生物种间互惠（facilitation）的生态学理论意义日益受到关注, 在退化生态系统恢复和可持续农业建立的应用也日益受到重视。本项目拟研究"农田系统中物种多样性的生态功能（高的资源利用效率和农田生产力）是否可通过物种之间相互促进（即互惠）来实现"。项目以稲鱼为稻田物种多样性共作模式，研究：（1）稻鱼共作系统中生物种间的互惠规律，重点探讨稻田环境中鱼对水稻有害生物控制的可能途径；探讨水稻对水体环境的改善作用进而对鱼病害发生控制的可能途径。（2）研究稻鱼共作系统中水稻与鱼对资源的互补利用，重点探讨氮素互补利用的可能途径以及氮素投入减量效应；（3）稻田鱼作系统中生物种间的互惠产生的效应，重点探讨共作系统中水稻有害生物和鱼病害的发生、资源利用效率和农田生产力。结果将揭示农田系统生物种间的相互作用规律及生态学效应，对进一步阐明农田生物多样性利用的原理和指导现代农田系统生物多样性的配置都有重要意义。

Facilitative interactions between species (one species makes conditions more favorable for another) are receiving increasing attention in Ecology. It is also been recognizing that exploiting facilitative interactions between species play an important in the restoration of degraded ecoysytems and in the development of sustainable agricuture with biodiversity. In agro-ecosystem, Although multiple-species cropping has showed over-yielding, however, additional species might not always increase agricultural productivity of the main crop due to competition (for nutrients, light, etc.). Thus in the utilization of species diversity in agriculture, it is critical to understand the characters of species interactions and to exploit the positive interaction (facilitation) between species. .The overall goal of this grant project is to examine how facilitative interactions between cultivated species in agro-ecosystem generates emergent ecosystem properties and how modern agricultural systems might be improved by exploiting synergies between species. The species-diverse rice system (i.g. rice-fish coculture) are used as model systems in this study. Specific objectives of this project are: (1) to examine whether and how the fish benefit rice by removing pests for rice, and how rice provides better water environment and reduces diseases for fish; (2) to quantify how fish and rice use nitrogen complementary in the co-culture system, to quantify and how much input fertilizer-nitrogen for rice can be reduced due to this nitrogen complementary use; (3) to characterize how facilitative interactions between rice and fish in co-culture systems generate low pest for both rice and fish, and high efficiency of natural resource utilization and high productivity. .Our project will reveal how facilitation between cultivated species in agroecoysytem can produce ecosystem functionnings. The significance of this project is to enhance our understanding in the principle of the untilization of biodiversity in agroecoysytem. Utilization of facilitation between cultivated species can be an important mechanism that leads to establish modern agriculture with species diversity.