Disentangling fine-scale effects of soil properties as key driver of plant community diversity on Roraima table mountain, Guayana Highlands

The Guayana Highlands (GH) represents a major center of Neotropical plant diversity and endemism. Considering the lack of information about the ecology of plant communities in this region, we analyzed the fine-scale pattern of vegetation diversity. Thus, we tested the fine-scale effects of abiotic filters (i.e. soil physicochemical properties and depth) on species richness and community composition in complex rocky outcrop landscapes at the Roraima table mountain summit. This tepui is located on the triple boundary shared by Brazil, Venezuela and Guyana. A total of 60 plots were allocated in three specific previously identified geoenvironments: Peaty Rupestrian Grassland, Bonnetia-Shrubby Rupestrian Grassland and Sandy Rupestrian Grassland. Overall, 4318 individuals were sampled, distributed among 60 species, especially belonging to the families Asteraceae and Bromeliaceae. Of this total, 27 (45%) species are endemic to GH. There were significant differences among the geoenvironments regarding species richness, community composition and soil attributes. The tested models demonstrated that species richness was influenced by variations in potential acidity; however, community composition was explained mainly by soil texture and depth effects. Our study revealed abiotic filters exerted crucial fine-scale effects on plant community diversity on the Roraima table mountain. Supplemental data for this article is available online at https://doi.org/10.1080/11263504.2021.1985003 .