The effects of planting substrate and sowing methods on germination and seedling growth of white oak (Quercus petraea (Matt.) Liebl.)

Background and Objective: Afforestation and forest restoration using native species are recognized as vital strategies for conserving natural resources and ensuring sustainable development. In Iran, where the climate is arid and the forest cover significantly lags behind optimal levels, these efforts are even more critical. The Arasbaran forests, a distinctive region of the country, are home to valuable species such as the white oak (Quercus petraea (Matt.) Liebl.), which plays a key role in forest ecosystem conservation due to its adaptability to a variety of environmental conditions, along with its ecological and economic importance. However, habitat destruction has restricted the distribution of this species. This study was designed to investigate the impact of planting beds and planting methods on the germination and early growth of white oak seedlings at the El-Goli nursery in Tabriz. The study aims to provide useful insights for afforestation and oak forest restoration projects in Iran and similar regions.
Material and Methods: This research was conducted as a factorial experiment with a completely randomized design to explore the effects of planting bed and planting method on the germination and initial growth of white oak (Q. petraea (Matt.) Liebl.). Seeds collected from the Arasbaran forests were prepared and planted in three different planting beds (Control: soil, compost, and sand in a 1:1:1 ratio; Bed 1: soil, compost, and sand in a 2:1:1 ratio; Bed 2: soil, compost, and sand in a 3:1:1 ratio) and three planting methods (horizontal, tip-up, tip-down) on February 4, 2023. The pots were irrigated regularly every two days using a misting system. Data collection on germination percentage, speed, and seedling growth (height and collar diameter) began when the first germination occurred (May 10, 2023) and continued until the conclusion of the experiment in September 2023. Statistical analysis was performed using two-way ANOVA and Duncan’s test in SPSS software (version 26).
Results: The results revealed that both planting method and bed type significantly influenced seed germination and growth characteristics. Analysis of variance showed that planting bed type had a significant effect on collar diameter (p < 0.05), while the planting method and the interaction between the two factors were not significant. The highest collar diameter was found in the horizontal planting method with Bed 2, with a mean value of 4.29 ± 0.25 cm, whereas the smallest diameter was recorded in the tip-down planting method with Bed 1 (2.93 ± 0.58 cm). In terms of seedling height, the planting method was significant (p < 0.05), with the horizontal planting method in Bed 2 showing the greatest mean height of 35.69 ± 3.88 cm, while the tip-down method with Bed 2 had the smallest height (22.17 ± 4.36 cm). However, neither the type of planting bed nor the interaction between planting bed and planting method had a significant impact. Root length was also influenced by planting method (p < 0.05), with the highest mean root length recorded in the horizontal planting method with Bed 2 (48.69 ± 3.54 cm) and the lowest in the tip-down method with Bed 2 (35.50 ± 5.21 cm). For germination traits, the highest germination percentage (100%) was achieved using the horizontal planting method with the control treatment, while the lowest germination percentage (13%) was observed with the tip-down planting method in Bed 1. In general, horizontal and tip-up planting methods resulted in higher germination percentages compared to the tip-down method, with the control and Bed 2 outperforming Bed 1.
Conclusion: This study highlighted the significant impact of planting methods and bed types on germination and seedling growth. The horizontal planting method was particularly effective in improving collar diameter, seedling height, and root length, while the tip-down method proved to be the least beneficial. Additionally, Bed 2 outperformed the other planting beds, particularly in terms of collar diameter and root length. The highest germination percentage was observed in the control treatment with the horizontal planting method. These findings emphasize the importance of selecting the appropriate planting method and bed to optimize seedling growth, contributing to the success of afforestation and restoration efforts. Furthermore, the study sets the stage for future research on the effects of various environmental and management factors on plant species growth.