Detailed Explanation of Key Techniques for Establishing a Seed Production Forest with Large Korean Pine Seedlings

Korean pine (Pinus koraiensis), of the family Pinaceae and genus Pinus, is an evergreen coniferous tree. It is mainly distributed in the Greater Khingan Mountains and Changbai Mountain areas of China, where its Korean pine forests form the climax community of the region, playing an enormous social, ecological and economic role. In the early years of the founding of New China, to meet the needs of economic construction, Korean pine timber was excessively logged, causing a massive decline in Korean pine trees; at present, only about 5 million mature Korean pine trees remain. Therefore, establishing Korean pine seed production forests on a large scale, rapidly and with high quality is of great significance for restoring and developing the climax Korean pine forest community in the Greater Khingan Mountains and Changbai Mountain areas.

Korean pine has a strong demand for light; it is slightly shade-tolerant at the seedling stage, and as the tree age increases, its light requirement gradually grows. It grows rapidly on fertile, slightly acidic sandy loam. Under suitable climatic conditions, natural Korean pine trees begin to bear fruit at 35 years of age, and planted Korean pine timber forests begin to bear fruit at 25 years of age; seed production forests established with large Korean pine seedlings have an expanded range of nutrient absorption and begin to bear fruit at 18 years, showing very obvious results. For this reason, based on practical experience, the techniques for establishing a seed production forest with large Korean pine seedlings are introduced as follows:

1. Selection of afforestation site: flat land or mountain land with a slope of less than 25 degrees in the Greater Khingan Mountains and Changbai Mountain areas, with slightly acidic sandy loam where the combined A+B soil horizons exceed 30 cm in thickness.

2. Site preparation: use line-marking to set points and pit-shaped site preparation, with a spacing of 3 m x 3 m, a pit diameter of 80 cm and a depth of 40 cm. The timing of site preparation is determined according to the climatic conditions of different regions, generally starting in mid-October and ending before the soil freezes. If site preparation is done too early, the soil tends to harden after rain and sun exposure. If done too late, the soil has already frozen solid, making site preparation more difficult. In addition, site preparation must not be done in spring, because after the soil thaws in spring, soil moisture evaporates, seeps away and is lost in excessive amounts, which is not conducive to the survival of the planted large Korean pine seedlings.

3. Seedling selection: use Korean pine seedlings of 7 to 9 years of age, and use seedling stock that has been transplanted twice. The seedling standards are: ground diameter greater than 0.8 cm, seedling height greater than 35 cm, main root length greater than 20 cm, and more than 20 lateral roots. The trunk is required to be straight, the terminal bud plump, the colour normal, with no pests or diseases, and no damage to the main root, lateral roots, trunk or lateral branches.

4. Lifting and packaging of seedlings: lift the seedlings within 7 days before planting, fill the root system of the selected seedlings with moist straw or soak it with rooting powder and a water-absorbing agent, then wrap the roots and crown separately and tightly with plastic bags, and place them in a moist, shaded, cool place for later use.

5. Planting: carry out when the soil thaws in mid-April. Remove the seedling packaging, take off the wrapping material around the seedling roots, and plant the seedlings in the prepared pits; the root system should be spread out, and the seedlings should be held upright. At the same time, evenly apply 0.25 kg of ammonium nitrate and phosphate fertiliser per pit, fill with soil in layers, firm it with the foot, water thoroughly, then cover with 2 cm of leaves or weeds to preserve soil moisture.

6. Tending of young forests: after the large Korean pine seedlings are planted, intercrop tall-stem crops such as sorghum or maize in the rows at a distance of more than 50 cm from the seedlings. First, this can provide shade for the Korean pine; second, the Korean pine can absorb part of the nutrients from the fertiliser applied to the crops. Use manual weeding when removing weeds; chemical herbicides are prohibited.

7. Rodent damage control: seed production forests established with large Korean pine seedlings are highly susceptible to rodent damage in spring and autumn. Rodenticide can be applied in early April and late October each year for control.