Impact of redistributed water by saprotrophic fungi on soil carbon mineralization
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Summer droughts are common in temperate forests and especially upper soil horizons experience drought. Drought events can be accompanied by negative effects for ecosystems but many plants can reduce drought stress by hydraulic redistribution (HR). HR is a passive relocation of water driven by a gradient in soil water potential via the root system. Similar processes were described for ECM networks but no information is available for saprotrophic fungi. We hypothesize that HR by saprotrophic fungi triggers mineralization of organic matter in soils under drought conditions.
Impact of HR was determined using mesocosms consisting of 2 chambers, separated by an air gap to prevent bulk flow of water. After fungal inoculation and a growth phase, both chambers were desiccated. Subsequently, only 1 chamber was rewetted while the other chamber was treated with 13C labelled plant material. CO2 samples were collected over 7 days and analyzed for stable isotope ratio. In addition, enzymatic activity in the dry chamber was determined after 7 days using soil zymographie. A negative control was provided by mesocosms with severed hyphal connections.
First results are presented and show the impact of HR by saprotrophic fungi on mineralization. Overall, a more than 2-fold higher total carbon mineralization of the labelled material was detectable in mescosms with intact hyphal connections compared to controls. In addition, HR also led to a strong increase of enzyme activities in the dry chambers.