The significance of creating mixed forests is introduced as follows:
(1) Advantages of mixed forests. First, a reasonable combination of various tree species can make full use of space and facilitate the use of light, water and nutrients. Second, the light in the mixed forest is weak, the temperature range is small, the humidity is high, the wind speed is low, and the composition of underground fallen leaves and branches is complex. Bears increase soil fertility and are conducive to the growth of trees.
Third, it can improve the quantity and quality of forest products. With the help of companion tree species, the main tree species have round and straight trunks. Fourth, mixed forests have dense canopies and deep root systems, which can better play the role of windbreak, sand fixation, and soil and water conservation. Fifth, some tree species, such as black locust and acacia acacia, can produce their own nutrients and promote the growth of the main tree species. Sixth, it can prevent fire and reduce insect pests.
(2) Mixed type. No. 1, mixed tree type. 2. Mixed type of trees and shrubs. The third is the comprehensive mixed type, that is, mixed tree species include trees and shrubs.
(3) Mixed forest construction method
① Massive mixed forest. One tree species is planted in regular or irregular blocks and another one or several tree species are arranged in blocks to form a mixed forest. According to the terrain, irregular block mixtures can be used in mountainous areas. For example, pine, arborvitae, oak, and loblolly trees can be planted in areas with poor soil on cracked ridges. Robinia and Ailanthus can be planted in areas with thicker soil on gully slopes. In areas with deep and fertile soil at the foothills, Catalpa trees are planted; catalpa trees are planted in the valleys. The right location and suitable trees can create an irregular mixed forest on a hilltop.
②Mixed rows. Mix two or more tree species in alternate rows. One row is mostly used as the main tree species, and the other row is the companion tree. In Shandong Province, one row of poplar trees and one row of Amorpha acacia are mostly used as poplar cultivation materials. Amorphous acacia is used to cultivate strip forests and provide green manure for poplar trees. The spacing between rows of poplar trees is 3 meters, and a row of Amorpha amorpha is planted in the middle. After 3-5 years, the poplar trees will be closed, and Amorpha amorpha can still grow under the forest.
③Zone-like mixing. A tree species is planted in more than 3 consecutive rows to form a belt, and the mixed method is configured in sequence. For example, mountainous areas can be planted with pines and oaks, and plain areas can be planted with poplars and locusts. These two trees grow at different speeds. If mixed rows are used, the slow-growing zone 1 will be suppressed by the fast-growing zone 1. If a band of 3N5 rows is formed, this numerical situation can be avoided.
④ Mixing between strains. Also called intermingling within the industry. It is two or more tree species that are mixed with each other or several trees apart in the row. This kind of hybrid is generally used for mixed trees and shrubs because the mixed tree species are relatively close to each other. For example, one or two pods of Sophora japonica, ash, and Chinese wolfberries are planted among the poplar trees in the protective forest belt to enhance the windproof effect.
No matter which method of mixing, the relationship between the mixed tree species must be properly handled, so that the main tree species benefit more and suffer less. Artificial adjustments can be made in the middle, such as stubble leveling, pruning, Technical measures such as tending, thinning, girdling, topping, and root cutting can weaken the growth of secondary tree species and meet the growth and development requirements of major tree species.