A test of naturalness indicator values to evaluate success in grassland restoration

Abstract

How should the somewhat vague term of restoration success be measured? This is a critical question rooted in European law, where in fact the creation of proper replacement habitats is a prerequisite for permitting projects that trigger a loss of species or habitats. Previous studies have used indices that relied on a comparison to reference sites, for example the number of a predefined pool of target species or compositional similarity. However, since restoration sites have rarely the same biotic and abiotic conditions as reference sites, plant communities in restored sites will not perfectly match the reference sites. Furthermore, such indices fail when reference sites are lacking or degraded. Hence, there is a need for an alternative approach that evaluates the conservation value of a restored site independently from reference sites. We propose that naturalness indicator values can be an option to measure restoration success. The approach of using naturalness indicator values makes use of the fact that plants are able to indicate environmental parameters, including degradation and regeneration. We compared and measured the restoration success of three well-established methods for grassland restoration (sod transplantation, hay transfer, seeding) with three commonly used indices (diversity, number of target species, similarity to reference sites). The results verified earlier studies and showed that sod transplantation led to the highest restoration success followed by hay transfer and seeding of sitespecific seed mixtures. Further, we used those well-established indices for an evaluation of novel, naturalness-based indices (unweighted and cover-weighted mean naturalness indicator values, the sum of naturalness indicator values). While calculating the means of naturalness indicator values failed to offer conclusive information on restoration success, we could show that the sum of naturalness indicator values was highly correlated with the number of target species and compositional similarity to reference sites. Thus, our case study demonstrated that naturalness indices can be an excellent option to estimate success in grassland restoration. Abbreviations: CWMNN-Cover-weighted mean Naturalness indicator values, DSH-Donor site for hay transfer, DSS-Donor site for sod transplantation, FPFI-Frequency positive fidelity index (Tichý 2005), Simpson-Simpson´s Index, SUMNN-Sum of Naturalness indicator values, TGSpN-Number of target species, UWMNN-Unweighted Mean Naturalness indicator values. Naturalness indicators of grassland restoration 185 similar habitat conditions as compared to available reference sites and (b) are rather close to the reference sites (White and Walker 1997, Valkó et al. 2017).

Habitat heterogeneity as a key to high conservation value in forest-grassland mosaics

“…Despite some criticism, bio-indication in general and naturalness indicators in particular have solid theoretical bases and obvious practical advantages (Diekmann, 2003). Earlier analyses have shown that mean naturalness values are able to indicate habitat naturalness/degradation (Erdős et al, 2017;Sengl et al, 2016Sengl et al, , 2017. Here, we calculated the unweighted mean value for each plot, as it is more efficient in site indication than cover-weighted approaches (Tölgyesi et al, 2014).…”

An Approach to Thresholds for Evaluating Post-Mining Site Reclamation

“…Additionally, influencing factors such as the distance to the mined sites, vegetation zone, geology, weather, encroachment, and disturbances should be considered. However, the traditional comparison to reference sites for similar composition and/or condition [37,38] is not enough; reclaimed sites rarely have similar biotic and abiotic conditions [21], and it may lack or degrade due to unavoidable disturbances (natural/anthropogenic), or fluctuate over time.…”

“…Adequate incorporation of these gaps demands active involvement of multidisciplinary stakeholders characterizing attributes of the new ecosystem and integrating both the ecological integrity and human well-being in a single framework [20,21]. It is interdisciplinary, cutting across traditional subject boundaries, and predicated on the hypothesis that ought to create an enabling avenue for diverse ecosystems and land-use systems with its sustainable and cultural values [4,14,15,22].…”

Assessment of Naturalness: The Response of Social Behavior Types of Plants to Anthropogenic Impact

“…The concept of naturalness reflects the degree of degradation of the natural state of the ecosystem and consists in comparing the current and natural states. Assessing naturalness or habitat degradation is one of the most important challenges of conservation biology (Erdős et al, 2017(Erdős et al, , 2018 because it helps in the designation of protected areas (Moravčík et al, 2010), supports management activities (Goncharenko, Yatsenko, 2020;Lykholat et al, 2021), and facilitates effective monitoring of restoration projects (Sengl et al, 2017;Yao et al, 2019;Côté et al, 2021). The naturalness is inversely related to degradation: the more degraded the habitat, the lower its naturalness (Winter, 2012).…”