A quantitative study of orchids and their proximate environments over an elevational gradient on the Northern slope of Montagne d’Ambre

This research investigated change in orchid populations and their proximate environments on the Northern slope of Montagne d’Ambre, a subhumid forest in Northern Madagascar. Orchid density, way of life (epiphyte or terrestrial), phenology, and associations were recorded over 100m elevation gradients and between forest types (primary, secondary, dry, and humid forests at the same altitude). Additionally, orchid preferences for certain heights in the forest and DBH of host trees were analyzed. The establishment of 50X20m plots in 100m elevation gradients combined with ground survey yielded significant results demonstrating change along with elevation as well as forest types. Orchid density increased along with increasing elevation, as did the proportion of terrestrial individuals. Correspondingly, orchid density was found to be highest at 0-2m in the forest. Such results demonstrate the adaptability of terrestrial orchids to fill an open niche at the peak. Changes in associations with other biota along with elevation and forest types demonstrated the complex webs of interactions in which orchids inhabit. Such results indicate the importance of conserving orchids in congruence with their natural habitats