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+, NO3- and NH4+ content and negatively related to increasing Ca2+ content, whereas the DRY were negatively associated with Al3+, NO3- 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 NO3- might influence the way the Cerrado woodland changes.

A fim de gerar conhecimento útil às iniciativas de proteção e manejo de fragmentos florestais, especificamente para florestas tropicais secas, que sofrem com frequentes atividades antrópicas e com a falta de estudos específicos, este artigo objetivou descrever a estrutura e a similaridade florística de três áreas de floresta estacional decidual em diferentes históricos de manejo. O estudo foi desenvolvido em Santana da Serra, distrito de Capitão Enéas, Norte de Minas Gerais, Brasil, onde foram avaliados três fragmentos, sendo um em regeneração há 30 anos, outro submetido a fogo ocasional e um terceiro com corte seletivo em pequena escala. A amostragem foi desenvolvida através do método de pontos quadrantes, considerando todos os indivíduos fanerófitos vivos com circunferência à altura do peito (CAP) > 15 cm. Nos três fragmentos foram amostrados 512 indivíduos distribuídos em 60 espécies, 47 gêneros e 23 famílias. As famílias mais representativas foram Fabaceae (26), Anacardiaceae (4), Bignoniaceae (3) e Combretaceae (3). Entretanto, 14 famílias foram representadas por apenas uma espécie. Apenas oito espécies foram comuns aos fragmentos, destacando-se Myracrodruon urundeuva que representou 26,9% de todos os indivíduos amostrados, enquanto que um grande número de espécies foi exclusivo a cada fragmento. As grandes diferenças florísticas e estruturais existentes entre os fragmentos estão possivelmente relacionadas ao histórico e intensidade de manejo em cada área, juntamente com as variações do terreno e a presença ou ausência de afloramentos de calcários. Esses resultados denotam a importância de cada fragmento, uma vez que a perda de um deles acarretaria impactos negativos sobre a flora regional e, consequentemente, à biodiversidade associada.

In order to produce useful knowledge to the initiatives of protection and management of forest fragments, more specifically for tropical dry forests which suffer with frequent anthropic activities, and due to the lack of specific studies, this article aimed describe the structure and the floristic similarity among three areas of dry forest with different management histories. The study was developed in Capitão Enéas municipality, Northern Minas Gerais, Brazil, where three fragments were evaluated, being one in regeneration for 30 years, another submitted to occasional fire and the third with selective cut in small scale. The sampling was developed through the point quarter method considering all the alive phanerophyte individuals with circumference at breast height (CBH) > 15 cm. In the three fragments, 512 individuals, distributed in 60 species, 47 genera, and 23 families were sampled. The most representative families were Fabaceae (26), Anacardiaceae (4), Bignoniaceae (3) and Combretaceae (3). However, fourteen families were represented by only one species. Only eight species were common to all fragments - Myracrodruon urundeuva standed out with 26.9% of all sampled individuals - while a great number of species were exclusive of each fragment. The floristic and structural differences between the fragments are possibly related to the history and intensity of management in each area besides the topography variations and the presence or absence of limestone outcrops. These results show the importance of each fragment, indicating that the loss of anyone would cause negative impacts on the regional flora and consequently to the associated biodiversity.