Dynamics of a dry forest fragment after the exclusion of human disturbance in southeastern Brazil.

Changes in the structure and composition of a dry forest fragment were described for a 4-yr period (1994-1998) in the southeastern Brazil (19°12′05″ S and 47°08′02″ W). This is the first dynamic study of a vanishing type of dry forest, which grows on base-rich soils originating from the basalt bedrock of western Minas Gerais State. A survey of trees ≥ 3.2 cm dbh (diameter at breast height, or 1.30 m) was conducted in 26 transects of 50 m × 6 m (0.78 ha). The species were classified into three regeneration guilds – pioneer, light-demanding and shade-tolerant – on the basis of others studies and personal observation. There was a decrease of 10.1% in the number of trees between 1994 and 1998. However, the basal area had an increase of 1.5% in the same period. Size class distributions in 1994 and 1998 were significantly different. The smallest trees (diameter < 10 cm) had the highest mortality rates. Although stand composition showed little change, a few species showed significant imbalance between recruitment and mortality. The studied fragment had mortality (2.3% yr^–1) and recruitment (1.6% yr^–1) rates similar to other tropical rain forests for trees ≥ 10 cm dbh. The present fragment of forest (turnover time = 39.5 yr, at cut level 10 cm dbh) lies among the most dynamic tropical forests. The main compositional changes were the increase of shade-tolerant trees and decline of pioneer species. The changes in composition and structure over the survey period may reflect the recovery of the forest after 4 yr of conservation. [ABSTRACT FROM AUTHOR]