Forest cutting mode
That is, the main cutting methods of forests. It can be divided into three types: selective cutting, clear cutting and clear cutting. The choice should be made according to forest species, soil quality, topography, renewal mode and business purpose.
Selective cutting
It is suitable for natural regeneration of multi-layered young forests and old forests. The operation is complicated and the technical requirements are high. Cutting operation does not have a certain renewal time, and a few trees are constantly selected for cutting. Land renewal adopts the methods of artificial renewal, natural seed renewal of surrounding trees or budding renewal of cut trees. Selective cutting can often keep the forest closed, the woodland will not be exposed, it can prevent soil erosion, help to maintain soil fertility and protect young trees, and it has great resistance to snow disasters and wind disasters, and has a good water conservation effect. However, due to repeated logging, it is difficult to implement mechanization and the cost of logging and collecting wood is high. It is mostly used in woodland areas with steep slopes and shelterbelts.
Clear cutting
Cutting operation mode of cutting all or most mature single-layer forests of the same age at one time. This method is simple in process, suitable for mechanized production, and beneficial to the formation of the same-age forest, the renewal of positive tree species that grow rapidly at a young age, and the transformation of mature and over-mature natural forests; High efficiency and low cost. The disadvantage of clear-cutting operation is that the forest land is exposed after clear-cutting, which is easy to cause the loss of topsoil and humus, which is not conducive to soil and water conservation. In order to strengthen the protection of the ecological environment, China and many countries in the world have restricted clear-cutting areas, focusing on small-area clear-cutting operations, and require timely artificial renewal and artificial promotion after logging.
Shelterbelt cutting
It is mainly distributed in mature single-layer forests with strong natural regeneration ability, or stands close to single-layer forests. Generally, cutting trees is divided into two or three times, and the whole cutting period does not exceed one age class. Shelterwood cutting's business includes the use of natural seeds to update and maintain the forest environment and prevent soil erosion. The first cutting in shelter forest cutting is called pre-cutting, which makes the crown get sunshine, promotes flowering and fruiting, and creates good stand conditions for seed germination and young tree growth. Its cutting strength is about 25 ~ 30%. The second cutting is called the next cutting, that is, in the year when a large number of trees bear fruit, the cutting intensity is 10 ~ 25%, which makes the trees sparse. The canopy density after cutting is about 0.4 ~ 0.6 to realize the survival and growth of mother tree seeds. The third felling is called post-felling, that is, with the growth of young trees, the mature reserved trees are gradually cut down.
Technical requirements of forest harvesting
(1) Forest cutting should be based on the investigation of cutting area resources, and reasonable cutting methods, regeneration methods and various production technical measures should be designed according to local conditions. Wood production must be conducive to forest regeneration and environmental protection, make full use of logging residues and improve the utilization rate of forest resources. (2) Before forest harvesting, the working area of the forest farm for one year should be divided into cutting areas. The principle of cutting area division is conducive to the comprehensive management of one ditch and one slope and the reasonable harvesting and transportation of wood, and its boundary should be combined with the division of forest management inventory as far as possible. (3) According to the logging system, the attraction area of the loading yard is divided into working areas. ④ In the working area, stands with the same site conditions, stand factors, cutting methods and management measures, and the same skidding system are divided into small categories. Small class is the smallest unit of organizing production and forest management, and it is also the basic unit of logging and forest management investigation and design. According to the skidding system, the boundary of small class is mainly divided into natural divisions, and its area is implemented according to national regulations. ⑤ To determine the cutting methods, we should conscientiously implement the cutting methods and relevant regulations stipulated in the National Forest Law and the Regulations on Forest Cutting Renewal, and we should not force unification according to local conditions. ⑥ On the basis of fully understanding the distribution of logging resources, logging renewal methods, site conditions and natural flow direction, design appropriate skidding methods and select corresponding skidding machinery. ⑦ The design of skidding track is based on the principles of attracting more wood, short skidding distance and safe operation. Should be conducive to the cohesion between aggregates, is conducive to the intensive management of forest resources, economic and reasonable, taking into account the requirements of forest management. ⑧ According to the distribution of forest resources and the direction of skidding, carry out careful reconnaissance and route selection, and then determine reasonable wiring through technical and economic comparison, and try to extend to the abdomen of cutting area where resources are concentrated. Pet-name ruby loading yard (stare blankly field) should be located in a dry place as far as possible on the basis of the selected wood fork line, according to the conditions such as resource distribution, the number of attracted wood, the skidding direction and the shortest skidding distance. Attending in order to improve the sanitary environment, prevent forest fires and diseases and insect pests, improve soil, promote forest regeneration, and make full use of logging residues, the logging land should be cleared. The cleaning method should be to select the top branches, semi-circular logs and small-diameter logs that can be transported out for use, and then spread the residues in low-lying places to let them rot, or pile them up dispersedly, and burn them when they are not fire-proof. ? Clear-cutting land should be mainly artificial regeneration. Clear-cut land that ensures selective cutting and natural regeneration of forest land and target trees in shelterbelt cutting can be promoted through artificial regeneration or natural regeneration.