人类活动对植被退化/恢复影响的空间格局——以陕西省为例

Research on spatial pattern of human-induced vegetation degradation and restoration:a case study of Shaanxi Province

基于陕西省1998～2005年SPOTVEG NDVI月数据和月降水序列的相关性分析,构建修正的归一化植被指数(C-NDVI)剔除降水量对NDVI的影响,探讨了人类活动对植被影响的空间格局。主要结论:①陕西省NDVI和降水量间存在显著的相关性,相关系数呈现出北高南低中间最低的空间格局,与所处气候带和土地利用状况的差异有关;②1998～2005年人类活动对植被的影响表现出显著的空间差异性,北部地区以植被恢复为主,年增长率在2.1%～4.1%,其驱动力主要是退耕还林(草)、防沙治沙工程中对植被的保护和恢复性措施;中部平原区水浇地、城镇用地集中分布,表现出水浇地区人为活动对植被变化基本无影响,而城镇用地扩展区导致植被退化;中北部、南部林地分布区地形坡度大、降水量相对丰富,人类活动对植被的影响表现为植被退化,可能是经济林、用材林的周期性采伐所致。研究可为区域优化土地利用结构,合理规划和调整生态建设布局提供依据。

Monitoring and mapping the effects of human activities on land performance change is necessary for optimizing regional land use structure and evaluating the effects of ecological programs. In this study, NDVI data derived from SPOT VEGETATION and monthly rainfall data during 1998 --2005 were used to estimate vegetation change in Shaanxi province. Corrected NDVI （C-NDVI） , the temporal trends in the differences between the observed NDVI and the NDVI predicted by the rainfall, was developed to evaluate the effects of human activities on vegetation change （ degradation and restoration）. through filtering out the effects of rainfall on NDVI-value change. Also, the spatial pattern of C-NDVI was analyzed. The results showed that, （i） there was a strong relationship between integrated monthly NDVI data and rainfall volume, while the correlation coefficient increased from south to north and it had the lowest value in central part of Shaanxi due to large areas of irrigated farmland, which had low dependence on rainfall. In the southern part of the province, which has a more humid climate low coefficient was delineated. （ii） The spatial patterns of human-induced vegetation change in 1998 --2005 were obviously different in four parts. In the north of Shaanxi, the C-NDVI suggested a upward trend in the capacity of vegetation restoration, with the annual increase rate of 2. 1%- 4. 1%, due to the ＂ Grain for Green＂ program and ＂preventing and combating desertification and sandification＂ program. With large areas of irrigated farmland and urban land, the C-NDVI in central part indicated degraded vegetation in urban sprawl areas and it had remained more or less constant over 8 years in irrigated field. In the central-northern part and southern parts, large areas of forestland represented a downward trend in vegetation coverage, which could be understood as the vegetation degradation, and the reason might be the seasonal disafforestation in economic forest land.