The Research On Growth Regularity And Biomass On Distribution Characteristics Of 30-year-old Keteleeria Cyclolepis Flous

Keteleeria cyclolepis Flous.is a unique tree species of Pinaceae in China.Its trunk shape is straight,growth is fast,wood hardness is moderate,value is high,at the same time,branches and leaves are luxuriant,evergreen all the year round,sprouting ability is strong,suitable for pruning modelling,is a good timber and garden greening tree species.With the improvement of forest quality and the implementation of tree species structure adjustment project in China,the research and development of Keteleeria cyclolepis Flous,a precious native tree species,has been intensified in recent years in China,especially in Guangxi.,and breakthroughs have been made in the selection of excellent provenance families,seedling breeding and cultivation techniques.However,due to the lack of systematic research on the growth law and biomass distribution characteristics of Keteleeria cyclolepis Flous,and the phenomenon of young stump seedlings takes a long time,and the understanding of the growth process and cycle of the tree species by forestry production units is seriously deviated,which has seriously hindered the promotion and planting of tree species.In order to change the above situation,this study took 30-year-old Keteleeria cyclolepis Flous from Hezhou,Guangxi,as the research object,and used the method of full digging standard trees in different layers and zones,through the investigation of tree measure factors and the analysis of tree trunk,to clarify the growth regularity and biomass composition of Keteleeria cyclolepis Flous.At the same time,the structure and distribution characteristics of biomass in different organs of Keteleeria cyclolepis Flous were systematically studied by constant weight drying method,aiming at providing theoretical basis for artificial cultivation,management and extension of cultivation for Keteleeria cyclolepis Flous.The research results showd that:(1)30-year-old Keteleeria cyclolepis Flous hasn't reach quantitative maturity.The average DBH of 30-year-old Keteleeria cyclolepis Flous was 27.9 cm,the average tree height was 18.8 m,the experimental form factor was 0.44,the breast-height form quotient was 0.74.Its trunk type is straight,its wood outturn is high,its growth is fast,and its annual DBH can reach more than 1 cm a year.It has the characteristics of excellent timber species and is worth popularizing and planting in its suitable areas.The DBH of 30-year-old Keteleeria cyclolepis Flous increased rapidly with tree age,and its annual growth experienced three periods of rapid growth fluctuation:4-8a,13-15a and 17-20a.The tree height showed an increasing trend with the growth of tree age,which was divided into slow adjustment growth period(1-12a),fast growth period(13-24a)and stable growth period(25-30a).The total average growth of tree height reached the maximum value of 0.68m/a at 24a.The volume growth increased from a slow growth to a fast growth process with tree age.The accumulated volume in the first 14 years was 0.0052 m3,accounting for only 1.0%of the total volume growth in 30 years.The rapid growth period of 15-30 years was accelerated year by year.The 30-year-old Keteleeria cyclolepis Flous in this experimental forest did not reach the quantitative maturity age and the technological maturity age.The order of average DBH,tree height and crown width of Keteleeria cyclolepis Flous is down slope>middle slope>upper slope.There were significant differences between the DBH of downhill position and middle and upper slope position,and there are significant differences between the height and crown width of uphill position and middle and downhill position.(2)The different section of slope Keteleeria cyclolepis Flous s biomass were significantly different.The order of biomass between organs on the ground was trunk>Branch>twig>bark>leaf.The order of biomass of each component of root system was thick root>main root>big root>small root,and wasn't effected by the section of slope.The order of biomass among organs of the whole plant was trunk>Branch>root>bark>leaf,and there was no significant difference in the proportion of biomass among slopes,which were 50%,22%-23%,15%-17%,8%,3%-4%,respectively.The proportion of trunk biomass was about twice that of branch,and that of lateral root was about twice that of main root.The order of biomass of the above-ground organs of Keteleeria cyclolepis Flous was not affected by slope position factors,which showed trunk>Branch>twig>bark>leaf,accounting for 59%-60%,16%-17%,10%-11%,9%-10%,4%respectively.The order of stem,branch,bark and total biomass was down slope>middle slope>upper slope,while the order of twig and leaf biomass was mid-slope>down slope>upper slope,but the value was very close.The order of biomass of root components was the same,which was thick root>main root>big root>small root,but the proportion difference range was increased compared with the aboveground part.The order of biomass of main roots and coarse roots was downhill>mid-slope>uphill,big roots were down slope>middle slope>upper slope,and small roots were contrary to main roots and coarse roots,which showed upper slope>middle slope>down slope.The tree height was positively correlated with DBH,trunk biomass and bark biomass,crown width was positively correlated with leaf biomass,negatively correlated with root biomass,trunk biomass was positively correlated with bark biomass,and root biomass was positively correlated with coarse root biomass.(3)The spatial distribution regularity of root biomass was obvious,and the slope position has a significant influence on the spatial distribution characteristics of root biomass components.In the vertical direction,the biomass of small root,big root and thick root decreased with the increase thickness of soil layer,but the proportion of biomass decreased significantly in each soil layer where was the main distribution of root,with the increase of root diameter.In 0-20 cm soil layer,the biomass of small root accounted for 71.7%,the proportion of big root was 53.4%,and the proportion of thick root accounted only 48.1%.There are different effects on biomass of different root systems when the slope position factors work in different soil layers.The order of total biomass of small roots is measured as uphill>mid-slope>downhill,total biomass of big roots is downhill>mid-slope>uphill,and the thick roots is measured as downhill>mid-slope>uphill.In the horizontal direction,the biomass of big roots and thick roots decreased gradually spread from the outside of tree pockets.In downhill position,the small roots decreased as near area>middle area>distant area.There are also differences in uphill position and middle slope position,small roots decreased as middle area>near area>distant area.In different locations,slope position factors had different effects on different root biomass.In summary,Keteleeria cyclolepis Flous is an excellent timber tree species,its main growth indicators have obvious regularity,the proportion of biomass components of various organs is stable,among which the trunk biomass is more than 50%,the trunk is straight,and the timber yield is high,so it is worth popularizing artificial planting widely.The key to solve the problem of stump seedling in the early stage of planting is worth further study.