干旱绿洲区核桃/小麦间作系统水热碳氮过程与耦合模拟

Agricultural production in the arid-oasis region of Southern Xinjiang has faced severe resource constraints and environmental pressures. In order to understand the dynamics of water-heat-carbon-nitrogen process in the typical agro-ecosystem in the oasis of Southern Xinjiang, field experiments and numerical modeling and simulations were planned in this research. The main concern is to solve the scientific problem, i.e., the quantification of coupled water-heat-carbon-nitrogen process of the agroforest intercropping system in the oasis region of Southern Xinjiang. From this work, we aim (1) to discover the interspecific competition and utilization for radiation, water and nitrogen in walnut and wheat intercropping system in the arid-oasis region, (2) to reveal the regulation mechanism of agroforest intercropping on soil carbon pool of farmland in the arid-oasis, (3) to revise and improve the 3D root architecture component, plant growth and development component, soil water and heat movement component, and soil solution movement component of the SPACSYS model, (4) to perform model validation and calibration, to simulate water and material cycles in the agroforest intercropping system with the revised version of SPACSYS model, and to optimize water and nitrogen management of the walnut/wheat intercropping system using scenario simulation. This research will innovate on the theory and methods of coupled water-heat-carbon-nitrogen process simulation in the arid-oasis region, establish scientific foundation to the understanding of water and material cycles in the oasis agro-ecosystem, and provide theoretical and technical supports on sustainable improvement of agricultural productivity and developing agricultural measures of soil carbon sequestration and emission reduction.

本项目以南疆干旱绿洲区农业生产面临日益加重的资源约束和环境压力为背景，以认识南疆绿洲典型农田生态系统的水热碳氮动态变化过程为主线，将通过田间试验和数学模拟的方法，重点解决绿洲区农林间作系统水热碳氮动态过程的耦合描述这一关键科学问题，揭示干旱绿洲区核桃/小麦间作群体种间对光热与水氮资源的竞争与利用过程，明确间作种植对土壤碳库的调控作用，修正与完善SPACSYS模型的3D根系结构模块、植物生长模块、土壤水热传输模块与溶质运移模块，对修正的SPACSYS模型校正和验证，模拟分析农林间作系统的水与物质循环过程，优化核/麦间作系统的水氮管理方案。本项目将创新干旱绿洲区农田水热碳氮运动理论与模拟方法，为深入认识绿洲农田生态系统的水与物质转化过程提供科学基础，为干旱绿洲区农业生产力的持续提高和农业固碳减排措施的制定提供理论依据和技术支持。

核桃/冬小麦间作在南疆地区被广泛应用，能有效提高土地、水肥、光热资源的利用率，有利于良性生态循环和农业可持续发展。然而，在生态脆弱的南疆干旱绿洲区，人类活动对当地的生态影响显著，因而，有必要进一步的研究干旱绿洲区的水热碳氮传输机制和原理，加深对区域农田生态水文过程的认识。本项目取得如下主要研究结果：1）明确了核桃和小麦根系的空间分布特征，构建了间作作物根系分布的3D模型。利用CT扫描成像技术获得了根系3D图像以及根际团聚体的三维结构，明确了环境因子对根系生长与根际水力导度的影响。2）揭示了水氮供应与株间竞争对植物生长、生理特性及激素调控的影响，阐明了干旱条件下水力信号对叶片水气传输的影响机理。探讨了环境胁迫对植株茎水力导度的影响机理，建立了微米尺度的水流运动模型。3）根据间作冠层几何结构建立了间作冠层辐射传输模型，将该模型嵌套于多源ERIN模型，模拟了间作群体内小麦和核桃的蒸腾量和土壤蒸发量。间作小麦条带和核桃条带的耗水量分别为间作群体耗水量的52%和48%。4）量化了核桃/小麦间作群体内作物根系吸水深度的季节变化，核桃和小麦的水分来源受降雨和灌溉的影响，存在明显的季节转换。明确了核桃/小麦间作群体的氮素转移特性，种植模式、生育期及其交互效应显著影响核桃和小麦的各器官15N分配率。5）阐明了核桃/小麦间作群体的温室气体排放规律及其影响因素。土壤全氮是核桃/小麦间作群体土壤CO2排放的主要调节因子。核桃/小麦间作群体的土壤全氮、铵态氮与土壤WFPS显著影响了N2O全球增温潜势。6）修正了SPACSYS模型的作物生长、碳氮循环等子模块，利用修正的SPACSYS模型模拟分析了核桃/小麦间作群体的水热碳氮过程。充分供水和水分亏缺条件下常规施氮和减氮处理的净N损失分别为93.21, 72.15, 78.64和 63.84 kg N ha-1 year-1。本项目研究结果为深入认识绿洲农田生态系统的水与物质转化过程提供科学基础，为干旱绿洲区农业生产力的持续提高和农业固碳减排措施的制定提供理论依据和技术支持。