WorldWideScience

Sample records for subalpine canopy removal

  1. Estimating under-canopy ablation in a subalpine red-fir forest, southern Sierra Nevada, California

    Science.gov (United States)

    Kirchner, P. B.; Bales, R. C.; Rice, R.; Musselman, K. N.; Molotch, N. P.

    2010-12-01

    Snow ablation in forested environments is a result of the multi-component energy balance between the snow surface, radiation, topography, and vegetation. While these processes have been successfully described and modeled over small to moderate spatial extents the required data are available from few locations and existing models are computationally intensive. The problem of applying these principals to determining snow coverage for large spatial extents and frequent time steps, required by satellite observations, has not been solved. We present a simplified approach for determining a melt-out date based on modeled incident radiation, percent canopy cover, and leaf area index. This method was tested using results from instrumental data, field observations, and readily available spatial data sets by calibrating the MODIS Snow Covered Area and Grain size/albedo (MODSCAG) model from a snow-dominated site in the Wolverton basin Sequoia National Park; part of the Southern Sierra Nevada Critical Zone Observatory. The percent snow cover determined by MODSCAG from peak accumulation and melt out during the 2008 and 2009 water years were compared to ground observations of both forest gaps and under canopies. Ground based measurements indicated that under-canopy melt out of snow-covered area began earlier and ended 1 to 4 weeks after that indicated by satellite observations, which can only view snow in forest gaps. In our study ablation rates, snow cover duration, leaf area index, canopy closure, and Incoming short and long wave radiation were measured on north and southeast facing plots in a subalpine red fir forest. Results from regression analysis yield an R2=0.99 between modeled and measured short wave radiation and an R2=0.82 between leaf area index and the difference between open and under canopy thermal infrared radiation. Canopy cover and leaf area index were also found to be good predictors of observed melt rates and the melt off date of snow under tree canopies. This

  2. Removing forest canopy cover restores a reptile assemblage.

    Science.gov (United States)

    Pike, David A; Webb, Jonathan K; Shine, Richard

    2011-01-01

    Humans are rapidly altering natural systems, leading to changes in the distribution and abundance of species. However, so many changes are occurring simultaneously (e.g., climate change, habitat fragmentation) that it is difficult to determine the cause of population fluctuations from correlational studies. We used a manipulative field experiment to determine whether forest canopy cover directly influences reptile assemblages on rock outcrops in southeastern Australia. Our experimental design consisted of three types of rock outcrops: (1) shady sites in which overgrown vegetation was manually removed (n = 25); (2) overgrown controls (n = 30); and (3) sun-exposed controls (n = 20). Following canopy removal, we monitored reptile responses over 30 months. Canopy removal increased reptile species richness, the proportion of shelter sites used by reptiles, and relative abundances of five species that prefer sun-exposed habitats. Our manipulation also decreased the abundances of two shade-tolerant species. Canopy cover thus directly influences this reptile assemblage, with the effects of canopy removal being dependent on each species' habitat preferences (i.e., selection or avoidance of sun-exposed habitat). Our study suggests that increases in canopy cover can cause declines of open-habitat specialists, as previously suggested by correlative studies from a wide range of taxa. Given that reptile colonization of manipulated outcrops occurred rapidly, artificially opening the canopy in ecologically informed ways could help to conserve imperiled species with patchy distributions and low vagility that are threatened by vegetation overgrowth. One such species is Australia's most endangered snake, the broadheaded snake (Hoplocephalus bungaroides).

  3. Experimental canopy removal enhances diversity of vernal pond amphibians.

    Science.gov (United States)

    Skelly, David K; Bolden, Susan R; Freidenburg, L Kealoha

    2014-03-01

    Vernal ponds are often treated as protected environments receiving special regulation and management. Within the landscapes where they are found, forest vegetation frequently dominates surrounding uplands and can grow to overtop and shade pond basins. Two bodies of research offer differing views of the role of forest canopy for vernal pond systems. Studies of landscape conversion suggest that removing forest overstory within uplands can cause local extinctions of amphibians by altering terrestrial habitat or hindering movement. Studies of canopy above pond basins imply an opposite relationship; encroachment of overstory vegetation can be associated with local extinctions potentially via changes in light, thermal, and food resource environments. Unresolved uncertainties about the role of forest canopy reveal significant gaps in our understanding of wetland species distributions and dynamics. Any misunderstanding of canopy influences is simultaneously important to managers because current practices emphasize promoting or conserving vegetation growth particularly within buffers immediately adjacent to ponds. We evaluated this apparent contradiction by conducting a landscape-scale, long-term experiment using 14 natural vernal ponds. Tree felling at six manipulated ponds was limited in spatial scope but was nevertheless effective in increasing water temperature. Compared with eight control ponds, manipulated ponds maintained more amphibian species during five years post-manipulation. There was little evidence that any species was negatively influenced, and the reproductive effort of species for which we estimated egg inputs maintained pretreatment population densities in manipulated compared with control ponds. Overall, our experiment shows that a carefully circumscribed reduction of overhead forest canopy can enhance the capacity of vernal ponds to support wildlife diversity and suggests a scale dependence of canopy influences on amphibians. These findings have

  4. Winter ecology of a subalpine grassland: Effects of snow removal on soil respiration, microbial structure and function.

    Science.gov (United States)

    Gavazov, Konstantin; Ingrisch, Johannes; Hasibeder, Roland; Mills, Robert T E; Buttler, Alexandre; Gleixner, Gerd; Pumpanen, Jukka; Bahn, Michael

    2017-07-15

    Seasonal snow cover provides essential insulation for mountain ecosystems, but expected changes in precipitation patterns and snow cover duration due to global warming can influence the activity of soil microbial communities. In turn, these changes have the potential to create new dynamics of soil organic matter cycling. To assess the effects of experimental snow removal and advanced spring conditions on soil carbon (C) and nitrogen (N) dynamics, and on the biomass and structure of soil microbial communities, we performed an in situ study in a subalpine grassland in the Austrian Alps, in conjunction with soil incubations under controlled conditions. We found substantial winter C-mineralisation and high accumulation of inorganic and organic N in the topsoil, peaking at snowmelt. Soil microbial biomass doubled under the snow, paralleled by a fivefold increase in its C:N ratio, but no apparent change in its bacteria-dominated community structure. Snow removal led to a series of mild freeze-thaw cycles, which had minor effects on in situ soil CO2 production and N mineralisation. Incubated soil under advanced spring conditions, however, revealed an impaired microbial metabolism shortly after snow removal, characterised by a limited capacity for C-mineralisation of both fresh plant-derived substrates and existing soil organic matter (SOM), leading to reduced priming effects. This effect was transient and the observed recovery in microbial respiration and SOM priming towards the end of the winter season indicated microbial resilience to short-lived freeze-thaw disturbance under field conditions. Bacteria showed a higher potential for uptake of plant-derived C substrates during this recovery phase. The observed temporary loss in microbial C-mineralisation capacity and the promotion of bacteria over fungi can likely impede winter SOM cycling in mountain grasslands under recurrent winter climate change events, with plausible implications for soil nutrient availability and

  5. Spectroscopic remote sensing of plant stress at leaf and canopy levels using the chlorophyll 680 nm absorption feature with continuum removal

    Science.gov (United States)

    Sanches, Ieda Del´Arco; Souza Filho, Carlos Roberto de; Kokaly, Raymond F.

    2014-01-01

    This paper explores the use of spectral feature analysis to detect plant stress in visible/near infrared wavelengths. A time series of close range leaf and canopy reflectance data of two plant species grown in hydrocarbon-contaminated soil was acquired with a portable spectrometer. The ProSpecTIR-VS airborne imaging spectrometer was used to obtain far range hyperspectral remote sensing data over the field experiment. Parameters describing the chlorophyll 680 nm absorption feature (depth, width, and area) were derived using continuum removal applied to the spectra. A new index, the Plant Stress Detection Index (PSDI), was calculated using continuum-removed values near the chlorophyll feature centre (680 nm) and on the green-edge (560 and 575 nm). Chlorophyll feature’s depth, width and area, the PSDI and a narrow-band normalised difference vegetation index were evaluated for their ability to detect stressed plants. The objective was to analyse how the parameters/indices were affected by increasing degrees of plant stress and to examine their utility as plant stress indicators at the remote sensing level (e.g. airborne sensor). For leaf data, PSDI and the chlorophyll feature area revealed the highest percentage (67–70%) of stressed plants. The PSDI also proved to be the best constraint for detecting the stress in hydrocarbon-impacted plants with field canopy spectra and airborne imaging spectroscopy data. This was particularly true using thresholds based on the ASD canopy data and considering the combination of higher percentage of stressed plants detected (across the thresholds) and fewer false-positives.

  6. Gainesville's urban forest canopy cover

    Science.gov (United States)

    Francisco Escobedo; Jennifer A. Seitz; Wayne Zipperer

    2009-01-01

    Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy cover. Urban forest cover is dynamic and changes over time due to factors such as urban development, windstorms, tree removals, and growth. The amount of a city's canopy cover depends on its land use, climate, and people's preferences. This fact sheet examines how...

  7. Airflow patterns in a small subalpine basin

    Science.gov (United States)

    G. Wooldridge; R. Musselman; B. Connell; D. Fox

    1992-01-01

    A study of mean wind speeds and directions has been completed in the Snowy Range of Southern Wyoming, U.S.A. It was conducted in a subalpine ecosystem at an altitude of 3 200 m to 3 400 m above sea level during the summers of 1988 and 1989. Indexes of deformation and axes of asymmetry due to wind shaping of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies...

  8. Automatic Coregistration Algorithm to Remove Canopy Shaded Pixels in UAV-Borne Thermal Images to Improve the Estimation of Crop Water Stress Index of a Drip-Irrigated Cabernet Sauvignon Vineyard.

    Science.gov (United States)

    Poblete, Tomas; Ortega-Farías, Samuel; Ryu, Dongryeol

    2018-01-30

    Water stress caused by water scarcity has a negative impact on the wine industry. Several strategies have been implemented for optimizing water application in vineyards. In this regard, midday stem water potential (SWP) and thermal infrared (TIR) imaging for crop water stress index (CWSI) have been used to assess plant water stress on a vine-by-vine basis without considering the spatial variability. Unmanned Aerial Vehicle (UAV)-borne TIR images are used to assess the canopy temperature variability within vineyards that can be related to the vine water status. Nevertheless, when aerial TIR images are captured over canopy, internal shadow canopy pixels cannot be detected, leading to mixed information that negatively impacts the relationship between CWSI and SWP. This study proposes a methodology for automatic coregistration of thermal and multispectral images (ranging between 490 and 900 nm) obtained from a UAV to remove shadow canopy pixels using a modified scale invariant feature transformation (SIFT) computer vision algorithm and Kmeans++ clustering. Our results indicate that our proposed methodology improves the relationship between CWSI and SWP when shadow canopy pixels are removed from a drip-irrigated Cabernet Sauvignon vineyard. In particular, the coefficient of determination (R²) increased from 0.64 to 0.77. In addition, values of the root mean square error (RMSE) and standard error (SE) decreased from 0.2 to 0.1 MPa and 0.24 to 0.16 MPa, respectively. Finally, this study shows that the negative effect of shadow canopy pixels was higher in those vines with water stress compared with well-watered vines.

  9. Hydrological Features on Subalpine Forest Zone in the East of Qinghai-Tibet Plateau

    Science.gov (United States)

    Zhong, X.; Cheng, G.; Guo, W.

    2008-12-01

    The Hengduan mountain chains of China is situated on the east of Qinghai-Tibet Plateau with area of more than 400,000 km2. Mountains and rivers run through in north-south direction, and are collocated side by side on east-west. Elevation difference between ridges and valleys has great disparity, normally of 1000-2500m, so the vertical zones of vegetation are very distinct. Subalpine coniferous forest zone, mainly composed of fir (Abies) and spruce (Picea), is on altitude of 2800-4200m, which is a chief component of the forested area in southwest China, and an important region for water conservation of several international rivers inlcuding Nujiang River and Lancangjiang River, as well as the world-famous Changjiang River. Thus, it has both theoretical and practical significance to study hydrological process and laws of forest in this region. The study area is located at the Gongga Mountain, on the east edge of the Hengduan mountain chains. Elevation of the main peak is 7556m, and elevation difference between ridge and valley on the eastern slope is 6400m. An ecological observation station was built at altitude of 3000m on the eastern slope of Gongga Mountain in 1988, mainly for alpine ecology and forest hydrology research. Based on the analysis of 20- years observation data from this station, it is revealed that hydrological process of forest in this area has several features as follows: (1) Canopy interception of primitive fir (Abies) forest is obviously greater than other tree species, and interception rate is 30-40%. Maximal canopy interception of one-time precipitation of primitive fir forest is commonly 2-5mm. According to observation data of canopy interception, a conceptual model of canopy interception of fir forest is established: R=1.69[(1-exp(-0.41P))+0.19P (P is precipitation in mm); (2) Natural valid moisture holding capacity in layer of moss-decayed wood and leaves beneath trees is up to 5.6mm. Porosity in soil surface layer and non-capillary porosity

  10. Eddy covariance fluxes and vertical concentration gradient measurements of NO and NO2 over a ponderosa pine ecosystem: observational evidence for within canopy removal of NOx

    Science.gov (United States)

    Min, K.-E.; Pusede, S. E.; Browne, E. C.; LaFranchi, B. W.; Wooldridge, P. J.; Cohen, R. C.

    2013-05-01

    Exchange of NOx (NO+NO2) between the atmosphere and biosphere is important for air quality, climate change, and ecosystem nutrient dynamics. There are few direct ecosystem scale measurements of the direction and rate of atmosphere-biosphere exchange of NOx. As a result, a complete description of the processes affecting NOx following emission from soils and/or plants as they transit from within the plant/forest canopy to the free atmosphere remains poorly constrained and debated. Here, we describe measurements of NO and NO2 fluxes and vertical concentration gradients made during the Biosphere Effects on AeRosols and Photochemistry EXperiment 2009. In general, during daytime we observe upward fluxes of NO and NO2 with counter-gradient fluxes of NO. We find that NOx fluxes from the forest canopy are smaller than calculated using observed flux-gradient relationships for conserved tracers and also smaller than measured soil NO emissions. We interpret these differences as evidence for the existence of a "canopy reduction factor". We suggest that at this site it is primarily due to chemistry converting NOx to higher nitrogen oxides within the forest canopy.

  11. [Dynamics of species diversity in artificial restoration process of subalpine coniferous forest].

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    Wu, Yan; Liu, Qing; He, Hai; Lin, Bo

    2004-08-01

    Through plot investigation and by adopting the concept of space as a substitute for time, the developments of species diversity of trees, shrubs and herbaceous plants in subalpine coniferous plantations at different restoration stages were studied, and the correlation coefficients of species in each layer were discussed. The results indicated that in the restoration process, the species richness, diversity and evenness in subalpine coniferous plantations were gradually increased in a fluctuating way. The restoration process of Picea asperata plantations showed a tendency of development that in favor of resuming species diversity. The indices of species richness (species number and Margalef index) and species diversity (Shannon-Wiener index and Simpson index) of trees increased rapidly from the early stages of plantation establishment to the stage of canopy closing (about 30 yr of stand age) and then presented a tendency of decrease with some slight fluctuations, while the index of species evenness showed a periodical rising trend. For the shrub layer, the indices of species richness (Simpson index and Macintosh index) gradually increased with increasing restoration years, whereas the indices of species diversity (Shannon-Wiener index) decreased in the early stages, sharply increased during the stages of canopy closing, and then slowly decreased, which exhibited a tendency of high-->low-->high. In the layer of herbaceous plants, the indices of species richness (Margalef index and number of species) and species diversity (Simpson index, Macintosh index and Shannon-Wiener index) presented a trend of decrease in the early stages of plantations establishment to canopy closing and increased later on. During this process, herbaceous species and their life forms changed greatly, with shade tolerant species gradually substituting the intolerant species. Among the plantations of different stand ages, the average correlation coefficients of trees, shrubs and herbaceous

  12. Summertime canopy albedo is sensitive to forest thinning

    OpenAIRE

    Otto, J.; Berveiller, D.; F. M. Bréon; Delpierre, N.; Geppert, G.; Granier, A.; Jans, W.W.P.; Knohl, A.; MOORS, E. J.

    2013-01-01

    Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, that is removing trees at a certain time during the forest rotation, on summertime canopy albedo. The effects of different forest species (pine, beech, oak) and four thinning strategies (light to int...

  13. Nitrogen deposition but not ozone affects productivity and community composition of subalpine grassland after 3 yr of treatment.

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    Bassin, Seraina; Volk, Matthias; Suter, Matthias; Buchmann, Nina; Fuhrer, Jürg

    2007-01-01

    A field experiment was established at 2000 m above sea level (asl) in the central Swiss Alps with the aim of investigating the effects of elevated ozone (O(3)) and nitrogen deposition (N), and of their combination, on above-ground productivity and species composition of subalpine grassland. One hundred and eighty monoliths were extracted from a species-rich Geo-Montani-Nardetum pasture and exposed in a free-air O(3)-fumigation system to one of three concentrations of O(3) (ambient, 1.2 x ambient, 1.6 x ambient) and five concentrations of additional N. Above-ground biomass, proportion of functional groups and normalized difference vegetation index (NDVI) were measured annually. After 3 yr of treatment, the vegetation responded to the N input with an increase in above-ground productivity and altered species composition, but without changes resulting from elevated O(3). N input > 10 kg N ha(-1) yr(-1) was sufficient to affect the composition of functional groups, with sedges benefiting over-proportionally. No interaction of O(3) x N was observed, except for NDVI; positive effects of N addition on canopy greenness were counteracted by accelerated leaf senescence in the highest O(3) treatment. The results suggest that effects of elevated O(3) on the productivity and floristic composition of subalpine grassland may develop slowly, regardless of the sensitive response to increasing N.

  14. Canopy Chemistry (OTTER)

    Data.gov (United States)

    National Aeronautics and Space Administration — Canopy characteristics: leaf chemistry, specific leaf area, LAI, PAR, IPAR, NPP, standing biomass--see also: Meteorology (OTTER) for associated meteorological...

  15. Soil carbon estimation from eucalyptus grandis using canopy spectra

    African Journals Online (AJOL)

    Mapping soil fertility parameters, such as soil carbon (C), is fundamentally important for forest management and research related to forest growth and climate change. This study seeks to establish the link between Eucalyptus grandis canopy spectra and soil carbon using raw and continuum-removed spectra. Canopy-level ...

  16. Response of subalpine grasslands communities to clear-cut and prescribed burnt to control shrub encroachment in Pyrenees

    Science.gov (United States)

    Alados, Concepción L.; Gartzia, Maite; Nuche, Paloma; Saiz, Hugo; Pueyo, Yolanda

    2017-04-01

    Anthropogenic activities have modified vegetation in subalpine belts for long time, lowering treeline ecotone and influencing landscape mainly through grazing and fire. During the last decades the abandonment of traditional land use practices and global warming are contributing largely to the colonization of woody species in subalpine grasslands causing irreversible changes in ecosystem functioning. To prevent those changes a variety of management strategies are carried out to stop the expansion of the highly encroaching shrubs, which require the use of fire and/or clear-cutting, particularly for the conservation of grasslands in subhumid high productive ecosystems. However, it is still poorly understood how different management strategies affect the recovery of subalpine grasslands. Using a field experiment we tested the impact of management treatments on soil properties and vegetation characteristics, including species richness, community structure, interspecies interaction, and complexity of network association. Vegetation was monitored during four years in eight stands (two stands per treatment) where the vegetation was removed by prescribed fire (Burnt treatment), or by mechanical removal (Clear-cut treatment). Two undisturbed E. horridum stands were used as a control (C-Erizón) and two grassland communities regularly grazed (C-Grass) were used as a control for subalpine grassland. Soils nutrients declined in Burnt treatment 3 years after fire, but not differences between Clear-cut and C-Erizón were observed. Species richness and diversity were larger in C-Grass and lower in C-Erizón. Burnt and Clear-cut treatments increased species diversity and richness gradually after 4 year treatment. The proportion of legume forbs, grasses and non-legume forbs did not reach the levels of C-Grass after 4 years of Clear-cut or Burnt treatments. Shrubs and sub-shrubs increased faster after 4 years of burning than after 4 years of clearing, although they did not reach the

  17. The canopy camera

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    Harry E. Brown

    1962-01-01

    The canopy camera is a device of new design that takes wide-angle, overhead photographs of vegetation canopies, cloud cover, topographic horizons, and similar subjects. Since the entire hemisphere is photographed in a single exposure, the resulting photograph is circular, with the horizon forming the perimeter and the zenith the center. Photographs of this type provide...

  18. Provenance variability in nursery growth of subalpine fir

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    Charlie Cartwright; Cheng Ying

    2011-01-01

    Subalpine fir (Abies lasiocarpa [Hook] Nutt.) is a wide-ranging, high-elevation species in the interior of British Columbia. It is commonly harvested for lumber, but replanting of it is limited. Some reticence is based upon wood quality and rate of growth, but there are also seed and nursery culturing difficulties. This study investigated seedling growth traits of 111...

  19. Soil, plant, and transport influences on methane in a subalpine forest under high ultraviolet irradiance

    Directory of Open Access Journals (Sweden)

    D. Baer

    2009-07-01

    Full Text Available Recent studies have demonstrated direct methane emission from plant foliage under aerobic conditions, particularly under high ultraviolet (UV irradiance. We examined the potential importance of this phenomenon in a high-elevation conifer forest using micrometeorological techniques. Vertical profiles of methane and carbon dioxide in forest air were monitored every 2 h for 6 weeks in summer 2007. Day to day variability in above-canopy CH4 was high, with observed values in the range 1790 to 1910 nmol mol−1. High CH4 was correlated with high carbon monoxide and related to wind direction, consistent with pollutant transport from an urban area by a well-studied mountain-plain wind system. Soils were moderately dry during the study. Vertical gradients of CH4 were small but detectable day and night, both near the ground and within the vegetation canopy. Gradients near the ground were consistent with the forest soil being a net CH4 sink. Using scalar similarity with CO2, the magnitude of the summer soil CH4 sink was estimated at ~1.7 mg CH4 m−2 h−1, which is similar to other temperate forest upland soils. The high-elevation forest was naturally exposed to high UV irradiance under clear sky conditions, with observed peak UVB irradiance >2 W m−2. Gradients and means of CO2 within the canopy under daytime conditions showed net uptake of CO2 due to photosynthetic drawdown as expected. No evidence was found for a significant foliar CH4 source in the vegetation canopy, even under high UV conditions. While the possibility of a weak foliar source cannot be excluded given the observed soil sink, overall this subalpine forest was a net sink for atmospheric methane during the growing season.

  20. Disturbance and Stand Development of a Colorado Subalpine Forest

    OpenAIRE

    Veblen, Thomas T.; Hadley, Keith S; Reid, Marion S

    1991-01-01

    Stand development patterns were examined in an Engelmann spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa) and lodgepole pine (Pinus contorta var. latifolia) forest in Rocky Mountain National Park in northern Colorado. Two old-growth stands (with fine-scale windthrows dominating dynamics) and a 260-yr-old post-fire stand were sampled for tree ages, sizes, growth, and replacement patterns in windthrow gaps. Visual assessment of frequency of growth releases in increment cores, and de...

  1. Evaluation of storage and filtration protocols for alpine/subalpine lake water quality samples

    Science.gov (United States)

    John L. Korfmacher; Robert C. Musselman

    2007-01-01

    Many government agencies and other organizations sample natural alpine and subalpine surface waters using varying protocols for sample storage and filtration. Simplification of protocols would be beneficial if it could be shown that sample quality is unaffected. In this study, samples collected from low ionic strength waters in alpine and subalpine lake inlets...

  2. Ozone and modeled stomatal conductance at a high elevation subalpine site in southeastern Wyoming

    Science.gov (United States)

    Robert C. Musselman; Karl F. Zeller; Nedialko T. Nikolov

    1998-01-01

    Ozone concentrations have been monitored at the Glacier Lakes Ecosystem Experiment Site (GLEES) in the Snowy Range of the Medicine Bow Mountains 55 km west of Laramie, Wyoming, USA. The site is located at 3,186 m elevation in a large subalpine meadow of a mature subalpine forest near timberline. Continuous ozone and meteorological monitoring are a part of the GLEES...

  3. Fire, fuel composition and resilience threshold in subalpine ecosystem.

    Directory of Open Access Journals (Sweden)

    Olivier Blarquez

    Full Text Available BACKGROUND: Forecasting the effects of global changes on high altitude ecosystems requires an understanding of the long-term relationships between biota and forcing factors to identify resilience thresholds. Fire is a crucial forcing factor: both fuel build-up from land-abandonment in European mountains, and more droughts linked to global warming are likely to increase fire risks. METHODS: To assess the vegetation response to fire on a millennium time-scale, we analyzed evidence of stand-to-local vegetation dynamics derived from sedimentary plant macroremains from two subalpine lakes. Paleobotanical reconstructions at high temporal resolution, together with a fire frequency reconstruction inferred from sedimentary charcoal, were analyzed by Superposed Epoch Analysis to model plant behavior before, during and after fire events. PRINCIPAL FINDINGS: We show that fuel build-up from arolla pine (Pinus cembra always precedes fires, which is immediately followed by a rapid increase of birch (Betula sp., then by ericaceous species after 25-75 years, and by herbs after 50-100 years. European larch (Larix decidua, which is the natural co-dominant species of subalpine forests with Pinus cembra, is not sensitive to fire, while the abundance of Pinus cembra is altered within a 150-year period after fires. A long-term trend in vegetation dynamics is apparent, wherein species that abound later in succession are the functional drivers, loading the environment with fuel for fires. This system can only be functional if fires are mainly driven by external factors (e.g. climate, with the mean interval between fires being longer than the minimum time required to reach the late successional stage, here 150 years. CONCLUSION: Current global warming conditions which increase drought occurrences, combined with the abandonment of land in European mountain areas, creates ideal ecological conditions for the ignition and the spread of fire. A fire return interval of less

  4. A canopy trimming experiment in Puerto Rico: the response of litter invertebrate communities to canopy loss and debris deposition in a tropical forest subject to hurricanes

    Science.gov (United States)

    Barbara A. Richardson; Michael J. Richardson; Grizelle Gonzalez; Aaron B. Shiels; Diane S. Srivastava

    2010-01-01

    Hurricanes cause canopy removal and deposition of pulses of litter to the forest floor. A Canopy Trimming Experiment (CTE) was designed to decouple these two factors, and to investigate the separate abiotic and biotic consequences of hurricane-type damage and monitor recovery processes. As part of this experiment, effects on forest floor invertebrate communities were...

  5. Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem.

    Directory of Open Access Journals (Sweden)

    Joshua P Averett

    Full Text Available Mountain environments are currently among the ecosystems least invaded by non-native species; however, mountains are increasingly under threat of non-native plant invasion. The slow pace of exotic plant invasions in mountain ecosystems is likely due to a combination of low anthropogenic disturbances, low propagule supply, and extreme/steep environmental gradients. The importance of any one of these factors is debated and likely ecosystem dependent. We evaluated the importance of various correlates of plant invasions in the Wallowa Mountain Range of northeastern Oregon and explored whether non-native species distributions differed from native species along an elevation gradient. Vascular plant communities were sampled in summer 2012 along three mountain roads. Transects (n = 20 were evenly stratified by elevation (~70 m intervals along each road. Vascular plant species abundances and environmental parameters were measured. We used indicator species analysis to identify habitat affinities for non-native species. Plots were ordinated in species space, joint plots and non-parametric multiplicative regression were used to relate species and community variation to environmental variables. Non-native species richness decreased continuously with increasing elevation. In contrast, native species richness displayed a unimodal distribution with maximum richness occurring at mid-elevations. Species composition was strongly related to elevation and canopy openness. Overlays of trait and environmental factors onto non-metric multidimensional ordinations identified the montane-subalpine community transition and over-story canopy closure exceeding 60% as potential barriers to non-native species establishment. Unlike native species, non-native species showed little evidence for high-elevation or closed-canopy specialization. These data suggest that non-native plants currently found in the Wallowa Mountains are dependent on open canopies and disturbance for

  6. Thirty Years of Change in Subalpine Forest Cover from Landsat Image Analysis in the Sierra Nevada Mountains of California

    Science.gov (United States)

    Potter, Christopher

    2015-01-01

    Landsat imagery was analyzed to understand changes in subalpine forest stands since the mid-1980s in the Sierra-Nevada region of California. At locations where long-term plot measurements have shown that stands are becoming denser in the number of small tree stems (compared to the early 1930s), the 30-year analysis of Landsat greenness index (NDVI) indicated that no consistent increases in canopy leaf cover have occurred at these same locations since the mid-1980s. Interannual variations in stand NDVI closely followed snow accumulation amounts recorded at nearby stations. In contrast, at eastern Sierra whitebark pine stand locations where it has been observed that widespread tree mortality has occurred, decreasing NDVI trends over the past 5-10 years were consistent with rapid loss of forest canopy cover. Landsat imagery was further analyzed to understand patterns of post-wildfire vegetation recovery, focusing on high burn severity (HBS) patches within burned areas dating from the late 1940s. Analysis of landscape metrics showed that the percentage of total HBS area comprised by the largest patch of recovered woody cover was relatively small in all fires that occurred since 1995, but increased rapidly with time since fire. Patch complexity of recovered woody cover decreased notably after more than 50 years of regrowth, but was not readily associated with time for fires that occurred since the mid 1990s. The aggregation level of patches with recovery of woody cover increased steadily with time since fire. The study approach using satellite remote sensing can be expanded to assess the consequences of stand-replacing wildfires in all forests of the region.

  7. Comparative phytosocioogical investigation of subalpine alder thickets in southwestern Alaska and the North Pacific

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — We present the first vegetation analysis of subalpine alder (Alnus viridis) thickets in southwestern Alaska. The data are primarily from mesic, hilly and mountainous...

  8. Use of passive UAS imaging to measure biophysical parameters in a southern Rocky Mountain subalpine forest

    Science.gov (United States)

    Caldwell, M. K.; Sloan, J.; Mladinich, C. S.; Wessman, C. A.

    2013-12-01

    Unmanned Aerial Systems (UAS) can provide detailed, fine spatial resolution imagery for ecological uses not otherwise obtainable through standard methods. The use of UAS imagery for ecology is a rapidly -evolving field, where the study of forest landscape ecology can be augmented using UAS imagery to scale and validate biophysical data from field measurements to spaceborne observations. High resolution imagery provided by UAS (30 cm2 pixels) offers detailed canopy cover and forest structure data in a time efficient and inexpensive manner. Using a GoPro Hero2 (2 mm focal length) camera mounted in the nose cone of a Raven unmanned system, we collected aerial and thermal data monthly during the summer 2013, over two subalpine forests in the Southern Rocky Mountains in Colorado. These forests are dominated by lodgepole pine (Pinus ponderosae) and have experienced insect-driven (primarily mountain pine beetle; MPB, Dendroctonus ponderosae) mortality. Objectives of this study include observations of forest health variables such as canopy water content (CWC) from thermal imagery and leaf area index (LAI), biomass and forest productivity from the Normalized Difference Vegetation Index (NDVI) from UAS imagery. Observations were, validated with ground measurements. Images were processed using a combination of AgiSoft Photoscan professional software and ENVI remote imaging software. We utilized the software Leaf Area Index Calculator (LAIC) developed by Córcoles et al. (2013) for calculating LAI from digital images and modified to conform to leaf area of needle-leaf trees as in Chen and Cihlar (1996) . LAIC uses a K-means cluster analysis to decipher the RGB levels for each pixel and distinguish between green aboveground vegetation and other materials, and project leaf area per unit of ground surface area (i.e. half total needle surface area per unit area). Preliminary LAIC UAS data shows summer average LAI was 3.8 in the most dense forest stands and 2.95 in less dense

  9. Canopy for VERAView Installation Guide

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ronald W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-12

    With the addition of the 3D volume slicer widget, VERAView now relies on Mayavi and its dependents. Enthought's Canopy Python environment provides everything VERAView needs, and pre-built Canopy versions for Windows, Mac OSX, and Linux can be downloaded.

  10. Estimating foliar biochemistry from hyperspectral data in mixed forest canopy

    DEFF Research Database (Denmark)

    Huber Gharib, Silvia; Kneubühler, Mathias; Psomas, Achilleas

    2008-01-01

    data to estimate the foliar concentration of nitrogen, carbon and water in three mixed forest canopies in Switzerland. With multiple linear regression models, continuum-removed and normalized HyMap spectra were related to foliar biochemistry on an individual tree level. The six spectral wavebands used...

  11. Boreal forest BVOC exchange: emissions versus in-canopy sinks

    Science.gov (United States)

    Zhou, Putian; Ganzeveld, Laurens; Taipale, Ditte; Rannik, Üllar; Rantala, Pekka; Petteri Rissanen, Matti; Chen, Dean; Boy, Michael

    2017-12-01

    A multilayer gas dry deposition model has been developed and implemented into a one-dimensional chemical transport model SOSAA (model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to calculate the dry deposition velocities for all the gas species included in the chemistry scheme. The new model was used to analyse in-canopy sources and sinks, including gas emissions, chemical production and loss, dry deposition, and turbulent transport of 12 featured biogenic volatile organic compounds (BVOCs) or groups of BVOCs (e.g. monoterpenes, isoprene+2-methyl-3-buten-2-ol (MBO), sesquiterpenes, and oxidation products of mono- and sesquiterpenes) in July 2010 at the boreal forest site SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations). According to the significance of modelled monthly-averaged individual source and sink terms inside the canopy, the selected BVOCs were classified into five categories: 1. Most of emitted gases are transported out of the canopy (monoterpenes, isoprene + MBO). 2. Chemical reactions remove a significant portion of emitted gases (sesquiterpenes). 3. Bidirectional fluxes occur since both emission and dry deposition are crucial for the in-canopy concentration tendency (acetaldehyde, methanol, acetone, formaldehyde). 4. Gases removed by deposition inside the canopy are compensated for by the gases transported from above the canopy (acetol, pinic acid, β-caryophyllene's oxidation product BCSOZOH). 5. The chemical production is comparable to the sink by deposition (isoprene's oxidation products ISOP34OOH and ISOP34NO3). Most of the simulated sources and sinks were located above about 0.2 hc (canopy height) for oxidation products and above about 0.4 hc for emitted species except formaldehyde. In addition, soil deposition (including deposition onto understorey vegetation) contributed 11-61 % to the overall in-canopy deposition. The emission sources peaked at about 0.8-0.9 hc, which was higher than 0.6 hc

  12. Estimating Canopy Dark Respiration for Crop Models

    Science.gov (United States)

    Monje Mejia, Oscar Alberto

    2014-01-01

    Crop production is obtained from accurate estimates of daily carbon gain.Canopy gross photosynthesis (Pgross) can be estimated from biochemical models of photosynthesis using sun and shaded leaf portions and the amount of intercepted photosyntheticallyactive radiation (PAR).In turn, canopy daily net carbon gain can be estimated from canopy daily gross photosynthesis when canopy dark respiration (Rd) is known.

  13. Climate, geography, and tree establishment in subalpine meadows of the Olympic Mountains, Washington, USA

    Science.gov (United States)

    Woodward, Andrea; Schreiner, Edward G.; Silsbee, D.G.

    1995-01-01

    Noticeable changes in vegetation distribution have occurred in the Pacific Northwest during the last century as trees have established in some subalpine meadows. To study the relationship of this process to climate, recently established trees were aged in six subalpine meadows in the Olympic Mountains, Washington. The sites represent three points along a steep precipitation gradient. Subalpine fir (Abies lasiocarpa) has been establishing at the dry end of the gradient, mountain hemlock (Tsuga mertensiana) at the wet end, and both species in the center. Establishment patterns were compared with deviations from the century-long average for these weather variables: winter precipitation, Palmer Drought Severity Index, and winter, October, and May temperatures. Results show that establishment occurred in dry areas when weather conditions were wetter than average, and in wet areas under drier than average conditions. Establishment at central sites did not show consistent relationships with climate. If future climatic conditions continue to warm, establishment of subalpine fir in subalpine meadows in dry areas may cease and mountain hemlock may resume in wet areas.

  14. Plant photomorphogenesis and canopy growth

    Energy Technology Data Exchange (ETDEWEB)

    Ballare, C.L.; Scopel, A.L. [Universidad de Buenos Aires (Argentina)

    1994-12-31

    An important motivation for studying photomorphogenesis is to understand the relationships among plant photophysiology in canopies, canopy productivity, and agronomic yield. This understanding is essential to optimize lighting systems used for plant farming in controlled environments (CE) and for the design of genetically engineered crop strains with altered photoresponses. This article provides an overview of some basic principles of plant photomorphogenesis in canopies and discusses their implications for (1) scaling up information on plant photophysiology from individual plants in CE to whole canopies in the field, and (2), designing lighting conditions to increase plant productivity in CE used for agronomic purposes [e.g. space farming in CE Life-Support-Systems]. We concentrate on the visible ({lambda} between 400 and 700 nm) and far red (FR; {lambda} > 700 nm) spectral regions, since the ultraviolet (UV; 280 to 400 nm) is covered by other authors in this volume.

  15. Canopy position has a profound effect on soybean seed composition

    Directory of Open Access Journals (Sweden)

    Steven C. Huber

    2016-09-01

    Full Text Available Although soybean seeds appear homogeneous, their composition (protein, oil and mineral concentrations can vary significantly with the canopy position where they were produced. In studies with 10 cultivars grown over a 3-yr period, we found that seeds produced at the top of the canopy have higher concentrations of protein but less oil and lower concentrations of minerals such as Mg, Fe, and Cu compared to seeds produced at the bottom of the canopy. Among cultivars, mean protein concentration (average of different positions correlated positively with mean concentrations of S, Zn and Fe, but not other minerals. Therefore, on a whole plant basis, the uptake and allocation of S, Zn and Fe to seeds correlated with the production and allocation of reduced N to seed protein; however, the reduced N and correlated minerals (S, Zn and Fe showed different patterns of allocation among node positions. For example, while mean concentrations of protein and Fe correlated positively, the two parameters correlated negatively in terms of variation with canopy position. Altering the microenvironment within the soybean canopy by removing neighboring plants at flowering increased protein concentration in particular at lower node positions and thus altered the node-position gradient in protein (and oil without altering the distribution of Mg, Fe and Cu, suggesting different underlying control mechanisms. Metabolomic analysis of developing seeds at different positions in the canopy suggests that availability of free asparagine may be a positive determinant of storage protein accumulation in seeds and may explain the increased protein accumulation in seeds produced at the top of the canopy. Our results establish node-position variation in seed constituents and provide a new experimental system to identify genes controlling key aspects of seed composition. In addition, our results provide an unexpected and simple approach to link agronomic practices to improve human

  16. Phenology of plants in relation to ambient environment in a subalpine forest of Uttarakhand, western Himalaya.

    Science.gov (United States)

    Bisht, Vinod K; Kuniyal, Chandra P; Bhandari, Arvind K; Nautiyal, Bhagwati P; Prasad, P

    2014-07-01

    Observations on phenology of some representative trees, shrubs, under-shrubs and herbs in a subalpine forest of Uttarakhand, western Himalaya were recorded. With the commencement of favorable growth season in April, occurrence of leaf fall was indicatory growth phenomenon in Quercus semecarpifolia, Q. floribunda and Abies spectabilis. However, active vegetative growth in herbaceous species starts onward April and fruit maturation and seed dehiscence are completed from mid of September to October. In general, vegetative growth and reproductive stages in majority of the studied species seems to be dependent on adequate moisture content and also flowering and fruiting in subalpine plants correlate ambient temperature.

  17. Forests and Their Canopies: Achievements and Horizons in Canopy Science.

    Science.gov (United States)

    Nakamura, Akihiro; Kitching, Roger L; Cao, Min; Creedy, Thomas J; Fayle, Tom M; Freiberg, Martin; Hewitt, C N; Itioka, Takao; Koh, Lian Pin; Ma, Keping; Malhi, Yadvinder; Mitchell, Andrew; Novotny, Vojtech; Ozanne, Claire M P; Song, Liang; Wang, Han; Ashton, Louise A

    2017-06-01

    Forest canopies are dynamic interfaces between organisms and atmosphere, providing buffered microclimates and complex microhabitats. Canopies form vertically stratified ecosystems interconnected with other strata. Some forest biodiversity patterns and food webs have been documented and measurements of ecophysiology and biogeochemical cycling have allowed analyses of large-scale transfer of CO2, water, and trace gases between forests and the atmosphere. However, many knowledge gaps remain. With global research networks and databases, and new technologies and infrastructure, we envisage rapid advances in our understanding of the mechanisms that drive the spatial and temporal dynamics of forests and their canopies. Such understanding is vital for the successful management and conservation of global forests and the ecosystem services they provide to the world. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Electromagnetic Scattering from Vegetation Canopies.

    Science.gov (United States)

    Sarabandi, Kamal

    Satellite-borne imaging radar has been proposed by the remote sensing community as a potential sensor for the acquisition of quantitative information about forested area on a global scale. To achieve this goal, it is necessary to develop retrieved algorithms that can provide reasonable estimate of vegetation biomass, leaf moisture content, and other physical parameters of tree canopies from multifrequency/multipolarization observations of their radar backscattering coefficients. Retrieval algorithms often are called "inverse problem" because their input/output parameters are the inverse of those associated with the direct problem, which in the present case refers to the development of a radar scattering model that relates the radar response to the canopy architecture and associated parameters. This thesis provides electromagnetic solutions to several problems associated with scattering from tree canopies. The forest canopy is modelled in the form of layers comprised of randomly distributed particles with known statistical properties. In Chapters 2-8 effective scattering models for different constituent particles of vegetation canopies are developed by employing appropriate asymptotic solutions and approximations. The effects of various physical features of the particles, such as curvature and variation in thickness for planar leaves and roughness for tree trunks, on their scattering behavior are examined. In Chapter 9 the scattering problem of inhomogeneous layered media is formulated via the vector radiative transfer equations and a first-order solution for the radar scattering coefficients is obtained. The radiative transfer solution is formulated in terms of two sets of input functions: the scattering matrices of the constituent particles, which are given in Chapters 2-8, and the size and orientation distribution functions of the particles. The radar scattering model and associated input functions can be used to conduct sensitivity analyses to determine the

  19. Using ground penetrating radar to assess the variability of snow water equivalent and melt in a mixed canopy forest, Northern Colorado

    Science.gov (United States)

    Webb, Ryan W.

    2017-09-01

    Snow is an important environmental variable in headwater systems that controls hydrological processes such as streamflow, groundwater recharge, and evapotranspiration. These processes will be affected by both the amount of snow available for melt and the rate at which it melts. Snow water equivalent (SWE) and snowmelt are known to vary within complex subalpine terrain due to terrain and canopy influences. This study assesses this variability during the melt season using ground penetrating radar to survey multiple plots in northwestern Colorado near a snow telemetry (SNOTEL) station. The plots include south aspect and flat aspect slopes with open, coniferous (subalpine fir, Abies lasiocarpa and engelman spruce, Picea engelmanii), and deciduous (aspen, populous tremuooides) canopy cover. Results show the high variability for both SWE and loss of SWE during spring snowmelt in 2014. The coefficient of variation for SWE tended to increase with time during snowmelt whereas loss of SWE remained similar. Correlation lengths for SWE were between two and five meters with melt having correlation lengths between two and four meters. The SNOTEL station regularly measured higher SWE values relative to the survey plots but was able to reasonably capture the overall mean loss of SWE during melt. Ground Penetrating Radar methods can improve future investigations with the advantage of non-destructive sampling and the ability to estimate depth, density, and SWE.

  20. Linkages between grazing history and herbivore exclusion on decomposition rates in mineral soils of subalpine grasslands

    Science.gov (United States)

    Alan G. Haynes; Martin Schutz; Nina Buchmann; Deborah S. Page-Dumroese; Matt D. Busse; Anita C. Risch

    2014-01-01

    Herbivore-driven changes to soil properties can influence the decomposition rate of organic material and therefore soil carbon cycling within grassland ecosystems. We investigated how aboveground foraging mammalian and invertebrate herbivores affect mineral soil decomposition rates and associated soil properties in two subalpine vegetation types (shortgrass and tall-...

  1. Human disturbance provides foraging opportunities for birds in primary subalpine forest

    DEFF Research Database (Denmark)

    DuBay, Shane G.; Hart Reeve, Andrew; Wu, Yongjie

    2017-01-01

    to species that naturally occur in edge, open, or disturbed habitats. With observations and experiments we provide evidence of insectivorous birds exploiting human disturbance in primary subalpine forest in the mountains of southern China, displaying behavioral flexibility to gain novel foraging...

  2. Net primary productivity of subalpine meadows in Yosemite National Park in relation to climate variability

    Science.gov (United States)

    Peggy E. Moore; Jan W. van Wagtendonk; Julie L. Yee; Mitchel P. McClaran; David N. Cole; Neil K. McDougald; Matthew L. Brooks

    2013-01-01

    Subalpine meadows are some of the most ecologically important components of mountain landscapes, and primary productivity is important to the maintenance of meadow functions. Understanding how changes in primary productivity are associated with variability in moisture and temperature will become increasingly important with current and anticipated changes in climate....

  3. Drought-driven disturbance history characterizes a southern Rocky Mountain subalpine forest

    Science.gov (United States)

    R. Justin DeRose; James N. Long

    2012-01-01

    The view that subalpine forest vegetation dynamics in western North America are "driven" by a particular disturbance type (i.e., fire) has shaped our understanding of their disturbance regimes. In the wake of a recent (1990s) landscape- extent spruce beetle (Dendroctonus rufipennis Kirby) outbreak in the southern Rocky Mountains, we re-examined the temporal...

  4. Water use patterns of three species in subalpine forest, Southwest China: the deuterium isotope approach

    Science.gov (United States)

    Qing Xu; Harbin Li; Jiquan Chen; Jiquan Cheng; Xiaoli Cheng; Shirong Liu; Shuqing An

    2011-01-01

    Determination of water sources of plant species in a community is critical for understanding the hydrological processes and their importance in ecosystem functions. Such partitioning of plant xylem water into specific sources (i.e. precipitation, groundwater) can be achieved by analyzing deuterium isotopic composition (δD) values for source waters. A subalpine dark...

  5. Comparison of the abundance and composition of litter fauna in tropical and subalpine forests

    Science.gov (United States)

    G. Gonzalez; T.R. Seastedt

    2000-01-01

    In this study, we quantify the abundance and composition of the litter fauna in dry and wet tropical forests and north- and south-facing subalpine forests. We used the same litter species contained in litterbags across study sites to standardize for substrate conditions, and a single method of fauna extraction from the litter (Tullgren method). Fauna densities were...

  6. Human-Related Forest Fires in the Subalpine Belt of the Spanish Pyrenees

    Science.gov (United States)

    Sanjuán, Yasmina; María García-Ruiz, José; Beguería, Santiago; Serrano-Muela, María Pilar; González-Sampériz, Penélope; Valero-Garcés, Blas; Arnáez, José

    2014-05-01

    The subalpine belt of the Central Pyrenees ranges approximately between 1700 and 2200 m a.s.l. This area should be covered with dense forests of Pinus sylvestris and P. uncinata, with increasingly open formations towards the upper forest limit. At present, most of the subalpine belt is occupied with grasslands due to human-induced deforestation for enlarging the area occupied by summer pastures. Two are the most important scientific problems related to deforestation of the subalpine belt: (i) the timing of deforestation, and (ii) the geomorphic consequences of a sudden substitution of forests by grasslands. Up to now, intense deforestation is clearly recorded in regional palaeoenvironmental sequences since the Middle Ages and, traditionally, this practice was usually attributed to large fires with the purpose of balance the winter and summer pasture resources. Nevertheless, the presence of abundant remnants of prehistoric monuments (dolmens, cromlechs, tumulus) in the subalpine belt induced to think in a previous seasonal presence of human populations, most probably practicing some primitive type of transhumance. This would only be possible if part of the subalpine forests would be burnt to allow a limited expansion of grasslands, despite the consequences in the landscape of this kind of practices were not permanent in time. We present here new dates of fire occurrence from charcoal obtained from soils in the hillslopes and from lacustrine sediments. Two periods of human-induced fires have been identified: (i) between 2500 and 2000 cal. yr BP, and (ii) between 1100 and 900 cal yr BP. The consequences of deforestation can be easily observed in the landscape, particularly shallow landslide activity, gelifluction, solifluction and the rapid development of parallel incisions in the steepest slopes.

  7. Manipulation of subalpine and alpine microclimate in the Alpine Treeline Warming Experiment

    Science.gov (United States)

    Kueppers, L. M.; Moyes, A. B.; Ferrenberg, S. M.; Christianson, D. S.; Castanha, C.; Germino, M. J.

    2011-12-01

    To experimentally test model projections of subalpine tree species' uphill migration with climate change, we have established the Alpine Treeline Warming Experiment at Niwot Ridge, CO. Common gardens subject to full factorial warming and watering experiments are replicated across three sites: near the lower limit of subalpine forest, within the alpine-treeline ecotone, and in the alpine tundra, beyond the current elevation ranges of the species. In 2010, differences in ambient climate among the three sites included 5.1° C greater growing-season air temperature and 0.5 kPa greater vapor pressure deficit in the lowest compared to the upper two sites. The lower subalpine site also experienced lower soil moisture compared to the upper two sites. Snowmelt date varied substantially between sites, with the longest snow-free period in the lower subalpine site and the shortest in the treeline site. In all sites, we observed advances in the timing of snowmelt in heated relative to control plots. The warming treatment also raised 5 cm soil temperatures by 3° C at the lower subalpine site, and by 1° C in the upper two sites, averaged over the growing season. More substantial wind in the alpine diminished the heating effect through sensible heat loss. Seasonal average volumetric soil moisture at 5-10 cm did not vary strongly among treatments even though seedling survival and gas exchange data suggest that water additions alleviated drought stress in some plots. These preliminary findings for identical warming and watering treatments across our three high mountain sites suggest that microclimate responses vary with radiation environment, patterns of snow accumulation, and wind speed. Some of these differences are realistic for a future warmer world, while others are artifacts of the experimental approach. Microclimate differences in 2011 reflect modified heating methods and a different spring hydroclimate (later snow accumulation and melt), highlighting the importance of

  8. A Comparison of Infrared Gas Analyzers Above a Subalpine Forest

    Science.gov (United States)

    Burns, S. P.; Metzger, S.; Blanken, P.; Burba, G. G.; Swiatek, E.; Li, J.; Conrad, B.

    2014-12-01

    Infrared gas analyzers (IRGAs) are a key component in theeddy-covariance measurement of water vapor and carbon dioxide exchangebetween the surface and atmosphere. Historically, closed-path IRGAshave been used for the fast (> 10 Hz) measurement of atmospheric H2Oand CO2. In order to use them in the field, these IRGAs were typicallyhoused in temperature-controlled enclosures or buildings that weretens of meters away from the measurement location. This necessitatedthe use of long tubing and pumps to bring the air sample to the IRGAcell. Attenuation of H2O and CO2 fluctuations within the tubing was apersistent problem with such a setup, especially for H2O. As analternative, open-path IRGAs have frequently been utilized, but thekey trade-offs with the open-path design are: (i) precipitation anddew-related data gaps, and (ii) the need to account for WPL densityeffects. Over the past five years a new type of closed-path IRGA hasemerged which is weather-proof, compact, and low-maintenance. Becauseof its small size, short intake tubing can be used, which places thesampling cell close to the sonic anemometer and reduces high frequencysignal loss. Two such IRGAs are the LI-COR LI-7200 and the CampbellScientific EC155, which is part of the CPEC200 eddy covariance system.The Niwot Ridge AmeriFlux tower has used a LI-COR LI-6262 IRGA tomeasure CO2 fluxes above a subalpine forest since November, 1998.Starting in summer 2013, a LI-7200 (along with an open-path LI-7500)were deployed at 21.5 m on the AmeriFlux tower. In Fall 2013, aEC155/CPEC200 was added so that a side-by-side comparison between allfour IRGAs was possible. The preliminary results presented in ourstudy compare the CO2 and H2O mean and variance measured by each IRGA,the vertical wind statistics from three side-by-side sonicanemometers, as well as the corresponding spectra and cospectra fromthese sensors as well as other important aspects of systemperformance.

  9. Remote canopy hemispherical image collection system

    Science.gov (United States)

    Wan, Xuefen; Liu, Bingyu; Yang, Yi; Han, Fang; Cui, Jian

    2016-11-01

    Canopies are major part of plant photosynthesis and have distinct architectural elements such as tree crowns, whorls, branches, shoots, etc. By measuring canopy structural parameters, the solar radiation interception, photosynthesis effects and the spatio-temporal distribution of solar radiation under the canopy can be evaluated. Among canopy structure parameters, Leaf Area Index (LAI) is the key one. Leaf area index is a crucial variable in agronomic and environmental studies, because of its importance for estimating the amount of radiation intercepted by the canopy and the crop water requirements. The LAI can be achieved by hemispheric images which are obtained below the canopy with high accuracy and effectiveness. But existing hemispheric images canopy-LAI measurement technique is based on digital SLR camera with a fisheye lens. Users need to collect hemispheric image manually. The SLR camera with fisheye lens is not suit for long-term canopy-LAI outdoor measurement too. And the high cost of SLR limits its capacity. In recent years, with the development of embedded system and image processing technology, low cost remote canopy hemispheric image acquisition technology is becoming possible. In this paper, we present a remote hemispheric canopy image acquisition system with in-field/host configuration. In-field node based on imbed platform, low cost image sensor and fisheye lens is designed to achieve hemispherical image of plant canopy at distance with low cost. Solar radiation and temperature/humidity data, which are important for evaluating image data validation, are obtained for invalid hemispherical image elimination and node maintenance too. Host computer interacts with in-field node by 3G network. The hemispherical image calibration and super resolution are used to improve image quality in host computer. Results show that the remote canopy image collection system can make low cost remote canopy image acquisition for LAI effectively. It will be a potential

  10. Forests and their canopies: Archievements and horizons in canopy science

    Czech Academy of Sciences Publication Activity Database

    Nakamura, A.; Kitching, R. L.; Cao, M.; Creedy, T. J.; Fayle, Tom Maurice; Freiberg, M.; Hewitt, C. N.; Itioka, T.; Koh, L. P.; Ma, K.; Malhi, Y.; Mitchell, A.; Novotný, Vojtěch; Ozanne, C. M. P.; Song, L.; Wang, H.; Ashton, L. A.

    2017-01-01

    Roč. 32, č. 6 (2017), s. 438-451 ISSN 0169-5347 R&D Projects: GA ČR(CZ) GA16-09427S; GA ČR GB14-36098G EU Projects: European Commission(XE) 669609 - Diversity6continents Institutional support: RVO:60077344 Keywords : biodiversity * canopy * cranes Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 15.268, year: 2016 http://www.sciencedirect.com/science/article/pii/S0169534717300599

  11. Characterizing water, energy and CO2 exchange for a Sky Island subalpine forest in the southwestern USA

    Science.gov (United States)

    Brown-Mitic, C. M.; Shuttleworth, J.; Harlow, C.; Bales, R.

    2003-04-01

    Among the ecosystems present in the semi-arid environment of the Southwestern U.S., Sky Island forest is unique and it has a unique relationship to the sparse surface-water resources available in the region. This ecosystem exists only at the top of mountains because it is only here that, as a long-term average, precipitation input exceeds evapotranspiration to the extent that forest vegetation can survive. Sky Island Forests, therefore, command potentially significant source areas for the water (some originally falling as snow) that ultimately leaves topographically high ground to recharge aquifers in the plains below by mountain-front recharge. They are also very recently recognized as important carbon sinks where very little or no understanding exist of the exchange/cycling dynamics. The Mount Bigelow project provides an empirically based understanding of the hydro- micrometeorological dynamics of a sky island sub-alpine forest in the southwestern U.S. It is the first study to attempt to document, understand, and model the water, energy, and (related) carbon exchanges of the uniquely interesting and, from the water resource standpoint, uniquely important Sky Island forest ecosystem. The fundamental science issues addressed are: the characteristics of the surface-atmosphere exchanges of water, energy and carbon; the storage of moisture and energy in plants and soil; partitioning of winter snow and rain between evapotranspiration/sublimation, deep drainage and the near-surface environmental water resource that sustains the forest. In order to achieve our objective, a network of four below canopy hydro-micrometeorological stations 10 m tall, and one above canopy 30 m tall high resolution eddy correlation tower, were deployed within a predominantly douglas fir/pine second growth forest. Our observations indicate that the surface flux potential (i.e. sensible heat flux (H) potential), defined as the surface-air temperature gradient varies significantly over space as

  12. Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

    Science.gov (United States)

    Anderson, R. Scott; Allen, Craig D.; Toney, J.L.; Jass, R.B.; Bair, A.N.

    2008-01-01

    Our understanding of the present forest structure of western North America hinges on our ability to determine antecedent forest conditions. Sedimentary records from lakes and bogs in the southern Rocky Mountains of Colorado and New Mexico provide information on the relationships between climate and vegetation change, and fire history since deglaciation. We present a new pollen record from Hunters Lake (Colorado) as an example of a high-elevation vegetation history from the southern Rockies. We then present a series of six sedimentary records from ???2600 to 3500-m elevation, including sites presently at the alpine?subalpine boundary, within the Picea engelmannii?Abies lasiocarpa forest and within the mixed conifer forest, to determine the history of fire in high-elevation forests there. High Artemisia and low but increasing percentages of Picea and Pinus suggest vegetation prior to 13 500 calendar years before present (cal yr BP) was tundra or steppe, with open spruce woodland to ???11 900 cal yr BP. Subalpine forest (Picea engelmannii, Abies lasiocarpa) existed around the lake for the remainder of the Holocene. At lower elevations, Pinus ponderosa and/or contorta expanded 11 900 to 10 200 cal yr BP; mixed conifer forest expanded ???8600 to 4700 cal yr BP; and Pinus edulis expanded after ???4700 cal yr BP. Sediments from lake sites near the alpine?subalpine transition contained five times less charcoal than those entirely within subalpine forests, and 40 times less than bog sites within mixed conifer forest. Higher fire episode frequencies occurred between ???12 000 and 9000 cal yr BP (associated with the initiation or expansion of south-west monsoon and abundant lightning, and significant biomass during vegetation turnover) and at ???2000?1000 cal yr BP (related to periodic droughts during the long-term trend towards wetter conditions and greater biomass). Fire episode frequencies for subalpine?alpine transition and subalpine sites were on average 5 to 10 fire

  13. Changes in canopy structure and ant assemblages affect soil ecosystem variables as a foundation species declines

    DEFF Research Database (Denmark)

    Kendrick, Joseph A.; Ribbons, Relena Rose; Classen, Aimee Taylor

    2015-01-01

    , we built ant exclosure subplots within all of the canopy manipulation plots to examine direct and interactive effects of canopy change and ant assemblage composition on soil and litter variables. Throughout HF-HeRE, T. canadensis was colonized by the adelgid in 2009, and the infested trees are now...... declining. The experimental removal of T. canadensis from the canopy was associated with an increase in the rate of cellulose decomposition by >50%, and exclosure of ants from subplots directly reduced their soil nitrate availability by 56%. Partial least squares path models revealed sequential interactive...... effects prior to adelgid infestation: canopy change (as a proxy for associated environmental changes) altered both decomposition and ant assemblage structure; changes in ant assemblage structure and decomposition rates altered nitrogen availability. The results illustrate that biotic changes directly...

  14. Variation in winter snowpack depth and duration influences summer soil respiration in a subalpine meadow

    Science.gov (United States)

    Arnold, C. L.; Ghezzehei, T. A.; Berhe, A. A.

    2012-12-01

    Subalpine meadows in the Sierra Nevada rely on the depth and duration of the winter snowpack to supply ample water to restore the water table in the meadow during the spring snowmelt. This study examines the role that interannual variability in the winter snowpack plays in the overall rate of summer soil respiration along a hydrologic gradient in a subalpine meadow. Carbon dioxide efflux from the meadow was measured from June through September in 2011 and 2012 using soil collars and a LICOR 8100A infrared gas analyzer. Preliminary results show that soil respiration rates are influenced by the hydrologic gradient across the meadow, with drier regions peaking earlier in the summer as compared to wetter regions. We also show that high snowpack years can suppress soil respiration in the meadow until late in the summer season as compared to low snowpack years, where soil respiration peaks early in the summer.

  15. Phenology of plants in relation to ambient environment in a subalpine forest of Uttarakhand, western Himalaya

    OpenAIRE

    Bisht, Vinod K.; Kuniyal, Chandra P.; Bhandari, Arvind K.; Nautiyal, Bhagwati P.; Prasad, P.

    2014-01-01

    Observations on phenology of some representative trees, shrubs, under-shrubs and herbs in a subalpine forest of Uttarakhand, western Himalaya were recorded. With the commencement of favorable growth season in April, occurrence of leaf fall was indicatory growth phenomenon in Quercus semecarpifolia, Q. floribunda and Abies spectabilis. However, active vegetative growth in herbaceous species starts onward April and fruit maturation and seed dehiscence are completed from mid of September to Octo...

  16. Bleaching of leaf litter and associated microfungi in subboreal and subalpine forests.

    Science.gov (United States)

    Hagiwara, Yusuke; Matsuoka, Shunsuke; Hobara, Satoru; Mori, Akira S; Hirose, Dai; Osono, Takashi

    2015-10-01

    Fungal decomposition of lignin leads to the whitening, or bleaching, of leaf litter, especially in temperate and tropical forests, but less is known about such bleaching in forests of cooler regions, such as boreal and subalpine forests. The purposes of the present study were to examine the extent of bleached area on the surface of leaf litter and its variation with environmental conditions in subboreal and subalpine forests in Japan and to examine the microfungi associated with the bleaching of leaf litter by isolating fungi from the bleached portions of the litter. Bleached area accounted for 21.7%-32.7% and 2.0%-10.0% of total leaf area of Quercus crispula and Betula ermanii, respectively, in subboreal forests, and for 6.3% and 18.6% of total leaf area of B. ermanii and Picea jezoensis var. hondoensis, respectively, in a subalpine forest. In subboreal forests, elevation, C/N ratio and pH of the FH layer, and slope aspect were selected as predictor variables for the bleached leaf area. Leaf mass per area and lignin content were consistently lower in the bleached area than in the nonbleached area of the same leaves, indicating that the selective decomposition of acid unhydrolyzable residue (recalcitrant compounds such as lignin, tannins, and cutins) enhanced the mass loss of leaf tissues in the bleached portions. Isolates of a total of 11 fungal species (6 species of Ascomycota and 5 of Basidiomycota) exhibited leaf-litter-bleaching activity under pure culture conditions. Two fungal species (Coccomyces sp. and Mycena sp.) occurred in both subboreal and subalpine forests, which were separated from each other by approximately 1100 km.

  17. Forest canopy height estimation using double-frequency repeat pass interferometry

    Science.gov (United States)

    Karamvasis, Kleanthis; Karathanassi, Vassilia

    2015-06-01

    In recent years, many efforts have been made in order to assess forest stand parameters from remote sensing data, as a mean to estimate the above-ground carbon stock of forests in the context of the Kyoto protocol. Synthetic aperture radar interferometry (InSAR) techniques have gained traction in last decade as a viable technology for vegetation parameter estimation. Many works have shown that forest canopy height, which is a critical parameter for quantifying the terrestrial carbon cycle, can be estimated with InSAR. However, research is still needed to understand further the interaction of SAR signals with forest canopy and to develop an operational method for forestry applications. This work discusses the use of repeat pass interferometry with ALOS PALSAR (L band) HH polarized and COSMO Skymed (X band) HH polarized acquisitions over the Taxiarchis forest (Chalkidiki, Greece), in order to produce accurate digital elevation models (DEMs) and estimate canopy height with interferometric processing. The effect of wavelength-dependent penetration depth into the canopy is known to be strong, and could potentially lead to forest canopy height mapping using dual-wavelength SAR interferometry at X- and L-band. The method is based on scattering phase center separation at different wavelengths. It involves the generation of a terrain elevation model underneath the forest canopy from repeat-pass L-band InSAR data as well as the generation of a canopy surface elevation model from repeat pass X-band InSAR data. The terrain model is then used to remove the terrain component from the repeat pass interferometric X-band elevation model, so as to enable the forest canopy height estimation. The canopy height results were compared to a field survey with 6.9 m root mean square error (RMSE). The effects of vegetation characteristics, SAR incidence angle and view geometry, and terrain slope on the accuracy of the results have also been studied in this work.

  18. Canopy Dynamics in Nanoscale Ionic Materials

    KAUST Repository

    Jespersen, Michael L.

    2010-07-27

    Nanoscale ionic materials (NIMS) are organic - inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. © 2010 American Chemical Society.

  19. VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine.

    Science.gov (United States)

    De Bei, Roberta; Fuentes, Sigfredo; Gilliham, Matthew; Tyerman, Steve; Edwards, Everard; Bianchini, Nicolò; Smith, Jason; Collins, Cassandra

    2016-04-23

    Leaf area index (LAI) and plant area index (PAI) are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI), canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants.

  20. Simulations of tropical rainforest albedo: is canopy wetness important?

    National Research Council Canada - National Science Library

    Silvia N.M. Yanagi; Marcos H. Costa

    2011-01-01

    .... Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy...

  1. Thermal constraints on foraging of tropical canopy ants.

    Science.gov (United States)

    Spicer, Michelle Elise; Stark, Alyssa Y; Adams, Benjamin J; Kneale, Riley; Kaspari, Michael; Yanoviak, Stephen P

    2017-04-01

    Small cursorial ectotherms risk overheating when foraging in the tropical forest canopy, where the surfaces of unshaded tree branches commonly exceed 50 °C. We quantified the heating and subsequent cooling rates of 11 common canopy ant species from Panama and tested the hypothesis that ant workers stop foraging at temperatures consistent with the prevention of overheating. We created hot experimental "sunflecks" on existing foraging trails of four ant species from different clades and spanning a broad range of body size, heating rate, and critical thermal maxima (CTmax). Different ant species exhibited very different heating rates in the lab, and these differences did not follow trends predicted by body size alone. Experiments with ant models showed that heating rates are strongly affected by color in addition to body size. Foraging workers of all species showed strong responses to heating and consistently abandoned focal sites between 36 and 44 °C. Atta colombica and Azteca trigona workers resumed foraging shortly after heat was removed, but Cephalotes atratus and Dolichoderus bispinosus workers continued to avoid the heated patch even after >5 min of cooling. Large foraging ants (C. atratus) responded slowly to developing thermal extremes, whereas small ants (A. trigona) evacuated sunflecks relatively quickly, and at lower estimated body temperatures than when revisiting previously heated patches. The results of this study provide the first field-based insight into how foraging ants respond behaviorally to the heterogeneous thermal landscape of the tropical forest canopy.

  2. Nondestructive, stereological estimation of canopy surface area

    DEFF Research Database (Denmark)

    Wulfsohn, Dvora-Laio; Sciortino, Marco; Aaslyng, Jesper M.

    2010-01-01

    a canopy using the smooth fractionator, (ii) sampling of leaves from the selected plants using the fractionator, and (iii) area estimation of the sampled leaves using point counting. We apply this procedure to estimate the total area of a chrysanthemum (Chrysanthemum morifolium L.) canopy and evaluate both...

  3. The impact of modifying antenna size of photosystem II on canopy photosynthetic efficiency – development of a new canopy photosynthesis model scaling from metabolism to canopy level processes

    Science.gov (United States)

    Canopy photosynthesis describes photosynthesis of an entire crop field and positively correlates with biomass production. Much effort in crop breeding has focused on improving canopy architecture and hence light distribution inside the canopy. Here, we develop a new integrated canopy photosynthesis ...

  4. Microwave Propagation Through Cultural Vegetation Canopies

    Science.gov (United States)

    Tavakoli, Ahad

    The need to understand the interaction of microwaves with vegetation canopies has markedly increased in recent years. This is due to advances made in remote sensing science, microwave technology, and signal processing circuits. One class of the earth's vegetation cover is man-made canopies, such as agricultural fields, orchards, and artificial forests. Contrary to natural vegetation terrain, location, spacing, and density of plants in a man-made vegetation canopy are deterministic quantities. As a result, the semi-deterministic nature of cultural vegetation canopies violate the random assumption of the radiative transfer theory and leads to experimented results that are in variance with model calculations. Hence, an alternative approach is needed to model the interaction of microwaves with such canopies. This thesis examines the propagation behavior through a canopy of corn plants. The corn canopy was selected as a representative of cultural vegetation canopies that are planted in parallel rows with an approximately fixed spacing between adjacent plants. Several experimental measurements were conducted to determine the transmission properties of a corn canopy in the 1-10 GHz range. The measurements which included horizontal propagation through the canopy as well as propagation at oblique incidence, were performed for defoliated canopies and for canopies with leaves. Through experimental observations and model development, the propagation behavior was found to be strongly dependent on the wavelength and the path length. At a wavelength in the neighborhood of 20 cm, for example, it was found that scattering by the stalks was coherent in nature for waves propagating horizontally through the canopy, which necessitated the development of a coherent-field model that uses Bragg scattering to account for the observed interference pattern in the transmitted beam. As the wavelength is made shorter, the semi-random spacing between plants becomes significant relative to the

  5. Warming and provenance limit tree recruitment across and beyond the elevation range of subalpine forest.

    Science.gov (United States)

    Kueppers, Lara M; Conlisk, Erin; Castanha, Cristina; Moyes, Andrew B; Germino, Matthew J; de Valpine, Perry; Torn, Margaret S; Mitton, Jeffry B

    2017-06-01

    Climate niche models project that subalpine forest ranges will extend upslope with climate warming. These projections assume that the climate suitable for adult trees will be adequate for forest regeneration, ignoring climate requirements for seedling recruitment, a potential demographic bottleneck. Moreover, local genetic adaptation is expected to facilitate range expansion, with tree populations at the upper forest edge providing the seed best adapted to the alpine. Here, we test these expectations using a novel combination of common gardens, seeded with two widely distributed subalpine conifers, and climate manipulations replicated at three elevations. Infrared heaters raised temperatures in heated plots, but raised temperatures more in the forest than at or above treeline because strong winds at high elevation reduced heating efficiency. Watering increased season-average soil moisture similarly across sites. Contrary to expectations, warming reduced Engelmann spruce recruitment at and above treeline, as well as in the forest. Warming reduced limber pine first-year recruitment in the forest, but had no net effect on fourth-year recruitment at any site. Watering during the snow-free season alleviated some negative effects of warming, indicating that warming exacerbated water limitations. Contrary to expectations of local adaptation, low-elevation seeds of both species initially recruited more strongly than high-elevation seeds across the elevation gradient, although the low-provenance advantage diminished by the fourth year for Engelmann spruce, likely due to small sample sizes. High- and low-elevation provenances responded similarly to warming across sites for Engelmann spruce, but differently for limber pine. In the context of increasing tree mortality, lower recruitment at all elevations with warming, combined with lower quality, high-provenance seed being most available for colonizing the alpine, portends range contraction for Engelmann spruce. The lower

  6. Warming and provenance limit tree recruitment across and beyond the elevation range of subalpine forest

    Science.gov (United States)

    Kueppers, Lara M.; Conlisk, Erin; Castanha, Cristina; Moyes, Andrew B.; Germino, Matthew; de Valpine, Perry; Torn, Margaret S.; Mitton, Jeffry B.

    2017-01-01

    Climate niche models project that subalpine forest ranges will extend upslope with climate warming. These projections assume that the climate suitable for adult trees will be adequate for forest regeneration, ignoring climate requirements for seedling recruitment, a potential demographic bottleneck. Moreover, local genetic adaptation is expected to facilitate range expansion, with tree populations at the upper forest edge providing the seed best adapted to the alpine. Here, we test these expectations using a novel combination of common gardens, seeded with two widely distributed subalpine conifers, and climate manipulations replicated at three elevations. Infrared heaters raised temperatures in heated plots, but raised temperatures more in the forest than at or above treeline because strong winds at high elevation reduced heating efficiency. Watering increased season-average soil moisture similarly across sites. Contrary to expectations, warming reduced Engelmann spruce recruitment at and above treeline, as well as in the forest. Warming reduced limber pine first-year recruitment in the forest, but had no net effect on fourth-year recruitment at any site. Watering during the snow-free season alleviated some negative effects of warming, indicating that warming exacerbated water limitations. Contrary to expectations of local adaptation, low-elevation seeds of both species initially recruited more strongly than high-elevation seeds across the elevation gradient, although the low-provenance advantage diminished by the fourth year for Engelmann spruce, likely due to small sample sizes. High- and low-elevation provenances responded similarly to warming across sites for Engelmann spruce, but differently for limber pine. In the context of increasing tree mortality, lower recruitment at all elevations with warming, combined with lower quality, high-provenance seed being most available for colonizing the alpine, portends range contraction for Engelmann spruce. The lower

  7. Transplantation of subalpine wood-pasture turfs along a natural climatic gradient reveals lower resistance of unwooded pastures to climate change compared to wooded ones.

    Science.gov (United States)

    Gavazov, Konstantin; Spiegelberger, Thomas; Buttler, Alexandre

    2014-04-01

    Climate change could impact strongly on cold-adapted mountain ecosystems, but little is known about its interaction with traditional land-use practices. We used an altitudinal gradient to simulate a year-round warmer and drier climate for semi-natural subalpine grasslands across a landscape of contrasting land-use management. Turf mesocosms from three pasture-woodland land-use types-unwooded pasture, sparsely wooded pasture, and densely wooded pasture-spanning a gradient from high to low management intensity were transplanted downslope to test their resistance to two intensities of climate change. We found strong overall effects of intensive (+4 K) experimental climate change (i.e., warming and reduced precipitation) on plant community structure and function, while moderate (+2 K) climate change did not substantially affect the studied land-use types, thus indicating an ecosystem response threshold to moderate climate perturbation. The individual land-use types were affected differently under the +4 K scenario, with a 60% decrease in aboveground biomass (AGB) in unwooded pasture turfs, a 40% decrease in sparsely wooded pasture turfs, and none in densely wooded ones. Similarly, unwooded pasture turfs experienced a 30% loss of species, advanced (by 30 days) phenological development, and a mid-season senescence due to drought stress, while no such effects were recorded for the other land-use types. The observed contrasting effects of climate change across the pasture-woodland landscape have important implications for future decades. The reduced impact of climate change on wooded pastures as compared to unwooded ones should promote the sustainable land use of wooded pastures by maintaining low management intensity and a sparse forest canopy, which buffer the immediate impacts of climate change on herbaceous vegetation.

  8. Effects of a long-term disturbance on arthropods and vegetation in subalpine wetlands: manifestations of pack stock grazing in early versus mid-season.

    Directory of Open Access Journals (Sweden)

    Jeffrey G Holmquist

    Full Text Available Conclusions regarding disturbance effects in high elevation or high latitude ecosystems based solely on infrequent, long-term sampling may be misleading, because the long winters may erase severe, short-term impacts at the height of the abbreviated growing season. We separated a long-term effects of pack stock grazing, manifested in early season prior to stock arrival, from b additional pack stock grazing effects that might become apparent during annual stock grazing, by use of paired grazed and control wet meadows that we sampled at the beginning and end of subalpine growing seasons. Control meadows had been closed to grazing for at least two decades, and meadow pairs were distributed across Sequoia National Park, California, USA. The study was thus effectively a landscape-scale, long-term manipulation of wetland grazing. We sampled arthropods at these remote sites and collected data on associated vegetation structure. Litter cover and depth, percent bare ground, and soil strength had negative responses to grazing. In contrast, fauna showed little response to grazing, and there were overall negative effects for only three arthropod families. Mid-season and long-term results were generally congruent, and the only indications of lower faunal diversity on mid-season grazed wetlands were trends of lower abundance across morphospecies and lower diversity for canopy fauna across assemblage metrics. Treatment x Season interactions almost absent. Thus impacts on vegetation structure only minimally cascaded into the arthropod assemblage and were not greatly intensified during the annual growing season. Differences between years, which were likely a response to divergent snowfall patterns, were more important than differences between early and mid-season. Reliance on either vegetation or faunal metrics exclusively would have yielded different conclusions; using both flora and fauna served to provide a more integrative view of ecosystem response.

  9. Effects of a long-term disturbance on arthropods and vegetation in subalpine wetlands: manifestations of pack stock grazing in early versus mid-season.

    Science.gov (United States)

    Holmquist, Jeffrey G; Schmidt-Gengenbach, Jutta; Haultain, Sylvia A

    2013-01-01

    Conclusions regarding disturbance effects in high elevation or high latitude ecosystems based solely on infrequent, long-term sampling may be misleading, because the long winters may erase severe, short-term impacts at the height of the abbreviated growing season. We separated a) long-term effects of pack stock grazing, manifested in early season prior to stock arrival, from b) additional pack stock grazing effects that might become apparent during annual stock grazing, by use of paired grazed and control wet meadows that we sampled at the beginning and end of subalpine growing seasons. Control meadows had been closed to grazing for at least two decades, and meadow pairs were distributed across Sequoia National Park, California, USA. The study was thus effectively a landscape-scale, long-term manipulation of wetland grazing. We sampled arthropods at these remote sites and collected data on associated vegetation structure. Litter cover and depth, percent bare ground, and soil strength had negative responses to grazing. In contrast, fauna showed little response to grazing, and there were overall negative effects for only three arthropod families. Mid-season and long-term results were generally congruent, and the only indications of lower faunal diversity on mid-season grazed wetlands were trends of lower abundance across morphospecies and lower diversity for canopy fauna across assemblage metrics. Treatment x Season interactions almost absent. Thus impacts on vegetation structure only minimally cascaded into the arthropod assemblage and were not greatly intensified during the annual growing season. Differences between years, which were likely a response to divergent snowfall patterns, were more important than differences between early and mid-season. Reliance on either vegetation or faunal metrics exclusively would have yielded different conclusions; using both flora and fauna served to provide a more integrative view of ecosystem response.

  10. Resurgence of human bothriocephalosis (Diphyllobothrium latum in the subalpine lake region

    Directory of Open Access Journals (Sweden)

    Renata BOUCHER-RODONI

    2001-02-01

    Full Text Available Human bothriocephalosis is once again being found in various catchment basins in the subalpine region, including Lago Maggiore and Lac Léman, which however are not isolated cases. Domestic animals are thought to be responsible for the survival of the parasite during the period when no human cases were reported. The new phenomenon of eating raw or poorly cooked fish is responsible for the resurgence of human bothriocephalosis, which affects various lake districts in Europe. This habit of eating raw fish might lead to the resurgence of a much more dangerous human parasitosis, transmitted in a similar way: infestation by Anisakis.

  11. The influence of apical and basal defoliation on the canopy structure and biochemical composition of Vitis vinifera cv. Shiraz grapes and wine

    Science.gov (United States)

    Zhang, Pangzhen; Wu, Xiwen; Needs, Sonja; Liu, Di; Fuentes, Sigfredo; Howell, Kate

    2017-07-01

    Defoliation is a commonly used viticultural technique to balance the ratio between grapevine vegetation and fruit. Defoliation is conducted around the fruit zone to reduce the leaf photosynthetic area, and to increase sunlight exposure of grape bunches. Apical leaf removal is not commonly practiced, and therefore its influence on canopy structure and resultant wine aroma is not well studied. This study quantified the influences of apical and basal defoliation on canopy structure parameters using canopy cover photography and computer vision algorithms. The influence of canopy structure changes on the chemical compositions of grapes and wines was investigated over two vintages (2010-11 and 2015-16) in Yarra Valley, Australia. The Shiraz grapevines were subjected to five different treatments: no leaf removal (Ctrl); basal (TB) and apical (TD) leaf removal at veraison and intermediate ripeness, respectively. Basal leaf removal significantly reduced the leaf area index and foliage cover and increased canopy porosity, while apical leaf removal had limited influences on canopy parameters. However, the latter tended to result in lower alcohol level in the finished wine. Statistically significant increases in pH and decreases in TA was observed in shaded grapes, while no significant changes in the color profile and volatile compounds of the resultant wine were found. These results suggest that apical leaf removal is an effective method to reduce wine alcohol concentration with minimal influences on wine composition.

  12. The Influence of Apical and Basal Defoliation on the Canopy Structure and Biochemical Composition of Vitis vinifera cv. Shiraz Grapes and Wine

    Directory of Open Access Journals (Sweden)

    Pangzhen Zhang

    2017-07-01

    Full Text Available Defoliation is a commonly used viticultural technique to balance the ratio between grapevine vegetation and fruit. Defoliation is conducted around the fruit zone to reduce the leaf photosynthetic area, and to increase sunlight exposure of grape bunches. Apical leaf removal is not commonly practiced, and therefore its influence on canopy structure and resultant wine aroma is not well-studied. This study quantified the influences of apical and basal defoliation on canopy structure parameters using canopy cover photography and computer vision algorithms. The influence of canopy structure changes on the chemical compositions of grapes and wines was investigated over two vintages (2010–2011 and 2015–2016 in Yarra Valley, Australia. The Shiraz grapevines were subjected to five different treatments: no leaf removal (Ctrl; basal (TB and apical (TD leaf removal at veraison and intermediate ripeness, respectively. Basal leaf removal significantly reduced the leaf area index and foliage cover and increased canopy porosity, while apical leaf removal had limited influences on canopy parameters. However, the latter tended to result in lower alcohol level in the finished wine. Statistically significant increases in pH and decreases in TA was observed in shaded grapes, while no significant changes in the color profile and volatile compounds of the resultant wine were found. These results suggest that apical leaf removal is an effective method to reduce wine alcohol concentration with minimal influences on wine composition.

  13. Bone Canopies in Pediatric Renal Osteodystrophy

    DEFF Research Database (Denmark)

    Pereira, Renata C; Levin Andersen, Thomas; Friedman, Peter A

    2016-01-01

    . This finding contrasts with the thin appearance reported in healthy individuals with normal kidney function. Furthermore, canopies in pediatric CKD patients showed immunoreactivity to the PTH receptor (PTHR1) as well as to the receptor activator of nuclear factor kappa-B ligand (RANKL). The number of surfaces...... with visible canopy coverage was associated with plasma parathyroid hormone (PTH) levels, bone formation rate, and the extent of remodeling surfaces. Collectively, these data support the conclusion that canopies respond to the elevated PTH levels in CKD and that they possess the molecular machinery necessary...

  14. The influence of warm-season precipitation on the diel cycle of the surface energy balance and carbon dioxide at a Colorado subalpine forest site

    Science.gov (United States)

    Burns, S. P.; Blanken, P. D.; Turnipseed, A. A.; Hu, J.; Monson, R. K.

    2015-12-01

    Precipitation changes the physical and biological characteristics of an ecosystem. Using a precipitation-based conditional sampling technique and a 14 year data set from a 25 m micrometeorological tower in a high-elevation subalpine forest, we examined how warm-season precipitation affected the above-canopy diel cycle of wind and turbulence, net radiation Rnet, ecosystem eddy covariance fluxes (sensible heat H, latent heat LE, and CO2 net ecosystem exchange NEE) and vertical profiles of scalars (air temperature Ta, specific humidity q, and CO2 dry mole fraction χc). This analysis allowed us to examine how precipitation modified these variables from hourly (i.e., the diel cycle) to multi-day time-scales (i.e., typical of a weather-system frontal passage). During mid-day we found the following: (i) even though precipitation caused mean changes on the order of 50-70 % to Rnet, H, and LE, the surface energy balance (SEB) was relatively insensitive to precipitation with mid-day closure values ranging between 90 and 110 %, and (ii) compared to a typical dry day, a day following a rainy day was characterized by increased ecosystem uptake of CO2 (NEE increased by ≈ 10 %), enhanced evaporative cooling (mid-day LE increased by ≈ 30 W m-2), and a smaller amount of sensible heat transfer (mid-day H decreased by ≈ 70 W m-2). Based on the mean diel cycle, the evaporative contribution to total evapotranspiration was, on average, around 6 % in dry conditions and between 15 and 25 % in partially wet conditions. Furthermore, increased LE lasted at least 18 h following a rain event. At night, even though precipitation (and accompanying clouds) reduced the magnitude of Rnet, LE increased from ≈ 10 to over 20 W m-2 due to increased evaporation. Any effect of precipitation on the nocturnal SEB closure and NEE was overshadowed by atmospheric phenomena such as horizontal advection and decoupling that create measurement difficulties. Above-canopy mean χc during wet conditions was

  15. The effect of warm-season precipitation on the diel cycle of the surface energy balance and carbon dioxide at a Colorado subalpine forest site

    Science.gov (United States)

    Burns, S. P.; Blanken, P. D.; Turnipseed, A. A.; Monson, R. K.

    2015-06-01

    Precipitation changes the physical and biological characteristics of an ecosystem. Using a precipitation-based conditional sampling technique and a 14 year dataset from a 25 m micrometeorological tower in a high-elevation subalpine forest, we examined how warm-season precipitation affected the above-canopy diel cycle of wind and turbulence, net radiation Rnet, ecosystem eddy covariance fluxes (sensible heat H, latent heat LE, and CO2 net ecosystem exchange NEE) and vertical profiles of scalars (air temperature Ta, specific humidity q, and CO2 dry mole fraction χc). This analysis allowed us to examine how precipitation modified these variables from hourly (i.e., the diel cycle) to multi-day time-scales (i.e., typical of a weather-system frontal passage). During mid-day we found: (i) even though precipitation caused mean changes on the order of 50-70% to Rnet, H, and LE, the surface energy balance (SEB) was relatively insensitive to precipitation with mid-day closure values ranging between 70-80%, and (ii) compared to a typical dry day, a day following a rainy day was characterized by increased ecosystem uptake of CO2 (NEE increased by ≈ 10%), enhanced evaporative cooling (mid-day LE increased by ≈ 30 W m-2), and a smaller amount of sensible heat transfer (mid-day H decreased by ≈ 70 W m-2). Based on the mean diel cycle, the evaporative contribution to total evapotranspiration was, on average, around 6% in dry conditions and 20% in wet conditions. Furthermore, increased LE lasted at least 18 h following a rain event. At night, precipitation (and accompanying clouds) reduced Rnet and increased LE. Any effect of precipitation on the nocturnal SEB closure and NEE was overshadowed by atmospheric phenomena such as horizontal advection and decoupling that create measurement difficulties. Above-canopy mean χc during wet conditions was found to be about 2-3 μmol mol-1 larger than χc on dry days. This difference was fairly constant over the full diel cycle

  16. Modification of VanWagner's canopy fire propagation model

    Science.gov (United States)

    James Dickinson; Andrew Robinson; Richy Harrod; Paul Gessler; Alistair Smith

    2007-01-01

    The conditions necessary for the combustion of canopy fuels are not well known but are assumed to be highly influenced by the volume through which the canopy fuels are dispersed, known as canopy bulk density (CBD). Propagating crown fire is defined as a continuous wall of flame from the bottom to the top of the canopy, implying crown fire propagation is actually...

  17. VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine

    Directory of Open Access Journals (Sweden)

    Roberta De Bei

    2016-04-01

    Full Text Available Leaf area index (LAI and plant area index (PAI are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI, canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants.

  18. BOREAS HYD-03 Canopy Density Data

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The BOREAS HYD-03 team collected several data sets related to the hydrology of forested areas. This data set contains measurements of canopy density...

  19. BOREAS HYD-03 Canopy Density Data

    Data.gov (United States)

    National Aeronautics and Space Administration — The BOREAS HYD-03 team collected several data sets related to the hydrology of forested areas. This data set contains measurements of canopy density (closure) from a...

  20. Bone Canopies in Pediatric Renal Osteodystrophy

    DEFF Research Database (Denmark)

    Pereira, Renata C; Levin Andersen, Thomas; Friedman, Peter A

    2016-01-01

    Pediatric renal osteodystrophy (ROD) is characterized by changes in bone turnover, mineralization, and volume that are brought about by alterations in bone resorption and formation. The resorptive and formative surfaces on the cancellous bone are separated from the marrow cavity by canopies...... and their association with biochemical and bone histomorphometric parameters in 106 pediatric chronic kidney disease (CKD) patients (stage 2-5) across the spectrum of ROD. Canopies in CKD patients often appeared as thickened multilayered canopies, similar to previous reports in patients with primary hyperparathyroidism....... This finding contrasts with the thin appearance reported in healthy individuals with normal kidney function. Furthermore, canopies in pediatric CKD patients showed immunoreactivity to the PTH receptor (PTHR1) as well as to the receptor activator of nuclear factor kappa-B ligand (RANKL). The number of surfaces...

  1. Is methane released from the forest canopy?

    DEFF Research Database (Denmark)

    Mikkelsen, Teis Nørgaard; Bruhn, Dan; Ambus, Per

    2011-01-01

    Laboratory experiments show that rates of CH4 emission from plant material depend exponentially on temperature and linearly on UV irradiance. The UV irradiance shall be spectrally weighted and shorter wavelengths results in higher CH4 emissions. Global upscaling models for estimating aerobic CH4......, based on lab results, have be conducted with varying results, but until now field measurements based on profile and eddy covariance measurements have failed to show CH4 emissions from forest canopies. To detect CH4 production or consumption in the canopy of a beech stand we connected a CH4 analyzer...... indications of periodic CH4 emissions in the canopy, but more data need to be analyzed before the magnitude of the canopy source of CH4 can be established....

  2. Modelling the canopy development of bambara groundnut

    DEFF Research Database (Denmark)

    Karunaratne, A.S.; Azam-Ali, S.N.; Al-Shareef, I.

    2010-01-01

    Canopy development of bambara groundnut (Vigna subterranea (L.) Verdc) is affected by temperature stress, drought stress and photoperiod. The quantification of these documented effects by means of a suitable crop model, BAMGRO is presented in this paper. Data on canopy development from five growth...... and drought stress. The leaf area expansion is calculated as a function of leaf number and individual leaf size. The canopy development of bambara groundnut is modelled (and tested) in BAMGRO model by means of leaf initiation and leaf area expansion and branching and stem production are not considered. Nash.......80) with maximum MAE less than ±0.50 thus explaining canopy development under temperature stress, drought stress and variable photoperiods....

  3. Estimating Canopy Nitrogen Content in a Heterogeneous Grassland with Varying Fire and Grazing Treatments: Konza Prairie, Kansas, USA

    Directory of Open Access Journals (Sweden)

    Bohua Ling

    2014-05-01

    Full Text Available Quantitative, spatially explicit estimates of canopy nitrogen are essential for understanding the structure and function of natural and managed ecosystems. Methods for extracting nitrogen estimates via hyperspectral remote sensing have been an active area of research. Much of this research has been conducted either in the laboratory, or in relatively uniform canopies such as crops. Efforts to assess the feasibility of the use of hyperspectral analysis in heterogeneous canopies with diverse plant species and canopy structures have been less extensive. In this study, we use in situ and aircraft hyperspectral data to assess several empirical methods for extracting canopy nitrogen from a tallgrass prairie with varying fire and grazing treatments. The remote sensing data were collected four times between May and September in 2011, and were then coupled with the field-measured leaf nitrogen levels for empirical modeling of canopy nitrogen content based on first derivatives, continuum-removed reflectance and ratio-based indices in the 562–600 nm range. Results indicated that the best-performing model type varied between in situ and aircraft data in different months. However, models from the pooled samples over the growing season with acceptable accuracy suggested that these methods are robust with respect to canopy heterogeneity across spatial and temporal scales.

  4. Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow–shrub interactions

    Science.gov (United States)

    Myers-Smith, Isla H; Hik, David S

    2013-01-01

    Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow–shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3-year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing ∼0.5 m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4–5°C warmer in January, and 2°C cooler in July under shrub cover. Natural shrub plots had 14–33 cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO2 fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted. PMID:24198933

  5. Phylogeny and ecophysiology of opportunistic "snow molds" from a subalpine forest ecosystem.

    Science.gov (United States)

    Schmidt, S K; Wilson, K L; Meyer, A F; Gebauer, M M; King, A J

    2008-11-01

    Mats of coenocytic "snow molds" are commonly observed covering the soil and litter of alpine and subalpine areas immediately following snow melt. Here, we describe the phylogenetic placement, growth rates, and metabolic potential of cold-adapted fungi from under-snow mats in the subalpine forests of Colorado. SSU rDNA sequencing revealed that these fungi belong to the zygomycete orders Mucorales and Mortierellales. All of the isolates could grow at temperatures observed under the snow at our sites (0 degrees C and -2 degrees C) but were unable to grow at temperatures above 25 degrees C and were unable to grow anaerobically. Growth rates for these fungi were very high at -2 degrees C, approximately an order of magnitude faster than previously studied cold-tolerant fungi from Antarctic soils. Given the rapid aerobic growth of these fungi at low temperatures, we propose that they are uniquely adapted to take advantage of the flush of nutrient that occurs at the soil-snow interface beneath late winter snow packs. In addition, extracellular enzyme production was relatively high for the Mucorales, but quite low for the Mortierellales, perhaps indicating some niche separation between these fungi beneath the late winter snow pack.

  6. Subalpine Pyrenees received higher nitrogen deposition than predicted by EMEP and CHIMERE chemistry-transport models

    Science.gov (United States)

    Boutin, Marion; Lamaze, Thierry; Couvidat, Florian; Pornon, André

    2015-08-01

    Deposition of reactive nitrogen (N) from the atmosphere is expected to be the third greatest driver of biodiversity loss by the year 2100. Chemistry-transport models are essential tools to estimate spatially explicit N deposition but the reliability of their predictions remained to be validated in mountains. We measured N deposition and air concentration over the subalpine Pyrenees. N deposition was found to range from 797 to 1,463 mg N m-2 year-1. These values were higher than expected from model predictions, especially for nitrate, which exceeded the estimations of EMEP by a factor of 2.6 and CHIMERE by 3.6. Our observations also displayed a reversed reduced-to-oxidized ratio in N deposition compared with model predictions. The results highlight that the subalpine Pyrenees are exposed to higher levels of N deposition than expected according to standard predictions and that these levels exceed currently recognized critical loads for most high-elevation habitats. Our study reveals a need to improve the evaluation of N deposition in mountains which are home to a substantial and original part of the world’s biodiversity.

  7. Biogeochemical impacts of wildfires over four millennia in a Rocky Mountain subalpine watershed.

    Science.gov (United States)

    Dunnette, Paul V; Higuera, Philip E; McLauchlan, Kendra K; Derr, Kelly M; Briles, Christy E; Keefe, Margaret H

    2014-08-01

    Wildfires can significantly alter forest carbon (C) storage and nitrogen (N) availability, but the long-term biogeochemical legacy of wildfires is poorly understood. We obtained a lake-sediment record of fire and biogeochemistry from a subalpine forest in Colorado, USA, to examine the nature, magnitude, and duration of decadal-scale, fire-induced ecosystem change over the past c. 4250 yr. The high-resolution record contained 34 fires, including 13 high-severity events within the watershed. High-severity fires were followed by increased sedimentary N stable isotope ratios (δ15N) and bulk density, and decreased C and N concentrations--reflecting forest floor destruction, terrestrial C and N losses, and erosion. Sustained low sediment C : N c. 20-50 yr post-fire indicates reduced terrestrial organic matter subsidies to the lake. Low sedimentary δ15N c. 50-70 yr post-fire, coincident with C and N recovery, suggests diminishing terrestrial N availability during stand development. The magnitude of post-fire changes generally scaled directly with inferred fire severity. Our results support modern studies of forest successional C and N accumulation and indicate pronounced, long-lasting biogeochemical impacts of wildfires in subalpine forests. However, even repeated high-severity fires over millennia probably did not deplete C or N stocks, because centuries between high-severity fires allowed for sufficient biomass recovery. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  8. Biological and physical influences on the carbon isotope content of CO2 in a subalpine forest snowpack, Niwot Ridge, Colorado

    Science.gov (United States)

    D. R. Bowling; W. J. Massman; S. M. Schaeffer; S. P. Burns; R. K. Monson; M. W. Williams

    2009-01-01

    Considerable research has recently been devoted to understanding biogeochemical processes under winter snow cover, leading to enhanced appreciation of the importance of many winter ecological processes. In this study, a comprehensive investigation of the stable carbon isotope composition (δ 13C) of CO2 within a high-elevation subalpine...

  9. Survival, frost susceptibility, growth, and disease resistance of corkbark and subalpine fir grown for landscape and Christmas trees

    Science.gov (United States)

    Trees from six corkbark fir (Abies lasiocarpa var. arizonica) and 10 subalpine fir (A. lasiocarpa var. lasiocarpa) seed sources were grown at the University of Idaho Sandpoint Research and Extension Center (SREC) and two commercial nurseries in Idaho and Oregon. Post transplant mortality was highest...

  10. Mean wind patterns and snow depths in an alpine-subalpine ecosystem as measured by damage to coniferous trees

    Science.gov (United States)

    G. L. Wooldridge; R. C. Musselman; R. A. Sommerfeld; D. G. Fox; B. H. Connell

    1996-01-01

    1. Deformations of Engelmann spruce and subalpine fir trees were surveyed for the purpose of determining climatic wind speeds and directions and snow depths in the Glacier Lakes Ecosystem Experiments Site (GLEES) in the Snowy Range of southeastern Wyoming, USA. Tree deformations were recorded at 50- and 100-m grid intervals over areas of c. 30 ha and 300 ha,...

  11. Mycorrhiza-plant colonization patterns on a subalpine glacier forefront as a model system of primary succession

    Science.gov (United States)

    Efren Cazares; James M. Trappe; Ari Jumpponen

    2005-01-01

    Lyman glacier in the North Cascades Mountains of Washington has a subalpine forefront characterized by a well-developed terminal moraine, inconspicuous successional moraines, fluting, and outwash. These deposits were depleted of symbiotic fungi when first exposed but colonized by them over time after exposure. Four major groups of plant species in this system are (1)...

  12. Elements of a dynamic systems model of canopy photosynthesis.

    Science.gov (United States)

    Zhu, Xin-Guang; Song, Qingfeng; Ort, Donald R

    2012-06-01

    Improving photosynthesis throughout the full canopy rather than photosynthesis of only the top leaves of the canopy is central to improving crop yields. Many canopy photosynthesis models have been developed from physiological and ecological perspectives, however most do not consider heterogeneities of microclimatic factors inside a canopy, canopy dynamics and associated energetics, or competition among different plants, and most models lack a direct linkage to molecular processes. Here we described the rationale, elements, and approaches necessary to build a dynamic systems model of canopy photosynthesis. A systems model should integrate metabolic processes including photosynthesis, respiration, nitrogen metabolism, resource re-mobilization and photosynthate partitioning with canopy level light, CO(2), water vapor distributions and heat exchange processes. In so doing a systems-based canopy photosynthesis model will enable studies of molecular ecology and dramatically improve our insight into engineering crops for improved canopy photosynthetic CO(2) uptake, resource use efficiencies and yields. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Evaluating the Importance of Plant Functional Traits: the Subalpine and Alpine

    Science.gov (United States)

    Sanchez, A.; Smith, W. K.

    2011-12-01

    Over the past several decades, researchers have attempted to characterize plant groups according to traits that are considered functional, i.e. contributing significantly to fitness. Due to the complexity of measuring fitness, the capability for photosynthetic carbon gain is often used as a proxy. Thus, this approach correlates structural differences to photosynthetic performance, especially those differences that are known to be associated with photosynthesis, are easily measured and inexpensive. At the often sharp boundary between the subalpine forest and alpine community (treeline ecotone), plant structural traits change dramatically, i.e. tall evergreen trees give way abruptly to low-stature shrubs, grasses, forbs, and herbs. Yet, the differences in functional traits, so abundant in the literature for a variety of species and communities, have not been compared contiguous communities such as the subalpine forest and alpine. Can differences in functional traits already identified in the literature also be used to characterize species of these two contrasting communities? Or are there other traits that are most functional and/or, possibly, unique to each community and not the most popular traits reported so far in the literature. Also, does the community structure itself help determine functional traits? For example, the top ten most frequently studied traits (145 total papers from approximately 63 different refereed journals) considered functional include the following (% of the 145 publications): specific leaf area or mass (SLA or SLM 39%), plant height (36%), leaf nitrogen content (34%), leaf size (19%), leaf area (16%), leaf photosynthetic performance (15%), leaf dry matter content (LDMC 15%), leaf mass per unit leaf area (LMA 15%), leaf thickness (15%), and seed mass (14%). In addition, another 120 traits were mentioned as functional, although all fell below a 14% citation rate. Particular focus was placed on this group due to the possibility that they might

  14. Flow and Dispersion in Urban Canopies

    Science.gov (United States)

    Britter, Rex; Hanna, Steven

    2001-11-01

    Atmospheric flow and pollutant dispersion within and above the urban canopy are important for urban air quality, for assessing the consequences of accidental releases of hazardous material within cities, for assessing the air exchange between buildings and their environment, and consequently for rationalising energy usage. Different techniques for parameterising the urban canopy will be described including the application of digital elevation models to several European and American cities. Models have been developed, guided by theory and experiment, to describe the flow and turbulence within and above cities and some observations based on these models will be discussed as will the exchange processes between the urban canopy and the flow above. The work has been extended to the dispersion of active and passive pollutants. The results of a novel field study in the City of Birmingham will be presented.

  15. An experimental analysis of canopy flows

    Science.gov (United States)

    Segalini, Antonio; Fransson, Jens H. M.; Alfredsson, P. Henrik

    2011-12-01

    An analysis of forest canopy flows with a wind tunnel model at high Reynolds number is presented and discussed. Measured mean velocity and Reynolds stress profiles agree with observations made in real canopies with no sensible Reynolds number dependence, adding confidence to the results obtained with the present setup. The analysis of power density spectra of the three velocity components and of the shear stress co-spectra is reported with new coordinate scalings able to improve the collapse of the spectra compared to standard normalizations. This scaling is mostly based on the respective integral time scale and a simple fit is proposed to estimate such a quantity in real canopies. From the analysis of joint probability density functions, three different regions have been localized where a change in the coherent structure behavior is supposed to take place, similarly to what happens in rough wall turbulent boundary layers.

  16. BOREAS TE-9 NSA Canopy Biochemistry

    Science.gov (United States)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Charest, Martin; Sy, Mikailou

    2000-01-01

    The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves. This data set contains canopy biochemistry data collected in 1994 in the NSA at the YJP, OJR, OBS, UBS, and OA sites, including biochemistry lignin, nitrogen, cellulose, starch, and fiber concentrations. These data were collected to study the spatial and temporal changes in the canopy biochemistry of boreal forest cover types and how a high-resolution radiative transfer model in the mid-infrared could be applied in an effort to obtain better estimates of canopy biochemical properties using remote sensing. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. [Standardization of technical methods for apple fluorescence canopy spectral detection].

    Science.gov (United States)

    Zhu, Xi-Cun; Zhao, Geng-Xing; Lei, Tong; Wang, Ling; Dong, Fang; Wang, Jing-An

    2010-06-01

    Aiming at spectral detection of apple fluorescence canopy, the present paper carried out spectral detection tests under different weather conditions, different detection times, and different detection heights and angles to apple canopy in the two years of 2008 and 2009, so as to analyze impacts of these factors on apple canopy spectral characteristics and explore standardized spectral detection methods for apple fluorescence canopy. The results indicated the regularity in spectral reflectance of apple fluorescence canopy to a certain degree under different conditions, especially in the 760-1 350 nm near-infrared bands. The authors found that canopy spectral reflectance declined along with the decrease in sunshine and it is appropriate to detect canopy spectrum in sunny days with few clouds. In addition, spectral reflectance tended to be stable when the wind scale was below grade 2. The discrepancy of canopy spectra is small during the time period from 10:00 to 15:00 of a day compared to that of other times. For maintaining stable spectral curves, the height of detector to apple canopy needed to be adjusted to cover the whole canopy within the field of view according to detection angle of the detector. The vertical or approximately vertical detection was the best for canopy spectral reflectance acquisition. The standardization of technical methods of spectral detection for apple fluorescence canopy was proposed accordingly, which provided theoretical references for spectral detection and information extraction of apple tree canopy.

  18. Mean and Turbulent Flow Statistics in a Trellised Agricultural Canopy

    Science.gov (United States)

    Miller, Nathan E.; Stoll, Rob; Mahaffee, Walter F.; Pardyjak, Eric R.

    2017-10-01

    Flow physics is investigated in a two-dimensional trellised agricultural canopy to examine that architecture's unique signature on turbulent transport. Analysis of meteorological data from an Oregon vineyard demonstrates that the canopy strongly influences the flow by channelling the mean flow into the vine-row direction regardless of the above-canopy wind direction. Additionally, other flow statistics in the canopy sub-layer show a dependance on the difference between the above-canopy wind direction and the vine-row direction. This includes an increase in the canopy displacement height and a decrease in the canopy-top shear length scale as the above-canopy flow rotates from row-parallel towards row-orthogonal. Distinct wind-direction-based variations are also observed in the components of the stress tensor, turbulent kinetic energy budget, and the energy spectra. Although spectral results suggest that sonic anemometry is insufficient for resolving all of the important scales of motion within the canopy, the energy spectra peaks still exhibit dependencies on the canopy and the wind direction. These variations demonstrate that the trellised-canopy's effect on the flow during periods when the flow is row-aligned is similar to that seen by sparse canopies, and during periods when the flow is row-orthogonal, the effect is similar to that seen by dense canopies.

  19. Effects of Costa Concordia shipwreck on epiphytic assemblages and biotic features of Posidonia oceanica canopy.

    Science.gov (United States)

    Bacci, T; Penna, M; Rende, S F; Trabucco, B; Gennaro, P; Bertasi, F; Marusso, V; Grossi, L; Cicero, A M

    2016-08-15

    This research provides first information about Posidonia oceanica canopy in the area affected by Costa Concordia wreck. Percentage cover of algal and animal taxa on the leaves was estimated and biotic features of the meadow were measured in the period just after the shipwreck until its removal from the impacted site. Changes in epiphytic assemblages and some biotic features were detected in the Disturbed site compared with Control ones, highlighting effects due to the wreck presence and activities related to its removal. A temporary decrease of encrusting macroalgae and an increase of erected macroalgae and foraminifers, as well as a temporary increase of tip erosion of the canopy were detected in the Disturbed site. The obtained results were discussed and hypotheses about possible synergic effects occurred near the wreck were commented. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Patterns of Canopy and Surface Layer Consumption in a Boreal Forest Fire from Repeat Airborne Lidar

    Science.gov (United States)

    Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

    2017-01-01

    Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaskas Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broad leaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from above ground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity

  1. West Coast Canopy-Forming Kelp, 1989-2014

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — These data include the general extents of canopy-forming kelp surveys from 1989 to 2014 and a compilation of existing data sets delineating canopy-forming kelp beds...

  2. West Coast Canopy-Forming Kelp, 1989-2014

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data include the general extents of canopy-forming kelp surveys from 1989 to 2014 and a compilation of existing data sets delineating canopy-forming kelp beds...

  3. 100-Meter Resolution Tree Canopy of Alaska - Direct Download

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map layer contains tree canopy data for Alaska, in an Albers Equal-Area Conic projection and at a resolution of 100 meters. The tree canopy data were derived...

  4. Seedling Canopy Reflectance Spectra, 1992-1993 (ACCP)

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The reflectance spectra of Douglas-fir and bigleaf maple seedling canopies were measured. Canopies varied in fertilizer treatment and leaf area density...

  5. ASSESSING THE CANOPY INTEGRITY USING CANOPY DIGITAL IMAGES IN SEMIDECIDUOUS FOREST FRAGMENT IN SÃO CARLOS - SP- BRAZIL1

    Directory of Open Access Journals (Sweden)

    Thiago Yamada

    2017-11-01

    Full Text Available ABSTRACT It is well-known that conducting experimental research aiming the characterization of canopy structure of forests can be a difficult and costly task and, generally, requires an expert to extract, in loco, relevant information. Aiming at easing studies related to canopy structures, several techniques have been proposed in the literature and, among them, various are based on canopy digital image analysis. The research work described in this paper empirically compares two techniques that measure the integrity of the canopy structure of a forest fragment; one of them is based on central parts of canopy cover images and, the other, on canopy closure images. For the experiments, 22 central parts of canopy cover images and 22 canopy closure images were used. The images were captured along two transects: T1 (located in the conserved area and T2 (located in the naturally disturbance area. The canopy digital images were computationally processed and analyzed using the MATLAB platform for the canopy cover images and the Gap Light Analyzer (GLA, for the canopy closure images. The results obtained using these two techniques showed that canopy cover images and, among the employed algorithms, the Jseg, characterize the canopy integrity best. It is worth mentioning that part of the analysis can be automatically conducted, as a quick and precise process, with low material costs involved.

  6. Comparison of remote sensing and plant trait-based modelling to predict ecosystem services in subalpine grasslands

    Czech Academy of Sciences Publication Activity Database

    Homolová, Lucie; Schaepman, M. E.; Lamarque, L.; Clevers, J.G.P.W.; de Bello, Francesco; Thuiller, W.; Lavorel, S.

    2014-01-01

    Roč. 5, č. 8 (2014), č. článku 100. ISSN 2150-8925 Institutional support: RVO:67179843 ; RVO:67985939 Keywords : land-use change * leaf chlorophyll content * imaging spectroscopy * water-content * aviris data * spectral reflectance * hyperspectral data * species richness * area index * vegetation * aisa * biomass * ecosystem properties * ecosystem services * linear regression * remote sensing * spatial heterogeneity * subalpine grasslands Subject RIV: EH - Ecology, Behaviour; EF - Botanics (BU-J) Impact factor: 2.255, year: 2014

  7. The Effect of Re-Planting Trees on Soil Microbial Communities in a Wildfire-Induced Subalpine Grassland

    OpenAIRE

    Ed-Haun Chang; Guanglong Tian; Chih-Yu Chiu

    2017-01-01

    Wildfire often causes tremendous changes in ecosystems, particularly in subalpine and alpine areas, which are vulnerable due to severe climate conditions such as cold temperature and strong wind. This study aimed to clarify the effect of tree re-planting on ecosystem services such as the soil microbial community after several decades. We compared the re-planted forest and grassland with the mature forest as a reference in terms of soil microbial biomass C and N (Cmic and Nmic), enzyme activit...

  8. Effects of long-term population fluctuations of a top predator on invertebrate communities in subalpine ponds in Colorado

    OpenAIRE

    Wissinger, S.; Whiteman, H.; Denoël, Mathieu; Greig, H.; Butkas, K.

    2006-01-01

    Experimental and comparative data from subalpine ponds with and without tiger salamanders (Ambystoma tigrinum nebulosum) suggest that this species is a keystone predator on benthic and planktonic prey communities. At our study site in central Colorado, the population size of salamanders has fluctuated cyclically over the past 20 years from fewer than 100 to over 5000 individuals. Here we present long-term benthic data that reveal taxon- and habitat-specific correlations with fluctuations in s...

  9. Climate Risk Modelling of Balsam Woolly Adelgid Damage Severity in Subalpine Fir Stands of Western North America.

    Science.gov (United States)

    Hrinkevich, Kathryn H; Progar, Robert A; Shaw, David C

    2016-01-01

    The balsam woolly adelgid (Adelges piceae (Ratzeburg) (Homoptera: Adelgidae)) (BWA) is a nonnative, invasive insect that threatens Abies species throughout North America. It is well established in the Pacific Northwest, but continues to move eastward through Idaho and into Montana and potentially threatens subalpine fir to the south in the central and southern Rocky Mountains. We developed a climatic risk model and map that predicts BWA impacts to subalpine fir using a two-step process. Using 30-year monthly climate normals from sites with quantitatively derived BWA damage severity index values, we built a regression model that significantly explained insect damage. The sites were grouped into two distinct damage categories (high damage and mortality versus little or no mortality and low damage) and the model estimates for each group were used to designate distinct value ranges for four climatic risk categories: minimal, low, moderate, and high. We then calculated model estimates for each cell of a 4-kilometer resolution climate raster and mapped the risk categories over the entire range of subalpine fir in the western United States. The spatial variation of risk classes indicates a gradient of climatic susceptibility generally decreasing from the Olympic Peninsula in Washington and the Cascade Range in Oregon and Washington moving eastward, with the exception of some high risk areas in northern Idaho and western Montana. There is also a pattern of decreasing climatic susceptibility from north to south in the Rocky Mountains. Our study provides an initial step for modeling the relationship between climate and BWA damage severity across the range of subalpine fir. We showed that September minimum temperature and a metric calculated as the maximum May temperature divided by total May precipitation were the best climatic predictors of BWA severity. Although winter cold temperatures and summer heat have been shown to influence BWA impacts in other locations, these

  10. The Response of Subalpine Vegetation to Climate Change and Bark Beetle Infestations: A Multi-Scale Interaction.

    Science.gov (United States)

    Foster, A.; Shuman, J. K.; Shugart, H. H., Jr.; Negrón, J. F.

    2015-12-01

    Mean annual temperatures in the western United States have increased in the last few decades, and are predicted to continue warming. In the subalpine zone of the Rocky Mountains, this warming is also predicted to increase the frequency and severity of spruce beetle outbreaks. Climate change itself may affect this vegetation, potentially leading to shifts in species compositions. These forests are a crucial part of the US's carbon budget, thus it is important to analyze how climate change and bark beetles in conjunction will affect the biomass and species composition of vegetation in subalpine zone. UVAFME is an individual-based gap model that simulates biomass and species composition of a forest. This model has been quantitatively tested at various Rocky Mountain sites in the Front Range, and has been shown to accurately simulate the vegetation dynamics in the region. UVAFME has been updated with a spruce beetle subroutine that calculates the probability for beetle infestation of each tree on a plot. This probability is based on site, climate, and individual tree characteristics, such as temperature; stand structure; and tree stress level, size, and age. These governing characteristics are based on data from the US Forest Service, and other studies on spruce susceptibility and spruce beetle phenology. UVAFME is then run with multiple climate change and beetle scenarios to determine the net effect of both variables on subalpine vegetation. These results are compared among the different scenarios and to current forest inventory data. We project that increasing temperatures due to climate change will cause an increase in the frequency and severity of spruce beetle outbreaks, leading to a decrease in the biomass and dominance of Engelmann spruce. These results are an important step in understanding the possible futures for the vegetation of subalpine zone in the Rocky Mountains.

  11. Climate Risk Modelling of Balsam Woolly Adelgid Damage Severity in Subalpine Fir Stands of Western North America.

    Directory of Open Access Journals (Sweden)

    Kathryn H Hrinkevich

    Full Text Available The balsam woolly adelgid (Adelges piceae (Ratzeburg (Homoptera: Adelgidae (BWA is a nonnative, invasive insect that threatens Abies species throughout North America. It is well established in the Pacific Northwest, but continues to move eastward through Idaho and into Montana and potentially threatens subalpine fir to the south in the central and southern Rocky Mountains. We developed a climatic risk model and map that predicts BWA impacts to subalpine fir using a two-step process. Using 30-year monthly climate normals from sites with quantitatively derived BWA damage severity index values, we built a regression model that significantly explained insect damage. The sites were grouped into two distinct damage categories (high damage and mortality versus little or no mortality and low damage and the model estimates for each group were used to designate distinct value ranges for four climatic risk categories: minimal, low, moderate, and high. We then calculated model estimates for each cell of a 4-kilometer resolution climate raster and mapped the risk categories over the entire range of subalpine fir in the western United States. The spatial variation of risk classes indicates a gradient of climatic susceptibility generally decreasing from the Olympic Peninsula in Washington and the Cascade Range in Oregon and Washington moving eastward, with the exception of some high risk areas in northern Idaho and western Montana. There is also a pattern of decreasing climatic susceptibility from north to south in the Rocky Mountains. Our study provides an initial step for modeling the relationship between climate and BWA damage severity across the range of subalpine fir. We showed that September minimum temperature and a metric calculated as the maximum May temperature divided by total May precipitation were the best climatic predictors of BWA severity. Although winter cold temperatures and summer heat have been shown to influence BWA impacts in other

  12. Modeling percent tree canopy cover: a pilot study

    Science.gov (United States)

    John W. Coulston; Gretchen G. Moisen; Barry T. Wilson; Mark V. Finco; Warren B. Cohen; C. Kenneth Brewer

    2012-01-01

    Tree canopy cover is a fundamental component of the landscape, and the amount of cover influences fire behavior, air pollution mitigation, and carbon storage. As such, efforts to empirically model percent tree canopy cover across the United States are a critical area of research. The 2001 national-scale canopy cover modeling and mapping effort was completed in 2006,...

  13. Canopy dynamics of a tropical rain forest in French Guiana

    NARCIS (Netherlands)

    Meer, van der P.J.

    1995-01-01

    The canopy dynamics (i.e. the formation and closure of canopy gaps) of a tropical rain forest in French Guiana are described. The formation of canopy gaps is investigated. The difficulties with gap size measurements are studied, and causes and consequences of treefalls and branchfalls are

  14. Regulation of leaf traits in canopy gradients.

    NARCIS (Netherlands)

    Pons, T.L.|info:eu-repo/dai/nl/069365822

    2016-01-01

    The gradient of leaf traits in a canopy from sunlit upper regions to shaded lower ones is regulated in response to the density of its leaf area. The gradients of environmental factors act as signals for the regulation. The result is improved resource use efficiency for carbon gain at the whole plant

  15. Analysis of algorithms for predicting canopy fuel

    Science.gov (United States)

    Katharine L. Gray; Elizabeth Reinhardt

    2003-01-01

    We compared observed canopy fuel characteristics with those predicted by existing biomass algorithms. We specifically examined the accuracy of the biomass equations developed by Brown (1978. We used destructively sampled data obtained at 5 different study areas. We compared predicted and observed quantities of foliage and crown biomass for individual trees in our study...

  16. Canopy Photosynthesis: From Basics to Applications

    NARCIS (Netherlands)

    Hikosaka, Kouki; Niinemets, Ülo; Anten, N.P.R.

    2016-01-01

    A plant canopy, a collection of leaves, is an ecosystem-level unit of photosynthesis that assimilates carbon dioxide and exchanges other gases and energy with the atmosphere in a manner highly sensitive to ambient conditions including atmospheric carbon dioxide and water vapor concentrations, light

  17. The Effect of Re-Planting Trees on Soil Microbial Communities in a Wildfire-Induced Subalpine Grassland

    Directory of Open Access Journals (Sweden)

    Ed-Haun Chang

    2017-10-01

    Full Text Available Wildfire often causes tremendous changes in ecosystems, particularly in subalpine and alpine areas, which are vulnerable due to severe climate conditions such as cold temperature and strong wind. This study aimed to clarify the effect of tree re-planting on ecosystem services such as the soil microbial community after several decades. We compared the re-planted forest and grassland with the mature forest as a reference in terms of soil microbial biomass C and N (Cmic and Nmic, enzyme activities, phospholipid fatty acids (PLFA composition, and denaturing gradient gel electrophoresis (DGGE. The Cmic and Nmic did not differ among the grassland, re-planted forest and mature forest soil; however, ratios of Cmic/Corg and Nmic/Ntot decreased from the grassland to re-planted forest and mature forest soil. The total PLFAs and those attributed to bacteria and Gram-positive and Gram-negative bacteria did not differ between the re-planted forest and grassland soil. Principle component analysis of the PLFA content separated the grassland from re-planted forest and mature forest soil. Similarly, DGGE analysis revealed changes in both bacterial and fungal community structures with changes in vegetation. Our results suggest that the microbial community structure changes with the re-planting of trees after a fire event in this subalpine area. Recovery of the soil microbial community to the original state in a fire-damaged site in a subalpine area may require decades, even under a re-planted forest.

  18. Responses Of Subalpine Conifer Seedling Germination And Survival To Soil Microclimate In The Alpine Treeline Warming Experiment

    Science.gov (United States)

    Castanha, C.; Moyes, A. B.; Torn, M. S.; Germino, M. J.; Kueppers, L. M.

    2011-12-01

    At Niwot Ridge, Colorado, we used common gardens and climate manipulations to investigate potential subalpine tree species range shifts due to climate change. In Fall 2009 we harvested seed from local populations of limber pine and Englemann spruce, which we sowed in 3 experimental sites spanning an elevation gradient from lower subalpine forest (3080m asl), to the upper subalpine treeline ecotone (3400m asl), to the alpine tundra (3550m asl). In October we turned on overhead infrared heaters designed to increase growing season surface soil temperature by 4-5°C, and following snowmelt in 2010 we crossed this heating treatment with manual watering, adding 3mm of water each week. Here we report on the species, site, and treatment effects on seedling emergence and survival as mediated by snowmelt date, soil temperature, and soil moisture. Depending on the site and plot, heating accelerated germination by 1 to 4 weeks. Germination degree days (heat accumulation required for seed germination) were greater for pine than for spruce and greater in drier plots. Seedling survival was explained by date of emergence, with older seedlings more likely to survive the season. Survival was also explained by drought degree days -- the number of days below critical soil moisture thresholds compounded by high temperature -- with lower thresholds for spruce than for pine. Our preliminary results indicate that a warmer environment will stimulate germination for both species, but that, survival - especially for spruce - will be critically modulated by summer soil moisture.

  19. Vibration parameters assessment to develop a continuous lateral canopy shaker for mechanical harvesting of traditional olive trees

    Energy Technology Data Exchange (ETDEWEB)

    Sola-Guirado, R.R.; Jimenez-Jimenez, F.; Blanco-Roldan, G.L.; Castro-Garcia, S.; Castillo-Ruiz, F.J.; Gil Ribes, J.A.

    2016-11-01

    The fruit harvesting is a key factor involving both product quality and profitability. Particularly, mechanical harvesting of traditional oil olive orchards is hint by tree training system for manual harvesting, tree size and several and slanted trunks which makes difficult trunk shaker work. Therefore, canopy shaker technology could be a feasible alternative to develop an integral harvester able to work on irregular canopies. The aim of this research was to determine vibration parameters applied to the olive tree for efficient mechanical harvesting by canopy shaker measuring fruit removal efficiency and debris. In this work, a continuous lateral canopy shaker harvester has been developed and tested on large olive trees in order to analyse the operating harvester parameters and tree properties to improve mutual adaptation. Vibration amplitude and frequency, rod density and ground speed were assessed. Vibration amplitude and frequency beside ground speed were decisive factors on fruit removal efficiency. Increasing rod density has not influenced on removal efficiency although it increased significantly debris. Promising results has been reached with 77.3% of removal efficiency, applying a 28 s shaking duration, 0.17 m amplitude vibration and 12 rod drum. This result was obtained reporting 0.26 s of accumulative shaking time over 200 m/s2 resultant acceleration. The canopy shaker mechanism enabled more than 65% of detached fruits to fall vertically, facilitating catch fruit. In order to improve removal efficiency it is advisable to adapt trees, set high amplitude in the shaker mechanism, and enhance the contact time between rods and tree. (Author)

  20. Canopy arthropod responses to experimental canopy opening and debris deposition in a tropical rainforest subject to hurricanes

    Science.gov (United States)

    Timothy D. Schowalter; Michael R. Willig; Steven J. Presley

    2014-01-01

    We analyzed responses of canopy arthropods on seven representative early and late successional overstory and understory tree species to a canopy trimming experiment designed to separate effects of canopy opening and debris pulse (resulting from hurricane disturbance) in a tropical rainforest ecosystem at the Luquillo Experimental Forest Long-Term Ecological Research (...

  1. Building capacity for providing canopy cover and canopy height at FIA plot locations using high-resolution imagery and leaf-off LiDAR

    Science.gov (United States)

    Rachel Riemann; Jarlath O' Neil-Dunne; Greg C. Liknes

    2012-01-01

    Tree canopy cover and canopy height information are essential for estimating volume, biomass, and carbon; defining forest cover; and characterizing wildlife habitat. The amount of tree canopy cover also influences water quality and quantity in both rural and urban settings. Tree canopy cover and canopy height are currently collected at FIA plots either in the field or...

  2. Ten-year variability in fluxes, meteorology, and environmental conditions at a Colorado subalpine forest site

    Science.gov (United States)

    Burns, S. P.; Turnipseed, A.; Bowling, D. R.; Hu, J.; Monson, R. K.

    2009-12-01

    Changing meteorological and environmental conditions affect fluxes; model analysis has shown that environmental variability directly accounts for about half the interannual variability in net ecosystem exchange (NEE) of CO2 whereas the other 50% is due to biotic responses to these changing variables (Richardson et al. 2007). In our study, ten years (1998-2008) of turbulent flux measurements of heat, water vapor, and CO2 at the Niwot Ridge AmeriFlux site (Monson et al. 2002) are examined with respect to meteorological conditions (atmospheric temperature, stability, precipitation, and cloudiness) as well as changes in environmental conditions, such as snow depth and soil moisture. The typical yearly cycle and an estimate of the magnitude of year-to-year variability in the diurnal fluxes and other variables for a high-elevation subalpine forest ecosystem are presented. Wintertime ecosystem respiration has an average 30-min NEE of 0.62 μmol m-2 s-1 with an interannual range between 0.5-1 μmol m-2 s-1. Uptake of CO2 in late summer has an average NEE of -0.71 μmol m-2 s-1 with an interannual range between -0.1 to -1.5 μmol m-2 s-1. Previous studies at the Niwot Ridge AmeriFlux site have described the importance of photosynthetic photon flux density (PPFD) (Monson et al. 2002) and also growing season length (Hu et al. 2009) on NEE. Water isotope ratios analyzed by Hu et al. (2009) have shown that trees at the site primarily rely on water from snowmelt to sustain them throughout the summer; combining this result with the SIPNET model, Hu et al. conclude that there is a limited connection between summer precipitation and the cumulative annual gross primary production (GPP). We have tested this conclusion more explicitly by examining the response of NEE to specific precipitation events and the effect of extended dry periods on the diel cycle of the fluxes, CO2 mole fraction, sap flow, and other meteorological and soil variables. Additionally, we examine the connection

  3. Assessing the Climate Sensitivity of Cold Content and Snowmelt in Seasonal Alpine and Subalpine Snowpacks

    Science.gov (United States)

    Jennings, K. S.; Molotch, N. P.

    2016-12-01

    In cold, high-elevation sites, snowpack cold content acts as a buffer against climate warming by resisting snowmelt during periods of positive energy fluxes. To test the climate sensitivity of cold content and snowmelt, we employed the physical SNOWPACK snow model, forced with a 23-year, hourly, quality-controlled, gap-filled meteorological dataset from the Niwot Ridge Long Term Ecological Research (LTER) site in the Front Range mountains of Colorado. SNOWPACK was run at two points with seasonal snowpacks within the LTER, one in the alpine (3528 m) and one in the subalpine (3022 m). Model output was validated using snow water equivalent (SWE), snowpack temperature, and cold content data from snow pits dug near the met stations and automated SWE data from nearby SNOTEL snow pillows. Cold content accumulates primarily through additions of new snow, while negative energy fluxes—cooling through longwave emission and sublimation—play a lesser role, particularly in the deeper snowpack of the alpine. On average, the snowpack energy balance becomes positive on April 1 in the alpine and March 8 in the subalpine. Peak SWE occurs after these dates and its timing is primarily determined by the amount of precipitation received after peak cold content, with persistent snowfall delaying the main snowmelt pulse. Years with lower cold content, due to reduced precipitation and/or increased air temperature, experience an earlier positive energy balance with more melt events occurring before the date of peak SWE, which has implications for soil moisture, streamflow volume and timing, water uptake by vegetation, and microbial respiration. Synthetic warming experiments show significant cold content reductions and increased late-winter/early-spring melt as positive energy balances occur earlier in the snow season (a forward shift between 5.1 and 21.0 days per °C of warming). These results indicate cold, high-elevation sites, which are critical for water resources in the western

  4. The Importance of Microtopography and Nurse Canopy for Successful Restoration Planting of the Slow-Growing Conifer Pilgerodendron uviferum

    Directory of Open Access Journals (Sweden)

    Jürgen Bauhus

    2013-01-01

    Full Text Available Recent studies have shown that, owing to a lack of seed trees, the natural rate of recovery of fire-disturbed bog forests previously dominated by the endemic and endangered conifer Pilgerodendron uviferum (D. Don Florin is extremely slow. Hence, increasing the number of seed trees in the landscape through restoration planting could remove the principal biotic filter, limiting recovery of these forests. Here, we analyzed how the success of restoration plantings may be improved through the choice or manipulation of microsites in P. uviferum forests on Chiloé Island in North Patagonia. For this purpose, we manipulated microtopography in water-logged sites in bogs (mounds, flat terrain, mineral soil and changed canopy conditions (gaps, semi-open, closed canopy in upland sites with better drainage. In bogs, there was no significant effect of microtopography on growth and survival of P. uviferum plantings. However, fluorescence measurements indicated lower stress in seedlings established on mounds. Seedlings in upland areas established beneath a nurse canopy had lower mortality and higher relative shoot growth, foliar nutrients, photosynthetic light use efficiency and chlorophyll fluorescence values than those planted in the open. This indicates that seedlings of the slow growing P. uviferum can tolerate extremely wet conditions, yet suffer from stress when grown in the open. Here, the removal of canopy appeared to have also removed or reduced mycorrhizal networks for seedlings, leading to poorer nutrition and growth. Based on these results, recommendations for restoration plantings in highly degraded P. uviferum forests are presented.

  5. Multi-scale patterns of subalpine fir mortality are driven by complex interactions among broad-scale climate, local topography, stand structure, and tree characteristics

    Science.gov (United States)

    Harvey, B. J.; Andrus, R. A.; Orrego, A.; Battaglia, M.; Negrón, J. F.; Veblen, T. T.

    2016-12-01

    Recent tree mortality events across much of western North America have been associated with warming temperatures and elevated drought stress, which can interact with forest stand-structure and tree vigor to drive outbreaks of native insect species. Although cross-scale interactions among drivers of tree-mortality events have been described for some beetle species (e.g., mountain pine beetle or spruce beetle) and their hosts (lodgepole pine and Engelmann spruce), less is known about how drivers at different scales interact to kill subalpine fir (Abies lasiocarpa) in a phenomenon simply dubbed "subalpine fir mortality" or "subalpine fir decline." Understanding the fate of subalpine fir is important, however, because this is commonly the tree species expected to establish and exhibit growth releases following outbreaks of mountain pine beetle or spruce beetle. In this study, we use three decades of field and remote data that span spatial scales from individual trees to sub-continental ecoregions to explore factors associated with subalpine fir mortality and how drivers interact across scales. Between 1991 and 2015, >5 million hectares (ha) of subalpine forest in the US Rocky Mountains have been affected by subalpine fir mortality. At the eco-region scale (1,000s of km), mortality was temporally associated with increases in regional drought stress, suggesting that climate is an important broad-scale driver. However, at the eco-region, landscape, and stand scales (several km to sub ha), mortality was greatest in cooler/wetter topographic locations and in areas with greater pre-mortality subalpine fir dominance. Conversely, mortality was lowest for fir trees in warmer/drier topographic locations and in areas of lesser pre-mortality subalpine fir dominance. This suggests that topographically driven differences in stand structure drive mortality dynamics at meso-scales and moderate the broad-scale influence of climate. Finally, at the tree and tree-neighborhood scale

  6. Canopy foliar nitrogen retrieved from airborne hyperspectral imagery by correcting for canopy structure effects

    Science.gov (United States)

    Wang, Zhihui; Skidmore, Andrew K.; Wang, Tiejun; Darvishzadeh, Roshanak; Heiden, Uta; Heurich, Marco; Latifi, Hooman; Hearne, John

    2017-02-01

    A statistical relationship between canopy mass-based foliar nitrogen concentration (%N) and canopy bidirectional reflectance factor (BRF) has been repeatedly demonstrated. However, the interaction between leaf properties and canopy structure confounds the estimation of foliar nitrogen. The canopy scattering coefficient (the ratio of BRF and the directional area scattering factor, DASF) has recently been suggested for estimating %N as it suppresses the canopy structural effects on BRF. However, estimation of %N using the scattering coefficient has not yet been investigated for longer spectral wavelengths (>855 nm). We retrieved the canopy scattering coefficient for wavelengths between 400 and 2500 nm from airborne hyperspectral imagery, and then applied a continuous wavelet analysis (CWA) to the scattering coefficient in order to estimate %N. Predictions of %N were also made using partial least squares regression (PLSR). We found that %N can be accurately retrieved using CWA (R2 = 0.65, RMSE = 0.33) when four wavelet features are combined, with CWA yielding a more accurate estimation than PLSR (R2 = 0.47, RMSE = 0.41). We also found that the wavelet features most sensitive to %N variation in the visible region relate to chlorophyll absorption, while wavelet features in the shortwave infrared regions relate to protein and dry matter absorption. Our results confirm that %N can be retrieved using the scattering coefficient after correcting for canopy structural effect. With the aid of high-fidelity airborne or upcoming space-borne hyperspectral imagery, large-scale foliar nitrogen maps can be generated to improve the modeling of ecosystem processes as well as ecosystem-climate feedbacks.

  7. Electromagnetic wave extinction within a forested canopy

    Science.gov (United States)

    Karam, M. A.; Fung, A. K.

    1989-01-01

    A forested canopy is modeled by a collection of randomly oriented finite-length cylinders shaded by randomly oriented and distributed disk- or needle-shaped leaves. For a plane wave exciting the forested canopy, the extinction coefficient is formulated in terms of the extinction cross sections (ECSs) in the local frame of each forest component and the Eulerian angles of orientation (used to describe the orientation of each component). The ECSs in the local frame for the finite-length cylinders used to model the branches are obtained by using the forward-scattering theorem. ECSs in the local frame for the disk- and needle-shaped leaves are obtained by the summation of the absorption and scattering cross-sections. The behavior of the extinction coefficients with the incidence angle is investigated numerically for both deciduous and coniferous forest. The dependencies of the extinction coefficients on the orientation of the leaves are illustrated numerically.

  8. Design of a Parachute Canopy Instrumentation Platform

    Science.gov (United States)

    Alshahin, Wahab M.; Daum, Jared S.; Holley, James J.; Litteken, Douglas A.; Vandewalle, Michael T.

    2015-01-01

    This paper discusses the current technology available to design and develop a reliable and compact instrumentation platform for parachute system data collection and command actuation. Wireless communication with a parachute canopy will be an advancement to the state of the art of parachute design, development, and testing. Embedded instrumentation of the parachute canopy will provide reefing line tension, skirt position data, parachute health monitoring, and other telemetry, further validating computer models and giving engineering insight into parachute dynamics for both Earth and Mars entry that is currently unavailable. This will allow for more robust designs which are more optimally designed in terms of structural loading, less susceptible to adverse dynamics, and may eventually pave the way to currently unattainable advanced concepts of operations. The development of this technology has dual use potential for a variety of other applications including inflatable habitats, aerodynamic decelerators, heat shields, and other high stress environments.

  9. Estimating the influence of different urban canopy cover types on atmospheric particulate matter (PM10) pollution abatement in London UK.

    Science.gov (United States)

    Tallis, Matthew; Freer-Smith, Peter; Sinnett, Danielle; Aylott, Matthew; Taylor, Gail

    2010-05-01

    In the urban environment atmospheric pollution by PM10 (particulate matter with a diameter less than 10 x 10-6 m) is a problem that can have adverse effects on human health, particularly increasing rates of respiratory disease. The main contributors to atmospheric PM10 in the urban environment are road traffic, industry and power production. The urban tree canopy is a receptor for removing PM10s from the atmosphere due to the large surface areas generated by leaves and air turbulence created by the structure of the urban forest. In this context urban greening has long been known as a mechanism to contribute towards PM10 removal from the air, furthermore, tree canopy cover has a role in contributing towards a more sustainable urban environment. The work reported here has been carried out within the BRIDGE project (SustainaBle uRban plannIng Decision support accountinG for urban mEtabolism). The aim of this project is to assess the fluxes of energy, water, carbon dioxide and particulates within the urban environment and develope a DSS (Decision Support System) to aid urban planners in sustainable development. A combination of published urban canopy cover data from ground, airborne and satellite based surveys was used. For each of the 33 London boroughs the urban canopy was classified to three groups, urban woodland, street trees and garden trees and each group quantified in terms of ground cover. The total [PM10] for each borough was taken from the LAEI (London Atmospheric Emissions Inventory 2006) and the contribution to reducing [PM10] was assessed for each canopy type. Deposition to the urban canopy was assessed using the UFORE (Urban Forest Effects Model) approach. Deposition to the canopy, boundary layer height and percentage reduction of the [PM10] in the atmosphere was assessed using both hourly meterological data and [PM10] and seasonal data derived from annual models. Results from hourly and annual data were compared with measured values. The model was then

  10. Improved Windshield and Canopy Protection Development Program

    Science.gov (United States)

    1974-06-01

    canopy shots, i.e., 8" from the beam, 12" from the forward arch. The Impact resulted in a penetration with a football -shaped plug blown Inward...i7;«MpiWW.,i«iS,i»f.«.^^^ CVJ Cte / teä <%1 ^ u- o ro O in H UJ o to o L HH Hh o «^ o = —I ro O \\ N__ o a. CM X UJ

  11. The influence of canopy snow parameterizations on snow albedo feedback in boreal forest regions

    Science.gov (United States)

    Thackeray, Chad W.; Fletcher, Christopher G.; Derksen, Chris

    2014-08-01

    Variation in snow albedo feedback (SAF) among Coupled Model Intercomparison Project phase 5 climate models has been shown to explain much of the variation in projected 21st century warming over Northern Hemisphere land. Prior studies using observations and models have demonstrated both considerable spread in the albedo and a negative bias in the simulated strength of SAF, over snow-covered boreal forests. Boreal evergreen needleleaf forests are capable of intercepting snowfall throughout the winter and consequently exert a significant impact on seasonal surface albedo. Two satellite data products and tower-based observations of albedo are compared with simulations from multiple versions of the Community Climate System Model (CCSM4) to investigate the causes of weak simulated SAF over the boreal forest. The largest bias occurs in April and May, when simulated SAF is one half the strength of SAF in observations. This is traced to two features of the canopy snow parameterizations used in the land model. First, there is no mechanism for the dynamic removal of snow from the canopy when temperatures are below freezing, which results in albedo values in midwinter that are biased high. Second, when temperatures do rise above freezing, all snow on the canopy is melted instantaneously, which results in an unrealistically early transition from a snow-covered to a snow-free canopy. These processes combine to produce large differences between simulated and observed monthly albedo and are the source of the weak bias in SAF. This analysis highlights the importance of canopy snow parameterizations for simulating the hemispheric scale climate response to surface albedo perturbations.

  12. Estimation of canopy carotenoid content of winter wheat using multi-angle hyperspectral data

    Science.gov (United States)

    Kong, Weiping; Huang, Wenjiang; Liu, Jiangui; Chen, Pengfei; Qin, Qiming; Ye, Huichun; Peng, Dailiang; Dong, Yingying; Mortimer, A. Hugh

    2017-11-01

    Precise estimation of carotenoid (Car) content in crops, using remote sensing data, could be helpful for agricultural resources management. Conventional methods for Car content estimation were mostly based on reflectance data acquired from nadir direction. However, reflectance acquired at this direction is highly influenced by canopy structure and soil background reflectance. Off-nadir observation is less impacted, and multi-angle viewing data are proven to contain additional information rarely exploited for crop Car content estimation. The objective of this study was to explore the potential of multi-angle observation data for winter wheat canopy Car content estimation. Canopy spectral reflectance was measured from nadir as well as from a series of off-nadir directions during different growing stages of winter wheat, with concurrent canopy Car content measurements. Correlation analyses were performed between Car content and the original and continuum removed spectral reflectance. Spectral features and previously published indices were derived from data obtained at different viewing angles and were tested for Car content estimation. Results showed that spectral features and indices obtained from backscattering directions between 20° and 40° view zenith angle had a stronger correlation with Car content than that from the nadir direction, and the strongest correlation was observed from about 30° backscattering direction. Spectral absorption depth at 500 nm derived from spectral data obtained from 30° backscattering direction was found to reduce the difference induced by plant cultivars greatly. It was the most suitable for winter wheat canopy Car estimation, with a coefficient of determination 0.79 and a root mean square error of 19.03 mg/m2. This work indicates the importance of taking viewing geometry effect into account when using spectral features/indices and provides new insight in the application of multi-angle remote sensing for the estimation of crop

  13. Voxel-Based Spatial Filtering Method for Canopy Height Retrieval from Airborne Single-Photon Lidar

    Directory of Open Access Journals (Sweden)

    Hao Tang

    2016-09-01

    Full Text Available Airborne single-photon lidar (SPL is a new technology that holds considerable potential for forest structure and carbon monitoring at large spatial scales because it acquires 3D measurements of vegetation faster and more efficiently than conventional lidar instruments. However, SPL instruments use green wavelength (532 nm lasers, which are sensitive to background solar noise, and therefore SPL point clouds require more elaborate noise filtering than other lidar instruments to determine canopy heights, particularly in daytime acquisitions. Histogram-based aggregation is a commonly used approach for removing noise from photon counting lidar data, but it reduces the resolution of the dataset. Here we present an alternate voxel-based spatial filtering method that filters noise points efficiently while largely preserving the spatial integrity of SPL data. We develop and test our algorithms on an experimental SPL dataset acquired over Garrett County in Maryland, USA. We then compare canopy attributes retrieved using our new algorithm with those obtained from the conventional histogram binning approach. Our results show that canopy heights derived using the new algorithm have a strong agreement with field-measured heights (r2 = 0.69, bias = 0.42 m, RMSE = 4.85 m and discrete return lidar heights (r2 = 0.94, bias = 1.07 m, RMSE = 2.42 m. Results are consistently better than height accuracies from the histogram method (field data: r2 = 0.59, bias = 0.00 m, RMSE = 6.25 m; DRL: r2 = 0.78, bias = −0.06 m and RMSE = 4.88 m. Furthermore, we find that the spatial-filtering method retains fine-scale canopy structure detail and has lower errors over steep slopes. We therefore believe that automated spatial filtering algorithms such as the one presented here can support large-scale, canopy structure mapping from airborne SPL data.

  14. Limnological research in the deep southern subalpine lakes: synthesis, directions and perspectives

    Directory of Open Access Journals (Sweden)

    Nico Salmaso

    2010-06-01

    Full Text Available Based on a selection of 230 papers published during the last 15 years in international journals, the present work aims at evaluating the state of the art of limnological research in the deep southern subalpine lakes (DSL: Garda, Iseo, Como, Lugano and Maggiore. Historically, most of the limnological research was fostered by the need to find solutions to the problems connected with eutrophication and pollution. Many data are available on the thermal structure, algal nutrient concentrations and phytoplankton of the DSL, while other topics still remain more or less constrained to single lakes. Apart from this geographical bias, a number of aspects emerged from this synoptic view. Limnological research is still linked to the concept of scientific monitoring, while experimental studies and modelling are confined to specific niches; the integration of different disciplines is held back by the division of studies on different compartments; integration of studies and synoptic analyses at a macro regional scale have been carried out only for specific research areas. The DSL are increasingly threatened by new pressures (climatic change, excessive proliferation of toxic cyanobacteria, introduction of new species and new micropollutants and by the interactions among these new and old stressors. In this rapidly changing situation, the paper emphasises the need to define criteria to be used to distinguish research able to produce relevant results and predictive models, which are essential elements for an efficient management of water resources.

  15. Patch-Scale Effects of Equine Disturbance on Arthropod Assemblages and Vegetation Structure in Subalpine Wetlands

    Science.gov (United States)

    Holmquist, Jeffrey G.; Schmidt-Gengenbach, Jutta; Ballenger, Elizabeth A.

    2014-06-01

    Assessments of vertebrate disturbance to plant and animal assemblages often contrast grazed versus ungrazed meadows or other larger areas of usage, and this approach can be powerful. Random sampling of such habitats carries the potential, however, for smaller, more intensely affected patches to be missed and for other responses that are only revealed at smaller scales to also escape detection. We instead sampled arthropod assemblages and vegetation structure at the patch scale (400-900 m2 patches) within subalpine wet meadows of Yosemite National Park (USA), with the goal of determining if there were fine-scale differences in magnitude and directionality of response at three levels of grazing intensity. Effects were both stronger and more nuanced than effects evidenced by previous random sampling of paired grazed and ungrazed meadows: (a) greater negative effects on vegetation structure and fauna in heavily used patches, but (b) some positive effects on fauna in lightly grazed patches, suggested by trends for mean richness and total and population abundances. Although assessment of disturbance at either patch or landscape scales should be appropriate, depending on the management question at hand, our patch-scale work demonstrated that there can be strong local effects on the ecology of these wetlands that may not be detected by comparing larger scale habitats.

  16. A molecular investigation of soil organic carbon composition across a subalpine catchment

    Science.gov (United States)

    Hsu, Hsiao-Tieh; Lawrence, Corey R.; Winnick, Matthew J.; Bargar, John R.; Maher, Katharine

    2018-01-01

    The dynamics of soil organic carbon (SOC) storage and turnover are a critical component of the global carbon cycle. Mechanistic models seeking to represent these complex dynamics require detailed SOC compositions, which are currently difficult to characterize quantitatively. Here, we address this challenge by using a novel approach that combines Fourier transform infrared spectroscopy (FT-IR) and bulk carbon X-ray absorption spectroscopy (XAS) to determine the abundance of SOC functional groups, using elemental analysis (EA) to constrain the total amount of SOC. We used this SOC functional group abundance (SOC-fga) method to compare variability in SOC compositions as a function of depth across a subalpine watershed (East River, Colorado, USA) and found a large degree of variability in SOC functional group abundances between sites at different elevations. Soils at a lower elevation are predominantly composed of polysaccharides, while soils at a higher elevation have more substantial portions of carbonyl, phenolic, or aromatic carbon. We discuss the potential drivers of differences in SOC composition between these sites, including vegetation inputs, internal processing and losses, and elevation-driven environmental factors. Although numerical models would facilitate the understanding and evaluation of the observed SOC distributions, quantitative and meaningful measurements of SOC molecular compositions are required to guide such models. Comparison among commonly used characterization techniques on shared reference materials is a critical next step for advancing our understanding of the complex processes controlling SOC compositions.

  17. Phytoplankton association patterns in the deep southern subalpine lakes (Part 2

    Directory of Open Access Journals (Sweden)

    Nico Salmaso

    2003-08-01

    Full Text Available The three following papers constitute the second, and final, part of a series of papers dedicated to the phytoplankton of the deep subalpine Italian lakes (DSL. The first part, comprising an introduction and three papers on lakes Garda, Como and Maggiore respectively, was published in the volume 61 (1 of this journal (J. Limnol., 61. The research, carried out for three years (two years in L.Como in the period 1997-2000, was a concerted effort by investigators of five Insitutes in Italy and Switzerland. It was generated by the awareness that, despite the large number of papers existing on the phytoplankton of the single DSL, those of a comprehensive nature are very few, and by the perceived interest of a comparative investigation on the phytoplankton of the large lakes in the Insubrian district in the light of the recent progress on the ecology of the freshwater algae. So, in the final paper following those on lakes Iseo and Lugano an effort is made to compare and characterize the different species assemblages in the background of geographical and morphological characteristics, and of recent changes in trophic gradients. Despite often important differences in these respects, and observed various community responses, a common pool of species seems to be identifiable in the district.

  18. Development of partial rock veneers by root throw in a subalpine setting

    Science.gov (United States)

    Osterkamp, W.R.; Toy, T.J.; Lenart, M.T.

    2006-01-01

    Rock veneers stabilize hillslope surfaces, occur especially in areas of immature soil, and form through a variety of process sets that includes root throw. Near Westcliffe, Colorado, USA, data were collected from a 20 ?? 500 m transect on the east slope of the Sangre de Cristo Mountains. Ages of pit/mound complexes with rock fragments exposed at the surface by root throw ranged from recent (freshly toppled tree) to unknown (complete tree decay). Calculations based on dimensions of the pit/mound complexes, estimated time of free topppling, sizes of exposed rock fragments, and percentage rock covers at pit/mound complexes, as well as within the transect area, indicate that recent rates of root throw have resulted in only partial rock veneering since late Pleistocene deglaciation. Weathering of rock fragments prevent development of an extensive rock veneer and causes a balance, achieved within an estimated 700 years, between the rates of rock-fragment exposure by root throw and clast disintegration by chemical reduction. The estimated rate of rock-fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western North America. Copyright ?? 2005 John Wiley & Sons, Ltd.

  19. Invasion of subalpine meadows by lodgepole pine in Yellowstone National Park, Wyoming, USA

    Energy Technology Data Exchange (ETDEWEB)

    Jakubos, B.; Romme, W.H. (Fort Lewis College, Durango, CO (United States))

    1993-11-01

    Many of the dry and mesic subalpine meadows in Yellowstone National Park are bordered by bands of small lodgepole pine trees. The authors asked whether these stands of small trees represent a directional process of meadow invasion, or alternatively, (1) small patches of postfire succession or; (2) more-or-less stable populations of trees having small stature because of adverse site conditions. Transect studies revealed that the bands of small trees were consistently younger than adjacent forest stands of obvious fire origin, that they lacked any evidence of fire, and that the trees were progressively younger as they approached the meadow. Soils under the young trees generally were more similar to meadow soils than to coniferous forest soils. The authors concluded, therefore, that meadow invasion has been occurring as a directional process since at least the mid- to late 1800s. Frequency of tree establishment in two dry meadows was positively correlated with mean June temperature and total summer precipitation (R[sup 2] = 0.49, P<0.0001, multiple stepwise regression). Thus, the major cause of tree invasion into dry meadows appears to be a regional climatic trend towards warmer and wetter growing seasons since the end of the Little Ice Age. Tree establishment in two mesic meadows was more weakly and inconsistently correlated with weather variables. Thus, the mechanism of invasion of mesic meadows may involve interactions of episodic seed crops and microhabitat changes at the forest border, as well as regional climatic variability. 30 refs., 7 figs., 1 tab.

  20. Targeted grazing for the restoration of sub-alpine shrub-encroached grasslands

    Directory of Open Access Journals (Sweden)

    Massimiliano Probo

    2016-12-01

    Full Text Available The decline of agro-pastoral activities has led to a widespread tree and shrub-encroachment of former semi-natural meso-eutrophic grasslands in many European mountain regions. Temporary night camp areas (TNCA and mineral mix supplements for targeted cattle were arranged over shrub-encroached areas to restore grassland vegetation within the Val Troncea Natural Park (Italy. From 2011 to 2015, their effects on vegetation structure and pastoral value of forage were assessed along permanent transects. Four years after treatments, both practices were effective in reducing the shrub cover and increasing the cover and average height of the herbaceous layer, but changes were more remarkable within TNCA. Moreover, the arrangement of TNCA decreased the cover of nanophanerophytes and increased the cover of graminoids and high quality species, as well as the overall forage pastoral value. In conclusion, TNCA were the most effective pastoral practice to contrast shrub-encroachment and increase herbage mass and forage quality of sub-alpine grasslands.

  1. Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado.

    Science.gov (United States)

    Calder, W John; Shuman, Bryan

    2017-10-01

    Ecosystems may shift abruptly when the effects of climate change and disturbance interact, and landscapes with regularly patterned vegetation may be especially vulnerable to abrupt shifts. Here we use a fossil pollen record from a regularly patterned ribbon forest (alternating bands of forests and meadows) in Colorado to examine whether past changes in wildfire and climate produced abrupt vegetation shifts. Comparing the percentages of conifer pollen with sedimentary δ18 O data (interpreted as an indicator of temperature or snow accumulation) indicates a first-order linear relationship between vegetation composition and climate change with no detectable lags over the past 2,500 yr (r = 0.55, P changed abruptly within a century of extensive wildfires, which were recognized in a previous study to have burned approximately 80% of the surrounding 1,000 km2 landscape 1,000 yr ago when temperatures rose ~0.5°C. The vegetation change was larger than expected from the effects of climate change alone. Pollen assemblages changed from a composition associated with closed subalpine forests to one similar to modern ribbon forests. Fossil pollen assemblages then remained like those from modern ribbon forests for the following ~1,000 yr, providing a clear example of how extensive disturbances can trigger persistent new vegetation states and alter how vegetation responds to climate. © 2017 by the Ecological Society of America.

  2. Litter Production, Decomposition, and Nutrient Release in Subalpine Forest Communities of the Northwest Himalaya

    Directory of Open Access Journals (Sweden)

    Vinod K. Bisht

    2014-01-01

    Full Text Available Production, decomposition, and release of nutrients from leaf and nonleaf litter were investigated in four subalpine forests of North-West Himalaya, India. Total annual litter fall in four communities varied from 2950.00 to 4040.00 kg ha−1 and was found significant (CD0.05 = 118.2. Decomposition of leaf litter varied from 1.82–3.5% during autumn-winter to 36.14–45.51 during summer rainy season in all stands and percent of mass loss was significantly varied in stands (CD6.00. Similarly, decomposition in nonleaf litter was varied from 0.3–1.1% during autumn-winter to 19.59–30.05% during summer rainy season and was significantly varied irrespective of seasons. However, percent decomposition of leaf litter and the values of decay constant (k were at par in all stands. Total standing state of nutrients in fresh litter as well as release of total nitrogen (N, phosphorus (P, and potassium (K in due course of decomposition (12 months was also varying significantly. The rate of nonleaf litter decomposition was significantly positively correlated with air temperature (r=0.63–0.74 in all communities. The significant correlation (r=0.85 was observed only in Rhododendron-Sorbus forest community (PRS. Study indicates that the air temperature is a major determinant for nonleaf litter decomposition in this region.

  3. Does the aboveground herbivore assemblage influence soil bacterial community composition and richness in subalpine grasslands?

    Science.gov (United States)

    Hodel, Melanie; Schütz, Martin; Vandegehuchte, Martijn L; Frey, Beat; Albrecht, Matthias; Busse, Matt D; Risch, Anita C

    2014-10-01

    Grassland ecosystems support large communities of aboveground herbivores that are known to directly and indirectly affect belowground properties such as the microbial community composition, richness, or biomass. Even though multiple species of functionally different herbivores coexist in grassland ecosystems, most studies have only considered the impact of a single group, i.e., large ungulates (mostly domestic livestock) on microbial communities. Thus, we investigated how the exclusion of four groups of functionally different herbivores affects bacterial community composition, richness, and biomass in two vegetation types with different grazing histories. We progressively excluded large, medium, and small mammals as well as invertebrate herbivores using exclosures at 18 subalpine grassland sites (9 per vegetation type). We assessed the bacterial community composition using terminal restriction fragment length polymorphism (T-RFLP) at each site and exclosure type during three consecutive growing seasons (2009-2011) for rhizosphere and mineral soil separately. In addition, we determined microbial biomass carbon (MBC), root biomass, plant carbon:nitrogen ratio, soil temperature, and soil moisture. Even though several of these variables were affected by herbivore exclusion and vegetation type, against our expectations, bacterial community composition, richness, or MBC were not. Yet, bacterial communities strongly differed between the three growing seasons as well as to some extent between our study sites. Thus, our study indicates that the spatiotemporal variability in soil microclimate has much stronger effects on the soil bacterial communities than the grazing regime or the composition of the vegetation in this high-elevation ecosystem.

  4. Do insects lose flight before they lose their wings? Population genetic structure in subalpine stoneflies.

    Science.gov (United States)

    McCulloch, Graham A; Wallis, Graham P; Waters, Jonathan M

    2009-10-01

    Wing reduction and flightlessness are common features of alpine and subalpine insects, and are typically interpreted as evolutionary adaptations to increase fecundity and promote local recruitment. Here, we assess the impact of wing reduction on dispersal in stoneflies (Plecoptera: Gripopterygidae: Zelandoperla) in southern New Zealand. Specifically, we present comparative phylogeographic analyses (COI; H3) of strong-flying Zelandoperla decorata (144 individuals, 63 localities) vs. the co-distributed but weak-flying Zelandoperla fenestrata species group (186 individuals, 81 localities). The latter group exhibits a variety of morphotypes, ranging from fully winged to completely wingless. Consistent with its capacity for strong flight-mediated dispersal, Z. decorata exhibited no substantial phylogeographic differentiation across its broad South Island range. Conversely the weak-flying fenestrata species group exhibited substantial genetic structure across both fine and broad geographic scales. Intriguingly, the variable degrees of wing development observed within the fenestrata species group had no apparent impact on levels of phylogeographic structure, which were high regardless of morphotype, suggesting that even fully winged specimens of this group do not fly. This finding implies that Zelandoperla flight loss occurs independently of wing loss, and might reflect underlying flight muscle reduction.

  5. A joined role of canopy and reversal cells in bone remodeling--lessons from glucocorticoid-induced osteoporosis.

    Science.gov (United States)

    Jensen, Pia Rosgaard; Andersen, Thomas Levin; Hauge, Ellen-Margrethe; Bollerslev, Jens; Delaissé, Jean-Marie

    2015-04-01

    Successful bone remodeling demands that osteoblasts restitute the bone removed by osteoclasts. In human cancellous bone, a pivotal role in this restitution is played by the canopies covering the bone remodeling surfaces, since disruption of canopies in multiple myeloma, postmenopausal- and glucocorticoid-induced osteoporosis is associated with the absence of progression of the remodeling cycle to bone formation, i.e., uncoupling. An emerging concept explaining this critical role of canopies is that they represent a reservoir of osteoprogenitors to be delivered to reversal surfaces. In postmenopausal osteoporosis, this concept is supported by the coincidence between the absence of canopies and scarcity of cells on reversal surfaces together with abortion of the remodeling cycle. Here we tested whether this concept holds true in glucocorticoid-induced osteoporosis. A histomorphometric analysis of iliac crest biopsies from patients exposed to long-term glucocorticoid treatment revealed a subpopulation of reversal surfaces corresponding to the characteristics of arrest found in postmenopausal osteoporosis. Importantly, these arrested reversal surfaces were devoid of canopy coverage in almost all biopsies, and their prevalence correlated with a deficiency in bone forming surfaces. Taken together with the other recent data, the functional link between canopies, reversal surface activity, and the extent of bone formation surface in postmenopausal- and glucocorticoid-induced osteoporosis, supports a model where bone restitution during remodeling demands recruitment of osteoprogenitors from the canopy onto reversal surfaces. These data suggest that securing the presence of functional local osteoprogenitors deserves attention in the search of strategies to prevent the bone loss that occurs during bone remodeling in pathological situations. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Optical Polarization of Light from a Sorghum Canopy Measured Under Both a Clear and an Overcast Sky

    Science.gov (United States)

    Vanderbilt, Vern; Daughtry, Craig; Biehl, Larry; Dahlgren, Robert

    2014-01-01

    Introduction: We tested the hypothesis that the optical polarization of the light reflected by a sorghum canopy is due to a Fresnel-type redirection, by sorghum leaf surfaces, of light from an unpolarized light source, the sun or overcast sky, toward the measuring sensor. If it can be shown that the source of the polarization of the light scattered by the sorghum canopy is a first surface, Fresnel-type reflection, then removing this surface reflected light from measurements of canopy reflectance presumably would allow better insight into the biochemical processes such as photosynthesis and metabolism that occur in the interiors of sorghum canopy leaves. Methods: We constructed a tower 5.9m tall in the center of a homogenous sorghum field. We equipped two Barnes MMR radiometers with polarization analyzers on the number 1, 3 and 7 Landsat TM wavelength bands. Positioning the radiometers atop the tower, we collected radiance data in 44 view directions on two days, one day with an overcast sky and the other, clear and sunlit. From the radiance data we calculated the linear polarization of the reflected light for each radiometer wavelength channel and view direction. Results and Discussion: Our experimental results support our hypothesis, showing that the amplitude of the linearly polarized portion of the light reflected by the sorghum canopy varied dramatically with view azimuth direction under a point source, the sun, but the amplitude varied little with view azimuth direction under the hemispherical source, the overcast sky. Under the clear sky, the angle of polarization depended upon the angle of incidence of the sunlight on the leaf, while under the overcast sky the angle of polarization depended upon the zenith view angle. These results support a polarized radiation transport model of the canopy that is based upon a first surface, Fresnel reflection from leaves in the sorghum canopy.

  7. The wave-driven current in coastal canopies

    Science.gov (United States)

    Abdolahpour, Maryam; Hambleton, Magnus; Ghisalberti, Marco

    2017-05-01

    Wave-driven flows over canopies of aquatic vegetation (such as seagrass) are characterized by the generation of a strong, shoreward mean current near the top of the canopy. This shoreward drift, which is observed to be up to 75% of the RMS above-canopy orbital velocity, can have a significant impact on residence times within coastal canopies. There have been limited observations of this current and an accurate formulation of its magnitude is still lacking. Accordingly, this study aims to develop a practical relationship to describe the strength of this current as a function of both wave and canopy characteristics. A simple model for the Lagrangian drift velocity indicates that the magnitude of the wave-driven current increases with the above-canopy oscillatory velocity, the vertical orbital excursion at the top of the canopy, and the canopy density. An extensive laboratory study, using both rigid and (dynamically scaled) flexible model vegetation, was carried out to evaluate the proposed model. Experimental results reveal a strong agreement between predicted and measured current velocities over a wide and realistic range of canopy and wave conditions. The validity of this model is also confirmed through available field measurements. Characterization of this wave-induced mean current will allow an enhanced capacity for predicting residence time, and thus key ecological processes, in coastal canopies.

  8. Canopy soil bacterial communities altered by severing host tree limbs

    Directory of Open Access Journals (Sweden)

    Cody R. Dangerfield

    2017-09-01

    Full Text Available Trees of temperate rainforests host a large biomass of epiphytic plants, which are associated with soils formed in the forest canopy. Falling of epiphytic material results in the transfer of carbon and nutrients from the canopy to the forest floor. This study provides the first characterization of bacterial communities in canopy soils enabled by high-depth environmental sequencing of 16S rRNA genes. Canopy soil included many of the same major taxonomic groups of Bacteria that are also found in ground soil, but canopy bacterial communities were lower in diversity and contained different operational taxonomic units. A field experiment was conducted with epiphytic material from six Acer macrophyllum trees in Olympic National Park, Washington, USA to document changes in the bacterial communities of soils associated with epiphytic material that falls to the forest floor. Bacterial diversity and composition of canopy soil was highly similar, but not identical, to adjacent ground soil two years after transfer to the forest floor, indicating that canopy bacteria are almost, but not completely, replaced by ground soil bacteria. Furthermore, soil associated with epiphytic material on branches that were severed from the host tree and suspended in the canopy contained altered bacterial communities that were distinct from those in canopy material moved to the forest floor. Therefore, the unique nature of canopy soil bacteria is determined in part by the host tree and not only by the physical environmental conditions associated with the canopy. Connection to the living tree appears to be a key feature of the canopy habitat. These results represent an initial survey of bacterial diversity of the canopy and provide a foundation upon which future studies can more fully investigate the ecological and evolutionary dynamics of these communities.

  9. Marsh canopy leaf area and orientation calculated for improved marsh structure mapping

    Science.gov (United States)

    Ramsey, Elijah W.; Rangoonwala, Amina; Jones, Cathleen E.; Bannister, Terri

    2015-01-01

    An approach is presented for producing the spatiotemporal estimation of leaf area index (LAI) of a highly heterogeneous coastal marsh without reliance on user estimates of marsh leaf-stem orientation. The canopy LAI profile derivation used three years of field measured photosynthetically active radiation (PAR) vertical profiles at seven S. alterniflora marsh sites and iterative transform of those PAR attenuation profiles to best-fit light extinction coefficients (KM). KM sun zenith dependency was removed obtaining the leaf angle distribution (LAD) representing the average marsh orientation and the LAD used to calculate the LAI canopy profile. LAI and LAD reproduced measured PAR profiles with 99% accuracy and corresponded to field documented structures. LAI and LAD better reflect marsh structure and results substantiate the need to account for marsh orientation. The structure indexes are directly amenable to remote sensing spatiotemporal mapping and offer a more meaningful representation of wetland systems promoting biophysical function understanding.

  10. Growth of soybean at future tropospheric ozone concentrations decreases canopy evapotranspiration and soil water depletion.

    Science.gov (United States)

    Bernacchi, Carl J; Leakey, Andrew D B; Kimball, Bruce A; Ort, Donald R

    2011-06-01

    Tropospheric ozone is increasing in many agricultural regions resulting in decreased stomatal conductance and overall biomass of sensitive crop species. These physiological effects of ozone forecast changes in evapotranspiration and thus in the terrestrial hydrological cycle, particularly in intercontinental interiors. Soybean plots were fumigated with ozone to achieve concentrations above ambient levels over five growing seasons in open-air field conditions. Mean season increases in ozone concentrations ([O₃]) varied between growing seasons from 22 to 37% above background concentrations. The objective of this experiment was to examine the effects of future [O₃] on crop ecosystem energy fluxes and water use. Elevated [O₃] caused decreases in canopy evapotranspiration resulting in decreased water use by as much as 15% in high ozone years and decreased soil water removal. In addition, ozone treatment resulted in increased sensible heat flux in all years indicative of day-time increase in canopy temperature of up to 0.7 °C. Published by Elsevier Ltd.

  11. Beyond CO2 - Tackling the full greenhouse gas budget of a sub-alpine forest ecosystem

    Science.gov (United States)

    Burri, Susanne; Merbold, Lutz; Meier, Philip; Eugster, Werner; Hörtnagl, Lukas; Buchmann, Nina

    2017-04-01

    In order to tackle the full greenhouse gas (GHG) budgets of forest ecosystems, it is desirable but challenging to quantify the three major GHGs, i.e. CO2, CH4 and N2O simultaneously in-situ. At the long-term forest research site Davos (Candidate Class I Ecosystem Station within the Integrated Carbon Observation System - ICOS), we have recently installed a state-of-the-art measuring system simultaneously to observe the three GHGs on a high temporal resolution and both within and above the forest canopy. Thereby, we combine above-canopy eddy covariance flux measurements and forest floor chamber flux measurements (using five custom-made fully automated chambers). Both systems are connected to a quantum cascade laser absorption spectrometer (QCL, Aerodyne) and measurements are switched between three hours of above-canopy and one hour of forest floor GHG flux measurements. Using this approach, we will be able to study the full GHG budget as well as the dynamics of the individual fluxes on two vertical levels within the forest using a single instrument. The first results presented here will highlight the suitability of this promising tool for quantifying the full GHG budget of forest ecosystems.

  12. A model of canopy photosynthesis incorporating protein distribution through the canopy and its acclimation to light, temperature and CO2

    Science.gov (United States)

    Johnson, Ian R.; Thornley, John H. M.; Frantz, Jonathan M.; Bugbee, Bruce

    2010-01-01

    Background and Aims The distribution of photosynthetic enzymes, or nitrogen, through the canopy affects canopy photosynthesis, as well as plant quality and nitrogen demand. Most canopy photosynthesis models assume an exponential distribution of nitrogen, or protein, through the canopy, although this is rarely consistent with experimental observation. Previous optimization schemes to derive the nitrogen distribution through the canopy generally focus on the distribution of a fixed amount of total nitrogen, which fails to account for the variation in both the actual quantity of nitrogen in response to environmental conditions and the interaction of photosynthesis and respiration at similar levels of complexity. Model A model of canopy photosynthesis is presented for C3 and C4 canopies that considers a balanced approach between photosynthesis and respiration as well as plant carbon partitioning. Protein distribution is related to irradiance in the canopy by a flexible equation for which the exponential distribution is a special case. The model is designed to be simple to parameterize for crop, pasture and ecosystem studies. The amount and distribution of protein that maximizes canopy net photosynthesis is calculated. Key Results The optimum protein distribution is not exponential, but is quite linear near the top of the canopy, which is consistent with experimental observations. The overall concentration within the canopy is dependent on environmental conditions, including the distribution of direct and diffuse components of irradiance. Conclusions The widely used exponential distribution of nitrogen or protein through the canopy is generally inappropriate. The model derives the optimum distribution with characteristics that are consistent with observation, so overcoming limitations of using the exponential distribution. Although canopies may not always operate at an optimum, optimization analysis provides valuable insight into plant acclimation to environmental

  13. Long-term reactive nitrogen loading alters soil carbon and microbial community properties in a subalpine forest ecosystem

    Science.gov (United States)

    Boot, Claudia M; Hall, Ed K.; Denef, Karolien; Baron, Jill S.

    2016-01-01

    Elevated nitrogen (N) deposition due to increased fossil fuel combustion and agricultural practices has altered global carbon (C) cycling. Additions of reactive N to N-limited environments are typically accompanied by increases in plant biomass. Soil C dynamics, however, have shown a range of different responses to the addition of reactive N that seem to be ecosystem dependent. We evaluated the effect of N amendments on biogeochemical characteristics and microbial responses of subalpine forest organic soils in order to develop a mechanistic understanding of how soils are affected by N amendments in subalpine ecosystems. We measured a suite of responses across three years (2011–2013) during two seasons (spring and fall). Following 17 years of N amendments, fertilized soils were more acidic (control mean 5.09, fertilized mean 4.68), and had lower %C (control mean 33.7% C, fertilized mean 29.8% C) and microbial biomass C by 22% relative to control plots. Shifts in biogeochemical properties in fertilized plots were associated with an altered microbial community driven by reduced arbuscular mycorrhizal (control mean 3.2 mol%, fertilized mean 2.5 mol%) and saprotrophic fungal groups (control mean 17.0 mol%, fertilized mean 15.2 mol%), as well as a decrease in N degrading microbial enzyme activity. Our results suggest that decreases in soil C in subalpine forests were in part driven by increased microbial degradation of soil organic matter and reduced inputs to soil organic matter in the form of microbial biomass.

  14. Trace elements in sub-alpine forest soils on the eastern edge of the Tibetan Plateau, China

    Science.gov (United States)

    Wang, Xiaodan; Cheng, Genwei; Zhong, Xianghao; Li, Mai-He

    2009-08-01

    Industrial development has increased fast in China during the last decades. This has led to a range of environmental problems. Deposition of trace elements to forest ecosystems via the atmosphere is one potential problem. In this paper, we report the results from a pilot study where the trace element levels of the sub-alpine forest soils on the eastern edge of the Tibetan Plateau have been measured. Possible relationships between soil properties and trace element concentrations have also been investigated. The obtained concentrations (mg kg-1) were boron (B) 48.06-53.70, molybdenum (Mo) 1.53-2.26, zinc (Zn) 68.18-79.53, copper (Cu) 36.81-42.44, selenium (Se) 0.33-0.49, cadmium (Cd) 0.16-0.29, lead (Pb) 25.80-30.71, chromium (Cr) 96.10-110.08, nickel (Ni) 30.16-45.60, mercury (Hg) 0.05-0.11, and arsenic (As) 3.09-4.17. With a few exceptions, the element concentration can be characterized as low in the investigated sub-alpine forest soils. No clear differences in trace element levels were found between topsoil and subsoil samples, indicating that the atmospheric deposition of trace element has been low. The soil parent material plays a key role to determine trace element levels. Soil properties, including pHw, organic carbon (OC), clay fraction, cation-exchange capacity (CEC), total iron (Fe), and total aluminum (Al) concentrations were related to trace element concentration using correlation analysis. Total Fe and Al showed the strongest relationships with concentrations of most trace elements in the sub-alpine forest soils. PCA analyses indicated that a significant increase in the number of cars with the fast development of local tourism may result in higher Pb concentration in the future.

  15. Radiation Distribution Within a Canopy Profile Calculated by a Multiple-Layer Canopy Scattering Model

    Science.gov (United States)

    Qualls, R. J.; Zhao, W.

    2004-05-01

    Remote sensing technology has tremendous potential for use in natural resource studies, agriculture, water and land use management because of the spatial information contained in remote sensing images and because of the ease and/or frequency of acquiring vast amounts of surface information. However, the quantitative application of remotely sensed data is restricted by several problems. One of them is that the entities a remote sensor views are not single targets. For example, measurement show that the skin temperature of many crops can exhibit more than a 10° C difference between the leaves at the bottom and those at the top of the canopy, in addition to the usually large difference between leaves and soil substrate. Directional radiometric surface temperatures measured from above a crop represent neither the skin temperature of the crop nor the surface temperature of the soil substrate but a complex aggregate of all elements viewed. When a remote sensing device views a vegetated surface from different view angles, different combinations of canopy and soil elements at different temperatures will be seen, producing different values of "remotely sensed surface temperature." As the first step in a series of models to be developed to simulate energy balance, sensible and latent heat fluxes, and temperature profiles within a vegetation canopy, a multiple-layer canopy scattering model to estimate short wave radiation distribution within a wheat canopy was developed. This model incorporates processes of radiation penetration through gaps between leaves, and radiation absorption, reflection and transmission in leaf layers. It is able to simulate the multiple scattering processes that occur among different canopy layers, and determine the vertical distributions of upwelling, downwelling, and reflected short wave radiation within the canopy, and at the soil surface. One of the primary advantages of this model, in contrast to other models, is that the multiple scattering

  16. CANOPY STRUCTURE AND DEPOSITION EFFICIENCY OF VINEYARD SPRAYERS

    OpenAIRE

    Gianfranco Pergher; Raffaella Petris

    2007-01-01

    A field study was performed to analyse how deposition efficiency from an axial-fan sprayer was affected by the canopy structure of vines trained to the High Cordon, Low Cordon and Casarsa systems, at beginning of flowering and beginning of berry touch growth stages. An empirical calibration method, providing a dose rate adjustment roughly proportional to canopy height, was used. The canopy structure was assessed using the Point Quadrat method, and determining the leaf area index (LAI) and the...

  17. Assessing heat fluxes and water quality trends in subalpine lakes from EO

    Science.gov (United States)

    Cazzaniga, Ilaria; Giardino, Claudia; Bresciani, Mariano; Elli, Chiara; Valerio, Giulia; Pilotti, Marco

    2017-04-01

    Lakes play a fundamental role in providing ecosystem services such as water supplying, hydrological regulation, climate change mitigation, touristic recreation (Schallenberg et al., 2013). Preserving and improving of quality of lakes waters, which is a function of either both natural and human influences, is therefore an important action to be considered. Remote Sensing techniques are spreading as useful instrument for lakes, by integrating classical in situ limnological measurements to frequent and synoptic monitoring capabilities. Within this study, Earth Observation data are exploited for understanding the temporal changes of water quality parameters over a decade, as well as for measuring the surface energy fluxes in recent years in deep clear lakes in the European subalpine ecoregion. According to Pareth et al. (2016), subalpine lakes are showing a clear response to climate change with an increase of 0.017 °C /year of lake surface temperature, whilst the human activities contribute to produce a large impact (agriculture, recreation, industry, fishing and drinking) on these lakes. The investigation is focused on Lake Iseo, which has shown a significant deterioration of water quality conditions since the seventies, and on Lake Garda, the largest Italian lake where EO data have been widely used for many purposes and applications (Giardino et al., 2014). Available ENVISAT-MERIS (2002-2012) and Landsat-8-OLI (2013-on going) imagery has been exploited to produce chlorophyll-a (chl-a) concentration maps, while Landsat-8-TIRS imagery has been used for estimating lake surface temperatures. MERIS images were processed through a neural network (namely the C2R processor, Doerffer et al., 2007), to correct the atmospheric effects and to retrieve water constituents concentration in optically complex deep waters. With regard to L8's images, some atmospheric correctors (e.g. ACOLITE and 6SV) were tested and validated to indentify, for each of the two lakes, the more accurate

  18. Hydrologic flow path development varies by aspect during spring snowmelt in complex subalpine terrain

    Science.gov (United States)

    Webb, Ryan W.; Fassnacht, Steven R.; Gooseff, Michael N.

    2018-01-01

    In many mountainous regions around the world, snow and soil moisture are key components of the hydrologic cycle. Preferential flow paths of snowmelt water through snow have been known to occur for years with few studies observing the effect on soil moisture. In this study, statistical analysis of the topographical and hydrological controls on the spatiotemporal variability of snow water equivalent (SWE) and soil moisture during snowmelt was undertaken at a subalpine forested setting with north, south, and flat aspects as a seasonally persistent snowpack melts. We investigated if evidence of preferential flow paths in snow can be observed and the effect on soil moisture through measurements of snow water equivalent and near-surface soil moisture, observing how SWE and near-surface soil moisture vary on hillslopes relative to the toes of hillslopes and flat areas. We then compared snowmelt infiltration beyond the near-surface soil between flat and sloping terrain during the entire snowmelt season using soil moisture sensor profiles. This study was conducted during varying snowmelt seasons representing above-normal, relatively normal, and below-normal snow seasons in northern Colorado. Evidence is presented of preferential meltwater flow paths at the snow-soil interface on the north-facing slope causing increases in SWE downslope and less infiltration into the soil at 20 cm depth; less association is observed in the near-surface soil moisture (top 7 cm). We present a conceptualization of the meltwater flow paths that develop based on slope aspect and soil properties. The resulting flow paths are shown to divert at least 4 % of snowmelt laterally, accumulating along the length of the slope, to increase the snow water equivalent by as much as 170 % at the base of a north-facing hillslope. Results from this study show that snow acts as an extension of the vadose zone during spring snowmelt and future hydrologic investigations will benefit from studying the snow and soil

  19. Conifer density within lake catchments predicts fish mercury concentrations in remote subalpine lakes

    Science.gov (United States)

    Eagles-Smith, Collin A.; Herring, Garth; Johnson, Branden L.; Graw, Rick

    2016-01-01

    Remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited mercury through freshwater food webs, as well as for evaluating the relative importance of mercury loading versus landscape influences on mercury bioaccumulation. The increase in mercury deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in mercury emissions may propagate to changes in Hg bioaccumulation and ecological risk. We evaluated mercury concentrations in resident fish from 28 high-elevation, sub-alpine lakes in the Pacific Northwest region of the United States. Fish total mercury (THg) concentrations ranged from 4 to 438 ng/g wet weight, with a geometric mean concentration (±standard error) of 43 ± 2 ng/g ww. Fish THg concentrations were negatively correlated with relative condition factor, indicating that faster growing fish that are in better condition have lower THg concentrations. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. We used a hierarchal statistical approach to evaluate the relative importance of physiological, limnological, and catchment drivers of fish Hg concentrations. Our top statistical model explained 87% of the variability in fish THg concentrations among lakes with four key landscape and limnological variables: catchment conifer density (basal area of conifers within a lake's catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. Conifer density within a lake's catchment was the most important variable explaining fish THg concentrations across lakes, with THg concentrations differing by more than 400 percent across the forest density spectrum. These results illustrate the importance of landscape characteristics in controlling mercury bioaccumulation in fish.

  20. Calcium induces long-term legacy effects in a subalpine ecosystem.

    Directory of Open Access Journals (Sweden)

    Urs Schaffner

    Full Text Available Human activities have transformed a significant proportion of the world's land surface, with profound effects on ecosystem processes. Soil applications of macronutrients such as nitrate, phosphorus, potassium or calcium are routinely used in the management of croplands, grasslands and forests to improve plant health or increase productivity. However, while the effects of continuous fertilization and liming on terrestrial ecosystems are well documented, remarkably little is known about the legacy effect of historical fertilization and liming events in terrestrial ecosystems and of the mechanisms involved. Here, we show that more than 70 years after the last application of lime on a subalpine grassland, all major soil and plant calcium pools were still significantly larger in limed than in unlimed plots, and that the resulting shift in the soil calcium/aluminium ratio continues to affect ecosystem services such as primary production. The difference in the calcium content of the vegetation and the topmost 10 cm of the soil in limed vs. unlimed plots amounts to approximately 19.5 g m(-2, equivalent to 16.3% of the amount that was added to the plots some 70 years ago. In contrast, plots that were treated with nitrogen-phosphorus-potassium fertilizer in the 1930s did not differ from unfertilized plots in any of the soil and vegetation characteristics measured. Our findings suggest that the long-term legacy effect of historical liming is due to long-term storage of added calcium in stable soil pools, rather than a general increase in nutrient availability. Our results demonstrate that single applications of calcium in its carbonated form can profoundly and persistently alter ecosystem processes and services in mountain ecosystems.

  1. Net primary productivity of subalpine meadows in Yosemite National Park in relation to climate variability

    Science.gov (United States)

    Moore, Peggy E.; Van Wagtendonk, Jan W.; Yee, Julie L.; McClaran, Mitchel P.; Cole, David N.; McDougald, Neil K.; Brooks, Matthew L.

    2013-01-01

    Subalpine meadows are some of the most ecologically important components of mountain landscapes, and primary productivity is important to the maintenance of meadow functions. Understanding how changes in primary productivity are associated with variability in moisture and temperature will become increasingly important with current and anticipated changes in climate. Our objective was to describe patterns and variability in aboveground live vascular plant biomass in relation to climatic factors. We harvested aboveground biomass at peak growth from four 64-m2 plots each in xeric, mesic, and hydric meadows annually from 1994 to 2000. Data from nearby weather stations provided independent variables of spring snow water content, snow-free date, and thawing degree days for a cumulative index of available energy. We assembled these climatic variables into a set of mixed effects analysis of covariance models to evaluate their relationships with annual aboveground net primary productivity (ANPP), and we used an information theoretic approach to compare the quality of fit among candidate models. ANPP in the xeric meadow was negatively related to snow water content and thawing degree days and in the mesic meadow was negatively related to snow water content. Relationships between ANPP and these 2 covariates in the hydric meadow were not significant. Increasing snow water content may limit ANPP in these meadows if anaerobic conditions delay microbial activity and nutrient availability. Increased thawing degree days may limit ANPP in xeric meadows by prematurely depleting soil moisture. Large within-year variation of ANPP in the hydric meadow limited sensitivity to the climatic variables. These relationships suggest that, under projected warmer and drier conditions, ANPP will increase in mesic meadows but remain unchanged in xeric meadows because declines associated with increased temperatures would offset the increases from decreased snow water content.

  2. Intraguild predation and cannibalism among larvae of detritivorous caddisflies in subalpine wetlands

    Science.gov (United States)

    Wissinger, S.A.; Sparks, G.B.; Rouse, G.L.; Brown, W.S.; Steltzer, Heidi

    1996-01-01

    Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats - Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same-sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density-dependent and occurred even at low larval densities. We

  3. Canopy interception variability in changing climate

    Science.gov (United States)

    Kalicz, Péter; Herceg, András; Kisfaludi, Balázs; Csáki, Péter; Gribovszki, Zoltán

    2017-04-01

    Tree canopies play a rather important role in forest hydrology. They intercept significant amounts of precipitation and evaporate back into the atmosphere during and after precipitation event. This process determines the net intake of forest soils and so important factor of hydrological processes in forested catchments. Average amount of interception loss is determined by the storage capacity of tree canopies and the rainfall distribution. Canopy storage capacity depends on several factors. It shows strong correlation with the leaf area index (LAI). Some equations are available to quantify this dependence. LAI shows significant variability both spatial and temporal scale. There are several methods to derive LAI from remote sensed data which helps to follow changes of it. In this study MODIS sensor based LAI time series are used to estimate changes of the storage capacity. Rainfall distribution derived from the FORESEE database which is developed for climate change related impact studies in the Carpathian Basin. It contains observation based precipitation data for the past and uses bias correction method for the climate projections. In this study a site based estimation is outworked for the Sopron Hills area. Sopron Hills is located at the eastern foothills of the Alps in Hungary. The study site, namely Hidegvíz Valley experimental catchment, is located in the central valley of the Sopron Hills. Long-term interception measurements are available in several forest sites in Hidegvíz Valley. With the combination of the ground based observations, MODIS LAI datasets a simple function is developed to describe the average yearly variations in canopy storage. Interception measurements and the CREMAP evapotranspiration data help to calibrate a simple interception loss equation based on Merriam's work. Based on these equation and the FORESEE bias corrected precipitation data an estimation is outworked for better understanding of the feedback of forest crown on hydrological

  4. Influence of canopy seasonal changes on turbulence parameterization within the roughness sublayer over an orchard canopy

    NARCIS (Netherlands)

    Shapkalijevski, M.; Moene, A.F.; Ouwersloot, Huug; Patton, E.G.; Vilà-Guerau De Arellano, J.

    2016-01-01

    In this observational study, the role of tree phenology on the atmospheric turbulence parameterization over 10-m-tall and relatively sparse deciduous vegetation is quantified. Observations from the Canopy Horizontal Array Turbulence Study (CHATS) field experiment are analyzed to establish the

  5. Evaporation from rain-wetted forest in relation to canopy wetness, canopy cover, and net radiation

    NARCIS (Netherlands)

    Klaassen, W.

    2001-01-01

    Evaporation from wet canopies is commonly calculated using E-PM, the Penman-Monteith equation with zero surface resistance. However, several observations show a lower evaporation from rain-wetted forest. Possible causes for the difference between E-PM and experiments are evaluated to provide rules

  6. Cataract removal

    Science.gov (United States)

    ... eye diseases and eye surgery. Adults are usually awake for the procedure. Numbing medicine (local anesthesia) is ... removed. Tips for recovering after cataract surgery: Wear dark sunglasses outside after you remove the patch. Wash ...

  7. Nevus Removal

    Science.gov (United States)

    ... find the answers you seek. What are the Negative Effects of Nevus Removal? Removal procedures are major ... Reunited Donor Challenge Met! Find Nevus Outreach on Facebook To New Parents of a Child With a ...

  8. Declines in low-elevation subalpine tree populations outpace growth in high-elevation populations with warming

    Science.gov (United States)

    Conlisk, Erin; Castanha, Cristina; Germino, Matthew J.; Veblen, Thomas T; Smith, Jeremy M.; Kueppers, Lara M.

    2017-01-01

    Species distribution shifts in response to climate change require that recruitment increase beyond current range boundaries. For trees with long life spans, the importance of climate-sensitive seedling establishment to the pace of range shifts has not been demonstrated quantitatively.Using spatially explicit, stochastic population models combined with data from long-term forest surveys, we explored whether the climate-sensitivity of recruitment observed in climate manipulation experiments was sufficient to alter populations and elevation ranges of two widely distributed, high-elevation North American conifers.Empirically observed, warming-driven declines in recruitment led to rapid modelled population declines at the low-elevation, ‘warm edge’ of subalpine forest and slow emergence of populations beyond the high-elevation, ‘cool edge’. Because population declines in the forest occurred much faster than population emergence in the alpine, we observed range contraction for both species. For Engelmann spruce, this contraction was permanent over the modelled time horizon, even in the presence of increased moisture. For limber pine, lower sensitivity to warming may facilitate persistence at low elevations – especially in the presence of increased moisture – and rapid establishment above tree line, and, ultimately, expansion into the alpine.Synthesis. Assuming 21st century warming and no additional moisture, population dynamics in high-elevation forests led to transient range contractions for limber pine and potentially permanent range contractions for Engelmann spruce. Thus, limitations to seedling recruitment with warming can constrain the pace of subalpine tree range shifts.

  9. Effects of tourism and topography on vegetation diversity in the subalpine meadows of the Dongling Mountains of Beijing, China.

    Science.gov (United States)

    Zhang, Jin-Tun; Xiang, ChunLing; Li, Min

    2012-02-01

    Subalpine meadows in the Dongling Mountains (located at E115º26'-115º40', N40º00'-40º05') of Beijing, China are important for tourism and the provision of ecosystem services. However, because of poor management serious degradation has occurred on these subalpine meadows. The aim of this paper is to present a quantitative analysis of effects of tourism disturbance and topography on the status and diversity of montane meadow communities and to provide direction for improved management. Sixty quadrats of 2 × 2 m(2) along 10 transects were set up to collect data on site characteristics and vegetation status. The relationships between community composition and structure, species diversity, and tourism disturbance and topographic variables were analyzed by multivariate methods (TWINSPAN and CCA). The results showed that eight meadow communities were identified by TWINSPAN. Most of them were seriously degraded. The first CCA axis identified an elevation and tourism disturbance intensity gradient, which illustrated that tourism disturbance and elevation were most important factors influencing meadow types, composition and structure. Some resistant species and response species to tourism disturbance were identified and can be used as indicator species of tourism disturbance. Species richness, heterogeneity and evenness were closely related to tourism disturbance and elevation. It is concluded that tourism disturbance must be controlled to enable grassland rehabilitation to occur in the meadows. Measures of effective management of the meadows were discussed.

  10. Effects of Tourism and Topography on Vegetation Diversity in the Subalpine Meadows of the Dongling Mountains of Beijing, China

    Science.gov (United States)

    Zhang, Jin-Tun; Xiang, Chunling; Li, Min

    2012-02-01

    Subalpine meadows in the Dongling Mountains (located at E115º26'-115º40', N40º00'-40º05') of Beijing, China are important for tourism and the provision of ecosystem services. However, because of poor management serious degradation has occurred on these subalpine meadows. The aim of this paper is to present a quantitative analysis of effects of tourism disturbance and topography on the status and diversity of montane meadow communities and to provide direction for improved management. Sixty quadrats of 2 × 2 m2 along 10 transects were set up to collect data on site characteristics and vegetation status. The relationships between community composition and structure, species diversity, and tourism disturbance and topographic variables were analyzed by multivariate methods (TWINSPAN and CCA). The results showed that eight meadow communities were identified by TWINSPAN. Most of them were seriously degraded. The first CCA axis identified an elevation and tourism disturbance intensity gradient, which illustrated that tourism disturbance and elevation were most important factors influencing meadow types, composition and structure. Some resistant species and response species to tourism disturbance were identified and can be used as indicator species of tourism disturbance. Species richness, heterogeneity and evenness were closely related to tourism disturbance and elevation. It is concluded that tourism disturbance must be controlled to enable grassland rehabilitation to occur in the meadows. Measures of effective management of the meadows were discussed.

  11. Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar

    Science.gov (United States)

    Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

    2017-05-01

    Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaska’s Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30 m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broadleaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from aboveground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn

  12. Subalpine vegetation pattern three decades after stand-replacing fire: Effects of landscape context and topography on plant community composition, tree regeneration, and diversity

    Science.gov (United States)

    Jonathan D. Coop; Robert T. Massatti; Anna W. Schoettle

    2010-01-01

    These subalpine wildfires generated considerable, persistent increases in plant species richness at local and landscape scales, and a diversity of plant communities. The findings suggest that fire suppression in such systems must lead to reduced diversity. Concerns about post-fire invasion by exotic plants appear unwarranted in high-elevation wilderness settings.

  13. Verification of satellite radar remote sensing based estimates of boreal and subalpine growing seasons using an ecosystem process model and surface biophysical measurement network information

    Science.gov (United States)

    McDonald, K. C.; Kimball, J. S.; Zimmerman, R.

    2002-01-01

    We employ daily surface Radar backscatter data from the SeaWinds Ku-band Scatterometer onboard Quikscat to estimate landscape freeze-thaw state and associated length of the seasonal non-frozen period as a surrogate for determining the annual growing season across boreal and subalpine regions of North America for 2000 and 2001.

  14. Carex sempervirens tussocks induce spatial heterogeneity in litter decomposition, but not in soil properties, in a subalpine grassland in the Central Alps

    Science.gov (United States)

    Fei-Hai Yu; Martin Schutz; Deborah S. Page-Dumroese; Bertil O. Krusi; Jakob Schneller; Otto Wildi; Anita C. Risch

    2011-01-01

    Tussocks of graminoids can induce spatial heterogeneity in soil properties in dry areas with discontinuous vegetation cover, but little is known about the situation in areas with continuous vegetation and no study has tested whether tussocks can induce spatial heterogeneity in litter decomposition. In a subalpine grassland in the Central Alps where vegetation cover is...

  15. Deforestation induces shallow landsliding in the montane and subalpine belts of the Urbión Mountains, Iberian Range, Northern Spain

    Science.gov (United States)

    García-Ruiz, José M.; Beguería, Santiago; Arnáez, José; Sanjuán, Yasmina; Lana-Renault, Noemí; Gómez-Villar, Amelia; Álvarez-Martínez, Javier; Coba-Pérez, Paz

    2017-11-01

    In this study the spatial distribution of shallow landslides in the upper montane and subalpine belts of the Urbión Mountains (Iberian Range, northern Spain) was investigated, particularly in relation to the spatial organization of deforestation and land cover. The upper montane and subalpine belts have been deforested several times since the Neolithic Period, to enlarge the area of summer grasslands for feeding transhumant sheep flocks. Consequently, the timberline was lowered by 400-600 m, and increased the occurrence of severe erosion processes, particularly shallow landslides. This study shows that most of the landslide scars are in the summer grasslands area, and that a remarkable extent of the subalpine belt area has been subjected to mass movements. In addition to land use, the soil characteristics and topography help explain the development of conditions most favorable to landsliding. Shallow landslide susceptibility was highest in the upper parts of the slopes near the divides, in areas having slope gradients of 10-30° and deep soils with an increasing proportion of clay with depth. The landslides were clustered and not randomly distributed, and the causes of this spatial distribution are discussed. The current trend of woody encroachment in the upper montane and subalpine belts, resulting from decreasing livestock pressure, will probably reduce the susceptibility of these areas to shallow landslides in the future.

  16. Lab and Field Warming Similarly Advance Germination Date and Limit Germination Rate for High and Low Elevation Provenances of Two Widespread Subalpine Conifers

    Directory of Open Access Journals (Sweden)

    Lara M. Kueppers

    2017-11-01

    Full Text Available Accurately predicting upslope shifts in subalpine tree ranges with warming requires understanding how future forest populations will be affected by climate change, as these are the seed sources for new tree line and alpine populations. Early life history stages are particularly sensitive to climate and are also influenced by genetic variation among populations. We tested the climate sensitivity of germination and initial development for two widely distributed subalpine conifers, using controlled-environment growth chambers with one temperature regime from subalpine forest in the Colorado Rocky Mountains and one 5 °C warmer, and two soil moisture levels. We tracked germination rate and timing, rate of seedling development, and seedling morphology for two seed provenances separated by ~300 m elevation. Warming advanced germination timing and initial seedling development by a total of ~2 weeks, advances comparable to mean differences between provenances. Advances were similar for both provenances and species; however, warming reduced the overall germination rate, as did low soil moisture, only for Picea engelmannii. A three-year field warming and watering experiment planted with the same species and provenances yielded responses qualitatively consistent with the lab trials. Together these experiments indicate that in a warmer, drier climate, P. engelmannii germination, and thus regeneration, could decline, which could lead to declining subalpine forest populations, while Pinus flexilis forest populations could remain robust as a seed source for upslope range shifts.

  17. The fauna and flora of a kelp bed canopy

    African Journals Online (AJOL)

    The fauna and flora of the canopy of a kelp bed off. Oudekraal, on the Cape Peninsula, is surveyed. Four species of epiphytic algae occur in the kelp canopy, three restricted to. Ecklonia maxima and the fourth to Laminaria pal/ida. Epiphyte biomass is equivalent to 4 - 9% of host standing crop amongst E. maxima, but less ...

  18. Hierarchical Canopy Dynamics of Electrolyte-Doped Nanoscale Ionic Materials

    KAUST Repository

    Jespersen, Michael L.

    2013-12-23

    Nanoscale ionic materials (NIMs) are organic-inorganic hybrids prepared from ionically functionalized nanoparticles (NP) neutralized by oligomeric polymer counterions. NIMs are designed to behave as liquids under ambient conditions in the absence of solvent and have no volatile organic content, making them useful for a number of applications. We have used nuclear magnetic resonance relaxation and pulsed-field gradient NMR to probe local and collective canopy dynamics in NIMs based on 18-nm silica NPs with a covalently bound anionic corona, neutralized by amine-terminated ethylene oxide/propylene oxide block copolymers. The NMR relaxation studies show that the nanosecond-scale canopy dynamics depend on the degree of neutralization, the canopy radius of gyration, and crowding at the ionically modified NP surface. Two canopy populations are observed in the diffusion experiments, demonstrating that one fraction of the canopy is bound to the NP surface on the time scale (milliseconds) of the diffusion experiment and is surrounded by a more mobile layer of canopy that is unable to access the surface due to molecular crowding. The introduction of electrolyte ions (Na+ or Mg2+) screens the canopy-corona electrostatic interactions, resulting in a reduced bulk viscosity and faster canopy exchange. The magnitude of the screening effect depends upon ion concentration and valence, providing a simple route for tuning the macroscopic properties of NIMs. © 2013 American Chemical Society.

  19. Synthesis and Experiments of Inherently Balanced Umbrella Canopy Designs

    NARCIS (Netherlands)

    van der Wijk, V.; Kiper, G.; Yasir, A.

    2015-01-01

    This paper shows how umbrella canopies and umbrella canopy-like mechanisms can be designed inherently balanced. Inherently balanced means that the center of mass of the moving parts remains stationary at a single point for any position of the mechanism simply because of the specific design of the

  20. Water stress effects on spatially referenced cotton crop canopy properties

    Science.gov (United States)

    rop canopy temperature is known to be affected by water stress. Canopy reflectance can also be impacted as leaf orientation and color respond to the stress. As sensor systems are investigated for real-time management of irrigation and nitrogen, it is essential to understand how the data from the sen...

  1. Forest canopy BRDF simulation using Monte Carlo method

    NARCIS (Netherlands)

    Huang, J.; Wu, B.; Zeng, Y.; Tian, Y.

    2006-01-01

    Monte Carlo method is a random statistic method, which has been widely used to simulate the Bidirectional Reflectance Distribution Function (BRDF) of vegetation canopy in the field of visible remote sensing. The random process between photons and forest canopy was designed using Monte Carlo method.

  2. Crop canopy BRDF simulation and analysis using Monte Carlo method

    NARCIS (Netherlands)

    Huang, J.; Wu, B.; Tian, Y.; Zeng, Y.

    2006-01-01

    This author designs the random process between photons and crop canopy. A Monte Carlo model has been developed to simulate the Bi-directional Reflectance Distribution Function (BRDF) of crop canopy. Comparing Monte Carlo model to MCRM model, this paper analyzes the variations of different LAD and

  3. Use spectral derivatives for estimating canopy water content

    NARCIS (Netherlands)

    Clevers, J.G.P.W.

    2010-01-01

    Hyperspectral remote sensing has demonstrated great potential for accurate retrieval of canopy water content (CWC). This CWC is defined by the product of the leaf equivalent water thickness (EWT) and the leaf area index (LAI). In this paper the spectral information provided by the canopy water

  4. Estimating wood volume from canopy area in deciduous woodlands ...

    African Journals Online (AJOL)

    In this study we tested the predictive ability of canopy area in estimating wood volume in deciduous woodlands of Zimbabwe. The study was carried out in four sites of different climatic conditions. We used regression analysis to statistically quantify the prediction of wood volume from canopy area at species and stand level ...

  5. Summertime canopy albedo is sensitive to forest thinning

    NARCIS (Netherlands)

    Otto, J.; Berveiller, D.; Bréon, F.M.; Delpierre, N.; Geppert, G.; Granier, A.; Jans, W.W.P.; Knohl, A.; Moors, E.J.

    2013-01-01

    Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning,

  6. Removing other Tree Species does not benefit the Timber Species ...

    African Journals Online (AJOL)

    The endemic canopy tree Cephalosphaera usambarensis is a valuable timber species in montane rainforest of Tanzania. Here we evaluate an experiment in which mature trees of species other than C. usambarensis were removed from an area in the East Usambara Mountains. We compared stage/size structure of the ...

  7. Air-Parcel Residence Times Within Forest Canopies

    Science.gov (United States)

    Gerken, Tobias; Chamecki, Marcelo; Fuentes, Jose D.

    2017-10-01

    We present a theoretical model, based on a simple model of turbulent diffusion and first-order chemical kinetics, to determine air-parcel residence times and the out-of-canopy export of reactive gases emitted within forest canopies under neutral conditions. Theoretical predictions of the air-parcel residence time are compared to values derived from large-eddy simulation for a range of canopy architectures and turbulence levels under neutral stratification. Median air-parcel residence times range from a few sec in the upper canopy to approximately 30 min near the ground and the distribution of residence times is skewed towards longer times in the lower canopy. While the predicted probability density functions from the theoretical model and large-eddy simulation are in good agreement with each other, the theoretical model requires only information on canopy height and eddy diffusivities inside the canopy. The eddy-diffusivity model developed additionally requires the friction velocity at canopy top and a parametrized profile of the standard deviation of vertical velocity. The theoretical model of air-parcel residence times is extended to include first-order chemical reactions over a range of of Damköhler numbers ( Da) characteristic of plant-emitted hydrocarbons. The resulting out-of-canopy export fractions range from near 1 for Da =10^{-3} to less than 0.3 at Da = 10. These results highlight the necessity for dense and tall forests to include the impacts of air-parcel residence times when calculating the out-of-canopy export fraction for reactive trace gases.

  8. Deploying Fourier Coefficients to Unravel Soybean Canopy Diversity.

    Science.gov (United States)

    Jubery, Talukder Z; Shook, Johnathon; Parmley, Kyle; Zhang, Jiaoping; Naik, Hsiang S; Higgins, Race; Sarkar, Soumik; Singh, Arti; Singh, Asheesh K; Ganapathysubramanian, Baskar

    2016-01-01

    Soybean canopy outline is an important trait used to understand light interception ability, canopy closure rates, row spacing response, which in turn affects crop growth and yield, and directly impacts weed species germination and emergence. In this manuscript, we utilize a methodology that constructs geometric measures of the soybean canopy outline from digital images of canopies, allowing visualization of the genetic diversity as well as a rigorous quantification of shape parameters. Our choice of data analysis approach is partially dictated by the need to efficiently store and analyze large datasets, especially in the context of planned high-throughput phenotyping experiments to capture time evolution of canopy outline which will produce very large datasets. Using the Elliptical Fourier Transformation (EFT) and Fourier Descriptors (EFD), canopy outlines of 446 soybean plant introduction (PI) lines from 25 different countries exhibiting a wide variety of maturity, seed weight, and stem termination were investigated in a field experiment planted as a randomized complete block design with up to four replications. Canopy outlines were extracted from digital images, and subsequently chain coded, and expanded into a shape spectrum by obtaining the Fourier coefficients/descriptors. These coefficients successfully reconstruct the canopy outline, and were used to measure traditional morphometric traits. Highest phenotypic diversity was observed for roundness, while solidity showed the lowest diversity across all countries. Some PI lines had extraordinary shape diversity in solidity. For interpretation and visualization of the complexity in shape, Principal Component Analysis (PCA) was performed on the EFD. PI lines were grouped in terms of origins, maturity index, seed weight, and stem termination index. No significant pattern or similarity was observed among the groups; although interestingly when genetic marker data was used for the PCA, patterns similar to canopy

  9. Canopy disturbance intervals, early growth rates, and canopy accession trends of oak-dominated old-growth forests

    Science.gov (United States)

    James S. Rentch; Ray R., Jr. Hicks

    2003-01-01

    Using a radial growth averaging technique, changes in growth rates of overstory oaks were used to quantify canopy disturbance events at five old-growth sites. On average, at least one canopy disturbance occurred on these sites every 3 years; larger multiple-tree disturbances occurred every 17 years. Although there was some variation by site and by historical period,...

  10. Impacts of differing aerodynamic resistance formulae on modeled energy exchange at the above-canopy/within-canopy/soil interface

    Science.gov (United States)

    Application of the Two-Source Energy Balance (TSEB) Model using land surface temperature (LST) requires aerodynamic resistance parameterizations for the flux exchange above the canopy layer, within the canopy air space and at the soil/substrate surface. There are a number of aerodynamic resistance f...

  11. Importance of nitrogen cycling hot spots in an alpine-subalpine ecosystem

    Science.gov (United States)

    Darrouzet-Nardi, A.; Bowman, W. D.

    2009-12-01

    Nitrogen (N) availability in soils is influenced by many microbially catalyzed reactions such as N fixation, denitrification, and N mineralization from soil organic matter (SOM). Reaction rates for these processes are heterogeneous across landscapes, often forming hot spots that have disproportionately high N cycling activity. N cycling hot spots have been documented in many ecosystems at hourly to weekly times scales; however, much less is known about the persistence and importance of N cycling hot spots over longer times scales. Furthermore, few studies have investigated multiple landscape-level measurements of different N cycling processes at the same site. Using a mathematical definition of hot spots, a time series of short-term measurements, ion exchange resins deployed for one year, and nitrogen isotopic signatures in SOM, we investigated the importance of hot spots over longer time scales in a 0.89 km2 alpine-subalpine ecosystem at the Niwot Ridge LTER site. Measurements of KCl-extractable inorganic N taken on multiple measurement dates showed that hot moments of N availabilty occurred in some but not all parts of the study site and at varying times throughout the season. Ion exchange resins deployed for one year showed that N availability hot spots were important though not completely dominant over one year (14% of values accounted for 58% of total resin-extractable inorganic N observed). In contrast, isotopic signatures in 219 SOM samples were well approximated by a normal distribution, suggesting that landscape-level N losses through leaching or gas efflux were more constrained. Denitrification was the possible exception: we saw evidence for several likely hot spots in the wetland areas of our study site. The results of this study suggest that short-term hot spots are important for plant ecological dynamics at our study site and for denitrification, but that long-term N cycling hot spots are less important for other parts of the soil N cycle such as N

  12. Fuel deposition rates of montane and subalpine conifers in the central Sierra Nevada, California, USA

    Science.gov (United States)

    van Wagtendonk, J.W.; Moore, P.E.

    2010-01-01

    Fire managers and researchers need information on fuel deposition rates to estimate future changes in fuel bed characteristics, determine when forests transition to another fire behavior fuel model, estimate future changes in fuel bed characteristics, and parameterize and validate ecosystem process models. This information is lacking for many ecosystems including the Sierra Nevada in California, USA. We investigated fuel deposition rates and stand characteristics of seven montane and four subalpine conifers in the Sierra Nevada. We collected foliage, miscellaneous bark and crown fragments, cones, and woody fuel classes from four replicate plots each in four stem diameter size classes for each species, for a total of 176 sampling sites. We used these data to develop predictive equations for each fuel class and diameter size class of each species based on stem and crown characteristics. There were consistent species and diameter class differences in the annual amount of foliage and fragments deposited. Foliage deposition rates ranged from just over 50 g m-2 year-1 in small diameter mountain hemlock stands to ???300 g m-2 year-1 for the three largest diameter classes of giant sequoia. The deposition rate for most woody fuel classes increased from the smallest diameter class stands to the largest diameter class stands. Woody fuel deposition rates varied among species as well. The rates for the smallest woody fuels ranged from 0.8 g m-2 year-1 for small diameter stands of Jeffrey pine to 126.9 g m-2 year-1 for very large diameter stands of mountain hemlock. Crown height and live crown ratio were the best predictors of fuel deposition rates for most fuel classes and species. Both characteristics reflect the amount of crown biomass including foliage and woody fuels. Relationships established in this study allow predictions of fuel loads to be made on a stand basis for each of these species under current and possible future conditions. These predictions can be used to

  13. Ice duration, winter stratification, and mixing behavior of subalpine lakes in western Maine

    Science.gov (United States)

    Daly, J.; Adams, S.; Abrams, R.; Engel, B.

    2011-12-01

    The timing and duration of both winter and summer periods of stratification periods is not well known for subalpine ponds in the northeastern United States. The remote nature of many of these lakes precludes detailed manual monitoring during the winter and the visual identification of major ice phenological events. These lakes are associated with ecological niches at or near their local elevation maximum that may be at risk due to climate change; historic ice-out records for larger regional lakes indicates a significant trend toward earlier ice-out in response to climate warming. We are using low-cost data loggers to develop high-resolution records characterizing water temperature variability at multiple depths in fifteen lakes 600 - 1000 m elevation. These lakes are located along a 175 km transect in western Maine; most are along the Appalachian Trail. The loggers are recording sub-hourly water temperature and light at the surface, two meters depth, and the bottom of each lake. The timing and duration of winter stratification and ice cover on these lakes are determined by distinctive temperature patterns recorded by the data loggers. The onset of winter stratification is marked by the expected temperature inversion and a slowly increasing hypolimnetic temperature; ice-on follows and is represented by the transition from daily heating cycles to a steady temperature over several days as the ice freezes in around the near-surface logger and energy loss is accomplished through a phase change rather than a drop in temperature. Once the ice is established, temperatures recorded by the near-surface logger vary daily, and are frequently below freezing in response to changing air temperature. Evaluation of winter 2009-2011 records shows that the duration of winter stratification exceeds ice duration at nearly every site. The timing of the onset of stratification is nearly uniform across the study area within each year of data, suggesting a nearly simultaneous response to

  14. Long-term landscape changes in a subalpine spruce-fir forest in central Utah, USA

    Directory of Open Access Journals (Sweden)

    Jesse L. Morris1

    2015-12-01

    Full Text Available Background: In Western North America, increasing wildfire and outbreaks of native bark beetles have been mediated by warming climate conditions. Bioclimatic models forecast the loss of key high elevation species throughout the region. This study uses retrospective vegetation and fire history data to reconstruct the drivers of past disturbance and environmental change. Understanding the relationship among climate, antecedent disturbances, and the legacy effects of settlement-era logging can help identify the patterns and processes that create landscapes susceptible to bark beetle epidemics. Methods: Our analysis uses data from lake sediment cores, stand inventories, and historical records. Sediment cores were dated with radiometric techniques (14C and 210Pb/137Cs and subsampled for pollen and charcoal to maximize the temporal resolution during the historical period (1800 CE to present and to provide environmental baseline data (last 10,500 years. Pollen data for spruce were calibrated to carbon biomass (C t/ha using standard allometric equations and a transfer function. Charcoal samples were analyzed with statistical models to facilitate peak detection and determine fire recurrence intervals. Results: The Wasatch Plateau has been dominated by Engelmann spruce forests for the last ~10,500 years, with subalpine fir becoming more prominent since 6000 years ago. This landscape has experienced a dynamic fire regime, where burning events are more frequent and of higher magnitude during the last 3000 years. Two important disturbances have impacted Engelmann spruce in the historical period: 1 high-grade logging during the late 19th century; and (2 a high severity spruce beetle outbreak in the late 20th century that killed >90 % of mature spruce (>10 cm dbh. Conclusions: Our study shows that spruce-dominated forests in this region are resilient to a range of climate and disturbance regimes. Several lines of evidence suggest that 19th century logging

  15. Momentum and scalar transport within a vegetation canopy following atmospheric stability and seasonal canopy changes: the CHATS experiment

    Directory of Open Access Journals (Sweden)

    S. Dupont

    2012-07-01

    Full Text Available Momentum and scalar (heat and water vapor transfer between a walnut canopy and the overlying atmosphere are investigated for two seasonal periods (before and after leaf-out, and for five thermal stability regimes (free and forced convection, near-neutral condition, transition to stable, and stable. Quadrant and octant analyses of momentum and scalar fluxes followed by space-time autocorrelations of observations from the Canopy Horizontal Array Turbulence Study's (CHATS thirty meter tower help characterize the motions exchanging momentum, heat, and moisture between the canopy layers and aloft.

    During sufficiently windy conditions, i.e. in forced convection, near-neutral and transition to stable regimes, momentum and scalars are generally transported by sweep and ejection motions associated with the well-known canopy-top "shear-driven" coherent eddy structures. During extreme stability conditions (both unstable and stable, the role of these "shear-driven" structures in transporting scalars decreases, inducing notable dissimilarity between momentum and scalar transport.

    In unstable conditions, "shear-driven" coherent structures are progressively replaced by "buo-yantly-driven" structures, known as thermal plumes; which appear very efficient at transporting scalars, especially upward thermal plumes above the canopy. Within the canopy, downward thermal plumes become more efficient at transporting scalars than upward thermal plumes if scalar sources are located in the upper canopy. We explain these features by suggesting that: (i downward plumes within the canopy correspond to large downward plumes coming from above, and (ii upward plumes within the canopy are local small plumes induced by canopy heat sources where passive scalars are first injected if there sources are at the same location as heat sources. Above the canopy, these small upward thermal plumes aggregate to form larger scale upward thermal plumes. Furthermore, scalar

  16. High within-canopy variation in isoprene emission potentials in temperate trees: Implications for predicting canopy-scale isoprene fluxes

    Science.gov (United States)

    Niinemets, ÜLo; Copolovici, Lucian; Hüve, Katja

    2010-12-01

    Isoprene emission potential (ES) varies in tree canopies, and such variations have potentially major implications for predicting canopy level emissions. So far, quantitative relationships of ES with irradiance are missing, and interspecific variation in ES plasticity and potential effects on canopy level emissions have not been characterized. ES, foliage structural, chemical, and photosynthetic characteristics were studied relative to integrated within-canopy daily quantum flux density (Qint) in temperate deciduous tree species Quercus robur, Populus tremula, Salix alba, and Salix caprea, and canopy isoprene emissions were calculated considering observed variation in ES and under different simplifying assumptions. Strong positive curvilinear relationships between nitrogen and dry mass per unit area, photosynthetic potentials and ES per area with Qint were observed. Structural, chemical, and photosynthetic traits varied 1.5-fold to 4-fold and ES per area 3-fold to 27-fold within the canopy. ES variation reflected accumulation of mesophyll cell layers and greater emission capacity of average cells. Species with largest structural and photosynthetic plasticity had greatest plasticity in ES. Relative to the simulation considering within-canopy variation in ES, the bias from assuming a constant ES varied between -8% and +68%, and it scaled positively with ES plasticity. The bias of big-leaf simulations varied between -22% and -35%, and it scaled negatively with ES plasticity. A generalized canopy response function of ES developed for all species resulted in the lowest bias between -11% and 6% and can be recommended for practical applications. The results highlight huge within-canopy and interspecific variation in ES and demonstrate that ignoring these variations strongly biases canopy emission predictions.

  17. Stressed but stable: canopy loss decreased species synchrony and metabolic variability in an intertidal hard-bottom community.

    Directory of Open Access Journals (Sweden)

    Nelson Valdivia

    Full Text Available The temporal stability of aggregate community properties depends on the dynamics of the component species. Since species growth can compensate for the decline of other species, synchronous species dynamics can maintain stability (i.e. invariability in aggregate properties such as community abundance and metabolism. In field experiments we tested the separate and interactive effects of two stressors associated with storminess--loss of a canopy-forming species and mechanical disturbances--on species synchrony and community respiration of intertidal hard-bottom communities on Helgoland Island, NE Atlantic. Treatments consisted of regular removal of the canopy-forming seaweed Fucus serratus and a mechanical disturbance applied once at the onset of the experiment in March 2006. The level of synchrony in species abundances was assessed from estimates of species percentage cover every three months until September 2007. Experiments at two sites consistently showed that canopy loss significantly reduced species synchrony. Mechanical disturbance had neither separate nor interactive effects on species synchrony. Accordingly, in situ measurements of CO(2-fluxes showed that canopy loss, but not mechanical disturbances, significantly reduced net primary productivity and temporal variation in community respiration during emersion periods. Our results support the idea that compensatory dynamics may stabilise aggregate properties. They further suggest that the ecological consequences of the loss of a single structurally important species may be stronger than those derived from smaller-scale mechanical disturbances in natural ecosystems.

  18. Stressed but Stable: Canopy Loss Decreased Species Synchrony and Metabolic Variability in an Intertidal Hard-Bottom Community

    Science.gov (United States)

    Valdivia, Nelson; Golléty, Claire; Migné, Aline; Davoult, Dominique; Molis, Markus

    2012-01-01

    The temporal stability of aggregate community properties depends on the dynamics of the component species. Since species growth can compensate for the decline of other species, synchronous species dynamics can maintain stability (i.e. invariability) in aggregate properties such as community abundance and metabolism. In field experiments we tested the separate and interactive effects of two stressors associated with storminess–loss of a canopy-forming species and mechanical disturbances–on species synchrony and community respiration of intertidal hard-bottom communities on Helgoland Island, NE Atlantic. Treatments consisted of regular removal of the canopy-forming seaweed Fucus serratus and a mechanical disturbance applied once at the onset of the experiment in March 2006. The level of synchrony in species abundances was assessed from estimates of species percentage cover every three months until September 2007. Experiments at two sites consistently showed that canopy loss significantly reduced species synchrony. Mechanical disturbance had neither separate nor interactive effects on species synchrony. Accordingly, in situ measurements of CO2-fluxes showed that canopy loss, but not mechanical disturbances, significantly reduced net primary productivity and temporal variation in community respiration during emersion periods. Our results support the idea that compensatory dynamics may stabilise aggregate properties. They further suggest that the ecological consequences of the loss of a single structurally important species may be stronger than those derived from smaller-scale mechanical disturbances in natural ecosystems. PMID:22574181

  19. Smartphone based hemispherical photography for canopy structure measurement

    Science.gov (United States)

    Wan, Xuefen; Cui, Jian; Jiang, Xueqin; Zhang, Jingwen; Yang, Yi; Zheng, Tao

    2018-01-01

    The canopy is the most direct and active interface layer of the interaction between plant and environment, and has important influence on energy exchange, biodiversity, ecosystem matter and climate change. The measurement about canopy structure of plant is an important foundation to analyze the pattern, process and operation mechanism of forest ecosystem. Through the study of canopy structure of plant, solar radiation, ambient wind speed, air temperature and humidity, soil evaporation, soil temperature and other forest environmental climate characteristics can be evaluated. Because of its accuracy and effectiveness, canopy structure measurement based on hemispherical photography has been widely studied. However, the traditional method of canopy structure hemispherical photogrammetry based on SLR camera and fisheye lens. This method is expensive and difficult to be used in some low-cost occasions. In recent years, smartphone technology has been developing rapidly. The smartphone not only has excellent image acquisition ability, but also has the considerable computational processing ability. In addition, the gyroscope and positioning function on the smartphone will also help to measure the structure of the canopy. In this paper, we present a smartphone based hemispherical photography system. The system consists of smart phones, low-cost fisheye lenses and PMMA adapters. We designed an Android based App to obtain the canopy hemisphere images through low-cost fisheye lenses and provide horizontal collimation information. In addition, the App will add the acquisition location tag obtained by GPS and auxiliary positioning method in hemisphere image information after the canopy structure hemisphere image acquisition. The system was tested in the urban forest after it was completed. The test results show that the smartphone based hemispherical photography system can effectively collect the high-resolution canopy structure image of the plant.

  20. TEMPORARY REMOVAL

    DEFF Research Database (Denmark)

    Calkins, Hugh; Hindricks, Gerhard; Cappato, Riccardo

    2017-01-01

    The publisher regrets that this article has been temporarily removed. A replacement will appear as soon as possible in which the reason for the removal of the article will be specified, or the article will be reinstated. The full Elsevier Policy on Article Withdrawal can be found at https://www.e...

  1. Influence of species on site selection and timber removal: a case study for West Virginia

    Science.gov (United States)

    William Luppold; Delton Alderman

    2007-01-01

    Over the last 40 years the composition of West Virginia forests has been changing as selective cutting practices have removed larger-diameter timber of specific species and partial canopy removal has fostered the regeneration of shade-tolerant species such as red maple. However, since the mid-1990s there has been considerable change in the number of markets accepting...

  2. Similarity of nutrient uptake and root dimensions of Engelmann spruce and subalpine fir at two contrasting sites in Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Yanai, R; McFarlane, K; Lucash, M; Kulpa, S; Wood, D

    2009-10-09

    Nutrient uptake capacity is an important parameter in modeling nutrient uptake by plants. Researchers commonly assume that uptake capacity measured for a species can be used across sites. We tested this assumption by measuring the nutrient uptake capacity of intact roots of Engelmann spruce (Picea engelmanni Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) at Loch Vale Watershed and Fraser Experimental Forest in the Rocky Mountains of central Colorado. Roots still attached to the tree were exposed to one of three concentrations of nutrient solutions for time periods ranging from 1 to 96 hours, and solutions were analyzed for ammonium, nitrate, calcium, magnesium, and potassium. Surprisingly, the two species were indistinguishable in nutrient uptake within site for all nutrients (P > 0.25), but uptake rates differed by site. In general, nutrient uptake was higher at Fraser (P = 0.01, 0.15, 0.03, 0.18 for NH{sub 4}{sup +}, NO{sub 3}{sup -}, Ca{sup 2+}, and K{sup +}, respectively), which is west of the Continental Divide and has lower atmospheric deposition of N than Loch Vale. Mean uptake rates by site for ambient solution concentrations were 0.12 {micro}mol NH{sub 4}{sup +} g{sub fwt}{sup -1} h{sup -1}, 0.02 {micro}mol NO{sub 3}{sup -} g{sub fwt}{sup -1}, 0.21 {micro}mol Ca{sup 2+} g{sub fwt}{sup -1} h{sup -1}, and 0.01 {micro}mol Mg{sup 2+} g{sub fwt}{sup -1} h{sup -1} at Loch Vale, and 0.21 {micro}mol NH{sub 4}{sup +} f{sub fwt}{sup -1}h{sup -1}, 0.04 {micro}mol NO{sub 3}{sup -} g{sub fwt}{sup -1} h{sup -1}, 0.51 {micro}mol Ca{sup 2+}g{sub fwt}{sup -1}h{sup -1}, and 0.07 {micro}mol Mg{sup 2+} f{sub fwt}{sup -1}h{sup -1} at Fraser. The importance of site conditions in determining uptake capacity should not be overlooked when parameterizing nutrient uptake models. We also characterized the root morphology of these two species and compared them to other tree species we have measured at various sites in the northeastern USA. Engelman spruce and subalpine fir

  3. [Effects of snow pack on soil nitrogen transformation enzyme activities in a subalpine Abies faxioniana forest of western Sichuan, China].

    Science.gov (United States)

    Xiong, Li; Xu, Zhen-Feng; Wu, Fu-Zhong; Yang, Wan-Qin; Yin, Rui; Li, Zhi-Ping; Gou, Xiao-Lin; Tang, Shi-Shan

    2014-05-01

    This study characterized the dynamics of the activities of urease, nitrate reductase and nitrite reductase in both soil organic layer and mineral soil layer under three depths of snow pack (deep snowpack, moderate snowpack and shallow snowpack) over the three critical periods (snow formed period, snow stable period, and snow melt period) in the subalpine Abies faxoniana forest of western Sichuan in the winter of 2012 and 2013. Throughout the winter, soil temperature under deep snowpack increased by 46.2% and 26.2%, respectively in comparison with moderate snowpack and shallow snowpack. In general, the three nitrogen-related soil enzyme activities under shallow snowpack were 0.8 to 3.9 times of those under deep snowpack during the winter. In the beginning and thawing periods of seasonal snow pack, shallow snowpack significantly increased the activities of urease, nitrate and nitrite reductase enzyme in both soil organic layer and mineral soil layer. Although the activities of the studied enzymes in soil organic layer and mineral soil layer were observed to be higher than those under deep- and moderate snowpacks in deep winter, no significant difference was found under the three snow packs. Meanwhile, the effects of snowpack on the activities of the measured enzymes were related with season, soil layer and enzyme type. Significant variations of the activities of nitrogen-related enzymes were found in three critical periods over the winter, and the three measured soil enzymes were significantly higher in organic layer than in mineral layer. In addition, the activities of the three measured soil enzymes were closely related with temperature and moisture in soils. In conclusion, the decrease of snow pack induced by winter warming might increase the activities of soil enzymes related with nitrogen transformation and further stimulate the process of wintertime nitrogen transformation in soils of the subalpine forest.

  4. Characterization of Atmospheric Nitrate Dynamics in a Sub-Alpine Watershed Using Δ17O and δ15N

    Science.gov (United States)

    Bourgeois, I.; Savarino, J. P.; Clement, J. C.

    2015-12-01

    Remote subalpine ecosystems are usually characterized by nutrient-poor soils (Körner, 2004; Seastedt et al., 2004), making them particularly susceptible to undergo changes due to increased atmospheric N deposition (Vitousek et al., 1997; Preunkert et al., 2003). Using Δ17O, a conserved tracer of atmospheric nitrate (NO3 atm) (Michalski et al., 2004; Tsunogai et al., 2010), and δ15N, indicator of NO3 biological sources (Kendall, 1998; Casciotti et al., 2009), we measured the seasonal variations of NO3 atm stable isotopic composition and concentration in several streams and soils originating from two sub-alpine watersheds in the French Alps. Our objective was to investigate whether or not NO3 atm impacts the soil N biogeochemical cycle by increasing nutrients availability for plants and bacteria. We coupled streams and soils measurements with snow-pits sampling and aerosols collection at the Lautaret Pass, to better emphasize the correlation between atmospheric deposition, soil retention and watersheds effluents response. Our results reveal that different temporal dynamics govern our study site: stream measurements show that in spring, snowmelt results in a NO3 atm impulse, accounting for ca. 31 % of the total stream NO3 budget; on the opposite in autumn, NO3 atm accounts only for ca. 3 % of the total stream NO3 budget, highlighting the presence of a NO3 bacterial pool (nitrification). We also inferred from the observed Δ17O variations two distinct phenomena in the spring/summer season: a fast snow run-off and a slower snow-water percolation. The later is believed to affect most the soil N cycle as it directly increases available NO3. Measured soil leachates and extracts confirm this hypothesis and point out the potential importance of anthropogenic N deposition as on average 7 to 10 % of the soil solutions NO3 derives directly from the atmosphere.

  5. Atmospheric stability effects on wind fields and scalar mixing within and just above a subalpine forest in sloping terrain

    Science.gov (United States)

    Burns, Sean P.; Sun, Jielun; Lenschow, D.H.; Oncley, S.P.; Stephens, B.B.; Yi, C.; Anderson, D.E.; Hu, Jiawen; Monson, Russell K.

    2011-01-01

    Air temperature Ta, specific humidity q, CO2 mole fraction ??c, and three-dimensional winds were measured in mountainous terrain from five tall towers within a 1 km region encompassing a wide range of canopy densities. The measurements were sorted by a bulk Richardson number Rib. For stable conditions, we found vertical scalar differences developed over a "transition" region between 0.05 1), the vertical scalar differences reached a maximum and remained fairly constant with increasing stability. The relationships q and ??c have with Rib are explained by considering their sources and sinks. For winds, the strong momentum absorption in the upper canopy allows the canopy sublayer to be influenced by pressure gradient forces and terrain effects that lead to complex subcanopy flow patterns. At the dense-canopy sites, soil respiration coupled with wind-sheltering resulted in CO2 near the ground being 5-7 ??mol mol-1 larger than aloft, even with strong above-canopy winds (near-neutral conditions). We found Rib-binning to be a useful tool for evaluating vertical scalar mixing; however, additional information (e.g., pressure gradients, detailed vegetation/topography, etc.) is needed to fully explain the subcanopy wind patterns. Implications of our results for CO2 advection over heterogenous, complex terrain are discussed. ?? 2010 Springer Science+Business Media B.V.

  6. Estimating canopy cover from standard forest inventory measurements in western Oregon

    Science.gov (United States)

    Anne McIntosh; Andrew Gray; Steven. Garman

    2012-01-01

    Reliable measures of canopy cover are important in the management of public and private forests. However, direct sampling of canopy cover is both labor- and time-intensive. More efficient methods for estimating percent canopy cover could be empirically derived relationships between more readily measured stand attributes and canopy cover or, alternatively, the use of...

  7. Canopy structure effects on the wind at a complex forested site

    DEFF Research Database (Denmark)

    Boudreault, Louis-Etienne; Bechmann, Andreas; Sørensen, Niels N.

    2014-01-01

    We investigated the effect of the canopy description in a Reynolds-averaged Navier-Stokes method based on key flow results from a complex forested site. The canopy structure in RANS is represented trough the frontal area of canopy elements per unit volume, a variable required as input in canopy...

  8. ForestCrowns: a software tool for analyzing ground-based digital photographs of forest canopies

    Science.gov (United States)

    Matthew F. Winn; Sang-Mook Lee; Phillip A. Araman

    2013-01-01

    Canopy coverage is a key variable used to characterize forest structure. In addition, the light transmitted through the canopy is an important ecological indicator of plant and animal habitat and understory climate conditions. A common ground-based method used to document canopy coverage is to take digital photographs from below the canopy. To assist with analyzing...

  9. Pheno-anomalies of sub-alpine Vaccinium heaths in response to climatic variations

    Science.gov (United States)

    Puppi, Giovanna; Monti, Alessandra; Bonafede, Fausto; Vignodelli, Michele; Zanotti, Anna Letizia

    2014-05-01

    reduction in seed production and could have therefore be disadvantaged in turn-over. This hypothesis is consistent with the results on vegetation changes: in fact, the comparison of the actual vegetation with the historical observations in the same sites, shows a reduction of herb (Hemicryptophytes) diversity and cover in time. It is noteworthy that many of the declining species flower in the driest and hottest weeks of the year. In a climate-warming scenario, the low extension of these sub-alpine islands of the Apennines leads to a high extinction risk of the most sensible species. So, the monitoring of this vulnerable vegetation type seems necessary in order to detect the current trends and should be continued in the future. Puppi and Speranza 1980, Arch. Bot. Biogeogr. Ital. 56(3/4) Puppi et al. 1994, Fitosociologia 26: 63-79

  10. Impact of land use change on soil organic matter dynamics in subalpine grassland

    Science.gov (United States)

    Meyer, Stefanie; Leifeld, Jens; Bahn, Michael; Fuhrer, Jürg

    2010-05-01

    Information regarding the response of soil organic matter (SOM) in soils to past and expected future land use changes in the European Alps is scarce. Understanding this response requires knowledge of size and residence times of SOM fractions with distinct stabilities. In order to quantify differences between types of land use in the amount, distribution and turnover rates of soil organic carbon (SOC) in subalpine grassland soils, we used soil aggregate and SOM density fractionation in combination with 14C dating. Samples were taken along gradients of different types of land use from meadow (M) to pasture (P) and to abandoned grassland (A) in the Stubai Valley and in the Matsch Valley. Sampling sites in both areas were located at equal altitude (1880 m and 1820 m, respectively) with the same parent material and soil type, but the Matsch Valley receives 400-500 mm less annual rainfall. SOC stocks in the top 10 cm were 2.47 ± 0.32 (M), 2.75 ± 0.32 (P), and 2.50 ± 0.31 kg C/m2 (A) in the Stubai Valley and 2.25 ± 0.14 (M), 3.45 ± 0.22 (P), 3.16 ± 0.27 kg C/m2(A) in the Matsch Valley. Three aggregate size classes were separated by wet sieving: 2 mm. The light floating fraction (wPOM, ρ >1 g/cm3) was included in the analysis. Free (f-) and occluded particulate organic matter (oPOM) were isolated from each aggregate size class (ρ >1.6 g/cm3). At both locations, more than 80% of SOC was stored in small (0.25-2 mm) and large (>2 mm) macroaggregates, but no trend in relation to the different types of land use could be detected. The fraction of C in fPOM and in oPOM in all aggregate size classes was highest for soil from abandoned grasslands. The bulk soil of the abandoned site in the Stubai Valley showed a significantly higher share of fPOM-C and oPOM-C and a higher amount of wPOM-C as compared to the soil from managed grassland, whereas in the Matsch Valley pasture soil had a significantly higher wPOM-C content. At both sites, 13C natural abundance analyses revealed

  11. Autotrophic and Heterotrophic Controls over Winter Soil Carbon Cycling in a Subalpine Forest Ecosystem

    Science.gov (United States)

    Monson, R. K.; Scott-Denton, L. E.; Lipson, D. A.; Weintrub, M. N.; Rosenstiel, T. N.; Schmidt, S. K.; Williams, M. W.; Burns, S. P.; Delany, A. E.; Turnipseed, A. A.

    2005-12-01

    that interannual variation in winter ecosystem respiration is positively correlated to interannual variation in the spring snow depth. Years with a with a deeper spring snow pack exhibited higher soil temperatures, and concomitantly higher soil respiration rates. Given the recently reported decadal-scale trend in decreasing snow pack in the Western U.S., which is coupled to warm climate anomalies, our observations indicate the potential for higher wintertime soil carbon sequestration due to lower winter ecosystem respiration rates in subalpine forests. Our studies of processes beneath the winter snow pack demonstrate that contrary to previous assumptions, winter biogeochemical processing of soil organic matter is an important component of ecosystem carbon budgets. Despite low temperatures and an inactive plant rhizosphere, winter microbial communities and exoenzymes appear to be active, carbon substrates appear to be in relatively high abundance and soil respiration rates appear to be sensitive to seasonal and interannual winter climate variability.

  12. Bias in lidar-based canopy gap fraction estimates

    NARCIS (Netherlands)

    Vaccari, S.; Leeuwen, van M.; Calders, K.; Coops, N.C.; Herold, M.

    2013-01-01

    Leaf area index and canopy gap fraction (GF) provide important information to forest managers regarding the ecological functioning and productivity of forest resources. Traditional measurements such as those obtained from hemispherical photography (HP) measure solar irradiation, penetrating the

  13. SAFARI 2000 Canopy Structural Measurements, Kalahari Transect, Wet Season 2001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains leaf area index (LAI), leaf inclination angle, and canopy dimension data from study sites along the Kalahari Transect in southwest Botswana....

  14. [Turbulent characteristics in forest canopy under atmospheric neutral condition].

    Science.gov (United States)

    Diao, Yi-Wei; Guan, De-Xin; Jin, Chang-Jie; Wang, An-Zhi; Pei, Tie-Fan

    2010-02-01

    Based on the micrometeorological data of broad-leaved Korean pine forest in Changbai Mountain in 2003, a second-order closure model was employed to calculate and analyze the turbulent characteristics within and above the canopy of the forest. The calculated mean wind profile was coincident with the measured one. The Reynolds stress within the forest was significantly attenuated. The turbulent strength, velocity flux, and skew were the largest at forest-atmosphere interface, as well the wind shear. With the increase of velocity skew, the turbulent intermittence became more significant, and the downward turbulent eddy within the canopy was limited. Most of the turbulent deeply within the forest canopy was produced by the non-local contributions above the canopy.

  15. An energy balance model for forest canopies: a case study

    Science.gov (United States)

    S. M. Goltz; James A. Smith

    1996-01-01

    The use of thermal scanning devices to map underlying terrain surface temperatures has been recognized as a potential tool for estimating evapotranspiration and latent heat flux densities in forest canopies.

  16. Development of a multispectral sensor for crop canopy temperature measurement

    Science.gov (United States)

    Quantifying spatial and temporal variability in plant stress has precision agriculture applications in controlling variable rate irrigation and variable rate nutrient application. One approach to plant stress detection is crop canopy temperature measurement by the use of thermographic or radiometric...

  17. Effects of species selection and management on forest canopy albedo

    OpenAIRE

    Otto, Juliane; Berveiller, Daniel; Bréon, François-Marie; Delpierre, Nicolas; Geppert , Gernot; Granier, André; Gunia, Katja; Jans, Wilma; Knohl, Alexander; Kuusk, Andres; Longdoz, Bernard; Moors, Eddy; Mund, Martina; Pinty, Bernard; Rautiainen, Miina

    2013-01-01

    Forest management is considered to be one of the key instruments available to mitigate climate change as it can lead to increased sequestration of atmospheric carbon dioxide. However, the changes in canopy albedo may neutralise or offset the climate benefits of carbon sequestration. Although there is an emerging body of literature linking canopy albedo to management, understanding is still fragmented. We make use of a generally applicable approach: we combine a stand-level forest gap model wi...

  18. Convection regime between canopy and air in a greenhouse

    OpenAIRE

    Atarassi,Roberto Terumi; Folegatti,Marcos Vinicius; Brasil,René Porfírio Camponez do

    2006-01-01

    The use of covering materials in protected environments modifies the air movement close to the crop canopy compared to external environment, which changes the heat and mass transfer between canopy and air. Several researches have been made in greenhouses to estimate mass and heat flux using dimensionless numbers to characterize the type of convection (forced, free or mixed). The knowledge of which one is dominant allows simplifications and specific approaches. The dominant convection regime b...

  19. Landscape-scale quantification of fire-induced change in canopy cover following mountain pine beetle outbreak and timber harvest

    Science.gov (United States)

    McCarley, T. Ryan; Kolden, Crystal A.; Vaillant, Nicole M.; Hudak, Andrew T.; Smith, Alistair M.S.; Kreitler, Jason R.

    2017-01-01

    Across the western United States, the three primary drivers of tree mortality and carbon balance are bark beetles, timber harvest, and wildfire. While these agents of forest change frequently overlap, uncertainty remains regarding their interactions and influence on specific subsequent fire effects such as change in canopy cover. Acquisition of pre- and post-fire Light Detection and Ranging (LiDAR) data on the 2012 Pole Creek Fire in central Oregon provided an opportunity to isolate and quantify fire effects coincident with specific agents of change. This study characterizes the influence of pre-fire mountain pine beetle (MPB; Dendroctonus ponderosae) and timber harvest disturbances on LiDAR-estimated change in canopy cover. Observed canopy loss from fire was greater (higher severity) in areas experiencing pre-fire MPB (Δ 18.8%CC) than fire-only (Δ 11.1%CC). Additionally, increasing MPB intensity was directly related to greater canopy loss. Canopy loss was lower for all areas of pre-fire timber harvest (Δ 3.9%CC) than for fire-only, but among harvested areas, the greatest change was observed in the oldest treatments and the most intensive treatments [i.e., stand clearcut (Δ 5.0%CC) and combination of shelterwood establishment cuts and shelterwood removal cuts (Δ 7.7%CC)]. These results highlight the importance of accounting for and understanding the impact of pre-fire agents of change such as MPB and timber harvest on subsequent fire effects in land management planning. This work also demonstrates the utility of multi-temporal LiDAR as a tool for quantifying these landscape-scale interactions.

  20. Modeling the impacts of life-history traits, canopy gaps, and establishment location on woodland shrub invasions.

    Science.gov (United States)

    Iannone, Basil V; Zellner, Moira L; Wise, David H

    2014-04-01

    We used an individual-based model to identify how localized patterns of woodland invasions by exotic shrubs are likely influenced by (1) observed variation in age at first reproduction and fecundity, (2) hypothesized effects of canopy gaps on these life-history traits and dispersal, and (3) initial establishment location. Rates of spread accelerated nearly twofold as age at first reproduction decreased from eight to three years or fecundity increased from 3 to 20 offspring per year, illustrating the need to better understand the factors that influence these life-history traits. Canopy gaps facilitated spread by influencing these life-history traits, but not through their effects on dispersal. Invasions starting at the woodland center spread more rapidly than do those starting along the woodland edge. These findings suggest that managers should not only prioritize the removal of shrubs that reproduce the earliest or produce the most offspring, but they should also focus on the invasions in woodlands with high canopy openness and/or that are located in woodland interiors. Investigated factors also affected other invasion characteristics, often in surprising ways. For example, those changes in age at first reproduction and fecundity that increased the rate of spread produced nonparallel patterns of change in the proportions of invasion reproducing, whether or not invasions exhibited clumped or scattered spatial arrangements, and invasional lag. Additionally, canopy gaps influenced these characteristics by increasing fecundity, but not by decreasing age at first reproduction or altering dispersal, suggesting that canopy gaps affect local patterns of exotic-shrub invasions primarily through their positive effects on fruit production.

  1. Tattoo removal.

    Science.gov (United States)

    Adatto, Maurice A; Halachmi, Shlomit; Lapidoth, Moshe

    2011-01-01

    Over 50,000 new tattoos are placed each year in the United States. Studies estimate that 24% of American college students have tattoos and 10% of male American adults have a tattoo. The rising popularity of tattoos has spurred a corresponding increase in tattoo removal. Not all tattoos are placed intentionally or for aesthetic reasons though. Traumatic tattoos due to unintentional penetration of exogenous pigments can also occur, as well as the placement of medical tattoos to mark treatment boundaries, for example in radiation therapy. Protocols for tattoo removal have evolved over history. The first evidence of tattoo removal attempts was found in Egyptian mummies, dated to have lived 4,000 years BC. Ancient Greek writings describe tattoo removal with salt abrasion or with a paste containing cloves of white garlic mixed with Alexandrian cantharidin. With the advent of Q-switched lasers in the late 1960s, the outcomes of tattoo removal changed radically. In addition to their selective absorption by the pigment, the extremely short pulse duration of Q-switched lasers has made them the gold standard for tattoo removal. Copyright © 2011 S. Karger AG, Basel.

  2. The canopy spiders (Araneae of the floodplain forest in Leipzig

    Directory of Open Access Journals (Sweden)

    Otto, Stefan

    2010-10-01

    Full Text Available The canopy spiders of the floodplain forest in Leipzig have become a focus of ecological studies in recent years. In 2006 we sampled 30 tree canopies in the ‘Burgaue’ nature reserve with pyrethrum knock-down fogging, recording 502 adult spiders belonging to 48 species and 11 families. Based on these data and the results of a previous fogging study, the studied spider community was dominated by forest and forest-edge species with a preference for the shrub and canopy strata as well as by spiders of the web spider feeding guild. The community structure was typical for arboreal spider communities from northern temperate forests but very different from communities in the tropics. Species richness and evenness were similar to the old growth near-primary Białowieża Forest in Poland. The checklist of 96 canopy spider species of the floodplain forest of Leipzig includes 54 additions to the spider fauna of Leipzig and vicinity by recent canopy studies and eight first canopy records for Leipzig from our field work. The theridiid Dipoena torva (Thorell, 1875 was recorded for the first time in Saxony. The floodplain forest of Leipzig sustains a large and species-rich arboreal spider community and is thus a valuable habitat for a large proportion of endangered species (12%.

  3. CANOPY STRUCTURE AND DEPOSITION EFFICIENCY OF VINEYARD SPRAYERS

    Directory of Open Access Journals (Sweden)

    Gianfranco Pergher

    2007-06-01

    Full Text Available A field study was performed to analyse how deposition efficiency from an axial-fan sprayer was affected by the canopy structure of vines trained to the High Cordon, Low Cordon and Casarsa systems, at beginning of flowering and beginning of berry touch growth stages. An empirical calibration method, providing a dose rate adjustment roughly proportional to canopy height, was used. The canopy structure was assessed using the Point Quadrat method, and determining the leaf area index (LAI and the leaf layer index (LLI. Spray deposits were measured by colorimetry, using a water soluble dye (Tartrazine as a tracer. Correlation between deposits and canopy parameters were analysed and discussed. Foliar deposits per unit leaf area were relatively constant, suggesting that empirical calibration can reduce deposit variability associated with different training systems and growth stages. Total foliar deposition ranged from 33.6% and 82.3% of total spray volume, and increased proportionally with the LLI up to LLI<4. Deposits on bunches significantly decreased with the LLI in the grape zone. The results suggest that sprayer efficiency is improved by a regular, symmetrical canopy, with few leaf layers in the grape zone as in Low Cordon. However, a LLI<3 over the whole canopy and >40% gaps in the foliage both reduced total deposition, and may increase the risk for larger drift losses.

  4. Estimating canopy fuel parameters for Atlantic Coastal Plain forest types.

    Energy Technology Data Exchange (ETDEWEB)

    Parresol, Bernard, R.

    2007-01-15

    Abstract It is necessary to quantify forest canopy characteristics to assess crown fire hazard, prioritize treatment areas, and design treatments to reduce crown fire potential. A number of fire behavior models such as FARSITE, FIRETEC, and NEXUS require as input four particular canopy fuel parameters: 1) canopy cover, 2) stand height, 3) crown base height, and 4) canopy bulk density. These canopy characteristics must be mapped across the landscape at high spatial resolution to accurately simulate crown fire. Currently no models exist to forecast these four canopy parameters for forests of the Atlantic Coastal Plain, a region that supports millions of acres of loblolly, longleaf, and slash pine forests as well as pine-broadleaf forests and mixed species broadleaf forests. Many forest cover types are recognized, too many to efficiently model. For expediency, forests of the Savannah River Site are categorized as belonging to 1 of 7 broad forest type groups, based on composition: 1) loblolly pine, 2) longleaf pine, 3) slash pine, 4) pine-hardwood, 5) hardwood-pine, 6) hardwoods, and 7) cypress-tupelo. These 7 broad forest types typify forests of the Atlantic Coastal Plain region, from Maryland to Florida.

  5. Isotopic characteristics of canopies in simulated leaf assemblages

    Science.gov (United States)

    Graham, Heather V.; Patzkowsky, Mark E.; Wing, Scott L.; Parker, Geoffrey G.; Fogel, Marilyn L.; Freeman, Katherine H.

    2014-11-01

    The geologic history of closed-canopy forests is of great interest to paleoecologists and paleoclimatologists alike. Closed canopies have pronounced effects on local, continental and global rainfall and temperature patterns. Although evidence for canopy closure is difficult to reconstruct from the fossil record, the characteristic isotope gradients of the ;canopy effect; could be preserved in leaves and proxy biomarkers. To assess this, we employed new carbon isotopic data for leaves collected in diverse light environments within a deciduous, temperate forest (Maryland, USA) and for leaves from a perennially closed canopy, moist tropical forest (Bosque Protector San Lorenzo, Panamá). In the tropical forest, leaf carbon isotope values range 10‰, with higher δ13Cleaf values occurring both in upper reaches of the canopy, and with higher light exposure and lower humidity. Leaf fractionation (Δleaf) varied negatively with height and light and positively with humidity. Vertical 13C enrichment in leaves largely reflects changes in Δleaf, and does not trend with δ13C of CO2 within the canopy. At the site in Maryland, leaves express a more modest δ13C range (∼6‰), with a clear trend that follows both light and leaf height. Using a model we simulate leaf assemblage isotope patterns from canopy data binned by elevation. The re-sampling (bootstrap) model determined both the mean and range of carbon isotope values for simulated leaf assemblages ranging in size from 10 to over 1000 leaves. For the tropical forest data, the canopy's isotope range is captured with 50 or more randomly sampled leaves. Thus, with a sufficient number of fossil leaves it is possible to distinguish isotopic gradients in an ancient closed canopy forest from those in an open forest. For very large leaf assemblages, mean isotopic values approximate the δ13C of carbon contributed by leaves to soil and are similar to observed δ13Clitter values at forested sites within Panamá, including the

  6. Ecohydrological responses of dense canopies to environmental variability: 2. Role of acclimation under elevated CO2

    Science.gov (United States)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    to elevated CO2. The unique metabolic pathways of the C3 soybean and C4 maize produce contrasting modes of response to elevated CO2 for each crop. To examine the relative roles of direct reduction in stomatal aperature, observed structural augmentation of leaf area, and biochemical down-regulation of Rubisco carboxylation capacity in soybean, a set of simulations were conducted in which one or more of these acclimations are synthetically removed. A 10% increase in canopy leaf area is shown to offset the ecophysiologically driven reduction in latent energy flux by 40% on average at midday. Considering all observed acclimations for soybean, average midday LE (H) were decreased (increased) by 10.5 (18) [W m-2]. A lack of direct stimulation of photosynthesis for maize, and no observed structural or biochemical acclimation resulted in decreases (increases) in average midday LE (H) by 40-50 [W m-2]. An examination of canopy-scale responses at a range of CO2 concentrations projected to be seen over the coming century showed a general continuation in the direction of flux responses. Flux responses showed little sensitivity to assumptions of constant versus linear trends in structural and biochemical acclimation magnitudes over the 400-700 [ppm] concentration range examined here.

  7. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters.

    Science.gov (United States)

    Yanagi, Sílvia N M; Costa, Marcos H

    2011-12-01

    This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS) to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS) and near-infrared (NIR) spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia) Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (χup) and to the reflectivity in the near-infrared spectral band (ρNIR,up), a smaller sensitivity to the reflectivity in the visible spectral band (ρVIS,up) and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are χup = 0.86, ρVIS,up = 0.062 and ρNIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.

  8. The influence of the forest canopy on nutrient cycling.

    Science.gov (United States)

    Prescott, Cindy E

    2002-11-01

    Rates of key soil processes involved in recycling of nutrients in forests are governed by temperature and moisture conditions and by the chemical and physical nature of the litter. The forest canopy influences all of these factors and thus has a large influence on nutrient cycling. The increased availability of nutrients in soil in clearcuts illustrates how the canopy retains nutrients (especially N) on site, both by storing nutrients in foliage and through the steady input of available C in litter. The idea that faster decomposition is responsible for the flush of nitrate in clearcuts has not been supported by experimental evidence. Soil N availability increases in canopy gaps as small as 0.1 ha, so natural disturbances or partial harvesting practices that increase the complexity of the canopy by creating gaps will similarly increase the spatial variability in soil N cycling and availability within the forest. Canopy characteristics affect the amount and composition of leaf litter produced, which largely determines the amount of nutrients to be recycled and the resulting nutrient availability. Although effects of tree species on soil nutrient availability were thought to be brought about largely through differences in the decomposition rate of their foliar litter, recent studies indicate that the effect of tree species can be better predicted from the mass and nutrient content of litter produced, hence total nutrient return, than from litter decay rate. The greater canopy complexity in mixed species forests creates similar heterogeneity in nutritional characteristics of the forest floor. Site differences in slope position, parent material and soil texture lead to variation in species composition and productivity of forests, and thus in the nature and amount of litter produced. Through this positive feedback, the canopy accentuates inherent differences in site fertility.

  9. How neighbor canopy architecture affects target plant performance

    Energy Technology Data Exchange (ETDEWEB)

    Tremmel, D.C.; Bazzaz, F.A. (Harvard Univ., Cambridge, MA (United States))

    1993-10-01

    Plant competition occurs through the negative effects that individual plants have on resource availability to neighboring individuals. Therefore competition experiments need to examine how different species change resource availability to their neighbors, and how different species respond to these changes-allocationally, architecturally, and physiologically-through time. In a greenhouse study we used a model system of annuals to examine how canopies of species having differing morphologies differed in their architectures and light-interception abilities, and how different species performed when grown in these canopies. Abutilon theophrasti, Datura stramonium, and Polygonum pensylvanicum were grown as [open quotes]targets[close quotes]. Plants were grown in pots, with one target plant and four neighbor plants. Detailed measurements of neighbor canopy structure and target plant canopy architecture were made at five harvests. Species with different morphologies showed large differences in canopy structure, particularly when grass and forb species were compared. Setaria, a grass, had a more open canopy than the other species (all forbs), and was a consistently weak competitor. Overall, however, the relative effects of different neighbors on target biomass varied with target species. Target biomass was poorly correlated with neighbor biomass and leaf area, but was highly correlated with a measure of target light-interception ability that took into account both target leaf deployment and neighbor light interception. Despite clear differences among neighbor species in canopy structure and effect on light penetration, the results suggest no broad generalizations about the effects of different species as neighbors. Knowledge of morphological, physiological, and life history characteristics of both the target and neighbor species may be necessary to explain the results of their competition. 53 refs., 4 figs., 4 tabs.

  10. A comparison between wet canopy evaporation estimated by stable isotope ratios of water and canopy interception measured by water balance

    Science.gov (United States)

    Murakami, Shigeki; Hattori, Shohei; Uemura, Ryu

    2017-04-01

    Some papers proved that canopy interception is proportional to rainfall not only on a rain event basis but also on an hourly basis (e.g. Murakami, 2006, J. Hydrol.; Saito et al., 2013, J. Hydrol.). However, theoretically, evaporation does not depend on rainfall amount. These results are enigmatic and we need to reevaluate wet canopy evaporation. We measured gross rainfall and net rainfall in a plastic Christmas tree stand with a height of 165 cm placed on a 180-cm square tray as described in Murakami and Toba (2013, Hydrol. Res. Lett.). The measurement was conducted outside under natural rainfall. We also estimated wet canopy evaporation using stable isotope ratios of water. During a rain event, we manually sampled gross and net rainwater on an hourly basis. Evaporation was calculated using the difference between the δ18O (or δ2H) values in gross and net rainfall using isotope fractionation factor. Total gross rainfall in a target rain event in October, 2014, was 28.0 mm and net rainfall (discharge from the tray) was 22.7 mm, i.e. canopy interception was 5.3 mm (18.9% of gross rainfall). The δ18O (or δ2H) value in net rainfall was higher than that in gross rainfall because of fractionation by evaporation on wet canopy surface. Hourly evaporation calculated by the values of δ18O varied from 2% to 24% of gross rainfall, and the weighted average by hourly gross rainfall was 5.2% of gross rainfall. Further, we estimated rainfall interception using a tank model (Yoshida et al., 1993) assuming constant evaporation rate, i.e. 20% of gross rainfall. Total net rainfall calculated by the model was 23.1 mm, i.e. calculated canopy interception was 4.9 mm (17.5% of gross rainfall). Then, keeping the parameters of the model, we simulated net rainfall using hourly surface evaporation obtained by the δ18O values. Calculated net rainfall was 25.6 mm, i.e. wet canopy evaporation was only 2.4 mm (8.6% of gross rainfall). So far, possible explanation of the discrepancy between

  11. Skin lesion removal

    Science.gov (United States)

    Shave excision - skin; Excision of skin lesions - benign; Skin lesion removal - benign; Cryosurgery - skin, benign; BCC - removal; Basal cell cancer - removal; Actinic keratosis - removal; Wart - removal; Squamous cell - removal; ...

  12. Characterization of Canopy Layering in Forested Ecosystems Using Full Waveform Lidar

    Directory of Open Access Journals (Sweden)

    Ralph Dubayah

    2013-04-01

    Full Text Available Canopy structure, the vertical distribution of canopy material, is an important element of forest ecosystem dynamics and habitat preference. Although vertical stratification, or “canopy layering,” is a basic characterization of canopy structure for research and forest management, it is difficult to quantify at landscape scales. In this paper we describe canopy structure and develop methodologies to map forest vertical stratification in a mixed temperate forest using full-waveform lidar. Two definitions—one categorical and one continuous—are used to map canopy layering over Hubbard Brook Experimental Forest, New Hampshire with lidar data collected in 2009 by NASA’s Laser Vegetation Imaging Sensor (LVIS. The two resulting canopy layering datasets describe variation of canopy layering throughout the forest and show that layering varies with terrain elevation and canopy height. This information should provide increased understanding of vertical structure variability and aid habitat characterization and other forest management activities.

  13. Throughfall deposition and canopy exchange processes along a vertical gradient within the canopy of beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst).

    Science.gov (United States)

    Adriaenssens, Sandy; Hansen, Karin; Staelens, Jeroen; Wuyts, Karen; De Schrijver, An; Baeten, Lander; Boeckx, Pascal; Samson, Roeland; Verheyen, Kris

    2012-03-15

    To assess the impact of air pollution on forest ecosystems, the canopy is usually considered as a constant single layer in interaction with the atmosphere and incident rain, which could influence the measurement accuracy. In this study the variation of througfall deposition and derived dry deposition and canopy exchange were studied along a vertical gradient in the canopy of one European beech (Fagus sylvatica L.) tree and two Norway spruce (Picea abies (L.) Karst) trees. Throughfall and net throughfall deposition of all ions other than H(+) increased significantly with canopy depth in the middle and lower canopy of the beech tree and in the whole canopy of the spruce trees. Moreover, throughfall and net throughfall of all ions in the spruce canopy decreased with increasing distance to the trunk. Dry deposition occurred mainly in the upper canopy and was highest during the growing season for H(+), NH(4)(+), NO(3)(-) and highest during the dormant season for Na(+), Cl(-), SO(4)(2-) (beech and spruce) and K(+), Ca(2+) and Mg(2+) (spruce only). Canopy leaching of K(+), Ca(2+) and Mg(2+) was observed at all canopy levels and was higher for the beech tree compared to the spruce trees. Canopy uptake of inorganic nitrogen and H(+) occurred mainly in the upper canopy, although significant canopy uptake was found in the middle canopy as well. Canopy exchange was always higher during the growing season compared to the dormant season. This spatial and temporal variation indicates that biogeochemical deposition models would benefit from a multilayer approach for shade-tolerant tree species such as beech and spruce. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Hair Removal

    Science.gov (United States)

    ... in girls who need it. Deciding to remove body hair is a personal choice. Getting rid of body hair doesn't make a person healthier, and you ... you don't want to. Some cultures view body hair as beautiful and natural, so do what feels ...

  15. Hair removal.

    Science.gov (United States)

    Haedersdal, Merete; Haak, Christina S

    2011-01-01

    Hair removal with optical devices has become a popular mainstream treatment that today is considered the most efficient method for the reduction of unwanted hair. Photothermal destruction of hair follicles constitutes the fundamental concept of hair removal with red and near-infrared wavelengths suitable for targeting follicular and hair shaft melanin: normal mode ruby laser (694 nm), normal mode alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), long-pulse Nd:YAG laser (1,064 nm), and intense pulsed light (IPL) sources (590-1,200 nm). The ideal patient has thick dark terminal hair, white skin, and a normal hormonal status. Currently, no method of lifelong permanent hair eradication is available, and it is important that patients have realistic expectations. Substantial evidence has been found for short-term hair removal efficacy of up to 6 months after treatment with the available systems. Evidence has been found for long-term hair removal efficacy beyond 6 months after repetitive treatments with alexandrite, diode, and long-pulse Nd:YAG lasers, whereas the current long-term evidence is sparse for IPL devices. Treatment parameters must be adjusted to patient skin type and chromophore. Longer wavelengths and cooling are safer for patients with darker skin types. Hair removal with lasers and IPL sources are generally safe treatment procedures when performed by properly educated operators. However, safety issues must be addressed since burns and adverse events do occur. New treatment procedures are evolving. Consumer-based treatments with portable home devices are rapidly evolving, and presently include low-level diode lasers and IPL devices. Copyright © 2011 S. Karger AG, Basel.

  16. A comparison of models to estimate in-canopy photosynthetically active radiation and their influence on canopy stomatal resistance

    Energy Technology Data Exchange (ETDEWEB)

    Leiming Zhang [Rumble Research, Ontario (Canada); Moran, M.D.; Brook, J. R. [Meteorological Service of Canada, Ontario (Canada)

    2001-07-01

    The models for photosynthetically active radiation (PAR) used in a multi-layer canopy stomatal resistance (CSR) model developed by Baldocchi et al. (Atmospheric Environment 21 (1987) 91-101) and in a two-big-leaf CSR model developed by Hicks et al. (Water, Air and Soil Pollution 36 (1987) 311) are investigated in this study. The PAR received by shaded leaves in Baldocchi et al. (1987) is found to be larger than that predicted by a canopy radiative-transfer model developed by Norman (in: Barfield, Gerber, (Eds.), Modification of the Aerial Environment of Crops. ASAE Monograph No. 2. American Society for Agricultural. Engineering, St. Joseph, MI, 1979, p. 249) by as much as 50% even though the Baldocchi et al. (1987) model is indirectly based on Norman's model. This larger value of PAR results in turn in a smaller CSR by as much as 30% for canopies with larger leaf area indexes. A new formula to predict vertical profiles for PAR received by shaded leaves inside a canopy is suggested in the present study based on Norman (1979) and agrees well with the original model of Norman (1979). The simple treatment used in Hicks et al. (1987) for canopy-average PAR received by shaded leaves is found to diverge for canopies with leaf area indexes not close to two A new empirical formula for canopy-average PAR is then suggested for use in a two-big-leaf model, and it is shown that under most conditions the modified two-big-leaf CSR model can predict reasonable values when compared with the more complex multi-layer CSR model. Both the modified multi-layer CSR model and the modified two-big-leaf CSR model are also shown to predict reasonable dry deposition velocities for 03 when compared to several sets of measurements. (author)

  17. Emergence time in forest bats: the influence of canopy closure

    Science.gov (United States)

    Russo, Danilo; Cistrone, Luca; Jones, Gareth

    2007-01-01

    The role of the forest canopy in protecting bats roosting in forest from predators is poorly known. We analysed the effect of canopy closure on emergence time in Barbastella barbastellus in a mountainous area of central Italy. We used radio-tracking to locate roosts and filmed evening emergence. Comparisons were made between roosts in open areas and those in dense forest. Median emergence time and illuminance were correlated. Moreover, from pregnancy to late lactation bats emerged progressively earlier, probably because of the exceptionally high wing loading affecting pregnant bats and the high energy demand of lactation. A significant influence of canopy closure on median emergence time was revealed after adjusting for the effects of light and reproductive state. Bats in open habitat emerged later than those roosting beneath closed canopy. In cluttered habitats, predators relying on vision may find it more difficult to detect and catch bats at light levels which would offer more chances of success when attacking prey in open habitats. Bats in dense forest are less vulnerable to predators and may take advantage of an earlier emergence by prolonging foraging. Although more vulnerable, lactating females roosting at open sites may benefit from warmer roosting conditions. Roosts in dense forest may be preferred under intense predation pressure. Forest management should favour canopy heterogeneity to provide bats with a range of roosting conditions. Our work emphasises the role of a fine-grained spatial scale in the roosting ecology of forest bats.

  18. Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies

    Directory of Open Access Journals (Sweden)

    Alexandre Escolà

    2011-02-01

    Full Text Available Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture.

  19. Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies

    Science.gov (United States)

    Escolà, Alexandre; Planas, Santiago; Rosell, Joan Ramon; Pomar, Jesús; Camp, Ferran; Solanelles, Francesc; Gracia, Felip; Llorens, Jordi; Gil, Emilio

    2011-01-01

    Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture. PMID:22163749

  20. Simulations of tropical rainforest albedo: is canopy wetness important?

    Science.gov (United States)

    Yanagi, Silvia N M; Costa, Marcos H

    2011-12-01

    Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  1. Simulations of tropical rainforest albedo: is canopy wetness important?

    Directory of Open Access Journals (Sweden)

    Silvia N.M. Yanagi

    Full Text Available Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  2. Performance of an ultrasonic ranging sensor in apple tree canopies.

    Science.gov (United States)

    Escolà, Alexandre; Planas, Santiago; Rosell, Joan Ramon; Pomar, Jesús; Camp, Ferran; Solanelles, Francesc; Gracia, Felip; Llorens, Jordi; Gil, Emilio

    2011-01-01

    Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture.

  3. Eo-1 Hyperion Measures Canopy Drought Stress In Amazonia

    Science.gov (United States)

    Asner, Gregory P.; Nepstad, Daniel; Cardinot, Gina; Moutinho, Paulo; Harris, Thomas; Ray, David

    2004-01-01

    The central, south and southeast portions of the Amazon Basin experience a period of decreased cloud cover and precipitation from June through November. There are likely important effects of seasonal and interannual rainfall variation on forest leaf area index, canopy water stress, productivity and regional carbon cycling in the Amazon. While both ground and spaceborne studies of precipitation continue to improve, there has been almost no progress made in observing forest canopy responses to rainfall variability in the humid tropics. This shortfall stems from the large stature of the vegetation and great spatial extent of tropical forests, both of which strongly impede field studies of forest responses to water availability. Those few studies employing satellite measures of canopy responses to seasonal and interannual drought (e.g., Bohlman et al. 1998, Asner et al. 2000) have been limited by the spectral resolution and sampling available from Landsat and AVHRR sensors. We report on a study combining the first landscape-level, managed drought experiment in Amazon tropical forest with the first spaceborne imaging spectrometer observations of this experimental area. Using extensive field data on rainfall inputs, soil water content, and both leaf and canopy responses, we test the hypothesis that spectroscopic signatures unique to hyperspectral observations can be used to quantify relative differences in canopy stress resulting from water availability.

  4. Estimating Canopy Height of a Temperate Forest from TanDEM-X and LVIS Data

    Science.gov (United States)

    Qi, W.; Dubayah, R.; Kugler, F.

    2014-12-01

    The recently launched TanDEM-X mission is the first single-pass polarimetric interferometer in space allowing global estimation of forest parameters without any temporal decorrelation. This study investigates the potential of single-polarized TanDEM-X data for forest height inversion and structure characterization. For this purpose, a temperate forest - Hubbard Brook Experimental Forest (HBEF) in New Hampshire is chosen for experiment. Stripmap-mode HH-polarized TanDEM-X bistatic data (with resolution at 3 m) acquired at different baselines was used. LVIS data was applied to remove the ground phase component of the TanDEM-X interferogram and to validate the derived results. Forest parameters, e.g. canopy height and extinction coefficient were estimated based on Random Volume over Ground (RVoG) model. Scattering phase height (SPH) was also calculated and validated against LVIS rh100. A clear correlation was observed between TanDEM-X SPH and the reference height with an r2 of around 0.6 at 150m resolution. The inverted tree height had an RMSE of less than 3.4 m and an r2 of around 0.7 at the same resolution. It is shown that TanDEM-X data has great potential for improving the understanding and quantification of global forest canopy height and structure.

  5. [Dynamic changes of topsoil organic carbon in subalpine spruce plantation at different succession stages in western Sichuan Province].

    Science.gov (United States)

    Jiang, Fa-Yan; Sun, Hui; Lin, Bo; Liu, Qing

    2009-11-01

    Soil samples at 0-30 cm depth were collected from the primary spruce (Picea asperata) forest and its plantations at different succession stages (22-, 47-, and 65-year-old) in subalpine zone of western Sichuan Province to study the dynamic changes of soil organic carbon stock and labile organic carbon content. The soil total organic carbon (TOC) stocks in 0-10, 10-20, and 20-30 cm soil layers decreased from 95.87, 79.08, and 71.55 t x hm(-2) in 22-year-old plantation to 56.12, 34.75, and 31.06 t x hm(-2) in 65-year-old plantation, respectively, and the TOC stocks in these soil layers in 47 and 65-year-old plantations were less than those (88.08, 71.16 and 64.81 t x hm(-2), respectively) in primary forest. The easily oxidizable organic carbon (EOC) contents in 0-10, 10-20, and 20-30 cm soil layers decreased from 35.89, 26.91, and 26.00 g x kg(-1) in primary forest to 20.25, 14.50, and 12.36 g x kg L(-1) in 65-year-old plantation, the microbial biomass carbon (MBC) contents decreased from 524.44, 273.26, and 257.97 mg x kg(-1) in primary forest to 312.41, 186.95, and 152.18 mg x kg(-1) in 65-year-old plantation, and the particulate organic carbon (POC) contents decreased from 40.23, 27.10, and 19.55 g x kg(-1) in primary forest to 12.33, 7.31, and 5.32 g x kg(-1) in 65-year-old plantation, respectively. The results suggested that within the long succession period of primary P. asperata forest to its plantations in the subalpine zone of western Sichuan Province, soil TOC and labile organic carbon were in the state of net consumption.

  6. Subalpine Conifer Seedling Demographics: Species Responses to Climate Manipulations Across an Elevational Gradient at Niwot Ridge, Colorado

    Science.gov (United States)

    Castanha, C.; Germino, M. J.; Torn, M. S.; Ferrenberg, S.; Harte, J.; Kueppers, L. M.

    2010-12-01

    The effect of climate change on future ranges of treeline species is poorly understood. For example, it is not known whether trees will recruit into the alpine, above the current treeline, and whether population-level differences in trees will mediate range shifts. At Niwot Ridge, Colorado, we used common gardens and climate manipulations to test predictions that warming will lead to greater recruitment at and beyond the cold edge of these species ranges, and will reduce recruitment at the warm edge. Seed from local populations of limber pine and Englemann spruce was harvested and reciprocally planted in 3 experimental sites spanning an elevation gradient from lower subalpine forest (10,000’), to the upper subalpine treeline ecotone (11,000’), to the alpine tundra (11,300’). In Fall 2009 seeds were sown into 20 plots at each site. Overhead infrared heaters targeted increases in growing season surface soil temperature of 4-5°C. The heating treatment, which began in October 2009, was crossed with manual watering, which was initiated following snowmelt in 2010. Over the 2010 growing season, we surveyed seedling germination and mortality weekly. Germination began in early May at the forest site, in early June at the krummholz site, and in early July at the alpine site. Depending on the site and plot, heating accelerated germination by 1 to 4 weeks. Seed source elevation, species, and site all affected germination, with effects for the two species also depending on site. At all sites, lower elevation, warm-edge populations had higher germination rates than high-elevation, cool-edge populations, indicating a potential bottleneck for germination of the high elevation seed sources in the adjacent alpine tundra. At all sites, survival was generally higher for pine than for spruce. Watering tended to enhance pine germinant survival while heating tended to depress spruce germinant survival. Our results indicate that the alpine tundra, generally considered an

  7. The MODIS Vegetation Canopy Water Content product

    Science.gov (United States)

    Ustin, S. L.; Riano, D.; Trombetti, M.

    2008-12-01

    Vegetation water stress drives wildfire behavior and risk, having important implications for biogeochemical cycling in natural ecosystems, agriculture, and forestry. Water stress limits plant transpiration and carbon gain. The regulation of photosynthesis creates close linkages between the carbon, water, and energy cycles and through metabolism to the nitrogen cycle. We generated systematic weekly CWC estimated for the USA from 2000-2006. MODIS measures the sunlit reflectance of the vegetation in the visible, near-infrared, and shortwave infrared. Radiative transfer models, such as PROSPECT-SAILH, determine how sunlight interacts with plant and soil materials. These models can be applied over a range of scales and ecosystem types. Artificial Neural Networks (ANN) were used to optimize the inversion of these models to determine vegetation water content. We carried out multi-scale validation of the product using field data, airborne and satellite cross-calibration. An Algorithm Theoretical Basis Document (ATBD) of the product is under evaluation by NASA. The CWC product inputs are 1) The MODIS Terra/Aqua surface reflectance product (MOD09A1/MYD09A1) 2) The MODIS land cover map product (MOD12Q1) reclassified to grassland, shrub-land and forest canopies; 3) An ANN trained with PROSPECT-SAILH; 4) A calibration file for each land cover type. The output is an ENVI file with the CWC values. The code is written in Matlab environment and is being adapted to read not only the 8 day MODIS composites, but also daily surface reflectance data. We plan to incorporate the cloud and snow mask and generate as output a geotiff file. Vegetation water content estimates will help predicting linkages between biogeochemical cycles, which will enable further understanding of feedbacks to atmospheric concentrations of greenhouse gases. It will also serve to estimate primary productivity of the biosphere; monitor/assess natural vegetation health related to drought, pollution or diseases

  8. Sunfleck dynamics and canopy structure in a Phaseolus vulgaris L. canopy

    Science.gov (United States)

    Barradas, Victor L.; Jones, Hamlyn G.; Clark, Jerry A.

    Photosynthetic photon flux density (PPFD) fluctuations were quantified in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. Two different methods were used to select sunflecks and shadeflecks. Four ranges of zenith angles (60-70°, 50-60°, 40-50° and 30-40°) were selected for analysing PPFD fluctuations. At the base of the canopy, sunflecks contributed 18%, 53%, 10% and 4% during the 1st, 3rd, 5th and 7th week of growth, respectively. At a height of 20 cm above the soil surface, the respective contributions were 28% and 21% during the 6th and 7th weeks. Sunfleck lengths of 0-5 s were the most frequent, with the greatest number being found with smaller zenith angles. The proportion of short duration sunflecks increased as the growth period advanced. The number of long sunflecks decreased with time, with very few longer than 100 s by the 5th and 7th weeks. The distributions of sunfleck irradiance were similar to normal distributions and irradiance ranged in μmol m-2 s-1 from 600-900, 800-1500 and 1000-1600 respectively at zenith angles of 50-60°, 40-50° and 30-40°. A multiple regression showed that short sunflecks (100 s) depended on zenith angle and Ls. Shadefleck distributions were similar to those for sunflecks but there were fewer of the shortest examples and more of the longest. The best statistical distribution to describe sunflecks and shadeflecks was the gamma distribution, which could provide the basis for the future development of a good model for sunfleck and shadefleck distributions.

  9. The Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS: model description and application to a temperate deciduous forest canopy

    Directory of Open Access Journals (Sweden)

    R. D. Saylor

    2013-01-01

    Full Text Available Forest canopies are primary emission sources of biogenic volatile organic compounds (BVOCs and have the potential to significantly influence the formation and distribution of secondary organic aerosol (SOA mass. Biogenically-derived SOA formed as a result of emissions from the widespread forests across the globe may affect air quality in populated areas, degrade atmospheric visibility, and affect climate through direct and indirect forcings. In an effort to better understand the formation of SOA mass from forest emissions, a 1-D column model of the multiphase physical and chemical processes occurring within and just above a vegetative canopy is being developed. An initial, gas-phase-only version of this model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS, includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer (PBL, near-explicit representation of chemical transformations, mixing with the background atmosphere and bi-directional exchange between the atmosphere and canopy and the atmosphere and forest floor. The model formulation of ACCESS is described in detail and results are presented for an initial application of the modeling system to Walker Branch Watershed, an isoprene-emission-dominated forest canopy in the southeastern United States which has been the focal point for previous chemical and micrometeorological studies. Model results of isoprene profiles and fluxes are found to be consistent with previous measurements made at the simulated site and with other measurements made in and above mixed deciduous forests in the southeastern United States. Sensitivity experiments are presented which explore how canopy concentrations and fluxes of gas-phase precursors of SOA are affected by background anthropogenic nitrogen oxides (NOx. Results from these experiments suggest that the

  10. THE PRE-PENUMBRAL MAGNETIC CANOPY IN THE SOLAR ATMOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    MacTaggart, David [School of Mathematics and Statistics University of Glasgow, Glasgow G12 8QW (United Kingdom); Guglielmino, Salvo L.; Zuccarello, Francesca [Dipartimento di Fisica e Astronomia—Sezione Astrofisica, Università di Catania, via S. Sofia 78, I-95123 Catania (Italy)

    2016-11-01

    Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction) magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra antipodal to the main region of flux emergence. The question of how highly inclined magnetic field can concentrate along the antipodal curves of umbrae, at least initially, remains to be answered. Previous observational studies have suggested the existence of some form of overlying magnetic canopy that acts as the progenitor for penumbrae. We propose that such overlying magnetic canopies are a consequence of how the magnetic field emerges into the atmosphere and are, therefore, part of the emerging region. We show, through simulations of twisted flux tube emergence, that canopies of highly inclined magnetic field form preferentially at the required locations above the photosphere.

  11. Quantitative detection of settled dust over green canopy

    Science.gov (United States)

    Brook, Anna

    2016-04-01

    NMF (SS-NMF), 6) Alternating Least-Square (ALS), and 2) Lin's Projected Gradient (LPG). The performance is evaluated on real hyperspectral imagery data via detailed experimental assessment. The study showed that in certain compression tasks content-adapted sparse representation is provided by state-of-the-art solutions. The NMF algorithm estimates endmembers that are used to remove spurious information. If computationally feasible, it should include interaction terms to make the model more flexible. The optimal NMF algorithms, such as ALS and LPG, are assumed to be the simplest methods that achieve the minimum error on the test set. In summary, this work shows that sediment dust can be assessed using airborne HSI data, making it a potentially powerful tool for environmental studies. References Keshava, N., Mustard, J. (2002). Spectral unmixing. IEEE Signal Process. Mag., 19(1), 44-57. Chudnovsky, A., & Ben-Dor, E. (2009). Reflectance spectroscopy as a tool for settled dust monitoring in office environment. International Journal of Environment and Waste Management, 4(1), 32-49. Brook, A. (2014). Quantitative Detection of Settled dust over Green Canopy using Sparse Unmixing of Airborne Hyperspectral Data. IEEE-Whispers 6th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2014, Switzerland, 4-8. Keshava, N., Mustard, J. (2002). Spectral unmixing. IEEE Signal Process. Mag., 19(1), 44-57. Bioucas-Dias et al. (2012). Hyperspectral unmixing overview: Geometrical, statistical, and sparse regression-based approaches, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 5(2), 354 -379.

  12. Spatial variability of leaf wetness duration in different crop canopies

    Science.gov (United States)

    Sentelhas, Paulo C.; Gillespie, Terry J.; Batzer, Jean C.; Gleason, Mark L.; Monteiro, José Eduardo B. A.; Pezzopane, José Ricardo M.; Pedro, Mário J.

    2005-07-01

    The spatial variability of leaf wetness duration (LWD) was evaluated in four different height-structure crop canopies: apple, coffee, maize, and grape. LWD measurements were made using painted flat plate, printed-circuit wetness sensors deployed in different positions above and inside the crops, with inclination angles ranging from 30 to 45°. For apple trees, the sensors were installed in 12 east-west positions: 4 at each of the top (3.3 m), middle (2.1 m), and bottom (1.1 m) levels. For young coffee plants (80 cm tall), four sensors were installed close to the leaves at heights of 20, 40, 60, and 80 cm. For the maize and grape crops, LWD sensors were installed in two positions, one just below the canopy top and another inside the canopy. Adjacent to each experiment, LWD was measured above nearby mowed turfgrass with the same kind of flat plate sensor, deployed at 30 cm and between 30 and 45°. We found average LWD varied by canopy position for apple and maize (P<0.05). In these cases, LWD was longer at the top, particularly when dew was the source of wetness. For grapes, cultivated in a hedgerow system and for young coffee plants, average LWD did not differ between the top and inside the canopy. The comparison by geometric mean regression analysis between crop and turfgrass LWD measurements showed that sensors at 30 cm over turfgrass provided quite accurate estimates of LWD at the top of the crops, despite large differences in crop height and structure, but poorer estimates for wetness within leaf canopies.

  13. Equivalence of airborne and ground-acquired wheat canopy temperatures

    Science.gov (United States)

    Millard, J. P.; Hatfield, J. L.; Goettelman, R. C.

    1979-01-01

    The relationship between airborne and ground-based measurements of soil and crop canopy temperatures is investigated for a partial crop canopy. Daily ground-based measurements using a wide-field-of-view radiometer oriented towards the nadir at a height of 1.5 m and airborne thermal imagery at two-week intervals were obtained throughout the entire growing season of a stand of wheat. When corrected for atmospheric effects, the airborne measurements were found to be virtually identical to ground-based measurements, with a regression line slope of 0.985, a standard deviation of 1.8 C and a correlation coefficient of 0.97.

  14. Inter-annual climate variability and zooplankton: applying teleconnection indices to two deep subalpine lakes in Italy

    Directory of Open Access Journals (Sweden)

    Marina Manca

    2014-08-01

    Full Text Available Investigating relation between meteo-climatic indices and between-year variation in Daphnia population density and phenology is crucial for e.g. predicting impact of climate change on lake ecosystem structure and functioning. We tested whether and how two teleconnection indices calculated for the winter period, namely the East Atlantic pattern (EADJF and the Eastern Mediterranean Pattern (EMPDJF were correlated with Daphnia population growth in two Italian subalpine lakes, Garda and Maggiore. We investigated between-lake temporal coherence in: i water temperature within the water layer in which Daphnia is distributed; ii timing of Daphnia initial and spring maximum population density peak and iii the level of Daphnia spring maximum population density peak over an eleven-year period (1998-2008 of unchanged predation pressure by fish and invertebrates, and of common oligotrophy. Between-lake temporal coherence was high for an earlier start, an earlier, and lower, Daphnia population spring density peak after milder winters. Peak density level was coherently, positively correlated with soluble reactive phosphorus (SRP concentration. We hypothesized that Daphnia peak densities were related to atmospheric modes of variability in winter and to the degree of late winter mixing promoting replenishment of algal nutrients into upper water layers and phytoplankton growth, enhancing food availability and Daphnia fecundity, promoting Daphnia peak. 

  15. Equine Grazing in Managed Subalpine Wetlands: Effects on Arthropods and Plant Structure as a Function of Habitat

    Science.gov (United States)

    Holmquist, Jeffrey G.; Schmidt-Gengenbach, Jutta; Haultain, Sylvia A.

    2013-12-01

    Grazing management necessarily emphasizes the most spatially extensive vegetation assemblages, but landscapes are mosaics, often with more mesic vegetation types embedded within a matrix of drier vegetation. Our primary objective was to contrast effects of equine grazing on both subalpine vegetation structure and associated arthropods in a drier reed grass ( Calamagrostis muiriana) dominated habitat versus a wetter, more productive sedge habitat ( Carex utriculata). A second objective was to compare reed grass and sedge as habitats for fauna, irrespective of grazing. All work was done in Sequoia National Park (CA, USA), where detailed, long-term records of stock management were available. We sampled paired grazed and control wet meadows that contained both habitats. There were moderate negative effects of grazing on vegetation, and effects were greater in sedge than in reed grass. Conversely, negative grazing effects on arthropods, albeit limited, were greater in the drier reed grass, possibly due to microhabitat differences. The differing effects on plants and animals as a function of habitat emphasize the importance of considering both flora and fauna, as well as multiple habitat types, when making management decisions. Sedge supported twice the overall arthropod abundance of reed grass as well as greater diversity; hemipteran and dipteran taxa were particularly abundant in sedge. Given the greater grazing effects on sedge vegetation, greater habitat provision for terrestrial arthropods, and value as aquatic arthropod habitat, the wetter sedge assemblage is worthy of additional consideration by managers when planning for grazing and other aspects of land usage.

  16. The effects of winter recreation on alpine and subalpine fauna: a systematic review and meta-analysis.

    Directory of Open Access Journals (Sweden)

    Chloe F Sato

    Full Text Available The ski industry is often perceived as having a negative impact on sensitive alpine and subalpine communities. However, empirical evidence of such impacts is lacking. We reviewed the available literature from the last 35 years to quantify the reported effects of winter recreation on faunal communities. Overall, using one-sample binomial tests ('sign tests' we found that the effects of all types of winter recreation-related disturbances (i.e. ski runs, resort infrastructure and winter tourism were more likely to be negative or have no effect, than be positive for wildlife. More specifically, in Europe, where the majority of the available research was conducted, the impacts of winter recreation were most often negative for fauna. In terms of specific taxa, birds and to a lesser extent mammals and arthropods, responded negatively to disturbance. Results from our meta-analysis confirmed the results from our binomial tests. Richness, abundance and diversity of fauna were lower in areas affected by winter recreation when compared with undisturbed areas. For most regions and taxa, however, empirical evidence remains too limited to identify clear impacts of winter recreation. We therefore conclude that the majority of ski resorts are operating in the absence of knowledge needed to inform effective strategies for biodiversity conservation and ecologically-sound management. Thus, there is an urgent need for more empirical research to be conducted throughout this increasingly threatened ecological community, especially given the indication from the available literature that fauna often respond negatively to winter recreation.

  17. Nutrient status in soil of Ski runs in the sub-alpine belt of Uludag Mountain, Bursa, Turkey.

    Science.gov (United States)

    Guleryuz, Gurcan; Kirmizi, Serap; Arslan, Hulya

    2010-01-01

    Large areas of land are disturbed in sensitive bio-diverse mountain environments by Skiruns. Restoration of vegetation on such disturbed mountain sites may be hampered by soil degradation but the severity and nature of the constraints is not well understood. This study was designed to compare the water holding and nutritional status of soil in three Ski runs which had different construction dates and disturbance levels, and the adjacent undisturbed site in the Abies bommuelleriana forest community in the sub-alpine belt of Uludag Mountain (Bithynian Olympus). The values of soil parameters were depressed in proportion to the disturbance level. Water holding capacity (WHC), total nitrogen (N), organic carbon (C) and calcium (Ca2+), magnesium (Mg2+) and potassium (K+) contents (mg kg(-1) dry weight) of soils in the Ski run which had the highest disturbance level were lower than that of the undisturbed adjacent sites. However the results indicated that the soil parameters were less degraded when secondary vegetation was growing on the disturbed areas.

  18. The Effects of Winter Recreation on Alpine and Subalpine Fauna: A Systematic Review and Meta-Analysis

    Science.gov (United States)

    Sato, Chloe F.; Wood, Jeff T.; Lindenmayer, David B.

    2013-01-01

    The ski industry is often perceived as having a negative impact on sensitive alpine and subalpine communities. However, empirical evidence of such impacts is lacking. We reviewed the available literature from the last 35 years to quantify the reported effects of winter recreation on faunal communities. Overall, using one-sample binomial tests (‘sign tests’) we found that the effects of all types of winter recreation-related disturbances (i.e. ski runs, resort infrastructure and winter tourism) were more likely to be negative or have no effect, than be positive for wildlife. More specifically, in Europe, where the majority of the available research was conducted, the impacts of winter recreation were most often negative for fauna. In terms of specific taxa, birds and to a lesser extent mammals and arthropods, responded negatively to disturbance. Results from our meta-analysis confirmed the results from our binomial tests. Richness, abundance and diversity of fauna were lower in areas affected by winter recreation when compared with undisturbed areas. For most regions and taxa, however, empirical evidence remains too limited to identify clear impacts of winter recreation. We therefore conclude that the majority of ski resorts are operating in the absence of knowledge needed to inform effective strategies for biodiversity conservation and ecologically-sound management. Thus, there is an urgent need for more empirical research to be conducted throughout this increasingly threatened ecological community, especially given the indication from the available literature that fauna often respond negatively to winter recreation. PMID:23691190

  19. Using time scales to characterize phytoplankton assemblages in a deep subalpine lake during the thermal stratification period: Lake Iseo, Italy

    Science.gov (United States)

    Marti, Clelia Luisa; Imberger, Jörg; Garibaldi, Letizia; Leoni, Barbara

    2016-03-01

    A combination of field observations and 3-D hydrodynamic simulations were used to identify the phytoplankton species and to estimate the various time scales of the dominant physical and biological processes in Lake Iseo, a deep subalpine lake located in northern Italy, during a stratified period (July 2010). By ordering the rate processes time scales, we derive a phytoplankton patch categorization and growth interpretation that provides a general framework for the spatial distribution of phytoplankton concentration in Lake Iseo and illuminates the characteristics of their ecological niches. The results show that the diurnal surface layer was well mixed, received strong diurnal radiation, had low phosphorus concentrations and the phytoplankton biomass was sustained by the green alga Sphaerocystis schroeterii. The vertical mixing time scales were much shorter than horizontal mixing time scales causing a depth-uniform chlorophyll a concentration. The horizontal patch scale was determined by horizontal dispersion balancing the phytoplankton growth time scale, dictating the success of the observed green algae. The strongly stratified nutrient-rich metalimnion had mild light conditions and Diatoma elongatum and Planktothrix rubescens made up the largest proportions of the total phytoplankton biomass at the intermediate and deeper metalimnetic layers. The vertical transport time scales were much shorter than horizontal transport and vertical dispersion leading to growth niche for the observed phytoplankton. The study showed that time-scale hierarchy mandates the essential phytoplankton attributes or traits for success in a particular section of the water column and/or water body.

  20. Using functional traits to assess the resistance of subalpine grassland to trampling by mountain biking and hiking.

    Science.gov (United States)

    Pickering, Catherine Marina; Barros, Agustina

    2015-12-01

    Functional traits reflect plant responses to disturbance, including from visitor impacts. The impacts of mountain biking and hiking on functional composition were compared using a common experimental protocol in a subalpine grassland in the Australian Alps. The overlapping cover of all species was recorded two weeks after different intensities of hiking (200 and 500 passes) and mountain biking (none, 25, 75, 200 and 500 passes). Species' functional trait data were combined with their relative cover to calculate community trait weighted means for plant height, leaf area, percentage leaf dry matter content and Specific Leaf Area (SLA). Species such as Poa fawcettiae with larger leaves and SLA but lower dry weight content of leaves were more resistant to use, with differences between bikers and hikers only apparent at the highest levels of use tested. This differs from some vegetation communities in Europe where plants with smaller leaves were more resistant to hiking. More research using functional traits may account for differences in species responses to trampling. Managers of conservation areas used for hiking and biking need to minimise off trail use by both user groups. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry

    Directory of Open Access Journals (Sweden)

    T. G. Karl

    2002-01-01

    Full Text Available A `virtual' disjunct eddy covariance (vDEC device was tested with field measurements of biogenic VOC fluxes at a subalpine forest site in the Rocky Mountains of the USA. A PTR-MS instrument was used as the VOC sensor. Daily peak emission fluxes of 2-methyl-3-buten-2-ol (MBO, methanol, acetone and acetaldehyde were around 1.5, 1, 0.8 and 0.4 mg m-2 h-1, respectively. High pass filtering due to long sampling lines was investigated in laboratory experiments, and suggested that VOC losses in PTFA lines are generally governed by diffusion laws. Memory effects and surface reactions did not seem to play a dominant role. Model estimates of MBO fluxes compared well with measured fluxes. The results also suggest that latent heat and sensible heat fluxes are reasonably well correlated with VOC fluxes and could be used to predict variations in VOC emissions. The release of MBO, methanol, acetone and acetaldehyde resulted in significant change of tropospheric oxidant levels and a 10--40% increase in ozone levels, as inferred from a photochemical box model. We conclude that vDEC with a PTR-MS instrument is a versatile tool for simultaneous field analysis of multiple VOC fluxes.

  2. Complex terrain alters temperature and moisture limitations of forest soil respiration across a semiarid to subalpine gradient

    Science.gov (United States)

    Berryman, Erin Michele; Barnard, H.R.; Adams, H.R.; Burns, M.A.; Gallo, E.; Brooks, P.D.

    2015-01-01

    Forest soil respiration is a major carbon (C) flux that is characterized by significant variability in space and time. We quantified growing season soil respiration during both a drought year and a nondrought year across a complex landscape to identify how landscape and climate interact to control soil respiration. We asked the following questions: (1) How does soil respiration vary across the catchments due to terrain-induced variability in moisture availability and temperature? (2) Does the relative importance of moisture versus temperature limitation of respiration vary across space and time? And (3) what terrain elements are important for dictating the pattern of soil respiration and its controls? Moisture superseded temperature in explaining watershed respiration patterns, with wetter yet cooler areas higher up and on north facing slopes yielding greater soil respiration than lower and south facing areas. Wetter subalpine forests had reduced moisture limitation in favor of greater seasonal temperature limitation, and the reverse was true for low-elevation semiarid forests. Coincident climate poorly predicted soil respiration in the montane transition zone; however, antecedent precipitation from the prior 10 days provided additional explanatory power. A seasonal trend in respiration remained after accounting for microclimate effects, suggesting that local climate alone may not adequately predict seasonal variability in soil respiration in montane forests. Soil respiration climate controls were more strongly related to topography during the drought year highlighting the importance of landscape complexity in ecosystem response to drought.

  3. The effects of winter recreation on alpine and subalpine fauna: a systematic review and meta-analysis.

    Science.gov (United States)

    Sato, Chloe F; Wood, Jeff T; Lindenmayer, David B

    2013-01-01

    The ski industry is often perceived as having a negative impact on sensitive alpine and subalpine communities. However, empirical evidence of such impacts is lacking. We reviewed the available literature from the last 35 years to quantify the reported effects of winter recreation on faunal communities. Overall, using one-sample binomial tests ('sign tests') we found that the effects of all types of winter recreation-related disturbances (i.e. ski runs, resort infrastructure and winter tourism) were more likely to be negative or have no effect, than be positive for wildlife. More specifically, in Europe, where the majority of the available research was conducted, the impacts of winter recreation were most often negative for fauna. In terms of specific taxa, birds and to a lesser extent mammals and arthropods, responded negatively to disturbance. Results from our meta-analysis confirmed the results from our binomial tests. Richness, abundance and diversity of fauna were lower in areas affected by winter recreation when compared with undisturbed areas. For most regions and taxa, however, empirical evidence remains too limited to identify clear impacts of winter recreation. We therefore conclude that the majority of ski resorts are operating in the absence of knowledge needed to inform effective strategies for biodiversity conservation and ecologically-sound management. Thus, there is an urgent need for more empirical research to be conducted throughout this increasingly threatened ecological community, especially given the indication from the available literature that fauna often respond negatively to winter recreation.

  4. LBA-ECO LC-15 Aerodynamic Roughness Maps of Vegetation Canopies, Amazon Basin: 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set, LBA-ECO LC-15 Aerodynamic Roughness Maps of Vegetation Canopies, Amazon Basin: 2000, provides physical roughness maps of vegetation canopies in the...

  5. Multiangular Observation of Canopy Sun-Induced Chlorophyll Fluorescence by Combining Imaging Spectroscopy and Stereoscopy

    National Research Council Canada - National Science Library

    Francisco Pinto; Mark Müller-Linow; Anke Schickling; M Pilar Cendrero-Mateo; Agim Ballvora; Uwe Rascher

    2017-01-01

    The effect that the canopy structure and the viewing geometry have on the intensity and the spatial distribution of passively measured sun-induced chlorophyll fluorescence at canopy scale is still not well understood...

  6. Tree Canopy Cover for the Circumpolar Taiga-Tundra Ecotone: 2000-2005

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides a map of selected areas with defined tree canopy cover over the circumpolar taiga-tundra ecotone (TTE). Canopy cover was derived...

  7. Will Canopy-Embedded Mild Detonating Cord Affect Aircrew Visual Performance?

    National Research Council Canada - National Science Library

    Gannon, Aaron

    1997-01-01

    .... These sections open upward and outward as the ejection seat penetrates the canopy. MDC thus eliminates the need to jettison the canopy prior to ejection, preserving the critical escape time requisite for aircrew survival...

  8. Canopy processes, fluxes and microclimate in a pine forest

    Energy Technology Data Exchange (ETDEWEB)

    Launiainen, S.

    2011-07-01

    Interaction between forests and the atmosphere occurs by radiative and turbulent transport. The fluxes of energy and mass between surface and the atmosphere directly influence the properties of the lower atmosphere and in longer time scales the global climate. Boreal forest ecosystems are central in the global climate system, and its responses to human activities, because they are significant sources and sinks of greenhouse gases and of aerosol particles. The aim of the present work was to improve our understanding on the existing interplay between biologically active canopy, microenvironment and turbulent flow and quantify. In specific, the aim was to quantify the contribution of different canopy layers to whole forest fluxes. For this purpose, long-term micrometeorological and ecological measurements made in a Scots pine (Pinus sylvestris) forest at SMEAR II research station in Southern Finland were used. The properties of turbulent flow are strongly modified by the interaction between the canopy elements: momentum is efficiently absorbed in the upper layers of the canopy, mean wind speed and turbulence intensities decrease rapidly towards the forest floor and power spectra is modulated by spectral short-cut . In the relative open forest, diabatic stability above the canopy explained much of the changes in velocity statistics within the canopy except in strongly stable stratification. Large eddies, ranging from tens to hundred meters in size, were responsible for the major fraction of turbulent transport between a forest and the atmosphere. Because of this, the eddy-covariance (EC) method proved to be successful for measuring energy and mass exchange inside a forest canopy with exception of strongly stable conditions. Vertical variations of within canopy microclimate, light attenuation in particular, affect strongly the assimilation and transpiration rates. According to model simulations, assimilation rate decreases with height more rapidly than stomatal

  9. Exploring Relationships between Canopy Architecture, Light Distribution, and Photosynthesis in Contrasting Rice Genotypes Using 3D Canopy Reconstruction.

    Science.gov (United States)

    Burgess, Alexandra J; Retkute, Renata; Herman, Tiara; Murchie, Erik H

    2017-01-01

    The arrangement of leaf material is critical in determining the light environment, and subsequently the photosynthetic productivity of complex crop canopies. However, links between specific canopy architectural traits and photosynthetic productivity across a wide genetic background are poorly understood for field grown crops. The architecture of five genetically diverse rice varieties-four parental founders of a multi-parent advanced generation intercross (MAGIC) population plus a high yielding Philippine variety (IR64)-was captured at two different growth stages using a method for digital plant reconstruction based on stereocameras. Ray tracing was employed to explore the effects of canopy architecture on the resulting light environment in high-resolution, whilst gas exchange measurements were combined with an empirical model of photosynthesis to calculate an estimated carbon gain and total light interception. To further test the impact of different dynamic light patterns on photosynthetic properties, an empirical model of photosynthetic acclimation was employed to predict the optimal light-saturated photosynthesis rate (Pmax ) throughout canopy depth, hypothesizing that light is the sole determinant of productivity in these conditions. First, we show that a plant type with steeper leaf angles allows more efficient penetration of light into lower canopy layers and this, in turn, leads to a greater photosynthetic potential. Second the predicted optimal Pmax responds in a manner that is consistent with fractional interception and leaf area index across this germplasm. However, measured Pmax , especially in lower layers, was consistently higher than the optimal Pmax indicating factors other than light determine photosynthesis profiles. Lastly, varieties with more upright architecture exhibit higher maximum quantum yield of photosynthesis indicating a canopy-level impact on photosynthetic efficiency.

  10. Exploring Relationships between Canopy Architecture, Light Distribution, and Photosynthesis in Contrasting Rice Genotypes Using 3D Canopy Reconstruction

    Directory of Open Access Journals (Sweden)

    Alexandra J. Burgess

    2017-05-01

    Full Text Available The arrangement of leaf material is critical in determining the light environment, and subsequently the photosynthetic productivity of complex crop canopies. However, links between specific canopy architectural traits and photosynthetic productivity across a wide genetic background are poorly understood for field grown crops. The architecture of five genetically diverse rice varieties—four parental founders of a multi-parent advanced generation intercross (MAGIC population plus a high yielding Philippine variety (IR64—was captured at two different growth stages using a method for digital plant reconstruction based on stereocameras. Ray tracing was employed to explore the effects of canopy architecture on the resulting light environment in high-resolution, whilst gas exchange measurements were combined with an empirical model of photosynthesis to calculate an estimated carbon gain and total light interception. To further test the impact of different dynamic light patterns on photosynthetic properties, an empirical model of photosynthetic acclimation was employed to predict the optimal light-saturated photosynthesis rate (Pmax throughout canopy depth, hypothesizing that light is the sole determinant of productivity in these conditions. First, we show that a plant type with steeper leaf angles allows more efficient penetration of light into lower canopy layers and this, in turn, leads to a greater photosynthetic potential. Second the predicted optimal Pmax responds in a manner that is consistent with fractional interception and leaf area index across this germplasm. However, measured Pmax, especially in lower layers, was consistently higher than the optimal Pmax indicating factors other than light determine photosynthesis profiles. Lastly, varieties with more upright architecture exhibit higher maximum quantum yield of photosynthesis indicating a canopy-level impact on photosynthetic efficiency.

  11. Responses of canopy transpiration and canopy conductance of peach (Prunus persica) trees to alternate partial root zone drip irrigation

    Science.gov (United States)

    Gong, Daozhi; Kang, Shaozhong; Zhang, Jianhua

    2005-08-01

    We investigated canopy transpiration and canopy conductance of peach trees under three irrigation patterns: fixed 1/2 partial root zone drip irrigation (FPRDI), alternate 1/2 partial root zone drip irrigation (APRDI) and full root zone drip irrigation (FDI). Canopy transpiration was measured using heat pulse sensors, and canopy conductance was calculated using the Jarvis model and the inversion of the Penman-Monteith equation. Results showed that the transpiration rate and canopy conductance in FPRDI and APRDI were smaller than those in FDI. More significantly, the total irrigation amount was greatly reduced, by 34.7% and 39.6%, respectively for APRDI and FPRDI in the PRDI (partial root zone drip irrigation) treatment period. The daily transpiration was linearly related to the reference evapotranspiration in the three treatments, but daily transpiration of FDI is more than that of APRDI and FPRDI under the same evaporation demand, suggesting a restriction of transpiration water loss in the APRDI and FPRDI trees. FDI needed a higher soil water content to carry the same amount of transpiration as the APRDI and FPRDI trees, suggesting the hydraulic conductance of roots of APRDI and FPRDI trees was enhanced, and the roots had a greater water uptake than in FDI when the average soil water content in the root zone was the same. By a comparison between the transpiration rates predicted by the Penman-Monteith equation and the measured canopy transpiration rates for 60 days during the experimental period, an excellent correlation along the 1:1 line was found for all the treatments (R2 > 0.80), proving the reliability of the methodology.

  12. Milk removal

    OpenAIRE

    Ferneborg, Sabine

    2016-01-01

    Milk from dairy cows is a staple dietary component for humans all over the world. Regardless of whether milk is consumed in its purest, unaltered form or as high-end products such as fine cheese or ice cream, it needs to be of high quality when taken from the cow, produced at a low price and produced in a system that consider aspects such as animal health, animal welfare and sustainability. This thesis investigated the role of milk removal and the importance of residual milk on milk yield...

  13. Correction of Erroneous LiDAR Measurements in Artificial Forest Canopy Experimental Setups

    Directory of Open Access Journals (Sweden)

    Renato Cifuentes

    2014-07-01

    Full Text Available Terrestrial laser scanning (TLS data makes possible to directly characterize the three-dimensional (3D distribution of canopy foliage elements. The scanned edges of these elements may result in incorrectly point measurements (i.e., “ghost points” impacting the quality of point cloud data. Therefore, estimation of the ghost points’ spatial visibilities, measurement of their characteristics and their removal are essential. In order to quantify the improvements on data quality, a method is developed in this study to efficiently correct for ghost points. Since the occurrence of ghost points is governed by a number of factors, (e.g., scanning resolution and distance, object properties, incident angle; the developed method is based on the analysis of the effects of these factors under controlled conditions where canopy-like objects (i.e., leaves, branches and layers of leaves were scanned using a continuous-wave TLS system that employs phase-shift technology. Manual extraction of ghost points was done in order to calculate the relative amount of ghost points per scan, or ghost points ratio (gpr. The gpr values were computed in order to: (i analyze their relationships with variables representing the above factors; and (ii be used as a reference to evaluate the performance of filters used for extraction of ghost points. The ghost points’ occurrence was modeled by fitting regression models using different predictor variables that represent the variables under study. The obtained results indicated that reduced models with three predictors were suitable for gpr estimation in artificial leaves and in artificial branches, with a relative root mean squared error (RMSE of 4.7% and 3.7%, respectively; while the full model with four predictors was appropriate for artificial layers of leaves, with relative RMSE of 4.5%. According to the statistical analysis, scanning distance was identified as the most important variable for modeling ghost points

  14. Comparison of LiDAR- and photointerpretation-based estimates of canopy cover

    Science.gov (United States)

    Demetrios Gatziolis

    2012-01-01

    An evaluation of the agreement between photointerpretation- and LiDARbased estimates of canopy cover was performed using 397 90 x 90 m reference areas in Oregon. It was determined that at low canopy cover levels LiDAR estimates tend to exceed those from photointerpretation and that this tendency reverses at high canopy cover levels. Characteristics of the airborne...

  15. Canopy structure on forest lands in western Oregon: differences among forest types and stand ages

    Science.gov (United States)

    Anne C.S. McIntosh; Andrew N. Gray; Steven L. Garman

    2009-01-01

    Canopy structure is an important attribute affecting economic and ecological values of forests in the Pacific Northwest. However, canopy cover and vertical layering are rarely measured directly; they are usually inferred from other forest measurements. In this study, we quantified and compared vertical and horizontal patterns of tree canopy structure and understory...

  16. The influence of multi-season imagery on models of canopy cover: A case study

    Science.gov (United States)

    John W. Coulston; Dennis M. Jacobs; Chris R. King; Ivey C. Elmore

    2013-01-01

    Quantifying tree canopy cover in a spatially explicit fashion is important for broad-scale monitoring of ecosystems and for management of natural resources. Researchers have developed empirical models of tree canopy cover to produce geospatial products. For subpixel models, percent tree canopy cover estimates (derived from fine-scale imagery) serve as the response...

  17. Abundance of green tree frogs and insects in artificial canopy gaps in a bottomland hardwood forest

    Science.gov (United States)

    Scott Horn; James L. Hanula; Michael D. Ulyshen; John C. Kilgo

    2005-01-01

    We found more green tree frogs (Hyla cinera) in canopy gaps than in closed canopy forest. Of the 331 gree ntree frogs observed, 88% were in canopy gaps. Likewise, higher numbers and biomasses of insects were captured in the open gap habitat. Flies were the most commonly collected insect group accounting for 54% of the total capture. These data...

  18. Estimation of in-canopy ammonia sources and sinks in a fertilized Zea mays field

    Science.gov (United States)

    An analytical model was developed that describes the in-canopy vertical distribution of NH3 source and sinks and vertical fluxes in a fertilized agricultural setting using measured in-canopy concentration and wind speed profiles. This model was applied to quantify in-canopy air-s...

  19. A meta-analysis of leaf nitrogen distribution within plant canopies

    NARCIS (Netherlands)

    Hikosaka, Kouki; Anten, Niels P.R.; Borjigidai, Almaz; Kamiyama, Chiho; Sakai, Hidemitsu; Hasegawa, Toshihiro; Oikawa, Shimpei; Iio, Atsuhiro; Watanabe, Makoto; Koike, Takayoshi; Nishina, Kazuya; Ito, Akihiko

    2016-01-01

    Background and aims Leaf nitrogen distribution in the plant canopy is an important determinant for canopy photosynthesis. Although the gradient of leaf nitrogen is formed along light gradients in the canopy, its quantitative variations among species and environmental responses remain unknown.

  20. Examining conifer canopy structural complexity across forest ages and elevations with LiDAR data

    Science.gov (United States)

    Van R. Kane; Jonathan D. Bakker; Robert J. McGaughey; James A. Lutz; Rolf F. Gersonde; Jerry F. Franklin

    2010-01-01

    LiDAR measurements of canopy structure can be used to classify forest stands into structural stages to study spatial patterns of canopy structure, identify habitat, or plan management actions. A key assumption in this process is that differences in canopy structure based on forest age and elevation are consistent with predictions from models of stand development. Three...

  1. Computing energy budget within a crop canopy from Penmann's ...

    Indian Academy of Sciences (India)

    layer model, is rede-fined as a function of micrometeorological and physiological profiles of crop canopy. The sources and sinks of sensible and latent heat uxes are assumed to lie on a fictitious plane called zero-displacement plane. Algorithms ...

  2. Amazonian functional diversity from forest canopy chemical assembly.

    Science.gov (United States)

    Asner, Gregory P; Martin, Roberta E; Tupayachi, Raul; Anderson, Christopher B; Sinca, Felipe; Carranza-Jiménez, Loreli; Martinez, Paola

    2014-04-15

    Patterns of tropical forest functional diversity express processes of ecological assembly at multiple geographic scales and aid in predicting ecological responses to environmental change. Tree canopy chemistry underpins forest functional diversity, but the interactive role of phylogeny and environment in determining the chemical traits of tropical trees is poorly known. Collecting and analyzing foliage in 2,420 canopy tree species across 19 forests in the western Amazon, we discovered (i) systematic, community-scale shifts in average canopy chemical traits along gradients of elevation and soil fertility; (ii) strong phylogenetic partitioning of structural and defense chemicals within communities independent of variation in environmental conditions; and (iii) strong environmental control on foliar phosphorus and calcium, the two rock-derived elements limiting CO2 uptake in tropical forests. These findings indicate that the chemical diversity of western Amazonian forests occurs in a regionally nested mosaic driven by long-term chemical trait adjustment of communities to large-scale environmental filters, particularly soils and climate, and is supported by phylogenetic divergence of traits essential to foliar survival under varying environmental conditions. Geographically nested patterns of forest canopy chemical traits will play a role in determining the response and functional rearrangement of western Amazonian ecosystems to changing land use and climate.

  3. Estimating foliar biochemistry from hyperspectral data in mixed forest canopy

    NARCIS (Netherlands)

    Huber, S.; Kneubühler, M.; Psomas, A.; Itten, K.I.; Zimmerman, N.E.

    2008-01-01

    Estimating canopy biochemical composition in mixed forests at the level of tree species represents a critical tool for a better understanding and modeling of ecosystem functioning since many species exhibit differences in functional attributes or decomposition rates. We used airborne hyperspectral

  4. Simulating canopy temperature for modelling heat stress in cereals

    Science.gov (United States)

    Crop models must be improved to account for the large effects of heat stress effects on crop yields. To date, most approaches in crop models use air temperature despite evidence that crop canopy temperature better explains yield reductions associated with high temperature events. This study presents...

  5. Computing energy budget within a crop canopy from Penmann's ...

    Indian Academy of Sciences (India)

    R. Narasimhan, Krishtel eMaging Solutions

    Computing energy budget within a crop canopy from. Penmann's formulae. Mahendra Mohan∗ and K K Srivastava∗∗. ∗Radio and Atmospheric Science Division, National Physical Laboratory, New Delhi 110012, India. ∗∗Department of Chemical Engineering, Institute of Technology, Banaras Hindu University, Varanasi.

  6. Estimating forest canopy bulk density using six indirect methods

    Science.gov (United States)

    Robert E. Keane; Elizabeth D. Reinhardt; Joe Scott; Kathy Gray; James Reardon

    2005-01-01

    Canopy bulk density (CBD) is an important crown characteristic needed to predict crown fire spread, yet it is difficult to measure in the field. Presented here is a comprehensive research effort to evaluate six indirect sampling techniques for estimating CBD. As reference data, detailed crown fuel biomass measurements were taken on each tree within fixed-area plots...

  7. Effect of forest canopy on GPS-based movement data

    Science.gov (United States)

    Nicholas J. DeCesare; John R. Squires; Jay A. Kolbe

    2005-01-01

    The advancing role of Global Positioning System (GPS) technology in ecology has made studies of animal movement possible for larger and more vagile species. A simple field test revealed that lengths of GPS-based movement data were strongly biased (P<0.001) by effects of forest canopy. Global Positioning System error added an average of 27.5% additional...

  8. Effect of Balanites glabra canopy cover on grass production, organic ...

    African Journals Online (AJOL)

    A study was undertaken in Kenya's southern savanna rangelands to determine the seasonal effect of Balanites glabra canopy cover on aboveground grass biomass, grass species composition, soil organic matter and soil moisture content. The study was conducted during the period June to December 1999 in order to

  9. Floristic Composition, Tree Canopy Structure and Regeneration in a ...

    African Journals Online (AJOL)

    Floristic composition, plant species diversity, tree canopy structure and regeneration were assessed in a degraded tropical humid rainforest in Nigeria using a systematic line transect sampling technique for plot demarcation. All plants in a plot were identified and classified into families while the diameters and heights of ...

  10. Mapping forest canopy disturbance in the Upper Great Lakes, USA

    Science.gov (United States)

    James D. Garner; Mark D. Nelson; Brian G. Tavernia; Charles H. (Hobie) Perry; Ian W. Housman

    2015-01-01

    A map of forest canopy disturbance was generated for Michigan, Wisconsin, and most of Minnesota using 42 Landsat time series stacks (LTSS) and a vegetation change tracker (VCTw) algorithm. Corresponding winter imagery was used to reduce commission errors of forest disturbance by identifying areas of persistent snow cover. The resulting disturbance age map was classed...

  11. Sources of sulphur in rain collected below a wheat canopy

    Energy Technology Data Exchange (ETDEWEB)

    Raybould, C.C.; Unsworth, M.H.; Gregory, P.J.

    1977-05-12

    The quantity of sulfur in rain collected below a maturing wheat canopy was measured. The measurement and calculations show that leaching of plant sulfur by rain was the main source of additional sulfur in throughfall and that most sulfur dry-deposited on leaf surfaces remained fixed there.

  12. Winter cereal canopy effect on cereal and interseeded legume productivity

    Science.gov (United States)

    Interseeding red clover (Trifolium pratense L.) or alfalfa (Medicago sativa L.) into winter cereals in the North Central USA can provide forage and a green manure crop. We hypothesize that winter cereal canopy traits such as leaf area index (LAI) and whole plant dry matter (DM) influence interseeded...

  13. Shading performance of a vertical deciduous climbing plant canopy

    Energy Technology Data Exchange (ETDEWEB)

    Ip, Kenneth; Lam, Marta; Miller, Andrew [Centre for Sustainability of the Built Environment, School of Environment and Technology, University of Brighton, Cockcroft Building, Lewes Road, Brighton BN2 4GJ, East Sussex (United Kingdom)

    2010-01-15

    Deciduous climbing plant canopies strategically integrated to building facades can act as dynamic solar shading devices responsive to the seasonal climatic changes. Maximum shading occurs in the summer when the plant is at its peak growth. The shedding of leaves in autumn and winter reduces the shading and allows beneficial solar radiation to be absorbed by the opaque surface of the building facade or penetrated through the windows to the building interior. Although climbing plants have long been used for moderating the microclimate of buildings, there are very few scientific investigations to quantify such effects. This paper reports the findings of a study with specific focus on the shading performance of a vertical deciduous climbing plant canopy. It justifies the selection of Virginia Creeper as an appropriate plant for growth in the UK climate and describes the planting, monitoring and analysis procedures adopted to determine a proposed dynamic Bioshading Coefficient Function - which is used to represent the shading performance of the climbing plant canopy over its annual growing and wilting cycle. A thermal model was developed which identified the key parameters required for establishing the Bioshading Coefficients. Two climbing plant canopies (referred to as Bioshaders) were set up in an existing building in Southeast UK and monitored for 2 years. Measured data were used to calculate a series of daily Bioshading Coefficients which were subsequently applied to establish the Bioshading Coefficient Function. The research also identified issues affecting the indoor environment as a result of the application of Bioshaders. (author)

  14. Estimates of forest canopy height and aboveground biomass using ICESat.

    Science.gov (United States)

    Michael A. Lefsky; David J. Harding; Michael Keller; Warren B. Cohen; Claudia C. Carabajal; Fernando Del Bom; Maria O. Hunter; Raimundo Jr. de Oliveira

    2005-01-01

    Exchange of carbon between forests and the atmosphere is a vital component of the global carbon cycle. Satellite laser altimetry has a unique capability for estimating forest canopy height, which has a direct and increasingly well understood relationship to aboveground carbon storage. While the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land...

  15. Whole-tree canopy enclosures: why cage a tree?

    Science.gov (United States)

    Jerome F. Grant; Abdul Hakeem; Paris L. Lambdin; Gregory J. Wiggins; Rusty J. Rhea

    2011-01-01

    The use of whole-tree canopy enclosures (i.e., cages) is not a typical approach to assessing biological parameters and interactions in a forest setting. However, the successful application of this technology may enable researchers to better understand certain types of tree/organismal interactions.

  16. Estimating canopy water content using hyperspectral remote sensing data

    NARCIS (Netherlands)

    Clevers, J.G.P.W.; Kooistra, L.; Schaepman, M.E.

    2010-01-01

    Hyperspectral remote sensing has demonstrated great potential for accurate retrieval of canopy water content (CWC). This CWC is defined by the product of the leaf equivalent water thickness (EWT) and the leaf area index (LAI). In this paper, in particular the spectral information provided by the

  17. The relation between canopy spread cover and the aboveground ...

    African Journals Online (AJOL)

    The canopy spread cover of Karoo bushes and grasses in the Nama Karoo was measured and related to the aboveground phytomass available to the grazing animal. A correlation coefficient of r = 0.7456, calculated for Karoo bushes, indicates that this method can be used to non-destructively estimate available phytomass.

  18. Base Cation Leaching From the Canopy of a Rubber ( Hevea ...

    African Journals Online (AJOL)

    Base cations are essential to the sustainability of forest ecosystems. They are important for neutralizing the acidifying effects of atmospheric deposition. There is the need for in-depth understanding of base cation depletion and leaching from forest canopy. This is important particularly due to the increasing acidification and ...

  19. Modeling canopy CO2 exchange in the European Russian Arctic

    DEFF Research Database (Denmark)

    Kiepe, Isabell; Friborg, Thomas; Herbst, Mathias

    2013-01-01

    In this study, we use the coupled photosynthesis-stomatal conductance model of Collatz et al. (1991) to simulate the current canopy carbon dioxide exchange of a heterogeneous tundra ecosystem in European Russia. For the parameterization, we used data obtained from in situ leaf level measurements...

  20. A Bayesian Analysis Shows That a Spruce Beetle Outbreak Reduces Snow Interception and Sublimation in a Subalpine Spruce-Fir Forest

    Science.gov (United States)

    Frank, J. M.; Massman, W. J.; Ewers, B. E.; Williams, D. G.

    2016-12-01

    Sublimation is a key component in the water cycle of cold, snow dominated ecosystems. In many high elevation spruce-fir forests of western North America, recent spruce beetle outbreaks have caused widespread tree mortality, opened the canopy, and potentially altered the processes that control sublimation. This study evaluates three hypotheses: in these ecosystems the dominant source for sublimation originates from canopy intercepted snow, the loss of canopy following a beetle disturbance leads to significantly less sublimation, and major sublimation events are driven by the flow of sensible heat into the canopy. Bayesian analysis is used to evaluate a two source energy and canopy mass model that explains seventeen years (2000-2016) of winter eddy-covariance flux data at the GLEES AmeriFlux sites where a spruce beetle outbreak caused 75-85% basal area mortality. The model estimated that the resistance to snow sublimation from the canopy was an order of magnitude less than from the snowpack and that the maximum snow loading in the canopy was reduced to 25-56% of its pre-outbreak capacity. Comparing model results obtained using the observed decrease in leaf area index versus a "no beetle" condition, there has been a significant decrease in ecosystem sublimation since 2011. In the past few years, a 5-11% increase in snowpack sublimation has been offset by 28-32% less sublimation from canopy intercepted snow, with the net being 17-25% less total sublimation. This is equivalent to 3-6% of the total precipitation. Informing the model with information other than the above-canopy fluxes indicates that a near snowpack eddy covariance system decreases the canopy contribution to sublimation, including observed sensible heat fluxes requires a correction to resolve the surface energy imbalance, and stable isotopes of water vapor extend sublimation events. Because tree growth and ecological succession are slow in spruce-fir forests, these results could persist for decades.

  1. Predicting tropical plant physiology from leaf and canopy spectroscopy

    Science.gov (United States)

    Doughty, C.; Asner, G. P.; Martin, R.

    2009-12-01

    A broad understanding of tropical forest leaf photosynthesis has long been a goal for tropical forest ecologists, but elusive, due to difficult canopy access and great species diversity. In this paper, we develop an empirical model to predict light saturated sunlit tropical leaf photosynthesis based on leaf and canopy spectra with the goal of developing a high resolution remote sensing technique to measure canopy photosynthesis. To develop this model, we used the partial least squares (PLS) regression technique on three tropical forest datasets (~168 species), two in Hawaii and one in the tropical rainforest module of Biosphere 2 (B2L). For each species, we measured light saturated photosynthesis (A), light and CO2 saturated photosynthesis (Amax), day respiration (R), leaf spectra (400-2500 nm with 1 nm sampling), leaf nitrogen (N), chlorophyll A and B, carotenoids, and specific leaf area (SLA). On a subset of species we measured Jmax and Vcmax based on light and Aci curves. The model best predicted A (r2 = 0.74, root mean square error (RMSE) = 2.85 µmol m-2 s-1), R (r2 of 0.48, RMSE of -0.52 µmol m-2 s-1) followed by Amax (r2 of 0.47, RMSE of 5.1 µmol m-2 s-1), Jmax, (R2 = 0.52, RMSE = 39) and VCmax (R2 = 0.39, RMSE = 36). The PLS weightings, which indicate which wavelengths most contribute to the model, indicated that physiology weightings were most similar to nitrogen weightings, followed by chlorophyll and SLA. We combined leaf-level reflectance and transmittance with a canopy radiative transfer model to simulate top-of-canopy reflectance, and found that canopy spectra are a better predictor of light saturated photosynthesis more strongly (RMSE = 2.4 µmol m-2 s-1) than are leaf spectra (RMSE = 2.85 µmol m-2 s-1). The results suggest that there is potential for this technique to be used with high fidelity imaging spectrometers to remotely sense tropical forest canopy photosynthesis.

  2. Mercury in forest mushrooms and topsoil from the Yunnan highlands and the subalpine region of the Minya Konka summit in the Eastern Tibetan Plateau.

    Science.gov (United States)

    Falandysz, Jerzy; Saba, Martyna; Liu, Hong-Gao; Li, Tao; Wang, Ji-Peng; Wiejak, Anna; Zhang, Ji; Wang, Yuan-Zhong; Zhang, Dan

    2016-12-01

    This study aimed to investigate and discuss the occurrence and accumulation of mercury in the fruiting bodies of wild-growing fungi (Macromycetes) collected from montane forests in two regions of southwestern China with differences in soil geochemistry, climate and geographical conditions. Fungal mycelia in soils of the subalpine region of the Minya Konka (Gongga Mountain) in Sichuan and in the highlands of Yunnan efficiently accumulated mercury in fruiting bodies (mushrooms). The examined sites in Yunnan with highly mineralized red and yellow soils showed Hg contents ranging from 0.066 to 0.28 mg kg -1 dry biomass (db) which is roughly similar to the results obtained for samples collected from sites with dark soils relatively rich in organic matter from a remote, the subalpine region of Minya Konka. Due to the remoteness of the subalpine section of Minya Konka, as well as its elevation and climate, airborne mercury from long-range transport could be deposited preferentially on the topsoil and the Hg levels determined in soil samples taken beneath the fruiting bodies were up to 0.48 mg kg -1 dry matter. In Yunnan, with polymetallic soils (Circum-Pacific Mercuriferous Belt), Amanita mushrooms showed mercury in caps of fruiting bodies of up to 7.3 mg kg -1 dry biomass. Geogenic Hg from the mercuriferous belt seems to be the overriding source of mercury accumulated in mushrooms foraged in the regions of Yunnan, while long-range atmospheric transport and subsequent deposition are the mercury sources for specimens foraged in the region of Minya Konka.

  3. Diphyllobothrium latum (Cestoda: Diphyllobothriidea in perch (Perca fluviatilis in three sub-alpine lakes: influence of biotic and abiotic factors on prevalence

    Directory of Open Access Journals (Sweden)

    Orlando PETRINI

    2009-08-01

    Full Text Available In recent years, human diphyllobothriosis has staged a comeback in Swiss, French and Italian sub-alpine regions. The main putative infective source of the causative agent (the tapeworm Diphyllobothrium latum in these areas is perch (Perca fluviatilis. Therefore, the occurrence of D. latum in this fish species was investigated between 2005 and 2008 in the sub-alpine lakes Maggiore, Lugano and Geneva. Prevalence in fish of Lake Maggiore was 14% (n = 880. In Lake Geneva, 5.1% fillets (n = 532 were infected, whereas perch from Lake Lugano were free from the parasite. These results are discussed in relation to previous studies. Data on fish size and weight indicate that infection of perch by D. latum is independent of age and sex. Abiotic factors considered critical for D. latum life cycle (water temperature and oxygen concentration characterize the three basins and were related to their infestation frequencies. The presence of this parasite was most likely favoured by warmer, well oxygenated waters. Previous studies indicate that the lake’s trophic state (i.e. content of total phosphorus influenced the availability of the first intermediate hosts (copepods of some pseudophyllideans. In our study, no correlation was observed between the amount of phosphorus and the number of copepods in populations of zooplankton. Nevertheless, the trophic states of the three lakes seemed to affect the degree of infection in fish. In conclusion, at least in sub-alpine lakes, abiotic factors such as water temperature, oxygenation and trophic state seem to have an influence on maintaining or preventing perch infection with D. latum.

  4. Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

    Science.gov (United States)

    Ussler, William, III; Chanton, Jeffrey P.; Kelley, Cheryl A.; Martens, Christopher S.

    1994-01-01

    A set of continuous, high-resolution atmospheric radon (Rn-222) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open-canopy lichen-spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1 +/- 4.8 Bq m(exp -2)/h. Radon surface flux from the two end-member forest floor cover types (lichen mat and bare soil) were 38.8 +/- 5.1 and 61.8 +/- 15.6 Bq m(exp -2)/h, respectively. Average total forest canopy resistances computed using a simple 'flux box' model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47 +/- 0.24 s cm(exp -1) to 2.65 +/- 1.61 cm(exp -1) for daytime hours (0900-1700 LT) and from 3.44 +/- 0.91 s cm(exp -1) to 10.55 +/- 7.16 s cm(exp -1) for nighttime hours (2000-0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible. where daily equipment maintenance is not possible.

  5. Distribution Pattern, Conservation Status, and Associated Flora of the Genus Juniperus in Subalpine Pastures of the Kashmir Himalayas

    Directory of Open Access Journals (Sweden)

    Hamayun Shaheen

    2017-11-01

    Full Text Available Juniperus is an evergreen gymnosperm genus with a broad geographical distribution in the Northern Hemisphere. Juniperus constitutes important vegetation associations in the Himalayan highlands that have significant ecological and socioeconomic importance. This research investigated the distribution pattern, community structure, and ecosystem services provided byJuniperus -dominated subalpine vegetation in the upper Neelum Valley, Pakistan. Vegetation attributes and geographical characteristics were systematically recorded at 4 selected sites. Two species of Juniperus, Juniperus communis L. and J. excelsa M. Bieb., were found to have average importance values of 23.4 and 20.02%, respectively. J. excelsa showed an average basal area of 0.30 m2 ha−1 and an average stem density of 46.95 ha−1; J. communis had an average basal area of 0.25 m2 ha−1 and an average stem density of 33.21 ha−1. A total of 56 Juniperus-associated plant species from 29 families were recorded, with Asteraceae as the dominant family, followed by Lamiaceae, Polygonaceae, Rosaceae, Caryophyllaceae, and Apiaceae. Predominant associated species included Thymus linearis, Aster falconeri, Rosa webbiana, Berberis lyceum, Anagallis arvensis, Rumex nepalensis, Poa alpina, Bistorta affinis, and Iris hookeriana. The calculated average values were Shannon's diversity, 3.07; Simpson's diversity, 0.94; species richness, 1.11; species evenness, 0.90; and maturity index, 45.90. Hemicryptophytes were the dominant lifeform in the area (57.14%, and microphylls (46.42% were the dominant leaf type. Overgrazing and fuelwood cutting were identified as serious threats to both Juniperus species. Restoration of the degraded juniper stands through collective efforts by government and local communities and regular monitoring is recommended.

  6. Vegetation types and climate conditions reflected by the modern phytolith assemblages in the subalpine Dalaoling Forest Reserve, central China

    Science.gov (United States)

    Traoré, Djakanibé Désiré; Gu, Yansheng; Liu, Humei; Shemsanga, Ceven; Ge, Jiwen

    2015-06-01

    This research describes modern phytolith records and distributions from subalpine surface soils in the Dalaoling Forest Reserve, and reveals its implications for local climate conditions with respect to the altitude gradient. Well-preserved phytolith morpho-types, assemblages, and climatic indices were used to study the relationship between local vegetation and climate conditions. The phytolith classification system is mainly based on the characteristics of detailed morpho-types described for anatomical terms, which are divided into seven groups: long cells, short cells, bulliform cells, hair cells, pteridophyte type, broad-leaved type, and gymnosperm type. Phytoliths originating from the Poaceae are composed of Pooideae (rondel and trapeziform), Panicoideae (bilobate, cross, and polylobate), Chloridoideae (short/square saddle), and Bambusoideae (oblong concave saddle). Based on the altitudinal distribution of the phytolith assemblages and the indices of aridity (Iph), climate (Ic), and tree cover density (D/P), five phytolith assemblage zones have revealed the five types of climatic conditions ranging from 1,169 m to 2,005 m in turn: warm-wet, warm-xeric to warm-mesic, warm-xeric to cool-mesic, cool-xeric, and cool-mesic to cool-xeric. The Bambusoideae, Panicoideae, and Chloridoideae are the dominant vegetation at the lower-middle of the mountains, while Pooideae is mainly distributed in the higher mountains. The close relationship between phytolith assembleages and changes of altitude gradient suggest that vegetation distribution patterns and plant ecology in the Dalaoling mountains are controlled by temperature and humidity conditions. Our results highlight the importance of phytolith records as reliable ecoclimatic indicators for vegetation ecology in subtropical regions.

  7. Mycorrhiza-plant colonization patterns on a subalpine glacier forefront as a model system of primary succession.

    Science.gov (United States)

    Cázares, Efrén; Trappe, James M; Jumpponen, Ari

    2005-09-01

    Lyman glacier in the North Cascades Mountains of Washington has a subalpine forefront characterized by a well-developed terminal moraine, inconspicuous successional moraines, fluting, and outwash. These deposits were depleted of symbiotic fungi when first exposed but colonized by them over time after exposure. Four major groups of plant species in this system are (1) mycorrhiza-independent or facultative mycotrophic, (2) dependent on arbuscular mycorrhizae (AM) (3) dependent on ericoid mycorrhiza (ERM) or ectomycorrhizae (EM), and (4) colonized by dark-septate (DS) endophytes. We hypothesized that availability of mycorrhizal propagules was related to the success of mycorrhiza-dependent plants in colonizing new substrates in naturally evolved ecosystems. To test this hypothesis roots samples of 66 plant species were examined for mycorrhizal colonization. The plants were sampled from communities at increasing distances from the glacier terminus to compare the newest communities with successively older ones. Long established, secondary successional dry meadow communities adjacent to the glacier forefront, and nearby high alpine communities were sampled for comparison. DS were common on most plant species on the forefront. Nonmycorrhizal plants predominated in the earlier successional sites, whereas the proportion of mycorrhizal plants generally increased with age of community. AM were present, mostly at low levels, and nearly absent in two sites of the forefront. ERM were present in all species of Ericaceae sampled, and EM in all species of Pinaceae and Salicaceae. Roots of plants in the long established meadow and heath communities adjacent to the forefront and the high alpine community all had one or another of the colonization types, with DS and AM predominating.

  8. Multi-scale comparison of the fine particle removal capacity of urban forests and wetlands

    OpenAIRE

    Zhenming Zhang; Jiakai Liu; Yanan Wu; Guoxin Yan; Lijuan Zhu; Xinxiao Yu

    2017-01-01

    As fine particle (FP) pollution is harmful to humans, previous studies have focused on the mechanisms of FP removal by forests. The current study aims to compare the FP removal capacities of urban forests and wetlands on the leaf, canopy, and landscape scales. Water washing and scanning electron microscopy are used to calculate particle accumulation on leaves, and models are used to estimate vegetation collection, sedimentation, and dry deposition. Results showed that, on the leaf scale, fore...

  9. Four years of experimental warming do not modify the interaction between subalpine shrub species.

    Science.gov (United States)

    Anadon-Rosell, Alba; Ninot, Josep M; Palacio, Sara; Grau, Oriol; Nogués, Salvador; Navarro, Enrique; Sancho, M Carmen; Carrillo, Empar

    2017-04-01

    Climate warming can lead to changes in alpine plant species interactions through modifications in environmental conditions, which may ultimately cause drastic changes in plant communities. We explored the effects of 4 years of experimental warming with open-top chambers (OTC) on Vaccinium myrtillus performance and its interaction with neighbouring shrubs at the Pyrenean treeline ecotone. We examined the effects of warming on height, above-ground (AG) and below-ground (BG) biomass and the C and N concentration and isotope composition of V. myrtillus growing in pure stands or in stands mixed with Vaccinium uliginosum or Rhododendron ferrugineum. We also analysed variations in soil N concentrations, rhizosphere C/N ratios and the functional diversity of the microbial community, and evaluated whether warming altered the biomass, C and N concentration and isotope composition of V. uliginosum in mixed plots. Our results showed that warming induced positive changes in the AG growth of V. myrtillus but not BG, while V. uliginosum did not respond to warming. Vaccinium myrtillus performance did not differ between stand types under increased temperatures, suggesting that warming did not induce shifts in the interaction between V. myrtillus and its neighbouring species. These findings contrast with previous studies in which species interactions changed when temperature was modified. Our results show that species interactions can be less responsive to warming in natural plant communities than in removal experiments, highlighting the need for studies involving the natural assembly of plant species and communities when exploring the effect of environmental changes on plant-plant interactions.

  10. Automatic measurement of crops canopy height based on monocular vision

    Science.gov (United States)

    Yu, Zhenghong; Cao, Zhiguo; Bai, Xiaodong

    2011-12-01

    Computer vision technology has been increasingly used for automatically observing crop growth state, but as one of the key parameters in the field of agro-meteorological observation, crop canopy height is still measured manually in the actual observation process up to now. In order to automatically measure the height based on the forward-and-downward-looking image in the existing monocular vision observation system, a novel method is proposed, that is, to measure the canopy height indirectly by the solving algorithm for the actual height of the vertical objects (SAAH) with the help of the intelligent sensor device. The experiment results verified the feasibility and validity of our method, and that the method could meet the actual observation demand.

  11. Effects of changing canopy directional reflectance on feature selection

    Science.gov (United States)

    Smith, J. A.; Oliver, R. E.; Kilpela, O. E.

    1973-01-01

    The use of a Monte Carlo model for generating sample directional reflectance data for two simplified target canopies at two different solar positions is reported. Successive iterations through the model permit the calculation of a mean vector and covariance matrix for canopy reflectance for varied sensor view angles. These data may then be used to calculate the divergence between the target distributions for various wavelength combinations and for these view angles. Results of a feature selection analysis indicate that different sets of wavelengths are optimum for target discrimination depending on sensor view angle and that the targets may be more easily discriminated for some scan angles than others. The time-varying behavior of these results is also pointed out.

  12. [Active crop canopy sensor-based nitrogen diagnosis for potato].

    Science.gov (United States)

    Yu, Jing; Li, Fei; Qin, Yong-Lin; Fan, Ming-Shou

    2013-11-01

    In the present study, two potato experiments involving different N rates in 2011 were conducted in Wuchuan County and Linxi County, Inner Mongolia. Normalized difference vegetation index (NDVI) was collected by an active GreenSeeker crop canopy sensor to estimate N status of potato. The results show that the NDVI readings were poorly correlated with N nutrient indicators of potato at vegetative Growth stage due to the influence of soil background. With the advance of growth stages, NDVI values were exponentially related to plant N uptake (R2 = 0.665) before tuber bulking stage and were linearly related to plant N concentration (R2 = 0.699) when plant fully covered soil. In conclusion, GreenSeeker active crop sensor is a promising tool to estimate N status for potato plants. The findings from this study may be useful for developing N recommendation method based on active crop canopy sensor.

  13. Strengthening the Ubuntu social canopy after the Afrophobic attacks

    Directory of Open Access Journals (Sweden)

    Zorodzai Dube

    2016-03-01

    Full Text Available In view of the aftermath of the Afrophobic attacks in South Africa, this study regards Paul�s emphasis concerning common humanity and morality as a possible lacuna towards strengthening Ubuntu. Paul taught that both the Jews and the Gentiles have their common ancestor � Adam, and that good morality is a better identity marker than ethnicity. In view of the aftermath of the Afrophobic attacks in South Africa, this study suggests that similar arguments can be used to amend the Ubuntu social canopy.Intradisciplinary and/or interdisciplinary implications: This study is interdisciplinary in nature in that it uses perspectives from social sciences to seek solutions towards a more inclusive communityKeywords: Afrophobia; Xenophobia; Ubuntu; Social Canopy; Christ-like Anthropology

  14. Canopy Measurements with a Small Unmanned Aerial System

    Science.gov (United States)

    Peschel, J.

    2015-12-01

    This work discusses the use of a small unmanned aerial system (UAS) for the remote placement of wireless environmental sensors in tree canopies. Remote presence applications occur when one or more humans use a robot to project themselves into an environment in order to complete an inaccessible or time-critical mission. The more difficult problem of physical object manipulation goes one step further by incorporating physical-based interaction, in additional to visualization. Forested environments present especially unique challenges for small UAS versus similar domains (e.g., disaster response, inspection of critical infrastructure) due to the navigation and interaction required with dense tree canopies. This work describes two field investigations that inform: i) the type of physical object manipulation and visualization necessary for sensor placement (ventral, frontal, dorsal), ii) the necessary display form (hybrid) for piloting and sensor placement, and iii) visual feedback mechanisms useful for handling human-robot team role conflicts.

  15. [Review of Crop Canopy Spectral Information Detection Technology and Methods].

    Science.gov (United States)

    Fang, Xiao-rong; Gao, Jun-feng; Xie, Chuan-qi; Zhu, Feng-le; Huang, Ling-xia; He, Yong

    2015-07-01

    Compared with the traditional chemical methods and the subjective visual ways for measuring plant physiology information indicators, the assessments of crop canopy information through spectral radiometer are more simple, rapid and accurate. The applications of different types of spectral radiometer, especially for international general used Cropscan multispectral radiometer, for predicting crop canopy leaf area index under different growth stage, biomass, nitrogen, chlorophyll and yield, and monitoring plant diseases and insect pests were summarized based on crop group information acquisition methods in recent years. The varity of vegetation indices (VIs) were concluded after comparing regression coefficients of related models among different crops. In general, the correlation coefficients of mathematical models were high and it can realize the crop detection of various kinds of physiological information. Besides, the combination of multispectral radiometer and other sensors can provide useful information to evaluate the status of crops growth, which is very important in practice.

  16. Tree diversity and canopy cover in cocoa systems in Ghana

    DEFF Research Database (Denmark)

    Asare, Richard; Ræbild, Anders

    2016-01-01

    Cocoa (Theobroma cacao L.) growing systems in Ghana and West Africa consist of diverse tree species and densities.This study was conducted to determine factors that influence tree species configurations and how tree characteristics affect canopy cover in cocoa farms. Eighty-six farmers...... and corresponding farms were selected in a systematic approach in four districts across two agro-ecological zones in Ghana. Results show that men tend to have larger farm sizes, higher tree density and diversity than women. Tree density and canopy cover of shade trees were low on large farms, but diversity...... increased with increasing farm sizes. Even though there was a significant correlation between diameter at breast height and crown area for all species investigated, tree species differed considerably in their crown area and thus the amount of ground cover provided. Current recommendations for shade...

  17. Euler-Lagrange coupling for porous parachute canopy analysis

    Directory of Open Access Journals (Sweden)

    Nicolas Aquelet

    2007-03-01

    Full Text Available We apply a new Euler-Lagrange coupling method to 3-D parachute problems, which generally involve fluid-structure interactions between a flexible, elastic, porous parachute canopy and a high-speed airflow. The method presented couples an Arbitrary Lagrange Euler formulation for the fluid dynamics and an updated Lagrangian finite element formulation for the parachute canopy. The Euler-Lagrange coupling handles fluid-structure interaction without matching the fluid and structure meshes. In order to take account of the effect of the parachute permeability, this coupling computes interaction forces based on the Ergun porous flow model. This paper provides validations for the technique when considering parachute applications and discusses the interest of this development to the parachute designer.

  18. Forest canopy gap fraction from terrestrial laser scanning

    OpenAIRE

    Danson, F. M.; Hetherington, D; Morsdorf, F; Koetz, B; Allgöwer, B

    2007-01-01

    A terrestrial laser scanner (TLS) was used to measure canopy directional gap fraction distribution in forest stands in the Swiss National Park, eastern Switzerland. A scanner model was derived to determine the expected number of laser shots in all directions, and these data were compared with the measured number of laser hits to determine directional gap fraction at eight sampling points. Directional gap fraction distributions were determined from digital hemispherical photographs recor...

  19. Identifying the interacting roles of stressors in driving the global loss of canopy-forming to mat-forming algae in marine ecosystems.

    Science.gov (United States)

    Strain, Elisabeth M A; Thomson, Russell J; Micheli, Fiorenza; Mancuso, Francesco P; Airoldi, Laura

    2014-11-01

    Identifying the type and strength of interactions between local anthropogenic and other stressors can help to set achievable management targets for degraded marine ecosystems and support their resilience by identifying local actions. We undertook a meta-analysis, using data from 118 studies to test the hypothesis that ongoing global declines in the dominant habitat along temperate rocky coastlines, forests of canopy-forming algae and/or their replacement by mat-forming algae are driven by the nonadditive interactions between local anthropogenic stressors that can be addressed through management actions (fishing, heavy metal pollution, nutrient enrichment and high sediment loads) and other stressors (presence of competitors or grazers, removal of canopy algae, limiting or excessive light, low or high salinity, increasing temperature, high wave exposure and high UV or CO2 ), not as easily amenable to management actions. In general, the cumulative effects of local anthropogenic and other stressors had negative effects on the growth and survival of canopy-forming algae. Conversely, the growth or survival of mat-forming algae was either unaffected or significantly enhanced by the same pairs of stressors. Contrary to our predictions, the majority of interactions between stressors were additive. There were however synergistic interactions between nutrient enrichment and heavy metals, the presence of competitors, low light and increasing temperature, leading to amplified negative effects on canopy-forming algae. There were also synergistic interactions between nutrient enrichment and increasing CO2 and temperature leading to amplified positive effects on mat-forming algae. Our review of the current literature shows that management of nutrient levels, rather than fishing, heavy metal pollution or high sediment loads, would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae, particularly in enclosed bays or estuaries because of the

  20. Geometry of the hemispherical radiometric footprint over plant canopies

    Science.gov (United States)

    Marcolla, B.; Cescatti, A.

    2017-11-01

    Radiometric measurements of hemispherical surface reflectance and long-wave irradiance are required to quantify the broadband albedo and the outgoing thermal radiation. These observations are typically integrated with eddy covariance measurements of sensible and latent heat fluxes to characterize the surface energy budget. While the aerodynamic footprint has been widely investigated, the geometry of the hemispherical radiometric footprint over plant canopies has been rarely tackled. In the present work, the size and shape of the hemispherical radiometric footprint are formalized for a bare surface and in presence of a vegetation cover. For this purpose, four idealized canopies are analyzed and the dependency of the radiometric footprint on leaf area index and canopy height is explored. Besides, the radiometric footprint is compared with the aerodynamic footprint in conditions of neutral stability. It was observed that almost 100% of the hemispherical radiometric signal originates within a distance of a few radiometer heights, while only about 50-80% of the cumulative aerodynamic signal is generated within a distance of about 20 sensor heights. In order to achieve comparable extensions of the footprint areas, hemispherical radiometric measurements should therefore be taken about 6-15 times higher than turbulent flux ones, depending on the vegetation type. The analysis also highlights that the size of the radiative footprint decreases at increasing leaf area index, whereas the aerodynamic footprint shows an opposite behavior. For the abovementioned reasons, this work may support the interpretation of energy flux measurements and the optimal design of eddy covariance stations located in heterogeneous sites.

  1. Streamwater Chemistry and Nutrient Export During Five Years of Bark Beetle Infestation of Subalpine Watersheds at the Fraser Experimental Forest

    Science.gov (United States)

    Rhoades, C.; Elder, K.; Hubbard, R.; Porth, L.

    2008-12-01

    Forested watersheds of western North America are currently undergoing rapid and extensive canopy mortality caused by a variety of insect species. The mountain pine bark beetle (Dendroctonus ponderosae) began to attack lodgepole pine (Pinus contorta) at the USFS Fraser Experimental Forest in central Colorado in 2002. By 2007, bark beetles had killed 78% of the overstory pine in Fraser research watersheds on average. The hydrologic, climatic, biogeochemical and vegetation records at the Fraser Experimental Forest provide a unique opportunity to quantify the impacts of this widespread, but poorly understood forest disturbance relative to a multi-decade pre-disturbance period. Here we compare seasonal streamwater chemistry and annual nutrient export for the five years since the bark beetle outbreak began with the pre- attack record. Patterns in post-outbreak streamwater biogeochemistry are compared to changes is species composition and proportional loss of overstory basal area for four basins. The influence of the outbreak will depend upon an aggregate of short (i.e. halted overstory water and nutrient use) and longer-term (i.e. altered canopy interception, windthrow, and understory growth) processes, so the hydrologic and biogeochemical implications of current beetle activity will not be fully realized for decades.

  2. Variation in canopy duration in the perennial biofuel crop Miscanthus reveals complex associations with yield

    Science.gov (United States)

    Robson, Paul R.H.; Farrar, Kerrie; Gay, Alan P.; Jensen, Elaine F.; Clifton-Brown, John C.; Donnison, Iain S.

    2013-01-01

    Energy crops can provide a sustainable source of power and fuels, and mitigate the negative effects of CO2 emissions associated with fossil fuel use. Miscanthus is a perennial C4 energy crop capable of producing large biomass yields whilst requiring low levels of input. Miscanthus is largely unimproved and therefore there could be significant opportunities to increase yield. Further increases in yield will improve the economics, energy balance, and carbon mitigation of the crop, as well as reducing land-take. One strategy to increase yield in Miscanthus is to maximize the light captured through an extension of canopy duration. In this study, canopy duration was compared among a diverse collection of 244 Miscanthus genotypes. Canopy duration was determined by calculating the number of days between canopy establishment and senescence. Yield was positively correlated with canopy duration. Earlier establishment and later senescence were also both separately correlated with higher yield. However, although genotypes with short canopy durations were low yielding, not all genotypes with long canopy durations were high yielding. Differences of yield between genotypes with long canopy durations were associated with variation in stem and leaf traits. Different methodologies to assess canopy duration traits were investigated, including visual assessment, image analysis, light interception, and different trait thresholds. The highest correlation coefficients were associated with later assessments of traits and the use of quantum sensors for canopy establishment. A model for trait optimization to enable yield improvement in Miscanthus and other bioenergy crops is discussed. PMID:23599277

  3. The impact of canopy managements on grape and wine composition of cv. 'Istrian Malvasia' (Vitis vinifera L.).

    Science.gov (United States)

    Rescic, Jan; Mikulic-Petkovsek, Maja; Rusjan, Denis

    2016-11-01

    The interest in producing wines preferred by consumers increases the need for improving practices to modify grape and wine composition. The aim of this study was to assess the impacts of three different canopy management measures, (1) early leaf removal in the cluster zone, (2) removal of young leaves above the second pair of wires and (3) Double Maturation Raisonnée, on the yield and chemical composition of 'Istrian Malvasia' grape and wine. Double Maturation Raisonnée had a significantly greater impact on phenolic compounds, while the highest soluble solids (24.3 and 23.5 °Brix) and titratable acidity (7.0 and 7.1 g L(-1) ) were measured at early leaf removal. Leaf removal at véraison caused an unexpected augmentation of flavonols in the berry skin. Early leaf removal resulted in significantly lower extracts of wine. Nevertheless, they reached the highest mark (16.5 out of 20.0 points) in sensory evaluation compared with leaf removal at véraison and Double Maturation Raisonnée (15.0 points) and control (16.0 points). Leaf removal at véraison and Double Maturation Raisonnée improved the phenolic composition of wine, producing a full-bodied wine. On the other hand, early leaf removal significantly augmented the yield and titratable acidity, hydroxycinnamic acids and flavanols of wine, which might have led to a fresher but less-bodied wine. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  4. Stochastic radiative transfer model for mixture of discontinuous vegetation canopies

    Energy Technology Data Exchange (ETDEWEB)

    Shabanov, Nikolay V. [Department of Geography, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 (United States)]. E-mail: shabanov@bu.edu; Huang, D. [Brookhaven National Laboratory, Environmental Sciences Department, P.O. Box 5000, Upton, NY 11973 (United States); Knjazikhin, Y. [Department of Geography, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 (United States); Dickinson, R.E. [School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Myneni, Ranga B. [Department of Geography, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 (United States)

    2007-09-15

    Modeling of the radiation regime of a mixture of vegetation species is a fundamental problem of the Earth's land remote sensing and climate applications. The major existing approaches, including the linear mixture model and the turbid medium (TM) mixture radiative transfer model, provide only an approximate solution to this problem. In this study, we developed the stochastic mixture radiative transfer (SMRT) model, a mathematically exact tool to evaluate radiation regime in a natural canopy with spatially varying optical properties, that is, canopy, which exhibits a structured mixture of vegetation species and gaps. The model solves for the radiation quantities, direct input to the remote sensing/climate applications: mean radiation fluxes over whole mixture and over individual species. The canopy structure is parameterized in the SMRT model in terms of two stochastic moments: the probability of finding species and the conditional pair-correlation of species. The second moment is responsible for the 3D radiation effects, namely, radiation streaming through gaps without interaction with vegetation and variation of the radiation fluxes between different species. We performed analytical and numerical analysis of the radiation effects, simulated with the SMRT model for the three cases of canopy structure: (a) non-ordered mixture of species and gaps (TM); (b) ordered mixture of species without gaps; and (c) ordered mixture of species with gaps. The analysis indicates that the variation of radiation fluxes between different species is proportional to the variation of species optical properties (leaf albedo, density of foliage, etc.) Gaps introduce significant disturbance to the radiation regime in the canopy as their optical properties constitute major contrast to those of any vegetation species. The SMRT model resolves deficiencies of the major existing mixture models: ignorance of species radiation coupling via multiple scattering of photons (the linear mixture

  5. Ash, Asterionella, and Anglers: A Paleolimnological Approach to Understanding Anthropogenic and Volcanogenic Disturbances in a Small Sub-Alpine Watershed

    Science.gov (United States)

    Howard, K. L.; Noble, P. J.

    2014-12-01

    This poster summarizes geochemical, biological, hydrological, and watershed data that characterize Manzanita Lake, a small sub-alpine catchment in Lassen Volcanic National Park, CA. The future objective is to use characteristics of this system to interpret variations in diatom and sediment composition dating back to the 1914 Mt. Lassen eruption from a recently recovered lake core. Manzanita Lake is a small (0.18 km2) lake with a ~30 km2 watershed area situated on the northwest flank of Mt. Lassen, one of the most active Cascade volcanoes, and is a valuable recreational spot for anglers and visitors. Hydraulic residence time is short; roughly 119 days, and is derived from lake volume (1.0 X 106m3) and estimates of stream inflow (~6 ft3/sec) and outflow (~3 ft3/sec) that were made from May 2014 sampling data. Limnological sampling in 2012-2014 suggests that Manzanita Lake exhibits stable thermal stratification in the summer months, which is unusual given the shallow depth (~10m), but possibly supported by the morphometry of the lake basin and inputs of cold snowmelt from the flank of Lassen Peak. The lake is a moderately conductive (100-114 μS), mesotrophic system with secchi depths ranging from 8m to the bottom (~10m). Total phosphorus (TP) ranges from 15-25 ppb and dissolved inorganic nitrogen (DIN) from 2-15 ppb, with ammonium in the epilimnion being the largest contributor. A high concentration of silica (Si) in surface water inputs (34 mg/L) to Manzanita Lake likely reflects the rhyodacitic bedrock geology and large drainage ratio (164) of the watershed. Variations in Si concentration in the lake seem to be coupled with diatom production. During the sampling period Manzanita Lake is has been dominated by diatom blooms throughout the summer and fall months. There is a seasonal succession in the diatom species present, with abundant Asterionella formosa in the spring, transitioning to abundant Fragilaria crotonensis in the summer months, to a mixed dominance of

  6. Spatio-seasonal variability in dissolved organic matter optical properties and its bioavailability in a subalpine lake

    Science.gov (United States)

    Stadler, Masumi; Ejarque, Elisabet; Kainz, Martin J.

    2017-04-01

    Allochthonous and autochothonous dissolved organic matter (DOM) in lakes mainly originate from terrestrial and aquatic primary production, respectively. Due to their differing biochemical composition the degradability of DOM by microorganisms is expected to vary. The carbon use efficiency of bacteria and DOM biodegradability determine whether the consumed DOM is incorporated into microbial biomass or respired to CO2 and ultimately emitted into the atmosphere. Thus, understanding the interaction of biodegradable DOM and its consumers is crucial to increase our knowledge on the role of lakes in the global carbon cycling. However, interactions of specific aquatic DOM signatures and the microbial population still remain widely debated. The aim of this study was to explore how DOM biodegradability changes along a stream-lake continuum at different seasons of the year. We monitored DOM quantity and its optical properties, inorganic nutrients, CO2 and bacterial growth over 20 days in dark bioassays with water from the inflow, outflow and at three layers of an oligotrophic subalpine lake. Preliminary results reveal highest microbial abundance in the metalimnion in winter and summer (0.7 106 and 2.5 106 cells mL-1, respectively) and the inflow in spring and autumn (1 106 and 1.4 106 cells mL-1, respectively) after 20 days. Surprisingly, with the exception of winter samples final inflow bacterial abundance results high, despite its lowest initial natural cell concentration, providing evidence for effective utilisation of terrestrial DOM, even with its high humic signature as indicated by the humification index (HIX). Nonetheless, after a microbial biomass peak with the inflow yielding mostly highest after three days, at the final experimental stage microbial biomass does only marginally differ between all sites with the exception of autumn samples where outflow and metalimnion turn out most productive. Even though the DOM of all lake sites and the lake outflow were

  7. Drought induced changes of plant belowground carbon allocation affect soil microbial community function in a subalpine meadow

    Science.gov (United States)

    Fuchslueger, L.; Bahn, M.; Fritz, K.; Hasibeder, R.; Richter, A.

    2012-12-01

    There is growing evidence that climate extremes may affect ecosystem carbon dynamics more strongly than gradual changes in temperatures or precipitation. Climate projections suggest more frequent heat waves accompanied by extreme drought periods in many parts of Europe, including the Alps. Drought is considered to decrease plant C uptake and turnover, which may in turn decrease belowground C allocation and potentially has significant consequences for microbial community composition and functioning. However, information on effects of drought on C dynamics at the plant-soil interface in real ecosystems is still scarce. Our study aimed at understanding how summer drought affects soil microbial community composition and the uptake of recently assimilated plant C by different microbial groups in grassland. We hypothesized that under drought 1) the microbial community shifts, fungi being less affected than bacteria, 2) plants decrease belowground C allocation, which further reduces C transfer to soil microbes and 3) the combined effects of belowground C allocation, reduced soil C transport due to reduced soil moisture and shift in microbial communities cause an accumulation of extractable organic C in the soil. Our study was conducted as part of a rain-exclusion experiment in a subalpine meadow in the Austrian Central Alps. After eight weeks of rain exclusion we pulse labelled drought and control plots with 13CO2 and traced C in plant biomass, extractable organic C (EOC) and soil microbial communities using phospholipid fatty acids (PLFA). Drought induced a shift of the microbial community composition: gram-positive bacteria became more dominant, whereas gram-negative bacteria were not affected by drought. Also the relative abundance of fungal biomass was not affected by drought. While total microbial biomass (as estimated by total microbial PLFA content) increased during drought, less 13C was taken up. This reduction was pronounced for bacterial biomarkers. It reflects

  8. Soil attributes and microclimate are important drivers of initial deadwood decay in sub-alpine Norway spruce forests.

    Science.gov (United States)

    Fravolini, Giulia; Egli, Markus; Derungs, Curdin; Cherubini, Paolo; Ascher-Jenull, Judith; Gómez-Brandón, María; Bardelli, Tommaso; Tognetti, Roberto; Lombardi, Fabio; Marchetti, Marco

    2016-11-01

    Deadwood is known to significantly contribute to global terrestrial carbon stocks and carbon cycling, but its decay dynamics are still not thoroughly understood. Although the chemistry of deadwood has been studied as a function of decay stage in temperate to subalpine environments, it has generally not been related to time. We therefore studied the decay (mass of deadwood, cellulose and lignin) of equal-sized blocks of Picea abies wood in soil-mesocosms over two years in the Italian Alps. The 8 sites selected were along an altitudinal sequence, reflecting different climate zones. In addition, the effect of exposure (north- and south-facing slopes) was taken into account. The decay dynamics of the mass of deadwood, cellulose and lignin were related to soil parameters (pH, soil texture, moisture, temperature) and climatic data. The decay rate constants of Picea abies deadwood were low (on average between 0.039 and 0.040y(-1)) and of lignin close to zero (or not detectable), while cellulose reacted much faster with average decay rate constants between 0.110 and 0.117y(-1). Our field experiments showed that local scale factors, such as soil parameters and topographic properties, influenced the decay process: higher soil moisture and clay content along with a lower pH seemed to accelerate wood decay. Interestingly, air temperature negatively correlated with decay rates or positively with the amount of wood components on south-facing sites. It exerted its influence rather on moisture availability, i.e. the lower the temperature the higher the moisture availability. Topographic features were also relevant with generally slower decay processes on south-facing sites than on north-facing sites owing to the drier conditions, the higher pH and the lower weathering state of the soils (less clay minerals). This study highlights the importance of a multifactorial consideration of edaphic parameters to unravel the complex dynamics of initial wood decay. Copyright © 2016 Elsevier

  9. Abundance of green tree frogs and insects in artificial canopy gaps in a bottomland hardwood forest.

    Energy Technology Data Exchange (ETDEWEB)

    Horn, Scott; Hanula, James L.; Ulyshen, Michael D.; Kilgo, John C.

    2005-01-01

    Horn, Scott, James L. Hanula, Michael D. Ulyshen, and John C. Kilgo. 2005. Abundance of green tree frogs and insects in artificial canopy gaps in a bottomland hardwood forest. Am. Midl. Nat. 153:321-326. Abstract: We found more green tree frogs (Hyla cinerea) in canopy gaps than in closed canopy forest. Of the 331 green tree frogs observed, 88% were in canopy gaps. Likewise, higher numbers and biomasses of insects were captured in the open gap habitat. Flies were the most commonly collected insect group accounting for 54% of the total capture. These data suggest that one reason green tree frogs were more abundant in canopy gaps was the increased availability of prey and that small canopy gaps provide early successional habitats that are beneficial to green tree frog populations.

  10. The influence of changes in soil moisture in association with geomorphic change on the formation of a subalpine coniferous forest on Mt. Akita-Komagatake, northern Japan

    Science.gov (United States)

    Konno, A.

    2015-12-01

    The coniferous forest (largely composed of Abies mariesii) is presently the typical vegetation of the subalpine zone in Japan. Pollen analysis revealed that few A. mariesii were present during the last glacial period, and the species began to expand to the subalpine zone during the Holocene (Morita, 1992). However, on Mt. Akita-Komagatake in northern Japan, the expected predominance of A. mariesii is not extensively observed, and the predominant vegetation is instead the dwarf bamboo (Sasa kurilensis). It is unknown why the area under coniferous forest is small in this region. Therefore, I examined this issue from the perspectives of (1) distribution of vegetation, (2) geomorphology, (3) soil moisture, and (4) vegetation history. (1) Precise digital elevation model data and photographic interpretation showed that this coniferous forest was densely distributed in a flat segment considered to be formed by a landslide; (2) this landslide is thought to have occurred up to 3,699 ± 26 yr BP because a boring-core specimen from the landslide included the AK-3 tephra layer (2,300-2,800 yr BP: Wachi et al, 1997) and the radiocarbon date of the lowermost humic soil layer was 3,699 ± 26 yr BP; (3) the soil in the forest area had higher volumetric water content than that in the non-forest area; and (4) phytolith analysis revealed that the main species in the study site was initially dwarf bamboo, but coniferous forest replaced it after the Towada-a tephra (1035 cal. BP, Machida and Arai, 1992) layer fell. These results suggest that soil water conditions changed because of the formation of the flat segment by the landslide, and the coniferous forest was consequently established. However, the landslide only indirectly affected the formation of the coniferous forest, because the forest developed over several thousand years after the landslide occurred. In other words, more direct reasons for the establishment of the coniferous forest may involve changes in soil moisture. This

  11. Development of models for thermal infrared radiation above and within plant canopies

    Science.gov (United States)

    Paw u, Kyaw T.

    1992-01-01

    Any significant angular dependence of the emitted longwave radiation could result in errors in remotely estimated energy budgets or evapotranspiration. Empirical data and thermal infrared radiation models are reviewed in reference to anisotropic emissions from the plant canopy. The biometeorological aspects of linking longwave models with plant canopy energy budgets and micrometeorology are discussed. A new soil plant atmosphere model applied to anisotropic longwave emissions from a canopy is presented. Time variation of thermal infrared emission measurements is discussed.

  12. Estimation of canopy structure parameters from multiangular measurements of scattering components

    DEFF Research Database (Denmark)

    Kirk, Kristian; Andersen, Hans Jørgen

    2006-01-01

    Structure parameters for characterization of vegetation canopies are often estimated from remote optical measurements. Existing methods include those based on measurements of gap fraction, spectral vegetation indices, or the inversion of spectral canopy reflectance models. This paper proposes...... a novel method based on inversion of multiangular measurements of the abundances of light scattering components, which may be estimated using spectral unmixing. An algorithm is described for predicting the abundances of various scattering components using Monte Carlo simulation with a Poisson canopy model...

  13. Tree Death Not Resulting in Gap Creation: An Investigation of Canopy Dynamics of Northern Temperate Deciduous Forests

    Directory of Open Access Journals (Sweden)

    Jean-Francois Senécal

    2018-01-01

    Full Text Available Several decades of research have shown that canopy gaps drive tree renewal processes in the temperate deciduous forest biome. In the literature, canopy gaps are usually defined as canopy openings that are created by partial or total tree death of one or more canopy trees. In this study, we investigate linkages between tree damage mechanisms and the formation or not of new canopy gaps in northern temperate deciduous forests. We studied height loss processes in unmanaged and managed forests recovering from partial cutting with multi-temporal airborne Lidar data. The Lidar dataset was used to detect areas where canopy height reduction occurred, which were then field-studied to identify the tree damage mechanisms implicated. We also sampled the density of leaf material along transects to characterize canopy structure. We used the dataset of the canopy height reduction areas in a multi-model inference analysis to determine whether canopy structures or tree damage mechanisms most influenced the creation of new canopy gaps within canopy height reduction areas. According to our model, new canopy gaps are created mainly when canopy damage enlarges existing gaps or when height is reduced over areas without an already established dense sub-canopy tree layer.

  14. BOREAS TE-23 Canopy Architecture and Spectral Data from Hemispherical Photos

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Hemispherical photographs collected in support of the effort to characterize and interpret information on estimates of canopy architecture and radiative...

  15. Examining vertical patterns in Arctic tundra shrub canopies: Implications for carbon cycling in a changing environment

    Science.gov (United States)

    Heskel, M.; Atkin, O.; Turnbull, M.; Rastetter, E.; Griffin, K. L.

    2012-12-01

    Climate change is facilitating the northward encroachment and expansion of woody shrub species into the Arctic tundra, which in turn is altering a number of physical and biogeochemical processes that are likely to affect how carbon is cycled in this region. Greater shrub presence also increases leaf area index and canopy complexity in the tundra, introducing the potential for vertical variation in nitrogen, photosynthesis, and respiration through the canopy. For these reasons, Arctic tundra shrub communities represent an ecologically relevant case study for investigating carbon cycling-nitrogen relationships and testing optimization models. Here, we measured photosynthesis, respiration in the dark and light, the light inhibition of respiration, stomatal conductance, leaf nitrogen, and related leaf traits at different heights representing variation in light availability in multiple Arctic Alaskan shrub communities dominated by Salix pulchra and Betula nana to examine if the relatively low-stature canopies exhibit vertical patterns. Highest rates of photosynthesis and respiration (P top of the canopy, suggesting substrate-limitation of respiration at lower, more shaded canopy levels. Leaves at the top of the canopy also exhibited the lowest inhibition of respiration by light (NS), and the highest nitrogen concentrations. (P photosynthesis, nitrogen, and a relaxation of light-inhibition to optimize metabolic efficiency. Data from this study was also used to test leaf-level and canopy nitrogen optimization models. These data emphasize the need to include canopy complexity in tundra carbon models, as neglecting physiological differences through a canopy may lead to an underestimation of stored carbon.

  16. Vertical stratification of beetles (Coleoptera) and flies (Diptera) in temperate forest canopies.

    Science.gov (United States)

    Maguire, Dorothy Y; Robert, Katleen; Brochu, Kristen; Larrivée, Maxim; Buddle, Christopher M; Wheeler, Terry A

    2014-02-01

    Forest canopies support high arthropod biodiversity, but in temperate canopies, little is known about the spatial distribution of these arthropods. This is an important first step toward understanding ecological roles of insects in temperate canopies. The objective of this study was to assess differences in the species composition of two dominant and diverse taxa (Diptera and Coleoptera) along a vertical gradient in temperate deciduous forest canopies. Five sugar maple trees from each of three deciduous forest sites in southern Quebec were sampled using a combination of window and trunk traps placed in three vertical strata (understory, mid-canopy, and upper-canopy) for three sampling periods throughout the summer. Coleoptera species richness and abundance did not differ between canopy heights, but more specimens and species of Diptera were collected in the upper-canopy. Community composition of Coleoptera and Diptera varied significantly by trap height. Window traps collected more specimens and species of Coleoptera than trunk traps, although both trap types should be used to maximize representation of the entire Coleoptera community. There were no differences in abundance, diversity, or composition of Diptera collected between trap types. Our data confirm the relevance of sampling all strata in a forest when studying canopy arthropod biodiversity.

  17. BOREAS TE-23 Canopy Architecture and Spectral Data from Hemispherical Photos

    Data.gov (United States)

    National Aeronautics and Space Administration — Hemispherical photographs collected in support of the effort to characterize and interpret information on estimates of canopy architecture and radiative transfer...

  18. What is the most prominent factor limiting photosynthesis in different layers of a greenhouse cucumber canopy?

    Science.gov (United States)

    Chen, Tsu-Wei; Henke, Michael; de Visser, Pieter H B; Buck-Sorlin, Gerhard; Wiechers, Dirk; Kahlen, Katrin; Stützel, Hartmut

    2014-09-01

    Maximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different components of photosynthetic limitations at the leaf level and to upscale these limitations to different canopy layers and the whole plant. A static virtual three-dimensional canopy structure was constructed using digitized plant data in GroIMP. Light interception of the leaves was simulated by a ray-tracer and used to compute leaf photosynthesis. Different components of photosynthetic limitations, namely stomatal (S(L)), mesophyll (M(L)), biochemical (B(L)) and light (L(L)) limitations, were calculated by a quantitative limitation analysis of photosynthesis under different light regimes. In the virtual cucumber canopy, B(L) and L(L) were the most prominent factors limiting whole-plant photosynthesis. Diffusional limitations (S(L) + M(L)) contributed Photosynthesis in the lower canopy was more limited by the biochemical capacity, and the upper canopy was more sensitive to light than other canopy parts. Although leaves in the upper canopy received more light, their photosynthesis was more light restricted than in the leaves of the lower canopy, especially when the light condition above the canopy was poor. An increase in whole-plant photosynthesis under diffuse light did not result from an improvement of light use efficiency but from an increase in light interception. Diffuse light increased the photosynthesis of leaves that were directly shaded by other leaves in the canopy by up to 55%. Based on the results, maintaining biochemical capacity of the middle-lower canopy and increasing the leaf area of the upper canopy would be promising strategies to improve canopy photosynthesis in a high-wire cucumber cropping system. Further analyses using the approach described in this study can be expected to

  19. Floristic and community diversity of sub-alpine and alpine grasslands and grazed dwarf-shrub heaths in the Romanian Carpathians

    Directory of Open Access Journals (Sweden)

    Coldea, Gheorghe

    1998-12-01

    Full Text Available Floristic diversity at community level and community diversity at landscape level are presented for the main grassland and dwarf-shrub communities in the sub-alpine and alpine zones in five mountain ranges of the Romanian Carpathians. The 30 plant communities studied had their floristic composition and distribution determined by geological substratum and pedo-climatic factors. The most diverse grasslands (Oxytropido-Elynetum, Seslerio haynaldianae-Caricetun were on calcareous substratum and on the mountain slopes (Festucetum pictae, whilst the lowest diversity was in the oligo-mesotrophic sub-alpine grasslands (Scorzonero- Festucetum nigricantis, Alchemillo-Poetum alpinae, Violo-Nardetum. The Shannon-Weaver diversity index for the communities increased almost linearly with the number of species per community, whilst community diversity in the five mountain ranges was a function of the number of communities per mountain range.

    [fr] Nous présentons dans ce travail la diversité floristique au niveau de la communauté et la diversité de communautés au niveau du paysage pour les principaux types de pâturages et de communautés à petits arbustes des étages subalpin et alpin de cinq chaînes montagneuses des Carpathes en Roumanie. Aussi bien la composition floristique que la distribution des 30 communautés étudiées dépendent de la nature géologique du terrain et des facteurs édapho-climatiques. Les pâturages les plus riches en diversité (Oxytropido-Elynetum, Seslerio haynaldianae- Caricetun se développent sur substrat calcaire et sur les versants des montagnes (Testucetum pictae; par contre la plus faible diversité a été rencontrée dans les pâturages oligo-mesotrophes subalpins (Scorzonero-Festucetum nigricantis, Alchemillo-Poetum alpinae, Violo-Nardetum. L'index de diversité de Shannon- Weaver augmente quasi linéairement avec le nombre d'espèces de chaque communauté, tandis que

  20. Responses of assemblages of Orthoptera to management and use of ski slopes on upper sub-alpine meadows in the Austrian Alps.

    Science.gov (United States)

    Illich, Ingeborg P; Haslett, John R

    1994-05-01

    The Orthoptera assemblages occurring on sub-alpine ski slopes were compared with those found on neighbouring unskied meadows by making frequent transect counts at two pairs of sites in the Gastein valley in the Austrian Central Alps. On one of the ski slopes no Orthoptera were present, although two species were abundant on the control meadow a few meters away. On the second ski slope, the Orthoptera assemblage exhibited reduced species richness, lower densities of individuals and a generally accelerated rate of nymphal development compared to the control meadow populations. These results may be explained in terms of the changed habitat conditions on the ski slopes and the known biologies of the species concerned. The implications of the findings for winter tourism management in high altitude ecosystems are briefly discussed.

  1. Impacts of removing Chinese privet from riparian forests on plant communities and tree growth five years later

    Science.gov (United States)

    Jacob R. Hudson; James L. Hanula; Scott Horn

    2014-01-01

    An invasive shrub, Chinese privet (Ligustrum sinense Lour.), was removed from heavily infested riparian forests in the Georgia Piedmont in 2005 by mulching machine or chainsaw felling. Subsequent herbicide treatment eliminated almost all privet by 2007. Recovery of plant communities, return of Chinese privet, and canopy tree growth were measured on...

  2. How to select the best tree planting locations to enhance air pollution removal in the MillionTreesNYC initiative

    Science.gov (United States)

    Arianna Morani; David J. Nowak; Satoshi Hirabayashi; Carlo Calfapietra

    2011-01-01

    Highest priority zones for tree planting within New York City were selected by using a planting priority index developed combining three main indicators: pollution concentration, population density and low canopy cover. This new tree population was projected through time to estimate potential air quality and carbon bene!ts. Those trees will likely remove more than 10...

  3. Effects of elevated CO₂ and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China.

    Science.gov (United States)

    Li, Yongping; Zhang, Yuanbin; Zhang, Xiaolu; Korpelainen, Helena; Berninger, Frank; Li, Chunyang

    2013-06-01

    The dwarf bamboo (Fargesia rufa Yi), growing understory in subalpine dark coniferous forest, is one of the main foods for giant panda, and it influences the regeneration of subalpine coniferous forests in southwestern China. To investigate the effects of elevated CO₂, temperature and their combination, the dwarf bamboo plantlets were exposed to two CO₂ regimes (ambient and double ambient CO₂ concentration) and two temperatures (ambient and +2.2°C) in growth chambers. Gas exchange, leaf traits and carbohydrates concentration were measured after the 150-day experiment. Elevated CO₂ significantly increased the net photosynthetic rate (Anet ), intrinsic water-use efficiency (WUEi ) and carbon isotope composition (δ¹³C) and decreased stomatal conductance (g(s)) and total chlorophyll concentration based on mass (Chl(m)) and area (Chl(a)). On the other hand, elevated CO₂ decreased specific leaf area (SLA), which was increased by elevated temperature. Elevated CO₂ also increased foliar carbon concentration based on mass (C(m)) and area (C(a)), nitrogen concentration based on area (N(a)), carbohydrates concentration (i.e. sucrose, sugar, starch and non-structural carbohydrates) and the slope of the A(net)-N(a) relationship. However, elevated temperature decreased C(m), C(a) and N(a). The combination of elevated CO₂ and temperature hardly affected SLA, C(m), C(a), N(m), N(a), Chl(m) and Chl(a). Variables Anet and Na had positive linear relationships in all treatments. Our results showed that photosynthetic acclimation did not occur in dwarf bamboo at elevated CO₂ and it could adjust physiology and morphology to enable the capture of more light, to increase WUE and improve nutritional conditions. Copyright © Physiologia Plantarum 2012.

  4. Leap frog in slow motion: Divergent responses of tree species and life stages to climatic warming in Great Basin subalpine forests.

    Science.gov (United States)

    Smithers, Brian V; North, Malcolm P; Millar, Constance I; Latimer, Andrew M

    2018-02-01

    In response to climate warming, subalpine treelines are expected to move up in elevation since treelines are generally controlled by growing season temperature. Where treeline is advancing, dispersal differences and early life stage environmental tolerances are likely to affect how species expand their ranges. Species with an establishment advantage will colonize newly available habitat first, potentially excluding species that have slower establishment rates. Using a network of plots across five mountain ranges, we described patterns of upslope elevational range shift for the two dominant Great Basin subalpine species, limber pine and Great Basin bristlecone pine. We found that the Great Basin treeline for these species is expanding upslope with a mean vertical elevation shift of 19.1 m since 1950, which is lower than what we might expect based on temperature increases alone. The largest advances were on limber pine-dominated granitic soils, on west aspects, and at lower latitudes. Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above-treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Although limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully "leap-frogging" over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment. This early-stage dominance indicates the potential for the species composition of treeline to change in response to climate change. More broadly, it shows how species differences in dispersal

  5. Combustion influences on natural abundance nitrogen isotope ratio in soil and plants following a wildfire in a sub-alpine ecosystem.

    Science.gov (United States)

    Huber, Edith; Bell, Tina L; Adams, Mark A

    2013-11-01

    This before-and-after-impact study uses the natural abundance N isotope ratio (δ(15)N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the (15)N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in (15)N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of (15)N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in (15)N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ(15)N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH4(+) into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar (15)N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of (15)N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire.

  6. [Contribution of soil fauna to the mass loss of Betula albosinensis leaf litter at early decomposition stage of subalpine forest litter in western Sichuan].

    Science.gov (United States)

    Xia, Lei; Wu, Fu-Zhong; Yang, Wan-Qin; Tan, Bo

    2012-02-01

    In order to quantify the contribution of soil fauna to the decomposition of birch (Betula albosinensis) leaf litter in subalpine forests in western Sichuan of Southwest China during freeze-thaw season, a field experiment with different mesh sizes (0.02, 0.125, 1 and 3 mm) of litterbags was conducted in a representative birch-fir (Abies faxoniana) forest to investigate the mass loss rate of the birch leaf litter from 26 October, 2010 to 18 April, 2011, and the contributions of micro-, meso- and macro-fauna to the decomposition of the leaf litter. Over the freeze-thaw season, 11.8%, 13.2%, 15.4% and 19.5% of the mass loss were detected in the litterbags with 0.02, 0. 125, 1 and 3 mm mesh sizes, respectively. The total contribution of soil fauna to the litter decomposition accounted for 39.5% of the mass loss, and the taxa and individual relative density of the soil fauna in the litterbags had the similar variation trend with that of the mass loss rate. The contribution rate of soil fauna to the leaf litter mass loss showed the order of micro- fauna, with the highest contribution of micro-fauna (7.9%), meso-fauna (11.9%), and macro-fauna (22.7%) at the onset of freezing stage, deeply frozen stage, and thawing stage, respectively. The results demonstrated that soil fauna played an important role in the litter decomposition in subalpine forests of western Sichuan during freeze-thaw season.

  7. Using stable water isotopes and borehole NMR to inform an ecohydrological model in a subalpine and upper montane catchment in the Rocky Mountains

    Science.gov (United States)

    Millar, D.; Parsekian, A.; Mercer, J.; Speckman, H. N.; Beverly, D.; Ewers, B. E.; Mackay, D. S.

    2016-12-01

    Recent work using stable water isotopes has revealed that vegetation across a range of different biomes preferentially take up tightly bound soil water over more mobile pools. This so called two water worlds hypothesis (TWWH) has important implications for hydrological modeling efforts in ecosystems where it holds true, since few if any ecohydrological models incorporate this phenomenon. Further, in ecosystems where the TWWH is supported, information regarding the proportion of soil water in the bound and mobile pools is necessary to inform plant-soil water dynamics in models. In this study, we investigate which soil water pools are used by dominant vegetation in an upper montane and subalpine catchment in the Rocky Mountains of southern Wyoming, and use this information to inform the Terrestrial Regional Ecosystem Exchange Simulator (TREES). Within each catchment, we test the TWWH using stable water isotope analyses in an upland coniferous forest and an adjacent, downgradient groundwater-supported wetland. The proportion of soil water in each pool within each ecosystem was inferred from borehole nuclear magnetic resonance (NMR). These field data are being incorporated into TREES, by partitioning plant water uptake between bound and mobile pools. NMR analyses were conducted in all four ecosystems down to a depth of approximately 75 cm and revealed that while mid growing season soil water content was approximately two-fold higher in the subalpine forest versus that of the upper montane forest, the vast majority of soil water, 86% on average, existed in the bound pool in both ecosystems. Alternatively, soils in both wetlands were saturated throughout their profiles, with a majority of the soil water existing in the mobile pool, 63% on average. These initial findings highlight the importance of bound soil water pools in both upland forests, as opposed to the wetlands, which had an abundance of water in both pools.

  8. Seasonal dynamics of the plant community and soil seed bank along a successional gradient in a subalpine meadow on the Tibetan Plateau.

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    Miaojun Ma

    Full Text Available BACKGROUND: Knowledge about how change the importance of soil seed bank and relationship between seed mass and abundance during vegetation succession is crucial for understanding vegetation dynamics. Many studies have been conducted, but their ecological mechanisms of community assembly are not fully understood. METHODOLOGY: We examined the seasonal dynamics of the vegetation and soil seed bank as well as seed size distribution along a successional gradient. We also explored the potential role of the soil seed bank in plant community regeneration, the relationship between seed mass and species abundance, and the relative importance of deterministic and stochastic processes along a successional gradient. PRINCIPAL FINDINGS: Species richness of seed bank increased (shallow layer and the total and seed density decreased (each layer and the total significantly with succession. Species richness and seed density differed significantly between different seasons and among soil depths. Seed mass showed a significant negative relationship with relative abundance in the earliest successional stage, but the relationships were not significant in later stages. Seed mass showed no relationship with relative abundance in the whole successional series in seed bank. Results were similar for both July 2005 and April 2006. CONCLUSIONS: The seed mass and abundance relationship was determined by a complex interaction between small and larger seeded species and environmental factors. Both stochastic processes and deterministic processes were important determinants of the structure of the earliest stage. The importance of seed bank decreased with succession. The restoration of abandoned farmed and grazed meadows to the species-rich subalpine meadow in Tibetan Plateau can be successfully achieved from the soil seed bank. However, at least 20 years are required to fully restore an abandoned agricultural meadow to a natural mature subalpine meadow.

  9. A multi-proxy record of hydroclimate, vegetation, fire, and post-settlement impacts for a subalpine plateau, Central Rocky Mountains U.S.A

    Science.gov (United States)

    Anderson, Lesleigh; Brunelle, Andrea; Thompson, Robert S.

    2015-01-01

    Apparent changes in vegetation distribution, fire, and other disturbance regimes throughout western North America have prompted investigations of the relative importance of human activities and climate change as potential causal mechanisms. Assessing the effects of Euro-American settlement is difficult because climate changes occur on multi-decadal to centennial time scales and require longer time perspectives than historic observations can provide. Here, we report vegetation and environmental changes over the past ~13,000 years as recorded in a sediment record from Bison Lake, a subalpine lake on a high plateau in northwestern Colorado. Results are based on multiple independent proxies, which include pollen, charcoal, and elemental geochemistry, and are compared with previously reported interpretations of hydroclimatic changes from oxygen isotope ratios. The pollen data indicate a slowly changing vegetation sequence from sagebrush steppe during the late glacial to coniferous forest through the late Holocene. The most dramatic vegetation changes of the Holocene occurred during the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA) with rapid replacement of conifer forest by grassland followed by an equally rapid return to conifer forest. Late Holocene vegetation responses are mirrored by changes in fire, lake biological productivity, and watershed erosion. These combined records indicate that subsequent disturbance related to Euro-American settlement, although perhaps significant, had acted upon a landscape that was already responding to MCA-LIA hydroclimatic change. Results document both rapid and long-term subalpine grassland ecosystem dynamics driven by agents of change that can be anticipated in the future and simulated by ecosystem models.

  10. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters

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    Sílvia N. M. Yanagi

    2011-12-01

    Full Text Available This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS and near-infrared (NIR spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (x up and to the reflectivity in the near-infrared spectral band (rNIR,up, a smaller sensitivity to the reflectivity in the visible spectral band (rVIS,up and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are Xup = 0.86, rVIS,up = 0.062 and rNIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.Este estudo avalia a sensibilidade do albedo da superfície pelo Simulador Integrado da Biosfera (IBIS a um conjunto de parâmetros que representam algumas propriedades arquitetônicas e óticas do dossel da floresta tropical Amazônica. Os parâmetros testados neste estudo são a orientação e refletância das folhas do dossel superior e inferior nas bandas espectrais do visível (VIS e infravermelho próximo (NIR. Os resultados são avaliados contra observações feitas no sítio K34 pertencente ao Instituto Nacional de Pesquisas da Amazônia (INPA na Reserva Biológica de Cuieiras. A análise de sensibilidade indica uma forte resposta aos parâmetros de orienta

  11. Phenology, Canopy Aging and Seasonal Carbon Balance as Related to Delayed Winter Pruning of Vitis vinifera L. cv. Sangiovese Grapevines.

    Science.gov (United States)

    Gatti, Matteo; Pirez, Facundo J; Chiari, Giorgio; Tombesi, Sergio; Palliotti, Alberto; Merli, Maria C; Poni, Stefano

    2016-01-01

    Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning (LWP) can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP) or late and very late winter pruning (LWP, VLWP) performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER) were followed throughout the season. Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs. 34 in SWP), highest maximum NCER/leaf area (+37% as compared to SWP) and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly cluster

  12. Phenology, canopy aging and seasonal carbon balance as related to delayed winter pruning of Vitis vinifera L. cv. Sangiovese grapevines

    Directory of Open Access Journals (Sweden)

    Matteo eGatti

    2016-05-01

    Full Text Available Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP or late and very late winter pruning (LWP, VLWP performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER was followed throughout the season.Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs 34 in SWP, highest maximum NCER/leaf area (+37% as compared to SWP and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly

  13. Organized turbulent motions in a hedgerow vineyard: effect of evolving canopy structure

    Science.gov (United States)

    Vendrame, Nadia; Tezza, Luca; Tha Paw U, Kyaw; Pitacco, Andrea

    2017-04-01

    Vegetation-atmosphere exchanges are determined by functional and structural properties of the plants together with environmental forcing. However, a fundamental aspect is the interaction of the canopy with the lower atmosphere. The vegetation deeply alters the composition and physical properties of the air flow, exchanging energy, matter and momentum with it. These processes take place in the bottom part of the atmospheric boundary layer where turbulence is the main mechanism transporting within-canopy air towards the mid- and upper atmospheric boundary layer and vice versa. Canopy turbulence is highly influenced by vegetation drag elements, determining the vertical profile of turbulent moments within the canopy. Canopies organized in rows, like vineyards, show peculiar turbulent transport dynamics. In addition, the morphological structure (phenology) of the vineyard is greatly variable seasonally, shifting from an empty canopy during vine dormancy to dense foliage in summer. The understanding of the canopy ventilation regime is related to several practical applications in vineyard management. For example, within-canopy turbulent motion is very important to predict small particles dispersion, like fungal spores, and minimize infection studying the effect on leaf wetness duration. Our study aims to follow the continuous evolution of turbulence characteristics and canopy structure during the growing season of a hedgerow vineyard, from bud break to fully developed canopy. The field experiment was conducted in a flat extensive vineyard in North-Eastern Italy, using a vertical array of five synchronous sonic anemometers within and above the canopy. Turbulent flow organization was greatly influenced by canopy structure. Turbulent coherent structures involved in momentum transport have been investigated using the classical quadrant analysis and a novel approach to identify dominant temporal scales. Momentum transport in the canopy was dominated by downward gusts showing

  14. Weak Environmental Controls of Tropical Forest Canopy Height in the Guiana Shield

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    Youven Goulamoussène

    2016-09-01

    Full Text Available Canopy height is a key variable in tropical forest functioning and for regional carbon inventories. We investigate the spatial structure of the canopy height of a tropical forest, its relationship with environmental physical covariates, and the implication for tropical forest height variation mapping. Making use of high-resolution maps of LiDAR-derived Digital Canopy Model (DCM and environmental covariates from a Digital Elevation Model (DEM acquired over 30,000 ha of tropical forest in French Guiana, we first show that forest canopy height is spatially correlated up to 2500 m. Forest canopy height is significantly associated with environmental variables, but the degree of correlation varies strongly with pixel resolution. On the whole, bottomland forests generally have lower canopy heights than hillslope or hilltop forests. However, this global picture is very noisy at local scale likely because of the endogenous gap-phase forest dynamic processes. Forest canopy height has been predictively mapped across a pixel resolution going from 6 m to 384 m mimicking a low resolution case of 3 points·km − 2 . Results of canopy height mapping indicated that the error for spatial model with environment effects decrease from 8.7 m to 0.91 m, depending of the pixel resolution. Results suggest that, outside the calibration plots, the contribution of environment in shaping the global canopy height distribution is quite limited. This prevents accurate canopy height mapping based only on environmental information, and suggests that precise canopy height maps, for local management purposes, can only be obtained with direct LiDAR monitoring.

  15. Thermal Imaging of Forest Canopy Temperatures: Relationships with Biological and Biophysical Drivers and Ecosystem Fluxes

    Science.gov (United States)

    Still, C. J.; Kim, Y.; Hanson, C. V.; Law, B. E.; Kwon, H.; Schulze, M.; Pau, S.; Detto, M.

    2015-12-01

    Temperature is a primary environmental control on plant processes at a range of spatial and temporal scales, affecting enzymatic reactions, ecosystem biogeochemistry, and species distributions. Although most focus is on air temperature, the radiative or skin temperature of plants is more relevant. Canopy skin temperature dynamics reflect biophysical, physiological, and anatomical characteristics and interactions with environmental drivers, and can be used to examine forest responses to stresses like droughts and heat waves. Direct measurements of plant canopy temperatures using thermocouple sensors have been challenging and offer limited information. Such measurements are usually conducted over short periods of time and a limited spatial extent of the canopy. By contrast, thermal infrared (TIR) imaging allows for extensive temporal and spatial measurement of canopy temperature regimes. We present results of TIR imaging of forest canopies at a range of well-studied forest sites in the United States and Panama. These forest types include temperate rainforests, a semi­arid pine forest, and a semi­deciduous tropical forest. Canopy temperature regimes at these sites are highly variable spatially and temporally and display frequent departures from air temperature, particularly during clear sky conditions. Canopy tissue temperatures are often warmer (daytime) and colder (nighttime) than air temperature, and canopy structure seems to have a large influence on the thermal regime. Additionally, comparison of canopy temperatures to eddy covariance fluxes of carbon dioxide, water vapor, and energy reveals relationships not apparent using air temperature. Initial comparisons between our forest canopy temperatures and remotely sensed skin temperature using Landsat and MODIS data show reasonably good agreement. We conclude that temporal and spatial changes in canopy temperature and its relationship to biological and environmental factors can improve our understanding of how

  16. Mercury bioaccumulation in fishes from subalpine lakes of the Wallowa-Whitman National Forest, northeastern Oregon and western Idaho

    Science.gov (United States)

    Eagles-Smith, Collin A.; Herring, Garth; Johnson, Branden L.; Graw, Rick

    2013-01-01

    Mercury (Hg) is a globally distributed pollutant that poses considerable risks to human and wildlife health. Over the past 150 years since the advent of the industrial revolution, approximately 80 percent of global emissions have come from anthropogenic sources, largely fossil fuel combustion. As a result, atmospheric deposition of Hg has increased by up to 4-fold above pre-industrial times. Because of their isolation, remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited Hg through freshwater food webs, as well as for evaluating the relative importance of Hg loading versus landscape influences on Hg bioaccumulation. The increase in Hg deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in Hg emissions may propagate to changes in Hg bioaccumulation and ecological risk. In this study, we evaluated Hg concentrations in fishes of high-elevation, sub-alpine lakes in the Wallowa-Whitman National Forest in northeastern Oregon and western Idaho. Our goals were to (1) assess the magnitude of Hg contamination in small-catchment lakes to evaluate the risk of atmospheric Hg to human and wildlife health, (2) quantify the spatial variability in fish Hg concentrations, and (3) determine the ecological, limnological, and landscape factors that are best correlated with fish total mercury (THg) concentrations in these systems. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. Importantly, our top statistical model explained 87 percent of the variability in fish THg concentrations among lakes with four key landscape and limnological variables— catchment conifer density (basal area of conifers within a lake’s catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. The basal area of conifers

  17. Effect of pre-bloom leaf removal on grape aroma composition and wine sensory profile of Semillon cultivar.

    Science.gov (United States)

    Alessandrini, Massimiliano; Battista, Fabrizio; Panighel, Annarita; Flamini, Riccardo; Tomasi, Diego

    2017-08-26

    Early leaf removal at pre-bloom is an innovative viticultural practice for regulating yield components and improving grape quality. The effects of this technique on vine performance, grape composition and wine sensory profile of Semillon variety were assessed. Pre-bloom leaf removal enhanced canopy porosity, total soluble solids in musts and reduced cluster compactness. This practice had a strong effect on glycoside aroma precursors, in particular by increasing glycoside terpenols and norisoprenoids. Metabolites of linalool were the most responsive to leaf removal. Wine produced from defoliated vines was preferred in tasting trials for its more intense fruity notes and mouthfeel attributes. Pre-bloom leaf removal is a powerful technique for modifying canopy microclimate, vine yield, grape composition and wine quality. The increase of glycoside aroma compounds in treated grapes has potential positive effect in improving the sensory profile of the resulting wines. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  18. [Study on spectral reflectance characteristics of hemp canopies].

    Science.gov (United States)

    Tian, Yi-Chen; Jia, Kun; Wu, Bing-Fang; Li, Qiang-Zi

    2010-12-01

    Hemp (Cannabis sativa L.) is a special economic crop and widely used in many field. It is significative for the government to master the information about planting acreage and spatial distribution of hemp for hemp industrial policy decision in China. Remote sensing offers a potential way of monitoring large area for the cultivation of hemp. However, very little study on the spectral properties of hemp is available in the scientific literature. In the present study, the spectral reflectance characteristics of hemp canopy were systematically analyzed based on the spectral data acquired with ASD FieldSpec portable spectrometer. The wavebands and its spectral resolution for discriminating hemp from other plants were identified using difference analysis. The major differences in canopy reflectance of hemp and other plants were observed near 530, 552, 734, 992, 1 213, 1 580 and 2 199 nm, and the maximal difference is near 734 nm. The spectral resolution should be 30 nm or less in visible and near infrared regions, and 50 nm or less in middle infrared regions.

  19. Validating spatial structure in canopy water content using geostatistics

    Science.gov (United States)

    Sanderson, E. W.; Zhang, M. H.; Ustin, S. L.; Rejmankova, E.; Haxo, R. S.

    1995-01-01

    Heterogeneity in ecological phenomena are scale dependent and affect the hierarchical structure of image data. AVIRIS pixels average reflectance produced by complex absorption and scattering interactions between biogeochemical composition, canopy architecture, view and illumination angles, species distributions, and plant cover as well as other factors. These scales affect validation of pixel reflectance, typically performed by relating pixel spectra to ground measurements acquired at scales of 1m(exp 2) or less (e.g., field spectra, foilage and soil samples, etc.). As image analysis becomes more sophisticated, such as those for detection of canopy chemistry, better validation becomes a critical problem. This paper presents a methodology for bridging between point measurements and pixels using geostatistics. Geostatistics have been extensively used in geological or hydrogeolocial studies but have received little application in ecological studies. The key criteria for kriging estimation is that the phenomena varies in space and that an underlying controlling process produces spatial correlation between the measured data points. Ecological variation meets this requirement because communities vary along environmental gradients like soil moisture, nutrient availability, or topography.

  20. A coupled energy transport and hydrological model for urban canopies

    Science.gov (United States)

    Wang, Z.; Bou-Zeid, E.; Smith, J. A.

    2011-12-01

    Urban land-atmosphere interaction has been attracting more research efforts in order to understand the complex physics of flow and mass and heat transport in urban surfaces and the lower urban atmosphere. In this work, we developed and implemented a new physically-based single-layer urban canopy model, coupling the surface exchange of energy and the subsurface transport of water/soil moisture. The new model incorporates sub-facet heterogeneity for each urban surface (roof, wall or ground). This better simulates the energy transport in urban canopy layers, especially over low-intensity built (suburban type) terrains that include a significant fraction of vegetated surfaces. We implemented detailed urban hydrological models for both natural terrains (bare soil and vegetation) and porous engineered materials with water-holding capacity (concrete, gravel, etc). The skill of the new scheme was tested against experimental data collected through a wireless sensor network deployed over the campus of Princeton University. The model performance was found to be robust and insensitive to changes in weather conditions or seasonal variability. Predictions of the volumetric soil water content were also in good agreement with field measurements, highlighting the model capability of capturing subsurface water transport for urban lawns. The new model was also applied to a case study assessing different strategies, i.e. white versus green roofs, in the mitigation of urban heat island effect.

  1. Vegetation canopy discrimination and biomass assessment using multipolarized airborne SAR

    Science.gov (United States)

    Ulaby, F. T.; Dobson, M. C.; Held, D. N.

    1985-01-01

    Multipolarized airborne Synthetic Aperture Radar (SAR) data were acquired over a largely agricultural test site near Macomb, Illinois, in conjunction with the Shuttle Imaging Radar (SIR-B) experiment in October 1984. The NASA/JPL L-band SAR operating at 1.225 GHz made a series of daily overflights with azimuth view angles both parallel and orthogonal to those of SIR-B. The SAR data was digitally recorded in the quadpolarization configuration. An extensive set of ground measurements were obtained throughout the test site and include biophysical and soil measurements of approximately 400 agricultural fields. Preliminary evaluation of some of the airborne SAR imagery indicates a great potential for crop discrimination and assessment of canopy condition. False color composites constructed from the combination of three linear polarizations (HH, VV, and HV) were found to be clearly superior to any single polarization for purposes of crop classification. In addition, an image constructed using the HH return to modulate intensity and the phase difference between HH and VV returns to modulate chroma indicates a clear capability for assessment of canopy height and/or biomass. In particular, corn fields heavily damaged by infestations of corn borer are readily distinguished from noninfested fields.

  2. Phylogenetic Structure of Foliar Spectral Traits in Tropical Forest Canopies

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    Kelly M. McManus

    2016-02-01

    Full Text Available The Spectranomics approach to tropical forest remote sensing has established a link between foliar reflectance spectra and the phylogenetic composition of tropical canopy tree communities vis-à-vis the taxonomic organization of biochemical trait variation. However, a direct relationship between phylogenetic affiliation and foliar reflectance spectra of species has not been established. We sought to develop this relationship by quantifying the extent to which underlying patterns of phylogenetic structure drive interspecific variation among foliar reflectance spectra within three Neotropical canopy tree communities with varying levels of soil fertility. We interpreted the resulting spectral patterns of phylogenetic signal in the context of foliar biochemical traits that may contribute to the spectral-phylogenetic link. We utilized a multi-model ensemble to elucidate trait-spectral relationships, and quantified phylogenetic signal for spectral wavelengths and traits using Pagel’s lambda statistic. Foliar reflectance spectra showed evidence of phylogenetic influence primarily within the visible and shortwave infrared spectral regions. These regions were also selected by the multi-model ensemble as those most important to the quantitative prediction of several foliar biochemical traits. Patterns of phylogenetic organization of spectra and traits varied across sites and with soil fertility, indicative of the complex interactions between the environmental and phylogenetic controls underlying patterns of biodiversity.

  3. Effects of kelp forest removal on associated fish assemblages in central California

    Science.gov (United States)

    Bodkin, James L.

    1988-01-01

    Visual surveys along subtidal belt transects were used to compare fish assemblages on an experimental and a control site before and after the removal of a canopy-forming kelp forest. The giant kelp Macrocystis pyrifera (L.) C.A. Agardh was removed at the holdfast from approximately equals 1 ha of high relief structurally complex rock substratum. The abundance of seven species of fish, of which five were considered midwater species, significantly declined after the kelp was removed. Results indicate that the presence of a giant kelp forest may increase the abundance and species diversity of the fish assemblages over a high relief rocky reef in central California, U.S.A.

  4. The impact of urban canopy meteorological forcing on summer photochemistry

    Science.gov (United States)

    Huszár, Peter; Karlický, Jan; Belda, Michal; Halenka, Tomáš; Pišoft, Petr

    2018-03-01

    The regional climate model RegCM4.4, including the surface model CLM4.5, was offline coupled to the chemistry transport model CAMx version 6.30 in order to investigate the impact of the urban canopy induced meteorological changes on the longterm summer photochemistry over central Europe for the 2001-2005 period. First, the urban canopy impact on the meteorological conditions was calculated performing a reference experiment without urban landsurface considered and an experiment with urban surfaces modeled with the urban parameterization within the CLM4.5 model. In accordance with expectations, strong increases of urban surface temperatures (up to 2-3 K), decreases of wind speed (up to -1 ms-1) and increases of vertical turbulent diffusion coefficient (up to 60-70 m2s-1) were found. For the impact on chemistry, these three components were considered. Additionally, we accounted for the effect of temperature enhanced biogenic emission increase. Several experiments were performed by adding these effects one-by-one to the total impact: i.e., first, only the urban temperature impact was considered driving the chemistry model; secondly, the wind impact was added and so on. We found that the impact on biogenic emission account for minor changes in the concentrations of ozone (O3), oxides of nitrogen NOx = NO + NO2 and nitric acid (HNO3). On the other hand, the dominating component acting is the increased vertical mixing, resulting in up to 5 ppbv increase of urban ozone concentrations while causing -2 to -3 ppbv decreases and around 1 ppbv increases of NOx and HNO3 surface concentrations, respectively. The temperature impact alone results in reduction of ozone, increase in NO, decrease in NO2 and increases of HNO3. The wind impact leads, over urban areas, to ozone decreases, increases of NOx and a slight increase in HNO3. The overall impact is similar to the impact of increased vertical mixing alone. The Process Analysis (PA) technique implemented in CAMx was adopted to

  5. Simulations of tropical rainforest albedo: is canopy wetness important?

    Directory of Open Access Journals (Sweden)

    Silvia N.M. Yanagi

    2011-12-01

    Full Text Available Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.A informação precisa do albedo superficial é essencial para a modelagem climática, especialmente para regiões, tais como a Amazônia, onde a resposta da circulação atmosférica regional às mudanças do albedo superficial é forte. Estudos preliminares têm indicado que os modelos ainda não são capazes de reproduzir corretamente os detalhes da variação sazonal do albedo superficial. Portanto, investigou-se o papel do molhamento foliar sobre o albedo simulado de uma floresta tropical por meio da modificação do código de transferência radiativa no dossel do IBIS para incorporar os efeitos do molhamento do dossel sobre a refletância da vegetação. Neste estudo, procederamse simulações usando três versões do modelo superf

  6. Forest canopy water fluxes can be estimated using canopy structure metrics derived from airborne light detection and ranging (LiDAR)

    DEFF Research Database (Denmark)

    Schumacher, Johannes; Christiansen, Jesper Riis

    2015-01-01

    Forests contribute to improve water quality, affect drinking water resources, and therefore influence water supply on a regional level. The forest canopy structure affects the retention of precipitation (Pr) in the canopy and hence the amount of water transferred to the forest floor termed canopy...... throughfall (TF). We investigated the possibilities of estimating TF based on bulk Pr and canopy structure estimated from airborne light detection and ranging (LiDAR) data. Bulk Pr and TF fluxes combined with airborne LiDAR data from 11 locations representing the most common forest types (mono......-species broadleaf/coniferous and mixed forests) in Denmark were used to develop empirical models to estimate TF on a monthly, seasonal, and annual basis. This new approach offers the opportunity to greatly improve predictions of TF on catchment wide scales. Overall, results show that TF can be estimated by Pr...

  7. An empirical model that uses light attenuation and plant nitrogen status to predict within-canopy nitrogen distribution and upscale photosynthesis from leaf to whole canopy.

    Science.gov (United States)

    Louarn, Gaëtan; Frak, Ela; Zaka, Serge; Prieto, Jorge; Lebon, Eric

    2015-10-03

    Modelling the spatial and temporal distribution of leaf nitrogen (N) is central to specify photosynthetic parameters and simulate canopy photosynthesis. Leaf photosynthetic parameters depend on both local light availability and whole-plant N status. The interaction between these two levels of integration has generally been modelled by assuming optimal canopy functioning, which is not supported by experiments. During this study, we examined how a set of empirical relationships with measurable parameters could be used instead to predict photosynthesis at the leaf and whole-canopy levels. The distribution of leaf N per unit area (Na) within the canopy was related to leaf light irradiance and to the nitrogen nutrition index (NNI), a whole-plant variable accounting for plant N status. Na was then used to determine the photosynthetic parameters of a leaf gas exchange model. The model was assessed on alfalfa canopies under contrasting N nutrition and with N2-fixing and non-fixing plants. Three experiments were carried out to parameterize the relationships between Na, leaf irradiance, NNI and photosynthetic parameters. An additional independent data set was used for model evaluation. The N distribution model showed that it was able to predict leaf N on the set of leaves tested. The Na at the top of the canopy appeared to be related linearly to the NNI, whereas the coefficient accounting for N allocation remained constant. Photosynthetic parameters were related linearly to Na irrespective of N nutrition and the N acquisition mode. Daily patterns of gas exchange were simulated accurately at the leaf scale. When integrated at the whole-canopy scale, the model predicted that raising N availability above an NNI of 1 did not result in increased net photosynthesis. Overall, the model proposed offered a solution for a dynamic coupling of leaf photosynthesis and canopy N distribution without requiring any optimal functioning hypothesis. Published by Oxford University Press on

  8. A polar grid estimator of forest canopy structure metrics using airborne laser scanning data

    Science.gov (United States)

    Nicholas R. Vaughn; Greg P. Asner; Christian P. Giardina

    2013-01-01

    The structure of a forest canopy is the key determinant of light transmission, use and understory availability. Airborne light detection and ranging (LiDAR) has been used successfully to measure multiple canopy structural properties, thereby greatly reducing the fieldwork required to map spatial variation in structure. However, lidar metrics to date do not reflect the...

  9. Integration of lidar and Landsat ETM+ data for estimating and mapping forest canopy height.

    Science.gov (United States)

    Andrew T. Hudak; Michael A. Lefsky; Warren B. Cohen; Mercedes Berterretche

    2002-01-01

    Light detection and ranging (LIDAR) data provide accurate measurements of forest canopy structure in the vertical plane; however, current LIDAR sensors have limited coverage in the horizontal plane. Landsat data provide extensive coverage of generalized forest structural classes in the horizontal plane but are relatively insensitive to variation in forest canopy height...

  10. Automated detection of branch dimensions in woody skeletons of leafless fruit tree canopies

    NARCIS (Netherlands)

    Bucksch, A.; Fleck, S.

    2009-01-01

    Light driven physiological processes of tree canopies need to be modelled based on detailed 3Dcanopy structure – we explore the possibilities offered by terrestrial LIDAR to automatically represent woody skeletons of leafless trees as a basis for adequate models of canopy structure. The automatic

  11. High-Resolution Forest Canopy Height Estimation in an African Blue Carbon Ecosystem

    Science.gov (United States)

    Lagomasino, David; Fatoyinbo, Temilola; Lee, Seung-Kuk; Simard, Marc

    2015-01-01

    Mangrove forests are one of the most productive and carbon dense ecosystems that are only found at tidally inundated coastal areas. Forest canopy height is an important measure for modeling carbon and biomass dynamics, as well as land cover change. By taking advantage of the flat terrain and dense canopy cover, the present study derived digital surface models (DSMs) using stereophotogrammetric techniques on high-resolution spaceborne imagery (HRSI) for southern Mozambique. A mean-weighted ground surface elevation factor was subtracted from the HRSI DSM to accurately estimate the canopy height in mangrove forests in southern Mozambique. The mean and H100 tree height measured in both the field and with the digital canopy model provided the most accurate results with a vertical error of 1.18-1.84 m, respectively. Distinct patterns were identified in the HRSI canopy height map that could not be discerned from coarse shuttle radar topography mission canopy maps even though the mode and distribution of canopy heights were similar over the same area. Through further investigation, HRSI DSMs have the potential of providing a new type of three-dimensional dataset that could serve as calibration/validation data for other DSMs generated from spaceborne datasets with much larger global coverage. HSRI DSMs could be used in lieu of Lidar acquisitions for canopy height and forest biomass estimation, and be combined with passive optical data to improve land cover classifications.

  12. Trait estimation in herbaceous plant assemblages from in situ canopy spectra

    NARCIS (Netherlands)

    Roelofsen, H.D.; Bodegom, van P.M.; Kooistra, L.; Witte, J.M.

    2013-01-01

    Estimating plant traits in herbaceous plant assemblages from spectral reflectance data requires aggregation of small scale trait variations to a canopy mean value that is ecologically meaningful and corresponds to the trait content that affects the canopy spectral signal. We investigated estimation

  13. Trait estimation in herbaceous plant assemblages from in situ canopy spectra.

    NARCIS (Netherlands)

    Roelofsen, H.D.; van Bodegom, P.M.; Kooistra, L.; Witte, J.P.M.

    2013-01-01

    Estimating plant traits in herbaceous plant assemblages from spectral reflectance data requires aggregation of small scale trait variations to a canopy mean value that is ecologically meaningful and corresponds to the trait content that affects the canopy spectral signal. We investigated estimation

  14. Effects of drought on mesophyll conductance and photosynthetic limitations at different tree canopy layers.

    Science.gov (United States)

    Cano, F Javier; Sánchez-Gómez, David; Rodríguez-Calcerrada, Jesús; Warren, Charles R; Gil, Luis; Aranda, Ismael

    2013-11-01

    In recent years, many studies have focused on the limiting role of mesophyll conductance (gm ) to photosynthesis (An ) under water stress, but no studies have examined the effect of drought on gm through the forest canopy. We investigated limitations to An on leaves at different heights in a mixed adult stand of sessile oak (Quercus petraea) and beech (Fagus sylvatica) trees during a moderately dry summer. Moderate drought decreased An of top and lowest beech canopy leaves much more than in leaves located in the mid canopy; whereas in oak, An of the lower canopy was decreased more than in sunlit leaves. The decrease of An was probably not due to leaf-level biochemistry given that VCmax was generally unaffected by drought. The reduction in An was instead associated with reduction in stomatal and mesophyll conductances. Drought-induced increases in stomatal limitations were largest in leaves from the top canopy, whereas drought-induced increases in mesophyll limitations were largest in leaves from the lowest canopy. Sensitivity analysis highlighted the need to decompose the canopy into different leaf layers and to incorporate the limitation imposed by gm when assessing the impact of drought on the gas exchange of tree canopies. © 2013 John Wiley & Sons Ltd.

  15. Piracy in the high trees: ectomycorrhizal fungi from an aerial 'canopy soil' microhabitat.

    Science.gov (United States)

    Orlovich, David A; Draffin, Suzy J; Daly, Robert A; Stephenson, Steven L

    2013-01-01

    The mantle of dead organic material ("canopy soil") associated with the mats of vascular and nonvascular epiphytes found on the branches of trees in the temperate rainforests along the southwestern coast of the South Island of New Zealand were examined for evidence of ectomycorrhizal fungi. DNA sequencing and cluster analysis were used to identify the taxa of fungi present in 74 root tips collected from the canopy soil microhabitat of three old growth Nothofagus menziesii trees in the South West New Zealand World Heritage Area. A diverse assemblage of ectomycorrhizal fungi was found to infect an extensive network of adventitious canopy roots of Nothofagus menziesii in this forest, including 14 phylotypes from nine genera of putative ectomycorrhizal fungi. Seven of the genera identified previously were known to form ectomycorrhizas with terrestrial roots of Nothofagus: Cortinarius, Russula, Cenococcum, Thelephora/Tomentella, Lactarius and Laccaria; two, Clavulina and Leotia, previously have not been reported forming ectomycorrhizas with Nothofagus. Canopy ectomycorrhizas provide an unexpected means for increased host nutrition that may have functional significance in some forest ecosystems. Presumably, canopy ectomycorrhizas on host adventitious roots circumvent the tree-ground-soil nutrient cycle by accessing a wider range of nutrients directly in the canopy than would be possible for non-mycorrhizal or arbuscular mycorrhizal canopy roots. In this system, both host and epiphytes would seem to be in competition for the same pool of nutrients in canopy soil.

  16. Comparing alternative tree canopy cover estimates derived from digital aerial photography and field-based assessments

    Science.gov (United States)

    Tracey S. Frescino; Gretchen G. Moisen

    2012-01-01

    A spatially-explicit representation of live tree canopy cover, such as the National Land Cover Dataset (NLCD) percent tree canopy cover layer, is a valuable tool for many applications, such as defining forest land, delineating wildlife habitat, estimating carbon, and modeling fire risk and behavior. These layers are generated by predictive models wherein their accuracy...

  17. Towards Automated Characterization of Canopy Layering in Mixed Temperate Forests Using Airborne Laser Scanning

    Directory of Open Access Journals (Sweden)

    Reik Leiterer

    2015-11-01

    Full Text Available Canopy layers form essential structural components, affecting stand productivity and wildlife habitats. Airborne laser scanning (ALS provides horizontal and vertical information on canopy structure simultaneously. Existing approaches to assess canopy layering often require prior information about stand characteristics or rely on pre-defined height thresholds. We developed a multi-scale method using ALS data with point densities >10 pts/m2 to determine the number and vertical extent of canopy layers (canopylayer, canopylength, seasonal variations in the topmost canopy layer (canopytype, as well as small-scale heterogeneities in the canopy (canopyheterogeneity. We first tested and developed the method on a small forest patch (800 ha and afterwards tested transferability and robustness of the method on a larger patch (180,000 ha. We validated the approach using an extensive set of ground data, achieving overall accuracies >77% for canopytype and canopyheterogeneity, and >62% for canopylayer and canopylength. We conclude that our method provides a robust characterization of canopy layering supporting automated canopy structure monitoring.

  18. The fauna and flora of a kelp bed canopy | Allen | African Zoology

    African Journals Online (AJOL)

    Since these organisms are mainly associated with the epiphytic algae they are most abundant amongst E. maxima in the shallower regions of the kelp bed. In such areas the biomass of the canopy fauna may exceed that of the relatively impoverished benthos, but further offshore the canopy fauna is insignificant in relation to ...

  19. ForestCrowns: a transparency estimation tool for digital photographs of forest canopies

    Science.gov (United States)

    Matthew Winn; Jeff Palmer; S.-M. Lee; Philip Araman

    2016-01-01

    ForestCrowns is a Windows®-based computer program that calculates forest canopy transparency (light transmittance) using ground-based digital photographs taken with standard or hemispherical camera lenses. The software can be used by forest managers and researchers to monitor growth/decline of forest canopies; provide input for leaf area index estimation; measure light...

  20. An integrated model of soil-canopy spectral radiances, photosynthesis, fluorescence, temperature and energy balance

    NARCIS (Netherlands)

    Tol, van der C.; Verhoef, W.; Timmermans, J.; Verhoef, A.; Su, Z.

    2009-01-01

    This paper presents the model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes), which is a vertical (1-D) integrated radiative transfer and energy balance model. The model links visible to thermal infrared radiance spectra (0.4 to 50 µm) as observed above the canopy to the fluxes of

  1. Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes

    Science.gov (United States)

    Xin, Q.; Gong, P.; Li, W.

    2015-02-01

    Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT) model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP) for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.

  2. Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes

    OpenAIRE

    Q. Xin; Gong, P.; W. Li

    2015-01-01

    Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we a...

  3. Analyzing transient closed chamber effects on canopy gas exchange for optimizing flux calculation timing

    NARCIS (Netherlands)

    Langensiepen, M.; Kupisch, M.; Wijk, van M.T.; Ewert, F.

    2012-01-01

    Transient type canopy chambers are still the only currently available practical solution for rapid screening of gas-exchange in agricultural fields. The technique has been criticized for its effect on canopy microclimate during measurement which affects the transport regime and regulation of plant

  4. Regional and historical factors supplement current climate in shaping global forest canopy height

    DEFF Research Database (Denmark)

    Zhang, Jian; Nielsen, Scott; Mao, Lingfeng

    2016-01-01

    Summary Canopy height is a key factor that affects carbon storage, vegetation productivity and biodiversity in forests, as well as an indicator of key processes such as biomass allocation. However, global variation in forest canopy height and its determinants are poorly known. We used global data...

  5. Fire frequency and tree canopy structure influence plant species diversity in a forest-grassland ecotone

    Science.gov (United States)

    David W. Peterson; Peter B. Reich

    2008-01-01

    Disturbances and environmental heterogeneity are two factors thought to influence plant species diversity, but their effects are still poorly understood in many ecosystems. We surveyed understory vegetation and measured tree canopy cover on permanent plots spanning an experimental fire frequency gradient to test fire frequency and tree canopy effects on plant species...

  6. 30 CFR 75.1710 - Canopies or cabs; diesel-powered and electric face equipment.

    Science.gov (United States)

    2010-07-01

    ...-powered and electric face equipment, including shuttle cars, be provided with substantially constructed... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Canopies or cabs; diesel-powered and electric... Miscellaneous § 75.1710 Canopies or cabs; diesel-powered and electric face equipment. In any coal mine where the...

  7. Ground-Based Robotic Sensing of an Agricultural Sub-Canopy Environment

    Science.gov (United States)

    Burns, A.; Peschel, J.

    2015-12-01

    Airborne remote sensing is a useful method for measuring agricultural crop parameters over large areas; however, the approach becomes limited to above-canopy characterization as a crop matures due to reduced visual access of the sub-canopy environment. During the growth cycle of an agricultural crop, such as soybeans, the micrometeorology of the sub-canopy environment can significantly impact pod development and reduced yields may result. Larger-scale environmental conditions aside, the physical structure and configuration of the sub-canopy matrix will logically influence local climate conditions for a single plant; understanding the state and development of the sub-canopy could inform crop models and improve best practices but there are currently no low-cost methods to quantify the sub-canopy environment at a high spatial and temporal resolution over an entire growth cycle. This work describes the modification of a small tactical and semi-autonomous, ground-based robotic platform with sensors capable of mapping the physical structure of an agricultural row crop sub-canopy; a soybean crop is used as a case study. Point cloud data representing the sub-canopy structure are stored in LAS format and can be used for modeling and visualization in standard GIS software packages.

  8. Seasonal Canopy Temperatures for Normal and Okra Leaf Cotton under Variable Irrigation in the Field

    Directory of Open Access Journals (Sweden)

    James R. Mahan

    2016-11-01

    Full Text Available Temperature affects a number of physiological factors in plants and is related to water use, yield and quality in many crop species. Seasonal canopy temperature, measured with infrared thermometers, is often used in conjunction with environmental factors (e.g., air temperature, humidity, solar radiation to assess crop stress and management actions in cotton. Normal and okra leaf shapes in cotton have been associated with differences in water use and canopy temperature. The okra leaf shape in cotton is generally expected to result in lower water use and lower canopy temperatures, relative to normal leaf, under water deficits. In this study canopy temperatures were monitored in okra and normal leaf varieties for a growing season at four irrigation levels. Differences in canopy temperature (<2 °C were measured between the two leaf shapes. As irrigation levels increased, canopy temperature differences between the leaf shapes declined. At the lowest irrigation level, when differences in sensible energy exchanges due to the okra leaf shape would be enhanced, the canopy temperature of the okra leaf was warmer than the normal leaf. This suggests that varietal differences that are not related to leaf shape may have more than compensated for leaf shape differences in the canopy temperature.

  9. Three-dimensional canopy fuel loading predicted using upward and downward sensing LiDAR systems

    Science.gov (United States)

    Nicholas S. Skowronski; Kenneth L. Clark; Matthew Duveneck; John. Hom

    2011-01-01

    We calibrated upward sensing profiling and downward sensing scanning LiDAR systems to estimates of canopy fuel loading developed from field plots and allometric equations, and then used the LiDAR datasets to predict canopy bulk density (CBD) and crown fuel weight (CFW) in wildfire prone stands in the New Jersey Pinelands. LiDAR-derived height profiles were also...

  10. Leaf-on canopy closure in broadleaf deciduous forests predicted during winter

    Science.gov (United States)

    Twedt, Daniel J.; Ayala, Andrea J.; Shickel, Madeline R.

    2015-01-01

    Forest canopy influences light transmittance, which in turn affects tree regeneration and survival, thereby having an impact on forest composition and habitat conditions for wildlife. Because leaf area is the primary impediment to light penetration, quantitative estimates of canopy closure are normally made during summer. Studies of forest structure and wildlife habitat that occur during winter, when deciduous trees have shed their leaves, may inaccurately estimate canopy closure. We estimated percent canopy closure during both summer (leaf-on) and winter (leaf-off) in broadleaf deciduous forests in Mississippi and Louisiana using gap light analysis of hemispherical photographs that were obtained during repeat visits to the same locations within bottomland and mesic upland hardwood forests and hardwood plantation forests. We used mixed-model linear regression to predict leaf-on canopy closure from measurements of leaf-off canopy closure, basal area, stem density, and tree height. Competing predictive models all included leaf-off canopy closure (relative importance = 0.93), whereas basal area and stem density, more traditional predictors of canopy closure, had relative model importance of ≤ 0.51.

  11. Daily cycle of Skewness and Kurtosis charateristics within and just above a crop canopy

    NARCIS (Netherlands)

    Jacobs, A.F.G.; Wiel, van de B.J.H.; Holtslag, A.A.M.

    2001-01-01

    A measurement program is carried out within as well as above a maize crop canopy. Statistical characteristics are analyzed for the velocity components as well as for temperature for a clear weather day as well as a cloudy day. During daytime it appears that the above and within-canopy

  12. A LiDAR method of canopy structure retrieval for wind modeling of heterogeneous forests

    DEFF Research Database (Denmark)

    Boudreault, Louis-Etienne; Bechmann, Andreas; Taryainen, Lasse

    2015-01-01

    The difficulty of obtaining accurate information about the canopy structure is a current limitation towards higher accuracy in numerical predictions of the wind field in forested terrain. The canopy structure in computational fluid dynamics is specified through the frontal area density...

  13. Nighttime exchange processes near the soil surface of a maize canopy

    NARCIS (Netherlands)

    Jacobs, A.F.G.; van Boxel, J.H.; Nieveen, J.

    1996-01-01

    The exchange process in the lower region of a maize canopy is analyzed for two nights. It appears that during calm nights a free convection state develops in the lower region of the canopy. Convective heat is released at the soil's surface and transported directly to the higher portion of the

  14. Secondary production of Gammarus pulex Linnaeus in small temperate streams that differ in riparian canopy cover

    NARCIS (Netherlands)

    Franken, R.J.M.; Gardeniers, J.J.P.; Peeters, E.T.H.M.

    2007-01-01

    Variation in the amount of riparian canopy cover affects bioenergetic processes in streams. Effects of canopy opening on environmental parameters including water temperature and the quality and quantity of food resources (leaf litter and/or associated biofilm) are likely to influence detritivore

  15. The 4-dimensional plant: effects of wind- induced canopy movement on light fluctuations and photosynthesis

    Directory of Open Access Journals (Sweden)

    Alexandra Jacquelyn Burgess

    2016-09-01

    Full Text Available Physical perturbation of a plant canopy brought about by wind is a ubiquitous phenomenon and yet its biological importance has often been overlooked. This is partly due to the complexity of the issue at hand: wind-induced movement (or mechanical excitation is a stochastic process which is difficult to measure and quantify; plant motion is dependent upon canopy architectural features which, until recently, were difficult to accurately represent and model in 3-dimensions; light patterning throughout a canopy is difficult to compute at high-resolutions, especially when confounded by other environmental variables. Recent studies have reinforced the expectation that canopy architecture is a strong determinant of productivity and yield; however, links between the architectural properties of the plant and its mechanical properties, particularly its response to wind, are relatively unknown. As a result, biologically relevant data relating canopy architecture, light dynamics and short-scale photosynthetic responses in the canopy setting are scarce. Here, we hypothesise that wind-induced movement will have large consequences for the photosynthetic productivity of our crops due to its influence on light patterning. To address this issue, in this study we combined high resolution 3D reconstructions of a plant canopy with a simple representation of canopy perturbation as a result of wind using solid body rotation in order to explore the potential effects on light patterning, interception and photosynthetic productivity. We looked at two different scenarios: firstly a constant distortion where a rice canopy was subject to a permanent distortion throughout the whole day; and secondly, a dynamic distortion, where the canopy was distorted in incremental steps between two extremes at set time points in the day. We find that mechanical canopy excitation substantially alters light dynamics; light distribution and modelled canopy carbon gain. We then discuss methods

  16. Effects of Tree Canopy Structure and Understory Vegetation on the Effectiveness of Open-Top-Chamber in Manipulating Boreal Forest Microclimate

    Science.gov (United States)

    Teuber, L. M.; Nilsson, M. C.; Wardle, D.; Dorrepaal, E.

    2014-12-01

    Open-top chambers (OTCs) are widely used to passively increase soil and air temperature in various open habitats, such as alpine and arctic tundra, and temperate grasslands. Several studies report warming effects of 1-2 °C in arctic and alpine tundra, and up to 6 °C in temperate grasslands. The variation between studies can be mostly attributed to differences in the abiotic environment, such as snow cover and solar irradiance. Vegetation height and openness affects the amount of irradiance that reaches the ground and may therefore indirectly impact the effectiveness of OTCs. The use of OTCs in forested ecosystems might therefore be limited by reduced canopy openness, while their effect on changes in soil temperature and soil moisture content might additionally be affected by the understory vegetation type and cover. Nevertheless, OTC's are an immensely useful tool in climate-change studies, and could benefit research in forest ecosystems. In this study we therefore investigated whether OTCs can be used to manipulate microclimate in the northern boreal forest and how tree canopy cover and understory vegetation influence OTC effects on air and soil temperature and on soil moisture content.We compared OTC effects at ten sites that were situated along a fire chronosequence in the northern boreal forest in Sweden. Sites were dominated by Pinus sylvestris and Picea abies, and time since the last fire ranged from 47-367 years, resulting in varying degrees of tree canopy openness. We applied full factorial combinations of OTC warming and dwarf shrub removal and moss removal at each site. We measured canopy cover using hemispherical photography; air and soil temperature as well as soil moisture were measured hourly from June until September. Preliminary analyses indicate that OTCs increased monthly mean air temperatures by up to 0.9 °C across all treatments and forest stands. However, the degree of warming showed clear relations with the presence or absence of the

  17. Mapping canopy gaps in an indigenous subtropical coastal forest using high resolution WorldView-2 data

    CSIR Research Space (South Africa)

    Malahlela, O

    2014-01-01

    Full Text Available Invasive species usually colonize canopy gaps in tropical and sub-tropical forests, which results in loss of native species. Therefore, an understanding of the location and distribution of canopy gaps will assist in predicting the occurrence...

  18. Hyperspectral data mining to identify relevant canopy spectral features for estimating durum wheat growth, nitrogen status, and yield

    Science.gov (United States)

    Modern hyperspectral sensors permit reflectance measurements of crop canopies in hundreds of narrow spectral wavebands. While these sensors describe plant canopy reflectance in greater detail than multispectral sensors, they also suffer from issues with data redundancy and spectral autocorrelation. ...

  19. Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: NLCD 2001 Tree Canopy

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set represents the mean percentage of tree canopy from the Canopy Layer of the National Land Cover Dataset 2001, (LaMotte and Wieczorek, 2010), compiled...

  20. The responses of light interception, photosynthesis and fruit yield of cucumber to LED-lighting within the canopy

    NARCIS (Netherlands)

    Trouwborst, G.; Oosterkamp, J.; Hogewoning, S.W.; Harbinson, J.; Ieperen, van W.

    2010-01-01

    Mathematical models of light attenuation and canopy photosynthesis suggest that crop photosynthesis increases by more uniform vertical irradiance within crops. This would result when a larger proportion of total irradiance is applied within canopies (interlighting) instead of from above (top

  1. Co-optimal Distribution of Leaf Nitrogen and Hydraulic Conductance in Plant Canopies

    Science.gov (United States)

    Peltoniemi, M.; Medlyn, B. E.; Duursma, R.

    2012-12-01

    Leaf properties vary significantly within plant canopies, due to the strong gradient in light availability through the canopy. Leaves near the canopy top have high nitrogen (N) and phosphorus content per unit leaf area, high leaf mass per area, and high photosynthetic capacity, compared to leaves deeper in the canopy. Variation of leaf properties has been explained by the optimal distribution of resources, particularly nitrogen, throughout the canopy. Studies of the optimal distribution of leaf nitrogen (N) within canopies have shown that, in the absence of other constraints, the optimal distribution of N is proportional to light. This is an important assumption in the big-leaf models of canopy photosynthesis and widely applied in current land-surface models. However, measurements have shown that the gradient of N in real canopies is shallower than the optimal distribution. One thing that has not yet been considered is how the constraints on water supply to leaves influence leaf properties in the canopy. Leaves with high stomatal conductance tend to have high stomatal conductance and transpiration rate, which suggests that for the the efficient operation of canopy, high light leaves should be serviced by more water. The rate of water transport depends on the hydraulic conductance of the soil-leaf pathway. We extend the work on optimal nitrogen gradients by considering the optimal co-allocation of nitrogen and water supply within plant canopies. We developed a simple "toy" two-leaf canopy model and optimised the distribution of N and hydraulic conductance (K) between the two leaves. We asked whether the hydraulic constraints to water supply can explain shallow N gradients in canopies. We found that the optimal N distribution within plant canopies is proportional to the light distribution only if hydraulic conductance is also optimally distributed. The optimal distribution of K is that where K and N are both proportional to incident light, such that optimal K is

  2. Changes of ndvi across vertical canopy layers in temperate deciduous forest during a litterfall period

    Science.gov (United States)

    Kim, J. M.; Ryu, Y.

    2015-12-01

    Normalized Difference Vegetation Index (NDVI) is a key variable indicating changes in vegetation dynamics and carbon flux. Previous studies have paid little attention to the changes in NDVI during litterfall period. In this study, we report the changes of NDVI across vertical canopy layers in a temperate deciduous forest during a litterfall period. To monitor changes in canopy structure, functions, and spectral properties during the litterfall period, we combined automatic observations of NDVI derived from LED-spectral sensors and LAI derived from digital cover photography installed at multiple canopy layer depths. Furthermore, we collected hyperspectral optical properties of leaves across multiple canopy layers and hyperspectral reflectance of forest background using ASD-FieldSpec. We found that NDVI in forest floor became greater than the NDVI measured from the top of canopy during the litterfall period. We discuss what satellite-derived NDVI exactly sees during the litterfall period, which will be useful to better understand forest autumn phenology at large scales.

  3. Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

    Science.gov (United States)

    Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

    2013-05-01

    diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

  4. Explaining the convector effect in canopy turbulence by means of large-eddy simulation

    Science.gov (United States)

    Banerjee, Tirtha; De Roo, Frederik; Mauder, Matthias

    2017-06-01

    Semi-arid forests are found to sustain a massive sensible heat flux in spite of having a low surface to air temperature difference by lowering the aerodynamic resistance to heat transfer (rH) - a property called the canopy convector effect (CCE). In this work large-eddy simulations are used to demonstrate that the CCE appears more generally in canopy turbulence. It is indeed a generic feature of canopy turbulence: rH of a canopy is found to reduce with increasing unstable stratification, which effectively increases the aerodynamic roughness for the same physical roughness of the canopy. This relation offers a sufficient condition to construct a general description of the CCE. In addition, we review existing parameterizations for rH from the evapotranspiration literature and test to what extent they are able to capture the CCE, thereby exploring the possibility of an improved parameterization.

  5. Explaining the convector effect in canopy turbulence by means of large-eddy simulation

    Directory of Open Access Journals (Sweden)

    T. Banerjee

    2017-06-01

    Full Text Available Semi-arid forests are found to sustain a massive sensible heat flux in spite of having a low surface to air temperature difference by lowering the aerodynamic resistance to heat transfer (rH – a property called the canopy convector effect (CCE. In this work large-eddy simulations are used to demonstrate that the CCE appears more generally in canopy turbulence. It is indeed a generic feature of canopy turbulence: rH of a canopy is found to reduce with increasing unstable stratification, which effectively increases the aerodynamic roughness for the same physical roughness of the canopy. This relation offers a sufficient condition to construct a general description of the CCE. In addition, we review existing parameterizations for rH from the evapotranspiration literature and test to what extent they are able to capture the CCE, thereby exploring the possibility of an improved parameterization.

  6. Coherence Effects in L-Band Active and Passive Remote Sensing of Quasi-Periodic Corn Canopies

    Science.gov (United States)

    Utku, Cuneyt; Lang, Roger H.

    2011-01-01

    Due to their highly random nature, vegetation canopies can be modeled using the incoherent transport theory for active and passive remote sensing applications. Agricultural vegetation canopies however are generally more structured than natural vegetation. The inherent row structure in agricultural canopies induces coherence effects disregarded by the transport theory. The objective of this study is to demonstrate, via Monte-Carlo simulations, these coherence effects on L-band scattering and thermal emission from corn canopies consisting of only stalks.

  7. Canopy tree species drive local heterogeneity in soil nitrogen availability in a lowland tropical forest

    Science.gov (United States)

    Osborne, B. B.; Nasto, M.; Asner, G. P.; Balzotti, C.; Cleveland, C. C.; Taylor, P.; Townsend, A. R.; Porder, S.

    2016-12-01

    The high phylogenetic and functional diversity of tree species in lowland tropical forests make field-based investigations of organismal influences on soil nutrient cycling challenging. Here, we used remotely-detected canopy nitrogen (N) data from the Carnegie Airborne Observatory to identify and characterize ¼ ha plots of a mature forest with either high or low canopy N on the Osa Peninsula in Costa Rica. Specifically we were interested in mechanisms by which foliar N might influence soil N, or the reverse. A non-dimensional scaling analysis suggested that high and low canopy N plots differ in their emergent (≥40 cm DBH) tree communities, though there were few putative N fixers in any of the plots. We found litterfall mass was similar beneath all canopies. However, mean DOC solubility of litter was 0.40% of dry biomass in low canopy N plots compared to 0.26% in high N plots. Additionally, litter leachate C:N was twice as high in litter from the low canopy N plots (61±1.4) compared with litter from the high N plots (30±1.4). We found strong positive correlations between canopy N and concentrations of soil KCl-extractable soil NO3- and net nitrification and net N mineralization rates (N=5; P<0.0001 in all cases). Under high canopy N, mean NO3-N concentrations were roughly an order of magnitude higher than beneath low N canopies (2.7±0.39 and 0.19±0.05, respectively). We hypothesize that differences in litter chemistry lead to differences in leachate quality that promote high soil N under canopies with high foliar N. Our findings suggest that remote sensing of foliar characteristics may offer an effective way to study spatial patterns in soil biogeochemistry in diverse tropical forests.

  8. Waveform- and Terrestrial Lidar Assessment of the Usual (Structural) Suspects in a Forest Canopy

    Science.gov (United States)

    van Aardt, J. A.; Romanczyk, P.; Kelbe, D.; van Leeuwen, M.; Cawse-Nicholson, K.; Gough, C. M.; Kampe, T. U.

    2015-12-01

    Forest inventory has evolved from standard stem diameter-height relationships, to coarse canopy metrics, to more involved ecologically-meaningful variables, such as leaf area index (LAI) and even canopy radiative transfer as a function of canopy gaps, leaf clumping, and leaf angle distributions. Accurate and precise measurement of the latter set of variables presents a challenge to the ecological and modeling communities; however, relatively novel remote sensing modalities, e.g., waveform lidar (wlidar) and terrestrial lidar systems (TLS), have the potential to adress this challenge. Research teams at Rochester Institute of Technology (RIT) and the Virginia Commonwealth University (VCU) have been collaborating with the National Ecological Observation Network (NEON) to assess vegetation canopy structure and variation at the University of Michigan Biological Research Station and the NEON Northeast domain (Harvard Forest, MA). Airborne small-footprint wlidar data, in-situ TLS data, and first-principles, physics-based simulation tools are being used to study (i) the impact of vegetation canopy geometric elements on wlidar signals (twigs and petioles have been deemed negligible), (ii) the analysis of airborne wlidar data for top-down assessment of canopy metrics such as LAI, and (iii) our ability to extract "bottom-up" canopy structure from TLS using scans registered to each other using a novel marker-free registration approach (e.g., basal area: R2=0.82, RMSE=7.43 m2/ha). Such studies indicate that we can potentially assess radiative transfer through vegetation canopies remotely using a vertically-stratified approach with wlidar, and augment such an approach via rapid-scan TLS technology to gain a better understanding of fine-scale variation in canopy structure. This in turn is key to quantifying and modeling radiative transfer based on understanding of forest canopy structural change as a function of ecosystem development, climate, and anthropogenic drivers.

  9. Predicting understorey structure from the presence and composition of canopies: an assembly rule for marine algae.

    Science.gov (United States)

    Irving, Andrew D; Connell, Sean D

    2006-06-01

    Assembly rules provide a useful framework for predicting patterns of community assembly under defined environmental conditions. Habitat created by canopy-forming algae (such as kelps) provides a promising system for identifying assembly rules because canopies typically have a large and predictable influence on understorey communities. Across >1,000 km of subtidal South Australian coastline, we identified natural associations between assemblages of understorey algae and (1) monospecific canopies of Ecklonia radiata, (2) canopies comprised of E. radiata mixed with Fucales (Cystophora spp. and Sargassum spp.), and (3) gaps among canopies of algae. We were able to recreate these associations with experimental tests that quantified the assembly of understorey algae among these three habitat types. We propose the assembly rule that understorey communities on subtidal rocky coast in South Australia will be (1) monopolised by encrusting coralline algae beneath monospecific canopies of E. radiata, (2) comprised of encrusting corallines, encrusting non-corallines, and sparse covers of articulated corallines, beneath mixed E. radiata-Fucales canopies, and (3) comprised of extensive covers of articulated corallines and filamentous turfs, as well as sparse covers of foliose algae and juvenile canopy-formers, within gaps. Consistencies between natural patterns and experimental effects demonstrate how algal canopies can act as a filter to limit the subsets of species from the locally available pool that are able to assemble beneath them. Moreover, the subsets of species that assemble to subtidal rocky substrata in South Australia appear to be predictable, given knowledge of the presence and composition of canopies incorporating E. radiata.

  10. The influence of current speed and vegetation density on flow structure in two macrotidal eelgrass canopies

    Science.gov (United States)

    Lacy, Jessica R.; Wyllie-Echeverria, Sandy

    2011-01-01

    The influence of eelgrass (Zostera marina) on near-bed currents, turbulence, and drag was investigated at three sites in two eelgrass canopies of differing density and at one unvegetated site in the San Juan archipelago of Puget Sound, Washington, USA. Eelgrass blade length exceeded 1 m. Velocity profiles up to 1.5 m above the sea floor were collected over a spring-neap tidal cycle with a downward-looking pulse-coherent acoustic Doppler profiler above the canopies and two acoustic Doppler velocimeters within the canopies. The eelgrass attenuated currents by a minimum of 40%, and by more than 70% at the most densely vegetated site. Attenuation decreased with increasing current speed. The data were compared to the shear-layer model of vegetated flows and the displaced logarithmic model. Velocity profiles outside the meadows were logarithmic. Within the canopies, most profiles were consistent with the shear-layer model, with a logarithmic layer above the canopy. However, at the less-dense sites, when currents were strong, shear at the sea floor and above the canopy was significant relative to shear at the top of the canopy, and the velocity profiles more closely resembled those in a rough-wall boundary layer. Turbulence was strong at the canopy top and decreased with height. Friction velocity at the canopy top was 1.5–2 times greater than at the unvegetated, sandy site. The coefficient of drag CD on the overlying flow derived from the logarithmic velocity profile above the canopy, was 3–8 times greater than at the unvegetated site (0.01–0.023 vs. 2.9 × 10−3).

  11. Analysis of coherent structures and atmosphere-canopy coupling strength during the CABINEX field campaign

    Directory of Open Access Journals (Sweden)

    A. L. Steiner

    2011-12-01

    Full Text Available Intermittent coherent structures can be responsible for a large fraction of the exchange between a forest canopy and the atmosphere. Quantifying their contribution to momentum and heat fluxes is necessary to interpret measurements of trace gases and aerosols within and above forest canopies. The primary objective of the Community Atmosphere-Biosphere Interactions Experiment (CABINEX field campaign (10 July 2009 to 9 August 2009 was to study the chemistry of volatile organic compounds (VOC within and above a forest canopy. In this manuscript we provide an analysis of coherent structures and canopy-atmosphere exchange during CABINEX to support in-canopy gradient measurements of VOC. We quantify the number and duration of coherent structure events and their percent contribution to momentum and heat fluxes with two methods: (1 quadrant-hole analysis, and (2 wavelet analysis. Despite differences in the duration and number of events, both methods predict that coherent structures contribute 40–50% to momentum fluxes and 44–65% to heat fluxes during the CABINEX campaign. Contributions associated with coherent structures are slightly greater under stable atmospheric conditions. By comparing heat fluxes within and above the canopy, we determine the degree of coupling between upper canopy and atmosphere, and find that they are coupled the majority of the time. Uncoupled canopy-atmosphere events occur in the early morning (4–8 a.m. local time approximately 30% of the time. This study confirms that coherent structures contribute significantly to the exchange of heat and momentum between the canopy and atmosphere at the CABINEX site, and indicates the need to include these transport processes when studying the mixing and chemical reactions of trace gases and aerosols between a forest canopy and the atmosphere.

  12. Analysis of coherent structures and atmosphere-canopy coupling strength during the CABINEX field campaign

    Science.gov (United States)

    Steiner, A. L.; Pressley, S. N.; Botros, A.; Jones, E.; Chung, S. H.; Edburg, S. L.

    2011-12-01

    Intermittent coherent structures can be responsible for a large fraction of the exchange between a forest canopy and the atmosphere. Quantifying their contribution to momentum and heat fluxes is necessary to interpret measurements of trace gases and aerosols within and above forest canopies. The primary objective of the Community Atmosphere-Biosphere Interactions Experiment (CABINEX) field campaign (10 July 2009 to 9 August 2009) was to study the chemistry of volatile organic compounds (VOC) within and above a forest canopy. In this manuscript we provide an analysis of coherent structures and canopy-atmosphere exchange during CABINEX to support in-canopy gradient measurements of VOC. We quantify the number and duration of coherent structure events and their percent contribution to momentum and heat fluxes with two methods: (1) quadrant-hole analysis, and (2) wavelet analysis. Despite differences in the duration and number of events, both methods predict that coherent structures contribute 40-50% to momentum fluxes and 44-65% to heat fluxes during the CABINEX campaign. Contributions associated with coherent structures are slightly greater under stable atmospheric conditions. By comparing heat fluxes within and above the canopy, we determine the degree of coupling between upper canopy and atmosphere, and find that they are coupled the majority of the time. Uncoupled canopy-atmosphere events occur in the early morning (4-8 a.m. local time) approximately 30% of the time. This study confirms that coherent structures contribute significantly to the exchange of heat and momentum between the canopy and atmosphere at the CABINEX site, and indicates the need to include these transport processes when studying the mixing and chemical reactions of trace gases and aerosols between a forest canopy and the atmosphere.

  13. ARSENIC REMOVAL BY IRON REMOVAL PROCESSES

    Science.gov (United States)

    Presentation will discuss the removal of arsenic from drinking water using iron removal processes that include oxidation/filtration and the manganese greensand processes. Presentation includes results of U.S. EPA field studies conducted in Michigan and Ohio on existing iron remo...

  14. Germination and establishment of Tillandsia eizii (Bromeliaceae) in the canopy of an oak forest in Chiapas, Mexico

    NARCIS (Netherlands)

    Toledo-Aceves, T.; Wolf, J.H.D.

    2008-01-01

    We assessed the effectiveness of repopulating the inner canopy and middle canopy of oak trees with seeds and seedlings of the epiphytic bromeliad Tillandsia eizii. Canopy germination was 4.7 percent, considerably lower than in vitro (92%). Of the tree-germinated seedlings, only 1.5 percent survived

  15. Multispectral determination of vegetative cover in corn crop canopy

    Science.gov (United States)

    Stoner, E. R.; Baumgardner, M. F.

    1972-01-01

    The relationship between different amounts of vegetative ground cover and the energy reflected by corn canopies was investigated. Low altitude photography and an airborne multispectral scanner were used to measure this reflected energy. Field plots were laid out, representing four growth stages of corn. Two plot locations were chosen-on a very dark and a very light surface soil. Color and color infrared photographs were taken from a vertical distance of 10 m. Estimates of ground cover were made from these photographs and were related to field measurements of leaf area index. Ground cover could be predicted from leaf area index measurements by a second order equation. Microdensitometry and digitzation of the three separated dye layers of color infrared film showed that the near infrared dye layer is most valuable in ground cover determinations. Computer analysis of the digitized photography provided an accurate method of determining precent ground cover.

  16. Marsh canopy structure changes and the Deepwater Horizon oil spill

    Science.gov (United States)

    Ramsey, Elijah W.; Rangoonwala, Amina; Jones, Cathleen E.

    2016-01-01

    Marsh canopy structure was mapped yearly from 2009 to 2012 in the Barataria Bay, Louisiana coastal region that was impacted by the 2010 Deepwater Horizon (DWH) oil spill. Based on the previously demonstrated capability of NASA's UAVSAR polarimetric synthetic aperture radar (PolSAR) image data to map Spartina alterniflora marsh canopy structure, structure maps combining the leaf area index (LAI) and leaf angle distribution (LAD, orientation) were constructed for yearly intervals that were directly relatable to the 2010 LAI-LAD classification. The yearly LAI-LAD and LAI difference maps were used to investigate causes for the previously revealed dramatic change in marsh structure from prespill (2009) to postspill (2010, spill cessation), and the occurrence of structure features that exhibited abnormal spatial and temporal patterns. Water level and salinity records showed that freshwater releases used to keep the oil offshore did not cause the rapid growth from 2009 to 2010 in marsh surrounding the inner Bay. Photointerpretation of optical image data determined that interior marsh patches exhibiting rapid change were caused by burns and burn recovery, and that the pattern of 2010 to 2011 LAI decreases in backshore marsh and extending along some tidal channels into the interior marsh were not associated with burns. Instead, the majority of 2010 to 2011 shoreline features aligned with vectors displaying the severity of 2010 shoreline oiling from the DWH spill. Although the association is not conclusive of a causal oil impact, the coexistent pattern is a significant discovery. PolSAR marsh structure mapping provided a unique perspective of marsh biophysical status that enhanced detection of change and monitoring of trends important to management effectiveness.

  17. Total canopy transmittance estimated from small-footprint, full-waveform airborne LiDAR

    Science.gov (United States)

    Milenković, Milutin; Wagner, Wolfgang; Quast, Raphael; Hollaus, Markus; Ressl, Camillo; Pfeifer, Norbert

    2017-06-01

    Canopy transmittance is a directional and wavelength-specific physical parameter that quantifies the amount of radiation attenuated when passing through a vegetation layer. The parameter has been estimated from LiDAR data in many different ways over the years. While early LiDAR methods treated each returned echo equally or weighted the echoes according to their return order, recent methods have focused more on the echo energy. In this study, we suggest a new method of estimating the total canopy transmittance considering only the energy of ground echoes. Therefore, this method does not require assumptions for the reflectance or absorption behavior of vegetation. As the oblique looking geometry of LiDAR is explicitly considered, canopy transmittance can be derived for individual laser beams and can be mapped spatially. The method was applied on a contemporary full-waveform LiDAR data set collected under leaf-off conditions and over a study site that contains two sub regions: one with a mixed (coniferous and deciduous) forest and another that is predominantly a deciduous forest in an alluvial plain. The resulting canopy transmittance map was analyzed for both sub regions and compared to aerial photos and the well-known fractional cover method. A visual comparison with aerial photos showed that even single trees and small canopy openings are visible in the canopy transmittance map. In comparison with the fractional cover method, the canopy transmittance map showed no saturation, i.e., there was better separability between patches with different vegetation structure.

  18. Ultrasonic and LIDAR sensors for electronic canopy characterization in vineyards: advances to improve pesticide application methods.

    Science.gov (United States)

    Llorens, Jordi; Gil, Emilio; Llop, Jordi; Escolà, Alexandre

    2011-01-01

    Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the use of ultrasonic and LIDAR sensors have been compared with the traditional manual and destructive canopy measurement procedure. For both methods the values of key parameters such as crop height, crop width, crop volume or leaf area have been compared. Obtained results indicate that an ultrasonic sensor is an appropriate tool to determine the average canopy characteristics, while a LIDAR sensor provides more accuracy and detailed information about the canopy. Good correlations have been obtained between crop volume (C(VU)) values measured with ultrasonic sensors and leaf area index, LAI (R(2) = 0.51). A good correlation has also been obtained between the canopy volume measured with ultrasonic and LIDAR sensors (R(2) = 0.52). Laser measurements of crop height (C(HL)) allow one to accurately predict the canopy volume. The proposed new technologies seems very appropriate as complementary tools to improve the efficiency of pesticide applications, although further improvements are still needed.

  19. Measuring the response of canopy emissivity spectra to leaf area index variation using thermal hyperspectral data

    Science.gov (United States)

    Neinavaz, Elnaz; Darvishzadeh, Roshanak; Skidmore, Andrew K.; Groen, Thomas A.

    2016-12-01

    One of the plant biophysical factors affecting the canopy spectral reflectance of plants in the optical domain to receive research attention in recent decades is leaf area index (LAI). Although it is expected that the value of LAI affects the emission of radiation, it not known how. To our knowledge, the effect of LAI on plant canopy emissivity spectra has not yet been investigated in the thermal infrared region (TIR 8-14 μm). The overall aim of this study was to demonstrate the effect of LAI on canopy emissivity spectra of different species at the nadir position. The 279 spectral wavebands in the TIR domain were measured under controlled laboratory condition using a MIDAC spectrometer for four plant species. The corresponding LAI of each measurement was destructively calculated. We found a positive correlation between canopy emissivity spectra at various LAI values, indicating that emissivity increases concomitantly with LAI value. The canopy emissivity spectra of the four species were found to be statistically different at various wavebands even when the LAI values of the species were similar. It seems that other biophysical or biochemical factors also contribute to canopy emissivity spectra: this merits further investigation. We not only quantify the role of LAI on canopy emissivity spectra for the first time, but also demonstrate the potential of using hyperspectral thermal data to estimate LAI of plant species.

  20. Surface renewal analysis to obtain sensible heat flux in rice, maize and soybean canopies

    Science.gov (United States)

    Maruyama, A.; Paw U, K.; Snyder, R. L.

    2013-12-01

    The thermal environment in the plant canopy affects plants' growth processes such as flowering and ripening. High temperatures often cause grain sterility and poor filling, and reduce crop production in tropical and temperate regions. With global warming predicted, these effects have become a major concern worldwide. In this study, surface renewal analysis, which is a novel method for estimating scalar fluxes, was applied to rice, maize and soybean canopies to understand the dynamics of sensible heat in crop canopies. Surface renewal analysis has advantages of (1) lower cost of equipment, (2) a shorter fetch requirement and (3) less disturbance in the field. The temperature of the atmosphere (T) at multiple heights was measured at 10 Hz with fine-wire thermocouples to calculate sensible heat flux (H) from the ramp pattern of T. Variations in H determined from the T measurements at canopy top was from -80 to 120 Wm-2 for rice, and it showed reasonable diurnal variation. However, H values determined from the T measurements within the canopies were smaller because of differences in temperature ramp frequency with height. These results suggest that not all turbulent structures penetrate deeply into canopies. The results for rice, maize and soybean canopies will be presented at the meeting.

  1. Diet After Gallbladder Removal

    Science.gov (United States)

    ... keep having diarrhea. Is there a gallbladder removal diet I should follow? Answers from Katherine Zeratsky, R. ... months. There isn't a specific gallbladder removal diet that you should follow, but there are a ...

  2. Canopy Stomatal Conductance Unlocks Partitioning of Ecosystem-Atmosphere Carbon and Water Exchanges

    Science.gov (United States)

    Wehr, R. A.; Munger, J. W.; McManus, J. B.; Nelson, D. D.; Zahniser, M. S.; Davidson, E. A.; Wofsy, S. C.; Saleska, S. R.

    2016-12-01

    Stomata are a key nexus in biosphere-atmosphere interactions: the gateway for both carbon gain and water loss by plant canopies. Accurate quantification of canopy stomatal conductance enables partitioning of both evapotranspiration (ET) and net ecosystem-atmosphere CO2 exchange (NEE)—the latter via CO2 isotope flux measurements. To those ends, we determined the behavior of canopy stomatal conductance in a temperate deciduous forest based on heat and water vapor flux measurements, and validated that determination based on uptake of carbonyl sulfide, which also passes through the stomata. We found that the canopy stomatal conductance followed a simple empirical function of leaf area index, light intensity, diffuse light fraction, and leaf-air water vapor gradient. The dependence on light intensity was highly linear, in contrast to the leaf scale, and in contrast to the behavior of canopy photosynthesis. Using canopy stomatal conductance, we partitioned ET and found that evaporation in this ecosystem peaks at the time of the year when soils are driest and atmospheric vapor pressure deficit is low—because soil temperature is an important driver. As stomatal conductance impacts not only the rate of photosynthesis but also the fractionation of carbon isotopes by photosynthesis, we were also able to combine canopy stomatal conductance with CO2 isotope flux measurements in order to partition NEE. We found that: (1) canopy respiration is much less during the day than at night, likely due to the inhibition of leaf respiration by light (that is, the Kok effect), and (2) canopy photosynthetic light-use efficiency does not decline through the summer, in contrast to standard estimates. These results clarify how leaf-level physiological dynamics impact ecosystem-atmosphere gas exchange, and demonstrate the utility of combining multiple tracers to constrain the processes underlying that exchange.

  3. Stochastic Transport Theory for Investigating the Three-Dimensional Canopy Structure from Space Measurements

    Science.gov (United States)

    Huang, Dong; Knyazikhin, Yuri; Wang, Weile; Deering, Donald W,; Stenberg, Pauline; Shabanov, Nikolay; Tan, Bin; Myneni, Ranga B.

    2008-01-01

    Radiation reflected from vegetation canopies exhibits high spatial variation. Satellite-borne sensors measure the mean intensities emanating from heterogeneous vegetated pixels. The theory of radiative transfer in stochastic media provides the most logical linkage between satellite observations and the three-dimensional canopy structure through a closed system of simple equations which contains the mean intensity and higher statistical moments directly as its unknowns. Although this theory has been a highly active research field in recent years, its potential for satellite remote sensing of vegetated surfaces has not been fully realized because of the lack of models of a canopy pair-correlation function that the stochastic radiative transfer equations require. The pair correlation function is defined as the probability of finding simultaneously phytoelements at two points. This paper presents analytical and Monte Carlo generated pair correlation functions. Theoretical and numerical analyses show that the spatial correlation between phytoelements is primarily responsible for the effects of the three-dimensional canopy structure on canopy reflective and absorptive properties. The pair correlation function, therefore, is the most natural and physically meaningful measure of the canopy structure over a wide range of scales. The stochastic radiative transfer equations naturally admit this measure and thus provide a powerful means to investigate the three-dimensional canopy structure from space. Canopy reflectances predicted by the stochastic equations are assessed by comparisons with the PARABOLA measurements from coniferous and broadleaf forest stands in the BOREAS Southern Study Areas. The pair correlation functions are derived from data on tree structural parameters collected during field campaigns conducted at these sites. The simulated canopy reflectances compare well with the PARABOLA data.

  4. Multidisciplinary Research on Canopy Photosynthetic Productivity in a Cool-Temperate Deciduous Broadleaf Forest in Japan

    Science.gov (United States)

    Muraoka, H.; Noda, H. M.; Saitoh, T. M.; Nagai, S.

    2014-12-01

    Forest canopy has crucial roles in regulating energy and material exchange between the atmosphere and terrestrial ecosystems and in ecological processes with respect to carbon cycle and growth in the ecosystems. Challenges to the canopy of tall forests for such research involve the access to the leaves for ecophysiological observations, responses of leaves to the changing environments from seconds to years, and up-scaling the leaf-level phenomena to canopy and landscape-levels. A long-term, multidisciplinary approach has been conducted in a cool-temperate deciduous broadleaf forest in Takayama site (ca. 1400m a.s.l.) in central Japan. This forest canopy is dominated by Quercus crispula and Betula ermanii. We have been focusing on the phenology of photosynthetic productivity from a single leaf to canopy, and to landscape level, by combining leaf ecophysiological research, optical observations by spectroradiometers and time-laps cameras with the aid of "Phenological Eyes Network (PEN)", and process-based modellings. The canopy-level photosynthesis is then compared with the micrometeorolgical observation of CO2 flux at the site. So far we have been clarifying that (1) inter-annual variations in seasonal growth rate and senescence rate of leaf photosynthetic capacity and canopy leaf area are largely responsible for the inter-annual change in forest photosynthesis, and (2) spectral vegetation indices such as enhanced vegetation index (EVI) and chlorophyll index (CCI) can be the indicator to observe the phenology of forest canopy photosynthesis. In addition to these efforts since 2003, we established an open-field warming experiment on the branches of the canopy trees, to investigate the possible influence of temperature increase on leaf photosynthetic and optical properties and then to examine whether the optical satellite remote sensing can detect the changes in photosynthetic capacity and phenology by ongoing global warming.

  5. Dry deposition profile of small particles within a model spruce canopy

    Energy Technology Data Exchange (ETDEWEB)

    Ould-Dada, Zitouni [Centre for Analytical Research in the Environment, (now EAS T.H. Huxley School), Imperial College of Science Technology and Medicine, Silwood Park, Ascot, SL57TE Berkshire (United Kingdom)

    2002-03-08

    Data on dry deposition of 0.82 {mu}m MMAD uranium particles to a small scale, 'model' Norway spruce (Picea abies) canopy have been determined by means of wind tunnel experiments. These are presented for both the total canopy and for five horizontal layers within the canopy. The results show a complex pattern of deposition within the canopy. The highest deposition velocity V{sub g} (0.19 cm s{sup -1}) was recorded for the topmost layer within the canopy (i.e. the layer in direct contact with the boundary layer) whereas the lowest V{sub g} (0.02 cm s{sup -1}) occurred at the soil surface. Vertical penetration of depositing aerosol through the canopy was influenced by variations in biomass, wind velocity and turbulence within the canopy. A total canopy V{sub g} of 0.5 cm s{sup -1} was obtained and this is in line with field measurements of V{sub g} reported in literature for both anthropogenic and radionuclide aerosols of similar size ranges. Extrapolation of wind tunnel data to 'real' forest canopies is discussed. The information presented here is of importance in predicting the likely contribution of dry deposition of aerosols to pollutant inputs to forest ecosystems, particularly in the context of radioactive aerosol releases from nuclear installations. The application of the present data may also be appropriate for other pollutant aerosols such as SO{sub 4}, NO{sub 3} and NH{sub 4}, which are characterised by particle sizes in the range used in this study.

  6. Temporal Variability of Canopy Light Use Efficiency and its Environmental Controls in a Subtropical Mangrove Wetland

    Science.gov (United States)

    Zhu, X.

    2016-12-01

    Mangrove wetlands play an important role in global carbon cycle due to their strong carbon sequestration resulting from high plant carbon assimilation and low soil respiration. However, temporal variability of carbon sequestration in mangrove wetlands is less understood since carbon processes of mangrove wetlands are influenced by many complicated and concurrent environmental controls including tidal activities, site climate and soil conditions. Canopy light use efficiency (LUE), is the most important plant physiological parameter that can be used to describe the temporal dynamics of canopy photosynthesis, and therefore a better characterization of temporal variability of canopy LUE will improve our understanding in mangrove photosynthesis and carbon balance. One of our aims is to study the temporal variability of canopy LUE and its environmental controls in a subtropical mangrove wetland. Half-hourly canopy LUE is derived from eddy covariance (EC) carbon flux and photosynthesis active radiation observations, and half-hourly environmental controls we measure include temperature, humidity, precipitation, radiation, tidal height, salinity, etc. Another aim is to explore the links between canopy LUE and spectral indices derived from near-surface tower-based remote sensing (normalized difference vegetation index, enhanced vegetation index, photochemical reflectance index, solar-induced chlorophyll fluorescence, etc.), and then identify potential quantitative relationships for developing remote sensing-based estimation methods of canopy LUE. At present, some instruments in our in-situ observation system have not yet been installed (planned in next months) and therefore we don't have enough measurements to support our analysis. However, a preliminary analysis of our historical EC and climate observations in past several years indicates that canopy LUE shows strong temporal variability and is greatly affected by environmental factors such as tidal activity. Detailed and

  7. PLANNING YOUR REMOVALS

    CERN Multimedia

    Service déménagement; ST Division

    1999-01-01

    To give you better service and avoid lengthy delays, the Removals Service advises you to refrain from programming moves between 26 July and 3 September, as large-scale removals are already planned during this summer period.Thanking you in advance for your co-operation and understanding.Removals Service STTel. 74185 / Mobile 164017

  8. Les Gorges de Trévans dans le front subalpin – Un site exceptionnel des Alpes de Haute-Provence

    Directory of Open Access Journals (Sweden)

    Jean Nicod

    2011-10-01

    Full Text Available Les canyons de Trévans sont incisés dans des unités calcaires jurassiques, dans la zone frontale subalpine, proche du piémont de Valensole. Ces reliefs sont en rapport avec les phases néotectoniques. Ce secteur fait principalement partie de la forêt domaniale du Montdenier, avec des écosystèmes montagnards et supra-méditerranéens, bois de hêtres et de chênes pubescents, large extension des brousses et d'importants reboisements en pins noirs. Les hautes surfaces conservent des traces d'un ancien aplanissement et des sols résiduels paléokarstiques. Sur les pentes, sous des escarpements démembrés, les éboulis et convois de blocs témoignent des processus périglaciaires hérités et, localement, des évènements séismiques. De nombreux processus dynamiques s'observent dans les canyons : éboulements provenant des parois affectées des effets de détente, coups de gouge et marmites de géant dans leur fond excavé par les écoulements turbulents dans les cascades… et le Pont de Tuf.The canyon system of Trevans has cut the blocks of the jurassic limestones, in subalpine over thrust front, near the Valensole piedmont. These landforms are in relationship with the neotectonic movements. This area belongs to the State Forest of Montdenier, woodland of various mountain and supra-mediterranean ecosystems, with beeches and white oaks Quercus pubescens, large extent of bush and important reforestation in black pines (Pinus nigra. The high surfaces preserve some relics of the old planation and paleokarstic forms and residual soils. On the slopes, under the break-up escarpments, the screes and landslides give the part of the periglacial processes and, locally, of the seismic events. Numerous dynamic processes occur in the canyons: rock-slides, in relationship with open fractures, scallops and pot-holes in the bottom excavated by the turbulent flows in the waterfalls of the creeks and, only case, a travertine bridge.

  9. Abundance of Green Tree Frogs and Insects in Artificial Canopy Gaps in a Bottomland Hardwood Forest.

    Energy Technology Data Exchange (ETDEWEB)

    Horn, Scott; Hanula, James, L.; Ulyshen, Michael D.; Kilgo, John, C.

    2005-04-01

    ABSTRACT - We found more green tree frogs ( Hyla cinerea) n canopv gaps than in closed canopy forest. Of the 331 green tree frogs observed, 88% were in canopv gaps. Likewise, higher numbers and biomasses of insects were captured in the open gap habitat Flies were the most commonlv collected insect group accounting for 54% of the total capture. These data suggest that one reason green tree frogs were more abundant in canopy gaps was the increased availability of prey and that small canopy gaps provide early successional habitats that are beneficial to green tree frog populations.

  10. Virtual Geographic Simulation of Light Distribution within Three-Dimensional Plant Canopy Models

    Directory of Open Access Journals (Sweden)

    Liyu Tang

    2017-12-01

    Full Text Available Virtual geographic environments (VGEs have been regarded as an important new means of simulating, analyzing, and understanding complex geological processes. Plants and light are major components of the geographic environment. Light is a critical factor that affects ecological systems. In this study, we focused on simulating light transmission and distribution within a three-dimensional plant canopy model. A progressive refinement radiosity algorithm was applied to simulate the transmission and distribution of solar light within a detailed, three-dimensional (3D loquat (Eriobotrya japonica Lindl. canopy model. The canopy was described in three dimensions, and each organ surface was represented by a set of triangular facets. The form factors in radiosity were calculated using a hemi-cube algorithm. We developed a module for simulating the instantaneous light distribution within a virtual canopy, which was integrated into ParaTree. We simulated the distribution of photosynthetically active radiation (PAR within a loquat canopy, and calculated the total PAR intercepted at the whole canopy scale, as well as the mean PAR interception per unit leaf area. The ParaTree-integrated radiosity model simulates the uncollided propagation of direct solar and diffuse sky light and the light-scattering effect of foliage. The PAR captured by the whole canopy based on the radiosity is approximately 9.4% greater than that obtained using ray tracing and TURTLE methods. The latter methods do not account for the scattering among leaves in the canopy in the study, and therefore, the difference might be due to the contribution of light scattering in the foliage. The simulation result is close to Myneni’s findings, in which the light scattering within a canopy is less than 10% of the incident PAR. Our method can be employed for visualizing and analyzing the spatial distribution of light within a canopy, and for estimating the PAR interception at the organ and canopy

  11. Characterization and Modeling of Atmospheric Flow Within and Above Plant Canopies

    Science.gov (United States)

    Souza Freire Grion, Livia

    The turbulent flow within and above plant canopies is responsible for the exchange of momentum, heat, gases and particles between vegetation and the atmosphere. Turbulence is also responsible for the mixing of air inside the canopy, playing an important role in chemical and biophysical processes occurring in the plants' environment. In the last fifty years, research has significantly advanced the understanding of and ability to model the flow field within and above the canopy, but important issues remain unsolved. In this work, we focus on (i) the estimation of turbulent mixing timescales within the canopy from field data; and (ii) the development of new computationally efficient modeling approaches for the coupled canopy-atmosphere flow field. The turbulent mixing timescale represents how quickly turbulence creates a well-mixed environment within the canopy. When the mixing timescale is much smaller than the timescale of other relevant processes (e.g. chemical reactions, deposition), the system can be assumed to be well-mixed and detailed modeling of turbulence is not critical to predict the system evolution. Conversely, if the mixing timescale is comparable or larger than the other timescales, turbulence becomes a controlling factor for the concentration of the variables involved; hence, turbulence needs to be taken into account when studying and modeling such processes. In this work, we used a combination of ozone concentration and high-frequency velocity data measured within and above the canopy in the Amazon rainforest to characterize turbulent mixing. The eddy diffusivity parameter (used as a proxy for mixing efficiency) was applied in a simple theoretical model of one-dimensional diffusion, providing an estimate of turbulent mixing timescales as a function of height within the canopy and time-of-day. Results showed that, during the day, the Amazon rainforest is characterized by well-mixed conditions with mixing timescales smaller than thirty minutes in the

  12. Sub-canopy radiant energy during snowmelt in non-uniform forests spanning a latitudinal transect

    Science.gov (United States)

    Link, T. E.; Essery, R.; Marks, D.; Pomeroy, J.; Hardy, J.; Sicart, J. E.

    2008-12-01

    In mountainous, forested environments, snowcover dynamics exert a strong control on hydrologic and atmospheric processes. Snowcover ablation patterns in forests are controlled by a complex combination of depositional patterns coupled with radiative and turbulent heat flux patterns related to topographic and canopy cover variations. Quantification of small-scale variations of radiant energy in forested environments is necessary to understand how canopy structure affects snowcover energetics to improve the representation of snowmelt processes in spatially-explicit physically-based snowmelt models. Incoming solar and thermal radiation were measured during the melt season within continuous and discontinuous forest stands, and at the interface between forest patches and small clearings along a transect spanning the North American Cordillera. Results indicate that reductions in solar radiation at the snow surface are partially balanced by increased thermal radiation from the forest canopy, relative to open locations. The differences between the transfer processes for solar and thermal radiation can produce two net incoming and net snowcover radiation paradoxes in heterogeneous environments. In discontinuous canopies, net radiation in forested areas may exceed radiation in open sites, whereas in other situations, net radiation may be less than net radiation in closed canopy forests. The empirical results coupled with theoretical modeling indicates that the effects of forest canopies on the radiative regimes at the snow surface are controlled by complex interactions of slope, aspect, gap sizes, canopy height, canopy density, canopy temperature, snow surface temperature and snowcover albedo. In higher latitude, closed canopy forests, radiative regimes may be characterized by relatively simple geometric optical radiation transfer methods, whereas at lower latitude and more non- uniform forests, other processes such as canopy and stem heating must be considered. These net

  13. Use of metabolic profiling to study grape skin polyphenol behavior as a result of canopy microclimate manipulation in a 'Pinot noir' vineyard.

    Science.gov (United States)

    Sternad Lemut, Melita; Sivilotti, Paolo; Franceschi, Pietro; Wehrens, Ron; Vrhovsek, Urska

    2013-09-18

    Canopy microclimate manipulation can have a significant effect on grapevine gene expression and can thus affect the yield of many important berry compounds. Focusing on only a few targeted phenolics in the past, advanced multimethod analytical approaches are opening up much wider possibilities to fill in the gaps of missing knowledge about plant secondary metabolism. Different leaf removal timings, leading to different microclimate scenarios, were thus introduced in a 'Pinot noir' vineyard to reveal related alterations of multiple classes of skin phenolics, including some rarely studied to date. Different accumulation trends during cluster development were detected not only between groups but also between individual compounds within groups. Although many significant changes were observed early in the season, these were later often less significant. However, at harvest, 31 of 72 detected compounds showed significant differences in comparison to control for at least one of three leaf removal approaches.

  14. Quantitative detection of settled coal dust over green canopy

    Science.gov (United States)

    Brook, Anna; Sahar, Nir

    2017-04-01

    The main task of environmental and geoscience applications are efficient and accurate quantitative classification of earth surfaces and spatial phenomena. In the past decade, there has been a significant interest in employing spectral unmixing in order to retrieve accurate quantitative information latent in in situ data. Recently, the ground-truth and laboratory measured spectral signatures promoted by advanced algorithms are proposed as a new path toward solving the unmixing problem in semi-supervised fashion. This study presents a practical implementation of field spectroscopy as a quantitative tool to detect settled coal dust over green canopy in free/open environment. Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, and pulverizing of coal. Since the inelastic nature of coal, coal dust can be created during transportation, or by mechanically handling coal. Coal dust, categorized at silt-clay particle size, of particular concern due to heavy metals (lead, mercury, nickel, tin, cadmium, mercury, antimony, arsenic, isotopes of thorium and strontium) which are toxic also at low concentrations. This hazard exposes risk on both environment and public health. It has been identified by medical scientist around the world as causing a range of diseases and health problems, mainly heart and respiratory diseases like asthma and lung cancer. It is due to the fact that the fine invisible coal dust particles (less than 2.5 microns) long lodge in the lungs and are not naturally expelled, so long-term exposure increases the risk of health problems. Numerus studies reported that data to conduct study of geographic distribution of the very fine coal dust (smaller than PM 2.5) and related health impacts from coal exports, is not being collected. Sediment dust load in an indoor environment can be spectrally assessed using reflectance spectroscopy (Chudnovsky and Ben-Dor, 2009). Small amounts of particulate pollution that may carry a signature

  15. Tree canopy temperature response under experimental warming and drought

    Science.gov (United States)

    Blair, S. N.; Garrity, S. R.; Cai, M.; McDowell, N. G.

    2012-12-01

    Tree mortality associated with rising temperatures and drought has been observed in numerous locations across the globe. Simulated global climate change experiments, such as increased air temperature and reduced precipitation, can help us understand tree response to altered climate regimes and identify key physiological mechanisms involved in tree stress response. We collected canopy-level leaf temperature measurements from several piñon (Pinus edulis) and one-seed juniper (juniperus monosperma) subjected to experimental warming, drought, combined warming and drought treatments, and control conditions in a field-based experiment in northern New Mexico beginning June 2012. We examined leaf temperature responses to the treatments by using continuous measurements from infrared thermocouples located above the tree canopy. We found that leaf temperatures were approximately 5 degrees warmer in heated chambers compared to leaf temperatures of trees outside chambers. Comparisons within each treatment demonstrated that, on average, piñon had higher absolute differences between leaf temperature and air temperature values compared to juniper trees. Stomatal conductance, measured with a leaf porometer showed that within each treatment, juniper had higher stomatal conductance relative to piñon, and that heated trees had lower stomatal conductance relative to non-heated trees. These differences may be attributable to the fact that piñon trees are isohydric, meaning that they have a lower tolerance to water stress. To date, we have not observed a significant drought effect on leaf temperature, however, this is likely due to the short duration of the drought treatment to date. We expect that as the experiment progresses, a drought effect will emerge. One of the key questions that we hope to answer as data continues to be collected is how tree physiology responds to drought, heat, and the interaction between both variables. Although this case study is being conducted in

  16. Up-scaling of water use efficiency from leaf to canopy as based on leaf gas exchange relationships and the modeled in-canopy light distribution

    DEFF Research Database (Denmark)

    Linderson, Maj-Lena; Mikkelsen, Teis Nørgaard; Ibrom, Andreas

    2012-01-01

    on incoming PAR below 500 μmol m−2 s−1 is independent, both of the canopy levels and of variations in the environmental parameters. The average WUEnormleaf for PAR above 500 μmol m−2 s−1 was found to be 5.5 μmol CO2 (mmol H2O)−1 hPa and, for the full range, 2.3 μmol CO2 (mmol H2O)−1 hPa. These results showed...... that WUE can be up-scaled from leaf to canopy on the basis of WUEnormleaf and the PAR distribution within the canopy. The up-scaling conducted was based on this WUEnormleaf – PAR relationship, the lightdistribution being assessed using the MAESTRA model, parameterized in accordance with measurements...

  17. Methodology for high-throughput field phenotyping of canopy temperature using airborne thermography

    Directory of Open Access Journals (Sweden)

    David Matthew Deery

    2016-12-01

    Full Text Available Lower canopy temperature (CT, resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time requiredto measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavours.We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1,000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis.Broad-sense heritability was routinely greater than 0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 x 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total imageacquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot. The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program.

  18. Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography.

    Science.gov (United States)

    Deery, David M; Rebetzke, Greg J; Jimenez-Berni, Jose A; James, Richard A; Condon, Anthony G; Bovill, William D; Hutchinson, Paul; Scarrow, Jamie; Davy, Robert; Furbank, Robert T

    2016-01-01

    Lower canopy temperature (CT), resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time required to measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavors. We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis. Broad-sense heritability was routinely >0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 × 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total image acquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot). The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program.

  19. Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography

    Science.gov (United States)

    Deery, David M.; Rebetzke, Greg J.; Jimenez-Berni, Jose A.; James, Richard A.; Condon, Anthony G.; Bovill, William D.; Hutchinson, Paul; Scarrow, Jamie; Davy, Robert; Furbank, Robert T.

    2016-01-01

    Lower canopy temperature (CT), resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time required to measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavors. We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis. Broad-sense heritability was routinely >0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 × 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total image acquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot). The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program. PMID:27999580

  20. Xylobolus subpileatus, a specialized basidiomycete functionally linked to old canopy gaps

    DEFF Research Database (Denmark)

    Taudiere, A.; Bellanger, J. M.; Moreau, P. A.

    2017-01-01

    Documenting succession in forest canopy gaps provides insights into the ecological processes governing the temporal dynamics of species within communities. We analyzed the fruiting patterns of a rare but widely distributed saproxylic macromycete, Xylobolus subpileatus, during the ageing of natura...

  1. Two-flow simulation of the natural light field within a canopy of submerged aquatic plants

    Science.gov (United States)

    Ackleson, S. G.; Klemas, V.

    1986-01-01

    A two-flow model is developed to simulate a light field composed of both collimated and diffuse irradiance within natural waters containing a canopy of bottom-adhering plants. To account for the effects of submerging a canopy, the transmittance and reflectance terms associated with each plant structure (leaves, stems, fruiting bodies, etc.) are expressed as functions of the ratio of the refractive index of the plant material to the refractive index of the surrounding media and the internal transmittance of the plant stucture. Algebraic solutions to the model are shown to yield plausible physical explanations for unanticipated variations in volume reflectance spectra. The effect of bottom reflectance on the near-bottom light field is also investigated. These indicate that within light-limited submerged aquatic plant canopies, substrate reflectance may play an important role in determining the amount of light available to the plants and, therefore, canopy productivity.

  2. Regional and historical factors supplement current climate in shaping global forest canopy height

    DEFF Research Database (Denmark)

    Zhang, Jian; Nielsen, Scott; Mao, Lingfeng

    2016-01-01

    for 32 304 forested 55-km grid cells using 1-km global canopy height data (maximum height of 1-km cells within a 55-km grid). Variation in Hmax was related to latitude and biomes, along with environmental and historical variables. Both spatial and non-spatial linear models were used to assess......Summary Canopy height is a key factor that affects carbon storage, vegetation productivity and biodiversity in forests, as well as an indicator of key processes such as biomass allocation. However, global variation in forest canopy height and its determinants are poorly known. We used global data...... on Light Detection and Ranging-derived maximum forest canopy height (Hmax) to test hypotheses relating Hmax to current climate (water availability, ambient energy and water–energy dynamics), regional evolutionary and biogeographic history, historical climate change, and human disturbance. We derived Hmax...

  3. Retrieval of canopy component temperatures through Bayesian inversion of directional thermal measurements

    NARCIS (Netherlands)

    Timmermans, J.; Verhoef, W.; Tol, van der C.; Su, Z.

    2009-01-01

    Evapotranspiration is usually estimated in remote sensing from single temperature value representing both soil and vegetation. This surface temperature is an aggregate over multiple canopy components. The temperature of the individual components can differ significantly, introducing errors in the

  4. Relative lack of regeneration of shade-intolerant canopy species in some South African forests

    CSIR Research Space (South Africa)

    Midgley, JJ

    1995-01-01

    Full Text Available Some species such as Celtis Africana, are experiencing relative recruitment bottlenecks, because there are usually fewer recruits [i.e. individuals <20 cm diameter at breast height, (dbh)] than canopy individuals. The species with low recruitment...

  5. CMS: Mangrove Canopy Characteristics and Land Cover Change, Tanzania, 1990-2014

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides canopy height, land cover change, and stand age estimates for mangrove forests in the Rufiji River Delta in Tanzania. The estimates were...

  6. 100-Meter Resolution Tree Canopy of the Conterminous United States - Direct Download

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map layer contains tree canopy data for the conterminous United States, in an Albers Equal-Area Conic projection and at a resolution of 100 meters. The tree...

  7. CMS: Mangrove Canopy Height from High-resolution Stereo Image Pairs, Mozambique, 2012

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides canopy height estimates for mangrove forests at 0.6 x 0.6 m resolution in three study sites located in southeastern Mozambique, Africa: two...

  8. CMS: Mangrove Canopy Height Estimates from Remote Imagery, Zambezi Delta, Mozambique

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides high resolution canopy height estimates for mangrove forests in the Zambezi Delta, Mozambique, Africa. The estimates were derived from three...

  9. CLPX-Ground: Sub-Canopy Energetics at the Local Scale Observation Site (LSOS), Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of solar and longwave radiation data from beneath two pine canopies (one uniform, one discontinuous) at the Local Scale Observation Site...

  10. Assimilating satellite-based canopy height within an ecosystem model to estimate aboveground forest biomass

    Science.gov (United States)

    Joetzjer, E.; Pillet, M.; Ciais, P.; Barbier, N.; Chave, J.; Schlund, M.; Maignan, F.; Barichivich, J.; Luyssaert, S.; Hérault, B.; von Poncet, F.; Poulter, B.

    2017-07-01

    Despite advances in Earth observation and modeling, estimating tropical biomass remains a challenge. Recent work suggests that integrating satellite measurements of canopy height within ecosystem models is a promising approach to infer biomass. We tested the feasibility of this approach to retrieve aboveground biomass (AGB) at three tropical forest sites by assimilating remotely sensed canopy height derived from a texture analysis algorithm applied to the high-resolution Pleiades imager in the Organizing Carbon and Hydrology in Dynamic Ecosystems Canopy (ORCHIDEE-CAN) ecosystem model. While mean AGB could be estimated within 10% of AGB derived from census data in average across sites, canopy height derived from Pleiades product was spatially too smooth, thus unable to accurately resolve large height (and biomass) variations within the site considered. The error budget was evaluated in details, and systematic errors related to the ORCHIDEE-CAN structure contribute as a secondary source of error and could be overcome by using improved allometric equations.

  11. CMS: LiDAR-derived Tree Canopy Cover for Pennsylvania, USA, 2008

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimated high-resolution (1-m) tree canopy cover for the state of Pennsylvania, USA, in 2008. The data were derived from 2006-2008...

  12. CMS: LiDAR-derived Canopy Height, Elevation for Sites in Kalimantan, Indonesia, 2014

    Data.gov (United States)

    National Aeronautics and Space Administration — This dataset provides canopy height and elevation data products derived from airborne LiDAR data collected over 90 sites on the island of Borneo in late 2014. The...

  13. CMS: GLAS LiDAR-derived Global Estimates of Forest Canopy Height, 2004-2008

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of forest canopy height derived from the Geoscience Laser Altimeter System (GLAS) LiDAR instrument that was aboard the NASA Ice,...

  14. Regional and historical factors supplement current climate in shaping global forest canopy height

    DEFF Research Database (Denmark)

    Zhang, Jian; Nielsen, Scott; Mao, Lingfeng

    2016-01-01

    Summary Canopy height is a key factor that affects carbon storage, vegetation productivity and biodiversity in forests, as well as an indicator of key processes such as biomass allocation. However, global variation in forest canopy height and its determinants are poorly known. We used global data...... on Light Detection and Ranging-derived maximum forest canopy height (Hmax) to test hypotheses relating Hmax to current climate (water availability, ambient energy and water–energy dynamics), regional evolutionary and biogeographic history, historical climate change, and human disturbance. We derived Hmax...... for 32 304 forested 55-km grid cells using 1-km global canopy height data (maximum height of 1-km cells within a 55-km grid). Variation in Hmax was related to latitude and biomes, along with environmental and historical variables. Both spatial and non-spatial linear models were used to assess...

  15. SAFARI 2000 Leaf Area Index and Canopy Structure, Kalahari Transect, 1999-2000

    Data.gov (United States)

    National Aeronautics and Space Administration — Data from the Tracing Radiation and Architecture of Canopies (TRAC) instrument were collected at five sites along the International Geosphere-Biosphere Programme...

  16. SAFARI 2000 Leaf Area Index and Canopy Structure, Kalahari Transect, 1999-2000

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Data from the Tracing Radiation and Architecture of Canopies (TRAC) instrument were collected at five sites along the International Geosphere-Biosphere...

  17. ECHIDNA LIDAR Campaigns: Forest Canopy Imagery and Field Data, U.S.A., 2007-2009

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains forest canopy scan data from the Echidna Validation Instrument (EVI) and field measurements data from three campaigns conducted in the United...

  18. ECHIDNA LIDAR Campaigns: Forest Canopy Imagery and Field Data, U.S.A., 2007-2009

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains forest canopy scan data from the Echidna Validation Instrument (EVI) and field measurements data from three campaigns conducted in...

  19. Tree STEM and Canopy Biomass Estimates from Terrestrial Laser Scanning Data

    Science.gov (United States)

    Olofsson, K.; Holmgren, J.

    2017-10-01

    In this study an automatic method for estimating both the tree stem and the tree canopy biomass is presented. The point cloud tree extraction techniques operate on TLS data and models the biomass using the estimated stem and canopy volume as independent variables. The regression model fit error is of the order of less than 5 kg, which gives a relative model error of about 5 % for the stem estimate and 10-15 % for the spruce and pine canopy biomass estimates. The canopy biomass estimate was improved by separating the models by tree species which indicates that the method is allometry dependent and that the regression models need to be recomputed for different areas with different climate and different vegetation.

  20. TREE STEM AND CANOPY BIOMASS ESTIMATES FROM TERRESTRIAL LASER SCANNING DATA

    Directory of Open Access Journals (Sweden)

    K. Olofsson

    2017-10-01

    Full Text Available In this study an automatic method for estimating both the tree stem and the tree canopy biomass is presented. The point cloud tree extraction techniques operate on TLS data and models the biomass using the estimated stem and canopy volume as independent variables. The regression model fit error is of the order of less than 5 kg, which gives a relative model error of about 5 % for the stem estimate and 10–15 % for the spruce and pine canopy biomass estimates. The canopy biomass estimate was improved by separating the models by tree species which indicates that the method is allometry dependent and that the regression models need to be recomputed for different areas with different climate and different vegetation.

  1. CMS: LiDAR-derived Biomass, Canopy Height and Cover, Sonoma County, California, 2013

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of above-ground biomass (AGB), canopy height, and percent tree cover at 30-m spatial resolution for Sonoma County, California, USA,...

  2. Canopy compass in nocturnal homing of the subsocial shield bug, Parastrachia japonensis (Heteroptera: Parastrachiidae)

    Science.gov (United States)

    Hironaka, Mantaro; Inadomi, Koichi; Nomakuchi, Shintaro; Filippi, Lisa; Hariyama, Takahiko

    2008-04-01

    In contrast to an open environment where a specific celestial cue is predominantly used, visual contrast of canopies against the sky through the gap, known as canopy cues, is known to play a major role for visually guided insect navigators in woodland habitats. In this paper, we investigated whether a subsocial shield bug, Parastrachia japonensis, could gauge direction using canopy cues on a moonless night. The results show that they could perform the round trip foraging behaviour even in an experimental arena with only an artificial round gap opened in the ceiling of the arena and adjust their homing direction for a new azimuth when the gap was rotated. Thus, P. japonensis can use slightly brighter canopy cues as a compass reference but not complex landmarks during nocturnal homing behaviour.

  3. LBA-ECO LC-15 Aerodynamic Roughness Maps of Vegetation Canopies, Amazon Basin: 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides physical roughness maps of vegetation canopies in the Amazon Basin. The images are estimates of aerodynamic roughness length (Z0)...

  4. Using the right slope of the 970 nm absorption feature for estimating canopy water content

    NARCIS (Netherlands)

    Clevers, J.G.P.W.; Kooistra, L.; Schaepman, M.E.

    2009-01-01

    Canopy water content (CWC) is important for understanding the functioning of terrestrial ecosystems. Biogeochemical processes like photosynthesis, transpiration and net primary production are related to foliar water. The first derivative of the reflectance spectrum at wavelengths corresponding to

  5. A One-Dimensional Mean Wind and Turbulence Model for a Uniform Urban Canopy

    National Research Council Canada - National Science Library

    Yee, Eugene

    2000-01-01

    A fully analytical model for the prediction of the one-dimensional mean wind speed, kinematic shear stress, turbulence kinetic energy, and velocity variances in a horizontally homogeneous canopy is described...

  6. Modeling and Analysis of Adjacent Grid Point Wind Speed Profiles within and Above a Forest Canopy

    National Research Council Canada - National Science Library

    Tunick, Arnold

    1999-01-01

    Adjacent grid point profile data from the canopy coupled to the surface layer (C-CSL) model are examined to illustrate the model's capability to represent effects of the surface boundary on wind flow...

  7. Soil characteristics under legume and non-legume tree canopies in ...

    African Journals Online (AJOL)

    %, 100% and 150% the distance from tree trunk to canopy edge of leguminous sabiá (Mimosa caesalpiniifolia Benth.) and espinheiro (Machaerium aculeatum Raddi) and non-legume cajueiro (Anacardium occidentale L.) and jaqueira ...

  8. CLPX-Ground: Sub-Canopy Energetics at the Local Scale Observation Site (LSOS)

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of solar and longwave radiation data from beneath two pine canopies (one uniform, one discontinuous) at the Local Scale Observation Site...

  9. Upper canopy pollinators of Eucryphia cordifolia Cav., a tree of South American temperate rain forest

    Directory of Open Access Journals (Sweden)

    Cecilia Smith-Ramírez

    2016-05-01

    Full Text Available Ecological processes in the upper canopy of temperate forests have been seldom studied because of the limited accessibility. Here, we present the results of the first survey of the pollinator assemblage and the frequency of insect visits to flowers in the upper branches of ulmo, Eucryphia cordifolia Cav., an emergent 30-40 m-tall tree in rainforests of Chiloé Island, Chile. We compared these findings with a survey of flower visitors restricted to lower branches of E. cordifolia 1- in the forest understory, 2- in lower branches in an agroforestry area. We found 10 species of pollinators in canopy, and eight, 12 and 15 species in understory, depending of tree locations. The main pollinators of E. cordifolia in the upper canopy differed significantly from the pollinator assemblage recorded in lower tree branches. We conclude that the pollinator assemblages of the temperate forest canopy and interior are still unknown.

  10. LEAF MICROMORPHOMETRY OF Schinus molle L. (ANARCADIACEAE) IN DIFFERENT CANOPY HEIGHTS

    National Research Council Canada - National Science Library

    Marinês Ferreira Pires; Márcio Paulo Pereira; Evaristo Mauro de Castro; Sandro Barbosa; Fabricio José Pereira

    2015-01-01

    .... The objective of this work is to study the leaflet anatomy and leaf biometrical characteristics at different canopy heights of Schinus molle plants as a function of its environmental and physiological modifications...

  11. Hydrology of the North Klondike River: carbon export, water balance and inter-annual climate influences within a sub-alpine permafrost catchment.

    Science.gov (United States)

    Lapp, Anthony; Clark, Ian; Macumber, Andrew; Patterson, Tim

    2017-10-01

    Arctic and sub-arctic watersheds are undergoing significant changes due to recent climate warming and degrading permafrost, engendering enhanced monitoring of arctic rivers. Smaller catchments provide understanding of discharge, solute flux and groundwater recharge at the process level that contributes to an understanding of how larger arctic watersheds are responding to climate change. The North Klondike River, located in west central Yukon, is a sub-alpine permafrost catchment, which maintains an active hydrological monitoring station with a record of >40 years. In addition to being able to monitor intra-annual variability, this data set allows for more complex analysis of streamflow records. Streamflow data, geochemistry and stable isotope data for 2014 show a groundwater-dominated system, predominantly recharged during periods of snowmelt. Radiocarbon is shown to be a valuable tracer of soil zone recharge processes and carbon sources. Winter groundwater baseflow contributes 20 % of total annual discharge, and accounts for up to 50 % of total river discharge during the spring and summer months. Although total stream discharge remains unchanged, mean annual groundwater baseflow has increased over the 40-year monitoring period. Wavelet analysis reveals a catchment that responds to El Niño and longer solar cycles, as well as climatic shifts such as the Pacific Decadal Oscillation. Dedicated to Professor Peter Fritz on the occasion of his 80th birthday.

  12. Dynamics of development and variability of surface degradation in the subalpine and alpine zones (an example from the Velká Fatra Mts., Slovakia

    Directory of Open Access Journals (Sweden)

    Lepeška Tomáš

    2016-01-01

    Full Text Available In the last five centuries, the inappropriate management of the Vel’ká Fatra Mts. sub-alpine and alpine areas has led to the development of different forms of surface destruction. For evaluation of the dynamics and variability of surface degradation the territory of the Hornojelenská valley was chosen. It is a significant avalanche area. It has clearly been destroyed by avalanches, water erosion and cryogenic erosion as well as anthropo-zoogenic processes. The forms of destruction were mapped on a scale of 1:200 based on the aerial photographs and satellite images taken in 1961, 2003, 2009 and 2012. The total area of degradative morphogenetic forms (DMF in 1961 was 5.5780 ha, 4.0650 ha in 2003, 4.5752 ha in 2009 and 4.9431 ha in 2012. The DMF reached its peak in 1961. In the mid-1960s, there were ambitions to reforest the highest areas of the study area that led to the decrease of DMF and the development of vegetation. The present exogenous geomorphologic processes are causing a gradual increase of the total destructed area.

  13. Effect of canopy density on litter invertebrate community structure in pine forests

    Directory of Open Access Journals (Sweden)

    Brygadyrenko Viktor V.

    2016-03-01

    Full Text Available We investigated the structure of the litter invertebrate community in 141 pine (Pinus sylvestris Linnaeus, 1753 forest sites with five variants of canopy density (30-44, 45-59, 60-74, 75-89 and 90-100% in the steppe zone of Ukraine. The total number of litter macrofauna specimens collected at each site decreased from an average of 84/100 trap-days in the sparsest stands (30-40% density to 4-39 specimens/100 trap-days in the forests with a denser canopy. The number of macrofauna species caught in the pitfall traps does not vary significantly with different degrees of canopy density. The Shannon-Weaver and Pielou diversity indexes show increases corresponding to increasing stages of canopy density. The average share of phytophages in the trophic structure of the litter macrofauna does not vary with canopy density. The relative number of saprophages decreases from 54% in the forests with the sparsest canopy to 11-13% in the forests with denser canopies. The relative number of saprophages in pine forests (22% is lower than that in deciduous forests (40%. The share of zoophages in the trophic structure of the litter macrofauna increases significantly with the increase in the pine forest canopy density (from 21% in the sparsest plots to 59% in the densest. The relative number of polyphages is highest (47-65% when the canopy density is 45-89%. At canopy densities below or above this range, the share of polyphages in the community decreases to 20 and 24%, respectively. Regardless of canopy density, Formicidae and Lycosidae invariably rank amongst the first three dominant families. Nine families of invertebrates dominate in the pine forest stands with the highest density (90-100%, and 5-7 families dominate in the stands with lower density. For the pine forest litter macrofauna, we have observed an extreme simplification of the community size structure compared with natural and planted deciduous forests of the steppe zone of Ukraine.

  14. Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway

    Science.gov (United States)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of

  15. Dam removal: Listening in

    Science.gov (United States)

    Foley, Melissa M.; Bellmore, James; O'Connor, James E.; Duda, Jeff; East, Amy E.; Grant, Gordon G.; Anderson, Chauncey; Bountry, Jennifer A.; Collins, Mathias J.; Connolly, Patrick J.; Craig, Laura S.; Evans, James E.; Greene, Samantha; Magilligan, Francis J.; Magirl, Christopher S.; Major, Jon J.; Pess, George R.; Randle, Timothy J.; Shafroth, Patrick B.; Torgersen, Christian; Tullos, Desiree D.; Wilcox, Andrew C.

    2017-01-01

    Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad-scale ecological effects, and gives managers information needed to understand and predict long-term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam-removal methods in the U.S.

  16. Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests.

    Directory of Open Access Journals (Sweden)

    Ondřej Košulič

    Full Text Available Traditional woodland management created a mosaic of differently aged patches providing favorable conditions for a variety of arthropods. After abandonment of historical ownership patterns and traditional management and the deliberate transformation to high forest after World War II, large forest areas became darker and more homogeneous. This had significant negative consequences for biodiversity. An important question is whether even small-scale habitat structures maintained by different levels of canopy openness in abandoned coppiced forest may constitute conditions suitable for forest as well as open habitat specialists. We investigated the effect of canopy openness in former traditionally coppiced woodlands on the species richness, functional diversity, activity density, conservation value, and degree of rareness of epigeic spiders. In each of the eight studied locations, 60-m-long transect was established consisting of five pitfall traps placed at regular 15 m intervals along the gradient. Spiders were collected from May to July 2012. We recorded 90 spider species, including high proportions of xeric specialists (40% and red-listed threatened species (26%. The peaks of conservation indicators, as well as spider community abundance, were shifted toward more open canopies. On the other hand, functional diversity peaked at more closed canopies followed by a rapid decrease with increasing canopy openness. Species richness was highest in the middle of the canopy openness gradient, suggesting an ecotone effect. Ordinations revealed that species of conservation concern tended to be associated with sparse and partly opened canopy. The results show that the various components of biodiversity peaked at different levels of canopy openness. Therefore, the restoration and suitable forest management of such conditions will retain important diversification of habitats in formerly coppiced oak forest stands. We indicate that permanent presence of small

  17. Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests

    Science.gov (United States)

    Košulič, Ondřej; Michalko, Radek; Hula, Vladimír

    2016-01-01

    Traditional woodland management created a mosaic of differently aged patches providing favorable conditions for a variety of arthropods. After abandonment of historical ownership patterns and traditional management and the deliberate transformation to high forest after World War II, large forest areas became darker and more homogeneous. This had significant negative consequences for biodiversity. An important question is whether even small-scale habitat structures maintained by different levels of canopy openness in abandoned coppiced forest may constitute conditions suitable for forest as well as open habitat specialists. We investigated the effect of canopy openness in former traditionally coppiced woodlands on the species richness, functional diversity, activity density, conservation value, and degree of rareness of epigeic spiders. In each of the eight studied locations, 60-m-long transect was established consisting of five pitfall traps placed at regular 15 m intervals along the gradient. Spiders were collected from May to July 2012. We recorded 90 spider species, including high proportions of xeric specialists (40%) and red-listed threatened species (26%). The peaks of conservation indicators, as well as spider community abundance, were shifted toward more open canopies. On the other hand, functional diversity peaked at more closed canopies followed by a rapid decrease with increasing canopy openness. Species richness was highest in the middle of the canopy openness gradient, suggesting an ecotone effect. Ordinations revealed that species of conservation concern tended to be associated with sparse and partly opened canopy. The results show that the various components of biodiversity peaked at different levels of canopy openness. Therefore, the restoration and suitable forest management of such conditions will retain important diversification of habitats in formerly coppiced oak forest stands. We indicate that permanent presence of small-scale improvements

  18. Responses of plant biochemical substances to reflectance spectra at leaf and canopy scales

    Science.gov (United States)

    Shi, Runhe; Zhang, Huifang; Sun, Juan; Gao, Wei; Zhuang, Dafang; Niu, Zheng

    2008-08-01

    Plants cover more than 70% of our earth's land surface and play an important role in the exchange of materials and energy between land and atmosphere. The biochemical substances existing in leaves have been proven to be critical factors in influencing, or even controlling, this exchange by means of various physiological processes, including photosynthesis, evaportranspiration, litter decomposition, etc. Compared to traditional wet chemistry methods, estimation of their contents through leaf and canopy reflectance spectra has become a rapid, efficient, and promising method over the past few decades, which had been physically based on the selective absorption features of a particular substance. This paper discusses the responses of plant biochemical substances to the reflectance spectra at both leaf and canopy scales. We use a leaf optical model PROSPECT and a leaf-canopy coupled optical model PROSAIL to generate large amounts of leaf and canopy spectra. Both of these models contain three biochemical parameters: cab-chlorophyll concentration, Cw-equivalent leaf water thickness, and Cm-dry matter concentration. Local and global sensitivity analysis (SA) methods are used on the simulated spectra to differentiate their contributions to the outcome spectra at both scales so as to investigate their scale effects. Results show that the maximum sensitivities of chlorophyll and water are much higher than that of dry matter at leaf scale, and they tend to decrease at canopy scale because canopy shape, soil, and incident/reflected geometric factors have a large influence on canopy spectra. However, the sensitivity of dry matter exceeds the maximum sensitivity of mesophyll structure parameters at canopy scale and becomes the top contributor at the beginning of near infrared.

  19. Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests.

    Science.gov (United States)

    Košulič, Ondřej; Michalko, Radek; Hula, Vladimír

    2016-01-01

    Traditional woodland management created a mosaic of differently aged patches providing favorable conditions for a variety of arthropods. After abandonment of historical ownership patterns and traditional management and the deliberate transformation to high forest after World War II, large forest areas became darker and more homogeneous. This had significant negative consequences for biodiversity. An important question is whether even small-scale habitat structures maintained by different levels of canopy openness in abandoned coppiced forest may constitute conditions suitable for forest as well as open habitat specialists. We investigated the effect of canopy openness in former traditionally coppiced woodlands on the species richness, functional diversity, activity density, conservation value, and degree of rareness of epigeic spiders. In each of the eight studied locations, 60-m-long transect was established consisting of five pitfall traps placed at regular 15 m intervals along the gradient. Spiders were collected from May to July 2012. We recorded 90 spider species, including high proportions of xeric specialists (40%) and red-listed threatened species (26%). The peaks of conservation indicators, as well as spider community abundance, were shifted toward more open canopies. On the other hand, functional diversity peaked at more closed canopies followed by a rapid decrease with increasing canopy openness. Species richness was highest in the middle of the canopy openness gradient, suggesting an ecotone effect. Ordinations revealed that species of conservation concern tended to be associated with sparse and partly opened canopy. The results show that the various components of biodiversity peaked at different levels of canopy openness. Therefore, the restoration and suitable forest management of such conditions will retain important diversification of habitats in formerly coppiced oak forest stands. We indicate that permanent presence of small-scale improvements

  20. Quantifying Ancient Maya Land Use Legacy Effects on Contemporary Rainforest Canopy Structure

    Directory of Open Access Journals (Sweden)

    Jessica N. Hightower

    2014-11-01

    Full Text Available Human land use legacies have significant and long-lasting ecological impacts across landscapes. Investigating ancient (>400 years legacy effects can be problematic due to the difficulty in detecting specific, historic land uses, especially those hidden beneath dense canopies. Caracol, the largest (~200 km2 Maya archaeological site in Belize, was abandoned ca. A.D. 900, leaving behind myriad structures, causeways, and an extensive network of agricultural terraces that persist beneath the architecturally complex tropical forest canopy. Airborne LiDAR enables the detection of these below-canopy archaeological features while simultaneously providing a detailed record of the aboveground 3-dimensional canopy organization, which is indicative of a forest’s ecological function. Here, this remote sensing technology is used to determine the effects of ancient land use legacies on contemporary forest structure. Canopy morphology was assessed by extracting LiDAR point clouds (0.25 ha plots from LiDAR-identified terraced (n = 150 and non-terraced (n = 150 areas on low (0°–10°, medium (10°–20°, and high (>20° slopes. We calculated the average canopy height, canopy openness, and vertical diversity from the LiDAR returns, with topographic features (i.e., slope, elevation, and aspect as covariates. Using a PerMANOVA procedure, we determined that forests growing on agricultural terraces exhibited significantly different canopy structure from those growing on non-terraced land. Terraces appear to mediate the effect of slope, resulting in less structural variation between slope and non-sloped land and yielding taller, more closed, more vertically diverse forests. These human land uses abandoned >1000 years ago continue to impact contemporary tropical rainforests having implications related to arboreal habitat and carbon storage.

  1. Flow adjustment inside homogeneous canopies after a leading edge - An analytical approach backed by LES

    Science.gov (United States)

    Kröniger, Konstantin; Banerjee, Tirtha; de Roo, Frederik; Mauder, Matthias

    2017-04-01

    A two-dimensional analytical model for describing the mean flow inside a vegetation canopy after a leading edge in neutral conditions was developed and tested by means of large eddy simulations (LES) employing the LES code PALM. The analytical model is able to predict the mean flow in the region directly after the canopy edge, the adjustment region, where one-dimensional canopy models fail due to the sharp change in roughness. The derivation of the adjustment region model is based on an analytic solution of the two-dimensional Reynolds averaged Navier-Stokes equation in neutral conditions for a canopy with constant plant area density (PAD). The main assumptions for solving the governing equations are separability of the velocity components concerning the spatial variables and the neglection of the Reynolds stress tensor gradients. These two assumptions are verified by means of LES. To determine the emerging model parameters, a fitting scheme is simultaneously applied to the velocity and pressure data of a reference LES simulation. Furthermore a sensitivity analysis of the adjustment region model, equipped with the previously calculated parameters, is performed varying the three relevant length scales, the canopy height (h), the canopy length and the adjustment length (Lc), in additional LES. Even if the model parameters are, in general, functions of h/Lc, it was found out that the model is capable of predicting the flow quantities in various cases, while using constant parameters. Finally, the adjustment region model is combined with the one-dimensional model of Massman [Boundary-Layer Meteorol., 83(3):407-421, 1997], which is applicable for the interior of the canopy, to attain an analytical model capable of describing the mean flow for the full canopy domain.

  2. Panicle blast and canopy moisture in rice cultivar mixtures.

    Science.gov (United States)

    Zhu, You-Yong; Fang, Hui; Wang, Yun-Yue; Fan, Jin Xiang; Yang, Shi-Sheng; Mew, Twng Wah; Mundt, Christopher C

    2005-04-01

    ABSTRACT Glutinous rice cultivars were sown after every fourth row of a nonglutinous, hybrid cultivar in an additive design. The glutinous cultivars were 35 to 40 cm taller and substantially more susceptible to blast than was the nonglutinous cultivar. Interplanting of glutinous and nonglutinous rice reduced the incidence and severity of panicle blast on the glutinous cultivars by >90%, and on the nonglutinous cultivar by 30 to 40%. Mixing increased the per unit area yield of glutinous rice by 80 to 90% relative to pure stand, whereas yield of the nonglutinous cultivar was essentially unaffected by mixing. To determine whether the different plant heights and canopy structures may contribute to a microclimate that is less favorable to blast infection, we monitored the moisture status of the glutinous cultivars in pure stand and mixture at 0800 h by measuring relative humidity at the height of the glutinous panicles using a swing psychrometer and by visually estimating the percentage of leaf area covered by dew. Averaged over the two seasons, the number of days of 100% humidity at 0800 h was 20.0 and 2.2 for pure stands and mixtures, respectively. The mean percentage of glutinous leaf area covered by dewwas 84 and 36% for the pure stands and mixtures, respectively. Although other mechanisms also were operative, reduced leaf wetness was likely a substantial contributor to panicle blast control in the mixtures.

  3. CrossVit: enhancing canopy monitoring management practices in viticulture.

    Science.gov (United States)

    Matese, Alessandro; Vaccari, Francesco Primo; Tomasi, Diego; Di Gennaro, Salvatore Filippo; Primicerio, Jacopo; Sabatini, Francesco; Guidoni, Silvia

    2013-06-13

    A new wireless sensor network (WSN), called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect air temperature, air humidity and solar radiation data to support vineyard management practices. The WSN consists of various levels: the Master/Gateway level coordinates the WSN and performs data aggregation; the Farm/Server level takes care of storing data on a server, data processing and graphic rendering; Nodes level is based on a network of peripheral nodes consisting of a MDA300 sensor board and Iris module and equipped with thermistors for air temperature, photodiodes for global and diffuse solar radiation, and an HTM2500LF sensor for relative humidity. The communication levels are: WSN links between gateways and sensor nodes by ZigBee, and long-range GSM/GPRS links between gateways and the server farm level. The system was able to monitor the agrometeorological parameters in the vineyard: solar radiation, air temperature and air humidity, detecting the differences between the canopy treatments applied. The performance of CrossVit, in terms of monitoring and reliability of the system, have been evaluated considering: its handiness, cost-effective, non-invasive dimensions and low power consumption.

  4. CrossVit: Enhancing Canopy Monitoring Management Practices in Viticulture

    Directory of Open Access Journals (Sweden)

    Alessandro Matese

    2013-06-01

    Full Text Available A new wireless sensor network (WSN, called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect air temperature, air humidity and solar radiation data to support vineyard management practices. The WSN consists of various levels: the Master/Gateway level coordinates the WSN and performs data aggregation; the Farm/Server level takes care of storing data on a server, data processing and graphic rendering; Nodes level is based on a network of peripheral nodes consisting of a MDA300 sensor board and Iris module and equipped with thermistors for air temperature, photodiodes for global and diffuse solar radiation, and an HTM2500LF sensor for relative humidity. The communication levels are: WSN links between gateways and sensor nodes by ZigBee, and long-range GSM/GPRS links between gateways and the server farm level. The system was able to monitor the agrometeorological parameters in the vineyard: solar radiation, air temperature and air humidity, detecting the differences between the canopy treatments applied. The performance of CrossVit, in terms of monitoring and reliability of the system, have been evaluated considering: its handiness, cost-effective, non-invasive dimensions and low power consumption.

  5. Remote sensing detection of droughts in Amazonian forest canopies.

    Science.gov (United States)

    Anderson, Liana O; Malhi, Yadvinder; Aragão, Luiz E O C; Ladle, Richard; Arai, Egidio; Barbier, Nicolas; Phillips, Oliver

    2010-08-01

    *Remote sensing data are a key tool to assess large forested areas, where limitations such as accessibility and lack of field measurements are prevalent. Here, we have analysed datasets from moderate resolution imaging spectroradiometer (MODIS) satellite measurements and field data to assess the impacts of the 2005 drought in Amazonia. *We combined vegetation indices (VI) and climatological variables to evaluate the spatiotemporal patterns associated with the 2005 drought, and explore the relationships between remotely-sensed indices and forest inventory data on tree mortality. *There were differences in results based on c4 and c5 MODIS products. C5 VI showed no spatial relationship with rainfall or aerosol optical depth; however, distinct regions responded significantly to the increased radiation in 2005. The increase in the Enhanced VI (EVI) during 2005 showed a significant positive relationship (P drought was associated with a positive response of forest photosynthesis to changes in the radiation income. We discuss the evidence that this increase could be related to structural changes in the canopy.

  6. A photosynthesis-based two-leaf canopy stomatal ...

    Science.gov (United States)

    A coupled photosynthesis-stomatal conductance model with single-layer sunlit and shaded leaf canopy scaling is implemented and evaluated in a diagnostic box model with the Pleim-Xiu land surface model (PX LSM) and ozone deposition model components taken directly from the meteorology and air quality modeling system—WRF/CMAQ (Weather Research and Forecast model and Community Multiscale Air Quality model). The photosynthesis-based model for PX LSM (PX PSN) is evaluated at a FLUXNET site for implementation against different parameterizations and the current PX LSM approach with a simple Jarvis function (PX Jarvis). Latent heat flux (LH) from PX PSN is further evaluated at five FLUXNET sites with different vegetation types and landscape characteristics. Simulated ozone deposition and flux from PX PSN are evaluated at one of the sites with ozone flux measurements. Overall, the PX PSN simulates LH as well as the PX Jarvis approach. The PX PSN, however, shows distinct advantages over the PX Jarvis approach for grassland that likely result from its treatment of C3 and C4 plants for CO2 assimilation. Simulations using Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) rather than LAI measured at each site assess how the model would perform with grid averaged data used in WRF/CMAQ. MODIS LAI estimates degrade model performance at all sites but one site having exceptionally old and tall trees. Ozone deposition velocity and ozone flux along with LH

  7. Effects of kaolin application on light absorption and distribution, radiation use efficiency and photosynthesis of almond and walnut canopies.

    Science.gov (United States)

    Rosati, Adolfo; Metcalf, Samuel G; Buchner, Richard P; Fulton, Allan E; Lampinen, Bruce D

    2007-02-01

    Kaolin applied as a suspension to plant canopies forms a film on leaves that increases reflection and reduces absorption of light. Photosynthesis of individual leaves is decreased while the photosynthesis of the whole canopy remains unaffected or even increases. This may result from a better distribution of light within the canopy following kaolin application, but this explanation has not been tested. The objective of this work was to study the effects of kaolin application on light distribution and absorption within tree canopies and, ultimately, on canopy photosynthesis and radiation use efficiency. Photosynthetically active radiation (PAR) incident on individual leaves within the canopy of almond (Prunus dulcis) and walnut (Juglans regia) trees was measured before and after kaolin application in order to study PAR distribution within the canopy. The PAR incident on, and reflected and transmitted by, the canopy was measured on the same day for kaolin-sprayed and control trees in order to calculate canopy PAR absorption. These data were then used to model canopy photosynthesis and radiation use efficiency by a simple method proposed in previous work, based on the photosynthetic response to incident PAR of a top-canopy leaf. Kaolin increased incident PAR on surfaces of inner-canopy leaves, although there was an estimated 20 % loss in PAR reaching the photosynthetic apparatus, due to increased reflection. Assuming a 20 % loss of PAR, modelled photosynthesis and photosynthetic radiation use efficiency (PRUE) of kaolin-coated leaves decreased by only 6.3 %. This was due to (1) more beneficial PAR distribution within the kaolin-sprayed canopy, and (2) with decreasing PAR, leaf photosynthesis decreases less than proportionally, due to the curvature of the photosynthesis response-curve to PAR. The relatively small loss in canopy PRUE (per unit of incident PAR), coupled with the increased incident PAR on the leaf surface on inner-canopy leaves, resulted in an estimated

  8. Soil types and forest canopy structures in southern Missouri: A first look with AIS data

    Science.gov (United States)

    Green, G. M.; Arvidson, R. E.

    1986-01-01

    Spectral reflectance properties of deciduous oak-hickory forests covering the eastern half of the Rolla Quadrangle were examined using Thematic Mapper (TM) data acquired in August and December, 1982 and Airborne Imaging Spectrometer (AIS) data acquired in August, 1985. For the TM data distinctly high relative reflectance values (greater than 0.3) in the near infrared (Band 4, 0.73 to 0.94 micrometers) correspond to regions characterized by xeric (dry) forests that overlie soils with low water retention capacities. These soils are derived primarily from rhyolites. More mesic forests characterized by lower TM band 4 relative reflectances are associated with soils of higher retention capacities derived predominately from non-cherty carbonates. The major factors affecting canopy reflectance appear to be the leaf area index (LAI) and leaf optical properties. The Suits canopy reflectance model predicts the relative reflectance values for the xeric canopies. The mesic canopy reflectance is less well matched and incorporation of canopy shadowing caused by the irregular nature of the mesic canopy may be necessary. Preliminary examination of high spectral resolution AIS data acquired in August of 1985 reveals no more information than found in the broad band TM data.

  9. Spectrodirectional Investigation of a Geometric-Optical Canopy Reflectance Model by Laboratory Simulation

    Science.gov (United States)

    Stanford, Adam Christopher

    Canopy reflectance models (CRMs) can accurately estimate vegetation canopy biophysical-structural information such as Leaf Area Index (LAI) inexpensively using satellite imagery. The strict physical basis which geometric-optical CRMs employ to mathematically link canopy bidirectional reflectance and structure allows for the tangible replication of a CRM's geometric abstraction of a canopy in the laboratory, enabling robust CRM validation studies. To this end, the ULGS-2 goniometer was used to obtain multiangle, hyperspectral (Spectrodirectional) measurements of a specially-designed tangible physical model forest, developed based upon the Geometric-Optical Mutual Shadowing (GOMS) CRM, at three different canopy cover densities. GOMS forward-modelled reflectance values had high levels of agreement with ULGS-2 measurements, with obtained reflectance RMSE values ranging from 0.03% to 0.1%. Canopy structure modelled via GOMS Multiple-Forward-Mode (MFM) inversion had varying levels of success. The methods developed in this thesis can potentially be extended to more complex CRMs through the implementation of 3D printing.

  10. Trait Estimation in Herbaceous Plant Assemblages from in situ Canopy Spectra

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    Hans D. Roelofsen

    2013-11-01

    Full Text Available Estimating plant traits in herbaceous plant assemblages from spectral reflectance data requires aggregation of small scale trait variations to a canopy mean value that is ecologically meaningful and corresponds to the trait content that affects the canopy spectral signal. We investigated estimation capacities of plant traits in a herbaceous setting and how different trait-aggregation methods influence estimation accuracies. Canopy reflectance of 40 herbaceous plant assemblages was measured in situ and biomass was analysed for N, P and C concentration, chlorophyll, lignin, phenol, tannin and specific water concentration, expressed on a mass basis (mg∙g−1. Using Specific Leaf Area (SLA and Leaf Area Index (LAI, traits were aggregated to two additional expressions: mass per leaf surface (mg∙m−2 and mass per canopy surface (mg∙m−2. All traits were related to reflectance using partial least squares regression. Accuracy of trait estimation varied between traits but was mainly influenced by the trait expression. Chlorophyll and traits expressed on canopy surface were least accurately estimated. Results are attributed to damping or enhancement of the trait signal upon conversion from mass based trait values to leaf and canopy surface expressions. A priori determination of the most appropriate trait expression is viable by considering plant growing strategies.

  11. Coupling Fine-Scale Root and Canopy Structure Using Ground-Based Remote Sensing

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    Brady S. Hardiman

    2017-02-01

    Full Text Available Ecosystem physical structure, defined by the quantity and spatial distribution of biomass, influences a range of ecosystem functions. Remote sensing tools permit the non-destructive characterization of canopy and root features, potentially providing opportunities to link above- and belowground structure at fine spatial resolution in functionally meaningful ways. To test this possibility, we employed ground-based portable canopy LiDAR (PCL and ground penetrating radar (GPR along co-located transects in forested sites spanning multiple stages of ecosystem development and, consequently, of structural complexity. We examined canopy and root structural data for coherence (i.e., correlation in the frequency of spatial variation at multiple spatial scales ≤10 m within each site using wavelet analysis. Forest sites varied substantially in vertical canopy and root structure, with leaf area index and root mass more becoming even vertically as forests aged. In all sites, above- and belowground structure, characterized as mean maximum canopy height and root mass, exhibited significant coherence at a scale of 3.5–4 m, and results suggest that the scale of coherence may increase with stand age. Our findings demonstrate that canopy and root structure are linked at characteristic spatial scales, which provides the basis to optimize scales of observation. Our study highlights the potential, and limitations, for fusing LiDAR and radar technologies to quantitatively couple above- and belowground ecosystem structure.

  12. Assessment of Light Environment Variability in Broadleaved Forest Canopies Using Terrestrial Laser Scanning

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    Dimitry Van der Zande

    2010-06-01

    Full Text Available Light availability inside a forest canopy is of key importance to many ecosystem processes, such as photosynthesis and transpiration. Assessment of light availability and within-canopy light variability enables a more detailed understanding of these biophysical processes. The changing light-vegetation interaction in a homogeneous oak (Quercus robur L. stand was studied at different moments during the growth season using terrestrial laser scanning datasets and ray tracing technology. Three field campaigns were organized at regular time intervals (24 April 2008; 07 May 2008; 23 May 2008 to monitor the increase of foliage material. The laser scanning data was used to generate 3D representations of the forest stands, enabling structure feature extraction and light interception modeling, using the Voxel-Based Light Interception Model (VLIM. The VLIM is capable of estimating the relative light intensity or Percentage of Above Canopy Light (PACL at any arbitrary point in the modeled crown space. This resulted in a detailed description of the dynamic light environments inside the canopy. Mean vertical light extinction profiles were calculated for the three time frames, showing significant differences in light attenuation by the canopy between April 24 on the one hand, and May 7 and May 23 on the other hand. The proposed methodology created the opportunity to link these within-canopy light distributions to the increasing amount of photosynthetically active leaf material and its distribution in the considered 3D space.

  13. NDVI as a predictor of canopy arthropod biomass in the Alaskan arctic tundra.

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    Sweet, Shannan K; Asmus, Ashley; Rich, Matthew E; Wingfield, John; Gough, Laura; Boelman, Natalie T

    2015-04-01

    The physical and biological responses to rapid arctic warming are proving acute, and as such, there is a need to monitor, understand, and predict ecological responses over large spatial and temporal scales. The use of the normalized difference vegetation index (NDVI) acquired from airborne and satellite sensors addresses this need, as it is widely used as a tool for detecting and quantifying spatial and temporal dynamics of tundra vegetation cover, productivity, and phenology. Such extensive use of the NDVI to quantify vegetation characteristics suggests that it may be similarly applied to characterizing primary and secondary consumer communities. Here, we develop empirical models to predict canopy arthropod biomass with canopy-level measurements of the NDVI both across and within distinct tundra vegetation communities over four growing seasons in the Arctic Foothills region of the Brooks Range, Alaska, USA. When canopy arthropod biomass is predicted with the NDVI across all four growing seasons, our overall model that includes all four vegetation communities explains 63% of the variance in canopy arthropod biomass, whereas our models specific to each of the four vegetation communities explain 74% (moist tussock tundra), 82% (erect shrub tundra), 84% (riparian shrub tundra), and 87% (dwarf shrub tundra) of the observed variation in canopy arthropod biomass. Our field-based study suggests that measurements of the NDVI made from air- and spaceborne sensors may be able to quantify spatial and temporal variation in canopy arthropod biomass at landscape to regional scales.

  14. Outdoor Thermal Comfort in a Transitional Space of Canopy in Schools in the UK

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    Choul Woong Kwon

    2017-09-01

    Full Text Available There has been a significant increase in opportunities to improve school environments in the UK. There has, however, been little study on the design of sheltered transitional spaces, despite growing architectural demand for this, examples of which can be easily found in most primary schools in the UK. Computer simulations (Rayman, Ecotect and Winair4 were performed to identify the influence of different parameters: that of having a canopy; the effect of the transmissivity of the canopy material (three transparencies 0%, 50% and 90% were considered; orientation (four orientations—north, east, south and west—were considered; and location (three cities: London, Manchester and Glasgow. The combined effects of canopy transparency and orientation were shown to be critical design considerations in affecting comfort conditions in outdoor spaces. It was found that outdoor comfort conditions in the transitional space can be enhanced by 41.5% in August by choosing a canopy of 0% transparency, compared with a canopy of 90% transparency in London. The fixed canopy with a higher transparency helped to increase outdoor thermal comfort in Glasgow, while one with a lower transparency showed better performance during summer in London. This research will help design environmentally sophisticated transitional spaces in schools.

  15. Canopy induced aberration correction in airborne electro-optical imaging systems

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    Harder, James A.; Sprague, Michaelene W.

    2011-11-01

    An increasing number of electro-optical systems are being used by pilots in tactical aircraft. This means that the afore mentioned systems must operate through the aircrafts canopy, unfortunately the canopy functions as a less than ideal lens element in the electro-optical sensor optical path. The canopy serves first and foremost as an aircraft structural component, considerations like minimizing the drag co-efficient and the ability to survive bird strikes take precedence over achieving optimal optical characteristics. This paper describes how the authors characterized the optical characteristics of an aircraft canopy. Families of modulation transfer functions were generated, for various viewing geometries through the canopy and for various electro-optical system entrance pupil diameters. These functions provided us with the means to significantly reduce the effect of the canopy "lens" on the performance of a representative electro-optical system, using an Astigmatic Corrector Lens. A comparison of the electro-optical system performance with and without correction is also presented.

  16. Can defensible estimates of canopy proximity be obtained based on single point eddy covariance measurements?

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    Hurdebise, Quentin; Heinesch, Bernard; De Ligne, Anne; Vincke, Caroline; Aubinet, Marc

    2017-04-01

    Understanding if and how the spatial and temporal variability of the surrounding environment affects turbulence is essential for long-term eddy covariance measurements above growing and heterogeneous ecosystems. It requires characterizing the surrounding environment. One way to achieve this is to analyse the canopy aerodynamic distance, which is the difference between measurement height (z) and displacement height (d). In this study, twenty years of eddy covariance measurements from the Vielsalm Terrestrial Observatory, a site located in a mixed temperate forest, were used. Canopy aerodynamic distance (z-d) estimates were obtained using two micrometeorological methods: the first one, which is original so far as we know, was based on analysing sensible heat cospectra; the second one was derived from the wind speed profile equation. Canopy height estimates based on inventories were used to validate both methods. The micrometeorological methods allowed the z-d variations due to changes in canopy or measurement height to be detected. In addition, the results obtained using the two methods were well correlated, spatially and temporally, with the z-d derived from canopy height measurements. The micrometeorological approaches used could therefore be a promising tool for investigating z-d variability at a high directional and temporal resolution. Questions remain, however, particularly with regard to the variability observed that cannot be explained by canopy or measurement height variation. Forest management practices and the non-fulfilment of similarity relationships were suspected to be the main explanatory factors.

  17. LEAF MICROMORPHOMETRY OF Schinus molle L. (ANARCADIACEAE IN DIFFERENT CANOPY HEIGHTS.

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    Marinês Ferreira Pires

    2015-03-01

    Full Text Available Leaf characterization of trees is essential for its identification and use, as well as to understand its relationships with environment. The objective of this work is to study the leaflet anatomy and leaf biometrical characteristics at different canopy heights of Schinus molle plants as a function of its environmental and physiological modifications. Leaves were collected at three different canopy heights: base, middle and upper canopy in a plantation of S. molle. Leaves were used for anatomical and biometrical analysis. For the anatomical analysis, leaves were fixed in FAA and stored in ethanol 70% and further submitted to transversal and paradermical sections. Slides were photomicrographed and image analysis was performed in UTHSCSA-Imagetool. For biometrical analysis leaf area, length, width, dry mass and specific leaf area were evaluated. The leaflets exhibited single layer epidermis, anomocytic and ciclocytic stomata, isobilateral mesophyll, subepidermal parenchyma layer in both adaxial and abaxial faces of epidermis, secretory vessels and lamellar collenchyma in midrib and leaf border. Leaf anatomy modifications occurred in cuticle and mesophyll thickness, vascular system, phloem thickness, and stomatal density in accordance with leaf canopy position. Leaves were smaller and with reduced leaf area at higher canopy positions. S. molle leaf anatomy is different from other species within Schinus genre with modifications under different environmental and physiological modifications promoted by its canopy height.

  18. Processing of Aerosols within a Mixed-Hardwood Forest Canopy: Results from the 2009 CABINEX Experiment

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    Erupe, M.; Mwaniki, G.; Rosenkrance, C.; Pressley, S. N.; Kanawade, V. P.; Lee, S.; Slade, J. H.; Shepson, P. B.; VanReken, T. M.

    2011-12-01

    During the summer of 2009 the Community Atmosphere Biosphere INteractions EXperiment (CABINEX) was conducted at the Program for Research on Oxidants: Photochemistry, Emissions, and Transport (PROPHET) facility in northern Michigan. A major goal of the study was to understand how aerosol physical and chemical properties are affected by emissions of biogenic volatile organic compounds (BVOCs) and by other environmental drivers within and just above the forest canopy. During CABINEX, extensive measurements of aerosol properties were made below the forest canopy, including particle size distribution, water-soluble composition, cloud-forming potential, and light scattering properties. Further measurements were made at two additional heights on the PROPHET tower and above the canopy from an airborne platform. This presentation synthesizes the available aerosol data from CABINEX to examine how processes on the canopy scale affect the aerosol population. The analysis will focus largely on two questions: 1) how does the variability in local turbulence conditions affect the gradient of particle size distribution through the canopy?; and 2) what are the hygroscopic properties of the aerosol population, and how do these measured properties reconcile with the available composition, size distribution, and light scattering data? Results of these analyses will be compared to meteorological and trace gas observations made during CABINEX to evaluate the importance of local canopy-scale aerosol processing relative to the larger-scale spatial and temporal variability.

  19. Hair removal in adolescence

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    Sandra Pereira

    2015-06-01

    Full Text Available Introduction: Due to hormonal stimulation during puberty, changes occur in hair type and distribution. In both sexes, body and facial unwanted hair may have a negative psychological impact on the teenager. There are several available methods of hair removal, but the choice of the most suitable one for each individual can raise doubts. Objective: To review the main methods of hair removal and clarify their indications, advantages and disadvantages. Development: There are several removal methods currently available. Shaving and depilation with chemicals products are temporary methods, that need frequent repetition, because hair removal is next to the cutaneous surface. The epilating methods in which there is full hair extraction include: epilation with wax, thread, tweezers, epilating machines, laser, intense pulsed light, and electrolysis. Conclusions: The age of beginning hair removal and the method choice must be individualized and take into consideration the skin and hair type, location, dermatological and endocrine problems, removal frequency, cost and personal preferences.

  20. Effects of structural complexity on within-canopy light environments and leaf traits in a northern mixed deciduous forest.

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    Fotis, Alexander T; Curtis, Peter S

    2017-10-01

    Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in red maple (Acer rubrum), american beech (Fagus grandifolia), white pine (Pinus strobus), and northern red oak (Quercus rubra) at different heights in plots with similar leaf area index but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaf phenotypes of F. grandifolia, Q. rubra and P. strobus were more sun-acclimated in the midstory of structurally complex canopies while leaf phenotypes of A. rubrum were more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further differences in acclimation with increased Narea and reduced Chlmass in leaves with higher LMA, while P. strobus showed no change in Narea and Chlmass with higher LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic