Carbon stocks and sequestration in plantation forests of the Republic of Ireland

The United Nations Framework Convention on Climate Change and its Kyoto Protocol (KP) have created a clear need for methods that enable accurate accounting of carbon (C) stocks and stock changes in forest ecosystems. The rate of accumulation of C in plantation forests in the Republic of Ireland was estimated for the period 1906-2002 using the record of afforestation and a dynamic C accounting model (C-flow). Projections for the period 2003-2012 were made using different afforestation rates. It was assumed that Sitka spruce planted in the period 1906-1989 was Yield Class (YC) 16 m³ ha ^-1 year^-1 and that after 1990 this increased to 20 m ³ ha^-1 year^-1. All other conifers were assumed to have the growth characteristics of YC 8 m³ ha^-1 year^-1 lodgepole pine. Broadleaves were assumed to have the growth characteristics of YC 6 m³ ha^-1 year^-1 beech. In 2002, the total forest C stock was 37.7 Mt C representing an increase of 14.8 Mt C since 1990. In 2002, the rate of increase in trees, products, litter and soil was 0.7, 0.1, 0.1 and 0.5 Mt C, respectively. Under a business-as-usual scenario, afforestation since 1990 is estimated to create an annual average C sink of 0.9 Mt C year^-1 during the period 2008-2012. This accounts for ∼22 per cent of Ireland's reduction commitment under the KP. Afforestation on peat soils was found to reduce the net C sink, although the extent to which it does so is highly dependent on assumptions regarding the rate of peat C loss.