基于GIMMS NDVI 3g.v1的近34年青海省植被生长季NDVI时空变化特征

在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠加,研究植被生长季NDVI变化的持续性特征,并揭示植被对气候变化及人类活动的响应规律。结果表明:1)近34年青海省植被NDVI整体呈从西北到东南的增加趋势;且变异系数显示,波动性较大地区集中在柴达木盆地周边和青南牧区西北部等植被NDVI较低的区域,波动性较小地区集中在祁连山东部、东部农业区和青南牧区东南部等植被NDVI较高的区域。2)近34年青海省植被NDVI整体呈增加趋势,增长率为0.38%·10a~(-1);且NDVI变化具有明显的阶段性,存在1994年和2000年两个突变点。3)近34年青海省植被改善区域(75.4%)远大于退化区域(24.6%),其中显著改善面积占植被覆盖区域面积的40.9%,退化区随时间变化在空间上表现出明显的转移现象。4)Hurst指数表明,青海省植被变化反持续性较强,趋势分析与Hurst指数叠加得出,由退化转为改善的区域占植被覆盖区面积的13.7%,由改善转为退化的区域占植被覆盖区面积的44.3%,另41.5%的区域无法确定未来变化趋势。5)青海省植被生长季NDVI受气候变化和人类活动的双重影响,且不同植被类型对气候变化的响应存在较大差异。

Spatial-temporal variations in NDVI in vegetation-growing season in Qinghai based on GIMMS NDVI 3g.v1 in past 34 years

Under the influence of climate change and human activities,the ecological environment in Qinghai Province has changed markedly.In this context,taking GIMMS NDVI3g.v1 as the data source,we analyzed temporal and spatial changes in NDVI of the vegetation coverage area in Qinghai Province from 1982 to 2015, using the Theil-Sen Median trend analysis and Maan-Kendall test.Both the trend analysis and R S analysis were superimposed to study the persistent characteristics of NDVI change during the vegetation growth season, and reveal the regularity of vegetation response to climate change and human activities.The results showed that:1)Vegetation NDVI in Qinghai Province increased from the Northwest to Southeast in the past 34 years,and the coefficient of variation indicated that a larger volatility region was concentrated in the lower NDVI re-gion of the Qaidam Basin and northwest of the Qingnan pastoral area;the volatility was concentrated in the eastern part of the Qilian Mountains,eastern agricultural area,and southwest of Qingnan pasture area with high vegetation NDVI.2)In the past 34 years,the overall NDVI of vegetation in Qinghai showed an increasing trend;growth rate was 0.38%?10 a-1,the change in NDVI was obvious in phases,and there were two abrupt changes in 1994 and 2000.3)The area of vegetation improvement in Qinghai Province (75.4%)from 1982 to 2015 was much larger than that of vegetation degradation (24.6%),of which the significant improvement area represented 40.9% of the area covered by vegetation,and the degradation zone showed a significant shift in space over time.4)The Hurst index showed that the reverse trend of vegetation change in Qinghai Province was remarkably persistent;the trend analysis and Hurst index obtained by superposition showed that 13.7% of the area affected by degradation was enhanced from degradation to improvement,and 44.3% of the area from improvement to degradation;future trends of 41.5% of the area could not be determined,and only 0.2%-0.3% of area was between continuous improvement and sustained degradation.5)The NDVI of vegetation growth in Qinghai Province was affected by climate change and human activities,and the response of different vegetation types to climate change was quite different.