Articles | Volume 10, issue 7
Biogeosciences, 10, 4991–5007, 2013
https://doi.org/10.5194/bg-10-4991-2013
Biogeosciences, 10, 4991–5007, 2013
https://doi.org/10.5194/bg-10-4991-2013

Research article 24 Jul 2013

Research article | 24 Jul 2013

Si cycling in a forest biogeosystem – the importance of transient state biogenic Si pools

M. Sommer1,2, H. Jochheim3, A. Höhn1, J. Breuer4, Z. Zagorski5, J. Busse6, D. Barkusky7, K. Meier8, D. Puppe1,9, M. Wanner9, and D. Kaczorek1,5 M. Sommer et al.
  • 1Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Soil Landscape Research, Eberswalder Str. 84, 15374 Müncheberg, Germany
  • 2University of Potsdam, Institute of Earth and Environmental Sciences, Karl-Liebknecht-Str. 24–25, 14476 Potsdam, Germany
  • 3Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Systems Analysis, Eberswalder Str. 84, 15374 Müncheberg, Germany
  • 4Landwirtschaftliches Technologiezentrum Augustenberg (LTZ), Referat 12, Neßlerstr. 23–32, 76227 Karlsruhe, Germany
  • 5Department of Soil Environment Sciences, Warsaw University of Life Science (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland
  • 6Leibniz Centre for Agricultural Landscape Research (ZALF), Institute for Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Müncheberg, Germany
  • 7Leibniz Centre for Agricultural Landscape Research (ZALF), Research Station Müncheberg, Eberswalder Str. 84, 15374 Müncheberg, Germany
  • 8Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Land Use Systems, Eberswalder Str. 84, 15374 Müncheberg, Germany
  • 9Brandenburg University of Technology Cottbus-Senftenberg, Chair General Ecology, 03013 Cottbus, Germany

Abstract. The relevance of biological Si cycling for dissolved silica (DSi) export from terrestrial biogeosystems is still in debate. Even in systems showing a high content of weatherable minerals, like Cambisols on volcanic tuff, biogenic Si (BSi) might contribute > 50% to DSi (Gerard et al., 2008). However, the number of biogeosystem studies is rather limited for generalized conclusions. To cover one end of controlling factors on DSi, i.e., weatherable minerals content, we studied a forested site with absolute quartz dominance (> 95%). Here we hypothesise minimal effects of chemical weathering of silicates on DSi. During a four year observation period (05/2007–04/2011), we quantified (i) internal and external Si fluxes of a temperate-humid biogeosystem (beech, 120 yr) by BIOME-BGC (version ZALF), (ii) related Si budgets, and (iii) Si pools in soil and beech, chemically as well as by SEM-EDX. For the first time two compartments of biogenic Si in soils were analysed, i.e., phytogenic and zoogenic Si pool (testate amoebae). We quantified an average Si plant uptake of 35 kg Si ha−1 yr−1 – most of which is recycled to the soil by litterfall – and calculated an annual biosilicification from idiosomic testate amoebae of 17 kg Si ha−1. The comparatively high DSi concentrations (6 mg L−1) and DSi exports (12 kg Si ha−1 yr−1) could not be explained by chemical weathering of feldspars or quartz dissolution. Instead, dissolution of a relictic, phytogenic Si pool seems to be the main process for the DSi observed. We identified canopy closure accompanied by a disappearance of grasses as well as the selective extraction of pine trees 30 yr ago as the most probable control for the phenomena observed. From our results we concluded the biogeosystem to be in a transient state in terms of Si cycling.

Download
Altmetrics
Final-revised paper
Preprint