Detailed Explanation of Spruce Seed Collection, Seedling Cultivation and Afforestation Techniques
Spruce, also known as Picea meyeri, coarse-branched spruce and rough-barked spruce. Its wood is relatively good, slightly soft, elastic and easy to work, and has many uses such as making high-quality building materials, furniture and mine props. Spruce is suited to a temperate humid climate and is one of the main timber tree species in North China, Northwest China and Southwest China.
1. Seed collection
In the natural forest areas of the northwest, spruce seeds mostly begin to mature in October, and seed collection can begin once the cones turn from green to yellow-brown or chestnut-brown. The mother trees for seed collection are best chosen from 30-50 year old plants that are robust in growth, excellent in stem form and free of pests and diseases. However, because the seed collection task in natural forest areas is relatively large, the method of purchasing seeds from forest farmers is often adopted, and seeds are also collected from established seed production stands and seed orchards.
The cones brought back should immediately be spread out and dried in the seed yard, threshed by beating with wooden sticks, and after winnowing to remove impurities, the pure seeds should be dried in the shade, packed into gunny bags and placed in a cool, dry and ventilated storage room, to await transport or sowing.
2. Seedling cultivation
Within its distribution range, spruce is the main tree species for regeneration of cut-over sites, and seedlings are mostly raised in forest nurseries or mountain nurseries in the forest.
(1) Nursery site selection The site should be chosen near the afforestation area or near the center of the seedling site, with convenient transportation and open terrain, and it is best to establish it on well-drained flat ground or gently sloping land of 10-30 degrees; soil texture is an important condition in choosing a nursery, and generally sandy loam and light clay loam with relatively high fertility are suitable; at the same time it should be close to a water source to facilitate irrigation, and it is forbidden to set up a nursery in places such as cold air accumulation areas, waterlogged lowlands, heavily saline-alkali land, light-blocked canyons and wind gaps.
(2) Land preparation In the rainy season of the year before sowing, before the weeds set seed, carry out one deep plowing (20-25 cm), then at the end of autumn turn the soil again and rake it level, pick out grass roots in preparation for making beds the following spring. When the ground thaws in early spring, immediately plow the land and make beds. Generally, in rainy areas raised beds are used, with a bed height of 15-20 cm, a bed width of 1.1 m, a length of 10 cm and a path of 50 cm, and the bed direction should preferably be north-south, mainly to prevent the seedlings from being damaged by sunscald in summer. In areas with little rain, flat beds are used. 3-5 days before sowing, disinfect the soil with quicklime water or ferrous sulfate. Shallow plow, then rake level and press fine.
(3) Sowing Spruce is generally sown from mid-to-late March to before the end of April, and seedlings emerge in about half a month. Generally the seeds are not subjected to pregermination treatment; they are only soaked in a 0.5% copper sulfate solution for half an hour before sowing, then dried and sown, to prevent root-rot-type damping-off. Drilling is generally used, preferably in an east-west direction, with a row width of 10-12 cm, a row spacing of 10-20 cm, and a covering soil thickness of 0.5-1 cm; the covering soil is best forest humus soil or sawdust, and the sowing rate per mu is 20-25 kg; immediately after sowing, cover with grass or lay bamboo blinds on the seedbed so as to shade, preserve moisture and heat, and prevent rain from beating the surface soil and causing the soil to harden and erode.
For full-light seedling cultivation of spruce, sow 30-50 kg per mu, and after sowing cover with fine sand and coarse humus to a thickness of about 1 cm, and finally press down. The sowing period for full-light seedling cultivation is late May, and the seedlings are fully emerged by early June, which allows them to avoid the last late frost and gives a high seedling survival rate. After sowing, sprinkle water once a day; after the seedlings emerge, sprinkle water twice a day, each time wetting the seedbed soil to a depth of about 2 cm. In full-light seedling cultivation of spruce, quite a few small seedlings die after overwintering, mainly because the winter and spring are dry and windy, the aboveground and underground parts lose water balance, causing death from growth drought; therefore, sufficient winter watering is very important. In late autumn and early winter, water the seedbed several times, and the last winter watering should cause a thin layer of ice 2 cm thick to form above the seedlings. In this way, after overwintering, spruce seedlings will not die from physiological drought, greatly increasing the seedling survival rate. With wide-band dense sowing of spruce, emergence is abundant, reaching about 2 million seedlings per mu in the first year. In the third year the seedlings grow faster, and at this time they must be transplanted to another bed, otherwise growth will be poor due to excessive density. Transplanting is carried out in spring, and generally 1 mu can be transplanted to 3-5 mu. When 5-year-old seedlings leave the nursery, the seedbed-retained seedlings produce about 150,000 seedlings per mu, and transplanted seedlings produce 100,000-150,000.
(4) Management To achieve the goal of cultivating strong seedlings and high yield, management must be strengthened after spruce sowing, and its main items are shading, pesticide spraying, irrigation, loosening soil and weeding, and cold protection.
Building a shade shed Once the seedlings are fully emerged, drive stakes and set up frames, and lay the bamboo blinds from the seedbed on the shed frame, using overhead shading, with the shade shed 20-30 cm above the ground, and a light transmittance of 25%-50% being better.
Disease prevention Spruce seedlings are easily infected by damping-off. Therefore, immediately after the seedlings emerge, spray pesticides for prevention and control, spraying 0.5% Bordeaux mixture or 0.5% ferrous sulfate solution once every 7-10 days, continuing for 2-3 months.
Weeding For spruce seedlings within one year, which are tender and weak, weeding is a key link; as long as weeds are found on the seedbed, they should be pulled out promptly. Weeding must be thorough and clean, while protecting the seedlings and not damaging the root system.
Cold protection If summer management is good, by autumn the seedlings can become lignified and overwintering is relatively easy, but winter cold protection is still needed for all, that is, in mid-November remove the bamboo blinds and spread wheat straw etc. on the seedbed, with a thickness sufficient to cover the seedlings, and then cover the bamboo blinds over the seedbed as well. In mid-to-late March of the following year, when the wild grass turns green, remove the blinds and the grass; the blinds should be removed first, and 4-5 days later the covering grass should be removed; removing the grass should be done later rather than earlier to prevent spring cold.
The above is mainly management of one-year-old seedlings; in the second year shading is still needed, mainly irrigation, disease prevention and weeding, but two-year-old seedlings do not need cold protection; after the third year, management is relatively extensive and full-light seedling cultivation can be used, with seedlings leaving the nursery in the fourth to fifth year, producing 150,000-200,000 seedlings per mu. As for fertilization, it is best to apply sufficient base fertilizer, with superphosphate, ash fertilizer and oil residue being suitable, and for topdressing, ammonium nitrate and ammonium sulfate etc. are better.
3. Afforestation
(1) Selection of afforestation sites For spruce afforestation, first of all afforestation within the distribution range should be considered, and at the same time terrain positions suitable for spruce growth should be selected for afforestation. In arid low-mountain areas, soil moisture and excessively strong light are important limiting factors for the survival and growth of spruce; therefore, shady slopes and semi-shady slopes should be selected for afforestation, and when necessary sunny slopes may also be used, but higher requirements should be set for afforestation techniques. In order to cultivate fast-growing and high-yielding large-diameter timber, afforestation should mainly be carried out on cut-over sites, burned sites and forest openings within the distribution range, or used for improvement of secondary forest.
(2) Composition and density In production, large areas of pure spruce forests are mostly established. As for plantations, there is not yet good ready-made experience for mixing spruce with other tree species, but in the improvement of low-value forests, shrub forests and some poplar-birch forests, planting spruce has provided great inspiration on the issue of mixed forests, and in areas with favorable conditions mixing with poplar and birch may be considered.
The afforestation density of spruce should vary with different site conditions. In low-mountain areas, considering the trunk development and branching characteristics of spruce as well as conditions such as moisture, the afforestation density should be somewhat greater, generally with a row spacing of 1.2-1.5 m, a plant spacing of 0.75-1 m, and 450-700 plants per mu; on cut-over sites with better site conditions, the row spacing is 1.5-2 m, the plant spacing can reach 1-1.5 m, and more than 300 plants per mu should be maintained.
(3) Afforestation methods Spruce mainly uses seedling planting for afforestation, and the afforestation season can be spring or autumn, mainly spring. In spring, in order to seize soil moisture and ensure timely afforestation, in natural forest areas afforestation should be carried out in the order of low mountains first and high mountains later, outside the gully first and inside the gully later, and sunny slopes first and shady slopes later.
For spruce seedling planting, 4-5 year old seedlings can be used, and where seedlings grow especially well, 3-year-old seedlings can be used. Generally, seedlings with a height of 15-20 cm, a root-collar diameter above 0.3 cm, well-developed roots, intact terminal buds and robust growth are required to go up the mountain, giving a relatively high survival rate.
The planting method generally uses hole planting, and the size of the hole surface should be adapted to local conditions. Generally, the specification for hole-surface site preparation is 40 x 40 cm or 30 x 30 cm, with a depth of 20-30 cm; planting should not be too deep, and is required to exceed the original soil mark by 2-3 cm; in addition, where the soil layer is relatively thick, there is less gravel, moisture conditions are good and land preparation has been done in advance, narrow planting may also be used, but the root system must be extended and the gaps must be firmed, which can also ensure the afforestation survival rate.
4. Tending management
The main contents of tending management for spruce plantations are soil management and weeding. After planting in the same year, in late May or early June, carry out earthing up, supporting the seedlings and firming. In late July, a small-area weeding can be carried out, limited to around the holes only. Comprehensive weeding is not necessary, to prevent sunscald of the seedlings. Generally tending is carried out continuously for 3 years, and in the latter two years it is mainly loosening soil and weeding. However, in natural forest areas, the contradiction between forestry and grazing is the main contradiction; on cut-over sites and burned sites, after afforestation the pasture grass grows luxuriantly, and cattle and sheep trampling destroy large areas of plantations, seriously affecting the afforestation survival rate; therefore, it is necessary to consult with the local villages and properly resolve the contradiction between forestry and grazing.