2000—2019年宁夏植被净初级生产力时空变化及其驱动因素

宁夏是我国重要的农牧交错区,开展该地区植被净初级生产力(NPP)时空变化及其驱动因素研究对于认知该地区NPP变化趋势及主导因素、揭示其植被恢复状况及成因具有重要作用。本研究基于MODIS NPP数据,利用Theil-Sen Median趋势分析、相关分析、叠加分析等方法分析宁夏植被NPP的时空变化及驱动因素。结果表明: 2000—2019年,宁夏植被NPP总体呈波动上升趋势,其线性增长速度为5.46 g C·m^-2·a^-1。研究区植被NPP在空间上呈现两高两低的分布特征,以南部山区最高,其次为引黄灌区,中部干旱带丘陵区和贺兰山一带最低。研究区84.2%的植被NPP处于显著恢复中,主要分布在中部及南部山区丘陵地,植被NPP随海拔变化显著,受地形影响明显。宁夏植被NPP重心总体向正南方向移动,南部植被NPP的增量和增速大于北部。宁夏地区年降水量呈增加趋势,年均温微弱降低,植被NPP主要受降水量的显著影响(R²=0.291),年均温与植被NPP相关性不显著。研究区96.9%的区域处于植被恢复状态,受气候变化和人类活动共同促进。

Temporal and spatial variation of vegetation net primary productivity and its driving factors in Ningxia,China from 2000 to 2019

Ningxia is an important agriculture-pastoral area in China. Research on the temporal and spatial variations of net primary productivity (NPP) in this area and its driving factors would help understand the trends and leading factors of NPP variations, and reveal vegetation restoration status and causes. Based on the NPP data of MODIS, we used Theil-Sen Median trend analysis, correlation analysis, overlay analysis and other methods to analyze the spatiotemporal variations and driving factors of NPP in Ningxia. The results showed that NPP of Ningxia vegetation showed a fluctuating upward trend during 2000-2019, with a linear growth rate of 5.46 g C·m^-2·a^-1. The NPP presented a spatial characteristics of “two high and two low”, with the highest in the southern mountain area, followed by the Yellow River irrigation area, and the lowest in the hilly area of the central arid zone and Helan Mountain. 84.2% of the NPP in the study area was under significant restoration, mainly distributed in the central and southern mountainous and hilly areas. The NPP varied significantly with altitude and was significantly affected by the terrain. NPP center of gravity had generally moved to the south, with the increase and growth rate of NPP of vegetation in the south being greater than that in the north. The annual precipitation in Ningxia had shown an increasing trend, while the average annual temperature had slightly decreased. The NPP was significantly affec-ted by precipitation (R²=0.291), whereas the correlation between mean annual temperature and NPP was weak. 96.9% of the study area was at a state of vegetation restoration, which was promoted by both climate change and human activities.