The effect of woody encroachment on taxonomic and functional diversity and soil properties in Cerrado wetlands

Abstract

The encroachment of woody species has been affecting wetlands in the Cerrado biome, Brazil. This process has resulted in changes in plant diversity, soil physicochemical properties, and water availability. This study assessed changes in the taxonomic and functional diversity of plants and soil in Veredas wetlands in process of reduction in water availability and woody plant encroachment. Over a 14-year interval, we quantified taxonomic and plant functional diversity, soil physicochemical properties, groundwater depth, and its relationship with historical soil moisture using remote sensing in veredas. We investigated the effect of increased groundwater depth, woody vegetation cover, and changes in soil properties on species cover and richness. We observed a five to seven-fold increase in woody vegetation cover, accompanied by an increased in the richness of woody species from 21.4 % to 28.9 %. Nevertheless, this was counterbalanced by a 15.8 % to 35.2 % reduction in overall species richness and taxonomic diversity. At the same time, functional diversity decreased, leading to a community with more acquisitive traits. Groundwater depth increased from 20 to 60 cm. Soil properties changed, especially organic matter content, which increased two to 14 times. Changes in species richness and cover were related to increased organic matter and groundwater depth. The surveyed veredas exhibited considerable changes in plant species richness, soil, and hydrological properties, as well as woody vegetation cover, over 14 years. The veredas formed distinct functional composition groups between sampling times. However, only one vereda exhibited a reduction in functional richness, and neither showed temporal functional divergence. Woody encroachments are leading these veredas to an alternative state with a reduced herbaceous diversity, structurally denser, and with more resource-acquisitive plant traits in the community. The Woody encroachment reducing soil water availability, may impact ecosystem services, particularly water provision and biodiversity loss in the Cerrado region.