Decomposition has been studied for decades due to its significance in understanding nutrient cycling and carbon sequestration processes. The current study identified the three interacting factors that control decomposion: the physicochemical environment, litter quality, and decomposer organisms. Exsiting biogeochemical models that that are derived by local cliamte and little quality parameters can explain about 70% of the variation in litter decomposition. However, the role of soil organisms has been largely ignored in these models that assume the functions of soil organisms are mainly controlled by temperature, moisture and litter quality. Recent studies suggest that leaf litters tend to decompose more rapidly in the habitat from which it was derived (i. e. home) than in other habitats (i. e. new home away from its origion) , this phenomena has been termed as the home鄄field advantage (HFA) in litter decomposition. In contrast to plant growth, leaf litter鄄soil feedbacks are expected to consistently cause positive feedback at a home habitat resulting in faster litter decay. This is because 1) leaf litter from different plant species often varies considerably in structure and chemical composition; and 2) leaf litter inputs are a major source of nutrients and energy for soil biota that access decomposed litter. Thus, competition among soil biota for accessing nutrients may create a selective pressure for
Footprint source area analysis is an important approach to study qualitatively and quantitatively the relationship between the flux information and the surface condition. Fluxes measured with eddy covariance system over a heterogeneous surface are usually of uncertainty, hard to control and difficult to interpret. As a result, the credibility of energy and mass exchanges between the atmosphere and the land surface could be questionable. Therefore, it is critically important to identify the fluxes measurement by improved understanding the footprint source area. We calculated the footprint source area from continuous flux measurement by an eddy covariance system from Jan 1, 2009 to Dec 31, 2009 using FSAM(Footprint Source Area Model) model over a poplar plantation in the southern part of Beijing (DanXing; 39毅31忆50义N,116毅15忆07E义). Our objectives are to analyze the spatiotemporal distribution of footprint source area and to interpret the representativeness of the flux measurement data. Changing with the seasons, the prevailing wind directions were 146. 25毅-213. 7毅 and 326郾 25毅-33. 75毅 and non鄄prevailing wind directions remained 33. 75毅-146. 25毅 and 213. 75毅-326. 25毅, respectively. On the spatial variation, stable stratification inhibits turbulence diffusion and contributes to the downwind flux information. Our results indicated that the more stable the atmosphere stability conditions were, the larger the source areas were. During
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