Pedochronology and development of peat bog in the environmental protection area pau-de-fruta - Diamantina, Brazil

José Ricardo Da Rocha Campos,Enilson De Barros Silva,Rafael Vitor Romão,Paulo Henrique Grazziotti,Leandro Lara Vasconcellos,Daniel Valladão Silva,Alexandre Christófaro Silva

doi:10.1590/s0100-06832010000600021

Abstract

In the region of the Serra do Espinhaço 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 Córrego 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 δ13C. 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.

Highlights

IntroductionIt is estimated that an area of about 400 million ha is covered with peat bog, equivalent to 3 % of the Earth’s surface
Peat bogs are pedoenvironments formed by successive accumulation of plant remains at sites under conditions where the activity of microbial decomposers is inhibited by excessive moisture, low pH, lack of oxygen and warm temperatures
The color analysis showed higher intensity and chroma in the uppermost soil layers, with a tendency to decrease with depth (Table 2), evidencing a darker color of the peat in deeper than in surface layers, indicating a more advanced stage of organic matter decomposition (Embrapa, 2006)

Summary

Introduction

It is estimated that an area of about 400 million ha is covered with peat bog, equivalent to 3 % of the Earth’s surface. Most of this area, about 350 million ha, is in the Northern Hemisphere and between 30.5 and 45.9 million in the Tropics (Rieley et al, 2008). Bahia and Piauí (Silva et al, 2005), peat is associated with other types of shallow and sandy soils. Silva (2004a,b,c; 2005) mapped 112,233 ha of land in four protected areas of the mountain range called Serra do Espinhaço Meridional (SdEM), of which 12,814 ha correspond to mapping units where Organosols (peatlands) occur in association with other soils Bahia and Piauí (Silva et al, 2005), peat is associated with other types of shallow and sandy soils. Silva (2004a,b,c; 2005) mapped 112,233 ha of land in four protected areas of the mountain range called Serra do Espinhaço Meridional (SdEM), of which 12,814 ha correspond to mapping units where Organosols (peatlands) occur in association with other soils

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