Aims Our objectives were to quantify the loss of coarse woody debris (CWD) mass, carbon (C) and nitrogen (N) and main influencing factors during the first three years of CWD decomposition of 11 major tree species in Chinese temperate forests based on an in situ long-term experiment.

Methods The experimental design was completely randomized blocking design of 11 species × 6 blocks × 4 sites. The species were white birch (Betula platyphylla), Amur linden (Tilia amurensis), Korean pine (Pinus koraiensis), Manchurian walnut (Juglans mandshurica), cork-tree (Phellodendron amurense), Mongolian oak (Quercus mongolica), Dahurian larch (Larix gmelinii), Mono maple (Acer mono), Manchurian ash (Fraxinus mandshurica), popular (Populus davidiana), and Japanese elm (Ulmus japonica). The four sites with various environmental conditions were Mongolian oak forest, hardwood forest, Korean pine plantation and open field. We randomly selected three CWD samples for each tree species in each site and cut a 5 cm-thick disc at the end of the CWD in October 2005 and October 2008, respectively, for measuring C concentration, C density, N concentration, N density, C/N ratio and CWD density.

Important findings The C concentration of CWD did not change significantly during the early stage of CWD decomposition for all species (p > 0.05). The CWD mass, C density, N concentration and N density decreased during decomposition, whereas the C/N ratio increased. The differences in these parameters among the species were significant (p < 0.001). The coniferous species had significantly lower decomposition rates than the broad-leaved species. There was a negative correlation between size and decay rate. Loss of mass and release of C and N of the CWD were positively correlated with the initial N content, but negatively correlated with the initial C/N ratio. The changes of mass and C and N content of CWD had similar patterns at the four sites. Our results indicated that the CWD tended to be C and N sources during the first 3-year decomposition process.