Litter decomposition involves multiple complex processes, including interactions between the physicochemical characteristics of litter species and various environmental factors. We selected four representative pine species in South Korea (Pinus densiflora Siebold & Zucc., Pinus thunbergii Parl., Pinus koraiensis Siebold & Zucc., and Pinus rigida Miller) to investigate the decay rate and effects of the physicochemical properties on decomposition. Needle litters were incubated in microcosms at 23 °C for 280 days and retrieved four times in about 70-day intervals. The mass loss showed significant differences among the species and was higher in the order of P. densiflora (30.5%), P. koraiensis (27.8%), P. rigida (26.5%), and P. thunbergii (23.6%). The needle litter decomposition showed a negative relationship with the initial surface area, volume, density, cellulose content, and lignin/nitrogen of the litter, and a positive relationship with the initial specific leaf area (SLA), surface-area-to-volume ratio (SA/V), and water- and ethanol-soluble substances. The decomposition rate was highly affected by the physical properties of litter when compared with the initial chemical litter quality, and it was strongly influenced by SLA and SA/V. Accordingly, the physical properties of pine needle litter, especially SLA and SA/V, may be the key factors, and they could be used as predictive indices for the decomposition rate of pine tree litters.

Litter decomposition is a critical process for the maintenance of terrestrial ecosystems. Although large quantities of organic matter and nutrients are supplied by branch litter, its decomposition has received little attention. In this study, we focused on Quercus mongolica, one of the most common temperate deciduous woody species in the Northern Hemisphere, to investigate the age-related decomposition rate of branches. Branches of different age classes (2, 4, 7, 10, and 13 years), downed after a summer windstorm, were collected, and mass loss was measured over 24 months using the litterbag method. Litterbag samples were retrieved every 4 months and analyzed for dry weight, carbon (C), nitrogen (N), lignin, and cellulose concentration, and also two litter quality indices (C/N and lignin/N) were calculated. Mass loss by decomposition was significantly faster in 2-year-old branches (34.78 %) than in 13-year-old branches (25.71 %). Branch decomposition showed a negative relationship with the initial C concentration, C/N, and lignin/N, but a positive relationship with the initial lignin and N concentrations. The decomposition rate differed significantly between different branch age classes and initial litter qualities and was strongly influenced by the initial N concentration and C/N. Overall, the results showed that total N and C/N might be the key factors in the decomposition of Q. mongolica woody materials, and they could be used as predictive indices of branch decomposition in future studies.

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