近10年陕甘宁黄土高原区植被覆盖时空变化特征

The Spatial-temporal Changes of Vegetation Restoration on Loess Plateau in Shaanxi-Gansu-Ningxia Region

基于2000-2009年MODIS-NDVI植被覆盖指数,采用线性趋势分析、Hurst指数和偏相关系数等数理分析方法,对陕甘宁地区"退耕还林还草"实施10a来植被覆盖时空变化特征、影响因素及其未来变化趋势进行分析。结果表明:①2000-2009年陕甘宁地区植被覆盖呈现明显增加趋势0.032/10a,远快于三北防护林工程区1982-2006年植被覆盖平均增速0.007/10a;②陕甘宁地区植被恢复具有阶段性,整体呈"S"型增长,具有两次明显的植被高恢复期;③陕甘宁地区植被恢复以轻微改善为主,中度改善次之,呈退化趋势区域比重较小(2.38%),零星分布于宁南八县、定边东部、甘肃陇东的环县和镇原;④陕甘宁地区植被覆盖度逐年提高、生态环境持续改善是人类活动和气候变化共同驱动,其中人类经济活动作用明显;⑤陕甘宁地区植被恢复具有一定的持续性,未来大部分区域将持续改善,退化区集中分布于陕北中东部、"彭阳—镇原"南部以及盐池北部。

The ＂Grain for Green Project＂ initiated by the governments since 1999 were the dominant contributors to the vegetation restoration in the agro-pastoral transitional zone of northern China. Climate change and human activities are responsible for the improvement and degradation to a certain degree. In order to monitor the vegetation variations and clarify the causes of rehabilitation in Shaanxi-Gansu-Ningxia Region, this paper, based on the MODIS-NDVI and climate data during the period 2000-2009, analyzes the main characteristics, temporal-spatial distribution and reasons of vegetation restoration, using methods of linear regression, the Hurst index, standard deviation and other methods. Results are shown as follows. （1） From 2000 to 2009, the NDVI of the study area was improved progressively, with a linear tendency being 0.032/10a, faster than the growth of the Three-North Shelter Forest Program （0.007/10a） from 1982 to 2006. （2） The vegetation restoration is characterized by two fast-growing periods, with an ＂S-shaped＂ increasing curve. （3） The largest proportion of the contribution to vegetation restoration was observed in the significantly improved area, followed by the slightly improved area and the significantly degraded area, the last of which is distributed sporadically over southern Ningxia as well as Huanxian, Zhengyuan and eastern Dingbian of Gansu. （4） Climate change and human activities are the two driving forces in vegetation restoration; moreover anthropogenic factors such as ＂Grain for Green Project＂ were the main causes leading to an increasing trend of NDVI on local scale. However, its influencing （5） The Hurst index of NDVI time series sustainable. It is expected that improvement in of the region. mechanism remains to be further investigated. shows that the vegetation restoration was vegetation cover will expand to the most parts