Composição e estrutura em trecho de floresta no Médio Paraíba do Sul, RJ

Abstract

A preliminary study of floristic and phytosociologycal was accomplished in a forest passage in the Experimental Field Santa Mônica (CEFSM) (22º22'S and 43º42'W), belonging Embrapa Gado de Leite, located in Barão of Juparanã, district of Marquês de Valença, middle section of the Basin of Rio Paraíba do Sul, RJ. The total area sample was of 0,3 ha subdividing in three areas of 1.000m2 each, with approximately 60, 80 and 120 years of natural regeneration starting from different occupation reports and abandonment. It was used the method of parcels and criterion of inclusion of diameters the height of the chest (DAP) equal or larger than 5cm. In the soil analysis it was observed that in a general way, the tenors of Ca+Mg, K, P, N and C came with superior values in the 120 year-old parcel, decreasing according to the age of the portions, in compensation, the litter stock as well as the tenors of Ca, P, N, C and the relationship C/N had been significantly equal for the three parcels used as a sample, despite that, discreet variation was observed as for the individuals of Leguminosae presence with nodules in their roots among the portions of 60 and 120, however the inadequacy parcels suggests larger investigation. The medium values of the litter stock can be considered low inside of the strip of variation occurred in other areas of Forest Atlântica.Com relationship to the measures of diversity of fauna of the soil, these they are with very close values among the three portions, suggesting larger investigation. As for the composition and structure was observed that the 60 year-old portion presented the lowest number of individuals (108), trunks still died in foot (1), however the number of goods (26) and species (31) as well as larger diversity index (3,02) and eqüability (0,87) they were above the sampled in the 80 year-old parcel, however, medium DAP and basal area, they are the more bass in relation to the portions of 80 and 120 years. In this portion the species Piptadenia gonoacantha, Miconia cinnamomifolia and Dalbergia nigra, for different attributes were the ones that obtained larger values of importance and they are representative of this portion. The high number of individuals (88%) with maximum height of up to 10m, being among these species as Xylopia brasiliensis and X. sericea that occupy emerging position in the dossal of forests in other Atlantic forest places, this allied observation to the parameters observed above suggest that this portion is in intermediate phase of successional development. The 80 year-old portion presented the highest number of individuals comparatively (172), low number of families (14), smaller number of goods (24) and species (27), consequently smaller diversity index (2,78) and eqüability (0,84). This portion presented medium DAP a little below to the observed for the one of 60 years and intermediate basal area among the three analyzed portions, these data suggest that disturbances that active and/or act are influencing unfavorably composition and structure. The species Siparuna guianensis, Piptadenia gonoacantha and Apuleia leiocarpa, can be considered as representative of this parcel. The 120 year-old parcel presented the largest number of trunks died (15), of goods and species, larger H' and eqüability, as well as smaller number of families and intermediate number of individuals, high number of exclusive species as well as the largest values of medium DAP and basal area, if compared with the others two parcels. In this parcel the species with larger VI’s were Vochysia oppugnata and Inga capitata, due to the high DoR, a little below is Lauraceae sp and Roupala longipetiolata, followed by Guapira opposita and Bauhinia forficata that presented larger number of individuals. Possibly, the access difficulty and time of permanence might have favored the largest complexity of this formation, suggesting that this it is in phase of advanced development of development, reinforced by the largest number of exclusive species, they put these data should be observed with reservation, due to the analysis species/area to have if shown insufficient. The floristic similarity (0,5) it was obtained between the parcels of 60 and 80 years, fact this favored possibly by the proximity age, space and historical of occupation also similar. The species G. opposita, C. sylvestris, C. oblongifolia, M. rostrata and P. gonoacantha are common to the three analyzed parcels. The vegetation of the Experimental Field Santa Mônica presented similarity, at the level of 0,24 in the index of Jaccard, with the forest formation of the Dam of Ribeirão of Lages, RJ, suggesting that the existent formations in the area of Medium Paraíba of the South possess peculiar characteristics. This initiative and with these results, allies the historical pressure antropic that has been suffering the forest remainders and the proven shortage of floristic and phytosociologia studies indicate the conservation need and preservation of the fragments of this area that still keep own species of these formations and the incentive to futures studies in the region