CN115462289A

CN115462289A - Method for promoting nitrogen form transformation of degenerated alpine grassland soil

Info

Publication number: CN115462289A
Application number: CN202211110852.7A
Authority: CN
Inventors: 周华坤; 邵新庆; 李宏林; 贺有龙; 陈哲; 孙建; 邓艳芳; 尚占环; 张中华; 马丽; 杜岩功; 魏晶晶; 刘选德; 师燕; 周彦艳
Original assignee: Northwest Institute of Plateau Biology of CAS
Current assignee: Northwest Institute of Plateau Biology of CAS
Priority date: 2022-09-13
Filing date: 2022-09-13
Publication date: 2022-12-13

Abstract

The invention relates to the technical field of soil nitrogen regulation and control, in particular to a method for promoting the transformation of nitrogen form of degenerated alpine grassland soil. The method is based on the soil nitrogen nutrient utilization capacity and utilization form of the superior pasture grasses in alpine grasses at different degradation stages, and is used for respectively carrying out different nitrogen form distribution tests, different regulation and control measure intervention tests and different nitrogen preference pasture mixed sowing tests. In the process of researching and developing degraded grassland recovery, nitrogen proportioning technologies with different forms on a soil-plant interface, a promotion technology of soil nitrogen form transformation and a configuration technology of grass seeds with different nitrogen preference degrees on a species level finally promote and optimize the proportion of excellent pasture, recover grassland biomass, improve the soil nutrient condition and recover grassland productivity. In order to explore the succession law of the degeneration of the alpine grassland, the method can accumulate the experience for the stability of the alpine grassland after being implemented and also provide scientific basis and new method for the recovery and reconstruction of the degenerated alpine grassland in the three river source regions.

Description

Method for promoting nitrogen form transformation of degenerated alpine grassland soil

Technical Field

The invention relates to the technical field of soil nitrogen regulation and control, in particular to a method for promoting the transformation of nitrogen form of degenerated alpine grassland soil.

Background

Along with the interference of human factors, the alpine grassland in the three river source regions has the degradation phenomenon of different degrees. In the current research on community structures and functions in the degradation succession process of alpine grassland at different degradation stages, the succession and development change of communities are mostly simulated by replacing time gradients with spatial gradients, and the research on the long-term stability system of the mixed-seeding grassland from the aspect of the utilization efficiency of nitrogen of different plant species is less. The technical directions of the physiological life and the ecological life of the root system of perennial pasture, the utilization of soil nitrogen pathway factors of the root system, community stability on the functional group level and the like are rarely considered.

Nitrogen is a mineral nutrient element with the largest demand in the plant growth process, and is one of essential nutrient elements for the normal growth and development of plants. Nitrogen is the main limiting factor for the production level of various ecosystems including grassland ecosystems. Researches show that the nitrogen available by grassland plants is one of the most important limiting factors for limiting the productivity of grasslands in northern China, so that the researches on the nitrogen availability of a plant-soil system and the influence factors thereof are beneficial to improving the technical measures of the nitrogen availability and improving the operation and management capacity of the grasslands. The nitrogen conversion process is controlled by ecological factors such as temperature, humidity and the like, namely the change of the effective nitrogen content is determined by the environmental ecological factors, and meanwhile, the community type, the species composition and the microorganism functional group also influence the soil quality, the soil nitrogen form and the effective nitrogen content.

In order to understand the application of the nitrogen regulation and control technology in the recovery and treatment technology of the degenerated alpine grassland, the research on the technology for promoting the nitrogen form transformation of the degenerated alpine grassland soil is necessary, and the research through the technology can provide scientific basis and new method for exploring the succession law and stability accumulation experience of alpine grasslands in different degeneration stages and also for the recovery and reconstruction of the degenerated grassland in the three-river source region.

Disclosure of Invention

In order to solve the above technical problems, the present invention aims to provide a method for promoting the transformation of nitrogen form in degenerated alpine grassland soil.

The invention provides a method for promoting nitrogen form transformation of soil in degenerated alpine grassland, which comprises the following steps:

step 1, selecting the following steps: selecting 3 sample plots of mild degeneration, moderate degeneration and severe degeneration in alpine grassy places respectively;

step 1, selecting in a similar way: selecting 3 sample plots with mild degeneration, moderate degeneration and severe degeneration in alpine grassy places respectively;

step 2, designing the nitrogen ratios of different forms: taking soil-plants as objects, designing three-factor three-level different-form nitrogen proportioning design by adopting orthogonal experiment on a mild deteriorated grassland, combining for 3 times for a total of 9 times, wherein each treatment cell is 3m multiplied by 3m, and the distance between each cell and the repetition is 1m;

step 3, ecological factor control design: selecting a good sample plot on the moderately degenerated grassland, carrying out regulation and control measure screening by using a water-retaining agent, mulching film mulching, plant ash addition and azotobacter microorganism input as ecological factors, carrying out 9 times of treatment for 3 times of repetition, wherein each treatment cell is 3m multiplied by 3m, and the distance between each cell and the repetition is 1m;

step 4, configuring and designing grass seeds with different nitrogen preference degrees: on severely degenerated grassland, adopting random block test design, selecting high grass, short grass and leguminous forage grass seeds with different nitrogen preference degrees to combine and proportion configuration screening, selecting high grass, short grass and leguminous forage grass to combine and mix seeding test, combining for 3 times for 8 times, wherein each processing cell is 3m multiplied by 3m, and the distance between each cell and the repeat is 1m;

step 5, index determination: aiming at the design of the steps 2-4, the following indexes are correspondingly determined: plant aboveground and underground biomass, soil functional character, plant functional character, isotope labeling and analyzing;

and 6, analyzing data: the samples were processed and analyzed using Microsoft Excel 2013 and SPSS 21.0.

Further, in the step 2, three factors are ammonium nitrogen, nitrate nitrogen and organic nitrogen, and the three levels are 20g/m ² ，10g/m ² ，0g/m ² And (5) fertilizing amount.

Further, in the step 3, 9 processes: the application amount of the water retention agent is 20g/m ² And 5g/m ² (ii) a Grass (Haw)The application amount of the wood ash is 100g/m ² And 20g/m ² (ii) a Covering the breathable brown mulching film for 10 days, 20 days and 30 days in the green turning period of the pasture; the content of viable bacteria of azotobacter chroococcum is more than or equal to 1 multiplied by 10 ¹⁰ The water is added into the mixture in a form of 1/g; group 1 control.

Further, in the step 4, the tall grass is selected from elymus nutans, the short grass is selected from poa pratensis, and the leguminous grass is selected from lucerne renbergii; the sowing amount of the pasture is implemented according to the local standard of planting the artificial grassland; 8 groups are unicast 3 groups, two mixed seeding 3 groups, three mixed seeding 1 groups and 1 group contrast.

Further, in the step 5, the aboveground biomass of the plant is measured by a harvesting method in the middle and last 8 months when the aboveground biomass of the plant reaches the maximum annual biomass, the species composition, the species abundance and the functional group of the plant are investigated, the underground biomass of the plant is measured by a root drill, and the grassland quality index is calculated according to the seed biomass; the soil functional properties comprise soil temperature and humidity, soil volume weight, soil organic matters, soil total nitrogen, soil total phosphorus, soil available phosphorus nitrogen, soil nitrogen mineralization rate, soil organic nitrogen, soil ammonium nitrogen and nitrate nitrogen, a soil sample of 0-30 cm in soil layer is collected and taken back to a laboratory for analyzing the soil functional properties, and the effectiveness of soil nutrients is determined and analyzed; the plant functional traits comprise measuring plant community coverage and plant height; isotope labeling and analyzing, namely measuring the absorption values of the plant species to different nitrogen compounds by using a stable nitrogen isotope tracing method; control and labeled plants were analyzed with an elemental analyzer (Flash EA1112 HT) -isotope mass spectrometer (Finnigan MATD eltaV advantage) ¹⁵ N abundance and nitrogen content (mg/g).

Compared with the prior art, the invention has the following beneficial effects:

according to the method, based on the utilization capacity and utilization form of soil nitrogen nutrients of the superior pasture grasses in alpine grasses at different degradation stages, different nitrogen form distribution tests, different control measure intervention tests and different nitrogen preference pasture mixed sowing tests are respectively carried out. In the process of researching and developing deteriorated grassland recovery, nitrogen proportioning technologies with different forms on a soil-plant interface, a promoting technology for soil nitrogen form transformation and a configuration technology for grass seeds with different nitrogen preference degrees on a species level finally promote and optimize the proportion of excellent pasture, recover grassland biomass, improve soil nutrient conditions and recover grassland productivity. In order to explore the succession law of the degeneration of the alpine grassland, the method can accumulate the experience for the stability of the alpine grassland after being implemented and also provide scientific basis and new method for the recovery and reconstruction of the degenerated alpine grassland in the three river source regions.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 shows the upper part of the sample space, the root part and the soil body ¹⁵ The percentage of Nrecovery;

FIG. 3 shows the soil's available nitrogen content (N-1) after each formulation;

FIG. 4 is the soil ammonium nitrogen content (N-2) after each formulation;

FIG. 5 is the total nitrogen content (N-3) of the soil after each formulation;

FIG. 6 is the soil organic carbon content (N-4) after each formulation;

FIG. 7 shows the aboveground biomass (N-5) after each distribution;

FIG. 8 shows the underground biomass (N-6) after each allocation;

FIG. 9 shows the content of the soil available nitrogen (T-1) after each adjustment;

FIG. 10 shows the content of ammonium nitrogen (T-2) in soil after each adjustment;

FIG. 11 shows the organic carbon content (T-3) of the soil after each adjustment;

FIG. 12 shows the nitrate nitrogen content (T-4) of the soil after each adjustment;

FIG. 13 shows the aboveground biomass (T-5) after each control;

FIG. 14 shows the underground biomass (T-6) after each adjustment;

FIG. 15 shows the available phosphorus content (M-1) of the soil after each treatment;

FIG. 16 shows the nitrate nitrogen content (M-2) of the soil after each treatment;

FIG. 17 shows the ammonium nitrogen content (M-3) of the soil after each treatment;

FIG. 18 shows the total phosphorus content (M-4) of the soil after each treatment;

FIG. 19 shows the aboveground biomass (M-5) after each treatment;

FIG. 20 shows the underground biomass (M-6) after each treatment.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

1. Sample plot selection

A military pasture test point (Marxin county army of Maqin province, confucian province, qinghai province, (longitude and latitude 34 degrees 22-34 degrees 20'N,100 degrees 30-100 degrees 29' E, altitude 4100 meters) of an observation station is researched in a Gaohan grassland area of Sanjiang origin in Qinghai-Tibet plateau, the area belongs to a typical continental plateau monsoon climate, and solar radiation intensity (annual total radiation 6194 MJ/m) ² ) Annual sunshine hours are 2493.6h, and no absolute frost period exists. According to long-term meteorological data (1961-2013), the annual average temperature is 1.5 ℃. The hottest month is in month 7 with an average temperature of 11.1 deg.C, while the coldest month is in month 1 with an average temperature of-9.7 deg.C. The air pressure is low, only 587hpa, less than 60% of the sea level air pressure. The average annual precipitation in 2010-2018 is 514.9mm, with more than 80% occurring in the growing season from 5 months to 10 months. The location research, the control experiment and the cell experiment demonstration are carried out by respectively selecting 3 samples with light degradation, moderate degradation and severe degradation.

2. Design of nitrogen proportioning of different forms

The soil-plant is taken as an object, and orthogonal experiments are adopted to design three-factor (ammonium nitrogen, nitrate nitrogen and organic nitrogen) nitrogen proportioning screening with different forms of three levels (high, medium and low fertilizing amounts) on a mild deteriorated grassland (see table 1 for details), wherein ammonium sulfate (20 g/m) is applied to the ammonium nitrogen ² ，10g/m ² ，0g/m ² ) (ii) a Sodium nitrate (20 g/m) is applied to nitrate nitrogen ² ，10g/m ² ，0g/m ² ) (ii) a Organic nitrogen application organic nitrogen fertilizer (20 g/m) ² ，10g/m ² ，0g/m ² ) A total of 9 combinations of 3 replicates (see table 2 for details), each treatment cell being 3 mx 3m; each cell and the distance between the repetitions are allIs 1m.

TABLE 1 Nitrogen dosing factors and levels

TABLE 2 Nitrogen dispensing test combination screening orthogonal design

3. Ecological factor control design

Selecting good sample plot on moderately degenerated grassland, and screening regulation and control measures with water-retaining agent, mulching film covering, plant ash adding and azotobacter microorganism inputting as ecological factors, wherein the water-retaining agent is mainly a Lubao group product, and the application amount is 2 levels (20 g/m) ² And 5g/m ² ) (ii) a The application amount of plant ash is 2 levels (100 g/m) ² And 20g/m ² ) (ii) a Covering the breathable brown mulching film for 10 days, 20 days and 30 days in the green turning period of the pasture; the content of viable bacteria of azotobacter chroococcum is not less than 1 × 10 ¹⁰ The water is added into the mixture in a form of 1/g; group 1 controls, 3 replicates of 9 treatments, each treatment cell 3m x 3m, and cell to replicate distance 1m (see table 3 for design combinations).

TABLE 3 ecological factor control design

Note: in the table, the letter M10 represents "mulching film 10 days", M20 represents "mulching film 10 days", and M30 represents "mulching film 10 days", the same applies below.

4. Configuration design of grass seeds with different nitrogen preference degrees

On severe degenerated grassland, adopting a random block test design, selecting high grass, short grass and leguminous grass seeds with different nitrogen preference degrees to combine and proportion to configure and screen, selecting high grass elymus nutans, short grass land poa pratensis and leguminous grass Hulunebere alfalfa to perform combined mixed sowing test, and repeating for 3 times in 8 combinations (3 groups for single sowing, 3 groups for two mixed sowing, 1 group for three mixed sowing and 1 group for comparison), wherein each treatment cell is 3m multiplied by 3m, and the distance between each cell and the repetition is 1m (see table 4 for details).

TABLE 4 configuration design of grass species with different nitrogen preference degrees

5. Index measurement

(1) Determination of aboveground and underground biomass

The aboveground biomass of the plant is measured by a harvesting method in the middle and last 8 months when the aboveground biomass of the plant reaches the maximum every year, the species composition, the species abundance and the functional group of the plant are investigated, the underground biomass of the plant is measured by a root drill, and the grassland quality index is calculated according to the seed biomass.

(2) Determination of soil functional character index

The soil functional properties comprise soil temperature and humidity, soil volume weight, soil organic matters, soil total nitrogen, soil total phosphorus, soil available nitrogen, soil nitrogen mineralization rate, soil organic nitrogen, soil ammonium nitrogen and nitrate nitrogen, a soil sample of 0-30 cm in soil layer is collected and taken back to a laboratory to analyze the soil functional properties, and the effectiveness of soil nutrients is determined and analyzed; wherein, the total phosphorus adopts a molybdenum-antimony colorimetric resistance method, the quick-acting phosphorus adopts a sodium bicarbonate leaching-molybdenum-antimony colorimetric resistance method, the total nitrogen and the quick-acting nitrogen adopt a Kjeldahl method and a convich method, and the organic matter content is measured by a potassium dichromate oil bath method. The volume weight of the soil is measured by a cutting ring method, and the temperature and humidity of the soil are measured by a TDR-200 humidity measuring instrument and an HOBO small meteorological station data temperature automatic recorder H21-002 (American On set HOBO). Based on the method, parameters such as the nitrogen demand for overground part growth, the nitrogen inventory of underground root systems, the nitrogen demand for underground root systems in the growth years, the total nitrogen demand for annual growth and the like of dominant plant species and functional groups are calculated by a method of Cao Guangxi et al (influence of change of soil-pasture nitrogen supply and demand conditions on succession of vegetation in alpine grassland and grassland degradation [ J ]. Journal of ecology, 2004 (06): 25-28.).

(3) Determination of plant functional trait indicators

The plant functional traits include plant height and coverage of a plant population, as determined by conventional methods.

(4) Isotopic labeling and analysis

Measuring the absorption values of different nitrogen compounds of plant species by using a stable nitrogen isotope tracer method; the control and labeled plants were analyzed for 15N abundance and nitrogen content (mg/g) using an elemental analyzer (Flash EA1112 HT) -isotope mass spectrometer (Finnigan MATD eltaV advantage).

6. Data analysis

The experimental data were processed and analyzed using Microsoft Excel 2013 and the data were expressed as mean. + -. Standard error (Means. + -. SE). Analysis of variance was achieved by One-way ANOVA module in SPSS 21.0, principal component analysis was achieved by SPSS 21.0, and mapping was achieved using Origin 2017.

7. Analysis of results

(1) Nitrogen balance of soil-plant system

Nitrogen has a major effect on the establishment of a plant organ, and the 15N uptake by the organ as a percentage of the total nitrogen content of the organ represents the importance of the current stage of nitrogen for establishment and development of the organ, as can be seen in Table 5: the recovery rates of glycine and nitrate nitrogen of the leaves of the Potentilla anserine in the current period reach 2.33 percent and 4.40 percent respectively, and are remarkably higher than those of the leaves of other plants (P < 0.05), which indicates that the nitrogen absorbed by the Potentilla anserine contributes to the leaves greatly. The recovery rate of organic nitrogen or inorganic nitrogen in the roots of the double-stigmatis scriptri is lower than that of other plants, which indicates that the nitrogen in the soil is not a dependent factor for the reproduction and growth of the double-stigmatis scriptri. The recovery rates of glycine and inorganic nitrogen from the roots of Elymus nutans are the highest, namely 4.58%, 5.04% and 5.54%, which indicates that the nitrogen contributes greatly to the roots of Elymus nutans. In summary, the pattern in which different plants, which live together in alpine-weed communities, take up organic and inorganic nitrogen in the soil through roots and then distribute to different organs of the plants, is different.

TABLE 5 plant-soil systems uptake of nitrogen from ¹⁵ Proportion of N

As can be seen from FIG. 2, the recovery rates of the three nitrogen sources from the different pools of the same species are shown in the overground part>Root of a tree>The soil body, and the overground part is obviously higher than the root and the soil body (P)<0.05). The overground part of the plant community is in glycine, nitrate nitrogen and ammonium nitrogen ¹⁵ The recovery rates of N reach 22.3%, 44.3% and 29.3%, and the nitrate nitrogen is obviously higher than glycine and ammonium nitrogen (P)<0.05). The root has the highest recovery rate of nitrate nitrogen, but the difference between the root and other two nitrogen sources is not obvious, and the recovery rate of ammonium nitrogen of the soil body is higher than that of glycine and nitrate nitrogen. Wherein, different capital letters indicate that the difference of different nitrogen sources in the same bank is obvious, and different lowercase letters indicate that the difference of the same nitrogen source in the overground part, the root and the soil body is obvious (P)<0.05)。

(2) Proportioning technology of nitrogen with different forms on soil-plant interface

1) Correlation and main factor analysis of soil nutrient indexes after different nitrogen elements are prepared and applied

As can be seen from Table 6, after 3 years of the slightly degenerated alpine grasses being matched with different forms of nitrogen, the contents of organic carbon (SOC) and Total Nitrogen (TN) in the alpine grasses soil of the test plots are in extremely obvious positive correlation (P < 0.01) and in obvious positive correlation with the content of Total Phosphorus (TP) (P < 0.05). The Total Nitrogen (TN) content of the soil is in extremely obvious positive correlation with Total Phosphorus (TP) and Available Phosphorus (AP) (P is less than 0.01). The content of Total Phosphorus (TP) in the soil is obviously negatively related to nitrate Nitrogen (NO) (P < 0.05) and is extremely obviously positively related to Available Phosphorus (AP) (P < 0.01). The content of the soil quick-Acting Nitrogen (AN) is in extremely obvious positive correlation (P < 0.01) with the content of nitrate Nitrogen (NO), and is in obvious positive correlation (P < 0.05) with the content of ammonium Nitrogen (NH). Indirectly shows that the content of Total Nitrogen (TN) in the soil is closely related to the phosphorus cycle, the quick-Acting Nitrogen (AN) is closely related to ammonium Nitrogen (NH) and nitrate Nitrogen (NO), and the content of Total Nitrogen (TN) and Total Phosphorus (TP) affects the carbon cycle in the process of distributing nitrogen elements with different forms.

TABLE 6 correlation analysis of soil nutrient index after different nitrogen elements are applied

Note: * Significant correlation at 0.01 level (bilateral) and significant correlation at 0.05 level (bilateral). In the table, the letters SOC represent "organic carbon", TN represents "total nitrogen", TP represents "total phosphorus", AN represents "quick-acting nitrogen", AP represents "quick-acting phosphorus", NO represents "nitrate nitrogen", NH represents "ammonium nitrogen", and the same applies below.

The principal component analysis was performed on 7 soil nutrient indexes after 3 years of nitrogen with different forms, and it can be seen from table 7 that 3 index characteristic values in the 7 soil nutrient indexes are all greater than 1 after the principal component analysis. The first principal component eigenvalue is 3.513, the variance contribution rate is 50.184%, the second principal component eigenvalue is 1.808, the variance contribution rate is 25.823%, the third principal component eigenvalue is 1.032, and the variance contribution rate is 10.461%. The cumulative contribution rate of the first three main components is 86.468%, and most contents of soil nutrients can be reflected. The number of the principal components is extracted according to the principle that the cumulative contribution rate is more than or equal to 85 percent, and 3 principal components are selected according to the contribution rate.

TABLE 7 analysis of soil nutrient index main factors after different nitrogen elements are applied

Note: the numbers in the categories represent common factors extracted by the analysis of the main factors, the same applies below

And analyzing the rotated component matrix of the principal component analysis for specifically determining an analysis index. As can be seen from table 8, the fast-Acting Nitrogen (AN) and ammonium Nitrogen (NH) loading values in the first major component were 0.922 and 0.858, respectively, and both were positive influences. The Total Nitrogen (TN) loading value in the second main component was 0.959, which is a positive influence. The organic carbon (SOC) load value in the third main component was 0.993, which is a positive influence. Therefore, four soil nutrient indexes of AN, NH, TN and SOC are selected as main analysis indexes of the influence of each test treatment on the soil nutrients.

TABLE 8 analysis of the major factors after the administration of different nitrogens

2) Change of soil nutrient after different nitrogen elements are applied

After the nitrogen elements with different forms are applied for 3 years, the nutrient indexes of the slightly degenerated alpine grassland soil are obviously changed. As can be seen in FIG. 3 (N-1), the quick-Acting Nitrogen (AN) contents of each formulation group are ranked as follows: LLL (low ammonium nitrogen + low nitrate nitrogen + low organic nitrogen) (control group) > MHL (medium ammonium nitrogen + high nitrate nitrogen + low organic nitrogen) > LMM (low ammonium nitrogen + medium nitrate nitrogen + medium organic nitrogen) > LHH (low ammonium nitrogen + high nitrate nitrogen + high organic nitrogen) > MLM (medium ammonium nitrogen + low nitrate nitrogen + medium organic nitrogen) > HHM (high ammonium nitrogen + high nitrate nitrogen + medium organic nitrogen) > HLH (high ammonium nitrogen + low nitrate nitrogen + high organic nitrogen) > HML (high ammonium nitrogen + medium nitrate nitrogen + low organic nitrogen) > MMH (medium ammonium nitrogen + medium nitrate nitrogen + high organic nitrogen). Wherein the LLL (control group) group has the highest content of quick-Acting Nitrogen (AN), has no significant difference with LMM, LHH, MLM and MHL groups, and has significant difference with MMH, HLH and HML groups (P < 0.05). The MHH formulation group had the lowest content of Available Nitrogen (AN). As can be seen from FIG. 4 (N-2), the sequence of the ammonium Nitrogen (NH) content of the soil in each application group is as follows: LMM > MHL > LHH > LLL > MMH > HHM > MLM > HLH > HML. Compared with each matched group, the LMM matched group has the highest content of soil ammonium Nitrogen (NH), but has no obvious difference with LLL (control group). The soil ammonium Nitrogen (NH) content of the HML dosed group was minimal, but also not significantly different from the LLL (control group). The content of ammonium Nitrogen (NH) in LMM, MHL and LLL mating group soil is obviously higher than that in MLM, MMH, HLH, HML and HHM (P < 0.05).

As can be seen in FIG. 5 (N-3), the Total Nitrogen (TN) content of the soil of each formulation group is ranked as follows: LMM > HLH > HHM > MHL > LLL > HML > MLM > MMH > LHH. Compared with each treatment group, the difference between the Total Nitrogen (TN) contents of the soil of each dispensing group is not obvious, the Total Nitrogen (TN) content of the LMM dispensing group is the highest, and the Total Nitrogen (TN) content of the LHH dispensing group is the lowest. As can be seen from FIG. 6 (N-4), the Soil Organic Carbon (SOC) content of each formulation group is ranked as follows: HHM > LMM > MLM > HLH > MHL > HML > LHH > MMH > LLL. Wherein, the difference between the Soil Organic Carbon (SOC) contents of all the distribution groups is not obvious, the Soil Organic Carbon (SOC) content of the HHM distribution group is the highest, and the Soil Organic Carbon (SOC) content of the LLL distribution group is the lowest.

3) Evaluation of soil nutrient status after different nitrogen preparation

And (3) allocating nitrogen with different forms to the soil nutrient indexes of the alpine grassland after 3 years by using a membership function method: the relative values of AN, NH, TN and SOC were calculated to obtain the overall situation of each treatment nutrient status, and the soil nutrient status under the test conditions was evaluated comprehensively (Table 9). LMM > MHL > HHM > HLH > LLL > MLM > LHH > HML > MMH, namely LMM (low ammonium nitrogen + medium nitrate nitrogen + medium organic nitrogen) is matched with the best soil nutrient condition, and MMH (medium ammonium nitrogen + medium nitrate nitrogen + high organic nitrogen) is matched with the worst soil nutrient condition. However, by combining the analysis of each soil nutrient index, the difference of the soil nutrient conditions among the distribution groups is not obvious, so that the overall soil nutrient condition is relatively good and bad.

TABLE 9 comprehensive evaluation values and ranks of major indicators under each distribution

4) Variation of biomass amount after different nitrogen formulations

After the nitrogen with different forms is applied for 3 years, the biomass of the slightly degenerated alpine grasses is obviously changed. As can be seen from FIG. 7 (N-5), the aboveground biomass of each of the various dispensing groups was ranked as: MMH > MLM > MHL > LHH > HML > HLH > LMM > HHM > LLL, and the aboveground biomass was increased in each dispensing group compared to the LLL (CK) group, wherein the MMH, MLM, MHL, LHH, HML, HLH dispensing groups reached significant levels (P < 0.05). The biomass of MMH distribution group is obviously higher than that of other distribution groups (P < 0.05), and is improved by 1.6 times compared with the LLL (CK) group. The aboveground biomass of both MLM and MHL dosed groups was significantly higher than that of each of the other dosed groups except that it was lower than that of the MMH dosed group (P < 0.05). As can be seen in FIG. 8 (N-6), the treatment groups have subsurface biomass in the order: MMH > MHL > MLM > LHH > HML > LMM > HLH > LLL > HHM. The underground biomass of the MMH dispensing group is obviously higher than that of other dispensing groups (P < 0.05), and is improved by 2.8 times compared with the LLL (CK) group. The underground biomass of MLM and MHL dispensing groups is obviously higher than that of other dispensing groups except that the underground biomass of MMH dispensing group is lower than that of the other dispensing groups (P < 0.05). Underground biomass differences among the HML, LMM, HLH, LLL (CK), HHM formulations were not significant.

In summary, the optimal combination of different forms of nitrogen in slightly degenerated alpine grasses is MMH (medium ammonium nitrogen + medium nitrate nitrogen + high organic nitrogen), i.e. 10g/m ² Ammonium nitrogen +10g/m ² Nitrate nitrogen +20g/m ² An organic nitrogen.

(3) Activation for promoting nitrogen form transformation by regulating ecological factors

1) Correlation and main factor analysis of soil nutrient indexes after different regulation and control interventions

As can be seen from table 10, after the moderately degenerated alpine region is intervened by different control measures for 3 years, the contents of organic carbon (SOC) and Total Nitrogen (TN), available Nitrogen (AN) and ammonium Nitrogen (NH) in the alpine region soil of the test region are in a very significant positive correlation (P < 0.01) and in a significant positive correlation (P < 0.05) with the content of Available Phosphorus (AP). The Total Nitrogen (TN) content of the soil is in extremely obvious positive correlation (P < 0.01) with the quick-Acting Nitrogen (AN) content, and the Total Phosphorus (TP) content and the quick-Acting Phosphorus (AP) content are in obvious positive correlation (P < 0.05). The content of the soil Available Nitrogen (AN) is in obvious positive correlation with the content of ammonium Nitrogen (NH) and Available Phosphorus (AP) (P < 0.05). The content of nitrate Nitrogen (NO) in soil and the content of ammonium Nitrogen (NH) are in extremely obvious positive correlation (P is less than 0.01). The content of ammonium Nitrogen (NH) in the soil is in very obvious positive correlation with the content of Available Phosphorus (AP) (P is less than 0.01). Indirectly shows that the carbon nitrogen circulation of the alpine grassland soil is closely related in the intervention process of different regulation measures, and simultaneously, the organic carbon (SOC) is closely related to the effectiveness of phosphorus. The Total Nitrogen (TN) content is closely related to the effectiveness of the nitrogen and the phosphorus cycle. The close relationship between ammonium Nitrogen (NH) and nitrate Nitrogen (NO) indicates the activity of the nitrogen conversion process.

TABLE 10 correlation analysis of soil nutrient index after different control interventions

Principal component analysis is performed on 7 nutrient indexes in soil, and as can be seen from table 11, after the 7 soil nutrient indexes are subjected to principal component analysis, the characteristic values of 4 components are greater than 1, wherein the characteristic value of the first principal component is 3.247, and the variance contribution rate is 46.393%. The second principal component eigenvalue is 1.544 and the variance contribution is 22.063%. The third principal component eigenvalue is 1.367 and the variance contribution rate is 12.389%. The fourth principal component eigenvalue was 1.033 and the variance contribution rate was 7.621%. The cumulative contribution rate of the first four main components is 88.465%, and most contents of soil nutrients can be reflected. The number of the main components is extracted according to the principle that the cumulative contribution rate is more than or equal to 85 percent, and 4 main components are selected according to the contribution rate.

TABLE 11 analysis of soil nutrient index major factors after different regulatory interventions

And analyzing the rotated component matrix of the principal component analysis for specifically determining an analysis index. As can be seen from table 12, the values of the quick-Acting Nitrogen (AN) loadings in the first principal component were 0.893, respectively, and were all positive effects. The ammonium Nitrogen (NH) load value in the second main component was 0.864, which is a positive influence. The organic carbon (SOC) load value in the third main component was 0.922, which is a positive influence. The nitrate Nitrogen (NO) loading value in the fourth main component was 0.908, which is a positive influence. Therefore, four soil nutrient indexes of AN, NH, SOC and NO are selected as main analysis indexes of the influence of each test treatment on the soil nutrients.

TABLE 12 analysis of different modulation stem prognosis principal factors

2) Changes in soil nutrients after different regulatory interventions

After different regulation measures intervene for 3 years, the soil nutrient indexes of the moderately degenerated alpine grassland are changed. As can be seen from FIG. 9 (T-1), the content of the Available Nitrogen (AN) in each control group is ranked as follows: PL (water-retaining agent Low) > M20 (mulch film covering for 20 days) > NB (azotobacter) > PH (water-retaining agent high) > M10 (mulch film covering for 10 days) > CK (control group) > WL (plant Ash Low) > M30 (mulch film covering for 30 days) > WH (plant Ash high). Wherein, the content of the soil Available Nitrogen (AN) of the PL control group is the highest, the difference is not significant compared with the CK group, and the difference is significant compared with the WH control group (P is less than 0.05). Except the WH regulation group, the difference among other regulation groups is not obvious. As can be seen from FIG. 10 (T-2), the sequence of the content of ammonium Nitrogen (NH) in soil of each control group is as follows: m10> NB > PL > M20> M30> CK > WL > WH. The influence of different regulation and control measures on the content of the soil ammonium Nitrogen (NH) is small, and the difference of the content of the soil ammonium Nitrogen (NH) among the regulation and control groups is not obvious. The content of the soil ammonium Nitrogen (NH) in the M10 regulation group is the highest, and the content of the soil ammonium Nitrogen (NH) in the WH regulation group is the lowest.

As can be seen from FIG. 11 (T-3), the Soil Organic Carbon (SOC) contents of each control group are ranked as follows: PL > M20> M10> NB > PH > CK > WH > M30> WL. The influence of different regulation and control measures on the content of ammonium Nitrogen (NH) in the soil is small, and the difference of the content of organic carbon (SOC) in the soil among the regulation and control groups is not obvious. The PL control group has the highest content of Soil Organic Carbon (SOC), and the WL control group has the lowest content of Soil Organic Carbon (SOC). As can be seen from the attached FIG. 12 (T-4), the soil nitrate Nitrogen (NO) content of each control group is ordered as follows: WL > PH > WH > CK > NB > M30> M10> M20> PL. The influence of intervention of different regulation measures on the soil nitrate Nitrogen (NO) content is small, the difference of the soil nitrate Nitrogen (NO) content among the regulation groups is not obvious, the WL regulation group has the highest soil nitrate Nitrogen (NO) content, and the PL regulation group has the lowest soil nitrate Nitrogen (NO) content.

3) Evaluation of soil nutrient status after different regulation and control interventions

And (3) interfering different regulation measures with the soil nutrient indexes of the alpine grassland after 3 years by using a membership function method: the relative values of AN, NH, SOC and NO were calculated to obtain the overall status of each treatment nutrient status, and the soil nutrient status under the test conditions was evaluated comprehensively (Table 13). The sequencing results are NB > PL > M20> PH > M10> CK > WL > M30> WH, namely the NB (azotobacter) intervenes the best soil nutrient condition, and the WH (water-retaining agent high) intervenes the worst soil nutrient condition. However, by combining the analysis of each soil nutrient index, the difference of the soil nutrient condition among the distribution groups is not obvious, so that the quality of the whole soil nutrient condition is relative.

TABLE 13 comprehensive evaluation values and ranking of major indicators under respective controls

4) Changes in biomass after different regulatory interventions

After different regulation measures are intervened for 3 years, the biomass of the moderately degenerated alpine grassland is obviously changed. As can be seen from FIG. 13 (T-5), the aboveground biomass of each regulatory group was ranked as: NB > M20> PL > M10> PH > CK > M30> WL > WH. Among them, the NB control group had the highest aboveground biomass, increased by about 1.6 times compared with the CK group, and differed significantly from each of the other control groups (P < 0.05). The aboveground biomass of the M20 regulation group is remarkably different from other regulation groups, and is remarkably higher than other regulation groups except that the aboveground biomass is lower than that of the NB regulation group (P < 0.05). Aboveground biomass of WH regulatory group was significantly lower than that of each of the other regulatory groups (P < 0.05). The aboveground biomass of the WH, WL and M30 control groups is significantly lower than that of the CK group (P < 0.05), and the aboveground biomass of the other control groups is significantly higher than that of the CK group (P < 0.05). As can be seen in FIG. 14 (T-6), the subsurface biomass of each treatment group was ranked as: NB > M20> PL > M10> PH > CK > M30> WL > WH. Among them, the underground biomass of the NB control group was the highest, increased by about 1.9 times compared with the CK group, and was significantly different from other control groups (P < 0.05). The underground biomass of the M20 regulation group is obviously different from that of other regulation groups, and is obviously higher than that of other regulation groups except that the underground biomass of the M20 regulation group is lower than that of the NB regulation group (P < 0.05). The underground biomass of the WH regulation group is obviously lower than that of other regulation groups (P < 0.05). The underground biomass of the WH, WL, M30 regulatory group was significantly lower than that of the CK group (P < 0.05). Therefore, after intervention of different regulation measures for 3 years, the overground biomass and the underground biomass of the moderately degenerated alpine grasses are obviously changed, and the improving effect of an NB (nitrogen-fixing bacteria) treatment group is most obvious.

In summary, the best control intervention measure in moderately degenerated alpine meadow is NB (azotobacter), namely 2mg/m azotobacter ² 。

(4) Configuration of grass seeds with different nitrogen preference degrees on species level

1) Correlation and main factor analysis of soil nutrient indexes after different mixed sowing treatments

As can be seen from table 14, after 3 years of mixed sowing of pastures with different nitrogen preferences, the contents of organic carbon (SOC) and Total Nitrogen (TN) in the alpine grassland soil of the test field are in a very significant positive correlation (P < 0.01) and in a significant positive correlation (P < 0.05) with the contents of Available Nitrogen (AN) and nitrate Nitrogen (NO). The Total Nitrogen (TN) content of the soil is in extremely obvious positive correlation (P is less than 0.01) with the quick-Acting Nitrogen (AN) content, and the Total Nitrogen (TN) content of the soil is in obvious positive correlation (P is less than 0.05) with the nitrate Nitrogen (NO) content. The content of nitrate Nitrogen (NO) in soil is in extremely obvious positive correlation with the content of Available Phosphorus (AP) (P is less than 0.01). Indirectly shows that the carbon nitrogen circulation of the soil of the alpine grassland is closely related in the implementation process of the pasture mixed sowing measure. Meanwhile, the Total Nitrogen (TN) content is closely related to the nitrogen conversion process. The nitrate Nitrogen (NO) and the Available Phosphorus (AP) are closely related.

TABLE 14 analysis of soil nutrient index correlation after different mixed sowing treatments

The principal component analysis is carried out on 7 soil nutrient indexes of pasture which is favored by different nitrogen after 3 years of mixed sowing, and as can be seen from table 15, after the principal component analysis, 3 index characteristic values in the 7 soil nutrient indexes are all larger than 1. The first principal component eigenvalue is 4.265, the variance contribution rate is 60.927%, the second principal component eigenvalue is 1.274, the variance contribution rate is 18.199%, the third principal component eigenvalue is 1.052, and the variance contribution rate is 15.024%. The cumulative contribution rate of the first three main components is 94.150%, and most contents of soil nutrients can be reflected. The number of the principal components is extracted according to the principle that the cumulative contribution rate is more than or equal to 85 percent, and 3 principal components are selected according to the contribution rate.

TABLE 15 analysis of soil nutrient index main factors after different mixed sowing treatments

And analyzing the rotated component matrix of the principal component analysis for specifically determining an analysis index. As can be seen from table 16, the loading values of the fast-Acting Phosphorus (AP) and nitrate Nitrogen (NO) in the first main component were 0.979 and 0.905, respectively, and both were positive influences. The ammonium Nitrogen (NH) loading value in the second major component was 0.975, which is a positive effect. The Total Phosphorus (TP) load value in the third main component was 0.992, which is a positive influence. Therefore, four soil nutrient indexes of AP, NO, NH and TP are selected as main analysis indexes of the influence of each test treatment on the soil nutrients.

TABLE 16 analysis results of the main factors after different multicast processing

2) Change of soil nutrient after different mixed sowing treatment

After different pastures are sowed in a mixed mode for 3 years, the soil nutrient indexes of severely degraded alpine grassland are obviously changed. As can be seen from FIG. 15 (M-1), the treatment groups have the following ordering of the Available Phosphorus (AP) content: EM (setaria pratense + renbergia lucerne) > EP (setaria pratense + pratense grass) > PM (pratense grass + renbergia lucerne) > CK (control group) > EPM (setaria pratense + pratense grass + renbergia lucerne) > E (setaria pratense) > P (pratense grass) > M (renbergia lucerne). Wherein, EM, EP and PM, the content of the soil Available Phosphorus (AP) of 3 treatment groups is higher than that of CK group, but the content of the soil Available Phosphorus (AP) of only EM treatment group is obviously higher than that of CK group (P < 0.05), and the content of the soil Available Phosphorus (AP) of only EM treatment group is higher than that of other treatment groups (P < 0.05). The soil Available Phosphorus (AP) content of the EPM, E, P and M treatment groups is obviously lower than that of the CK group (P < 0.05), but the difference among the 4 treatments is not obvious. As can be seen from FIG. 16 (M-2), the soil nitrate Nitrogen (NO) content of each treatment group is ranked as follows: EP > EM > PM > CK > M > EPM > E > P. Wherein, the content of nitrate Nitrogen (NO) in the soil in the EP and EM treatment groups is obviously higher than that in other treatment groups, including the CK group (P < 0.05). The content of soil nitrate Nitrogen (NO) of the EPM, E, P and M treatment groups is obviously lower than that of the CK group (P < 0.05). The content of soil nitrate Nitrogen (NO) in the P treatment group is the lowest, and the difference with other treatment groups is obvious (P < 0.05).

As can be seen from FIG. 17 (M-3), the ranking of the ammonium Nitrogen (NH) content of the soil for each treatment group is: m > PM > EP > E > EPM > EM > P > CK. Compared with the treatment groups, the content of ammonium Nitrogen (NH) in the soil fluctuates greatly, but the content is higher than that of the CK group, and the content of the ammonium Nitrogen (NH) in the soil is remarkably different except for the P treatment group (P < 0.05). The content of ammonium Nitrogen (NH) in the soil of the M treatment group is the highest, and is improved by about 1.2 times compared with the CK group (P is less than 0.05). Meanwhile, the content of soil ammonium Nitrogen (NH) between the PM treatment group and the EPM, EM and P treatment group reaches a significant level (P < 0.05), but the content between the EPM, EM and P treatment groups has no significant difference. The difference in soil ammonium Nitrogen (NH) content between the PM-treated group and the EP, E, M-treated groups did not reach a significant level. As can be seen from FIG. 18 (M-4), the soil Total Phosphorus (TP) content of each treatment group is ranked as follows: e > EM > EP > EPM > P > CK > PM > M. The Total Phosphorus (TP) content of the soil of the E treatment group is the highest and is obviously higher than that of the CK group (P < 0.05), and the difference of the E treatment group and each treatment group except the EP and EM treatment groups is obvious (P < 0.05). The soil Total Phosphorus (TP) content of each treatment group except the E treatment group is not significantly different from that of the CK group.

3) Evaluation of soil nutrient condition after different mixed sowing treatments

And (3) performing mixed sowing on different pastures by using a membership function method to obtain the soil nutrient indexes of the alpine grassland after 3 times of mixed sowing: the relative values of AP, NO, NH and TP were calculated to obtain the overall situation of the nutrient status of each treatment, and the soil nutrient status under the test conditions was evaluated comprehensively (Table 17). The sequencing result is that EM > EP > PM > E > P > EPM > M > P, namely the soil nutrient condition processed by EM (Elymus nutans and Hurenberg alfalfa) is the best, and the soil nutrient condition processed by P (Poa pratensis) is the worst.

TABLE 17 comprehensive evaluation values and rankings of the main indicators after different mixed broadcast processing

4) Variation of biomass amount after different mixed seeding treatment

After different pastures are sowed in a mixed mode for 3 years, the biomass of the severely degraded alpine grassland is obviously changed. As can be seen from FIG. 19 (M-5), the aboveground biomass of each treatment group was ranked as: EM > EPM > PM > E > P > EP > M > CK, and the aboveground biomass was significantly increased (P < 0.05) in each treatment group compared with the CK group. Among them, the above-ground biomass was highest in the EM treatment group and was increased by about 2.3 times as compared with the CK group. The above-ground biomass of the M-treated group was the lowest and increased by about 1.5-fold compared to the CK group. E. Aboveground biomass of both P and M treatment groups was significantly higher than CK group (P < 0.05), but did not significantly differ from each other. As can be seen in FIG. 20 (M-6), the subsurface biomass of each treatment group was ranked as: EM > PM > EPM > P > E > EP > M > CK, underground biomass was significantly increased (P < 0.05) for each treatment group compared to the CK group. Among them, EM-treated underground biomass was the highest, which was increased by about 2.7 times compared to the CK group. The M-treated underground biomass was the lowest, and increased by about 1.2-fold compared to the CK group. The difference ratio between EPM, E, P and M treatment groups is significant. The differences between the EM and PM treatment groups were not significant. Therefore, the method can also be seen that after different pastures are sowed in a mixed manner for 3 years, the aboveground biomass and the underground biomass of the severely degenerated alpine grasses show synchronism, and the improvement effect of an EM (Elymus nutans and Hulunbel alfalfa) treatment group is most obvious.

Comprehensively, the best pasture mixed sowing treatment in the severely degenerated alpine meadow is EM (elymus nutans and Hulunbei alfalfa), namely (13.5 + 6.75) g/9m ² 。

(5) To summarize

1) Nitrogen balance of soil-plant system

The pattern in which different plants co-living in the grass-dwarf community absorb organic and inorganic nitrogen in the soil through the roots and then distribute it to different organs of the plant is different. The recovery rates of the three different forms of nitrogen were all shown to be above ground > root > earth, with the above ground significantly higher than the root and earth (P < 0.05). The recovery of nitrate nitrogen is significantly higher above ground in the plant community than in ammonium nitrogen (P < 0.05). The root has the highest recovery rate of nitrate nitrogen, but the difference between the root and other two nitrogen elements is not obvious, and the recovery rate of the soil body to ammonium nitrogen is higher than that of nitrate nitrogen. Therefore, in the utilization process of the alpine grassland, great attention needs to be paid to the input proportion of nitrogen and the improvement of the nitrogen utilization efficiency.

2) Optimum nitrogen element proportion for recovery of degenerated alpine grassland

The nitrogen is one of the important factors for limiting the productivity of the degraded alpine grasses, and is obtained by developing nitrogen distribution tests with different forms and combining a principal component analysis method and a root cap ratio analysis method: MMH (middle ammonium nitrogen + middle nitrate nitrogen + high organic nitrogen), namely 10g/m ² Ammonium nitrogen +10g/m ² Nitrate nitrogen +20g/m ² The organic nitrogen treatment effect is best compared with the control group and other treatment combinations. Therefore, the fertilizer is applied to the moderate and deteriorated alpine grassland at the ratio of 10g/m ² Ammonium nitrogen +10g/m ² Nitrate nitrogen +20g/m ² The organic nitrogen can effectively promote the recovery process of the ecosystem of the moderately degenerated alpine grasses.

3) Optimum regulation ecological factor for recovery of degenerated alpine grassland

The utilization efficiency of nitrogen is one of important factors for restricting the recovery of the degenerated alpine grassland, and the application of external regulation ecological factors and the analysis of a principal component analysis method and a root-cap ratio can be combined to obtain that: the treatment effect of the plots inputted by NB (azotobacter) was the best compared with the control group and other treatment combinations. Therefore, the azotobacter applied to the moderately and severely degenerated alpine grassland can effectively promote the recovery process of the ecosystem of the moderately degenerated alpine grassland.

4) Optimum grass seed configuration for recovery of degenerated alpine grassland

In severe degeneration high and cold grassland, the configuration and planting of the Xizen grass seeds are carried out, and the analysis of the main component analysis method and the root-crown ratio is combined to obtain that: the treatment effect of the EM (Elymus nutans and Hurenberg alfalfa) treatment is the best, and compared with the control group, the effect is obvious. Therefore, the combined planting of the elymus nutans and the Hulenbel alfalfa in the severely degenerated alpine grassland can effectively promote the recovery process of the ecosystem of the severely degenerated alpine grassland.

5) Ecological driving mechanism for degrading morphological transformation and absorption utilization efficiency of Geranium alpinum

The grassland deterioration obviously reduces the net nitrification rate and the net amination rate of the soil in the alpine grassland. The number of nitrifying bacteria and ammonifying bacteria in the soil of 2 types of alpine grassland is reduced, and the activities of soil protease and urease are reduced. Remarkably reduce NH ₄ ⁺ -N and NO ₃ ^- The N content reduces the nitrogen content of the biomass of the microorganism. The soil nitrification rate and the ammoniation rate in the alpine grassland are closely related to the number of soil nitrifying bacteria and ammoniating bacteria, and protease and urease. Plant biomass, soil water content, organic carbon, total nitrogen content are major factors affecting soil nitrogen conversion by affecting microorganism count, microorganism biomass and enzyme activity. Thus, grassland deterioration reduces the soil nitrogen conversion rate and the soil available nitrogen supply by reducing the activity of nitrifying and ammonifying bacteria, soil enzymes in alpine grassland. Research on plant nitrogen absorption in the ecosystem of alpine grassland cannot be limited to nitrate nitrogen and ammonium nitrogen, and needs to be discussed from the perspective of soluble organic nitrogen formed in the last link of the ammonium nitrogen and the nitrate nitrogen. Furthermore, the preferential uptake of the nitrogen source by different species on the reconstituted artificial turf is very important, and planting species with different preferential uptake capacities reduces interspecies competition and increases the effectiveness of the soil nitrogen.

In conclusion, co-living in the grass-short-fleshy ground communityThe modes in which different plants absorb organic and inorganic nitrogen in the soil through roots and then distribute it to different organs of the plant are different; ammonium nitrogen [20g/m ] is applied in moderate-degradation high-cold grassland ² ]+ high nitrate nitrogen [20g/m ² ]+ high organic Nitrogen [20g/m ² ]The recovery process of the moderate degeneration alpine grassland ecosystem can be effectively promoted; the application of the azotobacter in moderate and severe degraded alpine grassland can effectively promote the recovery process of the ecosystem of the moderate degraded alpine grassland; the combined planting of the elymus nutans and the Hulunbei alfalfa in the severely degenerated alpine grassland can effectively promote the recovery process of the ecosystem of the severely degenerated alpine grassland. The grassland deterioration obviously reduces the net nitrification rate and the net amination rate of the soil in the alpine grassland. Remarkably reduce NH ₄ ⁺ -N and NO ₃ ^- The N content reduces the nitrogen content of the biomass of the microorganism.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for promoting nitrogen form transformation of degenerated alpine grassland soil is characterized by comprising the following steps:

step 3, ecological factor control design: selecting a sample plot on moderately degraded grassland, carrying out regulation and control measure screening by taking water-retaining agents, plastic film mulching, plant ash addition and azotobacter microorganism input as ecological factors, and repeating for 3 times by 9 times, wherein each treatment cell is 3m multiplied by 3m, and the distance between each cell and the repeat is 1m;

step 6, data analysis: the samples were processed and analyzed using Microsoft Excel 2013 and SPSS 21.0.

2. The method for promoting nitrogen morphological transformation of soil in degenerated alpine grasses as claimed in claim 1, wherein in step 2, three factors are ammonium nitrogen, nitrate nitrogen and organic nitrogen, and the three levels are 20g/m ² ，10g/m ² ，0g/m ² And (5) fertilizing amount.

3. The method for promoting nitrogen form transformation of degenerated alpine grassy soil according to claim 1, wherein in the step 3, 9 treatments: the application amount of the water retention agent is 20g/m ² And 5g/m ² (ii) a The application amount of the plant ash is 100g/m ² And 20g/m ² (ii) a Covering the breathable brown mulching film for 10 days, 20 days and 30 days in the green turning period of the pasture; the content of viable bacteria of azotobacter chroococcum is not less than 1 × 10 ¹⁰ The water is added into the mixture in a form of 1/g; group 1 control.

4. The method for promoting nitrogen morphology transformation in soil of degenerated alpine grasses as claimed in claim 1, wherein in step 4, tall grass is selected from elymus nutans, short grass is selected from poa pratensis, leguminous grass is selected from lucerne renbergii; the seeding rate of the pasture is implemented according to the local standard for planting the artificial grassland; 8 groups are unicast 3 groups, two mixed seeding 3 groups, three mixed seeding 1 groups and 1 group contrast.

5. The method for promoting the transformation of nitrogen forms in degenerated alpine grassland soil according to claim 1, wherein in step 5, aboveground biomass of plants is measured in the middle and late 8 months when the aboveground biomass of plants reaches the maximum each year, and the species composition, species abundance and functional groups of plants are investigated, underground biomass of plants is measured by root drill, and grassland quality index is calculated according to the seeded biomass; the functional properties of the soil are soil temperature, soil humidity, soil volume weight, soil organic matters, soil total nitrogen, soil total phosphorus, soil available phosphorus nitrogen, soil nitrogen mineralization rate, soil organic nitrogen, soil ammonium nitrogen and nitrate nitrogen, a soil sample with 0-30 cm of soil layer is collected and brought back to a laboratory for analyzing the functional properties of the soil, and the effectiveness of soil nutrients is determined and analyzed; the plant functional traits comprise measuring plant community coverage and plant height; isotope labeling and analyzing, namely measuring the absorption values of the plant species to different nitrogen compounds by using a stable nitrogen isotope tracing method; control and labelled plants were analysed with elemental analyser Flash EA1112 HT-isotope mass spectrometer Finnigan MATD eltaV advantage ¹⁵ N abundance and nitrogen content.