Land use change affects biogenic silica pool distribution in a subtropical soil toposequence
- 1EcosystemManagement Research Group, Department of Biology, University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium
- 2Earth and Life Institute, Environmental Sciences, Université catholique de Louvain, Croix du Sud 2 bte L7.05.10, 1348 Louvain-la-Neuve, Belgium
- 3Department Biosystem Engineering (BIOSE), Gembloux Agro-Bio Tech (GxABT), University of Liège (ULg), Avenue Maréchal Juin, 27, 5030 Gembloux, Belgium
- 4ICAAM, Instituto de Ciências Agrárias e Ambientais Mediterrânicas, University of Évora, Apartado 94, 7002-554 Évora, Portugal
- 5Universidade Federal de Santa Maria (UFSM), Department of Soil Science, 1000 Avenue Roraima, Camobi, CEP 97105-900 Santa Maria, RS, Brazil
- * Invited contribution by Dácil Unzué-Belmonte, recipient of the EGU Soil System Sciences Outstanding Student Poster Award 2014.
Abstract. Land use change (deforestation) has several negative consequences for the soil system. It is known to increase erosion rates, which affect the distribution of elements in soils. In this context, the crucial nutrient Si has received little attention, especially in a tropical context. Therefore, we studied the effect of land conversion and erosion intensity on the biogenic silica pools in a subtropical soil in the south of Brazil. Biogenic silica (BSi) was determined using a novel alkaline continuous extraction where Si ∕ Al ratios of the fractions extracted are used to distinguish BSi and other soluble fractions: Si ∕ Al > 5 for the biogenic AlkExSi (alkaline-extractable Si) and Si ∕ Al < 5 for the non-biogenic AlkExSi. Our study shows that deforestation can rapidly (< 50 years) deplete the biogenic AlkExSi pool in soils depending on the slope of the study site (10–53 %), with faster depletion in steeper sites. We show that higher erosion in steeper sites implies increased accumulation of biogenic Si in deposition zones near the bottom of the slope, where rapid burial can cause removal of BSi from biologically active zones. Our study highlights the interaction of erosion strength and land use for BSi redistribution and depletion in a soil toposequence, with implications for basin-scale Si cycling.