Detailed Explanation of Cultivation and Afforestation Techniques for Picea koraiensis (Korean Spruce)

Picea koraiensis is shade-tolerant, drought-tolerant, and cold-tolerant, with relatively fast growth. It is a major tree species in the forests from the Changbai Mountains to the Xiaoxing'anling Mountains in Northeast China, and is also a common nursery stock for landscaping. The following introduces the cultivation and afforestation techniques for Picea koraiensis.

Superior Seed Breeding

1. Select good crop rotation. For Picea koraiensis sowing land, Pinus sylvestris var. mongolica and Larix (larch) stubble are suitable. For the remaining seedbeds of these two tree species, if the operation area is small and the rotation cannot be adjusted, large amounts of organic fertilizer and base fertilizer should be applied, and disinfection must be done carefully.

2. Seed germination. Snow stratification treatment is best, as it results in rapid emergence, uniform sprouting, and strong resistance to various disasters.

3. Timely sowing. Generally, sowing operations are completed between May 5 and 15 of the same year, and sowing can also be done when the ground temperature at a soil depth of 5 cm stabilizes at 8-10 degrees C. Three conditions need to be met: first, the soil is fertile with good structure; second, the soil covering material after sowing is best to be peat soil or decomposed horse manure; third, timely irrigation, otherwise shading should be considered.

4. Select one-year-old seedlings for bed transfer, and larger seedlings for mountain planting. The advantage of transferring one-year-old seedlings is that it ensures the quality of bed transfer operations, improves the survival rate, provides uniform nutritional space for seedlings, and maintains appropriate density. For sowing seedlings transferred as one-year-old seedlings, thinning may not be needed in the same year, and all can be transferred the following year. With the same amount of seed, more than double the number of mature seedlings can be obtained, with obvious economic benefits.

Frost and Cold Protection

This tree species has relatively late leaf bud swelling and new growth node extension, so it is generally not affected by frost damage. However, it suffers severe damage from late frosts occurring in late May or early June. During this period, if the temperature reaches -2 degrees C, the seedling mortality rate is 24%; if it reaches -4 degrees C, the mortality rate is 34%; if it reaches -5 degrees C, although low-temperature protection measures can be taken, the seedling mortality rate exceeds 70%. For frost, comprehensive prevention and control measures should be adopted, such as smoke generation, covering with grass, covering with plastic film, and irrigation.

Site Condition Selection

According to the biological characteristics of Picea koraiensis, the optimal site conditions are: sunny slopes or semi-sunny slopes with a gradient of 8-12 degrees, deep soil layers, dark brown soil plots with a black soil layer of more than 20 cm and good drainage, especially on clear-cut sites. Under such site conditions, a 20-year-old planted forest can reach a height of more than 8 m, while under poor conditions it only reaches about 6 m. Growth and survival conditions also vary under different site conditions.

Site Preparation

Site preparation should preferably be carried out in the autumn of the previous year. It is best to do it in August and September, when there is more rainfall and high temperatures, which is beneficial for planting seedlings the following spring. Use open-hole site preparation to create conditions for planting on moist soil. The site preparation specification is 60 x 60 x 25 cm. First remove the sod, break up soil clods, pick out debris, and pile the soil from inside the hole on the north side outside the hole. In sections with strong grass root binding and poor drainage, adopt the block-style raised platform method, with a platform height of 30-40 cm and a specification of 1 m x 2 m, using group planting for afforestation. For clear-cut sites with a slope of less than 25 degrees, strip site preparation can be carried out.

Afforestation

Spring seedling lifting and spring afforestation is an important measure for the successful regeneration and afforestation of Picea koraiensis. It is required that the time from seedling lifting to planting should not exceed 2 days. For the specifications of seedlings taken to the mountain, select high-quality seedlings with a height of more than 25 cm, a ground diameter of more than 0.5 cm, a main root length of about 15 cm, more than 12 lateral roots, robust growth, good development, full terminal buds, and no pests or diseases. Strict quarantine must be carried out before being taken to the mountain.

When planting, place the seedling in the center of the hole, plant it upright, straighten it, spread the root system, cultivate soil in layers, lift gently and firm the soil. For group planting, 3 seedlings are appropriate. For the initial planting density of afforestation, if too dense, it not only increases site preparation and seedling costs, but also makes light thinning very labor-intensive, and the first thinning does not produce usable timber, which is economically unprofitable. From many years of practice, about 4,400 seedlings per hectare is relatively reasonable.

Young Forest Tending and Management

According to the characteristics of Picea koraiensis, young trees need a certain amount of light. Tending is carried out for 5 years following the pattern of 2, 3, 2, 2, 1. In particular, the first tending after afforestation is especially important, focusing on earthing up, straightening, and firming the soil. During tending, it is strictly forbidden to dig up the soil surface of the hole or injure the seedlings.

1. In the first year of tending, expand the hole by 50 cm, earth up 1-2 cm above the root collar of the seedling, and straighten seedlings leaning at more than 20 degrees.

2. In the second year, mainly weed and earth up.

3. In the third year, weed and cut brush.

4. In the fourth year, remove grasses or shrubs that hinder the growth of young trees.

5. In the fifth year, carry out strip operations for full weeding, cutting, and felling of competing plants, while retaining the three major hardwoods. If conditions permit, long-acting organic compound fertilizer can also be applied.

Light Thinning

Under normal light and moisture conditions, the annual height growth is usually more than 30 cm. Failure to meet this standard is due to insufficient light, showing a flat spruce crown, dark green color, and a thin, weak trunk. In such cases, light regulation measures must be taken promptly. Light regulation is completed within 5-15 years. Remove upper-story trees to release the lower layer, and artificial pruning can also be carried out.

Growth Thinning

Growth thinning generally begins from age class II in planted forests, and growth thinning for Picea koraiensis is completed within 15-20 years. It mainly adjusts the stand management density, creates the most suitable nutritional space for retained trees, and promotes fast forest growth and good stem form, so as to achieve high quality and high yield. Quantitative thinning technology should be promoted for thinning in spruce planted forests, and density can be determined according to site conditions and management level.

Pest and Disease Control

Several common diseases and control methods.

1. Spruce cone rust. Control method: Spray 0.1% 2,4-D within 200 m near the seed orchard to kill Rosaceae plants and Prunus padus, etc. Cut down severely diseased trees. Strictly select disease-free trees when collecting cones. Establish mixed conifer-broadleaf forests.

2. Spruce red band needle blight. Control method: For Pinus sylvestris var. mongolica forests around the nursery and spruce seedlings on seedbeds, use 75% chlorothalonil and spray twice from late May to early July, continuously for 3 years. The control effect is good.

3. Spruce gray felt wilt disease. Excessive stand density is the main predisposing factor for the occurrence of this disease. Control method: Adopt silvicultural measures such as forest sanitation, pruning, and light thinning for planted forests, with relatively good results.

Afforestation of Picea koraiensis is a relatively long process. We cannot be impatient and must care for it carefully and patiently in order to cultivate high-quality seedlings.