华北地区植被覆盖变化及其影响因子的相对作用分析

利用GIMMS NDVI数据和气象数据,采用趋势分析、残差分析和相对作用分析对华北地区1981—2006 年植被覆盖时空变化特征进行了分析,并计算了气候变化和人类活动在植被覆盖变化过程中的相对作用.结果表明,1981—2006 年华北地区植被NDVI呈现显著上升趋势,其增加速率为0.009/10 a,但却存在着明显的空间差异,且植被NDVI退化区域面积大于改善区域面积;华北地区植被覆盖变化与干燥度指数和气温有很好的相关性,说明气候变化是影响植被覆盖变化的重要因素;此外,无论在华北地区植被改善区域还是退化区域,人类活动起到的作用都占据了主导地位.在植被改善区,人类活动的相对作用为68.10%,大于气候变化的相对作用(31.90%),在植被退化区,人类活动的相对作用为71.88%,也远大于气候变化的相对作用(28.12%),且气候变化和人类活动的相对作用大小在不同空间位置上表现不同.

Analysis of the Vegetation Cover Change and the Relative Role of Its Influencing Factors in North China

Climate change and human activities are the main influencing factors for vegetation cover change and their relative role in vegetation cover change has been the hot point in related researches. Spatial and temporal vegetation cover change in North China was analyzed using methods of trend analysis, residual analysis and relative role analysis based on the GIMMS NDVI and meteorological data from 1981 to 2006. At the same time, the relative role of climate change and human activities in the process of vegetation cover change of North China from 1981 to 2006 was assessed in this study. We found that the vegetation was recovering well in the whole North China. North China vegetation cover showed an increasing trend and its growth rate has been 0.009/10 a from 1981 to 2006. However, there was an obvious spatial distribution between regions and the proportion of the greening area (25.14%) was smaller than the proportion of the degraded area (27.77%), which indicated that the situation of ecological environment of North China was still not optimistic. The vegetation cover change in North China was correlated with aridity index and annual mean temperature. During the years from 1981 to 2006, the vegetation cover change in North China had a significantly negative correlation with aridity index (r=-0.682), and the correlation between the vegetation cover change and annual mean temperature was significantly positive (r=0.438), which meant that climate change was an important factor driving vegetation cover change. In addition, human activities were also important causes resulting in vegetation cover change. Human activities'roles were always overwhelmingly dominant in the increased area and the decreased area of vegetation cover in North China from 1981 to 2006. The role of human activities was larger than that of climate change in the increased area of vegetation cover (they were 68.10% and 31.90% separately), yet the role of human activities came up to 71.88% in the decreased area of vegetation cover, while the role of climate change amounted to 28.12%. Besides, the relative role of climate change and human activities varied at different spatial scales in the process of vegetation cover change of North China. In the increased area of vegetation cover, the areas mainly induced by human activities are distributed in the east of Hinggan League, Xilingol League, the west of Chifeng, Hetao Plain, the northwest of Shanxi Province and the south area of Hohhot and Baotou; however, the areas mainly induced by climate change included the south of Hebei Province and the vicinity of Horqin Right Wing Middle Banner. In the decreased area of vegetation cover, the areas mainly induced by human activities are widely distributed in the middle and northeast of Hebei Province, the north area of Baotou and Hohhot, the central-south of Hulun Buir, Alxa Left Banner and the vicinity of Wuhai; however, the areas mainly induced by climate change are sporadically distributed in the Alxa Right Banner and the vicinity of Manzhouli City.