Pedocronologia e desenvolvimento da turfeira da ?rea de prote??o ambiental pau-de-fruta, Diamantina - MG

Na regi?o da Serra do Espinha?o Meridional, a forma??o de ambientes hidrom?rficos em ?reas deprimidas de superf?cies de aplainamento, aliada ? ocorr?ncia de uma vegeta??o adaptada ? condi??o de hidromorfismo, favorece o ac?mulo e a preserva??o de mat?ria org?nica, formando turfeiras. Esse pedoambiente desenvolve-se sobre rochas quartz?ticas, predominantes na regi?o. A turfeira da ?rea de Prote??o Ambiental - APA Pau-de-Fruta, localizada na microbacia do C?rrego das Pedras, munic?pio de Diamantina - MG, foi mapeada e tr?s perfis representativos foram caracterizados morfologicamente e amostrados para caracteriza??o f?sica, qu?mica e microbiol?gica. A mat?ria org?nica foi fracionada em ?cidos f?lvicos (AF), ?cidos h?micos (AH) e humina (H). Dois perfis tiveram amostras coletadas para determina??o da idade radiocarb?nica e do ?13C. Os tr?s perfis apresentam organiza??o estrutural homog?nea, sendo as duas primeiras camadas f?bricas, as duas subsequentes h?micas e as quatro mais profundas s?pricas, evidenciando que o est?dio de decomposi??o da mat?ria org?nica avan?a com a profundidade e as camadas mais profundas apresentam maior influ?ncia do material mineral. Os atributos f?sicos foram homog?neos entre os perfis, mas variaram entre as camadas amostradas. Os atributos qu?micos foram semelhantes entre as camadas, por?m o teor de Ca, a soma de bases e a satura??o por bases diferiram entre os perfis. Os teores de H predominaram sobre as fra??es mais sol?veis da mat?ria org?nica e se acumularam em maior propor??o nas camadas mais superficiais e nas mais profundas, enquanto os AH foram mais elevados nas camadas intermedi?rias e os AF nas camadas mais profundas. A atividade microbiol?gica n?o variou entre os perfis e foi mais elevada nas camadas superficiais, diminuindo com a profundidade. A partir dos resultados das data??es radiocarb?nicas e da composi??o isot?pica, inferiu-se que a turfeira come?ou a ser formada h? cerca de 20 mil anos e que, desde ent?o, a cobertura vegetal da ?rea n?o sofreu varia??es significativas.Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Empresa de Pesquisa Agropecu?ria de Minas Gerais (EPAMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)In the region of the Serra do Espinha?o Meridional, peat bog is formed in hydromorphic environments developed in sunken areas on the plain surfaces with vegetation adapted to hydromorphic conditions, favoring the accumulation and preservation of organic matter. This pedoenvironment is developed on the regionally predominant quartzite rocks. Peat bog in the Environmental Protection Area - APA Pau-de-Fruta, located in the watershed of C?rrego das Pedras, Diamantina,Brazil, was mapped and three representative profiles were morphologically characterized and sampled for physical, chemical and microbiological analyses. The organic matter was fractionated into fulvic acid (FA), humic acids (HA) and humin (H). Two profiles were sampled to determine the radiocarbon age and ?13C. The structural organization of the three profiles is homogeneous. The first two layers consist of fibric, the two subsequent of hemic and the four deepest of sapric peat, showing that organic matter decomposition advances with depth and that the influence of mineral materials in deeper layers is greater. Physical properties were homogeneous in the profiles, but varied in the sampled layers. Chemical properties were similar in the layers, but the Ca content, sum of bases and base saturation differed between profiles. Contents of H predominated in the more soluble organic matter fractions and were accumulated at a higher rate in the surface and deeper layers, while HA levels were higher in the intermediate and FA in the deeper layers. Microbial activity did not vary among profiles and was highest in the surface layers, decreasing with depth. From the results of radiocarbon dating and isotope analysis, it was inferred that bog formation began about 20 thousand years ago and that the vegetation of the area had not changed significantly since then