Site Analysis And Growth Regularity Of Eucalyptus Plantation In Southern Hunan

Eucalyptus is the general name of Eucalyptus species in Myrtle family.It is mostly tall evergreen trees.It is an important timber tree species in China with the characteristics of fast growth,high yield,barren tolerance and excellent dry type.Eucalyptus in southern Hunan is generally felled for about five years,which is far from mature in quantity.However,there is little research on near-mature or mature Eucalyptus forests in southern Hunan,and lack of production guidance Through setting standard plots and.sample trees in Eucalyptus stands in southern Hunan,this study studied the relationship between site factors and site quality of Eucalyptus plantations for more than seven years,the regularity of bud regeneration of near-mature stands,the regularity of stand growth process and the variation of stand height,DBH,individual wood volume and volume after density control,from site selection,growth process,selective cutting and tending.In order to provide some basic data for the near-mature Eucalyptus stand in southern Hunan,experiments were carried out in several stages,such as germination regeneration.The results are as follows:(1)Five principal components of site factors of Eucalyptus plantation in southern Hunan were extracted(mainly E.dunnii Maiden and "Changhan No.1"):soil texture,forest nutrition,soil thickness,slope and aspect.The variance contribution rates were 34.569%,17.120%,12.235%,11.319%and 8.861%,respectively.Six dominant factors,namely,non-capillary porosity(Por_nc),soil organic matter content(C),available potassium content(K),soil thickness(TH),available phosphorus content(P),soil acidity and alkalinity(pH),were screened out by factor analysis method,and use this as the self-variation factor to establish the multi-position index equation of 7a eucalyptus plantation in southern Hunan.And the available phosphorus content(P)and soil acidity and alkalinity(pH)were further eliminated by step analysis.At last,the equation was fitted:Ht = 12.619+0.053×Por_nc+0.168×C-0.021×K+0.645×THits determinant coefficient R2 was 0.720,adjusted R2 was 0.640,and the root mean square error(RMSE)was 0.606,and the estimation accuracy(EA)was 0.967。It can be used to predict the site index of 7-year-old Eucalyptus plantation in souther Hunan.(2)The results of the study on the germination process of Eucalyptus"Changhan No.1" were as follows:① he number of germination points did not significantly affect the number of sprouts at each germination point;②the number of sprouts on cutting piles had no significant correlation with the diameter of the main sprouts,but had a significant negative correlation with their length;③the number of sprouts at a certain germination point had no significant correlation with the diameter of the main sprouts at that point.④Higher cutting piles have more sprouts and can sprout more sprouts,but when they reach a certain height,the trend is restrained;⑤medium diameter cutting piles(12～18 cm)have the largest number of sprouts and sprouts;⑥the height and diameter of cutting piles have no significant effect on the height and diameter growth of main sprouts;⑦small diameter cutting piles have no significant effect on the growth of main sprouts.The main sprouts can be highlighted by cutting piles at low altitudes,and the fixed-pole operation of Eucalyptus germination renewal can also be facilitated.(3)The total height growth of Eucalyptus plantation"Changhan No.1" in southern Hunan can reach 19.10m～20.20m in 9 years.The average height growth and successive annual growth of Eucalyptus plantation in 0-9 years basically show a gradual decline law.The total growth of DBH can reach 13.50m～16.70m in 9a,and the average growth of DBH in 0-9a and annual growth also show a gradual decline.The total volume growth of single wood can reach 0.1531 m3～0.2155 m3 in 9a.The annual growth of single wood volume is gradually increasing,while the annual growth of single wood volume is always higher than the average growth during this period,and shows a trend of first increasing and then decreasing.The peak value is about 6a,and intersects with the average growth in 9a,and then is lower than the average growth.Therefore,the number of mature years of Eucalyptus plantation in southern Hunan is around 9 years.(4)Density control treatments of selective cutting methods have significant effects on DBH,tree height and individual volume of Eucalyptus plantation"Changhan No.1" in southern Hunan.The larger the selective cutting intensity,the greater the DBH,tree height and individual volume of Eucalyptus plantation in succession.However,the effect of regulation treatment on tree height was not as obvious as that on DBH and individual volume.There is no significant difference between the two-year increase of the stand volume of Eucalyptus plantation and the control group under the density control at the medium and low intensity level.Therefore,the density of Eucalyptus plantation in southern Hunan can be reduced by the medium and low intensity cutting method,which can not only improve the economic benefits,but also take into account the ecological benefits.