Microbial interactions and phosphorus mobilization in forest soils - effects of carbon, nitrogen and phosphorus availability

新建立的N x P应用试验将用于测试营养添加是否会改变真菌与真菌的相互作用，使腐殖型真菌具有更高的优势，这是因为森林土壤表面的菌丝生长强烈。营养添加实验中的真菌-真菌相互作用可能会改变，因为在碳有效性保持不变或略高的情况下，养分增加(由于植物生长增强)，但环剥减少了从树木到土壤环境的碳转移。因此，我们将测试来自根沉积的碳量的减少是否会降低外生菌根真菌(EMF)在土壤中共生动员磷的重要性。由于裂解高分子有机碳化合物的能力是微生物获得结合在根和凋落物等复杂生物结构中的含N和P化合物所必需的，因此我们想要研究腐生营养和电动势在有机化合物分解过程中的相对作用。氧化酶活性与水解酶活性的比值将指示排除电动势是否会改变土壤微生物群落在有机质分解过程中的行为，从而改变有机质养分释放过程中的行为。对我们的土壤生长实验中的主要电动势进行的宏基因组分析将证明电动势是否具有分解有机物的遗传潜力。在实验室条件下添加锰过氧化物酶将证明氧化酶是否可以释放出原本受保护的有机N和P化合物，以便随后的微生物分解。我们将继续与SPP内对植物与土壤微生物之间的相互作用感兴趣的其他小组进行密切合作。

The newly established N x P application experiment will be used to test whether nutrient addition changes fungal-fungal interactions towards higher dominance of saprotrophic fungi due to the resulting intense mycelial growth at the surface of forest soils. Fungal-fungal interactions in the nutrient addition experiment may change due to an increase in nutrients at either constant or slightly higher carbon availability (due to enhanced plant growth), but girdling decreases the C transfer from trees into the soil environment. Therefore, we will test whether a decrease in the amount of C derived from rhizodeposition reduces the importance of symbiotic P mobilization by ectomycorrhizal fungi (EMF) in soils. Since the ability to cleave high molecular organic carbon compounds is necessary for microorganisms to access N and P containing compounds bound up in complex biotic structures like roots and litter, we want to investigate the relative roles of saprotrophic and EMF during decomposition of organic compounds. The ratio of oxidative to hydrolytic enzyme activities will give us an indication whether the exclusion of EMF will modify the behaviour of the soil microbial community during decomposition of organic matter and consequently during the release of nutrients from organic matter. Metagenomic analyses of the dominant EMF in our soil-in-growth experiment will demonstrate whether EMF have the genetic potential to decompose organic matter. The addition of Mn peroxidase under lab conditions will prove whether oxidative enzymes might liberate otherwise protected organic N and P compounds for subsequent microbial decomposition. We will continue our intense collaborations with other groups within the SPP interested in interactions between plants and soil microorganisms.