title: Fire enhances solubility of biogenic silica.
abstract: Changing fire regimes in response to climate change are likely to have significant effects on terrestrial ecosystems and biogeochemical cycles. While effects of fire on some nutrient cycles have been quite well-studied, little attention has been paid to the silicon cycle. We used an alkaline continuous extraction to examine changes in the quantity and characteristics of alkaline extractable Si (AlkExSi) after applying two burning treatments (no heating, 350°C and 550°C) to three types of organic soil material (from spruce forest, beech forest and a commercial peat). The total AlkExSi measured was 25.1±2.1mgg-1and 15.4±0.9mgg-1for spruce and beech respectively, and 1.2±0.5mgg-1for peat. The alkaline extraction parameters confirm a purely biogenic AlkExSi source in untreated spruce and beech organic soil material samples. Organic soil material of beech forest had two biogenic silica pools, differing in reactivity during alkaline extraction. Burning severely alters the alkaline dissolution parameters suggesting a significant crystallization of biogenic Si (BSi) with increased burning severity. Additionally, dissolution experiments carried out in rain water showed that fire increased the solubility of BSi by a factor of 40 and 20 in the case of the spruce and beech organic soil material respectively. The extent of enhanced Si solubility appears to be a trade-off function between organic matter losses and degree of crystallization. The burned soils could provide a strong and immediate Si source for the environment. In situ ecosystem characteristics that affect the uptake-leaching balance will determine the fate of the dissolved Si. Ecosystems low in BSi, like Sphagnum peatland, will not show drastic alteration in the Si cycle due to fire.
authors.affiliation: Ecosystem Management Research Group, Department of Biology, University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium. Electronic address: dacil.unzuebelmonte@uantwerpen.be.
authors.forename: Dácil
authors.initials: D
authors.lastname: Unzué-Belmonte
authors.affiliation: Ecosystem Management Research Group, Department of Biology, University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium.
authors.forename: Eric
authors.initials: E
authors.lastname: Struyf
authors.affiliation: Department of Geology, Lund University, Sölvegaten 12, SE 223 62 Lund, Sweden.
authors.forename: Wim
authors.initials: W
authors.lastname: Clymans
authors.affiliation: Institute of Soil Science and Site Ecology, Faculty of Environmental Sciences, Technische Universität Dresden, 01737 Tharandt, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Tischer
authors.affiliation: Institute of Soil Science, Friedrich Schiller University Jena, 07743 Jena, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Potthast
authors.affiliation: Institute of Plant and Wood Chemistry, Faculty of Environmental Sciences, Technische Universität Dresden, 01737 Tharandt, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Bremer
authors.affiliation: Ecosystem Management Research Group, Department of Biology, University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Meire
authors.affiliation: Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany; Institute of General Ecology, Faculty of Environmental Sciences, Technische Universität Dresden, 01737 Tharandt, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Schaller
keywords: Alkaline extractable silica; Biogenic silica; Fire effects; Solubility