نتایج جستجو برای: lack of vegetation
تعداد نتایج: 21169415 فیلتر نتایج به سال:
Ecosystem responses to climate change can exert positive or negative feedbacks on climate, mediated in part by slow-moving factors such as shifts in vegetation community composition. Long-term experimental manipulations can be used to examine such ecosystem responses, but they also present another opportunity: inferring the extent to which contemporary climate change is responsible for slow cha...
In this Appendix, we summarize some basic properties of the three classes of functional diversity measures: (1) functional Hill number ) (Q D q which quantifies the effective number of equally abundant and equally distinct species in an assemblage with a constant species pairwise distance Q, where Q denotes Rao’s quadratic entropy; (2) mean functional diversity MD(Q) = Q Q D q × )] ( [ which qu...
The present study discusses a method used to produce updated information about vegetation cover in arid and semi-arid zones, using RS data and GIS technique. In this method, Landsat ETM+ data in 2002 was collected in an area of about 60000 ha in Nodoushan basin, Yazd, Iran. To collect the necessary ground data, 50 sites of different vegetation types were selected and the percentage of vegetatio...
Advances in understanding avian nesting ecology are hindered by a prevalent lack of agreement between nest-site characteristics and fitness metrics such as nest success. We posit this is a result of inconsistent and improper timing of nest-site vegetation measurements. Therefore, we evaluated how the timing of nest vegetation measurement influences the estimated effects of vegetation structure ...
the study of the exclosure effects on the vegetation changes undergrazing and non-grazing conditions in the rangeland areas has particularimportance in the rangeland improvement and revivification projects. theresearch was accomplished in semi-steppe khoybilehvar area, from 1999 to2005. vegetation cover was annually measured within fixed plots during transact.the results showed that during nine...
this paper discusses the importance of environmental aesthetics and scenic beauty of currentroadside vegetation in the highways, and the necessity for the contribution of users (motorists) preferences inthe integration of scenic beauty of roadside vegetation into its management plans. the results of a questionnairesurvey of motorist’s opinion on the landscape aesthetics and quality of some high...
extended abstract introduction the most important indicator of climate in a region is vegetation community. climate can be different over large areas, because of changes in vegetation community. vegetation influences weather and climate in its surrounding areas mostly by way of evapotranspiration and albedo so they play a role in the earth’s energy balance. these effects on the earth’s energy...
Drought as a complex ecosystem crisis can affect vegetation density and health. Iran with an arid and semi-arid climate is exposed to this phenomenon. Therefore, it is necessary to evaluate the effect of drought on vegetation. The purpose of this study is to evaluate the effect of meteorological drought on vegetation dynamics in Iran. In this regard, using MATLAB software, SPEI index with time ...
BACKGROUND Africa is an important part of the global carbon cycle. It is also a continent facing potential problems due to increasing resource demand in combination with climate change-induced changes in resource supply. Quantifying the pools and fluxes constituting the terrestrial African carbon cycle is a challenge, because of uncertainties in meteorological driver data, lack of validation da...
Vegetation indices have been developed to characterize and extract the Earth's vegetation cover from space using satellite images. For detection of vegetation changes, usually temporal images are independently analyzed or vegetation index differencing is implemented. A review on previous studies reveal that, in spite of developing several vegetation indices, to extract vegetation cover or veget...
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