Tree Diversity and Its Ecological Importance Value in Silvopastoral Systems: A Study along Elevational Gradients in the Sumaco Biosphere Reserve, Ecuadorian Amazon

Abstract

This study analyzes tree diversity and its ecological importance value in silvopastoral systems in the Sumaco Biosphere Reserve (SBR), Ecuador, along an altitudinal gradient of 400–2000 masl. Twenty-six plots distributed into low (400–700 masl), medium (701–1600 masl) and high (1601–2000 masl) zones were used. The Shannon index and the importance value index (IVI), based on abundance, dominance and relative frequency, were estimated. The results highlight that in pastures with dispersed trees, the richness of trees decreases with increasing altitude in the elevational gradient; they also show a higher tree density at lower altitudes in contrast to the Andean–Amazonian primary forests. The lower and middle zones showed higher diversity, linked to regeneration and the presence of nearby forests. Species of high commercial value, such as Cedrela odorata and Jacaranda copaia, were common, reflecting knowledge of the local timber market. In the lower and middle zones, the 10 most important species accounted for more than 70% of the trees, with up to 96% in the upper zone. A total of 51 taxa (including 42 species and nine taxa at the rank of genus) were identified, which were mostly native; 64.7% are classified by the IUCN as least-concern (LC) species, 31.4% as not evaluated (NE) species and 3.9% as vulnerable (VU) species, specifically highlighting Cedrela odorata and Cedrela montana. The study concludes with policy recommendations related to the importance of trees in silvopastoral systems for the conservation of species and the livelihoods of local communities, highlighting the need for responsible management of Amazonian pasturelands.