Relationship Among Condensed Tannins, Botanical Composition and Bare Soil of Rangelands in Pernambuco, Brazil.

Pasture attributes modify the chemical composition of plants, especially condensed tannins (CT) concentrations. The research was performed near Serra Talhada, Flores, Sertânia, Arcoverde, Pesqueira, Tacaimbó, Bezerros, and Vitória de Santo Antão, cities located along a physiographical transect in Pernambuco, Brazil representing 432- to 1056-mm average annual rainfall. Soils were loamy, eutrophic, with low acidity and average to high fertility at depths up to 20 cm. Forbs and shrubs (up to 5-mm diameter and 1.5-m height) were analyzed for CT; botanical composition and percent bare soil were also estimated. Data were subjected to principal components and cluster analysis by Tocher method. Condensed tannin concentrations were negatively related (-2.13) to the incidence of legumes, forbs and shrubs (2.43) which explained 74% of the total variation in the first principal components, maybe due to allelopathic effect. Bare soil (-0.61) and CT (-0.57) were negatively related to rainfall (0.92) which explained 77.9% of the total variation. Results indicated that, as regions became drier, forbs and shrubs synthesized more CT. Keywords: condensed tannins, principal components, semi-arid, rangeland. Acknowledgments: CAPES