Seed collection, seedling cultivation and afforestation techniques of eucalyptus

Eucalyptus is a world-famous fast-growing tree species with strong adaptability, diverse wood species, wide use and high economic value. it is not only a timber tree species, but also a road, garden and windbreak tree species. At present, eucalyptus afforestation covers 15 provinces in southern China, mainly distributed in Guangdong, Guangxi, Fujian, Jiangxi, Sichuan, Yunnan and other 6 provinces (regions). Eucalyptus urophylla, Eucalyptus lemon, Eucalyptus globulus, Eucalyptus grandis, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus urophylla, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus urophylla 12 and Eucalyptus urophylla are all promising. 1. The interspecies of the same subgenus of eucalyptus are easy to cross and produce new hybrids, which provides favorable conditions for seed selection, breeding and introduction. The superior trees of Eucalyptus in Guangdong and Guangxi were selected, and the seed orchards and mother forests were established, which created the necessary conditions for providing good hereditary seeds and building fast-growing and high-yield forests. Seed collection should be paid attention to from excellent mother trees and seed orchards. Eucalyptus urophylla can blossom and bear fruit about 3 years after afforestation, and the fruiting period is about 10 years. However, it is best to use more than 10-year-old as the mother tree, at this age phenotype and heredity are relatively stable. In the phenological period of Eucalyptus urophylla in Leizhou Peninsula, Guangdong Province, the fruit ripens from October to November, and the general rule is early in the south and late in the north. After the capsule is mature, it will not fall off after hanging on the tree for more than 1 year, and the seeds are not completely scattered. The capsule is dark green with brownish spots, which is the characteristic of seed maturity. After the capsule is harvested, it is usually exposed to the sun for 4 hours for 20 hours. the petal is cracked and the seeds are scattered. In order to avoid too long exposure time and affect the vigor of seeds, seeds can be collected in batches. The seed emergence rate of the capsule is 8%-12%, the purity is 8.6%, and the 1000-grain weight is 0.309g, 3.236 million grains per kilogram. The germination rate of the selected seeds can reach 85%. The seed bag of Eucalyptus urophylla is stored in a ventilated and dry place and its vitality can be maintained for more than one year. 2. Seedlings of Eucalyptus urophylla afforestation, with bare root seedlings and container seedlings (including nutrient brick) seedlings. In the past, bare-root seedlings were mostly used for afforestation, but now they are often used in camps? Brick seedlings carried out large-scale afforestation, and in some places, plastic bags, nutrition cups, nutrition baskets and other seedlings were used for afforestation, and good results were obtained. Container seedling afforestation is considered to be one of the key measures for rapid growth and high yield according to trees. Eucalyptus seedlings can be divided into four growth stages: ① germination stage. From seed germination until cotyledons turn green. The length of time varies from season to season. It takes 4-8 days in summer and 10-20 days in late winter and early spring. The characteristics of this period are seed water absorption and germination, initial root system, tender tissue, poor stress resistance, shade and humid, avoid hot sun and water collapse, easy to cause diseases and insect pests, and should strengthen management. ② true leaf opposite phase. From the first pair of leaves to 5-6 pairs of true leaves. Because most of the young leaves of eucalyptus seedlings are opposite, but only a few are alternate, it is called true leaf opposite stage. It takes about 10 days in summer and about 20 days in late winter and early spring. At this time, the seedling height is about 5 ~ 6 cm, the seedling is still delicate, the growth rate of underground part is almost the same as that of aboveground part, and the resistance to surface high temperature, drought, rainstorm and other adverse factors is still weak, but the fibrous root begins to elongate, the requirements for water, fertilizer and light gradually increase, and competition begins to appear among seedlings. Attention should be paid to fertilization, density adjustment and control of diseases and insect pests in management. ③ true leaves alternate stage, from true leaves opposite to alternate, until the leaves of seedlings meet on the bed. The seedling height is about 6~11cm, and it takes about 20 to 30 days in spring. The vegetative organs of the aboveground part of the seedlings increased, the tissue was more abundant, the stress resistance was strong, the growth rate began to become faster, and the competition for nutrient area among seedlings intensified. This stage is mainly inter-seedling, seedling replenishment, weeding and forced fertilization, and continue to control diseases and insect pests. In the fast-growing period of ④, the branches and leaves of the seedlings are connected to the nursery on the bed surface, and the seedling height is 12~20cm. At this time, the seedlings have stronger resistance to stress. As long as water and fertilizer are suitable, the daily height growth can reach 0.5~1.0cm, and it will take about 15 days to complete this stage in late spring and early summer. The main work is topdressing, watering and pest control. The sowing season of seedlings in separate beds is not very strict in warm climates. the rainstorm, hot sun and frost that may be encountered in summer and autumn at the initial stage of seedlings should be avoided, generally in February to March in spring and from September to October in autumn. Seed germination needs sufficient water, mainly keep the soil surface layer about 5 cm moist, should not be too wet. The shade addiction in the seedling stage is very short, and it is necessary to increase the light time and light intensity 10 days after germination. Therefore, the shade shed should be removed in time. Where there is frost damage, the shade canopy acts as a greenhouse. At the initial stage of seedlings, special attention should be paid to soil management to keep the seedbed moist and grass-free. After sowing for 1-2 months and autumn sowing for 2-3 months, the seedlings had to be transplanted at 6~10cm, and the seedlings were transplanted with soil to keep the roots intact without cutting leaves, and there was no need to go through a recovery period after transplanting, which showed great superiority in terms of survival and growth. Seedlings up to 30~60cm (small seedlings) or 1 × 1.5m (large seedlings) can be out of the nursery for afforestation. 3. The growth rate of afforestation eucalyptus largely depends on soil preparation. The effects of different soil preparation methods on the growth and root development of young eucalyptus forest in Lianyuan showed that the growth of machine ploughing full reclamation hole (depth 20~25cm) was the best, artificial hole (40 × 40 × 33 × 60 × 60 × 50cm) was the second, Niuli reclamation (depth l0cm) was the worst, and the growth of height and diameter in machine ploughing full reclamation cave was 20% higher than that in cattle plough zone. Machine ploughing is also better for root development. Different land preparation methods are adopted according to different land suitable for forest. In the platform below 50, machine ploughing should be carried out, with deep ploughing of 20 to 25 cm, or even more than 30~40cm. In the hilly land of 5-150, the land is reclaimed along the contour according to the topography, with a bandwidth of 100-120 cm and a depth of 30-40 cm. Both of them are dug at a fixed point of 60 × 60 × 50. Big hole. At fifteen. Eucalyptus should not be planted on the above steep slopes. In order to promote the rapid growth of Eucalyptus urophylla, base fertilizer should be applied in the hole. Equal high-level ditches can be built in thousands of arid areas to store water. The row spacing of Eucalyptus should not be too close. The planting density depends on the ecological conditions and the purpose of forest management, and the planting density should be 100-120 trees per mu, and the pulp forest with short rotation should be planted densely. The configuration of wide row spacing and narrow plant spacing, such as 1.5 × 4m and 2 × 3m, can make the trees make full use of the nutrient space, fully accept the side light, and be more convenient for mechanical tending. In the rectangular configuration, when afforesting and building soil and water conservation forests in hilly and mountainous areas, the rows should be consistent with the horizontal contours; in areas with strong winds, the direction of rows should be perpendicular to the direction of harmful wind; in flat areas at high latitudes, rows in the north-south direction are more beneficial to make full use of light than those in the east-west direction. The afforestation period of eucalyptus in Qianyuan is from February to March in spring and 9: 10 in autumn. Afforestation in early spring should pay attention to the weather, and it is not suitable for afforestation without rain for a long time. It can also be planted in case of rain from February to August, but it is appropriate to choose the interval between rainy days and 3-4 days after rain. In frost-free areas, afforestation can also be done in winter. Afforestation seedlings should not be too large. The height of big seedling was 80: 120 cm, and that of small seedling was 30: 60 cm. When planting large seedlings, cut off the branches and leaves of 2 / 3 or 3 / 4 before raising seedlings, and sometimes cut off the tender shoots; if the weather is dry or the afforestation season is too late, you can cut off the trunk, which should not be too high, generally cut off from the rhizosphere 5~10cm. Truncation should be carried out before or immediately after seedling emergence. After cutting and planting, there are a lot of shoots sprouting, so prematurely pruning should be avoided. It is best to keep 2-3 cuttings and keep one after a few months. Seedlings can be cut less or not when planted, and it is better to bring some persistent soil to the roots. Many local experiences have proved that afforestation with small seedlings is better than afforestation with large seedlings, which not only has a high survival rate, but also has a large growth rate. But the seedlings must be afforested in the same year? Nurture in time. 4. The main measures of tending young forest include loosening soil and weeding, fertilizing, fixing trees and planting green manure, etc. Soil loosening and weeding should be carried out in early spring, before the rainy season or after the rainy days in autumn, 2 or 3 times a year, for example, for 3 consecutive years. The ways are belt reclamation and hole reclamation, depending on the site and forest management conditions. In the area with gentle slope of the site, tractors or cattle ploughs can be used for reclamation and tending, with a bandwidth of 1.5m and a depth of 10m and 15 cm. Artificial reclamation is generally used in places where there is no machine reclamation or cattle plough conditions. Due to the shortage of labor or the limitation of conditions, artificial hole reclamation is usually used, with the plant as the center, with a radius of 0.5-0.6 m and a depth of 10cm. For the sites with few weeds and loose soil, the times of loosening soil should be reduced and fertilizer should be applied. The exposed scoured land should be nurtured according to the horizontal belt, fertilizing and planting green manure in order to store water and conserve soil to improve the site conditions. Although Eucalyptus urophylla does not have strict requirements for soil fertility, proper fertilization in its young forest stage can greatly promote growth and be conducive to the good development of stem shape. Fertilization is best carried out in early spring combined with loosening soil and weeding. The application of organic complete fertilizer or organic compost mixed with a certain proportion of ammonium sulfate and superphosphate fertilizer can be applied in ditch or hole. In the afforestation of container seedlings, there are generally two seedlings in each planting hole. After one year, the roots of most plants are continuous and begin to differentiate, and the plants should be fixed, that is, one with good stem shape and dominance in each hole. For the young forest with poor conditions on the opposite site, the plant setting can be delayed by one year. Planting green manure plants in young forests can inhibit the growth of weeds, reduce surface evaporation, increase soil fertility and promote the rapid growth and high yield of trees. Edamame bean, pig dung bean, hairy vine bean, Japanese grass, kudzu vine and tropical alfalfa can be planted, but the covering plants will more or less compete with the trees for water and fertilizer during the growth period, so the planting of green manure should be at a certain distance from the forests. and timely cutting and combined with young forest tending to press green fertilizer. The young plantation of Eucalyptus urophylla grows rapidly and becomes a forest after 3-5 years of afforestation. After the canopy closure of the stand, with the increase of the age of the forest, the contradiction between the competition for water, fertilizer and nutrient area among plants becomes increasingly acute, the natural pruning is fast, and the differentiation is obvious. When the trees are strongly differentiated, tending and thinning should be carried out in time to eliminate the fierce competition among trees and ensure the normal growth of the stand. In the process of tending, we mainly master the beginning period, method, intensity and repetition period of tending thinning. The initial period of tending thinning is usually 4 ~ 6 years old, that is, tending thinning begins when the trees strongly differentiate and the pressed trees account for 30% ~ 40% of the total number of trees. Most of the eucalyptus forests in Leizhou began to tending and thinning when the average height of the stand was more than 6m. Thinning in the lower layer is mostly used in the methods of tending thinning. The principle is: to remove the weak and retain the strong, to remove the bad and retain the good, to harm and retain benefits, and to take proper care of sparse density. That is, to retain the dominant, sub-dominant and medium-sized trees with normal development, straight stem shape and suitable for cultivation of wood; cut off the pressed wood and some other trees that are poorly developed, bent trunk, suffer from diseases and insect pests, and are not suitable for wood cultivation; in sparse areas, in order to avoid windowless and bare woodland after thinning, we should also keep them as thinning trees. The intensity of tending thinning accounts for 30%-40% in terms of the number of trees, 15%-25% in volume, and the repeated period of tending and thinning is 3-5 years, depending on the growth of the stand. Due to the good natural pruning, manual pruning is generally not carried out. Felling and renewal; the cutting age is determined according to the purpose of operation. Eucalyptus urophylla has a strong sprouting power, which uses short rotation and bud regeneration to cultivate all kinds of wood. This tree species has rapid growth and straight stem shape. Advantages such as quick intermediate income. Generally, new buds began to sprout in 10-20 days after cutting, peaked in 30-50 days, sprouted slowly in 70-80 days, and the germination rate reached 80%-95%. After cutting, the sprout was 3.5-4m in height and 2.5~2.8cm in breast diameter. The average height of 10-year-old is 1112 m, DBH 8~10cm, tree volume per mu 6.5~8.2m3, can be cut and utilized. The stem shape of Eucalyptus thunbergii sprouting regeneration forest accounts for more than 90%, and the forest phase is neat. The sprouting of each cutting root can be arranged at the age of 1 ~ 2 years, and after 3 ~ 4 years of age, the cutting can be carried out. The height is 450m / mu, the diameter of 3~5cm is 450m / mu, the 300~400kg of eucalyptus leaves is harvested, and the oil 2.5~3.5kg of eucalyptus leaves can be distilled. The best age of sprouting and regeneration forest is 6-10 years, and it is not suitable to be too late and too early. Sprouts can be renewed in all seasons, but winter is better in areas with typhoons and torrential rains, otherwise summer is better. Generally, the cutting height of regeneration should be 5 cm higher than that of the ground.