A near-natural vegetation zoning planting method for coastal restoration sand dune fixation

Abstract

The application discloses a kind of near-natural vegetation zoning planting methods for coastal restoration dune fixation, wherein the method includes: selecting a dune parallel to the side of sea; defining planting area at the top of the dune; the planting area is sequentially divided into front dune area, dune top area and back dune area from the sea side to the land side; planting adventitious root plants in front dune area, dune top area and back dune area; wherein the planting area of front dune area is greater than or equal to that of back dune area, which is greater than or equal to that of dune top area. The application carries out shrub restoration on artificial restoration dunes in tropical and subtropical regions, and can construct and form near-natural psammophytic vegetation on coastal dunes in a short time by using this method. Through reducing wind speed, intercepting particulate matter, forming unique sediment structure, reducing patch boundary fragmentation and other ways, it promotes the transformation of mobile dunes into fixed or semi-fixed dunes, protects the surface of newly built dunes from wind erosion and erosion, and improves biodiversity.

Description

Technical Field

[0001] This invention relates to the field of sand dune restoration technology, and more particularly to a restoration method using near-natural vegetation. Background Technology

[0002] Beaches are an important natural resource. As a natural barrier, they protect the coastline from the erosion and damage caused by storm surges. Their ecological and landscape benefits surpass those of current engineering measures (such as seawalls, groynes, and offshore breakwaters), and they are increasingly valued. The construction of artificial coastal dunes can slow down wave speeds, serving as a natural barrier to reduce wave impact on the coastline, protect the coastline and infrastructure from damage or erosion, prevent seawater intrusion, and maintain biodiversity. However, newly restored dunes are highly mobile and do not readily support vegetation growth. Before reaching a stable equilibrium, the ecosystem is often fragile and prone to shifting or deformation. Summary of the Invention

[0003] In view of this, the purpose of this invention is to propose a near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization. By carrying out shrub restoration on artificially restored sand dunes in tropical and subtropical regions, this method can quickly construct near-natural psammophytic vegetation on coastal sand dunes. By reducing wind speed, intercepting particulate matter, forming unique sediment structures, and reducing patch boundary fragmentation, it promotes the transformation of mobile sand dunes into fixed or semi-fixed sand dunes, protects the surface of newly formed sand dunes from wind erosion and erosion, and improves biodiversity.

[0004] According to one aspect of the present invention, a method for zoning and planting near-natural vegetation for coastal dune restoration is provided, comprising: Choose a sand dune parallel to the seaward side; A planting area was demarcated on the top of the dune; the planting area was divided into the front hill area, the top hill area, and the back hill area along the seaward side to the landward side. Plant adventitious root plants in the forehill area, hilltop area, and backhill area; Among them, the planting area in the front hill area is greater than or equal to the planting area in the back hill area and the planting area in the hilltop area.

[0005] In the above-mentioned technical solutions, the existing beach maintenance technology mainly focuses on factors such as hydrodynamics and coastal geomorphology, with the main purpose of maintaining beach stability. However, the implementation of beach maintenance projects increases the sediment on the beach surface, forming new sandy landform deposition units, raising the beach surface elevation, increasing the source of wind-blown sand, and easily causing new environmental problems. Studies have shown that the branches of sand-loving vines such as Bermuda grass extend horizontally, and after being buried by sand, adventitious roots easily grow on the branches, further increasing the material transport efficiency of the root system, thereby gaining an advantage in the habitat (Du Jianhui, Liu Anlong, Dong Yuxiang, et al. Characteristics of root system architecture of typical sand-loving plants on the coast of South China [J]. Acta Phytoecologica Sinica, 2014, 38(08): 888-895.). The key to this invention is to combine natural ecological laws and utilize the fact that the roots of plants that grow horizontally can grow adventitious roots after being buried by sand, increasing the proportion of absorbing roots and the gripping range, effectively improving the material transport efficiency, promoting their rapid settlement, and at the same time promoting the continuous deposition of sand around the plants. The interaction and feedback between waves and nearshore topography determine the geomorphic dynamics of the wavebreak zone / beach, while the interaction and feedback between wind dynamics and beach topography determine the volume and morphology of coastal dunes. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0006] Figure 1 This is a flowchart illustrating an embodiment of a near-natural vegetation zoning planting method for fixing sand dunes in coastal restoration according to the present invention. Figure 2 This is a schematic diagram of a typical cross-section design for coastal dune restoration, based on an embodiment of a near-natural vegetation zoning planting method for fixing coastal dunes according to the present invention. Figure 3 This is a schematic cross-sectional view of the planting location of coastal restoration dunes, according to an embodiment of a near-natural vegetation zoning planting method for fixing coastal restoration dunes. Detailed Implementation

[0007] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0008] This invention provides a near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization. By carrying out shrub restoration on artificially restored sand dunes in tropical and subtropical regions, this method can quickly establish near-natural psammophytic vegetation on coastal sand dunes. By reducing wind speed, intercepting particulate matter, forming unique sediment structures, and reducing patch boundary fragmentation, it promotes the transformation of mobile sand dunes into fixed or semi-fixed sand dunes, protects the surface of newly formed sand dunes from wind erosion and erosion, and improves biodiversity.

[0009] This patent employs a near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization, simulating the design of wild shrub dunes. A simplified design diagram is shown below. Figures 2-3 As shown. Specifically, it includes the following steps: (1) Minimum elevation for vegetation restoration: Based on the premise of economic feasibility, meeting the requirements of extreme hydrodynamic action and ensuring that the disaster prevention and mitigation effect is not reduced, in order to ensure the survival rate and effect of planting, the restoration area is a dry beach area that cannot be reached by average high tide seawater. Figure 2 The minimum elevation (H) of the repair area is calculated using the following formula: H = A + B In the formula, H is the lowest elevation of the restoration area; A is the height difference between the mean spring tide line and the mean high tide line, with the tidal range in Zhejiang, Fujian and Guangdong ranging from 2 to 3 m; B is the height difference between the lowest point of vegetation planting on the dry beach and the mean spring tide line, which is generally 50 cm.

[0010] (2) Slope: The toe angle θ2 of the windward slope is not greater than 20°, and the slope angle θ1 of the leeward slope is not greater than 30°. Figure 2 ), and θ2≥θ1.

[0011] (3) Slope length: The slope length of the leeward slope is usually shorter than that of the windward slope. Figure 2 ).

[0012] (4) Dune length restoration: The length of the dune parallel to the seaward side (dune minor axis) should be shorter than the length of the dune perpendicular to the seaward side (dune major axis). Figure 2 ); (5) Selection of suitable plants: Select native adventitious root plants that are wind-resistant, salt-tolerant, drought-tolerant, and tolerant of poor soil, including: Bermuda grass, purslane, seahorse purslane, thick vine, single-leaved vitex, and euryale ferox. (6) In some embodiments, the planting area of ​​the forecourt is 1 / 3 to 1 / 2 of the planting area. Figure 3 ); The planting area in the hilly area should be 7 / 15 to 1 / 4 of the total planting area, with a planting density of no less than 60% / m². 2 ( Figure 3 ); The planting area in the hilltop area is 1 / 5 to 1 / 4 of the total planting area, with a higher planting density than in the front and back hill areas. Furthermore, the spacing between plants in the direction parallel to the sea level is at least 4 / 5 of the vertical spacing. Figure 3 ).

[0013] Specifically: Example 1 Please see Figure 1 A near-natural vegetation zoning planting method for fixing sand dunes in coastal restoration includes: S1, selecting a sand dune parallel to the seaward side; In this embodiment, the distribution of natural shrub dunes in coastal sandy areas of tropical and subtropical regions often exhibits a greater slope on the windward side than on the leeward side, and the height of the shrub dunes has a significant effect on their volume. This patent employs a near-natural vegetation zoning planting method, thus the slope of the restored dunes simulates that of wild shrub dunes. Figure 2 Therefore, in this invention, the length of the sand dune parallel to the seaward side (short axis of the sand dune) should be shorter than the length of the sand dune perpendicular to the seaward side (long axis of the sand dune), the vertical height H of the contour lines of the sand dune should not be higher than 1-6 m, the slope toe θ2 of the windward slope should not be greater than 20°, the slope angle θ1 of the leeward slope should not be greater than 30°, and the ratio of the length of the front hill area to the back hill area should be greater than 1.5:1.

[0014] S2. Delineate a planting area on the top of the dune; the planting area is divided into a front hill area, a hilltop area, and a back hill area along the seaward side to the landward side; the distance between the lowest point of the planting area and the average high tide line is at least 25 m.

[0015] In this embodiment, newly restored sand dunes, having not yet reached a stable equilibrium, typically have fragile ecosystems and are prone to re-movement or deformation. Surface vegetation cover can protect the wind-eroded surface soil through various means, such as partially covering the sand surface, decomposing windblown sand, and blocking sand transport. Establishing shrub communities on the restored dunes as quickly as possible plays a positive role in the fragile ecosystem and contributes to the stability of the restored dunes. Therefore, it is necessary to clearly define the area for plant community restoration or construction, avoiding planting areas too close to the foreshore area that could be washed away by waves. Planting should be done in areas at least 2.5 m above the average high tide line.

[0016] S3. Plant adventitious root plants in the front hill area, hilltop area, and back hill area; among which, the planting area in the front hill area ≥ the planting area in the back hill area ≥ the planting area in the hilltop area.

[0017] In this embodiment, adventitious root plants include: *Gnaphalium affine*, *Portulaca oleracea*, *Cercis chinensis*, *Vitex negundo*, and *Gnaphalium affine*. The locations for dune restoration are typically in areas with salt spray, where salt mist adheres to the leaves, easily causing physiological dehydration. Simultaneously, these areas suffer from insufficient freshwater and relatively poor soil. The types of plants, coverage area, and height on the dunes all play a role in the later morphological evolution of the restored dunes. This invention focuses on a near-natural vegetation zoning planting method, based on the existing shrub dune topography, climate conditions, and limiting conditions for plant growth in tropical and subtropical coastal sandy areas across the country. It selects native plants with wind resistance, salt tolerance, drought tolerance, and tolerance to poor soil conditions, such as *Gnaphalium affine*. Spinifex littoreus ), Hippocampus ( Sesuvium portulacastru m), Thick vine ( Ipomoea pes-caprae ), single-leaved vitex ( Vitex rotundifolia ) and halophyte ( Wollastonia dentata Climbing plants such as sand vines have adventitious roots. Appropriate burial in sand will promote the growth of their above-ground parts, which will help the sand grains on the beach to continuously deposit around the plants and accelerate the restoration of the stability of the sand dunes.

[0018] In this embodiment, the planting area in the forehill area is 1 / 3 to 1 / 2 of the total planting area; the planting area in the rearhill area is 7 / 15 to 1 / 4 of the total planting area, and the planting density is not less than 60% / m². 2 The planting area on the top of the dunes should be 1 / 5 to 1 / 4 of the total planting area, with a higher planting density than the front and back dunes. The spacing between plants parallel to the sea level should be at least 4 / 5 of the vertical spacing. Strengthening vegetation cover on restored dunes is an effective measure to prevent wind erosion and sand transport. Generally, the denser the vegetation cover, the better the protective effect. Based on the distribution of shrubs on natural dunes in tropical and subtropical coastal sandy areas such as Fujian, Guangdong, and Guangxi, the planting area is approximately 30% to 40% of the dunes. Figure 2 The planting area in the front hill area is approximately 1 / 3 to 1 / 2 of the overall vegetation design area, and the planting area in the back hill area is approximately 7 / 15 to 1 / 4 of the overall vegetation design area, with a planting density of not less than 60% / m². 2 The planting area in the hilltop area is about 1 / 5 to 1 / 4 of the overall vegetation design range, with a higher density than the front and back hill areas. The spacing between plants in the direction parallel to the sea level is at least 4 / 5 of the vertical spacing. This near-natural configuration pattern has the lowest planting and maintenance costs under the premise of the same ecological benefits.

[0019] In this embodiment, the coastal beach in the strong wind zone experiences intense wind and sand activity. Existing beach maintenance technologies mainly focus on factors such as hydrodynamics and coastal geomorphology, aiming primarily at maintaining beach stability, but do not consider the environmental issues of mitigating the impact of wind and sand on sand dunes. The key to this invention lies in combining natural ecological principles, utilizing the adventitious roots that grow from the creeping branches of plants after being buried by sand. This increases the proportion of absorbing roots, effectively improving material transport efficiency and promoting rapid settlement, while simultaneously promoting the continuous deposition of sand around the plants. However, the use of adventitious roots to promote plant growth is mentioned in "Method for Planting Mangrove Trees in Coastal Areas" (CN111642311B). Mangrove trees are semi-mangrove plants that can live on land or in wetlands, but this patent does not specify the soil substrate, such as loam, silt, or sand, making it impossible to determine which substrate is best for growth. This patent, through numerical simulation results and years of field surveys of coastal sand dunes, clarifies the vertical height, slope, and planted species at the highest point of the dunes, as well as the location and area ratio of plant planting. To a certain extent, it can effectively save planting costs, improve survival rate, and reduce subsequent maintenance and management.

[0020] In this embodiment, how to achieve windbreak and sand fixation effects quickly through biological means using plant roots, promoting the continuous deposition of beach sand grains around the plants, and improving the stability of artificially restored sand dunes and the succession process of vegetation are key aspects of beach maintenance. This invention provides a near-natural vegetation zoning planting method for stabilizing coastal sand dunes. Based on the development and characteristics of wind-blown sand currents on the beach, and considering the problems existing in newly restored coastal dunes, combined with the main limiting factors for the growth of psammophytic vegetation, the first step is to minimize the growth of wind-blown sand currents from a physical perspective, thereby reducing their erosion of new dunes. The second step is to determine the elevation of the vegetation planting area on the restored dunes and its distance from the waterline. The third step is to select suitable species from a biological perspective, utilizing the gripping force of plant roots to intercept suspended particles in the wind-blown sand currents and cause them to settle, forming a near-natural vegetation community in a short period of time. This achieves rapid windbreak and sand fixation, buffers runoff speed, resists beach erosion, reduces the degree of fragmentation of patch boundaries, accelerates the succession of dune shrubs, improves biodiversity, optimizes and beautifies the landscape, reduces later maintenance costs, and improves disaster prevention and mitigation capabilities.

[0021] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for zoning and planting near-natural vegetation for stabilizing sand dunes in coastal restoration, characterized in that, Choose a sand dune parallel to the seaward side; A planting area was demarcated on the top of the dune; the planting area was divided into the front hill area, the top hill area, and the back hill area along the seaward side to the landward side. Plant adventitious root plants in the forehill area, hilltop area, and backhill area; Among them, the planting area of ​​the front hill area ≥ the planting area of ​​the back hill area ≥ the planting area of ​​the hill top area, and the area ratio is based on numerical simulation results and field survey of coastal sandy areas. The planting area in the forecourt is 1 / 3 to 1 / 2 of the total planting area; The planting area in the hilly area should be 7 / 15 to 1 / 4 of the total planting area, with a planting density of no less than 60% / m². 2 ; The planting area in the hilltop area is 1 / 5 to 1 / 4 of the total planting area. The planting density is higher than that in the front and back hill areas, and the spacing between plants in the direction parallel to the sea level is at least 4 / 5 of the spacing in the vertical direction. The planting area covers 30%-40% of the sand dune area.

2. The near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization as described in claim 1, characterized in that, In the top-view direction, the short axis of the dune parallel to the seaward side is shorter than the long axis of the dune perpendicular to the seaward side. The vertical height H of the sand dunes is between 1 and 6 m, the toe θ2 of the windward slope is no greater than 20°, the slope angle θ1 of the leeward slope is no greater than 30°, and the ratio of the length of the front hill area to the back hill area is greater than 1.5:

1.

3. The near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization as described in claim 1, characterized in that, The distance between the lowest point of the planting area and the average high tide line is more than 25 m.

4. The near-natural vegetation zoning planting method for coastal sand dune restoration and stabilization as described in claim 1, characterized in that, The adventitious root plants include: *Gnaphalium affine*, *Portulaca oleracea*, *Cercis chinensis*, *Vitex negundo*, and *Gnaphalium affine*.

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