A method for promoting natural regeneration of Larix principis-rupprechtii plantations

Abstract

The present invention relates to a method for promoting natural regeneration of Larix principis-rupprechtii plantations, which comprises the following measures taken in combination: A, thinning and windowing; B, diameter control to enhance the diversity of diameter structure and increase vertical layers; the forest to be tended is divided into several diameters according to different breast diameters, and the total number of thinned plants is distributed to plants of each diameter after felling in accordance with the principle that the remaining number of plants of each diameter class is close to the same; C, removing the obstruction of fallen leaves, exposing the soil, breaking the soil and tilling the soil to promote seed germination and settlement; D, taking measures to spray straw composting agent artificially to accelerate the decomposition of fallen leaves under the Larix principis-rupprechtii forest. The method of the present invention is scientific and rigorous, and adopts a combination of four measures to form a set of effective technical systems from the aspects of forest stand illumination, structure, soil, nutrients, etc., which solves the problem of difficult natural regeneration of Larix principis-rupprechtii plantations.

Description

Technical Field

[0001] The invention relates to the technical field of forest management, and in particular to a method for promoting natural regeneration of Larix principis-rupprechtii plantations. Background Art

[0002] Larix principis-rupprechtii is a tall tree of the genus Larix that is unique to China in the Pinaceae family. It is the main forest tree species in the alpine coniferous forest belt in North China. The area of ​​Larix principis-rupprechtii in Hebei Province is 3.8825 million mu, mainly planted in the 1960s and 1970s. Most of the stands have entered the mature stage and are concentrated in Chengde and Zhangjiakou. It is the main ecological and timber species in northern Hebei. Larix principis-rupprechtii plantations play an important role in the greening and ecological services of Hebei Province, but there are generally poor natural regeneration capabilities, difficulty in the renewal seedlings to become trees, and difficulty in forming uneven-aged multi-layer structures. The poor natural regeneration of Larix principis-rupprechtii plantations has become a bottleneck problem in the process of accurately improving forest quality, seriously affecting the positive succession and sustainable management of forests.

[0003] After years of investigation and research, the following are the main reasons for the difficulty in natural regeneration of Larix principis-rupprechtii: First, the initial planting density of the forest is too high, thinning and tending are delayed, and the light conditions suitable for the growth of young trees in the forest are insufficient. Second, the artificial larch forests are of the same age, with a consistent diameter structure and a lack of vertical layers. There is fierce competition for upper space, a large canopy density, and young trees do not have sufficient living space. Third, the accumulation of litter in the forest is thick and decomposes slowly, which seriously blocks the contact between larch seeds and the soil. The seeds that germinate in the litter cannot reach the soil because their roots cannot reach the soil, and the mortality rate in the following year is more than 80%. Fourth, the tree species in the pure forest are single, the biodiversity is low, and the litter types are single, which is not conducive to the rapid decomposition of litter to return soil nutrients. Summary of the invention

[0004] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for promoting natural regeneration of Larix principis-rupprechtii plantations, which promotes natural regeneration of Larix principis-rupprechtii plantations from the aspects of improving forest stand lighting conditions, enhancing forest stand diameter structure diversity, removing litter barriers, improving soil conditions, etc., thereby achieving positive forest succession and improving the sustainability of forest resources.

[0005] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0006] In a first aspect, the present invention provides a method for promoting natural regeneration of Larix principis-rupprechtii plantations, comprising taking the following measures in combination:

[0007] A. Thinning and opening windows for light

[0008] For mature Larix principis-rupprechtii forests with a canopy density of >70%, thinning should be carried out, and windows should be opened for light transmission. After thinning, the canopy density should be maintained at 60%-70%. For canopy density ≤70%, no treatment should be carried out. During thinning, under the principle of uniform thinning, the felling intensity should be 10 trees between n trees. The calculation method of n is as follows:

[0009] n=(10×S) / 100

[0010] Where: S is the felling intensity, %; n is the number of thinning plants, plant;

[0011] B. Diameter regulation to improve the diversity of diameter structure and increase vertical levels

[0012] Investigate the current DBH distribution of the forest stands to be tended, divide the plants into several diameter classes according to their DBH, and count the number of plants N in each diameter class. i ; And according to the felling intensity S, the total number of thinning trees N is calculated, N = S × the total number of trees in the nursery forest to be regulated;

[0013] According to the principle that the remaining number of plants of each diameter class after felling is close to the same, the total number of thinned plants N is allocated to each diameter class;

[0014] Measure B is carried out in combination with Measure A. If there is a conflict between the two, Measure B takes precedence over Measure A.

[0015] C. Remove dead leaves and promote seed germination and settlement

[0016] The litter under the Larix principis-rupprechtii forest is removed in blocks or strips to expose the soil. The removed litter is piled on the downslope edge of the exposed soil to help absorb and retain water and block surface runoff, breaking up the soil.

[0017] D. Accelerate the decomposition of litter and fertilize the forest soil

[0018] Artificial spraying of straw composting agents was adopted to accelerate the decomposition of litter under the Larix principis-rupprechtii forest.

[0019] According to a preferred embodiment of the present invention, in measure B, after the number of plants N of each diameter class is obtained by counting iAfterwards, the number of plants in each diameter class is sorted from large to small; on the premise of meeting the total number of thinned plants N, the number of plants in the first diameter class is thinned first. When the remaining number of plants after thinning to this diameter class is less than the number of plants in the second diameter class, the second diameter class is thinned to make the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class; the first and second diameter classes are thinned simultaneously to always keep the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class. When the remaining number of plants after thinning to the second diameter class is less than the number of plants in the third diameter class, the third diameter class is thinned to make the remaining number of plants in the third diameter class, the second diameter class, and the first diameter class equal. The first, second, and third diameter classes are thinned simultaneously to always keep the remaining number of plants in the first, second, and third diameter classes equal, and so on, until the total number of thinned plants N is fully thinned; if it is finally impossible to make the remaining number of plants in each diameter class strictly equal, plants of small diameter classes are retained first.

[0020] According to a preferred embodiment of the present invention, in measure B, the measured plant diameter at breast height is divided into 4-10 diameter grades; the grading interval is 3-5 cm per grade.

[0021] According to a preferred embodiment of the present invention, in measure B, the diameter ranges are divided into 6 levels: <5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm, and >25 cm, and the number of plants in each diameter level is N. 1 、N 2 、N 3 、N 4 、N 5 、N 6 The total number of thinned plants N is distributed to each diameter class range, and the number of plants remaining in each diameter class range after thinning is made consistent; if it is not completely consistent, large diameter plants are given priority.

[0022] According to a preferred embodiment of the present invention, the diameter grade regulation of measure B and the tending and thinning of measure A are carried out in combination, and measure B takes precedence over measure A.

[0023] According to a preferred embodiment of the present invention, in measure C, when clearing litter under the Larix principis-rupprechtii forest, the block clearing refers to that the exposed soil blocks cleared are evenly distributed in a grid pattern, so that the exposed soil blocks are located in the middle of the four plants, and the distances from the exposed soil blocks to the four plants are equal; the depth of clearing litter is to reach the humus layer and retain the humus layer.

[0024] Preferably, the bare soil plot is mainly square, rectangular or circular, and the area is determined according to 1 / 3-1 / 2 plant spacing × row spacing, or according to the density determined by the following formula:

[0025] S'=a×(10000 / p)

[0026] Where: S' is the clearing block area, m 2 ; p is the stand density, plant / hm 2 ; a is a parameter, the value is 1 / 3-1 / 2.

[0027] According to a preferred embodiment of the present invention, in measure C, when clearing litter under the Larix principis-rupprechtii forest, the strip-like clearing means that the exposed soil strip cleared is continuously distributed along the contour line, the exposed soil strip is located between two rows of plants, and its width is 1 / 3-1 / 2 of the row spacing; the depth of clearing litter is to reach the humus layer and retain the humus layer.

[0028] According to a preferred embodiment of the present invention, in measure C, after clearing the fallen leaves under the Larix principis-rupprechtii forest, tillage and loosening of the soil is carried out on the bare soil plot or bare soil strip, with a tillage depth of 5-10 cm, so as to facilitate the rooting, germination and settlement of the Larix principis-rupprechtii seeds in the soil.

[0029] According to a preferred embodiment of the present invention, in measure D, 1-2 parts by mass of the straw composting agent is evenly mixed with 20-30 parts by mass of the understory soil, and then evenly spread into the larch litter after rain, with an application amount of 50-80 kg / hm 2 .

[0030] Preferably, the straw composting agent is a mature product on the market, whose microbial active ingredients are mainly fungi, mainly from the genera Trichoderma, Penicillium, Toxoplasma, Verticillium and Mucor, and the microbial content is ≥ 200 million / g.

[0031] The beneficial effects of the present invention are:

[0032] After field investigation and analysis, it was found that the density of Larix principis-rupprechtii plantations was too high, the competition for space was fierce, the diameter classes were homogenized, the vertical layers were incomplete, and the slow decomposition of litter blocked the seedlings from taking root in the soil. These were the fundamental reasons that affected the difficulty in natural regeneration of the forest stands. To this end, the method of the present invention is based on thinning with reasonable density, opening windows for light transmission, and ensuring the light conditions for the growth of young trees under the forest; combining thinning with thinning to increase the diversity of diameter structure as much as possible and increase the vertical layers; manually clearing litter according to certain rules, exposing the soil and breaking the soil to promote seed germination and settlement; mixing soil with litter or spraying straw compost to promote decomposition, fertilizing the soil, and other technical measures to effectively solve the current problems and effectively solve the problem of poor natural regeneration of Larix principis-rupprechtii plantations, which is of great significance to promoting positive succession of forests, forming a multi-age structure, and improving the sustainability of forest resources.

[0033] Compared with the artificial afforestation regeneration method, the method of the present invention makes the age structure, diameter structure, and vertical layer of the forest stand more reasonable, which is helpful to form a forest stand structure with different ages and a stable and sustainable forest ecosystem, and realize the sustainable use of forest resources. Compared with the single method of cleaning the exposed ground with litter, the present invention can ensure that a certain number of seedlings eventually grow into trees. The former has a high survival rate in the first few years due to ignoring the spatial competition and light conditions of the forest stand, but in the later stage, when it grows to a certain height, it will still die in large numbers under fierce spatial competition (after many years of investigation, it was found that even young trees with a breast diameter of about 10 cm will still die under fierce competition); therefore, the measures for cleaning the litter exposed to the ground must be coordinated with the spatial structure adjustment to ensure the sustainability of the natural regeneration of larch. In addition, the method of the present invention can accelerate the decomposition of litter under the forest and fertilize the forest soil; while promoting the natural regeneration of larch, it can effectively control soil erosion; through the regular cleaning of litter, the distribution of larch natural regeneration seedlings is more even. Compared with the artificial afforestation method, the method of the present invention can not only improve the sustainable management of forest resources, but also save costs, and the thinning harvest of timber is larger, with better economic benefits.

[0034] The invention forms a technical system from the aspects of forest stand illumination, structure, soil, nutrients, etc. The methods are scientific and rigorous, and rely on each other to effectively solve the problem of natural regeneration difficulty of Larix principis-rupprechtii plantations. The method of the invention is particularly suitable for the management and application of Larix principis-rupprechtii ecological public welfare forests. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart for determining the number of thinning plants for each diameter class during diameter class regulation in Measure B of the present invention.

[0036] Figure 2 It is a schematic diagram of clearing litter in blocks under a Larix principis-rupprechtii forest in measure C of the present invention.

[0037] Figure 3 It is a schematic diagram of removing fallen leaves under a Larix principis-rupprechtii forest in strips in measure C of the present invention.

[0038] Figure 4 This is the diameter class distribution of Larix principis-rupprechtii plantations investigated and counted in Example 1.

[0039] Figure 5 This is the diameter grade distribution of the Larix principis-rupprechtii plantation after diameter grade control through thinning in Example 1.

[0040] Specific implementation measures

[0041] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below with reference to the accompanying drawings through specific implementation measures.

[0042] In order to solve the problem of difficult natural regeneration of Larix principis-rupprechtii plantations, the inventors have investigated and studied the reasons for many years and proposed countermeasures from four aspects: A. Tending and thinning, opening windows for light, and ensuring the light conditions for the growth of young trees under the forest; B. In combination with tending and thinning, the diversity of diameter structure is improved as much as possible, and the vertical layers are increased; C. According to certain rules, the fallen leaves are manually cleaned up, the soil is exposed and broken, and the germination and settlement of seeds (rooting in the soil) are promoted; D. A series of technical measures such as mixing soil with the fallen leaves or spraying straw compost to promote decomposition and fertilize the soil are adopted to promote the natural regeneration of Larix principis-rupprechtii plantations and realize positive forest succession.

[0043] The above four measures are carried out in combination, and the specific preferred methods are as follows:

[0044] A. Thinning and opening windows for light

[0045] For mature Larix principis-rupprechtii forests with a canopy density greater than 70%, thinning is carried out, and windows are opened for light transmission. After thinning, the canopy density is maintained at 60%-70%. No treatment is given to those with a canopy density not exceeding 70%. Under the principle of uniform thinning, the felling intensity is 10 trees per n trees. The calculation method of n is as follows:

[0046] n=(10×S) / 100

[0047] Where: S is the felling intensity, %; n is the number of thinning plants, plant;

[0048] Regarding felling intensity, its basic definition is (current density - target density) / current density * 100%. Specifically, the current density can be obtained based on the survey and measurement of the nursery forest, and the target density is a determined parameter. The target density can be determined by conducting a small-scale field test based on the target canopy density (60-70%), or determined based on the water resources carrying capacity. For example, the reasonable density of the current forest stand can be determined by referring to the method described in the applicant's prior patent application publication number CN113919747A "A method for determining a reasonable forest stand density based on forest-water relationship".

[0049] B. Diameter regulation to improve the diversity of diameter structure and increase vertical levels

[0050] Although most of the plants in the Larix principis-rupprechtii plantation have similar diameters, there are a few plants with obvious diameter differences due to long-term competition and a small amount of natural regeneration. In order to increase the diversity of diameter structure and vertical hierarchy, these plants with obvious diameter differences need to be retained. The specific steps of this treatment measure are: first investigate and count the current diameter distribution of the forest to be tended, divide it into several (such as 4-10) diameter classes according to different breast diameters, and count the number of plants N of each diameter class respectively. i, where i can be 4-10; calculate the total number of thinning plants N according to the felling intensity S, N = S × the total number of trees in the nursery forest to be regulated. Then, according to the principle that the remaining number of plants of each diameter class after felling is close to the same, the total number of thinning plants N is allocated to plants of each diameter class. The overall idea is to weaken the diameter class range with a large number of plants in a dominant position through thinning, and make the number of plants in each diameter class range as evenly distributed as possible. Among them, the diameter class range and the number of diameter classes can be formulated according to actual conditions.

[0051] The calculation process for determining the number of thinning trees for each diameter class is as follows: Figure 1 As shown (taking 6 diameter classes as an example): In the figure, N is the total number of thinned trees; Ni is the number of trees in the i-th diameter class, N 1 To N 6 Sort by plant number from largest to smallest; mi is the number of thinned plants in the i-th diameter class, and the sum of the number of thinned plants in each diameter class is N, that is, Σm 1→i = N. The range and number of diameter grades can be determined according to actual conditions.

[0052] For example, the diameter ranges can be divided into 6 categories: <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm. The number of plants in each diameter range is counted respectively, and then the number of plants in each diameter range is sorted from large to small. Assume that the number of plants in the above 6 diameter ranges is >25cm. 1 The largest and second largest number of plants with a diameter of 20-25 cm N 2 , then the number of plants with a diameter of 15-20 cm N 3 、Number of plants with diameter of 10-15cm 4 、Number of plants with diameter of 5-10cm 5 、Number of plants with diameter less than 5cm 6 , sorted from largest to smallest as N 1 >N 2 >N 3 >N 4 >N 5 >N 6, then when determining the number of thinning plants, on the premise that the total number of felled plants meets N, first determine the number of thinning plants from the plants with a diameter of >25cm. When the number of remaining plants in the diameter of >25cm is less than the number of plants in the diameter of 20-25cm, start to determine a certain number of thinning plants from the diameter of 20-25cm, so that the remaining number of plants in the diameter of 20-25cm is equal to the remaining number of plants in the diameter of >25cm. At this time, if the total number of felled plants N has not been reached, continue to determine the number of thinning plants from the two diameter classes of >25cm and 20-25cm. On the premise that the remaining number of plants in these two diameter classes is equal, compare the remaining number of plants with the number of plants in the diameter of 15-20cm. If the remaining number of plants is less than the number of plants in the diameter of 15-20cm, start to determine the number of thinning plants from the diameter of 15-20cm, so that the remaining number of plants in the diameter of 15-20cm is equal to the remaining number of plants in the two diameter classes felled previously. This process is repeated until the sum of the number of thinnings determined for each diameter class equals the total number of thinnings N. At this point, the computer program outputs the number of thinnings m for each diameter class. i .

[0053] If the final calculation result has a decimal, it will be rounded after giving priority to retaining small-diameter plants. If it cannot be completely consistent, large-diameter plants will be harvested first, and small-diameter plants will be retained and rounded. In this method, the first three diameters in the larch plantation can basically meet the total number of thinning plants N. This work should be combined with tending thinning, and diameter control should take precedence over tending thinning in measures.

[0054] C. Remove dead leaves and promote seed germination and settlement

[0055] By removing the litter under the forest, the litter barrier is broken and the seeds are promoted to take root in the soil. Specifically, the litter under the Larix principis-rupprechtii forest is removed in blocks or strips to expose the soil. The removed litter is accumulated on the downslope edge of the exposed soil to facilitate water absorption and retention and to block surface runoff. Preferably, block or strip removal is as follows. The two methods can be used in combination or separately. When the terrain is relatively flat or the distribution of plants is regular, the litter under the forest is removed in blocks. If the terrain slope is large or the distribution of plants is irregular, the litter under the forest is removed in strips.

[0056] (1) Block-based litter removal. Block-based litter removal is distributed evenly in a grid pattern. The spacing between the clearing blocks depends on the spacing between the trees in the forest. Generally, the clearing blocks are distributed in the middle of four adjacent trees (the distance between the clearing blocks and the four trees is equal), that is, the forest window position (such as Figure 2The depth of the clearing should reach the humus layer, but the humus layer should be retained to ensure soil fertility and water retention, so that the seeds dropped by the surrounding plants can obtain sufficient nutrition and water here, so as to germinate and take root and grow into young trees. The clearing blocks are mainly square, rectangular or circular, and the area is determined by 1 / 3-1 / 2 (plant spacing × row spacing), or determined by the density according to the following formula:

[0057] S'=a×(10000 / m)

[0058] Where: S' is the clearing block area (m 2 ); m is the stand density (plants / hm 2 ); a is a parameter, with a value of 1 / 3-1 / 2.

[0059] By clearing the fallen leaves, the soil at the forest window is exposed. At the same time, the size of the cleared soil is limited. This ensures that the young trees are kept at a large distance from the four surrounding large trees, which helps reduce the squeeze of the surrounding large trees on the early living space of the young trees growing on the cleared blocks, ensuring that the young trees get enough nutrients and sunlight, survive and grow taller. In addition, clearing the fallen leaves under the forest in this way allows the young trees that grow up in a few years to be relatively evenly distributed, effectively utilizing the growth space, providing space and conditions for the subsequent continuous renewal of the larch forest, and creating a virtuous cycle effect to ensure natural continuous renewal.

[0060] (2) Remove litter in strips.

[0061] Strip clearing means that the exposed soil strip is continuously distributed along the contour line, and the exposed soil strip is located between two rows of plants as much as possible (such as Figure 3 The width of the soil belt is 1 / 3-1 / 2 of the surrounding tree row spacing; the depth of litter removal is to reach the humus layer but retain the humus layer (to ensure soil fertility and water retention).

[0062] After clearing the litter in blocks or strips under the Larix principis-rupprechtii forest, in order to provide better soil conditions for the germination and rooting of Larix principis-rupprechtii seeds, the exposed soil needs to be plowed and loosened. The plowing depth should be 5-10cm.

[0063] The litter accumulation belt after strip removal forms a continuous water-blocking (water-absorbing) belt on the slope, which can reduce the runoff of rainwater on the slope and the loss of nutrients in the surface layer of the slope soil. In addition, strip removal is conducive to the subsequent mechanized tillage and loosening of the exposed soil belt. However, in block removal, since the blocks of exposed soil are not connected, it is difficult for mechanical equipment to move and continuously till. Therefore, both strip removal and block removal modes have their own advantages.

[0064] In actual operation, the above two methods of litter removal can be combined to combine the advantages of both. Alternatively, the litter under the forest can be removed in blocks, the soil can be exposed between four plants (forest window position) and the soil can be plowed, and the litter under the forest collected during the removal process can be piled up under the block of exposed soil in a continuous litter accumulation belt. Preferably, the litter accumulation belt is placed continuously along the contour line to form a continuous water interception (water absorption) belt, which can reduce the slope rainwater runoff and the loss of nutrients in the surface layer of the slope soil.

[0065] D. Accelerate the decomposition of litter and fertilize the forest soil

[0066] The decomposition of litter in Larix principis-rupprechtii forests is slow, mainly due to the following reasons: first, the stand density is too high, the diversity of understory species is low, and the litter types are single, which is not conducive to decomposition; second, the litter accumulation is thick, making it difficult for soil microorganisms to enter the middle and upper parts of the litter, affecting decomposition; third, the Larix principis-rupprechtii distribution area has long winters and short summers, the climate is cold, and the microbial activity is low.

[0067] In view of the above reasons, after the implementation of measures A (stand tending and thinning) and B (diameter structure regulation), the moisture and light conditions in the forest will be further improved, plant space competition will be weakened, some broad-leaved pioneer tree species will gradually appear, species diversity will be greatly improved, the types of litter will gradually become richer, and the mixing of different types of litter will help promote its decomposition.

[0068] To address the problem of thick litter accumulation and low microbial activity, artificial spraying of straw decomposition agent can be used to accelerate its decomposition. Specifically, 1-2 parts by mass of straw decomposition agent is evenly mixed with 20-30 parts by mass of forest soil, and then evenly spread into the larch litter after rain, with an application rate of 50-80 kg / hm2. 2 . Straw composting agents are mature products on the market, and their microbial active ingredients are mainly fungi, mainly Trichoderma, Penicillium, Toxoplasma, Verticillium, and Mucor, with a microbial content of ≥ 200 million / g. Mixing the understory soil with the straw composting agent can, on the one hand, evenly disperse the straw composting agent, and on the other hand, the soil also carries a large number of active microorganisms, which can save the amount and cost of the composting agent; at the same time, mixing into the soil can increase the viscosity, avoid the loss of the composting agent, and allow the composting agent to stay on the understory litter for a long time to promote the composting effect.

[0069] Preferably, the straw composting agent is a mature product on the market, whose microbial active ingredients are mainly fungi, mainly from the genera Trichoderma, Penicillium, Toxoplasma, Verticillium and Mucor, and the microbial content is ≥ 200 million / g.

[0070] The following is a description of the present invention in conjunction with specific embodiments. Example

[0071] The solution of the present invention was applied in the Larix principis-rupprechtii forest of Wangxidong Forest Farm in Xiaowutaishan National Nature Reserve, Hebei Province, with an application area of ​​4.0 hm 2 The current stand density is 975 trees / hm2. 2 , average DBH 21.7 cm, average canopy density 94.6%, forest age 45 years; untreated stands served as comparison (CK).

[0072] This example is a natural regeneration of Larix principis-rupprechtii plantations, and the following measures are implemented:

[0073] (1) Thinning and opening windows for light. The current forest canopy density is high, and the water and heat conditions in the forest are extremely unfavorable for the growth of small and medium-sized saplings and the regeneration of seedlings. It is urgent to thin and open windows for light. Based on small-scale field tests, the thinning intensity is determined to be 38.5%, and the target density is 600 trees / hm2. 2 In order to meet the requirements of thinning intensity, most of the trees are thinned to 4 between 10, and some are thinned to 3 between 10.

[0074] (2) Improve the diversity of diameter structure and increase vertical layers. Measure each tree in the forest stand and measure the diameter at breast height and coordinates. The forest stand is divided into six diameter at breast height grades: <5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm, and >25 cm. The diameter distribution is shown in Figure 4 According to the thinning intensity and the existing density of the forest stand, 375 trees per hectare need to be thinned. Figure 1 The diameter structure is regulated by the process. Currently, the diameters that need to be thinned are 20-25cm and >25cm. 337 and 38 trees are selected for thinning respectively, totaling 375 trees. The diameter distribution after regulation is shown in Figure 5 This work should be carried out in combination with tending and thinning, and diameter control should take precedence over tending and thinning in the measures.

[0075] (3) Break the barrier of litter and promote seed germination and settlement. Remove the litter under the Larix principis-rupprechtii forest in rectangular blocks with a side length of 2.0 m × 3.0 m and an area of ​​6 m 2 , the depth reaches the humus layer, and then the soil is loosened by plowing, the plowing depth is 10cm, and the removed litter is evenly deposited on the downslope edge of the exposed soil.

[0076] (4) Artificially add compost to accelerate the decomposition of litter and fertilize the forest soil. Mix 2 parts by weight of straw compost evenly with 30 parts by weight of forest soil and evenly spread it on the larch litter after rain. The application amount is 70 kg / hm 2 . Apply once in July every year for 3 consecutive years.

[0077] (5) Implementation Effect

[0078] According to the above measures, after 5 years of implementation, in the spring of the 6th year, through follow-up investigation of the treated stands and untreated adjacent stands (CK), it was found that the treated stands achieved significant results in seedling preservation, plant growth and litter decomposition. For specific data, please see Table 1-4.

[0079] Table 1 Regeneration effect of Larix principis-rupprechtii after 5 years of implementation

[0080]

[0081] Note: 1a: 2a: 3a: 4a: 5a means seedlings are 1st year old: 2nd year old: 3rd year old: 4th year old: 5th year old.

[0082] Table 24-5-year-old Larix principis-rupprechtii regeneration seedling distribution

[0083]

[0084] Table 3 Natural death of Larix principis-rupprechtii forest plants after 5 years of implementation

[0085]

[0086] Table 4 Decomposition of litter under Larix principis-rupprechtii forest after 5 years of implementation

[0087]

[0088] As shown in the table above, after treatment according to the method of this embodiment, the average number of Larix principis-rupprechtii seedlings was 369 plants / hm2. 2 , 1a: 2a: 3a: 4a: 5a seedlings were 144: 71: 63: 50: 41 plants / hm 2 ; while the seedling number of the control (CK) was 112 plants / hm 2 , 1a:2a:3a:4a:5a seedlings were 91:21:0:0:0 plants / hm 2 (Table 1); It can be seen that the seedlings in the control stand died after 2 years, with more than 80% dying in the same year, while the seedlings of all ages in the treated stands were preserved, with 91 seedlings / hm2 of 4-5-year-old seedlings preserved. 2, and most of them are distributed in litter removal blocks (Table 2). Since the roots of these seedlings can reach the soil and they are distributed in areas with good light in the forest windows, they can help larch forests form a heterogeneous multi-layer structure after years of regeneration, promoting the sustainable development of forest resources. In addition, due to the high density and homogeneous diameter class in the untreated forest (CK), the plants with a breast diameter of more than 20 cm are in a dominant position and have strong competitiveness. There are no natural dead plants; while the plants with a breast diameter of less than 20 cm have different degrees of death (Table 3), indicating that the forest has already experienced self-thinning. If there is no artificial intervention, the diameter class structure will gradually concentrate on the dominant layer and will be farther and farther away from the heterogeneous multi-layer structure. In addition, the treated forest also has a significant effect on litter decomposition, with a reduced litter accumulation thickness, an increased humus thickness, and an increased 0-20 cm soil organic matter content (Table 4), which plays an important role in promoting soil nutrient circulation in larch forests, fertilizing forest soil, and ensuring natural regeneration. The implementation results of this embodiment confirm that the scheme of the present invention is feasible, scientific and rigorous, and the implementation effect meets the expected goals of the transformation, has a high transformation efficiency, and has a significant promoting effect on the natural regeneration of forests.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for promoting natural regeneration of Larix principis-rupprechtii plantations, characterized in that: This includes jointly taking the following measures: A. Thinning and nurturing, opening windows for light For mature Larix principis-rupprechtii forests with a canopy density of >70%, thinning should be carried out, and windows should be opened for light transmission. After thinning, the canopy density should be maintained at 60%-70%. For canopy density ≤70%, no treatment should be carried out. During thinning, under the principle of uniform thinning, the felling intensity should be 10 trees between n trees. The calculation method of n is as follows: n = (10 × S) / 100; Where: S is the felling intensity, %; n is the number of thinning plants, plant; S = (current density - target density) / current density × 100%, the current density is obtained based on the survey and measurement of the nursery forest, and the target density is determined by a small-scale field test based on the target canopy density or based on the water resources carrying capacity; B. Diameter regulation to improve the diversity of diameter structure and increase vertical levels Investigate the current DBH distribution of the forest stands to be tended, divide the plants into several diameter classes according to their DBH, and count the number of plants N in each diameter class. i ; And according to the felling intensity S, the total number of thinning trees N is calculated, N = S × the total number of trees in the nursery forest to be regulated; According to the principle that the remaining number of plants of each diameter class after felling is close to the same, the total number of thinned plants N is allocated to each diameter class; After counting the number of plants of each diameter class N i Afterwards, sort the plants in each diameter range from large to small according to the number of plants in each diameter range; On the premise of meeting the total number of thinned plants N, first thin the number of plants in the first diameter class. When the number of remaining plants after thinning to this diameter class is less than the number of plants in the second diameter class, thin the second diameter class to make the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class. Thin the first diameter class and the second diameter class synchronously to always keep the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class. When the number of remaining plants after thinning to the second diameter class is less than the number of plants in the third diameter class, thin the third diameter class to make the remaining number of plants in the third diameter class, the second diameter class, and the first diameter class all equal. Thin the first diameter class, the second diameter class, and the third diameter class synchronously to always keep the remaining number of plants in the first diameter class, the second diameter class, and the third diameter class equal, and so on, until the total number of thinned plants N is fully thinned. If the number of remaining plants of each diameter class cannot be strictly equal, the plants of the smaller diameter class will be retained first; Measure B is carried out in combination with Measure A. If there is a conflict between the two, Measure B takes precedence over Measure A. C. Remove dead leaves and promote seed germination and settlement The litter under the Larix principis-rupprechtii forest is removed in blocks or strips to expose the soil. The removed litter is piled on the downslope edge of the exposed soil to facilitate water absorption and retention and block surface runoff, breaking up the soil. The depth of litter removal is to reach the humus layer and retain the humus layer; When clearing litter under the Larix principis-rupprechtii forest, the block clearing means that the exposed soil plots cleared are distributed evenly in a grid pattern, so that the exposed soil plots are located in the middle of the four plants, and the distances from the exposed soil plots to the four plants are equal; the exposed soil plots are mainly square, rectangular or circular, and the area is determined according to 1 / 3-1 / 2 plant spacing × row spacing, or determined according to the density by the following formula: S'=a×(10000 / p); where: S' is the clearing block area, m 2 ; p is the stand density, plant / hm 2 ; a is a parameter, the value is 1 / 3-1 / 2; When clearing litter under Larix principis-rupprechtii forest, the strip clearing means that the exposed soil strip cleared is continuously distributed along the contour line, the exposed soil strip is located between two rows of plants, and its width is 1 / 3-1 / 2 of the row spacing; D. Accelerate the decomposition of litter and fertilize the forest soil Take measures such as artificial spraying of straw compost to accelerate the decomposition of litter under the Larix principis-rupprechtii forest; specifically, evenly mix 1-2 parts by weight of straw compost with 20-30 parts by weight of soil under the forest, and evenly spread it on the litter of Larix principis-rupprechtii after rain, with an application rate of 50-80kg / hm 2 .

2. The method according to claim 1, characterized in that In measure B, the measured plant diameter at breast height is divided into 4-10 diameter grades, with 3-5 cm as one grade.

3. The method according to claim 2, characterized in that In measure B, the diameter ranges are divided into 6 categories: <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm. The number of plants in each diameter category is N1, N2, N3, N4, N5, and N6 respectively. The total number of thinned plants N is allocated to each diameter category, and the number of plants remaining in each diameter category after thinning is made to be consistent. If it is not possible to achieve complete consistency, large-diameter plants will be harvested first.

4. The method according to claim 1, characterized in that: In measure C, after clearing the fallen leaves under the Larix principis-rupprechtii forest, the bare soil plots or bare soil strips are tilled and loosened with a tillage depth of 5-10 cm to facilitate the rooting and germination of Larix principis-rupprechtii seeds in the soil.

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