Caracterização química e micromorfológica dos solos de Caxiuanã na área de influência do Programa de Pesquisa em Biodiversidade da Amazônia

Abstract

The Amazon Biodiversity Research Program consists of a detailed study of the components of fauna and flora in the region. The execution of the PPBio protocols will result in a computerized basic database on the biodiversity of the focused sites. The soil survey in the PPBio area in Caxiuanã is based on the collection of data on soil types in this area. Thus, the importance of the Basic Protocol of Soils, which consists of the study and classification of soil units and their chemical variation, with the aim of providing data for the other protocols of the PPBio, stands out. The objective of this work is to assist in the classification of soil units that occur in the PPBio grid by describing the chemical and micromorphological characteristics of the soils in the region. The Caxiuanã National Forest covers land in the municipalities of Portei and Melgaço in the state of Pará. The basic soil protocol was based on the methodologies proposed by Embrapa (1997 and 1999) and Lemos & Santos (2002). The field work comprised 90 simple collection points (Dutch auger) at depths of 0-5, 5-10 and 10-20 cm. Micromorphological analysis was performed from images obtained by Scanning Electron Microscopy (SEM) at the Museu Paraense Emílio Goeldi. The chemical analyses were performed in the Soil Analysis Laboratory of the Federal University of Viçosa according to the Manual of Methods and Soil Analysis of Embrapa (1997). According to the Brazilian System of Soil Classification (Embrapa, 1999), the results obtained indicate the existence of two soil classes on the PPBio grid: typical reddistrofic ARGISSOLO VERMELHO-AMARELO and typical hydrophic GLEISSOLO Tb. The micromorphology of the soils showed similar mineralogy with a predominance of 1:1 clay (kaolinite) and quartz grains in the soil. The PPBio presented very acidic soils, with pH ranging from 3.58 to 4.71. The base sum value was less than 1.87 cmol.dm>, reflecting the low Ca, K, Na and Mg contents, depleted from the soil due to the high rainfall rates of the region and the intense leaching to which they are submitted. The Cation Exchange Capacity (CEC) is low in both soils being less than 17.07 cmol.dm>, with negative charges in the soils occupied mainly by AI and H. The base saturation in both Argissolos and Gleissolos was less than 50% giving both a dystrophic character.