Propagule availability drives post-wildfire recovery of peatland plant communities

Question: Northern peatlands are increasingly threatened by wildfire. Severe peatland wildfires can provide opportunities for new non-peatland species to colonise post fire. Changes in plant colonisation could lead to longer-term shifts in community composition, compromising recovery of peatland structure and function. Understanding the process of post-fire recovery can thus inform restoration action and help restore peatland vascular plant communities. In this study, we ask: what drives initial vascular plant recovery following a peatland wildfire?. Location: Stalybridge moors, England (commonly referred to as the Saddleworth moors). Methods: We used a series of vegetation surveys and seed germination experiments to identify the composition of vascular plant community one-year post fire, along with potential propagule sources. We combined this with plant trait data and, using a series of null models, compared observed community trait values against random species assemblages. Results: Our data suggests that plant species are able to arrive at the burned site through multiple non-exclusive recolonisation pathways. This includes colonisation through the soil seed bank, along with dispersal from surrounding unburned peatland and non-peatland vegetation. The composition and structure of the recolonised communities was largely determined by the ability of species to reach the post-fire site from these donor communities. This resulted in a post-fire community composed of species possessing lower seed masses relative to the wider pool of potential colonisers. Conclusions: Our results highlight propagule availability as a driver of post-wildfire vascular plant recovery. This provides opportunities for new non-peatland species to colonise, potentially driving changes in the direction of vegetation recovery. Ensuring the availability of peatland species following a wildfire could therefore be key to the immediate recovery of these systems.