Land use change affects biogenic silica pool distribution in a subtropical
Dácil Unzué-Belmonte1, Yolanda Ameijeiras-Mariño2, Sophie Opfergelt2, Jean-Thomas Cornelis3, Lúcia Barão4, Jean Minella5, Patrick Meire1, and Eric Struyf11EcosystemManagement 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 iège (ULg), Avenue Maréchal Juin, 27, 5030 Gembloux, Belgium 4ICAAM, Instituto de Ciências Agrárias e Ambientais Mediterrânicas, University of Évora, Apartad o 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
Received: 21 Feb 2017 – Accepted for review: 27 Feb 2017 – Discussion started: 27 Feb 2017
Abstract. Land use change (deforestation) has several negative consequences for the soil system. It is known also to increase the erosion rate which affects 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 biogenic silica 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 will rapidly (< 50 years) deplete (10–53 %) the biogenic AlkExSi pool in soils . Depletion intensity depends on the slope of the study site. We demonstrate that higher erosion in steeply sloped sites implies increased deposition 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 the BSi redistribution and depletion in a soil toposequence, with strong implications for basin scale Si cycling.
Unzué-Belmonte, D., Ameijeiras-Mariño, Y., Opfergelt, S., Cornelis, J.-T., Barão, L., Minella, J., Meire, P., and Struyf, E.: Land use change affects biogenic silica pool distribution in a subtropical
soil toposequence, Solid Earth Discuss., doi:10.5194/se-2017-21, in review, 2017.