区域性气候变化对长江中下游流域植被覆盖的影响

利用2000─2010年MODIS EVI(增强型植被指数)数据和气候资料,对长江中下游流域区域性气候变化对植被覆盖的影响进行了综合研究. 结果显示:①2000—2010年间长江中下游流域植被覆盖度呈上升趋势,EVI年均值从0.302增至0.318,增幅达5.57%,增长主要出现在春季. 各植被类型中,常绿阔叶林、落叶阔叶林、混交林和人工农田植被覆盖度增加最为显著. ②研究区整体植被覆盖较好,但地域差异较大, EVI高值区分布在东南部南岭、武夷山、九岭山一带；中部江河湖泊区、长江两岸大型城市周边区域植被覆盖较差. ③气温是植被覆盖变化的主要影响因子,尤其春季表现最为显著；由于常年降水充沛,研究区降水量对植被覆盖影响程度不及气温；日照时数仅在夏季对当月植被覆盖有一定影响；相对湿度对植被覆盖影响较低,但在秋季对植被覆盖影响时间较长,可持续3个月. ④气候变化对自然植被覆盖的影响主要表现在湖南省和湖北省西部；对湖南省中部和安徽省中北部地区人工农田植被的影响较显著. ⑤空间相关性研究表明,长江中下游流域植被覆盖度增加除与自然条件改善有关外,国家近年来实施的各项生态工程也起到了积极的作用. 

Influence of Regional Climate Change on Vegetation Cover in the Middle and Lower Yangtze River Basin

The temporal-spatial vegetation coverage changes in the lower and middle Yangtze River basin were studied based on the MODIS EVI (enhanced vegetation index) and meteorological data from 2000-2010.The results showed that:1) Vegetation coverage increased successively as indicated by the annual EVI index change from 0.302 in 2000 to 0.318 in 2010, with an increment of 5.57%. The increments mainly happened in the spring. Among all vegetation types, evergreen broad-leaved forests, deciduous broad-leaved forests, mixed forests and artificial farmland vegetation coverage increased significantly. 2) The study areas were well covered by various vegetations with distinct regional differences. For instance, the southeast, Nanling and Mounts Wuyi and Jiuling were highly covered. The areas close to the rivers and lakes in the middle Yangtze basin and near the metropolis had poor vegetation coverage. 3) Temperature was a main factor influencing the vegetation coverage change, especially in the spring. For abundant precipitations, rainfall had less effect on vegetation than temperature. Sunshine duration had impacts on vegetation coverage only in the summer. Average relative humidity had low correlation with vegetation coverage, though the impacts in the autumn could last for three months. 4) The impact of climate change on the natural vegetation was mainly manifested in western Hunan and Hubei Provinces. In central Hunan and the north-central Anhui Provinces, climate change had an obvious impact on artificial farmland vegetation. 5) The spatial correlation coefficients indicated that the vegetation coverage increments in the lower and middle Yangtze River basin did not only benefit from the natural conditions improvement, but also from the ecological programs launched by the central government over the past years.