Floristica, Fitossociologia e Heterogeneidade em um povoamento com predominÃncia de Anadenanthera peregrina (Benth.)Speg. / FLORÃSTICS, PHYTOSOCIOLOGY AND HETEROGENEITY IN A STAND WITH PREDOMINANCE OF Anadenanthera peregrina (Benth.) Speg

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The present study was developed in an ancient abandoned area of planting of Anadenanthera peregrina, on the campus of the Federal University of Lavras, MG of about 7,56ha. It was aimed to report the floristic composition of this area as well as its phytosociological structure, paying attention to the ecologic aspects of the species, as the regeneration, dispersion guildas and aggregation standards. Besides, it was intended to understand as both the soil structural and nutritional standards can interfere on the spatial organization of the species with the purpose of creating a theoretical base which can assist future management interventions for the area. 81 plots of 10 x 10m were allocated, arranged in such a way to stand for the greatest apparent variation of physiognomic gradient of the vegetation. All the individuals with BHD (Breast Height Diameter) ≥ 5.0cm were recorded. For each individual, BHD and height values were and the structural phytosociological parameters were calculated. The biological diversity was evaluated through the indices of Shannon, Pielou, Jentsen and compared with areas ao entorno and region, as well as with histÃrico of similar use. The species found were classified according to the regeneration guildas defined by Swaine &Whitmore (1988) and for the classification of the species in dispersion guilds; the classification according to Van der Pijl (1982) was used. For the analysis of aggregation standards, MacGuinnesÂindex (1934) was utilized. The area sampled was divided into two sectors arbitrarily selected by the author according to differences observed in the field as to the composition of the species and soil samples were collected and sent to the Soil Analysis Laboratory of the UFLA Soil Science Department, for chemical and textural analyses performed according to the EMBRAPA protocol (1997). To perform the structural comparisons, a matrix based upon the occurrence of the species for a cluster analysis utilizing similarity distance of Jaccard and the cluster technique by cluster methods (Wardâs Method) was prepared (Kent &Coker, 1992). To perform the analysis of environmental and vegetation gradient, the analysis of the main components (PCA) (OrlÃci, 1966) was done. In the analysis of the data and making of plots and figures, the Exel, Microsoft Visual Basic 5.0 Professional Edition, Dives 2.0, SAS System for Windows V8 (Statistical Analysis System) and PC-ORD for Windows, version 4.14 were made use of. In the sampling performed, 1180 individuals distributed into 25 families and 66 species were recorded. The family with the greatest number of species is Fabaceae, with 16 species (24.24%). The genera of greatest floristic richness were Casearia, with four species, Machaerium and Rollinia, both with three -species and Anadenanthera, Tapirira, Cordia, Protium, Inga, Ocotea, Miconia, Cedrela and Myrcia, with two species each. ShannonÂs (Hâ) diversity index was of 1.47 nats.indivÃdual-1.denoting that the community in issue presents a poor diversity of species. Anadenanthera peregrine presented the highest absolute and relative values to all the structural phytosociologic parameters. The diametric distribution of the species, in general, is typical to tropical forests, that is, inverted J. out of the total of sampled species, 5 (8.2%) are pioneers, 14 (22.95%) are shade-tolerant and 42 (68.85%) of the species are light-demanding climax. The zoocoria predominated in all the strata, 42 (68.85%), the 61 species found in the sampling area presented such a way of dispersion; twelve presented anemocorica dispersion (19.67%) and seven species (11.48%) have autocÃrica dispersion. In the total of the species investigated as to the aggregation index, 21, that is, 60% showed in the minimum a trend to the cluster, possibly related with the visits of their dispersers and canopy architecture. Machaerium villosum and Piptadenia gonoacantha presented an irregular distribution between the first and second diametric class and between the third and fourth class, indicating that possibly some ârecenteâ disturbation may have taken place in the area. There are floristic, structural and diversity differences among the sectors sampled, the diversity and floristics being smaller for sector 1. Of the cluster analysis, the sector 1 presented three subdivisions (A,B and C) and some plots referred by the author as belonging to sector 2, were correlated with sector 1, this distinction being influenced by the density of individuals and richness of species, associated with the allelopathic and decidual properties of the angico. The presence of cipÃs, Celtis iguanea, and a great number of number of individuals regerantes of Anadenanthera in the under storey can be influencing negatively the recruiting of new species and also, performing a selective effect on the seed bank. By the ordering diagram Produced by the main component analysis in relation to soil variables, the plots of the sector lie in sites of low fertility and the plots of sector 2, in sites of accumulation of nutrients and not of losses.

ASSUNTO(S)

ecologia

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