Long-term effects of a single soil inoculation: shifts in soil microbial community composition and functioning after a community coalescence event in sand, clay, and peat grasslands.

Thriving communities of soil biota are a cornerstone of soil functionality. Intensification of land management with the aim to increase yield changes the biodiversity of soils, which comes at the cost of other soil functions, due to the destructive effect such management can have on soil biodiversity. While more nature-inclusive soil management practices may lead to more balanced soil multifunctionality, the recovery of biodiversity in long-term intensively managed soils is expected to take a long time. Inoculation with healthy soil may provide a jump start in the recovery of degraded soils, but only if the inoculated soil communities can become successfully established. Previous studies have shown that soil transplantation can result in greater recovery of soil communities compared to when single soil species are inoculated, but the effects on soil microbial communities and their contributions to soil functionality are not yet well-understood. Therefore, we used a four-years-old mesocosm experiment in order to test the long-term effects of soil inoculation by soil transplantation on the community composition and functionality of three types of grasslands soils. The experiment is composed of 60 intact soil cores of 95 cm diameter and 1 m depth that have been collected from three high input-output production grasslands on sand, clay, and peat. These grasslands had been exposed to high mowing frequencies, and had low vegetation diversity. At the start of the experiment, the soil cores were inoculated with soil from less intensively managed mid-successional grasslands, containing higher plant diversity than the intensively used grasslands. For half of the soil cores, the inoculate was sterilized beforehand to serve as a control. Bi-yearly measurements of yield, quarterly measurements of greenhouse gas emissions (CO₂, CH₄, N₂O), measurements of soil organic carbon, a vegetation analysis, and results from a recent litter decomposition experiment are combined with a time-series of amplicon sequence data of soil microbial communities. I will present the effects of inoculation on microbial community composition in sand, clay, and peat soils, and show that these inoculations can have functional consequences.