Functional antagonism between nitrogen-fixing leguminous trees and calcicole-drought-tolerant trees in the Cerrado

ABSTRACT

The Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. There are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fixing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al³⁺. The working hypothesis is that LEG and DRY are functional antagonists in terms of the acidification/alkalization processes involving different forms of inorganic nitrogen and pH, Ca²⁺ and Al³⁺ in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. The results suggest that LEG and DRY are antagonists. The LEG were positively associated with Al³⁺, NO^3- and NH⁴⁺ content and negatively related to increasing Ca²⁺ content, whereas the DRY were negatively associated with Al³⁺, NO^3- and NH⁴⁺ and positively associated with increasing Ca²⁺ content. The upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. The results suggest that LEG and DRY are functional antagonists and their preferences for NH⁴⁺ or NO^3- might influence the way the Cerrado woodland changes.

Keywords:
aluminum toxicity; calcicole species; dry forests; ecosystem function; nitrogen fixing; tropical savanna; woodlands