| The Pinus koraiensis forest in Xiao Xing'an Mountains is a pristine forest with Pinus koraiensis and Abies as the dominant species.There are abundant tree layer,shrub layer and herb layer.According to the present situation of Xiao Xing'an Mountains,some necessary management measures need to be carried out.Fertilizer application formula is a rapid and effective method to increase soil nutrients.Using Picea spruce and Korean pine forest in Xiaoxing'an Mountains as research sample,four nitrogen?N?treatment level plots with uniform site conditions were established as control(CK,0g N m-2·a-1)low N(LN,2.5 g N m-2·a-1).Medium N(MN,5.0 g N m-2·a-1)High N(HN,7.5g N m-2·a-1N)treatment.Three dominant trees and two shrubs were selected to determine the contents of C,N,P in litters,roots and fresh leaves at different N levels.The purpose of this study was to clarify the distribution pattern of the contents and stoichiometric ratios of the elements in the leaves and roots of the aboveground and underground organs of the plants in Xiaoxing'an Mountains,and to reveal the reabsorption rate of the elements before leaf withering.The correlation of elements and their stoichiometry and their responses to N deposition were discussed.The main results were as follows:?1?There were significant differences in N and P nutrient contents in fresh leaves,roots and litter of Acanthopanax senticosus,but N:P in fresh leaves of Acanthopanax senticosus had no significant effect.The N content of the root of Lonicera japonica Thunb was significantly lower than that of fresh leaves and litter.Different N treatments had no significant effect on the root and litter of fresh leaves of Lonicera japonica Thunb.The N content of fresh leaves of Lonicera japonica Thunb under MN treatment was higher than that of the control group.The contents of N and P in fresh leaves,roots and litter of Pinus koraiensis were significantly different,and each application of N had no significant effect on N:Pin fresh leaves.There were significant differences in C and N contents between fresh leaves and roots of Abies chinensis.Different N treatments had no significant effect on C:P,C:N and N:P,but fresh leaves and roots of Acer mongolicum had no significant effect on the contents of C and N,but there was no significant difference in C and N contents between fresh leaves and roots of Abies chinensis.Litter There was a significant difference in the N content,and the N:P of fresh leaves was not significantly affected by different N treatments.?2?There is a difference in the nutrient content of different functional groups,that is,the C content of the tree leaves in the dominant species of the Abies in the Xiaoxing'an Mountains is higher than that of the shrub,and the content of N and P of the fresh leaves of the arbor is significantly lower than that of the shrub.?3?The N:P of all the dominant species in the red pine forest of the Abies in the Xiaoxing'an Mountains is less than 14,indicating that the area is limited by the N,and the N:P increases with the application of the foreign N,and the shortage of the N is relieved.Therefore,proper N addition is beneficial to the growth of the plants in the Xiaoxing'an Mountains.?4?under different levels of nitrogen application,the N:P in the leaves of each dominant tree species in the Picea spruce forest in Xiaoxing'an Mountains was less than14,which indicated that the Xiao Xinganling Mountains was restricted by N. |
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