Species dynamics in a montane cloud forest: Identifying factors involved in changes in tree diversity and functional characteristics

Tropical montane cloud forests constitute a rare and fragile ecosystem, which is threatened in many of the areas in which it is found due to the pressure of human-originated disturbances. Cloud forests have been identified as a forest type with high levels of species endemism and biodiversity. The aim of this study, which focuses on a patch of cloud forest located in the Piura region of the Peruvian Andes, is to assess the changes in species composition and to identify the factors involved in the loss of biodiversity using data from a single inventory. Random sampling plots were established throughout the forest area. An index of the difference in species richness between recruitment and older trees (Tree Diversity Change index, TDC index) was calculated for each plot. A Tree Diversity Change Index (TDC) and an index of species replacement based on the second order properties of the diameter distribution (RE) were defined to assess changes in species richness and to characterize the change in the functional groups of tree species within the plot. The factors involved in these processes were also identified by means of a Universal Kriging model. The negative correlation between the TDC and the distance to the nearest track indicates that species richness is decreasing close to these tracks and that it is only maintained in the inner areas. The negative correlation of the RE index with altitude and deeper zones indicates that dynamic replacement of humid-condition species by dry-condition species is occurring at lower elevations. A loss in diversity along with a change towards species adapted to dryer conditions was observed throughout the forest. Zones at lower altitudes, on spurs or at the edges of the forest are more prone to these processes. This suggests that a change in the functions of the ecosystem has been taking place and that a minimum extension of cloud forest is required to maintain the ecological processes necessary for the continued existence of the cloud forest.