西北极端干旱区农林间作系统水分竞争与互补的生态位分离机制

Agro-forestry intercropping system, as an efficient and sustainable planting pattern, had played an important role in agricultural production in southern of Xinjiang. Interspecific relationship have been shown to influence intercrops water use continuously and deeply, but lack of theoretical basis for clarifying soil water competition and complementary from the angle of niche separation. In this project, field experiments will be carried out under different crop spatial distributions, row spacing and densities in jujube/cotton intercropping and their corresponding sole crops. The purpose of the research as following: (1) To determine tempo-spatial dynamics of soil evaporation, soil moisture, and available soil water, investigate tempo-spatial variation of the soil water, and clarify the tempo-spatial variation of water use in jujube and cotton intercropping system. (2) To evaluate the characteristics of tempo-spatial root distribution, explicit the main center for root growth and absorption, and the main area for completing water from soil, explain the coupling effects and mechanisms of root distribution with soil water in agro-forestry intercropping system. (3) To quantify the correlation index of competition and complementary, estimate the niche differentiation index combined with the yield density model, elucidate the response mechanism of niche differentiation index to crop spatial distribution in agro-forestry intercropping system. (4) To explore the niche theoretical basis of tempo-spatial and complementary utilization of soil water for jujube/cotton intercropping, construction the niche differentiation mechanism of water competition and complementary under agro-forestry intercropping system.. The results of this project will strengthen and deepen the theories on inter-specific interaction in compound systems, also will provide essential basis for development and extension of agro-forestry intercropping system in water-deficient areas.

农林间作系统作为一种高效的、可持续的种植模式在南疆地区农业生产中发挥着重要的作用。关于种间关系调控水分利用的研究持续而深入，但缺乏从生态位分离角度阐明水分竞争互补的理论依据，本项目以枣/棉间作为研究对象，在农作物不同的空间布局下：（1）研究土壤蒸发量、土壤含水量和有效水的时空动态，明确枣/棉间作系统水分的时空变异特征，解析枣/棉间作系统水分利用的时空变化规律。（2）研究农林间作系统根系时空分布特征，明确枣/棉根系生长与吸收中心及水分竞争利用的主要区域，探明农林间作群体根系分布与土壤水分的耦合机制。（3）量化竞争互补相关指标，结合产量-密度模型测算生态位分离指数，明确农林间作体系生态位分离指数对空间布局的响应机制。（4）探讨枣/棉间作水分时空互补利用的生态位理论基础，提出农林间作水分竞争互补的生态位分离机制。.项目成果将对深化种间关系理论，推动极端干旱区农林间作发展提供重要理论和技术支撑。

针对西北极端干旱区农林间作节水增效理论和技术研究体系不够完善，采用大田试验，以枣棉间作为研究对象，通过研究土壤耗水特性、根系时空分布、竞争互补、生态位分离指数等指标，结果表明：枣树/棉花中枣树表现出较强的种内竞争力（b22/b20=2.076）和种间竞争力（b22/b20 =1.355），显著高于棉花种内、种间竞争力。生态位分离指数（NDI）变化趋势与作物各时期水分互补特性吻合。在间作群体中尽管竞争的结果使得资源利用更有利于枣树的生长，但总体表现较好的互补性（NDI=1.202）。1-4龄幼龄枣园，枣树的行距为3m，距离红枣1米处种植4行棉花、棉花株距为12.5cm时，枣棉间作复合系统产量为7432kg/hm2，水分利用效率为11.37kg/hm2·mm，水分当量比最高为1.32。种间竞争导致生态位在时间和空间上发生分离，间作系统互补地利用水分，继而提高群体水分利用效率是农林间作复合系统水分竞争互补的生态位分离机制。.项目成果对深化种间关系理论，构建农林间作种植模式，乃至推动极端干旱区农林间作发展产生积极作用。