Aims Soil respiration is one of the most important components in the carbon (C) cycle in terrestrial ecosystems. To investigate the contribution of each component of C cycle to the total soil C efflux, we quantified the rates of litter, root, and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island, China.
Methods The seasonal dynamics of soil (R s), non-litter (R NL) and non-root (R NR) respiration rates were measured using an automatic chamber system (Li-8100). Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground C production. We estimated the annual C efflux of each component of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.
Important findings The annual total soil C efflux was significantly higher in the primary rain forest (1567±205g C m ?2 yr^-1) than that in the secondary forest (1300±70g C m ?2 yr^-1, P < 0.05). The litter, root, and mineral soils contributed 22% (349±185g C m ?2 yr^-1), 38% (589±100g C m ?2 yr^-1), and 40% (628±128g C m ?2 yr^-1) to the total soil C efflux in primary rain forest, respectively. In secondary forest, these three components contributed 11% (148±35g C m ?2 yr^-1), 45% (572±259g C m ?2 yr^-1), and 44% (580±226g C m ?2 yr^-1), respectively. The temperature sensitivity (Q 10) of R s (2.70±0.14) in the primary forest was significantly higher than that in the secondary forest (2.34±0.12), with the Q 10 values for respiration decreasing in the order of R NR> R s> R NL. These results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types. In addition, the litter respiration is more sensitive to the soil temperature than the other soil respiration components.