First, the impact of thinning on stand growth
(I) Impact of high growth
In practical forestry, it has been observed that tending has a limited effect on the average height growth of artificial larch forests (5-9). Tree height growth is influenced by site conditions and the age of the stand. Generally, under better site conditions, height growth is faster; in young forest stages, height growth rates are higher than in middle-aged or near-mature stands. However, when converting mixed forests into fast-growing, high-yield ones, removing some broad-leaved dominant trees can promote larch height growth. For example, in the 6/19–1 and 6/19–2 small classes of Da Zhou Jia Nan Ditch in Liujiaying Forest Park of Taoshan Forest Farm, which were reforested on 75-year-old broad-leaved cutting land, an intense light cut was carried out. This reduced the number of broadleaves from 40% to 20%. The 6/19-1 class became dominant with an average height of 11.3 meters, while the 6/19-2 class remained suppressed with an average height of only 9.7 meters.
Table 5-9: Effect of Thinning on Height and Diameter Growth of Larch Forests
Location of investigation: Shirenliang Forest Park, Taoshan Forest Farm
(b) Impact on Diameter Growth
The effect of thinning on diameter growth is significant. By reducing the number of trees per unit area through tending, the nutrient space for retained trees increases, promoting individual tree diameter growth and thereby enhancing the overall average diameter of the stand. Different levels of thinning have varying impacts on diameter growth. Generally, higher density stands show weaker effects, while lower density stands respond more strongly. Data in Table 5-10 indicate that the influence of thinning on diameter growth is proportional to the cutting intensity within certain limits—higher intensity leads to greater impact. However, once the number of trees per unit area reaches a certain level, diameter growth stabilizes.
Effect of Different Tending Intensity on Diameter Growth of Larch Stands
Schedule 5-10
Location: Shirenliang Forest Park
Small Class | Forest Age | Strength | Number of Acres | Average Diameter | Four Years Later Observations | Before Cutting | After Cutting | Average Diameter Growth |
---|---|---|---|---|---|---|---|---|
Wu Dao Yin Sha Po | 50/22 | 30 | 35.7 | 49 | 33 | 16.7 | 17.1 | 19.2 | 2.1 | 191
Control | 50/22 | 30 | 35.7 | 49 | 33 | 16.7 | 17.8 | 1.1 | 100
Wu Dao Yin Sha Po | 50/11 | 30 | 20.0 | 75 | 60 | 13.4 | 14.9 | 16.7 | 1.8 | 139
Second, the impact of thinning on forest quality
Tending improves tree quality because the preserved trees are mostly high-quality main species. They are naturally pruned, straight, and free of defects.
1. Impact on Wood Species
Table 5-11 shows that tending increases the proportion of wood species and commercial materials. The percentage of specification material increased by 201%, indicating improved economic output.
Table 5-11: Impact of Thinning on Forest Quality
Location: Taoshan Forest Farm, Shirenliang Yinglin District, 52/3 Small Class
Year | Total Wood | Specifications | Non-standard Materials | Small Rod | Byproducts |
---|---|---|---|---|---|
Control | 39.4% | 19.1% | 20.3% | 26.3% | 34.3% |
Year 89 Tending | 23.8% | 4.1% | 19.7% | 30.3% | 45.9% |
Year 92 Tending | 44.1% | 13.5% | 30.6% | 24.7% | 31.2% |
Year 96 Tending | 60.1% | 28.0% | 32.1% | 16.3% | 23.6% |
Year 99 Clear Cut | 71.8% | 38.4% | 33.4% | 11.7% | 16.5% |
2. Impact on Annual Rings
According to Ando et al., densely planted and poorly managed stands have smaller annual ring widths. Medium-density management increases annual ring width, and well-managed stands have the largest widths. Tending also increases autumn wood proportion, improving wood hardness and strength.
3. Impact on Trunk Shape
Higher stand density reduces trunk sharpness, while lower density increases it. Excessive tending can negatively affect trunk shape and reduce forest quality. Table 5-12 shows that as tending intensity increases, the number of trunks decreases, and sharpness increases.
Table 5-12: Changes in Trunk Shape and Sharpness of Spruce Forests with Different Tending Intensity
Raising Intensity | Tree Height (m) | Breast Diameter (cm) | Number of Trunks | Millimeters per Meter |
---|---|---|---|---|
Control | 13.1 | 11.7 | 0.731 | 5.3 |
Weakness | 14.4 | 14.8 | 0.732 | 6.2 |
Moderate | 15.2 | 17.2 | 0.739 | 6.4 |
Strength | 15.9 | 19.5 | 0.709 | 7.8 |
Extreme Strength | 17.3 | 23.7 | 0.709 | 8.6 |
4. Impact on Knots
Knot size and number depend on stand density. In dense stands, natural pruning is strong, leading to fewer knots and better wood quality. Less dense stands have more knots. Pruning should be done after tending to improve wood quality.
Third, increasing economic benefits through thinning
Timely and moderate tending of larch plantations in North China can shorten the cultivation cycle and advance the main cutting age. It also improves tree quality and the ratio of commercial materials. These are long-term economic benefits. From Table 5-13, we see that in 1987, the first intercropping of 20-year-old larch plantations generated 36.2 yuan per mu, with expenses of 16.05 yuan, resulting in a net income of 20.15 yuan per mu. In 1991, the second intercropping yielded 175.5 yuan per mu, with expenses of 39.7 yuan, resulting in a net income of 135.8 yuan per mu.
Table 5-13: Income and Expenditure of Larix principis-rupprechtii Tending
Location: Beigou Forest Farm, Dagouzigou, Beigouyinglin District, Site Type: Semi-sunny Slope
Year | Tending Number | Raising Intensity | Total Revenue | Specifications | Non-standard Materials | Byproducts | Total Expenses | Wage | Production Facilities | Materials | Short Shipping | Management Fee | Taxes | Other | Mu Income | Mu Expenditure | Mu Gain |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
12/8 | 87 | First Time | 3620 | 0 | 3120 | 500 | 1605 | 698 | 75 | 13 | 192 | 306 | 279 | 42 | 36.20 | 16.05 | 20.15 |
12/8 | 91 | Second Time | 17550 | 0 | 12800 | 4750 | 17550 | 880 | 420 | 32 | 720 | 1230 | 600 | 88 | 175.50 | 39.70 | 135.80 |
Therefore, the Mengzi Forestry Bureau focuses on strengthening larch forests. Although income varies based on economic conditions, stand status, and tending intensity, it generally results in economic benefits. Additionally, tending provides various forest by-products, supporting industries like timber processing and transportation. It also creates local employment opportunities, increasing income. Since the area lacks fuel, tending helps solve some burning issues. Thus, tending offers social and economic benefits.
High Density Polyethylene Pipe,Hot Fusion Ppr Plastic Pipe,Marine Ppr Plastic Pipe For Accommodation,Marine Ppr Plastic Pipe For Water Supply
Jingjiang Haihong Plastic & Rubeer Science -Technology Co.,Ltd , https://www.marineplasticpipe.com