نتایج جستجو برای: leaf canopy

تعداد نتایج: 96802  

2014
Xi Yang Jianwu Tang John F. Mustard

Plant phenology, a sensitive indicator of climate change, influences vegetation-atmosphere interactions by changing the carbon and water cycles from local to global scales. Camera-based phenological observations of the color changes of the vegetation canopy throughout the growing season have becomepopular in recent years. However, the linkages between camera phenological metrics and leaf bioche...

2004
P. D. Blanken T. A. Black

Annual fluxes of canopy-level heat, water vapour and carbon dioxide were measured using eddy covariance both above the aspen overstory (Populus tremuloides Michx.) and hazelnut understory (Corylus cornuta Marsh.) of a boreal aspen forest (53Ð629 °N 106Ð200 °W). Partitioning of the fluxes between overstory and understory components allowed the calculation of canopy conductance to water vapour fo...

2000
Patrick Meir John Grace Antonio C. Miranda

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 ...

2007
Kyu-Sung Lee Min-Jung Kook Jung-Il Shin Sun-Hwa Kim

Although there have been several studies on the spectral characteristics related to leaf water content, it remains unclear whether the spectral property of leaves can be extended to the canopy-level. In this study, we attempt to compare the spectral characteristics of forest vegetation in moderate drought condition observed by laboratory measurement and satellite hyperspectral image data. Spect...

2007
G. N. Flerchinger Qiang Yu

The ability to simulate the surface energy balance and microclimate within a plant canopy is contingent upon accurate simulation of radiation exchange within the canopy. Accurate radiation simulations require some assumption of leaf angle distribution to compute transmissivity, reflection and scattering of radiation. The ellipsoidal leaf angle density function can very closely approximate real ...

2009
Emile S. Gardiner Magnus Löf Joseph J. O’Brien John A. Stanturf Palle Madsen

Efforts inEurope to convertNorway spruce (Piceaabies) plantations tobroadleaf ormixedbroadleaf-conifer forests could be bolstered by an increased understanding of how artificial regeneration acclimates and functions under a range of Norway spruce stand conditions. We studied foliage characteristics and leaflevel photosynthesis on 7-year-old European beech (Fagus sylvatica) and pedunculate oak (...

Journal: :Computers & Geosciences 2006
Pablo J. Zarco-Tejada John R. Miller R. Pedrós Wout Verhoef M. Berger

The FluorMODgui Graphic User Interface (GUI) software package developed within the frame of the FluorMOD project Development of a Vegetation Fluorescence Canopy Model is presented in this manuscript. The FluorMOD project was launched in 2002 by the European Space Agency (ESA) to advance the science of vegetation fluorescence simulation through the development and integration of leaf and canopy ...

Journal: :Proceedings. Biological sciences 2012
Peter B Reich

Quantifying the mechanistic links between carbon fluxes and forest canopy attributes will advance understanding of leaf-to-ecosystem scaling and its potential application to assessing terrestrial ecosystem metabolism. Important advances have been made, but prior studies that related carbon fluxes to multiple canopy traits are scarce. Herein, presenting data for 128 cold temperate and boreal for...

2008
Edward P. Glenn Alfredo R. Huete Pamela L. Nagler Stephen G. Nelson

Vegetation indices (VIs) are among the oldest tools in remote sensing studies. Although many variations exist, most of them ratio the reflection of light in the red and NIR sections of the spectrum to separate the landscape into water, soil, and vegetation. Theoretical analyses and field studies have shown that VIs are near-linearly related to photosynthetically active radiation absorbed by a p...

Journal: :دانش علف های هرز ایران 0
مجید آقا علیخانی دانشگاه تربیت مدرس فائزه زعفریان کارشناسی ارشد اسکندر زند محقق حمید رحیمیان مشهدی استاد دانشگاه محمد رضوانی دکتری

in order to determine the role of plant leaf area in radiation distribution within the canopy and a better understanding of how crops and weeds intercept light a study of the complexity of plants is necessary. the  effect of intercropping on leaf area distribution and dry matter accumulation in corn, soybean and weeds canopy was studied in a  field experiment at a research field of tehran unive...

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