滹沱河流域植被覆盖时空演变及其与 SPEI 的相关关系

选择2001-2015年MODIS NDVI(250m)及14个气象站点气温、降水数据,通过计算标准化降水蒸散指数(SPEI),探究滹沱河流域近15年植被覆盖时空演变特征,分别从月、季节、年等尺度探究植被覆盖与SPEI的相关关系。结果显示:(1)近15年滹沱河流域归一化植被指数(NDVI)呈显著增加趋势,增速为0.024/(10a)。(2)植被恢复以明显改善为主,覆盖范围占整个流域面积的51.58%,主要分布于流域中、上游。(3)滹沱河流域SPEI总体上呈波动上升趋势,干旱程度有所降低,流域中游变湿趋势最显著。(4)6月、7月是干旱条件对植被覆盖影响最显著的月份,其中,6月气温对NDVI的影响大于降水,而7月降水对NDVI的影响大于气温;夏季干旱程度对植被覆盖度的影响最为明显;NDVI年际变化与SPEI具有显著正相关关系,干旱对植被生长状态有较大影响。

Spatial-temporal change of vegetation cover and its relationship with SPEI in Hutuo river basin

Spatial-temporal change of coverage is in favor of understanding the ecosystem response to climatic variability and human-induced land transformations. The objective of this study was to analysis veg etation dynamics its relationship with drought in Hutuo river basin, based on 250 m MODIS NDVI time-series data and monthly temperature and precipitation of 14 meteorological stations ( 2001-2015) . The characteristics of drought were studied using the drought index (standardized precipitation evapotranspiration index , SPEI) , and the monthly temperature and precipitation were used to compute the SPEI of 1, 3 and 12 month timescale. Results are show nas fo llows: (1) The NDVI of the study area was improvement progressively from 2001 to 2015, with a lineartendency being 0.024/(10a).(2) The largest proportion of the contribution to vegetation restoration was observed in the significantly improved area, and the area where the values of NDVI significantly increased accounts for reached 51.58% was mainly located in the upstream and midstream of Hutuo river basin. (3) The SPEI was fluctuating upward trend, which indicated that drought could be easing over the past 15 years in Hutuo river basin. And the trend was most marked in the midstream. (4) Correlation analysis results showed that the SPEI had a strong influence on vegetation coverage mainly occurred in June and July on the monthly , and temperature was the dominant factor affecting the change of vegetation in June, while precipitation was the dominant factor in July . Seasonally, drought in summer had more influence on vegetation coverage. There was a positive correlation between the annual NDVI and annual SPEI, and drought has a great influence on vegetation growth.