A method for determining grassland carrying capacity based on key field theory

Abstract

This invention relates to a method for determining grassland carrying capacity pressure based on critical field theory. The method divides grasslands into warm-season and cold-season pastures, and determines the theoretical carrying capacity, actual carrying capacity, and carrying capacity pressure for each. In other words, based on critical field theory, this invention takes the maximum carrying capacity pressure of warm-season and cold-season pastures as the regional annual carrying capacity pressure. Therefore, the method of this invention makes the obtained actual carrying capacity pressure more scientific and reliable, contributing to a better grassland-livestock balance and improving livestock output while protecting grassland ecology.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of geography, remote sensing and ecology, and in particular to a method for determining grassland carrying capacity pressure based on key field theory. Background Technology

[0002] In addition to the adverse effects of climate change, overgrazing can also easily cause large-scale grassland degradation in the short term.

[0003] To prevent grassland degradation, it is necessary to determine the amount of livestock to be raised based on the amount of grass available, reduce grazing pressure, rationally control the intensity of use, and achieve sustainable development of grasslands through a balance between grass and livestock.

[0004] To achieve a balance between grassland and livestock and to utilize grasslands while protecting their ecology, it is necessary to appropriately determine the grassland carrying capacity or the theoretical carrying capacity of the grassland. In existing technologies, methods for determining the theoretical carrying capacity of grassland can be divided into two main categories: yield-based carrying capacity and nutrient-based carrying capacity, including the total digestible nutrients (TDN) method and the digestible crude protein (DCP) method.

[0005] Productive carrying capacity (PLC) determines the number of livestock that can be supported per unit of pasture based on the amount of forage required by livestock. Nutritional carrying capacity (LCC), on the other hand, further considers the quality of forage, i.e., its nutritional value, and is more scientific and precise than PLC. Regardless of the method used, the theoretical carrying capacity is the amount of feed (nutrient content) that a region can provide within a certain timeframe (usually measured in years) and the amount of forage (nutrient content) required for livestock to maintain normal growth. In practical applications, many studies use annual forage yield to measure the theoretical carrying capacity. This method can lead to estimation errors due to the mismatch between forage growth patterns and livestock feed requirements in time and space. Furthermore, the existing methods do not consider actual grazing conditions and do not distinguish between warm-season and winter pastures: in actual grazing, herders divide pastures into warm-season and cold-season pastures, rotating them with the seasons. Summary of the Invention

[0006] The purpose of this invention is to propose a method for determining grassland carrying capacity pressure based on key field theory. This method determines the annual carrying capacity pressure of a region based on key field theory.

[0007] The method for determining grassland carrying capacity based on key field theory according to the present invention includes the following steps:

[0008] Step 1: Determine the boundaries of warm-season and cool-season pastures.

[0009] Based on the regional grassland distribution map, pastures are divided into warm-season pastures and cool-season pastures.

[0010] Step 2: Determine the theoretical carrying capacity of the area.

[0011] Using remote sensing NPP products, grassland aboveground biomass (i.e., forage yield) for different grassland types was converted. Based on the distribution maps of warm-season and cool-season pastures, the forage yields of warm-season and cool-season pastures were obtained. Using the forage yield, grassland utilization rate, proportion of edible forage, and supplementary feed amount during the warm season, the theoretical carrying capacity of warm-season pastures was calculated. Similarly, using the forage yield, grassland utilization rate, proportion of edible forage, natural biomass loss rate, nutrient loss rate, and supplementary feed amount during the cool season, the theoretical carrying capacity of cool-season pastures was calculated.

[0012] Step 3: Determine the actual carrying capacity of the area.

[0013] The actual carrying capacity of warm-season pastures is calculated based on the region's year-end livestock inventory and slaughter volume, converted to standard sheep units. The actual carrying capacity of cold-season pastures is also calculated based on the region's year-end livestock inventory, converted to standard sheep units. If there are large wild herbivores in the region, the carrying capacity of these large wild herbivores should be added to the actual carrying capacity of both warm-season and cold-season pastures.

[0014] Step 4: Determine the annual carrying capacity pressure of the region.

[0015] The ratio of the theoretical carrying capacity of warm-season pastures to the actual carrying capacity of warm-season pastures is the warm-season carrying pressure, and the ratio of the theoretical carrying capacity of cold-season pastures to the actual carrying capacity of cold-season pastures is the cold-season carrying pressure. According to the critical field theory, the regional annual carrying pressure is the higher of the carrying pressure of warm-season pastures and the carrying pressure of cold-season pastures.

[0016] Preferably, in step two, the theoretical carrying capacity of the warm-season pasture is determined by the following method:

[0017]

[0018] in,

[0019] This refers to the theoretical carrying capacity of a warm-season pasture, which is the number of sheep units (standard sheep units) that the area can support during the warm season.

[0020] warm-season pasture grassland type i The total grass yield is the grassland hay yield (standard hay) at 14% peak biomass moisture content.

[0021] Determine grassland type in warm-season pastures using the following methods i Total grass yield:

[0022]

[0023] n Number of grassland types;

[0024] Grassland types in warm-season pastures i Total NPP;

[0025] Grassland types in warm-season pastures i The area;

[0026] Grassland type i The proportion of aboveground NPP to total NPP;

[0027] Grassland type i The hay ratio coefficient;

[0028] Grassland type i Percentage of edible forage (%)

[0029] Grassland type i Utilization rate (%)

[0030] This refers to the daily feed intake of a sheep unit (kg / d). For example, each sheep unit requires 1.38 kg of standard hay per day.

[0031] : Number of days of grazing during the warm season (d);

[0032] : Supplemental feed amount during the warm season, including feed from sources other than natural grasslands in the region, including artificial grasslands, straw, and other supplemental feed amounts.

[0033] Preferably, in step two, the theoretical carrying capacity of the cold-season pasture is determined by the following method:

[0034]

[0035] Theoretical carrying capacity of cold-season pastures, i.e., the number of sheep units (standard sheep units) that can be carried in the cold season within a region.

[0036] Cool-season pasture grassland type i Total grass yield (kg) is the grass yield of grassland at 14% of peak biomass moisture content (standard hay).

[0037] Determine grassland type in cool-season pastures using the following methods i Total grass yield:

[0038]

[0039] Grassland types in cold-season pastures i Total NPP (kg);

[0040] Grassland types in cold-season pastures i The area;

[0041] Grassland type i The proportion of aboveground NPP to total NPP;

[0042] Grassland type i The hay ratio coefficient;

[0043] n Number of grassland types;

[0044] Natural loss rate of biomass on pastureland during the cold season;

[0045] : Nutrient loss rate of pastureland in the cold season;

[0046] Grassland type i Percentage of edible forage (%)

[0047] Grassland type i Utilization rate (%)

[0048] This refers to the daily feed intake of a sheep unit (kg / d). For example, each sheep unit requires 1.38 kg of standard hay per day.

[0049] : Number of days of grazing during the cold season (d);

[0050] : Cold season supplementary feed amount, which includes feed from sources other than natural grasslands in the region, including artificial grasslands, straw and other supplementary feed amounts.

[0051] Preferably, in step three, the actual carrying capacity of the warm-season pasture is determined by the following method:

[0052]

[0053] : Actual livestock carrying capacity of warm-season pastures (standard sheep units).

[0054] Livestock type j The year-end inventory (number of heads), where m is the number of livestock types;

[0055] Livestock type j Proportion of young and medium-sized livestock (%)

[0056] Livestock type j The conversion factor for young sheep units;

[0057] Livestock type j Conversion factor for adult sheep;

[0058] Livestock type j Number of animals slaughtered (number of animals);

[0059] Large wild herbivore carrying capacity (standard sheep units), which is the actual number of large wild herbivore sheep units (standard sheep units) that can be carried in the area.

[0060] Preferably, in step three, the actual carrying capacity of the cold-season pasture is determined in the following manner:

[0061]

[0062] : Actual livestock carrying capacity of pastures during the cold season (standard sheep units).

[0063] Livestock type j The year-end inventory (number of heads), where m is the number of livestock types;

[0064] Livestock type j Proportion of young and medium-sized livestock (%)

[0065] Livestock type j The conversion factor for young sheep units;

[0066] Livestock type j Conversion factor for adult sheep;

[0067] Large wild herbivore carrying capacity (standard sheep units), which is the actual number of large wild herbivore sheep units (standard sheep units) that can be carried in the area.

[0068] Preferably, in step four, the livestock carrying pressure in warm-season pastures is determined by the following method:

[0069]

[0070] : Livestock carrying pressure during warm season;

[0071] : Actual livestock carrying capacity of warm-season pastures (standard sheep units).

[0072] The theoretical carrying capacity of a warm-season pasture is the number of sheep units (standard sheep units) that a region can support during the warm season.

[0073] Preferably, in step four, the livestock carrying pressure in the cold season pasture is determined by the following method:

[0074]

[0075] : Pressure on livestock carrying capacity during the cold season;

[0076] : Actual livestock carrying capacity of pastures during the cold season (standard sheep units).

[0077] Theoretical carrying capacity of cold-season pastures, which is the number of sheep units (standard sheep units) that can be carried in the cold season within a region.

[0078] Preferably, in step four, the regional annual carrying capacity pressure is determined in the following manner:

[0079]

[0080] Regional annual livestock carrying capacity pressure;

[0081] : Livestock carrying pressure during warm season;

[0082] : Pressure on livestock during the cold season.

[0083] This invention improves upon traditional methods for determining livestock carrying capacity, making the obtained actual livestock carrying capacity more scientific, accurate, and applicable, which helps management departments implement more precise grass-livestock balance policies. Attached Figure Description

[0084] Figure 1 This is a flowchart of a method for determining grassland carrying capacity based on key field theory according to an embodiment of the present invention. Detailed Implementation

[0085] The inventors of this invention noted that the determination of the theoretical carrying capacity should take into account the actual production and lifestyle of the region; and that the critical field theory should be adopted, with the grazing season with the lowest carrying capacity as the maximum carrying capacity that the entire region can bear.

[0086] Furthermore, actual carrying capacity is another important indicator for measuring regional grassland-livestock balance. In current technology, actual carrying capacity data is generally derived from the current livestock inventory, usually the year-end inventory, converted into standard sheep units. This also affects the accurate determination of carrying capacity pressure. The current livestock inventory is a static indicator and cannot reflect the true number of livestock or the amount of forage consumed over a past period, because livestock numbers change dynamically with seasonal slaughter and farrowing, and the two can differ by 20-40%. Therefore, livestock numbers and year-end inventory are two different concepts and should be calculated separately. At the same time, livestock of different ages have different forage requirements. In addition, in areas with frequent wildlife activity, the consumption of natural grasslands by large herbivorous wild animals cannot be ignored.

[0087] According to an embodiment of the present invention, the grassland carrying capacity pressure is determined based on key field theory as follows. Specifically, based on grassland resource data, remote sensing data, and statistical data, the theoretical carrying capacity, actual carrying capacity, and carrying capacity pressure of a region are determined. The method includes the following four steps.

[0088] Step 1: Determine the boundaries of warm-season and cool-season pastures. This may involve the following five sub-steps.

[0089] (1.1) Using vector data, with the help of ArcGIS software, the “Clip” tool is used to obtain grassland resource vector data according to the vector boundaries.

[0090] (1.2) Based on grassland resource vector data, in ArcGIS software, the attribute filtering tool is used to filter out warm-season pasture patches, and the “Export Data” tool is used to obtain warm-season pasture grassland resource vector data.

[0091] (1.3) Based on grassland resource vector data, in ArcGIS software, the attribute filtering tool is used to filter out cold-season pasture patches, and the “Export Data” tool is used to obtain cold-season pasture grassland resource vector data.

[0092] (1.4) Based on the vector data of warm-season pasture grassland resources, the “Polygon to Raster” tool in ArcGIS software is used to obtain the raster data of warm-season pasture grassland resources.

[0093] (1.5) Based on the vector data of cold-season pasture grassland resources, the “Polygon to Raster” tool in ArcGIS software is used to obtain the raster data of cold-season pasture grassland resources.

[0094] Step 2: Determine the theoretical carrying capacity of the area. For example, this includes the following 11 sub-steps.

[0095] (2.1) Based on the spatial range, download the MODIS NPP product, i.e. MODIS17A3. The data can be obtained by downloading from USGS.

[0096] (2.2) The downloaded MODIS17A3 data was used to obtain warm-season pasture grassland NPP raster data in ArcGIS software using the "Extract by Mask" tool.

[0097] (2.3) Using the warm-season pasture grassland resource raster data and the warm-season pasture grassland NPP raster data, in ArcGIS software, use the "Raster Calculator" tool to determine the type of each grassland in the warm-season pasture according to the following formula. i The grass yield of all grid cells is used to obtain the warm-season pasture grass yield raster data.

[0098]

[0099] A certain grassland type in a warm-season pasture is i The grass yield of all grassland areas (in units such as kg); usually refers to the grass yield in one year.

[0100] A certain grassland type in a warm-season pasture is i The grid's NPP (units such as kg / m³) 2 (For example, it refers to within one year).

[0101] Net primary productivity (NPP), also known as vegetation net primary productivity, refers to the net amount of photosynthetic organic matter absorbed by vegetation per unit area (e.g., one square meter) per unit time (e.g., one year). In other words, it is the total amount of organic matter fixed by plants through net photosynthesis minus the total amount of organic matter consumed by plant respiration. In ecology, NPP is a very important ecological indicator that reflects the productivity and energy conversion efficiency of an ecosystem.

[0102] Grassland type i The proportion of above-ground NPP to total NPP (above-ground NPP / (above-ground NPP + underground NPP)) can be determined based on empirical data.

[0103] Grassland type i The hay ratio coefficient is uniformly set to 0.86.

[0104] Grassland type iThe total area of ​​all grid cells (in m², for example) 2 ), equal to the area of ​​each grid cell and the grass type. i The product of the corresponding number of graticules; for example, in MODIS17A3 data, the area of ​​each graticule is typically 250,000 (m²). 2 ).

[0105] For warm-season pastures It can be written as . Refers to grassland types in warm-season pastures i The area.

[0106] Besides using satellite rasterized imagery to determine the area, statistical survey data and empirical data can also be used. Alternatively, satellite raster imagery can be combined with statistical survey data and empirical data to determine the area. For example, when statistical survey data and empirical data are available, satellite raster imagery can be used to assist in verifying the distribution and area of ​​various grassland types; when statistical survey data and empirical data are unavailable, satellite raster imagery can be used to analyze and determine the distribution and area of ​​various grassland types.

[0107] (2.4) Using the raster data of grass yield in warm-season pastures, the “RasterCalculator” tool in ArcGIS software is used to determine the type of each grassland in the warm-season pastures according to the following formula. i The edible forage content of grasslands in all grid cells is used to obtain the grid data of edible forage content in warm-season pastures:

[0108]

[0109] A certain grassland type in a warm-season pasture is i The amount of edible forage in a grid (units such as kg); usually refers to the yield in a year.

[0110] Same as above;

[0111] Grassland type i The percentage of edible forage grass is determined according to the upper limit of the edible grass percentage in the grassland degradation index: 80% for non-degraded grassland, 70% for slightly degraded grassland, 50% for moderately degraded grassland, and 30% for severely degraded grassland.

[0112] Grassland type i Utilization rate (%): According to the regulations on grassland utilization rate, the upper limit of grazing utilization rate is 65%.

[0113] (2.5) Using the raster data of edible forage in warm-season pastures, the total edible forage in warm-season pastures was statistically calculated using the "ZonalStatistics" tool in ArcGIS software. (kg).

[0114] (2.6) Using the total edible forage amount of warm-season pastures and the supplementary feed amount from statistical yearbooks, determine the theoretical carrying capacity of warm-season pastures according to the following formula:

[0115]

[0116] Theoretical carrying capacity of warm-season pastures, which is the number of sheep units (standard sheep units) that can be carried in a region during the warm season.

[0117] Same as above;

[0118] : Supplemental feeding amount during warm season (kg);

[0119] This refers to the daily feed intake of a sheep unit (kg / d). For example, each sheep unit requires 1.38 kg of standard hay per day.

[0120] : Number of grazing days in the warm season (d), the warm season is calculated from May to September, 155 days.

[0121] (2.7) The downloaded MODIS17A3 data was used to obtain the NPP raster data of the cold season pasture grassland resource data in ArcGIS software by using the "Extract by Mask" tool.

[0122] (2.8) Using the cool-season pasture grassland resource raster data and the cool-season pasture grassland NPP raster data, in ArcGIS software, using the "Raster Calculator" tool, based on the following formula, after determining the grassland type of each raster in the cool-season pasture, the grassland type of a certain grassland in the cool-season pasture is obtained. i Raster data on grass yield;

[0123]

[0124] A certain grassland type in a cold-season ranch is i The total grass yield (kg) of all grid cells.

[0125] A certain grassland type in a cold-season ranch is i NPP of the grid (kg / m 2For example, it usually refers to within one year.

[0126] Refers to grassland types in cold-season pastures i The area can be determined by multiplying the area of ​​each grid cell by the number of grid cells corresponding to the relevant grassland type. Similar to warm-season pastures, The area can be determined using satellite raster imagery, statistical survey data, or empirical data. Alternatively, a combination of satellite raster imagery and statistical survey / empirical data can be used to determine the area. For example, when statistical survey / empirical data is available, satellite raster imagery can be used to assist in verifying the distribution and area of ​​various grassland types; when statistical survey / empirical data is unavailable, satellite raster imagery can be used to analyze and determine the distribution and area of ​​various grassland types.

[0127] Grassland type i The proportion of aboveground NPP to total NPP can be determined based on empirical data.

[0128] Grassland type i The hay ratio coefficient is uniformly set to 0.86.

[0129] Natural loss rate of aboveground biomass in cold-season pastures. Studies on aboveground biomass under grazing ban and free-grazing conditions show that aboveground biomass declines in both from August to April of the following year, with natural loss rates of 46.2% and 49.6%, respectively. The value is 40%.

[0130] Nutrient loss rate in cold-season pastures. According to studies on the DCP and TDN of various grassland types in summer / autumn and winter / spring pastures, the DCP of meadows, grasslands, and marshes in winter / spring pastures is only 23.4% of that in summer / autumn pastures, while the TDN of winter / spring pastures is 86.3%, 90.6%, and 85.2% of that in summer / autumn pastures, respectively. Taking into account the loss of both DCP and TDN, the nutrient loss rate is set at 20%.

[0131] (2.9) Using the raster data of grass yield in cool-season pastures, the “RasterCalculator” tool in ArcGIS software was used to determine the type of each grassland in cool-season pastures according to the following formula. i The amount of edible forage in grasslands was obtained, and raster data of the amount of edible forage in cool-season pastures was obtained:

[0132]

[0133] A certain grassland type in a cold-season ranch is i The amount of edible forage in all grids (e.g., in kg).

[0134] Same as above;

[0135] Same as (2.4);

[0136] Same as (2.4).

[0137] (2.10) Using the raster data of edible forage in cool-season pastures, the total edible forage in cool-season pastures was statistically calculated using the "ZonalStatistics" tool in ArcGIS software. (kg).

[0138] (2.11) Using the total edible forage amount of the cool-season pasture and the supplementary feed amount from the statistical yearbook, determine the theoretical carrying capacity of the cool-season pasture according to the following formula:

[0139]

[0140] Theoretical carrying capacity of cold-season pastures, i.e., the number of sheep units (standard sheep units) that can be carried in the cold season within a region.

[0141] Same as above;

[0142] : Supplemental feeding amount during the cold season (kg);

[0143] Same as (2.6);

[0144] : Number of grazing days in the cold season (d), which is calculated as 210 days from January to April and from October to December.

[0145] Step 3: Determine the actual carrying capacity of the area. For example, this includes the following two sub-steps:

[0146] (3.1) Based on the year-end livestock inventory and slaughter volume (or slaughter volume) from the statistical yearbook and survey data on wild large herbivores (if unavailable, set to 0), use Excel software to determine the actual carrying capacity of warm-season pastures according to the following formula:

[0147]

[0148] : Actual livestock carrying capacity of warm-season pastures (standard sheep units).

[0149] Livestock type j The year-end inventory (number of heads), where m is the number of livestock types;

[0150] Livestock type j Proportion of young and medium-sized livestock (%)

[0151] Livestock type j The conversion factor for young sheep units;

[0152] Livestock type j Conversion factor for adult sheep;

[0153] Livestock type j Number of animals slaughtered (number of animals);

[0154] Large wild herbivore carrying capacity (standard sheep units), which is the actual number of large wild herbivore sheep units (standard sheep units) that can be carried in the area.

[0155] When converting livestock to adult and marketable size, sheep = 1 sheep unit, yaks = 4 sheep units, and horses = 6 sheep units. When converting livestock numbers, the proportions of different types of young animals in the herd are as follows: young sheep (under 1 year old) account for 21.32% of the total herd, with each young animal equivalent to 0.4 sheep units; young horses (under 2 years old) account for 50% of the total herd, with each young animal equivalent to 3 sheep units; and young cattle (including yaks, yellow cattle, and dairy cattle) (under 2 years old) account for 49% of the total herd, with each young animal equivalent to 2.8 sheep units.

[0156] (3.2) Based on the year-end livestock inventory data and wild large herbivore survey data from the statistical yearbook (if unavailable, set to 0), for example, Excel software can be used to determine the actual carrying capacity of pastures in the cold season according to the following formula:

[0157]

[0158] : Actual livestock carrying capacity of pastures during the cold season (standard sheep units).

[0159] Livestock type j The year-end inventory (number of heads), where m is the number of livestock types;

[0160] Livestock type j Proportion of young and medium-sized livestock (%)

[0161] Livestock typej The conversion factor for young sheep units;

[0162] Livestock type j Conversion factor for adult sheep;

[0163] Large wild herbivore carrying capacity (standard sheep units), which is the actual number of large wild herbivore sheep units (standard sheep units) that can be carried in the area.

[0164] Step 4: Determine the annual carrying capacity of the region. This includes, for example, the following three sub-steps:

[0165] (4.1) Based on the theoretical and actual carrying capacity of warm-season pastures, the carrying pressure of warm-season pastures is determined according to the following formula:

[0166]

[0167] The pressure on livestock during the warm season.

[0168] Same as (3.1);

[0169] Same as (2.6).

[0170] (4.2) Based on the theoretical and actual carrying capacity of the cold-season pasture, the carrying pressure of the cold-season pasture is determined according to the following formula:

[0171]

[0172] : Pressure on livestock during the cold season.

[0173] Same as (3.2);

[0174] Same as (2.11).

[0175] (4.3) Based on the livestock carrying capacity of warm-season and cold-season pastures, the annual livestock carrying capacity of the region is determined in the following manner:

[0176]

[0177] Regional annual livestock carrying capacity pressure.

[0178] Same as (4.1);

[0179] Same as (4.2).

[0180] The methods described in the above embodiments of this invention are based on grassland distribution data, remote sensing NPP products, and regional statistical data, including livestock inventory, slaughter volume, and supplementary feeding volume. According to actual livestock production methods, the methods consider the consumption of pasture by livestock slaughtered within the year and the nutrient loss of pasture during the cold season. Based on nutrient carrying capacity and critical field theory, the above embodiments of this invention propose a novel method for determining carrying capacity pressure, which can more accurately determine carrying capacity pressure, thereby better promoting regional ecological environmental protection and sustainable development.

Claims

1. A method for determining grassland carrying capacity based on key field theory, characterized in that, The method includes the following steps: Step 1: Determine the boundaries of warm-season and cool-season pastures. Based on the regional grassland distribution map, pastures are divided into warm-season pastures and cool-season pastures. Step 2: Determine the theoretical carrying capacity of the area. Using remote sensing NPP products, grassland aboveground biomass (i.e., grass yield) for different grassland types was converted. Based on the distribution maps of warm-season and cool-season pastures, the grass yields of warm-season and cool-season pastures were obtained. Using the grass yield, grassland utilization rate, proportion of edible forage, and supplementary feed amount during the warm season, the theoretical carrying capacity of warm-season pastures was calculated. Similarly, using the grass yield, grassland utilization rate, proportion of edible forage, natural loss rate of grassland aboveground biomass, nutrient loss rate, and supplementary feed amount during the cool season, the theoretical carrying capacity of cool-season pastures was calculated. Step 3: Determine the actual carrying capacity of the area. The actual carrying capacity of warm-season pastures is calculated based on the region's year-end livestock inventory and slaughter volume, converted to standard sheep units. The actual carrying capacity of cold-season pastures is also calculated based on the region's year-end livestock inventory, converted to standard sheep units. If there are large wild herbivores in the region, the carrying capacity of these large wild herbivores should be added to the actual carrying capacity of both warm-season and cold-season pastures. Step 4: Determine the annual carrying capacity pressure of the region. The ratio of the theoretical carrying capacity to the actual carrying capacity of a warm-season pasture is the warm-season carrying pressure, and the ratio of the theoretical carrying capacity to the actual carrying capacity of a cold-season pasture is the cold-season carrying pressure. According to the critical field theory, the regional annual carrying pressure is the higher of the warm-season and cold-season carrying pressures. In step three, the actual carrying capacity of the warm-season pasture is determined as follows: : Actual livestock carrying capacity of pastures during the warm season, in standard sheep units; Livestock type j The year-end inventory is expressed in head count, where m represents the number of different types of livestock. Livestock type j The proportion of young and middle-aged livestock, in percentages (%) Livestock type j Conversion factor for young sheep; Livestock type j Conversion factor for adult sheep; Livestock type j The number of animals slaughtered, expressed in heads. Large herbivore carrying capacity, measured in standard sheep units (SMUs), which is the actual number of large herbivore sheep units that can be carried within a given area. In step three, the actual carrying capacity of the cold-season pasture is determined as follows: : Actual livestock carrying capacity of pastures during the cold season, in standard sheep units; Livestock type j The year-end inventory is expressed in head count, where m represents the number of different types of livestock. Livestock type j The proportion of young and middle-aged livestock, in percentages (%) Livestock type j Conversion factor for young sheep; Livestock type j Conversion factor for adult sheep; Large herbivore carrying capacity, measured in standard sheep units (SMUs), which is the actual number of large herbivore sheep units that can be carried within a given area. In step four, the warm-season pasture carrying capacity is determined as follows: : Livestock carrying pressure during warm season; : Actual livestock carrying capacity of pastures during the warm season, in standard sheep units; The theoretical carrying capacity of a warm-season pasture is the number of sheep units that a region can support during the warm season, measured in standard sheep units. In step four, the carrying capacity of the cold-season pasture is determined as follows: : Pressure on livestock carrying capacity during the cold season; : Actual livestock carrying capacity of pastures during the cold season, in standard sheep units; The theoretical carrying capacity of a cold-season pasture is the number of sheep units that a region can support during the cold season, measured in standard sheep units. In step four, the regional annual carrying capacity pressure is determined as follows: Regional annual livestock carrying capacity pressure; : Livestock carrying pressure during warm season; : Pressure on livestock during the cold season.

2. The method for determining grassland carrying capacity based on key field theory as described in claim 1, characterized in that, In step two, the theoretical carrying capacity of the warm-season pasture is determined using the following method: in, The theoretical carrying capacity of a warm-season pasture is the number of sheep units that a region can support during the warm season, and the unit is a standard sheep unit. warm-season pasture grassland type i The total grass yield is the hay yield of grassland at 14% of peak biomass moisture content. Determine grassland type in warm-season pastures using the following methods i Total grass yield: n Number of grassland types; Grassland types in warm-season pastures i Total NPP; Grassland types in warm-season pastures i The area; Grassland type i The proportion of aboveground NPP to total NPP; Grassland type i The hay ratio coefficient; Grassland type i The percentage of edible forage, expressed in % Grassland type i Utilization rate, in % This refers to the daily feed intake of a sheep, expressed in kg / d. : Number of days for grazing during the warm season, in days; : Supplemental feed amount during the warm season, including feed from sources other than natural grasslands in the region, including artificial grasslands, straw, and other supplemental feed amounts.

3. The method for determining grassland carrying capacity based on key field theory as described in claim 1, characterized in that, In step two, the theoretical carrying capacity of the cold-season pasture is determined using the following method: Theoretical carrying capacity of a pasture in the cold season, which is the number of sheep units that a region can support in the cold season, with the unit being the standard sheep unit; Cool-season pasture grassland type i Total grass yield, in kg, is the hay yield of grassland at 14% peak biomass moisture content; Determine grassland type in cool-season pastures using the following methods i Total grass yield: Grassland types in cold-season pastures i Total NPP, in kg; Grassland types in cold-season pastures i The area; Grassland type i The proportion of aboveground NPP to total NPP; Grassland type i The hay ratio coefficient; n Number of grassland types; Natural loss rate of biomass on pastureland during the cold season; : Nutrient loss rate of pastureland in the cold season; Grassland type i The percentage of edible forage, expressed in % Grassland type i Utilization rate, in % This refers to the daily feed intake of a sheep, expressed in kg / d. : Number of days for grazing during the cold season, in days; : Cold season supplementary feed amount, which includes feed from sources other than natural grasslands in the region, including artificial grasslands, straw and other supplementary feed amounts.

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