Microbial phosphorus cycling in forest soils as dependent on carbon, nitrogen and phosphorus availability

微生物磷(P)循环对森林营养至关重要。以前的研究主要集中在微生物量磷储量和磷酸酶活性上，但对微生物磷循环过程中结合磷的溶解、磷在微生物生物量中的周转和净磷矿化的速率知之甚少。该项目的目的是了解微生物磷循环依赖于碳(C)、氮(N)和磷在山毛榉森林土壤中的有效性。该项目的一般假设是，微生物磷循环的速度强烈依赖于碳和磷的有效性。首先，我们将在山毛榉森林中进行全因素氮和磷施用量试验，研究净磷矿化速率、磷酸酶活性和微生物磷固定。其次，我们将在环剥实验中通过用14C和33P标记微生物DNA来量化C和P在微生物生物量中的平均停留时间，以及在不同P有效性的森林土壤中。第三，我们将通过土壤提取物和添加矿物质P的培养实验来确定微生物群落溶解P的能力。这将是首次通过14C和33P标记微生物DNA来确定C和P在微生物生物量中的平均停留时间的研究。该项目的主要价值将是它将森林土壤中微生物P循环的速率与C、N和P的有效性联系起来。

Microbial phosphorus (P) cycling is crucial for forest nutrition. Previous research focused on microbial biomass P stocks and phosphatase activity, but little is known about the rates of microbial P cycling processes such as solubilization of bound P, turnover of P in the microbial biomass, and net P mineralization. The objective of this project is to gain understanding of microbial P cycling depending on carbon (C), nitrogen (N) and P availability in beech forest soils. The general hypothesis of the project is that rates of microbial P cycling depend strongly on C and P availability. We will, first, study net P mineralization rates, phosphatase activity and microbial P immobilization in a full factorial N and P application experiment in beech forests. We will, second, quantify the mean residence time of C and P in the microbial biomass by labeling microbial DNA with 14C and 33P in a girdling experiment and in forest soils differing in P availability. Third, we will determine the capacity of microbial communities to solubilize P based on incubation experiments with soil extracts and added mineral P. This will be the first study to determine the mean residence time of C and P in the microbial biomass by labeling microbial DNA with 14C and 33P. The main value of the project will be that it relates rates of microbial P cycling in forest soils to C, N and P availability.