Passive desert ecological restoration method and system based on biochar

Abstract

The invention discloses a passive desert ecological restoration method and system based on biochar, and belongs to the technical field of desert ecological restoration. The method comprises the following steps: laying a grass checkered sand barrier on the surface of a sand land, laying a waterproof / semi-waterproof layer at a depth of 40-200cm below the grass checkered sand barrier at intervals, and laying a first biochar mixing layer above the waterproof / semi-waterproof layer; according to different application working conditions of the protection forest and the cultivated land, whether a second charcoal mixing layer is laid below the grass checkered sand barrier layer by 0-30 cm is selected; and finally, drought-enduring plants are planted in grids of the grass checkered sand-protecting barriers. The device abandons electromechanical equipment for refrigeration, pumping, active ventilation and the like, realizes passive water regulation and control by virtue of adsorption-desorption characteristics of biochar and natural temperature difference between day and night in the desert area, has the technical advantages of zero energy consumption, low cost and no maintenance, and can remarkably improve the desert water fixing capacity and the vegetation survival rate; the method is suitable for various scenes such as desert protection forest construction and cultivated land development, and sustainable restoration of desert ecology is achieved.

Description

[0001] manual Technical Field

[0002] This invention belongs to the field of desert ecological restoration technology, specifically involving a passive desert ecological restoration method and system based on biochar, which is applicable to the construction of protective forests in various deserts and sandy lands in my country, the development of desert farmland, and the upgrading and transformation of existing desert sand fixation projects. Background Technology

[0003] Overview of existing technologies

[0004] The straw checkerboard sand barrier (1) is a core technology for desert sand fixation and control, unique to my country. Since its development in the 1950s, it has become a model technology for desertification control worldwide. This technology involves embedding materials such as straw and netting into the sand layer in a 1-meter square grid to form an interlocking sand-fixing protective belt. This effectively reduces surface wind speed, intercepts sand particles, and stabilizes the sand surface, creating basic conditions for desert vegetation restoration. It has been widely used in sand control projects in major deserts in my country, such as the Taklamakan Desert and the Tengger Desert, with a cumulative treatment area of ​​over 100 million mu.

[0005] However, traditional straw checkerboard sand barriers (1) have two major technical defects in practical applications: First, they have a short service life. The natural service life of traditional straw checkerboard sand barriers (1) is only 3-5 years. After the expiration, they need to be regularly repaired and maintained. With the reduction of social labor force and the rise in labor costs, large-scale desertification control projects face serious pressure on human resources and economic costs. Second, they have extremely poor water retention and water storage capacity. Desert areas themselves have little rainfall and strong evaporation. The sand layer has a weak natural water retention capacity. Traditional straw checkerboard sand barriers (1) cannot achieve effective water storage and regulation, resulting in a desert vegetation survival rate of only about 40%, which is far from meeting the actual needs of large-scale desert ecological restoration in my country.

[0006] To address the challenge of water retention in desert ecological restoration, a solar-powered thermostatic breathing water production technology has been proposed in recent years. This technology uses solar panels to generate electricity, which drives a chiller, pump, and ventilation system to create a low-temperature condensation zone underground in the desert, thus producing artificial water using the principle of temperature difference. For example, the solar-powered thermostatic breathing water production system disclosed in patent document CN103456789A, while alleviating the desert water shortage problem to some extent, still has many technical shortcomings, making it difficult to achieve large-scale promotion and application.

[0007] Deficiencies of existing technology

[0008] Solar-powered cooling and water production technology, represented by CN103456789A, and other similar desert water regulation technologies, mainly suffer from the following drawbacks:

[0009] 1. The system has a complex structure and is difficult to construct: It requires a variety of equipment and multi-layered structures, including solar panels, chillers, chiller pipes, pumps, high-temperature sand layers, surface organic insulation layers, and seepage-proof and heat-insulating water collection boards. The on-site construction procedures are complicated and the project construction period is long. It is not suitable for remote desert areas with inconvenient transportation and weak infrastructure.

[0010] 2. High initial investment cost and great economic pressure: Compared with traditional low-cost desertification control technologies such as straw checkerboard sand barriers (1), this type of technology requires high-priced equipment such as solar panels and refrigeration machines. The initial investment cost of the equipment is high, and there are obvious obstacles to its promotion and application in desertification control areas with limited funds.

[0011] 3. High maintenance requirements and large manpower input: Ground electromechanical equipment such as refrigeration units, pumps, and control systems are easily affected by the harsh environment of desert with high temperature, dryness, and sandstorms. Regular inspection, maintenance, and replacement are required, which increases the later operation and maintenance costs and manpower input.

[0012] 4. High energy dependence and operational stability affected by the environment: It is completely driven by solar or electric power. If there are continuous rainy days or sandstorms, the power generation efficiency of the solar panels will drop significantly, which will directly lead to the interruption of the water treatment system and poor water regulation stability.

[0013] Advantages of existing technology

[0014] Solar-powered refrigeration and water production technology also has certain technical advantages: by driving the refrigeration system with solar energy, a stable low-temperature condensation zone can be formed underground in the desert, with a large and controllable water production capacity; in addition to ground equipment such as refrigeration units, underground components such as pipes and water collection plates have high stability, are basically undamaged, and have a long service life; it can utilize cheap electricity resources such as abandoned and surplus electricity, and the actual electricity consumption per unit of water production is low, which meets the requirements of energy utilization efficiency.

[0015] In summary, there is a significant imbalance in the current technological approaches for desert ecological restoration: solar-powered cooling water production technology has strong water production capacity and controllable stability, but it is costly and requires high maintenance; traditional straw checkerboard sand barrier (1) technology is low-cost and easy to construct, but its water production and retention capacity is limited and its vegetation survival rate is low. Therefore, there is an urgent need in this field to develop a desert ecological restoration method and system that achieves a balance between cost, maintenance requirements, and water production and retention capacity, and is suitable for large-scale promotion. Summary of the Invention

[0016] Purpose of the invention

[0017] To address the technical shortcomings of traditional straw checkerboard sand barriers (1) in terms of short service life and limited water production and retention capacity, as well as the imbalances in cost, maintenance, and water production capacity of existing desert ecological restoration technologies such as solar-powered cooling water production, the present invention aims to provide a passive desert ecological restoration method and system based on biochar. This invention fully utilizes the adsorption-desorption characteristics of biochar and the large diurnal temperature range characteristic of desert regions to achieve passive autonomous regulation of sandy soil moisture. It requires no electromechanical equipment, features zero energy consumption, low cost, maintenance-free operation, and simple construction, significantly improving desert water retention capacity and vegetation survival rate, while extending the service life of straw checkerboard sand barriers (1). It is suitable for various desert ecological restoration scenarios, achieving sustainable desert governance.

[0018] Technical solution

[0019] To achieve the above-mentioned objectives and solve the technical problems existing in the prior art, the present invention adopts the following technical solution:

[0020] A passive desert ecological restoration method based on biochar

[0021] The method includes the following steps:

[0022] S1: Laying straw checkerboard sand barriers (1)

[0023] A grass checkerboard sand barrier (1) is laid on the sandy surface to form a grid-like sand-fixing structure. The grid size of the grass checkerboard sand barrier (1) is 1m×1m, the height exposed above the sand surface is 15-20cm, and the depth buried in the sand is 10-15cm. Its core function is to reduce the surface wind speed, intercept sand particles, and fix the sand surface, so as to create basic conditions for the planting and growth of drought-resistant plants (5).

[0024] S2: Construction Groundwater Control Layer

[0025] At a depth of 40-200cm below the grass checkerboard sand barrier (1), a waterproof / semi-waterproof layer (2) is laid intermittently, and a first biochar mixed layer (3) is laid on top of the waterproof / semi-waterproof layer (2);

[0026] • Waterproof / semi-waterproof layer (2): The materials selected are plastic film, geotextile, HDPE geomembrane and other seepage prevention materials. The non-continuous laying method is adopted, with no fixed width and interval requirements. The core is to achieve water isolation and blockage, while providing a channel for the roots of drought-resistant plants (5) to extend downwards. This reduces construction costs while ensuring the normal growth of plant roots.

[0027] • First biochar mixed layer (3): The thickness is 0.5-100mm, preferably 5-20mm, and it is made by mixing modified biochar and fine sand at a mass ratio of 1:2 to 1:50. The modified biochar is made from agricultural / forestry waste such as corn stalks, cotton stalks, and wood. It is prepared by pyrolysis and then modified by physical / chemical methods. The specific surface area is 300-2000m² / g, and it has excellent adsorption performance and water saturation capacity.

[0028] S3: Selective construction surface moisture regulation layer

[0029] Based on the application requirements of shelterbelt and cultivated land conditions, it is decided whether to lay a second biochar mixed layer (4) at a depth of 0-30cm below the grass checkerboard sand barrier (1) layer;

[0030] • Protective forest operation: No second biochar mixture layer (4) is laid, and water regulation and temperature regulation are achieved solely by the underground first biochar mixture layer (3);

[0031] • Farmland conditions: Lay a second biochar mixed layer (4), which is 20-30cm thick and is made of modified biochar and fine sand mixed in a mass ratio of 1:2 to 1:50. The core is to achieve two-way regulation of surface water and water retention at night.

[0032] S4: Plant drought-resistant plants (5) / drought-resistant crops (8)

[0033] Plant drought-resistant plants (5) / drought-resistant crops (8) within the grid of the grass checkerboard sand barrier (1), with a planting density of 150-300 plants per mu; drought-resistant plants (5) can be psammophytic plants such as Haloxylon ammodendron, Calligonum mongolicum, Caragana korshinskii, and Elaeagnus angustifolia, or drought-resistant crops such as sunflower (8) according to the needs of farmland conditions.

[0034] Construction sequence optimization: Before step S1, the construction sequence is determined according to the project scenario; if it is a afforestation scenario where existing grass checkerboard sand barrier (1) is being transformed, the original grass checkerboard sand barrier (1) is retained first and the surrounding sand is cleared before the groundwater regulation layer is constructed; if it is a new project, the groundwater regulation layer is constructed first, and then the grass checkerboard sand barrier (1) is laid.

[0035] The core feature of this invention is that it does not use any electromechanical equipment such as refrigeration equipment, pumps, or active ventilation systems throughout the entire process. It relies entirely on the adsorption-desorption characteristics of biochar and the natural diurnal temperature difference in desert areas to achieve autonomous regulation of sandy soil moisture, which is fundamentally different from the artificial intervention-based water production technology of the prior art.

[0036] A biochar-based passive desert ecological restoration system

[0037] This system is used to implement the above-mentioned biochar-based passive desert ecological restoration method, including a straw checkerboard sand barrier layer (1), a groundwater regulation layer, an optional surface water regulation layer, and a drought-resistant plant community (5) / drought-resistant crop community (8). The structures work together to achieve passive restoration of the desert ecosystem. The specific structural parameters are as follows:

[0038] 1. Grass checkerboard sand barrier layer (1): laid on the sandy surface, the grass checkerboard sand barrier (1) forms a 1m×1m grid-like sand-fixing structure, the grass checkerboard sand barrier (1) protrudes 15-20cm above the sand surface and is buried 10-15cm in the sand layer;

[0039] 2. Groundwater regulation layer: Located 40-200cm below the sandy land, it consists of an intermittently laid waterproof / semi-waterproof layer (2) and a first biochar mixed layer (3) above it; the waterproof / semi-waterproof layer (2) is made of plastic film / geotextile / HDPE geomembrane material and is laid in a fence-like discontinuous manner; the first biochar mixed layer (3) has a thickness of 0.5-100mm (preferably 5-20mm) and the mass ratio of modified biochar to fine sand is 1:2 to 1:50;

[0040] 3. Surface moisture regulation layer: Located at a depth of 0-30cm below the grass checkerboard sand barrier layer (1), it is set only for cultivated land conditions and includes a second biochar mixing layer (4). This layer is 20-30cm thick and the mass ratio of modified biochar to fine sand is 1:2 to 1:50.

[0041] 4. Drought-resistant plant community (5) / Drought-resistant crop community (8): Planted within the grass checkerboard sand barrier (1) grid, with a planting density of 150-300 plants per mu, consisting of drought-resistant plant community (5) or drought-resistant crop (8) composed of psammophytic plants.

[0042] The system is not equipped with any electromechanical equipment such as refrigeration, pumping, or active ventilation, and has no energy input requirements. It relies entirely on the adsorption-desorption characteristics of biochar and the natural diurnal temperature difference in the desert to achieve autonomous water regulation, making it suitable for various desert ecological restoration scenarios.

[0043] Working principle and water regulation mechanism

[0044] The working principle of this invention is based on the adsorption-desorption characteristics of biochar and the climate characteristics of large natural temperature differences between day and night in desert areas. At the same time, this invention reveals the core mechanism of desert water loss through extensive experimental research, providing a theoretical basis for the design of passive water regulation. The whole invention forms a unique passive water regulation system, which is completely different from the artificial intervention water production principle of existing technologies.

[0045] The core mechanism of desert water loss

[0046] This invention demonstrates through experiments that the main cause of water loss in desert areas is not the commonly recognized daytime surface evaporation, but rather the nighttime evaporation of groundwater vapor. The specific mechanism is as follows: during the day, the desert surface temperature is high while the underground temperature is low. Due to the vapor pressure difference, water vapor in the air permeates downwards into the underground sand layer. At night, the desert surface temperature drops sharply, while the underground temperature is higher than the surface temperature. The vapor pressure difference reverses, causing groundwater vapor to condense towards the surface and eventually evaporate and be lost. This mechanism is the core theoretical basis for the water regulation design of this invention.

[0047] Water regulation and the "air conditioning effect" under protective forest conditions

[0048] Under the protection forest condition, the system only sets up a groundwater regulation layer and does not set up a surface water regulation layer. The core relies on the first biochar mixing layer (3) to achieve the dual effects of water storage and ground cooling, specifically:

[0049] 1. Saturated reservoir effect: The modified biochar of the first biochar mixed layer (3) has a high specific surface area of ​​300-2000m² / g, excellent adsorption and saturation capacity, forming a huge saturated reservoir in the desert underground, providing a continuous and stable water supply for the roots of drought-resistant plants (5), ensuring rapid plant growth;

[0050] 2. Underground “air conditioning effect”: When the surface temperature drops at night, the water vapor in the underground sand layer evaporates through the first biochar mixed layer (3). The physical action of evaporation and heat absorption reduces the temperature of the underground strata by 3-5℃, effectively preventing the roots of drought-resistant plants (5) from being scalded by the high temperature of the desert, and providing a suitable temperature environment for root growth.

[0051] At the same time, a positive feedback loop mechanism of "water-temperature-vegetation" will be formed under the protection forest condition: the first biochar mixed layer (3) improves the sandy soil moisture conditions → drought-resistant plants (5) obtain sufficient water and grow rapidly → plants form surface shading → surface shading reduces desert surface temperature and increases surface relative humidity → temperature and humidity improvement further stabilizes underground water storage. This loop mechanism enables the protection forest condition to achieve good ecological restoration effect by relying only on the underground water regulation layer, without any artificial intervention.

[0052] Water cycle defense system under farmland conditions

[0053] Under farmland conditions, the system simultaneously sets up a groundwater regulation layer and a surface water regulation layer. The two layers work together to form a water cycle defense system, precisely addressing the core issue of groundwater vapor evaporation and loss in deserts at night. Specifically:

[0054] 1. The first underground biochar mixed layer (3): As the core area of ​​underground water storage, it accumulates a large amount of water with high water saturation, providing a continuous source of underground water for drought-resistant crops (8) in the cultivated land;

[0055] 2. Second biochar mixed layer on the surface (4): As a "water valve" and "defense barrier", it realizes two-way water regulation: during the day, it adsorbs water from the air and replenishes the underground sand layer through desorption, realizing two-way water replenishment from the surface to the ground; at night, it absorbs water from the sand layer through adsorption, forming a closed water barrier, blocking the evaporation path of groundwater vapor to the surface, and fundamentally preventing the large-scale loss of groundwater.

[0056] Through the synergistic effect of the two layers, the sandy land can achieve "daytime water storage + two-way water replenishment, nighttime water retention + evaporation blocking", which completely solves the problem of water loss in desert farmland and provides stable water conditions for the growth of drought-resistant crops (8).

[0057] The essential difference from existing technologies

[0058] This invention differs fundamentally from existing desert ecological restoration technologies (especially solar-powered cooling and water production technologies), as detailed in Table 1:

[0059] Table 1. Comparison of the technical routes of this invention with existing solar-powered cooling and water production technologies.

[0060] Comparison Dimensions This invention Existing solar-powered cooling water production technology technical route Relying on the adsorption-desorption properties of biochar and the natural diurnal temperature variation in the desert, it operates autonomously without human intervention. Active water production relies on equipment such as solar panels, chillers, and pumps, requiring manual intervention. Energy demand Zero energy consumption, requiring no input of electricity, solar energy, or other energy sources. It relies on a continuous input of solar / electric power and is highly dependent on energy. System complexity The structure is simple, consisting only of a straw checkerboard sand barrier (1), a biochar mixed layer (3)(4), and a waterproof / semi-waterproof layer (2). The structure is complex, containing at least six layers of sand and various refrigeration, water supply, and control electromechanical equipment. Construction difficulty Simple construction, few procedures, suitable for remote desert areas The construction process is complex, involves many steps, and places high demands on both the infrastructure and the construction team. Water control logic Utilizing the natural climate characteristics of the desert to achieve autonomous water regulation Artificial water production is achieved by modifying the local environment of the desert using artificial equipment. Maintenance requirements Maintenance-free, no mechanical or electrical equipment, no problems with malfunctions, aging, or damage. Regular maintenance requires inspection and replacement of equipment such as refrigeration units and pumps. Cost Structure Low initial investment, no subsequent operation and maintenance costs The initial equipment investment is high, and there are ongoing maintenance and labor costs. Water production stability Influenced by natural conditions such as diurnal temperature variation and air humidity, it is adapted to the original desert environment. Water production is large and controllable, but it is greatly affected by weather conditions (rainy days, dusty days). Applicable Scenarios Low-cost, large-scale desertification control, shelterbelt construction, farmland development, and renovation of old infrastructure. Localized desertification control scenarios with high water production requirements and sufficient funding

[0061] Beneficial effects

[0062] Compared with existing desert ecological restoration technologies, this invention has the following significant advantages:

[0063] 1. Completely passive, zero-energy operation: It eliminates all electromechanical equipment such as refrigeration, pumping, and active ventilation, and relies entirely on the adsorption-desorption characteristics of biochar and the natural temperature difference between day and night in the desert to achieve autonomous water regulation. There is no need for any energy input, which greatly reduces the operating cost of desert ecological restoration.

[0064] 2. Simple structure, convenient construction and low cost: The system consists of only straw checkerboard sand barrier (1), biochar mixed layer (3)(4) and waterproof / semi-waterproof layer (2). All materials used are low-cost conventional materials. The construction process is simple and easy. It does not require expensive equipment and professional construction team. The project cycle is short and it is suitable for large-scale promotion and application in remote desert areas with inconvenient transportation and weak infrastructure.

[0065] 3. Maintenance-free and long-term stable operation: There are no mechanical or electrical equipment, so there are no problems such as equipment failure, aging, or damage. Long-term stable operation can be achieved with one construction. It is suitable for the harsh environment of desert with high temperature, dryness, and sandstorms, and completely solves the problems of high maintenance costs and large manpower input of traditional technologies.

[0066] 4. Significantly extend the service life of the straw checkerboard sand barrier (1): Through the design of the underground waterproof / semi-waterproof layer (2) and the first biochar mixed layer (3), the damage of wind and sand erosion to the straw checkerboard sand barrier (1) is effectively reduced, while the moisture content of the sand layer is increased, the aging rate of the straw checkerboard sand barrier (1) material is reduced, and the service life of the straw checkerboard sand barrier (1) is extended from the traditional 3-5 years to 8-10 years, significantly reducing the frequency of sand control maintenance and economic costs.

[0067] 5. Significantly improve the water retention capacity of sandy land: The first underground biochar mixed layer (3) forms a saturated water reservoir, and the second surface biochar mixed layer (4) under cultivated land conditions blocks nighttime water evaporation, extending the effective water retention time of sandy land from 5-7 days in traditional grass checkerboard to 15-20 days, fundamentally improving the problem of poor water retention capacity of desert sand layers.

[0068] 6. Significantly improve the survival rate and growth rate of vegetation (5)(8): Improved water conditions in sandy areas + underground "air conditioning effect" reduces root temperature, increasing the survival rate of drought-resistant plants (5) / drought-resistant crops (8) to over 95%, and increasing plant growth rate by 50%-300% compared to traditional techniques, thus rapidly achieving desert vegetation restoration and coverage.

[0069] 7. Form a sustainable desert ecosystem: Through the positive feedback loop mechanism of "water-temperature-vegetation", after the plants (5)(8) grow and form surface shade, they further reduce the desert surface temperature and increase the relative humidity, gradually improve the desert soil structure, form a stable soil-vegetation ecosystem, and achieve long-term and sustainable governance of desert areas.

[0070] 8. Adaptable to multiple application scenarios and highly flexible: Designed with two differentiated structures for protective forest conditions (sand dunes not leveled) and cultivated land conditions (sand dunes leveled), which can be flexibly selected according to the actual needs of desertification control. It is also applicable to the transformation and upgrading of existing grass checkerboard sand barriers (1), greatly improving the applicability and promotion value of the technology.

[0071] 9. Resource utilization of agricultural and forestry waste with dual ecological benefits: Modified biochar uses agricultural / forestry waste such as corn stalks, cotton stalks, and wood as raw materials to realize the resource recycling of agricultural and forestry waste. This not only reduces the preparation cost of biochar but also reduces air pollution caused by the burning of agricultural and forestry waste. At the same time, the carbon sequestration properties of biochar achieve carbon sequestration and emission reduction, thus achieving dual ecological benefits of desert ecological restoration and carbon neutrality.

[0072] 10. No secondary pollution and environmentally friendly: All materials used in this invention are environmentally friendly conventional materials. Biochar is prepared from natural agricultural and forestry waste. The waterproof / semi-waterproof layer (2) is made of degradable or environmentally friendly seepage-proof materials. There are no pollutant emissions during construction and operation, and there is no secondary pollution to the desert ecological environment. Attached Figure Description

[0073] Figure 1. Schematic cross-sectional view of the system structure of the present invention under the working condition of a protective forest.

[0074] Illustration markings: (1) - straw checkerboard sand barrier, (2) - waterproof / semi-waterproof layer, (3) - first biochar mixed layer, (5) - drought-resistant plants;

[0075] Illustration: A grass checkerboard sand barrier (1) is laid on the sandy surface. A water-proof / semi-water-proof layer (2) is laid at intervals 40-200cm below it. A first biochar mixed layer (3) is laid on top of the water-proof / semi-water-proof layer (2). Drought-resistant plants (5) are planted in the grid of the grass checkerboard sand barrier (1). Their roots penetrate the sand layer to absorb the water stored in the first biochar mixed layer (3). There is no surface water regulation layer.

[0076] Figure 2. Schematic cross-sectional view of the system structure of the present invention under farmland conditions.

[0077] Illustration markings: (1) - straw checkerboard sand barrier, (2) - waterproof / semi-waterproof layer, (3) - first biochar mixed layer, (4) - second biochar mixed layer, (8) - drought-resistant crops;

[0078] Illustration: Based on the protective forest structure, a second biochar mixing layer (4) is added at a depth of 0-30cm below the grass checkerboard sand barrier (1) to form a surface-ground dual-layer water regulation system. Drought-resistant crops (8) are planted on the surface and are directly watered by the second biochar mixing layer (4), while the first biochar mixing layer (3) provides groundwater replenishment.

[0079] Unified Explanation of Attachment Labels:

[0080] (1) - Grass checkerboard sand barrier: A grid-like sand-fixing structure laid on the surface of sand to achieve the functions of sand fixation, wind speed reduction and sand trapping;

[0081] (2) - Waterproof / semi-waterproof layer: laid intermittently at a depth of 40-200cm below the sand to block water from seeping into the deep sand layer of the desert;

[0082] (3) - First biochar mixed layer: laid on top of the waterproof / semi-waterproof layer to achieve the "air conditioning effect" function of underground water storage, evaporative heat absorption and cooling;

[0083] (4) - Second biochar mixed layer: Optional layer, laid in sand at a depth of 0-30cm, to achieve the function of "defense barrier" for two-way surface water replenishment and nighttime water retention;

[0084] (5) - Drought-resistant plants: Psammophytic plants, planted in the grass checkerboard sand barrier grid of the shelterbelt project to realize the function of desert vegetation restoration;

[0085] (8) - Drought-resistant crops: planted on the surface of sandy land in arable conditions to realize the crop production function of desert arable land. Detailed Implementation

[0086] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. All technical solutions based on the present invention and without substantial changes are within the scope of protection of the present invention.

[0087] General parameters of this invention embodiment:

[0088] 1. Modified biochar: Made from agricultural / forestry waste through pyrolysis, and then modified by physical / chemical methods. The modified biochar has a specific surface area of ​​300-2000 m² / g.

[0089] 2. Waterproof / semi-waterproof layer (2): The material is plastic film, geotextile or HDPE geomembrane, and it is laid in a fence-like intermittent manner;

[0090] 3. Straw checkerboard sand barrier (1): Use straw or brush-shaped net rope straw checkerboard with a grid size of 1m×1m;

[0091] 4. Biochar Mixing Layer (3)(4): Modified biochar and fine sand are mixed at a mass ratio of 1:2 to 1:50. After mixing, the mixture is compacted in layers to ensure full contact with the sand.

[0092] Example 1: Construction of Shelterbelts in the Taklamakan Desert

[0093] Project Scenario: A 1,000-mu shelterbelt construction area in the Taklamakan Desert, where sand dunes are not leveled, adopting the shelterbelt construction method;

[0094] Implementation steps:

[0095] 1. Straw checkerboard sand barrier (1) Laying: Use brush-shaped net rope type straw checkerboard (1), with a height of 18cm exposed above the sand surface and 12cm buried in the sand;

[0096] 2. Mechanical excavation: In the middle of the grass grid (1), dig a pit with a depth of 150cm and a width of 0.5m, with a pit spacing of 1m;

[0097] 3. Laying of waterproof / semi-waterproof layer (2): Lay a waterproof / semi-waterproof layer (2) made of HDPE geomembrane at the bottom of the pit, with a laying width of 0.6m and extending 10cm beyond the edge of the pit;

[0098] 4. Backfilling of the first biochar mixed layer (3): Modified biochar is prepared by pyrolysis of corn stalks at 550℃, and mixed with fine sand at a mass ratio of 1:10. The mixture is then backfilled above the waterproof / semi-waterproof layer (2) to form a first biochar mixed layer (3) with a thickness of 10mm. The layers are then compacted.

[0099] 5. Planting of drought-resistant plants (5): Plant Haloxylon ammodendron seedlings as drought-resistant plants (5) within the grid of the grass checkerboard sand barrier (1), with a planting density of 200 plants per mu.

[0100] Results: After 3 years of implementation, the integrity rate of the grass checkerboard sand barrier (1) reached 90%, and its service life was extended to 9 years; the effective water retention time of the sandy land was extended to 18 days; the survival rate of Haloxylon ammodendron seedlings reached 96%, and the vegetation coverage was increased by 45% compared with traditional technology; the underground temperature was 3-5℃ lower than that of the surrounding untreated area, and there was no high temperature burn on the Haloxylon ammodendron roots; a stable positive feedback loop of "water-temperature-vegetation" was formed, the relative humidity of the surface was significantly increased, and the underground water storage remained stable.

[0101] Example 2: Farmland Development in the Tengger Desert

[0102] Project scenario: 500 mu of farmland development area in Tengger Desert, leveling sand dunes, using farmland construction conditions;

[0103] Implementation steps:

[0104] 1. Site leveling: The sand dunes in the selected area are leveled to create a flat arable planting area;

[0105] 2. Construction of groundwater control layer: Excavate a pit with a depth of 120cm and a width of 0.6m, with a pit spacing of 0.8m; lay a waterproof / semi-waterproof layer (2) made of organic plastic waterproof layer at the bottom of the pit, with a width of 0.7m; use cotton straw as raw material, pyrolyze it at 600℃ to prepare modified biochar, mix it with fine sand at a mass ratio of 1:6, and backfill it above the waterproof / semi-waterproof layer (2) to form a first biochar mixed layer (3) with a thickness of 12mm;

[0106] 3. Straw checkerboard sand barrier (1) Laying: Straw checkerboard sand barrier (1) is used, with 20cm exposed above the sand surface and 15cm buried in the sand;

[0107] 4. Laying the second biochar mixed layer (4): In the grass checkerboard sand barrier (1) grid, the modified biochar and fine sand are mixed at a mass ratio of 1:20 and laid to form a second biochar mixed layer (4) with a thickness of 25cm, and compacted in layers;

[0108] 5. Drought-resistant crops (8) Planting: Plant sunflowers as drought-resistant crops (8), with a planting density of 300 plants per mu.

[0109] Results of implementation: After implementation, the sunflower yield increased by 30% compared with the traditional desert planting method, and the soil moisture content of cultivated land increased by 25% compared with the traditional planting area; the effective water retention time of sandy land was extended to 15 days; the second biochar mixed layer (4) effectively blocked the evaporation of groundwater vapor at night, and the underground water storage remained stable. The sunflowers grew well throughout the process, without water shortage or high temperature damage.

[0110] Example 3: Afforestation and transformation of existing straw checkerboard sand barriers in the Tengger Desert.

[0111] Project Scenario: Upgrading and transforming a 300-mu (approximately 20 hectares) shelterbelt area in the Tengger Desert that already has straw checkerboard sand barriers using the shelterbelt construction method;

[0112] Implementation steps:

[0113] 1. Treatment of the original grass checkerboard sand barrier (1): retain the original grass checkerboard sand barrier (1) structure, clear the sand around the sand barrier (1) to ensure the sand fixation effect;

[0114] 2. Mechanical excavation: In the middle of the existing grass grid (1), dig a pit with a depth of 180cm and a width of 0.4m, with a pit spacing of 1.5m;

[0115] 3. Laying of waterproof / semi-waterproof layer (2): Lay a waterproof / semi-waterproof layer (2) made of geotextile at the bottom of the pit, with a laying width of 0.5m;

[0116] 4. Backfilling of the first biochar mixed layer (3): Modified biochar is prepared by pyrolysis of wood at 500℃, and mixed with fine sand at a mass ratio of 1:8. The mixture is then backfilled above the geotextile-made waterproof / semi-waterproof layer (2) to form a first biochar mixed layer (3) with a thickness of 8mm. The layers are compacted.

[0117] 5. Planting of drought-resistant plants (5): Mixed planting of Caragana korshinskii and Calligonum mongolicum as drought-resistant plants (5), with a total planting density of 250 plants per mu.

[0118] Results of implementation: Two years after implementation, the service life of the original grass checkerboard sand barrier (1) was extended to 8.5 years; the effective water retention time of the sandy land was extended to 16 days; the survival rate of Caragana korshinskii and Calligonum mongolicum reached 95%, and the vegetation coverage increased by 35% compared with before the transformation; the plant growth rate increased by 40% compared with the traditional desert afforestation method; the underground stratum temperature decreased by 4℃ compared with before the transformation, and the plant roots grew healthily, realizing the efficient ecological restoration and upgrading of the existing desert protection forest area.

[0119] Key technical points and points to be protected

[0120] 1. A completely passive method and system design for water regulation in sandy areas: without using any electromechanical equipment such as refrigeration, pumping, or active ventilation, it relies entirely on the adsorption-desorption characteristics of biochar and the natural diurnal temperature difference in the desert to achieve autonomous water regulation, which is fundamentally different from existing artificial intervention water production technologies.

[0121] 2. The dual-function design of the underground first biochar mixed layer (3): Under the protection forest conditions, it can not only realize the water storage function of the underground saturated water reservoir, but also form an underground "air conditioning effect" of 3-5℃ through nighttime evaporation and heat absorption, realize the high temperature protection of plant roots, and trigger the "water-temperature-vegetation" positive feedback cycle mechanism.

[0122] 3. Fence-like intermittent waterproof / semi-waterproof layer (2) laying design: adopting non-continuous laying, without fixed width and interval requirements, effectively blocking water from seeping into the deep desert, and providing a channel for plant roots to extend downward, reducing construction costs by 40%-60% compared to continuous laying.

[0123] 4. Preparation and Differentiated Application Process of Modified Biochar: It is prepared by pyrolysis of agricultural and forestry waste, and the specific surface area is increased to 300-2000m² / g through physical / chemical modification; and the mixing ratio and thickness are designed according to different underground and surface scenarios to meet the water regulation needs of different depths in the desert.

[0124] 5. “Defense Barrier” Functional Design of the Second Biochar Mixed Layer (4) on the Surface: Under the working conditions of cultivated land, it realizes the two-way regulation of daytime adsorption and desorption to replenish water and nighttime adsorption to form a closed water barrier, accurately solving the core problem of nighttime groundwater vapor evaporation and loss in desert areas.

[0125] 6. Differentiated structural design for two application conditions: The shelter forest condition is set with only an underground water regulation layer consisting of an impermeable / semi-impermeable layer (2) and a first biochar mixed layer (3), while the cultivated land condition is set with a surface + underground double water regulation layer consisting of a second biochar mixed layer (4), which are adapted to the different needs of desert shelter forest construction and cultivated land development, and are also suitable for the transformation and upgrading of existing grass checkerboard sand barriers (1).

[0126] 7. The core mechanism of desert water loss was revealed: For the first time, it was clearly identified that the main cause of desert water loss is the evaporation of groundwater vapor at night rather than the surface evaporation during the day, providing a core theoretical basis for the design of passive water regulation technology in deserts.

[0127] 8. Construction of the “moisture-temperature-vegetation” positive feedback loop mechanism: The moisture and temperature of the desert are improved through passive moisture regulation, which promotes the growth of vegetation (5)(8). The growth of vegetation (5)(8) further optimizes the temperature and humidity conditions of the desert, forming a sustainable desert ecosystem and realizing the long-term management of the desert.

[0128] 9. Synergistic design of straw checkerboard sand barrier (1) and biochar mixed layer (3)(4): The moisture regulation of biochar mixed layer (3)(4) improves the humidity of sand layer, reduces wind and sand erosion and material aging, and extends the service life of straw checkerboard sand barrier (1) from 3-5 years to 8-10 years, achieving dual synergistic effect of sand fixation and moisture regulation.

Claims

1. A passive desert ecological restoration method based on biochar, characterized by, The method comprises the following steps: S1: laying a grass grid sand barrier (1) on the sand surface to form a grid-shaped sand fixation structure; S2: laying a water-blocking / half-water-blocking layer (2) at a depth of 40-200 cm below the grass grid sand barrier (1) layer, and laying a first biochar mixed layer (3) above the water-blocking / half-water-blocking layer (2); S3: according to the application requirements of the shelter forest working condition and the farmland working condition, whether to lay a second biochar mixed layer (4) at a depth of 0-30 cm below the grass grid sand barrier (1) layer is selected; S4: planting drought-resistant plants (5) in the grid of the grass grid sand barrier (1); The method does not use refrigeration equipment, pump body or active ventilation system throughout the process, and completely relies on the adsorption-desorption characteristics of biochar and the natural temperature difference of desert areas day and night to realize the autonomous regulation of sand water.

2. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, In step S3, the laying rules and water regulation principles of different working conditions are as follows: Shelter forest working condition: no second biochar mixed layer (4) is laid, and only the first biochar mixed layer (3) forms a saturated water reservoir in the sand underground to provide continuous water supply for the root system of drought-resistant plants (5); at the same time, the underground water vapor evaporates at night to produce an evaporation heat absorption effect, which reduces the underground stratum temperature by 3-5℃, forms an underground "air conditioning effect", and reduces the risk of root system damage of drought-resistant plants (5) due to high temperature; Farmland working condition: the second biochar mixed layer (4) is laid, which releases water through desorption during the day and supplements the underground sand layer water, and forms a closed water barrier through adsorption at night to block the path of underground water vapor evaporation to the ground, preventing the loss of underground water.

3. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, In step S2, the preparation material of the water-blocking / half-water-blocking layer (2) is selected from one or more of plastic film, geotextile and HDPE geomembrane, and the width and interval are flexibly determined according to the sand terrain, plant root system distribution and construction conditions to realize the core requirement of isolating and blocking the sand water, and the non-continuous laying is adopted; the thickness of the first biochar mixed layer (3) is 0.5-100 mm, which is mixed by modified biochar and fine sand at a mass ratio of 1:2 to 1:

50.

4. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, In step S3, the thickness of the second biochar mixed layer (4) is 20-30 cm, which is mixed by modified biochar and fine sand at a mass ratio of 1:2 to 1:

50.

5. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, The modified biochar in the first biochar mixed layer (3) and the second biochar mixed layer (4) is prepared by pyrolysis process using agricultural waste or forestry waste as raw material, and then modified by physical modification method or chemical modification method, and the specific surface area of the modified biochar is 300-2000 m² / g to improve its adsorption performance and water retention capacity.

6. The biochar-based passive desert ecological restoration method according to claim 2, characterized in that, Under the shelterbelt working condition, the high water saturation of the first biochar mixed layer (3) improves the underground water storage of the sandy land, and after the underground temperature is reduced by the "air conditioner effect", a "water-temperature-vegetation" positive feedback cycle mechanism is gradually formed: the first biochar mixed layer (3) improves the water condition of the sandy land → the drought-tolerant plants (5) grow rapidly with sufficient water → the drought-tolerant plants (5) after growth form ground shading → the ground shading reduces the desert surface temperature and improves the surface relative humidity → the temperature and humidity improvement further stabilizes the underground water storage.

7. The biochar-based passive desert ecological restoration method according to claim 2, characterized in that, Under the farmland working condition, the first biochar mixed layer (3) and the second biochar mixed layer (4) form a water circulation defense system, in which the first biochar mixed layer (3) accumulates water as the core underground water storage area, and the second biochar mixed layer (4) realizes two-way water replenishment and night water retention as the surface water regulation layer, fundamentally solving the problem of water loss caused by night water vapor evaporation in desert areas.

8. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, Before step S1, there is also a construction sequence optimization step: if it is a reconstruction afforestation scene of an existing grass grid sand barrier (1), the original grass grid sand barrier (1) is first retained and the surrounding accumulated sand is cleaned, and then the underground water regulation layer composed of the water-resistant / half-water-resistant layer (2) and the first biochar mixed layer (3) is constructed in the middle of the grass grid sand barrier (1) grid; if it is a new desert ecological restoration project and no grass grid sand barrier (1) is laid, the underground water regulation layer is first constructed, and then the grass grid sand barrier (1) is laid on the surface of the sandy land.

9. The biochar-based passive desert ecological restoration method according to claim 1, characterized in that, In step S4, the planting density of the drought-tolerant plants (5) is 150-300 plants per mu, and the drought-tolerant plants (5) are selected from one or more of the following sand plants: Haloxylon ammodendron, Calligonum rubicundum, Caragana, and Elaeagnus angustifolia, or drought-tolerant crops (8) are selected according to the farmland working condition requirements.

10. A passive desert ecological restoration system based on biochar for implementing the passive desert ecological restoration method based on biochar according to any one of claims 1 to 9, characterized in that, It comprises a grass grid sand barrier layer (1), an underground water regulation layer, an optional surface water regulation layer, and a drought-tolerant plant community (5). The grass grid sand barrier layer (1) is laid on the surface of the sandy land and comprises a grid-shaped sand fixation structure formed by the grass grid sand barrier (1), which is used to reduce the ground wind speed, intercept sand particles, and fix the sand surface. The underground water regulation layer is located at a depth of 40-200 cm below the sandy land and comprises a water-resistant / half-water-resistant layer (2) laid in an interval and a first biochar mixed layer (3) laid above the water-resistant / half-water-resistant layer (2), which is used to realize underground accumulation, isolation, and temperature regulation of the water in the sandy land. The surface water regulation layer is located at a depth of 0-30 cm below the grass grid sand barrier layer (1) and comprises a second biochar mixed layer (4), which is only provided under the farmland working condition and not provided under the shelterbelt working condition, and is used to realize two-way regulation of the water on the surface of the sandy land and night water retention. The drought-tolerant plant community (5) is planted in the grid of the grass grid sand barrier (1) and is used to realize desert vegetation restoration and form a "water-temperature-vegetation" positive feedback cycle. The system is not configured with any refrigeration equipment, pump body, active ventilation system and other electromechanical control equipment, and completely relies on the adsorption-desorption characteristics of biochar and the natural temperature difference between day and night in desert areas to realize the autonomous regulation of sand water.

11. The biochar-based passive desert eco-repair system of claim 10, wherein, The grass checkerboard sand barrier (1) has a grid size of 1m*1m, the height of the grass checkerboard sand barrier (1) exposed to the sand surface is 15-20cm, and the depth buried in the sand layer is 10-15cm.

12. The biochar-based passive desert eco-repair system of claim 10, wherein, The water / semi-water isolation layer (2) is made of plastic film, geotextile or HDPE geomembrane material, and is laid in a fence-like interval, and the width and interval are determined flexibly according to the sand land terrain, plant root distribution and construction conditions, so as to realize the core requirements of water isolation and blockage and provide a channel for the downward extension of the drought-resistant plant (5) root system, without continuous laying.

13. The biochar-based passive desert eco-repair system of claim 10, wherein, The preferred thickness of the first biochar mixed layer (3) is 5-20mm, which is mixed by modified biochar and fine sand in a mass ratio of 1:2 to 1:50; the second biochar mixed layer (4) is mixed by modified biochar and fine sand in a mass ratio of 1:2 to 1:50, and the specific surface area of the modified biochar is 300-2000m² / g.

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