2000-2015年若尔盖地区植被覆盖度变化及气候因子驱动分析

Vegetation coverage change and how it drives climatic factors in the Zoige Region from 2000 to 2015

基于2000-2015年生长季(5-9月)MODIS-NDVI数据、植被类型图、土壤图和气象数据,结合像元二分模型估算若尔盖地区植被覆盖度,利用趋势分析、相关性分析和滞后性分析方法,分析若尔盖地区近16年植被覆盖度空间格局及其变化规律,并研究植被覆盖度对气候因子的响应。结果表明,1)2000-2015年若尔盖地区植被覆盖度均值在77%～82%,以每10年1.4%的速率波动增加。7种植被类型中,植被覆盖度最高的是阔叶林(87%),最低的为高山植被(44%),草原植被覆盖度以每10年-0.2%的速率减少。2)若尔盖地区植被覆盖度整体上呈现东高西低、由中心向外逐渐减少的分布特征,年际变化率介于-0.053～0.027,植被覆盖状况以高、极高覆盖等级为主(84.32%),两者面积有相互转化的趋势。3)滞后分析表明,生长季植被覆盖度与同期气温的相关性较好,对降水具有明显的滞后性,滞后时间约为1个月。4)在0.05显著性水平下,植被覆盖度变化受气候因子影响的区域占7.58%,气温驱动型面积占比2.85%,降水驱动型面积占比2.17%,气温、降水联合驱动以弱驱动为主,面积占1.67%;大部分地区受非气温和降水因素影响。

The vegetation coverage in the Zoige Region based on a pixel binary model was estimated in this study using the MODIS-NDVI data,vegetation map,soil map,and meteorological data.Then,the spatial pattern and variation rules of vegetation coverage from2000to2015,as well as the response of vegetation coverage to climatic factors were analyzed with a trend line,correlation analysis,and lag analysis.The results showed that1)The mean vegetation coverage in the Zoige Region fluctuated between77%and82%in16recent years,with a ratio increasing by1.4%per10years.Among the7types of vegetation,the coverage of the broad-leaved forest(87%)was the highest,and the alpine vegetation(44%)was the lowest;the grassland vegetation exhibited a slight downward trend with a ratio of-0.2%per10years.2)The vegetation coverage in the Zoige Region showed that the distribution features were high in the east and low in the west,decreasing from the center to the periphery,and the mean annual vegetation coverage change rate was between-0.053~0.027.In this region,the main vegetation coverage types were high and higher levels of vegetation coverage with a rate of84.32%,and the two areas had a tendency of mutual transformation.3)The lag analysis showed that the vegetation coverage in the growing season exhibited a good correlation with the contemporaneous air temperature,but the response to accumulated precipitation was evidently delayed for approximately1month.4)At the significance at the0.05level,the area change of vegetation coverage affected by climatic factors was7.58%,of which the air temperature drivers accounted for2.85%,the accumulated precipitation driver accounted for2.17%,and the air temperature and accumulated precipitation were weak drivers accounting for1.67%.Furthermore,most areas were affected by non-air temperature and accumulated precipitation factors.