Association analysis of <Castanopsis tungurrut> and the neighboring vegetation community in Cibodas Biosphere Reserve, Indonesia

Castanopsis tungurrut (Blume) A.DC. (Fagaceae) is an endangered species, specifically found in the tropical forests of Java and Sumatra. There is currently a lack of specific information regarding its interactions with other species across different life stages and natural habitats, particularly in relation to altitudine gradients. This study is aimed at investigating the relationship between Castanopsis tungurrut and the adjacent vegetation during different stages of its life cycle. The study also analyses the impact of this association on vegetation dynamics and propose effective strategies for C. tungurrut conservation strategy. The study established 41 plots across four distinct sites within the Cibodas Biosphere Reserve located in Gede Pangrango National Park. Identification of trees, poles, saplings, and wildings was carried out using the nested sampling method. A comprehensive list of 153 tree, 104 pole, 135 sapling, and 111 wilding species was documented and paired with C. tungurrut for association test, and a positive association was observed with the tree species Casearia coriacea and the wilding species Symplocos costata (Jaccard indices for these pairings were 0.34 and 0.33, respectively). In addition, a negative association was found for trees of C. tungurrut with Castanopsis javanica and Macropanax dispermus; Jaccard indices for pairings were 0.17 and 0.18, respectively. It was noted that C. tungurrut exhibited lower competitive ability and selectivity in less favorable habitats, and its facilitative effect on the surrounding vegetation was limited. The prevalence of negative association with neighbouring vegetation within the natural forest of Cibodas Biosphere Reserve indicates that C. tungurrut is isolated and facing threats such as environmental stress and competition. This condition contributes to the forest’s overall diversity and promotes the sustainability of the reserve by enhancing ecosystem stability.