祁连山国家公园植被净初级生产力时空演变及驱动因素分析

Spatio-temporal evolution of vegetation net primary productivity in Qilian Mountain National Park and its driving factors

祁连山国家公园具有涵养水源、维持生态平衡等重要作用,是河西乃至西北地区重要的生态安全屏障。本研究利用2000–2018年的MODIS NDVI遥感数据、气象数据及人类活动数据,采用NPP估算模型–CASA模型计算了植被净初级生产力(net primary productivity,NPP),并借助一元线性回归法与相关分析法,分析了研究区植被NPP的时空变化特征以及与地形、气候和人类活动等驱动因素的耦合关系。结果表明:1)祁连山国家公园植被NPP整体呈现波动上升的趋势,多年均值为167.35 g·(m2·a)–1;各月植被NPP的变化也呈增加趋势,增长速率存在明显的差异。2)空间上2000–2018年祁连山国家公园的植被NPP呈现出自东向西递减的趋势;月尺度上,植被NPP具有明显的季相变化特征,植被NPP累积量夏季最高,秋季次之,冬季最少。3)整体上祁连山国家公园植被NPP随海拔、坡度增加呈现出“先增加后减少”的变化趋势;植被NPP与降水的相关性较高,其相关性系数为0.632(P<0.01);当人类活动强度达到一定程度时(>20%),二者之间呈现明显的负相关关系。总体上,地形与气候因素对研究区植被NPP变化起主要作用。本研究可为科学评价祁连山国家公园生态治理成效以及生态政策的制定与生态环境的管护提供相应的参考,并可以为进一步实现区域自然–经济–社会的协调与可持续发展提供相关理论依据。

Qilian Mountain National Park plays an important role in water conservation and ecological balance and is an important ecological security barrier in Hexi and even northwest China.In the present study,the NPP estimation model-CASA model and MODIS NDVI remote sensing product were used to calculate NPP values for the 2000–2018 period,and univariate linear regression,correlation analysis,meteorological data,and human activities data,were used to analyze the temporal and spatial variation characteristics of NPP in the study area and to investigate relationships between terrain,climate,and human activities.1)During 2000–2018,the NPP of Qilian National Park exhibited an upward trend of fluctuation,with a multi-year average of 167.35 g·(m2·a)–1.Meanwhile,monthly changes in NPP exhibited increasing trends,and the growth rate was obviously different.Among them,the growth rate of vegetation NPP from May to September was significantly greater than that of other months.2)Multi-year mean NPP values decreased from southeast to northwest,and the vegetation NPP exhibited obvious seasonal variation,with NPP being highest during summer,followed by autumn,and lowest during winter.3)Overall,the NPP of Qilian Mountain National Park first increased and then decreased with increasing elevation and slope,and the vegetation NPP of overcast slopes was greater than that of sunny slopes.Compared with temperature,the correlation between vegetation NPP and precipitation was higher,with a correlation coefficient of 0.632(P<0.01).When the intensity of human activity reached>20%,there was an obvious negative correlation between NPP and human activity intensity.In general,topography and climate factors play a decisive role in the determination of vegetation NPP in the study area.The present study provides a reference for scientific evaluation of the ecological management of Qilian Mountain National Park,as well as for the development of ecological policy and management of the ecological environment,and provides relevant theoretical basis for the further realization of the regional natural-economicsocial coordination and sustainable development.