ETBC; Temperature sensitivity of substrate decomposition from enzymes to microbial communities

ETBC；

• 批准号: 0950095
• 负责人: Sharon Billings
• 金额: $ 59.6万
• 依托单位: University of Kansas Center for Research Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0950095&HistoricalAwards=false
• 关键词: ETBC; Temperature; sensitivity; substrate; decomposition

Soils contain more than 1.5 times the amount of carbon in vegetation and the atmosphere combined, much of it residing in compounds that turnover relatively slowly. Chemical theory predicts that decomposition of slow turnover compounds will be far more sensitive to a warming climate than compounds with faster turnover rates. The release of CO2 to the atmosphere from these compounds as they decompose would serve as a positive feedback to global warming. However, recent research suggests that microorganisms responsible for decomposing soil carbon may adapt or acclimate to warmer environments. Such adaptation or acclimation may mitigate the temperature sensitivity of soil organic carbon decomposition currently predicted by chemical theory. To date, acclimation and adaptation have yet to be incorporated into a predictive framework for the temperature sensitivity of soil organic carbon decomposition, because the influence of microbial acclimation and adaptation to a new temperature regime is, as yet, unknown. For this project then, investigators will determine: i) the influence of microbial acclimation and adaptation on carbon and nitrogen fluxes through microbes and on temperature sensitivities of decomposition for multiple types of carbon compounds; and ii) the influence of interactions between functionally different microbial populations on the temperature sensitivity of soil organic carbon decomposition. Data characterizing responses of microbial decomposition to warming will be incorporated into a theoretical framework to understand the influence of microbial acclimation and adaptation on the temperature sensitivity of soil organic carbon decomposition. Incubations will be performed across a range of complexity, including: simple, sterile mixtures of enzymes and substrates; soil-like media containing substrates of specified structure and isotopic composition, and inoculated with microbial populations representing a range of biogeochemical functions; and real soils with both introduced and natural microbial communities. The flow of carbon and nitrogen into microbes from soil compounds and subsequent release of CO2, shifts in substrate use, and changes in microbial community structure with temperature will be assessed. Models used to predict how soil organic carbon decomposition rates change with temperature are important because they can help predict future atmospheric CO2 concentrations. Currently, most models are based purely on the characteristics of soil organic carbon. Efforts to examine the acclimation and adaptation of the microorganisms that transform soil carbon into biomass and CO2 with changing temperature typically are thwarted due to the challenges associated with identifying microbial use of distinct soil carbon compounds. By conducting experiments across incremental levels of experimental complexity and integrating measurements of carbon and nitrogen flow through microorganisms into a new theoretical framework, this research will directly address these shortcomings. The work will support one post-doctoral scholar, one graduate student, and four undergraduates. Research results will be integrated into seven undergraduate and graduate courses, and educational outreach efforts will include dissemination of soil ecology and climate warming information via laboratory websites, and to middle school students and teachers from rural Kansan populations.

土壤中的碳含量是植被和大气中碳含量总和的1.5倍以上，其中大部分存在于周转相对较慢的化合物中。化学理论预测，周转慢的化合物比周转速度快的化合物对气候变暖的分解要敏感得多。这些化合物分解时向大气中释放的二氧化碳将对全球变暖起到积极的反馈作用。然而，最近的研究表明，负责分解土壤碳的微生物可能会适应或适应更温暖的环境。这种适应或驯化可能会缓解目前化学理论预测的土壤有机碳分解的温度敏感性。到目前为止，驯化和适应还没有被纳入土壤有机碳分解的温度敏感性的预测框架中，因为微生物驯化和适应对新的温度制度的影响尚不清楚。在这个项目中，研究人员将确定：i)微生物驯化和适应对通过微生物的碳和氮通量以及对多种类型碳化合物分解温度敏感性的影响；ii)不同功能微生物种群之间的相互作用对土壤有机碳分解温度敏感性的影响。描述微生物分解对气候变暖响应的数据将被纳入一个理论框架，以了解微生物驯化和适应对土壤有机碳分解的温度敏感性的影响。培养将在一系列复杂的情况下进行，包括：简单、无菌的酶和底物混合物；含有特定结构和同位素组成的底物的类似土壤的基质，并接种代表一系列生物地球化学功能的微生物种群；以及具有引进微生物群落和自然微生物群落的真实土壤。将评估从土壤化合物流入微生物的碳和氮以及随后释放的二氧化碳、底物使用的变化以及微生物群落结构随温度的变化。用于预测土壤有机碳分解速率如何随温度变化的模型很重要，因为它们可以帮助预测未来大气中的二氧化碳浓度。目前，大多数模型都是纯粹基于土壤有机碳的特性。研究将土壤碳转化为生物量和二氧化碳的微生物随温度变化的驯化和适应工作通常受阻，因为与确定微生物利用不同的土壤碳化合物有关的挑战。通过在实验复杂性的递增水平上进行实验，并将通过微生物流动的碳和氮流量的测量整合到一个新的理论框架中，这项研究将直接解决这些缺点。这项工作将支持1名博士后学者、1名研究生和4名本科生。研究成果将被整合到七门本科生和研究生课程中，教育推广工作将包括通过实验室网站传播土壤生态和气候变暖信息，以及向堪萨斯州农村人口的中学生和教师传播。