Authors: Runnel, Kadri; Lõhmus, Asko;Tamm, Heidi;

Globally, restoring degraded wetland ecosystems is a major topic. Restoring soil is a fundamental part of that, but it is addressed indirectly (e.g., by hydrological restoration) and actual measurements of the biotic responses in the soil are scarce. We studied the response of fungi and bacteria to ecosystem restoration activities in a large scale BACI experiment in bog forests in Estonia, hemiboreal Europe. The field treatments combined ditch closure and partial cutting to restore the original water level and stand structure. The soil samples and environmental data were collected before and four years after the treatments, the soil samples were sequenced for fungi and bacteria using Illumina MiSeq. The assemblages of both fungi and bacteria had a strong, rapid, but partly different response to ditch closure. The effect of partial cuttings was smaller. Within four years post treatment the assemblages became characterized by large yearly changes partly reflecting the annual water conditions, with no clear successional direction. We conclude that it is not obvious that hydrological restoration can reverse the soil succession in drained bog forests, and long term monitoring is needed.