Interactions between root C, microbial activity and turnover, and food web complexity

微生物活动是微生物生物量和土壤有机质周转的关键参数，它强烈依赖于作为主要碳源的根际沉积物和凋落物的有效性。除了呼吸，其他微生物活性参数从来没有与微生物和SOM的营业额。在这个项目中，我们挑战连接微生物和有机质周转估计的δ 13 C后C3/C4植被变化和13 C/14 C标记实验与20个参数的微生物活性，如底物限制和无限呼吸，最大和真实的比生长速率，底物亲和力和矿化潜力，酶的活性。时间和深度梯度将用于正在进行的和新的小麦/玉米田间试验，以评估根系对微生物活动参数的影响以及长期（数月至数年）微生物C和SOM基于δ13 C的周转。根碳对短期周转和活动参数的影响将在新的实验中比较根际和非根际土壤进行评估。在以二元联系、多营养相互作用和微生物环为重点的模型研究中，微生物活性参数将与微生物食草动物的复杂性和丰度联系起来。这些数据将被用于模拟土壤食物网和微生物营业额取决于放牧强度的C通量。最后，我们将建议微生物活动代理充分反映微生物营业额。

Microbial activity is the key parameter of turnover of microbial biomass and of soil organic matter (SOM) and it strongly depends on the availability of rhizodeposits and litter as the primary carbon (C) sources. Beside respiration, other microbial activity parameters were never linked with the turnover of microorganisms and of SOM. In this project we challenge to link microbial and SOM turnover estimated by δ13C after C3/C4 vegetation change and by 13C/14C labeling experiments with 20 parameters of microbial activity such as substrate limited and unlimited respiration, maximal and real specific growth rates, substrate affinity and mineralization potential, activities of enzymes. Time and depth gradients will be used in the ongoing and new wheat/maize field experiments for evaluation of root effects on microbial activity parameters and δ13 C based turnover of microbial C and SOM over long periods (months to years). The effects of root-C on short-term turnover and activity parameters will be evaluated comparing rhizosphere and bulk soil in new experiments. In model studies focused on binary links, multitrophic interactions and microbial loop the microbial activity parameters will be linked with complexity and abundance of microbial grazers. These data will be used for modeling of C fluxes within the soil food web and microbial turnover depending on grazing intensity. Finally we will suggest microbial activity proxies adequately reflecting microbial turnover.