Does topsoil removal in grassland restoration benefit both soil nematode and plant communities?

Abstract

1. Successful restoration of semi-natural grasslands on grasslands previously subject to intensive management needs to overcome manifold barriers. These include high soil fertility, the dominance of a few fast-growing plant species, degraded soil faunal communities and missing propagules of the targeted above-and belowground flora and fauna. A combination of removing the topsoil and introducing propagules of target plants has become one of the major tools for nature conservation agencies and practitioners to reduce soil fertility and restore former species-rich grasslands in various European countries.2. Using topsoil removal as a restoration measure has provoked an ongoing debate between supporting nature conservation and rejecting soil protection agencies. Although it favours species-rich plant communities, it strongly disturbs soil communities and affects physical and chemical soil properties and processes.Currently, there is a lack of long-term data to assess how restored grassland ecosystems develop and recover after topsoil removal. Here, we used two well-established bioindicators, soil nematodes and plants, to quantify restoration success of topsoil removal in comparison with alternative restoration measures and target communities 22 years after intervention.3. The nematode community composition indicated reduced nutrient availability in the restored systems, as was aimed at by topsoil removal. Nevertheless, after this 22-year period following topsoil removal, nematode composition and structure revealed successful recovery. 4. Plant communities benefitted from the reduction of soil nutrients after topsoil removal as indicated by higher numbers of plant species and higher Shannon diversity. Furthermore, topsoil removal strongly promoted the re-establishment of plant species of the target plant community. Synthesis and applications.Overall, our study demonstrates how a massive intervention by topsoil removal proved successful in converting intensively managed into species-rich grasslands. This contrasts with the mild intervention of repeated mowing and removing of the harvested plant material. We show that, in the long run, potential negative effects of topsoil removal on the soil fauna can be | 1783

Long‐term restoration success of insect herbivore communities in seminatural grasslands: a functional approach

“…Plant propagules were added on one‐half of the area where topsoil was removed via application of fresh, seed‐containing hay and hand‐collected propagules of target species originating from semi‐dry and semi‐wet species‐rich grasslands with local and regional provenance (within radius of 7–30 km) (1995, 1996, 1997; for further details see timeline in Appendix : Fig. S2, but also Resch et al 2019).…”

Evaluating long‐term success in grassland restoration: an ecosystem multifunctionality approach

“…The goal of all three methods was to lower the availability of soil nutrients and hence, facilitate ecosystem development toward the targeted nutrient-poor grasslands. These methods were Harvest only (hay harvest twice a year), Topsoil (removal of the nutrient-rich topsoil), and Topsoil + Propagules (topsoil removal combined with the application of hay from target vegetation; further details see Resch et al 2019). Plant biomass harvest (once a year in late summer/early autumn) commenced in Topsoil and Topsoil + Propagules five years after the soils were removed and is still ongoing today (see Appendix S1: Table S1).…”

“…We measured restoration success by comparing the three restoration methods with intensively managed (Initial) and seminatural grasslands (Target) 22 yr after restoration. Initial grassland sites share the same agricultural history as the restored sites: mowing and subsequent fertilizing (manure) up to five times a year, as well as different tillage regimes (see Appendix S1: Table S1; Resch et al 2019). Target sites were the sites from which hay for seeding the Topsoil + Propagules sites was collected.…”

“…Target sites were the sites from which hay for seeding the Topsoil + Propagules sites was collected. Soil conditions (i.e., soil types, soil texture) were comparable to those found in the restored grasslands (see Appendix S1: Table S1; Resch et al 2019). Additionally, Target sites were selected to represent a variety of seminatural grasslands, including semi-dry to semi-wet conditions.…”

“…Yet, to evaluate restoration success, usually only a few aboveground biotic properties, typically plant community composition, sometimes the presence/absence of selected insect species or taxa (e.g., grasshoppers, beetles) are used (e.g., Patzelt et al 2001, Kardol et al 2005, Kiehl and Wagner 2006, Kiehl and Pfadenhauer 2007, Klimkowska et al 2007, Verhagen et al 2008, Neff et al 2020). More exhaustive evaluations are lacking and only few studies assessed belowground community composition and soil properties to determine restoration success (e.g., Frouz et al 2009, Kardol et al 2009 b , Wubs et al 2016, Resch et al 2019). As restoration methods should enhance and reestablish biodiversity and ecosystem functioning both above‐ and belowground, success should be evaluated based on a comprehensive assessment of biotic and abiotic, above‐ and belowground properties, such as taxonomic and structural diversity, and soil functions and processes (Havlicek 2012, Greiner et al 2018, Gann et al 2019).…”