SGER: Assessing respiratory responses of plant respiration to climate change at the ecosystem level: a stable isotope tracer approach

陆地生态系统通过光合作用（导致总初级生产力GPP）和生态系统呼吸（Re）与大气交换约120Gt的碳(C)。越来越多的证据表明，在大多数生态系统中，大气CO2浓度升高会增加碳吸收，然而，Re及其组分对CO2浓度升高的响应尚不清楚。净生态系统生产力（NEP）被确定为GPP和Re之间的净平衡，通常是生态系统功能特性的敏感预测因子。稀土的一个重要组成部分是植物的呼吸作用。生态系统水平的植物呼吸难以测量，因为它包含了来自土壤异养生物的呼吸作用。本提案的主要目的是在现有的自由空气CO2富集（FACE）设施中开发一种使用同位素示踪剂测量林分植物呼吸及其组分的方法，在这种方法中同位素标签可以很容易地传递。该计划是在两个生长季节进行一系列为期一天的二氧化碳同位素脉冲实验。这些实验旨在反褶曲整株C处理，估计光合碳的平均停留时间（MRT），并分离自养和异养呼吸。这些实验将在一个由甜桉树种植园组成的落叶林中进行，在两个生长季节使用FACE暴露于环境和升高的二氧化碳中。根据这些实验的初步成功，该方法将扩展到农业生态系统- soyface -也使用FACE将大豆田暴露在升高的二氧化碳和O3中。该项目的结果将对旨在确定生物圈碳循环的全球气候模型具有直接的相关性和实用性。该研究的广泛结果将与碳通量监测倡议（Ameriflux、EuroFlux）、生物圈-大气-稳定同位素-网络和其他大规模生态系统研究直接相关。该项目也为学生在多学科研究方面的垂直整合训练提供了极好的机会。本科生将参与暑期实地和实验室研究实习。研究生将有独特的机会探索具有社会重要性的生态学的基础科学问题，在独特的实地设施中进行多学科的努力。将通过SROP和桥梁项目促进代表性不足的少数民族参与研究。该项目还将通过开设强调各学科融合的课程来整合本科和研究生教育。有超过1500名本科生参加了改革后的生物学学位课程，这里概述的教学计划是基于这一扩展计划，并建立在过去两年开展的推广活动的基础上。这些教学和推广活动包括对本科生和研究生的研究和指导，通过建立的本科生科学奖学金参与科学教育，以及使用互联网进行教学、推广和研究。

ABSTRACTTerrestrial ecosystems exchange about 120Gt of carbon (C) with the atmosphere, through the processes of photosynthesis (leading to gross primary productivity, GPP) and ecosystem respiration (Re). Increasing evidence indicates that raising atmospheric CO2 enhances carbon uptake in most ecosystems, however, responses of Re and its components to elevated CO2 are unclear. Net ecosystem productivity (NEP), is determined as the net balance between GPP and Re and is often a sensitive predictor of functional ecosystem properties. A large component of Re is plant respiration. Plant respiration at the ecosystem level is difficult to measure because is embedded with respiration from soil heterotrophs. The major thrust of this proposal is to develop a method to measure stand level plant respiration and its components using isotope tracers in current Free Air CO2 Enrichment (FACE) facilities in which the isotope label can be readily delivered. The proposal is to do a series of one-day isotopic CO2-pulse experiments several times during two growing season. These experiments are aimed at deconvolute whole-plant C processing, to estimate the mean residence time (MRT) of photosynthetic carbon and to separate autotrophic from heterotrophic respiration. These experiments will be done in a deciduous forest consisting of a sweet gum plantation exposed to ambient and elevated CO2 using FACE during two growing seasons. Depending on the initial success of these experiments the method will be extended to an Agroecosystem -SOYFACE- exposing soybean fields to elevated CO2 and O3 also using FACE. Results from the project will have direct relevance and utility to global climate models aimed at determining the carbon cycle of the biosphere. The broad outcome of the study will have direct relevance to C-flux monitoring initiatives (Ameriflux, EuroFlux), Biosphere-Atmosphere-Stable-Isotope-Network and other large-scale ecosystem studies. This project also offers an excellent opportunity for a vertically integrated student training in multidisciplinary research. Undergraduates will be involved with summer internships for field and laboratory research. Graduate students will have unique opportunities to explore fundamental scientific questions in ecology of societal importance, within a multidisciplinary effort at unique field facilities. Participation of underrepresented minorities in research will be promoted with the SROP and the Bridge programs. The project will also integrate undergraduate and graduate education by the initiation of courses that emphasize convergence of various disciplines. With more than 1500 undergraduates enrolled in the reformed biology degree, the teaching plan outlined here is based on this expanding program and builds upon outreach activities developed during the last two years. These teaching and outreach activities include research and mentoring for undergraduate and graduate students, participation in science education through established undergraduate science scholarships, and the use of the Internet for teaching, outreach, and research.