The roles of initial litter traits in regulating litter decomposition: a “common plot” experiment in a subtropical evergreen broadleaf forest

Background and aims Leaf litter decomposition constitutes a valuable ecosystem service by recycling nutrients, transferring energy, and sequestrating carbon (C) in terrestrial ecosystems. However, variations in microclimate and decomposers among studies have impeded a mechanistic understanding of what controls litter decomposition. We conducted a “common plot” experiment leveling-off impacts of environmental and biotic factors to explore roles of the initial leaf litter traits in decomposition. Methods The experiment was carried out in an evergreen broadleaf forest in the Wuyi Mountains from May 2017 to August 2018. Leaf litter was collected from Populus deltoids in a nitrogen (N) addition experiment at Dongtai Forest Farm, Liriodendron chinense × tulipifera and Platanus acerifolia on campus Nanjing Forestry University, and Quercus variabilis and Pinus taeda at Xiashu Forest Farm. Results Our results showed that N addition significantly increased leaf litter decomposition of P . deltoids . This may result from N induced increases in litter quality, indicated by a high N content and a low C:N ratio of leaf litter. Across the five tree species (with no litter from P . deltoids under N addition treatment), we found litter decomposition of the coniferous tree ( P. taeda ) was much lower than that of the other four broadleaf trees due to its lower litter quality. Multiple regression analyses indicated that the initial C:N ratio and sodium (Na) content that was critical for decomposers dominated decomposition. Conclusions Our results confirmed the importance of the initial litter quality, such as C:N ratio, in regulating leaf litter decomposition. In addition, our results suggest the Na control of the decomposition of leaf litter in subtropical ecosystems through Na limiting the activity and abundance of decomposers in brown food webs.