草地覆盖度变化对生态系统防风固沙服务的影响分析——以内蒙古典型草原区为例

锡林郭勒盟为我国北方典型草原区,草地的退化与恢复影响生态系统的防风固沙服务功能。为了便于制定区域生态恢复的防治措施,实现草地生态系统的可持续发展与防治土壤风蚀危害,本文基于气象、遥感数据,运用RWEQ(Revised Wind Erosion Equation)模型,结合锡林郭勒盟的草地覆盖度变化对20世纪90年代以来的防风固沙服务功能的时空变化趋势进行了定量评估,并分析了草地覆盖度变化对防风固沙服务功能的影响。研究表明:锡林郭勒盟土壤风蚀以微度和轻度侵蚀为主,主要集中在植被盖度较高、降水相对较多,风场强度相对较低的东部、中部和南部地区;中度以上区域主要集中在西部的荒漠草原区与浑善达克沙地区,且侵蚀面积随侵蚀强度的增加而递减;防风固沙服务功能量的分布趋势与土壤风蚀模数的分布趋势基本一致;防风固沙服务功能保有率的分布特征与植被盖度的分布特征基本一致,表现为由西北到东南逐渐增加的趋势;在气候暖干化背景下,受京津风沙源治理工程实施的影响,以微度和轻度侵蚀为主的草地覆盖度减小区转为以微度和轻度为主的覆盖度增加区,轻度和中度以上侵蚀为主的草地覆盖度减小区转为基本持衡区;草地覆盖度的降低与增加对土壤风蚀的加剧和抑制作用明显,大部分地区的防风固沙服务功能保有率的下降(提升)与风蚀季节草地覆盖度的减小与提升呈显著正相关(r0.6,p0.05)。

Effects of Vegetation Coverage Change on Soil Conservation Service of Typical Steppe in Inner Mongolia

China is one of the countries suffering severely from soil wind erosion in the world, especially in the typical northern steppe. Xilingol League in Inner Mongolia is a part of the typical steppe zone. Ever since Bei- jing-Tianjin Dust Storms Sources Control Project was established in 2002, the grassland degradation situation has been controlled. The change of vegetation coverage can affect the ecological function of windbreak and sand-fixation. In order to prepare the prevention and control measures for regional ecological restoration, to un- derstand the practical signiflcances of sustainable development of grassland ecosystem, and to control soil wind erosion, in this study, based on the meteorology and remote sensing data, combined with grassland degradation and recovery in Xilingol League, the Revised Wind Erosion Equation （RWEQ） was applied to quantitatively evaluate the spatio-temporal variations of soil conservation service function since the 1990s and to reveal the ef- fects of the change of vegetation coverage on soil wind erosion control service. The results are shown as follows. The intensity of soil wind erosion was low in the most regions of Xilingol League, Especially in the eastern, cen- tral and southern regions, with higher vegetation coverage, lower wind field intensity, and abundant rainfall. The wind erosion regions with medium and higher soil wind erosion intensity were mainly distributed in the western desert steppe and Otindag Sandy Land, and the area of these regions decreased progressively as the erosion inten- sity increased. The distribution pattern of soil retention was similar to soil wind erosion modulus. The distribu- tion characteristics of the soil retention rate were similar to the vegetation coverage, indicating a gradually in- creasing trend from northwest to southeast. Under the comprehensive influence of the warming-drying climate and the implementation of Beijing-Tianjin Dust storm Source Control Project, the vegetation coverage decreas- ing regions dominated by slight and micro erosion intensity turned into vegetation coverage increasing grassland dominated by slight and micro erosion intensity; the grassland having mild, medium or severe degree of vegeta- tion coverage reduction turned into the grassland with balanced vegetation coverage. The decrease or increase of vegetation coverage can significantly intensify or mitigate the soil wind erosion. Additionally, the soil retention rate showed a significant positive relationship with the grassland vegetation coverage in the spring seasons in most regions（r〉0.6, p〈0.05）.