Study on cultivation techniques of Mother Forest of Picea crassifolia

Qinghai spruce is the main native tree species in Qilian Mountains. It has a long history, wide distribution and large area. It is one of the main afforestation tree species in Tianzhu and even the whole northwest region. The main advantages of this tree species are cold tolerance, drought tolerance, barren resistance, strong resistance and extreme low temperature of-30 ℃. It is a lateral root tree species with good soil fixation performance, strong ability to conserve water and soil, and is a good water conservation tree species. It is evergreen in winter and summer, beautiful crown shape, and is the main tree species for urban, courtyard, park and corridor greening. The trunk is straight and perfect, the material is soft, flexible and easy to process, so it is a better timber tree species. In 1983, under the guidance of Gansu Forest seed Company, 6.67 hectares of fine Qinghai spruce forest was selected as parent forest cultivation object in Tianzhu County. After years of careful experiment and cultivation, all the indexes have met the standard requirements of mother forest construction.

I. the basic situation of the test area

The experimental area is located in 74 small classes of 5 forest classes in Heigou Forest area of Wushaoling Forest Farm, Tianzhu County, at the eastern end of Qilian Mountain, with an area of 6.67 hectares. The slope is northeastward, the slope is 14 °, the average elevation is 2850 meters, the soil is forest brown soil, and the average thickness of soil layer is 100cm. The annual average temperature is 1.4 ℃, the accumulated temperature of annual growth is 1400 ℃, the annual rainfall is 400mm, and the annual evaporation is 1200 mm. The mother forest is a natural multi-layer non-aged forest with vigorous growth, strong development, high purity and good quality, a natural type of coarse bark, straight and complete trunk, complete and narrow crown, conical shape, lower height under branches, thinner lateral branches, no diseases and insect pests, no mechanical damage, no large dead nodes and withered tops, no double rights, normal flowering and fruiting, excellent and fine trees account for 21%, and belong to excellent stands. The average age, canopy density, height, DBH and crown width are 61 years, 0.7,18.7m, 11.6cm and 3.1m, respectively. There are 1630 mother trees per hectare. There is no inferior stand within 100 meters, which is an ideal stand for the reconstruction of the mother forest.

II. Test method and process

1. Test method.

Through thinning, loosening soil, weeding, fertilization and other cultivation processes, the selected mother forest cultivation objects were made to meet the standard requirements of the mother forest, and then seed collection and seedling test were conducted to compare the seed production capacity and cultivation level of the mother forest.

two。 Cultivation process

The first thinning cultivation was carried out in 1983. According to the principle of keeping the best and eliminating the inferior, the method of annular thinning was adopted, and the combination of uniform thinning and natural thinning was adopted. The thinning objects are poor-growing inferior trees, crushed headless trees and some medium-sized trees that should not be left as mother trees. The thinning intensity is 26%, 1200 trees per hectare are retained after felling, cultivation measures such as loosening soil, weeding and fertilization are carried out once a year, diseases and insect pests are controlled in time, their growth, fruiting and phenology are observed and recorded, and super seedlings are replanted in the forest glades.

The second thinning cultivation was carried out in 1990, with an intensity of 26% of the accumulation and 30% of the number of trees, and 855 trees per hectare were retained after felling.

In 1994, the third thinning cultivation was carried out, with an intensity of 27% of the accumulation, 24% of the number of trees, 0.5 canopy density after felling, and 625 trees per hectare, of which 338 were excellent trees, accounting for 54%, and 287 medium trees, accounting for 46%. The average DBH of the retained mother tree is 16.3 cm, the tree height is 11.3 m, the crown width is 3.25 m, and the height under the branch is 1.9 m, which basically meets the standard requirements of mother forest culture.

3. Seedling raising experiment

In 1999, the seeds of Picea crassifolia were compared with the seeds of Qinghai spruce, and the comparative experiments were carried out in 6 repeats. After emergence, the observation records were carried out. Through statistical analysis, ideal results were obtained.

III. Test results and analysis

1. After the mother forest was completed in 1995, it continued to carry out cultivation and management. Every seed year in 1998, it was estimated that the seed yield per hectare reached 33 kg, and the seed was full, the purity was high, the 1000-grain weight reached 5.0 g, and the germination rate was 90%. The seed setting amount, 1000-grain weight and germination rate were 15%, 8% and 20% higher than those of ordinary Qinghai spruce seeds, respectively.

two。 Through the statistical analysis of the results of seedling raising experiment, the proportion of second-round leaf seedlings raised by mother forest seeds was 21% higher than that of the control. In 2002, the average seedling height was 8.3 cm, the ground diameter was 0.3 cm, and 850 seedlings per square meter emerged, which were higher than 33%, 30% and 21% of the control respectively. When it came out of the nursery in 2005, the height and ground diameter of the seedlings reached 32 cm and 0.8 cm respectively, which was 31% and 33% higher than that of the control.

IV. Conclusion and discussion

1. On the basis of natural or artificial excellent stand, through sparse felling transformation, the individuals with fast growth, good crown type and dry type were preserved, and the sparse stand with rich fruiting layer and good light transmittance was cultivated to promote the early fruiting of trees. increase seed yield, improve seed quality, reduce seed production cost, and offspring grow fast and yield is high. The production of a large number of high-quality forest seeds to meet the needs of forestry production, so as to achieve the purpose of improved forest varieties, is also of great value in the preservation of germplasm resources.

two。 The cultivation of Qinghai spruce mother forest must be carried out on the basis of excellent stand. In addition, we should select areas with good site conditions, sufficient light, relatively gentle terrain and convenient traffic. It is preferable to be a pure forest and a forest of the same age. if you must choose a mixed forest, the target tree species shall not be less than 50%. If it is a forest of different ages, the age difference of the mother tree should not be too large. In addition, priority should be given to the selection of real forest, and the canopy density is generally above 0.6.

3. The key to the cultivation of Qinghai spruce mother forest lies in thinning and transformation. It is necessary to cut down inferior wood such as dead standing wood, wind fallen wood, diseased rotten wood, pressed wood and poor shape wood and some medium wood. Thinning should be carried out in 2-3 times, once every 3-5 years to prevent excessive thinning. After each thinning, the tree should be measured and recorded, and the canopy density should be 0.5 after successful thinning.