Long-term forest use results in community plant functional trait convergence in a subtropical seasonally dry forest

GEORGINA CONTI; LUCAS ENRICO; DRIES HUYGENS; SANDRA DÍAZ

Pirenópolis

Congreso; 59th Symposium of the IAVS; 2016

International Association of Vegetation Science (IAVS)

A debate exists around the effect of forest use on processes and societal benefits provided by these ecosystems. Functional traits? the biological attributes of organisms - is expected to have important effects on these processes and also determine the community responses to environmental factors. Subtropical seasonally dry forest from South America has been experiencing accelerated land-cover changes in the last few decades. Over large areas, forests have been replaced by shrublands, as a result of historic logging and grazing. Here, we analyze changes in plant community functional diversity (including variety and identity) in response to long-term forest use in dry forests of central Argentina. Specifically, we addressed the following questions: (i) How does historic forest use affect plant community functional diversity (in terms of variety and identity)? ( ii) How does historic forest use modify community assembly rules of these communities? With that aim, we sampled 8 functional key traits of 30 dominant species across 16 sites resulting from different past and present land-use regimes (mainly selective logging and grazing). Our results showed that functional identity (i.e., the community weighted means of functional traits) remains mostly unchanged, except for architectural traits (height and wood density) that were reduced across sites as a result of historic forest extraction. Although changes in functional identity were not strong, functional variety, in terms of both multivariate indices (RaoQ and FDisp) and univariate indices (FDvar), tracked changes in nutrient availability and forest structure as a result of historic forest use. These results indicate that community functional variety is reduced across the historic forest use gradient, with functional convergence being an important component of community assemblage. Under the assumption (untested in this work) that a wider variety of functional traits should support a higher number of ecosystem benefits to people, our results suggest that forest management at relatively low intensities could provide several ecosystem benefits without risking their long-term provision. We also advocated the inclusion of different components of functional diversity as an important resource in the analysis of the impact of global changes in these subtropical dry forests, at present being seriously transformed.