Effect Of Nitrogen On The Root Respiration Of Pinus Tabulaeformis, Platycladus Orientalis And Pinus Bungeana

To explore the effect of nitrogen addition on root morphiology and root respiration, root architecture and root respiration charecteritics were studied on basis of Pinus bungeana, Pinus tabulaeformis and Platycladus orientalis trees in the paper. Results were as following:(1) Root length, root surface area, root volume in all diameter of three species were increased remarkably with the N fertilization. Comparing with the low nitrogen fertilization, root length, root surface area, root volume of the three trees with high nitrogen fertilization reduced. Fertilization can obviously influence the proportion of root length, root surface area, root volume account for total root length, root surface area, root volume of all diameter. The results showed that proper fertilization of N can promote the root length, root surface area, root volume extension, so that tree roots can absorb more moisture and nutrition, but fertilization of high nitrogen limits root extension.(2) Distributing range of different root order of the three species in different root diameter showed that the first root order distributed in smaller root diameter, along with the increasing of the root order, distributing range of the second, the third and the fourth order root length enlarged gradually, more than 90% of the first order root of total length distributed in the diameter<0.05mm range. The change trend of root surface area is the same with the root length.(3) The highest total root respiration rate of Pinus bungeana, Pinus tabulaeformis and Platycladus orientalis occurred in August or September, the highest total root respiration rate of Pinus tabulaeformis occurred in August, while Pinus bungeana and Platycladus orientalis in September. The lowest root respiration rate appeared in early May, and root respiration rate of Pinus tabulaeformis was the lowest, the second is Platycladus orientalis, Pinus bungeana is the highest, the most possible reasons maybe related to their physiology movement and species characteristics.(4) Root respiration rate of Pinus bungeana, Pinus tabulaeformis and Platycladus orientalis was obviously affected by the fertilization of nitrogen, root respiration rate of different root diameter and N treatments based on root surface area, volume and root mass are all reached the highest in low nitrogen treatment, and the control treatment is the lowest. The sensitivity of root respiration response to diameter was higher for three species than that for nitrogen treatment, but the difference of N treatment between them were significantly.(5) The change trend of the growth respiration of the tree three species was similar, root respiration of the three tree species that based on surface, volume and quantity all accounted for about 60% of the total root respiration And root respiration of Pinus tabulaeformis and Platycladus orientalis were greater than that of Pinus bungeana. However, the proportion of maintenance respiration accounted for the total respiration was different with that of growth respiration in all diameters.N treatment had significant influence on root maintenance respiration and growth respiration. Lower N treatment obviously increased both maintenance respiration and growth respiration, and the change trend of root respiration rate that based on surface, volume and weight was the same. Maintenance respiration of trees with lower N treatment was the highest, that of trees with higher N treatment was the second and that of the contrast was the lowest. For the proportion that maintenance respiration accounting for total respiration, that with higher N treatment was the highest in all. However, the difference among different treatments was not obvious.