Análise de gradientes de solo e vegetação em mata ciliar do Rio São Francisco, norte de Minas Gerais, para fins de restauração florestal

Abstract

The objective of the present study was the investigation of the shrub-tree component in a pedological-vegetation gradient of riparian forest with alluvial influence in Parque Estadual da Mata Seca, north of Minas Gerais. The study focused: (i) diversity and structure of vegetation and their relations with environmental variables; (ii) the influence of soil characteristics in the distribution of species, in order to provide information for the recovery of degraded areas in environmental conditions similar to those of the study area. The data from the shrubby-arboreal component were collected in continuous fragment of riparian forest, divided into 39 plots of 400m2 (20 m × 20 m), equally distributed in three studied area: São Francisco (soils with higher content of sand and less water saturation), Meio (soils with hight content of silt and flooding during most of the year) and Lagoa da Prata (clay soils with flooding during the rainy season), totaling 1.56 ha sampling. The information recorded in each plot were the diameter at breast height (dbh) ≥ 5 cm, height and botanical identity, over and above soil characteristics, which were submitted to chemical, granulometric analysis and moisture content. In the studied area were recorded 2,482 individuals, belonging to 36 species, 31 genera and 16 botanical families. The most important species to São Francisco were Celtis ehrenbergiana, followed by Inga vera and Ziziphus joazeiro. However, for the Middle and Lagoa da Prata were Albizia inundata, Chloroleucon foliolosum and Celtis ehrenbergiana. Shannon’s diversity index (H’) was 2.04. The diameter distribution of the community submitted a large number of the individuals concentred in the smallest classes. This value is expected for floodplain forests. Significant differences were found in number of individuals, basal area and dominance between the studied areas. The soil features (chemical, texture and moisture) seem to be important factors determining the gradient. The ordination of soil and vegetation data was done by the canonic correspondence analysis (CCA) which showed that soil and drainage factors were responsible for species ordination. Anadenanthera colubrina, Celtis ehrenbergiana, Inga vera, Maclura tinctoria, Chloroleucon dumosum and Talisia esculenta are most abundant in the São Francisco section, an area that has a higher fertility and lower humidity. Moreover, Savia dictyocarpa, Geoffroea spinosa, Senegalia polyphylla, Albizia inundata, Schinopsis brasiliensis and Mimosa tenuiflora are most abundant in Meio and Lagoa da Prata, which are more humid areas with low fertility. Thus, the soil variables determine the distribution of species in the gradient of riparian forest of the São Francisco river, and can be inferred from species with potential for restoration of riparian areas similar to the sites studied.