未来气候情景下青藏高原草地净初级生产力时空演变特征

Characteristics of Temporal and Spatial Evolution of Grassland Net Primary Productivity on the Qinghai-Tibet Plateau Under Future Climate Scenarios

[目的]揭示SSP126和SSP585两种气候情景下,不同气候因素(气温和降水)对青藏高原草地净初级生产力的影响,阐明青藏高原地区影响草地净初级生产力时空分布特征的主控气候因素,为未来青藏高原地区植被生态系统的综合治理提供理论依据。[方法]基于青藏高原48个气象站点基准期(1971—2020年)的日值气象数据、土壤类型数据以及模型所需要的站点管理数据,利用DAILY CENTURY(DAYCENT)模型,结合文献中对应站点的NPP实测值和MOD17A3遥感数据,对模型参数进行了校准,利用均方根误差、可决系数、效率系数等统计指标对模型模拟结果进行了评价。其次单向嵌套BCC-CSM1.1气候模式,对未来气候SSP126和SSP585情景下的青藏高原草地净初级生产力进行预测,并对预测结果进行了时空统计分析。[结果](1)在SSP126和SSP585情景下青藏高原草地NPP均呈现出由东南向西北递减的分布特征,且NPP值较高的区域主要位于青藏高原的东南部,NPP值较低的区域则位于青藏高原以西的区域;(2)在SSP126情景下,青藏高原草地净初级生产力总体呈现出下降趋势,波动范围最大的是长远期(2081—2100年),减小幅度为12.1%;在SSP585情景下,NPP总体呈现出平稳的上升趋势,其中近期(2021—2040年)的增长速率最高为12%;(3)与基准期(1971—2021年)相比,在SSP126和SSP585情景下,青藏高原85%以上的草地NPP呈现下降趋势,其中SSP126和SSP585与基准期(1971—2020)相比NPP值分别相对减少28%,23%。[结论]两种不同气候情景下,温度与NPP的相关性均高于降水。低温少雨是造成青藏高原西北地区草地NPP减少的主要原因。

[Objective]The aims of this study are to explore the effects of different climatic factors(temperature and precipitation)on the grassland Net Primary Productivity(NPP)of the Qinghai-Tibet Plateau(QTP)under the two climate scenarios SSP126 and SSP585,and to clarify the main climatic factors affecting the spatial and temporal distribution characteristics of grassland NPP on the QTP,so as to provide a theoretical basis for the comprehensive management of vegetation ecosystem on the QTP in the future.[Methods]Based on the daily value meteorological data and soil type data of 48 meteorological stations on the QTP during the base period(1971—2020)and the site management data required by the model,the model parameters were calibrated by using the DAILY CENTURY(DAYCENT)model,and the measured NPP values and MOD17A3 remote sensing data of corresponding stations in the literature,and the results were evaluated by means of the root-mean-square error,determinability coefficient,efficiency coefficient and other statistical indexes.Secondly,a one-way nested BCC-CSM1.1 climate model was used to predict the NPP of grassland on the QTP under the future climate SSP126 and SSP585 scenarios,and the prediction results were statistically analyzed on spatial and temporal scales.[Results](1)Under the SSP126 and SSP585 scenarios,the NPP of the QTP shows the decreasing distribution from southeast to northwest,and the area with higher NPP value was mainly located in the southeast of the QTP,while the area with lower NPP value will be located in the west of the QTP.(2)Under the SSP126 scenario,the NPP of grassland on the QTP generally shows the downward trend,and the largest fluctuation range will be in the long-term period(2081—2100),with a decrease rate of 12.1%.Under the SSP585 scenario,NPP generally presents a steady upward trend,with the highest growth rate of 12%in the near future(2021—2040).(3)Compared with the baseline period(1971—2021),under the SSP126 and SSP585 scenarios,the NPP of more than 85%grassland on the QTP shows the decreasing trend,and the NPP value of SSP126 and SSP585 will decrease by 28%and 23%,respectively,compared with the baseline period(1971—2020).[Conclusion]Under the two different climate scenarios,the correlation between temperature and NPP is higher than that of precipitation.Low temperature and lack of rainfall are the main reasons for the decrease of grassland NPP in the northwest of the QTP.