fun-C: Kuolleen sienibiomassan ja maan mikrobiston merkitys metsämaan hiilivarastoille

Globally, soils are significant reservoirs of carbon (C), and they store twice the amount of carbon present in our atmosphere currently. Thus, even slight changes in soil respiration can change the atmospheric CO2 concentrations drastically. When the climate warms, growing seasons will prolong and plant photosynthesis rate will increase. Soil microbes can utilize the increased photosynthetic carbon input by increasing their total activity and soil organic matter (SOM) degradation rate, leading to increased soil respiration. However, during the last years, it has been discovered that dead microbial biomass contributes to the soil C stocks significantly, and the amount of labile-C allocated to microbial growth might balance out the loss of soil C, which was respired from soil due to enhanced microbial
activity. Amino sugars are considered as good indicators for soil´s microbial necromass pool since amino sugars are part of microbial cell walls, and the contribution of fungal cell wall component, N-acetyl glucosamine (chitin), to soil amino sugar pool is important and well known. However, another group of fungal cell wall compounds, melanins, contain rather significant amounts of amino sugars, especially glucosamine and galactosamine, and the fungal hyphae melanin content is shown to affect the recalcitrance and decomposability of the fungal necromass. In this project, I will aim to reveal a linkage between soil colonizing microbial community, soil fungal hyphae´s melanin content, and the recalcitrance of microbial remains in soils. For this, I will utilize a Finnish-Estonian forests´ birch, spruce and pine gradients, and study: 1) how soil inhabiting microbial community and fungal mycelia´s melanin contribute to the soil amino sugar concentrations; 2) how fungal necromass decomposition rate is affected by its original melanin content; and 3) if the fungal necromass decomposition rate is determined more by its melanin content or other factors such as the structure of the initial decomposer community, soil fungi:bacteria ratio, or soil C:N ratio. At the end of this project, I will link the measurements from the field experiments together and incorporate them to an already existing soil model, CORPSE. The results of this project will lead to better understanding on how soil microbes contribute to soil C stocks and SOM build up. This information is critical for future development of climate models and predicting how changing climate will affect soil processes.