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The contribution of plant roots to CO2 fluxes from organic soils

Silvola, J., Alm, J., Ahlholm, U., Nykanen, H., Martikainen, P.J.
Biology and fertility of soils 1996 v.23 no.2 pp. 126-131
peatlands, organic soils, peat soils, carbon dioxide, biological activity in soil, drained conditions, virgin soils, grasslands, vegetation, roots, biogeochemical cycles, emissions, soil respiration, greenhouse gases, Finland
The CO2 released in soil respiration is formed from organic matter which differs in age and stability, ranging from soluble root exudates to more persistent plant remains. The contribution of roots, a relatively fast component of soil cycling, was studied in three experiments. (1) Willows were grown in a greenhouse and CO2 fluxes from the substrate soil (milled peat) and from control peat were measured. (2) CO2 fluxes from various peatland sites were measured at control points and points where the roots were severed from the plants. (3) CO2 fluxes in cultivated grassland established on peatland were measured in grassy subsites and in subsites where the growth of grass was prevented by regular tilling. The root-derived respiration followed the typical annual phenology of the vegetation, being at its maximum in the middle and late summer. All the experiments gave similar results, root-derived respiration accounting for 35-45% of total soil respiration in the middle and late summer at sites with an abundant vegetation. The root-derived respiration from the virgin peatland sites correlated well with the tree biomass, and also partly with the understorey vegetation, but in the drained sites the root effect was greater, even in the presence of less understorey vegetation than at virgin subsites.