Can we quantify plant functional group vulnerability in managed ecosystems? A case study in the Monte desert of South America

CHILLO, MARÍA VERÓNICA; ANAND, MADHUR Y OJEDA, RICARDO

Quebec City, Quebec, Canada

Congreso; V Annual Meeting of the Canadian Society of Ecology and Evolution (CSEE); 2010

Canadian Society of Ecology and Evolution

Assessing and preventing the impacts of species loss on ecosystems is of critical importance for sustaining the services that ecosystems provide. An ecosystem that contains species that performs similar functions but that respond differently to environmental factors can help to maintain stability in ecosystems subjected to environmental fluctuations. This variety in response to disturbance within functional effect groups had been called “response diversity”, and it can be quantified. We evaluate the use of response diversity as a qualitative measure of ecosystem vulnerability to disturbance. Our study case consisted of two treatments: paddocks with grazing exclosure (recovered) and the same sites with a reappeared disturbance (disturbed) (the time component). Plants were grouped into functional effect groups. Response diversity inside functional groups of the recovered sites was calculated using Rao’s coefficient. Decomposition rates were also assessed. Species richness in recovered sites was not significantly correlated with the value of response diversity. Decomposition rate was significantly higher in sites where all functional effect groups were present, showing that the loss of functional groups is positively related with losses of ecosystem functions. Richness inside functional effect groups in disturbed sites and response diversity values were significantly correlated. Functional groups with the lowest response diversity values were the most affected, losing species or even disappearing when the disturbance re-appeared. We suggest that high species richness alone does not necessarily ensure resilience, but functional response diversity is important. This is, the significant relationship between response diversity and the loss of richness and/or functional groups (and its relationship with diminishment of ecosystem function) suggests that this can be used as a quantitative indicator of ecosystem vulnerability. Synthesis and applications. The loss of functional effect groups, together with decrease in ecosystem function leads to the detection of a highly vulnerable state of an ecosystem. Calculating response diversity inside functional effect groups may give managers an idea of which are the most vulnerable groups, and thus, implement strategies and specific policies to manage diversity for insurance to cope with future changes in land-use and/or environmental fluctuations.