Global Ecosystem Response to Changing Light Environments and the Implications for Climate Feedbacks

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。通过光合作用产生的陆地生态系统生产力代表了全球最大的单一年度碳通量，约占每年120亿吨碳。 最近对光在生态系统尺度光合作用中的作用的研究表明，在漫射光条件下，光被云和气溶胶散射，碳吸收显著增强。 这种提高的扩散使用效率可对年初级生产总值产生重大影响，就火山气溶胶而言，对大气二氧化碳浓度产生可观察到的全球影响。 然而，目前还不知道DUE的普遍性如何，以及它如何在生态系统类型，水文气候和光照条件下变化，或者由于漫射光导致的全球陆地GPP增强有多大。 因此，研究人员不确定未来光照条件的变化可能对全球碳预算以及最终大气中二氧化碳浓度产生什么影响。 该项目的目标是产生一个地面上的净全球DUE的估计;调查的地理变化DUE的生态系统特征，气候和光制度的功能;并估计潜在的碳反馈的情况下，未来的变化区域光环境。 这将通过分析世界各地200多个二氧化碳通量塔站点的数据集来实现，每个站点提供多年的30分钟碳通量，辐射和气象数据。这个新的全球数据集是世界各地数百名研究人员做出巨大贡献的产物，涵盖所有主要生态区、大多数气候类别、110度纬度范围以及除南极洲以外的所有大陆。 分析将首先涉及主要利用碳通量和太阳辐射数据逐点确定DUE的参数。 这些将与一个空间生态区域模型合成，以估计全球DUE的大小，并将与生态系统，气候和光属性进行分析，以帮助了解控制DUE的地理分布和机制。 DUE参数化的全球空间模式也将与云和气溶胶变化的情景相结合，以近似未来光照状况变化对全球碳收支的影响，该项目将提供用于生态系统-气候模式的重要碳收支控制的基本参数化。 这将提高对控制DUE和碳预算影响的机制的基本理解，包括这一重要温室气体的大气浓度。 这将导致未来在全球气候模型中对这一重要反馈进行核算，这对于理解生态系统对环境变化的反应和改进对未来气候的预测至关重要。 该项目将为来自传统上得不到充分服务的社区的学生提供教育和教学机会，并将为环境研究人员和决策者提供宝贵的信息和见解。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Productivity of terrestrial ecosystems through photosynthesis represents the largest single planetary annual carbon flux, accounting for about 120 gigatons of carbon per year. Recent research into the role of light in ecosystem-scale photosynthesis has revealed a significant enhancement of carbon uptake under conditions of diffuse light, where light has been scattered by clouds and aerosols. This enhanced diffuse-use efficiency (DUE) can make a significant difference in annual gross primary production (GPP), and in the case of volcanic aerosols has an observable global impact on atmospheric carbon dioxide concentrations. It is not known how universal the DUE is, however, as well as how it varies across ecosystem types, hydroclimates, and light regimes or how large the global terrestrial GPP enhancement is due to diffuse light. As a result, researchers are unsure what impact future changes in light conditions might have on the global carbon budget and ultimately atmospheric concentrations of carbon dioxide. The objectives of this project are to produce a ground-up estimate of the net global DUE; to investigate the geographic variability in DUE as a function of ecosystem characteristics, climate, and light regime; and to estimate potential carbon feedbacks under scenarios of future changes to regional light environments. This will be accomplished through analysis of a dataset of more than 200 carbon dioxide flux tower sites around the world, each providing multiple years of 30-minute carbon fluxes, radiation and meteorological data. This new global dataset is the product of large contributions by hundreds of researchers around the world and covers all major ecoregions, most climate classes, a latitudinal range of 110 degrees, and all the continents except Antarctica. Analysis will first involve a site-by-site parameterization of the DUE primarily using carbon fluxes and solar radiation data. These will be synthesized with a spatial ecoregion model to estimate the magnitude of the global DUE and will be analyzed with ecosystem, climate, and light attributes to help understand the geographic distribution and mechanisms controlling DUE. A global spatial model of DUE parameterizations also will be combined with scenarios of cloud and aerosol change to approximate the global carbon budget impacts of future changes in light regimes.This project will provide foundational parameterizations of an important carbon budget control for use in ecosystem-climate models. This will improve basic understanding of the mechanisms controlling DUE and the carbon budget implications, including atmospheric concentrations of this important greenhouse gas. This will lead to future accounting of this important feedback in global climate models, which is critical for understanding ecosystem responses to environmental change and for improved prediction of future climates. The project will provide education and teaching opportunities for students from traditionally underserved communities, and it will provide valuable information and insights for environmental researchers and policy makers.