Short-term changes in belowground C, N stocks in recently clear felled Sitka spruce plantations on podzolic soils of North Wales

There is currently only limited understanding of the influence of conifer plantation management on soil carbon (C) and nitrogen (N) storage in maritime Europe. The study reported herein examined the effect of clear felling on belowground C and N stocks, and CO2 effluxes at paired clear-felled, and standing plantation sites in North Wales. Clear-felled conifer stands were compared in three different time lapses (3, 5 and 8 years after harvesting). The O horizon (and associated C) was completely absent on the year 3 and year 8 clear-felled stands. There was no significant influence of clear-felling on mineral soil C and N at 0–10 cm depth between clear felled and unharvested sites, however, differences were observed in subsoil depths (10–20 cm and 20–50 cm). Clear-felled sites exhibited an initial gain in surface soil C and N through year 5 (likely due to incorporation of the O horizon into the mineral soil) after which the C stock decreased by year 8. Approximately 50 Mg C and 3 Mg N ha−1 yr−1appear to have been lost from mineral soils 7 years after clear felling. Clear felling significantly (p < 0.05) increased soil CO2 efflux and soil surface temperature. Total CO2 emission from soils at clear felled sites was 148% higher than that of uncut plantations. Alternative harvest strategies should be considered that reduce C losses from plantations in North Wales.

► Clear-felling caused a total reduction in soil C and N pools up to 50 cm belowground.
► Distribution of C and N in the soil profile was altered by clear-felling.
► Clear-felled sites lost about 50 Mg ha−1of C and 3 Mg ha−1of N annually.
► Significantly higher CO2 efflux rate was recorded on clear-felled sites.