涪江流域植被净初级生产力时空变化及其对地形因子的响应

Spatio-temporal Variation of Net Primary Productivity of Vegetation and its Response to Topography in Fujiang River Basin

针对长江上游流域植被净初级生产力时空变化及其对地形因子响应研究不够深入的问题,基于MOD17A3HGF和DEM数据,采用趋势分析法、标准差法、相关系数法、空间统计法等方法,分析了涪江流域2000—2020年植被净初级生产力(NPP)的时空变化及其在地形上的分异规律.结果表明:(1)涪江流域植被NPP呈现波动性、阶段性.流域NPP均值456.40~664.74 gC·m^(-2)·a^(-1),增幅为8.25 gC·m^(-2)·a^(-1),整体NPP水平在增加;(2)植被NPP呈“西北高东南低”的空间分异特征,上游区是植被NPP高生产力聚集区,下游区是植被NPP低生产力聚集区.(3)流域内植被NPP空间变化以增加区域为主,呈“中波动较多,高低波动较少”的特征,上游区波动程度小于中下游区.(4)年均植被NPP随海拔、地形起伏度、坡度、地表粗糙度的增加先增高后降低,植被NPP对地形因子响应程度为:地形起伏度>坡度>海拔>地表粗糙度>坡向.

In order to address the issue of insufficient research on the spatiotemporal variations of vegetation net primary productivity(NPP)and its response to terrain factors in the upstream Yangtze River basin,based on MOD17A3HGF and DEM data,the trend analysis method,standard deviation method,correlation coefficient method,and spatial statistical method were used to analyze the spatiotemporal variations of vegetation NPP and their differentiation on terrain in the Fujiang River Basin from 2000 to 2020.The results showed that:(1)the vegetation NPP in the Fujiang River Basin exhibited fluctuation and periodicity.The average NPP in the basin fluctuated between 456.40 and 664.74 gC·m^(-2)·a^(-1),with an increase of 8.25 gC·m^(-2)·a^(-1).The overall NPP level was increasing;(2)the vegetation NPP showed a"high in the northwest and low in the southeast"spatial differentiation feature,where the upstream area was a high-productivity aggregation area,and the downstream area was a low-productivity aggregation area.(3)The spatial variation of vegetation NPP in the basin was mainly characterized by an increasing trend,with a"medium fluctuation and less high-low fluctuation"feature,and the fluctuation in the upstream area was smaller than that in the middle and downstream areas.(4)The annual average vegetation NPP increased first and then decreased with the increase of elevation,terrain roughness,slope,surface roughness,and slope direction,and the response of vegetation NPP to terrain factors was in the order of terrain roughness>slope>elevation>surface roughness>slope direction.