Study On Growth And Cold Hardiness Characteristics Of Zelkova Sinica And Zelkova Schneideriana Seedlings

Zelkova sinica Schneid is a rare native tree species in Shanxi. It is important for land greening and beautifying. Zelkova schneideriana, which is under national-level protection in China, has never been introduced in Shanxi. This study is on growth and cold hardiness characteristics of the two species seedlings in Shanxi Agricultural University nursery. Results show that:(1) The height growth of Zelkova sinica seedlings from seeds was not significant in the first year and second year, which were in average 100.13cm and 106.09cm respectively. Then, the height growth reduced with age. The seedlings diameter growth was high in the first and second year, reaching in average 1.42cm and 1.24cm respectively, and then gradually decreased and stabilized. The height and diameter growth of the current-year Zelkova sinica grafted seedlings, which were in average 163.09cm and 1.54cm respectively, indicated great Ulmus pumila rootstock growth advantage. However, the advantage decreased quickly from the second year.(2) The height and diameter growth of 1-3-year-old seedlings from seeds of Zelkova schneideriana showed no significant differences, reaching the maximum of 76.30cm and 0.78cm respectively. The grafted Zelkova schneideriana seedlings also showed their great Ulmus pulima rootstock advantage in height and diameter growth,which were 150.44cm and 1.78cm respectively. However, the growth advantage decreased quickly from the second to the third year.(3) The height and diameter growth of Zelkova sinica seedlings from seeds were significantly greater than Zelkova schneideriana in the first and second year, but they were similar in the third year. Both Zelkova sinica and Zelkova schneideriana seedlings from grafting with Ulmus pulima rootstocks showed a significant advantage of height and diameter growth in the current grafting year. The two species kept basically same groth trend in the first three years after grafting.(4) The five-year-old leaves of Zelkova sinica seedlings were significantly smaller than the three-year and four-year-old seedling leaves. The leaves of grafted seedling were smaller than the seedlings from seeds. Zelkova sinica twig length increased with age, but twig diameter had no significant differences. The twig numbers of grafted seedlings was significantly less than that of seedlings from seeds, but twig was significantly longer and thinner than that of the latter. Leaf chlorophyll content of the six-year-old Zelkova sinica seedling was significantly higher than that of yunger leaves. There was no significant difference for the phosphorus content of the seedling leaves with different ages.(5) The 1-3-year-old Zelkova sinica seedlings from seeds and grafted suffered varying degrees of frost damage overwintering, but they could safely overwinter after 3-4-year growth and adapting to the low temperature and strong wind in winter and later spring of Taigu area. The grafted Zelkova sinica seedlings significantly increased their hardiness than that of seedlings from seeds. Transplanting had adverse effects on overwintering of Zelkova sinica seedlings. The shelters from wind and facing south could help the seedlings overwinter safely. All the above results showed that Zelkova sinica seedlings can be successfully cultivated in field in Taigu area, with achievement of even better results under the shelters from wind and facing south.(6) Compared with Zelkova sinica, Zelkova schneideriana seedlings suffered more severe frost damage overwintering, but cold resistance of grafted seedlings increased significantly. All the test results showed that seedling field cultivation of Zelkova schneideriana is not appropriate in Taigu area, but is suitable for the areas southern than Houma in Shanxi province. Whether the Zelkova schneideriana seedlings from grafting with Ulmus pulima rootstocks can both survive and grow healthily in Taigu area still need carry out more tests and take longer time.(7) That the seedlings of Zelkova sinica, Zelkova schneideriana suffered from frost damage overwintering in Taigu was not only because of the low winter temperature in winter and early spring, but also the strong wind in winter and especial in early spring.(8) The average twig water content was not changing significantly during winter for the Zelkova sinica seedlings that overwintered safely, while twig water content was declining continually for the seedlings that suffered from frost damage. However, the average soluble sugar content had no much change during winter for the seedlings both overwintered safely and damaged by frost.The results of this study provides important references for breeding Zelkova sinica and Zelkova schneideriana seedlings and has great significance for enriching afforestation tree species and plant diversity protection in Shanxi province.