Exploring how disturbance and light availability shape the elevation ranges of multiple mountain tree and shrub species in the tropics

Context: Tropical mountains are hotspots of plant diversity, with a remarkable density of narrow ranged and endemic species. To develop effective in situ strategies for the conservation of species under changing climatic conditions we need to understand the mechanisms that shape their distributions. Objectives: We explore how disturbance shapes the elevation ranges of two shrubs and eight tree species (Hypericum irazuense, Vacciunium consanguineum, Escallonia myrtilloides, Schefflera rodriguesiana, Weinmannia pinnata, Rhamnus (Frangula) oreodendron, Styrax argenteus, Podocarpus oleifolius, Prumnopitys standleyi, Magnolia poasana) characteristic of the paramos and cloud forest of the Talamanca Mountains, Costa Rica. Methods: We used distance sampling transects along a 1400 m elevation range and “density surface models” to explore how the distribution of the selected species responds to changes in basal area and light availability after disturbance, across their elevation range. Results: The legacies of disturbance on forest structure and light availability clearly shaped the elevation ranges of seven species. H. irazuense had a clear light demanding strategy, only occurring at well-lit sites throughout their range. V. consanguineum, E. myrtilloides and S. rodriguesiana shifted from a shade tolerant to strictly light demanding distribution between their upper and lower range limit, showing a context dependent role of light availability along their elevation range. R. oreodendron, S. argenteus and W. pinnata occurred mainly under shaded and crowded conditions. The density of M. poasana, P. oleifolius and P. standleyi species was related only to elevation. Conclusions: Our study illustrates how light availability and disturbance are key to understand the elevation range dynamics of high elevation tropical trees and shrubs. Canopy openings after disturbances provide habitat for paramo and high elevation woody plant species to persist under warmer conditions. These findings can inform conservation efforts aimed at preserving high elevation plants species in the future.