Table 5-4 Comparison of the theoretical values ​​of measured DBH and canopy area of ​​Larch plantations Breast diameter Cm Crown area (meter 2) Breast diameter Cm Crown area (meter 2) Measured value Class value Difference Real side value Class value Difference 6 2.516 2.5675 +0.0515 14 5.147 5.684 0.501 7 3.237 2.9856 -0.2514 15 5.853 6.042 0.187 8 3.644 3.3257 -0.338 16 6.202 6.438 0.236 9 4.199 3.8077 -0.312 17 6.514 6.836 0.322 10 4.199 4.0918 -0.0272 18 7.306 7.236 -0.07 11 4.227 4.4781 0.2511 19 7.645 7.6379 -0.0071 12 4.600 4.8659 0.2659 20 8.093 8.0425 -0.0515 13 5.147 5.2559 0.1086 twenty one 8.973 8.4478 -0.525 With this empirical equation, the maximum density index of the stand can be calculated for different growth stages of the larch plantation. This indicator is naturally greater than the density of standing trees under the condition of stand growth. However, it is advisable to determine the reasonable management and management density of Larch plantations. Some positioning studies need to be done to obtain the most reliable data. At present, according to the data from the Hebei Academy of Forestry Science, according to the correlation between the growth of breast diameter and the density of standing trees, it is initially proposed that the operating density indexes of different DBH growth stages of the larch plantations should be referenced in Table 5-5 for tending. Table 5-5 Management Index of Larch Plantation Management Density Breast diameter (cm) Maximum density (1.0) (strain/hectare) Operating density (0.7-0.8) Strain/hectare Breast diameter (cm) Maximum density (1.0) (strain/hectare) Operating density (0.7-0.8) Strain/hectare 6 3940 2758-3152 16 1540 1078 to 1232 7 3392 2374-2714 17 1456 1019 to 1165 8 2980 2086～2384 18 1380 966 to 1104 9 2670 1869 to 2136 19 1311 901 to 1050 10 2404 1683 to 1923 20 1252 876 to 1002 11 2195 1537 to 1756 twenty one 1198 839-958 12 2020 1414-1616 twenty two 1148 804 to 918 13 1873 1311 to 1498 twenty three 1102 771-882 14 1746 1222 to 1397 twenty four 1060 742~848 15 1636 1145~1309 25 1022 715-818 For example, in the larch plantation of the Mengzi Forest Management Bureau's Longtoushan Forest Farm, after investigation, the existing stand density is 2170 plants/ha, the stand diameter is 11.6 cm, and the management density management indicator table is used as the forest stand. When the average DBH is 12 cm, the corresponding stand density is 1616/ha, or 1614/ha, while the existing stand has a density of 2170/ha. Obviously some of them are too dense, they need to defoliate 554 to 756/ In hectares, the invasive strength is 20% to 30%, which is to adapt to the normal growth of stands and stands. After tending, when the diameter of the stand grows to 15-17 cm, the next thinning will be carried out. When using the indicator of management density management, because some forests are densely planted at the time and the tending time is late, when the first thinning is conducted, if a reasonable management density management index is once felled, it will be feared. After the stand erection of the forest, there will be an abnormal change in the short term, such as pulling the bow. Therefore, when determining the number of reserved plants, it is appropriate to increase some of them so that they can gradually transition to a reasonable management and management density. Longtoushan Forest Farm summarized the experience of thinning larch plantation with thinning, according to the relationship between the height of the chest, the corresponding age of the forest and the number of reserved trees, a “reference table for tending and thinning†was established (Table 5-6). Table 5-6 Table of Criteria for Thinning Stand The beginning of thinning Reserve number Thinning intensity Interval (year) Diameter (cm) Age (years) Strain/hectare Number of plants (%) Volume(%) Larch Plantation 5-6 10 to 12 3500 to 4000 35-40 20 to 25 4 to 5 8 to 10 15 to 18 2000 to 2500 30～35 20 to 25 4 to 5 12 to 16 20 to 25 1200 to 1600 30～35 20 to 25 5-6 18-24 28 to 36 800 to 1000 25 to 30 20 to 25 5-6 2. Determine the average diameter of the retained wood after cutting and determine the number of reserved plants. The following formula is the Udaot empirical formula: N=10000/(square of 0.164d*d) Where: 0.164 - coefficient; N - the number of reserved trees after harvesting; d - retain the average diameter of the wood. The standard test of this formula is considered to be applicable in most cases. Using this formula to determine the thinning intensity, the average diameter of the reserved wood must be estimated in advance based on the thinning method used. According to the survey, statistics, calculations, and analysis results of the sixteen-year-old larch plantations, the number of remaining trees should be calculated using the Udaot formula before using the lower layer thinning: N=10000/(square of 0.164*9*9) = 2258 (9 is reserved wood D) This data is comparable to the application of several other calculation methods to calculate the appropriate number of preserved plants per hectare from 1750 to 2250 plants.
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