Rock drilling and soil covering method for planting mangrove forest with strongly weathered tuff substrate

Abstract

The invention relates to the technical field of ecological restoration, discloses a rock drilling and soil covering method for planting a mangrove forest with a strongly-weathered tuff substrate, and aims to solve the problems that the root system of the mangrove forest in a hard substrate area is difficult to plant, the soil is poor, and the cost of a traditional restoration project is high. The method comprises the following steps: mechanically crushing a surface layer to an average sea level elevation; the tuff on the lower layer is vibrated and crushed; and backfilling gradient structure planting soil. According to the method, water permeability, continuous fertilizer supply and salinity buffering functions are optimized through gradient planting soil design, the earth excavation volume is reduced in combination with the rock drilling technology, and the ecological restoration effect of the coastal strongly-weathered tuff substrate mangrove forest is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological restoration, and in particular to a mangrove planting method suitable for strongly weathered tuff substrate, which improves the planting habitat and increases the survival rate of mangroves by using rock drilling and soil covering technology. Background Art

[0002] In mangrove ecological restoration projects, traditional restoration methods typically involve excavating the tuff and backfilling with planting soil in areas with heavily weathered tuff substrates, due to their low degree of geological weathering, poor soil, and difficulty in root colonization. However, this method has drawbacks such as the large amount of rock excavation and transportation required, high costs, and the potential for ecological disturbance. For example, in the lagoon ecological restoration project in Shangxiapu Village, Eman Town, Danzhou City, the heavily weathered tuff substrate rendered traditional restoration methods inefficient and significantly increased costs.

[0003] In the prior art, patent document CN202010724799.4 discloses a method for afforestation of mangroves in intertidal zones with strongly weathered tuff geology and high elevation. The tuff is excavated to the average sea level through mechanical crushing, backfilled with high-organic green nutrient soil, and mangrove plants are planted in patchy planting areas. A waterway system is established to ensure root growth and water supply, and suitable native tree species are selected to improve the survival rate. However, this method does not take into account the influence of the diameter of the crushed stones and the backfill soil. The survival rate of mangroves is low, which greatly increases the probability of afforestation failure. Summary of the Invention

[0004] The present invention provides a rock drilling and soil covering method for planting mangroves on strongly weathered tuff substrate. Through mechanical crushing, drilling, gradient soil covering and other processes, the method solves the problems of difficult root colonization and poor soil in hard substrate, improves the survival rate of mangrove seedlings and reduces engineering costs.

[0005] In order to achieve the above object, the present invention provides a rock drilling and soil covering method for mangrove planting on a strongly weathered tuff substrate, characterized in that it comprises the following steps: (1) Surface excavation: Mechanically crush the surface of the repair area and excavate to the local average sea level; (2) Hard soil treatment: The tuff layer below the mean sea level is vibrated and crushed to a depth of ≥30 cm and the diameter of the crushed stones is controlled at 5-8 cm; (3) Backfilling of planting soil: Backfilling artificially prepared planting soil to an appropriate height; (4) Planting of seedlings: Select salt-tolerant mangrove plants for planting.

[0006] Furthermore, the planting soil has a gradient structure, with a bottom layer composed of a volcanic rock matrix and biochar, a middle layer composed of shell powder, humus, and slow-release microcapsules, and a surface layer of sea mud. The volcanic rock has well-developed pores, which can improve soil aeration, prevent water accumulation in the bottom layer from causing root hypoxia and rot, and make it easier for seedlings to take root. Volcanic rock particles with a particle size of 1-5 cm can be filled between larger crushed tuff particles to form a stable skeleton, enhancing the bearing capacity of the substrate, preventing the backfill soil layer from settling or being washed away by tides, and solving the problem of "easy loss of planting soil" in gravel or hard substrate areas. Biochar has a large specific surface area and can absorb water equivalent to 30% to 50% of its own weight. It slowly releases water in arid intertidal zones (such as high tide areas), alleviating intermittent drought stress on seedlings. The middle layer of shell powder, humus, and slow-release microcapsules continuously replenishes soil fertility. Shell powder is rich in calcium carbonate (≥90%) and trace elements (magnesium and strontium). It slowly dissolves in tidal water, providing essential minerals for mangroves and promoting chlorophyll synthesis in leaves and lignification in stems. Calcium carbonate buffers acidic soils, stabilizing soil pH within a suitable range and improving nutrient availability. Humus, containing active substances such as humic acid and fulvic acid and containing ≥40% organic matter, quickly replenishes the nitrogen, phosphorus, and potassium required for mangrove growth. It is particularly suitable for sandy soils (where organic matter is easily lost) or tuff substrates. The slow-release microcapsules gradually degrade under tidal infiltration, slowly releasing nutrients necessary for mangrove growth. This avoids the problem of traditional fertilization, which often results in high concentrations in the early stages and low fertility in the later stages, and improves fertilizer utilization. The surface mud, with a particle size of less than 0.002mm and natural viscosity, forms a dense layer on the surface, reducing water evaporation while buffering against extreme temperatures and maintaining a suitable rhizosphere temperature.

[0007] Furthermore, the volcanic rock matrix has a particle size of 1-3 cm, and the slow-release microcapsules contain nitrogen-fixing bacteria and Fe / Mn chelates.

[0008] Furthermore, the backfill thickness of the planting soil in step (3) is 40-60 cm. The main roots of mangrove plants (such as Kandelia candel and Rhizophora rubra) need to penetrate 20-40 cm into the soil to fix the plants and absorb deep water. The backfill thickness of 40-60 cm can provide sufficient growth space for the roots, avoid the roots circling on the surface due to too thin a soil layer, and reduce the risk of tidal erosion. Periodic flooding of intertidal soil can easily lead to hypoxia. The middle and lower layers of the 40-60 cm soil layer (20-50 cm from the surface) can form a micro-aerobic environment, which not only meets the ventilation needs of the lateral roots, but also avoids hypoxia and rot of the bottom layer caused by too thick a soil layer.

[0009] Furthermore, the planting density of the mangrove seedlings is 1.5-2.5m×1.5-2.5m.

[0010] Furthermore, it also includes the seedling fixing step: after planting, use bamboo poles to insert them into the soil ≥50 cm and tie them together with the seedlings to fix them.

[0011] Furthermore, in step (4), the salt-tolerant mangrove plant is selected from Kandelia obovata, Aegiceras corniculatum or Avicennia marina.

[0012] Furthermore, it also includes habitat diagnosis of the restoration area before planting, and analysis of limiting factors such as salinity, tide level, and physical and chemical properties of the bottom.

[0013] Furthermore, the mass ratio of volcanic rock matrix and biochar in the bottom layer is (7~9):1, and the mass ratio of shell powder, humus, and slow-release microcapsules in the middle layer is (1~2):(4~6):1.

[0014] Furthermore, the thickness of the bottom, middle, and surface layers of the planting soil increases in a gradient, with the thickness ratio of the bottom, middle, and surface layers being 1:2:3. This 1:2:3 gradient thickness increase among the bottom, middle, and surface layers of the planting soil is a three-dimensional optimization design based on the growth patterns of mangrove root systems, the hydrological characteristics of the intertidal zone, and the ecological functions of the soil. The thinner volcanic rock + biochar bottom layer provides an initial planting point for mangrove hypocotyls, and its rough surface and pore structure guide the roots downward. The thicker marine mud layer meets the deep penetration requirements of the taproot during maturity. Meanwhile, the fine particles in the surface layer (particle size <0.002mm) absorb nutrients from the tide. Through the design of "thin bottom layer for strong support, medium and thick layers for stable fertilization, and thick surface layer for optimal planting," an optimal balance between survival rate, growth, and cost is achieved.

[0015] Beneficial effects of the present invention: By mechanically crushing tuff to form a pore structure, anchoring space is provided for the roots. Combined with gradient planting soil design, the roots are guided to take root deeply, significantly improving the survival rate and growth rate of mangroves.

[0016] Innovative gradient planting soil structure realizes stratified optimization of soil functions. The bottom layer of volcanic rock + biochar enhances bearing capacity and water retention, the middle layer of shell powder + humus + slow-release microcapsules continuously provides fertilizer, and the surface sea mud simulates natural habitats. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a picture of a strongly weathered tuff substrate.

[0018] Figure 2 It is the intention of drilling holes to break up the rock and show the covering soil. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The following embodiments are not intended to limit the present invention but are merely intended to illustrate the present invention.

[0020] In the specific embodiments, steps, material selections, and numerical parameters that are not described in detail are all conventional choices in the prior art or any currently disclosed prior art.

[0021] Combine Figure 1 and Figure 2 , the specific implementation manner of the present invention is described as follows: Example 1: A strongly weathered tuff substrate area in a certain region was selected. Before restoration, the substrate was strongly weathered tuff, with a surface mud thickness of 0.1-0.4m and a low degree of rock weathering.

[0022] Surface excavation: Mechanically crush to mean sea level, retaining crushed rocks (5-8 cm in diameter). Crushed rocks are placed on-site to reduce the generation of construction solid waste.

[0023] Planting soil gradient structure: Bottom layer (thickness 10cm, volcanic rock: biochar = 8:1), volcanic rock particle size 1-3cm, biochar specific surface area 800m 2 / g, water holding rate 28%.

[0024] Middle layer (thickness 20cm, shell powder: humus: slow-release microcapsules = 1.5:5:1): humus organic matter content 45%, slow-release microcapsules containing nitrogen-fixing bacteria and Fe / Mn chelates, with a release period of 6-12 months.

[0025] Surface layer (thickness 30cm, sea mud): particle size <0.002mm, water holding capacity 35%, pH 8.0.

[0026] Total backfill thickness: 60cm Seedling selection: Kandelia ovata (seedling height 50-80cm), planting density 2m×2m, fixed with bamboo poles (≥50cm into the soil).

[0027] Comparative Example 1 The traditional full soil replacement repair method completely excavates the strongly weathered tuff (depth 1m), transports the waste outward, and then backfills with a single imported soil (sandy loam, thickness 100cm).

[0028] Comparative Example 2 The difference from Example 1 is that the backfill soil is ordinary planting soil and does not have a multi-layer structure. The rest is the same as Example 1.

[0029] Comparative Example 3 The difference from Example 1 is that the backfill soil is ordinary planting soil with a multi-layer structure, but the thickness of the bottom layer, middle layer and surface layer are the same, and the rest is the same as Example 1.

[0030] The experimental period is 3 years, and the monitoring indicators include seedling survival rate, plant height growth rate, soil organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) content. The experimental data are shown in Table 1:

[0031] Table 1 Group Preservation rate (%) Plant height growth rate (%) TOC (g / kg) TN (g / kg) TP (g / kg) Example 1 75 65 14.5 1.38 0.48 Comparative Example 1 50 30 9.2 0.32 0.095 Comparative Example 2 67 45 10.3 0.89 0.28 Comparative Example 3 70 50 12.6 0.92 0.32 The 75% survival rate in Example 1 was significantly higher than in the other groups. This advantage stems from the greater porosity of the bottom volcanic rock + biochar layer, which improves water permeability and prevents waterlogging and root rot; the intermediate layer of slow-release microcapsules (containing nitrogen-fixing bacteria and Fe / Mn chelates) continuously releases nutrients, preventing short-term nutrient depletion; and the surface sea mud provides a suitable salinity environment. The survival rate in Comparative Example 1 was 50%. This was due to the poor water and nutrient retention capacity of the single sandy loam soil and its lack of slow-release nutrients, which made the seedlings susceptible to salt stress and nutrient deficiency. In Comparative Example 2, the survival rate was lower than in Example 1 because the ordinary nutrient soil lacked a stratified structure, making nutrients easily lost with tides. Although Comparative Example 3 has a layered structure that can partially retain nutrients, its three-layer structure does not have a gradient thickness distribution. The bottom layer is too thick, resulting in poor permeability and restricted root development. The surface layer is too thin and cannot stabilize salinity and water retention. Example 1 optimizes the synergistic effects of water permeability-water retention, fertilizer supply-fertilizer fixation, and salinity buffering through a layering ratio of 1:2:3, thereby significantly improving the survival rate and growth efficiency of mangroves.

[0032] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A rock drilling and soil covering method for mangrove planting on strongly weathered tuff substrate, characterized in that: The following steps are involved: (1) Surface excavation: Mechanically crush the surface of the repair area and excavate to the local average sea level; (2) Hard soil treatment: The tuff layer below the mean sea level is vibrated and crushed to a depth of ≥30 cm and the diameter of the crushed stones is controlled at 5-8 cm; (3) Backfilling of planting soil: Backfilling artificially prepared planting soil to an appropriate height; (4) Planting of seedlings: Select salt-tolerant mangrove plants for planting.

2. The method according to claim 1, characterized in that The planting soil has a gradient structure, wherein the bottom layer is composed of volcanic rock matrix and biochar, the middle layer is composed of shell powder, humus, and slow-release microcapsules, and the surface layer is sea mud.

3. The method according to claim 2, characterized in that The volcanic rock matrix has a particle size of 1-3 cm, and the slow-release microcapsules contain nitrogen-fixing bacteria and Fe / Mn chelates.

4. The method according to claim 1, wherein The planting soil backfill thickness in step (3) is 40-60 cm.

5. The method according to claim 1, wherein The planting density of the mangrove seedlings is 1.5-2.5m×1.5-2.5m.

6. The method according to claim 1, wherein It also includes the seedling fixing step: after planting, use bamboo poles to insert them into the soil ≥50 cm and tie them together with the seedlings to fix them.

7. The method according to claim 1, characterized in that In the step (4), the salt-tolerant mangrove plant is selected from Kandelia candel, Tung blossom tree or Avicennia marina.

8. The method according to claim 1, characterized in that It also includes habitat diagnosis of the restoration area before planting, and analysis of limiting factors such as salinity, tide level, and physical and chemical properties of the bottom soil.

9. The method according to claim 1, characterized in that The mass ratio of volcanic rock matrix and biochar in the bottom layer is (7~9):1, and the mass ratio of shell powder, humus and slow-release microcapsules in the middle layer is (1~2):(4~6):

1.

10. The method according to claim 1, characterized in that The thicknesses of the bottom layer, middle layer and surface layer of the planting soil increase gradually, and the thickness ratio of the bottom layer, middle layer and surface layer is 1:2:3.

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