"Hubei Larix Pine Fast-growing and High-yielding Forest Cultivation Technique"
5, thinning interval
After the first thinning, the second time of thinning should be determined according to the increase and decrease trend of the mother trees and the degree of canopy closure. According to the observation, the interval of 2 to 3 years is appropriate. If the time is too long, the canopy develops quickly, the branches are staggered, the transparency is reduced, the natural pruning is serious, and the damage of the mother tree crown directly affects the seed yield and quality. The number of reserved trees per acre for the second thinning should be 50-70, and the number of reserved trees per acre for the third thinning should be 30-50. In terms of canopy closure, it should be maintained at around 0.5 after each thinning.
5, the removal of objects
The main targets of removal are trees and trees damaged by pests and diseases, dead trees, mechanical damage, abnormal development, bent trunks, bifurcated trees, and sparsely coniferous forests. Under the principle of not affecting the degree of canopy closure, forest trees and non-purpose tree species that grow slowly and have low seed load should also be removed.
7, thinning method
Generally, the “homogeneous†thinning is used, and the reserved trees are distributed evenly without leaving a large space.
(b) Tree Management of Mother Trees
Larix principis-rupprechtii is a strong positive tree species, and the natural pruning process is rapid and significant. Therefore, for the purpose of seed collection, it is necessary to use artificial intervention methods and comprehensive treatment to avoid tree crown development and decline. The tree management of the mother tree includes pruning, truncating, girdling, and cutting roots.
1. Pruning and pruning can adjust the nutrient space of the mother tree, so that it can achieve the ideal crown shape, and promote the early solid and more solid.
In the selection of natural types of Larix principis-rupprechtii, through the experimental observation and summary, the intuitive and easy-to-see trees were classified into six types: dense branches, thin branches, twigs, rough branches, narrow crowns, and partial males.
There are two main methods for pruning, namely, thinning and thinning. The so-called secret repair thin refers to the dense branches of the mother tree, cut away the consumption of branches, overlapping branches, so that their levels are clear, the main branch at a glance, up and down staggered ventilation and light transmission; the so-called thinning of the dense refers to a small number of backbone branches, layers Sparse saplings with large branches and few branches are added to new branches through technical measures such as eye injury and tipping. No matter which method, we must emphasize comprehensive pruning so that we can not only adjust the reasonable nutritional area and nutrition space of the tree itself, but also greatly increase the amount of new branches.
2. The truncated truncation is to cut off the upward main branch at a certain height of the mother tree to promote lateral branch extension, because the Larix principis-rupprechtii is a tree species with high growth and strong growth, which is not suitable for truncation, which is not conducive to the development of lateral branches. Not conducive to seed production. The truncated height is generally 4 to 5 meters, and the truncated tree age is 8 to 10 years.
In addition, the use of ring cutting, girdling, root-cutting and other measures, can reduce the parent tree to transport nutrients down to promote flower bud differentiation, conducive to fruitful. However, implementing these methods for many years in a row will damage the physiology of the mother tree and weaken the tree. The rotation of the two-year treatment process implemented by France and other Western European countries is worth learning from.
(iv) Soil management of mother trees
The soil management of the mother trees includes the repair of water basins, loose soil weeding, and cutting irrigation. The watering basin is a round or semi-circular basin with a diameter of the crown of each tree, and the outer area of ​​the basin is low and high to facilitate water conservation. In order to reduce the competition for weeds and shrubs on nutrients and improve the air permeability of young female trees, weeding and cutting irrigation must be carried out. Loose earth weeding is generally conducted in June, with the removal of weeds in the net hole as the loose soil. Cut irrigation is generally conducted in July. The bushes and grasses that affect the growth of the mother tree are fully cut and the height of the cut is no higher than 5 cm.
(v) Water and fertilizer management of mother trees
1. Effect of fertilization and watering Reasonable fertilization is beneficial to promoting early flowering and fruiting of the mother tree, increasing the yield and quality of the seed, and shortening the seedling solid interval. Larix principis-rupprechtii is very sensitive to fertilization and watering, not only can promote the growth of the mother tree, enlarge the solid area, but also help flower bud differentiation and increase seed yield. When the mother tree enters the flowering stage and the young fruit formation period, watering with combined fertilization has a significant effect on increasing the number of male flowers in the mother tree. See Table 2-2 and Table 2-3.
Table 2-2 Effect of Fertilizing and Watering on Growth of Mother Trees
Standard location number
Test content
Average breast diameter M
Average tree height m
Average crown
m
Standard branch average
Full length m
Number of newborn branches
ratio
%
New branch length m
ratio
%
III
Fertilizer
6.5
5.3
2.60
1.60
90.5
138
9.73
145
II
Control
6.4
5.3
2.58
1.70
65.4
100
6.72
100
Note: The 1974 investigation of Longtoushan Forest Farm Test Area.
Table 2-3 Fertilizing water to promote the effect of mother tree
Test content
Seed yield
ratio%
Reducing sugar%
Leaf color
Flower bud
Fertilizer
1.6
139
4.58
Dark green
many
Control
1.15
100
3.91
Yellow green
less
Table 2-2 and Table 2-3 demonstrate that fertilization and watering can increase the amount of new shoots by 45% and increase seed production by 39%. The characteristics of larch are the highest in the branch trees of the second year, and decrease with the increase of the branch age. Therefore, the main effect of fertilizer and water is to increase the fertile amount by increasing the number of new branches and increasing the fertile area of ​​the crown.
2. Fertilizer types and methods: The weight and proportion of various fertilizer elements to be applied shall be determined according to the age of the mother tree and the site conditions. Applying nitrogen fertilizer to young mother trees with appropriate amount of phosphate fertilizer can promote the vegetative growth of young forests, accelerating the accumulation of nutrients in forest trees, and enabling the early establishment of young forests. Phosphorus fertilizer and potash fertilizer can improve the seed yield and quality of young mother trees, and the combined effects of nitrogen, phosphorus and potassium are better. Among them, nitrogen is mainly urea, phosphorus is mainly calcium superphosphate, and potassium is mainly potassium dihydrogen phosphate. From May to July, it was divided into two or three times. The center of the trunk was applied to an annular groove with a diameter of 80 to 100 cm. After covering the soil, the water was poured and the principle of slushing was used.
(vi) Pest control of the mother tree (see Chapter VII, Pest Control).
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