Biological soil crust with improved salt and alkali tolerance, and preparation method and application thereof

Abstract

The present application relates to a kind of biological soil crusts for improving salt-tolerant, and preparation method and application, the biological soil crust includes natural biological crust and 1%~5% of clay mineral of natural biological crust dry weight.This application applies clay mineral to natural biological crust, it is easy to form organic mineral aggregate structure and biological membrane-mineral structure, wherein structure body has the function of retaining water and nutrient substance, maintains the function of biological membrane expansion, and establishes a mineral barrier to external environment;Clay mineral can provide key fine-grained material and adhesive force for the formation of soil aggregate as inorganic component of biological soil crust, and provide certain protection for crust biological, so as to strengthen the ability of crust resistance and promote the role of crust formation, improve its salt-tolerant.This application can apply clay mineral directly to natural biological crust, also can form biological soil crust and then carry out sand fixation application, realize the ecological restoration of saline-alkali soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biological soil crust, and particularly relates to a biological soil crust with improved salt and alkali tolerance, a preparation method and application thereof. BACKGROUND

[0002] Soil salinization refers to an environmental deterioration phenomenon caused by excessive accumulation of water-soluble salts in the soil surface or weathering layer, i.e., the presence of high concentrations of soluble salts in the soil. Soil salinization seriously affects microbial community composition and soil enzyme activity through changes in osmotic pressure and ionic effects, aggravates biodiversity loss and land desertification, and further has negative impacts on agricultural production, economic benefits, and sustainable development of environmental health. In particular, in arid regions, the interaction of salinization and desertification has adverse effects on the ecological environment, economy, and social activities. Compared with physical and chemical methods, bioremediation is considered as a more sustainable method to restore degraded soil.

[0003] Biological soil crust has ecological functions such as stabilizing the ground surface and resisting wind erosion, and plays an important role in maintaining the stability of desert ecosystems, and its ground cover in desert areas reaches more than 40%. However, the intensification of global climate change and human disturbance may exacerbate the negative effects of salinization, leading to global degradation of biological soil crust. Studies have shown that biological soil crust not only can directly affect the soil surface, but also can affect soil properties, and biological soil crust can be used as a soil salt reducer to help improve soil quality under arid climatic conditions. Biological soil crust can be considered as a soil protection strategy and is actively used for soil remediation and ecosystem restoration. Therefore, finding an effective way to improve the salt and alkali tolerance of biological soil crust itself so as to restore it has extremely important practical significance for the improvement of land salinization and the prevention of desertification.

[0004] The existing methods for improving saline-alkali soil mainly include: (1) improving water conservancy from irrigation, drainage, silt discharge, and seepage prevention; (2) planting salt and alkali tolerant plants, or planting forage grasses, green manure, and afforestation to improve the physical and chemical properties of soil, but it takes a long time and costs a lot; (3) using chemical substances such as gypsum, phosphogypsum, and calcium sulfite for chemical improvement, which has relatively fast effect, but is not a long-term solution. Overall, these methods have achieved good results in improving saline-alkali soil, but mainly have problems such as high cost, long time consumption, and inconvenient operation, and are not suitable for biological soil crust in desert areas. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies, and provides a biological soil crust with improved salt and alkali tolerance, a preparation method and application thereof, which solves the technical problems of high cost, long time consumption, and inconvenient operation in the prior art for improving the salt and alkali tolerance of biological soil crust.

[0006] To achieve the above technical purposes, the technical scheme provided by the present application is:

[0007] In a first aspect, the present application provides a biological soil crust with improved salt and alkali resistance, comprising natural biological crust and clay mineral accounting for 1-5% of the dry weight of the natural biological crust.

[0008] Preferably, the natural biological crust is a developed and matured algal crust.

[0009] Preferably, the clay mineral is kaolinite.

[0010] Preferably, the clay mineral accounts for 1-2% of the dry weight of the natural biological crust.

[0011] In a second aspect, the present application provides a preparation method of a biological soil crust with improved salt and alkali resistance, comprising the following steps:

[0012] Adding clay mineral accounting for 1-5% of the dry weight of the natural biological crust to the natural biological crust, mixing and incubating uniformly to obtain a biological soil crust with high salt and alkali resistance.

[0013] Preferably, the incubation is carried out in a natural environment.

[0014] In a third aspect, the present application provides the use of the above biological soil crust in sand fixation.

[0015] Preferably, the biological soil crust is uniformly laid on bare sand.

[0016] Further preferably, the thickness of the laid biological soil crust is 2-10 mm.

[0017] Preferably, the salinity of the sand soil for sand fixation is 17.6 g kg -1 The following.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The present application applies clay mineral to the natural biological crust, which is easy to form organic mineral aggregate structure and biological membrane-mineral structure, wherein the structure has the function of retaining water and nutrients, maintains the function of biological membrane expansion, and establishes a mineral barrier to the external environment; at the same time, the clay mineral as an inorganic component of soil aggregate can provide key fine particle material and bonding force for the formation of biological crust, and provide certain protection for the crust organisms, thereby playing the role of strengthening the resistance of the crust and promoting the formation of the crust, improving the salt and alkali resistance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The changes in Chl-a in biocrusts with different amounts of kaolinite (different lowercase letters indicate significant differences between treatments, p < 0.05).

[0021] Figure 2 The changes in EPS in biocrusts with different amounts of kaolinite (different lowercase letters indicate significant differences between treatments, p < 0.05).

[0022] Figure 3 O2 in biological crusts with different amounts of kaolinite - Changes (different lowercase letters indicate significant differences between treatments, p < 0.05);

[0023] Figure 4 The changes in SOD activity in biological crusts with different amounts of kaolinite (different lowercase letters indicate significant differences between treatments, p < 0.05).

[0024] Figure 5 The changes in SOD activity in biological crusts with different amounts of kaolinite (different lowercase letters indicate significant differences between treatments, p < 0.05). Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The main microbial community in biocrusts is desert algae. The mechanism by which desert algae cope with salt stress is consistent with the mechanism by which algal cells resist drought stress: by secreting extracellular polysaccharides (EPSs) to maintain osmotic pressure balance inside and outside the cell, thus buffering the entry and exit of water molecules and the accumulation of toxic ions. On the other hand, they also resist stress by accumulating organic solutes such as sucrose that do not interfere with metabolic activities. This invention enhances the stress resistance of biocrusts, i.e., improves the soil's ability to withstand salinity and alkalinity, by co-culturing them with kaolinite (a clay mineral).

[0027] The clay mineral particle size is small, the surface area is large, and the hydrophilicity and hydrophobicity are combined. The clay mineral is directly applied to the natural biological soil crust, and the organic mineral aggregate structure and biological membrane-mineral structure are easily formed. These structures have the functions of retaining water and nutrients, maintaining the expansion of the biological membrane, and establishing a mineral barrier to the external environment, thereby changing the content of water, gas and chemical substances passing through the inside of the aggregate structure. As an inorganic component of soil aggregates, the clay mineral can provide key fine particles and adhesion for the formation of biological crust, and provide protection for the biological crust, thereby enhancing the resistance of the biological crust and promoting the formation of the biological crust, and improving the salt-tolerant property.

[0028] The kaolinite used in the application is a kind of clay mineral, and its surface has two structures: a siloxane type surface with permanent electric charge and a hydroxyl type surface with variable electric charge, which can attach soil microorganisms with different functional group organic surfaces to produce different electrochemical behaviors; the kaolinite used in the application can simultaneously play the roles of physical protection and nutrient supply, can significantly improve the resistance of soil microorganisms to adversity and is beneficial to the survival and development of the soil microorganisms in adversity. Therefore, it is feasible to combine the biological crust with the clay mineral to improve the salt-tolerant property of the biological crust.

[0029] The application provides a method for improving the salt-tolerant property of a biological soil crust. The method is simple, easy to implement and economical and effective. By introducing a suitable amount of kaolinite into the biological soil crust, the biochemical characteristics of the biological soil crust are improved, and the degradation phenomenon caused by salinization is particularly improved. The method can improve the salt-tolerant property of the biological soil crust and improve the physical and chemical properties of the soil at a lower economic cost.

[0030] The application will be further described in detail through specific examples.

[0031] To avoid redundancy, the following kaolinite is purchased from the National Pharmaceutical Chemical Reagent Co., Ltd. The main chemical components include: Al 2.4 O 4.8 Si 0.6 , SiO2, Fe2O3 and TiO2.

[0032] Example 1

[0033] In the application, kaolinite is added to the crushed biological crust under salt stress, and the application of different amounts of kaolinite in the resistance of the biological crust to salt stress is explored. The specific steps include:

[0034] (1) Sampling: the mature (5mm thick) algal crust is collected from the Gurbantunggut Desert, the collected sample crust is collected in a sterile culture dish, and is fixed. The collected sample is timely sent back to the laboratory and stored in a desiccator for standby. (2) Preparation of the sample: the sample is crushed and mixed with kaolinite, and then placed in a sterile culture dish.

[0035] (2) Soil treatment: The wild collected bare sand was passed through a 10 mesh sieve, then loaded into a container and sterilized in a sterilization pot, the temperature was 121℃, the time was 30 min, and the sterilization was repeated 3 times. After cooling, the sand was divided and loaded into a 15 cm diameter culture dish, and 200 g of sand was loaded into each culture dish.

[0036] (3) Inoculation: The collected sample crust was naturally air-dried and crushed in a sterile plastic culture dish. Then, 25 g of natural crust was weighed and uniformly mixed with different amounts of kaolin (ground to pass through a 600 mesh sieve), and the addition ratio of kaolin was 0%, 1%, 2% and 5% of the mass of the natural crust, respectively, to prepare a natural biological crust-kaolin (w / w) composite inoculum treatment group.

[0037] Performance test

[0038] The different proportions of the composite inoculum were uniformly spread on the sterilized bare sand, and the thickness was 2 mm, and 3 replicates were set for each treatment. All treatment groups were placed in a laboratory 40 μE m -2 s -1 Light intensity and 25±2℃ light incubator, light and dark ratio 12:12. In order to simulate the gradient change of salt stress in natural environment, during this period, 0.5 mol L -1 NaCl solution 10 mL was added to the culture dish every 2 days (the salinity ranged from 3.5 g kg -1 -17.6 g kg -1 between the initial and final stages, i.e. from moderate salinization to severe salinization), and Chl-a, EPS, MDA, SOD, O2 - was measured every 7 days.

[0039] Note: The purpose of measuring Chl-a, EPS, MDA and SOD in the present application is:

[0040] Chl-a: The content of Chl-a represents the biomass of biological crust, and reflects the growth trend of biological crust.

[0041] EPS: The product of biological crust growth and metabolism, is one of the carbon sources used by microorganisms, and plays an important role in biological crust stress resistance.

[0042] Malondialdehyde (MDA): The amount of malondialdehyde in plants indicates the degree of damage to plant cell membranes. MDA content reflects the degree of lipid peroxidation in plant cell membranes; high MDA content indicates a high degree of cell membrane peroxidation and severe damage to the cell membrane. MDA content is a good indicator of the degree of membrane peroxidation in biological crusts under stress conditions (salt-alkali environments).

[0043] Superoxide dismutase (SOD): SOD is a type of oxidoreductase produced in microorganisms or plants. It is an active substance derived from living organisms, a metal-containing active protease that can eliminate harmful substances produced during metabolism. SOD has special physiological activity and is the primary substance for scavenging free radicals in organisms. The level of SOD in an organism is a direct indicator of aging and death.

[0044] Superoxide anion (O2) - ): Certain metabolic byproducts of oxygen, such as reactive oxygen species (ROS), can accumulate and damage algal cells. Superoxide anions (O2) - ) is a representative free radical of ROS, which contains two unpaired electrons and is characterized by extremely high chemical reactivity and an extremely short biological half-life.

[0045] MDA, O2 - The relationship between MDA and SOD: MDA is a product that causes fatal damage to organelles. It is produced by the peroxidation of polyunsaturated fatty acids (PUFAs) by ROS. As an important physiological indicator of stress resistance, the concentration of MDA reflects both the intensity of lipid peroxidation and the degree of damage to the cell's biomembrane system. To resist peroxidation damage, organisms will use their own enzymatic systems to remove O2 from cells. - Accumulation-induced toxicity balances the redox potential of cells, and superoxide dismutase (SOD) is one of the key enzymes that plays a role in this process.

[0046] like Figure 1 As shown, the initial biomass (expressed as Chl-a) of each treatment group was 1.7 μg g. -1 Around 7 days, the early development of the crust was good, with a significant increase in biomass, reaching its peak on day 7. The group with 5% kaolinite added had the highest biomass of 5.32 μg / g. -1As salt stress intensified, biomass began to decline. Notably, the rate and extent of biomass decline in the control group (0%) were significantly higher than those in the kaolinite-added group (p < 0.05). Furthermore, the chlorophyll a content in the 1% and 2% kaolinite-added groups was significantly higher than that in the 5% treatment group (p < 0.05). This preliminarily suggests that kaolinite plays a promoting role in the process of crust formation to resist stress and maintain growth, and has the best protective effect within a certain range (1%–2%).

[0047] like Figure 2 As shown, during the crust growth process, the change in EPS content exhibited a different trend than Chl-a, except that the 2% treatment group showed a rapid increase, reaching a peak of 118.44 mg / g on day 7. -1 Apart from the control group, the other treatment groups all showed a trend of "first decreasing, then increasing, and then stabilizing". It was clearly observed that the EPS secretion levels in the 2% and 5% kaolinite addition groups were significantly higher than those in the 0% and 1% kaolinite addition groups (p < 0.05). Overall, the 2% kaolinite addition group exhibited the best secretion performance, which corresponds to the changes in Chl-a content.

[0048] like Figure 3 As shown, after 7 days of salt stress on biological crusts, the intracellular superoxide anion free radicals (O2) increased. - Significant accumulation occurred, with the contents of the 0% and 1% kaolinite-added groups exceeding 50 μM g. -1 This indicates that the oxidative stress was severe, but the accumulation in the 2% and 5% kaolinite addition groups was less than 20 μM g. -1 This indicates that the organism's crust quickly adapted to the new, stressful environment, O2 - The content remained at a low accumulation level. The 5% treatment group scavenged O2 in the cells of the biological crust during the first 28 days of cultivation. - Accumulation yielded the best results, but with continued stress, the 2% treatment showed the best clearance effect, with O2 at the end of the experiment. - Accumulation amount less than 20 μM g -1 Throughout the culture period, the O2 in the control group (0%) was... - The content has remained at a high cumulative level, reaching its highest level in all time periods.

[0049] like Figure 4 As shown, SOD activity changed little in the initial 14 days; activity decreased in the 0% and 1% treatment groups, remained stable in the 2% group, and increased significantly in the 5% group. This result explains the small changes in SOD activity during the initial culture period due to O2. -The reason for the large accumulation in the control group (0%) and the low clay group (1%) is that the SOD activity of the enzymatic system cannot reach the intensity of clearing the ROS in the cell body. However, after the cultivation time exceeds 14 days, the SOD activity of each treatment group is greatly improved, indicating that the biological crust produced an active role in response to salt stress, and the increase multiples of each group on the 7th day are 5.6, 1.9, 6.7 and 12.3, respectively, wherein the activity of the 2% treatment group is the largest, which is 833.65 U mg -1 .

[0050] As shown in Figure 5 , under salt stress, the change trend of the MDA content in the cells of the biological crust has obvious correspondence with the change trend of the SOD activity, that is, both of them have a large change around the 14th day, the SOD activity starts to increase significantly after 14 days, and the MDA content decreases significantly around 14 days. In the early cultivation period, the high accumulation of MDA in the cell body is probably due to the accumulation of excessive ROS, the biological crust does not have a good adaptability to the stress environment, and the SOD activity is also at a low level, resulting in that each treatment group does not actively respond to the oxidation reaction in the environment. However, the results show that this phenomenon is reversed after 14 days, the MDA content of each group is maintained at a low level ( <0.5 μmol mg -1 ), and continues until the end of the experiment. During the entire experiment, the MDA content of the kaolinite added group is lower than that of the control group (0%), indicating that kaolinite plays an active role in promoting the process of clearing MDA in the system.

[0051] From the determination of each index and the relationship between them, it can be seen that the mixed inoculation of kaolinite and natural biological crust has obvious positive effects on the increase of the salt-tolerant ability of the biological crust, and the addition amount of kaolinite is not the higher the better, but there is an optimal addition range (1%~2%). In the present application, by artificially spraying 0.5 mol L -1 NaCl solution to simulate the change of salinity in nature, the kaolinite is introduced into the natural biological crust to study the change of the salt-tolerant ability, from the research results, it is concluded that the addition of 2% of kaolinite has the best effect on the improvement of the salt-tolerant ability of the biological crust, and the trace addition of kaolinite is easy to obtain and feasible from the economic point of view, which indicates the feasibility and great application potential of the technology.

[0052] In summary, the present application has the following advantages:

[0053] (1) The clay algal crust constructed by the application has good salt and alkali resistance. By mixing kaolinite with natural crust and inoculating on bare sand, and through early cultivation, it can be seen from various physiological indicators that the addition of kaolinite plays a certain protective role on the crust and enhances its salt and alkali resistance. The 2% kaolinite addition group accumulates the most EPS in the same time compared with other groups, and the accumulation of MDA and O2 - is the least, and the activity of SOD is the highest, so an optimal amount of clay mineral addition can be obtained, which has wide reference significance.

[0054] (2) The biological soil crust improvement method provided by the application observes the indicators such as chlorophyll a (Chl-a), extracellular polysaccharide (EPS), malondialdehyde (MDA), superoxide dismutase (SOD) and superoxide anion free radical (O2 - ) during the entire experiment, and uses single factor variance analysis (ANOVA) to test the differences under different kaolinite gradients and salt stress environment, so that the biological crust constructed by the application can improve the salt and alkali resistance of soil in a short time, at the same time, kaolinite is widely available, cheap and easy to obtain, which shows the feasibility and great application prospect of the technology.

[0055] The specific embodiments of the application described above do not constitute a limitation on the protection scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application shall be included in the protection scope of the claims of the application.

Claims

1. A biological soil crust for improving salinity tolerance, characterized in that, The natural biological crust and clay minerals accounting for 1-2% of the dry weight of the natural biological crust; The natural biological crust is a developed and mature algal crust; The clay mineral is kaolinite.

2. The preparation method of the biological soil crust for improving salt-alkali tolerance according to claim 1, characterized in that, The method comprises the following steps: adding clay minerals accounting for 1-2% of the dry weight of the natural biological crust to the natural biological crust, mixing and incubating to obtain biological soil crust with high salt and alkali resistance.

3. The method for preparing a biological soil crust for improving salt-alkali tolerance according to claim 2, characterized in that, The incubation is carried out in a natural environment.

4. The biological soil crust of claim 1 in sand fixation.

5. Use of the biological soil crust according to claim 4 for sand fixation, characterized in that, The biological soil crust is uniformly laid on bare sand.

6. Use of the biological soil crust according to claim 5 for sand fixation, characterized in that, The thickness of the laid biological soil crust is 2-10 mm.

7. Use of the biological soil crust according to claim 4 for sand fixation, characterized in that, The sand soil salinity after sand fixation is 17.6 g kg -1 The following.

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