Abstract: No data are available on greenhouse gas flux characteristics of biological soil crust (BSCs) in subtropical forests, which brings great uncertainty for estimating the regional greenhouse gas fluxes. In this study, we investigated the patterns of CO₂, CH₄ and N₂O exchange of BSCs and soils in condition of light or dark in a mid-subtropical Cunninghamia lanceolata plantation. Equal pressure sampling method was used to minimize the disturbance of soils. The gas samples were analyzed with gas chromatography (GC) (Shimadzu). Random forest algorithm was used to compare the effects of light and BSCs on the fluxes of greenhouse gases. The results showed that BSCs, light and their interaction significantly affected CO₂ flux (P<0.001). BSCs and light had significant effects on CH₄ absorption flux (P<0.001). Light and its interaction with BSCs exerted significant effects on the N₂O flux (P<0.001). Our results indicated that BSCs and light played important roles in soil greenhouse gas emissions in the study site. BSCs restrained soil CO₂ emission under dark condition. BSCs slightly increased N₂O flux and significantly increased CH₄ absorption flux (P<0.01). Moreover, CO₂, CH₄ and N₂O fluxes of BSCs were significantly decreased under light condition. Light had greater effect on CO₂ and N₂O flux than on BSCs, whereas BSCs had greater effect on CH₄ flux than light. Such a result indicated that the CO₂ and N₂O fluxes were associated with the photoautotroph of BSCs while chemoautotroph played a great role in CH₄ flux.

Key words: light inhibition, broad-leaved Korean pine forest., mature tree, sapling, leaf dark respiration