Positive trends in plant, dragonfly, and butterfly diversity of rewetted montane peatlands

Abstract

Drainage and afforestation of peatlands cause extensive habitat degradation and species losses. Restoration supports peatland biodiversity by creating suitable habitat conditions, including stable high water tables. However, colonization by characteristic species can take decades or even fail. Peatland recovery is often monitored shortly after restoration, but initial trends may not continue, and results might differ among taxonomic groups. This study analyzes trends in plant, dragonfly, and butterfly diversity within 18 years after rewetting of montane peatlands in central Germany. We compared diversity and species composition of 19 restored sites with three drained peatlands and one near‐natural reference site. Restoration resulted in improved habitat conditions and benefited species diversity, but there were marked differences among taxonomic groups. Dragonflies rapidly colonized small water bodies but their diversity did not further increase in older restoration sites. Characteristic peatland vegetation recovered slowly, since it depended on a high water holding capacity that was only reached after peat started accumulating. Generally, plant diversity developed toward reference conditions albeit incompletely, even 18 years after restoration. Butterflies responded less to peatland restoration; generalists increased only temporarily and specialists could not establish. In conclusion, peatland restoration improves habitat conditions and biodiversity, while trajectories of recovery are nonlinear and incomplete after two decades. This highlights the need for long‐term monitoring and a strategic selection of indicator species for evaluation of restoration success.

Integrated assessment of ecosystem recovery using a multifunctionality approach

“…; Appendix S1: Fig. The intact reference site was only marginally affected by these processes (Strobl et al 2019). Geologically, the study area belongs to the eastern base rock mountains of Bavaria.…”

“…The continuity in peatland rewetting and the similarity of the sites in terms of bedrock, landform, hydrological conditions, past peat formation, degradation history, restoration action, and current management allowed a regional monitoring scheme using a chronosequence approach (see Strobl et al 2019). Afterward, sites remained unmanaged and were left to natural succession.…”

“…At the 23 ditches, we randomly chose transects of 65 m following active and restored drainage ditches (Strobl et al 2019). Transects were considered as independent, as they were separated by dense spruce stands, restored in different years, and were at least 50 m apart, while rewetting effects do not go beyond this distance (see Hedberg et al 2012).…”

“…Transects were considered as independent, as they were separated by dense spruce stands, restored in different years, and were at least 50 m apart, while rewetting effects do not go beyond this distance (see Hedberg et al 2012). The plots outside the ditch were placed at 1, 2, 4, 7, and 11 m distance from the ditch margin (Strobl et al 2019). The plots outside the ditch were placed at 1, 2, 4, 7, and 11 m distance from the ditch margin (Strobl et al 2019).…”

“…Results are based on generalized additive models (GAMs) using ditch as a parametric term, age (i.e., time since restoration) as a smooth term (s), and transect as a random factor. Acidic peatlands naturally host highly specialized species but often have low species richness (Minayeva et al 2017), and rather, re-establishment of specialists or increasing their cover should be priority, while maximizing overall species richness is less important (see also Strobl et al 2019). Significant results at the 0.05 level are printed in bold.…”