Trade-offs between fire suppression and biodiversity: vegetation recovery in burnt grasslands and firebreaks under different restoration treatments

Abstract Background Wildfire is an important component of many grassland ecosystems, but it is often suppressed in modern landscapes to protect infrastructure and human safety. Disk-harrowed firebreaks are frequently used to stop wildfire spread; however, this method represents a severe soil disturbance that may alter grassland species composition and structure. We studied the effects of a low-intensity growing-season wildfire on the vegetation of pristine and restored Central European dry grasslands, and evaluated vegetation recovery on firebreaks for 3 years post-fire. Firebreaks were subjected to passive restoration (disk-harrowing), assisted natural regeneration (rolling) or active restoration (rolling combined with grass seed sowing). In total, 180 permanent vegetation plots were surveyed for 3 years. Results Several grassland specialist species were associated with burnt grasslands during the first two post-fire years, but these patterns disappeared by the third year and did not affect overall specialist richness or cover. Fire did not promote disturbance-tolerant or weed species in the long run. Grassland specialists were able to re-establish in disk-harrowed and rolled firebreaks from the seed bank and seed rain; however, their cover remained substantially lower than in reference grasslands. Sowing seeds of the competitive perennial grass Festuca rupicola accelerated the development of a continuous grass cover and substantially reduced the proportion of weeds. Even in the third year after disturbance, firebreak vegetation remained dominated by disturbance-tolerant and weed species. Recovery of specialists was faster in restored grasslands, characterized by species typical of mid-successional stages, than in pristine grasslands. Conclusion Low-intensity growing-season wildfire had moderate and temporary effects on dry grasslands, indicating that fire represents an endogenous disturbance to which these communities respond with a short-term internal reorganization. In contrast, mechanical soil disturbance associated with firebreak establishment represented an exogenous disturbance with longer-lasting effects on vegetation composition and structure. Although species richness of target grassland species recovered quickly, their cover remained lower than in reference grasslands even for the third year. Sowing a dominant perennial grass effectively suppressed weeds, but increased competition may limit the establishment of other grassland species. Our results highlight a trade-off between short-term fire safety and long-term biodiversity conservation, suggesting that firebreak establishment should be cautiously applied and accompanied by appropriate monitoring and targeted management.