云南中部地区植被覆盖时空变化特征及其影响因素研究

Study on the spatial-temporal variation and associated driving forces of vegetation coverage in central Yunnan

基于MODIS NDVI数据通过像元二分模型提取植被覆盖,利用线性趋势、相关分析方法分析了云南中部地区2000-2016年植被覆盖的时空分布特征与变化趋势,并探讨了气候因子、地形因子、人类活动对其植被覆盖的影响。研究结果为:云南中部地区植被覆盖春季最低(平均58.75%),秋季最高(平均66.30%),大部分地区年植被覆盖度的平均值在50%-70%之间;植被覆盖高值区主要分布在曲靖境内(>80%);滇池周边人口高密度区植被覆盖常年最低(<20%)。近17年来云南中部地区植被覆盖总体呈现增长趋势,年平均增长率0.3%·a^-1,其中秋季增幅最大(0.42%·a^-1)。坡度对植被覆盖影响较大,坡度≤8°地区的植被覆盖明显较低。除了冬季降水量与植被覆盖呈现显著正相关关系,其他季节多呈现负相关关系;气温与植被覆盖多呈现正相关关系,云南中部地区植被覆盖变化主要受气温影响。人类活动对植被覆盖变化影响较大,造林面积变化与植被覆盖趋势变化具有相对一致性,经济发展水平较高的昆明市区植被覆盖为常年最低。

Based on MODIS NDVI data, vegetation coverage by dimidiate pixel method was extracted in this study. Then the spatial-temporal variations and associated driving forces of vegetation coverage in central Yunnan from 2000 to 2016 were analyzed by the linear trend and correlation analysis. The results showed that the vegetation coverage was lowest in spring while the highest was in autumn, and the annual average value was 50-70%. The spatial distribution of vegetation coverage differed greatly, the high-value area was mainly distributed in Qujing, and the low-value area was mainly distributed around the Dianchi Lake. The vegetation coverage in central Yunnan had generally increased with an annual average growth rate of 0.3%·a^-1 in the last 17 years, during which the largest increase was in autumn (0.42%·a^-1). The terrain slope had great influence on the vegetation coverage. The vegetation coverage in the region with a terrain slope less than 8 degrees was significantly lower than that in the area with slope more than 8 degrees. In addition to the significant positive correlation between winter precipitation and vegetation coverage, precipitation and vegetation coverage in other seasons showed negative correlation. The temperature was positively correlated with vegetation coverage, which was the main control factor in vegetation coverage variation. The vegetation coverage was strongly influenced by human activities in central Yunnan. The change of afforestation area was consistent with the annual trend of vegetation cover. The vegetation coverage in Kunming which had a relatively higher level of economic development was the lowest in all years.