| Catalpa bungei C.A.Mey(Bignoniaceae)is a deciduous broadleaf trees.It is a valuable native species which distribute broadly because of strong adaptability and ecological value.Catalpa bungei is valuable timber species and commonly used ornamental trees.Its wood is known as the “wood king” and is also an important tree species in the current forestry industrial restructuring.With the people’s demand for precious wood has increased dramatically,to cultivate largediameter-class and non-knot timbe is very impotrant.Artificial pruning is a key technical measure in the process of largediameter-class timber cultivation,and there were few research on the artificial pruning technology for the precious timber species of northern China.Therefore,this study used four-year-old Catalpa bungei young forests as research objects to study the growth,nutrient physiology,non-structural carbohydrates,leaf functional traits and pruning incision healing of young forest Catalpa bungei from different pruning strengths.To explore the effects of different pruning strength on the productivity of Catalpa bungei young forest plantations,and would provide technical support for the scientific formulation of Catalpa bungei young forest pruning scheme.The experimental study plot was located in Shishou City,Hubei Province.A total of 3 pruning strengths and 1 no pruning control were set,and 1/2,1/3,1/4 crown height and CK no pruning control were removed.Spring pruning test was conducted on March 24,2018.A total of 3 pruning combinations(1/2,1/3,1/4)and 1 no pruning control(CK)treatment,3 replicates per treatment,a total of 12 plots,each plot 60 Catalpa bungei trees.The tree height,DBH,height of the branches and conventional soil data of all Catalpa bungei trees in the plot were measured before pruning.After that,the growth,leaf functional traits,nutritional physiology and incision healing of Catalpa bungei were measured every two months.The main findings of this study are as follows:(1)The different pruning strengths of the experiment have little effect on the growth of young Catalpa bungei forests.During the year of pruning,different pruning strengths only have a significant effect on the DBH increment and height-diameter ratio(P<0.05).The effect on tree height increment and single plant volume was not significant(P>0.05).The DBH increase,tree height increase,height-diameter ratio and single-crop volume of the Catalpa bungei under the pruning intensity of 1/3 crown were less than the control group,and were higher than the 1/4 crown and 1/2 crown.Pruning strength treatment;(2)Different pruning strength had no significant effect on the nutrition and physiology of young Catalpa bungei forests(P>0.05);however,the results showed that pruning reduced the organic carbon content and phosphorus content of leaves in comparison with no pruning.Potassium content in shoots and shoots,organic carbon content,total nitrogen content and total potassium content of shoots were higher than those of the other two treatments under the treatment of 1/3 crown and 1/4 crown,and total nitrogen,total phosphorus and total potassium were observed.The content increases with the increase of the pruning strength;(3)The content of non-structural carbohydrates in annual branches and leaves of young Catalpa bungei forests was significantly affected by pruning strength(P<0.05),and only the soluble sugar content of shoots was significantly affected by pruning strength(P<0.05),the starch content of the shoots and the soluble sugar content and starch content of the leaves were not significantly correlated with the pruning strength(P>0.05).The soluble sugar content of the branches treated with 1/2 crown was significantly lower than that of the no pruning control;(4)The functional traits of young Catalpa bungei forests were also statistically significant due to the pruning intensity,which had a significant effect(P<0.05).In the study,only the stomata width,stomatal shape index and specific leaf weight were observed.The effect of pruning intensity was significant(P<0.05).The stomatal density,length,area and perimeter were not significantly related to pruning strength(P>0.05),but the overall trend was to remove the 1/4 crown treated leaves.The stomatal index was the highest,and the treatment of removing 1/3 of the crown height was second,but the specific leaf weight of the 1/3 crown was the largest;(5)The incision healing rate of young leaves of Catalpa bungei forest was not significantly affected by pruning intensity within one year after pruning(P>0.05),and was significantly affected by the diameter of the incision(P<0.05).The diameter of the incision was less than 5 cm.The healing rate of the incision was significantly larger than that of the incision of more than 5 cm.From the relationship between the healing rate of the incision and the pruning intensity,although the statistical significance was not reached,the incision healing rate was the highest under the pruning intensity of the 1/3 crown,the treatment of 1/2 crown height is the lowest.Based on the above research results,the pruning strength of 1/3 crown can be restored to the recovery and growth of Catalpa bungei after one year in the Catalpa bungei artificial young forest.The best short-term Catalpa bungei young forest pruning technology plan was proposed,which provided technical support for the Catalpa bungei large-diameter cultivating of sapwood. |
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