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全文摘要次数: 41 全文下载次数: 29
引用本文:

DOI:

10.11834/jrs.20243428

收稿日期:

2023-10-17

修改日期:

2024-05-29

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1982—2015年全球森林GPP和NEP对大气CO2施肥效应响应的时空变化趋势研究
孔祥祺, 王斌, 卞少杰, 陈研西, 李明泽, 范文义
东北林业大学
摘要:

近年来,关于大气CO2施肥效应(β)的定量研究逐渐成为全球碳循环研究的热点。大气中的CO2浓度不断上升在很大程度上影响着总初级生产力(GPP)的变化,进而可能对净生态系统生产力(NEP)产生影响。因此在全球气候变化背景下,准确定量描述GPP对于大气CO2上升的响应( βgpp)以及NEP对于大气CO2上升的响应( βnep),探究其时空变化趋势,对于充分理解大气CO2施肥效应的作用机制有着重要意义。本研究以全球森林作为研究对象,利用EC-LUE GPP数据集和Jena CarboScope NEP数据集,结合随机森林回归模型,定量βgpp 和βnep 的时空变化趋势,以及探究不同森林类型和不同气候带βgpp 和βnep 的差异。研究结果表明,1982—2015年全球森林的βgpp 和 βnep均值分别为(18.3±14.9)%/100 ppm和(7.4±4.0)%/100 ppm,并呈显著下降趋势,年均下降速率分别为0.14%/100 ppm/yr和0.11%/100 ppm/yr。大气CO2浓度的上升对全球森林大部分区域的GPP(80.1%)和NEP(81.6%)具有显著的促进作用,然而其中大部分区域的 βgpp(52.4%)和 (βnep59.2%)呈现出了显著的下降趋势。随着气候带纬度的升高, βnep下降速率呈逐渐降低的趋势, βgpp呈逐渐升高的趋势。常绿阔叶林βgpp 下降速率最慢,落叶阔叶林 βgpp下降速率最快。阔叶林 βnep下降速率大于针叶林。通过本研究,期望为深入了解全球森林对大气CO2施肥效应的响应规律以及评估森林在全球碳循环中扮演的角色,对制定合理的气候变化应对政策提供科学依据。

Spatial and temporal variation trends in the response of global forest GPP and NEP to CO2 fertilization effects from 1982 to 2015
Abstract:

Objective In recent years, quantitative studies on the CO2 fertilization effects(β) have also gradually become a hotspot in global carbon cycle research. The rising atmospheric CO2 concentration largely affects the changes in gross primary productivity (GPP), which in turn may have an impact on net ecosystem productivity (NEP). Therefore, in the context of global climate change, it is of great significance to accurately quantify the response of GPP to the rise of atmospheric CO2 (βgpp ) and the response of NEP to the rise of atmospheric CO2 (βnep ), and to explore their spatial and temporal trends, to fully understand the mechanism of CO2 fertilization effects. Method In this study, the global forest was taken as the research object, and the EC-LUE GPP dataset based on the Eddy Covariance-Light Use Effi-ciency (EC-LUE) model and Jena CarboScope NEP dataset based on atmospheric transport model, respectively, to quantify the spatial and temporal trends of the effects of GPP and NEP on CO2 fertilization effects during 1982?2015, as well as to investigate the effects of βgpp and βnep on CO2 fertilization effects in different forest stand types and different climatic zones. This study used the random forest regression algorithm and set up two CO2 concentration scenario models for both GPP datasets and NEP datasets to reconstruct the changes of GPP and NEP in the global for-est growing seasons during the period of 1982?2015. The differences in GPP and NEP between the two scenarios were calculated and combined with the differences in CO2 concentration to quantitatively estimate βgpp and βnep , and finally, the spatial and temporal trends of βgpp and βnep over the period 1982?2015 were analyzed by setting a moving window of 15 years and using the Mann-Kendall trend test on a pixel-by-pixel basis. Result The mean values of βgpp and βnep in global forests from 1982 to 2015 were (18.3±14.9)%/100 ppm and (7.4±4.0)%/100 ppm, respectively, and showed a significant decreasing trend with annual average rates of 0.14%/100 ppm/yr and 0.11%/100 ppm/yr, respec-tively. The increase in atmospheric CO2 concentration had a significant contributing effect on GPP (80.1%) and NEP (81.6%) in most regions of the global forests, however, most of them showed a significant decreasing trend in βgpp (52.4%) and βnep (59.2%). As the latitude of the climatic zone increased, the rate of decline of βnep showed a gradu-ally decreasing trend, and βgpp showed a gradually increasing trend. Evergreen broadleaf forests showed the slowest decline in βgpp, and deciduous broadleaf forests showed the fastest decline in βgpp . The decline rate of βnep in broadleaf forests was greater than that in coniferous forests. Conclusion The response of GPP and NEP in global for-ests to the increasing atmospheric CO2 concentration shows a declining trend. Neglecting this decline would impact the future estimation of global forest carbon sequestration potential and the achievement of carbon neutrality goals. Therefore, in the process of achieving carbon neutrality, timely adjustments should be made to optimize forest age structure, improve forest site conditions, and implement forest management practices aimed at enhancing forest car-bon sequestration capacity.

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