Effects of resource quality and availability on soil microorganisms and their carbon assimilation

在该项目的第一阶段，我们调查了资源质量，资源可用性和季节条件的变化如何改变细菌和真菌对有机物分解的贡献，并因此改变土壤食物网。真菌能量途径的重要性/优势从CM处理中麦角固醇级分中玉米衍生碳的富集高达76.3%可见。在该项目的第二阶段，我们希望使用不同的SIP方法（PLFA-SIP，麦角甾醇-SIP和NA-SIP）在野外条件下分别跟踪草食动物和食草动物食物链中的碳流。我们预计通过食草动物食物链的碳流动将比通过食腐动物食物链的速度更快。为了加深我们对食腐动物食物网的理解，我们将使用不同年龄的垃圾材料进行实验室实验。使用13 C和12 C玉米凋落物的土壤芯顶部的相互移植将使我们能够遵循碳流入微生物食物网（细菌，真菌，原生动物）的特定成员，并计算这些微生物在玉米分解的不同阶段的周转时间。为了了解农业生态系统中食草动物和食肉动物的食物链，迫切需要不同微生物群体中碳库大小和停留时间的数据。

During the first phase of the project we investigated how changes in resource quality, resource availability and seasonal conditions modify the bacterial and fungal contribution to organic matter decomposition and – as a consequence – to the soil food web. The importance/dominance of the fungal energy pathway was seen from an enrichment of maize derived carbon in the ergosterol fraction of up to 76.3 percent in the CM treatment. During the second phase of the project we want to follow the carbon flow separately through the herbivore and detritivore food chains under field conditions using different SIP based methods (PLFA-SIP, ergosterol-SIP and NA-SIP). We expect that carbon flow through the herbivore food chain will be faster than through the detritivore food chain. To deepen our understanding of the detritivore food web, we will perform a lab experiment using litter material of different ages. Using reciprocal transplantation of 13C and 12C maize litter on top of soil cores will allow us to follow the carbon flow into specific members of the microbial food web (bacteria, fungi, protozoa) and to calculate the turnover times of these microorganisms at different stages of maize decomposition. Data on pool size and residence time of carbon in different microbial groups are urgently needed in order to understand herbivore and detritivore food chains in agro-ecosystems.