Transplanting success of two alpine plant species in combination with mulching during restoration of a high-elevation peatland

Abstract

Many high-elevation wetlands have been degraded by activities related to the skiing industry. However, few studies exist on their restoration in this harsh environment. From 2010 to 2017, we set up an experiment on a degraded bog located at 2500 m within the ski resort of Val-Thorens (France). We tested (1) if transplanting two sedge species, Trichophorum cespitosum and Eriophorum scheuchzeri effectively helped to initiate the restoration of the bog vegetation and (2) if different planting combinations of the species under different mulch treatments affected transplant survival and cover. After stabilising the bare peat with wood fascines and installed weirs in the incised gully that drained the bog, we planted tussocks of T. cespitosum and ramets of E. scheuchzeri, each alone or in mixture. We used straw mulch or a “biomulch” made of live shoots of Polytrichum moss. After a slight increase the first 2 years, the number of E. scheuchzeri ramets decreased continuously in all treatments and reached zero in 2016. T. cespitosum had a low mortality in all treatments; its annual survival rate and cover were significantly higher with biomulch. Because of strong winds and snow action, all the straw was removed after 2 years while the biomulch cover remained between 10 and 25% from the third to the fifth year then was close to zero from 2016. Nevertheless, this low cover seemed sufficient to favour the survival and growth of T. cespitosum. In 2017, bare soil was lower in all treatments with biomulch and T. cespitosum. This treatment appears to be the best restoration option, but it is likely that more than 7 to 10 years will be required to establish adequate plant cover at degraded high-elevation sites.