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ŠUMARSKI LIST 5-6/2023 str. 37     <-- 37 -->        PDF

carbon dioxide emission from soil (Adachi et al., 2006). The results of the the presented study show that soil temperature and moisture had different influence on the CO2 flux, also depending on the anthropogenic and environmental factors. The influence of topography and vegetation cover can be very important for soil respiration rate, since they significantly affect microsite factors, such as soil temperature and soil moisture (Li et al., 2008). Also, silvicultural treatments can change the microclimate conditions of the stand (Ma et al., 2010). The effect of thinning the forest stand contribute to the evapotranspiration increment within the ecosystem (Boczoń et al., 2016). During the last phase of regeneration cutting of pedunculate oak, all mature trees were removed. Consequently, it enabled larger quantity of sunlight and rainfall to reach the surface of the soil. The negative correlation between soil temperature and soil water content was detected in temperate mixed hardwood forest in central Massachusetts (Davidson et al., 1998). Increased insolation had an influence on a quick warming of soil as well as more intensive soil evaporation, while rapid drop of soil water content was recorded due to the rise of soil temperature.
Within the various type of soils, soil temperature and soil moisture can have different influence on soil respiration, where one of these two factors can be more dominant than another (Koizumi et al., 1999). Presented results showed that CO2 flux gave different responses to soil temperature and moisture within various type of soil. The soil water content was dominant driver in natural soils, but for the anthropogenic soil, the main limitation factor of the CO2 emission was soil temperature.
In deciduous and coniferous forests, the contribution of soil respiration to total ecosystem respiration varied during different seasons (Curiel Yuste et al., 2005). The variation of CO2 emission was pronounced during the summer period, especially within the plots that were under the anthropogenic influence. Tang et al. (2006) suggested that within successional forests, CO2 flux was significantly lower during the cool and dry season, compared to the hot and humid one. Our study was carried out during the warmest period of the year. At the beginning, as well as at the end of the observation period, the low values of CO2 flux appeared as consequence of decreased temperature and moisture of the soil.
Some pesticides can intensify CO2 emission from the soil, whereas others reduce it, or do not have any effect (Jezierska-Tys et al., 2021). Herbicides which were used to control broadleaf weeds in agricultural crops caused significant raise of CO2 emission from the soil during the two-year study (Shi et al., 2020). Glyphosate, widely used herbicide in agriculture, stimulated microbial activity which resulted in increased soil respiration (Araújo et al., 2003). The application of herbicides in the regeneration of oak forests such as nicosulfuron, imazamoxare and cycloxydim can cause an increase in number of actinomycetes and fungi (Vasić et al., 2018). The largest part of heterotrophic respiration from the soil is evolved by microorganisms, so they are the one of the most important agents in the soil which produce CO2 (Kuzyakov, 2005). For dry habitats, such as steppes, precipitation is limiting factor which affects soil microbial respiration. Soil heterotrophic respiration in these regions is being increased with the rise of precipitation (Zhao et al., 2016). The increased emission of CO2 within the plot which was under the influence of pesticides (Plot 2) application compared to the control plot (Plot 1) can be explained by stimulating effect of pesticides on the microbial activity in the soil. Furthermore, within Plot 2, more intensive increase of the CO2 flux was recorded with the rise of soil water content in comparison to Plot 1.
                The average value of CO2 emission from urban soil was 20 g CO2 m-2 day-1 in Beijing (China) (Fu et al., 2013), whereas 17 g CO2 m-2 day-1 was recorded in Boston (USA) (Decina et al., 2016). However, Sarzhanov et al. (2017) suggested that CO2 emission from urban soil was substantially greater in comparison to Chernic Phaeozem (natural soil), which is the result of low sustainability of organic carbon in the urban soil. Our study showed similar results, where the CO2 flux from anthropogenic soil (Plot 3) was higher compared to the natural soil (Plot 1). High soil temperatures caused emissions which were approximately equal to the emissions in the urban environments. It indicates that the modification of soil in natural ecosystems can induce a similar emission of CO2 like in urban areas.
CONCLUSION
ZAKLJUČAK
The change of microsite conditions due to the trees removal in the last phase of regeneration cutting had a very important influence on the key drivers of emission (soil temperature and soil moisture). The plots which were under anthropogenic influence (Plot 2 and Plot 3) had predominantly higher values of CO2 flux compared to the control plot (Plot 1) during the observation period.
The soil temperature and moisture as the most dominant factors of the emission had various impact on the soil respiration depending on the soil type. The main limitation factor of emission within natural soils (Gleysol), (Plot 1 and Plot 2) was soil water content, whereas CO2 flux from anthropogenic soil (Anthrosol), (Plot 3) was primarily controlled by the soil temperature. The simple linear models showed that the strongest relationship was obtained between CO2 emission and the soil water content within the plot where the treatment of pesticides was conducted (Plot 2), while the best multiple linear regression model for CO2 flux as a function of the soil temperature and moisture was found for the third plot (Plot 3).