内蒙古温性草原区典型草地管理利用方式差异对生态系统水分利用效率的影响机制研究

By changing the structural characteristics of the ecosystem, the land use and cover changes caused by human activities exert a substantial influence on the water and carbon budget of the ecosystem, even the water and carbon material balance of the region. The water use efficiency, which links the water cycle and the carbon cycle, is an important ecosystem feature that connects the water consumption of the land vegetation and the carbon budget changes. The farming-pasture ecotone area of temperate steppe in Inner Mongolia is one of the regions with the most intense changes on LUCC in China. The water use efficiency in this region, which is subject to the changes of human management patterns, is of concern to the climate and ecosystem stability in the region. Focusing on the three typical use/management patterns on the Inner Mongolian temperate steppe: grazed steppe, grazing excluded steppe and steppe cultivated to cropland, the present research obtains and compares the continuous dynamic difference of the ecosystem water use efficiency between the different management patterns in a long term, with the elaborately split data from controlled experiments and the long-term observation data of the Eddy Covariance System. With observations on the dynamic changes of the communities, this research aims at analyzing the adjusting mechanism in the reaction of the long-term water use efficiency of steppe to the human management pattern changes.This research will provide theoretical and data support to the development and enhancement of the regional water and carbon cycle models which include land use scenarios. Therefore, it could offer theoretical and technological support to the elaboration of land use policies in the farming and grazing areas on the temperate steppe, in order to alleviate and adapt the region to the climate changes.

土地利用、覆盖变化通过改变生态系统结构特征，能显著影响生态系统水碳收支，甚至区域水碳物质平衡。水分利用效率连接水循环和碳循环，是关联地表植被水碳收支变化的重要生态系统特征。内蒙古温性草原农牧交错区域是我国LUCC变化最为剧烈的典型区之一，区域内生态系统水分利用效率受人类管理利用方式变化的影响，将关系区域内气候、生态稳定。本研究以内蒙古温性草原三种典型草地管理利用方式（放牧、禁牧恢复和开垦）为研究对象。通过结合控制实验精细拆分数据和涡度相关系统长期观测数据，可获取、比较各典型管理利用方式生态系统水分利用效率长时间连续动态差异。结合观测群落动态变化，尝试解析草地长时间水分利用效率响应人类管理利用方式变化的调节机制。研究将为开发与改进包含土地利用情景的区域水碳循环模型提供理论和数据支持，从而为科学制定温性草原农牧交错区土地管理利用政策，帮助区域缓解、适应气候变化提供理论、技术支持。

人类活动造成的土地利用、覆盖变化通过改变生态系统结构特征，能显著影响生态系统水碳收支，甚至区域水碳物质平衡。作为生态系统碳水循环的耦合指标,水分利用效率(WUE)是衡量区域资源转化效率的重要参考。水分利用效率连接水循环和碳循环，是关联地表植被水分消耗和碳收支变化的重要生态系统特征。草原区域是我国LUCC变化最为剧烈的若干典型区之一，区域内生态系统水分利用效率受人类管理利用方式变化的影响，将关系区域内气候、生态稳定。为了解开垦对放牧草地生态系统水分利用效率的影响,研究以放牧和开垦区域毗邻的两套涡度相关系统监测数据为基础,结合群落调查和采样测定,对比分析了两种管理利用方式下生态系统水分利用效率(WUEGPP)的动态差异和影响因素。结果显示：1)WUEGPP在夏季达到全年峰值,6月份开垦站点日均WUEGPP 3.61gC·kg-1 H2O，较放牧站点高58%,全年WUEGPP 3.07gC·kg-1 H2O， 较放牧站点2.11 gC·kg-1 H2O提升约50%；2)开垦站点较高的WUEGPP归咎于生长季较高的总初级生产力(GPP)和非生长季更低的蒸散耗水(ET)；3)ET变化对放牧站点WUEGPP变异解释程度较高(26%, P<0.001),而GPP对开垦站点WUEGPP变化的解释程度(45%, P<0.001)高于ET；4)环境因子中,土壤含水量对WUEGPP变化的调控作用最强,两者负相关关系在开垦站点、放牧站点均达到极显著水平(P<0.001)。研究结果能为合理规划区域土地利用,促进干旱区关键资源高效利用提供有益参考。