The effect of tree species diversity on phosphorus availability and cycling

在拥有大面积人工林的热带地区，通过物种多样性森林维持土壤肥力可能是一项重要的生态系统服务。初步调查结果表明，土壤磷含量很低，大部分速效磷存在于有机土壤中，许多物种的叶片和凋落物磷含量都是磷的指示性限制。然而，磷组织浓度的高度变化表明了多种物种特异性机制可以用来限制磷的供应。考虑到生物有效土壤磷化合物的范围很大，以及植物获取磷的多种机制，我们假设共存的植物物种分配土壤有机磷以减少竞争。基于此，我们假设：(a)土壤有效组分中磷的比例随样地树种多样性的增加而增加，(b)邻近树种多样性影响土壤磷组分和单株树的营养，(c)树种多样性对生产力下降（互补性降低）的影响随土壤有机磷源多样性的减少而降低。此外，我们将探索是否可以根据其光谱特性区分不同的土壤P组分，这将大大减少分析工作。

The maintenance of soil fertility through species diverse forests might be an important ecosystem service in tropical regions with their large areas of forest plantations. Preliminary investigations at the Comparative Study Plots of BEF China have shown, that soil P concentrations are very low, a large proportion of available P is in organic from, and that many of the species show of leaf and litter P concentrations that are indicative P limitation. However, the high variation of P tissue concentrations points to a variety of species-specific mechanisms to adopt to limited P supply. Given the large range of biologically available soil P compounds, and the variety of mechanisms by which plants can access P, we assume that co-existing plant species partition soil organic P to reduce competition. Based on this we hypothesize that (a) the proportion of soil P in available fractions increases with increasing tree species diversity of plots, (b) neighbourhood tree species diversity affects soil P fractions and nutrition of individual trees, and (c) effects of tree species diversity on productivity decline (complementarity reduction) with decreasing diversity of soil organic P sources. In addition, we will explore whether the different soil P fractions can be distinguished on the basis of their spectral properties, which would greatly reduce analytical efforts.