(v) Quantitative thinning according to volume In Finland, pine forests are subjected to thinning for 2 to 4 times during the rotation period, and the method of controlling the strength by volume is adopted. This method is called: “rushing into thinning†and the thinning age is designed according to a certain growth prediction equation. The advantages are high and the controlled thinning amount (Table 5-8). Table 5-8 Sparseness Scale with Age and Superiority age High advantage (m) Logging volume per hectare (cubic meters) Thinning volume percentage (%) 18 5 8 40 33 11 48 33 53 17 108 38 73 21.5 101 32 This high intensity of directed thinning, the first thinning is to make 2200 per hectare; the second and third thinning harvest is mostly rod, and finally get the main building materials. According to tree species, site conditions, forest management objectives (cultivation period or species of production materials, etc.), design the ideal number of standing trees, and develop a thinning density management table. For example, the Longtoushan Forest Farm has been based on the law of tree height change over the past few years, taking the height of the upper forest stand as a parameter, showing the rule that the diameter and volume change with the stand density, ie, the growth rule of tree height, stand density The effect, maximum density curve, natural sparseness, etc. sparse density curve and equal diameter curve constitute the stand growth model, and are drawn into two easy-to-use “site index curves†Figure 5-2 and “density management map†Figure 5 - 3, according to the actual height of the stand (in the 500-2000 m2 sample plot, select the largest forest tree per 100 O for the upper forest, the average height of the upper tree) and the stand index curve "Check the site index, and then according to this index and the corresponding site-type retention sparse density, check the number of plants and volume that should be retained in the density management map." Based on this, the thinning intensity can be determined. With this kind of chart, it is also possible to design a directional cultivation process according to the predetermined cultivation period and the predetermined wood species specifications, so that the forest cultivation work can reach the level of prediction and orientation. For example, if the diameter of a plantation larch is D=12 cm and the density is N=2000 plants/ha, the sparse density after thinning is required to be not less than 0.8, the yield is M, the density is P, the height is H, and the number of thinning plants is △N. The volume of logs was △M and the diameter of cut D1. Check Figure 5-3. Production Production Production Production Production Production Production Production Production Meter 20 18 16 14 12 10 8 6 4 Age Figure 5-2 Site index curve of artificial larch forest (Another picture) Figure 5-3 Density control map of artificial larch forest 1. According to the D and N drawn, the volume of M = 174m3/ha was read on the scale of the ordinate, at the intersection of the equidistant line marked with 12cm and the line with the abscissa 2,000 lines per hectare (there are X marks). 2. Since the intersection point lies between the density density line and saturation density line marked with 0.9, P = 0.94 can be read out in proportion to the increase in the upper layer height. 3. Therefore, the intersection point is marked between the two tree line heights of 14m and 16m. Therefore, H = 15m can be read in proportion to the increase in the upper floor height. 4. According to the measured retention density of 0.8, the upper layer height is 15m. When the isodensity line marked with 0.8 is intersected with the imagined 15m tree line (there is the point), the retention after the thinning is determined by the ordinate. Quantity M1 = 148 m2/ha. The reserved density N1 = 1,400 plants/ha was determined on the abscissa. The diameter D1 = 13.3 M after the thinning was determined on the scale of the adjacent straight line. 5. According to the volume and density after thinning, the number of thinning and the volume of the thinning were determined. The results were as follows: ΔN=NC N1 = 2000 C 1400 = 600 plants/ha ΔM=MC M1 = 174 C 148 = 26 m2/ha In recent years, considerable progress has been made in experimental research on quantitative thinning, and mathematical analysis, mathematical statistics, and various variables of forest stand have been used (eg, the number of trees per hectare, average height of stand, average diameter at breast height per hectare. Changes in the time and space between canopy diameter, crown height ratio, forest height, site conditions, etc., use computer to solve regression equations and linear equations, design stand growth models, and even sustainable management models to solve each Tree species growth forecasting and tending thinning problems, and explore long-term management and sustainable use of the way. To sum up, in the process of forest cultivation, according to the direction of cultivation of fast-growing and high-yield forests, site conditions, and growth factors of forest trees, comprehensive consideration is given to the application of thinning and thinning techniques. Mediate forest growth environment and achieve fast-growing and high-yield targets. In the production application, the “harvesting wood†selection criteria can be flexibly selected according to the growth status of the stand. Sixth, survey design In the forest stand, select a representative area for the layout of standard plots and thinly press the different tending methods (lower, upper, integrated, or mechanical). Referring to the principles of "forest classification" and "three cuts and three stays", the selection of the cuttings will be carried out and marked. Then, the intensities of thinning, timber production, estimates of revenues and expenditures, etc. shall be calculated on a standard basis. This section does not describe in detail.
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