黄河源区植被NDVI演变及其与降水、气温的关系

Variation of Vegetation NDVI and Its Relationship with Climate Factors in the Yellow River Source Region

为分析1982—2018年黄河源区不同季节植被NDVI空间演变规律及其影响因子,根据流域内及周边气象站点的同期降水、气温观测资料,运用趋势检验法和相关分析等方法,在像元尺度上揭示了NDVI演变趋势及其与降水气温的关系。结果表明:黄河源区各季节气温上升趋势显著,年平均升温率达到了0.54℃/10 a。流域内降水年际内略有波动,无显著变化趋势,冬季降水略有减少趋势。源区内超过90%的地区NDVI值全年呈增长趋势,植被状况呈现改善态势,而中下游地区这一趋势比上游及源头地区更为显著。NDVI与气温呈显著的正相关关系,气温的升高对植被生长起到显著的正面促进作用;除冬季之外,绝大多数地区NDVI与降水的相关性都不显著(p>0.05),夏季约有50%的地区NDVI与降水量呈正相关关系,源头玛多县地区降水的增加有助于植被生长。残差分析结果表明:冬季人类活动对流域NDVI变化的影响微弱;达日站—久治站区间和河南站—兴海站区间受人类活动影响较为显著,2000年以后人类活动所导致的植被退化情势减缓,黄河源区植被情况得到一定的改善。

In order to analyze the spatial changing characteristics of vegetation NDVI and its influencing factors in different seasons in the Yellow River source area(YRSA) from 1982 to 2018, based on the precipitation and temperature observation data from 8 meteorological stations, trends detection approach, correlation analysis and other methods were used to reveal the changing characteristics of NDVI at the pixel scale. The results show that the air temperature rose significantly in all seasons, and the annual average warming rate reached 0.54℃/decade;the precipitation fluctuated slightly, the change trend was not very significant;the precipitation in winter decreased slightly;in most areas of YRSA, the NDVI value showed an increasing trend and the vegetation showed an improvement trend;The NDVI was positively correlated with temperature;the increase in air temperature had a significant positive effect on vegetation growth;except for winter, the correlation between NDVI and precipitation was not significant(p>0.05);In summer, about 50% of the areas showed positive correlation between NDVI and precipitation, concentrated on the Maduo County, which contributed to vegetation growth to some extent. Residual analysis results showed that the impact of human activities in winter on the NDVI change was weak;the Dari-Jiuji region and Henan-Xinghai region were more sensitive to human activities. The vegetation degradation caused by human activities had slowed down after 2000, and the vegetation in the YRSA had been improved to a certain extent.