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The clumping index measures the spatial aggregation (clumped, random and regular) of foliage elements. The global mapping of the clumping index with a limited eight-month multi-angular POLDER 1 dataset is expanded by integrating new, complete year-round observations from POLDER 3. We show that terrain-induced shadows can enhance bi-directional reflectance distribution function variation and negatively bias the clumping index (i.e. indicating more vegetation clumping) in rugged terrain. Using a global high-resolution digital elevation model, a topographic compensation function is devised to correct for this terrain effect. The clumping index reductions can reach up to 30% from the topographically non-compensated values, depending on terrain complexity and land cover type. The new global clumping index map is compared with an assembled set of field measurements from 32 different sites, covering four continents and diverse biomes.  相似文献   
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Comments on the characteristics of turbulent velocity components in the surface layer under convective conditions
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Ecotoxicological investigations are generally undertaken in the laboratory on some constituents of ecosystems. The complementary synthetic aspect, comprising the analysis of the overall effect of a pollutant on an ecosystem, also falls within the framework of the science of pollution. The present study deals with the effects of a crude Kuwait oil on the primary production of experimental ecosystems  相似文献   
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The distribution of trace elements like Cu, Zn, Ni, Co and Mn in the waters of Pulicat lake has been studied in four aqueous environments — northern, central, southern and channel parts. It is observed that the concentration of the trace elements increase with increase of pH, chlorides and sodium in both monsoon and dry seasons. The concentration and the behaviour of the trace elements are controlled by adsorption, supplemented by organic reactions and by precipitation in sulphide-rich environments.  相似文献   
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