河西走廊植被净初级生产力时空变化及其影响因子研究

Temporal and spatial change of Net Primary Productivity of vegetation and its determinants in Hexi Corridor

干旱半干旱区植被NPP变化对全球碳循环有重要影响,该区域NPP对气候变化的响应表现出较大的时空异质性,其驱动机制并不十分清楚。选择中国河西走廊,利用随机森林算法估算了2002—2018年的NPP,基于偏导数法计算了气候与人类活动对NPP的影响。结果表明:(1)随机森林算法能较好的适用于干旱半干旱区NPP估算。(2)2002—2018年间河西走廊年NPP的平均值为153.32 gC m^(-2) a^(-1),总量为37.468 Tg C/a,呈东南向西北递减的分布特征,研究期间NPP呈2.37 gC m^(-2) a^(-1)(P=0.09)增长趋势。(3)河西走廊NPP变化52.51%由气候因子贡献,47.49%由人类活动贡献。(4)在气候变化对NPP的影响中,降水主导了该区72.21%的区域,温度对NPP变化量的贡献占73.71%,前者影响着NPP变化格局,后者主导NPP变化数量。升温和增湿均有利于该区NPP增加,随着西北地区气候暖湿化,河西走廊植被会持续改善,该研究有助于理解干旱半干旱区NPP对气候变化的响应机制,为适应气候变化政策制定提供理论依据。

The variation of vegetation Net Primary Productivity(NPP) has an important impact on the global carbon cycle in arid and semi-arid regions. The response of NPP to climate change in this region shows great spatial and temporal heterogeneity, while its driving mechanism is not clear. In this study, the Hexi Corridor in China was selected as study area, and the NPP from 2002 to 2018 was estimated using a random forest algorithm. The effects of climate and human activities on NPP were calculated based on the partial derivative method. The results showed that(1) random forest algorithms presented good performance in the NPP estimation in arid and semi-arid areas.(2) The average annual NPP of Hexi Corridor from 2002 to 2018 was 153.32 gC m^(-2) a^(-1), and the total amount was 37.468 Tg C/a, which indicated a decreasing distribution pattern from southeast to northwest. During the study period, the NPP showed an increasing trend of 2.37 gC m^(-2) a^(-1)(P=0.09).(3) 52.51% of the NPP variation in the Hexi Corridor was contributed by climate factors, and 47.49% was contributed by human activities.(4) For the impact of climate change on the NPP, precipitation dominated 72.21% of the area, and temperature contributed 73.71% of the amount of NPP variation. The former affected the NPP change pattern and the latter dominated the amount of NPP variation. Both warming and humidification are conducive to the increase of NPP in this area. With the warm and humid climate in the Northwest China, the vegetation in the Hexi Corridor will continue to increase. This study is helpful for understanding the response mechanisms of the NPP to climate change in arid and semi-arid areas, and provides a theoretical basis for decision making in adaptation to climate change.