Wildfire Effects on Rangeland Health in Three Thermo-Mediterranean Vegetation Types in a Small Islet of Eastern Aegean Sea

Sclerophyllous scrub formations, the main vegetation type in many islands of the Aegean area, provide many goods and services to humans, such as biodiversity, soil protection, and forage for livestock and wildlife. Dominant shrub species of sclerophyllous formations are well adapted to dry season conditions due to various anatomical and physiological mechanisms. As a result, their biomass acts as very flammable, fine fuel, and consequently, wildfires are very common in these ecosystems. Wildfire effects on vegetation and biodiversity in the Mediterranean basin have been studied, and the results are diverse, depending mainly on the vegetation type and frequency of fires. Additionally, post-fire vegetation establishment and structure are critical factors for the implementation of grazing management. The aim of this study was to evaluate the effects of wildfire on species composition, floristic diversity, forage quality, and rangeland health indices related to ecosystem stability and function in three thermo-Mediterranean vegetation types: (1) Sarcopoterium spinosum low formations, (2) low formations of Cistus creticus, and (3) low formations of Cistus creticus in abandoned terraces. The research was conducted on the Oinousses islet, which is located northeast of Chios Island, in May 2013 (one year after the fire). Vegetation sampling was performed along five transects placed in recently burned and adjacent unburned sites of each vegetation type. The plant cover was measured, while the floristic composition, diversity, evenness, and dominance indices were determined for the vegetation data. Additionally, the forage quality was determined in terms of crude protein (CP) and fiber content. The vegetation cover was significantly lower, and the floristic diversity was significantly higher in burned areas in comparison to those in the unburned areas. Woody species, followed by grasses and forbs, dominated in both the burned and unburned areas. However, the percentage of woody species was significantly decreased in the burned areas of Sarcopoterium spinosum and Cistus creticus low formations. On the other hand, the percentage of grasses, forbs, and legumes increased in all cases except in Cistus creticus terraces. The lowest value of the Jaccard Index of similarity between the burned and unburned sites (beta diversity) was observed for Cistus creticus, indicating the effect of fire on the species composition of this vegetation type. The forage quality was found to be improved in all the burned areas, especially in those dominated by Cistus creticus. Finally, fire has a positive impact on the ecosystem's functions, mainly for Sarcopoterium spinosum low formations.