Grazing livestock increases both vegetation and seed bank diversity in remnant and restored grasslands

Abstract

Questions Restoring grasslands is of great importance to biodiversity conservation to counteract widespread, ongoing losses of plant species diversity. Using source populations in remnant habitats and increasing functional connectivity mediated by grazing animals within and between habitats can benefit grassland restoration efforts. Here we investigate how grazing contributes to vegetation and seed bank diversity and composition in remnant and restored grassland communities in fragmented landscapes. Location Stockholm archipelago, Sweden. Methods We investigated the effects of the presence or absence of grazing animals as potential elements of functional connectivity on grassland species composition in both the vegetation layer and in the seed bank. Species inventory and seed bank sampling were carried out in 2 m × 2 m plots in remnant grassland habitats and adjacent restored grasslands on former arable fields. Results Species composition varied between remnant and restored grasslands, with management‐dependent species more common in remnant grasslands. Remnant habitats with active grazing management contained a higher number of species in both the vegetation and seed bank compared to restored grasslands, but grazing reduced dispersal limitation from higher distance to source populations for specialist species. Where grazing was absent fewer plant species occurred in both the vegetation and in the seed bank. Conclusion Our results show that grazing livestock play a key role in facilitating both spatial and temporal dispersal in fragmented grasslands. This results in increased species diversity in the vegetation and the seed bank of grazed grasslands compared to those maintained by mowing only. Functional connectivity provided by grazing management increases the possibility for species establishment from both the below‐ground seed bank and the surrounding landscape, thus increasing the resilience of plant communities against disturbances or climatic changes.

Soil phosphorus availability determines the contribution of small, individual grassland remnants to the conservation of landscape‐scale biodiversity

“…They may then gain dominance in the community and outcompete stress‐tolerant, low‐statured and slow‐growing grassland specialists as their rapidly extending herbaceous canopy deprives these specialists of light (Duprè & Diekmann, 2001; Hautier et al, 2009; Ceulemans et al, 2011; Auffret et al, 2017a). The continued grazing management of semi‐natural grasslands, on the other hand, keeps elevated P‐induced biomass production in check (Duprè & Diekmann, 2001), and maintains grassland habitat heterogeneity (Dirzo et al, 2014), crucial for the establishment and persistence of grassland specialists (Figure 4; Bullock et al, 1994; Kapás et al, 2020). Management may thus maintain high grassland species richness despite P eutrophication.…”

Habitat conservation state and plant diversity respond to different drivers in semi‐natural grasslands

“…A proper grazing regime directly maintains the habitat by hampering both an increase in sward height and litter accumulation and favours habitat characteristic diversity (Riesch et al, 2020), with opposite effects on derived diversity. Grazing livestock was also found to have positive effects on the semi‐natural grassland seed bank, thus countering local extinction processes in the mid‐term (Kapás et al, 2020). Our models suggest a number of livestock units very similar to those indicated in the rural development programmes for the studied regions (0.3–1.2 livestock units per hectare) to obtain grassland biodiversity‐related subsidies.…”

The importance of dispersal and species establishment in vegetation dynamics and resilience

“…Török and Helm, 2017, and citation therein). While Lipoma et al (2020, this issue) found that land‐use intensification decreased the role of biodiversity reservoirs (seed and bud banks) in resilience processes of the resident vegetation, Kapás et al (2020, this issue) showed that grazing livestock play a key role in facilitating both spatial and temporal dispersal in fragmented grasslands. Functional connectivity provided by grazing management also increases the possibility for species establishment from the propagule bank and the establishment of dispersed propagules from the surrounding landscape.…”