| Being a superior native broad-leaved tree species in Guangxi,Michelia macclurei has straight stem and fine texture.With the traits of disease-resistance,wind-resistance,fireproofing and relatively fast growth speed,it is one of the superior afforestation species for establishing compound storied forest and improving plantation structures of tree species.This research collects ten provenances from the natural distribution areas of Michelia macclurei in Guangxi and Guangdong,and selects Yulin Forestry Research Institute(L1),Dayi Forest Farm(L2)and Lipu Forest Farm(L3)as the representative research sites from the potential distribution areas after seedlings according to the different geographical climates.Then the growth traits and variance of different Michelia macclurei provenances in different areas are under research and genetic testing by reginal testing of provenances,thereby early selection of superior provenances can be conducted.With the stem analysis method,the growth rule of the DBH(diameter at breast height),height and stem volume of superior and common provenances of Michelia macclurei at fast-growing stage are analyzed and a growth mathematical model of its superior provenances is established,laying a basis for the further researches on the selection of stand,individual plants and provenance crossbreeding of Michelia macclurei.The main results of this research are as follows:1.By testing the survival and preserving rates of the provenances at the three research sites,the average survival rate of annual Michelia macclurei is L1>L2>L3,with the highest ones being BL(99.69%)and PB(99.00%,93.11%)and the lowest ones being BB(84.00%)and PN(80.25%,80.13%);while that of triennial Michelia macclurei also shows L1>L2>L3,with the highest ones being DY(83.88%),XY(81.44%)and BB(74.12%)and the lowest ones being DRS(54.19%),PN(58.0007%)and DC(57.37%).Comparing with the survival rate,the preserving rate is seen a decline at all research sites with a drop of L3>L2>L1.In sum,the survival and preserving rates are highest at L1 and lowest at L3,in which the 10 provenances of Michelia macclurei have easy and difficult adaption respectively.2.There is a significant difference in height,DBH,canopy and individual stem volume of 10 provenances of Michelia macclurei at the three research sites.With the analysis of variance and the multiple comparison on the grow index of provenances at different research sites,it is indicated that:(1)at L1,DY has the best growth performance,showing an average of height,DBH,canopy and individual stem volume as 2.95m,5.55cm,1.81m and 0.0037 m3 respectively;PB,ZY and FZ has a relatively better growth performance,which varies greatly from that of PN(the worst);(2)at L2,DY also has the best growth performance,showing an average of height,DBH,canopy and individual stem volume as 3.48m,5.40cm,1.59m and 0.0043 m3 respectively;ZY and BB has a relatively better growth performance,which varies greatly from that of PN(also the worst);(3)while at L3,BB has the best growth performance,showing an average of height DBH,canopy and individual stem volume as 3.49m,4.12cm,1.92m and 0.0027 m3 respectively;LZ and ZY has a relatively better growth performance,which varies greatly from that of PN(still the worst).3.By analyzing the growth performance,there is a significant difference in the average height,DBH,canopy and individual stem volume of 10 provenances of Michelia macclurei at the three research sites,among which the average height and canopy reach maximum at L3 with 3.33m and 1.85m respectively,and the average DBH and individual stem volume reach maximum at L2 with 5.06m and 0.0035m3 respectively.The height shows a significant difference in mutual influence of research sites and 10 provenances,while the DBH,canopy and stem volume show no significant difference in them.Generally speaking,Michelia macclurei shows the best growth performance at L2.4.Early selection of superior provenances of Michelia macclurei is conducted at the three research sites.On the basis of a selection criterion combining the average value of four growth traits(height,DBH,canopy and individual stem volume)with the breeding value of growth indexes,ZY,BB,DY,LC and PB are selected as superior provenances,with a selection rate of 41.67%.Among the five selected provenances,ZY has the highest genetic gain of height with 6.27%,DY has the highest one of DBH and individual stem volume with 5.98%and 0.16%respectively;and BB has the highest one of canopy with 3.53%.5.With the stem analysis,further research is conducted on the growth rule of height,DBH and stem volume of the superior provenances of six-year-old Michelia macclurei at fast-growing stage.In general,the growth of height,DBH and stem volume of the superior ones is higher than that of the common ones.For the superior provenances,the height,DBH and stem volume grow with the forest age and especially fast since the fifth year,with the current annual increment of 1.20m,1.80cm and 0.000398m3.At young stage,the superior ones grow rapidly and are unlikely to be affected by climate and environment,thus fertilization management should be taken care to effectively promote the growth.6.Putting figures of DBH,height and individual stem volume of the superior provenances of Michelia macclurei into five common growth model of experiential forest,the forecasted optimal models will be as follows:DBH growth model(Logistic):D = 6.047-ln(1+179.322*exp(-0.916*T));height growth model(Schumacher):H = 23.857*exp(-12.330/(T+2.930));and stem volume growth model(Logistic):V = 1.695-ln(1+4.446*exp(-1.227*T)). |
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