半干旱区不同杨树品种及造林密度对林分生长和叶片抗旱性状的影响OA

[Objective]This study explored the growth and leaf drought resistance-related traits of poplar under natural semi-arid conditions in response to different plantation densities,thereby offering valuable insights for the precise matching of poplar varieties to site conditions in semi-arid regions.[Method]At the Meng'e Shasheng Plant Park in Dalate Banner,Inner Mongolia,three poplar varieties,Populus deltoides'Zhelin 4',P.×simonii'Huilin 88'and P.deltoides×P.suaveolens'Zhongxiong 4',planted in high plantation density(2 m×3 m)and low plantation density(3 m×3 m),at their five years old,were selected as the research objects,the characteristics of growth,leaf anatomical structure,photosynthetic parameters,proline and other physiological and biochemical indexes were observed and analyzed.Principal component analysis and membership function synthesis method were used to evaluate the differences.[Result](1)The average DBH and average tree height of the three poplar varieties under low plantation density were significantly higher than those under high plantation density,with an average increase of 45.73%and 20.52%,respectively.The growth performance of'Zhongxiong 4'under the two plantation densities was better,and the leaf thickness was significantly higher than that of other varieties.Under low plantation density,the leaf thickness and palisade to spongy ratio of'Zhongxiong 4'were significantly increased compared with high plantation density,indicating that the leaf structure of'Zhongxiong 4'was more suitable for low plantation density.(2)From low plantation density to high plantation density,the net photosynthetic rate(Pn)of the three poplar varieties decreased significantly.The Pn of'Zhongxiong 4'and'Huilin 88'decreased by 12.02%and 16.05%,respectively,while the Pn of'Zhelin 4'decreased by 48.26%.The transpiration rate(Tr),instantaneous water use efficiency(WUEi)and stomatal conductance(Gs)of'Zhongxiong 4'and'Huilin 88'were not significantly different between the two plantation densities.Tr and Gs of'Zhelin 4'decreased significantly under high plantation density and were lower than those of other varieties,indicating that the photosynthetic capacity of poplar was stronger under low plantation density.(3)At high plantation density,there was no significant difference in the contents of proline and soluble sugar among the three poplar varieties,the soluble protein content of'Zhongxiong 4'was significantly higher than that of other varieties.However,at low density,'Zhelin 4','Huilin 88',and'Zhongxiong 4'exhibited the highest concentrations of soluble sugar,proline,and soluble protein.This suggests that different poplar varieties may adapt to drought environment with different osmotic regulatory substances.[Conclusion]Under natural semi-arid conditions,low plantation density is more conducive to poplar growth,and different poplar varieties respond to plantation density through differenttrait indicators to adjust the drought adaptability of trees.The growth and drought resistance of the leaves of'Zhongxiong 4'were better under the two plantation densities,which could adapt to the construction of plantations with more plantation densities under the natural conditions of semi-arid region.