Integrated system for photosynthesis and greenhouse gas flux measurements

非二氧化碳温室气体对推动气候变化的净气候强迫的贡献率约为30%：一氧化二氮(N2O)和甲烷(CH4)尤其重要，陆地生态系统既是这些气体的重要汇，也是这些气体的源。最近从政策的角度强调了非二氧化碳温室气体，因为排放是无意的，往往是经济损失，但需要有重要的科学空白来指导政策和管理实践。直到最近，人们一直认为土壤是N2O和CH4交换的主要场所；然而，最近的研究发现，这些气体的大量交换是通过植物，特别是树木进行的。需要更好地了解这些通量，以制定减少非二氧化碳温室气体的源和汇的管理做法。光合作用气体交换是植物与大气交换气体的主要生理过程，包括二氧化碳和水蒸气以及溶解在木质部中的痕量气体；然而，很少有测量将二氧化碳通量与其他温室气体的通量联系起来。我们的研究小组最近记录了安大略省受管理森林的树叶对CH4的大量吸收，但了解了其中的机制(例如，CH4的氧化是由于树叶中的甲烷营养细菌？)和控制(例如，这如何随光和温度的变化而变化？)因为这些过程需要一个气体交换系统，该系统将光合作用测量与痕量气体通量相结合。除了CH4通量外，植物介导的N2O通量在城市森林和绿化屋顶等高N输入的管理系统中可能也很重要。最近在气体光谱分析方面的创新使得能够快速准确地测量N2O和CH4的浓度。我们要求资金建立一个独一无二的系统，该系统将光合作用测量与快速N2O和现有的现场便携式CH4分析仪相结合，允许研究所有三种温室气体(N2O、CH4和CO2)的叶、茎和其他植物器官的通量，以及土壤和整个系统的通量的测量。该系统所允许的测量将使人们能够更好地了解管理生态系统中温室气体交换所涉及的机制，并将促进制定管理方法，最终目标是通过管理森林和城市生活基础设施加强气候缓解。

Non-CO2 greenhouse gases contribute ~30% to net climate forcing that drives climate change: nitrous oxide (N2O) and methane (CH4) are of particular importance, with terrestrial ecosystems acting as both important sinks and sources for these gases. Non-CO2 greenhouse gases have recently been emphasized from a policy perspective, as emissions are unintentional and often represent economic losses, but there are important science gaps needed to inform policy and management practices. Until recently it was assumed that soils were the primary sites of exchange of N2O and CH4; however, recent studies have discovered that substantial exchange of these gases that occurs through plants, in particular trees. A better understanding of these fluxes is needed to develop management practices that reduce sources and enhance sinks of non-CO2 greenhouse gases. Photosynthetic gas-exchange is the main physiological process by which plants exchange gases with the atmosphere - including CO2 and water vapor as well as trace gases dissolved in the xylem stream; however, there have been few measurements that link CO2 flux with the flux of other greenhouse gases. Our research group has recently documented substantial uptake of CH4 by tree foliage in managed forests in Ontario but understanding the mechanisms (e.g., is CH4 oxidation due to methanotrophic bacteria within tree leaves?) and controls (e.g., how does this vary with changes in light and temperature?) for these processes requires a gas-exchange system that integrates photosynthesis measurements with trace gas fluxes. In addition to CH4 flux, N2O flux mediated by plants is likely to be important in managed systems with high N inputs, such as urban forests and green roofs. Recent innovations in spectroscopic gas analysis allow for rapid and accurate measurements of both N2O and CH4 concentrations. We request funds for a one-of-a-kind system that integrates photosynthetic measurements with a rapid N2O and existing field-portable CH4 analyzer, allowing for studies of fluxes of all three greenhouse gases (N2O, CH4 and CO2) by leaves, stems, and other plant organs, as well as measurements of soil and whole-system fluxes. The measurements allowed by this system will permit a better understanding of mechanisms involved in greenhouse gas exchange in managed ecosystems and will facilitate development of management approaches with the ultimate goal of enhancing climate mitigation by managed forests and urban living infrastructure.