Diversidade funcional e estratégias nutricionais de espécies arbustivo-arbóreas de cerrado e floresta estacional

Abstract

Soil fertility is one of the main determinants of the abrupt boundaries between the cerrado and the seasonal forest. Given that the remaining patches of cerrado are surrounded by agricultural matrices and may be impacted by eutrophication, understanding whether the dystrophic soils of cerrado drive plant strategies and diversity might help us predict the risk of cerrado replacement by forest vegetation and avoid loss of species and functions. In the first chapter, we compared cerrado and seasonal forest species in terms of nitrogen and phosphorus concentration in green and senesced leaves and resorption efficiencies. We quantified the relationships among these traits, with other key leaf traits, and with soil features. Nitrogen and phosphorus concentration in green and senesced leaves were more strongly related to generalised measures of soil fertility than to soil total nitrogen and available phosphorus, but this pattern was not so clear for resorption efficiencies. Besides, leaf nitrogen:phosphorus ratio was lower in cerrado, despite the lack of difference in soil nitrogen and phosphorus between both vegetation types. In the second chapter, we tested whether cerrado and seasonal forest communities were assembled by different processes, despite their physical proximity. We calculated the pairwise functional-phylogenetic distances in cerrado and seasonal forest communities. We tested whether these distances were related to soil properties in each environment. Cerrado and seasonal forest were not assembled by different rules, and soil fertility determined the functional differences between both vegetation types, even though it was not the only force shaping the communities. In the third chapter, we studied patterns in chemical and structural traits in green leaves of cerrado and forest species, in their response to soil fertility, and in their effect on litter decomposition rates. Despite the large effect of taxonomy, soil exerted strong effect through multipleelement control over species functional traits and strategies. The effect of such different strategies on functioning, however, was less prominent.