基于MODIS的长江源植被NPP时空变化特征及其水文效应

植被净初级生产力是反映植被生态系统对气候变化响应的重要指标。基于2000—2010年MODIS NPP数据,结合同期年径流、气温、降水数据,运用趋势分析法、相关分析法以及径流过程指标法等方法,研究了长江源区2000—2010年植被aNPP的时空变化特征及其水文效应。研究结果表明：1） 近11 a来,长江源区植被aNPP呈增加的趋势,增加趋势不显著,线性增长率为48.22 gC/m²;在水热条件的影响下,植被aNPP增长呈现出空间异质性,增加幅度由东南向西北逐渐减少。2） 不同植被类型的aNPP增长趋势不同,其中针叶林、灌丛、高寒草甸和高寒草原的aNPP增长率分别为3.03、2.68、1.43和0.85 gC/(m²·a)。3） 植被aNPP与6—9月的气温、5—8月的降水量呈显著相关。4） 径流系数和水源涵养指数的增大进一步验证植被aNPP的增加趋势,并对源区的水资源量产生有利影响。

The Spatial-Temporal Variations and Hydrological Effects of Vegetation NPP Based on MODIS in the Source Region of the Yangtze River

Vegatation NPP is considered to be a key factor of ecological responses to climate change. The objective of this study was to analyze the spatial-temporal variations and hydrological effects in the source region of the Yangtze River. Trend analysis, correlation analysis and runoff process indexes were applied based on MODIS NPP products over the period of 2000-2010, as well as annual runoff, temperature and precipitation data in the same period. The results indicated that during the period 2000-2010, the annual NPP (aNPP) of vegetation tended to increase at a rate of 48.22 gC/m². Influenced by water and heat resources, vegetation aNPP increased from northwest to southeast, which showed an obvious spatial heterogeneity. Moreover, the increase rate of different vegetation types varied across the study region. The aNPP of coniferous forest increased fastest among all vegetation types with a rate of 3.03 gC/(m²·a), followed by shrub, alpine meadow and alpine grass, the rates of which were 2.68, 1.43 and 0.85 gC/(m²·a), respectively. The increase of vegetation NPP was distinctively related to temperature from June to September and precipitation from May to August, which showed a significant positive correlation. The increases of runoff coefficient and water conservation index during the period 2000-2010 were also shown in the increase of vegetation aNPP, which was advantageous to water resources in the source region of the Yangtze River.