Aims Government policy in Ireland is to increase the national forest cover from the current 10%to 18%of the total land area by 2020.This represents a major land use change that is expected to impact on the national ca...Aims Government policy in Ireland is to increase the national forest cover from the current 10%to 18%of the total land area by 2020.This represents a major land use change that is expected to impact on the national carbon(C)stocks.While the C stocks of ecosystem bio-mass and soils of Irish grasslands and coniferous forests have been quantified,little work has been done to assess the impact of broad-leaf afforestation on C stocks.Methods In this study,we sampled a chronosequence of ash(Fraxinus excel-sior)forests aged 12,20,27,40 and 47 years on brown earth soils.A grassland site,representative of the pre-afforestation land use,was sampled as a control.Important Findings Our results show that there was a significant decline(P<0.05)in the carbon density of the soil(0-30 cm)following afforestation from the grassland(90.2 Mg C ha^(−1))to the 27-year-old forest(66.7 Mg C ha^(−1)).Subsequently,the forest soils switched from being a C source to a C sink and began to sequester C to 71.3 Mg C ha^(−1) at the 47-year-old forest.We found the amount of C stored in the above-and belowground biomass increased with age of the forest stands and offset the amount of C lost from the soil.The amount of C stored in the above-and belowground biomass increased on average by 1.83 Mg C ha^(−1) year^(−1).The increased storage of C in the biomass led to an increase in the total ecosystem C,from 90.2 Mg C ha^(−1) at the grassland site to 162.6 Mg C ha^(−1) at the 47-year-old forest.On a national scale,projected rates of ash afforestation to the year 2020 may cause a loss of 290752 Mg C from the soil compared to 2525936 Mg C sequestered into the tree biomass.The effects of harvesting and reforestation may further modify the development of ecosystem C stocks over an entire ash rotation.展开更多
基金Irish Council for Forest Research and Development(COFORD),Department of Agriculture Fisheries and Food(DAAF)Science,Technology,Research and Innovation for the Environment(STRIVE)programme 2007-2013(2008-CCRP-1.1A),Irish Environmental Protection Agency(EPA).
文摘Aims Government policy in Ireland is to increase the national forest cover from the current 10%to 18%of the total land area by 2020.This represents a major land use change that is expected to impact on the national carbon(C)stocks.While the C stocks of ecosystem bio-mass and soils of Irish grasslands and coniferous forests have been quantified,little work has been done to assess the impact of broad-leaf afforestation on C stocks.Methods In this study,we sampled a chronosequence of ash(Fraxinus excel-sior)forests aged 12,20,27,40 and 47 years on brown earth soils.A grassland site,representative of the pre-afforestation land use,was sampled as a control.Important Findings Our results show that there was a significant decline(P<0.05)in the carbon density of the soil(0-30 cm)following afforestation from the grassland(90.2 Mg C ha^(−1))to the 27-year-old forest(66.7 Mg C ha^(−1)).Subsequently,the forest soils switched from being a C source to a C sink and began to sequester C to 71.3 Mg C ha^(−1) at the 47-year-old forest.We found the amount of C stored in the above-and belowground biomass increased with age of the forest stands and offset the amount of C lost from the soil.The amount of C stored in the above-and belowground biomass increased on average by 1.83 Mg C ha^(−1) year^(−1).The increased storage of C in the biomass led to an increase in the total ecosystem C,from 90.2 Mg C ha^(−1) at the grassland site to 162.6 Mg C ha^(−1) at the 47-year-old forest.On a national scale,projected rates of ash afforestation to the year 2020 may cause a loss of 290752 Mg C from the soil compared to 2525936 Mg C sequestered into the tree biomass.The effects of harvesting and reforestation may further modify the development of ecosystem C stocks over an entire ash rotation.
