Changes in plant community attributes and carbon stocks in altimontane forest islands in the Atlantic Forest-Cerrado transition under different conservation conditions

Background: Ecotonal regions in tropical mountains, such as the Altimontane Forest Islands, are home to unique, highly biodiverse, and vulnerable plant communities. Human activities alter the functionality, structure, diversity, and provision of ecosystem services in these ecosystems. Uncertainties persist regarding their resilience to human impacts and the most effective ways to conserve them. Questions: How do the species composition, vegetation structure, and diversity differ between protected and unprotected forest islands subject to anthropogenic disturbances? Are there differences in the carbon stocks of these forest islands? Studied species: Vascular plants of the Cerrado-Atlantic Forest. Study site: Forest Islands in Minas Gerais, Brazil. Methods: We calculated alpha and beta diversity and estimated aboveground biomass and aboveground carbon stocks from tree samples (diameter at breast height ≥ 5 cm) collected in Forest Islands. Results: We found that protected and unprotected areas had similar alpha diversity but differed in floristic composition. We observed high beta dissimilarity between protected and unprotected Altimontane Tropical Forest Islands (βsor = 0.93 and βbray = 0.94). Unprotected islands show greater species substitution (90 %), unimodal vertical structure, greater susceptibility to colonization by new generalist species, and lower carbon stock (80.70 Mg C ha-1). Conclusions: Changes in species composition, vegetation structure, and carbon storage were observed on unprotected islands, demonstrating the need to protect these unique ecosystems.