A degenerated alpine meadow grading management method based on Ligularia virgaurea invasion strategy

Abstract

The application discloses a degradation alpine meadow grading management method based on Ligusticum mutellina invasion strategy, relates to the technical field of agricultural management, and comprises the following steps: determining a management reference index of an alpine meadow to be managed; the management reference index comprises a plant community diversity index and a soil physical and chemical property index; the plant community diversity index comprises a Patrick index, a Shannon-Wiener index, an important value of Ligusticum mutellina and a species number; determining a degradation grade of the alpine meadow to be managed according to the management reference index and grading standards; the degradation grade is divided into a mild degradation type, a moderate degradation type or a severe degradation type; and corresponding grading management measures are carried out according to the degradation grade of the alpine meadow to be managed, and the application is based on the grading precise management of the invasion strategy of deep nitrogen mineralization driving of Ligusticum mutellina.

Description

Technical Field

[0001] This application relates to the field of agricultural management technology, and in particular to a graded management method for degraded alpine grasslands based on the invasion strategy of Ligustrum lucidum. Background Technology

[0002] In recent years, the alpine grasslands of the Sanjiangyuan region have suffered severe degradation, forming large areas of secondary bare "black soil beaches," with the invasion of poisonous weeds being one of the key driving factors. *Ligularia virgaurea*, a typical poisonous weed, has rapidly expanded in degraded grasslands, severely inhibiting the growth of high-quality forage grasses, leading to a decline in biodiversity and degradation of ecosystem functions. Currently, there is a lack of systematic and targeted methods for controlling the invasion of *Ligularia virgaurea*. Traditional single-measures (such as simple mowing or fertilization) are ineffective and may even exacerbate nutrient imbalances. Therefore, a tiered and precise control technology based on its invasion mechanism is urgently needed. Summary of the Invention

[0003] The purpose of this application is to provide a graded management method for degraded alpine grassland based on the invasion strategy of Ligustrum lucidum. Based on the invasion strategy of Ligustrum lucidum driven by deep nitrogen mineralization, measures are designed to address the core contradictions of different degradation stages (mild: resource grabbing; moderate: positive feedback of deep nitrogen pump; severe: system collapse), making the management highly targeted.

[0004] To achieve the above objectives, this application provides the following solution.

[0005] This application provides a hierarchical management method for degraded alpine grasslands based on the invasion strategy of Ligustrum lucidum, including: Determine the reference indicators for the treatment of alpine grasslands; the reference indicators include plant community diversity indicators and soil physicochemical properties indicators; the plant community diversity indicators include Patrick index, Shannon-Wiener index, importance value of Ligustrum lucidum and species number; The degradation level of the alpine grassland to be treated is determined according to the governance reference indicators and grading standards; the degradation level is divided into mild degradation, moderate degradation or severe degradation. Based on the degradation level of the alpine grassland to be treated, corresponding graded treatment measures shall be implemented.

[0006] Optionally, soil physicochemical properties include soil organic carbon, total nitrogen, LAP enzyme activity, carbon-nitrogen ratio, and ammonium nitrogen; The grading criteria are as follows: Mildly degraded type: Patrick index ≥8, Shannon-Wiener index ≥1.7, Ligustrum lucidum importance value <0.35, soil organic carbon ≥40g / kg, total nitrogen ≥3.5g / kg; Moderate degradation type: 6 < Patrick index < 8, 1.3 < Shannon-Wiener index < 1.7, 0.35 < Ligularia virgaurea importance value < 0.60, the increase amplitude of LAP enzyme activity is greater than the set value, and carbon-nitrogen ratio < 10.5; Severe degradation type: Patrick index ≤ 6, Shannon-Wiener index ≤ 1.3, Ligularia virgaurea importance value > 0.60, number of species ≤ 6, and ammonium nitrogen ≤ 1.0 mg / kg.

[0007] Optionally, the control measures for the mild degradation type include: Oversowing high-quality shallow-rooted forages: mix Elymus nutans and Festuca sinensis at a mass ratio of 2:1, the sowing rate is 40–60 seeds per square meter, perform drill sowing in autumn with a row spacing of 20 cm and a sowing depth of 1–2 cm; Light mowing suppression: at the early flowering stage of Ligularia virgaurea, mow with a stubble height of 5 cm, and remove the mowed materials from the sample plot; No nitrogen fertilizer application: if the total soil nitrogen is less than 3.2 g / kg, supplement 3 tons of decomposed sheep manure per hectare at one time.

[0008] Optionally, the control measures for the moderate degradation type include: Deep plowing + shallow-rooted plant reconstruction: when the soil water content is 15%–25% in autumn, perform deep plowing to 20–25 cm; then perform cross drill sowing to oversow grasses and leguminous plants; Phosphorus fertilizer regulation: after deep plowing, apply 85–100 kg of superphosphate per hectare at one time; Selective suppression: at the green-up stage of Ligularia virgaurea, directionally spray a glufosinate-ammonium aqueous solution with an effective concentration of 0.3%.

[0009] Optionally, the grasses are a mixture of Elymus nutans and Poa crymophila at a mass ratio of 3:1, with a sowing rate of 50–70 seeds per square meter; the leguminous plants are Medicago ruthenica or Medicago falcata, with a sowing rate of 20–30 seeds per square meter.

[0010] Optionally, the control measures for the severe degradation type include complete eradication of Ligularia virgaurea, soil improvement and organic fertilization, multi-layer vegetation reconstruction, and directional microbial recovery; The complete eradication of Ligularia virgaurea is as follows: at the vigorous growth stage of Ligularia virgaurea, spray a glufosinate-ammonium aqueous solution with an effective concentration of 0.5%, with an eradication rate ≥ 90%, and manually dig out the missed-sprayed or newly grown plants 15 days later; The soil improvement and organic fertilization are as follows: after eradication, apply 15–20 tons of decomposed sheep manure or peat soil per hectare, perform deep plowing to 25–28 cm, and apply a phosphate-solubilizing bacterial agent; The multi-layer vegetation reconstruction is as follows: perform broadcast sowing of oats as pioneer plants in the autumn of the first year; perform drill sowing of the grass combination and broadcast sowing of leguminous plants in the spring of the second year; Microbial targeted restoration involves mixing the topsoil from adjacent undegraded alpine meadows with fine sand at a ratio of 3:1 in the spring of the second year, spreading the mixture evenly over the restoration area, and then performing shallow rotary tillage.

[0011] Optionally, the phosphate-solubilizing agent is a mixture of Bacillus subtilis and Bacillus megaterium in a 1:1 live bacteria ratio, with an effective live bacteria count ≥ 2 × 10⁻⁶. 8 The dosage is 30–40 kg of inoculum powder per hectare or 6–8 L of liquid inoculum per hectare, at a rate of CFU / g.

[0012] Optionally, the grass combination is *Leymus chinensis*, *Poa qinghaiensis*, and *Poa glabra*, with a seeding rate of 50–70 seeds per square meter; the legume is *Alfalfa* and *Vicia sativa*, with a seeding rate of 20–30 seeds per square meter.

[0013] Optionally, the method for graded management of degraded alpine grasslands based on the invasion strategy of Ligularia zebrina further includes: After implementing the corresponding graded management measures, long-term maintenance and monitoring are carried out: monitoring plant community diversity and key soil indicators during the peak growing season each year; if the importance value of Ligustrum lucidum increases for two consecutive years, the management measures are upgraded; if the available phosphorus in the soil remains below 8 mg / kg, phosphate fertilizer is applied once every 3 years; if the leucine aminopeptidase activity is abnormally increased and the soil carbon-nitrogen ratio is <10, a 20 cm deep tillage is carried out.

[0014] Optionally, the method for graded management of degraded alpine grasslands based on the invasion strategy of Ligularia zebrina further includes: After implementing corresponding graded management measures, grazing bans are set according to the degradation level: grazing bans for 1 year in lightly degraded areas, 2 years in moderately degraded areas, and 3-4 years in severely degraded areas; once the vegetation cover stabilizes at over 85% and the proportion of grasses exceeds 60%, light seasonal grazing is resumed, with the carrying capacity controlled at 1.5-2.0 sheep units per hectare.

[0015] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a graded management method for degraded alpine grasslands based on the invasion strategy of *Ligularia cirrhosa*. For the first time, it utilizes *Ligularia cirrhosa*'s "deep nitrogen mineralization-driven" invasion strategy and designs measures targeting the core contradictions at different degradation stages (mild: resource extraction; moderate: positive feedback from deep nitrogen pumps; severe: system collapse). The management is highly targeted. Based on the revelation of *Ligularia cirrhosa*'s "deep nitrogen mineralization-driven" invasion strategy under different degradation levels, a graded management approach is proposed. Degradation levels are determined through key ecological indicators, and management measures—competitive substitution, interruption of positive feedback from deep nitrogen pumps, and system reconstruction—are adopted for mild, moderate, and severe degraded grasslands, respectively, to achieve efficient and sustainable ecological restoration. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 A flowchart illustrating a graded management method for degraded alpine grassland based on the invasion strategy of Ligularia zebrina, provided as an embodiment of this application; Figure 2 A schematic diagram of the underground biomass of *Ligularia glomerata* provided for an embodiment of this application; Figure 3 This is a schematic diagram of principal component analysis of a soil system under the invasion of Ligularia rubra var. ... Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] In one exemplary embodiment, such as Figure 1 As shown, a hierarchical management method for degraded alpine grassland based on the invasion strategy of Ligularia zebrina is provided. The method includes the following steps S1 to S3.

[0020] S1, determine the reference indicators for the treatment of alpine grasslands to be treated; the reference indicators include plant community diversity indicators and soil physicochemical properties indicators; the plant community diversity indicators include Patrick index, Shannon-Wiener index, importance value of Ligustrum lucidum and number of species.

[0021] S2. Determine the degradation level of the alpine grassland to be treated based on the governance reference indicators and grading standards; the degradation level is divided into mild degradation, moderate degradation or severe degradation.

[0022] S3, corresponding graded management measures are implemented based on the degradation level of the alpine grassland to be managed.

[0023] Implementing steps S1 to S3 above, for the first time, based on the invasion strategy of *Ligustrum lucidum* driven by deep nitrogen mineralization, measures are designed to address the core contradictions at different degradation stages (mild: resource extraction; moderate: positive feedback of deep nitrogen pumps; severe: system collapse). The governance is highly targeted. Based on the revelation of the invasion strategy of *Ligustrum lucidum* driven by deep nitrogen mineralization at different degradation levels, a graded governance method is provided. This method determines the degradation level through key ecological indicators and adopts governance measures such as competitive substitution, interruption of positive feedback of deep nitrogen pumps, and system reconstruction for mild, moderate, and severe degraded grasslands, respectively, to achieve efficient and sustainable ecological restoration.

[0024] The following study focuses on mildly, moderately, and severely degraded alpine grasslands in Junmuchang, Maqin County, Guoluo Prefecture, Qinghai Province, on the eastern edge of the Qinghai-Tibet Plateau. Sample plots with *Ligularia zebrina* as the dominant poisonous weed were selected. Soil samples were collected, and the physicochemical properties of the soil and the extracellular enzyme activity of microorganisms were measured. High-throughput sequencing was used to analyze the diversity of bacteria and fungi. Based on comprehensive statistical analysis, targeted management methods were proposed for the *Ligularia zebrina* sample plots, providing a reference for future management of similar degraded sample plots.

[0025] Junchangmu Village in Maqin County, Guoluo Prefecture, Qinghai Province, was selected as the experimental site. With an average altitude of 4000 m, it has a typical continental plateau monsoon climate. The main vegetation type at the experimental site is degraded alpine grassland ("black soil beach"), and the soil is alpine meadow soil. This study site is representative, and the results are applicable to the restoration and management of alpine meadows at altitudes below 2000–5000 m in Qinghai Province, particularly black soil beaches dominated by *Ligularia zebrina*.

[0026] When determining the reference indicators for restoration, a sample plot survey method was adopted, using space to represent time. Degraded sample plots with *Ligularia zebrina* as the dominant species were selected, and three types of sample plots (degradation levels) were set up according to the degree of degradation: slightly degraded, moderately degraded, and severely degraded. Four replicates were set up in the same degree of degradation of the alpine grassland to be restored, for a total of 12 sample plots. The sample plot area was 1m × 1m.

[0027] The quadrat method was used to conduct community surveys during the peak of the growing season. The species composition of the community was investigated within the quadrats, specifically including species type, number, height, cover, total cover of the quadrat, and species sub-cover. Underground biomass was measured using the root-drilling and water-washing method. Within the small quadrats where biomass was harvested, soil samples were collected in layers at depths of 0-10cm, 10-20cm, and 20-30cm, with three samples collected from each layer. The samples were mixed, stored in cloth bags, and brought back to the laboratory. A portion of the fresh soil was stored at 4°C for determining soil enzyme activity and microbial indicators, while another portion was air-dried in a cool, shaded place for determining soil physicochemical properties.

[0028] For each quadrat of the alpine grassland to be treated, all species present were recorded, and the height (average of 5 plants), canopy coverage, number of plants, and total canopy coverage of each species were measured. Importance values ​​were calculated using three metrics: relative canopy coverage, relative height, and relative number of plants. (Importance value is a core quantitative indicator used to comprehensively measure the status and role of a plant species in the community. Its fundamental significance lies in using a single numerical value to calculate the "relative dominance" of a species.) The formula is: Importance value = (relative canopy coverage + relative height + relative number of plants) / 3; where: relative canopy coverage = species canopy coverage / total quadrat canopy coverage; relative height = average height of species / sum of average heights of all species in the quadrat; relative number of plants = number of plants of a species / total number of plants in the quadrat.

[0029] Then calculate the relative importance value of *Ligularia gloriosa* ( (i.e., the proportion of the importance value of this species to the sum of the importance values ​​of all species in the quadrat), and calculate the diversity indices, including the Patrick index (i.e., the Patrick richness index), the Shannon-Wiener index (i.e., the Shannon-Wiener diversity index), the Simpson dominance index, and the Pielou evenness index.

[0030] Patrick exponent: R = S; where This represents the number of species within the quadrat.

[0031] The formula for calculating the Shannon-Wiener index is as follows: ; in, The Shannon-Wiener diversity index, For species The importance value.

[0032] The formula for calculating the Simpson dominance index is as follows: ; in, This is the Simpson dominance index.

[0033] The formula for calculating the Pielou uniformity index is as follows: ; in, This is the Pielou uniformity index.

[0034] Soil samples were taken from the sample plots of alpine grassland to be treated, air-dried, and passed through a 2mm soil sieve to remove coarse roots and gravel. The samples were then pulverized and set aside. The methods for determining the soil physicochemical properties are as follows: Soil pH: determined using a pH meter (soil-water ratio 1:2.5); Soil organic carbon (SOC): determined using the potassium dichromate oxidation-external heating method; Total nitrogen (TN): determined using the Kjeldahl method; Total phosphorus (TP): determined using the molybdenum-antimony colorimetric method (sulfuric acid-perchloric acid digestion); Ammonium nitrogen (NH4+)... + -N): determined by potassium chloride extraction-indophenol blue colorimetric method; nitrate nitrogen (NO3) - -N): determined by potassium chloride extraction-ultraviolet spectrophotometry; available phosphorus (AP): determined by sodium bicarbonate extraction-molybdenum antimony colorimetric method; soluble organic carbon (DOC): determined by deionized water extraction-TOC analyzer; and the activities of five soil extracellular enzymes were determined by microplate fluorescence analysis.

[0035] The specific microbial analysis methods are as follows: (1) Soil microbial DNA extraction: Soil microbial total DNA was extracted using a soil DNA extraction kit. The integrity and purity of the DNA were detected by 1% agarose gel electrophoresis, and the concentration and purity of the DNA were detected by NanoDropOne.

[0036] (2) PCR amplification and sequencing: bacterial 16S rRNA gene amplification: primer pair 515F (5'-GTGCCAGCMGCCGCGGTAA-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3') were used to amplify the V4 region.

[0037] Fungal ITS amplification: ITS1 region was amplified using primer pairs ITS1F (5'-CTTGGTCATTTAGAGGAAGTAA-3') and ITS2R (5'-GCTGCGTTCTTCATCGATGC-3').

[0038] After purification and quantification, PCR products were used to construct sequencing libraries, and high-throughput sequencing was performed using the Illumina HiSeq 2500 platform. Sequencing was completed by Guangdong Megagene Technology Co., Ltd.

[0039] (3) Bioinformatics analysis: The raw sequencing data were spliced, quality controlled, and dechimeric to obtain valid sequences. OTUs (Operational Taxonomic Units) were obtained by clustering with 97% similarity using USEARCH software. Bacterial species were annotated using the Greengenes database (v13.8), and fungal species were annotated using the UNITE database (v7.2). The plant community diversity indices of *Ligularia zebrina* under different degradation levels are shown in Table 1.

[0040] Table 1. Plant community diversity index of Ligustrum lucidum under different degrees of degradation

[0041] As can be seen from Table 1, with the increase in the degree of degradation, the number of species (Patrick index) and Shannon diversity index of the dominant communities of the three types of poisonous plants showed a significant downward trend, while the Simpson dominance index (reflecting the concentration of dominant species) increased and the Pielou evenness index decreased. Taking *Ligularia spp.* as an example, in the case of mild degradation, the number of species reached 9.3 ± 0.8, and the Shannon-Wiener index was 1.89 ± 0.11, indicating a relatively rich and even community composition. In the case of moderate degradation, the number of species decreased to 7.8 ± 1.0, the Shannon-Wiener index decreased to 1.56 ± 0.15, and the Simpson index increased to 0.69 ± 0.05, indicating an increased dominance of poisonous weeds. In the case of severe degradation, the number of species was only 5.8 ± 0.8, the Shannon-Wiener index decreased to 1.21 ± 0.13, and the Simpson index increased to 0.58 ± 0.06, indicating a trend towards homogenization of the community structure, with poisonous weeds becoming the absolutely dominant species. These results indicate that the invasion of poisonous weeds significantly alters the community structure of alpine grassland plants. With increasing invasion intensity, species diversity is lost, community evenness decreases, and the dominance of dominant species continuously strengthens.

[0042] like Figure 2 As shown, the underground biomass of *Ligularia zebrina* is relatively evenly distributed across the three soil layers, with a considerable proportion remaining in the deeper layers (20-30 cm). This uniform deep-root distribution forms the structural basis of *Ligularia zebrina*'s "deep nitrogen pump" strategy: the relatively developed deep root system can explore and acquire deep water and nutrients inaccessible to shallow-rooted plants, and activate microbial activity in the deeper soil through root exudates, particularly stimulating nitrogen mineralization (LAP activity is abnormally elevated in the deeper layers). *Ligularia zebrina* achieves a mechanism of "pumping" deep nitrogen pools into the plant body by absorbing mineralized inorganic nitrogen, thus altering the traditional distribution of nitrogen in the soil profile. This strategy allows it to maintain its advantage in the later stages of invasion due to its unique ability to acquire deep resources, but it also poses a long-term threat to the depth stability of the soil nitrogen pool. The soil physicochemical properties and enzyme activity characteristics of *Ligularia zebrina* under different degrees of degradation are shown in Table 2.

[0043] Table 2. Soil physicochemical properties and enzyme activity characteristics of Ligustrum lucidum under different degrees of degradation.

[0044] BG represents -1,4-glucosidase, NAG represents... -1,4-N-acetylglucosidase; CGH represents cellobiose hydrolase; LAP represents leucine aminopeptidase.

[0045] As shown in Table 2, the soil's basic nutrient pool exhibits characteristics of "nitrogen depletion, carbon loss, and decreased phosphorus availability" with increasing degradation. Total nitrogen content decreased continuously from 3.84 g / kg in mildly degraded areas to 2.77 g / kg in severely degraded areas (a decrease of 27.9%), while ammonium nitrogen content decreased sharply from 3.06 mg / kg to 0.80 mg / kg (a decrease of 73.9%), indicating a severe shrinkage of the soil's active nitrogen pool. Organic carbon content decreased from 47.12 g / kg to 30.29 g / kg (a decrease of 35.7%), reflecting a decline in soil carbon sequestration capacity. The total phosphorus content did not decrease significantly (0.59→0.63 g / kg), but the available phosphorus decreased significantly after moderate degradation (20.46→10.21 mg / kg, a decrease of nearly 50%). The bioavailability of phosphorus became a key limiting factor, which was confirmed by the surge in alkaline phosphatase (ALP) activity during severe degradation (315.88→417.03 mg / g, an increase of 32.0%). Microorganisms had to synthesize large amounts of ALP to "plunder" phosphorus from organic phosphorus.

[0046] The effects of *Ligularia zebrina* were as follows: the activities of carbon-acquired enzymes (BG, NAG, CBH) remained stable or increased in the surface layer (0-10 cm) with increasing invasion intensity, but were inhibited in the middle and deeper layers (10-30 cm). The activities were higher in mild invasion than in moderate and severe invasion, indicating that severe invasion of *Ligularia zebrina* significantly inhibited carbon cycling processes in deeper soil layers. Most notably, the response of LAP (lower root exudate) was observed: under moderate invasion conditions, LAP activity significantly increased with soil depth, contrary to conventional understanding (activity decreases with depth), indicating that nitrogen mineralization processes in deeper soil layers were specifically activated. This anomalous distribution may stem from the stimulation of deep root exudates from *Ligularia zebrina*, or moderate invasion may have created a specific microbial community structure that preferentially invests in the decomposition of organic nitrogen to obtain nitrogen.

[0047] like Figure 3As shown, the sample points of *Ligularia zebrina* are separated in the ordination space according to the degree of invasion, with moderately invaded samples forming relatively independent clusters far from other groups. The PC1 axis (51.8%) depicts a continuous spectrum from "eutrophic-high C and N metabolism" (right side) to "oligotrophic-high nitrogen mineralization emergency state" (left side), with the LAP arrow pointing to the left, opposite to the core nutrient pool and carbon cycling enzymes. The strong leftward shift of moderately invaded samples confirms the conclusion that "moderate invasion activates deep LAP," consistent with the negative correlation between LAP and C / N ratio in the heatmap. The PC1 axis indicates that *Ligularia zebrina* does not simply increase or decrease all indicators, but rather drives the system as a whole to slide towards a new functional state marked by "high nitrogen mineralization emergency response," antagonizing the basic nutrient enrichment state, exhibiting a threshold effect for state transition. *Ligularia zebrina* can therefore be regarded as an "ecosystem reconstructor."

[0048] In summary, the core mechanism of *Ligularia zebrina* invasion is the specific activation of deep soil nitrogen mineralization. Its relatively uniform root distribution leads to an abnormal increase in deep soil nitrogen saturation (LAP) activity under moderate invasion. The negative correlation between LAP and the C / N ratio indicates that *Ligularia zebrina* meets its own nitrogen requirements by promoting nitrogen mineralization and altering soil stoichiometry. PCA analysis shows a shift towards a "high nitrogen mineralization emergency state," exhibiting a threshold effect. Regarding the microbial community, the highest number of bacterial-specific OTUs were observed, with enrichment of nitrogen-fixing bacteria such as *Methylobacterium* and basidiomycete mycorrhizal fungi, primarily driven by carbon and nitrogen factors. As a "reconstructor," *Ligularia zebrina* poses a long-term threat to the depth stability of the soil nitrogen pool by altering nutrient supply depth and activating deep nitrogen cycling.

[0049] Based on the invasion strategies of *Ligularia zebrina* under different degrees of degradation and its differentiated impacts on soil nutrient pools, microbial communities, and enzyme activity, this application proposes a graded management method. This method classifies alpine grasslands into three degradation levels: slightly degraded, moderately degraded, and severely degraded, and then adopts targeted graded management measures (ecological restoration measures) for each level. The grading criteria are shown in Table 3.

[0050] Table 3 Grading Standards

[0051] Soil physicochemical properties include soil organic carbon, total nitrogen, LAP enzyme activity, carbon-nitrogen ratio, and ammonium nitrogen; The grading criteria are as follows: 1) Mildly degraded type: Patrick index ≥8, Shannon-Wiener index ≥1.7, Ligustrum lucidum importance value <0.35, soil organic carbon ≥40g / kg, total nitrogen ≥3.5g / kg; 2) Moderate degradation type: 6 < Patrick index < 8, 1.3 < Shannon-Wiener index < 1.7, 0.35 < Ligularia virgaurea importance value < 0.60, the increase range of LAP enzyme activity is greater than the set value (i.e., LAP enzyme activity increases significantly), and carbon-nitrogen ratio < 10.5; 3) Severe degradation type: Patrick index ≤ 6, Shannon-Wiener index ≤ 1.3, Ligularia virgaurea importance value > 0.60, number of species ≤ 6, and ammonium nitrogen ≤ 1.0 mg / kg.

[0052] (1) Light degradation type: Block resource appropriation at the initial stage of invasion. Core strategy: Before Ligularia virgaurea forms a driving mechanism for deep nitrogen mineralization, its expansion is inhibited by competitive substitution and surface resource regulation.

[0053] The control measures for the light degradation type include oversowing high-quality shallow-rooted forage, light mowing inhibition, and no nitrogen fertilizer application.

[0054] 1) Oversowing high-quality shallow-rooted forage: Forage species selection: Elymus nutans (germination rate ≥ 85%) and Festuca sinensis (germination rate ≥ 80%), mixed at a mass ratio of 2:1.

[0055] Sowing rate: 40–60 seeds per square meter (approximately 2.5–3.5 g / m 2 ).

[0056] Sowing time: Autumn (mid-late September to early October), with surface temperature ≥ 5°C.

[0057] Sowing method: Drill sowing, with row spacing of 20 cm, sowing depth of 1–2 cm, and light harrowing for soil covering after sowing.

[0058] The specific measures for oversowing high-quality shallow-rooted forage are: mixing Elymus nutans and Festuca sinensis at a mass ratio of 2:1, with a sowing rate of 40–60 seeds per square meter, and performing drill sowing in autumn at a row spacing of 20 cm and a sowing depth of 1–2 cm.

[0059] 2) Light mowing inhibition: Time: The pre-flowering stage of Ligularia virgaurea (July 15 to July 25, depending on the accumulated temperature of the current year). Stubble height: 5 cm (to ensure that the tillering nodes of grasses are not damaged). Mowing residue treatment: Spread the mowed materials on the spot for 2 days, then collect and transport them out of the sample plot to avoid nutrient return.

[0060] The specific measures for light mowing inhibition can be: mowing at a stubble height of 5 cm in the pre-flowering stage of Ligularia virgaurea, and removing the mowed materials out of the sample plot; 3) No nitrogen fertilizer application: The application of any nitrogen-containing chemical fertilizers or organic fertilizers is strictly prohibited. If the total nitrogen in the soil is <3.2 g / kg (close to the threshold), well-rotted sheep manure can be added (3 tons per hectare, applied only once), but this must be strictly controlled; in this case, 3 tons of well-rotted sheep manure should be added per hectare at a time. Key results after implementing remediation measures for mildly degraded soil are shown in Table 4.

[0061] Table 4 Key Results After Implementation of Governance Measures for Mildly Degraded Types

[0062] (2) Moderately degraded type: Disrupt the positive feedback of the "deep nitrogen pump". The core strategy is that moderate degradation is the key stage in which the "deep nitrogen mineralization driving mechanism" of Ligustrum lucidum is activated (LAP activity is abnormally increased in the deep layer, and PCA shows that the system is shifting towards the "high nitrogen mineralization emergency state"). The focus of the treatment is to disrupt the positive feedback of the deep nitrogen pump and weaken its nutrient acquisition advantage.

[0063] Management measures for moderately degraded plants include deep tillage combined with shallow-rooted plant restoration, phosphorus fertilizer regulation, and selective inhibition.

[0064] 1) Deep plowing + shallow root plant reconstruction: Deep plowing time: autumn (early to mid-October), when the soil moisture content is 15%–25%; Deep plowing depth: 20–25 cm (the root network of Ligustrum lucidum below 20 cm must be cut off); Deep plowing equipment: moldboard plow or disc harrow, with matching tractor power ≥ 50 horsepower.

[0065] Reseeding grass seed mix: Grasses: Winged Leymus chinensis + Kentucky bluegrass (Poa crymophila), weight ratio 3:1. Legumes: Medicago ruthenica or Medicago falcata.

[0066] Seeding rate: 50–70 seeds of grass per square meter (3.5–5.0 g / m²) 2 Leguminosae: 20–30 seeds per square meter (1.0–1.5 g / m²) 2 ).

[0067] Sowing method: cross row sowing (row spacing 15 cm, sowing once in each direction), cover with 1 cm of soil after sowing.

[0068] The specific measures for deep plowing and shallow-rooted plant reconstruction can be as follows: when the soil moisture content is 15%–25% in autumn, plow to a depth of 20–25 cm; then, cross-sow grasses and legumes. The grasses are a mixture of creeping wheatgrass and Kentucky bluegrass in a mass ratio of 3:1, with a seeding rate of 50–70 seeds per square meter; the legumes are alfalfa or yellow alfalfa, with a seeding rate of 20–30 seeds per square meter.

[0069] 2) Phosphate fertilizer regulation: Fertilizer type: superphosphate (P2O5≥ 12%, free acid≤ 5.5%).

[0070] Application rate: 85–100 kg per hectare (10–12 kg / hm of pure P2O5) 2 ).

[0071] Application time: Apply immediately after deep tillage and mix with the topsoil.

[0072] Application cycle: Apply only once and do not repeat to avoid phosphorus fixation.

[0073] Specific measures for phosphate fertilizer regulation include: applying 85–100 kg of superphosphate per hectare in a single application after deep plowing.

[0074] 3) Selective inhibition: Chemical: Glufosinate (200 g / L aqueous solution of active ingredient).

[0075] Dilution concentration: 0.3% of active ingredient (i.e., 1.5 L of reagent per 100 L of water).

[0076] Application rate: 1.5–2.0 L of pesticide per hectare (diluted with 600–800 L of water).

[0077] Application time: Spray during the greening period of Ligustrum lucidum (May 20 – June 5), when the temperature is 15–25℃ and the wind speed is <3.

[0078] Spraying method: directional spraying, avoiding the emergence points of reseeded pasture (if the reseeded pasture has already emerged, use a protective cover).

[0079] Selective suppression measures include: applying a 0.3% effective concentration of glufosinate-ammonia aqueous solution during the greening stage of *Ligularia zebrina*. Key results after implementing control measures for moderately degraded plants are shown in Table 5.

[0080] Table 5 Key Results After Implementation of Governance Measures for Moderately Degraded Areas

[0081] (3) Severely degraded type: Reconstruct the soil-microbe-vegetation system. The core strategy is that in the severe degradation stage, the species are extremely homogeneous (number of species ≤ 6), the soil active nitrogen pool is severely shrunken (ammonium nitrogen ≤ 0.80 mg / kg), and organic carbon loss exceeds 35%. The system has slid into an "oligotrophic-high nitrogen mineralization emergency state". Natural recovery is extremely difficult and habitat reconstruction is required.

[0082] Severe degradation control measures include complete eradication of Ligustrum lucidum, soil improvement and organic fertilization, multi-layered vegetation reconstruction, and targeted microbial restoration.

[0083] 1) To completely eradicate Ligustrum lucidum: During the vigorous growth period of Ligustrum lucidum, spray with glufosinate-ammonium aqueous solution with an effective concentration of 0.5%, with an eradication rate of ≥90%. After 15 days, manually dig up any missed spraying or newly grown plants.

[0084] Year 1 (Forceful Extermination): Reagent: glufosinate (200 g / L aqueous solution), effective concentration 0.5% (2.5 L of reagent per 100 L of water).

[0085] Application rate: 3.0–3.5 L of pesticide per hectare (diluted with 600–700 L of water).

[0086] Time: Peak growing season (July 5th – July 15th), when the plant height of *Ligustrum lucidum* is 15–25 cm.

[0087] Number of applications: 1, with a required eradication rate of ≥90% (based on the number of plants).

[0088] Additional measures: Inspect the plants 15 days after application and manually remove any missed areas or newly grown plants (uprooting them). Second year (residual removal): Reduce the pesticide concentration to 0.3%, 1.5–2.0 L per hectare, and spray once each during the greening period (early June) and mid-growth period (late July). In autumn, manually inspect and remove all visible Ligustrum lucidum plants.

[0089] 2) Soil improvement and organic fertilization: After pest control, apply 15–20 tons of well-rotted sheep manure or peat moss per hectare, deep plow to a depth of 25–28 cm, and apply a phosphate-solubilizing agent; the phosphate-solubilizing agent is a mixture of Bacillus subtilis and Bacillus megaterium at a live bacteria ratio of 1:1, with an effective live bacteria count ≥2×10⁻⁶. 8 The dosage is 30–40 kg of inoculum powder per hectare or 6–8 L of liquid inoculum per hectare, at a rate of CFU / g.

[0090] Organic materials: well-rotted sheep manure (C / N ratio 18–22, moisture content ≤30%, free of weed seeds) or peat moss (organic matter ≥45%).

[0091] Application rate: 15–20 tons per hectare (dry weight).

[0092] Application time: After the first year of eradicating the Yellow Broom Ligustrum lucidum (mid to late August), combined with deep plowing.

[0093] Deep plowing depth: 25–28 cm (using a large moldboard plow) to break up the compacted layer of "black soil".

[0094] Phosphate-solubilizing bacterial agent: Bacterial strains: Bacillus subtilis + Bacillus megaterium, viable ratio 1:1; effective viable count: ≥2×10⁻⁶8 CFU / g; Dosage: 30–40 kg of bacterial powder per hectare (or 6–8 L of liquid bacterial agent diluted 100 times per hectare for spraying); Application method: Mix with organic fertilizer and spread evenly, then till 15 cm.

[0095] 3) The multi-layered vegetation reconstruction is as follows: oats are sown as pioneer plants in the autumn of the first year; in the spring of the second year, a combination of grasses and legumes are sown in rows; the grass combination is Leymus chinensis, Kentucky bluegrass and Kentucky bluegrass, with a sowing rate of 50-70 seeds per square meter; the legumes are alfalfa and wild pea, with a sowing rate of 20-30 seeds per square meter.

[0096] Year 1 (Pioneer Plant Establishment): Grass seed: Oat (Avena sativa, variety "Qingyan No. 1"), germination rate ≥90%.

[0097] Seeding rate: 80–100 seeds per square meter (8–10 g / m²) 2 ).

[0098] Sowing time: Sow immediately after eradicating the yellow broom thorn and tilling the land (late August to early September).

[0099] Sowing method: Broadcast the seeds, then lightly rake them and cover with 1–2 cm of soil.

[0100] Function: Quickly covers the ground surface (coverage ≥70%), suppresses annual weeds, and provides initial organic matter to the soil.

[0101] Second year (establishment of perennial communities): Grass mix: Leymus chinensis (40%), Poa pratensis cv. Qinghai (30%), and Poa pratensis cv. Qinghai (30%).

[0102] Leguminous plants: alfalfa (50%) + wild pea (Vicia amoena, 50%).

[0103] Seeding rate: 50–70 seeds of grass per square meter (4–6 g / m²) 2 Leguminosae: 20–30 seeds per square meter (1.5–2.0 g / m²) 2 ).

[0104] Sowing time: Spring (late April to early May), when the ground surface temperature is ≥5℃ after thawing.

[0105] Sowing method: Sow grasses in rows (20 cm spacing), and broadcast legumes between the grass rows, then compact the soil after sowing.

[0106] 4) Microbial targeted restoration: In the second spring, the topsoil of the adjacent undegraded alpine meadow was mixed with fine sand at a ratio of 3:1, and evenly spread on the restoration area and shallowly tilled.

[0107] Healthy soil source: nearby undegraded alpine meadow (distance ≤ 5 km), take the top 0–20 cm of soil, avoiding patches of poisonous weeds.

[0108] Soil application: 3–5 tons per hectare (fresh weight, with a moisture content of about 30%).

[0109] Application method: Mix healthy soil with fine sand in a 3:1 ratio (to improve fluidity), spread evenly on the remediation area, and then lightly till 5–8 cm.

[0110] Application time: early spring of the second year (mid to late April), simultaneously with the sowing of perennial forage grasses.

[0111] The effects of remediation in the first year are negligible, so severe degradation is generally assessed from the second year onwards. Since moderate degradation is more severe and involves more indicators than the previous two types, the key results after implementing remediation measures for severe degradation are shown in Table 6.

[0112] Table 6 Key Results After Implementation of Governance Measures for Severely Degraded Areas

[0113] This graded management method for degraded alpine grassland based on the invasion strategy of Ligustrum lucidum requires long-term maintenance and monitoring after the corresponding graded management measures are implemented: monitoring plant community diversity and key soil indicators during the peak growing season each year; upgrading management measures if the importance value of Ligustrum lucidum increases for two consecutive years; applying phosphate fertilizer every 3 years if the available phosphorus in the soil remains below 8 mg / kg; and carrying out a 20 cm deep tillage if the leucine aminopeptidase activity is abnormally high and the soil carbon-nitrogen ratio is <10.

[0114] Regardless of the tiered governance measures adopted, a long-term monitoring and adaptive management mechanism must be established. Annual monitoring indicators: During the peak growing season (August) each year, monitor plant community diversity (Patrick index, Shannon-Wiener index, Ligustrum lucidum importance value) and key soil indicators (organic carbon, total nitrogen, ammonium nitrogen, available phosphorus, LAP enzyme activity).

[0115] Dynamic adjustment: If monitoring shows that the important value of Ligustrum lucidum increases for two consecutive years, the degradation level needs to be reassessed and the treatment measures upgraded; if the available phosphorus in the soil is consistently below 8 mg / kg, phosphate fertilizer (50 kg per hectare) can be applied once every 3 years; if the LAP enzyme activity is abnormally high and the C / N ratio is <10, it indicates that the deep nitrogen pump has been reactivated, and a deep plowing (20 cm) is required to destroy the root network.

[0116] The graded management method for degraded alpine grasslands based on the invasion strategy of Ligustrum lucidum also includes: after implementing corresponding graded management measures, setting grazing ban periods according to the degradation level: grazing ban for 1 year in lightly degraded areas, grazing ban for 2 years in moderately degraded areas, and grazing ban for 3-4 years in severely degraded areas; lightly degraded areas are alpine grasslands to be managed with a degradation level of lightly degraded, moderately degraded areas are alpine grasslands to be managed with a degradation level of moderately degraded, and severely degraded areas are alpine grasslands to be managed with a degradation level of severely degraded; after the vegetation cover stabilizes at more than 85% and the proportion of grasses exceeds 60%, light seasonal grazing is restored, that is, the carrying capacity is controlled at 1.5-2.0 sheep units per hectare.

[0117] This application also provides an application scenario in which the above-mentioned method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia cirrhosa* is applied. Specifically, the method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia cirrhosa* provided in this embodiment can be applied in a graded management scenario for degraded alpine grassland. The graded management scenario for degraded alpine grassland includes a content production stage, a graded management link for degraded alpine grassland, and a post-management maintenance and monitoring stage. Requests to be processed enter the graded management link for degraded alpine grassland from the content production stage, obtain corresponding graded management measures through human-machine collaboration, and then enter the downstream post-management maintenance and monitoring stage. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia cirrhosa* provided in this embodiment belongs to the graded management link for degraded alpine grassland. Specifically, in the process of graded management of degraded alpine grassland for a request, the management reference indicators of the alpine grassland to be managed can be measured, the degradation level of the alpine grassland to be managed can be determined according to the management reference indicators and grading standards, and corresponding graded management measures can be implemented according to the degradation level of the alpine grassland to be managed.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for graded management of degraded alpine grasslands based on the invasion strategy of *Ligularia zebrina*, characterized in that, The graded management method for degraded alpine grassland based on the invasion strategy of Ligularia virgaurea comprises: Determining management reference indicators of the alpine grassland to be managed; the management reference indicators include plant community diversity indicators and soil physicochemical property indicators; the plant community diversity indicators include Patrick index, Shannon-Wiener index, Ligularia virgaurea importance value and species number; Determining the degradation grade of the alpine grassland to be managed according to the management reference indicators and grading criteria; the degradation grades are classified as light degradation type, moderate degradation type or severe degradation type; Implementing corresponding graded management measures according to the degradation grade of the alpine grassland to be managed.

2. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that, The soil physicochemical property indicators include soil organic carbon, total nitrogen, LAP enzyme activity, carbon-nitrogen ratio and ammonium nitrogen; The grading criteria are: Light degradation type: Patrick index ≥ 8, Shannon-Wiener index ≥ 1.7, Ligularia virgaurea importance value < 0.35, soil organic carbon ≥ 40 g / kg, total nitrogen ≥ 3.5 g / kg; Moderate degradation type: 6 < Patrick index < 8, 1.3 < Shannon-Wiener index < 1.7, 0.35 < Ligularia virgaurea importance value < 0.60, the increase amplitude of LAP enzyme activity is greater than the set value, carbon-nitrogen ratio < 10.5; Severe degradation type: Patrick index ≤ 6, Shannon-Wiener index ≤ 1.3, Ligularia virgaurea importance value > 0.60, species number ≤ 6, ammonium nitrogen ≤ 1.0 mg / kg.

3. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that... The management measures for the light degradation type comprise: Overseeding high-quality shallow-rooted forages: mixing Elymus nutans and Festuca sinensis at a mass ratio of 2:1, with a seeding rate of 40–60 seeds per square meter, performing strip seeding in autumn at a row spacing of 20 cm, with a seeding depth of 1–2 cm; Light mowing suppression: mowing at a stubble height of 5 cm in the early flowering stage of Ligularia virgaurea, and removing the mowed materials from the plot; No nitrogen fertilizer application: if the soil total nitrogen is less than 3.2 g / kg, supplementing 3 tons of decomposed sheep manure per hectare at one time.

4. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that, The management measures for the moderate degradation type comprise: Deep plowing + shallow-rooted plant reconstruction: performing deep plowing to 20–25 cm when the soil water content is 15%–25% in autumn; then performing cross strip seeding to overseed grasses and leguminous plants; Phosphorus fertilizer regulation: applying 85–100 kg of superphosphate per hectare at one time after deep plowing; Selective suppression: directionally spraying a glufosinate-ammonium aqueous solution with an effective concentration of 0.3% in the green-up stage of Ligularia virgaurea.

5. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 4, characterized in that... The grasses are a mixture of Elymus nutans and Poa crymophila at a mass ratio of 3:1, with a seeding rate of 50–70 seeds per square meter; the leguminous plants are Melilotoides ruthenicus or Medicago falcata, with a seeding rate of 20–30 seeds per square meter.

6. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that, The management measures for the severe degradation type comprise complete elimination of Ligularia virgaurea, soil improvement and organic fertilization, multi-layer vegetation reconstruction and directional microbial recovery; The complete elimination of Ligularia virgaurea is: spraying a glufosinate-ammonium aqueous solution with an effective concentration of 0.5% in the vigorous growth period of Ligularia virgaurea, with an elimination rate of ≥ 90%, and manually digging out the missed-sprayed or newly grown plants after 15 days; Soil improvement and organic fertilization are as follows: After eradication, apply 15-20 tons of well-rotted sheep manure or peat moss per hectare, plow deeply to a depth of 25-28 cm, and apply phosphate-solubilizing bacteria. The multi-layered vegetation reconstruction was carried out as follows: oats were sown as pioneer plants in the autumn of the first year; and grass combinations were sown in rows and legumes were sown in the spring of the second year. Microbial targeted restoration involves mixing the topsoil from adjacent undegraded alpine meadows with fine sand at a ratio of 3:1 in the spring of the second year, spreading the mixture evenly over the restoration area, and then shallowly tilling it.

7. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 6, characterized in that, The phosphate-solubilizing agent is a mixture of Bacillus subtilis and Bacillus megaterium at a live bacteria ratio of 1:1, with an effective live bacteria count ≥2×10⁻⁶. 8 The dosage is 30–40 kg of inoculum powder per hectare or 6–8 L of liquid inoculum per hectare, at a rate of CFU / g.

8. The method for graded management of degraded alpine grassland based on the invasion strategy of Ligustrum lucidum as described in claim 6, characterized in that, The grass combination consists of *Leymus chinensis*, *Poa qinghaiensis*, and *Poa glabra*, with a seeding rate of 50–70 seeds per square meter; the legumes are *Alfalfa* and *Vicia sativa*, with a seeding rate of 20–30 seeds per square meter.

9. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that, The method for graded management of degraded alpine grasslands based on the invasion strategy of Ligularia zebrina also includes: After implementing the corresponding graded management measures, long-term maintenance and monitoring are carried out: monitoring plant community diversity and key soil indicators during the peak growing season each year; if the importance value of Ligustrum lucidum increases for two consecutive years, the management measures are upgraded; if the available phosphorus in the soil remains below 8 mg / kg, phosphate fertilizer is applied once every 3 years; if the leucine aminopeptidase activity is abnormally increased and the soil carbon-nitrogen ratio is <10, a 20 cm deep tillage is carried out.

10. The method for graded management of degraded alpine grassland based on the invasion strategy of *Ligularia zebrina* as described in claim 1, characterized in that, The method for graded management of degraded alpine grasslands based on the invasion strategy of Ligularia zebrina also includes: After implementing corresponding graded management measures, grazing bans are set according to the degradation level: grazing bans for 1 year in lightly degraded areas, 2 years in moderately degraded areas, and 3-4 years in severely degraded areas; once the vegetation cover stabilizes at over 85% and the proportion of grasses exceeds 60%, light seasonal grazing is resumed, with the carrying capacity controlled at 1.5-2.0 sheep units per hectare.

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