Temperature sensitivity of soil carbon dioxide efflux in beech-hornbeam stand (Case study: Shast-kalateh Forest, Gorgan)

The way temperature affects the soil respiration remains still unknown, which causes uncertainties in predictions of future trajectories of the global carbon cycle. Temperature sensitivity of soil respiration (Q10) is a key indicator for estimating soil respiration feedback to global warming. The purpose of this study was to investigate the temperature sensitivity of total soil respiration based on temporal changes in soil temperature and moisture contents in a beech-hornbeam stand. Therefore, we first determined 12 sample plots (six sample plots in the gaps and six under canopy cover) with 3×3-meter dimension. Sampling was conducted in three randomized points of each sample plot. At each sample point, soil respiration was monthly measured using a closed dynamic chamber throughout the year. The results showed a significant correlation between Q10 and some environmental variables, including soil temperature and moisture contents and also air temperature (p < 0.05 and p < 0.01). In addition, the temperature sensitivity of soil respiration was higher under canopy cover plots than that of in gaps. Although the lowest soil respiration rate was observed in winter (0.94 mmol m-2 s-1), the highest temperature sensitivity of soil respiration in this season (4.23) was observed under canopy cover plots. Thus, a slight increase in soil temperature, especially in winter, would result in a significant change in the rate of respiration of the entire soil and the adoption of a carbon cycle equilibrium in the forest stands of this area.