基于改进的CASA模型三峡库区NPP时空特征及气候驱动机制

Temporal-spatial variations of NPP and its climatic driving mechanism in the Three Gorges Reservoir Area based on modified CASA model

采用改进后的CASA模型对三峡库区2001—2015年的NPP进行了估算。通过Sen斜率的方法,对NPP的年内及年际时空变化趋势及分布特征进行了分析;基于相关性分析方法,深入探讨了气候因子对NPP的驱动机制;并以气候模式模拟结果为输入项,对NPP的未来变化趋势进行了预测,得到如下结论:(1)2001—2015年间,三峡库区NPP的月值呈单峰型季节变化趋势,峰值达到160 gC m^(-2)月^(-1),发生于7月。NPP年际变化呈波动型上升趋势,幅度较小,多年平均值为727 gC m^(-2)a^(-1)。空间分布上,主要表现为库首库尾较高、库腹较低和长江以北高于长江以南的特点。(2)NPP与降水、气温及净辐射等气候因子之间均呈显著正相关,其中与气温的相关性最强,与降水的相关性最弱,植被生产力对气温的变化更为敏感。(3)未来15年NPP多年平均值为859 gC m^(-2)a^(-1),总体呈微弱减小趋势,幅度为4.14 gC m^(-2)10a^(-1)。与现状对比来看,未来NPP表现出一定程度的增加,总体而言,三峡库区植被长势趋好,呈良性稳定态势发展。

Net primary production(NPP)in the Three Gorges Reservoir Area(TGRA)during 2001—2015 was estimated using a modified parameter CASA model.The spatial and temporal variation and distribution characteristics of the NPP were analyzed on annual and inter-annual scale based on Sen′s slope.According to the correlation analysis method,the driving mechanism of climate factors to NPP was discussed.Then,the NPP in the future was predicted with climate model simulation results as input.The results showed that:(1)from 2001 to 2015,the monthly value of NPP in the TRGA presented a single-peak seasonal variation trend,reached its maximum value of 160 gC m^(-2)month^(-1)in July.The annual variability of NPP showed a rising trend of fluctuation with a small range,and the multiyear average value of NPP was 727 gC m^(-2)a^(-1).In terms of the spatial distribution,the main features are higher in head and tail of the reservoir,lower belly of the reservoir and higher north of the Yangtze River than south.(2)The NPP was significantly positively correlated with precipitation,temperature and solar radiation,with the strongest correlation with temperature and the weakest correlation with precipitation,indicating that the vegetation productivity was more sensitive to the change of temperature.(3)In the next 15 years,the multiyear average value of NPP was 859 gC m^(-2)a^(-1),showed a slight decrease trend,with a range of 4.14 gC m^(-2)10 a^(-1).Compared with the current situation,the NPP showed a certain increase in the future.Generally speaking,the vegetation in the TGRA was growing well and developing in a benign and stable way.