Soil carbon change and carbon storage in litter on the forest floor after land use change from native pasture to pine plantation

From our meta-analysis of worldwide data, soil carbon content decreased following land use change from pasture to conifer plantation. However, carbon stored in litter on the forest floor may balance the carbon lost from mineral soil. A paired study (a native pasture with 'Themeda triandra' dominant, and a 16-year-old 'Pinus radiata' plantation) at Kowen Forests, ACT, Australia, assessed the soil carbon change, carbon accumulation in litter on the forest floor and annual carbon return to soil surface via litterfall after land use change from native pasture to pine plantation. Results show that carbon stocks in the top 1 m mineral soil had decreased by 18% from 75 to 61 t/ha, 16 years after the land use change. However, approximately 10 t C/ha in litter had accumulated on the forest floor (including 3.2 t/ha in woody debris mostly from pruning/thinning). In the last two (local drought) years (July 2002-June 2004) approximately 2 t C/ha/yr returned to the soil surface via litterfall. Hence, C in the litter pool could substantially compensate the C loss from soil. Thus, considering the significant amount of carbon likely to be stored in plant biomass, a pine ecosystem planted onto prior pasture should be a net sink for C despite possible losses in soil C.