Techniques of rebuilding Pinus sylvestris var.mongolica young forest into Korean pine nut forest

In recent years, the establishment of Pinus koraiensis fruit forest and Pinus koraiensis nut forest in Heilongjiang and Jilin Province has developed rapidly. However, due to the deviation of people's understanding, they ignored the selection of excellent seed ears for grafting to establish forests, and the selected seed ears were rarely identified as excellent varieties. Thus, the establishment of Korean pine nut forests without selection could not only guarantee the yield and quality of seeds, but also ensure premature, high and stable yields.

The practice proves that the young Pinus sylvestris var. mongolica forest can be used to reconstruct the fruit forest of Pinus koraiensis quickly and effectively. This paper introduces the necessity, possibility and main operation techniques of establishing Pinus sylvestris var. mongolica young forest into Pinus koraiensis nut forest.

1 Necessity

Forestry in the future should be efficient forestry with ecological, social and economic benefits. Efficient forestry emphasizes the goal of input, the intensity of management and the efficiency of output.

At present, Pinus sylvestris var. mongolica forests built in various places have ecological significance, but their social and economic benefits are relatively low, affecting economic income. If the forest is transformed into nut forest, it can not only beautify the ecological environment, but also increase the income of employees, which is an important way for the forest area to get out of economic difficulties.

2 Possibilities

Pinus sylvestris var. mongolica has strong adaptability, cold resistance, drought resistance, barren resistance, sand resistance, especially easy reproduction, low seedling and afforestation costs, and rapid growth, but its economic and ecological benefits are far inferior to those of Pinus koraiensis. Grafting Pinus koraiensis with Pinus sylvestris var. mongolica as rootstock can indeed make Pinus koraiensis grow healthily and blossom and bear fruit ahead of time. In the 1950s, Omsk, the former Soviet Union, adopted Pinus sylvestris as rootstock to graft Pinus sibirica in the southern forest steppe area, succeeded in afforestation and obtained seeds, which improved the local ecological environment and economic conditions. In order to speed up the nut production of Pinus sibirica in Siberia, Russia, scions of Pinus sibirica were grafted on 5~7 years old Pinus sylvestris by means of cross-stock grafting. Seeds could be obtained in 3 years and 110~200kg/ha (maximum yield 270~340kg/ha) after 15 years. Muling Forestry Bureau established timber forest with cross-stock grafting Pinus koraiensis in 1960s, and obtained fast-growing Pinus koraiensis forest successfully, and set fruit. Pinus koraiensis was grafted on 20-year-old Pinus sylvestris var. mongolica in Hongqi Forest Farm of Daqing City in 2000, and began to flower and bear fruit in 2004. The growth rate of inter-rootstock grafting is indeed faster than that of same-rootstock grafting. Pinus sibirica was grafted on Pinus sylvestris var. mongolica var. mongolica var. mongol

Some people suggested that grafting between Pinus sylvestris var. mongolica and Pinus koraiensis might not heal well, or appear big and small feet phenomenon, affecting forest establishment. According to Russian expert investigation, there are about 25% grafting elephant foot phenomenon, generally appeared in grafting 25 years later. Russia used provenance selection and individual selection to select good compatibility of European red pine varieties, which solved this defect.

3 Technical regulations for forest establishment

3.1 Survey and Planning of Forest Land

3.1.1 Site condition investigation Before investigation, stand evolution and meteorological and hydrological data are collected. Survey the topography, topography, soil, diseases, insects, rodents and the condition of Korean pine forest nearby. It is better to draw topographic maps of forest land, mark roads and rivers, investigate forest vegetation and tree measurement factors in detail, and provide reliable information for planning and design.

3.1.2 According to the topography, forest map and forest stand condition, the location and trend of shelter forest, pollen forest and road shall be determined. According to the stand condition, the grafting plant, row spacing and stand strengthening methods were determined. General plant, row spacing for 5×5m, grafting before the best use of red paint registration, in order to facilitate grafting workers operation. (1) Design and construction of shelterbelt In order to make Korean pine nuts have a high yield and harvest, reduce wind damage, conserve water sources and conserve water and soil, shelterbelt must be designed in the main wind direction. According to the forest land position, the area size concrete design shelter forest type and the disposition way. (2) The design of pollen forest and grafting. The nut orchard of Pinus koraiensis often lacks enough high-quality pollen at the initial stage of fruiting, which affects the yield and quality of seeds. It is necessary to graft high-quality pollination trees in the main wind direction and around the fruit forest to ensure that there are enough pollen in the forest, and at the same time, it has the function of blocking inferior pollen from entering the forest. Road design Road is an important hub for the internal and external connection of nut forest, with the functions of transportation, traffic, fire prevention, ventilation and drainage, and should have long-term plans. The distance between roads should not be too close. The width of roads is generally 3~4m, and the slope exceeds 10°. The road around mountains can be built. 4. Grafting configuration diagram of Pinus koraiensis fruit forest Before grafting, draw grafting construction configuration diagram. Female and male arrangements are generally 4∶ 1,3 ∶1 and 2∶1, but we use 4∶1.

3.2 Strengthening of Pinus sylvestris var. mongolica before grafting

1~2 years before the reconstruction of fruit forest, it is necessary to strengthen the management. Mainly for light tending, weeding, loosening, pruning and disease, insect, rodent pest control, the purpose is to achieve pre-grafting tree healthy growth, improve grafting survival rate. If the number of rootstock is not enough or uneven, we should timely replant large-seedling Pinus sylvestris var. mongolica to make it evenly distributed and improve seed yield.

3.2.1 Light transmission tending Before light transmission tending, light transmission tending investigation and design must be carried out, and construction shall be carried out according to the design. The method comprises the following steps of: adopting comprehensive light transmission tending of single trees, ensuring that the quasi-grafted trees are not squeezed by shrubs and trees, and creating convenient conditions for grafting construction. Conditions but also loose soil, weeding, application of organic fertilizer or inorganic fertilizer.

3.2.2 Pruning, shaping and controlling diseases, insects and rodents are important means to improve resistance of quasi-grafted trees. Dead branches, diseased branches, weak branches, overlord branches, bore branches, overlapping branches, horizontal branches should be pruned, and double branches can also be pruned. Pine withered shoot disease, red spot infectious disease is very strong, should be controlled with chemicals. Rat pests should also be prevented and eliminated in time.

3.3 A well-prepared scion of a good variety

Scion of fine variety is one of the important conditions to ensure high and stable yield of Pinus koraiensis fruit forest. Must apply after variety identification of fruit and good quality of fine clone branches as scion, do not arbitrarily use bad varieties as scion. A 9-year continuous investigation was carried out in Qingshan Seed Garden of Weihe Forestry Bureau of Heilongjiang Province to evaluate the clonal mother trees of Pinus koraiensis. Fifteen excellent clones of nut type were selected from 200 clones as excellent varieties for developing nut production of Pinus koraiensis. 124, 56, 117 and 179, and 52, 58, 118 and 121. These two types of fine tree species have obvious phenotypic characteristics. Characteristics of high and stable yield type: crown width, crown length, fruiting layer thickness accounting for 3/4 of tree height, bearing more seeds every year; characteristics of high yield pollen tree with large fruit: crown width narrow, crown short, pruning obvious, fruiting layer thickness accounting for only 1/5 of tree height, cone length but less quantity, pollen yield high and good quality.

3.4 grafting

Grafting technology and grafting time are related to the success or failure of forest establishment and the cost of forest establishment. Because grafting technique is not perfect, it affects grafting survival rate and preservation rate; different grafting methods also affect grafting survival rate and preservation rate.

3.4.1 Grafting time can be in spring and summer grafting, we use spring sap flow (April 17~20) grafting. Too early grafting time resulted in late callus formation and low survival rate, too late grafting time resulted in easy freezing injury of grafted shoots. Therefore, to judge the grafting time correctly, the general experience is that the best grafting time is when the average temperature of day and night reaches about 10℃.

3.4.2 Scion collection and storage scion storage time should be short, it is best to collect in hibernation, storage cellar temperature should be kept at 0~5℃, scion should be buried with ice and snow, to achieve the purpose of moisture preservation.

3.4.3 Grafting methods Grafting methods are determined according to the technical proficiency of grafting workers. The grafting length should be more than 10cm, and the grafting position should be the top of the central leading branch and the top of the first to third whorls. If the tree is tall, the bark of the central leading branch is thick, and the grafting is not well matched with the rootstock, it is easy to cause the grafting survival rate to be low, so it should be grafted at the position of 1~3 whorls. In order to keep moisture and prevent late frost from damaging the terminal buds, a breathable white plastic bag should be immediately covered after grafting.

3.4.4 After grafting management May 6, the grafted terminal bud gradually began to sprout, the plastic bag was removed in time, the grafted rootstock terminal bud and lateral bud were cut off, and then the wound was smeared with lead oil. The first release was carried out from May 30 to June 10, and the dead plants were completely untied. From July 25 to July 31, the second loosening was carried out, and all the top and lateral buds of whorls exceeding the grafting height were cut off. After cutting the branches of Pinus sylvestris var. mongolica in the current year, many adventitious buds grow and form many young branches. The rootstock should be cut again in autumn, but the vegetative branches should not be cut all at once, otherwise it will affect the grafting survival and overwintering.

3.5 Disaster and growth surveys

In autumn, the disease, insect pest and growth condition of grafted plants should be investigated. 68% scions had two times of growth, the average growth of grafted plants was 8.9cm, and the highest was 14cm. Because the secondary growth exceeds 60%, the secondary growth seedlings are covered with white breathable plastic bags at the beginning of November after winter to prevent freezing damage to the new branches that are not completely lignified.