Elevation and Soil Properties Determine Community Composition, but Not Vascular Plant Richness in Tropical Andean Roadside

Abstract

Roadsides are common ecosystems worldwide, with specific environmental characteristics and multiple effects on plant diversity. As such, they represent examples of highly dynamic anthropogenic ecosystems. Our objective was to assess patterns of vascular species diversity in response to elevation and soil characteristics on a roadside in the Andean mountains of Ecuador. The study area was located in the southern Ecuadorian Andes, at five elevations ± 400 m a.s.l. (2600, 2200, 1800, 1400 and 1000 m a.s.l.), where we recorded species richness and abundance in transects perpendicular to the road. The effects of elevation and soil characteristics on species abundance and richness were analyzed using generalized linear mixed models (GLMMs), while species composition was assessed with a non-metric multidimensional scaling analysis (NMDS) and its relationship to environmental variables. We used indicator species analyses (ISA) to identify which species significantly characterized specific elevation and soil factors from primary succession for restoration processes at the roadside. Although elevation and soil characteristics do not condition vascular species richness, the composition is more similar at elevations E1 and E2 (2600 m and 2200 m a.s.l.), differing from low elevations E4 and E5 (1400 m and 1000 m a.s.l.), which in turn are more similar to each other, while intermediate elevation E3 is similar to the highest and lowest elevations. Soil variables that limited plant communities were pH, bulk density (gr/cm3), silt (%), and sand (%) contents. The indicator species showed a preference for specific environmental and soil condition requirements associated with the different microhabitats and, thus, can be suggested for potential use in roadside revegetation processes in tropical areas. These results can help decision-makers in the implementation of biodiversity conservation and roadside environmental restoration projects in areas of Andean mountain ecosystems which have been affected by the construction of road infrastructure.