Carbon in Dutch forest ecosystems

Abstract

Present stock of carbon in living biomass, litter and stable humus and annual accumulation of carbon in stems of 15 forest types was quantified from inventory data on growth and standing volume, and forest soil information in combination with literature data on forest biomass, as part of the Dutch National Research Programme on Global Air Pollution and Climate Change. Forest area in the Netherlands is about 330 000 ha, mainly young plantations of conifers (Scots pine, Douglas-fir, larch) on poor, dry sandy soils. Average age is about 50 yr. Present average standing volume is 170 msuperscript 3/ha and average annual volume increment was 9.0 msuperscript 3/ha in 1984-89. About 63.7 Mt C is stored in the entire forest, including dead organic matter in forest soil, almost 60% as stable humus in the soil compartment. Average carbon stock in the stable humus is 113 t C/ha, whereas only 59 t C/ha is contained in living biomass and 19 t C/ha in litter layer. Average stock in living biomass is largest for beech stands (124 t C/ha). Annually, about 0.66 Mt C of atmospheric carbon is stored in stem volume increment when harvesting is not considered. On average, about half of annual storage is harvested each year, which means that forest acts as a net carbon sink for about 0.33 Mt C/yr. Largest net annual accumulation is attained in beech stands (1.8 t C/ha). Average annual net accumulation for the entire forested area amounts at present to some 0.97 t C/ha. Long rotations with species like oak, beech and Douglas-fir which may build-up a large standing biomass and which produce durable wood products, are most suitable for a long-term storage of carbon.