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

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，其中大部分存在于循环相对缓慢的化合物中。化学理论预测，分解速度慢的化合物比分解速度快的化合物对气候变暖更敏感。这些化合物在分解过程中向大气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。这种适应或驯化可以减轻目前化学理论预测的土壤有机碳分解的温度敏感性。迄今为止，驯化和适应尚未被纳入土壤有机碳分解温度敏感性的预测框架，因为微生物对新温度制度的驯化和适应的影响尚不清楚。因此，对于这个项目，研究人员将确定：i)微生物的驯化和适应对通过微生物的碳和氮通量的影响以及对多种碳化合物分解的温度敏感性的影响；ii)不同功能微生物种群间相互作用对土壤有机碳分解温度敏感性的影响。微生物分解对增温响应的特征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：简单的、无菌的酶和底物混合物；类土介质，含有特定结构和同位素组成的基质，并接种了代表一系列生物地球化学功能的微生物群体；真实的土壤中既有引入的微生物群落，也有天然的微生物群落。将评估从土壤化合物中流入微生物的碳和氮以及随后释放的二氧化碳、基质利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的大气二氧化碳浓度。目前，大多数模型都是纯粹基于土壤有机碳的特征。由于确定微生物利用不同土壤碳化合物的挑战，研究微生物在温度变化下将土壤碳转化为生物量和二氧化碳的驯化和适应性的努力通常受到阻碍。通过在实验复杂性的增量水平上进行实验，并将微生物中碳和氮流动的测量整合到一个新的理论框架中，本研究将直接解决这些缺点。资助博士后1人、研究生1人、本科生4人。研究成果将整合到7门本科和研究生课程中，教育推广工作将包括通过实验室网站传播土壤生态学和气候变暖信息，并向堪萨斯州农村人口的中学生和教师传播。

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.