摘要:
基于MODIS-NDVI数据,利用像元二分模型估算获得中国西南地区2000-2014年间的250 m分辨率月度植被覆盖度(fractional vegetation cover,FVC),结合气象数据,采用趋势分析、相关分析和残差分析方法,对西南地区近15 a间FVC时空变化及与气候、人类活动的关系进行了综合分析.结果表明: ①2000-2014年间西南地区森林生态系统的年最大FVC显著增加,增加速率为0.096 2 a-1(p<0.05),农田年最大FVC增幅最小(0.031 1 a-1,p=0.582);②FVC变化存在明显的空间差异,滇北、黔渝地区的森林和灌丛、三江源地区的草地以及广西南部的农田FVC显著增加,但汶川、横断山、川西北等地FVC显著下降;③西南地区年最大FVC与秋季降水和夏季均温的相关性最好,相关系数分别为0.320和0.281;④2000-2014年间西南地区FVC残差的增加速率为0.023 2 a-1,说明人类活动对西南地区植被生长整体上起促进作用.
Abstract:
Fractional vegetation cover (FVC) is a critical indicator for vegetation and eco-environment.It is frequently used as a basic input for hydrology, meteorology and water-soil protection studies at regional or global scales.Southwestern China is an important ecological barrier and the major water supplying area in China.It is important to carry out the study of changes of regional fractional vegetation cover for the protection of eco-environment.In this paper, based on the MODIS-NDVI data obtained from 2000 to 2014, the authors estimated fractional vegetation cover of southwestern China by using the method of dimidiate pixel model, and analyzed the spatial-temporal variation characteristics of the FVC.The results show that, in the past 15 years, the FVC of southwestern China has shown an increasing trend in general but decreased in some meadow areas over the northwest of the study area and the urban expanded areas.In different kinds of ecosystem types, the forest shows the largest average increase of the annual maximum FVC (0.096 2 a-1, p<0.05), while the grassland shows the smallest increase (0.031 1 a-1, p=0.582).Fractional vegetation cover has increased in different degrees in most seasons in the past 15 years in southwestern China, with the increase in autumn being most rapid (0.229 8 a-1) and has most significant trend (p<0.01), followed by spring.For better understanding the effects of climate change on FVC, the correlation coefficients of climatic factors and the annual maximum FVC in different temporal durations were calculated.The results suggest that the annual maximum FVC is significantly related to accumulated precipitation of autumn and mean temperature in summer, showing correlation coefficients of 0.320 and 0.281.In addition, human activities are also important causes resulting in FVC change and the effect has increased in both positive and negative aspects.
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