准噶尔盆地南缘荒漠植被斑块状格局对土壤水分运移过程的响应机理

The two-phase mosaic pattern of vegetation patches and bare patches are main features in arid desert area. Soil moisture transfer process affects the evolution of patchy pattern directly, has a close relationship with the conservation of the fragile ecological environment. Therefore, discuss the ecological vegetation patches response mechanism to soil moisture migration process with eco-hydrology viewpoint has great significance for the regional ecological security. This study adopts located observation in the field, through the analysis the water cycle process of patchy distribution of vegetation pattern to determine the spatial variability of soil hydrological characteristics of vegetation patches, clarify the rules of moisture transport, keeping and redistribution between vegetation patches and bare patches, reveal the relationship of soil and vegetation during soil moisture migration in patches. Analysis the source species and proportion of vegetation water utilization with stable isotope technique, establish a patchy pattern of eco-hydrological model on water transport, explore the eco- hydrological effects of soil water movement on the formation of patchy pattern, simulate the eco-hydrological process of vegetation patches pattern and explore the sustainable maintaining mechanism of desert ecosystem vegetation patches pattern. The results can provide an important basis for the sustainable development of artificial ecological restoration and reconstruction of oasis in arid area.

干旱荒漠区以植被斑块和裸地斑块两相镶嵌的斑块状格局为主要特征。土壤水分运移过程直接影响着斑块状格局的演变，与脆弱生态环境的保育有着密切的关系，因此从生态水文学角度更深层次探讨植被斑块状格局对土壤水分运移过程的生态响应机理，对于区域生态安全具有重要意义。本研究将野外试验观测与室内模拟试验结合，通过分析植被斑块状分布格局的水分运移过程，确定植被斑块和裸地斑块土壤水文物理特征空间变异性，阐明植被斑块与裸地斑块间水分的传输、保持与再分布规律，揭示水分驱动作用下斑块内土壤与植被的耦联关系；结合稳定同位素技术分析植被水分利用来源的种类及比例，建立植被斑块状格局对水分运移响应的生态水文耦合模型，研究荒漠植被土壤水文过程及斑块状格局对土壤水分分布规律及运移过程的响应机理，揭示荒漠生态系统植被斑块状格局可持续稳定维持机制，为干旱区人工生态恢复重建及绿洲的可持续发展提供重要依据。

项目以准噶尔盆地南缘绿洲-荒漠交错带典型斑块状格局梭梭植被为研究对象，揭示土壤水文物理特性以及天然植被水分运移规律，回答了荒漠植被水分利用来源及水分运移规律以及植被斑块状格局生态水文过程的科学问题，主要结论如下：.1.植被斑块土壤温度形成以植被斑块为中心的“冷岛效应”。植被斑块土壤水分呈明显反“S”型分布，形成以梭梭植株为中心的“湿岛”；植被斑块与裸地斑块土壤总盐含量均呈“正S型”曲线，并形成以梭梭植株为中心的“低盐区”。.2.植被斑块与裸地斑块土壤八大离子中阳离子以Ca2+和Na+为主，阴离子以SO42-和Cl-为主。其中SO42-和Ca2+呈现出明显浅集表聚的分布特征，少部分离子往土壤深处迁移如Cl- 和Na+，土壤中盐分以硫酸钙、硫酸钠和氯化钠为主。由土壤水化学类型分布图可知研究区土壤盐碱化严重。.3.原生梭梭对水分的吸收和传输呈现出极强的环境适应性。降雨前梭梭水分利用来源中地下水的比例最高，为34.14%；降雨后梭梭主要依靠吸收浅层土壤水(土层深度≤1.2m)，为33.19%。.4.梭梭对水分的吸收和传输受气象环境的影响，太阳辐射、大气温度和湿度气象因子与梭梭液流速率呈显著相关性，茎流变化滞后于气象因子变化约1h；各气象因子对梭梭茎流速率影响程度为：太阳辐射(0.826)>大气温度(0.598)>湿度(-0.573)。.5.植被斑块梭梭根系对水分具有再分配作用，降低干旱气候条件对梭梭植被的胁迫，使梭梭植被能够更好的生存于干旱环境。