Aims Partitioning the soil respiration is an important step in understanding ecosystem-level carbon cycling. In addition, the heterotrophic and autotrophic components of soil respiration may respond differently to climate change. Our objectives were to evaluate the impact of soil temperature and water content on soil respiration and its components in Castanopsis carlesii and Cunninghamia lanceolata plantations, to determine the relative contributions of autotrophic and heterotrophic respiration to soil respiration, and to explore how different forest types would affect soil respiration and its components.
Methods The study site is located in the Nature Reserve of Castanopsis kawakamii, Fujian Province, eastern China. By using a field setup through trenching method and LI-8100 open soil carbon flux system, the dynamics of soil respiration were measured from August 2012 through July 2013. Soil temperature at 5 cm depth and water content of the 0-12 cm soil layer were measured concurrently with the measurements of soil respiration. Relationships of soil respiration with soil temperature and water content were determined by fitting both an exponential model and a two-factor model.
Important findings Soil respiration and its components showed significant correlations with soil temperature. There were significant monthly changes, in the form of a single-peaked curve, in soil respiration and its components in the two forest types. Soil temperature explained 70.3%, 73.4%, and 58.2% of the monthly variations in soil respiration, autotrophic respiration, and heterotrophic respiration, respectively, in the Castanopsis carlesii plantation; whilst it explained 77.9%, 65.7%, and 79.2% of the monthly variations in the three variables in the Cunninghamia lanceolata plantation. There was no significant relationship between soil respiration and soil water content in both forest types. The annual estimates of CO2 efflux through autotrophic respiration in the two types forests were 4.00 and 2.18 t C·hm-2·a-1, respectively, accounting for 32.5% and 24.1% of soil respiration. The annual estimates of CO2 efflux through heterotrophic respiration were 8.32 and 6.88 t C·hm-2·a-1, respectively, accounting for 67.5% and 75.9% of soil respiration. The annual estimates of CO2 efflux through soil respiration and partitioning of the components were all higher in the Castanopsis carlesii plantation than in theCunninghamia lanceolata plantation.