Restoring functional forested peatlands by combining ditch-blocking and partial cutting: An amphibian perspective

Abstract

Artificial drainage for forestry has caused major degradation of temperate peatland ecosystems. Partial restoration of those ecosystems is now widely considered, but feasible targets and effectiveness of restoration practices are not well established. In this study, we analyse a forested peatland restoration experiment in Estonia from a functional perspective of amphibian populations. In 2014–2020, we surveyed a before-after-control-impact experiment that combined two habitat manipulations: partial cuttings for restoring sparse tree canopy cover, and ditch blocking with soil filling to restore the water table. We monitored the responses in the aquatic habitats and breeding of brown frogs (moor frog Rana arvalis and common frog R. temporaria). Along with the expected habitat changes (ditch blocking quadrupled water depths and tree cutting reduced the shade), we found that ditch blocking restored the soil-type specific water acidity levels that the draining had homogenized. Partial ditch blocking reduced frog breeding activity in the first year, but it recovered and increased later on, specifically on sapric Histosols and supported by temporary wetlands, floods and pools created. However, the number of offspring did not clearly respond to the restoration and instead varied much among years. Our results indicate that, in drained forested wetlands: (i) near-natural aquatic habitats are a distinct restoration target and several years of post-restoration monitoring are needed to confirm the development of ecological integrity; (ii) increased breeding activity of amphibians may not result in improved recruitment; and thus, (iii) integrative wetland restoration techniques could benefit from an “amphibian perspective” of sustaining their whole life cycles and the food webs they support.