DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu



ŠUMARSKI LIST 5-6/2023 str. 32     <-- 32 -->        PDF

Within the first plot (Plot 1) there was no anthropogenic influence, so this plot was defined as the control plot, while the treatment of pesticides was previously carried out on the second plot (Plot 2) during regeneration period. According to Rađević et al. (2020), on this plot, the pesticides application was conducted in order to protect oak seedlings from weeds, different pests and diseases. Rapid growth of weed vegetation can have adverse effects on the natural regeneration of oak stands (Posarić, 2010; Vasić et al., 2014; Vasić et al., 2022). Pesticide treatments were performed in accordance with the FSC policy (Rađević et al., 2020). The main goal of pesticides application was a successful regeneration of oak stands. Both plots (Plot 1 and Plot 2) were placed on natural soils. Based on the morphological features of the observed soil profiles, Gleysol was detected within the first and the second plot (Figure 2A and Figure 2B). The third location (Plot 3) was established on the anthropogenic soil, where the treatment of pesticides was not conducted. On the third plot, Gleysol as natural soil was under considerable anthropogenic influence, which diagnostic horizons are significantly altered and modified. Therefore, this soil type was determined as Anthrosol (Figure 2C). This soil type was formed during a site preparation for regeneration of stand. Soil organic carbon content in topsoil (0-10 cm depth) at Plot 1, Plot 2 and Plot 3 ranged from 0.93%, 4.1% and 0.11%, respectively. Ratio between CO2 flux and carbon stock is widely used parameter for determination of carbon sustainability in soil (Sarzhanov et al., 2017).
The total soil respiration (autotrophic and heterotrophic respiration) was measured using the closed chambers method. According to Schindlbacher et al. (2009) the contribution of autotrophic soil respiration to total soil respiration is the greatest in summer period. The field observation of CO2 emission was conducted during summer season (Jun, July and August) in 2021. The air sampling was performed using soil respiratory chambers (Avilov et al., 2014). The plastic base of each chamber was installed in the soil at the depth of 10 cm within each plot. The installation of bases was done two weeks before observation period in order to stabilize fluxes after soil disturbance (Buchmann, 2000). The first air sampling was carried out two weeks after insertion of bases to minimize the influence of severed fine roots on soil respiration (Laganière et al., 2012). Before sampling, the cylindrical chambers were attached on the top of the base, in hermetic condition. The air inside the chambers was homogenized by small fan, fixed at the top of the chamber. During sampling period, five chambers were placed at each plot. Gas extraction valve was installed on the chamber, and the sampling of air was carried out with a medical syringe. Three air samples were taken from each chamber. The air was sampled at 15, 30 and 45-min intervals (Heinemeyer and McNamara, 2011; Ming et al., 2018), after placing the chambers on the bases. Air samples were injected into glass vials and sent to the laboratory for analyses. The sampling was conducted at each plot once in every ten days. Samples collection was performed from 8:00 a.m. to 9:00 a.m. (five times during the season) as well as between 12:00 p.m. and 13:00 p.m. (two times during the season). Sampling was carried out at the same time on all experimental plots. Collected samples were analysed using the gas chromatograph Agilent 8890 (Agilent Technologies, Santa Clara, California, USA). A total of 315 samples was collected and analysed. CO2 flux was calculated for each plot using the formula according to Ming et al. (2018) based on the linear increase of the gas concentration inside closed chambers during the sampling time. The average values of CO2 flux were obtained based on values of emissions from five chambers placed within each plot. The obtained values of flux are expressed in g CO2 m-2 per day (Sarzhanov et al., 2015).