Ecological restoration method for improving quality and efficiency of declined artificial haloxylon ammodendron forest

Abstract

The invention discloses an ecological restoration method for improving quality and efficiency of a declined artificial haloxylon ammodendron forest, and belongs to the technical field of desert vegetation restoration. According to the method, a comprehensive decline index is calculated by measuring multiple indexes such as the ratio of dead and dead trees in the haloxylon ammodendron forest, the canopy coverage loss rate of the haloxylon ammodendron forest, the shoot withering rate of the haloxylon ammodendron forest, the total vegetation coverage of the haloxylon ammodendron forest and the root exposure rate of the haloxylon ammodendron forest, and the haloxylon ammodendron forest is accurately divided into four grades of non-degradation, mild decline, moderate decline and severe decline. Then differentiated restoration is carried out according to different decline grades, wherein redundant branches are mainly pruned in light decline forests; thinning two-stage branches and cleaning secondary dead branches in the moderately declined forest; in the severe decline forest, stumping is carried out on the trunk withered plants. And the branches obtained by pruning or stumping are laid on the spot to form a sand barrier, so that resource recycling is realized. The problems that in the prior art, degradation grade division is fuzzy, repairing measures are homogenized, the cost for supplementing other sand barrier materials is high, and the environmental hidden danger is large are solved, precise diagnosis and targeted repairing of the declined haloxylon ammodendron forest are achieved, and the ecological function and stability of the forest stand are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of desert vegetation restoration technology, specifically relating to an ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests. Background Technology

[0002] In the arid and semi-arid, ecologically fragile areas of Northwest China, desertification has become a core issue threatening regional ecological security and sustainable development. Haloxylon ammodendron, as an important pioneer tree species for windbreak and sand fixation in this region, exhibits remarkable drought resistance, high-temperature tolerance, and cold resistance under extreme climatic conditions. Based on the irreplaceable ecological functions of Haloxylon ammodendron in maintaining the stability of desert ecosystems, suppressing wind and sand erosion, and improving soil structure, large-scale artificial Haloxylon ammodendron forest creation projects have been implemented in the Northwest desert region, becoming a key support for constructing an ecological security barrier for the northern sand-control belt.

[0003] However, in recent years, the decline of artificial Haloxylon ammodendron forests has significantly intensified due to the combined effects of natural factors and human disturbance. Large areas of forest stands are showing signs of weakened growth and functional degradation, threatening regional ecological security. Under the new "Three-North" Project, the restoration technology system for declining Haloxylon ammodendron windbreak and sand-fixing forests has significant limitations and cannot meet the actual needs of improving forest quality and efficiency: First, existing technologies rely heavily on single indicators or experience to judge the degree of degradation of Haloxylon ammodendron forests, resulting in vague classification of degradation levels and incomplete identification of causes, failing to provide accurate basis for restoration; second, existing technologies mostly adopt a uniform intervention model and do not implement differentiated restoration for different stages of degradation. For example, in coppicing rejuvenation techniques, some schemes stipulate a coppicing intensity of 100%, which can easily cause irreversible damage to the plants; other schemes adopt a "coppicing every other strip" pattern with a width of 20-30m, which results in excessively wide coppicing strips, leading to a significant weakening of the windbreak and sand-fixing function of the forest stand during the restoration period, and even causing local wind and sand erosion to intensify; thirdly, in terms of sand barrier-assisted restoration, traditional plastic mesh sand barriers pose environmental safety hazards and are prone to causing soil pollution; straw checkerboard sand barriers are limited by the small wheat planting area in sandy areas and the shortage of straw (most of which is used for livestock feed and needs to be transported across provinces), resulting in high costs; clay sand barriers are only suitable for areas with local clay distribution, while sandy areas are mainly composed of shifting sand, and clay needs to be transported over long distances, making them both economically and practically inadequate; fourthly, existing Haloxylon ammodendron coppicing rejuvenation techniques have not solved the problem of on-site utilization of branches after coppicing, resulting in the abandonment of a large number of branches, which not only wastes resources but also increases cleanup costs, failing to achieve the synergistic effect of "restoration-resource recycling".

[0004] Furthermore, the core deficiency lies in the lack of a phased and targeted restoration technology framework. Existing technologies neither clearly define the classification standards for degraded Haloxylon ammodendron forests nor develop appropriate restoration methods for different degradation levels, resulting in low efficiency in the utilization of restoration resources. Some measures even have the opposite effect, exacerbating forest stand decline. Therefore, constructing a precise diagnostic technology system for Haloxylon ammodendron forest degradation and developing targeted ecological restoration technologies based on degradation levels and regions, while simultaneously addressing the problems of ambiguous diagnosis, homogeneous strategies, and insufficient resource utilization in existing technologies, is of significant scientific value and urgent practical significance for curbing the degradation trend of Haloxylon ammodendron forests, rebuilding the benign vegetation-soil interaction relationship in desert ecosystems, enhancing windbreak and sand fixation functions, and ensuring ecological security in arid Northwest China. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention discloses an ecological restoration method for improving the quality and efficiency of degraded artificial Haloxylon ammodendron forests, so as to solve the technical problem of poor restoration effect of Haloxylon ammodendron forests with different degrees of degradation in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: an ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests, comprising the following steps: S1: Measure the proportion of dead trees in Haloxylon ammodendron forest (A), canopy cover loss rate (B), shoot dieback rate (C), total vegetation cover (D), and root exposure rate (E); then calculate the comprehensive decline index (DC) according to the following formula; let their weights be wA, wB, wC, wD, and wE, and satisfy wA+wB+wC+wD+wE=1, then calculate the comprehensive decline index DC according to the following formula; DC= wA×A + wB×B + wC×C +wD×D + wE×E; Based on the comprehensive decline index value, the Haloxylon ammodendron forests are further divided into non-degraded Haloxylon ammodendron forests, mildly degraded Haloxylon ammodendron forests, moderately degraded Haloxylon ammodendron forests, and severely degraded Haloxylon ammodendron forests. DC < 0.2 indicates an undegraded Haloxylon ammodendron forest; 0.2 ≤ DC < 0.35 indicates a slightly degraded Haloxylon ammodendron forest; 0.35 ≤ DC < 0.75 indicates a moderately degraded Haloxylon ammodendron forest; and 0.75 ≤ DC ≤ 1 indicates a severely degraded Haloxylon ammodendron forest. S2: Implement differentiated repair based on the level of recession: For mildly declining Haloxylon ammodendron forests, prune redundant branches and lay the pruned branches as flat sand barriers; For moderately declining Haloxylon ammodendron forests, first prune the secondary dead branches in the middle and lower parts of the plant, then thin out the secondary branches on the main branches in the middle and upper parts, and lay the pruned branches in rows to form sand barriers. For severely degraded Haloxylon ammodendron forests, the main trunks of dead or dying plants should be cut back, leaving a stubble height of 5-20cm, and then the pruned branches should be laid out as square sand barriers.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the measurement period was from July to August. The following formulas were used to calculate the proportion of dead trees in the Haloxylon ammodendron forest (A), the canopy cover loss rate of the Haloxylon ammodendron forest (B), the dieback rate of the Haloxylon ammodendron forest (C), the total vegetation cover of the Haloxylon ammodendron forest (D), and the root exposure rate of the Haloxylon ammodendron forest (E). The percentage of dead trees in a Haloxylon ammodendron forest = (sum of the percentages of dead trees in all quadrats / total number of quadrats) × 100%; Haloxylon ammodendron canopy cover loss rate (B) = [(average canopy projection area of ​​healthy Haloxylon ammodendron forest - average canopy projection area of ​​degraded Haloxylon ammodendron forest) / average canopy projection area of ​​healthy Haloxylon ammodendron forest] × 100%; The dieback rate (C) of Haloxylon ammodendron forest = (sum of dieback rates of all sample plants / total number of sample plants) × 100%; Total vegetation cover (D) of Haloxylon ammodendron forest = (sum of total vegetation cover of all quadrats / total number of quadrats) × 100%; Root exposure rate (E) of Haloxylon ammodendron forest = (sum of root exposure rates of all sample plants / total number of sample plants) × 100%; The root exposure rate of a single plant is calculated as follows: (length of roots exposed to the ground / total root length) × 100%.

[0009] Furthermore, redundant branches include dead branches, crossing branches with a crossing angle ≤15°, overlapping branches with a projected overlapping area ≥50%, and diseased or weak branches.

[0010] Furthermore, when pruning redundant branches, first prune the redundant branches at the base and on the inner side, and then prune the redundant branches on the outer side and on the upper part; the angle between the direction of the cut and the axis of the branch should be 45°, and the cut should be 5-10mm away from the base of the branch; the number of redundant branches pruned for each Haloxylon ammodendron should be 15-30% of the total number of branches per plant.

[0011] Furthermore, for moderately declining Haloxylon ammodendron forests, when thinning the secondary branches on the upper and middle main branches, the secondary branches to be thinned must meet one of the following conditions: the secondary branch is dead or the distance between the secondary branch and other secondary branches is <5cm.

[0012] Furthermore, when thinning out secondary branches, the thinning rate of secondary branches on a single main branch is 40-50%.

[0013] Furthermore, for moderately declining Haloxylon ammodendron forests, when pruning secondary dead branches, the cut should be 3-5 mm from the base of the branch, and the angle between the cut direction and the branch axis should be 45-60°; when thinning out secondary branches, 1-2 plump buds should be retained at the cut.

[0014] Furthermore, the coppicing period is from November to March of the following year; when the plant diameter is <2cm, the stubble height is 5~10cm; when the plant diameter is 2~5cm, the stubble height is 10~15cm; when the plant diameter is >5cm, the stubble height is 15~20cm.

[0015] Furthermore, after the cut is smoothed, apply a wound healing agent with a thickness of 0.5~1mm to the cut.

[0016] Furthermore, for mildly declining Haloxylon ammodendron forests, the pruned redundant branches are directly laid flat in areas of strong wind erosion within the forest. For moderately declining Haloxylon ammodendron forests, the row-and-row sand barriers are laid perpendicular to the prevailing wind direction, with each sand barrier being 2-3m long, 20-30cm wide, and 10-15cm thick, and the spacing between sand barriers is 1.5-2m. For severely declining Haloxylon ammodendron forests, the square unit area of ​​the grid sand barriers is 2-6m², with the main strip spacing being 1-2m and the secondary strip spacing being 2-3m.

[0017] The beneficial effects of this invention are: 1. This invention constructs a Haloxylon ammodendron forest degradation index to evaluate the degree of degradation of Haloxylon ammodendron forests and solves the problem of classifying the degree of degradation; then, based on the determination of the degree of degradation of Haloxylon ammodendron forests, it formulates differentiated restoration plans to solve the problem of homogeneous restoration; and it uses the coppiced or pruned Haloxylon ammodendron branches to make sand barriers on-site, solving the problem of how to utilize the branches after coppicing, without the need for additional sand barrier material input, and solving the problems of high cost and environmental hazards of sand barrier materials.

[0018] 2. When restoring mildly degraded Haloxylon ammodendron forests, accurately remove redundant branches from the canopy, retaining main branches and healthy assimilating branches to reduce ineffective transpiration, optimize water distribution efficiency, and enhance the canopy microclimate regulation function. When restoring moderately degraded Haloxylon ammodendron forests, firstly, remove secondary dead branches and reasonably thin out the number of second-order branches to reduce canopy transpiration load and concentrate water supply to healthy branches; secondly, use the pruned branches to form rows of sand barriers on-site to reduce near-surface wind speed and the risk of root exposure, thereby reducing ineffective water consumption and promoting root function recovery. When restoring severely degraded Haloxylon ammodendron forests, implement coppicing rejuvenation on dead or dying main trunks, leaving a stubble height of 5-20cm, retaining healthy basal suckers to promote new branch growth, and using the coppiced branches to form sand barriers on-site to construct windbreak and sand-fixing barriers, reducing surface sand transport, interrupting the degradation chain, and rebuilding a benign vegetation-soil interaction relationship. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0020] Example 1 An ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests, characterized by the following steps: Step 1: Construction, measurement, and evaluation of the assessment system for the degree of decline The degree of degradation in Haloxylon ammodendron forests was assessed using indicators such as the proportion of dead trees, canopy cover loss rate, shoot dieback rate, total vegetation cover, and root exposure rate. The proportion of dead trees represents the percentage of dead trees out of the total number of trees, reflecting the stand's health and indicating desertification risk. The canopy cover loss rate represents the reduction in canopy cover area between degraded and healthy Haloxylon ammodendron trees, reflecting the degree of canopy structure deterioration. The shoot dieback rate represents the percentage of dead shoots out of the total number of branches, comprehensively reflecting the degree of plant degradation. The total vegetation cover represents the percentage of the vertical projection area of ​​all above-ground vegetation within a plot to the total area of ​​the plot, a core ecological indicator for measuring surface vegetation cover. The root exposure rate represents the percentage of root length exposed above the ground out of the total root length, reflecting the degree of root damage caused by insufficient sand burial depth or wind erosion.

[0021] Evaluation index weights: The weight of the proportion of dead trees in the Haloxylon ammodendron forest is 0.3; the weight of the canopy cover loss rate in the Haloxylon ammodendron forest is 0.2; the weight of the dieback rate in the Haloxylon ammodendron forest is 0.1; the weight of the total vegetation cover in the Haloxylon ammodendron forest is 0.3; and the weight of the root exposure rate in the Haloxylon ammodendron forest is 0.1.

[0022] Calculation of the degree of recession: Degradation level (DC) = 0.3 × proportion of dead trees in Haloxylon ammodendron forest + 0.2 × canopy cover loss rate in Haloxylon ammodendron forest + 0.1 × dieback rate in Haloxylon ammodendron forest + 0.3 × total vegetation cover in Haloxylon ammodendron forest + 0.1 × root exposure rate of Haloxylon ammodendron.

[0023] Classification of recession degree: No degradation: DC < 0.2; Mild degradation: 0.2 ≤ DC < 0.35; Moderate degradation: 0.35 ≤ DC < 0.75; Severe degradation: 0.75 ≤ DC ≤ 1.0.

[0024] ① Calculate the proportion of dead trees in the Haloxylon ammodendron forest Within the target forest stand, three representative areas (each 1 hectare) were selected to establish sample plots, with five 10m × 10m quadrats within each plot. Within each quadrat, the total number of Haloxylon ammodendron trees was investigated and recorded, and the number of dead trees (those completely dead and lifeless) was identified and counted. The proportion of dead trees in the Haloxylon ammodendron forest was calculated using the following formula: The percentage of dead trees in a Haloxylon ammodendron forest = (sum of the percentages of dead trees in all quadrats / total number of quadrats) × 100%; ② Calculate the canopy cover loss rate of Haloxylon ammodendron Determination of healthy canopy baseline: Three undegraded healthy Haloxylon ammodendron forest plots (each plot area is 1 hectare) were selected, and five 10m×10m quadrats were set up in each plot. Canopy orthophotos were obtained by UAV low-altitude aerial survey (flight altitude 5m, resolution 0.01m). The canopy projection area of ​​each Haloxylon ammodendron was interpreted by image processing software, and the average canopy coverage area (S0) of healthy Haloxylon ammodendron was calculated.

[0025] Field measurement of degraded canopy: Quadrats corresponding to healthy quadrats were set up in the degraded sample area. Images were acquired using the same UAV parameters, and the average canopy coverage area (S1) of the degraded Haloxylon ammodendron was interpreted. The canopy coverage loss rate was calculated using the following formula; Canopy cover loss rate = [(S0-S1) / S0]×100%.

[0026] Precautions: Drone aerial surveys must be conducted under windless and clear conditions to avoid blurring of the canopy image. If drone monitoring is not possible, a quadrat method can be used as an auxiliary method. Specifically, four marker points are set at the edge of the Haloxylon ammodendron canopy projection, the longest diameter (L) and the shortest vertical diameter (W) of the canopy are measured, and the canopy area is estimated using the ellipse area formula (S=π×L×W / 4).

[0027] ③ Calculate the rate of twig dieback on Haloxylon ammodendron Sample selection: In the middle of the growing season (July to August), set up 5 10m×10m quadrats in each hectare of Haloxylon ammodendron forest, and randomly select 2 to 3 Haloxylon ammodendron plants with uniform growth in each quadrat as standard sample plants (avoiding extremely weak or abnormally robust individuals).

[0028] Branch survey: A full branch count was conducted for each sample plant, distinguishing between dead branches (branch tips and above the top 1 / 3 lacking green growth and with shriveled bark) and healthy branches (branch with overall green growth). The number of dead branches and the total number of branches for each sample plant were recorded. For densely branched plants, the count was performed in stratification by "main branch - lateral branch" to ensure no omissions or duplicates. The dead branch rate was calculated using the following formula; Single-plant dieback rate = (Number of dieback branches per plant / Total number of branches per plant) × 100%; The percentage of dead shoots in a quadrat is calculated as follows: (Sum of the percentages of dead shoots in all quadrats / Total number of quadrats) × 100%.

[0029] ④ Calculate the total vegetation cover of Haloxylon ammodendron forest Within the target forest stand, three representative areas (each 1 hectare) were selected to establish sample plots, with five 10m × 10m quadrats within each plot. Within each quadrat, the length and width of the Haloxylon ammodendron canopy were measured, and the projected area of ​​all Haloxylon ammodendron plants was calculated using the formula: Projected Area = π × (Length / 2) × (Width / 2). Simultaneously, three 1m × 1m quadrats were established within each quadrat to measure the length and width of herbaceous plant canopies, and the projected area of ​​all herbaceous plants was calculated using the formula: Projected Area = π × (Length / 2) × (Width / 2). The total vegetation cover of the Haloxylon ammodendron forest was calculated using the following formula: Total vegetation cover (D) of Haloxylon ammodendron forest = (sum of total vegetation cover of all quadrats / total number of quadrats) × 100%; ⑤ Calculate the root exposure rate of Haloxylon ammodendron Sample plant selection: Using the typical sampling method, five 10m×10m quadrats were set up per hectare. Two Haloxylon ammodendron plants with uniform growth were randomly selected from each quadrat as standard sample plants (avoiding extremely weak or abnormally robust individuals).

[0030] Sample plant and root system survey: Two Haloxylon ammodendron plants with obvious exposed roots were selected in each degraded quadrat. The distribution of exposed roots was measured along four directions (east, south, west, and north) with the base of the plant as the center.

[0031] Root system measurement: The total root length (L) was measured using ground-penetrating radar. 总 ), and the length of the root system exposed on the ground (L) 暴露 Record auxiliary information such as root diameter and exposure location (distance from the trunk), and calculate the exposure rate according to the following formula; Single plant root exposure rate = (L 暴露 / L 总 ) × 100%; Root exposure rate of sample area = (sum of root exposure rates of all sample plants / total number of sample plants) × 100%.

[0032] Step 2: Restoration methods for Haloxylon ammodendron forests with different degrees of degradation (1) Restoration methods for mildly declining Haloxylon ammodendron forests 1. Branch classification: Retained branches: main branches and healthy assimilation branches (bright green color, free from disease and pest spots).

[0033] Pruned branches: redundant branches, including dead branches (the branches are grayish-brown in color), crossing branches (two branches crossing at an angle of ≤15° and pressing against each other), overlapping branches (two branches with an overlapping area of ​​≥50% and located inside the canopy), and diseased or weak branches (leaf leaves showing signs of powdery mildew or other pest and disease attachments); mark the base of the pruned branches with red environmentally friendly paint.

[0034] 2. Precise pruning Pruning sequence: Follow the principle of pruning the inner side of the canopy before the outer side, and the lower part before the upper part. First prune the redundant branches at the base and on the inner side, and then deal with the redundant branches on the outer side and on the upper part to reduce collision damage to the remaining branches.

[0035] Pruning angle and position: When pruning, make the angle between the cut and the branch axis 45°, the cut 5-10mm away from the base of the remaining branch, and the cut should be smooth without splitting to avoid forming a "horseshoe" shaped wound and reduce the risk of pathogen invasion.

[0036] Pruning intensity control: The number of marked pruning branches per plant should be controlled at 15-30% of the total number of branches to avoid over-pruning.

[0037] 3. Post-pruning residue treatment If the pruned branches are free of pests and diseases, they should be used to create sand barriers on-site; if the pruned branches carry pests and diseases, they should be transported to areas outside the forest for burning to prevent the spread of pests and diseases.

[0038] (2) Restoration methods for moderately declining Haloxylon ammodendron forests 1. Remove secondary dead branches and thin out second-order branches. Secondary dead branches: The branches are dark brown or black in color, with a dull bark, and are not flexible and break easily when bent. They are marked with a white label.

[0039] Secondary branches: Select the main branch as the reference branch and mark the secondary branches that need to be thinned (meeting any of the following conditions: the secondary branch is dead or the distance between the secondary branch and other secondary branches is <5cm). Mark them with yellow labels. The thinning rate of secondary branches of a single main branch should be controlled at 40~50%.

[0040] 2. Removal and Reduction Operation sequence: First remove secondary dead branches in the lower and middle part of the plant (0.3~0.6m from the ground), then thin out the marked second-level branches on the main branches in the middle and upper parts, to avoid reducing the canopy support due to thinning first.

[0041] Pruning requirements: When removing dead branches, the cut should be 3-5mm away from the base of the main branch or secondary branch, and the angle between the cut direction and the branch axis should be 45-60° to ensure a smooth cut; when thinning secondary branches, the cut should retain 1-2 plump buds to prevent subsequent branch sprouting from being hindered.

[0042] Intensity control: The reduction rate of secondary branches on a single main branch should be controlled at 40-50% to avoid excessive pruning that would lead to insufficient photosynthetic area of ​​the plant.

[0043] 3. Construction and installation of row-style sand barriers after pruning branches Classification and screening: The removed secondary dead branches are used as the main material for sand barriers, and the thinned healthy second-level branches are used as auxiliary materials.

[0044] Sand barrier dimensions: Each sand barrier is 2-3m long, 20-30cm wide, and 10-15cm thick. The spacing between adjacent sand barriers is 1.5-2m, and they are arranged in a "row and column" pattern. The direction of the row and column sand barriers is perpendicular to the prevailing wind direction.

[0045] Sand barrier installation: First, arrange the branches evenly along the laying direction, then fix them at both ends and the middle of the sand barrier with U-shaped ground nails (20~25cm in length and ≥5mm in diameter) (3 ground nails per meter of sand barrier). The ground nails should be inserted into the ground to a depth of ≥15cm to ensure the wind resistance stability of the sand barrier.

[0046] Edge treatment: The edges of the sand barrier must be in close contact with the ground surface. Fill the gaps at the edges with fine sand to prevent wind and sand from entering from the edges and causing the sand barrier to shift.

[0047] (3) Restoration methods for severely degraded Haloxylon ammodendron forests 1. Rejuvenation of plants with dead or dying main stems by coppicing. Dead main trunk: Assimilating branches have completely fallen off or dried up, with no green parts, marked with a red sign.

[0048] Dying plants: Assimilation branches are sparse and severely withered and yellowed, with more than 2 / 3 of the branches dead, marked with an orange tag.

[0049] Coppicing time: November to March of the following year.

[0050] Stubble height control: Adjust the stubble height according to the plant diameter. When the plant diameter is <2cm, the stubble height is 5~10cm; when the plant diameter is 2~5cm, the stubble height is 10~15cm; when the plant diameter is >5cm, the stubble height is 15~20cm. Ensure that the stubble section is 3~5cm away from the top healthy sprout (avoid damaging the bud).

[0051] Incision requirements: The incision surface should be smooth and free of splits. Apply wound healing agent (composition: 5% thiophanate-methyl + 10% humic acid) to the incision with a thickness of 0.5~1mm to prevent bacterial invasion and moisture loss.

[0052] Post-cutting protection: Prevent livestock from grazing on the stubble.

[0053] 2. Setting up sand barriers with coppiced branches Healthy branches after pruning should be selected as sand barrier materials. If the pruned branches carry pests or diseases, they should be transported to the outside of the forest for burning to prevent the spread of pests and diseases.

[0054] Sand barrier type and size: Square sand barriers are used, with the main strip (perpendicular to the prevailing wind direction) spaced 1~2m apart and the secondary strip (parallel to the prevailing wind direction) spaced 2~3m apart, forming a square unit of 2~6m².

[0055] Surface pretreatment: In the area where sand barriers are deployed, mark the locations of the main and secondary sand barrier zones along the prevailing wind direction.

[0056] Sand barrier fixing: First, mark the main strip and insert the tightly bundled branches vertically into the sand body for 10-15cm, so that the top of the sand barrier is 15-20cm above the ground surface; the secondary strips are sparsely inserted vertically into the sand body for 10-15cm, so that the top of the sand barrier is 15-20cm above the ground surface.

[0057] Edge reinforcement: At the corners and both ends of the sand barrier, use wooden stakes with a length of 50cm and a diameter of ≥1.5cm to reinforce the barrier (the stakes are inserted 30cm into the ground). Use wire to bind the branches of the sand barrier to the stakes (the wire diameter is 2mm and the binding spacing is 10cm) to prevent the sand barrier from shifting due to wind and sand impact.

[0058] Repair effect ① Mild repair effect Plant growth indicators: Within one growth cycle after pruning, the average growth of the main branches increases by 20-25%, and the number of healthy assimilated branches increases by 15-20%.

[0059] Forest stand functional indicators: Within two growth cycles after pruning, vegetation coverage increased by 25-35%, near-surface wind speed in the forest decreased by 70-80% (10-15% higher than before pruning), and the windbreak and sand fixation functions were significantly enhanced.

[0060] Soil environmental indicators: After pruning, the mulch can increase the moisture content of the top layer of soil (0~30cm) by 0.5~1.0%, reduce the soil bulk density by 0.05~0.1g / cm³, and improve the soil structure.

[0061] In terms of optimizing water allocation: by removing redundant branches, the ineffective transpiration area is reduced (15-20% reduction per plant), and the daily transpiration water consumption of the plant is reduced (12-18% reduction compared to before pruning), so that more water is allocated to the main branches and healthy assimilating branches, thereby improving the plant's water use efficiency (8-12% increase after pruning).

[0062] In terms of canopy microclimate regulation: after pruning, the ventilation and light penetration of the canopy are improved, reducing the stress of high temperature and drought on plant growth, while promoting the photosynthesis of assimilating branches on the inner side of the canopy (the photosynthetic rate is increased by 10-15% compared with before pruning); in terms of disease control, timely pruning of diseased and weak branches cuts off the transmission path of diseases and pests, reduces the parasitic carriers of pathogens (such as powdery mildew pathogens), and reduces the incidence of diseases and pests (the incidence of diseases and pests after pruning is reduced by 30-40% compared with the control plants).

[0063] ② Moderate repair effect Plant growth recovery effect: Within one growth cycle after repair, the number of healthy branches increased by 55-65%, and the average growth of the main branches reached 18-23cm (an increase of 50-60% compared with before repair).

[0064] Forest stand function enhancement effect: Within two growth cycles after restoration, vegetation coverage increases by 18-25%, near-surface wind speed in the forest decreases by 60-75%, and windbreak and sand fixation function reaches more than 85% of that of mildly degraded forest stands after restoration.

[0065] Soil environment improvement effect: The sand barrier can reduce the soil bulk density by 0.08~0.12g / cm³, and the soil moisture content of 0~60cm can be stabilized at 1.8~2.5%, which meets the normal growth needs of Haloxylon ammodendron.

[0066] Regarding the water supply and demand optimization mechanism, by removing secondary dead branches (which have no transpiration function but consume water) and thinning out redundant second-level branches, the ineffective transpiration area of ​​the plant is reduced by 40-50% (the daily transpiration water consumption per plant is reduced by 25-30%), allowing the water absorbed by the roots to be concentrated on healthy main branches and assimilating branches, thus improving the plant's water use efficiency by 10-12%. Regarding the near-surface windbreak and sand fixation mechanism, flat sand barriers reduce near-surface wind speed, reducing wind and sand erosion on the roots of *Haloxylon ammodendron*, and the root exposure rate can be reduced to below 5%. Simultaneously... Sand barriers can trap some dust and gradually improve the micro-topography of the ground, creating a stable environment for root growth. In terms of root function recovery mechanism: after the sand barriers are laid, the moisture content of the top layer of soil (0~30cm) increases by 1.0~1.5%, avoiding root damage due to extreme temperature or drought. At the same time, the photosynthesis of healthy branches is enhanced (the photosynthetic rate increases by 25%~30% compared with before the repair), the nutrients transported to the roots increase, and the new root germination is promoted (the number of new roots increases by 40%~50% compared with before the repair), and the root absorption capacity is gradually restored.

[0067] ③Severe repair effect Plant rejuvenation effect: Within one growth cycle after coppicing, the germination rate of basal suckers is ≥90%, the number of new branches reaches 10~26 branches / plant, and the average length of new branches is ≥25cm.

[0068] Forest stand function restoration effect: After two growth cycles of restoration, vegetation coverage increased by 12-15%, forest stand breakage rate decreased to ≤15%; near-surface wind speed in the forest decreased by 42-60%, and windbreak and sand fixation function reached more than 75% of that of moderately degraded forest stands after restoration.

[0069] Soil environment improvement effect: The sand barrier can increase the soil surface moisture content (0~30cm) to 1.2~1.8%, which meets the soil conditions for the continuous growth of new branches of Haloxylon ammodendron and realizes the reconstruction of the benign interaction between vegetation and soil.

[0070] Regarding the coppicing rejuvenation mechanism, removing dead / dying main trunks eliminates ineffective nutrient consumption, allowing plant nutrients to be concentrated on healthy basal shoots, activating the germination potential of dormant buds (the germination rate of shoots is 80-90% higher than that of uncoppiced plants); precise control of stubble height ensures sufficient sunlight for buds, promoting rapid growth of new branches; regarding the sand barrier windbreak and sand fixation mechanism, sand barriers reduce surface sand transport by more than 75%, reducing wind and sand erosion on coppiced plant stubble and soil, creating a stable microenvironment for new branch growth; regarding the vegetation-soil interaction and reconstruction mechanism, after new branches sprout, their roots extend into deeper soil layers to absorb deep water and nutrients; the organic matter intercepted by sand barriers and the decomposition of dead branches and fallen leaves can increase the organic matter content of the soil surface, forming a virtuous cycle of "sand barrier fixation - new branch growth - soil improvement," thus breaking the forest stand degradation chain.

[0071] While specific embodiments of the present invention have been described in detail, they should not be construed as limiting the scope of protection of the present invention. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of the present invention.

Claims

1. An ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests, characterized in that, Includes the following steps, S1: Measure the proportion of dead trees in Haloxylon ammodendron forest (A), canopy cover loss rate (B), shoot dieback rate (C), total vegetation cover (D), and root exposure rate (E) of Haloxylon ammodendron forest; set their weights as wA, wB, wC, wD, and wE, respectively, and satisfy wA+wB+wC+wD+wE=1, then calculate the comprehensive decline index DC according to the following formula; DC= wA×A + wB×B + wC×C +wD×D + wE×E; Based on the comprehensive decline index value, the Haloxylon ammodendron forests are further divided into non-degraded Haloxylon ammodendron forests, mildly degraded Haloxylon ammodendron forests, moderately degraded Haloxylon ammodendron forests, and severely degraded Haloxylon ammodendron forests. DC < 0.2 indicates an undegraded Haloxylon ammodendron forest; 0.2 ≤ DC < 0.35 indicates a slightly degraded Haloxylon ammodendron forest; 0.35 ≤ DC < 0.75 indicates a moderately degraded Haloxylon ammodendron forest; and 0.75 ≤ DC ≤ 1 indicates a severely degraded Haloxylon ammodendron forest. S2: Implement differentiated repair based on the level of recession: For the mildly declining Haloxylon ammodendron forest, redundant branches are pruned and the pruned branches are laid out as flat sand barriers. For the moderately declining Haloxylon ammodendron forest, first prune the secondary dead branches in the middle and lower part of the plant, then thin out the second-level branches on the main branches in the middle and upper part, and lay the pruned branches in rows to form sand barriers. For the severely degraded Haloxylon ammodendron forest, the plants with dead or dying trunks are coppiced, leaving a stubble height of 5-20cm, and then the pruned branches are laid out to form a square sand barrier.

2. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: The measurement period was from July to August. The following formulas were used to calculate the percentage of dead trees in the Haloxylon ammodendron forest (A), the canopy cover loss rate of the Haloxylon ammodendron forest (B), the dieback rate of the Haloxylon ammodendron forest (C), the total vegetation cover of the Haloxylon ammodendron forest (D), and the root exposure rate of the Haloxylon ammodendron forest (E). The percentage of dead trees in a Haloxylon ammodendron forest = (sum of the percentages of dead trees in all quadrats / total number of quadrats) × 100%. Haloxylon ammodendron canopy cover loss rate = [(average canopy projection area of ​​healthy Haloxylon ammodendron forest - average canopy projection area of ​​degraded Haloxylon ammodendron forest) / average canopy projection area of ​​healthy Haloxylon ammodendron forest] × 100%; The dieback rate of Haloxylon ammodendron forest = (sum of dieback rates of all sample plants / total number of sample plants) × 100%; Total vegetation cover of Haloxylon ammodendron forest = (sum of total vegetation cover of all quadrats / total number of quadrats); The root exposure rate of Haloxylon ammodendron forest = (sum of root exposure rates of all sample plants / total number of sample plants) × 100%.

3. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: The redundant branches include dead branches, crossing branches with a crossing angle of ≤15°, overlapping branches with a projected overlap area of ​​≥50%, and diseased or weak branches.

4. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 3, characterized in that: When pruning redundant branches, first prune the redundant branches at the base and on the inner side, and then prune the redundant branches on the outer side and on the upper part; the angle between the direction of the cut and the axis of the branch is 45°, and the cut is 5-10mm away from the base of the branch; the number of redundant branches pruned for each Haloxylon ammodendron is 15-30% of the total number of branches of each plant.

5. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: For the moderately declining Haloxylon ammodendron forest, when thinning the secondary branches on the upper and middle main branches, the secondary branches to be thinned must meet one of the following conditions: the secondary branch is dead or the distance between the secondary branch and other secondary branches is <5cm.

6. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 5, characterized in that: When thinning out secondary branches, the thinning rate of secondary branches on a single main branch is 40-50%.

7. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: For the moderately declining Haloxylon ammodendron forest, when pruning secondary dead branches, the cut should be 3-5 mm from the base of the branch, and the angle between the cut direction and the branch axis should be 45-60°; when thinning out secondary branches, 1-2 plump buds should be retained at the cut.

8. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: The coppicing period is from November to March of the following year; when the plant diameter is <2cm, the stubble height is 5~10cm; when the plant diameter is 2~5cm, the stubble height is 10~15cm; when the plant diameter is >5cm, the stubble height is 15~20cm.

9. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 8, characterized in that: After cutting, apply a wound healing agent with a thickness of 0.5~1mm to the cut.

10. The ecological restoration method for improving the quality and efficiency of declining artificial Haloxylon ammodendron forests according to claim 1, characterized in that: For mildly degraded Haloxylon ammodendron forests, flat sand barriers are concentrated in areas with severe wind erosion; for moderately degraded Haloxylon ammodendron forests, row-style sand barriers are laid perpendicular to the prevailing wind direction, with each sand barrier being 2-3m long, 20-30cm wide, and 10-15cm thick, and the spacing between sand barriers being 1.5-2m; for severely degraded Haloxylon ammodendron forests, the square unit area of ​​the grid sand barriers is 2-6m², with the main strip spacing being 1-2m and the secondary strip spacing being 2-3m.