基于MODIS的2006-2016年西藏生态质量综合评价及其时空变化

Comprehensive evaluation and spatial-temporal changes of eco-environmental quality based on MODIS in Tibet during 2006-2016

针对缺少基于遥感数据产品的西藏地区植被生态参数筛选及综合评价的研究现状,以2006年和2016年西藏地区MODIS卫星遥感产品反演得到的植被覆盖度、叶面积指数、植被总初级生产力、区域热度与改进的湿度5项指标为基础,提出了基于主成分分析法的西藏植被生态环境质量评价方法,并探索了其时空变化规律及机理。结果表明:①西藏地区植被生态质量整体较为脆弱,且区域差异明显,呈现东南优、西北差的分布格局。②2006-2016年间西藏地区植被生态质量总体呈现变好的趋势。在时间序列上,2006-2016年间改善、退化的区域占比分别为31.88%和4.13%;在空间分布上,变好的区域分布在西北、中部和东部,变差的区域集中在东南部。③水热状况改善特别是降水量的增加和人为保护政策使得研究区西部和中部地区生态质量有所提高。社会经济活动加强是研究区东南部生态质量变差的主要原因。

In view of the lack of research on the screening and comprehensive evaluation of vegetation ecological parameters based on remotely sensed date products,this paper firstly proposes a method to evaluate the vegetation eco- environmental quality in Tibet by PCA (principal component analysis).Based on five indicators,including fractional vegetation coverage (FVC),leaf area index (LAI),gross primary productivity (GPP),land surface temperature (LST) and modified wet (Wet) from MODIS satellite data,the law and mechanism of spatial- temporal changes of eco- environmental quality in Tibet in the last 10 years are explored.The experimental results show that:(1) The comprehensive quality of the ecoenvironmental quality in Tibet is relatively fragile,and the spatial difference in ecoenvironmental quality is significant.It is excellent in the southeast but poor in the northwest.(2) During the period from 2006 to 2016,the eco-environmental quality in Tibet shows a trend of improving overall.In terms of time series,the proportion of areas improved and degraded in the past 10 years was 31.88% and 4.13% respectively.In terms of spatial distribution,the improved areas are distributed in the northwestwen,central and eastern parts,but but the degraded areas are distributed in the southeastern parts.(3) Improvements in hydrothermal conditions (especially the increase in precipitation) and human protection policies have led to improvements in the eco- environmental quality in the western and central Tibet.The strengthening of social and economic activities is the main reason for the deterioration of the eco-environmental quality in the southeast of Tibet.