"North China Larch Pine Fast-growing and High-yielding Forest Cultivation Technique"

3. According to the relationship between DBH and crown amplitude, find the appropriate nutrient area and determine the number of reserved trees. The slope tree farm uses the least square method to set the regression equation of the crown and DBH:

y = 0.9533+0.118x+0.0013x2

In the formula: y-crown;

X- breast diameter.

This is a quadratic parabola relationship, and the number of plants preserved in the shaded slopes of Larch plantations based on nutrient areas is determined (Table 5-7).

For a 14-year-old larch plantation in a small class, the number of trees per hectare is 3755, the optimum nutrient area per plant is 3.14O, and the suitable number of plants per hectare is 3185, and 570 plants should be thinned, and the thinning intensity ( According to the number of plants) is 15%.

Table 5-7 Diameter of Breast Diameter and Diameter of Larch Plantation

(IV) Quantitative thinning based on the chest height area

It is generally difficult to determine the tree height of the stand and the error is relatively large. Using the angle gauge method to determine the area of ​​the forest branch can be easily measured without setting a standard or a wooden ruler. According to the purpose of the operation, the developmental stages of the stand were determined to determine the optimum chest standoff area for the stand and then the optimal chest

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Note: The upper dashed line indicates the thinning, and the lower dashed line indicates the thinning.

Figure 5-1 Schematic diagram of the changes in the breaking area of ​​forests during cutting periods.

The high cutting area determines the thinning intensity for thinning. As shown in Figure 5-1, there are two horizontal line areas, and the important one is the horizontal line below, because it defines the forest area after each thinning. During the entire rotation period, the plan to control the forest density is mainly determined by the lower limit of the area of ​​the area that is retained after each thinning. For example, in order to promote the growth of forest tree diameter without reducing the total yield of forest stands, the suitable horizontal line for retaining the cross-sectional area ranges from about 11 to 40 O/ha. Generally, conifers are higher than the broad-leaved trees and the shade-tolerant tree species are higher than the hi-light tree species. For example, spruce and fir are about 30 to 40 O/ha, while those with negative resistance to negative resistance are 14 to 30 O/ha, and the broad-leaved trees from light to hardwood are 10 to 23 O/ha.

There is no certainty as to whether or not the size of the reserved area is related to site conditions. It is generally believed that for the same tree species, there should be more cut-off area reserved for forest land with good site conditions.

Figure 5-2: The horizontal line of the lower limit of the middle section can refer to the growth process table of the tree species under management, or use the natural sparse process of the tree species to convert the number of trees into the sectional area, and the age, diameter at breast height, and area at chest height can also be used. The regression relationship, or based on the actual survey material, is calculated graphically.

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