نتایج جستجو برای: canopy density
تعداد نتایج: 422904 فیلتر نتایج به سال:
Intake of animals grazing grass pasture is in part infl uenced by canopy density. Our objective was to determine the vertical distribution of dry matter and neutral detergent fi ber (NDF) within temperate perennial grass swards. The study was conducted in 2004 and 2005 on a Plano silt loam (fi ne-silty, mixed, superactive, mesic Typic Argiudolls). When leaf height of each grass reached 25 cm in...
In the present study, an attempt was made to produce a precise 3D image of a tomato canopy using a portable high-resolution scanning lidar. The tomato canopy was scanned by the lidar from three positions surrounding it. Through the scanning, the point cloud data of the canopy were obtained and they were co-registered. Then, points corresponding to leaves were extracted and converted into polygo...
Many current vegetation–atmosphere models require structural information describing the canopy in order to calculate rates of mass and energy exchange. One of the most important pieces of information is the variation with height in leaf area density, ρ (m2 leaf area per m3 canopy volume), but it is notoriously difficult to measure this in forest canopies. Consequently, very few data on ρ exist ...
Little is known of the co-occurrence and implications of competitive and facilitative interactions within sites. Here we show spatially disjunct competition and facilitation at forest edges, with beneficial influences of trees on seedling growth via increased ectomycorrhizal infection apparent from 12 to 20 m while closer to trees seedling growth is negatively correlated with canopy closure. As...
Responses of understory plant diversity to nitrogen (N) additions were investigated in reforested forests of contrasting disturbance regimes in southern China from 2003 to 2008: disturbed forest (with harvesting of understory vegetation and litter) and rehabilitated forest (without harvesting). Experimental additions of N were administered as the following treatments: Control, 50 kg N ha(-1) yr...
Quantification of rice biophysical properties is important not only for rice growth monitoring and cropping management, but for understanding carbon cycle in agricultural ecosystems. In this study, a rice canopy scattering model (RCSM) was firstly utilized to simulate rice backscatter with a root mean square error (RMSE) <1 dB in comparison with the C-band, HH-polarization Radarsat-2 images. An...
Data from Spanish and Italian olive orchards with different cultivars (‘‘Manzanilla’’, ‘‘Frantoio’’, ‘‘Leccino’’, ‘‘Razzola’’ and ‘‘Taggiasca’’) growing in different environments (southern Spain; north, centre and south of Italy) were used to illustrate how models on water use and photosynthetic behaviour of the olive tree can be useful tools for choosing pruning intensity and canopy shape for ...
In this paper, a new method for estimation of vertical leaf area density (LAD) profile of tree canopy using portable scanning lidar is proposed. In this method, which we refer to as the voxel-based canopy profiling (VCP) method, several measurement points surrounding the canopy and optimally inclined laser beams are adopted to facilitate full laser beam illumination of whole canopy up to the in...
Land-use dynamics and climatic gradients have large effects on many terrestrial systems. Exurban development, one of the fastest growing forms of land use in the United States, may affect wildlife through habitat fragmentation and building presence may alter habitat quality. We studied the effects of residential development and temperature gradients on bird species occurrence at 140 study sites...
Presence of invasive species on rangelands is a degradation sign. The aim of this study was to evaluate the effects of invasive species Leucanthemum vulgare Lam. on the structural and functional characteristics of Fandoghlou rangelands in the Namin county of Ardabil province. The model used for sampling was the stratified random systematic. Two main sites with the presence and absence of L. vul...
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