2000—2015年滦河流域植被净初级生产力时空分布特征及其驱动因子分析

植被净初级生产力(NPP)可以反映植被生长状况,是表征地区生态质量的重要指标。本文以滦河流域为研究区,调查采集植被NPP、气象、土地利用结构及变化等多时空数据,利用Sen趋势、Hurst指数及残差分析等多种方法,综合考虑自然环境和人为利用的影响,对2000—2015年植被NPP的时空变化特征、未来演变趋势及驱动因子进行分析和研究,并定量识别不同区域内的主导驱动因子,旨在为该流域的生态环境治理工作提供依据。研究结果表明:1)2000—2015年,滦河流域植被NPP年均值为455.04g(C)·m~(-2)·a~(-1),整体呈波动上升趋势,显著增加区占流域总面积的32.94%,且未来同向变化趋势略强于反向变化趋势;2)该流域植被NPP空间差异较为显著,表现为东南高西北低的格局,受地形影响较大,流域中游的低山丘陵区为植被NPP高值区;3)驱动机制上,流域植被NPP变化与温度和降水均为正相关关系,水热耦合共同作用于植被NPP的积累,人类活动则是通过改变土地利用强度或生态建设工程等影响植被NPP的变化,且在不同地形区域内,植被NPP变化的主导驱动因子不同,整体上以气候和人类活动共同正向促进作用为主,但在平原区以单因子的反向抑制作用为主。

Spatio-temporal distribution of net primary productivity and its driving factors in the Luanhe River Basin from 2000 to 2015

Net primary productivity (NPP) is an important indicator of regional ecological quality and can reflect the growth status of vegetation. We selected the Luanhe River Basin as the study area, and used trend analysis, Hurst index, and residual trend analysis to examine the spatio-temporal distribution of NPP and investigated the effects of climate change, topographic factors, and human activities. This study analyzed NPP based on meteorological data, land use maps, and remote sensing data MOD17A3 from 2000 to 2015 and aimed to provide a basis for the ecological environmental governance of the river basin. The results showed that: 1) The average annual NPP was 455.04 g(C)·m^-2·a^-1, and the inter-annual variability showed overall growth from 2000 to 2015. Of the total basin area, 32.94% had a significant increase in NPP, whereas 6.98% had a significant decrease. The Hurst index analysis indicated that most NPP changes were in the same direction. 2) There were regional NPP differences in the Luanhe River Basin; the multi-year NPP average was lowest in the low hilly area, intermediate in the plain country, and highest in the middle mountain region. The maximum NPP was in Chengde and Lulong Counties in the Beijing-Tianjin-Hebei water conservation ecological function reserve, with characteristically superior natural environmental conditions. 3) The watershed NPP was positively correlated with the annual average precipitation and the annual average temperature, indicating that temperature was the main climatic factor affecting NPP in the Luanhe River Basin. The accumulation of vegetation NPP was affected by the combined effects of temperature and precipitation. Human activities affected the vegetation NPP by changing the land use intensity, ecological construction, and improving the environment, with positive and negative effects on NPP. Among the different terrain areas, the dominant factors affecting vegetation NPP varied. Overall, the prevailing reasons for NPP increases were climatic factors and human activities; only 1.74% of the regional climate and anthropogenic activities contributed to NPP reduction. The driving characteristics were similar in the low hilly area and the middle and high mountain areas. However, in the low-altitude plain areas, climatic factors or human activity alone led to more significant NPP reductions, accounting for 51.63% of the area. Taken together, this study showed that spatial distribution of NPP was determined by climatic and topographic characteristics, and climate change and human activities strongly affected vegetation NPP.