Some factors determining species diversity of prepuna and puna vegetations in a Bolivian Andes region

Background and aims - The only semi-arid plant formations that occur in Andean Bolivia are prepuna with its associated dry valleys and puna. A quantitative ecological study was conducted in the district of Apillapampa, which is situated on the transition between the latter vegetation types. Methods - Vegetation was sampled in twenty-nine 50 x 2 m(2) transects, yielding a total of 280 different plant taxa. Key results - Floristic and ecological findings correspond well with comparable studies in prepuna and puna vegetations in Bolivia and significantly contribute to the still severely understudied Bolivian flora. Our research suggests that a significant part of the variation in species abundances in the sampled transects is explained by a combination of some of the natural and anthropogenic variables we measured. The latter include altitude, travel time (as a measure of site accessibility), proximity to a (temporal) river or stream, and evidence of firewood harvesting. Furthermore, we detected an inverse relationship between diversity of plants in transects and altitude. Of the anthropogenic disturbance variables, only cultivation of exotic tree or shrub species had a negative impact on plant diversity in transects. Conclusions - Vegetation in Apillapampa is highly fragmented and of secondary nature, mainly as a consequence of past and present human activities