Land use change affects biogenic silica pool distribution in a subtropical soil toposequence

Article, Other literature type English OPEN
Unzué-Belmonte, Dácil ; Ameijeiras-Mariño, Yolanda ; Opfergelt, Sophie ; Cornelis, Jean-Thomas ; Barão, Lúcia ; Minella, Jean ; Meire, Patrick ; Struyf, Eric (2017)

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&thinsp;>&thinsp;5 for the biogenic AlkExSi (alkaline extractable Si) and Si/Al&thinsp;<&thinsp;5 for the non-biogenic AlkExSi. Our study shows that deforestation will rapidly (<&thinsp;50 years) deplete (10&ndash;53&thinsp;%) 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.
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