title: Soil carbon and belowground carbon balance of a short-rotation coppice: assessments from three different approaches.
abstract: Uncertainty in soil carbon (C) fluxes across different land-use transitions is an issue that needs to be addressed for the further deployment of perennial bioenergy crops. A large-scale short-rotation coppice (SRC) site with poplar (Populus) and willow (Salix) was established to examine the land-use transitions of arable and pasture to bioenergy. Soil C pools, output fluxes of soil CO2, CH4, dissolved organic carbon (DOC) and volatile organic compounds, as well as input fluxes from litter fall and from roots, were measured over a 4-year period, along with environmental parameters. Three approaches were used to estimate changes in the soil C. The largest C pool in the soil was the soil organic carbon (SOC) pool and increased after four years of SRC from 10.9 to 13.9 kg C m-2. The belowground woody biomass (coarse roots) represented the second largest C pool, followed by the fine roots (Fr). The annual leaf fall represented the largest C input to the soil, followed by weeds and Fr. After the first harvest, we observed a very large C input into the soil from high Fr mortality. The weed inputs decreased as trees grew older and bigger. Soil respiration averaged 568.9 g C m-2yr-1. Leaching of DOC increased over the three years from 7.9 to 14.5 g C m-2. The pool-based approach indicated an increase of 3360 g C m-2in the SOC pool over the 4-year period, which was high when compared with the -27 g C m-2estimated by the flux-based approach and the -956 g C m-2of the combined eddy-covariance + biometric approach. High uncertainties were associated to the pool-based approach. Our results suggest using the C flux approach for the assessment of the short-/medium-term SOC balance at our site, while SOC pool changes can only be used for long-term C balance assessments.
authors.affiliation: Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology University of Antwerp Universiteitsplein 1 B-2610 Wilrijk Belgium.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Berhongaray
authors.affiliation: Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology University of Antwerp Universiteitsplein 1 B-2610 Wilrijk Belgium.
authors.forename: Melanie S
authors.initials: MS
authors.lastname: Verlinden
authors.affiliation: Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology University of Antwerp Universiteitsplein 1 B-2610 Wilrijk Belgium.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Broeckx
authors.affiliation: Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology University of Antwerp Universiteitsplein 1 B-2610 Wilrijk Belgium.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Janssens
authors.affiliation: Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology University of Antwerp Universiteitsplein 1 B-2610 Wilrijk Belgium.
authors.forename: Reinhart
authors.initials: R
authors.lastname: Ceulemans
keywords: Populus sp.; bioenergy; carbon fluxes; carbon pools; land‐use change; poplar; second‐generation biofuels; soil organic carbon