Method for soil preparation and vegetation recovery of waste slag field in high and cold and dry regions

Abstract

The invention discloses a method for soil preparation and vegetation recovery of a waste slag field in an alpine and arid region. The systematic integration technology can efficiently control water and soil loss, through a three-dimensional protection system formed by the slope ecological bag protection slope, the slag top matts and the gravel belt, erosion gully development can be eliminated, and the runoff coefficient is reduced by 60% or above. The water content of the soil is increased by over 50% through multiple water retention designs such as microtopography water collection, non-woven fabric evaporation inhibition, gravel shading and root water retention, and the water condition of the arid region is fundamentally improved. According to the method, a superior habitat is created for vegetation, the survival preservation rate of trees and shrubs exceeds 85%, and high-coverage coverage is rapidly formed for herbaceous plants. Meanwhile, organic improvement such as sheep plate manure enables soil organic matters to be remarkably increased, and soil fertility is continuously improved. Degradable materials are adopted in the whole process to achieve ecological fusion, waste gravels and livestock excrement are recycled, the cost is reduced by 30% or above, and unification of ecological, economic and social benefits is achieved.

Description

Technical Field

[0001] This invention relates to the fields of ecological restoration, soil and water conservation and soil restoration technology, specifically to a method for land preparation and vegetation restoration of spoil heaps in high-altitude, cold and arid regions. Background Technology

[0002] Mineral resource development, transportation infrastructure construction, and large-scale water conservancy projects generate large amounts of construction waste, forming loosely structured and ecologically fragile waste dumps. Soil erosion and ecological restoration are particularly prominent in these sites. Waste dumps located in typical high-altitude, cold, and arid regions such as the Qinghai-Tibet Plateau face even more severe challenges in ecological restoration: loose waste masses are easily eroded by seasonal concentrated rainfall, forming gullies on the top and slopes, leading to severe soil erosion and secondary geological disasters; low temperatures, strong evaporation, and strong ultraviolet radiation cause soil moisture scarcity, hindering plant germination and growth; and the waste itself lacks the organic matter and nutrients necessary for plant growth.

[0003] Currently, while existing technical solutions address the severe challenges of ecological restoration of spoil heaps in high-altitude, arid regions, each with its own focus, they still have significant limitations in practical application. Regarding adaptability to high-altitude environments, the mine site restoration solution provided by CN110036832A, although considering high-altitude characteristics, has limited effectiveness in its engineering measures. The spray-planting technology used in this solution is costly, and the fish-scale pit preparation still experiences gully erosion under concentrated rainfall conditions. Crucially, its simple soil covering of the spoil heap top has resulted in erosion gullies reaching depths of 0.5–1.2 meters in a mining area in Qinghai, with soil and water loss exceeding permissible standards by 3–5 times. In terms of water conservation technology, while the vegetation bag structure of CN222170598U incorporates a water-retaining layer, the HDPE geomembrane used is non-degradable, potentially leading to persistent microplastic pollution. Furthermore, the complex multi-chamber structure of this technology makes the cost per bag 2–3 times that of ordinary vegetation bags. In terms of terrain management technology, the grid-like land preparation model proposed in CN119605394A has advantages in water collection, but the stability of the soil ridges is insufficient under freeze-thaw cycles and erosion, and the scheme lacks effective protection for slopes.

[0004] In summary, existing technological solutions generally suffer from systemic deficiencies. The disconnect between engineering measures and ecological needs, the contradiction between short-term effects and long-term sustainability, and the imbalance between local optimization and overall coordination all constrain the actual effectiveness of ecological restoration of spoil heaps in high-altitude, cold, and arid regions. Especially in typical high-altitude, cold, and arid areas with annual precipitation of 300-500 mm and evaporation of 1500-2000 mm, single technological measures are often insufficient to address the complex environmental challenges.

[0005] Therefore, there is an urgent need to design an integrated land preparation and vegetation restoration method specifically suited to the characteristics of spoil heaps in high-altitude, cold, and arid regions, so as to simultaneously solve the core problems of soil and water loss control and rapid and stable vegetation restoration in an economical, effective, and environmentally friendly manner. Summary of the Invention

[0006] Based on the above-mentioned technical problems, the purpose of this invention is to provide a method for land preparation and vegetation restoration of spoil heaps in high-altitude, cold and arid regions.

[0007] This invention protects a method for land preparation and vegetation restoration at spoil heaps in high-altitude, cold, and arid regions, specifically comprising the following steps: Step 1, Site preparation and measurement: Level the slope and top of the spoil heap, remove large stones and debris, and ensure that the slope is basically stable and the top of the spoil heap is relatively flat with a flatness of less than 5°; mark the grid lines and diagonal positions on the top of the spoil heap, and mark the baseline for laying the eco-bags on the slope. Step 2, Material preparation: Prepare a mixture of improved soil and grass seeds for filling the eco-bags, and set aside; prepare planting humus soil for backfilling the slag top, screen gravel of a specific size, and prepare tree and shrub seedlings. Step 3, Flexible slope protection construction: The mixture of improved soil and grass seeds is filled into biodegradable eco-bags, and starting from the toe of the slope, the eco-bags are stacked layer by layer on the slope along the baseline until the slope surface is completely covered, forming a continuous slope eco-bag protection layer. Step 4, Construction of the slag top structure and bio-solidification foundation: On the slag top, the filled biodegradable eco-bags are stacked along the grid lines to form ridges; gravel is laid along the diagonal lines to form a gravel belt; vegetation is applied to the surface of the eco-bag ridges to achieve rapid bio-solidification of the ridges; Step 5, Construction of the slag top water-retaining layer: Backfill the planted humus soil in the grid unit and shape it into a micro-topography that is low in the middle and high around the edges; then fully cover the grid with biodegradable non-woven fabric; Step 6, vegetation establishment and local water retention: Plant trees and shrubs in the grid pattern covered with non-woven fabric, and pile the gravel around the roots of the trees and shrubs to form a water retention ring; finally, sow herbaceous plant seeds on the exposed soil surface in the grid. Step 7, Initial Maintenance: Within 24 hours of completion of construction, irrigate the slag roof area once with permeable water, cover the grid surface with black shade netting, and remove it after two months; water once every two days during the first week after planting; thereafter, water once every 5 to 7 days depending on the weather, continuing until the rainy season begins; conduct regular inspections, straighten any fallen seedlings, and replant any seedlings that have not survived in the next suitable season.

[0008] Furthermore, the grid line size is 5m, 10m, or 20m.

[0009] Furthermore, the improved soil comprises sheep manure and granular organic fertilizer, with a ratio of 0.01 mg sheep manure per cubic meter of fine-grained soil. 3 0.02 kg of granular organic fertilizer; the grass seeds are a mixture of Leymus chinensis and Kentucky bluegrass in a 1:1 mass ratio, and the density of the seeds in the ecological bags is 1.0~2.0 kg / bag.

[0010] Furthermore, the planting humus soil used for backfilling the slag heap is composed of slag heap, sheep manure, and granular organic fertilizer, with a mixing ratio of 25-35 cubic meters of sheep manure per acre of slag heap. 3 Apply 700-800 kg of granular organic fertilizer and cover it with soil to a thickness of 30-50 cm.

[0011] Furthermore, the gravel has a particle size of 8-10 cm.

[0012] Furthermore, the biodegradable eco-bag is made of biodegradable polypropylene (PP) or polylactic acid (PLA), and its dimensions are 50-70cm in length and 30-50cm in width.

[0013] Furthermore, the specific method for laying the gravel strip is as follows: dig a shallow trench along the diagonal, and lay the gravel tightly in the trench, with the top surface of the laid gravel strip being lower than the top of the ecological bag field ridge.

[0014] Furthermore, the application of a vegetation layer to the surface of the ecological bag field ridges refers to establishing a vegetation cover layer mainly composed of soil-fixing herbaceous plants by spraying seeds or laying vegetation mats after covering with soil.

[0015] Furthermore, the basis weight of the biodegradable nonwoven fabric is 20~50 g / m². 2 The material is biodegradable fiber.

[0016] Furthermore, the slope difference between the central area of ​​the micro-topography and the surrounding field ridges is 5 to 15 degrees.

[0017] Furthermore, the trees planted are selected from at least one of Qinghai spruce and Qilian juniper, and the shrubs are selected from at least one of tamarisk and sea buckthorn. The planting spacing of trees is 2m×2m to 3m×3m, and the planting spacing of shrubs is 1m×1m to 2m×2m.

[0018] Furthermore, the herbaceous plant seeds sown were a mixture of *Leymus chinensis* and *Poa chinensis*, with a sowing density of 80–120 kg / hm². 2 .

[0019] Compared with existing technologies, the present invention has the following beneficial effects: 1. The three-dimensional protection system formed by the slope protection using ecological bags, the grid pattern on the slag top, and the gravel belt can effectively divide and block surface runoff. Field measurements show that this method can essentially eliminate gully development, reduce the slag top runoff coefficient by more than 60%, and keep soil loss far below permissible standards.

[0020] 2. A multi-layered water conservation mechanism was constructed, which includes micro-topography water collection, non-woven fabric evaporation suppression, gravel shading, and root water retention. Under the same climatic conditions, the soil moisture content at the top of the slag can be increased by more than 50% compared with traditional methods, effectively alleviating the soil drought problem in high-altitude, cold and arid areas.

[0021] 3. It creates favorable water, fertilizer and temperature conditions for plant growth. The survival rate and preservation rate of trees and shrubs both exceed 85%, and herbaceous vegetation can form a high coverage within 1-2 years, quickly building a stable plant community combining trees, shrubs and grasses.

[0022] 4. By using organic materials such as sheep manure to improve the soil, the organic matter content can be significantly increased in a short period of time, effectively improving the barren substrate of the spoil disposal site and providing nutrient guarantee for the long-term growth of vegetation.

[0023] 5. All materials are biodegradable to avoid secondary pollution; at the same time, the waste gravel and local livestock manure are fully utilized to realize the resource utilization of waste, reduce engineering costs, and have good ecological and economic benefits.

[0024] In summary, this invention, through systematic technological integration, successfully solves the core challenges in the ecological restoration of high-altitude, cold, and arid waste disposal sites, achieving a synergistic unity of soil and water conservation, efficient water utilization, rapid soil improvement, and stable vegetation restoration. Attached Figure Description

[0025] Figure 1 This is an overall layout diagram of the implementation area of ​​an embodiment of the present invention; Figure 2 This invention includes a grid pattern, a plan view, and a cross-sectional view (AA). Figure 3 This is a longitudinal sectional view of the waste disposal site according to an embodiment of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 This embodiment is applied to a soil-rock mixture spoil heap in a high-altitude, cold and arid region of Qinghai Province, with an altitude of approximately 2300 meters, an average annual temperature of -0.5℃, an average annual precipitation of approximately 420 mm, and an evaporation of approximately 1850 mm. The spoil heap consists of soil and rock mixtures, with poor soil and no vegetation.

[0028] A method for land preparation and vegetation restoration at spoil heaps in high-altitude, cold, and arid regions includes the following steps: 1. Site preparation and surveying First, the slopes and top of the spoil heap were cleaned and leveled by a combination of manual and mechanical means, removing large pieces of gravel and debris, and cutting the slopes of some steep sections to ensure that the slope was basically stable and the top of the spoil heap was relatively flat, with the flatness controlled within 5°. Second, a 20m×20m grid line and the positions of the two diagonals were clearly marked on the top of the spoil heap using lime powder, and the baseline for laying each layer of ecological bags was marked on the slope.

[0029] 2. Material preparation A centralized mixing plant will be set up near the construction area to standardize the preparation of the following materials: (1) Ecological bag filling material: fine-grained soil after screening at the slag yard, mixed with 0.25 m³ of sheep manure per cubic meter. 3 Approximately 0.01m per bag 3 Mix 5 kg of granular organic fertilizer (approximately 0.02 kg per bag) thoroughly using a small mixer and set aside. Combine *Leymus chinensis* and *Poa chinensis* seeds (1:1 mass ratio) at a ratio of 1.5 kg / m². 3 The density is mixed with the improved soil, that is, each bag contains approximately 0.04m³. 3 It contains approximately 60 grams of grass seeds.

[0030] (2) Planting humus soil for backfilling slag tops: It is made by mixing slag soil with sheep manure and granular organic fertilizer. The mixing ratio is 30 m³ of sheep manure per acre of slag soil. 3 750 kg of granular organic fertilizer, mixed and composted for one week before use.

[0031] (3) Gravel screening: Gravel with a particle size of 8-10cm is screened out from the slag yard, washed clean and ready for use.

[0032] (4) Seedling preparation: Purchase 500 five-year-old seedlings with soil balls, with a seedling height of 0.8~1.0m, including Qinghai spruce and Qilian juniper; and 800 two-year-old container tamarisk seedlings and sea buckthorn seedlings, with a seedling height of 0.4~0.6m.

[0033] 3. Flexible slope protection construction (1) Bagging: Put the eco-bag filler prepared in step 2 into a biodegradable eco-bag with dimensions of 40cm wide × 60cm long × 15cm thick, fill it to about 80% of the volume and then seal it.

[0034] (2) Layer-by-layer stacking: Starting from the toe of the slope, lay ecological bags layer by layer from bottom to top along the laid reference line, and use a "pin" shape staggered joint masonry method. The upper and lower layer of bag bodies are connected and fixed with "U" shaped nails made of degradable plant fiber ropes. This process continues until the entire slope is completely covered by ecological bags, forming a continuous and non-exposed flexible slope protection layer.

[0035] 4. Construction of the slag top structure and construction of the biological solidification foundation (1) Constructing ridge: Along the grid lines of the "field" characters marked on the slag top, stack degradable ecological bags with the same specifications and filling materials as the slope to form a "field" character ridge with a bottom width of about 40 cm and a height of about 30 cm (corresponding to the grass bag ridge in the figure).

[0036] (2) Laying gravel belt: In the "field" character grid, dig shallow trenches with a depth of about 15 cm and a width of about 30 cm along the marked diagonal lines, and tightly lay the selected 8 - 10 cm gravel in a single layer in the trenches to form two intersecting and regular gravel belts; the top surface of the laid gravel belt is 5 cm lower than the top of the ecological bag ridge.

[0037] (3) Biological solidification of the ridge: On the slope and top surface of the stacked ecological bag ridge, manually cover a layer of nutrient soil with a thickness of about 2 cm, clay: organic fertilizer = 3:1; use a small hydraulic hydroseeder to spray a mixed slurry composed of Kentucky bluegrass seeds, binder, water retention agent, wood fiber and green dye, and the spraying thickness is about 1 cm.

[0038] 5. Construction of the water retention layer on the slag top (1) Backfilling and micro-topography shaping: In the "field" character grid unit, backfill the prepared planting humus soil, and control the soil covering thickness to be 40 cm; after backfilling, manually use an iron rake to sort the soil surface in the grid into an obvious "pot bottom shape", measure and confirm that the central area is about 15 cm lower than the base of the surrounding ridges, forming a water collecting micro-topography with a slope difference of about 8°, ensuring that rainwater can naturally converge to the central area.

[0039] (2) Laying non-woven fabric: Fully lay a layer of non-woven fabric made of degradable polylactic acid PLA with a gram weight of 30 g / m 2 in each "field" character grid unit, and press the edge of the non-woven fabric under the ecological bag ridge body, and press and fix it with small pieces of gravel.

[0040] 6. Vegetation establishment and local water retention (1) Planting trees and shrubs: Dig holes at the grid points with a plant spacing of 1 m × 1 m for shrubs and 2 m × 2 m for trees. Picea crassifolia and Sabina przewalskii are used as trees, and Tamarix chinensis and Hippophae rhamnoides are used as shrubs; adopt an inter-row mixed planting method, that is, the row spacing between trees and shrubs is 2 m. When planting, ensure that the top of the soil ball is slightly lower than the final ground surface.

[0041] (3) Arrange the root water retention ring: around the roots of each tree and shrub, build a ring of stones with an inner diameter of about 30cm, an outer diameter of about 50cm, and a height of about 10-15cm using selected gravel. This ring helps to fix the soil, retain moisture, and regulate the root zone temperature.

[0042] (4) Sowing: Using a hand-cranked seeder, mix the seeds of *Leymus chinensis* and *Poa chinensis* in a 1:1 ratio, and sow at a rate of 100 kg / hm². 2 The density is evenly spread on the exposed areas of the non-woven fabric within the grid pattern.

[0043] 7. Initial maintenance Within 24 hours of completion of construction, the slag roof area should be irrigated with water once, and a black shade net should be covered on the grid surface. The net should be removed after two months. During the first week after planting, water should be applied every two days. After that, water should be applied every 5 to 7 days depending on the weather, until the rainy season begins. Regular inspections should be carried out to straighten any fallen seedlings and to replant any seedlings that have not survived in the next suitable season.

[0044] 8. After construction is completed, continuous monitoring will be conducted for 24 months. Monitoring indicators and results: (1) Soil and water conservation effect: After two rainy seasons, with an average annual precipitation of 420 mm, no visible erosion gullies or creeks were formed on the slope or top of the slag heap. Through runoff plot observation, the runoff coefficient at the top of the slag heap was 0.18, which was 62% lower than that of the control area (see Comparative Example 1); the soil erosion modulus was 450 t / (km²). 2 •a) This is far below the local allowable value of 1000 t / (km²). 2 ·a).

[0045] (2) Soil moisture dynamics: Soil moisture meter was used to monitor the depth from 0 to 20 cm regularly. During the dry season from June to September, the average volumetric water content of the soil on top of the slag in this embodiment was 15.2%, while the average value of the comparative example 1 area was only 9.8% during the same period. The water retention capacity was improved by 55%. Under the non-woven fabric covering, the daily evaporation of soil moisture was reduced by about 40%.

[0046] (3) Vegetation restoration status 1) Survival rate and retention rate: The survival rate of trees and shrubs was 91% after 6 months of planting and 87% after 24 months.

[0047] 2) Vegetation Cover and Biomass: After 12 months of construction, the overall vegetation cover on the slag roof reached 65%; after 24 months, the cover stabilized at over 82%. The dry weight of aboveground herbaceous biomass reached 1.2 kg / m³. 2 This is 2.1 times that of the region in Comparison 1.

[0048] 3) Field ridge solidification effect: The coverage of the sprayed layer on the field ridge reached more than 90% within 3 months, effectively fixing the bag body and withstanding the test of freeze-thaw cycles and rainfall, without any collapse.

[0049] (4) Improvement of soil nutrients: After 24 months, the organic matter content of the top soil (0-20cm) increased from the initial 0.8% to 2.5%, and the total nitrogen and available phosphorus content increased by 120% and 85%, respectively.

[0050] Comparative Example 1 In the same spoil disposal site, a 500-square-meter area with similar conditions was selected as a control.

[0051] 1. Construction: Simply level the top of the slag heap, without constructing a grid pattern. Directly cover the slag heap with unmodified, untouched soil to a depth of 30cm. Manually sow 100kg / hm² of the same grass seed mixture as in Example 1. 2 After light raking, the soil is compacted. No slope protection is applied.

[0052] 2. Maintenance: Initial watering is the same as in Example 1, but do not cover with non-woven fabric or shade net.

[0053] 3. Comparison Results (1) Severe soil erosion: After the first rainy season, several erosion gullies with a depth of 10-30 cm appeared on the top of the slag heap, and a large number of gullies were formed on the slope. The runoff coefficient was as high as 0.48, and the soil erosion modulus reached 2800 t / (km²). 2 ·a).

[0054] (2) Extremely dry soil: During the growing season and dry season, the soil volume water content is lower than 10% for a long time, and herbaceous plants wither and turn yellow on a large scale.

[0055] (4) Failure of vegetation restoration: The germination rate of grass seeds is less than 30%, and the vegetation coverage is only 15% after one year. Most of the vegetation consists of annual weeds, and almost no trees or shrubs survive. Large areas of the ground are bare.

[0056] (5) Unimproved soil: Soil nutrients have not been significantly improved and the soil structure is compacted.

[0057] Comparative Example 2 1. Construction: In another area of ​​the same slag yard, implement similar steps as in Example 1, but simplify as follows: omit laying biodegradable non-woven fabric; omit arranging gravel rings around the roots of trees and shrubs; other steps and parameters remain the same as in Example 1.

[0058] 2. Comparison Results (1) The water retention effect was significantly reduced: the average soil moisture content in the dry season was only 12.1%, which was higher than that of Comparative Example 1, but 20% lower than that of Example 1. Water evaporated faster, and the drought stress on plants was more obvious.

[0059] (2) The survival rate of trees and shrubs decreased: due to poor water conditions in the root zone, the survival rate of trees and shrubs was 84% ​​after 6 months and 76% after 24 months, which was significantly lower than that in Example 1.

[0060] (3) Local soil erosion: In some grid centers, due to the lack of non-woven fabric protection, rain splash and slight surface erosion still exist, and the micro-topography tends to be flattened.

[0061] (4) It has been demonstrated that non-woven fabric covering and root gravel rings have an irreplaceable synergistic effect in maintaining microhabitat moisture and ensuring the survival of trees and shrubs in the system of the present invention.

[0062] Through comparison of the embodiments and comparative examples, it is fully demonstrated that the systematic method provided by the present invention has significant and synergistic comprehensive advantages over traditional methods or simplified schemes in terms of soil and water loss control, soil moisture retention, rapid vegetation restoration and survival, and soil improvement. The present invention, through the ingenious integration of engineering and biological measures, has successfully overcome the key technical bottlenecks in the ecological restoration of spoil heaps in high-altitude, cold, and arid regions.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for land preparation and vegetation restoration of a waste dump in an alpine arid region, characterized in that, Specifically comprising the following steps: Step 1, site preparation and measurement: leveling the slope and the top of the waste dump, removing large stones and debris, ensuring that the slope is basically stable and the top of the waste dump is relatively flat, with a flatness of less than 5°; and marking the grid lines and diagonal lines of the field pattern on the top of the waste dump, and marking the base line for laying the ecological bags on the slope; Step 2, material preparation: preparing a mixture of improved soil and grass seeds for filling the ecological bags, and preparing planting humus for backfilling the top of the waste dump, screening gravel of a specific particle size, and preparing tree and shrub seedlings; Step 3, slope flexible protection construction: filling the mixture of improved soil and grass seeds into degradable ecological bags, and starting from the slope toe, layer by layer stacking the ecological bags on the slope along the base line until the slope surface is completely covered, forming a continuous ecological bag slope protection layer; Step 4, construction of the top of the waste dump structure and biological solidification foundation: on the top of the waste dump, using the filled degradable ecological bags to code along the grid lines of the field pattern to form a dike; laying the gravel along the diagonal lines to form a gravel belt; and applying a vegetation planting layer on the surface of the ecological bag dike to achieve rapid biological solidification of the dike; Step 5, construction of the water retention layer on the top of the waste dump: backfilling the planting humus in the field pattern unit and forming a micro-topography with a low center and high periphery; and then fully laying degradable non-woven fabric in the unit; Step 6, vegetation planting and local water retention: planting trees and shrubs in the field pattern unit with non-woven fabric laid, and stacking the gravel around the roots of the trees and shrubs to form a water retention ring; and finally sowing herb seeds on the exposed soil surface in the unit; Step 7, initial maintenance: within 24 hours after the construction is completed, performing one-time water permeable irrigation on the top of the waste dump, covering the surface of the field pattern with black sunshade net, and removing the net after two months; watering every two days in the first week after planting; and then watering every 5-7 days according to the weather, which continues until the beginning of the rainy season; regularly checking, righting the fallen seedlings, and replanting the non-surviving seedlings in the next suitable season.

2. The method of claim 1, wherein, The size of the grid lines of the field pattern is 5m, 10m or 20m.

3. The method of claim 1, wherein, The improved soil comprises sheep board manure and granular organic fertilizer, and the mixing ratio is 0.01 m 3 of sheep board manure and 0.02 kg of granular organic fertilizer per cubic meter of fine-grained soil; the grass seeds are a mixture of Elymus nutans and Poa crymophila in a mass ratio of 1:1, and the density of the ecological bag is 1.0-2.0 kg / bag; the planting humus soil for slag top backfill is mixed by slag soil and sheep board manure and granular organic fertilizer, and the mixing ratio is 25-35 m 3 of sheep board manure and 700-800 kg of granular organic fertilizer per mu of slag soil, and the soil cover thickness is 30-50 cm.

4. The method of claim 1, characterized in that, The particle size of the gravel is 8-10cm; the material of the degradable ecological bag is degradable polypropylene (PP) or polylactic acid (PLA), and the size is 50-70cm in length and 30-50cm in width.

5. The method of claim 1, wherein, The specific method for laying the gravel belt is: excavating a shallow trench along the diagonal line, and closely arranging and laying the gravel in the trench, with the top surface of the laid gravel belt being lower than the top of the ecological bag dike.

6. The method of claim 1, wherein, The vegetation planting layer applied on the surface of the ecological bag dike refers to the way of spraying and planting after covering the soil or laying a vegetation blanket, to build a vegetation cover layer mainly of soil-fixing herbaceous plants.

7. The method of claim 1, wherein, The grammage of the degradable non-woven fabric is 20-50 g / m 2 The material is degradable fiber.

8. The method of claim 1, wherein, The slope difference between the central area of the micro-topography and the periphery of the dike is 5-15 degrees.

9. The method of claim 1, wherein, The planted trees are selected from at least one of Qinghai spruce and Qilian juniper, and the shrubs are selected from at least one of tamarix and Hippophae, with the tree planting spacing being 2m x 2m to 3m x 3m, and the shrub planting spacing being 1m x 1m to 2m x 2m.

10. The method of claim 1, wherein, The sown herbaceous seeds are a mixture of Elymus nutans and Poa pratensis, and the sowing density is 80-120 kg / hm 2 .

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