Scrub encroachment promotes biodiversity in temperate European wetlands under eutrophic conditions

Wetlands are important habitats, often threatened by drainage, eutrophication and suppression of grazing. In many countries, considerable resources are spent combatting scrub encroachment. Here, we hypothesize that encroachment may benefit biodiversity – especially under eutrophic conditions where asymmetric competition among plants compromises conservation targets. We studied the effects of scrub cover, nutrient levels and soil moisture on richness of vascular plants, bryophytes, soil fungi and microbes in open and overgrown wetlands. We also tested the effect of encroachment, eutrophication and soil moisture on indicators of conservation value (red-listed species, indicator species and uniqueness). Plant and bryophyte species richness peaked at low soil fertility, whereas soil fertility promoted soil microbes. Soil fungi responded negatively to increasing soil moisture. Lidar-derived variables reflecting degree of scrub cover had predominantly positive effects on species richness meas...