=30 m(3)ha(-1)) even in lower concentrations. The Entisol is extremely sandy, with low cation exchange capacity (CEC), and this may be the reason for the higher toxicity on soil fauna, with the soil not being able to hold large amounts of pollutants (e.g. toxic metals), but leaving them in bioavailable forms. These results should be a warning of the necessity to consider soil parameters (e.g. texture and CEC) when evaluating soil contamination by means of ecotoxicological assays, as there still are no standards for natural soils in tropical regions. E. andrei earthworms act as indicators for a soil to support disposal of swine manure without generating harm to agriculture and ecosystems. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Influence of perennial colonies of piscivorous birds on soil nutrient contents in a temperate humid climate

    DEFF Research Database (Denmark)

    Breuning-Madsen, Henrik; Ehlers-Koch, Camilla; Gregersen, Jens

    2010-01-01

    conductivity and content of carbon, nitrogen, phosphorus, calcium and potassium in a reference area and in two cormorant sub-colonies. In general, the soils exposed to cormorant guano had lower pH and higher contents of plant available phosphorus, calcium and potassium compared to the control reference soil...

  10. Differences in microbial community structure and nitrogen cycling in natural and drained tropical peatland soils.

    Science.gov (United States)

    Espenberg, Mikk; Truu, Marika; Mander, Ülo; Kasak, Kuno; Nõlvak, Hiie; Ligi, Teele; Oopkaup, Kristjan; Maddison, Martin; Truu, Jaak

    2018-03-16

    Tropical peatlands, which play a crucial role in the maintenance of different ecosystem services, are increasingly drained for agriculture, forestry, peat extraction and human settlement purposes. The present study investigated the differences between natural and drained sites of a tropical peatland in the community structure of soil bacteria and archaea and their potential to perform nitrogen transformation processes. The results indicate significant dissimilarities in the structure of soil bacterial and archaeal communities as well as nirK, nirS, nosZ, nifH and archaeal amoA gene-possessing microbial communities. The reduced denitrification and N 2 -fixing potential was detected in the drained tropical peatland soil. In undisturbed peatland soil, the N 2 O emission was primarily related to nirS-type denitrifiers and dissimilatory nitrate reduction to ammonium, while the conversion of N 2 O to N 2 was controlled by microbes possessing nosZ clade I genes. The denitrifying microbial community of the drained site differed significantly from the natural site community. The main reducers of N 2 O were microbes harbouring nosZ clade II genes in the drained site. Additionally, the importance of DNRA process as one of the controlling mechanisms of N 2 O fluxes in the natural peatlands of the tropics revealed from the results of the study.

  11. Bacterial diversity in a tropical crude oil-polluted soil undergoing ...

    African Journals Online (AJOL)

    The bacterial diversity in a tropical soil experimentally polluted with crude oil during a 57 days bioremediation was investigated in five 1 m2 plots using total culturable hydrocarbon utilizing bacteria, heterotrophic bacteria and gas chromatographic analyses. Four out of the five experimental plots received each 4 L of Bonny ...

  12. Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests

    Science.gov (United States)

    Daniela F. Cusack; Whendee L. Silver; Margaret S. Torn; Sarah D. Burton; Mary K. Firestone

    2011-01-01

    Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of...

  13. Formation and degradation of ethylenethiourea (ETU) in soil and water under tropical conditions

    NARCIS (Netherlands)

    Ruiz-Suárez, L.E.; Geissen, V.; Jarquin Sánchez, A.; Castro Chan, R.A.; Bello-Mendoza, R.

    2013-01-01

    Mancozeb is a fungicide frequently used in tropical countries. It rapidly decomposes into ethylenethiourea (ETU), a more stable and toxic metabolite than mancozeb that is, therefore, regarded as a pollutant of concern. The objective was to study ETU formation and decay kinetics in soil and water

  14. (Tropical) soil organic matter modelling: problems and prospects

    NARCIS (Netherlands)

    Keulen, van H.

    2001-01-01

    Soil organic matter plays an important role in many physical, chemical and biological processes. However, the quantitative relations between the mineral and organic components of the soil and the relations with the vegetation are poorly understood. In such situations, the use of models is an

  15. Aluminium tolerance of Mucuna : A tropical leguminous cover crop

    NARCIS (Netherlands)

    Hairiah, Kurniatun

    1992-01-01

    In the humid tropics leaching of N and other nutrients to the subsoil may occur throughout the growing season. Typically, soils in this zone have a low soil pH, a high Al saturation of the cation exchange complex and low levels of Ca and P in the subsoil. Efficiency of N-use under such conditions

  16. Some physical properties of wetland soils with reference to the tropics

    International Nuclear Information System (INIS)

    Obi, M.E.

    1989-10-01

    Some physical properties of wetland soils are reviewed with reference to the tropical regions. The soils have a common feature periodic flooding during the year. They exhibit wide variability in mechanical composition in accordance with their genesis and location. Bulk densities range from 1.0 to 1.9 Mg m -3 for mineral soils with moderate organic matter content and from about 0.02 to 0.2 Mg m -3 for organic soils. Total porosities are generally high with dominance of micropores in organic and clayey wetland soils. Shrink-swell potential is also generally high in many of these wetland types with consequent problems of crack formation. Anaerobiosis condition is a common feature in wetland soils. Also carbon dioxide levels may be excessive for normal crop development. Water-retentivity has been found to be high to very high to in a number of tropical wetland soils of medium to fine texture. In some organic soils values of over 100% (mass basis) are not uncommon. In particular, a value of up to 3000% has been reported. Water infiltration and percolation are highly variable. The heat capacities are generally high with resultant reduced temperatures. Land use and management strategies are proferred in the light of the properties. (author). 44 refs, 9 tabs

  17. Improving a native pasture with the legume Arachis pintoi in the humid tropics of México

    NARCIS (Netherlands)

    Castillo Gallegos, E.

    2003-01-01

    The objective of this study was to determine the effect of introducing the legume Arachis pintoi CIAT 17434 into a native pasture where native grasses dominated the botanical composition, on establishment, persistence, standing dry matter, botanical composition, soil variables, animal performance,

  18. Genotypic Diversity of Escherichia coli in the Water and Soil of Tropical Watersheds in Hawaii ▿

    Science.gov (United States)

    Goto, Dustin K.; Yan, Tao

    2011-01-01

    High levels of Escherichia coli were frequently detected in tropical soils in Hawaii, which present important environmental sources of E. coli to water bodies. This study systematically examined E. coli isolates from water and soil of several watersheds in Hawaii and observed high overall genotypic diversity (35.5% unique genotypes). In the Manoa watershed, fewer than 9.3% of the observed E. coli genotypes in water and 6.6% in soil were shared between different sampling sites, suggesting the lack of dominant fecal sources in the watershed. High temporal variability of E. coli genotypes in soil was also observed, which suggests a dynamic E. coli population corresponding with the frequently observed high concentrations in tropical soils. When E. coli genotypes detected from the same sampling events were compared, limited sharing between the soil and water samples was observed in the majority of comparisons (73.5%). However, several comparisons reported up to 33.3% overlap of E. coli genotypes between soil and water, illustrating the potential for soil-water interactions under favorable environmental conditions. In addition, genotype accumulation curves for E. coli from water and soil indicated that the sampling efforts in the Manoa watershed could not exhaust the overall genotypic diversity. Comparisons of E. coli genotypes from other watersheds on Oahu, Hawaii, identified no apparent grouping according to sampling locations. The results of the present study demonstrate the complexity of using E. coli as a fecal indicator bacterium in tropical watersheds and highlight the need to differentiate environmental sources of E. coli from fecal sources in water quality monitoring. PMID:21515724

  19. Evaluation of Biological and Enzymatic Activity of Soil in a Tropical Dry Forest: Desierto de la Tatacoa (Colombia) with Potential in Mars Terraforming and Other Similar Planets

    Science.gov (United States)

    Moreno Moreno, A. N.

    2009-12-01

    Desierto de la Tatacoa has been determined to be a tropical dry forest bioma, which is located at 3° 13" N 75° 13" W. It has a hot thermal floor with 440 msnm of altitude; it has a daily average of 28° C, and a maximum of 40° C, Its annual rainfall total can be upwards of 1250 mm. Its solar sheen has a daily average of 5.8 hours and its relative humidity is between 60% and 65%. Therefore, the life forms presents are very scant, and in certain places, almost void. It was realized a completely random sampling of soil from its surface down to 6 inches deep, of zones without vegetation and with soils highly loaded by oxides of iron in order to determine the number of microorganisms per gram and its subsequent identification. It was measured the soil basal respiration. Besides, it was determined enzymatic activity (catalase, dehydrogenase, phosphatase and urease). Starting with the obtained results, it is developes an alternative towards the study of soil genesis in Mars in particular, and recommendations for same process in other planets. Although the information found in the experiments already realized in Martian soil they demonstrate that doesnt exist any enzymatic activity, the knowledge of the same topic in the soil is proposed as an alternative to problems like carbonic fixing of the dense Martian atmosphere of CO2, the degradation of inorganic compounds amongst other in order to prepare the substratum for later colonization by some life form.

  20. Soil type and texture impacts on soil organic carbon accumulation in a sub-tropical agro-ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Gonçalves, Daniel Ruiz Potma; Sa, Joao Carlos de Moraes; Mishra, Umakant; Cerri, Carlos Eduardo Pellegrino; Ferreira, Lucimara Aparecida; Furlan, Flavia Juliana Ferreira

    2016-11-02

    Soil organic carbon (C) plays a fundamental role in tropical and subtropical soil fertility, agronomic productivity, and soil health. As a tool for understand ecosystems dynamics, mathematical models such as Century have been used to assess soil's capacity to store C in different environments. However, as Century was initially developed for temperate ecosystems, several authors have hypothesized that C storage may be underestimated by Century in Oxisols. We tested the hypothesis that Century model can be parameterized for tropical soils and used to reliably estimate soil organic carbon (SOC) storage. The aim of this study was to investigate SOC storage under two soil types and three textural classes and quantify the sources and magnitude of uncertainty using the Century model. The simulation for SOC storage was efficient and the mean residue was 10 Mg C ha-1 (13%) for n = 91. However, a different simulation bias was observed for soil with <600 g kg-1 of clay was 16.3 Mg C ha-1 (18%) for n = 30, and at >600 g kg-1 of clay, was 4 Mg C ha-1 (5%) for n = 50, respectively. The results suggest a non-linear effect of clay and silt contents on C storage in Oxisols. All types of soil contain nearly 70% of Fe and Al oxides in the clay fraction and a regression analysis showed an increase in model bias with increase in oxides content. Consequently, inclusion of mineralogical control of SOC stabilization by Fe and Al (hydro) oxides may improve results of Century model simulations in soils with high oxides contents

  1. Changes in Fire-Derived Soil Black Carbon Storage in a Sub-humid Woodland

    Science.gov (United States)

    White, J. D.; Yao, J.; Murray, D. B.; Hockaday, W. C.

    2014-12-01

    Fire-derived black carbon (BC) in soil, including charcoal, represents a potentially important fraction of terrestrial carbon cycling due to its presumed long persistence in soil. Interpretation of site BC retention is important for assessing feedbacks to ecosystem processes including nutrient and water cycling. However, interaction between vegetation disturbance, BC formation, and off site transport may exist that complicate interpretation of BC addition to soils from wildfire or prescribed burns directly. To investigate the relationship between disturbance and site retention on soil BC, we determined BC concentrations for a woodland in central Texas, USA, from study plots in hilly terrain with a fire scar dendrochronology spanning 100 years. BC values were determined from 13C nuclear magnetic resonance (NMR) spectroscopy. Estimated values showed mean BC concentration of 2.73 ± 3.06 g BC kg-1 (0.91 ± 0.51 kg BC m-2) for sites with fire occurrence within the last 40 years compared with BC values of1.21 ± 1.70 g BC kg-1 soil (0.18 ± 0.14 kg BC m-2) for sites with fire 40 - 100 years ago. Sites with no tree ring evidence of fire during the last 100 years had the lowest mean soil BC concentration of 0.05 ± 0.11 g BC kg-1 (0.02 ± 0.03 kg BC m-2). Molecular proxies of stability (lignin/N) and decomposition (Alkyl C/O-Alky C) showed no differences across the sites, indicating that low potential for BC mineralization. Modeled soil erosion and time since fire from fire scar data showed that soil BC concentrations were inversely correlated. A modified the ecosystem process model, Biome-BGC, was also used simulate the effects of fire disturbance with different severities and seasonality on C cycling related to the BC production, effect on soil water availability, and off-site transport. Results showed that BC impacts on ecosystem processes, including net ecosystem exchange and leaf area development, were predominantly related to fire frequency. Site BC loss rates were

  2. Development of a neutron probe for soil humidity measurements using 6 LiI(Eu) detector

    International Nuclear Information System (INIS)

    Silva, Iran Jose Oliveira da; Khoury, Helen; Carneiro, Clemente J.G.

    2002-01-01

    A prototype of soil moisture probe was build using a crystal of 6 LiI(Eu) as a thermal neutron detector. Light pulses are produced by the exoergic nuclear reaction 6 Li (n,α) 3 He and transmitted through the light guide to a photomultiplier tube on the soil surface. Liquid light guides have several advantages when compared with bundle of glass fibers. First, liquid guides do not suffer from packing fraction losses spaces between fibers that cause reduced coupling efficiency. Second, repeated handling of liquid light guides does not result in the breakage typical of glass bundles, which reduces efficiency over time. Third, liquid guides have excellent UV transmission properties with a cut off the near infrared spectrum yielding an optimum transmission for visible applications. The major advantage of this prototype is the elimination of the electromagnetic interference inside of the soil. Tests were carried out aiming the improvement of electronic and technical viability aspects of neutrons probes. The soil moisture probe calibration curve was carried out in a drum of 60 cm diameter and 42 cm height. This drum was completely filled with an air dry soil. Counts in the center of the drum with the dry and saturated soils make possible to obtain the curves of the soil water content versus the normalized counts for two thermal neutron detectors. The medium value of the counts, the standard deviation and the number of counts were obtained for 6 LiI(Eu) and 3 He detectors, respectively for water, air dry, and saturated soil. From those measurements, a linear calibration curve was obtained for each of detectors. (author)

  3. Erodibility of cement-stabilized tropical soils in highway engineering in Togo

    International Nuclear Information System (INIS)

    Eklu-Natey, T.E.D.

    1992-01-01

    This work contains a methodical study on the suceptibility to weather of cement-stabilized tropical soils of Togo by simulating on the one hand the climatic conditions of the original surroundings and on the other hand the variations occuring in situ of the degree of saturation and compaction. The chosen tests ensure for the first time a simple execution and at the same time reproducible numerical values of the results achieved. From results of the slaking, erosion, adhesion, durability and swelling tests clear parameters and classification criteria were derived which help to forecast the susceptibility to weather of soils in tropical climates. A method for the determination of the reaction to water of soils is proposed consisting of a particular process of derivation and interpretation of the consistency value for a given swelling rate. Moreover a possibility is recommended with which the time-consuming and expensive mineralogical analyses which were frequently used in the past for torpical soils can be avoided. The proposed evaluation criteria provides civil engineers working in permanently moist, arid or intermittently moist tropical regions with practical and theoretical bases for the estimation of the erodibility of soils. (orig./BBR) [de

  4. Phosphate fertilisers and management for sustainable crop production in tropical acid soils

    International Nuclear Information System (INIS)

    Chien, S.H.; Friesen, D.K.

    2000-01-01

    Extensive research has been conducted over the past 25 years on the management of plant nutrients, especially N and P, for crop production on acidic infertile tropical soils. Under certain conditions, the use of indigenous phosphate rock (PR) and modified PR products, such as partially acidulated PR or compacted mixtures of PR with superphosphates, are attractive alternatives, both agronomically and economically, to the use of conventional water-soluble P fertilisers for increasing crop productivity on Oxisols and Ultisols. A combination of the effects of proper P and N management including biological N 2 fixation, judicious use of lime, and the use of acid-soil tolerant and/or P-efficient cultivars in cropping systems that enhance nutrient cycling and use efficiency, can provide an effective technology to sustainably increase crop productivity and production in tropical agro-ecosystems dominated by these acid soils. (author)

  5. Evaluating residues from batai trees (Paraserianthes falcataria) as alternative sources of nitrogen for grain corn (zeas mays l.) in the humid tropics

    International Nuclear Information System (INIS)

    Zaharah, A.R.; Chintu, R.; Ghizan, S.

    2002-01-01

    The use of chemical fertilizers for mitigating N deficiency is unsustainable in many tropical areas because of economic constraints and possible deleterious effects on environmental quality. Although organic inputs such as green manures and litter from legumes have shown some potential for improving soil N status, the synchrony of N release from these residues with crop demand needs to be seriously addressed. The potential of above- and below-ground residues of Batai (Paraserianthes falcataria) to improve soil N availability and uptake by corn in an Ultisol (Bungor series) was evaluated under field and controlled conditions. The effect of residue quality on the kinetics of N release and accumulation in the soil was studied in field and laboratory incubation studies, whilst N uptake by grain corn was quantified using direct and indirect 1 5 N isotope labeling techniques. Treatments consist of fresh leaves, roots and 1:1 mixture of roots and leaves of Batai. Residue quality in terms of lignin + polyphenol-to-N ratio, and N mineralization was in the order roots 3 -N leaching occurred between 30 and 60 days after treatment (DAT). Significant amounts of Ca, Mg and K were also leached beyond 20 cm after 60 days. Both 15 N-labeling methods showed that N recovery in corn was much higher in the root than the leaf treatments. However, integrating Batai residues with an inorganic N source could be a more effective management strategy for improving N use efficiency and mitigating soil acidity. (Author)

  6. Sorption of thiabendazole in sub-tropical Brazilian soils.

    Science.gov (United States)

    de Oliveira Neto, Odilon França; Arenas, Alejandro Yopasa; Fostier, Anne Hélène

    2017-07-01

    Thiabendazole (TBZ) is an ionizable anthelmintic agent that belongs to the class of benzimidazoles. It is widely used in veterinary medicine and as a fungicide in agriculture. Sorption and desorption are important processes influencing transport, transformation, and bioavailability of xenobiotic compounds in soils; data related to sorption capacity are therefore needed for environmental risk assessments. The aim of this work was to assess the sorption potential of TBZ in four Brazilians soils (sandy, sandy-clay, and clay soils), using batch equilibrium experiments at three pH ranges (2.3-3.0, 3.8-4.2, and 5.5-5.7). The Freundlich sorption coefficient (K F ) ranged from 9.0 to 58 μg 1-1/n  (mL) 1/n  g -1 , with higher values generally observed at the lower pH ranges (2.3-3.0 and 3.8-4.2) and for clay soils. The highest organic carbon-normalized sorption coefficients (K OC ) obtained at pH 3.8-5.7 (around the natural pH range of 4.1-5.0) for both clay soils and sandy-clay soil were 3255 and 2015 mL g -1 , respectively. The highest correlations K F vs SOM (r = 0.70) and K F vs clay content (r = 0.91) were observed at pH 3.8-4.2. Our results suggest that TBZ sorption/desorption is strongly pH dependent and that its mobility could be higher in the studied soils than previously reported in soils from temperate regions.

  7. Securing tropical forest carbon

    DEFF Research Database (Denmark)

    Scharlemann, Jörn P. W.; Kapos, Valerie; Campbell, Alison

    2010-01-01

    Forest loss and degradation in the tropics contribute 6-17% of all greenhouse gas emissions. Protected areas cover 217.2 million ha (19.6%) of the world's humid tropical forests and contain c. 70.3 petagrams of carbon (Pg C) in biomass and soil to 1 m depth. Between 2000 and 2005, we estimate...... that 1.75 million ha of forest were lost from protected areas in humid tropical forests, causing the emission of 0.25-0.33 Pg C. Protected areas lost about half as much carbon as the same area of unprotected forest. We estimate that the reduction of these carbon emissions from ongoing deforestation...... in protected sites in humid tropical forests could be valued at USD 6,200-7,400 million depending on the land use after clearance. This is >1.5 times the estimated spending on protected area management in these regions. Improving management of protected areas to retain forest cover better may be an important...

  8. Design of autonomous sensor nodes for remote soil monitoring in tropical banana plantation

    Science.gov (United States)

    Tiausas, Francis Jerome G.; Co, Jerelyn; Macalinao, Marc Joseph M.; Guico, Maria Leonora; Monje, Jose Claro; Oppus, Carlos

    2017-09-01

    Determining the effect of Fusarium oxysporum f. sp. cubense Tropical Race 4 on various soil parameters is essential in modeling and predicting its occurrence in banana plantations. One way to fulfill this is through a sensor network that will continuously and automatically monitor environmental conditions at suspect locations for an extended period of time. A wireless sensor network was developed specifically for this purpose. This sensor network is capable of measuring soil acidity, moisture, temperature, and conductivity. The designed prototype made use of off-the-shelf Parrot Flower Power soil sensor, pH sensor, Bluno Beetle, battery, and 3D-printed materials, catering specifically to the conditions of tropical banana plantations with consideration for sensor node size, communication, and power. Sensor nodes were tested on both simulated tropical environments and on an actual banana plantation in San Jose, General Santos City, Philippines. Challenges were resolved through iterative design and development of prototypes. Several tests including temperature and weather resilience, and structural stress tests were done to validate the design. Findings showed that the WSN nodes developed for this purpose are resilient to high tropical temperatures for up to 12 hours of continuous exposure, are able to withstand compressive forces of up to 8880.6 N, and can reliably collect data automatically from the area 47.96% of the time at an hourly frequency under actual field conditions.

  9. [Fine root dynamics and its relationship with soil fertility in tropical rainforests of Chocó].

    Science.gov (United States)

    Quinto, Harley; Caicedo, Haylin; Thelis Perez, May; Moreno, Flavio

    2016-12-01

    The fine roots play an important role in the acquisition of water and minerals from the soil, the global carbon balance and mitigation of climate change. The dynamics (productivity and turnover) of fine roots is essential for nutrient cycling and carbon balance of forest ecosystems. The availability of soil water and nutrients has significantly determined the productivity and turnover of fine roots. It has been hypothesized that fine roots dynamics increases with the availability of soil resources in tropical forest ecosystems. To test this hypothesis in tropical rainforests of Chocó (ecosystems with the highest rainfall in the world), five one-ha permanent plots were established in the localities of Opogodó and Pacurita, where the productivity and turnover of fine roots were measured at 0-10 cm and 10-20 cm depth. The measurement of the fine root production was realized by the Ingrowth core method. The fine root turnover was measured like fine roots production divided mean annual biomass. In addition, soil fertility parameters (pH, nutrients, and texture) were measured and their association with productivity and turnover of fine roots was evaluated. It was found that the sites had nutrient-poor soils. The localities also differ in soil; Opogodó has sandy soils and flat topography, and Pacurita has clay soils, rich in aluminum and mountainous topography. In Opogodó fine root production was 6.50 ± 2.62 t/ha.yr (mean ± SD). In Pacurita, fine root production was 3.61 ± 0.88 t/ha.yr. Also in Opogodó, the fine root turnover was higher than in Pacurita (1.17 /y and 0.62 /y, respectively). Fine root turnover and production in the upper soil layers (10 cm upper soil) was considerably higher. Productivity and turnover of fine roots showed positive correlation with pH and contents of organic matter, total N, K, Mg, and sand; whereas correlations were negative with ECEC and contents of Al, silt, and clay. The percentage of sand was the parameter that best explained

  10. Calibration of the century, apsim and ndicea models of decomposition and n mineralization of plant residues in the humid tropics

    Directory of Open Access Journals (Sweden)

    Alexandre Ferreira do Nascimento

    2011-06-01

    Full Text Available The aim of this study was to calibrate the CENTURY, APSIM and NDICEA simulation models for estimating decomposition and N mineralization rates of plant organic materials (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum, Stylosanthes guyanensis for 360 days in the Atlantic rainforest bioma of Brazil. The models´ default settings overestimated the decomposition and N-mineralization of plant residues, underlining the fact that the models must be calibrated for use under tropical conditions. For example, the APSIM model simulated the decomposition of the Stizolobium aterrimum and Calopogonium mucunoides residues with an error rate of 37.62 and 48.23 %, respectively, by comparison with the observed data, and was the least accurate model in the absence of calibration. At the default settings, the NDICEA model produced an error rate of 10.46 and 14.46 % and the CENTURY model, 21.42 and 31.84 %, respectively, for Stizolobium aterrimum and Calopogonium mucunoides residue decomposition. After calibration, the models showed a high level of accuracy in estimating decomposition and N- mineralization, with an error rate of less than 20 %. The calibrated NDICEA model showed the highest level of accuracy, followed by the APSIM and CENTURY. All models performed poorly in the first few months of decomposition and N-mineralization, indicating the need of an additional parameter for initial microorganism growth on the residues that would take the effect of leaching due to rainfall into account.

  11. Climate-based statistical regression models for crop yield forecasting of coffee in humid tropical Kerala, India

    Science.gov (United States)

    Jayakumar, M.; Rajavel, M.; Surendran, U.

    2016-12-01

    A study on the variability of coffee yield of both Coffea arabica and Coffea canephora as influenced by climate parameters (rainfall (RF), maximum temperature (Tmax), minimum temperature (Tmin), and mean relative humidity (RH)) was undertaken at Regional Coffee Research Station, Chundale, Wayanad, Kerala State, India. The result on the coffee yield data of 30 years (1980 to 2009) revealed that the yield of coffee is fluctuating with the variations in climatic parameters. Among the species, productivity was higher for C. canephora coffee than C. arabica in most of the years. Maximum yield of C. canephora (2040 kg ha-1) was recorded in 2003-2004 and there was declining trend of yield noticed in the recent years. Similarly, the maximum yield of C. arabica (1745 kg ha-1) was recorded in 1988-1989 and decreased yield was noticed in the subsequent years till 1997-1998 due to year to year variability in climate. The highest correlation coefficient was found between the yield of C. arabica coffee and maximum temperature during January (0.7) and between C. arabica coffee yield and RH during July (0.4). Yield of C. canephora coffee had highest correlation with maximum temperature, RH and rainfall during February. Statistical regression model between selected climatic parameters and yield of C. arabica and C. canephora coffee was developed to forecast the yield of coffee in Wayanad district in Kerala. The model was validated for years 2010, 2011, and 2012 with the coffee yield data obtained during the years and the prediction was found to be good.

  12. Isotope-aided studies of nutrient cycling and soil fertility assessment in humid pasture systems

    International Nuclear Information System (INIS)

    Wilkinson, S.R.

    1983-01-01

    Maintenance of primary productivity in grazed ecosystems depends on the orderly cycling of mineral nutrients. Potential applications of nuclear techniques to the study of soil fertility assessment and nutrient cycling are discussed for the plant nutrients N, P, K and S. The bioavailability of extrinsic and intrinsic sources of mineral nutrients are also discussed. With improvements in analytical technology, it appears feasible to use 15 N in grazed pasture ecosystems for N cycling studies. Sulphur cycling in soil/plant/grazing animal systems has been successfully studied, and further opportunities exist using 35 S to study nutrient flows in grazed grassland systems. Opportunities also appear for increased application of tracer technology in the evaluation of mineral intakes and mineral bioavailability to ruminants grazing semi-arid grassland herbage under native soil fertility, with supplemental fertilization, and in the evaluation of mineral supplementation procedures. Root system distribution and function also can be studied advantageously using tracer techniques. (author)

  13. Geotechnical behavior of a tropical residual soil contaminated with gasoline

    Directory of Open Access Journals (Sweden)

    Óscar Echeverri-Ramírez

    2015-01-01

    Full Text Available La infraestructura para transporte de hidrocarburos ha crecido de manera importante debido a la necesidad de abastecer la mayo r cantidad de poblaciones; sin embargo por pro blemas en las redes de sumin istro, se presentan derrames accidentales que contaminan los su elos bajo los cuales se apoyan estas estructuras. Los suelos contaminados , en este caso particular con gasolina, son la motivación del p resente artículo, el cual pretende analizar los cambios que ocurren en un suelo d e origen residual tropical al ser contaminado con éste; mediant e pruebas de laboratorio específicos para caracterizar este tipo de suelos (Clasificación Miniatura Compactado Tropical, Succión, Pinhole Test, Índice de Colapso, Difracción de rayos “X”, Microscopía Electrónica de Barrido, determinación de pH y de ensayos tradicionales (hume dad natural, gravedad específica, granulometría, límites de Atterbe rg, corte directo, etc, tanto con muestras en estado natural c omo contaminadas que permitan percibir las posibles variaciones en las características mecánicas del material.

  14. Cesium and strontium sorption by selected tropical and subtropical soils around nuclear facilities

    International Nuclear Information System (INIS)

    Chiang, P.N.; Wang, M. K.; Huang, P.M.; Wang, J.J.; Chiu, C.Y.

    2010-01-01

    The dynamics of Cs and Sr sorption by soils, especially in the subtropics and tropics, as influenced by soil components are not fully understood. The rates and capacities of Cs and Sr sorption by selected subtropical and tropical soils in Taiwan were investigated to facilitate our understanding of the transformation and dynamics of Cs and Sr in soils developed under highly weathering intensity. The Langmuir isotherms and kinetic rates of Cs and Sr sorption on the Ap1 and Bt1 horizons of the Long-Tan (Lt) and the A and Bt1 horizons of the Kuan-Shan (Kt), Mao-Lin (Tml) and Chi-Lo (Cl) soils were selected for this study. Air-dried soil ( -5 to 1.88 x 10 -3 M of CsCl (pH 4.0) or 1.14 x 10 -4 to 2.85 x 10 -3 M of SrCl 2 (pH 4.0) solutions at 25 deg. C. The sorption maximum capacity (q m ) of Cs by the Ap1 and Bt1 horizons of the Lt soil (62.24 and 70.70 mmol Cs kg -1 soil) were significantly (p -1 soil in Kt soil and 34.83 and 29.96 mmol Cs kg -1 soil in Cl soil, respectively), however, the sorption maximum capacity values of the Lt and Tml soils did not show significant differences. The amounts of pyrophosphate extractable Fe (Fe p ) were correlated significantly with the Cs and Sr sorption capacities (for Cs sorption, r 2 = 0.97, p -4 ; for Sr sorption, r 2 = 0.82, p -3 ). The partition coefficient of radiocesium sorbed on soil showed the following order: Cl soil >> Kt soil > Tml soil > Lt soil. It was due to clay minerals. The second-order kinetic model was applied to the Cs and Sr sorption data. The rate constant of Cs or Sr sorption on the four soils was substantiality increased with increasing temperature. This is attributable to the availability of more energy for bond breaking and bond formation brought about by the higher temperatures. The rate constant of Cs sorption at 308 K was 1.39-2.09 times higher than that at 278 K in the four soils. The activation energy of Cs and Sr sorbed by the four soils ranged from 7.2 to 16.7 kJ mol -1 and from 15.2 to 22.4 kJ mol

  15. Soil 137Cs activity in a tropical deciduous ecosystem under pasture conversion in Mexico

    International Nuclear Information System (INIS)

    Garcia-Oliva, F.; Maass, J.M.

    1995-01-01

    Soil profiles of 137 Cs were measured in a tropical deciduous ecosystem under pasture conversion on the Pacific Coast of Mexico. Soil samples were taken from unperturbed forest, and from pasture plots following forest conversion. The average total 137 Cs areal activity of non-eroded forest sites indicated a base level of 5 315 ± 427 Bq m -2 . On average, total areal activity on hill-tops was significantly higher (range 10-47%) in the forest than in the pastures. A significant correlation was found between the total 137 Cs areal activity and soil organic matter content (r 2 = 0.16). This correlation can be explained by a soil physical-protection hypothesis. The redistribution of 137 Cs in the landscape is explained by soil erosion processes. (author)

  16. Anaerobic decomposition of switchgrass by tropical soil-derived feedstock-adapted consortia.

    Science.gov (United States)

    DeAngelis, Kristen M; Fortney, Julian L; Borglin, Sharon; Silver, Whendee L; Simmons, Blake A; Hazen, Terry C

    2012-01-01

    Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To investigate how TEAs affect decomposition, we cultivated feedstock-adapted consortia (FACs) derived from two tropical forest soils collected from the ends of a rainfall gradient: organic matter-rich tropical cloud forest (CF) soils, which experience sustained low redox, and iron-rich tropical rain forest (RF) soils, which experience rapidly fluctuating redox. Communities were anaerobically passed through three transfers of 10 weeks each with switchgrass as a sole carbon (C) source; FACs were then amended with nitrate, sulfate, or iron oxide. C mineralization and cellulase activities were higher in CF-FACs than in RF-FACs. Pyrosequencing of the small-subunit rRNA revealed members of the Firmicutes, Bacteroidetes, and Alphaproteobacteria as dominant. RF- and CF-FAC communities were not different in microbial diversity or biomass. The RF-FACs, derived from fluctuating redox soils, were the most responsive to the addition of TEAs, while the CF-FACs were overall more efficient and productive, both on a per-gram switchgrass and a per-cell biomass basis. These results suggest that decomposing microbial communities in fluctuating redox environments are adapted to the presence of a diversity of TEAs and ready to take advantage of them. More importantly, these data highlight the role of local environmental conditions in shaping microbial community function that may be separate from phylogenetic structure. After multiple transfers, we established microbial consortia derived from two tropical forest soils with different native redox conditions. Communities derived from the rapidly fluctuating redox environment maintained a capacity to use added terminal electron acceptors (TEAs) after multiple

  17. Stand-scale soil respiration estimates based on chamber methods in a Bornean tropical rainforest

    Science.gov (United States)

    Kume, T.; Katayama, A.; Komatsu, H.; Ohashi, M.; Nakagawa, M.; Yamashita, M.; Otsuki, K.; Suzuki, M.; Kumagai, T.

    2009-12-01

    This study was undertaken to estimate stand-scale soil respiration in an aseasonal tropical rainforest on Borneo Island. To this aim, we identified critical and practical factors explaining spatial variations in soil respiration based on the soil respiration measurements conducted at 25 points in a 40 × 40 m subplot of a 4 ha study plot for five years in relation to soil, root, and forest structural factors. Consequently, we found significant positive correlation between the soil respiration and forest structural parameters. The most important factor was the mean DBH within 6 m of the measurement points, which had a significant linear relationship with soil respiration. Using the derived linear regression and an inventory dataset, we estimated the 4 ha-scale soil respiration. The 4 ha-scale estimation (6.0 μmol m-2 s-1) was nearly identical to the subplot scale measurements (5.7 μmol m-2 s-1), which were roughly comparable to the nocturnal CO2 fluxes calculated using the eddy covariance technique. To confirm the spatial representativeness of soil respiration estimates in the subplot, we performed variogram analysis. Semivariance of DBH(6) in the 4 ha plot showed that there was autocorrelation within the separation distance of about 20 m, and that the spatial dependence was unclear at a separation distance of greater than 20 m. This ascertained that the 40 × 40 m subplot could represent the whole forest structure in the 4 ha plot. In addition, we discuss characteristics of the stand-scale soil respiration at this site by comparing with those of other forests reported in previous literature in terms of the soil C balance. Soil respiration at our site was noticeably greater, relative to the incident litterfall amount, than soil respiration in other tropical and temperate forests probably owing to the larger total belowground C allocation by emergent trees. Overall, this study suggests the arrangement of emergent trees and their bellow ground C allocation could be

  18. Monitoring groundwater storage changes in the highly seasonal humid tropics: Validation of GRACE measurements in the Bengal Basin

    Science.gov (United States)

    Shamsudduha, M.; Taylor, R. G.; Longuevergne, L.

    2012-02-01

    Satellite monitoring of changes in terrestrial water storage provides invaluable information regarding the basin-scale dynamics of hydrological systems where ground-based records are limited. In the Bengal Basin of Bangladesh, we test the ability of satellite measurements under the Gravity Recovery and Climate Experiment (GRACE) to trace both the seasonality and trend in groundwater storage associated with intensive groundwater abstraction for dry-season irrigation and wet-season (monsoonal) recharge. We show that GRACE (CSR, GRGS) datasets of recent (2003 to 2007) groundwater storage changes (ΔGWS) correlate well (r = 0.77 to 0.93, p value CSR. Changes in surface water storage estimated from a network of 298 river gauging stations and soil-moisture derived from Land Surface Models explain 22% and 33% of ΔTWS, respectively. Groundwater depletion estimated from borehole hydrographs (-0.52 ± 0.30 km3 yr-1) is within the range of satellite-derived estimates (-0.44 to -2.04 km3 yr-1) that result from uncertainty associated with the simulation of soil moisture (CLM, NOAH, VIC) and GRACE signal-processing techniques. Recent (2003 to 2007) estimates of groundwater depletion are substantially greater than long-term (1985 to 2007) mean (-0.21 ± 0.03 km3 yr-1) and are explained primarily by substantial increases in groundwater abstraction for the dry-season irrigation and public water supplies over the last two decades.

  19. Effect of the pH on the radiocesium adsorption in tropical soils

    International Nuclear Information System (INIS)

    Roque, Mario Lucio; Boaretto, Antonio E.; Moniz, Antonio C; Smolders, Erik E. T.

    2002-01-01

    The objective was to demonstrate that the pH dependent charges are specific change sites for radiocesium. Clay minerals occurrence in superficial samples of eight tropical soils was analyzed by X-Ray diffractometry. The variation of superficial charge of these soils were quantify by potentiometric titration in a range from 3 to 8 pH values. The results of radiocesium interception potential showed the presence of specific sites of adsorption of this radionuclide for all the soils. The variation of radiocesium adsorption for all soils was quantified in a pH defined range. The increase on the pH values caused increase on the radiocesium adsorption by the soils and a consequent decrease in the radiocesium activity in the equilibrium solution. The soil with predominance of the 2:1 clay minerals showed higher radiocesium adsorption than the soils with 1:1 clay minerals or iron and aluminum oxides. The increase on the negative charge in consequence of pH increase caused increase on radiocesium adsorption. The correction of soil acidity with lime by increasing the specific sites charge for radiocesium and decreasing the radionuclide activity in soil solution may cause decrease on the transference of radiocesium from soil to plant. (author)

  20. Assessment of chemical properties of tropical peatland soil in ...

    African Journals Online (AJOL)

    The chemical assessment of the peatland in oil palm plantation in South Selangor Peatland Swamp in Malaysia were evaluated in this study. Soil samples were obtained from fifteen (15) different locations within the study area at three different depths of 0.5m, 1.5 m, and 2.5 m in three replicates at each depth, using peat ...

  1. Carbonyl sulfide (OCS) as a proxy for GPP: Complications derived from studies on the impact of CO2, soil humidity and sterilization on the OCS exchange between soils and atmosphere

    Science.gov (United States)

    Bunk, Rüdiger; Behrendt, Thomas; Yi, Zhigang; Kesselmeier, Jürgen

    2016-04-01

    Carbonyl sulfide is discussed to be used as a proxy for gross primary productivity (GPP) of forest ecosystems. However, soils may interfere. Soils play an important role in budgeting global and local carbonyl sulfide (OCS) fluxes, yet the available data on the uptake and emission behavior of soils in conjunction with environmental factors is limited. The work of many authors has shown that the OCS exchange of soils depends on various factors, such as soil type, atmospheric OCS concentrations, temperature or soil water content (Kesselmeier et al., J. Geophys. Res., 104, No. D9, 11577-11584, 1999; Van Diest & Kesselmeier, Biogeosciences, 5, 475-483, 2008; Masyek et al., PNAS, 111, No 25, 9064-9069, doi: 10.1073/pnas.1319132111, 2014; Whelan and Rhew, J. Geophys. Res. Biogeosciences., 120, 54-62, doi: 10.1002/2014JG002661, 2015) and the light dependent and obviously abiotic OCS production as reported by Whelan and Rhew (2015). To get a better constraint on the impact of some environmental factors on the OCS exchange of soils we used a new laser based integrated cavity output spectroscopy instrument (LGR COS/CO Analyzer Model 907-0028, Los Gatos, Mountain View, California, USA) in conjunction with an automated soil chamber system (as described in Behrendt et al, Biogeosciences, 11, 5463-5492, doi: 10.5194/bg-11-5463-2014, 2014). The OCS exchange of various soils under the full range of possible soil humidity and various CO2 mixing ratios was examined. Additionally OCS exchange of chloroform sterilized subsamples was compared to their live counterparts to illuminate the influence of microorganisms. Results were quite heterogeneous between different soils. With few exceptions, all examined soils show dependence between OCS exchange and soil humidity, usually with strongest uptake at a certain humidity range and less uptake or even emission at higher and lower humidity. Differences in CO2 mixing ratio also clearly impacts on OCS exchange, but trends for different soils

  2. Using Remotely Sensed Fluorescence and Soil Moisture to Better Understand the Seasonal Cycle of Tropical Grasslands

    Science.gov (United States)

    Smith, Dakota Carlysle

    Seasonal grasslands account for a large area of Earth's land cover. Annual and seasonal changes in these grasslands have profound impacts on Earth's carbon, energy, and water cycles. In tropical grasslands, growth is commonly water-limited and the landscape oscillates between highly productive and unproductive. As the monsoon begins, soils moisten providing dry grasses the water necessary to photosynthesize. However, along with the rain come clouds that obscure satellite products that are commonly used to study productivity in these areas. To navigate this issue, we used solar induced fluorescence (SIF) products from OCO-2 along with soil moisture products from the Soil Moisture Active Passive satellite (SMAP) to "see through" the clouds to monitor grassland productivity. To get a broader understanding of the vegetation dynamics, we used the Simple Biosphere Model (SiB4) to simulate the seasonal cycles of vegetation. In conjunction with SiB4, the remotely sensed SIF and soil moisture observations were utilized to paint a clearer picture of seasonal productivity in tropical grasslands. The remotely sensed data is not available for every place at one time or at every time for one place. Thus, the study was focused on a large area from 15° E to 35° W and from 8°S to 20°N in the African Sahel. Instead of studying productivity relative to time, we studied it relative to soil moisture. Through this investigation we found soil moisture thresholds for the emergence of grassland growth, near linear grassland growth, and maturity of grassland growth. We also found that SiB4 overestimates SIF by about a factor of two for nearly every value of soil moisture. On the whole, SiB4 does a surprisingly good job of predicting the response of seasonal growth in tropical grasslands to soil moisture. Future work will continue to integrate remotely sensed SIF & soil moisture with SiB4 to add to our growing knowledge of carbon, water, and energy cycling in tropical grasslands.

  3. Strontium-Doped Hematite as a Possible Humidity Sensing Material for Soil Water Content Determination

    OpenAIRE

    Tulliani, Jean-Marc; Baroni, Chiara; Zavattaro, Laura; Grignani, Carlo

    2013-01-01

    The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prep...

  4. Chemical evolution of soil profile from humid regions: The role of the rare elements

    Directory of Open Access Journals (Sweden)

    Yu.N. Vodyanitskii

    2016-06-01

    Full Text Available Eluvial-illuvial distribution of rare metals in forest soils is expressed more vividly than the distribution of Fe and Al the more. This is applies primarily to lanthanides: Y, La, Ce. In particular, this difference is noticeable in light Al–Fe-humus podzols, where highly differentiated elements of platinum group. The type of metals exposed to eluvial-illuvial distribution depends on the mineralogical composition of the parent rock and has a pronounced regional dimension.

  5. Soil nitrogen levels are linked to decomposition enzyme activities along an urban-remote tropical forest gradient

    Science.gov (United States)

    D. F. Cusack

    2013-01-01

    Urban areas in tropical regions are expanding rapidly, with significant potential to affect local ecosystem dynamics. In particular, nitrogen (N) availability may increase in urban-proximate forests because of atmospheric N deposition. Unlike temperate forests, many tropical forests on highly weathered soils have high background N availability, so plant growth is...

  6. Pre-exposure to drought increases the resistance of tropical forest soil bacterial communities to extended drought

    Science.gov (United States)

    Nicholas J. Bouskill; Hsiao Chien Lim; Sharon Borglin; Rohit Salve; Tana Wood; Whendee L. Silver; Eoin L. Brodie

    2013-01-01

    Global climate models project a decrease in the magnitude of precipitation in tropical regions. Changes in rainfall patterns have important implications for the moisture content and redox status of tropical soils, yet little is known about how these changes may affect microbial community structure. Specifically, does exposure to prior stress confer increased resistance...

  7. Climatic controls on the isotopic composition and availability of soil nitrogen in mountainous tropical forests

    Science.gov (United States)

    Weintraub, S. R.; Cole, R. J.; Schmitt, C. G.; All, J.

    2014-12-01

    Tropical forests in mountainous regions are often assumed to be nitrogen (N) limited, yet N dynamics across rugged terrain can be complex due to gradients in climate and topography. Elucidating patterns of N availability and loss across such gradients is necessary to predict and manage tropical forest response to environmental changes such as increasing N deposition and rising temperatures. However, such data is currently lacking, particularly in remote locations that are of high conservation value. To address this gap, a research expedition organized by the American Climber Science Program recently made a coast-to-coast journey across a remote region of Costa Rica, travelling over the Cordillera Talamanca and through La Amistad International Park. Numerous biological, chemical and hydrologic measurements were made en-route across montane to premontane wet tropical forests, spanning nearly 2,000 m in elevation and 200 km. Surface soil samples collected at regular intervals along this transect illuminate environmental drivers of N dynamics across the region. The dataset reveals strong links between soil natural abundance N isotopic composition (δ15N) and elevation and temperature parameters, and weaker links to precipitation and topography. This is in general agreement with global scale observations, but divergence from some previously published works is apparent and will be discussed. δ15N mass balance models suggest that N isotope patterns reflect differences in forms of N loss and the relative importance of fractionating and non-fractionating pathways. When combined with data on several other edaphic properties, especially C:N stoichiometry, the results points toward notable variation in soil N availability and N constraints across the transect. This study illustrates large, but predictable, variation in key N cycle traits across the premontane to montane wet tropical forest transition. These findings have management-relevant implications for tropical regions.

  8. Growth of four tropical tree species in petroleum-contaminated soil and effects of crude oil contamination

    NARCIS (Netherlands)

    Pérez-Hernández, I.; Ochoa-Gaona, S.; Adams, R.H.; Rivera-Cruz, M.C.; Pérez-Hernández, V.; Jarquín-Sánchez, A.; Geissen, V.; Martínez-Zurimendi, P.

    2017-01-01

    Under greenhouse conditions, we evaluated establishment of four tree species and their capacity to degrade crude oil recently incorporated into the soil; the species were as follows: Cedrela odorata (tropical cedar), Haematoxylum campechianum (tinto bush), Swietenia macrophylla (mahogany), and

  9. Effects of Successive Harvests on Soil Nutrient Stocks in Established Tropical Plantation Forests

    Science.gov (United States)

    Mendoza, L.; McMahon, D.; Jackson, R. B.

    2017-12-01

    Large-scale plantation forests in tropical regions alter biogeochemical processes, raising concerns about the long-term sustainability of this land use. Current commercial practices result in nutrient export with removed biomass that may not be balanced by fertilizer application. Consequent changes in a landscape's nutrient distributions can affect the growth of future plantations or other vegetation. Prior studies have reported changes in soil chemical and physical properties when plantation forests replace pastures or native vegetation, but few have examined the impacts of multiple harvest cycles following plantation establishment. This study analyzed macronutrient and carbon content of soil samples from the world's most productive plantation forests, in southeastern Brazil, to understand the long-term effects of plantation forests on soil nutrient stocks and soil fertility. Soil was collected from Eucalyptus plantation sites and adjacent vegetation in 2004 and again in 2016, after at least one full cycle of harvesting and replanting. We found that within surface soil (0-10 cm) Mg and N did not change significantly and C, P, K and Ca concentrations generally increased, but to varying extents within individual management units. This trend of increasing nutrient concentrations suggests that additional harvests do not result in cumulative nutrient depletion. However, large changes in Ca and K concentrations in individual plantation units indicate that added fertilizer does not consistently accumulate in the surface soil. Analysis of deeper soil layers and comparison to unfertilized vegetation will help to determine the fate of fertilizers and native soil nutrients in repeatedly harvested plantations. These results address the necessity of long-term investigation of nutrient changes to better understand and determine the impacts of different types of land use in the tropics.

  10. Effects of Nonnative Ungulate Removal on Plant Communities and Soil Biogeochemistry in Tropical Forests

    Science.gov (United States)

    Cole, R. J.; Litton, C. M.; Giardina, C. P.; Sparks, J. P.

    2014-12-01

    Non-native ungulates have substantial impacts on native ecosystems globally, altering both plant communities and soil biogeochemistry. Across tropical and temperate ecosystems, land managers fence and remove non-native ungulates to conserve native biodiversity, a costly management action, yet long-term outcomes are not well quantified. Specifically, knowledge gaps include: (i) the magnitude and time frame of plant community recovery; (ii) the response of non-native invasive plants; and (iii) changes to soil biogeochemistry. In 2010, we established a series of paired ungulate presence vs. removal plots that span a 20 yr. chronosequence in tropical montane wet forests on the Island of Hawaii to quantify the impacts and temporal legacy of feral pig removal on plant communities and soil biogeochemistry. We also compared soil biogeochemistry in targeted areas of low and high feral pig impact. Our work shows that both native and non-native vegetation respond positively to release from top-down control following removal of feral pigs, but species of high conservation concern recover only if initially present at the time of non-native ungulate removal. Feral pig impacts on soil biogeochemistry appear to last for at least 20 years following ungulate removal. We observed that both soil physical and chemical properties changed with feral pig removal. Soil bulk density and volumetric water content decreased while extractable base cations and inorganic N increased in low vs. high feral pig impact areas. We hypothesize that altered soil biogeochemistry facilitates continued invasions by non-native plants, even decades after non-native ungulate removal. Future work will concentrate on comparisons between wet and dry forest ecosystems and test whether manipulation of soil nutrients can be used to favor native vs. non-native plant establishment.

  11. Mineralogical controls on microbial biomass accumulation on two tropical soils

    Science.gov (United States)

    Block, K. A.; Pena, S. A.; Katz, A.; Gottlieb, P.; Volta, A.

    2017-12-01

    The characteristics of soil organic matter (SOM) generated by microbes and associated with minerals are not well defined. This information is critical to reducing uncertainty in climate models related to C cycling and ecosystem feedbacks. The resistance to degradation of mineral-associated SOM is influenced by aggregate structure, mineral chemistry and microbial community. In this work we examine the influence of mineral composition, including amorphous coatings on the biomass yield and aggregate structure through thermogravimetric analysis, X-ray diffraction and electron microscopy. Two soil organisms, Pseudomonas phaseolicola, and Streptomyces griseosporus, were each incubated over a 72-hour period in minimal media with the cultured under the same conditions. In all samples, approximately half of the sample mass loss occurred between 175 ºC - 375 ºC, which we attribute to biomolecules accumulated on the mineral surfaces. We observed a slightly larger mass loss in the Inceptisol than in the Oxisol, most of which corresponded to compounds that underwent pyrolysis at 300 ºC. HRTEM micrographs and TEM-EDS image maps showing the spatial relationship of microbial necromass to soil minerals will be reported.

  12. Use of expanded vermiculite as a soil conditioner in the tropics

    International Nuclear Information System (INIS)

    Libardi, P.L.; Salati, E.; Reichardt, K.

    1983-01-01

    Expanded vermiculite is used as a soil conditioner to improve soil-water retention and cation exchange properties of poor tropical soils (alfisols and oxisols). Results show that fresh laboratory mixtures of soil and expanded vermiculite increase the amount of water retained, the process being affected by the rate of application, origin and granule size of the vermiculite. Pot experiments show that the incorporation of vermiculite into the soil increases soil-water storage capacity without affecting evapotranspiration rates. This indicates that crops grown in soils conditioned with vermiculite lose the same quantities of water through evapotranspiration, but support plants for longer periods without water addition. Diminishing irrigation frequency raises the possibility of irrigating larger areas and/or using irrigation equipment more rationally. Field experiments have been developed to examine the potential use of vermiculite, at low application rates, in extensive agriculture. Encouraging results have been obtained regarding crop resistance to drought spells, and yield in vermiculite conditioned soils. This new management practice seems to be one solution for semi-arid agriculture and for areas of soil with poor water retention properties subjected to irregular rainfall patterns. Experiments show also that vermiculite addition improves root growth and affects soil nutrient ratios. This depends again on soil type, vermiculite origin and granule size, application rates, form of incorporation into the soil and type of crop. It affects Ca/K, Ca/Mg and Mg/K ratios in soil extracts and the availability of micronutrients. Tracers were used to study some aspects of the dynamics of N and P. (author)

  13. Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.

    Science.gov (United States)

    Turner, Benjamin L

    2010-10-01

    Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

  14. Differential geochemical behaviour of natural isotopes of U and Th in an aquifer in humid tropical terrain

    International Nuclear Information System (INIS)

    Bonotto, D.M.

    1989-01-01

    Uranium and thorium isotopic analyses were performed on spoil samples from the saturated zone of a borehole drilled in the main ore body of a high grade thorium/rare earth ore, and on groundwaters from a borehole drilled in the zone. The deposit is located at Morro do Ferro, a hill near the centre of the Pocos de Caldas Plateau (MG), where an aquifer system developed in the weathered mantle due to in situ intense alteration. For extraction of uranium and thorium a long chemical process was applied to the samples; activities of Th-228 and Th-232 isotopes (4n series) and also of U-238, U-234 and Th-230 isotopes (4n+2 series) were determined by the alpha spectrometry method. U-234/U-238 activity ratios in groundwaters were between 1 and 2 but Th-228/Th-232 activity ratios showed marked isotopic fractionation between these nuclides. The mechanism of mobilization of uranium by complexation with humic substances is considered. U-234/U-238, Th-228/Th-232 and Th-230/U-234 activity ratios in soil samples allowed consider action of other possible mechanisms related to the mobilization of uranium, such as, ion-exchange reaction and adsorption by Fe and Mn oxides. (author) [pt

  15. Ohcratoxin producing Aspergillus spp. Isolated from tropical soils in Sarawak, Malaysia

    Directory of Open Access Journals (Sweden)

    J.S.S. Seelan

    2010-03-01

    Full Text Available Aspergillus strains isolated from tropical soils were selected for additional characterization and for ochratoxin analysis, which was determined by ELISA method and high performance liquid chromatography (HPLC profiles. Because of its great morphological variability and mycotoxin production availability, 18 isolates of Aspergillus species were selected for this study. Only two isolates of these tropical soils, A. sulphureus and A. carbonarius, showed positive results for ohcratoxin (OA in lower concentration (0.05-0.10 µg/ml. Ochratoxin production by these species was confirmed by high performance liquid chromatography. HPLC analysis for ochratoxin producing A. sulphureus and A. carbonarius showed retention time, Rt value = 4.417 and Rt value = 4.081 respectively.

  16. Effects of Litter and Nutrient Additions on Soil Carbon Cycling in a Tropical Forest

    Science.gov (United States)

    Cusack, D. F.; Halterman, S.; Turner, B. L.; Tanner, E.; Wright, S. J.

    2014-12-01

    Soil carbon (C) dynamics present one of the largest sources of uncertainty in global C cycle models, with tropical forest soils containing some of the largest terrestrial C stocks. Drastic changes in soil C storage and loss are likely to occur if global change alters plant net primary production (NPP) and/or nutrient availability in these ecosystems. We assessed the effects of litter removal and addition, as well as fertilization with nitrogen (N), phosphorus (P), and/or potassium (K), on soil C stocks in a tropical seasonal forest in Panama after ten and sixteen years, respectively. We used a density fractionation scheme to assess manipulation effects on rapidly and slowly cycling pools of C. Soil samples were collected in the wet and dry seasons from 0-5 cm and 5-10 cm depths in 15- 45x45 m plots with litter removal, 2x litter addition, and control (n=5), and from 32- 40x40 m fertilization plots with factorial additions of N, P, and K. We hypothesized that litter addition would increase all soil C fractions, but that the magnitude of the effect on rapidly-cycling C would be dampened by a fertilization effect. Results for the dry season show that the "free light" C fraction, or rapidly cycling soil C pool, was significantly different among the three litter treatments, comprising 5.1 ± 0.9 % of total soil mass in the litter addition plots, 2.7 ± 0.3 % in control plots, and 1.0 ± 0.1 % in litter removal plots at the 0-5cm depth (means ± one standard error, p < 0.05). Bulk soil C results are similar to observed changes in the rapidly cycling C pool for the litter addition and removal. Fertilization treatments on average diminished this C pool size relative to control plots, although there was substantial variability among fertilization treatments. In particular, addition of N and P together did not significantly alter rapidly cycling C pool sizes (4.1 ± 1.2 % of total soil mass) relative to controls (3.5 ± 0.4 %), whereas addition of P alone resulted in

  17. Phytoremediation of some tropical soils contaminated with petroleum crude oil

    International Nuclear Information System (INIS)

    Oyibo, Charles

    2013-12-01

    This study was undertaken in three phases to identify (phase 1), screen (phase 11) and evaluate (phase 111) plants for their phytoremediation potential. In Phase 1, 15 plant species made up of grasses and legumes namely: Paspalum. vaginatum, Cynodon.dactylon, Pueraria. phaseoloides, Centrosema. pubescens, Panicum. maximum, Schrankia. leptocarpa, Eclipta. alba (Linn.), Cyperus. haspen (Linn.), Melastromastrum. capitatum, Acreceras. zizanoides Dandy, Pteridum aquilinum (Linn), Ludwigia.decurrens Walt,Setaria longiseta P.Beauv., Physalis angulata (Linn.), and Desmodium scorpiurus Desv.were identified on sites previously polluted by crude oil spills in the Niger Delta Area of Nigeria. The first 6 species were used in phase 11 while the first four species were earmarked (rolled over) for phase 111. Responses to Questionnaire indicated that majority of residents in the selected sites/communities had lived in these areas for 10 or more years had mainly JHS/SHS education; were self employed – mainly farmers and fishers although most were unemployed in the public sector. Adverse effects of the operations of oil companies particularly oil spillage on the environment and local residents include: loss of vegetation and farmlands, soil and water body contamination, weak social and cultural institutions (disrespect by youth for elders and institutions), militancy and hostage taking among youth from the area. In phase 11, seeds of legumes among the six selected species were collected from Accra, Aburi environs and Kusi in the Eastern region of Ghana; they were scarified, cultured in growth medium and the seedlings which emerged from them were transplanted into experimental pots, each containing 2000g of either Alajo or Toje soil series. One week after transplanting, each pot was simulated with a corresponding serial crude oil concentration of 0% (control) 1 % (24ml), 3% (83ml), 5.5% (130ml) and 8% (189ml) or 10% (237ml) in three replicates. These concentrations were arrived at

  18. Exotic grasses and nitrate enrichment alter soil carbon cycling along an urban-rural tropical forest gradient.

    Science.gov (United States)

    Cusack, Daniela F; Lee, Joseph K; McCleery, Taylor L; LeCroy, Chase S

    2015-12-01

    Urban areas are expanding rapidly in tropical regions, with potential to alter ecosystem dynamics. In particular, exotic grasses and atmospheric nitrogen (N) deposition simultaneously affect tropical urbanized landscapes, with unknown effects on properties like soil carbon (C) storage. We hypothesized that (H1) soil nitrate (NO3 (-) ) is elevated nearer to the urban core, reflecting N deposition gradients. (H2) Exotic grasslands have elevated soil NO3 (-) and decreased soil C relative to secondary forests, with higher N promoting decomposer activity. (H3) Exotic grasslands have greater seasonality in soil NO3 (-) vs. secondary forests, due to higher sensitivity of grassland soil moisture to rainfall. We predicted that NO3 (-) would be positively related to dissolved organic C (DOC) production via changes in decomposer activity. We measured six paired grassland/secondary forest sites along a tropical urban-to-rural gradient during the three dominant seasons (hurricane, dry, and early wet). We found that (1) soil NO3 (-) was generally elevated nearer to the urban core, with particularly clear spatial trends for grasslands. (2) Exotic grasslands had lower soil C than secondary forests, which was related to elevated decomposer enzyme activities and soil respiration. Unexpectedly, soil NO3 (-) was negatively related to enzyme activities, and was lower in grasslands than forests. (3) Grasslands had greater soil NO3 (-) seasonality vs. forests, but this was not strongly linked to shifts in soil moisture or DOC. Our results suggest that exotic grasses in tropical regions are likely to drastically reduce soil C storage, but that N deposition may have an opposite effect via suppression of enzyme activities. However, soil NO3 (-) accumulation here was higher in urban forests than grasslands, potentially related to of aboveground N interception. Net urban effects on C storage across tropical landscapes will likely vary depending on the mosaic of grass cover, rates of N

  19. Tropical Land Use Conversion Effects on Soil Microbial Community Structure and Function: Emerging Patterns and Knowledge Gaps

    Science.gov (United States)

    Seeley, M.; Marin-Spiotta, E.

    2016-12-01

    Modifications in vegetation due to land use conversions (LUC) between primary forests, pasture, cropping systems, tree plantations, and secondary forests drive shifts in soil microbial communities. These microbial community alterations affect carbon sequestration, nutrient cycling, aboveground biomass, and numerous other soil processes. Despite their importance, little is known about soil microbial organisms' response to LUC, especially in tropical regions where LUC rates are greatest. This project identifies current trends and uncertainties in tropical soil microbiology by comparing 56 published studies on LUC in tropical regions. This review indicates that microbial biomass and functional groups shifted in response to LUC, supporting demonstrated trends in changing soil carbon stocks due to LUC. Microbial biomass was greatest in primary forests when compared to secondary forests and in all forests when compared to both cropping systems and tree plantations. No trend existed when comparing pasture systems and forests, likely due to variations in pasture fertilizer use. Cropping system soils had greater gram positive and less gram negative bacteria than forest soils, potentially resulting in greater respiration of older carbon stocks in agricultural soils. Bacteria dominated primary forests while fungal populations were greatest in secondary forests. To characterize changes in microbial communities resulting from land use change, research must reflect the biophysical variation across the tropics. A chi-squared test revealed that the literature sites represented mean annual temperature variation across the tropics (p-value=0.66).

  20. Enhanced degradation of 14C-HCB in two tropical clay soils using multiple anaerobic–aerobic cycles

    International Nuclear Information System (INIS)

    Orori Kengara, Fredrick; Doerfler, Ulrike; Welzl, Gerhard; Ruth, Bernhard; Munch, Jean Charles; Schroll, Reiner

    2013-01-01

    The aim of the study was to induce and enhance the degradation of hexachlorobenzene (HCB), a highly-chlorinated persistent organic pollutant, in two ecologically different tropical soils: a paddy soil (PS) and a non-paddy soil (FS). The degradation of HCB was enhanced using two anaerobic–aerobic cycles in model laboratory experiments. There was greater degradation of HCB in the PS (half-life of 224 days) relative to the FS (half-life of 286 days). It was further shown that soils amended with compost had higher metabolite concentrations relative to the non-amended soils. In the first cycle, there was little degradation of HCB in both soils. However, in the second cycle, there was enhanced mineralization in the PS under aerobic conditions, with the compost-treated samples showing higher mineralization. There was also extensive volatilization in both soils. The metabolite pattern revealed that the increased mineralization and volatilization was due to the formation of lower chlorinated benzenes. - Highlights: ► Two anaerobic–aerobic cycles enhanced the dissipation of HCB in two tropical soils – a paddy and non-paddy soil. ► The paddy soil was more effective in degrading HCB. ► The non-paddy soil adapted and degraded HCB in the second anaerobic–aerobic cycle. ► An additional carbon source enhanced degradation and mineralisation of HCB in both soils. - Two anaerobic–aerobic cycles enhance the degradation of HCB in two ecologically different tropical clay soils.

  1. 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...

  2. 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 ...

  3. The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

    Science.gov (United States)

    Oliver, Viktoria; Oliveras, Imma; Kala, Jose; Lever, Rebecca; Arn Teh, Yit

    2017-12-01

    Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF), especially at the lower depths (10-20 and 20-30 cm). In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt-grazed soil had the smallest recovery of the free LF (10 %) and a significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the not-burnt soils (7 %) and there was no significant difference among the treatments in the heavy fraction (F) ( ˜ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant

  4. Prediction of spatial patterns of collapsed pipes in loess-derived soils in a temperate humid climate using logistic regression

    Science.gov (United States)

    Verachtert, E.; Den Eeckhaut, M. Van; Poesen, J.; Govers, G.; Deckers, J.

    2011-07-01

    Soil piping (tunnel erosion) has been recognised as an important erosion process in collapsible loess-derived soils of temperate humid climates, which can cause collapse of the topsoil and formation of discontinuous gullies. Information about the spatial patterns of collapsed pipes and regional models describing these patterns is still limited. Therefore, this study aims at better understanding the factors controlling the spatial distribution and predicting pipe collapse. A dataset with parcels suffering from collapsed pipes (n = 560) and parcels without collapsed pipes was obtained through a regional survey in a 236 km² study area in the Flemish Ardennes (Belgium). Logistic regression was applied to find the best model describing the relationship between the presence/absence of a collapsed pipe and a set of independent explanatory variables (i.e. slope gradient, drainage area, distance-to-thalweg, curvature, aspect, soil type and lithology). Special attention was paid to the selection procedure of the grid cells without collapsed pipes. Apart from the first piping susceptibility map created by logistic regression modelling, a second map was made based on topographical thresholds of slope gradient and upslope drainage area. The logistic regression model allowed identification of the most important factors controlling pipe collapse. Pipes are much more likely to occur when a topographical threshold depending on both slope gradient and upslope area is exceeded in zones with a sufficient water supply (due to topographical convergence and/or the presence of a clay-rich lithology). On the other hand, the use of slope-area thresholds only results in reasonable predictions of piping susceptibility, with minimum information.

  5. Extreme emission of N2O from tropical wetland soil (Pantanal, South America)

    DEFF Research Database (Denmark)

    Jensen, Lars Liengård; Nielsen, Lars Peter; Revsbech, Niels Peter

    2013-01-01

    Nitrous oxide (N(2)O) is an important greenhouse gas and ozone depleter, but the global budget of N(2)O remains unbalanced. Currently, ~25% of the global N(2)O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. Here we present...... the first study of soil N(2)O emission from the Pantanal indicating that this South American wetland may be a significant natural source of N(2)O. At three sites, we repeatedly measured in situ fluxes of N(2)O and sampled porewater nitrate [Formula: see text] during the low water season in 2008 and 2009....... In 2010, 10 sites were screened for in situ fluxes of N(2)O and soil [Formula: see text] content. The in situ fluxes of N(2)O were comparable to fluxes from heavily fertilized forests or agricultural soils. An important parameter affecting N(2)O emission rate was precipitation, inducing peak emissions...

  6. Insecticide dissipation from soil and plant surfaces in tropical horticulture of southern Benin, West Africa.

    Science.gov (United States)

    Rosendahl, Ingrid; Laabs, Volker; Atcha-Ahowé, Cyrien; James, Braima; Amelung, Wulf

    2009-06-01

    In Sub-Saharan Africa, horticulture provides livelihood opportunities for millions of people, especially in urban and peri-urban areas. Although the vegetable agroecosystems are often characterized by intensive pesticide use, risks resulting therefrom are largely unknown under tropical horticultural conditions. The objective of this study therefore was to study the fate of pesticides in two representative horticultural soils (Acrisol and Arenosol) and plants (Solanum macrocarpon L.) after field application and thus to gain first insight on environmental persistence and dispersion of typical insecticides used in vegetable horticulture in Benin, West Africa. On plant surfaces, dissipation was rapid with half lives ranging from 2 to 87 h (alpha-endosulfan < beta-endosulfan < deltamethrin). Soil dissipation was considerably slower than dissipation from plant surfaces with half-lives ranging from 3 (diazinon) to 74 d (total endosulfan), but persistence of pesticides in soil was still reduced compared to temperate climates. Nevertheless, for deltamethrin and endosulfan, a tendency for mid-term accumulation in soil upon repeated applications was observed. The soil and plant surface concentrations of the metabolite endosulfan sulfate increased during the entire trial period, indicating that this compound is a potential long-term pollutant even in tropical environments.

  7. 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.

  8. APPRAISAL OF THE SNAP MODEL FOR PREDICTING NITROGEN MINERALIZATION IN TROPICAL SOILS UNDER EUCALYPTUS

    Directory of Open Access Journals (Sweden)

    Philip James Smethurst

    2015-04-01

    Full Text Available The Soil Nitrogen Availability Predictor (SNAP model predicts daily and annual rates of net N mineralization (NNM based on daily weather measurements, daily predictions of soil water and soil temperature, and on temperature and moisture modifiers obtained during aerobic incubation (basal rate. The model was based on in situ measurements of NNM in Australian soils under temperate climate. The purpose of this study was to assess this model for use in tropical soils under eucalyptus plantations in São Paulo State, Brazil. Based on field incubations for one month in three, NNM rates were measured at 11 sites (0-20 cm layer for 21 months. The basal rate was determined in in situ incubations during moist and warm periods (January to March. Annual rates of 150-350 kg ha-1 yr-1 NNM predicted by the SNAP model were reasonably accurate (R2 = 0.84. In other periods, at lower moisture and temperature, NNM rates were overestimated. Therefore, if used carefully, the model can provide adequate predictions of annual NNM and may be useful in practical applications. For NNM predictions for shorter periods than a year or under suboptimal incubation conditions, the temperature and moisture modifiers need to be recalibrated for tropical conditions.

  9. Research on soil microbial communities and enzymatic activity in tropical soils in puerto rico

    Science.gov (United States)

    Soil enzymes are important components of soil quality and its health because of their involvement in ecosystem services related to biogeochemical cycling, global C and organic matter dynamics, and soil detoxification. This talk will provide an overview of the field of soil enzymology, the location a...

  10. Phytoremediation of metal-contaminated soil in temperate humid regions of British Columbia, Canada.

    Science.gov (United States)

    Padmavathiamma, Prabha K; Li, Loretta Y

    2009-08-01

    The suitability of five plant species was studied for phytoextraction and phytostabilisation in a region with temperate maritime climate of coastal British Columbia, Canada. Pot experiments were conducted using Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue), Helianthus annuus L (sunflower), Poa pratensis L (Kentucky bluegrass) and Brassica napus L (rape) in soils treated with three different metal (Cu, Pb, Mn, and Zn) concentrations. The bio-metric characters of plants in soils with multiple-metal contaminations, their metal accumulation characteristics, translocation properties and metal removal were assessed at different stages of plant growth, 90 and 120 DAS (days after sowing). Lolium was found to be suitable for the phytostabilisation of Cu and Pb, Festuca for Mn and Poa for Zn. Metal removal was higher at 120 than at 90 days after sowing, and metals concentrated more in the underground tissues with less translocation to the aboveground parts. Bioconcentration factors indicate that Festuca had the highest accumulation for Cu, Helianthus for Pb and Zn and Poa for Mn.

  11. Methods to quantify the impacts of water erosion on productivity of tropical soils

    International Nuclear Information System (INIS)

    Obando, Franco H

    2000-01-01

    A review on methods to quantify the impacts of water erosion on soil properties and crop yield is presented. On the basis of results of soil losses through plastic shading meshes on oxisols in the eastern plains of Colombia, the experimental design to quantify erosion induced losses in soil productivity suggested by Stocking (1985) for tropical soils is modified. With the purpose of producing contrasting levels of natural erosion, simple 33% and 45% shading rates meshes, and superposed 33% and 45% meshes were used. These were stretched out on stocking 5 m x 10 m run-off plots at 40 cm height from soil surface. Annual soil losses produced under the above mentioned shading meshes treatments did not present significant differences. It was demonstrated that 33%, 45% as well as superposed 33% and 45% produce an equivalent surface cover, CVE, greater than 90% comparable to that produced by zero grazing Brachiaria decumbens pasture. Such results allowed presenting modifications to the stocking design. It is recommended to use alternated stripes of bare soil and shading meshes of different width to produce contrasting levels of equivalent soil surface cover and consequently contrasting erosion rates. Design of the modified stocking run-off plots, including collecting channels, collecting tanks and a Geib multibox divisor are presented

  12. Correlation between soil physicochemical properties and vegetation parameters in secondary tropical forest in Sabal, Sarawak, Malaysia

    Science.gov (United States)

    Karyati, K.; Ipor, I. B.; Jusoh, I.; Wasli, M. E.

    2018-04-01

    The tree growth is influenced by soil morphological and physicochemical properties in the site. The purpose of this study was to describe correlation between soil properties under various stage secondary forests and vegetation parameters, such as floristic structure parameters and floristic diversity indices. The vegetation surveys were conducted in 5, 10, and 20 years old at secondary tropical forests in Sarawak, Malaysia. Nine sub plots sized 20 m × 20 m were established within each study site. The Pearson analysis showed that soil physicochemical properties were significantly correlated to floristic structure parameters and floristic diversity indices. The result of PCA clarified the correlation among most important soil properties, floristic structure parameters, and floristic diversity indices. The PC1 represented cation retention capacity and soil texture which were little affected by the fallow age and its also were correlated by floristic structure and diversity. The PC2 was linked to the levels of soil acidity. This property reflected the remnant effects of ash addition and fallow duration, and the significant correlation were showed among pH (H2O), floristic structure and diversity. The PC3 represented the soil compactness. The soil hardness could be influenced by fallow period and it was also correlated by floristic structure.

  13. Field dissipation of oxyfluorfen in onion and its dynamics in soil under Indian tropical conditions.

    Science.gov (United States)

    Janaki, P; Sathya Priya, R; Chinnusamy, C

    2013-01-01

    Oxyfluorfen, a diphenyl-ether herbicide is being used to control annual and perennial broad-leaved weeds and sedges in a variety of field crops including onion. The present study was aimed to investigate the dynamics and field persistence of oxyfluorfen in onion plant, bulb and soil under Indian tropical conditions. Application of four rates of oxyfluorfen viz., 200, 250, 300 and 400 g AI ha(-1) as pre-emergence gave good weed control in field experiment with onion. The oxyfluorfen residue dissipated faster in plant than in soil respectively, with a mean half-life of 6.1 and 11.2 days. Dissipation followed first-order kinetics. In laboratory column leaching experiments, 17 percent of the applied oxyfluorfen was recovered from the soil and indicates its solubility in water and mobility in sandy clay loam soil was low. A sorption study revealed that the adsorption of oxyfluorfen to the soil was highly influenced by the soil organic carbon with the Koc value of 5450. The study concludes that the dissipation of oxyfluorfen in soil and onion was dependent on the physico-chemical properties of the soil and environmental conditions.

  14. Decomposition of rice residue in tropical soils, 2

    International Nuclear Information System (INIS)

    Yoneyama, Tadakatsu; Yoshida, Tomio

    1977-01-01

    The decomposition processes of intact rice residue (leaf blades) in the Maahas soil in the Philippines were investigated. Three sets of beakers simulating both lowland and upland conditions were incubated in the dark at 30 deg. C. One set of beakers had neither rice residue nor fertilizer. Pieces of leaf blades weighing 204 mg (dry weight) were inserted in the second set. Pieces of leaf blades were inserted in the third set, and 200 ppm of fertilizer nitrogen as 15 N-labelled ammonium sulfate was added. The experiment dealt with the nitrogen immobilization by rice residue under lowland and upland conditions. The rice residue which has contained low nitrogen absorbed nitrogen from the soil and from the added fertilizer (ammonium sulfate) during its decomposition under both conditions. Under the lowland condition, the amount of nitrogen immobilized was small during the first week, but became large after 2 or 3 weeks. Under the upland condition, the immobilized nitrogen reached its maximum during the first week, but the amount was not so large as that under the lowland condition. The added fertilizer stimulated the decrease of weight of the rice residue in the early incubation period, but retarded it later under both conditions. The absorption of fertilizer by the rice residue ceased at the early stage of residue decomposition, but the nitrogen content of the residue continued to increase. (Iwakiri, K.)

  15. Modeling Spatial Soil Water Dynamics in a Tropical Floodplain, East Africa

    Directory of Open Access Journals (Sweden)

    Geofrey Gabiri

    2018-02-01

    Full Text Available Analyzing the spatial and temporal distribution of soil moisture is critical for ecohydrological processes and for sustainable water management studies in wetlands. The characterization of soil moisture dynamics and its influencing factors in agriculturally used wetlands pose a challenge in data-scarce regions such as East Africa. High resolution and good-quality time series soil moisture data are rarely available and gaps are frequent due to measurement constraints and device malfunctioning. Soil water models that integrate meteorological conditions and soil water storage may significantly overcome limitations due to data gaps at a point scale. The purpose of this study was to evaluate if the Hydrus-1D model would adequately simulate soil water dynamics at different hydrological zones of a tropical floodplain in Tanzania, to determine controlling factors for wet and dry periods and to assess soil water availability. The zones of the Kilombero floodplain were segmented as riparian, middle, and fringe along a defined transect. The model was satisfactorily calibrated (coefficient of determination; R2 = 0.54–0.92, root mean square error; RMSE = 0.02–0.11 on a plot scale using measured soil moisture content at soil depths of 10, 20, 30, and 40 cm. Satisfying statistical measures (R2 = 0.36–0.89, RMSE = 0.03–0.13 were obtained when calibrations for one plot were validated with measured soil moisture for another plot within the same hydrological zone. Results show the transferability of the calibrated Hydrus-1D model to predict soil moisture for other plots with similar hydrological conditions. Soil water storage increased towards the riparian zone, at 262.8 mm/a while actual evapotranspiration was highest (1043.9 mm/a at the fringe. Overbank flow, precipitation, and groundwater control soil moisture dynamics at the riparian and middle zone, while at the fringe zone, rainfall and lateral flow from mountains control soil moisture during the

  16. Biodegradação de alcoóis, ftalatos e adipatos em um solo tropical contaminado Biodegradation of alcohol, phthalates and adipates in a tropical soil

    Directory of Open Access Journals (Sweden)

    Ieda Domingues Ferreira

    2010-01-01

    Full Text Available The adipic and phthalic acid esters are plasticizers, have low water solubility, high partition octanol/water coefficients (Kow and accumulate in soil and sediments. These compounds are considered teratogenic, carcinogenic and endocrine disruptors chemicals. This study evaluated the bioremediation of tropical soil contaminated with plasticizers process wastes, in aerobic conditions, with and without introduction of acclimated bacteria. It was selected 200 kg of contaminated tropical soil for the biodegradation study. The plasticizers concentrations in soil ranged between 153 mgDOA/kg up to 15552 mgDIDP/kg and after 90 days of biodegradation, the lower removal efficiencies were 72% with a 1-2 log simultaneous bacterial growth.

  17. NUTRITIVE QUALITY OF TEN GRASSES DURING THE RAINY SEASON IN A HOT-HUMID CLIMATE AND ULTISOL SOIL

    Directory of Open Access Journals (Sweden)

    Rodrigo Ortega-Gómez

    2011-11-01

    Full Text Available The nutritive quality of ten grasses harvested at 3, 6, 9 and 12 weeks of regrowth was assessed during the rainy season (August-October 2008, in the humid tropics of Veracruz, Mexico. Grasses tested included four Brachiaria spp.: “insurgente”–B. brizantha, “signal”–B. decumbens, Chetumal–B. humidicola, “mulato I”–B. brizantha x B. ruziziensis; three Panicum maximum: Mombasa, “privilegio”, Tanzania; and three Pennisetum spp.: Taiwán, and the hybrids P. purpureum x P. glaucum “Cuban” king grass and “purple” king grass. Means for crude protein by grass group were: Pennisetum spp. (9.9 % = P. maximum (8.7 % > Brachiaria spp. (7.6 %, whereas means for in situ dry matter disappearance (ISD were: Pennisetum spp. (69.7 % > Brachiaria spp. (65.1 % > P. maximum (59.7 %. Crude protein and ISD significantly decreased by 0.42 % and 1.50 % per week. Neutral detergent fiber was not affected by model effects (mean 71.4 %. Means for acid detergent fiber (ADF by grass group were: P. maximum (47.6 % = Pennisetum spp. (44.0 % > Brachiaria spp. (42.8 %, whereas means for lignin (LIG were: P. maximum (8.5 % > Pennisetum spp. (7.6 % > Brachiaria spp. (6.7 %. The ADF and LIG significantly increased by 1.21 % and 0.19 % per week. Pennisetum spp. had the highest nutritive value at all regrowth ages.

  18. Soil biogeochemical and fungal patterns across a precipitation gradient in the lowland tropical rainforests of French Guiana

    Science.gov (United States)

    Soong, J.; Verbruggen, E.; Janssens, I.

    2016-12-01

    The Guyafor network contains over 12 pristine tropical rainforest long-term research sites throughout French Guiana, with a focus on vegetation and environmental monitoring at regular intervals. However, biogeochemical and belowground insights are needed to complete the picture of ecosystem functioning in these lowland tropical rainforests, which are critical to Earth's water and energy balance. Improving our biogeochemical understanding of these ecosystems is needed to improve Earth System Models, which poorly represent tropical systems. In July 2015 we sampled soils and litter from 12 of the Guyafor permanent plots in French Guiana spanning a mean annual precipitation gradient of over 2000 mm per year. We measured soil texture, pH, C, N and available P stocks in the top 30 cm, and fungal biodiversity using ITS DNA sequencing and characterized soil organic matter (SOM) C, N and P distribution among physically defined SOM fractions. We also measured litter layer standing stocks and CNP stoichiometry. We found significant stocks of SOM in the top 30 cm of the soil varying by a factor of 4 in the top 30 cm of soil with a negative correlation of arbuscular mycorrhizal fungi and soil C and N with available P. Available P was also a strong predictor of fungal community composition. Furthermore there is evidence for precipitation and mineralogical influences on leaf litter and SOM dynamics highlighting the importance of heterogeneity in tropical soil substrates and sub-climates in better understanding the biogeochemistry of tropical ecosystems.

  19. Soil compaction during harvest operations in five tropical soils with different textures under eucalyptus forests

    Directory of Open Access Journals (Sweden)

    Paula Cristina Caruana Martins

    Full Text Available ABSTRACT Traffic of farm machinery during harvest and logging operations has been identified as the main source of soil structure degradation in forestry activity. Soil susceptibility to compaction and the amount of compaction caused by each forest harvest operation differs according to a number of factors (such as soil strength, soil texture, kind of equipment, traffic intensity, among many others, what requires the adequate assessment of soil compaction under different traffic conditions. The objectives of this study were to determine the susceptibility to compaction of five soil classes with different textures under eucalyptus forests based on their load bearing capacity models; and to determine, from these models and the precompression stresses obtained after harvest operations, the effect of traffic intensity with different equipment in the occurrence of soil compaction. Undisturbed soil samples were collected before and after harvest operations, being then subjected to uniaxial compression tests to determine their precompression stress. The coarse-textured soils were less resistant and endured greater soil compaction. In the clayey LVd2, traffic intensity below four Forwarder passes limited compaction to a third of the samples, whereas in the sandy loam PVd all samples from the 0-3 cm layer were compacted regardless of traffic intensity. The Feller Buncher and the Clambunk presented a high potential to cause soil compaction even with only one or two passes. The use of soil load bearing capacity models and precompression stress determined after harvest and logging operations allowed insight into the soil compaction process in forestry soils.

  20. Quorum quenching properties of Actinobacteria isolated from Malaysian tropical soils.

    Science.gov (United States)

    Devaraj, Kavimalar; Tan, Geok Yuan Annie; Chan, Kok-Gan

    2017-08-01

    In this study, a total of 147 soil actinobacterial strains were screened for their ability to inhibit response of Chromobacterium violaceum CV026 to short chain N-acyl homoserine lactone (AHL) which is a quorum sensing molecule. Of these, three actinobacterial strains showed positive for violacein inhibition. We further tested these strains for the inhibition of Pseudomonas aeruginosa PAO1 quorum sensing-regulated phenotypes, namely, swarming and pyocyanin production. The three strains were found to inhibit at least one of the quorum sensing-regulated phenotypes of PAO1. Phylogenetic analysis of the 16S rRNA gene sequences indicated that these strains belong to the genera Micromonospora, Rhodococcus and Streptomyces. This is the first report presenting quorum quenching activity by a species of the genus Micromonospora. Our data suggest that Actinobacteria may be a rich source of active compounds that can act against bacterial quorum sensing system.

  1. Soil seed banks along elevational gradients in tropical, subtropical and subalpine forests in Yunnan Province, southwest China

    Directory of Open Access Journals (Sweden)

    Xiaqin Luo

    2017-10-01

    Full Text Available Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration. Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients in different climatic zones is still unknown. This paper investigates seed density, species composition and nonconstituent species of forest soil seed banks in Yunnan Province, southwest China. Similarity between the soil seed bank and standing vegetation was also examined. We collected soil samples from sites spanning 12 elevations in tropical rain forests, subtropical evergreen broad-leaved forests and subalpine coniferous forests, and transported them to a glasshouse for germination trials for species identification. The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests. Seeds of woody species dominated the soil seed banks of tropical and subtropical forests, while herbs dominated those of subalpine forests. The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests, followed by subtropical forests but were completely absent from subalpine forests.

  2. Soil seed banks along elevational gradients in tropical, subtropical and subalpine forests in Yunnan Province, southwest China

    Institute of Scientific and Technical Information of China (English)

    Xiaqin Luo; Min Cao; Min Zhang; Xiaoyang Song; Jieqiong Li; Akihiro Nakamura; Roger Kitching

    2017-01-01

    Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported,how soil seed banks vary with elerational gradients in different climatic zones is still unknown.This paper investigates seed density,species composition and nonconstituent species of forest soil seed banks in Yunnan Province,southwest China.Similarity between the soil seed bank and standing vegetation was also examined.We collected soil samples from sites spanning 12 elevations in tropical rain forests,subtropical evergreen broadleaved forests and subalpine coniferous forests,and transported them to a glasshouse for germination trials for species identification.The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests.Seeds of woody species dominated the soil seed banks of tropical and subtropical forests,while herbs dominated those of subalpine forests.The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests,followed by subtropical forests but were completely absent from subalpine forests.

  3. Human Effects and Soil Surface CO2 fluxes in Tropical Urban Green Areas, Singapore

    Science.gov (United States)

    Ng, Bernard; Gandois, Laure; Kai, Fuu Ming; Chua, Amy; Cobb, Alex; Harvey, Charles; Hutyra, Lucy

    2013-04-01

    Urban green spaces are appreciated for their amenity value, with increasing interest in the ecosystem services they could provide (e.g. climate amelioration and increasingly as possible sites for carbon sequestration). In Singapore, turfgrass occupies approximately 20% of the total land area and is readily found on both planned and residual spaces. This project aims at understanding carbon fluxes in tropical urban green areas, including controls of soil environmental factors and the effect of urban management techniques. Given the large pool of potentially labile carbon, management regimes are recognised to have an influence on soil environmental factors (temperature and moisture), this would affect soil respiration and feedbacks to the greenhouse effect. A modified closed dynamic chamber method was employed to measure total soil respiration fluxes. In addition to soil respiration rates, environmental factors such as soil moisture and temperature, and ambient air temperature were monitored for the site in an attempt to evaluate their control on the observed fluxes. Measurements of soil-atmosphere CO2 exchanges are reported for four experimental plots within the Singtel-Kranji Radio Transmission Station (103o43'49E, 1o25'53N), an area dominated by Axonopus compressus. Different treatments such as the removal of turf, and application of clippings were effected as a means to determine the fluxes from the various components (respiration of soil and turf, and decomposition of clippings), and to explore the effects of human intervention on observed effluxes. The soil surface CO2 fluxes observed during the daylight hours ranges from 2.835 + 0.772 umol m-2 s-1 for the bare plot as compared to 6.654 + 1.134 umol m-2 s-1 for the turfed plot; this could be attributed to both autotrophic and heterotrophic respiration. Strong controls of both soil temperature and soil moisture are observed on measured soil fluxes. On the base soils, fluxes were positively correlated to soil

  4. Persistence of Pathogenic and Non-Pathogenic Escherichia coli Strains in Various Tropical Agricultural Soils of India.

    Directory of Open Access Journals (Sweden)

    S Naganandhini

    Full Text Available The persistence of Shiga-like toxin producing E. coli (STEC strains in the agricultural soil creates serious threat to human health through fresh vegetables growing on them. However, the survival of STEC strains in Indian tropical soils is not yet understood thoroughly. Additionally how the survival of STEC strain in soil diverges with non-pathogenic and genetically modified E. coli strains is also not yet assessed. Hence in the present study, the survival pattern of STEC strain (O157-TNAU was compared with non-pathogenic (MTCC433 and genetically modified (DH5α strains on different tropical agricultural soils and on a vegetable growing medium, cocopeat under controlled condition. The survival pattern clearly discriminated DH5α from MTCC433 and O157-TNAU, which had shorter life (40 days than those compared (60 days. Similarly, among the soils assessed, the red laterite and tropical latosol supported longer survival of O157-TNAU and MTCC433 as compared to wetland and black cotton soils. In cocopeat, O157 recorded significantly longer survival than other two strains. The survival data were successfully analyzed using Double-Weibull model and the modeling parameters were correlated with soil physico-chemical and biological properties using principal component analysis (PCA. The PCA of all the three strains revealed that pH, microbial biomass carbon, dehydrogenase activity and available N and P contents of the soil decided the survival of E. coli strains in those soils and cocopeat. The present research work suggests that the survival of O157 differs in tropical Indian soils due to varied physico-chemical and biological properties and the survival is much shorter than those reported in temperate soils. As the survival pattern of non-pathogenic strain, MTCC433 is similar to O157-TNAU in tropical soils, the former can be used as safe model organism for open field studies.

  5. Methyl Mercury Production In Tropical Hydromorphic Soils: Impact Of Gold Mining.

    Science.gov (United States)

    Guedron, S.; Charlet, L.; Harris, J.; Grimaldi, M.; Cossa, D.

    2007-12-01

    Artisanal alluvial gold mining is important in many tropical developing countries and several million people are involved worldwide. The dominant use of mercury for gold amalgamation in this activity leads to mercury accumulation in soils, to sediment contamination and to methyl mercury (MMHg) bioaccumulation along the food chain. In this presentation we will present recent data on methyl mercury production in hydromorphic soils and tailing ponds from a former gold mining area located in French Guiana (South America). Comparison of specific fluxes between a pristine sub watershed and the contaminated watershed shows that former mining activities lead to a large enhancement of dissolved and particulate MMHg emissions at least by a factor of 4 and 6, respectively. MMHg production was identified in sediments from tailing ponds and in surrounding hydromorphic soils. Moreover, interstitial soil water and tailing pond water profiles sampled in an experimental tailing pond demonstrate the presence of a large MMHg production in the suboxic areas. Both tailing ponds and hydromorphic soils present geochemical conditions that are favorable to bacterial mercury methylation (high soil Hg content, high aqueous ferric iron and dissolved organic carbon concentrations). Although sulfate-reducing bacteria have been described as being the principal mercury methylating bacteria, the positive correlation between dissolved MMHg and ferrous iron concentrations argue for a significant role of iron-reducing bacteria. Identifications by sequencing fragments of 16S rRNA from total soil DNA support these interpretations. This study demonstrates that current and past artisanal gold mining in the tropics lead to methyl mercury production in contaminated areas. As artisanal activities are increasing with increasing gold prices, the bio- magnification of methyl mercury in fish presents an increasing threat to local populations whose diet relies on fish consumption.

  6. Earthworms and Plant Residues Modify Nematodes in Tropical Cropping Soils (Madagascar: A Mesocosm Experiment

    Directory of Open Access Journals (Sweden)

    Cécile Villenave

    2010-01-01

    Full Text Available Free-living nematodes present several characteristics that have led to their use as bioindicators of soil quality. Analyzing the structure of nematofauna is a pertinent way to understand soil biological processes. Earthworms play an important role in soil biological functioning and organic matter dynamics. Their effects on soil nematofauna have seldom been studied. We studied the effect of the tropical endogeic earthworm, Pontoscolex corethrurus, on nematode community structure in a 5-month field mesocosm experiment conducted in Madagascar. Ten different treatments with or without earthworms and with or without organic residues (rice, soybean were compared. Organic residues were applied on the soil surface or mixed with the soil. The abundance of nematodes (bacterial and fungal feeders was higher in presence of P. corethrurus than in their absence. The type of plant residues as well as their localisation had significant effects on the abundance and composition of soil nematodes. The analysis of nematode community structure showed that earthworm activity led to an overall activation of the microbial compartment without specific stimulation of the bacterial or fungal compartment.

  7. Earthworms and Plant Residues Modify Nematodes in Tropical Cropping Soils (Madagascar): A Mesocosm Experiment

    International Nuclear Information System (INIS)

    Villenave, C.; Kichenin, E.; Djigal, D.; Blanchart, E.; Rabary, B.; Djigal, D.

    2010-01-01

    Free-living nematodes present several characteristics that have led to their use as bio indicators of soil quality. Analyzing the structure of nematofauna is a pertinent way to understand soil biological processes. Earthworms play an important role in soil biological functioning and organic matter dynamics. Their effects on soil nematofauna have seldom been studied. We studied the effect of the tropical endogeic earthworm, Pontoscolex corethrurus, on nematode community structure in a 5-month field mesocosm experiment conducted in Madagascar. Ten different treatments with or without earthworms and with or without organic residues (rice, soybean) were compared. Organic residues were applied on the soil surface or mixed with the soil. The abundance of nematodes (bacterial and fungal feeders) was higher in presence of P. corethrurus than in their absence. The type of plant residues as well as their localisation had significant effects on the abundance and composition of soil nematodes. The analysis of nematode community structure showed that earthworm activity led to an overall activation of the microbial compartment without specific stimulation of the bacterial or fungal compartment.

  8. Adsorption properties of subtropical and tropical variable charge soils: Implications from climate change and biochar amendment

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Ren-Kou; Qafoku, Nikolla; Van Ranst, Eric; Li, Jiu-yu; Jiang, Jun

    2016-01-25

    This review paper attempts to summarize the progress made in research efforts conducted over the last years to study the surface chemical properties of the tropical and subtropical soils, usually called variable charge soils, and the way they response to different management practices. The paper is composed of an introductory section that provides a brief discussion on the surface chemical properties of these soils, and five other review sections. The focus of these sections is on the evolution of surface chemical properties during the development of the variable charge properties (second section), interactions between oppositely charged particles and the resulting effects on the soil properties and especially on soil acidity (third section), the surface effects of low molecular weight organic acids sorbed to mineral surfaces and the chemical behavior of aluminum (fourth section), and the crop straw derived biochar induced changes of the surface chemical properties of these soils (fifth section). A discussion on the effect of climate change variables on the properties of the variable charge soils is included at the end of this review paper (sixth section).

  9. Soil Erosion from Agriculture and Mining: A Threat to Tropical Stream Ecosystems

    Directory of Open Access Journals (Sweden)

    Jan H. Mol

    2013-09-01

    Full Text Available In tropical countries soil erosion is often increased due to high erodibility of geologically old and weathered soils; intensive rainfall; inappropriate soil management; removal of forest vegetation cover; and mining activities. Stream ecosystems draining agricultural or mining areas are often severely impacted by the high loads of eroded material entering the stream channel; increasing turbidity; covering instream habitat and affecting the riparian zone; and thereby modifying habitat and food web structures. The biodiversity is severely threatened by these negative effects as the aquatic and riparian fauna and flora are not adapted to cope with excessive rates of erosion and sedimentation. Eroded material may also be polluted by pesticides or heavy metals that have an aggravating effect on functions and ecosystem services. Loss of superficial material and deepening of erosion gullies impoverish the nutrient and carbon contents of the soils; and lower the water tables; causing a “lose-lose” situation for agricultural productivity and environmental integrity. Several examples show how to interrupt this vicious cycle by integrated catchment management and by combining “green” and “hard” engineering for habitat restoration. In this review; we summarize current findings on this issue from tropical countries with a focus on case studies from Suriname and Brazil.

  10. SOIL ORGANIC CARBON FRACTIONS AS INFLUENCED BY SOYBEAN CROPPING IN THE HUMID PAMPA OF ARGENTINA

    Directory of Open Access Journals (Sweden)

    Marta E. Conti

    2014-07-01

    Full Text Available The sustainability of continuous cropping systems depends heavily on the years of intensive agricultural production and the choice of crop sequence that alters the fractions of soil organic matter. The aim of this study was to evaluate the impact of continuous soybean cultivation on fractions of organic carbon in the vertic Argiudolls of the Argentinean Pampas. Total organic carbon (TOC, particulate organic carbon (POC , fulvic acids (FA, humic acids (HA, humin (H and carbon produced by microbial respiration (Cresp were assessed in plots with continuous production of soybean for over 15 years (SP and grassland plots that were considered the change control (GP. A significant reduction of TOC and POC variables in cultured soybean SP plots, relative to grassland GP, was observed. The POC / TOC and Cresp / TOC ratios were significantly lower in soybean plots than in grasslands used as controls. These ratios were interpreted as a preferential tendency to maintain high rates of mineralization of labile carbon forms and increased biological stability of humified forms in cultured soybean plots. The shapes of the humic fractions of less complexity, FA and HA, were significantly reduced in the latter plots compared with grasslands, while no significant changes occurred in the more stable and recalcitrant forms of carbon, such as humin, in either plot type.

  11. Study on Flexible Pavement Failures in Soft Soil Tropical Regions

    Science.gov (United States)

    Jayakumar, M.; Chee Soon, Lee

    2015-04-01

    Road network system experienced rapid upgrowth since ages ago and it started developing in Malaysia during the colonization of British due to its significant impacts in transportation field. Flexible pavement, the major road network in Malaysia, has been deteriorating by various types of distresses which cause descending serviceability of the pavement structure. This paper discusses the pavement condition assessment carried out in Sarawak and Sabah, Malaysia to have design solutions for flexible pavement failures. Field tests were conducted to examine the subgrade strength of existing roads in Sarawak at various failure locations, to assess the impact of subgrade strength on pavement failures. Research outcomes from field condition assessment and subgrade testing showed that the critical causes of pavement failures are inadequate design and maintenance of drainage system and shoulder cross fall, along with inadequate pavement thickness provided by may be assuming the conservative value of soil strength at optimum moisture content, whereas the exiting and expected subgrade strengths at equilibrium moisture content are far below. Our further research shows that stabilized existing recycled asphalt and base materials to use as a sub-base along with bitumen stabilized open graded base in the pavement composition may be a viable solution for pavement failures.

  12. Short-term nitrous oxide profile dynamics and emissions response to water, nitrogen and carbon additions in two tropical soils

    Science.gov (United States)

    A. D. Nobre; M. Keller; P. M. Crill; R. C. Harriss

    2001-01-01

    Tropical soils are potentially the highest and least studied nitrous oxide (N2O) production areas in the world. The effect of water, nitrate and glucose additions on profile concentrations and episodic emissions of N2O for two volcanic soils in Costa Rica was examined. Magnitudes of episodic N2O pulses, as well as overall N2O emissions, varied considerably and...

  13. Increases in mean annual temperature do not alter soil bacterial community structure in tropical montane wet forests

    Science.gov (United States)

    Paul C. Selmants; Karen L. Adair; Creighton M. Litton; Christian P. Giardina; Egbert Schwartz

    2016-01-01

    Soil bacteria play a key role in regulating terrestrial biogeochemical cycling and greenhouse gas fluxes across the soil-atmosphere continuum. Despite their importance to ecosystem functioning, we lack a general understanding of how bacterial communities respond to climate change, especially in relatively understudied ecosystems like tropical montane wet...

  14. Effects of land use change on soil organic carbon: a pan-tropic study

    Science.gov (United States)

    van Straaten, O.; Veldkamp, E.; Wolf, K.; Corre, M. D.

    2012-04-01

    Tropical forest deforestation is recognized as one of the major contributors to anthropogenic greenhouse gas emissions. In contrast to aboveground carbon stocks, comparatively little is known on deforestation's effect on the magnitude and the factors affecting soil organic carbon (SOC). In this regional scale study, we focused on tropical sites with deeply weathered, low-activity clays soils in three countries: Indonesia, Cameroon and Peru. Using a clustered sampling design we compared soil carbon stocks in the top 3 m of soil in undisturbed forests (the reference) with converted land uses that had been deforested. The most predominant land use trajectories relevant for each region were investigated. These included (a) conversions from forest to cash-crop plantations (rubber, oil palm, cacoa), (b) conversions from forest to cattle grazing pastures and (c) conversion from forest to shifting cultivation. Preliminary results from the Indonesian case study, found that the conversion of forests to oil palm plantation caused a loss of 20.1 ± 4.4 Mg C ha-1 within 20 years from the top 3 m of soil, while deforestation followed by the establishment of rubber plantations caused a release of 7.2 ± 4.2 Mg C ha-1 for the same time period and depth. SOC losses were most pronounced in the top 30 cm, and less so below. Additionally, regional scale constraints such as soil physical and chemical characteristics (texture, CEC, pH) and climate (precipitation, temperature) effect on SOC emissions have been identified using multivariate statistical methods. The results from the Cameroon and Peru case studies are expected imminently.

  15. Electrical Conductivity and Chemical Composition of Soil Solution: Comparison of Solution Samplers in Tropical Soils

    Directory of Open Access Journals (Sweden)

    Davi Lopes do Carmo

    2016-01-01

    Full Text Available ABSTRACT Soil solution samplers may have the same working principle, but they differ in relation to chemical and physical characteristics, cost and handling, and these aspects exert influence on the chemical composition of the soil solution obtained. This study was carried out to evaluate, over time, the chemical composition of solutions extracted by Suolo Acqua, with the hydrophilic membrane (HM as a standard, using soils with contrasting characteristics, and to determine the relationship between electrical conductivity (EC and concentration of ions and pH of soil solution samples. This study was carried out under laboratory conditions, using three soils samples with different clay and organic matter (OM contents. Soil solution contents of F−, Cl−, NO−3, Br−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+, were analyzed, as well as inorganic, organic, and total C contents, pH, and EC, in four successive sampling times. Soil solution chemical composition extracted by the Suolo Acqua sampler is similar to that collected by the HM, but the Suolo Acqua extracted more Na+ and soluble organic C than the HM solution. Solution EC, cation and anion concentrations, and soluble C levels are higher in the soil with greater clay and OM contents (Latossolo and Cambissolo in this case. Soil solution composition varied over time, with considerable changes in pH, EC, and nutrient concentrations, especially associated with soil OM. Thus, single and isolated sampling of the soil solution must be avoided, otherwise composition of the soil solution may not be correctly evaluated. Soil solution EC was regulated by pH, as well as the sum of cation and anion concentrations, and the C contents determined in the soil liquid phase.

  16. Rain-induced changes in soil CO2 flux and microbial community composition in a tropical forest of China.

    Science.gov (United States)

    Deng, Qi; Hui, Dafeng; Chu, Guowei; Han, Xi; Zhang, Quanfa

    2017-07-17

    Rain-induced soil CO 2 pulse, a rapid excitation in soil CO 2 flux after rain, is ubiquitously observed in terrestrial ecosystems, yet the underlying mechanisms in tropical forests are still not clear. We conducted a rain simulation experiment to quantify rain-induced changes in soil CO 2 flux and microbial community composition in a tropical forest. Soil CO 2 flux rapidly increased by ~83% after rains, accompanied by increases in both bacterial (~51%) and fungal (~58%) Phospholipid Fatty Acids (PLFA) biomass. However, soil CO 2 flux and microbial community in the plots without litters showed limited response to rains. Direct releases of CO 2 from litter layer only accounted for ~19% increases in soil CO 2 flux, suggesting that the leaching of dissolved organic carbon (DOC) from litter layer to the topsoil is the major cause of rain-induced soil CO 2 pulse. In addition, rain-induced changes in soil CO 2 flux and microbial PLFA biomass decreased with increasing rain sizes, but they were positively correlated with litter-leached DOC concentration rather than total DOC flux. Our findings reveal an important role of litter-leached DOC input in regulating rain-induced soil CO 2 pulses and microbial community composition, and may have significant implications for CO 2 losses from tropical forest soils under future rainfall changes.

  17. Role of litter turnover in soil quality in tropical degraded lands of Colombia.

    Science.gov (United States)

    León, Juan D; Osorio, Nelson W

    2014-01-01

    Land degradation is the result of soil mismanagement that reduces soil productivity and environmental services. An alternative to improve degraded soils through reactivation of biogeochemical nutrient cycles (via litter production and decomposition) is the establishment of active restoration models using new forestry plantations, agroforestry, and silvopastoral systems. On the other hand, passive models of restoration consist of promoting natural successional processes with native plants. The objective in this review is to discuss the role of litter production and decomposition as a key strategy to reactivate biogeochemical nutrient cycles and thus improve soil quality in degraded land of the tropics. For this purpose the results of different projects of land restoration in Colombia are presented based on the dynamics of litter production, nutrient content, and decomposition. The results indicate that in only 6-13 years it is possible to detect soil properties improvements due to litter fall and decomposition. Despite that, low soil nutrient availability, particularly of N and P, seems to be major constraint to reclamation of these fragile ecosystems.

  18. 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.

  19. Characterization of bacterial community structure in a hydrocarbon-contaminated tropical African soil.

    Science.gov (United States)

    Salam, Lateef B; Ilori, Mathew O; Amund, Olukayode O; LiiMien, Yee; Nojiri, Hideaki

    2018-04-01

    The bacterial community structure in a hydrocarbon-contaminated Mechanical Engineering Workshop (MWO) soil was deciphered using 16S rRNA gene clone library analysis. Four hundred and thirty-seven clones cutting across 13 bacterial phyla were recovered from the soil. The representative bacterial phyla identified from MWO soil are Proteobacteria, Bacteroidetes, Chloroflexi, Acidobacteria, Firmicutes, Actinobacteria, Verrucomicrobia, Planctomycetes, Ignavibacteriae, Spirochaetes, Chlamydiae, Candidatus Saccharibacteria and Parcubacteria. Proteobacteria is preponderant in the contaminated soil (51.2%) with all classes except Epsilonproteobacteria duly represented. Rarefaction analysis indicates 42%, 52% and 77% of the clone library is covered at the species, genus and family/class delineations with Shannon diversity (H') and Chao1 richness indices of 5.59 and 1126, respectively. A sizeable number of bacterial phylotypes in the clone library shared high similarities with strains previously described to be involved in hydrocarbon biodegradation. Novel uncultured genera were identified that have not been previously reported from tropical African soil to be associated with natural attenuation of hydrocarbon pollutants. This study establishes the involvement of a wide array of physiologically diverse bacterial groups in natural attenuation of hydrocarbon pollutants in soil.

  20. A laboratory feasibility study on electrokinetic injection of nutrients on an organic, tropical, clayey soil.

    Science.gov (United States)

    Schmidt, Celina A B; Barbosa, Maria Claudia; de Almeida, Márcio de S S

    2007-05-17

    Based on the results of an environmental investigation program, carried out on an oil production field at Brazilian Northeast, a contamination diagnosis was made. The field was contaminated by crude oil and saline production water and the use of in situ electrokinetic bioremediation techniques in situ were suggested for the remediation of the contaminated site. The analyzed soil is a very humid clayey silt, with high plasticity, high electrical conductivity, low hydraulic conductivity, low density, large buffering capacity and high cation exchange capacity. The soil is rich in organic matter and poor in nitrogen. The removal of the contaminated soil for ex situ treatment is not advisable in contaminated studied area due to the restrictions imposed by local environmental authority, as well as operational impediments caused by the presence of vegetation and flooded conditions. After the diagnosis a program of laboratory tests was carried out on soil from the location in an electrical cell which was developed for this purpose. The study showed the feasibility of injecting nitrate and ammonium to this kind of soil, though the injection of phosphorous did not prove to be successful. It is recommended to control variations changes in pH, caused by the application of electrokinesis, in order not to harm the biodegradation process.

  1. Long-term persistence of pioneer species in tropical forest soil seed banks

    Energy Technology Data Exchange (ETDEWEB)

    Dalling, J W; Brown, T A

    2008-10-05

    In tropical forests, pioneer species regenerate from seeds dispersed directly into canopy gaps, and from seeds that persisted in soil seed banks before gap formation. However, life-history models suggest that selection for long-term persistence of seeds in soil should be weak, as persistence incurs a fitness cost resulting from prolonged generation time. We use a carbon dating technique to provide the first direct measurements of seed persistence in undisturbed tropical forest seed banks. We show that seeds germinate successfully from surface soil microsites up to 38 years after dispersal. Decades-long persistence may be common in pioneers with relatively large mass, and appears to be unrelated to specific regeneration requirements. In Croton billbergianus, a sub-canopy tree that recruits in abundant small gaps, long-term persistence is associated with short-distance ballistic seed dispersal. In Trema micrantha, a canopy tree with widespread dispersal, persistence is associated with a requirement for large gaps that form infrequently in old-growth forest.

  2. 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.

  3. Physical Conditions Regulate the Fungal to Bacterial Ratios of a Tropical Suspended Soil

    Directory of Open Access Journals (Sweden)

    Julian Donald

    2017-12-01

    Full Text Available As a source of ‘suspended soils’, epiphytes contribute large amounts of organic matter to the canopy of tropical rain forests. Microbes associated with epiphytes are responsible for much of the nutrient cycling taking place in rain forest canopies. However, soils suspended far above the ground in living organisms differ from soil on the forest floor, and traditional predictors of soil microbial community composition and functioning (nutrient availability and the activity of soil organisms are likely to be less important. We conducted an experiment in the rain forest biome at the Eden Project in the U.K. to explore how biotic and abiotic conditions determine microbial community composition and functioning in a suspended soil. To simulate their natural epiphytic lifestyle, bird’s nest ferns (Asplenium nidus were placed on a custom-built canopy platform suspended 8 m above the ground. Ammonium nitrate and earthworm treatments were applied to ferns in a factorial design. Extracellular enzyme activity and Phospholipid Fatty Acid (PLFA profiles were determined at zero, three and six months. We observed no significant differences in either enzyme activity or PLFA profiles between any of the treatments. Instead, we observed decreases in β-glucosidase and N-acetyl-glucosaminidase activity, and an increase in phenol oxidase activity across all treatments and controls over time. An increase in the relative abundance of fungi during the experiment meant that the microbial communities in the Eden Project ferns after six months were comparable with ferns sampled from primary tropical rain forest in Borneo.

  4. Distinct responses of soil respiration to experimental litter manipulation in temperate woodland and tropical forest.

    Science.gov (United States)

    Bréchet, Laëtitia M; Lopez-Sangil, Luis; George, Charles; Birkett, Ali J; Baxendale, Catherine; Castro Trujillo, Biancolini; Sayer, Emma J

    2018-04-01

    Global change is affecting primary productivity in forests worldwide, and this, in turn, will alter long-term carbon (C) sequestration in wooded ecosystems. On one hand, increased primary productivity, for example, in response to elevated atmospheric carbon dioxide (CO 2 ), can result in greater inputs of organic matter to the soil, which could increase C sequestration belowground. On other hand, many of the interactions between plants and microorganisms that determine soil C dynamics are poorly characterized, and additional inputs of plant material, such as leaf litter, can result in the mineralization of soil organic matter, and the release of soil C as CO 2 during so-called "priming effects". Until now, very few studies made direct comparison of changes in soil C dynamics in response to altered plant inputs in different wooded ecosystems. We addressed this with a cross-continental study with litter removal and addition treatments in a temperate woodland (Wytham Woods) and lowland tropical forest (Gigante forest) to compare the consequences of increased litterfall on soil respiration in two distinct wooded ecosystems. Mean soil respiration was almost twice as high at Gigante (5.0 μmol CO 2  m -2  s -1 ) than at Wytham (2.7 μmol CO 2  m -2  s -1 ) but surprisingly, litter manipulation treatments had a greater and more immediate effect on soil respiration at Wytham. We measured a 30% increase in soil respiration in response to litter addition treatments at Wytham, compared to a 10% increase at Gigante. Importantly, despite higher soil respiration rates at Gigante, priming effects were stronger and more consistent at Wytham. Our results suggest that in situ priming effects in wooded ecosystems track seasonality in litterfall and soil respiration but the amount of soil C released by priming is not proportional to rates of soil respiration. Instead, priming effects may be promoted by larger inputs of organic matter combined with slower turnover rates.

  5. Soil water retention, air flow and pore structure characteristics after corn cob biochar application to a tropical sandy loam

    DEFF Research Database (Denmark)

    Amoakwah, Emmanuel; Frimpong, Kwame Agyei; Okae-Anti, D

    2017-01-01

    Soil structure is a key soil physical property that affects soil water balance, gas transport, plant growth and development, and ultimately plant yield. Biochar has received global recognition as a soil amendment with the potential to ameliorate the structure of degraded soils. We investigated how...... corn cob biochar contributed to changes in soil water retention, air flow by convection and diffusion, and derived soil structure indices in a tropical sandy loam. Intact soil cores were taken from a field experiment that had plots without biochar (CT), and plots each with 10 t ha− 1 (BC-10), 20 t ha...... to significant increase in soil water retention compared to the CT and BC-10 as a result of increased microporosity (pores biochar had minimal impact. No significant influence of biochar was observed for ka and Dp/D0 for the BC treatments compared to the CT despite...

  6. Soil transport parameters of potassium under a tropical saline soil condition using STANMOD

    Science.gov (United States)

    Suzanye da Silva Santos, Rafaelly; Honorio de Miranda, Jarbas; Previatello da Silva, Livia

    2015-04-01

    Environmental responsibility and concerning about the final destination of solutes in soil, so more studies allow a better understanding about the solutes behaviour in soil. Potassium is a macronutrient that is required in high concentrations, been an extremely important nutrient for all agricultural crops. It plays essential roles in physiological processes vital for plant growth, from protein synthesis to maintenance of plant water balance, and is available to plants dissolved in soil water while exchangeable K is loosely held on the exchange sites on the surface of clay particles. K will tend to be adsorbed onto the surface of negatively charged soil particles. Potassium uptake is vital for plant growth but in saline soils sodium competes with potassium for uptake across the plasma membrane of plant cells. This can result in high Na+:K+ ratios that reduce plant growth and eventually become toxic. This study aimed to obtain soil transport parameters of potassium in saline soil, such as: pore water velocity in soil (v), retardation factor (R), dispersivity (λ) and dispersion coefficient (D), in a disturbed sandy soil with different concentrations of potassium chlorate solution (KCl), which is one of the most common form of potassium fertilizer. The experiment was carried out using soil samples collected in a depth of 0 to 20 cm, applying potassium chlorate solution containing 28.6, 100, 200 and 500 mg L-1 of K. To obtain transport parameters, the data were adjusted with the software STANMOD. At low concentrations, interaction between potassium and soil occur more efficiently. It was observed that only the breakthrough curve prepared with solution of 500 mg L-1 reached the applied concentration, and the solution of 28.6 mg L-1 overestimated the parameters values. The STANMOD proved to be efficient in obtaining potassium transport parameters; KCl solution to be applied should be greater than 500 mg L-1; solutions with low concentrations tend to overestimate

  7. 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.

  8. Relations of microbiome characteristics to edaphic properties of tropical soils from Trinidad

    Directory of Open Access Journals (Sweden)

    Vidya eDe Gannes

    2015-09-01

    Full Text Available Understanding how community structure of Bacteria, Archaea and Fungi varies as a function of edaphic characteristics is key to elucidating associations between soil ecosystem function and the microbiome that sustains it. In this study, non-managed tropical soils were examined that represented a range of edaphic characteristics, and a comprehensive soil microbiome analysis was done by Illumina sequencing of amplicon libraries that targeted Bacteria (universal prokaryotic 16S rRNA gene primers, Archaea (primers selective for archaeal 16S rRNA genes or Fungi (internal transcribed spacer region. Microbiome diversity decreased in the order: Bacteria > Archaea > Fungi. Bacterial community composition had a strong relationship to edaphic factors while that of Archaea and Fungi was comparatively weak. All communities were significantly more similar within soils, than they were between soils (ANOSIM p < 0.001; bacterial communities were 70-80% alike, while communities of Fungi and Archaea had 40-50% similarity. Communities differed in species turnover patterns, such that two soils with relatively similar bacterial communities could not be predicted to be similar in composition of Archaea or Fungi. Bacterial and archaeal diversity had significant (negative correlations to pH, whereas fungal diversity was not correlated to pH. Edaphic characteristics that best explained variation between soils in bacterial community structure were: total carbon, sodium, magnesium and zinc. For fungi, the best variables were: sodium, magnesium, phosphorus, boron and C/N. Archaeal communities had two sets of edaphic factors of equal strength, one contained sulphur, sodium, and ammonium-N and the other was composed of clay, potassium, ammonium-N, and nitrate-N. Collectively, the data indicate that Bacteria, Archaea and Fungi did not closely parallel one another in community structure development, and thus microbiomes in each soil acquired unique identities. This divergence

  9. Biodegradation of polyethylene glycol (PEG) in three tropical soils using radio labelled PEG

    Energy Technology Data Exchange (ETDEWEB)

    Abdalla, A.L. [Laboratory of Animal Nutrition, Centre for Nuclear Energy in Agriculture, University of Sao Paulo (CENA/USP), Piracicaba SP (Brazil)]. E-mail: abdalla@cena.usp.br; Regitano, J.B.; Tornisielo, V.L.; Marchese, L. [Laboratory of Ecotoxicology, Piracicaba SP (Brazil); Pecanha, M.R.S.R.; Vitti, D.M.S.S. [Laboratory of Animal Nutrition, Centre for Nuclear Energy in Agriculture, University of Sao Paulo (CENA/USP), Piracicaba SP (Brazil); Smith, T. [School of Agriculture, Policy and Development, University of Reading, Reading (United Kingdom)

    2005-08-19

    Polyethylene glycol (PEG) may be added to forage based diets rich in tannins for ruminant feeding because it binds to tannins and thus prevent the formation of potentially indigestible tannin-protein complexes. The objective of this work was to determine the in vitro biodegradation (mineralization, i.e., complete breakdown of PEG to CO{sub 2}) rate of PEG. {sup 14}C-Polyethylene glycol ({sup 14}C-PEG) was added to three different tropical soils (a sandy clay loam soil, SaCL; a sandy clay soil, SaC; and a sandy loam soil, SaL) and was incubated in Bartha flasks. Free PEG and PEG bound to tannins from a tannin rich local shrub were incubated under aerobic conditions for up to 70 days. The biodegradation assay monitored the {sup 14}CO{sub 2} evolved after degradation of the labelled PEG in the soils. After incubation, the amount of {sup 14}CO{sub 2} evolved from the {sup 14}C-PEG application was low. Higher PEG mineralization values were found for the soils with higher organic matter contents (20.1 and 18.6 g organic matter/kg for SaCL and SaC, respectively) than for the SaL soil (11.9 g organic matter/kg) (P < 0.05). The extent of mineralization of PEG after 70 days of incubation in the soil was significantly lower (P < 0.05) when it was added as bound to the browse tannin than in the free form (0.040 and 0.079, respectively). (author)

  10. Phosphorus dynamics in a tropical soil amended with green manures and natural inorganic phosphate fertilizers

    International Nuclear Information System (INIS)

    Zaharah Abd Rahman; Bah Abd R

    2002-01-01

    Alleviating P deficiency with natural inorganic phosphates and organic residues has significant economic and environmental advantages in the tropics. However, adapting this technology to various agroecosystems requires greater understanding of P dynamics in such systems. This was studied in an amended Bungor soil in laboratory incubation and glasshouse experiments. Treatments were a factorial combination of green manures GMs (Calopogonium caeruleum, Gliricidia sepium and Imperata cylindrica) and P fertilizers (phosphate rocks (PRs) from China and Algeria, in 3 replications. The GMs were labeled with 33 P in the glasshouse trial. Olsen P, mineral N, exchangeable Ca and pH were monitored in the incubation at 0,1,2,4,8,16,32 and 64 weeks after establishment (WAE). Soil P fractions were also determined at 64 WAE. Phosphorus available from the amendments at 4, 8, 15, and 20 WAE, was quantified by 33 P- 32 P double isotopic labeling in the glasshouse using Setaria sphacelata (Setaria grass) as test crop. Olsen P was unaffected by the sole P fertilizers, and hardly changed within 16 WAE in the legume GM and legume GM+PR treatments as NH 4 + -N accumulated and soil pH increased. Afterwards Olsen P and exchangeable Ca increased as NH 4 + -N and soil pH declined. The legume GMs augmented reversibly sorbed P in Al-P and Fe-P fractions resulting in high residual effect, but fertilizers was irreversibly retained. GM-P availability was very low (< 4%), but GMs enhanced PR solubility and mobilized soil P irrespective of quality, probably by the action of organic acids. Calcium content had negative effect on available P and should be considered when selecting compatible materials in integrated systems. The results are further evidence of the importance of the soil P mobilization capacity of organic components in integrated P management systems. Even low quality Imperata can augment soil P supply when combined with the reactive APR, probably by conserving soil moisture. (Author)

  11. Reproductive and productive performances of Santa Inês ewes submitted to breeding in different periods of the Amazonian humid tropical climate.

    Science.gov (United States)

    Soares, Felipe Nogueira; Oliveira, Maria Emilia Franco; Padilha-Nakaghi, Luciana Cristina; de Oliveira, Luís Guilherme; Feliciano, Marcus Antônio Rossi; de Oliveira, Felipe Brener Bezerra; Teixeira, Pedro Paulo Maia; Vicente, Wilter Ricardo Russiano; Faturi, Cristian; Rodrigues, Luiz Fernando de Souza

    2015-12-01

    The objective of this study was to evaluate the reproductive and productive performance of Santa Inês ewes bred at different times of the year in humid tropical climate. One hundred and forty-eight Santa Inês ewes were grouped according to the time of the year of their breeding season (i.e., mating period) (dry/wet, wet, wet/dry, and dry season). The service type was natural mating and the ewes and rams were kept together every night for 45 days. Reproductive efficiency was assessed by service, pregnancy, lambing, prolificacy, twinning, pregnancy loss, weaning, and lamb mortality rates. Ewes were weighed at the beginning and at the end of the breeding season and before and after parturition, and sequential weighing of the lambs was performed (at birth, 15, 30, 60, and 90 days). Reproductive efficiency index (number of lambs weaned/total of served ewes) and productive efficiency (kg of weaned lamb/kg of served or lambed ewes) were calculated. All ewes expressed estrus early in the breeding season; however, a higher percentage (53.5 and 7.1 % at 30 and 45 days, respectively) of ewes returned to estrus during the wet/dry period. The lower rates (13.9 %) of return to estrus at 30 days were during the wet season (P  0.05) effects of breeding seasons on the remaining reproductive rates. Ewes that lambed during the wet/dry transition period weighted less, before (40.5 ± 2.5 kg) and after (38.6 ± 1.6 kg) parturition, than those of other groups (P ewes, respectively; P ewes served in the dry season. The reproductive performance of Santa Inês ewes was not significantly influenced by the period of the year in which the breeding seasons took place, allowing for four breeding seasons a year in the Amazon region. Variations between periods in return to estrus rates, weight of ewes close to parturition and lamb weight at weaning indicate that climate changes can also affect reproductive rates.

  12. 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...

  13. [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.

  14. Conversion of lowland tropical forests to tree cash crop plantations loses up to one-half of stored soil organic carbon.

    Science.gov (United States)

    van Straaten, Oliver; Corre, Marife D; Wolf, Katrin; Tchienkoua, Martin; Cuellar, Eloy; Matthews, Robin B; Veldkamp, Edzo

    2015-08-11

    Tropical deforestation for the establishment of tree cash crop plantations causes significant alterations to soil organic carbon (SOC) dynamics. Despite this recognition, the current Intergovernmental Panel on Climate Change (IPCC) tier 1 method has a SOC change factor of 1 (no SOC loss) for conversion of forests to perennial tree crops, because of scarcity of SOC data. In this pantropic study, conducted in active deforestation regions of Indonesia, Cameroon, and Peru, we quantified the impact of forest conversion to oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), and cacao (Theobroma cacao) agroforestry plantations on SOC stocks within 3-m depth in deeply weathered mineral soils. We also investigated the underlying biophysical controls regulating SOC stock changes. Using a space-for-time substitution approach, we compared SOC stocks from paired forests (n = 32) and adjacent plantations (n = 54). Our study showed that deforestation for tree plantations decreased SOC stocks by up to 50%. The key variable that predicted SOC changes across plantations was the amount of SOC present in the forest before conversion--the higher the initial SOC, the higher the loss. Decreases in SOC stocks were most pronounced in the topsoil, although older plantations showed considerable SOC losses below 1-m depth. Our results suggest that (i) the IPCC tier 1 method should be revised from its current SOC change factor of 1 to 0.6 ± 0.1 for oil palm and cacao agroforestry plantations and 0.8 ± 0.3 for rubber plantations in the humid tropics; and (ii) land use management policies should protect natural forests on carbon-rich mineral soils to minimize SOC losses.

  15. Conversion of lowland tropical forests to tree cash crop plantations loses up to one-half of stored soil organic carbon

    Science.gov (United States)

    van Straaten, Oliver; Corre, Marife D.; Wolf, Katrin; Tchienkoua, Martin; Cuellar, Eloy; Matthews, Robin B.; Veldkamp, Edzo

    2015-01-01

    Tropical deforestation for the establishment of tree cash crop plantations causes significant alterations to soil organic carbon (SOC) dynamics. Despite this recognition, the current Intergovernmental Panel on Climate Change (IPCC) tier 1 method has a SOC change factor of 1 (no SOC loss) for conversion of forests to perennial tree crops, because of scarcity of SOC data. In this pantropic study, conducted in active deforestation regions of Indonesia, Cameroon, and Peru, we quantified the impact of forest conversion to oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), and cacao (Theobroma cacao) agroforestry plantations on SOC stocks within 3-m depth in deeply weathered mineral soils. We also investigated the underlying biophysical controls regulating SOC stock changes. Using a space-for-time substitution approach, we compared SOC stocks from paired forests (n = 32) and adjacent plantations (n = 54). Our study showed that deforestation for tree plantations decreased SOC stocks by up to 50%. The key variable that predicted SOC changes across plantations was the amount of SOC present in the forest before conversion—the higher the initial SOC, the higher the loss. Decreases in SOC stocks were most pronounced in the topsoil, although older plantations showed considerable SOC losses below 1-m depth. Our results suggest that (i) the IPCC tier 1 method should be revised from its current SOC change factor of 1 to 0.6 ± 0.1 for oil palm and cacao agroforestry plantations and 0.8 ± 0.3 for rubber plantations in the humid tropics; and (ii) land use management policies should protect natural forests on carbon-rich mineral soils to minimize SOC losses. PMID:26217000

  16. Comparative Bioremediation of Crude Oil-Amended Tropical Soil Microcosms by Natural Attenuation, Bioaugmentation, or Bioenrichment

    Directory of Open Access Journals (Sweden)

    Vanessa Marques Alvarez

    2011-01-01

    Full Text Available Bioremediation is an efficient strategy for cleaning up sites contaminated with organic pollutants. In this study, we evaluated the effectiveness of monitored natural attenuation, bioenrichment, and bioaugmentation using a consortium of three actinomycetes strains in remediating two distinct typical Brazilian soils from the Atlantic Forest and Cerrado biomes that were contaminated with crude oil, with or without the addition of NaCl. Microcosms were used to simulate bioremediation treatments over a 120-day period. During this period, we monitored total petroleum hydrocarbons (TPHs and n-alkanes degradation and changes in bacterial communities. Over time, we found the degradation rate of n-alkanes was higher than TPH in both soils, independent of the treatment used. In fact, our data show that the total bacterial community in the soils was mainly affected by the experimental period of time, while the type of bioremediation treatment used was the main factor influencing the actinomycetes populations in both soils. Based on these data, we conclude that monitored natural attenuation is the best strategy for remediation of the two tropical soils studied, with or without salt addition.

  17. The impact of tropical forest logging and oil palm agriculture on the soil microbiome.

    Science.gov (United States)

    Tripathi, Binu M; Edwards, David P; Mendes, Lucas William; Kim, Mincheol; Dong, Ke; Kim, Hyoki; Adams, Jonathan M

    2016-05-01

    Selective logging and forest conversion to oil palm agriculture are rapidly altering tropical forests. However, functional responses of the soil microbiome to these land-use changes are poorly understood. Using 16S rRNA gene and shotgun metagenomic sequencing, we compared composition and functional attributes of soil biota between unlogged, once-logged and twice-logged rainforest, and areas converted to oil palm plantations in Sabah, Borneo. Although there was no significant effect of logging history, we found a significant difference between the taxonomic and functional composition of both primary and logged forests and oil palm. Oil palm had greater abundances of genes associated with DNA, RNA, protein metabolism and other core metabolic functions, but conversely, lower abundance of genes associated with secondary metabolism and cell-cell interactions, indicating less importance of antagonism or mutualism in the more oligotrophic oil palm environment. Overall, these results show a striking difference in taxonomic composition and functional gene diversity of soil microorganisms between oil palm and forest, but no significant difference between primary forest and forest areas with differing logging history. This reinforces the view that logged forest retains most features and functions of the original soil community. However, networks based on strong correlations between taxonomy and functions showed that network complexity is unexpectedly increased due to both logging and oil palm agriculture, which suggests a pervasive effect of both land-use changes on the interaction of soil microbes. © 2016 John Wiley & Sons Ltd.

  18. Cadmium phytoextraction from loam soil in tropical southern China by Sorghum bicolor.

    Science.gov (United States)

    Wang, Xu; Chen, Can; Wang, Jianlong

    2017-06-03

    The cadmium (Cd) uptake characteristics by Sorghum bicolor cv. Nengsi 2# and Cowley from the acidic sandy loam soil (pH = 6.1) during the entire growth period (100 days) were investigated in pot outdoors in a tropical district of southern China, Hainan Island. The Cd-spiked levels in soil were set as 3 and 15 mg/kg. Correspondingly, the available Cd levels in soil extracted by Mehlich III solution were 2.71 and 9.41 mg/kg, respectively. Basically, two varieties in a full growth period (100 days) did not show a significant difference in their growth and Cd uptake. Under high Cd stress, the plant growth was inhibited and its biomass weight and height decreased by 38.7-51.5% and 27.6-28.5%, respectively. However, S. bicolor showed higher bioaccumulation capability of Cd from soil to plant [bioconcentration factor (BCF)>4], and higher transfer capability of Cd from roots to shoots [translocation factor (TF)>1] under high Cd stress; Cd contents in the roots, stems, and leaves of S. bicolor reached 43.79-46.07, 63.28-70.60, and 63.10-66.06 mg/kg, respectively. S. bicolor exhibited the potential phytoextraction capability for low or moderate Cd-contamination in acidic sandy loam soil.

  19. Influence of organic fertilization on the sorption mechanisms of 241 Am in tropical soils

    International Nuclear Information System (INIS)

    Pereira, Tatiane Rocha

    2009-01-01

    In this work the mechanisms involved in the sorption of 241 Am were investigated depending on the physicochemical properties of some Brazilian soils and on alterations promoted by organic amendment. This experimental study was conducted in a controlled area, where pots containing different kinds of soils (histisol, ferralsol and nitisol), with different organic amendment doses (without amendment; 2 kg m -2 and 4 kg m -2 ) were artificially contaminated by radioactive solution water, which contained 241 Am. Migration studies, distribution (or partition) coefficient (KJ), bioavailability and organic matter were carried out in these soils, with ar without organic amendment. In order to evaluate the effective bioavailability of radionuclides, radish (Raphanus sativus L.) was cultivated in these pots, and later the concentration of 241 Am in radish's roots was measured. The main results show that 241 Am tends to be strongly attached to organic matter and that organic amendment in tropical soils minimizes the radionuclide studied desorption. Also, distribution (or partition) coefficient values for 241 Am were generated and these values are smaller than those ones determined for soils from temperate zones. Physical and chemical fractioning of organic matter were carried out. (author)

  20. Chlordecone fate and mineralisation in a tropical soil (andosol) microcosm under aerobic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fernández-Bayo, Jesus D., E-mail: fernanje@supagro.inra.fr [IRD, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1 (France); INRA, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1 (France); Saison, Carine [IRD, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1 (France); Voltz, Marc [INRA, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1 (France); Disko, Ulrich; Hofmann, Diana; Berns, Anne E. [Forschungszentrum Jülich GmbH, IBG 3, 52425 Jülich (Germany)

    2013-10-01

    Chlordecone is a persistent organochlorine insecticide that, even decades after its ban, poses a threat to the environment and human health. Nevertheless, its environmental fate in soils has scarcely been investigated, and elementary data on its degradation and behaviour in soil are lacking. The mineralisation and sorption of chlordecone and the formation of possible metabolites were evaluated in a tropical agricultural andosol. Soil microcosms with two different soil horizons (S-A and S-B) were incubated for 215 days with {sup 14}C-chlordecone. At five different times (1, 33, 88, 150 and 215 days) the extractability of {sup 14}C-chlordecone was analysed. Mineralisation was monitored using {sup 14}CO{sub 2} traps of NaOH. The appearance of metabolites was studied using thin layer and gas chromatography techniques. At the end of the experiment, the water soluble {sup 14}C-activity was 2% of the remaining {sup 14}C-chlordecone for S-A and 8% for S-B. Only 12% of the remaining activity was non extractable and more than 80% remained extractable with organic solvents. For the first time to our knowledge, a significant mineralisation of chlordecone was measured in a microcosm under aerobic conditions (4.9% for S-A and 3.2% for S-B of the initial {sup 14}C-activity). The drastically lower emission of {sup 14}CO{sub 2} in sterilised microcosms indicated the biological origin of chlordecone mineralisation in the non-sterilised microcosms. No metabolites could be detected in the soil extracts. The mineralisation rate of chlordecone decreased by one order of magnitude throughout the incubation period. Thus, the chlordecone content in the soil remained large. This study confirms the existence of chlordecone degrading organisms in a tropical andosol. The reasons why their activity is restricted should be elucidated to allow the development of bioremediation approaches. Possible reasons are a heterogeneous distribution a chlordecone between sub-compartments with different

  1. Chlordecone fate and mineralisation in a tropical soil (andosol) microcosm under aerobic conditions

    International Nuclear Information System (INIS)

    Fernández-Bayo, Jesus D.; Saison, Carine; Voltz, Marc; Disko, Ulrich; Hofmann, Diana; Berns, Anne E.

    2013-01-01

    Chlordecone is a persistent organochlorine insecticide that, even decades after its ban, poses a threat to the environment and human health. Nevertheless, its environmental fate in soils has scarcely been investigated, and elementary data on its degradation and behaviour in soil are lacking. The mineralisation and sorption of chlordecone and the formation of possible metabolites were evaluated in a tropical agricultural andosol. Soil microcosms with two different soil horizons (S-A and S-B) were incubated for 215 days with 14 C-chlordecone. At five different times (1, 33, 88, 150 and 215 days) the extractability of 14 C-chlordecone was analysed. Mineralisation was monitored using 14 CO 2 traps of NaOH. The appearance of metabolites was studied using thin layer and gas chromatography techniques. At the end of the experiment, the water soluble 14 C-activity was 2% of the remaining 14 C-chlordecone for S-A and 8% for S-B. Only 12% of the remaining activity was non extractable and more than 80% remained extractable with organic solvents. For the first time to our knowledge, a significant mineralisation of chlordecone was measured in a microcosm under aerobic conditions (4.9% for S-A and 3.2% for S-B of the initial 14 C-activity). The drastically lower emission of 14 CO 2 in sterilised microcosms indicated the biological origin of chlordecone mineralisation in the non-sterilised microcosms. No metabolites could be detected in the soil extracts. The mineralisation rate of chlordecone decreased by one order of magnitude throughout the incubation period. Thus, the chlordecone content in the soil remained large. This study confirms the existence of chlordecone degrading organisms in a tropical andosol. The reasons why their activity is restricted should be elucidated to allow the development of bioremediation approaches. Possible reasons are a heterogeneous distribution a chlordecone between sub-compartments with different microbial activities or a degradation of

  2. Effect of elevated CO2 on chlorpyriphos degradation and soil microbial activities in tropical rice soil.

    Science.gov (United States)

    Adak, Totan; Munda, Sushmita; Kumar, Upendra; Berliner, J; Pokhare, Somnath S; Jambhulkar, N N; Jena, M

    2016-02-01

    Impact of elevated CO2 on chlorpyriphos degradation, microbial biomass carbon, and enzymatic activities in rice soil was investigated. Rice (variety Naveen, Indica type) was grown under four conditions, namely, chambered control, elevated CO2 (550 ppm), elevated CO2 (700 ppm) in open-top chambers and open field. Chlorpyriphos was sprayed at 500 g a.i. ha(-1) at maximum tillering stage. Chlorpyriphos degraded rapidly from rice soils, and 88.4% of initially applied chlorpyriphos was lost from the rice soil maintained under elevated CO2 (700 ppm) by day 5 of spray, whereas the loss was 80.7% from open field rice soil. Half-life values of chlorpyriphos under different conditions ranged from 2.4 to 1.7 days with minimum half-life recorded with two elevated CO2 treatments. Increased CO2 concentration led to increase in temperature (1.2 to 1.8 °C) that played a critical role in chlorpyriphos persistence. Microbial biomass carbon and soil enzymatic activities specifically, dehydrogenase, fluorescien diacetate hydrolase, urease, acid phosphatase, and alkaline phosphatase responded positively to elevated CO2 concentrations. Generally, the enzyme activities were highly correlated with each other. Irrespective of the level of CO2, short-term negative influence of chlorpyriphos was observed on soil enzymes till day 7 of spray. Knowledge obtained from this study highlights that the elevated CO2 may negatively influence persistence of pesticide but will have positive effects on soil enzyme activities.

  3. The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

    Directory of Open Access Journals (Sweden)

    V. Oliver

    2017-12-01

    Full Text Available Montane tropical soils are a large carbon (C reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF, especially at the lower depths (10–20 and 20–30 cm. In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt–grazed soil had the smallest recovery of the free LF (10 % and a significantly lower C content (14 %. The burnt soils had a much higher proportion of C in the occluded LF (12 % compared to the not-burnt soils (7 % and there was no significant difference among the treatments in the heavy fraction (F ( ∼  70 %. The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2

  4. Soil and water pollution in a banana production region in tropical Mexico.

    Science.gov (United States)

    Geissen, Violette; Ramos, Franzisco Que; de J Bastidas-Bastidas, Pedro; Díaz-González, Gilberto; Bello-Mendoza, Ricardo; Huerta-Lwanga, Esperanza; Ruiz-Suárez, Luz E

    2010-10-01

    The effects of abundant Mancozeb (Mn, Zn-bisdithiocarbamate) applications (2.5 kg ha⁻¹week⁻¹ for 10 years) on soil and surface-, subsurface- and groundwater pollution were monitored in a banana production region of tropical Mexico. In soils, severe manganese accumulation was observed, wheras the main metabolite ethylenethiourea was near the detection limit. Surface and subsurface water was highly polluted with ethylenethiourea, the main metabolite of Mancozeb (22.5 and 4.3 μg L⁻¹, respectively), but not with manganese. In deep ground water, no ethylenethiourea was detected. The level of pollution in the region presents a worrisome risk for aquatic life and for human health.

  5. Chlorpyrifos causes decreased organic matter decomposition by suppressing earthworm and termite communities in tropical soil

    Energy Technology Data Exchange (ETDEWEB)

    De Silva, P. Mangala C.S., E-mail: msilva@falw.vu.n [Department of Animal Ecology, VU University, De Boelelaan 1085, 1081 HV Amsterdam (Netherlands); Department of Zoology, Faculty of Science, University of Ruhuna, Matara (Sri Lanka); Pathiratne, Asoka [Department of Zoology, Faculty of Science, University of Kelaniya, Kelaniya (Sri Lanka); Straalen, Nico M. van; Gestel, Cornelis A.M. van [Department of Animal Ecology, VU University, De Boelelaan 1085, 1081 HV Amsterdam (Netherlands)

    2010-10-15

    Effects of pesticides on structural and functional properties of ecosystems are rarely studied under tropical conditions. In this study litterbag and earthworm field tests were performed simultaneously at the same tropical field site sprayed with chlorpyrifos (CPF). The recommended dose of CPF (0.6 kg a.i. ha{sup -1}) and two higher doses (4.4-8.8 kg a.i. ha{sup -1}) significantly decreased litter decomposition during the first 3 months after application, which could be explained from lower earthworm and termite abundances during this period. Species-specific effects of CPF on organism abundance and biomass were observed, with termites being mostly affected followed by the earthworm Perionyx excavatus; the earthworm Megascolex sp. was least affected. Recovery was completed within 6 months. Decomposition in the controls and lowest two treatments was completed within 4 months, which suggests the need for modification of standard test guidelines to comply with faster litter degradation under tropical conditions. - Effects of chlorpyrifos on functional and structural endpoints in soil.

  6. Chlorpyrifos causes decreased organic matter decomposition by suppressing earthworm and termite communities in tropical soil

    International Nuclear Information System (INIS)

    De Silva, P. Mangala C.S.; Pathiratne, Asoka; Straalen, Nico M. van; Gestel, Cornelis A.M. van

    2010-01-01

    Effects of pesticides on structural and functional properties of ecosystems are rarely studied under tropical conditions. In this study litterbag and earthworm field tests were performed simultaneously at the same tropical field site sprayed with chlorpyrifos (CPF). The recommended dose of CPF (0.6 kg a.i. ha -1 ) and two higher doses (4.4-8.8 kg a.i. ha -1 ) significantly decreased litter decomposition during the first 3 months after application, which could be explained from lower earthworm and termite abundances during this period. Species-specific effects of CPF on organism abundance and biomass were observed, with termites being mostly affected followed by the earthworm Perionyx excavatus; the earthworm Megascolex sp. was least affected. Recovery was completed within 6 months. Decomposition in the controls and lowest two treatments was completed within 4 months, which suggests the need for modification of standard test guidelines to comply with faster litter degradation under tropical conditions. - Effects of chlorpyrifos on functional and structural endpoints in soil.

  7. Sorption of Atrazine in Tropical Soil by Biochar Prepared from Cassava Waste

    Directory of Open Access Journals (Sweden)

    Hui Deng

    2014-09-01

    Full Text Available Biochar (BC is a carbonaceous and porous product generated from the incomplete combustion of biomass and has been recognized as an efficient adsorbent. This study evaluated the ability of BC to sorb atrazine pesticide in tropical soil, and explored potential environmental values of BC on mitigating organic micro-pollutants. BC was produced from cassava waste via pyrolyzation under oxygen-limiting conditions at 350, 550, and 750 °C (MS350, MS550, and MS750, respectively. Three biochars were characterized and investigated as sorbents for the removal atrazine from tropical soil. BC pyrolyzed at higher temperatures more quickly reached equilibrium. The pseudo-second-order model perfectly simulated the sorption kinetics for atrazine with the coefficients R2 above 0.996, and the sorption amount at equilibrium (qe was 0.016 mg/g for MS350, 0.025 mg/g for MS550 and 0.050 mg/g for MS750. The isotherms of MS350 displayed relatively linear behavior, whereas the sorption of atrazine on MS550 and MS750 followed a nonlinear isotherm. The sorption data were well described by the Freundlich model with logKF of 0.476 for MS350, 0.771 for MS550, 1.865 for MS750. A thermodynamic study indicated that the sorption of atrazine in BC-added soil was a spontaneous and endothermic process and was primarily controlled by physisorption. In addition, lower pH was conducive to the sorption of atrazine in BC-added soil.

  8. Runoff and soil erosion for an undisturbed tropical woodland in the Brazilian Cerrado

    Science.gov (United States)

    Oliveira, Paulo Tarso S.; Nearing, Mark; Wendland, Edson

    2015-04-01

    The Brazilian Cerrado is a large and important economic and environmental region that is experiencing major loss of its natural landscapes due to pressures of food and energy production, which has caused large increases in soil erosion. However the magnitude of the soil erosion increases in this region is not well understood, in part because scientific studies of surface runoff and soil erosion are scarce or nonexistent in undisturbed Cerrado vegetation. In this study we measured natural rainfall-driven rates of runoff and soil erosion for an undisturbed tropical woodland classified as "cerrado sensu stricto denso" and bare soil to compute the Universal Soil Loss Equation (USLE) cover and management factor (C-factor) to help evaluate the likely effects of land use change on soil erosion rates. Replicated data on precipitation, runoff, and soil loss on plots (5 x 20 m) under bare soil and cerrado were collected for 55 erosive storms occurring in 2012 and 2013. The measured annual precipitation was 1247.4 mm and 1113.0 mm for 2012 and 2013, resulting in a rainfall erosivity index of 4337.1 MJ mm ha-1 h-1 and 3546.2 MJ mm ha-1 h-1, for each year respectively. The erosive rainfall represented 80concentrated in the wet season, which generally runs from October through March. In the plots on bare soil, the runoff coefficient for individual rainfall events (total runoff divided by total rainfall) ranged from 0.003 to 0.860 with an average value and standard deviation of 0.212 ± 0.187. Moreover, the runoff coefficient found for the bare soil plots (~20infiltration capacity. In forest areas the leaf litter and the more porous soil tend to promote the increase of infiltration and water storage, rather than rapid overland flow. Indeed, runoff coefficients ranged from 0.001 to 0.030 with an average of less than 1under undisturbed cerrado. The soil losses measured under bare soil and cerrado were 15.68 t ha-1yr-1 and 0.24 t ha-1 yr-1 in 2012, and 14.82 t ha-1 yr-1, 0.11 t ha-1

  9. Multiscale analysis of depth-dependent soil penetration resistance in a tropical soil

    Science.gov (United States)

    Paiva De Lima, Renato; Santos, Djail; Medeiros Bezerra, Joel; Machado Siqueira, Glécio; Paz González, Antonio

    2013-04-01

    Soil penetration resistance (PR) is widely used because it is linked to basic soil properties; it is correlated to root growth and plant production and is also used as a practical tool for assessing soil compaction and to evaluate the effects of soil management. This study investigates how results from multifractal analysis can quantify key elements of depth-dependent PR profiles and how this information can be used at the field scale. We analyzed multifractality of 50 PR vertical profiles, measured from 0 to 40 cm depth and randomly located on a 6.5 ha sugar cane field in north-eastern Brazil. According to the Soil Taxonomy, the studied soil was classified as an Orthic Podsol The scaling property of each profile was typified by singularity and Rényi spectra estimated by the method of moments. The Hurst exponent was used to parameterize the autocorrelation of the vertical PR data sets. Singularity and Rènyi spectra showed the vertical PR data sets exhibited a well-defined multifractal structure. Hurst exponent values were close to one indicating strong persistence in PR variation with soil depth. Also Hurst exponent was negatively and significantly correlated to coefficient of variation (CV) and skewness of the depth-dependent PR. Multifractal analysis added valuable information to describe the spatial arrangement of depth-dependent penetrometer data sets, which was not taken into account by classical statistical indices. Multifractal parameters were mapped over the experimental field and compared with mean, maximum and minimum values of PR; these maps showed the multifractal approach also may complete information provided by descriptive statistics at the field scale.

  10. Tritium behavior pattern in some soil-plant systems in a tropical environment

    International Nuclear Information System (INIS)

    Soman, S.D.; Iyengar, T.S.; Sadarangani, S.H.; Vaze, P.K.

    1975-01-01

    A study of the distribution pattern of tritium in the soil/plant environment gives valuable ecological information on the natural water balance. The results of such a study for the conditions obtaining in India are given in this paper. Field studies are carried out by injection of tritium into some soil/plant systems and following the transfer pathways. The method of extraction for tissue-free-water-tritium (TFWT) is based on the vacuum freeze-drying technique while the tissue-bound-tritium (TBT) is estimated by a modified version of the Shoniger method. The determination of residence time of tritium in aqueous and organic phase in a number of tropical trees has been carried out both for stem-injection as well as intake from the soil. From the results of this study the tree biomass and transpiration rates have been determined. The tritium profile over time, for an acute exposure in certain trees such as Morinda Tinetoria, Achras Sapota etc. shows significantly different patterns compared to the normal pattern shown by Mangifera Indica, Terminalia Catappa, Ficus Glomerata etc. The period of investigation in each case varied from 400 to 1000 h. In most of the cases, the TBT fractions were very low compared to TFWT fractions in the initial stages. The tritium behavior in the tree reflects significant characteristics of the tritium behavior in the soil system. The authors have found that the leaf sampling can be used as an indicator of total environmental tritium behavior. (author)

  11. Carbon leaching from tropical peat soils and consequences for carbon balances

    Directory of Open Access Journals (Sweden)

    Tim Rixen

    2016-07-01

    Full Text Available Drainage and deforestation turned Southeast (SE Asian peat soils into a globally important CO2 source, because both processes accelerate peat decomposition. Carbon losses through soil leaching have so far not been quantified and the underlying processes have hardly been studied. In this study, we use results derived from nine expeditions to six Sumatran rivers and a mixing model to determine leaching processes in tropical peat soils, which are heavily disturbed by drainage and deforestation. Here we show that a reduced evapotranspiration and the resulting increased freshwater discharge in addition to the supply of labile leaf litter produced by re-growing secondary forests increase leaching of carbon by ~200%. Enhanced freshwater fluxes and leaching of labile leaf litter from secondary vegetation appear to contribute 38% and 62% to the total increase, respectively. Decomposition of leached labile DOC can lead to hypoxic conditions in rivers draining disturbed peatlands. Leaching of the more refractory DOC from peat is an irrecoverable loss of soil that threatens the stability of peat-fringed coasts in SE Asia.

  12. EFFECT OF COVER CROPS ON SOIL ATTRIBUTES, PLANT NUTRITION, AND IRRIGATED TROPICAL RICE YIELD

    Directory of Open Access Journals (Sweden)

    ANDRE FROES DE BORJA REIS

    2017-01-01

    Full Text Available In flood plains, cover crops are able to alter soil properties and significantly affect rice nutrition and yield. The aims of this study were to determine soil properties, plant nutrition, and yield of tropical rice cultivated on flood plains after cover crop cultivation with conventional tillage (CT and no-tillage system (NTS at low and high nitrogen (N fertilization levels. The experimental design was a randomized block in a split-split-plot scheme with four replications. In the main plots were cover crops sunhemp (Crotalaria juncea and C. spectabilis, velvet bean (Mucuna aterrima, jackbean (Canavalia ensiformis, pigeon pea (Cajanus cajan, Japanese radish (Raphanus sativus, cowpea (Vigna unguiculata and a fallow field. In the subplots were the tillage systems (CT or NTS. The nitrogen fertilization levels in the sub-subplots were (10 kg N ha-1 and 45 kg N ha-1. All cover crops except Japanese radish significantly increased mineral soil nitrogen and nitrate concentrations. Sunhemp, velvet bean, and cowpea significantly increased soil ammonium content. The NTS provides higher mineral nitrogen and ammonium content than that by CT. Overall, cover crops provided higher levels of nutrients to rice plants in NTS than in CT. Cover crops provide greater yield than fallow treatments. Rice yield was higher in NTS than in CT, and greater at a higher rather than lower nitrogen fertilization level.

  13. Assessing risk to human health from tropical leafy vegetables grown on contaminated urban soils

    International Nuclear Information System (INIS)

    Nabulo, G.; Young, S.D.; Black, C.R.

    2010-01-01

    Fifteen tropical leafy vegetable types were sampled from farmers' gardens situated on nine contaminated sites used to grow vegetables for commercial or subsistence consumption in and around Kampala City, Uganda. Trace metal concentrations in soils were highly variable and originated from irrigation with wastewater, effluent discharge from industry and dumping of solid waste. Metal concentrations in the edible shoots of vegetables also differed greatly between, and within, sites. Gynandropsis gynandra consistently accumulated the highest Cd, Pb and Cu concentrations, while Amaranthus dubius accumulated the highest Zn concentration. Cadmium uptake from soils with contrasting sources and severity of contamination was consistently lowest in Cucurbita maxima and Vigna unguiculata, suggesting these species were most able to restrict Cd uptake from contaminated soil. Concentrations of Pb and Cr were consistently greater in unwashed, than in washed, vegetables, in marked contrast to Cd, Ni and Zn. The risk to human health, expressed as a 'hazard quotient' (HQ M ), was generally greatest for Cd, followed successively by Pb, Zn, Ni and Cu. Nevertheless, it was apparent that urban cultivation of leafy vegetables could be safely pursued on most sites, subject to site-specific assessment of soil metal burden, judicious choice of vegetable types and adoption of washing in clean water prior to cooking.

  14. The Effect of Soil Warming on Decomposition of Biochar, Wood, and Bulk Soil Organic Carbon in Contrasting Temperate and Tropical Soils

    Science.gov (United States)

    Torn, Margaret; Tas, Neslihan; Reichl, Ken; Castanha, Cristina; Fischer, Marc; Abiven, Samuel; Schmidt, Michael; Brodie, Eoin; Jansson, Janet

    2013-04-01

    Biochar and wood are known to decay at different rates in soil, but the longterm effect of char versus unaltered wood inputs on soil carbon dynamics may vary by soil ecosystem and by their sensitivity to warming. We conducted an incubation experiment to explore three questions: (1) How do decomposition rates of char and wood vary with soil type and depth? (2) How vulnerable to warming are these slowly decomposing inputs? And (3) Do char or wood additions increase loss of native soil organic carbon (priming)? Soils from a Mediterranean grassland (Hopland Experimental Research Station, California) and a moist tropical forest (Tabunoco Forest, Puerto Rico) were collected from two soil depths and incubated at ambient temperature (14°C, 20°C for Hopland and Tabonuco respectively) and ambient +6°C. We added 13C-labeled wood and char (made from the wood at 450oC) to the soils and quantified CO2 and 13CO2 fluxes with continuous online carbon isotope measurements using a Cavity Ringdown Spectrometer (Picarro, Inc) for one year. As expected, in all treatments the wood decomposed much (about 50 times) more quickly than did the char amendment. With few exceptions, amendments placed in the surface soil decomposed more quickly than those in deeper soil, and in forest soil faster than that placed in grassland soil, at the same temperature. The two substrates were not very temperature sensitive. Both had Q10 less than 2 and char decomposition in particular was relatively insensitive to warming. Finally, the addition of wood caused a significant increase of roughly 30% in decomposition losses of the native soil organic carbon in the grassland and slightly less in forest. Char had only a slight positive priming effect but had a significant effect on microbial community. These results show that conversion of wood inputs to char through wildfire or intentional management will alter not only the persistence of the carbon in soil but also its temperature response and effect on

  15. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India.

    Science.gov (United States)

    Jena, Santanu K; Tayung, Kumanand; Rath, Chandi C; Parida, Debraj

    2015-03-01

    Similipal Biosphere Reserve (SBR) is a tropical moist deciduous forest dominated by the species Shorea robusta . To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1-6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 10 (4) -2.1 × 10 (5) and 5.1 × 10 (4) -4.7 × 10 (5) cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI) was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher's alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (%) of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium.

  16. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India

    Science.gov (United States)

    Jena, Santanu K.; Tayung, Kumanand; Rath, Chandi C.; Parida, Debraj

    2015-01-01

    Similipal Biosphere Reserve (SBR) is a tropical moist deciduous forest dominated by the species Shorea robusta . To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1–6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 10 4 –2.1 × 10 5 and 5.1 × 10 4 –4.7 × 10 5 cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI) was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher’s alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (%) of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium . PMID:26221092

  17. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India

    Directory of Open Access Journals (Sweden)

    Santanu K. Jena

    2015-03-01

    Full Text Available Similipal Biosphere Reserve (SBR is a tropical moist deciduous forest dominated by the species Shorea robusta. To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1–6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 104–2.1 × 105 and 5.1 × 104–4.7 × 105 cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher’s alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (% of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium.

  18. A cost-efficient method to assess carbon stocks in tropical peat soil

    Directory of Open Access Journals (Sweden)

    M. W. Warren

    2012-11-01

    Full Text Available Estimation of belowground carbon stocks in tropical wetland forests requires funding for laboratory analyses and suitable facilities, which are often lacking in developing nations where most tropical wetlands are found. It is therefore beneficial to develop simple analytical tools to assist belowground carbon estimation where financial and technical limitations are common. Here we use published and original data to describe soil carbon density (kgC m−3; Cd as a function of bulk density (gC cm−3; Bd, which can be used to rapidly estimate belowground carbon storage using Bd measurements only. Predicted carbon densities and stocks are compared with those obtained from direct carbon analysis for ten peat swamp forest stands in three national parks of Indonesia. Analysis of soil carbon density and bulk density from the literature indicated a strong linear relationship (Cd = Bd × 495.14 + 5.41, R2 = 0.93, n = 151 for soils with organic C content > 40%. As organic C content decreases, the relationship between Cd and Bd becomes less predictable as soil texture becomes an important determinant of Cd. The equation predicted belowground C stocks to within 0.92% to 9.57% of observed values. Average bulk density of collected peat samples was 0.127 g cm−3, which is in the upper range of previous reports for Southeast Asian peatlands. When original data were included, the revised equation Cd = Bd × 468.76 + 5.82, with R2 = 0.95 and n = 712, was slightly below the lower 95% confidence interval of the original equation, and tended to decrease Cd estimates. We recommend this last equation for a rapid estimation of soil C stocks for well-developed peat soils where C content > 40%.

  19. Composition and fate of mine- and smelter-derived particles in soils of humid subtropical and hot semi-arid areas

    Energy Technology Data Exchange (ETDEWEB)

    Ettler, Vojtěch, E-mail: ettler@natur.cuni.cz [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Johan, Zdenek [BRGM, Avenue Claude Guillemin, 45082 Orléans Cedex 2 (France); Kříbek, Bohdan; Veselovský, František [Czech Geological Survey, Geologická 6, 152 00 Praha 5 (Czech Republic); Mihaljevič, Martin [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Vaněk, Aleš; Penížek, Vít [Department of Soil Science and Soil Protection, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6 (Czech Republic); Majer, Vladimír [Czech Geological Survey, Geologická 6, 152 00 Praha 5 (Czech Republic); Sracek, Ondra [Department of Geology, Faculty of Science, Palacký University in Olomouc, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Mapani, Ben; Kamona, Fred [Department of Geology, Faculty of Science, University of Namibia, Private Bag 13301, Windhoek (Namibia); Nyambe, Imasiku [University of Zambia, School of Mines, P. O. Box 32 379, Lusaka (Zambia)

    2016-09-01

    We studied the heavy mineral fraction, separated from mining- and smelter-affected topsoils, from both a humid subtropical area (Mufulira, Zambian Copperbelt) and a hot semi-arid area (Tsumeb, Namibia). High concentrations of metal(loid)s were detected in the studied soils: up to 1450 mg As kg{sup −1}, 8980 mg Cu kg{sup −1}, 4640 mg Pb kg{sup −1}, 2620 mg Zn kg{sup −1}. A combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS), and electron probe microanalysis (EPMA) helped to identify the phases forming individual metal(loid)-bearing particles. Whereas spherical particles originate from the smelting and flue gas cleaning processes, angular particles have either geogenic origins or they are windblown from the mining operations and mine waste disposal sites. Sulphides from ores and mine tailings often exhibit weathering rims in contrast to smelter-derived high-temperature sulphides (chalcocite [Cu{sub 2}S], digenite [Cu{sub 9}S{sub 5}], covellite [CuS], non-stoichiometric quenched Cu–Fe–S phases). Soils from humid subtropical areas exhibit higher available concentrations of metal(loids), and higher frequencies of weathering features (especially for copper-bearing oxides such as delafossite [Cu{sup 1+} Fe{sup 3+} O{sub 2}]) are observed. In contrast, metal(loid)s are efficiently retained in semi-arid soils, where a high proportion of non-weathered smelter slag particles and low-solubility Ca–Cu–Pb arsenates occur. Our results indicate that compared to semi-arid areas (where inorganic contaminants were rather immobile in soils despite their high concentrations) a higher potential risk exists for agriculture in mine- and smelter-affected humid subtropical areas (where metal(loid) contaminants can be highly available for the uptake by crops). - Highlights: • Mining- and smelter-derived particles identified in subtropical and semi-arid soils • Sulphides, oxides, and metal-bearing arsenates most frequently encountered

  20. Biochar from sugarcane filtercake reduces soil CO2 emissions relative to raw residue and improves water retention and nutrient availability in a highly-weathered tropical soil.

    Science.gov (United States)

    Eykelbosh, Angela Joy; Johnson, Mark S; Santos de Queiroz, Edmar; Dalmagro, Higo José; Guimarães Couto, Eduardo

    2014-01-01

    In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions.

  1. Biochar from Sugarcane Filtercake Reduces Soil CO2 Emissions Relative to Raw Residue and Improves Water Retention and Nutrient Availability in a Highly-Weathered Tropical Soil

    Science.gov (United States)

    Eykelbosh, Angela Joy; Johnson, Mark S.; Santos de Queiroz, Edmar; Dalmagro, Higo José; Guimarães Couto, Eduardo

    2014-01-01

    In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions. PMID:24897522

  2. Biochar from sugarcane filtercake reduces soil CO2 emissions relative to raw residue and improves water retention and nutrient availability in a highly-weathered tropical soil.

    Directory of Open Access Journals (Sweden)

    Angela Joy Eykelbosh

    Full Text Available In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w. were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w. raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w. in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions.

  3. Silicate fertilization of tropical soils: silicon availability and recovery index of sugarcane

    Directory of Open Access Journals (Sweden)

    Mônica Sartori de Camargo

    2013-10-01

    Full Text Available Sugarcane is considered a Si-accumulating plant, but in Brazil, where several soil types are used for cultivation, there is little information about silicon (Si fertilization. The objectives of this study were to evaluate the silicon availability, uptake and recovery index of Si from the applied silicate on tropical soils with and without silicate fertilization, in three crops. The experiments in pots (100 L were performed with specific Si rates (0, 185, 370 and 555 kg ha-1 Si, three soils (Quartzipsamment-Q, 6 % clay; Rhodic Hapludox-RH, 22 % clay; and Rhodic Acrudox-RA, 68 % clay, with four replications. The silicon source was Ca-Mg silicate. The same Ca and Mg quantities were applied to all pots, with lime and/or MgCl2, when necessary. Sugarcane was harvested in the plant cane and first- and second-ratoon crops. The silicon rates increased soil Si availability and Si uptake by sugarcane and had a strong residual effect. The contents of soluble Si were reduced by harvesting and increased with silicate application in the following decreasing order: Q>RH>RA. The silicate rates promoted an increase in soluble Si-acetic acid at harvest for all crops and in all soils, except RA. The amounts of Si-CaCl2 were not influenced by silicate in the ratoon crops. The plant Si uptake increased according to the Si rates and was highest in RA at all harvests. The recovery index of applied Si (RI of sugarcane increased over time, and was highest in RA.

  4. Bioremediation potential of a tropical soil contaminated with a mixture of crude oil and production water.

    Science.gov (United States)

    Alvarez, Vanessa Marques; Santos, Silvia Cristina Cunha Dos Santos; Casella, Renata da Costa; Vital, Ronalt Leite; Sebastin, Gina Vasquez; Seldin, Lucy

    2008-12-01

    A typical tropical soil from the northeast of Brazil, where an important terrestrial oil field is located, was accidentally contaminated with a mixture of oil and saline production water. To study the bioremediation potential in this area, molecular methods based on PCR-DGGE were used to determine the diversity of the bacterial communities in bulk and in contaminated soils. Bacterial fingerprints revealed that the bacterial communities were affected by the presence of the mixture of oil and production water, and different profiles were observed when the contaminated soils were compared with the control. Halotolerant strains capable of degrading crude oil were also isolated from enrichment cultures obtained from the contaminated soil samples. Twenty-two strains showing these features were characterized genetically by amplified ribosomal DNA restriction analysis (ARDRA) and phenotypically by their colonial morphology and tolerance to high NaCl concentrations. Fifteen ARDRA groups were formed. Selected strains were analyzed by 16S rDNA sequencing, and Actinobacteria was identified as the main group found. Strains were also tested for their growth capability in the presence of different oil derivatives (hexane, dodecane, hexadecane, diesel, gasoline, toluene, naphthalene, o-xylene, and p-xylene) and different degradation profiles were observed. PCR products were obtained from 12 of the 15 ARDRA representatives when they were screened for the presence of the alkane hydroxylase gene (alkB). Members of the genera Rhodococcus and Gordonia were identified as predominant in the soil studied. These genera are usually implicated in oil degradation processes and, as such, the potential for bioremediation in this area can be considered as feasible.

  5. Distinctive tropical forest variants have unique soil microbial communities, but not always low microbial diversity

    Directory of Open Access Journals (Sweden)

    Binu M Tripathi

    2016-04-01

    Full Text Available There has been little study of whether different variants of tropical rainforest have distinct soil microbial communities and levels of diversity. We compared bacterial and fungal community composition and diversity between primary mixed dipterocarp, secondary mixed dipterocarp, white sand heath, inland heath, and peat swamp forests in Brunei Darussalam, northwest Borneo by analyzing Illumina Miseq sequence data of 16S rRNA gene and ITS1 region. We hypothesized that white sand heath, inland heath and peat swamp forests would show lower microbial diversity and relatively distinct microbial communities (compared to MDF primary and secondary forests due to their distinctive environments. We found that soil properties together with bacterial and fungal communities varied significantly between forest types. Alpha and beta-diversity of bacteria was highest in secondary dipterocarp and white sand heath forests. Also, bacterial alpha diversity was strongly structured by pH, adding another instance of this widespread pattern in nature. The alpha diversity of fungi was equally high in all forest types except peat swamp forest, although fungal beta-diversity was highest in primary and secondary mixed dipterocarp forests. The relative abundance of ectomycorrhizal (EcM fungi varied significantly between forest types, with highest relative abundance observed in MDF primary forest. Overall, our results suggest that the soil bacterial and fungal communities in these forest types are to a certain extent predictable and structured by soil properties, but that diversity is not determined by how distinctive the conditions are. This contrasts with the diversity patterns seen in rainforest trees, where distinctive soil conditions have consistently lower tree diversity.

  6. Impacts of Dust on Tropical Volcanic Soil Formation: Insights from Strontium and Uranium-Series Isotopes in Soils from Basse-Terre Island, French Guadeloupe

    Science.gov (United States)

    Pereyra, Y.; Ma, L.; Sak, P. B.; Gaillardet, J.; Buss, H. L.; Brantley, S. L.

    2015-12-01

    Dust inputs play an important role in soil formation, especially for thick soils developed on tropical volcanic islands. In these regions, soils are highly depleted due to intensive chemical weathering, and mineral nutrients from dusts have been known to be important in sustaining soil fertility and productivity. Tropical volcanic soils are an ideal system to study the impacts of dust inputs on the ecosystem. Sr and U-series isotopes are excellent tracers to identify sources of materials in an open system if the end-members have distinctive isotope signatures. These two isotope systems are particularly useful to trace the origin of atmospheric inputs into soils and to determine rates and timescales of soil formation. This study analyzes major elemental concentrations, Sr and U-series isotope ratios in highly depleted soils in the tropical volcanic island of Basse-Terre in French Guadeloupe to determine atmospheric input sources and identify key soil formation processes. We focus on three soil profiles (8 to 12 m thick) from the Bras-David, Moustique Petit-Bourg, and Deshaies watersheds; and on the adjacent rivers to these sites. Results have shown a significant depletion of U, Sr, and major elements in the deep profile (12 to 4 m) attributed to rapid chemical weathering. The top soil profiles (4 m to the surface) all show addition of elements such as Ca, Mg, U, and Sr due to atmospheric dust. More importantly, the topsoil profiles have distinct Sr and U-series isotope compositions from the deep soils. Sr and U-series isotope ratios of the top soils and sequential extraction fractions confirm that the sources of the dust are from the Saharan dessert, through long distance transport from Africa to the Caribbean region across the Atlantic Ocean. During the transport, some dust isotope signatures may also have been modified by local volcanic ashes and marine aerosols. Our study highlights that dusts and marine aerosols play important roles in element cycles and

  7. Phosphorus dynamics in a tropical soil amended with green manures and natural inorganic phosphate fertilizers

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Zaharah Abd; R, Bah Abd [Universiti Putra Malaysia, Serdang (Malaysia). Dept of Land Management

    2002-07-01

    Alleviating P deficiency with natural inorganic phosphates and organic residues has significant economic and environmental advantages in the tropics. However, adapting this technology to various agroecosystems requires greater understanding of P dynamics in such systems. This was studied in an amended Bungor soil in laboratory incubation and glasshouse experiments. Treatments were a factorial combination of green manures GMs (Calopogonium caeruleum, Gliricidia sepium and Imperata cylindrica) and P fertilizers (phosphate rocks (PRs)) from China and Algeria, in 3 replications. The GMs were labeled with {sup 33}P in the glasshouse trial. Olsen P, mineral N, exchangeable Ca and pH were monitored in the incubation at 0,1,2,4,8,16,32 and 64 weeks after establishment (WAE). Soil P fractions were also determined at 64 WAE. Phosphorus available from the amendments at 4, 8, 15, and 20 WAE, was quantified by {sup 33}P-{sup 32}P double isotopic labeling in the glasshouse using Setaria sphacelata (Setaria grass) as test crop. Olsen P was unaffected by the sole P fertilizers, and hardly changed within 16 WAE in the legume GM and legume GM+PR treatments as NH{sub 4}{sup +}-N accumulated and soil pH increased. Afterwards Olsen P and exchangeable Ca increased as NH{sub 4}{sup +}-N and soil pH declined. The legume GMs augmented reversibly sorbed P in Al-P and Fe-P fractions resulting in high residual effect, but fertilizers was irreversibly retained. GM-P availability was very low (< 4%), but GMs enhanced PR solubility and mobilized soil P irrespective of quality, probably by the action of organic acids. Calcium content had negative effect on available P and should be considered when selecting compatible materials in integrated systems. The results are further evidence of the importance of the soil P mobilization capacity of organic components in integrated P management systems. Even low quality Imperata can augment soil P supply when combined with the reactive APR, probably by

  8. Toxicity of four veterinary pharmaceuticals on the survival and reproduction of Folsomia candida in tropical soils.

    Science.gov (United States)

    Zortéa, Talyta; Segat, Julia C; Maccari, Ana Paula; Sousa, José Paulo; Da Silva, Aleksandro S; Baretta, Dilmar

    2017-04-01

    This study aimed to evaluate the effect of veterinary pharmaceuticals (VPs) used to control endo- and ectoparasites in ruminants, on the survival and reproduction of the collembolan species Folsomia candida. Standard ecotoxicological tests were conducted in Tropical Artificial Soil and the treatments consisted of increasing dosages of four commercial products with different active ingredients: ivermectin, fipronil, fluazuron and closantel. Ecotoxicological effects were related to the class and mode of action of the different compounds. Fipronil and ivermectin were the most toxic compounds causing a significant reduction in the number of juveniles at the lowest doses tested (LOEC reprod values of 0.3 and 0.2 mg kg -1 of dry soil, respectively) and similar low EC 50 values (fipronil: 0.19 mg kg -1 dry soil, CL 95% 0.16-0.22; ivermectin: 0.43 mg kg -1 dry soil, CL 95% 0.09-0.77), although the effects observed in the former compound were possibly related to a low adult survival (LC 50 of 0.62 mg kg -1 dry soil; CL 95% : 0.25-1.06). For the latter compound no significant lethal effects were observed. Fluazuron caused an intermediate toxicity (EC 50 of 3.07 mg kg -1 dry soil, CL 95% : 2.26-3.87), and also here a decrease in adult survival could explain the effects observed at reproduction. Closantel, despite showing a significant reduction on the number of juveniles produced, no dose-response relationship nor effects higher than 50% were observed. Overall, all tested compounds, especially ivermectin, when present in soil even at sub-lethal concentrations, can impair the reproduction of collembolans and possibly other arthropods. However, the actual risk to arthropod communities should be further investigated performing tests under a more realistic exposure (e.g., by testing the dung itself as the contaminated matrix) and by deriving ecotoxicologically relevant exposure concentration in soil derived from the presence of cattle dung. Copyright © 2017 Elsevier

  9. Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils.

    Science.gov (United States)

    Hemingway, Jordon D; Hilton, Robert G; Hovius, Niels; Eglinton, Timothy I; Haghipour, Negar; Wacker, Lukas; Chen, Meng-Chiang; Galy, Valier V

    2018-04-13

    Lithospheric organic carbon ("petrogenic"; OC petro ) is oxidized during exhumation and subsequent erosion of mountain ranges. This process is a considerable source of carbon dioxide (CO 2 ) to the atmosphere over geologic time scales, but the mechanisms that govern oxidation rates in mountain landscapes are poorly constrained. We demonstrate that, on average, 67 ± 11% of the OC petro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized in soils, leading to CO 2 emissions of 6.1 to 18.6 metric tons of carbon per square kilometer per year. The molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals that OC petro remineralization is microbially mediated. Rapid oxidation in mountain soils drives CO 2 emission fluxes that increase with erosion rate, thereby counteracting CO 2 drawdown by silicate weathering and biospheric OC burial. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  10. Soil fertility and species traits, but not diversity, drive productivity and biomass stocks in a Guyanese tropical rainforest

    NARCIS (Netherlands)

    Sande, van der M.T.; Arets, E.J.M.M.; Pena Claros, M.; Hoosbeek, M.R.; Caceres-Siani, Yasmani; Hout, van de P.; Poorter, L.

    2018-01-01

    1.Tropical forests store and sequester large amounts of carbon in above- and below-ground plant biomass and soil organic matter (SOM), but how these are driven by abiotic and biotic factors remains poorly understood.
    2.Here, we test the effects of abiotic factors (light variation, caused by

  11. Effects of different land use on soil chemical properties, decomposition rate and earthworm communities in tropical Mexico

    NARCIS (Netherlands)

    Geissen, V.; Peña-Peña, K.; Huerta, E.

    2009-01-01

    The effects of land use on soil chemical properties were evaluated, and earthworm communities and the decomposition rate of three typical land use systems in tropical Mexico, namely banana plantations (B), agroforestry systems (AF) and a successional forest (S) were compared. The study was carried

  12. Belowground Response to Drought in a Tropical Forest Soil. II. Change in Microbial Function Impacts Carbon Composition

    Science.gov (United States)

    Nicholas J. Bouskill; Tana E. Wood; Richard Baran; Zhao Hao; Zaw Ye; Ben P. Bowen; Hsiao Chien Lim; Peter S. Nico; Hoi-Ying Holman; Benjamin Gilbert; Whendee L. Silver; Trent R. Northen; Eoin L. Brodie

    2016-01-01

    Climate model projections for tropical regions show clear perturbation of precipitation patterns leading to increased frequency and severity of drought in some regions. Previous work has shown declining soil moisture to be a strong driver of changes in microbial trait distribution, however...

  13. The response of heterotrophic activity and carbon cycling to nitrogen additions and warming in two tropical soils

    Science.gov (United States)

    Daniela F. Cusack; Margaret S. Torn; William H. McDowell; Whendee L. Silver

    2010-01-01

    Nitrogen (N) deposition is projected to increase significantly in tropical regions in the coming decades, where changes in climate are also expected. Additional N and warming each have the potential to alter soil carbon (C) storage via changes in microbial activity and decomposition, but little is known about the combined effects of these global change factors in...

  14. Radiological aspects of choice of a system of cultivation of sod-podzolic sandy loam soils with different degree of humidity on lands of Mogilev region contaminated with 137Cs

    International Nuclear Information System (INIS)

    Lazarevich, S.S.; Ermolenko, A.V.; Shapsheeva, T.P.

    2010-01-01

    In the conditions of the Republic of Belarus there were presented data about the influence of technological factors on entry of 137Cs into plant products (grain and green mass). In course of the study there were analyzed the following variants of soil cultivation: moldboard plowing; subsurface chisel soil tillage; subsurface surface soil tillage; minimal tillage. There were presented data on specific activity of 137Cs in plant product samples of oat (Avena sativa) grain; field pea (Pisum arvense L.) and oat mixture grain and green mass; wheat (Triticum aestivum) grain. There were determined the main principles of influence of cultivation systems of sod-podzolic sandy loam soil with different degree of humidity on transition of 137Cs into plants depending on the degree of soil and crop humidity. On the automorphic soil there was revealed a tendency of increased transition of 137Cs into grain and green mass after application of subsurface surface soil tillage system

  15. Restoration of soil fertility and improvement of cropping systems for sustainable development in the humid savannahs of Cote d'Ivoire

    International Nuclear Information System (INIS)

    Bachmann, T.

    1999-01-01

    The present FAO-project addresses the soil fertility problems by combining organic with inorganic nutrient sources and actively involving farmers and other beneficiaries in an integrated, long-term development process. A major objective of the project is the participatory on-farm testing and validation of available technological innovations for soil fertility improvement. The results should fulfill two main requirements: (i) provide the farmer with a short-term production increase and (ii) improve/maintain soil fertility in the medium and long-term. The strategic framework of the project is based on the following three main elements: the need to take into account all aspects of soil fertility restoration including areas concerned, cost of fertility restoration, and economic profitability and sustainability; - the need to test all fertility improving measures at farm level in representative agro-ecozones of the humid and sub-humid savannas before their extension at large; the need to identify major macro-economic constraints (e.g. marketing) which impede sustainable agricultural development in the savannah region. The primary goal of the project is to replace traditional shifting cultivation in the humid savannas of the country by economically, ecologically and socially more sustainable production systems. In order to achieve this development objective the project focuses on the following main issues: restoration of soil fertility through improved land and crop management and more efficient use of mineral and organic fertilizers; crop diversification through more efficient use of water resources (irrigation); introduction of new cropping systems which have been successfully tested in countries with similar agro-ecological conditions; adapting traditional land tenure to the market economy; involving the private sector in all aspects of regional development assisted by Government through the creation of a favorable environment. Phase 1: constraint analysis and

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

    Science.gov (United States)

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

    1999-07-01

    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 20-22% and 8-9% in the young and the mature stands respectively. Monthly ET was related to forest leaf area index and was much higher than that for the kind of tall fire-climax Pennisetum polystachyon grassland replaced by the forests. Grassland reforestation resulted in a maximum decrease in annual water yield of 1180 mm on a plot basis, although it is argued that a reduction of (at least) 500-700 mm would be more realistic at the catchment scale. The impact of reforesting grassland on the water resources in southwest Viti Levu is enhanced by its location in a maritime, seasonal climate in the outer tropics, which favors a larger difference between annual forest and grassland evaporation totals than do equatorial regions.

  17. Impacts of Sewage Sludge in Tropical Soil: A Case Study in Brazil

    International Nuclear Information System (INIS)

    Bettiol, W.; Ghini, R.

    2011-01-01

    A long-term assay was conducted to evaluate the environmental impacts of agriculture use of sewage sludge on a tropical soil. This paper describes and discusses the results obtained by applying a interdisciplinary approach and the valuable insights gained. Experimental site was located in Jaguariuna (SP, Brazil). Multiyear comparison was developed with the application of sewage sludge obtained from wastewater treatment plants at Barueri (domestic and industrial sewage) and Franca (domestic sewage), Sao Paulo State. The treatments were control, mineral fertilization, and sewage sludge applied based on the N concentration that provides the same amount of N as in the mineral fertilization recommended for corn crop, two, four, and eight times the N recommended dosage. The results obtained indicated that the amount of sewage sludge used in agricultural areas must be calculated based on the N crop needs, and annual application must be avoided to prevent over applications.

  18. Analysis of physical properties controlling steady-state infiltration rates on tropical savannah soils

    International Nuclear Information System (INIS)

    Mbagwu, J.S.C.

    1993-10-01

    A knowledge of physical properties influencing the steady-state infiltration rates (ic) of soils is needed for the hydrologic modelling of the infiltration process. In this study evidence is provided to show that effective porosity (Pe) (i.e. the proportion of macro pore spaces with equivalent radius of > 15 μm) and dry bulk density are the most important soil physical properties controlling the steady-state infiltration rates on a tropical savannah with varying land use histories. At a macro porosity value of ≤ 5.0% the steady-state infiltration rate is zero. Total porosity and the proportion of water-retaining pores explained only a small fraction of the variation in this property. Steady-state infiltration rates can also be estimated from either the saturated hydraulic conductivity (Ks) by the equation, i c = 31.1 + 1.06 (Ks), (R 2 = 0.8104, p ≤ 0.001) or the soil water transmissivity (A) by the equation, i c = 30.0 + 29.9(A), (R 2 = 0.8228, ρ ≤ 0.001). The Philip two-parameter model under predicted steady-state infiltration rates generally. Considering the ease of determination and reliability it is suggested that effective porosity be used to estimate the steady-state infiltration rates of these other soils with similar characteristics. The model is, i c 388.7(Pe) - 10.8(R 2 = 0.7265, p ≤ 0.001) where i c is in (cm/hr) and Pe in (cm 3 /cm 3 ). (author). 20 refs, 3 figs, 4 tabs

  19. Electrochemical techniques implementation for corrosion rate measurement in function of humidity level in grounding systems (copper and stainless steel) in soil samples from Tunja (Colombia)

    Science.gov (United States)

    Salas, Y.; Guerrero, L.; Blanco, J.; Jimenez, C.; Vera-Monroy, S. P.; Mejía-Camacho, A.

    2017-12-01

    In this work, DC electrochemical techniques were used to determine the corrosion rate of copper and stainless-steel electrodes used in grounding, varying the level of humidity, in sandy loam and clay loam soils. The maximum corrosion potentials were: for copper -211 and -236mV and for stainless steel of -252 and -281mV, in sandy loam and clay loam respectively, showing that in sandy loam the values are higher, about 30mV. The mechanism by which steel controls corrosion is by diffusion, whereas in copper it is carried out by transfer of mass and charge, which affects the rate of corrosion, which in copper reached a maximum value of 5mm/yr and in Steel 0.8mm/yr, determined by Tafel approximations. The behaviour of the corrosion rate was mathematically adjusted to an asymptotic model that faithfully explains the C.R. as a function of humidity, however, it is necessary to define the relation between the factor □ established in the model and the precise characteristics of the soil, such as the permeability or quantity of ions present.

  20. A simple daily soil-water balance model for estimating the spatial and temporal distribution of groundwater recharge in temperate humid areas

    Science.gov (United States)

    Dripps, W.R.; Bradbury, K.R.

    2007-01-01

    Quantifying the spatial and temporal distribution of natural groundwater recharge is usually a prerequisite for effective groundwater modeling and management. As flow models become increasingly utilized for management decisions, there is an increased need for simple, practical methods to delineate recharge zones and quantify recharge rates. Existing models for estimating recharge distributions are data intensive, require extensive parameterization, and take a significant investment of time in order to establish. The Wisconsin Geological and Natural History Survey (WGNHS) has developed a simple daily soil-water balance (SWB) model that uses readily available soil, land cover, topographic, and climatic data in conjunction with a geographic information system (GIS) to estimate the temporal and spatial distribution of groundwater recharge at the watershed scale for temperate humid areas. To demonstrate the methodology and the applicability and performance of the model, two case studies are presented: one for the forested Trout Lake watershed of north central Wisconsin, USA and the other for the urban-agricultural Pheasant Branch Creek watershed of south central Wisconsin, USA. Overall, the SWB model performs well and presents modelers and planners with a practical tool for providing recharge estimates for modeling and water resource planning purposes in humid areas. ?? Springer-Verlag 2007.

  1. Tropical forest response to a drier future: Measurement and modeling of soil organic matter stocks and turnover

    Science.gov (United States)

    Finstad, K. M.; Campbell, A.; Pett-Ridge, J.; Zhang, N.; McFarlane, K. J.

    2017-12-01

    Tropical forests account for over 50% of the global terrestrial carbon sink and 29% of global soil carbon, but the stability of carbon in these ecosystems under a changing climate is unknown. Recent work suggests moisture may be more important than temperature in driving soil carbon storage and emissions in the tropics. However, data on belowground carbon cycling in the tropics is sparse, and the role of moisture on soil carbon dynamics is underrepresented in current land surface models limiting our ability to extrapolate from field experiments to the entire region. We measured radiocarbon (14C) and calculated turnover rates of organic matter from 37 soil profiles from the Neotropics including sites in Mexico, Brazil, Costa Rica, Puerto Rico, and Peru. Our sites represent a large range of moisture, spanning 710 to 4200 mm of mean annual precipitation, and include Andisols, Oxisols, Inceptisols, and Ultisols. We found a large range in soil 14C profiles between sites, and in some locations, we also found a large spatial variation within a site. We compared measured soil C stocks and 14C profiles to data generated from the Community Land Model (CLM) v.4.5 and have begun to generate data from the ACME Land Model (ALM) v.1. We found that the CLM consistently overestimated carbon stocks and the mean age of soil carbon at the surface (upper 50 cm), and underestimated the mean age of deep soil carbon. Additionally, the CLM did not capture the variation in 14C and C stock profiles that exists between and within the sites across the Neotropics. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-736060.

  2. Changes in the Diversity of Soil Arbuscular Mycorrhizal Fungi after Cultivation for Biofuel Production in a Guantanamo (Cuba) Tropical System

    Science.gov (United States)

    Alguacil, Maria del Mar; Torrecillas, Emma; Hernández, Guillermina; Roldán, Antonio

    2012-01-01

    The arbuscular mycorrhizal fungi (AMF) are a key, integral component of the stability, sustainability and functioning of ecosystems. In this study, we characterised the AMF biodiversity in a native vegetation soil and in a soil cultivated with Jatropha curcas or Ricinus communis, in a tropical system in Guantanamo (Cuba), in order to verify if a change of land use to biofuel plant production had any effect on the AMF communities. We also asses whether some soil properties related with the soil fertility (total N, Organic C, microbial biomass C, aggregate stability percentage, pH and electrical conductivity) were changed with the cultivation of both crop species. The AM fungal small sub-unit (SSU) rRNA genes were subjected to PCR, cloning, sequencing and phylogenetic analyses. Twenty AM fungal sequence types were identified: 19 belong to the Glomeraceae and one to the Paraglomeraceae. Two AMF sequence types related to cultured AMF species (Glo G3 for Glomus sinuosum and Glo G6 for Glomus intraradices-G. fasciculatum-G. irregulare) did not occur in the soil cultivated with J. curcas and R. communis. The soil properties (total N, Organic C and microbial biomass C) were higher in the soil cultivated with the two plant species. The diversity of the AMF community decreased in the soil of both crops, with respect to the native vegetation soil, and varied significantly depending on the crop species planted. Thus, R. communis soil showed higher AMF diversity than J. curcas soil. In conclusion, R. communis could be more suitable for the long-term conservation and sustainable management of these tropical ecosytems. PMID:22536339

  3. Changes in the diversity of soil arbuscular mycorrhizal fungi after cultivation for biofuel production in a Guantanamo (Cuba tropical system.

    Directory of Open Access Journals (Sweden)

    Maria del Mar Alguacil

    Full Text Available The arbuscular mycorrhizal fungi (AMF are a key, integral component of the stability, sustainability and functioning of ecosystems. In this study, we characterised the AMF biodiversity in a native vegetation soil and in a soil cultivated with Jatropha curcas or Ricinus communis, in a tropical system in Guantanamo (Cuba, in order to verify if a change of land use to biofuel plant production had any effect on the AMF communities. We also asses whether some soil properties related with the soil fertility (total N, Organic C, microbial biomass C, aggregate stability percentage, pH and electrical conductivity were changed with the cultivation of both crop species. The AM fungal small sub-unit (SSU rRNA genes were subjected to PCR, cloning, sequencing and phylogenetic analyses. Twenty AM fungal sequence types were identified: 19 belong to the Glomeraceae and one to the Paraglomeraceae. Two AMF sequence types related to cultured AMF species (Glo G3 for Glomus sinuosum and Glo G6 for Glomus intraradices-G. fasciculatum-G. irregulare did not occur in the soil cultivated with J. curcas and R. communis. The soil properties (total N, Organic C and microbial biomass C were higher in the soil cultivated with the two plant species. The diversity of the AMF community decreased in the soil of both crops, with respect to the native vegetation soil, and varied significantly depending on the crop species planted. Thus, R. communis soil showed higher AMF diversity than J. curcas soil. In conclusion, R. communis could be more suitable for the long-term conservation and sustainable management of these tropical ecosytems.

  4. Analyses of the influencing factors of soil microbial functional gene diversity in tropical rainforest based on GeoChip 5.0.

    Science.gov (United States)

    Cong, Jing; Liu, Xueduan; Lu, Hui; Xu, Han; Li, Yide; Deng, Ye; Li, Diqiang; Zhang, Yuguang

    2015-09-01

    To examine soil microbial functional gene diversity and causative factors in tropical rainforests, we used a microarray-based metagenomic tool named GeoChip 5.0 to profile it. We found that high microbial functional gene diversity and different soil microbial metabolic potential for biogeochemical processes were considered to exist in tropical rainforest. Soil available nitrogen was the most associated with soil microbial functional gene structure. Here, we mainly describe the experiment design, the data processing, and soil biogeochemical analyses attached to the study in details, which could be published on BMC microbiology Journal in 2015, whose raw data have been deposited in NCBI's Gene Expression Omnibus (accession number GSE69171).

  5. Changes in soil biological quality under legume- and maize-based farming systems in a humid savanna zone of Côte d’Ivoire

    Directory of Open Access Journals (Sweden)

    Tano Y.

    2008-01-01

    Full Text Available Studying the impact of farming systems on soil status is essential in determining the most relevant for a given agroecological zone. A trial was conducted in a West Africa humid savanna, aiming at assessing the short-term effects of farming systems on soil (0-10 cm organic carbon (SOC content and some soil microbiological properties. A randomized complete block experimental design with three replications, and the following treatments were used: Mucuna pruriens (Mucuna, Pueraria phaseoloides (Pueraria, Lablab purpureus (Lablab, a combination of these three legumes (Mixed-legumes, maize + urea (Maize-U, maize + triple super phosphate (Maize-Sp, maize + urea + triple super phosphate (Maize-USp, fertilizer-free maize continuous cropping (Maize-Tradi. Results indicated that SOC content was improved over time under legume-based systems. The relative increase was the highest with the legume association and Lablab, where SOC varied from 7.5 to 8.6 g.kg-1 (i.e. 14.7% and from 7.2 to 8.3 g.kg-1 (i.e. 15.3% respectively, between the start and the end of the trial. Besides, applying grass and maize residues as mulch on the ground, in association with inorganic fertilizers may be a way of improving SOC content in the short-term. Although legume-based systems exhibited highest values, microbial biomass carbon (MBC did not show any statistical significant differences between treatments. However, soil C mineralization and soil specific respiration were influenced by the farming systems, with higher mean values under legume-based systems (42 ± 7.6 mg C-CO2.g-1 Corg and 0.4 mg C-CO2.g-1 biomass C, respectively, compared to maize continuous cropping systems (33.1 ± 1.6 mg C-CO2.g-1 Corg and 0.3 mg C-CO2.g-1 biomass C, respectively. Thus, these parameters can be used as sensitive indicators of the early changes in soil organic matter quality. The integration of legumes cover crops in farming systems may contribute to improve soil quality that would lead to

  6. Soil carbon dioxide emissions from a rubber plantation on tropical peat.

    Science.gov (United States)

    Wakhid, Nur; Hirano, Takashi; Okimoto, Yosuke; Nurzakiah, Siti; Nursyamsi, Dedi

    2017-03-01

    Land-use change in tropical peatland potentially results in a large amount of carbon dioxide (CO 2 ) emissions owing to drainage, which lowers groundwater level (GWL) and consequently enhances oxidative peat decomposition. However, field information on carbon balance is lacking for rubber plantations, which are expanding into Indonesia's peatlands. To assess soil CO 2 emissions from an eight-year-old rubber plantation established on peat after compaction, soil CO 2 efflux was measured monthly using a closed chamber system from December 2014 to December 2015, in which a strong El Niño event occurred, and consequently GWL lowered deeply. Total soil respiration (SR) and oxidative peat decomposition (PD) were separately quantified by trenching. In addition, peat surface elevation was measured to determine annual subsidence along with GWL. With GWL, SR showed a negative logarithmic relationship (p0.05). Peat surface elevation varied seasonally in almost parallel with GWL. After correcting for GWL difference, annual total subsidence was determined at 5.64±3.20 and 5.96±0.43cmyr -1 outside and inside the trenching, respectively. Annual subsidence only through peat oxidation that was calculated from the annual PD, peat bulk density and peat carbon content was 1.50cmyr -1 . As a result, oxidative peat decomposition accounted for 25% of total subsidence (5.96cmyr -1 ) on average on an annual basis. The contribution of peat oxidation was lower than those of previous studies probably because of compaction through land preparation. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Characterization of Trapped Lignin-Degrading Microbes in Tropical Forest Soil

    Energy Technology Data Exchange (ETDEWEB)

    DeAngelis, Kristen; Allgaier, Martin; Chavarria, Yaucin; Fortney, Julian; Hugenholtz, Phillip; Simmons, Blake; Sublette, Kerry; Silver, Whendee; Hazen, Terry

    2011-07-14

    Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in the soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition.

  8. Characterization of trapped lignin-degrading microbes in tropical forest soil

    Energy Technology Data Exchange (ETDEWEB)

    DeAngelis, K.M.; Allgaier, M.; Chavarria, Y.; Fortney, J.L.; Hugenholz, P.; Simmons, B.; Sublette, K.; Silver, W.L.; Hazen, T.C.

    2011-03-01

    Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in the soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition.

  9. 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.

  10. Effects of different management regimes on soil erosion and surface runoff in semi-arid to sub-humid rangelands

    NARCIS (Netherlands)

    Oudenhoven, van A.P.E.; Veerkamp, C.J.; Alkemade, Rob; Leemans, Rik

    2015-01-01

    Over one billion people's livelihoods depend on dry rangelands through livestock grazing and agriculture. Livestock grazing and other management activities can cause soil erosion, increase surface runoff and reduce water availability. We studied the effects of different management regimes on soil

  11. Farm management, not soil microbial diversity, controls nutrient loss from smallholder tropical agriculture

    Directory of Open Access Journals (Sweden)

    Stephen A Wood

    2015-03-01

    Full Text Available Tropical smallholder agriculture supports the livelihoods of over 900 million of the world’s poorest people. This form of agriculture is undergoing rapid transformation in nutrient cycling pathways as international development efforts strongly promote greater use of mineral fertilizers to increase crop yields. These changes in nutrient availability may alter the composition of microbial communities with consequences for rates of biogeochemical processes that control nutrient losses to the environment. Ecological theory suggests that altered microbial diversity will strongly influence processes performed by relatively few microbial taxa, such as denitrification and hence nitrogen losses as nitrous oxide, a powerful greenhouse gas. Whether this theory helps predict nutrient losses from agriculture depends on the relative effects of microbial community change and increased nutrient availability on ecosystem processes. We find that mineral and organic nutrient addition to smallholder farms in Kenya alters the taxonomic and functional diversity of soil microbes. However, we find that the direct effects of farm management on both denitrification and carbon mineralization are greater than indirect effects through changes in the taxonomic and functional diversity of microbial communities. Changes in functional diversity are strongly coupled to changes in specific functional genes involved in denitrification, suggesting that it is the expression, rather than abundance, of key functional genes that can serve as an indicator of ecosystem process rates. Our results thus suggest that widely used broad summary statistics of microbial diversity based on DNA may be inappropriate for linking microbial communities to ecosystem processes in certain applied settings. Our results also raise doubts about the relative control of microbial composition compared to direct effects of management on nutrient losses in applied settings such as tropical agriculture.

  12. Impact of soil characteristics and land use on pipe erosion in a temperate humid climate: Field studies in Belgium

    Science.gov (United States)

    Verachtert, E.; Van Den Eeckhaut, M.; Martínez-Murillo, J. F.; Nadal-Romero, E.; Poesen, J.; Devoldere, S.; Wijnants, N.; Deckers, J.

    2013-06-01

    This study investigates the role of soil characteristics and land use in the development of soil pipes in the loess belt of Belgium. First, we tested the hypothesis that discontinuities in the soil profile enhance lateral flow and piping by impeding vertical infiltration. We focus on discontinuities in soil characteristics that can vary with soil depth, including texture, saturated hydraulic conductivity, penetration resistance, and bulk density. These characteristics as well as soil biological activity were studied in detail on 12 representative soil profiles for different land use types. Twelve sites were selected in the Flemish Ardennes (Belgium): four pastures with collapsed pipes (CP), four pastures without CP, two sites under arable land without CP and two sites under forest without CP. Secondly, this study aimed at evaluating the interaction of groundwater table positions (through soil augerings) and CP in a larger area, with a focus on pastures. Pasture is the land use where almost all CP in the study area are observed. Therefore, the position of the groundwater table was compared for 15 pastures with CP and 14 pastures without CP, having comparable topographical characteristics in terms of slope gradient and contributing area. Finally, the effect of land use history on the occurrence of pipe collapse was evaluated for a database of 84 parcels with CP and 84 parcels without CP, currently under pasture. As to the first hypothesis, no clear discontinuities for abiotic soil characteristics in soil profiles were observed at the depth where pipes occur, but pastures with CP had significantly more earthworm channels and mole burrows at larger depths (> 120 cm: mean of > 200 earthworm channels per m2) than pastures without CP, arable land or forest (> 120 cm depth, a few or no earthworm channels left). The land use history appeared to be similar for the pastures with and without CP. Combining all results from soil profiles and soil augering indicates that intense

  13. EDITORIAL: Humidity sensors Humidity sensors

    Science.gov (United States)

    Regtien, Paul P. L.

    2012-01-01

    All matter is more or less hygroscopic. The moisture content varies with vapour concentration of the surrounding air and, as a consequence, most material properties change with humidity. Mechanical and thermal properties of many materials, such as the tensile strength of adhesives, stiffness of plastics, stoutness of building and packaging materials or the thermal resistivity of isolation materials, all decrease with increasing environmental humidity or cyclic humidity changes. The presence of water vapour may have a detrimental influence on many electrical constructions and systems exposed to humid air, from high-power systems to microcircuits. Water vapour penetrates through coatings, cable insulations and integrated-circuit packages, exerting a fatal influence on the performance of the enclosed systems. For these and many other applications, knowledge of the relationship between moisture content or humidity and material properties or system behaviour is indispensable. This requires hygrometers for process control or test and calibration chambers with high accuracy in the appropriate temperature and humidity range. Humidity measurement methods can roughly be categorized into four groups: water vapour removal (the mass before and after removal is measured); saturation (the air is brought to saturation and the `effort' to reach that state is measured); humidity-dependent parameters (measurement of properties of humid air with a known relation between a specific property and the vapour content, for instance the refractive index, electromagnetic spectrum and acoustic velocity); and absorption (based on the known relation between characteristic properties of non-hydrophobic materials and the amount of absorbed water from the gas to which these materials are exposed). The many basic principles to measure air humidity are described in, for instance, the extensive compilations by Wexler [1] and Sonntag [2]. Absorption-type hygrometers have small dimensions and can be

  14. The magnitude and persistence of soil NO, N20, CH4, and C02 fluxes from burned tropical savanna in Brazil

    Science.gov (United States)

    Mark Poth; Iris Cofman Anderson; Heloisa Sinatora Miranda; Antonia Carlos Miranda; Philip J. Riggan

    1995-01-01

    Among all global ecosystems, tropical savannas are the most severely and extensively affected by anthropogenic burning. Frequency of fire in cerrado, a type of tropical savanna covering 25% of Brazil, is 2 to 4 years. In 1992 we measured soil fluxes of NO, N20, CH4, and C02 from cerrado sites that had...

  15. Root-induced Changes in the Rhizosphere of Extreme High Yield Tropical Rice: 2. Soil Solution Chemical Properties

    Directory of Open Access Journals (Sweden)

    Mitsuru Osaki

    2012-09-01

    Full Text Available Our previous studies showed that the extreme high yield tropical rice (Padi Panjang produced 3-8 t ha-1 without fertilizers. We also found that the rice yield did not correlate with some soil properties. We thought that it may be due to ability of root in affecting soil properties in the root zone. Therefore, we studied the extent of rice root in affecting the chemical properties of soil solution surrounding the root zone. A homemade rhizobox (14x10x12 cm was used in this experiment. The rhizobox was vertically segmented 2 cm interval using nylon cloth that could be penetrated neither root nor mycorrhiza, but, soil solution was freely passing the cloth. Three soils of different origins (Kuin, Bunipah and Guntung Papuyu were used. The segment in the center was sown with 20 seeds of either Padi Panjang or IR64 rice varieties. After emerging, 10 seedlings were maintained for 5 weeks. At 4 weeks after sowing, some chemical properties of the soil solution were determined. These were ammonium (NH4+, nitrate (NO3-, phosphorus (P and iron (Fe2+ concentrations and pH, electric conductivity (EC and oxidation reduction potential (ORP. In general, the plant root changed solution chemical properties both in- and outside the soil rhizosphere. The patterns of changes were affected by the properties of soil origins. The release of exudates and change in ORP may have been responsible for the changes soil solution chemical properties.

  16. Iron addition to soil specifically stabilized lignin

    Science.gov (United States)

    Steven J. Hall; Whendee L. Silver; Vitaliy I. Timokhin; Kenneth E. Hammel

    2016-01-01

    The importance of lignin as a recalcitrant constituent of soil organic matter (SOM) remains contested. Associations with iron (Fe) oxides have been proposed to specifically protect lignin from decomposition, but impacts of Fe-lignin interactions on mineralization rates remain unclear. Oxygen (O2) fluctuations characteristic of humid tropical...

  17. Isolation of a novel strain of Planomicrobium chinense from diesel contaminated soil of tropical environment.

    Science.gov (United States)

    Das, Reena; Tiwary, Bhupendra N

    2013-09-01

    A novel bacterial strain (B6) degrading high concentration of diesel oil [up to 2.5% (v/v)] was isolated from a site contaminated with petroleum hydrocarbons in the state of Chhattisgarh, India. The strain demonstrated efficient degradation for diesel oil range alkanes (C14 to C36 i.e., mostly linear chain alkanes). It was identified to be 99% similar to Planomicrobium chinense on the basis of partial 16S rRNA gene sequencing and biochemical characteristics. The efficiency of degradation was optimized at pH 7.2 and temperature at 32 °C. GC analysis demonstrated complete mineralization of higher chain alkanes into lower chain alkanes within 96 h. The organism also displayed surface tension reduction by producing stable emulsification on the onset of stationary phase. A multidimensional characteristics of the strain to grow at a high temperature range, resistance to various heavy metals as well as tolerance to moderate concentration of NaCl makes it suitable for bioremediation of soil contaminated with diesel oil in tropical environment. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Different hydraulic traits of woody plants from tropical forests with contrasting soil water availability.

    Science.gov (United States)

    Zhu, Shi-Dan; Chen, Ya-Jun; Fu, Pei-Li; Cao, Kun-Fang

    2017-11-01

    In southwestern China, tropical karst forests (KF) and non-karst rain forests (NKF) have different species composition and forest structure owing to contrasting soil water availability, but with a few species that occur in both forests. Plant hydraulic traits are important for understanding the species' distribution patterns in these two forest types, but related studies are rare. In this study, we investigated hydraulic conductivity, vulnerability to drought-induced cavitation and wood anatomy of 23 abundant and typical woody species from a KF and a neighboring NKF, as well as two Bauhinia liana species common to both forests. We found that the KF species tended to have higher sapwood density, smaller vessel diameter, lower specific hydraulic conductivity (ks) and leaf to sapwood area ratio, and were more resistant to cavitation than NKF species. Across the 23 species distinctly occurring in either KF or NKF, there was a significant tradeoff between hydraulic efficiency and safety, which might be an underlying mechanism for distributions of these species across the two forests. Interestingly, by possessing rather large and long vessels, the two Bauhinia liana species had extremely high ks but were also high resistance to cavitation (escaping hydraulic tradeoff). This might be partially due to their distinctly dimorphic vessels, but contribute to their wide occurrence in both forests. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  19. Geoecohydrological mechanisms couple soil and leaf water dynamics and facilitate species coexistence in shallow soils of a tropical semiarid mixed forest.

    Science.gov (United States)

    Rodríguez-Robles, Ulises; Arredondo, J Tulio; Huber-Sannwald, Elisabeth; Vargas, Rodrigo

    2015-07-01

    Trees growing on shallow rocky soils must have exceptional adaptations when underlying weathered bedrock has no deep fractures for water storage. Under semiarid conditions, hydrology of shallow soils is expected to decouple from plant hydrology, as soils dry out as a result of rapid evaporation and competition for water increases between coexisting tree species. Gas exchange and plant-water relations were monitored for 15 months for Pinus cembroides and Quercus potosina tree species in a tropical semiarid forest growing on c. 20-cm-deep soils over impermeable volcanic bedrock. Soil and leaf water potential maintained a relatively constant offset throughout the year in spite of high intra-annual fluctuations reaching up to 5 MPa. Thus, hydrology of shallow soils did not decouple from hydrology of trees even in the driest period. A combination of redistribution mechanisms of water stored in weathered bedrock and hypodermic flow accessible to oak provided the source of water supply to shallow soils, where most of the actively growing roots occurred. This study demonstrates a unique geoecohydrological mechanism that maintains a tightly coupled hydrology between shallow rocky soils and trees, as well as species coexistence in this mixed forest, where oak facilitates water access to pine. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  20. Soils Newsletter. V. 15, no. 2

    International Nuclear Information System (INIS)

    1992-12-01

    This newsletter contains reports of the five Research Co-ordination Meetings held in 1992; the descriptions of the meetings on ''The use of nuclear and related techniques in the management of nitrogen-fixing trees for enhancing soil fertility and soil conservation'' and ''The use of isotope studies on increasing and stabilizing plant productivity in low phosphate and semi-arid and sub-humid soils of the tropics and sub-tropics'' contain excerpts from presented reports. Also included is a feature on some of the the Technical Co-operation Projects coming under the umbrella of the Regional African Project on Biological Nitrogen Fixation

  1. Impacts of afforestation and silviculture on the soil C balance of tropical tree plantations: belowground C allocation, soil CO2 efflux and C accretion (Invited)

    Science.gov (United States)

    Epron, D.; Koutika, L.; Mareschal, L.; Nouvellon, Y.

    2013-12-01

    Tropical forest plantations will provide a large part of the global wood supply which is anticipated to increase sharply in the next decades, becoming a valuable source of income in many countries, where they also contribute to land use changes that impact the global carbon (C) cycle. Tropical forest plantations established on previous grasslands are potential C sinks offsetting anthropogenic CO2 emissions. When they are managed on short rotations, the aboveground biomass is frequently removed and transformed into wood products with short lifetimes. The soil is thus the only compartment for durable C sequestration. The soil C budget results from the inputs of C from litterfall, root turnover and residues left at logging stage, balanced by C losses through heterotrophic respiration and leaching of organic C with water flow. Intensive researches have been conducted these last ten years in eucalypt plantations in the Congo on the effects of management options on soil fertility improvement and C sequestration. Our aim is to review important results regarding belowground C allocation, soil CO2 efflux and C accretion in relation to management options. We will specifically address (i) the soil C dynamics after afforestation of a tropical savannah, (ii) the impact of post-harvest residue management, and (iii) the beneficial effect of introducing nitrogen fixing species for C sequestration. Our results on afforestation of previous savannah showed that mechanical soil disturbance for site preparation had no effect on soil CO2 efflux and soil C balance. Soil C increased after afforestation despite a rapid disappearance of the labile savannah-derived C because a large fraction of savannah-derived C is stable and the aboveground litter layer is as the major source of CO2 contributing to soil CO2 efflux. We further demonstrated that the C stock in and on the soil slightly increased after each rotation when large amounts of residues are left at logging stage and that most of

  2. Restoration of soil fertility and improvement of cropping systems for sustainable development in the humid savannahs of the Ivory Coast

    International Nuclear Information System (INIS)

    Bachmann, T.

    2000-01-01

    In late 1998, FAO launched a Technical Co-operation Project to assist the government of the Ivory Coast in rural development by promoting agricultural production as the main source of economic growth, and by improving the management of natural resources. The sustainable development of the humid-savannah region and western highlands is being allotted primary consideration. The goal of the project is to replace traditional shifting cultivation with more-sustainable production systems. This paper describes the origins and scope of the problem and the research strategies being considered and employed. The project will be executed in three phases: constraint analysis and formulation of a pilot project, execution of the pilot project (1999-2003), and long-term extension (15 years) from 2004, based on the data generated in the pilot phase. (author)

  3. Restoration of soil fertility and improvement of cropping systems for sustainable development in the humid savannahs of the Ivory Coast

    Energy Technology Data Exchange (ETDEWEB)

    Bachmann, T [Food and Agriculture Organization of the United Nations, Rome (Italy)

    2000-06-01

    In late 1998, FAO launched a Technical Co-operation Project to assist the government of the Ivory Coast in rural development by promoting agricultural production as the main source of economic growth, and by improving the management of natural resources. The sustainable development of the humid-savannah region and western highlands is being allotted primary consideration. The goal of the project is to replace traditional shifting cultivation with more-sustainable production systems. This paper describes the origins and scope of the problem and the research strategies being considered and employed. The project will be executed in three phases: constraint analysis and formulation of a pilot project, execution of the pilot project (1999-2003), and long-term extension (15 years) from 2004, based on the data generated in the pilot phase. (author)

  4. Evaluation of deoxyribonucleic acid (DNA) isolated from human bloodstains exposed to ultraviolet light, heat, humidity, and soil contamination

    International Nuclear Information System (INIS)

    McNally, L.; Shaler, R.C.; Baird, M.; Balazs, I.; De Forest, P.; Kobilinsky, L.

    1989-01-01

    This study was designed to analyze the effects of common environmental insults on the ability to obtain deoxyribonucleic acid (DNA) restriction fragment-length polymorphisms (RFLP) patterns from laboratory prepared specimens. The environmental conditions studied include the exposure of dried bloodstains to varying amounts of relative humidity (0, 33, 67, and 98%), heat (37 degree C), and ultraviolet light for periods of up to five days. In addition, the effect of drying over a four-day period in whole blood collected with and without ethylenediaminetetraacetate (EDTA) was examined. The results of the study showed that, under the conditions studied, the integrity of DNA is not altered such that false RFLP patterns are obtained. The only effect observed was that the overall RFLP pattern becomes weaker, but individual RFLP fragments are neither created nor destroyed

  5. Disentangling the long-term effects of disturbance on soil biogeochemistry in a wet tropical forest ecosystem.

    Science.gov (United States)

    Gutiérrez Del Arroyo, Omar; Silver, Whendee L

    2018-04-01

    Climate change is increasing the intensity of severe tropical storms and cyclones (also referred to as hurricanes or typhoons), with major implications for tropical forest structure and function. These changes in disturbance regime are likely to play an important role in regulating ecosystem carbon (C) and nutrient dynamics in tropical and subtropical forests. Canopy opening and debris deposition resulting from severe storms have complex and interacting effects on ecosystem biogeochemistry. Disentangling these complex effects will be critical to better understand the long-term implications of climate change on ecosystem C and nutrient dynamics. In this study, we used a well-replicated, long-term (10 years) canopy and debris manipulation experiment in a wet tropical forest to determine the separate and combined effects of canopy opening and debris deposition on soil C and nutrients throughout the soil profile (1 m). Debris deposition alone resulted in higher soil C and N concentrations, both at the surface (0-10 cm) and at depth (50-80 cm). Concentrations of NaOH-organic P also increased significantly in the debris deposition only treatment (20-90 cm depth), as did NaOH-total P (20-50 cm depth). Canopy opening, both with and without debris deposition, significantly increased NaOH-inorganic P concentrations from 70 to 90 cm depth. Soil iron concentrations were a strong predictor of both C and P patterns throughout the soil profile. Our results demonstrate that both surface- and subsoils have the potential to significantly increase C and nutrient storage a decade after the sudden deposition of disturbance-related organic debris. Our results also show that these effects may be partially offset by rapid decomposition and decreases in litterfall associated with canopy opening. The significant effects of debris deposition on soil C and nutrient concentrations at depth (>50 cm), suggest that deep soils are more dynamic than previously believed, and can serve as

  6. Lead and stable Pb-isotope characteristics of tropical soils in north-eastern Brazil

    International Nuclear Information System (INIS)

    Schucknecht, Anne; Matschullat, Jörg; Reimann, Clemens

    2011-01-01

    Stable Pb-isotope ratios are widely used as tracers for Pb-sources in the environment. Recently, a few publications have challenged the predominating view of environmental applications of Pb-isotopes. Present applications of Pb-isotopic tracers in soils largely represent the northern hemisphere. This study focuses on tropical soils from Paraíba, north-eastern Brazil. Lead concentrations and Pb-isotopic signatures (both 7N HNO 3 ) were determined at 30 sites along a 327 km E–W-transect, from the Atlantic coast at João Pessoa to some kilometers west of Patos, to identify possible processes for the observed (and anticipated) distribution pattern. Thirty samples each of litter (ORG) and top mineral soil (TOP) were taken on pasture land at suitable distance from roads or other potential contamination sources. Lead-content was determined by inductively-coupled plasma atomic emission spectrometry (ICP-AES) and the ratios of 206 Pb/ 207 Pb, 206 Pb/ 208 Pb, and 208 Pb/ 207 Pb by ICP-sector field mass spectrometry (ICP-SFMS). Both sample materials show similarly low Pb-concentrations with a lower median in the ORG samples (ORG 3.4 mg kg −1 versus TOP 6.9 mg kg −1 ). The 206 Pb/ 207 Pb ratios revealed a large spread along the transect with median 206 Pb/ 207 Pb ratios of 1.160 (ORG) and 1.175 (TOP). The 206 Pb/ 207 Pb ratios differ noticeably between sample sites located in the Atlantic Forest biome along the coast and sample sites in the inland Caatinga biome. The “forest” sites were characterised by a significant lower median and a lower spread in the 206 Pb/ 207 Pb and 206 Pb/ 208 Pb ratios compared to the Caatinga sites. Results indicate a very restricted influence of anthropogenic activities (individual sites only). The main process influencing the spatial variability of Pb-isotope ratios is supposed to be precipitation-dependent bioproductivity and weathering.

  7. On the Breeding of Bivoltine Breeds of the Silkworm, Bombyx mori L. (Lepidoptera: Bombycidae, Tolerant to High Temperature and High Humidity Conditions of the Tropics

    Directory of Open Access Journals (Sweden)

    Harjeet Singh

    2010-01-01

    Full Text Available The hot climatic conditions of tropics prevailing particularly in summer are contributing to the poor performance of the bivoltine breeds and the most important aspect is that many quantitative characters such as viability and cocoon traits decline sharply when temperature is high. Hence, in a tropical country like India, it is very essential to develop bivoltine breeds/hybrids which can withstand the high temperature stress conditions. This has resulted in the development of CSR18 × CSR19, compatible hybrid for rearing throughout the year by utilizing Japanese thermotolerant hybrids as breeding resource material. Though, the introduction of CSR18 × CSR19 in the field during summer months had considerable impact, the productivity level and returns realized do not match that of other productive CSR hybrids. Therefore, the acceptance level of this hybrid with the farmers was not up to the expected level. This has necessitated the development of a temperature tolerant hybrid with better productivity traits than CSR18 × CSR19. Though, it was a difficult task to break the negative correlation associated with survival and productivity traits, attempts on this line had resulted in the development of CSR46 × CSR47, a temperature tolerant bivoltine hybrid with better productivity traits than CSR18 × CSR19. However, though, these hybrids are tolerant to high temperature environments, they are not tolerant to many of the silkworm diseases. Keeping this in view, an attempt is made to develop silkworm hybrids tolerant to high temperature environments.

  8. Effect of Interactions on the Nutrient Status of a Tropical Soil Treated with Green Manures and Inorganic Phosphate Fertilizers

    Directory of Open Access Journals (Sweden)

    Abdul R. Bah

    2004-01-01

    Full Text Available Integrated nutrient management systems using plant residues and inorganic P fertilizers have high potential for increasing crop production and ensuring sustainability in the tropics, but their adoption requires in-depth understanding of nutrient dynamics in such systems. This was examined in a highly weathered tropical soil treated with green manures (GMs and P fertilizers in two experiments conducted in the laboratory and glasshouse. The treatments were factorial combinations of the GMs (Calopogonium caeruleum, Gliricidia sepium, and Imperata cylindrica and P fertilizers (phosphate rocks [PRs] from North Carolina, China, and Algeria, and triple superphosphate replicated thrice. Olsen P, mineral N, pH, and exchangeable K, Ca, and Mg were monitored in a laboratory incubation study for 16 months. The change in soil P fractions and available P was also determined at the end of the study. Phosphorus available from the amendments was quantified at monthly intervals for 5 months by 33P-32P double isotopic labeling in the glasshouse using Setaria sphacelata as test crop. The GMs were labeled with 33P to determine their contribution to P taken up by Setaria, while that from the P fertilizers was indirectly measured by labeling the soil with 32P. The P fertilizers hardly changed Olsen P and exchangeable cations during 16 months of incubation. The legume GMs and legume GM+P did not change Olsen P, lowered exchangeable Ca, and increased exchangeable K about threefold (4.5 cmol[+]kg−1 soil in the first 4 months, even as large amounts of NH4-N accumulated (~1000 mg kg soil−1 and soil pH increased to more than 6.5. Afterwards, Olsen P and exchangeable Ca and Mg increased (threefold as NH4+-N and soil pH declined. The legume GMs also augmented reversibly sorbed P in Al-P and Fe-P fractions resulting in high residual effect in the soil, while fertilizer-P was irreversibly retained. The GMs increased PR-P utilization by 40 to over 80%, mobilized soil P, and

  9. Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest

    Science.gov (United States)

    Itoh, M.; Kosugi, Y.; Takanashi, S.; Hayashi, Y.; Kanemitsu, S.; Osaka, K.; Tani, M.; Nik, A. R.

    2010-09-01

    To clarify the factors controlling temporal and spatial variations of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, we investigated these gas fluxes and environmental factors in a tropical rainforest in Peninsular Malaysia. Temporal variation of CO2 flux in a 2-ha plot was positively related to soil water condition and rainfall history. Spatially, CO2 flux was negatively related to soil water condition. When CO2 flux hotspots were included, no other environmental factors such as soil C or N concentrations showed any significant correlation. Although the larger area sampled in the present study complicates explanations of spatial variation of CO2 flux, our results support a previously reported bipolar relationship between the temporal and spatial patterns of CO2 flux and soil water condition observed at the study site in a smaller study plot. Flux of CH4 was usually negative with little variation, resulting in the soil at our study site functioning as a CH4 sink. Both temporal and spatial variations of CH4 flux were positively related to the soil water condition. Soil N concentration was also related to the spatial distribution of CH4 flux. Some hotspots were observed, probably due to CH4 production by termites, and these hotspots obscured the relationship between both temporal and spatial variations of CH4 flux and environmental factors. Temporal variation of N2O flux and soil N2O concentration was large and significantly related to the soil water condition, or in a strict sense, to rainfall history. Thus, the rainfall pattern controlled wet season N2O production in soil and its soil surface flux. Spatially, large N2O emissions were detected in wet periods at wetter and anaerobic locations, and were thus determined by soil physical properties. Our results showed that, even in Southeast Asian rainforests where distinct dry and wet seasons do not exist, variation in the soil water condition related to rainfall history controlled the

  10. Compilation of a global N{sub 2}O emission inventory for tropical rainforest soils using a detailed biogeochemical model

    Energy Technology Data Exchange (ETDEWEB)

    Werner, C.

    2007-09-15

    Nitrous oxide (N{sub 2}O) is a potent trace gas contributing to approximately 6% to the observed anthropogenic global warming. Soils have been identified to be the major source of atmospheric N{sub 2}O and tropical rainforest soils are thought to account for the largest part. Furthermore, various studies have shown that the magnitude of N{sub 2}O emissions from tropical rainforest soil is highly variable on spatial and temporal scales. Detailed, process-based models coupled to Geographic Information Systems (GIS) are considered promising tools for the calculation of N{sub 2}O emission inventories. This methodology explicitly accounts for the governing microbial processes as well as the environmental controls. Moreover, mechanistic biogeochemical models operating in daily time-steps (e.g. ForestDNDC-tropica) have been shown to capture the observed intra- and inter-annual variations of N{sub 2}O emissions. However, detailed N{sub 2}O emission datasets are required for model calibration and testing, but are currently few in numbers. In this study an automated measurement system was used to derive detailed datasets of N{sub 2}O, methane (CH{sub 4}) and carbon dioxide (CO{sub 2}) soil-atmosphere exchange and important environmental parameters from tropical rainforest soils in Kenya and Southwest China. Distinct differences were identified in the magnitude of the C and N soil-atmosphere exchange at the investigated sites and forest types. However, common features such as N{sub 2}O pulse emissions after dry season or the pronounced soil moisture dependency of N{sub 2}O emissions were observed at both sites. The derived datasets are unique for these tropical regions as so far no information about the source strength of these regions was available and, for the first time, the N{sub 2}O, CH{sub 4} and CO{sub 2} soil-atmosphere exchange was recorded in sub-daily resolution. The datasets were utilized in conjunction with available high-resolution datasets from Australian

  11. Impact of Amendments on the Physical Properties of Soil under Tropical Long-Term No Till Conditions.

    Directory of Open Access Journals (Sweden)

    Antonio C A Carmeis Filho

    Full Text Available Tropical regions have been considered the world's primary agricultural frontier; however, some physico-chemical deficiencies, such as low soil organic matter content, poor soil structure, high erodibility, soil acidity, and aluminum toxicity, have affected their productive capacity. Lime and gypsum are commonly used to improve soil chemical fertility, but no information exists about the long-term effects of these products on the physical attributes and C protection mechanisms of highly weathered Oxisols. A field trial was conducted in a sandy clay loam (kaolinitic, thermic Typic Haplorthox under a no-tillage system for 12 years. The trial consisted of four treatments: a control with no soil amendment application, the application of 2.1 Mg ha-1 phosphogypsum, the application of 2.0 Mg ha-1 lime, and the application of lime + phosphogypsum (2.0 + 2.1 Mg ha-1, respectively. Since the experiment was established in 2002, the rates have been applied three times (2002, 2004, and 2010. Surface liming effectively increased water-stable aggregates > 2.0 mm at a depth of up to 0.2 m; however, the association with phosphogypsum was considered a good strategy to improve the macroaggregate stability in subsoil layers (0.20 to 0.40 m. Consequently, both soil amendments applied together increased the mean weight diameter (MWD and geometric mean diameter (GMD in all soil layers, with increases of up to 118 and 89%, respectively, according to the soil layer. The formation and stabilization of larger aggregates contributed to a higher accumulation of total organic carbon (TOC on these structures. In addition to TOC, the MWD and aggregate stability index were positively correlated with Ca2+ and Mg2+ levels and base saturation. Consequently, the increase observed in the aggregate size class resulted in a better organization of soil particles, increasing the macroporosity and reducing the soil bulk density and penetration resistance. Therefore, adequate soil chemical

  12. Impact of Amendments on the Physical Properties of Soil under Tropical Long-Term No Till Conditions.

    Science.gov (United States)

    Carmeis Filho, Antonio C A; Crusciol, Carlos A C; Guimarães, Tiara M; Calonego, Juliano C; Mooney, Sacha J

    2016-01-01

    Tropical regions have been considered the world's primary agricultural frontier; however, some physico-chemical deficiencies, such as low soil organic matter content, poor soil structure, high erodibility, soil acidity, and aluminum toxicity, have affected their productive capacity. Lime and gypsum are commonly used to improve soil chemical fertility, but no information exists about the long-term effects of these products on the physical attributes and C protection mechanisms of highly weathered Oxisols. A field trial was conducted in a sandy clay loam (kaolinitic, thermic Typic Haplorthox) under a no-tillage system for 12 years. The trial consisted of four treatments: a control with no soil amendment application, the application of 2.1 Mg ha-1 phosphogypsum, the application of 2.0 Mg ha-1 lime, and the application of lime + phosphogypsum (2.0 + 2.1 Mg ha-1, respectively). Since the experiment was established in 2002, the rates have been applied three times (2002, 2004, and 2010). Surface liming effectively increased water-stable aggregates > 2.0 mm at a depth of up to 0.2 m; however, the association with phosphogypsum was considered a good strategy to improve the macroaggregate stability in subsoil layers (0.20 to 0.40 m). Consequently, both soil amendments applied together increased the mean weight diameter (MWD) and geometric mean diameter (GMD) in all soil layers, with increases of up to 118 and 89%, respectively, according to the soil layer. The formation and stabilization of larger aggregates contributed to a higher accumulation of total organic carbon (TOC) on these structures. In addition to TOC, the MWD and aggregate stability index were positively correlated with Ca2+ and Mg2+ levels and base saturation. Consequently, the increase observed in the aggregate size class resulted in a better organization of soil particles, increasing the macroporosity and reducing the soil bulk density and penetration resistance. Therefore, adequate soil chemical management

  13. Benefits of biochar, compost and biochar–compost for soil quality, maize yield and greenhouse gas emissions in a tropical agricultural soil

    Energy Technology Data Exchange (ETDEWEB)

    Agegnehu, Getachew [College of Science, Technology and Engineering, Centre for Tropical Environmental and Sustainability Science, James Cook University, PO Box 6811, Cairns, Queensland 4870 (Australia); Bass, Adrian M. [Hawkesbury Institute for the Environment, University of Western Sydney, Science Road, Richmond, New South Wales 2753 (Australia); Nelson, Paul N.; Bird, Michael I. [College of Science, Technology and Engineering, Centre for Tropical Environmental and Sustainability Science, James Cook University, PO Box 6811, Cairns, Queensland 4870 (Australia)

    2016-02-01

    Soil quality decline represents a significant constraint on the productivity and sustainability of agriculture in the tropics. In this study, the influence of biochar, compost and mixtures of the two on soil fertility, maize yield and greenhouse gas (GHG) emissions was investigated in a tropical Ferralsol. The treatments were: 1) control with business as usual fertilizer (F); 2) 10 t ha{sup −1} biochar (B) + F; 3) 25 t ha{sup −1} compost (Com) + F; 4) 2.5 t ha{sup −1} B + 25 t ha{sup −1} Com mixed on site + F; and 5) 25 t ha{sup −1} co-composted biochar–compost (COMBI) + F. Total aboveground biomass and maize yield were significantly improved relative to the control for all organic amendments, with increases in grain yield between 10 and 29%. Some plant parameters such as leaf chlorophyll were significantly increased by the organic treatments. Significant differences were observed among treatments for the δ{sup 15}N and δ{sup 13}C contents of kernels. Soil physicochemical properties including soil water content (SWC), total soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), nitrate-nitrogen (NO{sub 3}{sup −} N), ammonium-nitrogen (NH{sub 4}{sup +}-N), exchangeable cations and cation exchange capacity (CEC) were significantly increased by the organic amendments. Maize grain yield was correlated positively with total biomass, leaf chlorophyll, foliar N and P content, SOC and SWC. Emissions of CO{sub 2} and N{sub 2}O were higher from the organic-amended soils than from the fertilizer-only control. However, N{sub 2}O emissions generally decreased over time for all treatments and emission from the biochar was lower compared to other treatments. Our study concludes that the biochar and biochar–compost-based soil management approaches can improve SOC, soil nutrient status and SWC, and maize yield and may help mitigate greenhouse gas emissions in certain systems. - Graphical abstract: Grain yield, cation exchange capacity (CEC), soil

  14. Benefits of biochar, compost and biochar–compost for soil quality, maize yield and greenhouse gas emissions in a tropical agricultural soil

    International Nuclear Information System (INIS)

    Agegnehu, Getachew; Bass, Adrian M.; Nelson, Paul N.; Bird, Michael I.

    2016-01-01

    Soil quality decline represents a significant constraint on the productivity and sustainability of agriculture in the tropics. In this study, the influence of biochar, compost and mixtures of the two on soil fertility, maize yield and greenhouse gas (GHG) emissions was investigated in a tropical Ferralsol. The treatments were: 1) control with business as usual fertilizer (F); 2) 10 t ha"−"1 biochar (B) + F; 3) 25 t ha"−"1 compost (Com) + F; 4) 2.5 t ha"−"1 B + 25 t ha"−"1 Com mixed on site + F; and 5) 25 t ha"−"1 co-composted biochar–compost (COMBI) + F. Total aboveground biomass and maize yield were significantly improved relative to the control for all organic amendments, with increases in grain yield between 10 and 29%. Some plant parameters such as leaf chlorophyll were significantly increased by the organic treatments. Significant differences were observed among treatments for the δ"1"5N and δ"1"3C contents of kernels. Soil physicochemical properties including soil water content (SWC), total soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), nitrate-nitrogen (NO_3"− N), ammonium-nitrogen (NH_4"+-N), exchangeable cations and cation exchange capacity (CEC) were significantly increased by the organic amendments. Maize grain yield was correlated positively with total biomass, leaf chlorophyll, foliar N and P content, SOC and SWC. Emissions of CO_2 and N_2O were higher from the organic-amended soils than from the fertilizer-only control. However, N_2O emissions generally decreased over time for all treatments and emission from the biochar was lower compared to other treatments. Our study concludes that the biochar and biochar–compost-based soil management approaches can improve SOC, soil nutrient status and SWC, and maize yield and may help mitigate greenhouse gas emissions in certain systems. - Graphical abstract: Grain yield, cation exchange capacity (CEC), soil organic carbon (SOC), soil water content (SWC) and N_2O

  15. Clastic sediment flux to tropical Andean lakes: records of glaciation and soil erosion

    Science.gov (United States)

    Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.; Smith, Jacqueline A.; Abbott, Mark B.

    2008-08-01

    . The interval between 20 and 18 ka was marked by near-Holocene levels of clastic sediment flux, and appears to have been an interval of much reduced ice extent. An abrupt increase in clastic sediment flux 18 ka heralded the onset of an interval of expanded ice cover that lasted until ˜14 ka. Clastic sediment flux declined thereafter to reach the lowest levels of the entire length of record during the early-middle Holocene. A middle Holocene climatic transition is apparent in nearly all records and likely reflects the onset of Neoglaciation and/or enhanced soil erosion in the tropical Andes.

  16. Lime and phosphogypsum impacts on soil organic matter pools in a tropical Oxisol under long-term no-till conditions

    Science.gov (United States)

    Improving soil organic matter (SOM) quality in tropical acid soils is important for increasing the sustainability of agricultural ecosystems. This research evaluated the effect of the surface application of lime and phosphogypsum on the quality and amount of SOM in a long-term crop rotation under no...

  17. Effects of earthworms on slopewash, surface runoff, and fine-litter transport on a humid-tropical forested hillslope in eastern Puerto Rico: Chapter G in Water quality and landscape processes of four watersheds in eastern Puerto Rico

    Science.gov (United States)

    Larsen, Matthew C.; Liu, Zhigang Liu; Zou, Xiaoming; Murphy, Sheila F.; Stallard, Robert F.

    2012-01-01

    Rainfall, slopewash (the erosion of soil particles), surface runoff, and fine-litter transport were measured in tropical wet forest on a hillslope in the Luquillo Experimental Forest, Puerto Rico, from February 1998 until April 2000. Slopewash data were collected using Gerlach troughs at eight plots, each 2 square meters in area. Earthworms were excluded by electroshocking from four randomly selected plots. The other four (control) plots were undisturbed. During the experiment, earthworm population in the electroshocked plots was reduced by 91 percent. At the end of the experiment, the electroshocked plots had 13 percent of earthworms by count and 6 percent by biomass as compared with the control plots. Rainfall during the sampling period (793 days) was 9,143 millimeters. Mean and maximum rainfall by sampling period (mean of 16 days) were 189 and 563 millimeters, respectively. Surface runoff averaged 0.6 millimeters and 1.2 millimeters by sampling period for the control and experimental plots, equal to 0.25 and 0.48 percent of mean rainfall, respectively. Disturbance of the soil environment by removal of earthworms doubled runoff and increased the transport (erosion) of soil and organic material by a factor of 4.4. When earthworms were removed, the erosion of mineral soil (soil mass left after ashing) and the transport of fine litter were increased by a factor of 5.3 and 3.4, respectively. It is assumed that increased runoff is a function of reduced soil porosity, resulting from decreased burrowing and reworking of the soil in the absence of earthworms. The background, or undisturbed, downslope transport of soil, as determined from the control plots, was 51 kilograms per hectare and the "disturbance" rate, determined from the experimental plots, was 261 kilograms per hectare. The background rate for downslope transport of fine litter was 71 kilograms per hectare and the disturbance rate was 246 kilograms per hectare. Data from this study indicate that the reduction

  18. Mercury critical concentrations to Enchytraeus crypticus (Annelida: Oligochaeta) under normal and extreme conditions of moisture in tropical soils - Reproduction and survival.

    Science.gov (United States)

    Buch, Andressa Cristhy; Schmelz, Rüdiger M; Niva, Cintia Carla; Correia, Maria Elizabeth Fernandes; Silva-Filho, Emmanoel Vieira

    2017-05-01

    Soil provides many ecosystem services that are essential to maintain its quality and healthy development of the flora, fauna and human well-being. Environmental mercury levels may harm the survival and diversity of the soil fauna. In this respect, efforts have been made to establish limit values of mercury (Hg) in soils to terrestrial fauna. Soil organisms such as earthworms and enchytraeids have intimate contact with trace metals in soil by their oral and dermal routes, reflecting the potentially adverse effects of this contaminant. The main goal of this study was to obtain Hg critical concentrations under normal and extreme conditions of moisture in tropical soils to Enchytraeus crypticus to order to assess if climate change may potentiate their acute and chronic toxicity effects. Tropical soils were sampled from of two Forest Conservation Units of the Rio de Janeiro State - Brazil, which has been contaminated by Hg atmospheric depositions. Worms were exposed to three moisture conditions, at 20%, 50% and 80% of water holding capacity, respectively, and in combination with different Hg (HgCl 2 ) concentrations spiked in three types of tropical soil (two natural soils and one artificial soil). The tested concentrations ranged from 0 to 512mg Hg kg -1 dry weight. Results indicate that the Hg toxicity is higher under increased conditions of moisture, significantly affecting survival and reproduction rate. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. The effect of climate and soil conditions on tree species turnover in a Tropical Montane Cloud Forest in Costa Rica.

    Science.gov (United States)

    Häger, Achim

    2010-12-01

    On a global level, Tropical Montane Cloud Forests constitute important centers of vascular plant diversity. Tree species turnover along environmental gradients plays an important role in larger scale diversity patterns in tropical mountains. This study aims to estimate the magnitude of beta diversity across the Tilardn mountain range in North-Western Costa Rica, and to elucidate the impact of climate and soil conditions on tree species turnover at a local scale. Seven climate stations measuring rainfall, horizontal precipitation (clouds and wind-driven rain) and temperatures were installed along a 2.5km transect ranging from 1200 m.a.s.l. on the Atlantic to 1200 m.a.s.l. on the Pacific slope. The ridge top climate station was located at 1500 m.a.s.l. Climate data were recorded from March through December 2003. Additionally, seven 0.05 ha plots were established. On all plots soil moisture was monitored for one year, furthermore soil type and soil chemistry were assessed. Woody plants with a diameter at breast height (dbh) > or = 5 cm were identified to species. Species' distributions were explored by feeding pairwise Serensen measures between plots into a Principal Component Analysis. Relationships between floristic similarity and environmental variables were analyzed using Mantel tests. Pronounced gradients in horizontal precipitation, temperatures and soil conditions were found across the transect. In total, 483 woody plants were identified, belonging to 132 species. Environmental gradients were paralleled by tree species turnover; the plots could be divided in three distinctive floristic units which reflected different topographic positions on the transect (lower slopes, mid slopes and ridge). Most notably there was a complete species turnover between the ridge and the lower Pacific slope. Floristic similarity was negatively correlated with differences in elevation, horizontal precipitation, temperatures and soil conditions between plots. It is suggested that

  20. Effects of land clearing techniques and tillage systems on runoff and soil erosion in a tropical rain forest in Nigeria.

    Science.gov (United States)

    Ehigiator, O A; Anyata, B U

    2011-11-01

    This work reports runoff and soil loss from each of 14 sub-watersheds in a secondary rain forest in south-western Nigeria. The impact of methods of land clearing and post-clearing management on runoff and soil erosion under the secondary forest is evaluated. These data were acquired eighteen years after the deforestation of primary vegetation during the ' West bank' project of the International Institute for Tropical Agriculture (IITA). These data are presented separately for each season; however, statistical analyses for replicates were not conducted due to differences in their past management. Soil erosion was affected by land clearing and tillage methods. The maximum soil erosion was observed on sub-watersheds that were mechanically cleared with tree-pusher/root-rake attachments and tilled conventionally. A high rate of erosion was observed even when graded-channel terraces were constructed to minimize soil erosion. In general there was much less soil erosion on manually cleared than on mechanically cleared sub-watersheds (2.5 t ha(-1) yr(-1) versus 13.8 t ha(-1) yr(-1)) and from the application of no-tillage methods than from conventionally plowed areas (6.5 t ha(-1) yr(-1) versus 12.1 t ha(-1) yr(-1)). The data indicate that tillage methods and appropriate management of soils and crops play an important role in soil and water conservation and in decreasing the rate of decline of soil quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Efeito da umidade do solo sobre a capacidade de Canavalia ensiformis e Stizolobium aterrimum em remediar solos contaminados com herbicidas Effect of soil humidity on Canavalia ensiformis and Stizolobium aterrimum capacity of remediating soils contaminated by herbicides

    Directory of Open Access Journals (Sweden)

    A.F. Belo

    2007-01-01

    L utilizados na primeira etapa e colocadas em vasos de 0,5 L. Em seguida, cultivaram-se as espécies indicadoras de resíduo dos herbicidas no solo: sorgo (Sorghum bicolor para o trifloxysulfuron-sodium e soja (Glycine max para o tebuthiuron. Estas plantas foram colhidas 20 dias após a semeadura, época em que se avaliaram a altura, a MSPA e o grau de intoxicação delas pelos herbicidas. Canavalia ensiformis não sobreviveu até a época de avaliação (60 DAS em solo contaminado pelo tebuthiuron, independentemente do nível de umidade mantido no solo. S. aterrimum sobreviveu quando cultivada em solo com teor de água entre 0,287 e 0,358 kg kg-1 e, quando comparada a C. ensiformis, foi mais eficiente na descontaminação do solo com residual do tebuthiuron. Nos solos contaminados com trifloxysulfuron-sodium ou com tebuthiuron, com o cultivo prévio das espécies remediadoras, o crescimento do sorgo e da soja foi melhor se comparado ao daquelas plantas cultivadas no solo onde não foi feito o cultivo das espécies remediadoras. De maneira geral, a variação da umidade não interferiu no processo de remediação, sendo os efeitos observados no desenvolvimento das espécies remediadoras. O melhor desenvolvimento de C. ensiformis e S. aterrimum foi observado em solo com teor de água mantido em torno de 0,431 kg kg-1; contudo, nesse teor de água, o tebuthiuron é mais facilmente disponibilizado para a solução do solo.This paper aimed to evaluate the effect of soil humidity on Canavalia ensiformis and Stizolobium aterrimum capacity of remediating soil contaminated with tebuthiuron and trifloxysulfuron-sodium. The experiment was divided into two stages. In the first stage, soil at different levels of humidity were used, contaminated or not with herbicide, to evaluate C. ensiformis and S. aterrimum growth. Treatments consisted of a combination of tebuthiuron, trifloxysulfuron-sodium and herbicide absence, associated to four levels of soil water content (0.287, 0

  2. Timber tree regeneration along abandoned logging roads in a tropical Bolivian forest

    DEFF Research Database (Denmark)

    Nabe-Nielsen, J.; Severiche, W.; Fredericksen, T.

    2007-01-01

    Sustainable management of selectively logged tropical forests requires that felled trees are replaced through increased recruitment and growth. This study compares road track and roadside regeneration with regeneration in unlogged and selectively logged humid tropical forest in north-eastern Boli......Sustainable management of selectively logged tropical forests requires that felled trees are replaced through increased recruitment and growth. This study compares road track and roadside regeneration with regeneration in unlogged and selectively logged humid tropical forest in north......-eastern Bolivia. Some species benefited from increased light intensities on abandoned logging roads. Others benefited from low densities of competing vegetation on roads with compacted soils. This was the case for the small-seeded species Ficus boliviana C.C. Berg and Terminalia oblonga (Ruiz & Pav.) Steud. Some...

  3. Methane and CO2 fluxes from peat soil, palm stems and field drains in two oil palm plantations in Sarawak, Borneo, on different tropical peat soil types.

    Science.gov (United States)

    Manning, Frances; Lip Khoon, Kho; Hill, Tim; Arn Teh, Yit

    2017-04-01

    Oil palm plantations have been expanding rapidly on tropical peat soils in the last 20 years, with 50 % of SE Asian peatlands now managed as industrial or small-holder plantations, up from 11% in 1990. Tropical peat soils are an important carbon (C) store, containing an estimated 17 % of total peatland C. There are large uncertainties as to the soil C dynamics in oil palm plantations on peat due to a shortage of available data. It is therefore essential to understand the soil C cycle in order to promote effective management strategies that optimise yields, whilst maintaining the high C storage capacity of the soil. Here we present CO2 and CH4 fluxes from two oil palm plantations in Sarawak, Malaysia on peat soils. Data were collected from different surface microforms within each plantation that experienced different surface management practices. These included the area next to the palm, in bare soil harvest paths, beneath frond piles, underneath cover crops, from the surface of drains, and from palm stems. Data were collected continuously over one year and analysed with different environmental variables, including soil temperature, WTD, O2, soil moisture and weather data in order to best determine the constraints on the dataset. Total soil respiration (Rtot) varied between 0.09 and 1.59 g C m-2 hr-1. The largest fluxes (0.59 - 1.59 g C m-2 hr-1) were measured next to the palms. Larger CO2 fluxes were observed beneath the cover crops than in the bare soil. This trend was attributed to priming effects from the input of fresh plant litter and exudates. Peat soil type was shown to have significantly different fluxes. The different plantations also had different environmental drivers best explaining the variation in Rtot - with soil moisture being the most significant variable on Sabaju series soil and soil temperature being the most significant environmental variable in the plantation with the Teraja series soil. Rtot was shown to reduce significantly with increasing

  4. The use of nuclear techniques in the management of nitrogen fixation by trees to enhance fertility of fragile tropical soils. Results of a co-ordinated research project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture initiated in 1990 a Co-ordinated Research Project on The Use of Nuclear or Related Techniques in Management of Nitrogen Fixation by Trees for Enhancing Soil Fertility and Soil Conservation in Fragile Tropical Soils. This document contains nine papers referring to the results of the project. A separate abstract was prepared for each paper Refs, figs, tabs

  5. The use of nuclear techniques in the management of nitrogen fixation by trees to enhance fertility of fragile tropical soils. Results of a co-ordinated research project

    International Nuclear Information System (INIS)

    1998-11-01

    The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture initiated in 1990 a Co-ordinated Research Project on The Use of Nuclear or Related Techniques in Management of Nitrogen Fixation by Trees for Enhancing Soil Fertility and Soil Conservation in Fragile Tropical Soils. This document contains nine papers referring to the results of the project. A separate abstract was prepared for each paper

  6. Species and rotation frequency influence soil nitrogen in simplified tropical plant communities.

    Science.gov (United States)

    Ewel, John J

    2006-04-01

    Among the many factors that potentially influence the rate at which nitrogen (N) becomes available to plants in terrestrial ecosystems are the identity and diversity of species composition, frequency of disturbance or stand turnover, and time. Replicated suites of investigator-designed communities afforded an opportunity to examine the effects of those factors on net N mineralization over a 12-year period. The communities consisted of large-stature perennial plants, comprising three tree species (Hyeronima alchorneoides, Cedrela odorata, and Cordia alliodora), a palm (Euterpe oleracea), and a large, perennial herb (Heliconia imbricata). Trees were grown in monoculture and in combination with the other two life-forms; tree monocultures were subjected to rotations of one or four years, or like the three-life-form systems, left uncut. The work was conducted on fertile soil in the humid lowlands of Costa Rica, a site with few abiotic constraints to plant growth. Rates of net N mineralization and nitrification were high, typically in the range of 0.2-0.8 microg x g(1) x d(-1), with net nitrification slightly higher than net mineralization, indicating preferential uptake of ammonium (NH4+) by plants and microbes. Net rates of N mineralization were about 30% lower in stands of one of the three tree species, Hyeronima, than in stands of the other two. Contrary to expectations, short-rotation management (one or four years) resulted in higher net rates of N mineralization than in uncut stands, whether the latter were composed of a single tree species or a combination of life-forms. Neither additional species richness nor replenishment of leached N augmented mineralization rates. The net rate at which N was supplied tended to be lowest in stands where demand for N was highest. Careful choice of species, coupled with low frequency of disturbance, can lead to maintenance of N within biomass and steady rates of within-system circulation, whereas pulses, whether caused by cutting

  7. Characterization and phylogenetic affiliation of Actinobacteria from tropical soils with potential uses for agro-industrial processes.

    Science.gov (United States)

    Dornelas, J C M; Figueiredo, J E F; de Abreu, C S; Lana, U G P; Oliveira, C A; Marriel, I E

    2017-08-31

    Secondary metabolites produced by Actinobacteria of tropical soils represent a largely understudied source of novel molecules with relevant application in medicine, pharmaceutical and food industries, agriculture, and environmental bioremediation. The present study aimed to characterize sixty-nine Actinobacteria isolated from compost and tropical soils using morphological, biochemical, and molecular methods. All the isolates showed high variation for morphological traits considering the color of pigments of the aerial and vegetative mycelium and spore chain morphology. The enzymatic activity of amylase, cellulase, and lipase was highly variable. The amylase activity was detected in 53 (76.81%) isolates. Eighteen isolates showed enzymatic index (EI) > 4.0, and the isolates ACJ 45 (Streptomyces curacoi) and ACSL 6 (S. hygroscopicus) showed the highest EI values (6.44 and 6.42, respectively). The cellulase activity varied significantly (P ≤ 0.05) among the isolates. Twenty-nine isolates (42.02%) showed high cellulase activity, and the isolates ACJ 48 (S. chiangmaiensis) and ACJ 53 (S. cyslabdanicus) showed the highest EI values (6.56 for both isolates). The lipase activity varied statistically (P ≤ 0.05) with fourteen isolates (20.29%) considered good lipase producers (EI > 2.0). The isolate ACSL 6 (S. hygroscopicus) showed the highest EI value of 2.60. Molecular analysis of partial 16S rRNA gene sequencing revealed the existence of 49 species, being 38 species with only one representative member and 11 species represented by one or more strains. All species belonged to three genera, namely Streptomyces (82.61%), Amycolatopsis (7.25%), and Kitasatospora (10.14%). The present results showed the high biotechnological potential of different Actinobacteria from tropical soils.

  8. Tillage for soil and water conservation in the semi-arid Tropics

    NARCIS (Netherlands)

    Hoogmoed, W.

    1999-01-01

    Soil tillage is the manipulation of soil which is generally considered as necessary to obtain optimum growth conditions for a crop. In the same time the resulting modification of soil structure has serious implications for the behaviour of the soil to erosive forces by water and wind. In

  9. Phosphorus fertility recapitalization of nutrient-depleted tropical acid soils with reactive phosphate rock: An assessment using the isotopic exchange technique

    International Nuclear Information System (INIS)

    Fardeau, J.-C.; Zapata, F.

    2002-01-01

    A 'soil P fertility recapitalization' initiative utilizing large rates of phosphate rocks (PRs) was proposed to improve the soil P status and increase the sustainable food production in acid and P-deficient tropical soils. Two series of experiments were carried out using five tropical acid soils treated with heavy applications of Gafsa phosphate rock (GPR). In the first series, the soils were mixed with GPR at the following application rates: 0, 500, 1000 and 2000 mg P·kg -1 , and incubated for one month in moist conditions. In another series, 1000 mg P kg -1 applied as GPR was added to three soils and incubated for 1.5 month; thereafter 50 mg P kg -1 as triple superphosphate (TSP) were added. The 32 P isotopic exchange method was utilized to assess the contribution of GPR to the available soil P. Changes in amounts, E, of P transferred with time as phosphate ions from the soil particles to the soil solution as well as changes in pH, calcium and phosphate concentrations in soil suspensions were determined. It was found that: (i) the contribution of P from GPR to recapitalization of soil P fertility was mainly assessed by E pool size, pH, calcium and phosphate concentrations; other variables were not significant at the 0.1 level; (ii) heavy applications of GPR did not saturate all the P sorption sites, P freshly applied as water-soluble P was still sorbed; (iii) recapitalization of soil P fertility using GPR was partly obtained in some acid tropical soils; (iv) Upon dissolution, GPR provided calcium ions to crops and to soils, thus reducing Al toxicity, but its liming effect was limited. To explain these effects with heavy application rates of GPR, it was postulated that a coating of Al and Fe compounds is formed around PR particles with time, thus reducing further dissolution. (author)

  10. Comparative Bioremediation of Crude Oil-Amended Tropical Soil Microcosms by Natural Attenuation, Bio augmentation, or Bio enrichment

    International Nuclear Information System (INIS)

    Alvarez, V.M; Marques, J.M; Korenblum, E; Seldin, L

    2011-01-01

    Bioremediation is an efficient strategy for cleaning up sites contaminated with organic pollutants. In this study, we evaluated the effectiveness of monitored natural attenuation, bio enrichment, and bio augmentation using a consortium of three actinomycetes strains in remediating two distinct typical Brazilian soils from the Atlantic Forest and Cerrado biomes that were contaminated with crude oil, with or without the addition of NaCl. Microcosms were used to simulate bioremediation treatments over a 120-day period. During this period, we monitored total petroleum hydrocarbons (TPHs) and n-alkanes degradation and changes in bacterial communities. Over time, we found the degradation rate of n-alkanes was higher than TPH in both soils, independent of the treatment used. In fact, our data show that the total bacterial community in the soils was mainly affected by the experimental period of time, while the type of bioremediation treatment used was the main factor influencing the actinomycetes populations in both soils. Based on these data, we conclude that monitored natural attenuation is the best strategy for remediation of the two tropical soils studied, with or without salt addition.

  11. Effect of Soil Water Content on the Distribution of Diuron into Organomineral Aggregates of Highly Weathered Tropical Soils.

    Science.gov (United States)

    Regitano, Jussara B; Rocha, Wadson S D; Bonfleur, Eloana J; Milori, Debora; Alleoni, Luís R F

    2016-05-25

    We evaluated the effects of soil water content on the retention of diuron and its residual distribution into organomineral aggregates in four Brazilian oxisols. (14)C-Diuron was incubated for days at 25, 50, and 75% of maximum water-holding capacity for each soil. After 42 days, the physical fractionation method was used to obtain >150, 53-150, 20-53, 2-20, and retention increased with increasing soil water content for all soils. At lower soil water content, diuron's retention was higher in the sandier soil. It was mostly retained in the fine (retention was higher in the coarse aggregates (>53 μm). The sorption coefficients (Kd and Koc) generated by batch studies should be carefully used because they do not provide information about aggregation and diffusion effects on pesticides soil sorption.

  12. 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

  13. The effect of organic amendment on mobility of cesium in tropical soils - The effect of organic amendment on sorption mechanisms for cesium and cobalt in tropical soils

    Energy Technology Data Exchange (ETDEWEB)

    Wasserman, M.A.V.; Santos-Oliveira, R. [Instituto de Engenharia nuclear/CNEN. Rua Helio de Almeida, 75. Cidade Universitaria - Ilha do Fundao, Rio de Janeiro, RJ. CEP 21941-906 (Brazil); Garcia, R.J.L.; Ferreira, A.C.M.; Rochedo, E.R.R.; Sobrinho, G.A.N. [Instituto de Radioprotecao e Dosimetria/CNEN. Av. Salvador Allende s /no. Rio de Janeiro, RJ. CEP: 22780-160 (Brazil); Perez, D.V. [Centro Nacional de Pesquisa de Solos/EMBRAPA. R. Jardim Botanico, 1024.Rio de Janeiro, RJ, CEP: 22460-000 (Brazil); Wasserman, J.C. [dUFF Network of Environment and Sustainable Development (REMADS-UFF), University Federal Fluminense, Niteroi, RJ (Brazil)

    2014-07-01

    This work aimed to investigate the mechanisms involved in the sorption of {sup 137}Cs and {sup 60}Co as a function of the physico-chemical properties of some types of Brazilian soils and the changes on the behavior of these radionuclides due to changes in soil properties promoted by organic amendment. The experimental study was conducted in a controlled area, where pots containing different types of soils (Ferralsol, Nitisol and Histosol) and different doses of organic amendment (no amendment; 2 kg.m{sup -2} and 4 kg.m{sup -2}) were spiked with {sup 137}Cs and {sup 60}Co. The organic amendment used in this experiment was obtained in the Unit of Compost of the Organic Material of Pinheiral (RJ, Brazil), where the compost is made up from the leaves swept from the streets of the Pinheiral city. The mobility of these radionuclides in the soil was assessed through sequential chemical extraction and desorption studies as a function of pH. The bioavailability was evaluated through the effective absorption of radionuclide by root crops (Raphanus sativus, L). This study evidenced that the organic amendment plays an important role in the desorption processes of cobalt and cesium, reducing desorption of both nuclides beneath higher organic amendment dose. This behavior was observed in acid conditions as well in alkaline. However extreme acid conditions may mobilize both radionuclides, although cobalt mobility was shown to be more sensitive to low pH than cesium. (authors)

  14. Analyses of the influencing factors of soil microbial functional gene diversity in tropical rainforest based on GeoChip 5.0

    Directory of Open Access Journals (Sweden)

    Jing Cong

    2015-09-01

    Full Text Available To examine soil microbial functional gene diversity and causative factors in tropical rainforests, we used a microarray-based metagenomic tool named GeoChip 5.0 to profile it. We found that high microbial functional gene diversity and different soil microbial metabolic potential for biogeochemical processes were considered to exist in tropical rainforest. Soil available nitrogen was the most associated with soil microbial functional gene structure. Here, we mainly describe the experiment design, the data processing, and soil biogeochemical analyses attached to the study in details, which could be published on BMC microbiology Journal in 2015, whose raw data have been deposited in NCBI's Gene Expression Omnibus (accession number GSE69171.

  15. Soil properties, greenhouse gas emissions and crop yield under compost, biochar and co-composted biochar in two tropical agronomic systems

    Energy Technology Data Exchange (ETDEWEB)

    Bass, Adrian M., E-mail: adrian.bass@glasgow.ac.uk [Centre for Tropical Environmental and Sustainability Science, College of Science, Technology and Engineering, James Cook University, Cairns, Queensland 4870 (Australia); Bird, Michael I. [Centre for Tropical Environmental and Sustainability Science, College of Science, Technology and Engineering, James Cook University, Cairns, Queensland 4870 (Australia); Kay, Gavin [Terrain Natural Resource Management, 2 Stitt Street, Innisfail, Queensland 4860 (Australia); Muirhead, Brian [Northern Gulf Resource Management Group, 317 Byrnes Street, Mareeba, Queensland 4880 (Australia)

    2016-04-15

    ABSTRACT: The addition of organic amendments to agricultural soils has the potential to increase crop yields, reduce dependence on inorganic fertilizers and improve soil condition and resilience. We evaluated the effect of biochar (B), compost (C) and co-composted biochar (COMBI) on the soil properties, crop yield and greenhouse gas emissions from a banana and a papaya plantation in tropical Australia in the first harvest cycle. Biochar, compost and COMBI organic amendments improved soil properties, including significant increases in soil water content, CEC, K, Ca, NO{sub 3}, NH{sub 4} and soil carbon content. However, increases in soil nutrient content and improvements in physical properties did not translate to improved fruit yield. Counter to our expectations, banana crop yield (weight per bunch) was reduced by 18%, 12% and 24% by B, C and COMBI additions respectively, and no significant effect was observed on the papaya crop yield. Soil efflux of CO{sub 2} was elevated by addition of C and COMBI amendments, likely due to an increase in labile carbon for microbial processing. Our data indicate a reduction in N{sub 2}O flux in treatments containing biochar. The application of B, C and COMBI amendments had a generally positive effect on soil properties, but this did not translate into a crop productivity increase in this study. The benefits to soil nutrient content, soil carbon storage and N{sub 2}O emission reduction need to be carefully weighed against potentially deleterious effects on crop yield, at least in the short-term. - Highlights: • Biochar and compost amendment has potential to improve tropical agriculture. • We monitored soil health, gas fluxes and crop yield under biochar and compost. • Biochar improved soil nutrient content, water retention and reduced N{sub 2}O emissions. • Biochar significantly reduced banana yield performance and did not affect papaya yield. • Organic amendment is not an ‘always win’ scenario for tropical

  16. Soil properties, greenhouse gas emissions and crop yield under compost, biochar and co-composted biochar in two tropical agronomic systems

    International Nuclear Information System (INIS)

    Bass, Adrian M.; Bird, Michael I.; Kay, Gavin; Muirhead, Brian

    2016-01-01

    ABSTRACT: The addition of organic amendments to agricultural soils has the potential to increase crop yields, reduce dependence on inorganic fertilizers and improve soil condition and resilience. We evaluated the effect of biochar (B), compost (C) and co-composted biochar (COMBI) on the soil properties, crop yield and greenhouse gas emissions from a banana and a papaya plantation in tropical Australia in the first harvest cycle. Biochar, compost and COMBI organic amendments improved soil properties, including significant increases in soil water content, CEC, K, Ca, NO_3, NH_4 and soil carbon content. However, increases in soil nutrient content and improvements in physical properties did not translate to improved fruit yield. Counter to our expectations, banana crop yield (weight per bunch) was reduced by 18%, 12% and 24% by B, C and COMBI additions respectively, and no significant effect was observed on the papaya crop yield. Soil efflux of CO_2 was elevated by addition of C and COMBI amendments, likely due to an increase in labile carbon for microbial processing. Our data indicate a reduction in N_2O flux in treatments containing biochar. The application of B, C and COMBI amendments had a generally positive effect on soil properties, but this did not translate into a crop productivity increase in this study. The benefits to soil nutrient content, soil carbon storage and N_2O emission reduction need to be carefully weighed against potentially deleterious effects on crop yield, at least in the short-term. - Highlights: • Biochar and compost amendment has potential to improve tropical agriculture. • We monitored soil health, gas fluxes and crop yield under biochar and compost. • Biochar improved soil nutrient content, water retention and reduced N_2O emissions. • Biochar significantly reduced banana yield performance and did not affect papaya yield. • Organic amendment is not an ‘always win’ scenario for tropical agriculture.

  17. Threshold responses to soil moisture deficit by trees and soil in tropical rain forests: insights from field experiments

    Science.gov (United States)

    Patrick Meir; Tana Wood; David R. Galbraith; Paulo M. Brando; Antonio C.I. Da Costa; Lucy Rowland; Leandro V. Ferreira

    2015-01-01

    Many tropical rain forest regions are at risk of increased future drought. The net effects of drought on forest ecosystem functioning will be substantial if important ecological thresholds are passed. However, understanding and predicting these effects is challenging using observational studies alone. Field-based rainfall exclusion (canopy throughfall exclusion; TFE)...

  18. Comparative short-term effects of sewage sludge and its biochar on soil properties, maize growth and uptake of nutrients on a tropical clay soil in Zimbabwe

    Institute of Scientific and Technical Information of China (English)

    Willis Gwenzi; Moreblessing Muzava; Farai Mapanda; Tonny P Tauro

    2016-01-01

    Soil application of biochar from sewage could potentialy enhance carbon sequestration and close urban nutrient balances. In sub-Saharan Africa, comparative studies investigating plant growth effect and nutrients uptake on tropical soils amended with sewage sludge and its biochar are very limited. A pot experiment was conducted to investigate the effects of sewage sludge and its biochar on soil chemical properties, maize nutrient and heavy metal uptake, growth and biomass partitioning on a tropical clayey soil. The study compared three organic amendments; sewage sludge (SS), sludge biochar (SB) and their combination (SS+SB) to the unamended control and inorganic fertilizers. Organic amendments were applied at a rate of 15 t ha–1 for SS and SB, and 7.5 t ha–1 each for SS and SB. Maize growth, biomass production and nutrient uptake were signiifcantly improved in biochar and sewage sludge amendments compared to the unamended control. Comparable results were observed with F, SS and SS+SB on maize growth at 49 d of sowing. Maize growth for SB, SS, SS+SB and F increased by 42, 53, 47, and 49%, respectively compared to the unamended control. Total biomass for SB, SS, SS+SB, and F increased by 270, 428, 329, and 429%, respectively compared with the unamended control. Biochar amendments reduced Pb, Cu and Zn uptakes by about 22% compared with sludge alone treatment in maize plants. However, there is need for future research based on the current pot experiment to determine whether the same results can be produced under ifeld conditions.

  19. Electrochemical attributes and availability of nutrients, toxic elements, and heavy metals in tropical soils Atributos eletroquímicos e disponibilidade de nutrientes, elementos tóxicos e metais pesados em solos tropicais

    Directory of Open Access Journals (Sweden)

    Mauricio Paulo Ferreira Fontes

    2006-12-01

    Full Text Available Electrochemical properties of soils are very important for the understanding of the physico-chemical phenomena which affect soil fertility and the availability of nutrients for plants. This review highlights the electrochemical properties of tropical soils, the behavior and the availability of nutrients, toxic elements and heavy metals in the soil, especially for soils with predominant variable charge minerals. Availability of the elements is related to ionic exchange, solution speciation, and electrostatic and specific adsorptive soil properties. Empirical and surface complexation models are briefly described, and some results of their application in tropical soils are presented. A better understanding of the role of the double diffuse layer of charges and CEC on nutrient cation availability for highly weathered soils is required, as well as a solid comprehension of surface complexation models, in order to improve the knowledge regarding the behavior of anions in soils. More studies have to be conducted to generate results that enable the use of chemical speciation concepts and calculation of several constants used in surface complexation models, especially for highly weathered soils from the humid tropics. There has to be a continuing development and use of computer softwares that have already incorporated the concepts of chemical speciation and adsorption models in the study of nutrients, toxic elements and heavy metal availability in the soil-plant system.As propriedades eletroquímicas dos solos tropicais são muito importantes para entendimento dos fenômenos físico-químicos que afetam a fertilidade do solo e a disponibilidade dos nutrientes das plantas. Essa revisão destaca os atributos eletroquímicos de solos e o comportamento e a disponibilidade de nutrientes, elementos tóxicos e metais pesados no solo, especialmente aqueles com predominância de minerais com cargas variáveis. A disponibilidade dos elementos é relacionada com a

  20. The effect of Piper aduncum invasion on soil in tropical ecosystems of Papua New Guinea

    Science.gov (United States)

    Kukla, Jaroslav; Frouz, Jan

    2017-04-01

    Piper aduncum is successful Neotropical invasive species in Papua New Guinea. Despite its interaction with aboveground part of ecosystem has been extensively studied little is known about its effect on soil. Here we report two studies, in first we compare soil chemistry and soil biota in sites invaded and non-invaded by P. aduncum near Wanang village. In other study we use benefit of previous experiment when P. aduncum was experimentally removed near Ohu village. Here we compare soil chemistry and chemistry of plant leaves growing in garden originating by slashing and burning two adjacent patches with and without P. aduncum. Soil under P. aduncum had significantly less phosphorus in 0-5 cm soil layer and less nitrates, nitrogen and carbon in 5-10 cm soil layer than soil in old gardens uninvaded by P. aduncum. P. aduncum soil also harbors fewer microfloras than uninvaded soil as shown by PLFA analysis. No difference was found in fauna communities. Gardens created on patches where old P. aduncum was removed did not differ in soil chemistry from plots which were overgrown by P. aduncum, but leaves of sweet potatoes (Ipomoea batatas) in gardens where P. aduncum was previously removed contained more nitrogen. Results suggest that P. aduncum invasion may affect some chemical and microbial properties in invaded soil. P. aduncum has negative effect on traditional shifting agriculture.

  1. Biological Activity Assessment in Mexican Tropical Soils with Different Hydrocarbon Contamination Histories

    OpenAIRE

    Riveroll-Larios, Jessica; Escalante-Espinosa, Erika; Fócil-Monterrubio, Reyna L.; Díaz-Ramírez, Ildefonso J.

    2015-01-01

    The use of soil health indicators linked to microbial activities, such as key enzymes and respirometric profiles, helps assess the natural attenuation potential of soils contaminated with hydrocarbons. In this study, the intrinsic physicochemical characteristics, biological activity and biodegradation potential were recorded for two soils with different contamination histories (>5 years and

  2. 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.

  3. Temporal and spatial variations of patches, corridors and matrix in humid soil (mallín in the mid-west of the province of Neuquén

    Directory of Open Access Journals (Sweden)

    Ricardo Gandullo

    2006-01-01

    Full Text Available Natural processes, like human activities, change the landscape. This reality is somehow related to humid soils (mallines in Patagonia. The mallines are important natural ecosystems that provide forage to extensive animal husbandry. They represent 4 of the Patagonic surface. The wet and dry periods modify the hydrologic dynamics of the mallín, producing an effect on the evolution of patches, corridors and matrix, which worsens with the anthropic activity. In a temporal sequence, the habitat fragmentation can be observed, i.e. in the variation and size of the number of patches, their shape, connectivity and isolation, which together with other factors affect the numerous ecological processes. Knowledge of the temporal and spatial dynamics of the patches, corridors and matrix between wet and dry periods in humid soils allows for the planning of the use of the vegetation resources, since the spatial standards strongly control their movements, flows and changes.

  4. Sorption of water vapour by the Na+-exchanged clay-sized fractions of some tropical soil samples

    International Nuclear Information System (INIS)

    Yormah, T.B.R.; Hayes, M.H.B.

    1993-09-01

    Water vapour sorption isotherms at 299K for the Na + -exchanged clay-sized (≤ 2μm e.s.d.) fraction of two sets of samples taken at three different depths from a tropical soil profile have been studied. One set of samples was treated (with H 2 O 2 ) for the removal of much of the organic matter (OM); the other set (of the same samples) was not so treated. The isotherms obtained were all of type II and analyses by the BET method yielded values for the Specific Surface Areas (SSA) and for the average energy of adsorption of the first layer of adsorbate (E a ). OM content and SSA for the untreated samples were found to decrease with depth. Whereas removal of organic matter made negligible difference to the SSA of the top/surface soil, the same treatment produced a significant increase in the SSA of the samples taken from the middle and from the lower depths in the profile; the resulting increase was more pronounced for the subsoil. It has been deduced from these results that OM in the surface soil was less involved with the inorganic soil colloids than that in the subsoil. The increase in surface area which resulted from the removal of OM from the subsoil was most probably due to disaggregation. Values of E a obtained show that for all the samples the adsorption of water vapour became more energetic after the oxidative removal of organic matter; the resulting ΔE a also increased with depth. This suggests that in the dry state, the ''cleaned'' surface of the inorganic soil colloids was more energetic than the ''organic-matter-coater surface''. These data provide strong support for the deduction that OM in the subsoil was in a more ''combined'' state than that in the surface soil. (author). 21 refs, 4 figs, 2 tabs

  5. Predicting the impact of logging activities on soil erosion and water quality in steep, forested tropical islands

    Science.gov (United States)

    Wenger, Amelia S.; Atkinson, Scott; Santini, Talitha; Falinski, Kim; Hutley, Nicholas; Albert, Simon; Horning, Ned; Watson, James E. M.; Mumby, Peter J.; Jupiter, Stacy D.

    2018-04-01

    Increasing development in tropical regions provides new economic opportunities that can improve livelihoods, but it threatens the functional integrity and ecosystem services provided by terrestrial and aquatic ecosystems when conducted unsustainably. Given the small size of many islands, communities may have limited opportunities to replace loss and damage to the natural resources upon which they depend for ecosystem service provisioning, thus heightening the need for proactive, integrated management. This study quantifies the effectiveness of management strategies, stipulated in logging codes-of-practice, at minimizing soil erosion and sediment runoff as clearing extent increases, using Kolombangara Island, Solomon Islands as a case study. Further, we examine the ability of erosion reduction strategies to maintain sustainable soil erosion rates and reduce potential downstream impacts to drinking water and environmental water quality. We found that increasing land clearing—even with best management strategies in place—led to unsustainable levels of soil erosion and significant impacts to downstream water quality, compromising the integrity of the land for future agricultural uses, consistent access to clean drinking water, and important downstream ecosystems. Our results demonstrate that in order to facilitate sustainable development, logging codes of practice must explicitly link their soil erosion reduction strategies to soil erosion and downstream water quality thresholds, otherwise they will be ineffective at minimizing the impacts of logging activities. The approach taken here to explicitly examine soil erosion rates and downstream water quality in relation to best management practices and increasing land clearing should be applied more broadly across a range of ecosystems to inform decision-making about the socioeconomic and environmental trade-offs associated with logging, and other types of land use change.

  6. Losses of soil carbon by converting tropical forest to plantations: erosion and decomposition estimated by δ(13) C.

    Science.gov (United States)

    Guillaume, Thomas; Damris, Muhammad; Kuzyakov, Yakov

    2015-09-01

    Indonesia lost more tropical forest than all of Brazil in 2012, mainly driven by the rubber, oil palm, and timber industries. Nonetheless, the effects of converting forest to oil palm and rubber plantations on soil organic carbon (SOC) stocks remain unclear. We analyzed SOC losses after lowland rainforest conversion to oil palm, intensive rubber, and extensive rubber plantations in Jambi Province on Sumatra Island. The focus was on two processes: (1) erosion and (2) decomposition of soil organic matter. Carbon contents in the Ah horizon under oil palm and rubber plantations were strongly reduced up to 70% and 62%, respectively. The decrease was lower under extensive rubber plantations (41%). On average, converting forest to plantations led to a loss of 10 Mg C ha(-1) after about 15 years of conversion. The C content in the subsoil was similar under the forest and the plantations. We therefore assumed that a shift to higher δ(13) C values in plantation subsoil corresponds to the losses from the upper soil layer by erosion. Erosion was estimated by comparing the δ(13) C profiles in the soils under forest and under plantations. The estimated erosion was the strongest in oil palm (35 ± 8 cm) and rubber (33 ± 10 cm) plantations. The (13) C enrichment of SOC used as a proxy of its turnover indicates a decrease of SOC decomposition rate in the Ah horizon under oil palm plantations after forest conversion. Nonetheless, based on the lack of C input from litter, we expect further losses of SOC in oil palm plantations, which are a less sustainable land use compared to rubber plantations. We conclude that δ(13) C depth profiles may be a powerful tool to disentangle soil erosion and SOC mineralization after the conversion of natural ecosystems conversion to intensive plantations when soils show gradual increase of δ(13) C values with depth. © 2015 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

  7. After more than a decade of soil moisture deficit, tropical rainforest trees maintain photosynthetic capacity, despite increased leaf respiration.

    Science.gov (United States)

    Rowland, Lucy; Lobo-do-Vale, Raquel L; Christoffersen, Bradley O; Melém, Eliane A; Kruijt, Bart; Vasconcelos, Steel S; Domingues, Tomas; Binks, Oliver J; Oliveira, Alex A R; Metcalfe, Daniel; da Costa, Antonio C L; Mencuccini, Maurizio; Meir, Patrick

    2015-12-01

    Determining climate change feedbacks from tropical rainforests requires an understanding of how carbon gain through photosynthesis and loss through respiration will be altered. One of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability. In this study we examine if and how both leaf photosynthesis and leaf dark respiration acclimate following more than 12 years of experimental soil moisture deficit, via a through-fall exclusion experiment (TFE) in an eastern Amazonian rainforest. We find that experimentally drought-stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought-induced mortality. We hypothesize that photosynthetic capacity is maintained across all treatments and taxa to take advantage of short-lived periods of high moisture availability, when stomatal conductance (gs ) and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times. Average leaf dark respiration (Rd ) was elevated in the TFE-treated forest trees relative to the control by 28.2 ± 2.8% (mean ± one standard error). This mean Rd value was dominated by a 48.5 ± 3.6% increase in the Rd of drought-sensitive taxa, and likely reflects the need for additional metabolic support required for stress-related repair, and hydraulic or osmotic maintenance processes. Following soil moisture deficit that is maintained for several years, our data suggest that changes in respiration drive greater shifts in the canopy carbon balance, than changes in photosynthetic capacity. © 2015 John Wiley & Sons Ltd.

  8. Beyond the Dams: Linking Rural Smallholder Soil and Water Management Practices in Tropical Deltas to Sea Level Rise Vulnerability

    Science.gov (United States)

    Rogers, K. G.; Syvitski, J. P.; Brondizio, E. S.

    2014-12-01

    The increased vulnerability of deltaic communities to coastal flooding as a result of upstream engineering has been acknowledged for decades. What has received less attention is the sensitivity of deltas to the interactions of river basin modifications and cultivation and irrigation in their coastal regions, particularly in tropical deltas. Embanking, tilling, and crop or stock choice all affect the movement of sediment and water on deltas. Combined with reduced river and sediment discharge, soil and water management practices in coastal areas may in fact exacerbate the risk of tidal flooding, erosion of arable land, and salinization of soils and groundwater associated with sea level rise. Thus exists a cruel irony to smallholder subsistence farmers whose priorities are food, water and economic security, rather than sustainability of the regional environment. Such issues challenge disciplinary approaches and require integrated social-biophysical models able to understand and diagnose these complex relationships. The complementary Institutional Analysis and Development and SocioEcological Systems frameworks are applied to the southwestern Bengal Delta (Bangladesh). The method helps to define the relevant social and physical units operating on the common pool of environmental resources, those of climate, water and sediment. The conceptual frameworks are designed to inform development of a nested geospatial analysis and a dynamic coupled model to identify the social-biophysical feedbacks associated with smallholder soil and water management practices, coastal dynamics, and climate vulnerability in rural Bangladesh. Our presentation will discuss components of the conceptual frameworks and will introduce a bi-directional pilot study designed for obtaining and disseminating information about environmental change to farmers in southwest Bangladesh with potential application to rural farming communities in other tropical deltas.

  9. The relative importance of above- versus belowground competition for tree growth and survival during early succession of a tropical moist forest

    NARCIS (Netherlands)

    Breugel, van M.; Breugel, van P.; Jansen, P.A.; Martinez-Ramos, M.; Bongers, F.

    2012-01-01

    Competition between neighboring plants plays a major role in the population dynamics of tree species in the early phases of humid tropical forest succession. We evaluated the relative importance of above- versus below-ground competition during the first years of old-field succession on soil with low

  10. Fitting maize into sustainable cropping systems on acid soils of the tropics

    International Nuclear Information System (INIS)

    Horst, W.J.

    2000-01-01

    One of the key elements of sustainable cropping systems is the integration of crops and/or crop cultivars with high tolerance of soil acidity and which make most efficient use of the nutrients supplied by soil and fertilizer. This paper is based mainly on on-going work within an EU-funded project combining basic research on plant adaptation mechanisms by plant physiologists, and field experimentation on acid soils in Brazil, Cameroon, Colombia and Guadeloupe by breeders, soil scientists and a agronomists. The results suggest that large genetic variability exists in adaptation of plants to acid soils. A range of morphological and physiological plant characteristics contribute to tolerance of acid soils, elucidation of which has contributed to the development of rapid techniques for screening for tolerance. Incorporation of acid-soil-tolerant species and cultivars into cropping systems contributes to improved nutrient efficiency overall, and thus reduces fertilizer needs. This may help to minimize maintenance applications of fertiliser through various pathways: (i) deeper root growth resulting in more-efficient uptake of nutrients from the sub-soil and less leaching, (ii) more biomass production resulting in less seepage and less leaching, with more intensive nutrient cycling, maintenance of higher soil organic-matter content, and, consequently, less erosion owing to better soil protection by vegetation and mulch. (author)

  11. Evaluation of statistical and geostatistical models of digital soil properties mapping in tropical mountain regions

    Directory of Open Access Journals (Sweden)

    Waldir de Carvalho Junior

    2014-06-01

    Full Text Available Soil properties have an enormous impact on economic and environmental aspects of agricultural production. Quantitative relationships between soil properties and the factors that influence their variability are the basis of digital soil mapping. The predictive models of soil properties evaluated in this work are statistical (multiple linear regression-MLR and geostatistical (ordinary kriging and co-kriging. The study was conducted in the municipality of Bom Jardim, RJ, using a soil database with 208 sampling points. Predictive models were evaluated for sand, silt and clay fractions, pH in water and organic carbon at six depths according to the specifications of the consortium of digital soil mapping at the global level (GlobalSoilMap. Continuous covariates and categorical predictors were used and their contributions to the model assessed. Only the environmental covariates elevation, aspect, stream power index (SPI, soil wetness index (SWI, normalized difference vegetation index (NDVI, and b3/b2 band ratio were significantly correlated with soil properties. The predictive models had a mean coefficient of determination of 0.21. Best results were obtained with the geostatistical predictive models, where the highest coefficient of determination 0.43 was associated with sand properties between 60 to 100 cm deep. The use of a sparse data set of soil properties for digital mapping can explain only part of the spatial variation of these properties. The results may be related to the sampling density and the quantity and quality of the environmental covariates and predictive models used.

  12. Adsorption-desorption reactions of selenium (VI) in tropical cultivated and uncultivated soils under Cerrado biome.

    Science.gov (United States)

    Lessa, J H L; Araujo, A M; Silva, G N T; Guilherme, L R G; Lopes, G

    2016-12-01

    Soil management may affect selenium (Se) adsorption capacity. This study investigated adsorption and desorption of Se (VI) in selected Brazilian soils from the Cerrado biome, an area of ever increasing importance for agriculture expansion in Brazil. Soil samples were collected from cultivated and uncultivated soils, comprising clayed and sandy soils. Following chemical and mineralogical characterization, soil samples were subjected to Se adsorption and desorption tests. Adsorption was evaluated after a 72-h reaction with increasing concentrations of Se (0-2000 μg L -1 ) added as Na 2 SeO 4 in a NaCl electrolyte solution (pH 5.5; ionic strength 15 mmol L -1 ). Desorption, as well as distribution coefficients (K d ) for selenate were also assessed. Soil management affected Se adsorption capacity, i.e., Se adsorbed amounts were higher for uncultivated soils, when compared to cultivated ones. Such results were also supported by data of K d and maximum adsorption capacity of Se. This fact was attributed mainly to the presence of greater amounts of competing anions, especially phosphate, in cultivated soils, due to fertilizer application. Phosphate may compete with selenate for adsorption sites, decreasing Se retention. For the same group of soils (cultivated and uncultivated), Se adsorption was greater in the clayed soils compared to sandy ones. Our results support the idea that adding Se (VI) to the soil is a good strategy to increase Se levels in food crops (agronomic biofortification), especially when crops are grown in soils that have been cultivated over the time due to their low Se adsorption capacity (high Se availability). Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Fine root dynamics and trace gas fluxes in two lowland tropical forest soils.

    Science.gov (United States)

    WHENDEE L. SILVER; ANDREW W. THOMPSON; MEGAN E . MCGRODDY; RUTH K. VARNER; JADSON D. DIAS; HUDSON SILVA; CRILL PATRICK M.; MICHAEL KELLER

    2005-01-01

    Fine root dynamics have the potential to contribute significantly to ecosystem-scale biogeochemical cycling, including the production and emission of greenhouse gases. This is particularly true in tropical forests which are often characterized as having large fine root biomass and rapid rates of root production and decomposition. We examined patterns in fine root...

  14. No signs of soil organic matter accumulation and of changes in nutrient (N-P) limitation during tropical secondary forest succession in the wet tropics of Southwest Costa Rica

    Science.gov (United States)

    Wanek, Wolfgang; Oberdorfer, Sarah; Oberleitner, Florian; Hietz, Peter; Dullinger, Stefan; Zehetner, Franz

    2017-04-01

    Secondary forests comprise large tracts of the tropical land area, due to ongoing changes in land-use, including selective logging and agricultural land abandonment. Recent meta-analyses demonstrated