北方农牧交错区微地形土地利用对生态系统服务垂直分异作用机制研究

The development process of desertification has been primarily curbed in general but kept expanding in partial locations in the agro-pastoral ecotone in northern China. At this circumstance, research on the mechanism of land use on ecosystem services’ vertical differentiation at the micro-topography of undulating sand dunes and marshy lands is not only conducive to further achieve anti-desertification, but also beneficial for further implementation of ecological restoration for the agro-pastoral ecotone in northern China. Taking Wudantala Village as a case study, based on ecosystem services comprehensive view, applying methods of field experiment, field survey, spatial analysis, this project builds typical land use pattern identification at micro-topography → vertical differentiation law of ecosystem services → vertical differentiation mechanism of ecosystem services→ land use adjustment research framework. Typical land use patterns at the micro-topography of undulating sand dunes and marshy lands are identified. Vertical differentiation law of ecosystem service types and their intensities at micro-topography are revealed. From aspects of vertical differentiation of natural factors’ properties and farmers’ land use decision-making mechanism at micro-topography, vertical differentiation mechanism of ecosystem service types and their intensities are explored. According to relationships between vertical changes of ecosystem service types and their intensities and sandy desertification degrees, land use adjustment is conducted at micro-topography. In theory, the project reveals the vertical differentiation law and mechanism of ecosystem services at the micro-topography of undulating sand dunes and marshy lands which extends and deepens differentiation mechanism studies of ecosystem services. In practice, this project provides scientific basis and practical reference for micro-topography land use adjustment to further realize anti-desertification and ecological restoration in the agro-pastoral ecotone in northern China.

在北方农牧交错区荒漠化呈整体逆转、局部扩展的背景下，研究坨甸微地形土地利用对生态系统服务垂直分异的作用机制对进一步实现该区域荒漠化防治和生态恢复具有重要意义。项目以乌旦塔拉嘎查为例，基于生态系统服务的综合视角，运用野外实验、实地调查、空间分析等方法，按照微地形典型土地利用模式识别→生态系统服务垂直分异规律→生态系统服务垂直分异机制→土地利用调整的研究思路，识别坨甸微地形的典型土地利用模式，揭示微地形生态系统服务类型及其强度的垂直分异规律，基于微地形自然要素的垂直分异和农民土地利用决策机制阐述生态系统服务类型及其强度的垂直分异机制，依据生态系统服务类型与强度的垂直变化及其与土地沙化的关系进行微地形土地利用调整。理论上，揭示北方农牧交错区坨甸微地形生态系统服务垂直分异规律和机制，扩展并深化生态系统服务分异机制研究；实践上，为进一步实现北方农牧交错区荒漠化防治和生态恢复提供科学依据与实践参考。

针对坨甸地形区是荒漠化扩张的典型区和生态系统服务研究在微地形垂直方向上的不足，本项目研究坨甸微地形生态系统服务垂直分异规律及其机制，并提出坨甸微地形土地利用调整方案。以坨甸广布的乌旦塔拉嘎查为研究区，基于地形和土地利用数据，分析了土地利用在高程上分布特点。基于野外采样、实验室分析，研究了粮食供给、玉米叶子供给、牧草供给、防风固沙等生态系统服务在高程上的变化规律。利用监测的土壤水分，揭示了土地利用和生态系统服务的垂直变异机制。据此提出了坨甸微地形土地利用调整方案。. 耕地和林地主要分布在241m以下区域，灌木主要分布在243m以下区域，草地主要分布在245m以下区域，沙地主要分布在高于239m区域。粮食供给服务强度随高程增加呈下降趋势，强度突变高程点为241m。玉米叶子供给服务强度随高程增加也呈下降趋势，但其在垂直方向上的变化较小。牧草供给服务强度呈高程低（＜237m）和高（＞249m）的区域强度较大，中部区域强度较小。防风固沙生态系统服务强度也呈现高程低（＜241m）和高（＞251m）的区域强度较大，中部区域强度较小。. 降雨后，坨甸地形高程小的土壤剖面的含水量并没有比高程大的土壤剖面的含水量大，表明降雨后沙质土壤水分以垂直入渗为主。连续无降雨时，地下水影响的土壤剖面的含水量远高于不受地下水影响的土壤剖面的含水量。降雨后，不受地下水影响的土壤剖面的含水量增加比受地下水影响的土壤剖面的含水量增加小很多，且完全受地下水影响的土壤剖面的含水量基本不变。因此，距离地下水位远近决定了坨甸地形土壤水分含量高低，地下水埋深是造成坨甸地形土壤水分分异并由此导致土地利用和生态系统服务分异的根本原因。. 根据土地利用分异、生态系统服务强度垂直变化、地下水水位（235m），提出北方农牧交错区坨甸地区在地下水埋深6m以内的区域可利用为耕地，其他区域应恢复为林草，以防治荒漠化和恢复生态。