A method of rehabilitating a degraded grassland

Abstract

The present application belongs to the field of grassland restoration, and discloses a kind of restoration method of degraded grassland, and the specific steps are 1) identifying the different sedimentary facies structure characteristics of vertical stratum in research area;2) the characteristics of grassland degradation indicator plant in research area are studied, and the degradation degree is divided;3) analysis of grassland degradation geological mechanism, including analysis of the influence of topography on the distribution of Stellera chamaejasme, and the synergistic or antagonistic main control factor of the influence of sedimentary facies change on the growth of indicator plant;4) construct the grassland degradation model based on the sedimentary facies constraint of similar habitat conditions based on the concept of geology;5) indoor grass seed screening based on drought resistance coefficient;6) demonstration area mixed planting tank planting, and the comprehensive management method of degraded grassland is proposed.The present application starts from the root of degraded grassland, based on the background condition of ecological geological environment, follows the principle of adapting measures to local conditions, scientifically selects suitable grass seeds, adheres to the correct support of artificial and the guidance of ecological system natural restoration, and ensures the minimum economic and environmental risk of ecological protection and restoration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grassland restoration, and particularly relates to a restoration method of degraded grassland. BACKGROUND

[0002] Grassland degradation is a common problem faced by the world, especially in arid and semi-arid regions, where the grassland ecosystem is very fragile and sensitive to the influence of internal and external dynamic geological processes, climate change and human activities. The resulting grassland degradation has become a serious obstacle to economic and social development. Stellera chamaejasme is a perennial herb of the Stellera Linn. genus of the Thymelaeaceae family, and its roots, stems and leaves are highly toxic. In ecologically fragile areas, it has been regarded as a warning plant of grassland degradation and a potential indicator of deteriorating ecology. Previous research on the invasion of Stellera chamaejasme or grassland degradation has mainly focused on the surface layer and supergene geological processes, and some scholars have also studied the relationship between shallow soil and plant distribution.

[0003] At present, there are relatively mature technologies for restoring degraded grasslands: fence enclosure, a low-cost grassland ecological restoration technology; aerial seeding, which uses an airplane to spread pasture seeds at a certain height and speed over a planned area, characterized by low investment, wide area and fast speed; shallow plowing, which destroys the original sod through shallow plowing (15-20 cm) to increase soil permeability, promote soil microbial activity and organic matter decomposition, increase soil temperature, and improve the efficiency of root water and mineral nutrient absorption, thus creating new conditions for better growth and reproduction of pasture; no-tillage seeding, which uses advanced no-tillage machinery to directly sow while plowing, avoiding soil turning and reducing soil water evaporation and organic matter loss. In addition, there are also zone rotation and time-limited grazing. However, the above restoration technologies are mainly controlled by humans. There is a lack of natural restoration technology support. For example, fence enclosure is not a natural restoration method, but a form of human interference. It completely excludes the regulation of animals on the grassland. This exclusion of livestock will inevitably lead to strong rebound of the degraded grassland due to overcompensation growth of plants, so long-term enclosure is not a natural restoration measure for natural grasslands.

[0004] The soil of natural grassland is mainly constrained by soil parent material, geological formation and various geological actions. Therefore, scientifically screening the repair mode and path needs to take the geological environment composed of the lithosphere, the soil sphere, the water sphere and the like around the human being as the research subject, analyze the motion exchange, transformation of material flow, energy flow and information flow in the ecological geological system and the influence on the biology, and strive to seek the geological reason for the deterioration of the grassland ecological environment. According to the background condition of the ecological geological environment, the principle of adapting to the local conditions according to the grass and the desert, the suitable grass species are scientifically screened, the artificial correct support and the natural repair guidance of the ecological system are adhered to, and the minimum risk of ecological protection and repair is ensured. SUMMARY

[0005] The present application aims to provide a repair method of degraded grassland, to solve the technical problem of lacking natural recovery in the prior art, that is, to seek the geological reason for the deterioration of the grassland ecological environment, according to the background condition of the ecological geological environment, the principle of adapting to the local conditions according to the grass and the desert, the suitable grass species are scientifically screened, the artificial correct support and the natural repair guidance of the ecological system are adhered to, and the minimum risk of ecological protection and repair is ensured.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] A repair method of degraded grassland, comprising the following steps:

[0008] S1, identifying the different sedimentary facies characteristics of the vertical stratum (about 2 meters) of the research area;

[0009] S2, researching the characteristics of the grassland degradation indicator plants in the research area, and dividing the degradation degree;

[0010] S3, analyzing the geological mechanism of grassland degradation, including analyzing the influence of topography on the distribution of indicator plants, and the synergistic or antagonistic main control factors of the influence of sedimentary facies change on the growth of indicator plants;

[0011] S4, constructing a grassland degradation model based on the sedimentary facies constraint under similar habitat conditions based on the concept of geology;

[0012] S5, indoor grass species screening based on drought resistance coefficient;

[0013] S6, planting in the demonstration area mixed planting tank, and putting forward a comprehensive management method of degraded grassland.

[0014] Further, the identification of the different sedimentary facies characteristics of the vertical stratum (about 2 meters) of the research area refers to finding out the different sedimentary facies structure characteristics of the research area under similar climate conditions by researching the sedimentary environment and climate characteristics of the research area, identifying different sedimentary facies units by the nearest neighbor propagation clustering algorithm, and according to the curve kurtosis, distribution interval and transport mode.

[0015] Further, the indicator plant is Stellaria chamaejasme.

[0016] Further, the research on the characteristics of the indicator plant of grassland degradation specifically includes the following steps: first, a quadrat survey of the grassland degradation area is conducted, i.e., representative sites are selected according to different Stellaria chamaejasme growth densities, ground plant combinations, and soil-forming parent material types, and a quadrat survey is conducted, focusing on measuring the number of Stellaria chamaejasme plants, the maximum / minimum / average number of individual branches, the maximum / minimum / average height of Stellaria chamaejasme, the Stellaria chamaejasme base coverage, the total Stellaria chamaejasme coverage (ground projection of each Stellaria chamaejasme branch), and the total vegetation coverage survey data in the quadrat; then, the number of Stellaria chamaejasme plants, the number of individual branches of Stellaria chamaejasme, the height of Stellaria chamaejasme, the total coverage, the Stellaria chamaejasme coverage, and the physiological and biochemical phenotypes of the plants in each survey quadrat in the study area are analyzed to determine the different growth distribution characteristics of Stellaria chamaejasme in the study area; finally, the degree of grassland degradation is divided according to the growth distribution characteristics of Stellaria chamaejasme on the ground, the degree of density, and in combination with the reduction amount of the original plant community, the vegetation coverage, and the grass species type.

[0017] Further, the method for analyzing the influence of topography on the distribution of Stellaria chamaejasme includes the following steps: combining the DEM elevation data of the study area, using ArcGIS raster surface analysis, spatial analysis tools, generalized additive models (GAM), and statistical analysis tools of Origin to identify the response relationship between topography and the distribution of Stellaria chamaejasme; specifically including:

[0018] 1) Identification and extraction of topographic factors: based on the DEM elevation data of the study area with a resolution of 1 meter, the 3D raster surface analysis module of ArcGIS is used to extract five topographic index parameter factors related to the spatial distribution of the indicator plant in the study area, which are elevation, slope, aspect, plan curvature, and profile curvature.

[0019] 2) Analysis of the response relationship between topography and the distribution of Stellaria chamaejasme: based on the parameters such as Stellaria chamaejasme height and branch number obtained from the quadrat survey, the biomass of Stellaria chamaejasme is estimated, a generalized additive model of topographic response is constructed based on the aboveground biomass data of Stellaria chamaejasme, a Spline function is used for fitting, and the contribution values of different topographic variables are calculated.

[0020] Further, the analysis of the synergistic or antagonistic master control factors of the influence of sedimentary facies changes on the growth of the indicator plant includes the following steps: analyzing the response relationship between loose sediment particle size and the growth distribution of Stellaria chamaejasme, the response relationship between the water characteristics of loose sediments and Stellaria chamaejasme, and the influence of the element geochemical process of loose sediments on Stellaria chamaejasme.

[0021] The analysis of the response relationship between loose sediment particle size and the growth and distribution of Euphorbia fischeriana was conducted by studying the soil particle size classification characteristics and the different sedimentary facies differentiation characteristics based on the AP clustering algorithm in the study area, combined with the distribution characteristics of the indicator plant Euphorbia fischeriana, to identify the main influencing factors of soil physical properties on the growth and distribution of Euphorbia fischeriana.

[0022] The analysis of the moisture characteristics of loose sediments and their response to Euphorbia fischeriana was conducted by analyzing the burial depth and hydrochemical characteristics of shallow groundwater in the region and the capillary rise characteristics of different sedimentary facies to reveal the bottom-up eco-hydrological processes of the vertical profile, and by analyzing the infiltration relationship between soil water and atmospheric precipitation to reveal the top-down eco-hydrological processes of the vertical profile, in order to study the moisture response relationship between soil water and Euphorbia fischeriana.

[0023] The analysis of the impact of loose sediment elemental geochemical processes on *Euphorbia fischeriana* specifically involves using multivariate statistics, mass migration coefficients, principal component analysis, and hierarchical clustering tree methods to analyze the elemental characteristics and vertical migration patterns of different sedimentary facies, and to analyze the ecological geochemical characteristics and distribution control from the perspective of geochemical processes.

[0024] Furthermore, the construction of the grassland degradation model specifically involves taking the rhizosphere soil, indicator plant roots, and leaves of sedimentary facies structures in different *Euphorbia milii* growing areas as research objects. By conducting research on the migration and enrichment characteristics, geochemical behavior, and influencing factors of elements between soil and plants, the model aims to identify the migration and accumulation patterns of geochemical elements in sedimentary facies and the distribution response characteristics of indicator plants. It also explores and analyzes the eco-hydrological and geochemical processes affected by the spatial heterogeneity of sedimentary facies, thereby constructing a conceptual model of grassland degradation under similar habitat conditions based on geoscience principles and the influence of multiple factors.

[0025] Furthermore, the screening of indoor grass species based on drought resistance coefficient specifically involves selecting sandy soil, which is the sedimentary facies structural unit with the worst soil nutrient conditions, as the grass seed culture soil, and conducting potted simulated drought experiments under greenhouse conditions to screen for suitable forage grasses for the study area.

[0026] Furthermore, the planting in the mixed-sowing trenches of the demonstration area specifically involves using drought-resistant grass species selected from greenhouse pot drought simulation experiments as experimental materials to conduct experiments in the demonstration area. The sedimentary facies with the strongest degradation and the sedimentary facies with the lightest degradation represent two end-members of the grassland degradation degree in the study area. Demonstration areas are established in these two areas respectively, and grass species selected from indoor cultivation experiments are planted in the demonstration areas. Comparative experiments on artificial planting of grass species with different mixed-sowing ratios are carried out in order to find the best grass species mixed-sowing planting method that can be used in vegetation restoration in degraded land areas of the study area.

[0027] In summary, the present invention has the following beneficial effects:

[0028] 1. The present application finds that the number of plants, the coverage of Stellera chamaejasme and the base coverage of Stellera chamaejasme in the dense area are obviously higher than those in the sparse area through the research on the characteristics of the degraded grassland indicator plants, sample collection and analysis, and the total coverage in the area without Stellera chamaejasme shows obvious bimodal distribution characteristics, that is, in the grassland with good vegetation growth or the sandy land with low vegetation coverage, and the results of the generalized additive model show that the planar spatial pattern of Stellera chamaejasme growth mainly depends on the slope direction and slope of the terrain characteristic factor.

[0029] 2. The present application finds that the soil moisture content in the rhizosphere layer is obviously higher than that in the surface soil layer, and the dense area is obviously higher than the sparse area through the research on the geological mechanism of grassland degradation, which shows that Stellera chamaejasme can obtain more water supply from the rhizosphere soil layer in the dense area, thereby affecting the water acquisition of other pastures in the growing season, and through the analysis of the soil water infiltration rate characteristics and the capillary water rise height characteristics of different sedimentary facies, the sedimentary facies and structure beneficial to the soil water holding and groundwater supply in arid / semi-arid areas can be determined.

[0030] 3. The present application identifies different sedimentary facies units in the study area by the affinity propagation clustering algorithm and according to the curve kurtosis, distribution interval and transport mode, and combines the research on the geological mechanism of grassland degradation, the sedimentary facies heterogeneity and the spatial differentiation of water and soil elements affected thereby to propose a grassland degradation model based on the sedimentary facies constraint under similar habitat conditions based on the geology concept, which reveals the influence mechanism of multiple factors on Stellera chamaejasme growth under similar habitat conditions, that is, the grassland degradation is mainly related to the structure of different types of sedimentary facies.

[0031] 4. The present application also screens drought-resistant grass species under pot simulation of drought environment, completes artificial grass seed sowing comparison tests with different mixed sowing ratios, demonstrates and applies different mixed sowing technologies of drought-resistant grass species, proposes an artificial supplementary sowing grass seed scheme with mixed sowing ratios suitable for the accumulation sedimentary environment in the study area, and the scheme is based on the ecological geological environment background conditions, follows the principle of adapting measures to local conditions, scientifically selects suitable grass species, adheres to the correct support of artificial and the guidance of ecological system natural restoration, and ensures the minimum risk of ecological protection and restoration. DETAILED DESCRIPTION

[0032] Figure 1 It is the AP clustering 8 cluster intensity distribution curve characteristic graph of different stratigraphic sections in the embodiments of the present application.

[0033] Figure 2 It is the AP clustering 6 cluster intensity distribution curve characteristic graph of different stratigraphic sections in the embodiments of the present application.

[0034] Figure 3 It is the particle size curve characteristics of four types of sedimentary facies in the embodiments of the present application.

[0035] Figure 4A correlation analysis chart of the stratigraphic structure particle size stratification and the distribution of the wolfberry in the embodiment of the present application;

[0036] Figure 5 A soil particle size particle grading chart of different sedimentary facies in the embodiment of the present application;

[0037] Figure 6 A monthly soil moisture box chart of the vertical structure stratification of the wolfberry distribution dense area and the sparse area in the embodiment of the present application;

[0038] Figure 7 A soil water and wolfberry root and leaf moisture content chart of different wolfberry distribution root layers in the research area in the embodiment of the present application;

[0039] Figure 8 A grassland degradation conceptual chart based on the hydrological process in the embodiment of the present application;

[0040] Figure 9 A comparison analysis chart of the aboveground biomass of four mixed combinations in different years in the river facies environment demonstration area in the embodiment of the present application;

[0041] Figure 10 A repair effect chart of the river facies and the aeolian facies environment demonstration area in the embodiment of the present application (A-local germination characteristics in the river facies in the chart I, B-soil surface characteristics in the river facies, C-soil surface characteristics in the river facies, D-germination effect of the first year as a whole, E-local characteristics in the second year, F-local characteristics in the second year, G-degraded grassland before repair, H-germination effect of the second year as a whole after repair); Figure II Middle (left)-local germination characteristics in the aeolian facies, (right)-soil surface characteristics in the aeolian facies, that is, local germination characteristics). DETAILED DESCRIPTION

[0042] The present application will be further described in detail below in combination with the drawings and embodiments. The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The experimental materials used in the following embodiments are all conventional biochemical reagents purchased from a reagent store unless otherwise specified.

[0043] The research area of the present application is: Weichang County, Weichang County, Hebei Province.

[0044] A repair method of degraded grassland, comprising the following steps:

[0045] S1, identifying the vertical stratum (about 2 meters) of different sedimentary facies characteristics;

[0046] The identifying the different sedimentary facies characteristics of the vertical strata (about 2 meters) in the study area refers to identifying the different sedimentary facies structural characteristics of the different sediments in the study area under similar climate conditions by studying the sedimentary environment and climate characteristics in the region, and recognizing different sedimentary facies units by the affinity propagation clustering algorithm (AP clustering algorithm) according to the curve kurtosis, distribution interval and transport mode.

[0047] First, 85 vertical profiles are constructed by shallow drilling, each profile taking into account the geological sedimentary facies characteristics, and sediment samples are collected at intervals of 0-20 cm, 20-50 cm and 50-100 cm, a total of 255 samples. The Mastersizer 2000 laser particle size analyzer is used to determine the particle size analysis of the sedimentary sediments. The standardized original data is selected, and the Euclidean distance is used as the similarity measure between the sediment grain size frequency distribution curves. The AP clustering algorithm divides the grain size frequency curves of the sediments of the 85 profiles in the study area into 14 clusters (see Figure 1 and Figure 2 ). The class representative curve is used as the typical sample curve of each cluster curve, and the 14 cluster curves are further divided into 4 groups according to the curve kurtosis, distribution range and transport mode (see Figure 3 ). The 4 groups of grain size frequency distribution curves each represent a relatively consistent sedimentary environment. The 4 groups of sedimentary facies units are identified by the Φ value clustering results, which are aeolian facies, fluvial facies, mixed facies and residual facies.

[0048] According to the soil particle size test analysis data, combined with the AP clustering four different sedimentary facies combination results, the particle size proportion indicators d 10 (minimum value), d 50 (median value), d 90 (maximum value), ave (average value) and the lithology proportion indicators clay percentage, silt percentage, sand percentage and stone percentage are selected to further analyze the 2m or less sedimentary facies characteristic parameters. The results show that the 4 different sedimentary characteristics in the study area have obvious differences in grain size distribution characteristics. The aeolian facies is mainly medium-coarse sand, with a small percentage of clay and stone content, and almost no clay particle component. The fluvial facies is still mainly sand, with a significant increase in fine sand, very fine sand and clay components. The sediment grain size characteristics of the mixed facies are between the two. The sediment grain size component of the residual facies is close to aeolian sand, with a medium content of fine sand.

[0049] The different sediments in the study area were divided into five periods of 19.6-15.0 Ka, 10.9 Ka, 5.1-5.7 Ka, 3.3-3.8 Ka, and 1.3-1.5 Ka by optically stimulated luminescence dating. It can be known from the chronological study that the climate in the study area experienced the evolution process of cold and dry, early warming in dry and cold, relatively humid and warm, warm and humid, and warm and dry to cold and dry in the five different stages. It can be known from the grain size of the sedimentary facies that the grassland degradation is not a linear development, but changes with the fluctuation of the climate. The grassland in the degradation process alternately evolves the phenomena of sanding period and reverse period. The straight cold and dry stage of the climate in the study area is a main factor leading to the grassland degradation.

[0050] S2, the characteristics of the indicator plants of the grassland degradation in the study area are studied, and the degradation degree is divided;

[0051] The characteristics of the indicator plants of the grassland degradation in the study area, i.e., Stellera chamaejasme, are studied, specifically as follows:

[0052] Firstly, the sample investigation in the grassland degradation area is carried out. According to the different growth density of Stellera chamaejasme, the ground plant combination, and the soil parent material type, the representative sections are selected to arrange the sample investigation. The size of the sample is 2m x 2m. The plant number of Stellera chamaejasme, the maximum / minimum / average individual branch number, the maximum / minimum / average Stellera chamaejasme height, the Stellera chamaejasme base coverage, the total coverage of Stellera chamaejasme (the ground projection of each Stellera chamaejasme branch), the total vegetation coverage, and other investigation data in the sample are measured.

[0053] Then, according to the characteristics of the Stellera chamaejasme seed population with "near mother plant dispersion", the dispersion radius is less than 15cm, the Stellera chamaejasme plant number, the Stellera chamaejasme individual branch number, the Stellera chamaejasme height, the total coverage, the Stellera chamaejasme sub-coverage, and the plant physiological and biochemical phenotype indexes in each investigation sample in the study area are analyzed to find out the different growth distribution characteristics of Stellera chamaejasme in the study area. The statistical characteristics of the Stellera chamaejasme plant growth distribution in the sample investigation in the study area are shown in Table 1.

[0054] Table 1 Statistical characteristics of Stellera chamaejasme plant growth distribution in the study area

[0055]

[0056] The correlation between the above characteristics of Stellera chamaejasme in different distribution areas is analyzed by the Spearman correlation coefficient. According to the growth distribution characteristics of Stellera chamaejasme on the ground, the density degree is mainly combined with the original plant community reduction amount, the vegetation coverage, and the grass species type to divide the grassland degradation degree into four regions of light degradation, moderate degradation, severe degradation, and extremely serious degradation.

[0057] S3, the mechanism of the grassland degradation geological action is analyzed, including the analysis of the influence of the topography on the distribution of the indicator plants and the synergistic or antagonistic main control factors of the sedimentary facies change on the growth of the indicator plants

[0058] The method for studying and analyzing the influence of topography on the distribution of Stellera chamaejasme is to combine the DEM elevation data of the study area, use ArcGIS raster surface analysis, spatial analysis tools, generalized additive model (GAM) and statistical analysis means of Origin to identify the response relationship of topography to the distribution of Stellera chamaejasme; specifically including:

[0059] 1) Identification and extraction of topographic factors: According to the DEM elevation data with a resolution of 1 meter in the study area, the 3D raster surface analysis module of ArcGIS is used to extract five topographic index parameters for indicating the spatial distribution correlation analysis of the plant in the study area, which are elevation, slope, aspect, plan curvature and profile curvature.

[0060] 2) Analysis of the response relationship between topography and the distribution of Stellera chamaejasme: According to the parameters such as plant height and branch number of the sample survey, the biomass of Stellera chamaejasme is estimated, and the generalized additive model (GAM) of topographic response is constructed according to the aboveground biomass data of Stellera chamaejasme; the Spline function is used for fitting to calculate the contribution value of different topographic variables, as shown in Table 2.

[0061] Table 2 Contribution rate of different topography to the biomass (distribution) of Stellera chamaejasme

[0062] Terrain feature Contribution rate Aspect 42.1％ Slope 37.2％ Plan curvature 14.2％ Profile curvature 5.5％

[0063] The analysis of the synergistic or antagonistic master control factors of the influence of sedimentary facies change on the growth of indicator plants includes: the response relationship between loose sediment particle size and the growth distribution of Stellera chamaejasme, the response relationship between the water characteristics of loose sediments and Stellera chamaejasme, and the influence of the element geochemical process of loose sediments on Stellera chamaejasme.

[0064] The response relationship analysis between loose sediment particle size and the growth distribution of Stellera chamaejasme is to analyze the correlation degree by studying the soil particle size grading characteristics and the different sedimentary facies differentiation characteristics based on the AP clustering algorithm, and combining the distribution characteristics of the indicator plant Stellera chamaejasme to identify the main influencing factors of the soil physical properties of the growth distribution of Stellera chamaejasme,

[0065] The principal component analysis results are shown in Figure 4 The results show that the growth distribution characteristics of Stellera chamaejasme have a significant positive correlation with sedimentary facies, and have a higher correlation degree with medium powder particles, coarse powder particles, fine sand particles and d 50 fraction percentage, indicating that the growth distribution of Stellera chamaejasme has the highest correlation with the average content of soil particle size. That is, the larger the soil particle size, the larger the porosity, which is conducive to the growth of Stellera chamaejasme.

[0066] The analysis of the relationship between the water characteristics of loose deposits and the response of Stellera chamaejasme is as follows: the ecological hydrological process from bottom to top of the vertical profile is revealed by analyzing the regional shallow groundwater depth and water chemical characteristics and the capillary water rising characteristics of different sedimentary facies. The analysis results show that the water chemical types of the surface water and the groundwater are similar in the study area as a whole, and there is an obvious hydraulic exchange relationship between the groundwater and the surface water. According to the empirical value table of the capillary water rising height in the hydrogeological manual theory (see Table 3), the aeolian facies deposition unit is mainly concentrated in 0.04-1.20 m; the capillary water theoretical rising height of the fluvial facies deposition unit is mainly concentrated in 0.35-6.0 m; the capillary water theoretical rising height of the mixed facies deposition unit is mainly concentrated in 0.04-1.2 m; and the capillary water theoretical rising height of the residual facies deposition unit is mainly concentrated in 0.35-2.5 m. For the vertical stratigraphic structure underlying the fluvial facies or the residual facies deposition, the soil water of the rhizosphere soil layer can obtain groundwater recharge through capillary action, thereby being able to provide potential necessary water recharge for the formation and expansion of Stellera chamaejasme.

[0067] Table 3 Empirical value table of theoretical capillary water rising height (from the 58th edition of hydrogeology)

[0068]

[0069]

[0070] The ecological hydrological process from top to bottom of the vertical profile is revealed by analyzing the relationship between the soil water and the atmospheric precipitation infiltration; and the soil particle size gradation of different sedimentary facies units is analyzed based on AP clustering, Figure 5 The soil particle size gradation of different sedimentary facies units is illustrated by Figure 5 It can be seen that the soil infiltration characteristic curve range of the aeolian facies deposition unit is relatively wide, and the unit time infiltration amount is relatively large; the soil pore ratio of the fluvial facies deposition unit is relatively large, and the unit time infiltration amount is relatively small, and it quickly tends to be stable with time; and the soil infiltration of the mixed facies and the residual facies deposition units is between the two. The soil permeability coefficient when tending to be stable has the characteristics of aeolian facies > mixed facies > residual facies > fluvial facies.

[0071] The soil water content of different depths of the strata of each of the four typical profiles under different Stellera chamaejasme formation and distribution is monitored, and the water content of the roots and leaves of Stellera chamaejasme in the growth season of the flowering period is determined, as shown in Figure 6 , 7The results show that the soil moisture content in the rhizosphere layer of E. przewalskii is significantly higher than that in the surface soil layer. In the growing season of E. przewalskii, the soil moisture content in the dense area is significantly higher than that in the sparse area. The deepest soil moisture content in the dense area is relatively high, even higher than the overlying soil moisture content. The rhizosphere soil in the dense area of E. przewalskii can obtain more water supply, which affects the degree of water acquisition of other pasture in the growing season, and thus changes the stability of the ecological system to some extent. The leaf water content in the sparse area of E. przewalskii is slightly higher than that in the dense area, indicating that water redistribution may occur in the plant body, especially in the downward water redistribution process in the dense area.

[0072] The analysis of the influence of loose sediment element geochemical process on E. przewalskii is as follows: through the use of multivariate statistics, mass transfer coefficient, principal component analysis and system clustering tree method, the element characteristics and vertical migration law of different sedimentary facies are analyzed, and the ecological geochemical characteristics and distribution control are analyzed from the geochemical process.

[0073] S4, constructing a grassland degradation model based on the sedimentary facies constraint under similar habitat conditions based on the concept of geology;

[0074] The construction of the grassland degradation model is as follows: taking the rhizosphere soil of different E. przewalskii growth areas, plant roots and leaves as the research objects, the element migration and enrichment characteristics between soil and plant, geochemical behavior and influencing factors are analyzed, the sedimentary facies geochemical element migration law and the distribution response characteristics of the indicator plant are found out, the ecological hydrological process and geochemical process affected by the spatial heterogeneity of sedimentary facies are explored and analyzed, and the differences in hydrogeological process affected by the structure, physical and chemical properties of different sedimentary facies revealed by the vertical section are proposed. Under similar habitat conditions, the sedimentary facies constraint based on the hydrological process grassland degradation conceptual model is proposed, as shown in Table 4, Figure 8 as shown.

[0075] Table 4 Parameter characteristics of the grassland degradation conceptual model based on hydrological process

[0076]

[0077] As shown in Table 4, Figure 8 the aeolian sediment has the worst grassland growth conditions, and the aeolian sediment has the best grassland growth conditions.

[0078] S5, indoor grass seed screening based on drought resistance coefficient;

[0079] Ten perennial forage grasses commonly used in northern China were selected as test materials, including legume forage white clover, red clover, alfalfa and sandveld, gramineous forage perennial ryegrass, cocksfoot, smooth brome, annual brome, Elymus dahuricus and thin ice grass. The seeds were provided by Beijing Klawo Forage Technology Development Center.

[0080] The soil with the worst nutrient condition, aeolian facies sandy soil, was selected as the grass seed culture soil, and pot simulation drought experiment was conducted in the greenhouse to screen the suitable pasture in the study area. The effects of drought stress on the drought resistance coefficients of the growth indexes of 10 grass seeds are shown in Table 5.

[0081] Table 5 Drought stress on the drought resistance coefficients (ω value) of the growth indexes of 10 test materials

[0082]

[0083]

[0084] After the plant is stressed, its growth and physiological changes are complex and are affected by multiple factors. It is difficult to truly reflect the strength of the plant drought resistance by using a single growth index to evaluate the drought resistance of the plant. The comprehensive evaluation by using the membership function value method and the standard deviation coefficient weighting method is more objective and scientific. See Table 6.

[0085] Table 6 Comprehensive evaluation D value and order of drought resistance of 10 grass seedlings

[0086]

[0087] The correlation analysis, principal component analysis, and membership function method were used to comprehensively evaluate the drought resistance of the 6 kinds of pasture with strong drought resistance. See Table 7.

[0088] Table 7 Comprehensive index value CIx, membership function value (x), comprehensive evaluation D value, and drought resistance type of the test materials

[0089]

[0090] The results show that the drought resistance of the 6 kinds of pasture is in the order of Agropyron elongatum > Elymus dahuricus > Hedysarum leave > Bromus inermis > Medicago sativa > Agropyron cristatum.

[0091] S6, planting in the demonstration area mixing tank, and proposing a comprehensive management method for degraded grassland.

[0092] The drought-resistant grass seeds screened out by the greenhouse pot simulation drought experiment were used as the test materials in the demonstration area. The soil with the worst nutrient condition, aeolian facies, and the soil with the best nutrient condition, river facies, represent the two end members of the grassland degradation degree in the study area. The indoor cultivation experiment was conducted in the demonstration area, and the grass seeds screened out by the indoor cultivation experiment were planted in the demonstration area. Comparative tests of different mixing ratios of artificial planting of grass seeds were conducted. The same experimental materials and seeding methods were used in the two experimental areas. The test materials were Agropyron elongatum, Elymus dahuricus, Bromus inermis, Hedysarum leave, and Medicago sativa screened out by the greenhouse simulation drought experiment. Four mixing combinations were set up in each sample area, as shown in Table 8.

[0093] Table 8. Mixed Seeding Methods and Proportions

[0094]

[0095] The parent material in the fluvial sedimentary environment demonstration area was mainly alluvial sand from river channels. The parent material had high nutrient content, a shallow water table, and increased clay particles, forming a good water-retaining layer, which was conducive to herbaceous growth and restoration. This demonstration area primarily assessed the ecological restoration effects of degraded grassland under similar climatic conditions without human intervention. The aboveground biomass results of four mixed seeding combinations at different ages in this demonstration area are shown in […]. Figure 9 ,Depend on Figure 9 It can be seen that the aboveground biomass of different mixed grasslands in 2021 and 2022 was group D (high-lying grass: awnless brome: saxaul: alfalfa = 3:3:2:2), that is, 30% high-lying grass + 30% awnless brome + 20% saxaul + 20% alfalfa (high-lying grass 0.45 kg·mu). -1 +0.45 kg / mu of awnless bromegrass -1 +0.2 kg / mu of sadawang -1 +0.2 kg / mu of alfalfa -1 The highest values ​​were found in groups A, B, and C (P < 0.05).

[0096] The parent material of the aeolian facies demonstration area mainly comes from aeolian sand, and the soil and hydrological nutrient conditions are extremely poor (see...). Figure 10 The groundwater level is deep, and the soil layer has poor water and fertilizer retention. This demonstration area mainly adopts a combined artificial and natural remediation model under similar climatic conditions. Grass seeding alone is ineffective for remediation; the best-performing group (D) had a germination rate of less than 5%, and the later grass growth was also unsatisfactory, with almost zero coverage after reseeding. This indicates that in aeolian sedimentary environments, natural remediation by grass seed in the short term is very difficult and requires a phased approach. Firstly, drought-resistant shrubs with well-developed root systems, such as Caragana korshinskii, are planted as pioneer plants to remediate aeolian and mixed-phase sediments about 1 meter below the surface. Once the soil conditions in the 0-20cm depth area reach at least the level of fluvial soil, the selected grass species from this study can be mixed and sown according to the planting methods described in the fluvial sedimentary environment sample plots.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of rehabilitating a degraded grassland, characterized by, It comprises the following steps: S1, identifying the different sedimentary facies structure characteristics of the vertical strata in the study area; S2, studying the characteristics of the degraded grassland indicator plants in the study area and classifying the degradation degree; The indicator plant is Stellaria chamaejasme; the study on the characteristics of the degraded grassland indicator plants specifically comprises the following steps: firstly, conducting a sample survey in the degraded grassland area; then, analyzing the plant physiological and biochemical phenotype indexes in each survey sample in the study area to find out the different growth distribution characteristics of Stellaria chamaejasme in the study area; finally, classifying the degradation degree of the grassland according to the growth distribution characteristics of Stellaria chamaejasme on the ground, the density, and combining the reduction amount of the original plant community, the vegetation coverage and the grass type; S3, analyzing the geological mechanism of grassland degradation, including analyzing the influence of topography on the distribution of the indicator plants and the synergistic or antagonistic main control factors of the sedimentary facies change on the growth of the indicator plants; The method for analyzing the influence of topography on the distribution of Stellaria chamaejasme comprises the following steps: combining the DEM elevation data of the study area, using the raster surface analysis, spatial analysis tool, generalized additive model and statistical analysis means of Origin to identify the response relationship between topography and the distribution of Stellaria chamaejasme; specifically comprising: 1) identification and extraction of topographic factors: according to the DEM elevation data with a resolution of 1 meter in the study area, using the 3D raster surface analysis module of ArcGIS to extract 5 topographic index parameter factors for the spatial distribution correlation analysis of the indicator plants in the study area, which are elevation, slope, aspect, plan curvature and profile curvature; 2) analysis of the response relationship between topography and the distribution of Stellaria chamaejasme: according to the parameter superposition of the sample survey, the biomass of Stellaria chamaejasme is estimated, the topographic response generalized additive model is constructed according to the above-ground biomass data of Stellaria chamaejasme, the Spline function is used for fitting, and the contribution value of different topographic variables is calculated; S4, constructing a grassland degradation model based on the sedimentary facies constraint under similar habitat conditions based on the geosciences concept; S5, indoor grass species screening based on drought resistance coefficient; S6, planting in the demonstration area mixing tank, and proposing a comprehensive management method for degraded grassland.

2. A method of rehabilitating a degraded grassland according to claim 1, wherein, The identification of the different sedimentary facies structure characteristics of the vertical strata in the study area refers to finding out the different sedimentary facies structure characteristics of the study area under similar climate conditions by studying the sedimentary environment and climate characteristics in the study area, and identifying different sedimentary facies structure units by using the nearest neighbor propagation clustering algorithm and according to the curve kurtosis, distribution interval and transport mode.

3. The method of claim 1, wherein, The sample survey specifically comprises the following steps: according to the different Stellaria chamaejasme growth density, ground plant combination and soil parent material type, selecting a representative site to arrange the sample survey, and focusing on measuring the plant number, maximum, minimum and average individual branch number, maximum, minimum and average plant height, base coverage, total coverage and total vegetation coverage of Stellaria chamaejasme in the sample; the plant physiological and biochemical phenotype index refers to the plant number, individual branch number, plant height, total coverage, Stellaria chamaejasme coverage and Stellaria chamaejasme base coverage.

4. The method of claim 1, wherein, The analysis of the synergistic or antagonistic master factors of the deposition facies change affecting the growth of the indicator plant includes the analysis of the response relationship between loose sediment particle size and the growth distribution of the plant, the response relationship between loose sediment moisture characteristics and the plant, and the influence of loose sediment element geochemical processes on the plant.

5. A method of rehabilitating a degraded grassland according to claim 4, wherein, The analysis of the response relationship between loose sediment particle size and the growth distribution of the plant is to identify the main influencing factors of the soil physical properties of the growth distribution of the plant by studying the soil particle size grading characteristics and the different deposition facies differentiation characteristics based on the AP clustering algorithm, and analyzing the correlation degree of the distribution characteristics of the indicator plant.

6. A method of rehabilitating a degraded grassland according to claim 5, wherein, The analysis of the response relationship between loose sediment moisture characteristics and the plant is to reveal the ecological hydrological processes from bottom to top in the vertical profile by analyzing the regional shallow groundwater depth and water chemical characteristics and the capillary water rising characteristics of different deposition facies, and to reveal the ecological hydrological processes from top to bottom in the vertical profile by analyzing the soil water and precipitation infiltration relationship, so as to study the water response relationship between the soil water and the plant.

7. A method of rehabilitating a degraded grassland according to claim 6, characterised in that, The analysis of the influence of loose sediment element geochemical processes on the plant is to analyze the element characteristics and vertical migration and aggregation rules of different deposition facies by using multivariate statistics, mass transfer coefficient, principal component analysis and system clustering tree method, and to analyze the ecological geochemical characteristics and distribution control from the geochemical processes.

8. The method of claim 1, wherein, The construction of the grassland degradation model is to take the rhizosphere layer soil in the vertical stratum of the deposition facies structure, the roots and leaves of the indicator plant in different growth areas of the plant as the research objects, to analyze the element migration and enrichment characteristics, geochemical behavior and influencing factors between the soil and the plant, to find out the element migration and aggregation rules of the deposition facies geochemistry and the distribution response characteristics of the indicator plant, to explore and analyze the ecological hydrological processes and geochemical processes affected by the spatial heterogeneity of the deposition facies, and to construct the grassland degradation model under similar habitat conditions based on the geoscience concept and the influence of multiple factors. The indoor grass seed screening based on the drought resistance coefficient is to select the sandy soil in the accumulation deposition facies structure with the worst soil nutrient condition as the grass seed culture soil, to do the pot culture simulation drought test under the greenhouse condition, and to screen the pasture suitable for the study area.

9. The method of claim 1, wherein, The planting in the demonstration area mixing tank is to take the drought-resistant grass seed screened out by the greenhouse pot culture simulation drought test as the test material to do the test in the demonstration area, to take the accumulation deposition facies with the strongest degradation and the accumulation deposition facies with the lightest degradation as the two end members representing the degradation degree of the grassland in the study area, to establish the demonstration area in the two areas respectively, to plant the grass seed screened out by the indoor cultivation experiment in the demonstration area, to do the comparative test of different mixing ratios of artificial planting of the grass seed, and to find out the best grass seed mixing planting mode suitable for the vegetation restoration in the degraded soil area in the study area.

10. A method of reclamation of a degraded grassland according to any one of claims 1 to 9, characterized in that, ​

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