Factors C ontrolling C ompositional C hanges in a N orthern A ndean P áramo ( L a R usia, C olombia)

In this study, we aimed to assess the processes controlling compositional change in a N orthern A ndean páramo highly affected by human‐induced disturbances over the last few decades ( L a R usia, C olombia). Along the 3000–3800 m asl altitudinal range, we randomly sampled fifty 10 × 10 m plots. Therein, we measured altitude and variables related to soil conditions ( i.e., moisture, nutrient contents, bulk density, and texture), occurrence of human‐induced disturbances ( i.e., fire, vegetation clearing, potato cultivation, and cattle grazing), and land‐use history. We also recorded richness and abundance of plant species, identifying them as exotic or native. We differentiated four groups of plots according to their species composition. The groups had significant differences in altitude, soil conditions, land‐use history, and particularly, in richness of exotic species and exotic/native cover ratio. They could be ascribed to shrub‐ and grass‐páramo vegetation types based on their relative dominance of woody and herbaceous species; however, these groups were not arranged according to the hypothetical composition of altitudinal belts, but rather formed a mosaic of patches. This mosaic was determined not only by altitude but also by soil conditions and disturbance history of sites. Our results corroborate recent findings which highlight shrub‐ and grass‐páramo vegetation types as patches of contrasting species composition and structure that depend on local environmental variables, as well as human‐induced disturbances as a major determinant of compositional discontinuities in these ‘high mountain’ tropical ecosystems.