Species Composition and Distribution of Terrestrial Herbs in a High Montane Forest in Ecuador

Abstract

In mountain tropical forests, understory herbs have received little attention compared to trees, and their commonness and rarity are virtually unknown. We studied ground herbs to explore how they are assembled in a full one-hectare plot and to test the influence of light intensity (LI) and topographic habitats in species composition. The plot is a humid montane forest located in the Pasochoa Volcano, at 3300 m. We found 43 genera and 50 perennial species (30 angiosperms in 17 families, and 20 ferns). Interestingly, herbs are 64% richer in species than trees in the same study plot (50 vs. 32). Herbs were mostly obligately terrestrial (70% of the species), while 30% were fallen climbers and epiphytes rooted in the ground. Across the forest, there were 31,119 individuals that covered 8.5% of the ground. We concluded that both LI and topography shaped the species distribution, the floristic composition, and the community structure of ground herbs. For instance, 12% of the species were exclusively found in places with high LI; the rest of species grew in medium- to low-LI environments. Concerning rarity, we found that 39% of the species are rare (judging by botanical collections; <100), which stresses the need of conservation strategies for this group of plants.