Climate and Vegetation Drivers of Terrestrial Carbon Fluxes: A Global Data Synthesis
The terrestrial carbon (C) cycle plays an important role in global climate change, but the vegetation and environmental drivers of C fluxes are poorly understood. We established a global dataset with 1194 available data across site-years including gross primary productivity (GPP), ecosystem respiration (ER), net ecosystem productivity (NEP), and relevant environmental factors to investigate the variability in GPP, ER and NEP, as well as their covariability with climate and vegetation drivers. The results indicated that both GPP and ER increased exponentially with the increase in mean annual temperature (MAT) for all biomes. Besides MAT, annual precipitation (AP) had a strong correlation with GPP (or ER) for non-wetland biomes. Maximum leaf area index (LAI) was an important factor determining C fluxes for all biomes. The variations in both GPP and ER were also associated with variations in vegetation characteristics. The model including MAT, AP and LAI explained 53% of the annual GPP variations and 48% of the annual ER variations across all biomes. The model based on MAT and LAI explained 91% of the annual GPP variations and 92.9% of the annual ER variations for the wetland sites. The effects of LAI on GPP, ER or NEP highlighted that canopy-level measurement is critical for accurately estimating ecosystem-atmosphere exchange of carbon dioxide. The present study suggests a significance of the combined effects of climate and vegetation (e.g., LAI) drivers on C fluxes and shows that climate and LAI might influence C flux components differently in different climate regions.
Keywordsnet ecosystem productivity gross primary productivity ecosystem respiration controlling factors vegetation model
陆地生态系统碳循环在全球气候变化中起着关键作用, 但其植被和环境驱动力尚未研究清楚. 我们建立了1个包含全球 1194 组不同观测地点或年份的总初级生产 (GPP), 生态系统呼吸 (ER), 净生态系统生产 (NEP) 和相关环境因子的数据集来研究 GPP, ER 和 NEP 的变异性以及这3个碳通量与气候和植被驱动因子的关系. 结果表明, 对于所有生物区系来说, GPP 和 ER 均随年平均温度的增加而增加, 非湿地生物区系的 GPP 和 ER 与年降水量存在极大的相关性, 在所有生物区系中一年中的最大叶面积指数也是影响碳通量时空变异的关键因子. 我们建立的基于所有生物区系的包含年平均温度, 年降水量和叶面积指数的模型解释了53%, 48%的 GPP 和 ER 的时空变异, 基于年平均温度和叶面积指数的模型可模拟湿地中 91%的 GPP变异和93%的ER变异. 叶面积指数对 GPP, ER和 NEP 的影响显示了冠层水平的测定对准确估计生态系统−大气的 CO2交换起着关键作用. 基于不同温度和降水阈值划分的不同气候区的模拟结果表明气候和植被驱动力 (如叶面积指数) 对陆地生态系统碳通量具有复合影响作用且其影响作用在不同的气候区存在差异.
关键词净生态系统生产 总初级生产 生态系统呼吸 驱动因子 植被 模型
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This study was financially supported by the National Natural Science Foundation of China (Grant Nos. 41775151, 41530533 and 41775152). Thousands of researchers who measured the C flux data collected here contributed greatly to this study. Their field measurement work is the basis of this global synthesis. We are grateful to the two anonymous reviewers for their helpful comments on our earlier draft.
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