A method for drilling and backfilling for mangrove planting in a strongly weathered tuff substrate

Abstract

The present application relates to the technical field of ecological restoration, and discloses a rock drilling and soil covering method for planting mangrove in strongly weathered tuff bottom, aiming to solve the problems of mangrove root system planting difficulty, soil barrenness and high cost of traditional restoration engineering in hard bottom area. The method comprises the following steps: mechanically breaking the surface layer to the average sea level elevation; vibrating and breaking the lower tuff; and backfilling gradient structure planting soil. The present application optimizes the water permeability, continuously supplies fertilizer and buffers the salinity through gradient planting soil design, and reduces the earthwork excavation amount by combining the rock drilling and boring technology, thereby improving the ecological restoration effect of coastal strongly weathered tuff bottom mangrove.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology, specifically to a method for planting mangroves on strongly weathered tuff substrates. The method improves the planting habitat and increases the survival rate of mangroves by using rock drilling and soil covering techniques. Background Technology

[0002] In mangrove ecological restoration projects, areas with highly weathered tuff substrates often suffer from low geological weathering, poor soil, and difficulties in root establishment. Traditional restoration methods typically involve excavating the tuff and backfilling with planting soil. However, this method has drawbacks such as large-scale rock excavation and transportation, high costs, and potential ecological disturbance. For example, in the lagoon ecological restoration project in Shangxiapu Village, E'man Town, Danzhou City, the highly weathered tuff substrate resulted in low efficiency and significantly increased restoration costs due to traditional methods.

[0003] In the prior art, patent document CN202010724799.4 discloses a method for afforestation of mangroves in strongly weathered tuff geology and high-elevation intertidal zones. This method involves mechanically breaking and excavating the tuff to mean sea level, backfilling with high-organic-matter nutrient soil, planting mangroves in patchy planting areas, establishing a waterway system to ensure root growth and water supply, and selecting suitable native tree species to improve survival rates. However, this method does not consider the influence of the diameter of the broken rocks and the backfill soil, resulting in low mangrove survival rates and significantly increasing the probability of afforestation failure. Summary of the Invention

[0004] This invention provides a method for planting mangroves on a strongly weathered tuff substrate by drilling holes and covering the soil. Through mechanical crushing, drilling, and gradient soil covering, it solves the problems of difficult root establishment and poor soil in hard substrates, improves the survival rate of mangrove seedlings, and reduces project costs.

[0005] To achieve the above objectives, the present invention provides a method for drilling and backfilling soil for planting mangroves on strongly weathered tuff substrates, characterized by comprising the following steps: (1) Surface excavation: Mechanically break up the surface layer of the repair area and excavate to the local average sea level. (2) Hard bottom treatment: Vibrate and crush the tuff layer below the mean sea level, with a crushing depth ≥30 cm and the diameter of the crushed stones controlled at 5-8 cm; (3) Backfilling with planting soil: Backfill with artificially prepared planting soil to a suitable height; (4) Planting of seedlings: Select salt-tolerant mangrove plants for planting.

[0006] Furthermore, the planting soil has a gradient structure: the bottom layer consists of volcanic rock matrix and biochar, the middle layer consists of shell powder, humus, and slow-release microcapsules, and the top layer is marine mud. The volcanic rock has well-developed pores, which improves soil aeration, prevents root rot caused by waterlogging at the bottom layer, and facilitates seedling rooting. Volcanic rock particles with a diameter of 1-5 cm can fill the spaces between larger, broken tuff particles to form a stable framework, enhancing the bearing capacity of the substrate and preventing the backfill soil from settling or being washed away by tides. This solves the problem of easy soil loss in gravel or hard substrate areas. The biochar has a large specific surface area and can absorb 30% to 50% of its own weight in water, slowly releasing water in dry intertidal zones (such as high tide areas) to alleviate intermittent drought stress on seedlings. The middle layer, consisting of shell powder, humus, and slow-release microcapsules, provides a continuous supply of soil fertility. The shell powder, rich in calcium carbonate (≥90%) and trace elements (magnesium, strontium), slowly dissolves in the tidal water, providing essential minerals for mangroves and promoting chlorophyll synthesis in leaves and lignification of stems. Calcium carbonate buffers acidic soils, stabilizing soil pH within a suitable range and improving nutrient availability. Humus contains active substances such as humic acid and fulvic acid, with an organic matter content ≥40%, rapidly replenishing the nitrogen, phosphorus, and potassium needed 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 soaking, slowly releasing the nutrients needed for mangrove growth, avoiding the problems of "high concentration in the early stages and nutrient deficiency in the later stages" associated with traditional fertilization, thus improving fertilizer utilization. The surface layer, marine mud with a particle size <0.002mm, has natural viscosity, forming a dense layer that reduces water evaporation and buffers extreme temperatures, maintaining the rhizosphere temperature within a suitable range.

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

[0008] Furthermore, in step (3), the backfill thickness of the planting soil is 40-60 cm. The taproot of mangrove plants (such as Kandelia candel and Rhizophora mangifera) needs to penetrate 20-40 cm into the soil to fix the plant and absorb deep water. A backfill thickness of 40-60 cm can provide sufficient growth space for the roots, avoid the roots from coiling on the surface due to the soil layer being too thin, and reduce the risk of tidal erosion. Periodic flooding of intertidal soil can easily lead to oxygen deficiency. The middle and lower layers of the 40-60 cm soil layer (20-50 cm from the surface) can form a micro-oxygen environment, which can meet the aeration needs of lateral roots and avoid the bottom layer from rotting due to oxygen deficiency caused by an excessively thick soil layer.

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

[0010] Furthermore, the procedure also includes securing the seedlings: after planting, use bamboo poles inserted ≥50 cm into the soil to tie and secure them to the seedlings.

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

[0012] Furthermore, this also includes conducting habitat diagnosis of the restoration area before planting, and analyzing limiting factors such as salinity, tidal level, and the physical and chemical properties of the substrate.

[0013] Furthermore, the mass ratio of volcanic rock matrix to 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 top layers of the planting soil increases in a gradient, with a thickness ratio of 1:2:3. This gradient of thickness (1:2:3) is a three-dimensional optimization design based on the root growth patterns of mangroves, the hydrological characteristics of the intertidal zone, and the ecological functions of the soil. The relatively thin volcanic rock and biochar bottom layer provides an initial planting point for the mangrove hypocotyl, and its rough surface and porous structure guide the roots to penetrate downwards. The thicker marine mud layer meets the needs of deep root development during the mature stage, while the fine-grained structure (particle size <0.002mm) of the top layer absorbs nutrients from the tidal water. Through the design of "thin bottom layer for strong support, medium-thick layer for stable fertilization, and thick top layer for optimal planting," the best balance between survival rate, growth, and cost is achieved.

[0015] The beneficial effects of this invention are: By mechanically breaking up tuff to create a porous structure, anchoring space is provided for the roots. Combined with gradient planting soil design, the roots are guided to grow deep, significantly improving the survival rate and growth rate of mangroves.

[0016] An innovative gradient planting soil structure optimizes soil function through stratified layering. The bottom layer of volcanic rock and biochar enhances bearing capacity and water retention, while the middle layer of shell powder, humus, and slow-release microcapsules provides continuous fertilization, and the top layer of marine mud mimics a natural habitat. Attached Figure Description

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

[0018] Figure 2 The intention is to break up rocks by drilling holes to indicate the purpose of covering them with soil. Detailed Implementation

[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 only used to illustrate the present invention.

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

[0021] Combination Figure 1 and Figure 2 The specific embodiments of the present invention are described below: Example 1: A region with a strongly weathered tuff substrate was selected. Before restoration, the substrate was strongly weathered tuff with a surface silt thickness of 0.1-0.4m and a low degree of rock weathering.

[0022] Surface excavation: Mechanically break rocks to average sea level, retaining broken stones (5-8cm in diameter). The broken stones are placed in situ to reduce the amount of construction solid waste generated.

[0023] Gradient structure of planting soil: Bottom layer (10cm thick, volcanic rock: biochar = 8:1), volcanic rock particle size 1-3cm, biochar specific surface area 800m². 2 / g, water holding capacity 28%.

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

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

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

[0027] Comparative Example 1 The traditional complete soil replacement remediation method involves completely excavating the strongly weathered tuff (1m deep), transporting the waste material away, and then backfilling with a single type of topsoil (sandy loam, 100cm thick).

[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; otherwise, it 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 top layer is the same, and the rest is the same as Example 1.

[0030] The experiment lasted for 3 years, and the monitoring indicators included seedling survival rate, plant height growth rate, soil organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) content.

[0031] The experimental data are shown in Table 1:

[0032] Table 1 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 In Example 1, the survival rate of 75% was significantly higher than that of other groups. This advantage stemmed from the fact that the bottom layer of volcanic rock and biochar had a high porosity, improving permeability and preventing root rot from waterlogging; the middle layer of slow-release microcapsules (containing nitrogen-fixing bacteria and Fe / Mn chelates) continuously released nutrients, preventing short-term nutrient depletion; and the surface layer of marine mud provided a suitable salinity environment. In Comparative Example 1, the survival rate was 50%. Due to the poor water and fertilizer retention capacity of the single sandy loam soil and the lack of slow-release nutrients, the seedlings were prone to death due to salt stress and malnutrition. In Comparative Example 2, the ordinary nutrient soil lacked a layered structure, making it easy for nutrients to be lost with the tides, resulting in a lower survival rate compared to Example 1. 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 water permeability and restricted root development, while the top layer is too thin, which cannot stabilize salinity and retain water. In contrast, Example 1, through a layer ratio of 1:2:3, optimizes the synergistic effect of water permeability-water retention, fertilizer supply-fertilizer fixation, and salinity buffering, thereby significantly improving the survival rate and growth efficiency of mangroves.

[0033] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A method of overburdening of a rock drilling hole for planting of a mangrove on a strongly weathered tuff substrate, characterized in that, Includes the following steps: (1) Surface excavation: Mechanically break up the surface layer of the repair area and excavate to the local average sea level. (2) Hard bottom treatment: Vibrate and crush the tuff layer below the mean sea level, with a crushing depth ≥30 cm and the diameter of the crushed stones controlled at 5-8 cm; (3) Backfilling with planting soil: Backfill with artificially prepared planting soil to a suitable height; The planting soil has a gradient structure, with the bottom layer consisting of volcanic rock matrix and biochar, the middle layer consisting of shell powder, humus and slow-release microcapsules, and the surface layer consisting of marine mud. The thickness of the bottom, middle, and top layers of the planting soil increases in a gradient, with a thickness ratio of 1:2:

3. 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. The backfill thickness of the planting soil is 40-60 cm. The mass ratio of volcanic rock matrix to 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. (4) Planting of seedlings: Select salt-tolerant mangrove plants for planting.

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

3. The method of claim 1, wherein, It also includes the seedling fixing steps: after planting, use bamboo poles to insert ≥50 cm into the soil and tie them to the seedlings for fixation.

4. The method of claim 1, wherein, In step (4), the salt-tolerant mangrove plants are selected from Kandelia obovata, Aegiceras corniculatum, or Avicennia marina.

5. The method of claim 1, wherein, It also includes conducting habitat diagnosis of the restoration area before planting, and analyzing limiting factors such as salinity, tidal level, and the physical and chemical properties of the substrate.

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