秦巴山区近15年植被NPP时空演变特征及自然与人为因子解析

植被NPP作为衡量陆地生态系统的关键指标和地表碳循环的重要组成部分,能够合理地评价生态系统变化及其可持续性。基于MOD17A3数据,借助GIS空间分析、相关性分析及地理探测器模型等方法,探讨了2000—2014年秦巴山区NPP时空格局及演变特征,并对影响NPP的自然和人为因子进行量化研究。结果表明:(1)秦巴山区近15年NPP总量整体呈波动增加趋势,增速0.65TgC a~(-1),单位面积NPP均值为493.09gC m~(-2) a~(-1),呈"西高东低"空间特征,地域差异明显;(2)不同植被类型的NPP总量存在差异,阔叶林和栽培植被是对秦巴山区生态系统最具贡献的植被类型;(3)NPP随高程、坡度均呈阶段性变化特征,其中坡度影响NPP变化的幅度弱于高程,NPP与降雨、气温、实际蒸散量均呈显著正相关关系;(4)自然因子对NPP贡献率存在显著差异(P0.01),依次排序为:实际蒸散量降雨气温高程坡度,且研究区NPP受多种自然因子的交互影响;(5)人为因子对NPP的影响表现为土地利用类型变化造成NPP总量的损益,可分为还林还草的积极效应及城市发展和人类破坏等的消极效应。

Spatio-temporal variations of net primary productivity and its natural and human factors analysis in Qinling-Daba Mountains in the past 15 years

As a key indicator for measuring terrestrial ecosystems and an important part of the surface carbon cycle, net primary productivity (NPP) can reasonably assess ecosystem changes and sustainability. Based on MOD17A3 data and using GIS spatial analysis, correlation analysis, and geodetector model, this paper discussed the spatio-temporal pattern and dynamic variations of NPP in Qinling-Daba Mountains from 2000 to 2014. At the same time, the quantitative analysis on the natural and human factors affecting NPP were carried out in order to identify the main influence factors. The results showed that:(1) in the past 15 years, the growth rate of total NPP in Qinling-Daba Mountains was 0.65TgC a^-1 with a fluctuating increase trend. The average NPP per unit area was 493.09gC m^-2 a^-1 with obviously regional differences. The NPP was higher in the west and lower in the east part of study area. (2) The total NPP of different vegetation types was different. Broad-leaved forest and cultivated vegetation were the most important types contributing to the ecosystems of Qinling-Daba Mountains. (3) The NPP changes in stages with elevation and slope, among which the extent of slope''s influence on NPP was weaker than that of elevation, and NPP had a significant positive correlation with rain, temperature, and evapotranspiration. (4) There were significant differences in the contribution rate of the natural factors to the NPP (P < 0.01) with the order of ET > rain > temperature > elevation > slope. The contribution rate of interaction between any two natural factors was higher than that of single factor, that is, the NPP in the study area was affected by interaction of multiple natural factors. (5) The impact of human factors on the NPP was manifested as the profit and loss of total NPP caused by the change of land use type, which can be divided into the positive effect of returning forest and grassland and the negative effects of urban development and human destruction.