Section IV Forestry Survey First, sample selection (standard) selection The method is to select one or several typical standard sites in the forest stand as samples, and use the survey results as a standard to calculate the method of the entire forest stand. In the area of ​​survey, secondary forest tending investigation, artificial forest tending investigation, afforestation design, forest growth and pest and disease survey commonly used standard survey method. According to the purpose and requirements of the survey, a certain number of representative lands that can reflect the average mark of the tested stand should be set in the forest. It is the epitome of the entire forest, through which it can obtain various forestry quality and quality standards. The results of the investigation of the standard grounds will be enlarged by area, and the results of the survey of the entire forest will be obtained. The standard is divided into temporary and fixed categories. Temporary standard sites are set up to meet the needs in a timely manner and provide information quickly. Only one survey is conducted. The permanent standards are set for conducting scientific research and testing within a relatively long period of time and the system is continuously collecting data. A number of investigations should be conducted and the requirements for measurement and design should be strict. (I) Standard setting principles 1. Must conduct a comprehensive survey of the forest land under investigation and master the characteristics of the whole forest, such as tree species composition, forest age, tree height, diameter, canopy density, sparse density and site conditions. 2. According to the characteristics of the forest stand, select a representative lot in the forest as the standard place, that is, the standard place is selected in the common stand. The choice of standard land can reflect the characteristics of the entire forest stand from the stand density, stock volume, and site conditions. 3, the size of the standard area, generally based on the required accuracy and the stand structure changes, with small classes as the unit for selection, the standard area shall not be less than 5% of the class area. 4. If the forest phase and topography change greatly, choose a standard land to not represent the entire forest stand, you should set a few more standard lands or set the strip standard land along the slope according to the actual situation. 5. If a standard place is set up, if it is necessary to observe it for a long period of time, the standard place must be located away from forest margins, roads, and survey lines from places where it is artificially damaged. (II) Calculation of standard area n=(t*t*c*c)/(p*p) Where: n - the number of plants that should be included in the standard plot; t - reliability index (when reliability index is 95%, t=2); c - diameter variation factor; p - allow error. In practical work, the number of plants that should be included in the standard land set in the near and mature forest should be no less than 250, and the number of plants that should be included in the standard land set in the young forest should not be less than 300. According to this principle to determine the size of the standard area. Investigators can select a small sample of 400O in the forest land to check the number of the main tree species and use the method of proportionality to calculate the area of ​​the standard land that meets the number of plants. Second, the stand factor investigation Characteristic signs that describe the quantity and quality of forests, such as: site, area, forest class, small class, tree species, origin, species composition, forest age, canopy density, average tree height, average diameter, density and stock volume, year after year Growth, growth rate, etc. The details include altitude, slope direction, slope position, slope, soil texture, soil thickness, parent rock, undergrowth, ground cover, etc. Section V Raising Thinning Construction Technology The tendril construction mainly includes construction organization and preparation work (refer to Chapter 6: Final Cut and Update). The key technology for tending and thinning is to determine felling timber. Before the construction, the organization technicians determine the harvested wood at the determined construction site. The purpose is to Ensure good growth and development of the wood, and remove trees that hinder the growth of wood and defective wood. The principle of forest tree grading standards is an important basis for the scientific selection of logging, and both qualitative and quantitative thinning should be established on this basis. The essence of tending and thinning is the elimination of forest trees. Therefore, according to different tending methods and selection requirements, correct and correct determination of felling timber is the key to realizing tending purposes. Because of the site conditions, growth stages, initial planting density, number of tending, and business objectives of the forest stand, combined with the complexity of the forest, it is difficult to determine the logging work. Therefore, when selecting logging, technicians are required to carefully observe and compare the selection of trees and then make the right choice. Generally, the following principles should be followed when selecting timber for tending thinning: 1. Strictly select the wood according to the cutting intensity and the object to be harvested, and try to keep the retained wood distributed evenly. 2, can not be caused by improper selection of wood exposed, forming a sunroof. 3. In order, select the damaged wood, disease wood, decay wood, pressed wood, curved wood, double-wood, general wood and individual fine wood. 4. When the “cutting object†has a certain effect on the growth of the preserved wood or the forest cover, the logging timber should be deferred. 5. From the consideration of maintaining ecological balance, attention should be paid to the selection of wood for wildlife that live in forest stand. For forests built with nests, except for diseased wood, they should generally be preserved. Undergrowth shrubs and undergrowth should not be completely removed without affecting the growth of the main tree species to adjust the composition of litter and improve soil pH. At present, there are two different specific practices when selecting logging in a forest stand. One is to emphasize the growth of individual plants that retain wood, that is, in the more dilute state, each tree is cultivated in a directed manner and kept until the main cutting. In dense forest stands, a certain number of excellent and well-developed trees of good quality are selected in the forest stand first, and the sign is used as “final loggingâ€, and is retained until the final logging period, so that each time the forest is thinned At the time, the harvested wood was determined based only on the relationship of the final logging, and a good growth environment was created for the growth and development of the final logging to the maximum extent. The general care for the rest of the temporarily preserved forests was still based on the above principle of eliminating trees. This method is suitable for cultivating large-diameter materials and adopts the methods of large-intensity, long-interval, low-density management, which saves labor and does not require the advantage of selecting wood for each person. Another approach is to focus on the growth of the entire forest when selecting trees, and to create a good growth space for all the reserved wood at the time of tending, and to select only a period of time before the main cutting. "The final logging." This approach is suitable for the cultivation of small and medium-diameter timber, and uses management methods with low intensity, short interval, and high density. The advantage is that it can be used to take down the harvested timber, compared with the stand used for the stand differentiation of forests. At present, this method is mainly adopted for forestation and thinning of Larix principis-rupprechtii in Mengzi Forestry Bureau. Through many years of practice, the selection of thinning of larch forests for felling and harvesting of timber is carried out according to the following conditions: First of all, after the relevant departments at the higher level approved the plan, the technical staff and construction personnel who participated in the operation should be organized to study the program and the requirements for approval. The design principles and technical requirements of the plan should be thoroughly understood so that the bottom of the mind can be clearly understood. Secondly, before the construction, the small class involved shall be reviewed. The transposing method is generally adopted, mainly reviewing the locations of small classes, forest classes, small classes, tree species, the number of pre-digging acres, the volume of pre-harvest acres, and other factors such as review and verification. The design plan is in line with the next step. In addition, technicians and constructors must make comprehensive investigations on the small class before the number is marked, so as to fully understand the specific conditions of the small class and the distribution of forest stand, so that the situation in the heart can be cleared. The following two principles must be followed when marking numbers: First, respect the design proposal and strictly follow the design plan; second, follow the five principles for determining logging. When marking the number, use 1.2-1.5 meters of the trunk to mark the upper and lower sides with colored paint. The numbering method is used to perform the marking twice in the first pass. The number of strains is controlled in the first pass. The total number of cuttings in the small class is determined according to the design scheme; the approximate row spacing between the reserved woods is calculated based on the number of reserved plants per acre; combined with the number of trees and the actual conditions of the small class, Determine the principle of harvesting wood for registration; the first pass must hit the total number of harvested trees. After the end of the first pass, the sample should be set within the forest stand for backtesting. For example, if the consumption is accumulated and the number of reserved plants is within plus or minus 5% of the design, there is no irrational reserve wood in the stand and it is not harvested properly. To carry out operations, such as out of the error range, there is an unreasonable phenomenon will need to be adjusted to hang the second pass number. Section VI Effect and Impact of Thinning
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