2001-2013年洞庭湖流域植被覆盖度时空变化特征

本文基于2001-2013年MODIS NDVI多时序数据,采用像元二分模型估算了洞庭湖流域植被覆盖度,分析了区域近13年来植被覆盖度的变化特征及趋势,并结合同期气象数据,阐明了植被覆盖度变化对气候因素的响应。结果表明：（1）近13年洞庭湖流域植被覆盖度的整体变化较为稳定,呈微弱减少趋势,速率为-0.3%/10a。（2）洞庭湖流域绝大部分区域植被覆盖状况良好,植被覆盖度呈自西向东递减趋势,高植被覆盖度及中高植被覆盖度占整个流域面积的88.63%,水体或低植被覆盖度及中低植被覆盖度仅占2.57%。（3）洞庭湖流域植被覆盖度变化趋势为北部强于南部、东部强于西部。流域内植被覆盖度极显著与显著减少的面积比例为5.30%、增加面积的比例为4.29%,植被覆盖度变化不显著占90.40%。该区域植被覆盖度变化受人为因素影响更大。

Spatial-Temporal Variations of Vegetation Coverage in the Lake Dongting Basin from 2001 to 2013

Based on the multi-temporal MODIS NDVI and meteorological data for the period from 2001 to 2013, we estimated the vegetation coverage in the Lake Dongting Basin. At the same time, we explored the spatial-temporal variations of vegetation coverage and the determinants driving the observed variations through dimidiate pixel principle, linear regression analysis, correlation analysis and significance testing. The results show that: (1) generally, the ground surface of the whole basin was well-covered with vegetation, i.e. the vegetation coverage for 88.63% of the total area was categorized as high and moderately high cover. Also, the vegetation coverage presented a declining trend from the west to the east inside our study area. (2) During the last 13 years, the vegetation coverage decreased slightly with an average annual speed of 0.03%. (3) The variations of vegetation coverage in the northern and eastern areas are relatively stronger than the rest of the Lake Dongting Basin. Significant to highly significant changes in the vegetation coverage was observed to be approximately 5.3% and 4.29% of the study area, respectively. Geographically, these changes mainly occurred in the vicinity of water bodies (rivers and lakes) and densely populated areas. In contrast, the rest parts of the basin, which were mainly covered by perennial vegetation, did not show any recognizable change. Taken all information together, it is suggested that both the climate variations and human activities are the major driving factors behind the spatial-temporal patterns/variations for the vegetation coverage in the study area. It is also noteworthy that the former factor tends to exert a profound impact on the vegetation coverage over large spatial and temporal scales. Meanwhile, the latter could change the vegetation coverage in disseminated areas (e.g. cities and river) within a relative short time period.