Caracterização de solos em uma topoclimossequência no maciço de Triunfo - Sertão de Pernambuco

Abstract

High altitude forest in mountain of Northeast Brazil are islands of the Humid Atlantic forest in the middle of semi-arid region, with an atypical climatic condition, improved by the occurrence of orographic precipitions that can reach more than 1200mm per year. In Pernambuco state scientific studies in these humid sites were only related to botanic and biological aspects, with very little information about soils. Therefore it is important the development of studies on soil characterization and genesis aiming to support actions for the sustainable management of these areas and the reclamation of degraded sites. Aiming to study the soils of the humid mountains in the semi-arid of Pernambuco state and to evaluate the influence of the several soil forming factors, mainly climate, in their morphological development, physical, chemical and mineralogical characterization of 3 soil profiles was carried out in Triunfo Mountain, at different levels of altitude. The soil profiles were located at the municipalities of Serra Talhada (P1), Santa Cruz da Baixa Verde (P2) and Triunfo (P3), along a moisture gradient (topoclimosequence). The soils showed some morphological similarities related to the small degree of development, particularly soil profile P3 (Triunfo) and P2 (Santa Cruz), classificated respectively, as Latossolic Tb Eutrophic Haplic Cambisol and Typic Tb Eutrophic Haplic Cambisol (according to Brazilian Soil Classification System). Soil profile P1 (Serra Tallhada) showed small clay content and greater clay gradient being classificated as cambic abruptic Distrophic Red Yellow Argisol. The results showed that all studied soils were pre-weathered, at least partially, in the upper part of the climosequence (Triunfo) and transported to the lower positions. The soil of Triunfo, with the highest rainfall levels, showed higher degree of development, than the others. Climate however was not the only soil forming factor responsible for soil variation along the sequence. The petrographic analysis concluded that the soil parent materials showed different compositions, even belonging to the same batholit and were associated with sienites, particularly in Serra Talhada. The sandier texture and textural gradient of this profile can be related to differences in parent materials, due to the topographic position, which favors the presence of transported materials from upper positions. Mineralogical analysis showed a dominance of kaolinite in the clay fraction. The influence of granitic rocks in parent material of Serra Talhada soil is responsible for the dystrophic character.