Abstract: By using a dynamic IRGA method, seasonal changes of stem respiration rate in two larch plantations with different ages were studied. Relationship between stem respiration rate and environmental factors were analyzed. Stem respiration rates of larches of both ages increased during spring and summer, and peaked in July (the mature forest) and August (the young forest). During autumn, stem respiration rates declined sharply. Stem respiration rate of the young larch stand, ranged from 1.99 to 6.15 μmol·m^-2·s^-1, was significantly higher than that of the mature larch stand, ranged from 1.52 to 3.38 μmol·m^-2·s^-1(P<0.05).There was an exponential correlation between stem respiration rate and stem temperature. The temperature coefficient Q₁₀ values for stem respiration of the mature forest and the young forest were 1.96 and 3.44 respectively. There was no obvious regularity between stem respiration rate and relative humidity at the lower atmospheric relative humidity, however, stem respiration was apparently promoted at higher relative humidity range.

Key words: Larix gmelinii, stem respiration, stem temperature, Q₁₀, atmospheric relative humidity