What is the impact of afforestation on the carbon stocks of Irish mineral soils?

Ireland has implemented a large afforestation program in recent decades, with much of this taking place since the mid 1980s. This presents Ireland with the opportunity to offset carbon emissions through carbon sequestration in forests, as the latter are known to sequester a large amount of carbon into the tree biomass. However, the effects of afforestation on soil organic carbon in the Irish humid temperate climate are not well understood. In this study we use the paired site methodology to assess the impact of afforestation on the soil organic carbon density (SOCD) of 21 * 2 sites across Ireland. We found that afforestation of Irish soils (0–30 cm depth) resulted in no significant change in SOCD. However, the low number of sites within the study is a source of uncertainty and more work must be done to assess SOCD change before any firm conclusions can be made. This work provides baseline data and future work estimating soil C changes due to land use or management changes should use the equivalent soil mass (ESM) correction method instead of the volume based method. The latter can over- or underestimate SOCD change due to variability in soil bulk density after afforestation. The large afforestation programmes to be implemented in Ireland in the next decade provides an opportunity to greatly improve estimates of Irish SOCD change. We suggest implementing a large number of resampling studies, measuring the change in SOCD following afforestation for a number of factors for a number of years.

► Afforestation led to no significant change in soil C in Ireland.
► ESM is a suitable method for determining afforestation induced soil C change.
► Additional sites should be sampled to improve the conclusions of this study.