Abstract: By using a Li 820 infra red CO₂ gas analyzer, an in situ measurement of  Schima superba stem CO₂ efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO₂ concentration were measured. The stem CO₂ efflux had a diurnal variation of “S” pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO₂ efflux and stem temperature (0.24<R²<0.78). The temperature coefficient (b) and regression coefficient (R²) were higher at nighttime than at daytime, and the Q₁₀ value ranged from 2.01 to 2.79. The stem CO₂ efflux correlated significantly with the xylem CO₂ concentration, and the best regression curve was cubic (R²=0.48). Excluding the effects of stem temperature, the stem CO₂ efflux showed a significant negative correlation with xylem sap flux density (r = -0.462). Therefore, only using simple temperature function to estimate stem CO₂ efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO₂ efflux estimation.

Key words: Earthworm feces, Systemic induction resistance, Polyphenol oxidase, Peroxidase, Phenylalanine ammonia-lyase, Anthracnose