Soil carbon and belowground carbon balance of a short‐rotation coppice: assessments from three different approaches |
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Authors: | Gonzalo Berhongaray Melanie S. Verlinden Laura S. Broeckx Ivan A. Janssens Reinhart Ceulemans |
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Affiliation: | Department of Biology, Research Centre of Excellence on Plant and Vegetation Ecology, University of Antwerp, Wilrijk, Belgium |
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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?2 yr?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?2 in the SOC pool over the 4‐year period, which was high when compared with the ?27 g C m?2 estimated by the flux‐based approach and the ?956 g C m?2 of 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. |
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Keywords: | bioenergy carbon fluxes carbon pools land‐use change poplar Populus sp. second‐generation biofuels soil organic carbon |
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