Section IV: Forestry Survey
The standard survey method is widely used in forest management for various purposes, including secondary forest tending, artificial forest tending, afforestation design, and the monitoring of forest growth and pest infestations. This approach involves selecting one or more representative standard plots within a forest stand to serve as a reference. The data collected from these plots are then used to estimate the characteristics of the entire forest.
When setting up standard sites, it is essential to choose areas that reflect the average conditions of the forest. These plots act as a microcosm of the larger forest, allowing for the collection of accurate forestry data such as tree species composition, age, height, diameter, canopy density, and site quality. The selection of standard plots should be based on the survey’s objectives and should ensure that they represent the overall condition of the forest.
Standard plots can be either temporary or permanent. Temporary plots are established for short-term surveys and provide quick results, while permanent plots are used for long-term research and continuous data collection. Permanent plots require strict measurement and recording protocols to maintain accuracy over time.
Principles for Setting Up Standard Plots:
1. Conduct a comprehensive survey of the area to understand the overall characteristics of the forest, including species composition, age, height, diameter, canopy density, and site conditions.
2. Select representative plots that reflect the general conditions of the forest in terms of density, volume, and site quality.
3. Determine the size of the plot based on the required accuracy and the variability of the stand. Typically, the plot should cover at least 5% of the class area.
4. If the forest has significant variations in topography or stage of development, additional plots may be needed to ensure accurate representation.
5. For long-term monitoring, standard plots should be placed away from edges, roads, and areas prone to human disturbance.
Calculation of Standard Plot Size:
The number of trees (n) to be included in a standard plot can be calculated using the formula:
n = (t² × c²) / p²
Where:
- n = Number of trees in the plot
- t = Reliability index (e.g., 2 for 95% confidence)
- c = Diameter variation factor
- p = Allowable error
In practice, the number of trees in a standard plot for mature forests should be no less than 250, while for young forests, it should be at least 300. Investigators can also use a sample of 400 trees to estimate the main species and calculate the appropriate plot size based on proportionality.
Second, Stand Factor Investigation:
This process involves collecting detailed information about the forest, including site conditions, area, forest type, small class, tree species, origin, species composition, age, canopy density, average height, diameter, density, volume, growth trends, and other ecological factors. Additional details such as elevation, slope direction, soil texture, and undergrowth are also recorded.
Section V: Tending Thinning Construction Technology
Tending thinning involves the careful selection and removal of trees to promote healthy forest growth. Key to this process is determining which trees to cut, based on the forest's growth stage, density, and management goals. Proper thinning helps create space for remaining trees to grow and improves overall forest health.
The principles of tree grading are crucial for making informed decisions about which trees to remove. Both qualitative and quantitative thinning should be based on these standards. When selecting trees for thinning, the following guidelines should be followed:
1. Select trees according to the cutting intensity and objectives, ensuring even distribution of retained trees.
2. Avoid creating large gaps that could lead to excessive sunlight exposure.
3. Prioritize removing damaged, diseased, decayed, crowded, bent, or low-quality trees.
4. Delay logging if the selected trees negatively affect the growth of the remaining forest.
5. Consider wildlife habitat and maintain undergrowth unless it hinders the main tree species' growth.
There are two main approaches to thinning: one focuses on individual tree growth, while the other emphasizes the overall health of the forest. The former is suitable for large-diameter timber, while the latter is ideal for small and medium-sized timber.
Through years of experience, specific criteria have been developed for larch forest thinning, including proper planning, review of forest classes, and marking of trees for harvest. Marking is done using colored paint on the trunk, and careful sampling ensures accuracy. Adjustments are made if the results fall outside the acceptable range.
Section VI: Effects and Impacts of Thinning
Thinning plays a critical role in maintaining forest health and productivity. It enhances light penetration, reduces competition among trees, and promotes better growth conditions. Additionally, it helps control pests and diseases by improving air circulation and reducing overcrowding. Over time, well-executed thinning operations contribute to the long-term sustainability of forest ecosystems.
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