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Effects of Land Use Change on Soil Quality Indicators in Forest Landscapes of the Western Amazon

Abstract:

Western Amazon has the highest forest biodiversity in the world; however, farming, pasture, or subsistence farming has cleared extensive forest areas, impacting soil quality. This study evaluates the variations in soil quality indicators such as organic carbon (OC), NH4+, available P, soil texture, and pH, taking into account changes of land use from forest to disturbed areas in four different landscape positions: plains, peneplains, piedmont, and periandes piedmont. We used three vegetation cover maps of 1990-2000-2008 and 1,820 soil samples in an estimated area of 40,000 km2. Cokriging and regression kriging of each edaphic attribute and maps of land use were crossed. Analysis of variance for each landscape position was applied in order to identify significant differences in soil quality indicators between different land use categories (forest and disturbed areas). Results suggest changes in biogeochemical soil dynamics. We reported statistically significant reduction in the percentage of OC for disturbed areas and an increase in available P, which is remarkable. NH4+ stocks were lower for disturbed areas; however. In piedmont and periandes piedmont landscapes, forests presented the highest concentrations of OC (3.99 ± 1.1 and 5.06 ± 1.41, respectively) in comparison to disturbed areas (3.56 ± 0.87 and 3.98 ± 1.41, respectively). Changes in soil quality main indicators suggest a potential drop in ecosystem services production for the western Amazon of Ecuador. Management decisions should consider sustainable land use strategies oriented to maintain the resilience of soil quality indicators.