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ROSIK JIŘI, FABIANEK TOMAS, MARKOVA IRENA: Soil CO2 effl ux in young Norway spruce stands with diff erent silviculture practices. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 6, pp. 1845–1851 Seasonal changes of soil CO2 effl ux were investigated in two young Norway spruce stands with diff erent silviculture practices (below and above thinning) during the 2010–2012 at the Ecosystem Station of Rajec – Němcice (the Drahanska vrchovina Highland, the Czech Republic). Soil CO2 effl ux was almost about 20% higher in the plot with above thinning compared to the plot with bellow thinning. Soil CO2 effl ux between the studied plots was signifi cant in the studied years 2010 and 2012. Soil CO2 effl ux was positively related to soil temperature in the both studied spruce plots. Silviculture practices had eff ect on soil CO2 effl ux in studied young Norway spruce stand. seasonal changes in soil respiration, growing season, thinning Soil CO2 effl ux is the second largest carbon fl ux in terrestrial ecosystems, and plays an important role in global carbon cycle (Raich and Schlesinger, 1992; Davidson et al., 2002). It is estimated that approximately 45–90 % of forest ecosystem CO2 effl ux is from soil cycling (Davidson et al., 1998; Epron et al., 1999; Bolstad et al., 2004; Guan et al., 2006). Therefore, soil CO2 effl ux has a great eff ect on CO2 atmospheric concentration, as one of the greenhouse gases, and consequently on global warming. CO2 effl ux from the soil results from the combination of biological processes (i.e. production of CO2 by roots, soil micro-organisms and soil macro-fauna) and physical processes (i.e. CO2 diff usion from sources to soil surface) (Le Dante et al., 1999). In the temporal dynamics of soil CO2 effl ux, soil temperature and soil moisture are the most important factors. There is mostly positive relationship between soil temperature and soil CO2 effl ux (Lloyd and Taylor, 1994; Janssens et al., 1999) and this relationship is o en described as exponential (Davidson et al., 2006a). Numerous models have been developed to express the temperature sensitivity of soil CO2 effl ux (Reichstein et al., 2003; Tuomi et al., 2008). Soil moisture is the other dominant factor infl uencing the soil CO2 effl ux (Epron et al., 1999). Soil CO2 effl ux can be furthermore aff ected by the amount of root biomass (Tang et al., 2005; Ruehr and Buchmann, 2010), organic matter in the soil (Sikora and Rawls, 2000; Tang et al., 2009), litter thickness on the soil cover (Fang et al., 1998; Makiranta et al., 2008), C/N ratio in soil profi le (Craine and Wedin, 2002) or leaf area index of a stand canopy (Yuste et al., 2003). The aim of this article is description of seasonal changes of soil CO2 effl ux in two young Norway spruce (Picea abies [L.] Karst.) stand with diff erent silviculture practices. MATERIALS AND METHODS Seasonal changes of soil CO2 effl ux were investigated in two young Norway spruce plots with diff erent silviculture practices during the 2010– 2012 at the Ecosystem Station of Rajec – Němcice (the Drahanska vrchovina Highland, the Czech Republic) (Tab. I). The studied spruce stand (Picea abies [L.] Karst.) was established by artifi cial planting in the spring of 1978 (3-years-old spruce seedlings in the clip 2.5 × 1846 Jiři Rosik, Tomas Fabianek, Irena Markova 2 meters) on the clearing created a er cutting of the previous adult spruce stand. The spruce stand was divided into several experimental plots (area 25 × 25 meters) where diff erent silvicultural practices were carried out. Thinning were performed in 1986, 2002 and 2010. Two experimental plots were selected for the soil CO2 effl ux investigation, one with above thinning and the other one with below thinning (Tab. II). All measurements of soil CO2 effl ux were carried out a er last thinning in 2010. Thinning from above removes trees from middle and upper crown classes to open canopy to favor development of most promising trees. Dominants trees are mostly removed (some dominants and intermediates trees). In thinning from below, trees are removed from lower crown classes. This kind of thinning simulates and accelerates natural processes. Measurements of soil CO2 effl ux in both studied spruce plots were carried out manually using a portable closed gasometric system LI–8100 (LI– COR Inc., USA) during the growing season (May – October) in 2010–2012. The system consisted of a chamber (diameter of 20 cm), an infrared gas analyser CO2 (IRGA), soil thermometer, soil hygrometer, air thermometer and PC with additional hardware, In each studied spruce stand 17 circles (diameter of 20 cm) were installed in a regular net for measuring of soil respiration (Fig. 1). The circles were recessed into the soil approximately 10 cm below the soil surface. Soil CO2 effl ux was measured manually every 14 days during the whole growing seasons. Simultaneously with the soil CO2 effl ux measurement soil temperature and soil moisture were measured 1 cm beside the measurement point below overlaying humus layer (depth of 4.5 cm). Moreover, soil temperature in the depth of 4.5 cm was measured continuously during the whole growing season using the sensor Pt 1000 (Sensit, Czech Republic). Values of CO2 fl ux from the soil obtained in both studied spruce plots during the growing seasons in 2010–2012 were analysed according to Van’t Hoff (1898) and Pavelka at al. (2007). Statistical processing of the data was made using program STATISTICA 10.0 (StatSo Inc., USA). The description statistic method and ANOVA method were used. Statistical signifi cance was evaluated at confi dence level of  = 0.05. For estimation of Q10 coeffi cient was used QCExpert 3.3 (TrilloByte Statistical So ware, Czech Republic) and for elimination outliers Williams Graph (TrilloByte Statistical So ware, Czech Republic).

Soil CO<sub>2</sub> efflux in young Norway spruce stands with different silviculture practices