【目的】研究不同施肥水平下赤皮青冈1年生容器苗生长和根系发育的动态变化,探讨根系形态对不同施肥水平的适应策略,为提高其容器苗培育水平提供技术支撑。【方法】基于容器苗缓释肥添加试验,设置5个基质缓释肥添加水平(1.50、2.25、3.00、3.75和4.50 kg/m³),研究不同施肥水平对赤皮青冈芽苗移栽后速生期(苗龄9~11月)苗木生长和根系发育的影响。【结果】苗龄9月赤皮青冈容器苗苗高对施肥量的变化不敏感,10和11月龄容器苗苗高对施肥量变化的响应显著增加,并以缓释肥添加量3.00 kg/m³时最高;地径对施肥量的变化总体不敏感。随着容器苗苗龄增加,缓释肥添加对幼苗生长和根系发育的影响不断增强,1.50 kg/m³缓释肥添加量对9月龄容器苗生长和根系发育有较好促进作用,2.25~3.00 kg/m³缓释肥添加量对10和11月龄容器苗有较好促进作用。9~11月龄赤皮青冈容器苗根长均以≤0.2 mm径级最高,随着径级的增加,不同径级根长呈显著下降趋势。不同施肥水平下容器苗根系径级分布的差异随苗龄增加逐渐增大,根系生长和发育指标间的相关性也发生显著变化,分形维数与其他指标的相关性显著增强,其他指标两两间的相关性总体降低。【结论】赤皮青冈不同苗龄容器苗对缓释肥添加的响应存在显著差异,相对偏低的养分环境有利于芽苗移栽后幼苗的生长和根系发育,待幼苗苗龄10~11月时适当追肥,可实现节约用肥和培育优质容器苗的目的。

【Objective】This study investigated the dynamic changes in the growth and root development of one-year-old container seedlings under different fertilization levels to overcome the late emergence and slow seedling growth in the cultivation of container seedlings of Cyclobalanopsis gilva. Moreover, the adaptation strategies of root morphology to different fertilization levels were explored to improve the cultivation level of container seedlings and to promote the early emergence of seedlings by enhancing their growth and root development.【Method】Slow-release fertilizer addition tests were conducted on container seedlings at five levels (1.50, 2.25, 3.00, 3.75 and 4.50 kg/m³). Seedling growth indicators such as the seedling height, ground diameter, and dry mass of roots, stems, and leaves of seedlings (ages from 9 to 11 months) were continuously monitored during the rapid growth period. Root development indexes of different diameter grades including root length and root surface area were analyzed using a plant root scanner (EPSON Perfection V700/V750 3.83) and root analysis system software (WinRHIZO). SPSS 20.0 was employed to conduct one-way ANOVA to determine the variation of different slow-release fertilizer supplemental levels in promoting seedling growth and root development, as well as the adaptation strategies of seedling root morphology to different fertilization levels. 【Result】The effects of different fertilization levels on leaf, stem and root biomass and the root-top ratio increased gradually with the growth of C. gilva seedlings. The seedling height of 9-month-old container seedlings was not sensitive to change in the fertilizer application amount, However, the response of seedling height of 10 and 11-month-old container seedlings to such a change increased significantly. The optimal slow-release fertilizer addition amount was determined as 3.00 kg/m³. The ground diameter of the container seedlings was not sensitive to changes in fertilizer application amount. The growth indexes of container seedlings exhibited an increasing trend with the container seedling age. In particular, the root system of the container seedlings increased its contact area with the soil through continuous lateral growth, thus absorbing more nutrients. Moreover, the effect of slow-release fertilizer addition on seedling growth and root development was continuously enhanced, and the appropriate fertilization level was able to promote the root development of seedlings. The addition of 1.50 kg/m³ slow-release fertilizer had a better effect on the growth and root development of 9-month-old container seedlings compared to 10 and 11-month-old seedlings, while the addition of 2.25-3.00 kg/m³ slow-release fertilizer had a better effect on the growth of 10 and 11-months- seedlings. From 9 to 10 months of seedling growth, the fractal dimension of container seedlings was relatively low, while that for 11-month-old container seedlings increased significantly. The maximum root fractal dimension of container seedlings of different ages was observed at 4.50 kg/m³, while the root tip number of container seedlings was maximized at 1.50 kg/m³. The number of root tips decreased with the increase in slow-release fertilizer. In addition, the slow-release fertilizer addition of 3.75 kg/m³ resulted in the highest specific root length and specific surface area of container seedlings. From 9 to 11 months of seedling age, the root length of C. gilva container seedlings was the highest in the 0-0.2 mm diameter class, and the root length of different diameter classes showed a significant decreasing trend with the increase in diameter class. The adaptation strategies of container seedling roots to the nutrient status varied with the growth stage. For the 9 and 10-month-old seedlings, more roots were formed under the relatively low-nutrient status, while the medium nutrient status was conducive to the formation of more roots in the 11-month-old seedlings. Under different fertilization levels, the difference in the root diameter class distribution of container seedlings gradually increased with the seedling age. The correlation between root growth and the development indexes also changed markedly with the increase in seedling age. The correlation between the fractal dimension and other indexes increased significantly, while the correlation between other indexes decreased. 【Conclusion】Significant differences were observed in the response of C. gilva container seedlings at different seedling ages to slow-release fertilizer. The low-nutrient environment of container seedlings with a seedling age of less than 9 months can ensure the high growth of seedlings and aid in forming a better root structure. The root growth of container seedlings is vigorous during the rapid growth period of 10-11 months, and the nutrient content of the substrate should be appropriately increased to meet the growth needs of seedlings. A relatively low-nutrient environment is conducive to the growth and root development of the seedlings after 4-months-old container seedling transplanting. When the seedlings are 10-11 months old, an appropriate topdressing should be applied to promote the root development of seedlings to save fertilizer and cultivate high-quality container seedlings.