农田系统生物种间的互惠（facilitation）及其生态学效应

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.

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。

生物种间互惠（facilitation）的生态学意义日益受到关注, 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）农田系统中生物种间互惠的规律和实现的途径;（2）农田系统中生物种间互惠的生态学效应，重点探讨资源利用效率和农田生产力；（3）农田系统中生物种间氮素的互补利用原理。经4年研究，完成了项目计划的研究内容和目标, 重要研究进展如下：(1) 揭示农田系统利用多物种共存实现产量稳定的途径，大样本的分析表明，稻“鱼”系统生产力的稳定维持取决于水稻与水产生物产量之间的权衡。稻鱼系统中，共存生物之间的适当比例可以产生互惠效应，水稻产量从而能维持稳定，且氮肥和农药显著下降。（2）阐明农田系统物种间的互惠及资源利用的生态学效应，摄像记录统计表明，水产生物在整个稻田空间活动，将定点喂食的、未被同化利用的饲料氮通过排泄的方式释放到稻田整个区域范围，起到“不间断性”的施肥作用，促进稻田的养分循环和水稻生长；稳定性同位素13C(碳)和 15N（氮）测定发现， “田鱼”体内δ13C和δ15N值的16.8%和12.5%来源于稻田系统内生资源（包括各类昆虫、杂草、水稻基部叶片、藻类、浮游植物等），从而扩大了系统的资源利用。（3）证实生物之间互补利用氮素可降低农田氮素的输入，稳定性同位素15N标志实验表明，系统输入的饲料-N和肥料-N被水稻和鱼循环互补利用，当饲料-N和肥料-N的比重分别为63%和37%时，系统能很好的维持系统N平衡和稻鱼产量，肥料-N的输入显著降低。这些研究结果发表在《Frontiers in Ecology and the Environment》（2014, 12(9): 507–514）、《Scientific Reports》（2016，doi:10.1038/srep28728）、《Agriculture, Ecosystems & Environment》（2016, 224, 116-122；2013,177: 28-34）、《中国生态农业学报》（2015,23(3): 268-275）、《应用生态学报》（2017,28（1）；2017,28(3)）。项目共培养博士2名，硕士2名