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Section 1: Afforestation Effect of Seedlings Cultivated from Mother Trees
In the young plantations of *Larix principis-rupprechtii*, high-quality stands were selected and reworked. Management practices such as watering, fertilizing, and pruning were implemented to establish mother trees. The genetic gain achieved is shown in Table 4-4.
Table 4-4: Afforestation Effect of Seedlings from *Larix principis-rupprechtii* Mother Trees
| Forest Species | Age (a) | Breast Diameter (cm) | Tree Height (m) | Volume (m³) |
|----------------|---------|----------------------|------------------|-------------|
| Mother Tree Seed Stands | 10 | 5.70 | 5.17 | 0.0081 |
| Ordinary Seed Stands | 10 | 5.40 | 5.07 | 0.0071 |
| Mother Tree Gain (%) | / | 5.56 | 1.97 | 14.08 |
After afforestation using seedlings from mother trees and ordinary seeds in Longjiangshan Forest Farm, the DBH, tree height, and volume increased by 5.56%, 1.97%, and 14.08%, respectively.
Section 2: Afforestation Effect of Seedlings from Seed Garden Seeds
Seed orchards are established through artificial selection of superior trees, producing seeds and seedlings with excellent genetic quality and high viability. Compared to ordinary forests, the DBH, height, and volume of these seedlings increased by 8.74%, 13.01%, and 27.06% respectively (Table 4-5).
Table 4-5: Afforestation Effect of North China Superior Trees
| Category | Age (a) | Breast Diameter (cm) | Tree Height (m) | Volume (m³) |
|----------|---------|----------------------|------------------|-------------|
| Excellent Tree Substitute Forest | 15 | 10.20 | 10.16 | 0.0493 |
| Control | 15 | 9.38 | 8.99 | 0.0388 |
| Sub-generation Forest Gain (%) | / | 8.74 | 13.01 | 27.06 |
Section 3: Asexual Propagation for Afforestation
Asexual propagation methods like cuttings are widely used. Using full-light spray cutting techniques, the physiological and genetic characteristics of *Larix principis-rupprechtii* cuttings are utilized to promote root formation. This method ensures quick growth and stable economic traits, making it a key technique for fast-growing and high-yield larch forests.
In Hebei Province, experiments showed that 1.5-year-old cutting seedlings had similar growth rates to 2-year-old seedlings after 6 years of planting, indicating that cuttings can maintain the优良 growth characteristics of their parent trees (Table 4-6).
Table 4-6: Comparison of Young Tree Growth Between Cuttings and Seedlings
| Seedling Type | Base Path | Breast Diameter | Plant Height | New Shooter |
|---------------|-----------|------------------|--------------|-------------|
| Cutting Seedlings | 2.81 | 0.91 | 196.6 | 50.0 |
| Seedlings | 3.01 | 0.96 | 202.0 | 51.5 |
Section 4: Afforestation Season and Methods
To establish a fast-growing and high-yield forest of *Larix principis-rupprechtii*, it's crucial to choose the right season and method. With proper density, soil preparation, good seeds, and strong seedlings, improper timing or methods can affect survival and growth. Therefore, choosing the right afforestation season and method, combined with intensive management, is essential for achieving rapid growth and high yield.
1. Afforestation Season
Determining the best time for planting involves considering biological, ecological, climatic, and socioeconomic factors. Spring and autumn are generally recommended for planting *Larix principis-rupprechtii*.
Spring afforestation benefits from higher soil moisture and dormancy of seedlings, leading to higher survival rates. However, spring conditions can be challenging due to limited labor and weather variability.
Autumn afforestation is also suitable, especially in areas prone to spring droughts or strong winds. Seedlings planted in autumn enter dormancy, reducing water loss and improving survival rates. However, winter damage and dry shoots can occur if not properly managed.
2. Afforestation Methods
Afforestation methods include sowing, planting seedlings, and division. For high-yield *Larix principis-rupprechtii* plantations, planting seedlings is preferred.
(A) Advantages of Seedling Planting
Planting seedlings allows for faster early growth, shortening the cultivation cycle. It is suitable for various site conditions and improves survival rates.
(B) Technical Requirements for Seedling Planting
Selecting high-quality seedlings with specific dimensions and conditions is essential. Proper handling, transport, and planting techniques ensure successful establishment.
(C) Seedling Storage
If planting in spring after fall, seedlings must be stored properly. Winter storage methods like cellaring help protect seedlings from frost and dehydration.
(D) Planting Techniques
Proper planting depth, root expansion, and compaction are critical. Seedlings should be planted upright, ensuring good contact with the soil.
(E) Rooting Powder, Moisturizer, and Mycorrhizal Technology
Using rooting powder and mycorrhizal agents significantly enhances survival and growth. Experiments show that 50 μg/g rooting powder yields the best results, increasing biomass and survival rates.
Section 5: Young Forest Tending
After afforestation, tending measures are essential to ensure healthy growth. Activities such as re-stepping, loosening soil, weeding, and fertilization improve environmental conditions, enhance survival rates, and promote rapid growth. These practices are vital for establishing fast-growing and high-yield forests.
(F) Re-stepping
Re-stepping helps compact the soil around seedlings, ensuring good root-soil contact and maintaining moisture levels.
(G) Soil Loosening and Weeding
Loosening the soil and removing weeds reduce competition for water, nutrients, and light, promoting healthy growth.
(H) Chemical Weed Control
Herbicides like glyphosate are effective for controlling weeds, especially in large-scale operations. They reduce labor costs and improve efficiency.
(I) Fertilization
Fertilization increases soil fertility, supporting better growth and higher yields. Organic and inorganic fertilizers are used based on site conditions and availability.
(J) Water Resource Conservation
Protecting and utilizing natural precipitation and soil moisture is crucial for sustainable afforestation. Techniques like deep site preparation and ground cover protection help retain water.
(K) Replanting
Replanting is necessary when some seedlings die, ensuring a high survival rate. Using same-species, same-age seedlings maintains consistency and promotes uniform growth.
(L) Pruning
Pruning helps shape the tree and remove competing branches, enhancing growth and quality. It is done selectively to avoid damaging the main trunk.
By implementing these comprehensive tending measures, young forests can achieve optimal growth, laying a solid foundation for future productivity and quality.
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