Impacts of nitrogen fertilisation and coppicing on total and heterotrophic soil CO2 efflux in a short rotation poplar plantation

Abstract

Short rotation forests can serve as sources of renewable energy and possibly for soil C storage. However, the high frequency of management practices and the fertilisation could reduce C storage into the soil, by increasing CO2 emissions and annulling the potential of C sequestration. The objectives of this work were to evaluate the impacts of coppicing and fertilisation on total soil CO2 efflux, soil heterotrophic processes and consequent changes of soil C storage in a short rotation poplar plantation. Field soil CO2 efflux, heterotrophic soil CO2 efflux and soil organic C were compared before and after coppicing. Temporal dynamics of fine root biomass and water-soluble carbon after coppicing were also analysed. Coppicing increased total soil CO2 efflux by more than 50%, while heterotrophic soil CO2 efflux remained unchanged. Nevertheless, an increase in total organic carbon was observed as a result of above and belowground litter inputs, as well as root re-growth and exudation. This trend was more evident in fertilised soils due to lower heterotrophic and autotrophic soil CO2 effluxes. Fertilisation can reduce the increase of CO2 emissions after coppicing. Although soil organic C storage increased, the accumulation of labile fractions may trigger microbial respiration in the following years.