荒漠草原植被根—土系统响应环境变化的自调控机理研究

Arid and semi-arid grassland is a water-limited fragile ecosystem, the efficient use of water resources is urgent priority due to the shortage of water resources. Plants absorb Soil water from through the roots, while adapting themselves to adaptability, self-regulation and self-feedback functions according to the soil water condition. While root soil water is a bridge between water supply and water demand, the efficient use of water resources and the precise development of the water-saving irrigation system largely depend on the timely and accurately control and predict the hydrodynamic process of soil water in the root zone. Because the results about researching systematicly and rationally the relationship between desert grassland plants roots and soil environment is rare, the root water absorption rules and self-regulation mechanism under changing environment are unclear, it’s an urgent need for further research. The project aims to study the dynamic change of Soil environmental parameters in roots and the self-regulation mechanism of root-soil system in vegetation response environment through field experiment and mechanism test, and revise root water absorption dynamics model to achieve the modeling and prediction in root zone, which is of great significance to the restoration and reconstruction of damaged ecosystem of desert grassland, biodiversity conservation, sustainable management and regulation of water resources and sustainable development of regional socio-economy.

干旱半干旱草原区是水分限制型脆弱生态系统，水资源的短缺使水资源的高效利用成为当务之急。植物通过根系吸收土壤水分，同时又根据土壤的水分状况自行作出适应性调节即自适应、自调节与自反馈功能。而根区土壤水是供水与用水需求之间的“桥梁”，水资源的高效利用及节水灌溉制度的精准制定在很大程度上取决于及时、准确地掌控及预测根区土壤水分的水动力学过程。荒漠草原根与土壤环境之间作用关系的系统性、机理性研究成果罕见，响应变化环境下的根系吸水规律及自调控机理不明了，亟待进行深入的研究。本项目拟通过现场实验与机理试验，研究根际土壤环境参数动态变化规律，植被响应环境根—土系统的自调控机理，并对根系吸水动力学模型进行修正实现根区土壤水运动的模拟与预测，对荒漠草原受损生态系统植被恢复与重建、生物多样性保护、水资源可持续管理与调控及区域社会经济可持续发展具有重要意义。

草原是我国北疆绿色生态安全屏障。荒漠草原气候干旱，水资源匮乏，水文过程与植物群落生态生理特征之间相互作用显著。本项目通过野外现场试验和实验室化验，进行了内蒙古荒漠草原上东河小流域植物根土系统对环境响应的研究，研究分析了不同退化程度以及增雨梯度下的植物群落特征、植物生理特征以及土壤水分、养分的变化，重点分析了植物对外界环境变化的自身调节功能。研究主要结果：植物的单株功能性状指标随着草原退化程度的加剧呈降低趋势；随着草原退化程度的加剧植物叶片解剖结构的厚度增加，日平均蒸腾速率和净光合速率降低，短花针茅对土壤水分变化的适应性更强，抗旱性最强；优势植物的株高和地上生物量均随增雨梯度表现出先增大后减小的趋势；植物叶片、角质层和主脉厚度随增雨梯度增大呈逐渐降低的趋势，维管束面积/叶面积随雨量增大而下降趋势明显；重度放牧样地内植物叶片解剖结构特征对水分环境的变化最敏感，变动幅度最大；长期放牧导致的草地退化显著减低了土壤有机质含量；增水对植物生长的促进作用增加了对土壤有效氮、有效磷的吸收，从而加剧了土壤养分循环速率；对于荒漠草原的植物来说，根系吸水的主要来源介于土壤10cm至20cn的深度区间；土壤有效重量含水量临界值为7%左右，此时土壤的负压绝对值较高，植物根系则难以吸收水分；土壤重量含水量达到20.8%时，土壤负压值为零，说明此时土壤含水量达到饱和。本项目研究对对荒漠草原放牧管理、生态修复中水分利用管理以及草地生态修复物种选择等提供强有力的理论支撑与依据。