Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; China University of Geosciences, Beijing 100083, China.
Sci Total Environ. 2022 Jan 10;803:149948. doi: 10.1016/j.scitotenv.2021.149948. Epub 2021 Aug 27.
The temperate steppe in northern China is important for sandstorm control and food/livestock production. Understanding the influence and regulatory control of cultivation on the water balance and water use efficiency (WUE) of this water-limited region would promote the sustainability of local ecosystem and food supply. This study combined eddy covariance system observational data and the Shuttleworth-Wallace model to investigate evapotranspiration (ET) and its composition in paired sites, including a free-grazing steppe site and an adjacent site reclaimed for spring wheat cultivation in Xilinhot, Inner Mongolia. Further, analysis of the WUE of both the ecosystem (WUE) and the canopy (WUE) under the two sites showed that the mean daily gross primary productivity (GPP) of the cultivation site was 3.84 gC·m·d, i.e., 15.7% higher than that of the free-grazing site (3.32 gC·m·d). Compared with the free-grazing site (1.76 kgHO·m·d), the mean daily ET of the cultivation site (1.40 kgHO·m·d) was reduced by 20.7%. The difference in ET was due mainly to suppression of evaporation at the cultivation site from increased shading associated with a higher leaf area index (LAI). The largely increased GPP of the cultivation site fundamentally contributed to the 54.7% higher WUE (4.75 gC·kgHO) in comparison with the free-grazing site (3.08 gC·kgHO). The WUE of the cultivation site was 57.9% higher than that of the free-grazing site. The variation of transpiration of the free-grazing site explained 64% of the change of WUE. These results indicate that land use differences in the temperate steppe area changed vegetation productivity substantially. Moreover, ecosystem ET and its composition, as well as large-scale land use change, might influence the regional water use pattern and mass balance. Our findings help clarify the impact of typical land use change on regional WUE, and could promote development of visionary and effective strategies for the use of the limited resources in arid-semiarid regions.
中国北方的温带草原对于控制沙尘暴和提供食物/牲畜生产非常重要。了解耕作对这个水资源受限地区的水量平衡和水分利用效率（WUE）的影响和调控控制，将促进当地生态系统和粮食供应的可持续性。本研究结合涡度相关系统观测数据和 Shuttleworth-Wallace 模型，研究了内蒙古锡林浩特配对样地（一个自由放牧草原样地和一个相邻开垦种植春小麦的样地）的蒸散及其组成。此外，对两个样地的生态系统（WUE）和冠层（WUE）的 WUE 进行分析表明，种植样地的日平均总初级生产力（GPP）为 3.84 gC·m·d，即比自由放牧样地（3.32 gC·m·d）高 15.7%。与自由放牧样地（1.76 kgHO·m·d）相比，种植样地的日平均蒸散量（1.40 kgHO·m·d）减少了 20.7%。蒸散差异主要是由于种植样地的叶面积指数（LAI）较高，导致遮荫增加，从而抑制了蒸发。种植样地的 GPP 大幅增加，是其 WUE 比自由放牧样地（3.08 gC·kgHO）高 54.7%（4.75 gC·kgHO）的根本原因。种植样地的 WUE 比自由放牧样地高 57.9%。自由放牧样地的蒸腾变化解释了 WUE 变化的 64%。这些结果表明，温带草原地区的土地利用差异极大地改变了植被生产力。此外，生态系统蒸散及其组成以及大规模土地利用变化可能会影响区域用水模式和质量平衡。我们的研究结果有助于阐明典型土地利用变化对区域 WUE 的影响，并可以促进制定有远见和有效的干旱半干旱地区有限资源利用策略。
