Floristic, biogeographical, and vegetational aspects of Pre-Cambrian rock outcrops (inselbergs) in eastern Bolivia

Abstract

Pre-Cambrian rock outcrops (inselbergs) are insular and azonal habitats within forest formations. In the context of a global inselberg research project first insights into the flora and vegetation of inselbergs (,lajas‘) of eastern Bolivia are given. The few mentions in literature and own field observations in the provinces of Ñuflo de Chavez and Velasco (Dept. Santa Cruz) are considered. The typical flora is characterized. Some inselberg endemics are known but the majority of the species shows a wide distribution and occurrence in other habitats. E.g. the Guianan Vellozia tubiflora and the Chacoan Cereus (Monvillea) kroenleinii have been found in Bolivia for the first time. A preliminary physiognomic characterization of the most important formations of the vegetation (e.g. exposed rock surfaces, rock pools, plant-mats) is realized. The floristic and vegetational observations fit well into the patterns known from other tropical inselbergs. Ideas are proposed, which refer to natural processes of vegetation change – the floristic diversity on the Pre-Cambrian rock outcrops is maintained by succession and degradation.