Dead wood changes in pristine, drained and restored peatlands

Dead wood is a fundamental structural element in forest ecosystems, yet its characteristics in peatland forests remain poorly quantified. Using a large-scale field experiment of peatland restoration across Finland (n = 138 sites), we examined changes in dead wood quantity and quality in six peatland types (poor and rich spruce mires, pine mires and open mires) over ten years. Restored sites were compared with corresponding drained sites and pristine reference sites. Dead wood densities and volumes varied markedly among peatland types and among sites. The average volume of dead wood was highest in spruce mires (mean = 48 m 3 ha −1 per site), intermediate in pine mires (7 m 3 ha −1 ) and lowest in open mires (2 m 3 ha −1 ). In general, drained sites and restored sites contained more dead wood than pristine sites. Peatland types also differed in dead wood characteristics, i.e. in the proportion of standing vs. downed trees and tree species composition. Following restoration, temporal changes in dead wood characteristics were clear but only partly attributable to restoration. Overall, our results indicate that restoration alters dead wood quantity and quality, and generates a short-term resource pulse, particularly in rich spruce mires. However, a decade after restoration, dead wood amounts and characteristics in restored mires still do not fully converge with those of pristine peatlands.