Changes in functional plant groups on burned abandoned agricultural fields in the Mediterranean environment (Croatia)

The agricultural practice of burning straw or vine stem is widespread in the Mediterranean to control excess biomass. Although the practice is widespread, the long-term effects on the structure of the flora, natural ecological restoration and the impact on biodiversity remain poorly understood and researched. Mediterranean species have post-fire ecological strategies, such as the ability to resprout, the persistence of the seed bank, or the ability to grow or disperse. In this work, an abandoned agricultural field (AAF) was burned by an induced fire. Fifteen rings (diameter 0.2 m2) were established on the studied area, five for each variant: I. unburned (UB), II. moderately intensive (MB) and III. high intensive (HB). The results showed that the functional group (FG) of grasses dominated in the MB variant, in contrast to the dominance of legumes in the HB variant. Compared to the AAF, the number of grasses FG slightly decreased in both burn variants (MB, HB). The predominant strategy was competitors (C), followed by ruderal plants (R), the number of which increased slightly after burning in the MB and HB variants, while stress tolerance decreased significantly in both variants. These results indicate that the intensity of HB does not promote the survival of grasses in the first year after burning, while legumes and grasses are more resistant to higher fire intensity and therefore have a higher chance of survival. In summary, the burning of straw or vine stem on AAF initiates complex ecological processes that shape the landscape and can significantly influence the biodiversity of the area.