A method for promoting natural regeneration of oak forest seedlings

Abstract

The present invention provides a method for promoting the natural regeneration of oak seedlings, comprising the following steps: S1, dividing the site type and selecting a suitable area for natural regeneration; S2, opening windows for light transmission in the oak forest to be transformed, and retaining the mother trees on a preferential basis; S3, digging a seed collection ditch under the mother tree to promote the settlement of oak seeds; S4, subsequent maintenance of seedlings; S5, orderly repeating the method until the forest stand transformation is completed. The present invention starts from several major limiting factors affecting natural regeneration, such as the excessive density of oak secondary forests, fierce competition for space, early sprouting seedlings squeezing the nutrient space of seedlings, litter blocking seeds from contacting the soil, poor site conditions such as soil and water, and serious pests and rodents, and effectively solves the problem of poor natural regeneration of oak secondary forest seedlings through a series of technical measures such as selecting sites, opening large forest windows, removing felling piles, and digging reverse slope seed collection ditch, promoting the positive succession of oak forests, and achieving rapid recovery of the ecological functions of oak forests.

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 oak forest seedlings. Background Art

[0002] Oaks are highly resistant to drought and barrenness, and have wide adaptability. They are widely distributed in various regions of my country, accounting for 10.15% of the total forest area and 8.76% of the total volume. As the main ecological tree species in Hebei Province, oaks play an important role in national afforestation and ecological services. However, due to historical reasons, large areas of natural secondary forests have been formed in the mountainous areas of northern my country after the felling of oaks. Currently, they are mainly multi-generational budding dwarf forests, with many problems such as clumping of young trees, poor trunk shape, slow growth, low productivity, and continuous degradation of ecological functions. Therefore, although there are 969,000 hm2 of oak forests in Hebei Province, the current situation is not good. 2 , ranking first among the main forest vegetation types in the province, but the average standing stock per hectare is only 20.74m 3 , which is only 26.8% of the national average oak forest volume.

[0003] The main reason why most of the oaks in our province are currently multi-generation sprout dwarf forests is that the oak secondary forests have more sprouting and renewal, and less seedling renewal. Sprouting seedlings have many problems with stem shape, lifespan, health, etc. compared to seedlings. The growth rate of sprouting seedlings slows down after 2-3 years, and basically stops growing in about 5-6 years. Few can grow into forests, and they cannot form forests with complete ecological functions. In addition, the more times the offspring sprout, the worse the growth of the sprouting seedlings, and the lower the forest productivity and ecological benefits. Therefore, the poor natural regeneration of oak forest seedlings has become a bottleneck in the process of accurately improving forest quality, seriously affecting forest health and sustainable management.

[0004] After years of research, it is found that the main reasons for the difficulty in regeneration of oak forest seedlings are as follows:

[0005] 1. The stand density is too high, the canopy density is too high, and the young trees do not have enough living space;

[0006] Second, the competitiveness of the germinating seedlings for nutrient space is strong in the early stage, which results in the squeezing of the growth space of the seedlings;

[0007] 3. Oak fruit is seriously damaged by insects and rodents, which affects seed preservation and germination;

[0008] Fourth, oaks are mostly found in the middle and upper slopes of deep mountain steep slopes, where soil, water and other site conditions are poor;

[0009] 5. Shrubs, grasses, and fallen leaves in the forest block the contact between seeds and the soil, affecting the seeds' rooting in the soil.

[0010] Therefore, how to promote the natural regeneration of oak seedlings has become an urgent problem to be solved in order to improve the development of oak forests. Summary of the invention

[0011] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a method for promoting the natural regeneration of oak seedlings.

[0012] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0013] A method for promoting natural regeneration of oak forest seedlings, comprising the following steps:

[0014] S1. Classify site types and select suitable areas for natural regeneration

[0015] Based on the topography, soil thickness and slope of the forest area as site factors, suitable areas for promoting natural regeneration of seedlings were selected as the oak forest land to be transformed;

[0016] S2. Open windows to let in light in the oak forest to be transformed, and select the best mother trees to be preserved

[0017] According to 200m per mu 2 Open forest gaps with the specifications of the proposed transformation oak forest land; select n trees with a breast diameter higher than the average breast diameter in each forest gap as mother trees according to the principle of relatively uniform distribution; fell all oak trees except the mother trees in the forest gap and remove the felled stumps;

[0018] S3. Dig a seed collection trench under the mother tree to promote the settlement of oak seeds

[0019] Clear the ground surface of shrubs, grass and fallen objects to expose the soil; dig a seed collection ditch below the vertical projection of the mother tree's crown to collect the seeds dropped by the mother tree, reshape the surface microenvironment, and allow the seeds to settle in the seed collection ditch and grow naturally;

[0020] S4. Subsequent maintenance of seedlings

[0021] The following year, check the natural regeneration of oak seedlings, including all seedlings in the seedling collection ditch and other untreated forest gaps, and ensure that the 200m 2 More than 50 seedlings are retained in the forest gap. If there are less than 50 seedlings, the seed collection trench will continue to be maintained until the number of seedlings reaches 50.

[0022] S5. Repeat this method in an orderly manner until the stand transformation is completed

[0023] 1 to 3 years after the first transformation, the lignification degree of the surviving seedlings increases, and the above method can be repeated to continue transforming the remaining forest stands until the entire transformation is completed.

[0024] The site type classification method in step S1 is:

[0025]

[0026] The site type is slope-medium soil-gentle slope (code II 2 ), Slope-thick soil-gentle slope (code III 2 The oak forest distribution areas of gully-middle soil (code V) and gully-thick soil (code VI) are suitable areas for promoting the natural regeneration of seedlings.

[0027] In step S2, the shape of the forest window is square, rectangular, circular or elliptical, and the distance between the outermost mother tree in the forest window and the edge of the forest window is 2m to 3m.

[0028] The number of mother trees n retained in each forest gap is determined according to the average crown area S of the mother trees:

[0029] When S≤6m 2 , n = 20;

[0030] When 6m 2 <S≤12m 2 , n = 15;

[0031] When S>12m 2 , n=10.

[0032] In step S3, there are multiple seed collection trenches, which are respectively arranged around the mother tree, and their distribution range covers the vertical projection of the crown of the mother tree.

[0033] Furthermore, the width of the seed collection trench is 30cm to 40cm, and the depth is 15cm to 25cm; 4 to 6 seed collection trenches are dug around each mother tree.

[0034] Furthermore, the seed collecting ditch patterns include two modes: vertical slope on the uphill side + reverse slope on the downhill side, and following slope on the uphill side + reverse slope on the downhill side.

[0035] Furthermore, the downhill side reverse slope angle α is 60° to 80°, and the uphill side along slope angle β is in the range of α-10°≤β≤α+10°.

[0036] In the step S3, diversion ridges are also provided on the upslope and side slopes of the seed collecting ditch.

[0037] The method of the invention is suitable for the natural regeneration of ecological public welfare forests of Quercus mongolica, Quercus variabilis, Quercus sutchuenensis, Quercus sutchuenensis and Quercus acutissima.

[0038] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0039] The present invention discloses a method for promoting natural regeneration of oak seedlings in a forest. Starting from several main limiting factors affecting natural regeneration, such as excessive density of oak secondary forests, fierce competition for space, early sprouted seedlings squeezing the nutritional space of seedlings, fallen objects blocking seeds from contacting soil, poor site conditions such as soil and water, and serious pests and rodents, the method effectively solves the problem of poor natural regeneration of oak secondary forest seedlings through a series of technical measures, such as selecting sites, opening large forest windows, removing felled stakes, and digging reverse slope seeding trenches, promotes positive succession of oak forests, and achieves rapid recovery of the ecological functions of oak forests.

[0040] Specifically, the method of the present invention:

[0041] ① By dividing the site conditions, select oak forests with potential for transformation and carry out artificial promotion operations;

[0042] ② By opening large forest windows, we can effectively solve the problem of fierce spatial competition among oak seedlings and meet the light-loving characteristics of oak seedlings; at the same time, we can retain excellent mother trees to exert their continuous seed dispersal ability and ensure the number of seeds and seedlings preserved;

[0043] ③ By digging reverse slope seed collection ditches and using runoff erosion and collapse to naturally cover the seeds, the problem of seeds and soil barriers can be solved, the soil moisture conditions at the seed settlement site can be improved, the seeds can be protected and rodent damage can be reduced, and seed germination and seedling growth can be promoted;

[0044] Although oak seeds are seriously susceptible to insect pests, the existence of mother trees and the large seed quantity are sufficient to meet the requirements of seedling renewal. In line with the principle of cost saving, no insect prevention operations are carried out.

[0045] The several steps of the present invention rely on each other, cooperate closely, and are indispensable. If site screening is ignored and transformation is carried out blindly, the water and soil resources for forest growth will be too poor, and seedlings will be difficult to survive; if the development of large forest windows is ignored, the light of oak, a light-loving tree species, will be insufficient, and the seedlings will be poorly renewed; if the reverse slope seed collection ditch is ignored, the seeds will have poor soil contact and soil coverage, and rodent damage will be serious, and the seed germination rate will be reduced. At the same time, the smaller control factors in the steps of the present invention will also greatly affect the renewal effect. For example, if all oak plants except the mother tree in the forest window are not felled, it will affect the light of the seedlings and compete for the nutrition of the seedlings, making it difficult for them to survive. If the felling piles are not removed, many sprouted seedlings will sprout, competing for the light and nutrition of the seedlings, affecting their survival. If the surface shrubs and dead leaves are not cleaned and the soil is exposed, it will affect the germination of seeds outside the distribution area of ​​the seed collection ditch; and because the surface roughness is high, the seeds are not easy to roll on the surface, which will affect the number of seeds collected in the seed collection ditch and the number of germinating seedlings.

[0046] In addition, compared with the artificial clear-cutting afforestation and regeneration method, the method of the present invention has a higher survival rate of seedlings due to the existence of mother trees and the field training of seedlings; due to the local gradual transformation, the human damage is relatively light, and the ecological function of the forest stand can be continuously exerted; and the age structure and vertical level of the transformed forest stand are more reasonable, which is conducive to the formation of a forest stand structure with different ages and a stable and sustainable forest ecosystem. The reverse slope seed collection ditch adopted by the method of the present invention rationally utilizes natural forces for seed coverage, which not only reduces rodent damage, but also ensures that seeds are buried in the soil, and can also collect slope runoff, reduce soil erosion, improve the microenvironment for oak seed settlement, and promote seed germination and seedling growth; through the uniform distribution of the seed collection ditch, the distribution of oak natural renewal seedlings is more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram selected for the forest gap of the present invention;

[0048] Figure 2 This is a schematic diagram of selecting mother trees in a forest gap;

[0049] Figure 3 This is a schematic diagram of the distribution of seed collection trenches;

[0050] Figure 4 It is a cross-sectional schematic diagram of the uphill side vertical slope + downhill side reverse slope seeding ditch mode;

[0051] Figure 5 for Figure 4 A partial enlarged schematic diagram of the Zhongji seed ditch;

[0052] Figure 6 It is a cross-sectional schematic diagram of the upslope side downslope + downslope side reverse slope seeding ditch mode;

[0053] Figure 7 for Figure 6 A partial enlarged schematic diagram of the Zhongji seed ditch;

[0054] Figure 8 is a schematic diagram of the cross section of the diversion earth ridge;

[0055] Fig. 9 A top view schematic diagram of the layout of the diversion earth ridge.

[0056] In the picture, 1. One acre of oak forest, 2. Forest window, 3. Mother tree, 4. Seeding ditch, 5. Uphill side, 6. Downhill side, 7. Diversion ridge. DETAILED DESCRIPTION

[0057] The present invention will be described in detail below with reference to the accompanying drawings.

[0058] A method for promoting natural regeneration of oak forest seedlings, comprising the following steps:

[0059] S1. Classify site types and select suitable areas for natural regeneration

[0060] According to the topography, soil thickness and slope of the forest area as site factors, the site is divided into slope land-thin soil-steep slope (code I 1 ), Slope-thin soil-gentle slope (code I 2 ), Slope-Middle-Slope (Code II 1 ), Slope-Middle soil-Gentle slope (Code II 2 ), Slope-thick soil-steep slope (code III 1 ), Slope-thick soil-gentle slope (code Ⅲ 2 ), gully-thin soil (code Ⅳ), gully-medium soil (code Ⅴ), gully-thick soil (code Ⅵ) (see Table 1), and suitable areas for promoting natural regeneration of seedlings were selected as the proposed oak forest land for transformation.

[0061] The classification method of site types is shown in Table 1.

[0062] Table 1 Site type classification table

[0063]

[0064]

[0065] Since the oak distribution area generally has poor site conditions, through the reasonable division of site types, we plan to find oak stands with management potential as the proposed oak forest land for seedling natural regeneration promotion. 2 , III 2 , V, VI) are suitable areas for promoting natural regeneration of seedlings, while other site types (i.e. 1 Ⅰ 2 Ⅱ 1 , III 1 , IV) The oak forest stands do not have the material basis for management due to the thin soil layer or steep slope. It is sufficient to maintain the original growth state of the oak and play the role of soil and water conservation.

[0066] S2. Open windows to let in light in the oak forest to be transformed, and select the best mother trees to be preserved

[0067] According to 200m per mu 2 The forest gaps were opened with the specifications of 1000 trees, so that the forest gaps were evenly distributed in the oak forest land to be transformed. According to the principle of relatively uniform distribution, n trees with a breast diameter higher than the average breast diameter in the forest gap were selected as mother trees in each forest gap, and all the oak plants except the mother trees in the forest gap were felled, and the felled stumps were removed to avoid the rapid development of the sprouted seedlings.

[0068] The shape of the forest window can be square, rectangular, circular or elliptical. For ease of operation, the shape of the forest window is preferably a rectangle of 10m×20m.

[0069] The edge of the forest gap is rich in seeds due to the existence of plants in the original forest stand, which may affect the growth of oak seeds. Therefore, when selecting mother trees, the edge of the forest gap should be avoided as much as possible. The distance between the outermost mother tree in the forest gap and the edge of the forest gap is generally 2m to 3m.

[0070] The number of mother trees n retained in each forest gap is determined based on the average crown area S of the mother trees:

[0071] When S≤6m 2 , n = 20;

[0072] When 6m 2 <S≤12m 2 , n = 15;

[0073] When S>12m 2 , n=10.

[0074] The calculation of the average crown area S of the mother tree is shown in Formula 1:

[0075] S=a×b (1)

[0076] In the formula, S is the average crown width of the mother tree (m 2 ),

[0077] a---average length of the mother tree crown from north to south (m),

[0078] b---Average east-west length of the mother tree's crown (m).

[0079] S3. Dig a seed collection trench under the mother tree to promote the settlement of oak seeds

[0080] Clear the surface shrubs, grass and dead materials to expose the soil; then dig a seed collection ditch below the vertical projection of the mother tree's crown to collect the seeds dropped by the mother tree, reshape the surface microenvironment, and allow the seeds to settle in the seed collection ditch and grow naturally.

[0081] The number and size of the seed collection trenches are determined according to the crown width of the mother tree. It is advisable that the distribution range of the seed collection trenches covers the vertical projection of the crown width of the mother tree to ensure that the seeds dropped by the mother tree can be fully collected in the seed collection trenches. Generally speaking, the width of the seed collection trench is 30cm to 40cm and the depth is 15cm to 25cm; it is recommended to dig 4 to 6 seed collection trenches around a mother tree.

[0082] Regarding the layout form of the seed collection ditches, it can be specifically set according to the crown width of the mother trees and the slope of the slope. Generally speaking, when the forest land type is valley-bottom land with gentle slope - medium soil (Type V), valley-bottom land with thick soil (Type VI), the difference between the vertical projection area and the actual area of the mother tree crown is not significant. The seed collection ditches are preferably arranged circumferentially and evenly centered on the mother tree, which can basically cover the vertical projection of the mother tree crown. When the forest land type is sloping land with gentle slope - medium soil (Type II 2 ), sloping land with gentle slope - thick soil (Type III 2 ), due to the large slope of the forest land, the vertical projection area of the mother tree crown in the downhill direction is larger than the actual area of the crown, and the oak seeds are relatively large and heavy. After clearing the shrubs and grasses, if the ground surface is relatively smooth, there may be a situation of rolling down the slope. Therefore, in order to fully collect and retain the oak seeds, usually several seed collection ditches need to be set more in the downhill direction of the mother tree; as Figure 3 shown, a total of six seed collection ditches are set around the mother tree. Among them, one seed collection ditch is set in the uphill direction, left side direction, and right side direction of the mother tree, and the three are arranged in a "pin" shape; three seed collection ditches are also set in the downhill direction of the mother tree, also arranged in a "pin" shape, and the two seed collection ditches at the lowest end in the downhill direction of the mother tree are respectively set below the left side seed collection ditch and the right side seed collection ditch, and the longitudinal spacing between the seed collection ditches is 0.25 to 0.5 times the longitudinal crown width of the mother tree.

[0083] The specific patterns of the seed collection ditches are two types: vertical slope on the uphill side + reverse slope on the downhill side, and gentle slope on the uphill side + reverse slope on the downhill side. The gentle slope on the uphill side + reverse slope on the downhill side pattern is preferred. With the gentle slope on the uphill side + reverse slope on the downhill side pattern, the angle α between the ditch wall and the bottom surface of the seed collection ditch is an acute angle. Under the action of gravity, the seeds are more likely to enter the α angle of the seed collection ditch and are not easy to roll out again, and it also has a good effect of collecting and retaining the seeds rolling down the slope; in addition, under the scouring action of the surface runoff, after the ditch wall of the seed collection ditch collapses, it will naturally cover the seeds in the ditch, and the soil carried by the runoff can also cover the seeds. The natural covering of the soil is not only beneficial to the germination of oak seeds, but also beneficial to reducing the rodent damage to the seeds, and can also collect the surface runoff, reduce soil erosion, and improve the microenvironment for the settlement of oak seeds.

[0084] Figure 4 、 Figure 5 shows the vertical slope on the uphill side + reverse slope on the downhill side seed collection ditch pattern, Figure 6 、 Figure 7 shows the gentle slope on the uphill side + reverse slope on the downhill side seed collection ditch pattern. The angle α of the reverse slope on the downhill side depends on the soil quality and should be controlled at 60° - 80° to ensure that it is not easy to collapse after excavation. The value range of the angle β of the gentle slope on the uphill side in the gentle slope on the uphill side + reverse slope on the downhill side is α - 10° ≤ β ≤ α + 10°.

[0085] The best time to dig the seed collection ditch is after the rainy season and before planting in autumn. It should not be too early to prevent it from being eroded by runoff and collapsing before planting. In northern Hebei, the best time to dig the ditch is from late August to early to mid-September.

[0086] Since oak seeds are produced in large quantities, the amount of seeds collected in the seed collection ditch can fully meet the demand for seedlings, and there is no need for manual replanting and inspection.

[0087] In order to further ensure the collection effect of the seed collection ditch, a diversion ridge is also arranged on the upslope of the seed collection ditch to meet the need for runoff to carry soil. When the upstream runoff flows through the diversion ridge, part of the soil carried along with the runoff flows into the seed collection ditch to cover the seeds, thereby expanding the collection range of runoff and seeds, and facilitating the settlement, soil coverage and germination of seeds in the ditch.

[0088] The diversion earth ridge is formed by piling up soil, for example, the soil excavated from the seed collection ditch is directly piled up at the edge of the ditch, and the soil of the diversion earth ridge is loose. Figure 8 As shown, the cross-section of the diversion ridge is an isosceles triangle with a base length of L and an angle θ on both sides. The base length L≤20cm and the angle θ on both sides>60°. The base should not be too wide. Because the function of the diversion ridge is to provide carrying soil for runoff, its surface is loose. If the base is too wide, the area occupied by the diversion ridge will be too large. When oak seeds fall, they are easily embedded in the loose ridge and are not easy to roll off, thus affecting the collection of seeds by the seed collection ditch. The length of the diversion ridge depends on the distance to other surrounding seed collection ditches and the volume of excavated soil, and it is advisable not to touch other surrounding seed collection ditches.

[0089] In order to ensure that the runoff carries the soil, do not pat the top of the earth ridge into a flat shape when piling it up, and do not pat the earth ridge so that it is suitable for being washed and carried by rainwater.

[0090] The diversion ridges can be set as two or three. When the size of the seed collection ditch is small, a diversion ridge can be symmetrically set on the left and right sides of the seed collection ditch, and the stem body close to the side of the seed collection ditch forms an angle of 120° with the side edge of the seed collection ditch. When the size of the seed collection ditch is large, in order to ensure the diversion effect, a diversion ridge can be added in the vertical direction of the midline of the long side of the uphill side of the seed collection ditch, such as Fig. 9 shown.

[0091] S4. Subsequent maintenance of seedlings

[0092] In the spring of the following year, the natural regeneration of oak seedlings was checked, including all seedlings in the seedling collection ditch and other untreated forest gaps, 200m 2 It is sufficient to keep more than 50 seedlings in the forest gap. If the number is insufficient, repeat step S3 after the rainy season and before planting in autumn in the second year, continue to collect the seeds of the mother trees and let them grow naturally until 200m 2Until the number of seedlings in the forest gap reaches 50.

[0093] The work of repeating step S3 includes: clearing the surface shrubs and dead objects to expose the soil; maintaining the shape of the seed collection ditch so that it can repeatedly restore the seed collection function. It should be noted that when maintaining the seed collection ditch, it is necessary to avoid the seedlings. If there are no seedlings, you can dig in situ. If there are seedlings, you can dig in the unexcavated area to avoid them. Digging in the unexcavated area can also play the role of breaking the soil and tilling the land, which is beneficial to the settlement and growth of seedlings. Due to the existence of oak mother trees, after the seedling quantity requirement is reached, even if the maintenance of the seed collection ditch is stopped, some seedlings will be unearthed every year to offset the dead seedlings, which can ensure the survival and growth of a certain number of seedlings, and it is also easier to form a multi-layer structure of different ages.

[0094] S5. Repeat this method in an orderly manner until the stand transformation is completed

[0095] 1 to 3 years after the first transformation, the lignification degree of the surviving seedlings increases, and the damage caused by birds and rodents is reduced. The above method can be repeated to continue to transform the remaining stands until all the transformation is completed. The gradual transformation is conducive to the continued ecological function of the original stands, and also helps to meet the current requirements for the intensity of forest tending and thinning. In the early stage of transformation, the stands that have not been transformed can retain enough oak seeds as food for rodents, birds, etc., to avoid rodents and birds from harming the germinating seedlings in the transformed stands due to lack of food; the newly germinated seedlings are relatively young and tender due to their low degree of lignification, and are also an important period of damage. After 1 year, the lignification degree of the seedlings increases, and rodents and birds basically will not harm the seedlings.

[0096] During the transformation process, if a few seedlings die later, there is no need to replant, which will not affect the overall transformation and development of the forest stand. The reasons are: 1. Since the mother trees exist in the forest gap, seedlings will still sprout and grow; 2. The number of seedlings retained is 50 / 200m 2 , a sufficient number has been reserved for gradual death elimination.

[0097] The method of the present invention is suitable for the sustainable management of oak ecological public welfare forests, which may specifically include Mongolian oak, cork oak, oak, oak, oak, and acuta australis.

[0098] The present invention is further described below using examples.

[0099] Example 1

[0100] The invention was applied in the Mongolian oak secondary forest of Caijiayu Forest Farm in Yi County, Hebei Province, with an application area of ​​2.0 hm 2 .

[0101] S1. Classify site types and manage them by category

[0102] The current density of the forest stand is 1975 trees / hm22 , average breast diameter 9.5cm, average tree height 8.3m, canopy density 85.5%; altitude 1293m, shady slope, medium slope, slope 22°, soil thickness 53cm~72cm; associated trees are Betula acanthopanax and Acer truncatum, accounting for 1 / 8 of the total number, and the main shrubs and grasses are Akebia, Aglaonema, Spiraea, Sedge, Saussurea, and Thalictrum lucidum, with a coverage of 80%.

[0103] From the basic situation of the forest stand, it can be seen that the experimental site belongs to the slope-thick soil-gentle slope (Ⅲ 2 ) type of site, meeting the conditions for renovation and reconstruction.

[0104] The test site was divided into five blocks, each with an area of ​​5000m 2 , in order to conduct control experiments.

[0105] Experimental method in Block 1 (labeled as C1): only forest gaps were opened, and the ground surface was not treated;

[0106] Experimental method in block 2 (marked as C2): opening forest window + reverse slope seeding ditch (downslope to reverse slope + upslope to vertical slope);

[0107] Experimental method in block three (marked as C3): opening forest window + reverse slope seeding ditch (downslope to reverse slope + upslope to along slope);

[0108] Experimental method of block 4 (marked as C4): forest window + ordinary ditch (the side walls of the ditch are all vertical walls);

[0109] Block 5 (marked as CK) Experimental method: No treatment was done on the forest stands.

[0110] The size, number and position of the seed collecting trenches in the above-mentioned blocks 2, 3 and 4 are the same, only the style patterns of the seed collecting trenches are different.

[0111] S2. Open windows in the forest area to let in light and select the best mother trees to be preserved

[0112] From July to August 2019, in Blocks 1 to 4, the land area is 200 m3 per mu. 2 The forest windows are opened with the specifications of 10m×20m, so that they are evenly distributed in the oak forest land to be transformed. According to the principle of relatively uniform distribution, 10 mother trees with an average breast diameter of 13.9cm are retained in each forest window, which is more than 2m away from the edge of the forest window. All oak plants except mother trees in the forest window are felled, the felled stumps are removed, and other associated tree species are retained.

[0113] The same measures were adopted for C1~C4, and CK was the adjacent unmodified forest stand.

[0114] S3. Dig a seed collection trench under the mother tree to promote the settlement of oak seeds

[0115] Implement surface treatment measures from September 8th to 15th, 2019.

[0116] C1: No treatment was done on the surface.

[0117] C2: Clear the shrubs, grasses and litter on the surface to expose the soil; Dig 6 seed - collecting grooves under the vertical projection of the crown of the mother tree, arranged in a "pin" shape (see Figure 3 ), with a horizontal spacing of 0 m and a vertical spacing of 1 m; The width of the seed - collecting groove is 40 cm, the length is 1.5 m, the depth is 20 cm, the reverse slope angle is 60°, and the opposite side of the reverse slope is a 90° vertical slope.

[0118] C3: Except that the opposite side of the reverse slope is a 60° forward slope, the rest is the same as C2.

[0119] C4: Clear the shrubs, grasses and litter on the surface to expose the soil; Dig 6 ordinary grooves under the vertical projection of the crown of the mother tree, arranged in a "pin" shape, with a horizontal spacing of 0 m and a vertical spacing of 1 m; The width of the ordinary pit is 40 cm, the length is 1.5 m, the depth is 20 cm, and the two sides are 90° vertical slopes.

[0120] S4. Subsequent maintenance of seedlings

[0121] One year after the implementation of this method, in the spring of the second year, by tracking and investigating each treated forest stand and the adjacent untreated forest stand (CK), the tracking data are shown in Table 2 and Table 3.

[0122] Table 2 Natural regeneration effect of Quercus mongolica under different treatments after 1 year of implementation

[0123]

[0124] Note: When there is a decimal after averaging the number of seedlings, round it to the nearest integer.

[0125] Table 3 Natural regeneration distribution of Quercus mongolica seedlings under different treatments

[0126]

[0127] Note: When there is a decimal after averaging the number of seedlings, round it to the nearest integer.

[0128] From the data in Table 2 and Table 3, it can be seen that the average number of seedlings per forest gap in C2 and C3 treatments is significantly higher than other treatments, reaching 68 and 81 respectively; and the seedlings are mainly composed of seedlings, reaching 58 and 69 respectively; both meet the condition that there are more than 50 seedlings in a 200 m 2 forest gap; and the C3 treatment is better. Among the remaining C1, C4, and CK, the number of seedlings in a 200 m 2 forest gap does not reach 50.

[0129] After analysis, it is possible that in the downslope to reverse slope + upslope to slope mode, seeds are more likely to enter the α angle under the action of gravity, which is conducive to natural soil coverage. Compared with the C4 ordinary ditch, the number of seedlings is only 26, and the number of seedlings is only 15, which shows that the reverse slope ditch is obviously better than the ordinary ditch. At the same time, the survey found that most of the reverse slope ditch walls collapsed and covered the seeds, while the ordinary ditch did not; the seedlings in a small number of reverse slope ditches that did not collapse were poorly renewed; it can be seen that soil coverage is important for the preservation, germination, and growth of Mongolian oak seeds.

[0130] Table 3 shows that the seedling regeneration of C1, which only opened forest gaps and did not do surface treatment, was poor. Among the 26 regeneration seedlings in each forest gap, only 4 seedlings were regenerated, and the rest were sprouted seedlings. This shows the importance of appropriate surface treatment for the natural regeneration of Mongolian oak seedlings. In the control forestland CK without any treatment, there was basically only sprouted seedling regeneration. A very small number of seedlings were difficult to survive in the end due to fierce competition. No seedling Mongolian oak saplings with a breast diameter of more than 5 cm were found in the survey.

[0131] S5. Repeat this method in an orderly manner until the stand transformation is completed

[0132] 1 to 3 years after the first transformation, the lignification degree of the surviving seedlings will increase, and the damage caused by birds and rodents will be reduced. Repeat the above method to continue transforming the remaining forest stands until the entire transformation is completed.

[0133] The forest stand has undergone the second phase of transformation in 2021, all using C2 or C3 treatment methods, reaching 50 plants / 200m 2 The expected effect is achieved and the transformation effect is good.

[0134] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for promoting natural regeneration of oak seedlings, characterized in that The following steps are involved: S1. Classify site types and select suitable areas for natural regeneration Based on the topography, soil thickness and slope of the forest area as site factors, suitable areas for promoting natural regeneration of seedlings were selected as the oak forest land to be transformed; The site type classification method is: The oak forest distribution areas with the site types of slope land-middle soil-gentle slope, slope land-thick soil-gentle slope, valley land-middle soil, valley land-thick soil are suitable areas for promoting natural regeneration of seedlings; S2. Open windows to let in light in the oak forest to be transformed, and select the best mother trees to be preserved According to 200m per mu 2 Open forest gaps with the specifications of the forest, so that the forest gaps are evenly distributed in the oak forest land to be transformed; according to the principle of relatively uniform distribution, select n plants with a breast diameter higher than the average breast diameter in the forest gap as mother trees in each forest gap; All oak trees except the mother tree in the forest gap shall be felled and the felled stumps shall be removed; S3. Dig a seed collection trench under the mother tree to promote the settlement of oak seeds Clear the ground surface of shrubs, grass and fallen objects to expose the soil; dig a seed collection ditch below the vertical projection of the mother tree's crown to collect the seeds dropped by the mother tree, reshape the surface microenvironment, and allow the seeds to settle in the seed collection ditch and grow naturally; S4. Subsequent maintenance of seedlings The following year, check the natural regeneration of oak seedlings, including all seedlings in the seedling collection ditch and other untreated forest gaps, and ensure that the 200m 2 More than 50 seedlings are retained in the forest gap. If there are less than 50 seedlings, the seed collection trench will continue to be maintained until the number of seedlings reaches 50. S5. Repeat this method in an orderly manner until the forest stand transformation is completed 1 to 3 years after the first transformation, the lignification degree of the surviving seedlings increases, and the above method can be repeated to continue transforming the remaining forest stands until the entire transformation is completed.

2. A method for promoting natural regeneration of oak seedlings according to claim 1, characterized in that: In step S2, the shape of the forest window is square, rectangular, circular or elliptical, and the distance between the outermost mother tree in the forest window and the edge of the forest window is 2m to 3m.

3. A method for promoting natural regeneration of oak seedlings according to claim 2, characterized in that: The number of mother trees n retained in each forest gap is determined according to the average crown area S of the mother trees: When S≤6m 2 , n = 20; 6m 2 <S≤12m 2 , n = 15; When S>12m 2 , n=10.

4. A method for promoting natural regeneration of oak seedlings according to claim 1, characterized in that: In step S3, there are multiple seed collection trenches, which are respectively arranged around the mother tree, and their distribution range covers the vertical projection of the crown of the mother tree.

5. A method for promoting natural regeneration of oak seedlings according to claim 4, characterized in that: The width of the seed collection trench is 30cm to 40cm, and the depth is 15cm to 25cm; 4 to 6 seed collection trenches are excavated around each mother tree.

6. A method for promoting natural regeneration of oak seedlings according to claim 5, characterized in that: The seed collecting ditch patterns include two modes: vertical slope on the uphill side + reverse slope on the downhill side, and following slope on the uphill side + reverse slope on the downhill side.

7. A method for promoting natural regeneration of oak seedlings according to claim 6, characterized in that: The reverse slope angle α on the downhill side is 60° to 80°, and the value range of the slope angle β on the uphill side is α-10°≤β≤α+10°.

8. The method for promoting natural regeneration of oak seedlings according to claim 1, characterized in that: The upward slope and side slope of the seed collecting ditch are also provided with diversion earth ridges.

9. A method for promoting natural regeneration of oak seedlings according to claim 1, characterized in that: The method is suitable for the natural regeneration of ecological public welfare forests of Quercus mongolica, Quercus variabilis, Quercus sutchuenensis, Quercus sutchuenensis and Quercus acutissima.

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