| Phoebe zhennan,is an endemic tree species in China,belongs to the national sclass II protected plant.P.zhennan wood has a special flavor and is resistant to insects.Its texture is straight and its structure is fine.It is not easy to deform and crack.It is often used to make high-grade furniture and high-grade buildings.Because of its beautiful texture,it is recognized as the best tree species of"Phoebe"in the domestic wood industry.At the same time,P.zhennan has straight trunk,tall and straight,luxuriant branches and leaves,evergreen all the year round.It is also a famous ornamental tree species as court shade tree or street tree.P.zhennan requires high growth conditions,so it has a small range of producing areas.It is mainly distributed in the Western Sichuan Basin,Guizhou,Hubei and other subtropical areas with an altitude of 1000-1500m,such as shady valleys,valleys and riversides.The wood of P.zhennan in Sichuan Province is the best.Because of the high application value of P zhennan,it has been cut down and used wildly in the past dynasties.As a result,P.zhennan has become an endangered tree species,resulting in insufficient wood reserves.The climate environment in Sichuan is very suitable for the growth of P.zhennan.Therefore,the whole province is vigorously developing P.zhennan.Leshan City is determined as one of the bases for developing P.zhennan precious timber forest.The development of P.zhennan 16000 hm2 requires a large amount of seedlings of P.zhennan.In order to meet the needs of seedlings of P.zhennan in large-scale afforestation as soon as possible,it was decided to establish a superior seed forest of P.zhennan in Leshan City to provide germplasm resources for the breeding of P.zhennan.In this study,through the on-the-spot investigation of Leshan City,P.zhennan stand with good geographical traffic conditions,good management conditions and convenient seed collection was selected.Taking the qualified forest as the object,the proportion of excellent trees in the stand was analyzed according to the scale of each tree,and the alternative stand of the mother forest was selected.The selected provenances were planted in Qianwei County,Mabian County,Shizhong District and Gaoxian county with the same propagation techniques(planting methods and management conditions).The seed phenotype,germination characteristics,seedling growth characteristics and other comprehensive characteristics of P.zhennan from different provenances were measured and compared to explore the excellent provenance and suitable planting range,High quality seed stand of P.zhennan was selected.It is of great significance to improve the improved seed level and utilization rate of P.zhennan in Sichuan Province,the construction of P.zhennan seed orchard in the next step and to speed up the development of P.zhennan resources in Sichuan.The main results are as follows:(1)The area of P.zhennan forest in Jiajiang County is about 6.67 hm~2.The forest ownership belongs to collective management.The terrain is relatively steep.The canopy density of the stand is about 0.8.The number of excellent and medium-sized trees accounts for 99.13%of the stands.The forest area of P.zhennan forest in Qianwei county is about0.33 hm~2,which belongs to collective and individual management,the terrain is concave and steep,the canopy density of the stand is about 0.8,and the number of excellent and medium trees accounts for 44.24%of the stand.The area of P.zhennan forest is about 4.33hm~2 in Emei Mountain.The state-owned forest right is managed,the terrain is gentle,the canopy density is about 0.6,and the proportion of superior and middle trees is more than96%.The results of local survey show that P.zhennan forest in Qianwei county has steep terrain,which is not convenient for seed collection,and the proportion of excellent trees is less than 60%,so it is not suitable to be used as seed forest;although P.zhennan forest in Jiajiang County is not convenient for seed collection,but the proportion of excellent trees is more than 90%,as an alternative seed forest;P.zhennan forest in Emei Mountain area not only has good traffic conditions,good management conditions,but also is convenient for seed collection Good trees account for more than 90%of the total.(2)There were significant differences in 1000 seed weight and 100 seed drainage volume between P.zhennan of Jiajiang County and P.zhennan of Emei Mountain(P<0.05).The highest 1000 seed weight and 100 seed drainage volume were 315.92 g and 23.65 cm3,respectively.According to the comparative analysis of the difference of seed size,the coefficients of variation of long diameter,short diameter and the ratio of length to short diameter of seeds in Emei Mountain were lower than those of P.zhennan of Jiajiang County.There are some differences in germination rate among different provenances,the highest germination rate is Emeishan species,which is as high as 90.15%,and there is a significant difference in germination rate between P.zhennan of Jiajiang County and Emeishan species(P<0.05).The highest seed germination potential was P.zhennan of Emei Mountain,and the highest was 82.37%.There was a significant difference between the species in Emei Mountain and those in Mount Emei(P<0.05).Generally speaking,the phenotypic and germinating characteristics of P.zhennan in Emeishan area were better than those in Jiajiang County.(3)The results showed that the average tree height,diameter at breast height,crown width and individual volume of 1-year-old,2-year-old,3-year-old and 4-year-old progeny forest of Zhennan in Emeishan were significantly higher than those of the whole Jiajiang County(P<0.05),which were significantly higher than those of Zhennan in Jiajiang County.The results showed that Zhennan in Emeishan had better genetic performance than Zhennan in Jiajiang County,and it was suitable for planting in Qianwei County,Mabian County,Shizhong District and Gaoxian county.Through the comparative analysis of seed phenotype and germination characteristics,stand site conditions,forest characteristics and offspring forest performance,it is concluded that Zhennan forest in Emei Mountain has good traffic and management conditions,and the related forest characteristics of offspring forest are better than Zhennan seed in Jiajiang County,with obvious advantages.Zhennan forest in Emei Mountain is finally selected as an excellent parent forest The annual total seed amount of mother tree is about 200 kg,which can basically meet the demand of Zhennan seedlings in Leshan. |
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