干旱绿洲区枣棉复合系统根系生态位竞争与土壤水分在种间分配响应关系

Agroforestry system is one kind of important agricultural management mode in arid oasis area and high efficiency use of water is the key to sustainable development of agroforestry system. Because of competitive capacity of roots to soil water can expressed by evapotranspiration diversity in different species, therefore effection of different species roots interaction to characteristic of evapotranspiration gradually became hot topics in agricultural engineering research field. But the research of niche competition between crops and trees roots in underground space and evapotranspiration distribution on the ground of compound system are at the very beginning, especially research to agroforestry system in arid oasis area was barely reported. In this project agroforestry system under the condition of drip irrigation will be taken as research objects, based on the preliminary study and thermal dissipation method as well as soil core method will be used in field experiment, mainly studied the influence of competition capacity in jujube-cotton agroforestry system to soil water distribution between jujube and cotton roots under different soil moisture conditions, based on the soil productivity mechanism of high efficiency use of water in jujube-cotton agroforestry system will be clarified, Explores the influence mechanism of annual change of jujube-cotton agroforestry system roots competition to system evapotranspiration and moisture distribution, in order to provide the theoretical basis to establish irrigation program scientifically and update the schema reasonably of jujube-cotton agroforestry system.

在干旱绿洲区，农林复合系统是一种重要的农业经营模式，水分高效利用则是农林复合系统持续发展的关键。由于根系对土壤水分的竞争能力是通过种间蒸散量的差异表现的，因此，在农林复合系统中，根系之间的相互作用对蒸散特征的影响，成为近年来农业工程领域研究的热点。但关于农、林种间根系在地下空间生态位的竞争与地上复合系统的水分蒸散分配关系研究尚处于起步阶段，尤其对干旱绿洲区农林复合系统研究鲜有报道。本项目以滴灌条件下的枣农复合系统为研究对象，以前期研究为基础，采用热扩散法、根钻法等技术，通过田间定位试验，重点研究在不同土壤水分条件下，枣棉复合系统根系竞争能力对土壤水分在种间分配的影响，揭示枣棉复合系统水分高效利用机制，探索年际间枣棉复合系统根系竞争关系的变化对系统蒸散量和水分分配关系的影响机理。为科学制定枣棉复合系统灌溉制度和合理更新复合系统模式提供理论依据。

在干旱绿洲区，农林复合系统是一种重要的农业经营模式，明晰种间水分竞争关系，是农林复合系统水分高效利用和持续发展的关键。通过4年的田间定位小区试验，重点研究在不同土壤水分条件下，枣棉复合系统根系竞争能力对土壤水分在种间分配的影响，揭示枣棉复合系统水分高效利用机制，探索年际间枣棉复合系统根系竞争关系的变化对系统蒸散量和水分分配关系的影响机理。取得如下重要结果：对比单、间作模式下枣树、棉花根系分布，种间竞争核心区由水平20-40cm逐渐外移至40-60cm处；竞争主导优势由棉花逐渐转移到枣树；枣棉复合系统根区土壤水分在棉花苗期无竞争关系，各处理土壤水分效应为正效应，值为6.27~8.96%，而在棉花蕾期-花铃期存在竞争关系，土壤水分效应为负效应，其值分别-4.93~-2.86%、-11.61~-2.78%，表明随着棉花生育进程的发展，种间竞争有逐渐激烈的趋势；运用大型称重式蒸渗仪对枣棉复合系统的耗水规律进行分析，单作枣树在花期日均耗水强度达到最大，为4.42mm/d，其次在幼果期，为4.09mm/d，枣树从萌芽期到成熟期的腾发总量约为640.83mm；枣棉复合系统在幼果期日均耗水强度达到最大，为6.79mm/d，其次在果实发育期，为5.64mm/d，腾发总量约为842.92mm；运用微型蒸渗仪分析枣棉复合系统下枣树的棵间土壤蒸发强度，发现在萌芽展叶期各处理棵间土壤蒸发强度基本一致，在枣树花期-果实膨大期，单作棵间蒸发显著高于间作棵间蒸发，差幅在8%—16%之间，间作棵间总蒸发量相比单作在整个生育期中减少了约32mm。明确种间根系竞争关系，揭示枣棉复合系统的耗水规律，对科学制定枣棉复合系统灌溉制度,提高水分利用效率，具有重大的理论及现实意义。