Mixing of Poplar and Korean Pine

The eastern mountain area of Northeast China is the hometown of Pinus koraiensis. In the natural state, many Korean pine species are associated with certain species of broad-leaved trees in the whole growth and development process, forming a coniferous and broad-leaved mixed forest. With the development and utilization of forest resources in forest area, Korean pine forest is reduced in a large area, and the consumption of forest resources is very high. in order to restore forest resources as soon as possible, although the introduced varieties of larch and poplar grow rapidly, but it is not conducive to the full utilization of woodland productivity and the restoration of ecological community, and will cause the deterioration of woodland soil conditions and reduce woodland productivity. According to the characteristics and growth law of Pinus koraiensis, Populus tomentosa and Populus davidiana, the formation of fast-growing and high-yield Korean pine broad-leaved mixed forest is not only in line with the current forestry development direction of building mixed forest, but also conducive to the restoration of zonal climax community in the eastern mountainous area of Northeast China. Its main advantage is to obtain a reasonable stand structure in accordance with the natural law through human activities. In nearly 20 years, a large amount of poplar wood was obtained and Korean pine forest was formed.

1. The characteristics and growth law of Korean pine and big green poplar.

The biological characteristics and growth rules of tree species are the main theoretical basis for building a mixed forest. The main characteristics of the two tree species are briefly described as follows:

Pinus koraiensis is one of the main tree species in the eastern mountainous area of Northeast China, and it is the main component of the climax community in this area. it likes the dark brown soil with good drainage, moist and fertile soil, which grows slowly in its infancy, has strong shade tolerance and needs some shade. With the increase of age, the shade tolerance gradually weakened, the demand for light gradually strengthened, and the growth rate accelerated. It grows best when it has a certain canopy density and adjusts its size properly.

Populus tomentosa is a native tree species in Northeast China, which is cold-resistant and humid, has good drainage in the middle and lower abdomen of the mountain, grows best in the deep and fertile soil, and is not resistant to shade, which requires sufficient light. The growth peak of Populus tomentosa came relatively early, the height growth rate was the fastest 10 years ago, the annual growth reached more than 1 meter, and began to decline gradually after 10 years. The growth of DBH is the fastest in 6-15 years, the annual growth can reach more than 1 cm, and then decreases year by year. It only takes about 25 years for a round of felling Lang.

2. theoretical analysis of the mixture of Populus tomentosa and Pinus koraiensis.

According to the characteristics of tree species, the early fast-growing tree species of Populus tomentosa can grow into wood in 20-25 years, and its height, DBH and volume all reach the peak, which can be felled and utilized. Pinus koraiensis grows slowly when it is young, and its growth increases rapidly after 20 years with the increase of age. The mixture of the two can learn from each other's strong points to make up for their weaknesses and obtain greater benefits.

From the perspective of ecological conditions, the two tree species like to grow in places with fertile soil, moist soil and good drainage, often accompanied by light, while Korean pine needs shade when it is young. Therefore, the formation of mixed forest at the initial stage of regeneration can not only meet their own ecological habits, but also avoid competition with each other. When the growth rate of Korean pine is accelerated and the demand for light is strengthened, it happens to be in the cutting period of Populus tomentosa, which adjusts the canopy density and liberates the Korean pine. Because the fast-growing period of the two tree species is quite different, especially the Korean pine grows very slowly in the first 10 years, the nutrient requirement is less, and the two will not have a bad effect on the nutrient demand.

According to the situation of production and management, under the same site conditions, the growth of Populus tomentosa in pure forest is similar to that in mixed forest. Under the same site conditions, Pinus koraiensis is slightly lower in tree height and DBH, but there is little difference. It can be seen that if the density of Daqing poplar is adjusted timely and reasonably, not only the growth of Korean pine will not be affected, but also the effect of double harvest of Korean pine and poplar can be obtained.

In a word, the mixing of Korean pine and poplar is feasible both in theory and in practice.

Third, mixed mode and density of poplar and Korean pine.

To determine the mixed mode and density, we should mainly consider the ecological habits, growth rules, forest management measures, rotation period, product specifications and other aspects of tree species. It is necessary to create a good ecological environment to facilitate the growth of trees. At the same time, it can make full use of woodland productivity, but also conducive to the conduct and management of various production operations.

According to the ecological habits and growth rules of tree species, the method of banded or clump mixing should not be adopted, because these two methods are not conducive to the side shade of Korean pine, make Korean pine in full light, and is not conducive to the implementation of various management measures. the way of interrow mixing should be adopted, that is, Korean pine should be planted at the intersection of adjacent four poplar trees. In order to improve the preservation rate, the planting method of large seedlings of poplar and Korean pine should be adopted, so that the Korean pine is basically in the side shade, and the poplar occupies space quickly and enters the fast-growing period because of its rapid growth.

According to the requirements of wood species and the characteristics of poplar species, poplar plantation should have a row spacing of 3 m x 3 m or 6 m x 6 m, with poor growth of overdense trees, early canopy closure and low thinning value, and low volume per unit area for a long time, and a large number of natural broad-leaved trees will be mixed, which is disadvantageous to management.

Fourth, the analysis of management effect

In terms of wood material, poplar grows rapidly, the trunk is straight, and the growth period is short, about 200 cubic meters of wood per hectare can be obtained in about 20 years. At the same time, due to the role of poplar, it can change the phenomenon that Korean pine is easy to bifurcate in bare land and improve the material quality of Korean pine.

In terms of ecological benefits, while cutting poplars, Korean pine grown for more than 20 years was retained, which was equivalent to shortening the cultivation years of Korean pine and giving full play to the productivity of woodland. At the same time, because of the vegetation cover, it can prevent soil erosion and form the regional climax community-Korean pine broad-leaved forest in the eastern mountain area of Northeast China.