The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology
The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology
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DOI：
10.1016/j.agrformet.2018.09.001
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发表时间：
2018-12-15
影响因子：
6.2
通讯作者：
Stoy, Paul C.
中科院分区：
文献类型：
--
作者：
Fu, Zheng;Gerken, Tobias;Stoy, Paul C.
热带雨林通过调节气候、维持生物多样性和固碳在地球系统中发挥着核心作用。它们受到砍伐森林等直接人为影响和气候变化的间接人为影响的威胁。迄今为止，尚未对决定热带雨林生物群落中不同森林在场地规模上的二氧化碳净生态系统交换（NEE）的因素进行综合。在这里，我们研究NEE及其组成部分，总生态系统生产力（GEP）和生态系统呼吸（RE），在热带雨林生物群落内的13个自然和管理的森林与63个总站点年的涡度协方差数据。我们的研究结果表明，具有最大的光合作用年总碳吸收量（即GEP > 3000 g Cm（-2）y（-1））的五个生态系统具有最低的净碳吸收-甚至碳损失与其他研究生态系统相比，因为RE具有相似的量级。提供子冠层CO2存储观测的网站有较高的平均GEP和RE和较低的平均NEE的幅度，突出了测量方法的重要性，了解在生态系统中的碳动力学与典型的高大，茂密的植被。通径分析表明，在大多数研究地点，在光饱和条件下，蒸汽压亏缺（VPD）比土壤湿度或气温在限制GEP方面发挥更大的作用，但在-0.31至-0.87 μ mol CO2 m（-2）s（-1）hPa（-1）范围内的作用程度不同。在产生8.5 W m（-2）辐射强迫的代表性浓度路径下，来自13个大气环流模式（CMIP 5）的气候预测表明，目前温度范围低端的许多热带雨林地点可能在2050年达到与目前较温暖地点相似的气候空间，较温暖的地点将达到目前没有经历过的气候，所有的森林都可能经历更高的VPD。结果表明，有必要量化成熟的热带树木是否以及如何适应热量和水分胁迫，并进一步开发通量分区和填补空白的算法，在热带雨林中的碳交换的防御估计。
Tropical rainforests play a central role in the Earth system by regulating climate, maintaining biodiversity, and sequestering carbon. They are under threat by direct anthropogenic impacts like deforestation and the indirect anthropogenic impacts of climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) at the site scale across different forests in the tropical rainforest biome has not been undertaken to date. Here, we study NEE and its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), across thirteen natural and managed forests within the tropical rainforest biome with 63 total site-years of eddy covariance data. Our results reveal that the five ecosystems with the largest annual gross carbon uptake by photosynthesis (i.e. GEP > 3000 g C m(-2) y(-1)) have the lowest net carbon uptake - or even carbon losses versus other study ecosystems because RE is of a similar magnitude. Sites that provided sub canopy CO2 storage observations had higher average magnitudes of GEP and RE and lower average magnitudes of NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in ecosystems with characteristically tall and dense vegetation. A path analysis revealed that vapor pressure deficit (VPD) played a greater role than soil moisture or air temperature in constraining GEP under light saturated conditions across most study sites, but to differing degrees from -0.31 to -0.87 mu mol CO2 m(-2) s(-1) hPa(-1). Climate projections from 13 general circulation models (CMIP5) under the representative concentration pathway that generates 8.5 W m(-2) of radiative forcing suggest that many current tropical rainforest sites on the lower end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, warmer sites will reach a climate not currently experienced, and all forests are likely to experience higher VPD. Results demonstrate the need to quantify if and how mature tropical trees acclimate to heat and water stress, and to further develop flux-partitioning and gap-filling algorithms for defensible estimates of carbon exchange in tropical rainforests.