内蒙古典型草原区地表干湿状况变化趋势及影响因素分析

分析气候变化对典型草原区干湿状况的影响，对于了解草原退化原因、恢复草原生态环境有重要的指导意义。本文根据FAO推荐的彭曼一孟蒂斯方程，利用典型草原区1961—2008年25个地面气象站资料，通过计算潜在蒸发量、地表干燥度指数和水分盈亏量，分析了典型草原区地表干湿状况的空间分布规律及其年代际变化趋势，并探讨了它们与气候要素的相互关系。结果表明：（1）典型草原区牧草生长季干燥度指数均在2．0以上，水分亏缺量在400mm以上，属于地表干燥、水分亏缺状态。且整个牧草生长季4—9月，地表仍以干燥、水分亏缺为主。（2）典型草原区地表干湿状况存在着明显的阶段性变化特征。20世纪60、70年代水分亏缺多、干燥度大，属于气候相对干燥时期；80、90年代水分亏缺减少、干燥度降低；2001—2008年，水分亏缺量和干燥度指数逐渐增大，甚至达历史最大值，成为气候最为干燥时期，且变干倾向显著。（3）对典型草原区地表干湿状况影响最显著的因子为降水量和相对湿度（相关系数在0．8以上），其次为日照时数（相关系数在0．6以上），平均气温和平均风速对其影响相对较小。

Analysis on Dry and Wet Variation of Ground Surface and Influenced Factors in Typical Grassland Areas of Inner Mongolia

It was important for understanding the reason of pasture degradation and recovering the grasslands ecological environments to analyze the impact of climate change on dry and wet conditions in typical grassland areas. The new factors, including potential evaporation amount, aridity index of ground surface and water budget, were calculated by using the Penman-Monteith equation, based on meteorological data from 25 stations during 1961 to 2008 in typical grassland areas. The temporal and spatial variation of dry and wet conditions of ground surface in typical grassland areas was analyzed, the relationship between meteorological factors and dry and wet conditions was discussed. The result showed that all the aridity indexes were above 2 during grass growing season in typical grassland areas, the water budget was more than 400mm. Dry and wet condition change temporal in typical grassland areas obviously, the severe water budget and high aridity index occurred during 1960s - 1970s and 2001 - 2008, but not occurred during 1980s and 1990s. Precipitation and relative humidity were key factors to wet and dry conditions of ground surface in typical grassland areas （ r 〉 0.8）, followed by sunshine duration （ r 〉 0. 6）, average temperature and average velocity.