Soil physicochemical and biological profiles as indicators for Araucaria forest disturbance levels

Abstract

The Araucaria forest is a sub-type of Atlantic Forest and it is critically endangered because of deforestation. Despite significant researchers’ attention, little is known about the microbial and functional soil diversity of this ecosystem. Our aim was to assess structural diversity (phospholipid fatty acid; PLFA), functional diversity (Biolog ecoplates) and physicochemical soil properties to identify which indicators are the most sensitive to alterations in the Araucaria ecosystems. Soils of three different areas (disturbed, reforested, and native Araucaria forest soils), in two parks of Southeast Brazil, were collected in contrasting seasons (dry and rainy). Principal components analysis (PCA) showed that fatty acid profiles, Biolog and physicochemical properties in Araucaria forest soils were more dissimilar between the different park geographic locations than by forest disturbance levels. However, discriminant analysis identified several variables with greater power to discriminate among forest disturbance levels (native, disturbed, and reforested) within each season. Reforested soils were lower in pH, Al+3, and base cation content compared to disturbed and native soils. Soils disturbed by recreational and understory deforestation were sandier in texture and elevated in P compared to native and deforested soils. Native soil microbial communities utilized certain Biolog substrates to a greater extent, depending on season, compared to communities of disturbed and reforested soils. The best discriminating variable among native, disturbed, and reforested soils for both seasons was γ-hydroxybutyric acid consumption, which was positively related to native, and negatively correlated to disturbed and reforested soils. Thus, γ-hydroxybutyric acid consumption may be a useful indicator to monitor the recovery of reforested and disturbed Araucaria soils in reference to its native state.