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Temperature sensitivity ( Q 10 ) of soil organic carbon (SOC) decomposition is an important index to estimate the dynamics of soil C budget. However, the spatial variation of Q 10 and its influencing factors remain largely uncertain. In this study, we reviewed the effects of climate environment, spatial geographic pattern, soil physicochemical property, vegetation type, microbial community composition and function, and global climate change on Q 10 to summarize the general rule of each factor influencing Q 10 and compare the relative contribution of each factor to Q 10 in different ecosystems. The results showed that Q 10 decreases with the increases of temperature and precipitation, but increases with the rise of latitude and altitude. The Q 10 value is higher in grassland than that in forest, and also in coniferous forest and deciduous forest than that in evergreen broad-leaved forest. Carbon quality is negatively correlated with Q 10 , but the C quality hypothesis is not always valid with exogenous substrate input. For example, the increment of substrate availability may significantly increase Q 10 in low-quality soils. Q 10 decreases with the enhanced proportion of r-strategy microorganisms (Proteobacteria and Ascomycetes), but increases with the enhanced proportion of K-strategy microorganisms (Acidobacteria and Basidiomycetes). Q 10 increases with elevated CO 2 concentration, but declines with atmospheric nitrogen deposition. In natural ecosystems, Q 10 is mainly regulated by temperature and C quality. Temperature is the main factor regulating Q 10 in the topsoil while C quality is the main factor in deep soil. Our review provided a theoretical support to improve the coupled climate-C cycle model and achieved the C neutral strategy under global warming.

A experiment on leaf litter decomposition was carried out to evaluate the effects of UV-B radiation on the chemical composition and subsequent decomposition of leaf litter in humid subtropical forest systems. The leaf litter was derived from Cyclobalanopsis glauca seedlings exposed to elevated and ambient ultraviolet B (UV-B) radiation treatments during growth for one year. The results showed that UV-B treatment significantly increased the original N, K and P content of leaf litter by 154.9%, 29.8% and 9.7%, respectively, and decreased the ratios of C: N, lignin: N and C: P of leaf litter by 60.5%, 61.7% and 8.5%, respectively (P < 0.05), but had no significant effect on C and lignin content. The decomposition of leaf litter derived from seedlings exposed to elevated UV-B treatment during growth was faster, but did not show significant difference from that of ambient UV-B treatment. Exposure to elevated UV-B radiation during growth did not significantly influence the K release, but promoted the P release and retarded the N accumulation during leaf litter decomposition. Our result will contribute to the better understanding of the role of UV-B radiation in moist subtropical forest ecosystem.

An investigation was made on the soil seed banks in the logging gaps of Populus davidiana--Betula platyphylla secondary forest, secondary broad-leaved forest, and broad-leaved Korean pine mixed forest at their different succession stages in Changbai Mountains. Among the test forests, secondary broad-leaved forest had the highest individual density (652 ind x m(-2)) in its soil seed bank. With the succession of forest community, the diversity and uniformity of soil seed bank increased, but the dominance decreased. The seed density of climax species such as Pinus koraiensis, Abies nephrolepis, and Acer mono increased, whereas that of Maackia amurensis and Fraxinus mandshurica decreased. Moreover, the similarity in species composition between soil seed bank and the seedlings within logging gaps became higher. The individual density and similarity between soil seed bank and the seedlings in non-logging gaps were similar to those in logging gaps. All of these indicated that soil seed bank provided rich seed resources for forest recovery and succession, and the influence of soil seed bank on seedlings regeneration increased with the succession.

The litters of seven tree species representing the dominant plant species in three main successional stages in subtropical China, i.e., Pinus massoniana in early successional forests, Schima superba and Cinnamanun camphora in transitional forests, and Castanopsis eyeri, Cyclobalanopsis gracilis, Cyclobalanopsis glauca, and Michelia chapensis in late successional forests, were collected, and their decomposition rates were measured with litterbags. The results showed that M. chapensls and C. gracilis had the highest litter decomposition rate (k = 1.12 and 0.89, respectively), followed by C. camphora and S. superba (k = 0.61 and 0.55, respectively), and P. massoniana (k = 0.51), indicating that there was a trend of litter decomposition rate being increased with succession stage. Litter decomposition rate had significant correlations with the litter' s initial P, N, and lignin contents, lignin/N ratio (P < 0.01), and C/N ratio (P < 0.05), suggesting that the initial P, N, and lignin contents and lignin/N ratio of leaf litter could be the good indictors of litter decomposition rate.