Study On Root Respiration Of Natural Fraxinus Mandshurica Trees In Changbai Mountain

To explore root function, scientifically and reasonably classifying root diameter, root respiration of natural Fraxinus mandshurica trees grown in the Changbai Mountain and its short-term responses to temperature, humidity and nutrient availability were studied in the paper. And the main results were as follow:1. The highest total root respiration rate of Fraxinus mandshurica occurred in July when the forest root growth and physiological activity is more active. The minimum value of root respiration rate of the trees of 16,25,29 and 47year-old appeared on May, and followed by November. The most possible reasons may be related to the low soil temperature and the physiologically unactive root.2. The root respiration rate of different root diameter would increase with the root diameter, and was obviously diffrenet among the root in different diameter(sP<0.01). But, the root respiration rate per root volume was significantly decrease with the increase of root diameter (P=0.048) while the specific root respiration rate was not significantly increase with diameter (P = 0.11).3. Based on the root surface area and root mass, the relationship is consistent with total root respiration rate, which are between maintenance root respiration rate, growth respiration rate and different root diameter relations. That is basing on root surface area , root respiration rate of different root diameter was increase with diameter ; and basing on dry root biomass , it reduces with diameter. The relation between growth respiration rate and different root diameter which is determined in the base of root volume, is also consistent with total root respiration rate, but is opposite with maintenance respiration. And the proportion that maintenance respiration ccounting for is increased with the increasing of the diameter.4. Root respiration rate of Fraxinus mandshurica was obviously increase with temperature. At the same temperature, root respiration rate based on root surface increases with the increase of root diameter while root respiration rate based on volume and mass changed oppositely.5. Root respiration rate of Fraxinus mandshurica was obviously affected by the fertilization of nitrogen.The sensitivity of root respiration based on root volume and mass response to the fertilization of nitrogen was higher than root respiration based on root surface area, but the difference of N treatment between them were both significantly (P <0.001).6. Respiration rate of root in diameter of <2mm, 2~5mm and >5mm positively correlated to the soil temperature, soil moisture and soil nitrogen, namely, root respiration rate of different root diameter increased with soil temperature, soil moisture and soil nitrogen contents in a certain extent.