Mean soil CO2 efflux from a mixed forest:: Temporal and spatial integration

In situ soil CO2 efflux was measured with a corrected soda lime technique for almost two years in four different types of vegetation in a very heterogeneous mixed coniferous/deciduous forest in the Campine region of Belgium. These experimental data were used to develop an empirical model of soil CO2 efflux in relation to soil moisture and soil temperature. In all four vegetation types, the model fitted the data rather well (R-2: 0.84-0.94), and most of the variation was explained by soil temperature. Accumulated yearly totals (1997) ranged from 10.3 t ha(-1) under a coniferous canopy without understory to 28.2 t ha(-1) under a deciduous cover with an undergrowth of grasses. Mean soil CO2 efflux for the entire forest was scaled up from the weighted contribution of each vegetation type to the forested area, and was estimated to be 16.7 t ha(-1) y(-1) (or 4.6 carbon t ha(-1) y(-1)).