磷（P）是植物生长发育不可缺少的营养元素，是热带和亚热带地区森林生长的限制性因素。营造混交林可能是提高土壤P素有效性，充分利用土壤潜在的P资源的重要举措。土壤磷素形态的多样性以及不同植物对土壤P限制吸收策略的多样性可能会产生共生植物P吸收的生态位分化，从而提高对土壤P的利用效率。本项目拟在林分尺度和邻域树种多样性水平研究凋落物分解和细根周转等生物过程对土壤P素形态构成及生物有效性的影响；通过不同P形态供应源的树种多样性盆栽实验，解析树种多样性对不同土壤P形态的互补利用机制，并验证以下三个科学假说：（1）土壤生物有效态P随着森林演替增加，但土壤总磷含量下降；（2）土壤有效态P随着树种多样性的增加而增加；（3）土壤P的总吸收效率随着生物多样性的增加而增加，而且这种互补效应因共生菌根的作用而增强，但随着土壤有机磷形态多样性的下降而减弱。项目的研究结果将为生物多样性保育和P的有效管理提供理论依据。

Phosphorus (P) is an essential element required for plant growth. Efficient P management is mandatory because P often limits primary productivity in subtropical and tropical regions. The maintenance of soil P availability through species diverse forests might be an important ecosystem service as enhanced mineralization, accelerated nutrient cycle via higher litter production and decomposition, decreased nutrient loss in diverse mixed forests. Meanwhile, given the large range of biologically available soil P forms and compounds, and the variety of mechanisms by which plants can access P, we assume that co-existing plant species partition soil P to increase P use efficiency and reduce competition. . Here the aims of this study are to investigate the impacts of tree functional traits and tree species diversity on P forms formation on the stand level and neightbourhood species diversity combinations, and to assess possible niche separation among four native tree species, comprising two early successional species (Pinus massoniana and Choerospondias axillaris) and two late successional species (Lithocarpus glaber and Cyclobalanopsis glauca), for the utilization of different sources of soil P in a bioassay greenhouse experiment by using different substrates that contain some amount of total P per pot, but different forms of P derived from: a) topsoil with large proportion of organic P; b) subsoil with mostly inorganic P; c) mixed litter with solely organic P; d) mineral inorganic P fertilizer. Based on this we hypothesize: (i) soil P availability increases, while total P decreases with forest succession; (ii) soil P availability increases with tree species diversity; (iii) the overall efficiency of soil P utilization increases with tree species diversity and this complementary effect is more pronounced in substrates containing more diverse organic P sources (i.e. topsoil and litter substrates). In addition, the contributions of mycorrhizal symbiosis will be assessed. This project could provide valuable theoretical information for species diversity conservation and efficient P management in subtropical mixed forests.