Abstract:

To research seasonal variation and influence factor of tree root respiration,the seasonal dynamics of root respiration of Fraxinus mandushurica were measured at a mixed forest of broad-leaved and Korean pine in the Changbai Mountain of Jilin,China.CO₂ effluxes rate was monitored using an infrared gas exchange analyzer (LI-COR-6400-06) from May to October 2007,and the influence factors,such as soil temperature,soil moisture and soil N contents were also measured in the forest.The results showed that the seasonal variation of root respiration accorded with that of the soil temperature at 10 cm depth,exhibiting single peak,with the maximum occurred in July and the minimum in October.The root respiration rate of the different diameter was between 1.02 μmol·g^-1s^-1 and 9.27 μmol·g^-1s^-1 during the growing season.A significant exponential correlation was found between the root respiration rate and soil temperature at 10 cm depth.The relationship between root respiration rate and the soil moisture could be described by a quadratic equation,and soil humidity in a certain range would promote root respiration rate，but excessive water in soil would inhibit root respiration rate.The root respiration rate increased linearly with soil N content,and its correlation decreased with increasing age of trees.The Q₁₀ values ranged from 2.21 to 2.71 at different diameters,which were enlarged with increasing age of trees.Q₁₀ value decreased with increasing the root diameter,and this result indicated the fine roots were more sensitive to the variable of soil temperature than the thick roots.

Key words: Changbai Mountain, Fraxinus mandushurica, root respiration, seasonal dynamics