Comparative Ecosystem Ecology: Acclimation of ecosystem function to warmer temperatures and altered moisture

比较生态系统生态学：生态系统功能对气温升高和湿度变化的适应

• 批准号: RGPIN-2019-05195
• 负责人: Flanagan, Lawrence
• 金额: $ 2.4万
• 依托单位: University of Lethbridge
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=744731
• 关键词: Comparative; Ecosystem; Ecology; Acclimation; ecosystem

Photosynthesis and plant productivity are essential for supporting the operation of our biosphere. A current consensus suggests that future climate warming will result in reduced photosynthesis and net loss of carbon dioxide from ecosystems, but there is large uncertainty about the mechanisms involved, the magnitude of the expected positive feedback, and the consequences for future ecosystem function. Despite this consensus, several recent measurements, made at the global-scale, indicate that photosynthesis and net ecosystem CO2 uptake have been increasing for the last several decades. Two important mechanisms proposed for higher global-scale photosynthesis are: (i) shifts in the timing and duration of leaf area and photosynthetic activity, and (ii) increases in water-use efficiency (WUE). Further studies are required to test if these mechanisms, which have contributed to the ecosystem service of enhanced global photosynthesis, could be altered or restricted by further changes in environmental conditions. I propose to investigate the mechanisms that control how plants and ecosystems respond and acclimate to warmer temperatures and altered precipitation. A comparative approach, involving a network of four sites instrumented with eddy covariance flux towers, will be used to study ecosystems dominated by two different plant functional types (grassland, deciduous forest) in two locations in southwestern Alberta. The first objective is to test the effect of warmer temperatures on shifts in the timing and duration of photosynthesis and the associated consequences for growing season net carbon gain. In addition, we will determine the role of water stress and photoperiod in limiting potential warming-induced extensions to the growing season and ecosystem carbon gain. The second objective will test for temperature acclimation of photosynthesis and respiration at the ecosystem-scale and determine how this potential acclimation interacts with other environmental changes. Temperature acclimation of either or both photosynthesis and ecosystem respiration can lead to an altered temperature response of net carbon dioxide exchange, although it is not yet clear which acclimation process would have the largest effect on growing season net carbon uptake. The third objective will test the sensitivity of plant- and ecosystem-scale WUE to changes in environmental conditions and determine whether potential future increases in WUE will be constrained by projected warmer and drier conditions. Data from these studies will be compared to the predictions of quantitative models to gain further understanding of the mechanistic controls and the reasons for the observed responses of plants and ecosystems to the environmental changes. Finally, the new information generated from these studies will be used to improve models that evaluate the consequences of global environmental changes for photosynthesis and ecosystem productivity.

光合作用和植物生产力对于支持我们生物圈的运作至关重要。目前的共识表明，未来的气候变暖将导致光合作用减少和生态系统中二氧化碳的净损失，但有关机制，预期的正反馈的大小以及对未来生态系统功能的影响存在很大的不确定性。尽管有这一共识，但最近在全球范围内进行的几项测量表明，光合作用和生态系统净二氧化碳吸收量在过去几十年中一直在增加。两个重要的机制提出了更高的全球规模的光合作用：（i）在时间和持续时间的叶面积和光合活性的变化，和（ii）提高水分利用效率（WUE）。需要进一步研究，以检验这些机制是否会因环境条件的进一步变化而改变或受到限制，这些机制有助于增强全球光合作用的生态系统服务。我建议研究控制植物和生态系统如何应对和适应温度升高和降水变化的机制。一个比较的方法，涉及四个站点的网络与涡度协方差通量塔，将被用来研究生态系统为主的两个不同的植物功能类型（草地，落叶林）在西南阿尔伯塔的两个位置。第一个目标是测试温度升高对光合作用时间和持续时间变化的影响，以及生长季节净碳增益的相关后果。此外，我们将确定水分胁迫和光周期的作用，限制潜在的变暖引起的延长生长季节和生态系统的碳增益。第二个目标是在生态系统尺度上测试光合作用和呼吸作用的温度适应，并确定这种潜在的适应如何与其他环境变化相互作用。光合作用和生态系统呼吸的温度驯化可以导致净二氧化碳交换的温度响应改变，尽管目前还不清楚哪个驯化过程对生长季净碳吸收的影响最大。第三个目标将测试植物和生态系统规模的WUE对环境条件变化的敏感性，并确定WUE未来的潜在增长是否会受到预测的温暖和干燥条件的限制。这些研究的数据将与定量模型的预测进行比较，以进一步了解植物和生态系统对环境变化的反应的机制控制和原因。最后，这些研究产生的新信息将用于改进评估全球环境变化对光合作用和生态系统生产力的影响的模型。