太行山区植被NPP时空变化特征及其驱动力分析

Spatio-temporal variations in vegetation NPP and the driving factors in Taihang Mountain Area

  • 摘要: 本文基于2000-2014年MODIS NPP数据,结合同期土地利用变化、气温、降水和DEM数据,运用趋势分析法、相关系数法及分区统计法等方法,研究了太行山区2000-2014年植被NPP时空变化特征,分析了气温、降水等气候因素和人为因素对植被NPP变化的影响,为太行山区植被资源管理及生态环境调控提供参考。研究结果表明:(1)太行山区植被NPP多年平均值为284.0 g(C)·m-2·a-1,耕地、林地和草地的NPP均值分别为302.5 g(C)·m-2·a-1、258.1 g(C)·m-2·a-1、286.5 g(C)·m-2·a-1。(2)2000-2014年太行山区植被NPP整体呈上升趋势,但大部分植被NPP变化未达到显著水平;16.17%的植被NPP显著或极显著升高,主要分布在太行山区西侧;0.88%的植被NPP显著或极显著降低,零散分布在研究区内。(3)不同植被类型NPP变化速率为草地>耕地>林地。(4)基于区域平均计算,太行山区植被NPP与降水显著正相关(P < 0.05),与气温负相关(P>0.05)。基于像元计算,植被NPP与降水显著或极显著正相关区面积比例为23.82%,主要分布在太行山区北段,几乎没有显著负相关区;植被NPP与气温显著或极显著负相关区面积比例为8.42%,主要分布在太行山区西侧,显著或极显著正相关区面积比例为0.81%,主要分布在太行山区最北端。(5)研究期内气候因子对植被NPP的升高整体上表现为促进作用,而人为因素主要表现为抑制作用。太行山区生态环境保护仍应以减少人为干扰为主。

     

    Abstract: Net primary productivity (NPP) is an important indicator for the condition of vegetation in a given region. Research on NPP is not only important for the management of vegetation resources, but also a key element of global change. Technological development (such as remote sensing, geographic information system and global positioning system) had created the conditions for the establishment of complex process-based NPP models. On this basis, global NPP products today that continuously release data for long periods of time (e.g., MODIS NPP data appeared) greatly enhance research on NPP of regional vegetation. The objective of this study was to analyze the spatio-temporal variations in NPP of vegetation in Taihang Mountain Area for the period 2000-2014 using MODIS NPP data. At the same time, the study investigated the effects of climatic factors (e.g., temperature and precipitation) and of human factors (e.g., farming) on the change in NPP of vegetation in the region. Also trend analysis, correlation coefficient and zonal statistics were used in the study to analyze the various dataset (e.g., LUCC, temperature, precipitation and DEM). Results showed that the average NPP values of the study area was 284.0 g (C)·m-2·a-1, while those of farmland, forest and grassland were 302.5 g (C)·m-2·a-1, 258.1 g (C)·m-2·a-1 and 286.5 g (C)·m-2·a-1, respectively. Geographical location, topography, development history and human management influenced the distribution of the NPP of vegetation in the study area. Poor geographical environment was the main reason for the small NPP of forest vegetation in the region. The NPP of vegetation generally showed an upward trend, but was not significant for most of study area. About 16.17% area had significantly or extremely significantly increased vegetation NPP, which was mainly in the west of study area. In another 0.88% area, NPP significantly or extremely significantly dropped. The order of the NPP change rate of different vegetation types was-grassland > farmland > forest. Grassland vegetation was more effective for environmental rehabilitation because it had a better adaptability to the local conditions. Based on calculated regional averages, the vegetation NPP was significantly positively correlated with precipitation (P < 0.05), but negatively correlated with temperature (P>0.05). About 23.82% of the study area had a significantly or extremely significantly positive correlation between NPP of vegetation and precipitation, which mainly distributed in the northern section of Taihang Mountain. No significantly negative correlation was observed. Furthermore, about 8.42% of the study area had a significantly or extremely significantly negative correlation between vegetation NPP and temperature, and this was mainly in the west side of Taihang Mountain. In another 0.81% area, the vegetation NPP was significantly or extremely significantly positively correlated with temperature, which was mainly distributed in the extreme north of the study area. Also the rate of NPP change and the correlation coefficient between NPP and climatic factors was positively correlated with altitude and slope gradients-both relatively smaller at low altitude and small slope, where human activity intensity was relatively higher. The area with significantly or extremely significantly reduced vegetation NPP was across the study area, especially around construction lands, which was not as a result of climatic factors. It was therefore suggested that while climatic factors generally enhanced vegetation NPP, human factors mainly inhibited vegetation NPP in the study area during the study period.

     

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