Study on the effect of forest age and afforestation density on the timber properties of Larix principis-rupprechtii pulpwood in Saihanba
[Objective]To explore the influence of forest age and afforestation density on the timber properties of Larix principis-rupprechtii pulp forests,and to provide a theoretical and practical basis for the directional cultivation of L.principis-rupprechtii in the Saihanba area.[Method]Take L.principis-rupprechtii of 3 different ages(15,20,25 a)and 3 different initial planting densities(low density 2 500 plants·hm-2,medium density 3 300 plants·hm-2,high density 4 400 plants·hm-2)in Saihanba as the research object to study the influence of afforestation density on forest timber properties by two-factor randomized complete block design.[Result]1)The basic density of wood was only a significant difference between 20 a(0.439 g·cm-3)and 25 a(0.387 g·cm-3)at high density levels(P＜0.05),but there was no significant effect on afforestation density at different forest age levels.2)At the high density level,the latewood rate of wood first increased and then decreased with the increase of forest age(P＜0.05),which was similar to the change of the basic density of wood.At 15 a,the low-density(19%)stand was significantly smaller than the other two stands(P＜0.05).3)At 15 and 20 a,the annual rings width decreased significantly with the increase of afforestation density,and its peak and the age of the peak gradually decreased.At 25 a,there was no significant difference in the annual rings width between different afforestation densities,and its peak values(5.9,6.1,6.2 mm)and its occurrence(7,6,8 a)were similar,and it was considered that these standed enter the growth stability period from 25 a.4)At different density levels,with the increase of forest age,the tillering activity of the tree-forming layer gradually decreased,the intercellular space became smaller,the wood material became denser,and the annual rings width became smaller.5)When the forest age and planting density were small,the growth rate of the trees was faster,the fiber cells grew rapidly and evenly in the lateral and longitudinal directions,the cell wall was thicker,the fiber aspect ratio was small,and the fiber wall cavity ratio was large.When the forest age and the planting density gradually increased,the lateral growth of the fiber cells gradually slowed down,the cell wall gradually became thinner,the fiber length and width ratio increased(56.40-77.15),the wall cavity ratio became smaller(0.48-0.25),and the content of holocellulose decreased(73.18%-53.09%),indicating that the fiber cells had been fully elongated.6)The content of acid-insoluble lignin did not fluctuate much between forest fractions(20.98%-29.74%),and it increased slightly with the increase of forest age.There was no obvious consistent variation of the content of one percent sodium hydroxide solubility,phenyl alcohol extract and ash at the level of forest age or afforestation density.7)The pulp yield per hectare only varied significantly between stands with different afforestation densities in 15 a,and showed an upward trend with the increase of afforestation density,and the highest content among all stands was 15a high-density stand(68.47 t·hm-2).At the level of low-and medium-density stands,the pulp yield per hectare increased significantly with the older the forest.However,at the high density level,there was no significant difference between different forest ages.[Conclusion]According to principal component analysis and composite ranking,it was preliminarily believed that the 15 a 2500 plants·hm-2 stand had the best comprehensive pulp properties among the study stands,which could be used as the selection direction of directional cultivation of paper pulp materials in Saihanba area.
Larix principis-rupprechtiipulpwoodplanting densitypulp propertiesage of stand
万方数据
维普
