**Section II: Survey Design**
Survey design is a critical task that must be completed before any harvesting operations begin. It serves as the foundation for forest harvesting activities and plays a vital role in improving production efficiency, reducing operational blindness, and minimizing waste. A well-conducted survey and design process ensures that all aspects of the operation are planned thoroughly and systematically. This work must be carried out by qualified professionals or certified survey and design units to ensure accuracy and compliance with industry standards.
The main steps involved in the survey design process include:
**I. Field Investigation**
**(A) Stand Inspection**
Before conducting any surveys, it is essential to inspect the forest stand to gather baseline information. This includes understanding the orientation of the small class, tree distribution, past operations, tree height, diameter at breast height (DBH), density, and dryness. This data helps investigators create accurate reference materials and allows internal teams to evaluate whether the design parameters are reasonable. During fieldwork, all surveying groups should maintain constant communication to avoid disjointed efforts and ensure high survey accuracy.
**(B) Plot Layout**
Depending on the condition of the stand, square or circular plots can be established in areas with uniform distribution and smaller size. Larger, more complex stands often use strip samples. A starting point is selected on the edge of the forest stand for GPS positioning. This point must be chosen so that the transposed strip can cross through the entire small class.
The sample belt width is 6 meters, with a length of 50 meters, covering an area of 0.45 mu. The sampling rate should be at least 5%. For forests less than 100 mu, a "V" or "inverted V" shaped belt is used. For areas between 100–200 mu, an "M"-shaped belt with a polyline is appropriate. For larger areas over 300 mu, additional fold lines are added to ensure full coverage and achieve an accuracy of over 90%.
When setting up transects, it is important to consider the upper, middle, and lower parts of the stand. Due to human activity, the lower part of the slope may have sparse stands, while the upper part might lack proper measurements due to thinning or low-quality trees. Balancing these areas helps reduce errors in material volume and structure, thus improving overall design accuracy. If the volume accuracy exceeds 90%, the survey is considered acceptable. Otherwise, additional sample zones may be added to meet the required precision.
**(C) Sample Survey**
1. **Tree Measurement**: For each tree, a 50-meter measuring rope is used, with 3 meters measured on each side. A 3-meter ruler is used for precise measurement. A scale marked at 1.3 meters is placed on the rod to determine the DBH and measure it accurately.
Trees with a DBH of 6 cm or more are measured, with a 5-meter interval. Trees below 5 meters in DBH are only counted, without being included in the stand factor or material design.
All rulers must be fully extended. In older forests where bark has deteriorated, inspections should be conducted or adjustments made to ensure accuracy.
2. **Visual Inspection**: Material design is primarily based on visual assessment. Factors such as trunk height, shape quality (sharpness, curvature, side branch thickness), and market demand are considered. The principle of material selection is typically 2 meters or longer. For clear-cutting operations, dense stands can be designed normally, while large-diameter, small-pole, and mine timber designs need careful control, especially in remote areas.
For tending operations, strict control over the design of certain products is necessary. For trees with a dry bend exceeding 3%, long products are prioritized, and short materials are minimized. Separate statistics are kept for logs, poles, and other components.
When visually measuring, after determining the DBH, the dryness of the trunk is assessed. Based on this, decisions are made on whether to classify the material as commercial or non-commercial. The trunk is then measured from 3 to 4 meters to determine the final product dimensions, which are generally 50–75% of the tree’s total height.
3. **Cutting Sample Trees**: Depending on the operating area and method, 3–7 trees per small class are cut down for growth rate and material design. Clear-cut operations require 3 trees for areas under 100 mu, 5 trees for 100–200 mu, and 7 trees for over 200 mu. Tending operations require 3 trees for under 200 mu and 5 trees for over 200 mu.
After cutting, the average DBH, tree height, and dryness are calculated. A representative standard tree is selected to determine growth rates and material design. Other felled trees are selected based on deviations from the average DBH, ensuring symmetry and equal numbers on both sides. For example, if the average DBH is 14.2 cm and 3 trees are selected, two others can be taken from 12 cm and 16 cm. For 5 trees, 10 cm, 12 cm, 16 cm, and 18 cm can be used. For 7 trees, 8 cm, 10 cm, 12 cm, 16 cm, 18 cm, and 20 cm are suitable.
Cut trees should be selected from the upper, middle, and lower parts of the stand and at least 8 meters away from the forest edge.
**(D) Area Measurement and Job Design Drawing**
1. **Area Measurement**: The actual boundary and area of the forest must be measured for the design. The closing difference should not exceed 1%, otherwise the measurement must be repeated. A forestry director or forest patrol officer must be present during the measurement. Information such as forest maps, topographic maps, ownership documents, and classification boundaries must be reviewed, especially in state-owned or cooperative forests.
It is forbidden to measure multiple small classes together; each must be designed separately. The starting point is marked using a handheld GPS.
2. **Job Design Drawing**: Based on forest phase maps, topographic maps, and field survey data, job design drawings are created. Natural objects, boundaries, and nearby features close to the survey boundary are recorded in detail, with sketches made on-site when necessary. Handheld GPS is used for positioning. Computer mapping and area calculations are performed in the internal design. All relevant details are marked on the map.
Once approved, the design plan, cutting permit, and site markings serve as the basis for forest operations. The design boundaries must be clearly painted and marked. If it's an isolated small class, it is marked outside the forest; otherwise, it is marked inside the design area. After completion, the operating forest is marked at the root of the cut trees.
**Second, Industry Design**
Based on the Hebei Forest Management Technical Specifications (Trial) and field investigation results, internal design is carried out. Key elements include:
1. **Schedule 1**: The actual measured area of the operating zone must be recorded, with all vacant land deducted. The small class account is also registered. Stand types are determined through field surveys, including slope position, direction, soil depth, and herbaceous undergrowth. These details are supplemented by the small class account to ensure accuracy for future redesigns.
2. **Age Determination**: The forest age is verified using a ledger or standard wood samples.
3. **Species Composition**: Dominant species are noted, with "+" indicating 2–5% presence and "-" for less than 2%.
4. **Density and Volume Calculation**: The number of trees per acre is calculated by dividing the total number of plots by the plot area. The average DBH is derived from statistical summaries, weighted by the number of trees. Total volume per mu is calculated by dividing the total plot volume by the plot area.
5. **Growth Volume**: Actual results from analytical wood are used.
6. **Closed Degree Survey**: Using the rope statistics method, sample points are set every 5 meters, and the percentage of canopy coverage is calculated.
**Third, Design Accuracy Index**
- Small class area error within 1%.
- Area error within ±5%.
- Accumulation accuracy over 90%.
- Commercial material error within 5%.
- By-product error within ±20%.
- Number of acres error within 5%.
- DBH error within ±0.2 cm.
After completing field investigations, internal calculations, and preparing the job design program, the work is publicized weekly according to the requirements of the logging permitting authority. Once approved by higher forestry authorities, the project can proceed.
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