Carbon Budget of Undrained and Drained Nutrient-Rich Organic Forest Soil

Abstract

The impact of the moisture regime on the carbon budget of organic soils with different nutrient statuses has not been fully studied in hemiboreal forests thus far. This study evaluated soil carbon (C) stock changes in forests with drained and undrained nutrient-rich organic soils by estimating C loss through respiration and C input through the litter. The study sites included forest stands dominated by Norway spruce (Picea abies), silver birch (Betula pendula), black alder (Alnus glutinosa), and clear-cuts. Soil respiration was measured using the chamber method, and to estimate the soil C input by litter—the biomass and the C content of the foliar litter, ground vegetation, and fine-root production were measured. The soil in forest stands acted as a C sink. The carbon dioxide (CO2) removal rates of 0.4 ± 0.4 t C ha−1 year−1 and 0.1 ± 0.4 t C ha−1 year−1 were estimated for undrained and drained soil in forest stands, respectively. The soil in the clear-cuts acted as a CO2 source, and the annual emissions ranged from 0.4 ± 0.4 t C ha−1 year−1 in undrained to 0.9 ± 0.7 t C ha−1 year−1 in drained conditions. The reason for the soil in clear-cuts being a C source was increased C loss by respiration and reduced soil C input by litter. Furthermore, the mean soil C input by ground vegetation biomass in the clear-cuts was considerably higher than in the forest stands, which did not compensate for the increase in soil respiration and the absence of C input by foliar litter and the fine roots of trees. The results of the study on annual soil C stock changes can be used as an emission factor in national greenhouse gas inventories of forest land in the hemiboreal zone.