Detailed Explanation of Seed Collection, Germination Promotion and Seedling Cultivation Techniques for Picea koraiensis
Picea koraiensis Nakai, also known as red-barked spruce and white pine, is an important timber forest tree species and landscaping tree species in China. It is mainly distributed in the Xiaoxing'anling, Zhangguangcailing and Changbai Mountain regions, with a small amount also distributed along the river valleys in the eastern and northern parts of the Greater Khingan Mountains.
1 Biological characteristics and economic value
Picea koraiensis is an evergreen large tree with dense branches and leaves, strong shade tolerance and cold resistance, and slight tolerance to saline-alkali conditions and drought. It is a shallow-rooted tree species, easily blown over by wind, and has relatively high soil requirements. Picea koraiensis has a straight trunk form and good wood quality, and is an important timber for construction, vehicles, aviation and papermaking. Because of its attractive tree form and relatively slow growth in the juvenile stage, in recent years it has often been used as an important tree species for landscaping and bonsai planting.
2 Cultivation techniques
2.1 Seed collection. The flowering period of Picea koraiensis is in late May, but the cones develop for a short time and generally mature in late September. When mature, the color of the cones changes from the initial green or purplish red to yellow-green or brown. Once the cones of Picea koraiensis mature, seed collection must be carried out immediately; otherwise the seed scales crack open and the seeds scatter, making them difficult to collect. The main methods of seed collection for Picea koraiensis are manual collection by climbing the tree or collection with high-branch shears. Picea koraiensis trees are tall, so when climbing the tree for seed collection, attention must be paid to personal safety and protection of the branches. If high-branch shears are used for seed collection, attention should be paid to protecting the branches of the mother tree, trying to cut only the cones and taking as few branches as possible, and also noting that collection should be carried out before the cones crack open; if the cones have already partially cracked, the seeds scatter when the cones fall, so tarpaulins, plastic films, etc. must be placed below to catch them.
2.2 Seed threshing. After the cones of Picea koraiensis are picked, they can be sun-dried for threshing. Generally after spreading them out to dry for 7-8 days, the scales crack open and the seeds come out. If rainy weather occurs, they can be treated on a heated kang, with the kang surface temperature maintained at 25-30°C, and attention should be paid to turning them to avoid scorching the seeds. After the seeds come out, the wings must be removed. Removing the wings of Picea koraiensis is very easy, and either screening or winnowing can be used. After removing the wings, drying, seed cleaning and other work must also be carried out, and then the seeds should be placed in a ventilated, dry, cool seed storage room or sealed container for low-temperature storage over winter.
2.3 Germination promotion treatment. The seeds of Picea koraiensis are small and have a high germination rate, generally reaching about 80%; however, in order to make the seeds germinate quickly and uniformly, germination promotion treatment is needed before sowing. The main germination promotion methods are three: snow storage germination promotion, warm water soaking germination promotion, and mixed sand stratification germination promotion.
2.3.1 Snow storage germination promotion. Before the soil freezes, choose a shady place with a relatively low groundwater level, and first dig a storage trench. The width and depth of the trench are both 1 m, and the length depends on the quantity of seeds. After the soil freezes and snow falls, place 10-15 cm of snow at the bottom of the trench, then mix the seeds and snow at a ratio of 1:3 and place them into the trench, cover with snow and soil on top, and cover with straw and other materials. In the spring of the following year, 5-7 days before sowing, take out the seeds and mix with sand for germination promotion.
2.3.2 Warm water soaking germination promotion. Five days before sowing, soak the seeds in warm water at about 40°C for 1-2 days and nights. During soaking, pay attention to stirring 3-4 times a day so as to dissipate heat in time. Then take them out and air-dry them. The air-drying temperature must not be too high and should be controlled at about 25°C. After air-drying for 2-3 days, they can be sown. For Picea koraiensis, warm water soaking germination promotion is a fast and efficient germination promotion method. If used properly, the germination rate can reach more than 95%.
2.3.3 Mixed sand germination promotion. Control the moisture of the sand, then mix wet sand and seeds evenly at a ratio of 3:1, and pile them indoors or in a shady place. Adjust the pile temperature to 5-8°C, and pay attention to turning the pile 1-2 times a day to dissipate heat in time and maintain moisture. When 30%-50% of the seeds have cracked open, they can be sown.
2.4 Seedling cultivation techniques. The seeds of Picea koraiensis are small and have relatively high requirements for soil and land preparation. For seedling cultivation, choose a sandy loam with good drainage, rich nutrients, deep soil layer and loose texture, and require careful land preparation; for high beds and flat beds (low beds are less effective), soil disinfection is also needed. Picea koraiensis mainly uses sowing and seedling cultivation. When the soil temperature at 5 cm underground reaches 8°C, sowing can begin. The natural mortality rate of Picea koraiensis seedlings is relatively high, so appropriate dense sowing can be used, with a seeding rate of 7.5-9 kg per mu. Drilling can be used, and broadcasting can also be used. After sowing, cover with about 0.4 cm of soil, and lightly press and cover with grass. Generally, the seedlings can emerge completely within half a month, and after complete emergence the grass cover should be removed. Picea koraiensis seedlings have weak resistance, so after removing the grass, shading should be carried out to avoid sunscald damage, and attention should be paid to timely irrigation, intertillage, weeding, fertilization and pest and disease control. Cold protection and overwintering of Picea koraiensis seedlings in the first year is a key measure to increase seedling survival rate, mainly by covering with soil for cold protection or by irrigating with frozen water. Soil-covering cold protection is usually carried out in early winter before the soil freezes. Note that the soil covering thickness must be 4-5 cm higher than the seedlings to achieve the cold protection effect, and it must be removed in time after the dry winds in the spring of the following year. In short, the seedling cultivation technique for Picea koraiensis is not difficult. As long as these key points are mastered, it is easy to succeed and relatively high economic benefits can be obtained.