Impact of litterfall addition and exclusion on soil respiration in Cunninghamia lanceolata plantation and secondary Castanopsis carlesii forest in mid-subtropical China

Abstract

Aims Under elevated atmospheric CO2 concentration, an increase in the net primary production is likely to enhance the amount of litter inputs to forest soil. This study aims to determine the dynamics of soil respiration and soil carbon pool as affected by increased litterfall production. Methods A litterfall manipulation experiment was conducted in Cunninghamia lanceolata plantations and secondary Castanopsis carlesii forest stands in Chenda township of Sanming in Fujian Province, China, from January 2013 to December 2014, with treatments of litterfall exclusion, litter addition, and control (normal litterfall condition). Important findings (1) The value of temperature sensitivity index (Q10) shows a positive relationship with soil water content in the range 10% 25%, and drops below 1 at water content < 10%. Drought stress altered Q10 value and interrupted the coupling between temperature and soil respiration, as it reduced the diffusion of soluble carbon substrate and the extracellular enzymes, consequently, limited the microbial activity. (2) Linear regression analysis shows that soil respiration is significantly correlated with monthly litter mass (p < 0.05). In the treatments of the control and litter addition in the Cunninghamia lanceolata stands and that of the control in the Castanopsis carlesii stands, soil respiration was best correlated with litter mass two months ago in the treatment of the litter addition in the Castanopsis carlesii stands, soil respiration was best correlated with litter mass of the current month. (3) On average, the annual CO2 efflux was significantly reduced by litterfall exclusion, by about (362.0 ± 64.9) gC•m2•a1 in the Castanopsis carlesii stands and (96.2 ± 37.3) g C•m2•a1 in the Cunninghamia lanceolata stands compared with the control. Litter respiration contributed to 34.4% of soil respiration in the Castanopsis carlesii stands and 15.1% in the Cunninghamia lanceolata stands. Litter addition increased the soil respiration rate in both Castanopsis carlesii and Cunninghamia lanceolata stands, but the magnitude of the increase did not match up with the doubling of litter inputs, implying that under elevated atmospheric CO2 concentration, an increased litterfall inputs due to increases in the net primary production would be advantageous to the forest soil carbon sequestration.