Microbial regulation of organic matter decomposition at the regional scale

我们的项目为改进地球化学模型的参数化提供了分析基础（例如，DAISY-EXPERTN）通过引入地下社区和气候之间的动态反馈。鉴于我们目前测量了参与碳循环的土壤微生物过程的温度敏感性函数的季节性和区域性变化，我们将专注于集团特定的周转时间在下一阶段的项目中，将在这两个地区的农田中建立一个微观实验，（Swabian Alb和Kraichgau）使用13 C-PLFA和13 C-麦角固醇谱分析方法研究细菌和真菌生物质的周转时间。我们假设真菌储存新同化的碳（13 C信号）比细菌更长的时间，因为它们的周转时间较慢。在田间实验中操纵资源的输入将使我们能够分别研究通过细菌和真菌的C流。我们将选择以下标记化合物：（1）13 C葡萄糖（主要用于细菌C掺入）和（2）13 C苯酚/木质素前体（主要用于真菌C掺入）。我们将建立一年四次（早春，夏季，秋季和深秋）的缩影。将通过测量13 C-底物掺入微生物生物质的不同组分（Cmic、细菌和真菌PLFA、麦角甾醇）以及在安装微生态系统后长达48小时的田间13 CO2损失来评估微生物效率。我们的研究结果将被项目合作伙伴用于检查多室碳模型（例如CN DAISY）对微生物生长效率改变的敏感性。此外，我们将测试以下哪一项：基质质量，特定的微生物分解群落，或非生物土壤特性，是在区域尺度上凋落物分解空间变异的主要驱动因素。

Our project provides the analytical basis for improving the parameterisation of biogeochemical models (e.g., DAISY-EXPERTN) by introducing dynamic feedbacks between belowground communities and climate. Whereas we currently measure seasonal and regional variation of temperature sensitivity functions of soil microbial processes involved in carbon cycling, we will focus on group specific turnover times (bacteria and fungi) and flow of carbon into specific groups of soil microorganisms and their seasonal substrate use efficiency during the next phase of the project.A microcosm experiment will be established in cropped plots at both regions (Swabian Alb and Kraichgau) to study the turnover times of bacterial and fungal biomass using the 13C-PLFA and 13C-ergosterol profiling approach. We hypothesise that fungi store newly assimilated carbon (13C signal) for a longer period than bacteria due to their slower turnover times. Manipulating the input of resources in a field experiment will allow us to investigate separately the C flow through bacteria and fungi. We will choose the following labelled compounds: (1) 13C glucose (to account for mainly bacterial C incorporation) and (2) 13C phenol/lignin precursors (to account for mainly fungal C incorporation). We will establish the microcosms four times a year (early spring, summer, autumn and late autumn). Microbial efficiency will be assessed by measuring 13C-substrate incorporation into different components of the microbial biomass (Cmic, bacterial and fungal PLFAs, ergosterol) and loss as 13CO2 in the field for up to 48 hours after installation of the microcosms. Our results will be used by project partners to examine the sensitivity of multi-compartment carbon models (e.g. CN DAISY) to altered microbial growth efficiency. In addition, we will test which of the following: substrate quality, site specific microbial decomposer communities, or abiotic soil properties, is the dominant driver of spatial variation in litter decomposition at the regional scale.