| Taking two experimental areas of young and middle-aged Picea asperata plantation in Shatan national forest park,Gansu as the research objectives.The spatial structure(mingling degree,neighborhood comparison,uniform angle index),non-spatial structure(stand age,DBH,height,volume)and ecological service function(soil conservation,accumulation of nutrients,atmosphere purification,biodiversity conservation)of forest after five different adjustment measures and a no-optimizing(control)treatment were investigated and analyzed continuously for 6years.The five kinds of structural adjustment methods are The forsook,sanitary cutting,mechanical thinning(Cut one row every one row,Cut one row every two rows),and ecological thinning adjustment measures,hereinafter referred to as FJ,WF,JF1,JF2 and SF.In order to analyze the effect of different structural adjustment methods on the structure and growth of forest,the structure adjustment scheme and function recovery model of different age Picea asperata plantation were discussed.It provides the basis for the scientific,efficient and sustainable management of the Picea asperata plantation in subalpine region,and promotes the ecological recovery process of high altitude ecological fragile area.The main results are as follows:(1)We found that structural adjustment were significantly influenced the average DBH of the stand,growth of height and diameter,individual volume and volume growth.After ecological thinning 6 years,the growth of diameter,height,individual volume,volume in the middle-aged forest respectively were21.5,14,18.1 and 18.2times higher than that of control trees.the growth(6years)of diameter,height,individual volume,volume in the young forest respectively were 14.2,8.4,10.2 and10.4 times higher than that of control trees.the effect is most obvious.After structural adjustment,the 6 years growth of diameter,height,individual volume,volume of young forest were higher than that of the middle-aged forest.The growth rate of average biomass of the middle-aged forest was higher than that of young forest in 6years.(2)The structure adjustment not differ significantly increased the degree of spatial separation,which had less influence on the size differentiation of trees,and the forest uniform angle index was decreased significantly.The left side of the frequency is greater than the right side,it was near the normal distribution,and the stand spatial distribution pattern was adjusted for random distribution or uniform distribution.(3)After the structural adjustment of 6 years in young and middle-aged Picea asperata plantation,the shrub and herbaceous community richness of SF and JF2were significantly increased compared with that of the control group.shrub,herbaceous diversity index and evenness index of JF2 was the highest,while community dominance index was the lowest.After the adjustment of the same structure,the diversity index,evenness index and dominance index of the middle-aged forest were lower than that of the young forest.After SF,soil bulk density of young and middle-aged forest change is the largest,the bulk density is the least,which were 0.609~0.897g/cm~3 and 0.503~0.691g/cm~3,and the maximum porosity were between 63.0%~77.0%and 57.0%~71.0%.The surface soil saturated water content,the capillary water content,and the field water holding of SF were the highest,respectively,the middle-aged forest was 3.2,3.0 and 2.0 times higher than that of the control group,the young forest was 2.7,1.9 and 2.6 times higher than that of the control group.The soil porosity,saturated water content,capillary water content and field water content gradually decrease with the increase of soil depth,and soil bulk density gradually increases with the increase of soil depth.(4)The pH value of soil was not obvious after structural adjustment,and the pH value of soil was between 5.87 and 7.16.There was no significant difference in total nutrient content and effective nutrient content of middle-aged andyoung forest soil.Soil organic matter,total N content,total P content,total K content change significantly,organic matter content between 4.779~16.976 g/kg,total N content between 0.53~6.52 g/kg,total P content between 0.621~3.84 g/kg,total K content between 14.83~34.32 g/kg,After sanitary cutting 6 years,organic matter,total N content,total P content,total K content were the highest;There was a significant change of soil available nutrient in forestland.the available N,K of WF have the highest content,the available P of JF1 has the highest content.The content of soil organic matter,total N content and total P content decreased with the increase of soil depth,and the total K content did not decrease with the increase of soil depth.(5)The leaf area index of young and middle-aged Picea asperata plantation was decreased after structural adjustment,and the leaf area index of SF and JF forest was significantly different,and its LAI was significantly less than that of control.(6)There was significant difference in the concentration of atmospheric oxygen anion of different structural adjustment,and the concentration of atmospheric oxygen anion of the ecological thinning was significantly higher than that of other structural adjustment methods.Diumal changes manifested as concentration of atmospheric oxygen anion in the afternoon is less than in the morning.The results of our comprehesive analysis show that the most effective forest adjustment measures for Picea asperata plantation is to conduct SF and JF2 in young forests which the stand density was 3675~4800 trees per hectare,but only SF in middle-aged forests which the stand density was 1630~2151 trees per hectare.However,to achieve an increase in stand DBH and total volume growth,the stand density should be 3030~3240 trees per hectare in young forests,around 1500 trees per hectare in middle-aged forests. |
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