Ecologia da paisagem de Mata Atlântica na Bacia do Rio Doce, estado de Minas Gerais

Abstract

The present study was carried out in two eucalyptus plantation areas in eastern Minas Gerais, Brazil. It aimed to use tools such as aerial photographs, map and softwares, combined with environmental sciences to diagnose and give support to environmental conservation of fragmented ecosystems. Thus, two square areas totaling 6.400,00 hectares each, were studied, one in a mountainous region, known as Cocais, and the other situated in a softly undulated relief, known as Ipaba. Mapping and classification of the preserved native vegetation was conducted based on the parameters established by CONAMA, Resolution no. 10, October 1, 1993. Classification per class size, isolation degree, position in the relief and shape factor were obtained by using mapping software and geographical information systems. The results highlighted that initial and medium sucessional stage vegetations predominated in Cocais, accounting for 52% and 31%, respectively, of the preserved total areas. In Ipaba, the predominant areas were medium stage and eucalyptus reserves, accounting for 33% and 25%, respectively, of the total preserved areas. A higher percentage of autochthonous forest cover was found in Cocais, as compared to Ipaba, 68% and 60%, respectively. A higher concentration of small size class preserved areas (< 5 ha) was verified, corresponding to 69.5% (169 fragments) in Cocais and 68.9% (135 fragments) in Ipaba. However, the fragments up to 5 hectares were observed to correspond to only 10% of the total preserved area in Cocais and only 6% in Ipaba. It was also observed that the fragments larger than 50 hectares in Cocais accounted to only 4% of the total, although representing 53% of the total preserved area. This relation became more evident in Ipaba, where the fragments larger than 50 hectares accounted for only 6% of the total, representing 67% of the total preserved area. The isolation degree analysis showed that the 35 fragments considered as isolated, totaled 98.25 hectares, corresponding only to 3.99% of the total preserved areas in Cocais. On the other hand, 19 fragments were considered isolated in Ipaba, totaling 56.28 hectares and corresponding to only 1.94% of the total preserved areas. Regarding the shape factor of the forest fragments situated in the studied areas, it was evidenced that most of it was below 5.0 hectares, with low levels of shape factor. It was verified that the larger fragments had higher shape factor values, indicating a tendency towards more stable fragments. The space distribution standards for drainage network on the studied areas were distinct and their analysis stressed that demarcation of legal reserves must always be conducted along with permanent area preservation, so as to form fauna corridors. The differences between standards indicate that in Cocais the fauna corridors are formed by permanent preservation areas interconnecting with legal reserve areas, while in Ipaba, these corridors are formed by the legal reserve areas interconnecting with more distant, and, in some cases, isolated, permanent preservation areas. The analyses of the parameters studied are fundamental for the elaboration of strategies and management proposals aiming at environmental conservation of fragmented ecosystems using landscape management techniques. The use of the proposed methodology allows the establishment of a network of legal reserve and permanent preservation areas connected in distinct reliefs, guaranteeing fauna corridor establishment and, at a large scale, biodiversity corridors.