Influência de fatores abióticos na diversidade de espécies do estrato herbáceo-subarbustivo em Cerrado, FLONA de Paraopeba, MG

Abstract

The Cerrado is formed by a set of physiognomies ranging from open fields to woodlands, wher is possible to distinguish perfectly two vegetation types: the herbaceou-subshrubby and the shrubby-arboreous. These differences reflect the heterogeneity of environments, especially variations on soils and climate that influence the physiognomy, floristic, phytossociology and productivity vegetation. This work focused on the structure and diversity of herbaceous- subshrubby vegetation in four Cerrado vegetation types wich are distinguished by the type of soil and light, and aimed to evaluate the influence of the light and quimic aspects of the soils on the physiognomy, floristic and structure of the herbaceous-subshrubby vegetation in four Cerrado vegetatin at FLONA of Paraopeba. Plants sprecies were sampled in 100 plots de 1m 2 , 25 in each vegetation type: Cerradão (woodland) on Red Latosol, Cerrado stricto sensu on Red-Yellow Latosol, Cerrado stricto sensu on Yellow Cambisol and Cerrado stricto sensu on Yellow Latosol. The sampling was carried in the dry and rainy seasons. The data collected were abundance, diversity, degree of coverage and species in fertile period. The horizontal structure was analized in the dry and rainy seasons to all the FLONA of Praopeba and to each vegetation type. To analyze the diversity, the indices utilized were Shannon and Pileou. To cluster analysis the indice utilizes was Jaccard. Soils were sampled with 40 samples at depth 0-10 cm, and analyzed chemically. Light environments were characterized by 100 hemispherical fisheye lens photographs taken on the apex of each sample, The light reaching the sampling was computed with the software GLA 2. 308 species and 88 families were found. Only 168 were in fertile period. The prediminants families were Asteraceae, Fabaceae and Poaceae. The predominant life forms were phanerophyt and hemicriptophyt. In the phytossociologic analyze, in rainy season there are more three species than dry season. The abundance and degree of coverage in dry season were lower than rainy season. The species with the highest importance in the dry season were Aristida torta, Qualea sp. 2 e Miconia albicans, while in the rainy season were Echinolaena inflexa, A. torta e M. albicans. The horizontal structure was different to four vegetation types, especially in Cerradão (woodland), because your species with highest importance were different in each vegetation type. The species E. inflexa, A. torta e M. albicans had the highest importance values several times. In the similarity analysis, the Cerradão (woodland) had the lowest floristic similarity with the others vegetation types. It was noted a gradient of light along the four vegetation types and a positive correlation between the abundance and degree of coverage of vegetation. Soils of Cerradão (woodland) were different of soils from other areas, with lower pH and exchangeable acidity, higher potencial acidity. Two groups were formed, one consisting of plots of Cerradão, and other group consisting of plots of Cerrado stricto sensu on Yellow Cambisol and on Yellow Latosol. The most influential variables on distribuition of species were light, pH and potential acidity. The environmental conditions of light and soils of Cerradão are very different of other vegetation types at FLONA, reflecting in the low floristic and structure similarity. Many species that were not known to FLONA Paraopeba were recorded, especially of herbaceous vegetation, and it’s estimate that the diversity is still grater, because the negative impact of minhocuçu’s extraction.