近30年长江口崇明东滩植被对于气候变化的响应特征

Vegetation responses to climatic change in Yangtze River Delta wetlands during the past 30 years

在分析近30年来长江口区域气候变化特征基础上,利用107景Landsat系列卫星的TM和ETM+遥感数据,计算了1984—2013年间长江口崇明东滩湿地的归一化植被指数(NDVI),并以此为湿地植被活动的指标,研究植被年际及季节变化特征。结果表明:(1)长江口地区气候变化特征为:年均温显著增加,日照时数显著下降,年降水量变化趋势不显著。就各个季节而言,气温存在显著增加趋势(冬季除外),降水量和日照时数变化趋势相对不显著。(2)不同季节植被年际变化特征一致,NDVI皆随时间增加,但增加的强度和显著性有所差异。植被NDVI在冬季和春季增加较大且极显著,增速分别为0.07·10a?1和0.06·10a?1;夏季增速稍低,为0.04·10a?1;秋季增加不显著。(3)年内季节变化方面,湿地植被NDVI呈现单峰的变化特征,从春季开始增加,在夏末(全年的第188或189天)达到最大值(NDVImax=0.63),然后下降在冬季降至最低。植被的年内季节变化特征主要受月均温的控制(R2=0.84)。

Based on the analysis of the past 30 years climate change characteristics in Yangtze estuary area, the normalized difference vegetation index （NDVI） of the Chongming Dongtan Wetland in Yangtze River Delta was calculated on the basis of 107 TM and ETM＋ images, which were collected by the Landsat satellites. The wetland vegetation activities were shown by the index. By studying their characteristics of seasonal vegetation activity during 1984-2013, the control factors of intra-annual and inter-annual vegetation activity were revealed. Moreover, this study showed the wetland vegetation＇s response characteristics to climate changes. The results can be summarized as follows. （1） Climate variation in Yangtze River Delta was that the temperature increased and sunshine duration decreased significantly, while there was no significant variation of the precipitation. The temperature increased significantly in different seasons （except winter）, while the tendency of precipitation and sunshine duration was not significant. （2） The seasonal variation characteristics of wetland vegetation were identical in the last 30 years. NDVI increased with time, but its velocity and significance varied. NDVI growth rates in winter and spring were larger, with 0.07＂ 10a-1 and 0.06＇ 10a-l; growth rate in summer was slightly lower with 0.04＇ 10a-1, the tendency in fall was not significant. （3） The NDVI of wetland vegetation showed a single-peaked variation characteristic in term of seasonal variation in one year. They increased in spring and reached the maximum （NDVImax=0.63） in midsummer （the 188th day and 189th day in the year）, then the value began to decrease and reach the lowest value in winter. Seasonal variation characteristics of the vegetation NDVI were mainly controlled by monthly mean temperature （R2 = 0.84）.