物种多样性维持农田生态系统生产力长期稳定的地下部生态机制

The relationship between biodiversity and ecosystem functioning, especially between diversity and ecosystem stability, is one of the mort important issues in ecological research, which is progressed well in natural and semi-natural ecosystems. However, there is less work in agroecosystems yet. The proposed project will investigate the relationship between crop species diverstiy and the temporal and spatial stability of productivity in different intercropping ecosystems with gradient of soil fertility, based on 4 long-term field experiemnts established at Wuwei, Jingyuan of Gansu province, and Hongsibu in Ningxia in Northwestern part of China. One field experiment at Wuwei has been carried out for 12 years, and the left three ones at Wuwei, Jingyuan and Hongsibu have been carried for 6 years, and all of them will be additional 5 years during the proposed project implementation. On other hand, we will reveal the new mechanism underlying the relationship between diversity and stability of ecosystem in intercropping through testing the hypothesis that crop species diversity (intercropping) drives the improvement of soil fertility (soil aggregation, bulk density, soil organic matter, soil total N etc) with plant-soil interactions, especially for changed structure of microbial community (i.e. fungi and bacteria). The altered soil fertility, in return, enhances resistence to abiotic stress, such as water, nutrient, and salinization; and adjusts interspecific competition and facilitation. The research results will have importance not only for ecological theory in terms of diversity-stability relationship, but also for practical applications towards sustainability of intercropping development.

生物多样性与生态系统功能的关系，特别是与生产力稳定性的关系是生态学研究领域的核心问题，近年来在自然生态系统取得了显著成就。然而，在农田生态系统这一研究则非常薄弱。本项目拟在甘肃武威、靖远和宁夏红寺堡3个不同肥力土壤上已建立的一个12年和三个6年的田间试验基础上，研究农田生态系统作物物种多样性（间套作和轮作等）在不同土壤肥力梯度上系统生产力的长期稳定性；基于前人和我们的前期研究，提出作物多样性体系通过植物-土壤相互作用改变土壤肥力，反过来影响生态系统稳定性的科学假设。即物种多样性连续种植驱动土壤肥力因子(土壤水稳性团聚体，容重，土壤C和N含量)改善，增强系统对非生物（养分、水分和盐分）胁迫的抗性，调控作物种间竞争和种间促进等过程，增加系统生产力稳定性。研究结论不仅有利于在农田生态系统水平阐明生物多样性与稳定性的关系及其机制，而且对于间套作多年连续高产和高养分移出条件下的可持续性提供科学依据。

生物多样性与生产力稳定性的关系是生态学研究领域的核心问题，近年来在自然生态系统取得了显著成就。但在农田生态系统相关研究相对薄弱。本项目依托2003和2009年先后在甘肃武威、靖远和宁夏红寺堡等地3个不同肥力土壤上建立的4个长期间套作及相应单作田间定位试验，研究了农田生态系统作物物种多样性在不同土壤肥力梯度上系统生产力的长期稳定性及其机制。主要结果如下：1）不同作物组合的平均生产力与稳定性呈正相关，即生产力越高的系统，稳定性越高。间作体系生产力时间稳定性取决于与作物组合，且与间作中处于劣势的作物稳定性正相关。长期间套作种植能够增加体系生产力10.3-32.3%。长期间作改善或者维持土壤肥力，增加了所有3种土壤上土壤水稳性大团聚体含量，增加了低肥力土壤的有机质和全氮含量，降低土壤有效磷和钾。间作在一定程度上能够增加土壤总有机碳累积，C3作物的贡献大于C4作物。作物多样性驱动的土壤微生物群落结构改变，可以解释水稳性团聚体的改善和贫瘠土壤碳氮的增加。2）长期间作促进豆科的生物固氮，玉米根系分泌物在强化玉米/蚕豆间作体系豆科作物结瘤固氮中具有重要作用。物种间的补偿和选择效应是间套作体系磷获取优势的重要机制，豆科作物与玉米间作能够更充分的利用土壤中的氮并维持土壤氮养分平衡。3）小麦/玉米间作的根系分布和氮吸收的可塑性有助于玉米生长后期的恢复，玉米与豆科作物间作降低玉米叶片锈病发生，并与玉米叶片Zn营养的改善相关。总之，研究证实了我们提出的作物多样性体系通过植物-土壤相互作用改变土壤肥力，反过来提高了生态系统稳定性的科学假设。即物种多样性连续种植驱动土壤肥力因子(土壤水稳性团聚体，容重，土壤C和N含量)改善，增强系统对非生物胁迫的抗性，调控作物种间竞争和种间促进作用，增加系统生产力稳定性。结论不仅增加了我们对农田生态系统中生物多样性与稳定性的关系的理解，而且对于间套作多年连续高产和高养分移出条件下的可持续性提供了科学依据。