A mangrove ecological restoration method for a silted lagoon

Abstract

This invention discloses a method for mangrove ecological restoration of silted lagoons, belonging to the field of environmental ecological restoration technology. The method involves raising the average elevation of the lagoon beach according to the topography to solve the problems of seawater exchange and flooding during the rainy season. Mangrove seedlings are planted in the raised areas, and tidal channels and waterways are dug to provide habitats and foraging grounds for organisms. Mangroves and semi-mangroves are planted together. The restoration area is enclosed by a 1.3m high steel plate. A cutter suction dredger is used to pump silt into the restoration area to raise the beach level. After stabilization, the steel plate is removed, and a wooden pile dike is constructed. The average elevation is taken as the average of the dry season tide level and the rainy season tide level; for example, if the dry season tide level is 50cm and the rainy season tide level is 1.3-1.5m, 90cm is set. During the dry season, seawater is pumped in to irrigate the seedlings every two weeks. After 3-5 years, the root system grows longer, and pumping is no longer necessary. The advantages of this invention are: simple operation, high seedling survival rate, significant environmental improvement effect, and can be widely used in lagoon wetlands blocked by silt and polluted to reconstruct the mangrove wetland ecosystem.

Description

Technical Field

[0001] This invention relates to the field of environmental ecological restoration technology, specifically to a method for the ecological restoration of mangroves in silted lagoons. Background Technology

[0002] Mangroves are wetland ecosystems composed of true mangrove plants and semi-mangrove plants, distributed in the intertidal zone of tropical and subtropical coasts worldwide. They serve as ecological transition zones between land and sea, exhibiting high productivity and ecological complexity, possessing multiple important ecological values, and providing habitats and breeding grounds for numerous organisms. Lagoons are an important part of wetland ecosystems and are habitats for mangrove communities. In the past thirty years, land reclamation and other activities have caused numerous problems in lagoons, leading to a reduction in mangrove area. Although my country has taken measures to increase mangrove area, problems remain, hindering their restoration and sustainable development.

[0003] To address the problem, a mangrove restoration method for silted lagoons is proposed, including environmental surveys and measurements, assessment of tidal levels and water depths to determine the restoration area and raise the beach elevation, planting native mangrove plants that purify wastewater, constructing wooden pile dikes, pumping seawater for irrigation, and monitoring and maintenance, in order to meet the growth requirements of mangroves. Summary of the Invention

[0004] The purpose of this invention is to provide a method that is simple to operate, has a high seedling survival rate, and has a significant environmental improvement effect. This method can be widely used in lagoon wetland ecosystems that are blocked by silt and polluted to reconstruct mangrove wetland ecosystems.

[0005] This invention relates to a method for the restoration of mangroves in silted lagoons, comprising the following steps:

[0006] a. On lagoon beaches with low seawater exchange due to siltation, the average elevation of the beach surface is artificially raised according to the tidal flat landform of the mangrove restoration area. This solves the problems of low seawater exchange caused by siltation and narrow inlet, as well as long-term submersion of plants due to high tides during the rainy season. Mangrove seedlings are planted on the raised beach surface, and lower areas are excavated for use as tidal channels and water areas to provide habitats or foraging grounds for benthic and marine life and birds.

[0007] b. Select healthy native tree seedlings with well-developed root systems, healthy leaves, and intact bark for planting. The seedlings should be medium-sized (50-60cm). Plant them on the artificially raised beach using a mixed planting method of mangroves and semi-mangroves. After planting, in view of the characteristics of newly planted mangrove seedlings being easily washed away by waves and blown down by sea winds, build wooden stakes around the newly planted mangroves on the bay beach and use the wooden stake dike method to prevent waves and sea winds from uprooting the mangrove seedlings.

[0008] c. During the dry season, seawater is pumped to irrigate newly planted mangrove seedlings on the lagoon mudflats to maintain the normal water requirements of the mangrove seedlings. During the rainy season, there is no need to pump seawater.

[0009] Preferably, a 1.3m high steel plate is used to enclose the lagoon beach surface that needs to be raised as a mangrove ecological restoration area, and a 20m long and 4.5m wide cutter suction dredger equipped with a 12-inch delivery pump is used to extract the mud and sand outside the restoration area into the restoration area.

[0010] Preferably, the average elevation of the artificially raised beach surface is the average of the sum of the dry season tide level and the rainy season tide level. For example, if the dry season tide level is 50cm and the water level reaches 1.3-1.5m during the rainy season floods, and the seawater cannot be discharged to the open sea in time during the rainy season, then the average elevation of the designed beach surface is set at 90cm.

[0011] Preferably, the mangrove seedlings for artificial planting should be native species adapted to the local area, such as Rhizophora stylosa, Rhizophora mukorossi, Kandelia candel, Tung tree, Cocos nucifera, Excoecaria agallocha, Hibiscus syriacus, Phellodendron amurense, Mangos japonica, and Pteris vittata. They should be planted in a mixed manner, with a planting depth of 20cm and a planting density of 1.5m×1.5m. Depending on the size of the wind and waves, 1.3m high wooden stakes should be set up around the lagoon estuary to enclose the mangrove ecological restoration area within the lagoon.

[0012] Preferably, in step c, seawater is pumped into the mangrove forest on the bay's mudflats using a pump. Irrigation is carried out during the dry season, with the need for irrigation concentrated in the dry season each year. The irrigation frequency is about once every two weeks, and the water is thoroughly soaked. After about 3-5 years of seawater irrigation, as the seedlings grow and their root systems develop, the interval between pumping will lengthen, and eventually, pumping will no longer be necessary.

[0013] Compared with existing technologies, the beneficial effects of the technical solution of this invention are:

[0014] The technical solution provided by this invention targets lagoon wetland ecosystems characterized by years of sludge accumulation, narrow estuaries, and low seawater exchange. These ecosystems are characterized by low water levels during the dry season (droughts typically occur from December to May of the following year) and high water levels during the rainy season (floods often occur during typhoons in October and November). The narrow estuary prevents effective drainage of water from the lagoon into the ocean. The solution involves artificially raising the average elevation of the mangrove restoration area to prevent the mangrove ecosystem within the lagoon from being submerged and dying due to prolonged flooding. The tree species used for ecological restoration include native species such as *Rhizophora stylosa*, *Rhizophora mukorossi*, *Kandelia candel*, *Symplocos buergeriana*, *Cocos nucifera*, *Excoecaria agallocha*, *Hibiscus syriacus*, *Phellodendron amurense*, *Mangosteeniae*, and *Pteris vittata*, and specific species are selected for their growth. Healthy, robust seedlings with well-developed root systems, healthy leaves, and intact, undamaged bark were selected. The planting mix consisted of true and semi-mangrove trees, as well as a mixture of trees and shrubs, and the use of wooden stakes to create embankments ensured the survival of the mangroves. After planting, during the dry season, seawater was regularly pumped from outside the restoration area to irrigate the newly planted mangroves. This ensured the mangroves' normal water needs and accelerated water exchange between the lagoon and the open sea, reducing the impact of polluted marine mud on the mangroves. This method aligns with the fundamental principles of holistic environmental protection, respect for nature, scientific restoration, adaptation to local conditions, and orderly implementation, thus promoting the overall protection of the mangrove ecosystem.

[0015] In summary, the present invention has the following outstanding advantages:

[0016] 1. Adapt to local conditions and address the problem of mangroves being unable to survive in lagoons due to years of sludge accumulation;

[0017] 2. The operation is simple, and the methods of filling and irrigation are mature and reliable;

[0018] 3. Mangrove restoration has a short cycle; after 3-5 years, mangrove plants with well-developed root systems can grow and reproduce naturally. Detailed Implementation

[0019] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0020] A method for the ecological restoration of mangroves in silted lagoons includes the following steps:

[0021] S1: On the lagoon beach with low seawater exchange due to marine mud accumulation, the average elevation of the beach is artificially raised according to the tidal flat landform of the mangrove restoration area. This solves the problems of low seawater exchange caused by marine mud accumulation and narrow inlet, as well as long-term submersion of plants due to excessively high tides during the rainy season. Mangrove seedlings are planted on the raised beach area, and lower areas are excavated to be used as tidal channels and water areas to provide habitats or foraging grounds for benthic and marine life and birds.

[0022] S2: Select healthy native tree seedlings with well-developed root systems, healthy leaves, and intact bark for planting. The seedlings should be medium-sized, with an individual height of 50-60cm. Plant them on the artificially raised beach using a mixed planting method of mangroves and semi-mangroves. After planting, in view of the characteristics of newly planted mangrove seedlings being easily washed away by waves and blown down by sea winds, build wooden stakes around the newly planted mangroves on the bay beach to prevent waves and sea winds from uprooting the mangrove seedlings.

[0023] S3: During the dry season, seawater is pumped to irrigate newly planted mangrove seedlings on the lagoon mudflats to maintain the normal water requirements of the mangrove seedlings. During the rainy season, there is no need to pump seawater.

[0024] A 1.3m high steel plate was used to enclose the lagoon beach that needed to be raised to create a mangrove ecological restoration area. A 20m long and 4.5m wide cutter suction dredger equipped with a 12-inch pump was used to extract the silt from outside the ecological restoration area into the restoration area to raise the beach elevation.

[0025] The average elevation of the artificially raised beach surface is taken as the average of the sum of the dry season tide level and the rainy season tide level. For example, if the dry season tide level is 50cm and the water level reaches 1.3-1.5m during the rainy season floods, and at the same time, the seawater cannot be discharged to the open sea in time during the rainy season, then the average elevation of the designed beach surface is set at 90cm.

[0026] The mangrove seedlings planted are native species adapted to the local area, including Rhizophora stylosa, Rhizophora mukorossi, Kandelia candel, Tung tree, Cocos nucifera, Excoecaria agallocha, Hibiscus syriacus, Phellodendron amurense, Mangos japonica, and Pteris vittata. They are planted in a mixed manner, with a planting depth of 20cm and a planting density of 1.5m×1.5m. Depending on the size of the waves, 1.3m high wooden stakes are set up around the lagoon estuary to enclose the mangrove ecological restoration area within the lagoon.

[0027] In step S3, seawater is pumped into the mangrove forest on the bay's mudflats using a pump. During the dry season, the mangroves are irrigated by pumping seawater. The irrigation is concentrated in the dry season of each year, and the irrigation frequency is once every two weeks. The water is thoroughly soaked. This seawater irrigation is carried out for about 3-5 years. After the seedlings grow and their root systems develop, the interval between pumping will lengthen and eventually, pumping will no longer be necessary.

[0028] Example

[0029] Wanning City's Relocation of Aquaculture Farms to Beaches and Mangrove Ecological Protection and Restoration

[0030] (1) An investigation was conducted on the current status of the mangrove community in Xiaohai Lagoon, Wanning. Mangrove / semi-mangrove plants are widely distributed around Xiaohai. A total of 7 species of mangrove plants from 5 families and 6 species of semi-mangrove plants from 5 families were observed.

[0031] (2) The average tidal range of the sea in all four seasons is only about 17.6cm. The tidal range changes in the dry season and the rainy season are not at the same elevation (the lowest water level in the dry season is 50cm and the lowest water level in the rainy season is 1.3m). Therefore, it is decided to set the average elevation of the beach surface at 90cm. The difference between the established elevation of 90cm and the lowest water level of 50cm in the dry season is 40cm. The seedling planting depth is 20cm and the planting density is 1.5m×1.5m.

[0032] (3) From December 2020 to March 2021, select healthy native tree species seedlings (50-60cm) and plant them in Xiaohai. Use wooden stakes to build embankments to protect the mangrove seedlings.

[0033] (4) During the dry season, irrigation is carried out by pumping seawater. The irrigation is concentrated in April, May and June each year, and the irrigation frequency is about once every two weeks. As the mangrove seedlings grow, the interval between pumping will be longer, and irrigation will not be needed after about 2 years.

[0034] (5) Two years after the project was implemented, the Xiaohai mangrove forest was growing well. The seedlings, which were 50-60cm tall when planted, grew to 1-1.2m in two years. The main tree species, red sea olive, was well developed with well-developed prop roots. Some species, such as sea lotus and sea lacquer, had thick root necks that reached 10cm in diameter. The water coconut was growing even better. When planted, it was about 50cm tall with two or three leaves. Now it is lush and has grown to more than 2m and no longer needs irrigation.

[0035] (6) By implementing mangrove ecological protection and restoration, the project will gradually form artificial wetlands, providing food sources and habitats for marine organisms, increasing the diversity of benthic organisms, and playing a significant ecological role in purifying water quality, sequestering carbon, mitigating the effects of atmospheric warming, and improving marine biodiversity. As mangroves grow taller and carbon emissions peak, and with the strengthening of carbon emission trading, the economic benefits generated by the project will become increasingly apparent.

[0036] (7) The mangroves planted in the Wanning City Reclamation and Mangrove Ecological Protection and Restoration Project are growing well, with a survival rate of up to 85%. Some mangrove species, such as sea lotus and tung tree, have matured and fallen to the ground naturally, and have grown into second-generation seedlings. The second-generation seedlings are more adapted to the environment.

[0037] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for the ecological restoration of mangroves in silted lagoons, characterized in that, Includes the following steps: S1: In lagoons with low seawater exchange due to marine siltation, the average elevation of the beach surface will be artificially raised according to the tidal flat landform of the mangrove restoration area. The average tidal range of the lagoon is 17.6 cm throughout the four seasons, with the lowest tide elevation of 50 cm in the dry season and 1.3 m in the rainy season. The average elevation of the beach surface will be raised to 90 cm to solve the problems of low seawater exchange caused by marine siltation and narrow inlet, as well as long-term submersion of plants caused by excessively high tides in the rainy season. Mangrove seedlings will be planted on the raised beach surface, and lower areas will be excavated for use as tidal channels and water areas to provide habitats or foraging grounds for benthic and marine organisms and birds. S2: Select healthy native tree seedlings with well-developed root systems, healthy leaves, and intact bark for planting. The seedlings should be medium-sized, with an individual height of 50-60cm. Plant them on the artificially raised beach using a mixed planting method of mangroves and semi-mangroves. After planting, in view of the characteristics of newly planted mangrove seedlings being easily washed away by waves and blown down by sea winds, build wooden stakes around the newly planted mangroves on the bay beach to prevent waves and sea winds from uprooting the mangrove seedlings. S3: During the dry season, seawater is pumped to irrigate newly planted mangrove seedlings on the lagoon mudflats. The irrigation frequency is on average once every two weeks to maintain the normal water needs of the mangrove seedlings. During the rainy season, there is no need to pump seawater. As the mangrove seedlings grow, the pumping interval will be lengthened, and irrigation will be stopped after two years.

2. The method for ecological restoration of mangroves in silted lagoons according to claim 1, characterized in that: A 1.3m high steel plate was used to enclose the lagoon beach that needed to be raised to create a mangrove ecological restoration area. A 20m long and 4.5m wide cutter suction dredger equipped with a 12-inch pump was used to extract the silt from outside the ecological restoration area into the restoration area to raise the beach elevation.

3. The method for ecological restoration of mangroves in silted lagoons according to claim 1, characterized in that: The mangrove seedlings planted are native species adapted to the local area, including Rhizophora stylosa, Rhizophora mukorossi, Kandelia candel, Tung tree, Cocos nucifera, Excoecaria agallocha, Hibiscus syriacus, Phellodendron amurense, Mangos japonica, and Pteris vittata. They are planted in a mixed manner, with a planting depth of 20cm and a planting density of 1.5m×1.5m. Depending on the size of the waves, 1.3m high wooden stakes are set up around the lagoon estuary to enclose the mangrove ecological restoration area within the lagoon.