title: Silica uptake and release in live and decaying biomass in a northern hardwood forest.
abstract: In terrestrial ecosystems, a large portion (20-80%) of the dissolved Si (DSi) in soil solution has passed through vegetation. While the importance of this "terrestrial Si filter" is generally accepted, few data exist on the pools and fluxes of Si in forest vegetation and the rate of release of Si from decomposing plant tissues. We quantified the pools and fluxes of Si through vegetation and coarse woody debris (CWD) in a northern hardwood forest ecosystem (Watershed 6, W6) at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA. Previous work suggested that the decomposition of CWD may have significantly contributed to an excess of DSi reported in stream-waters following experimental deforestation of Watershed 2 (W2) at the HBEF. We found that woody biomass (wood + bark) and foliage account for approximately 65% and 31%, respectively, of the total Si in biomass at the HBEF. During the decay of American beech (Fagus grandifolia) boles, Si loss tracked the whole-bole mass loss, while yellow birch (Betula alleghaniensis) and sugar maple (Acer saccharum) decomposition resulted in a preferential Si retention of up to 30% after 16 yr. A power-law model for the changes in wood and bark Si concentrations during decomposition, in combination with an exponential model for whole-bole mass loss, successfully reproduced Si dynamics in decaying boles. Our data suggest that a minimum of 50% of the DSi annually produced in the soil of a biogeochemical reference watershed (W6) derives from biogenic Si (BSi) dissolution. The major source is fresh litter, whereas only ~2% comes from the decay of CWD. Decay of tree boles could only account for 9% of the excess DSi release observed following the experimental deforestation of W2. Therefore, elevated DSi concentrations after forest disturbance are largely derived from other sources (e.g., dissolution of BSi from forest floor soils and/or mineral weathering).
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, Lund, SE-22362, Sweden.
authors.forename: Wim
authors.identifier: 0000-0003-0541-0239
authors.initials: W
authors.lastname: Clymans
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, Lund, SE-22362, Sweden.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Conley
authors.affiliation: Department of Environmental Science, Policy and Management, University of California, 130 Mulford Hall, Berkeley, California 94720, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Battles
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, Lund, SE-22362, Sweden.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Frings
authors.affiliation: Department of Civil and Environmental Engineering, Syracuse University, Syracuse, New York 13244, USA.
authors.forename: Mary Margaret
authors.initials: MM
authors.lastname: Koppers
authors.affiliation: Cary Institute of Ecosystem Studies, Millbrook, New York 12545, USA.|Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: Gene E
authors.initials: GE
authors.lastname: Likens
authors.affiliation: Department of Civil and Environmental Engineering, Syracuse University, Syracuse, New York 13244, USA.
authors.forename: Chris E
authors.initials: CE
authors.lastname: Johnson
mesh_terms: D018533:Biomass; D065928:Forests; D010944:Plants / Q000378:metabolism*; D012822:Silicon Dioxide / Q000737:chemistry* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D012822:Silicon Dioxide
keywords: coarse woody debris; decomposition; deforestation; silica