Effects of litter exclusion and addition on soil respiration of major forest communities at two successional stages in Maolan karst forest of southwestern China.

With communities at two successional stages, i.e., primary forest (PF) and secondary forest (SF), in karst region of Maolan National Nature Reserve as the research object, and using the portable system of infrared gas exchange analyzer (LI-Cor-6400-09), we studied the effect of litter exclusion and addition on soil respiration rate and soil temperature at the depth of 5 cm by changing the litter input. The results showed that there was no significant difference in soil temperature (P0.05) between two successional stages when changing the litter input, both following the order of litter additioncontrollitter exclusion. In the litter addition experiment, the annual soil respiration rate was 2.98 mol/(m2s) in PF and 3.31 mol/(m2s) in SF, which was 32.21% and 26.20% higher than that of control. In the litter exclusion treatment, the annual soil respiration rate was 2.07 mol/(m2s)in PF and 2.14 mol/(m2s) in SF, which was 17.41% and 22.36% lower than control, respectively. The results demonstrated that forest litter was an important factor affecting forest CO2 flux. At both successional stages, there was a significantly exponential correlation between soil respiration rate and soil temperature at 5 cm depth (P0.001), which could explain more than 85% of variation in soil respiration rate (R2 ranged from 0.877 0-0.957 7). The temperature sensitivity coefficient of soil respiration Q10 of litter exclusion, litter addition and control treatment were 2.97, 3.89, 3.82 in PF and 2.74, 3.29, 2.87 in SF, respectively, and they all presented the order of litter exclusioncontrollitter addition.