基于植被-气候最大响应模型的草地退化评价

Estimation of grassland degradation based on maximum response of vegetation to climate

草地植被生长现状及变化趋势的宏观监测,对草地资源的管理及生态建设有着重要的理论指导和实践监督意义。然而,多数的草地退化程度评价都没有考虑草地植被对气候条件年际变化的敏感性,评价"基准"不一,致使对草地退化程度评价的结果也无从比较,给草地生态建设恢复工作的实施与监督带来不便。基于植被-气候最大响应模型的草地退化评价方法,认为非气候因子(如病虫害、野火、放牧和人类活动等等)如果对草地植被的生长影响过度,就会造成草地植被生产力下降等后果。因此,利用长期的遥感数据和气象观测资料的空间插值结果,查找特定气候条件下同种类型草地植被所能达到的最大生产力,即可建立一定时间空间范围内草地植被生产力与气候条件的最大响应模型,以此作为草地退化的评价"基准",可对草地植被的生长状态及其变化过程进行监测与评价。对锡林郭勒盟草地植被退化状态及其变化趋势的评价结果表明:非气候因子导致的锡林郭勒盟草地退化非常严重,但从多年变化趋势来看,全盟的草地退化面积和平均退化程度均有减小的趋势。

Grassland degradation is a complicated process of multi-system interaction. Observation on grassland vegetation growth and change is of critical importance to grassland resource management and environment construction. However, most of estimations on grassland degradation neglected sensitivity of grassland vegetation to annual climate change. Uncertainty of assessment baseline results in inconsistent and incomparable estimations, which further leads to inconvenience of implementing and supervising grassland environment recovery. This paper presents a new estimation method of grassland degradation based on the maximum response model of vegetation to climate. Assuming that non-climatic factors, such as insects, wild fire, grazing and human activities, would decrease the growth of grassland vegetation with excessive effects, a maximum response model of grassland vegetation production to climate was constructed based on long time series of remote sensing data and spatial interpolated meteorological data. This model theoretically presents a better quantitative discription of vegetation-climate response, which excludes the effects of human activities and other non-climatic factors on vegetation growth. Using this model as the benchmark of grassland degradation estimation, the degradation of grassland in Xilin Gole League, Inner Mongolia from 1982 to 2000 was evaluated. Estimation of its trend was also given in this paper. Results are consistent with those acquired based on grountl observation, which shows that non-climatic factors had resulted in severe grassland degradation in Xilin Gole League,but the multi-year changing trend of grassland degradation is slowing down.