Forest Ecology and Management 262 (2011) 65–70 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco Comparison of soil CO 2 flux between uncleared and cleared windthrow areas in Estonia and Latvia Kajar Köster a,∗ , Ülle Püttsepp b , Jukka Pumpanen c a Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia b Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Estonia c Department of Forest Sciences, University of Helsinki, Finland article info Article history: Received 5 March 2010 Received in revised form 10 September 2010 Accepted 15 September 2010 Available online 23 October 2010 Keywords: Soil respiration Carbon dioxide Disturbance Windthrow management abstract Storms can turn a great proportion of forests’ assimilation capacity into dead organic matter because of windthrow and thus its role as a carbon sink will be diminished for some time. However, little is known about the magnitude or extent to which storms affect carbon efflux. We compared soil CO 2 fluxes in wind-thrown forest stands with different time periods since a storm event, and with different man- agement practices (deadwood cleared or left on-site). This study examined changes in soil CO 2 efflux in two windthrow areas in north-eastern Estonia and one area in north-western Latvia, which experi- enced severe wind storms in the summers of 2001, 2002 and 1967, respectively. We measured soil CO 2 fluxes in stands formerly dominated by Norway spruce (Picea abies L. Karst.) with total and partial canopy destruction (all trees or roughly half of the trees in stand damaged by storm), in harvested areas (material removed after the wind storm) and in control areas (no damage by wind). Removal of wind-damaged material decreased instantaneous CO 2 flux from the soil surface. The highest instantaneous fluxes were measured in areas with total and partial canopy destruction (0.67 g CO 2 m -2 h -1 in both cases) compared with fluxes in the control areas (0.51 g CO 2 m -2 h -1 ), in the new storm-damaged areas where the mate- rial was removed (0.57 g CO 2 m -2 h -1 ) and in the old storm-damaged area where wood was left on site (0.55 g CO 2 m -2 h -1 ). The only factor affecting soil CO 2 flux was location of the measuring collar (plastic collar with diameter 100 mm, height 50 mm) – either on undamaged forest ground or on the uprooted tree pit, where the mineral soil was exposed after disturbance. New wind-thrown stands where residues are left on site would most likely turn to sources of CO 2 for several years until forest regeneration reaches to substantial assimilation rates. New wind-thrown stands where residues are left on site would most likely tend to have elevated CO 2 fluxes for several years until forest regeneration reaches to substantial assimilation rates. However, forest managers might be concerned about the amounts of CO 2 immediately released into the atmosphere if the harvested logs are burned. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In forest ecosystems, carbon is stored not only in the above- ground biomass of trees, but also in the understorey vegetation, on the forest floor and in the soil. Forests have an important role in the management of soil carbon stock because they occupy a vast land area and have large carbon pools. Soil in coniferous forests contains one of the largest stable pools of carbon in forest ecosys- tems (Bonan and Shugart, 1989; Kasischke et al., 1995), and this pool is thought to be fairly stable even after different disturbances (Harden et al., 2000). Soil organic carbon exists in two forms: labile and stable organic carbon (Tolunay, 2009). Labile soil organic car- bon can be decomposed in less than a few years (Landsberg and ∗ Corresponding author. E-mail address: kajar.koster@emu.ee (K. Köster). Gower, 1997). Stable carbon can stay in the soil for thousands of years. The oxidation of labile soil organic carbon drives the CO 2 flux between the soil and the atmosphere (Zou et al., 2005). The carbon pool of soil is regulated by the balance between above-ground and below-ground production of plant litter and decomposition of that material by soil microorganisms. Measured from the soil surface, soil CO 2 flux provides an esti- mate of the total respiration from plant, animal and microbial sources combined. Root and associated rhizosphere organisms are supported directly from assimilates of photosynthesis while the heterotrophic component of respiration is the result of the activity of free-living soil decomposers (Högberg et al., 2001; Sulzman et al., 2005; Gaumont-Guay et al., 2008). Among these sources, rhi- zosphere respiration may account for up to 50% of the total soil respiration (Högberg et al., 2001; Gaumont-Guay et al., 2008). The largest proportion of fine root biomass is located in the upper organic-rich soil layer (Püttsepp et al., 2006; Helmisaari et al., 0378-1127/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2010.09.023