CN104217103A - Establishment and Digital Representation Method of a Subtype of Grassland Vegetation - Google Patents

Abstract

The invention relates to a method for establishing and digitalizing grassland vegetation subtypes, which comprises the following steps: 1) marking the survey area, and conducting vegetation surveys on the survey sample points obtained; 2) calculating the vegetation density in each survey sample point. Plant species dominance; 3) According to the plant species and species dominance of each survey sample point, it is judged whether they are the same vegetation subtype. When the vegetation subtype changes, the boundary coordinates of different vegetation subtypes are actually measured to obtain the survey area. 4) Construct the attribute data table of each vegetation subtype, and draw the digitized vector distribution map of each vegetation subtype through the adjustment and superposition of layer transparency; 5) The obtained vegetation subtype The digitized vector maps were put together to finally generate a digitized vector distribution map showing the distribution of vegetation subtypes in the survey area and the composition and distribution of dominant species in each vegetation subtype. The invention can be widely used in practical applications such as research on the evolution of grassland vegetation, agricultural production and monitoring of grassland vegetation resources.

Description

Establishment and Digital Representation Method of a Subtype of Grassland Vegetation

technical field

The invention relates to an informatization and digital representation method of grassland vegetation, in particular to an establishment and digital representation method of a grassland vegetation subtype. the

Background technique

In terms of the classification of grassland types, scholars at home and abroad have proposed dozens of methods in seven categories. Academician Ren Jizhou of my country proposed the famous comprehensive sequence classification system for grasslands. According to this system, grasslands can be divided into: class-based on meteorological factors temperature and precipitation, sub-category-based on soil factors, type-based on vegetation factors, under type According to the characteristics of vegetation, it can be divided into subtype, miniature and so on. Since the beginning of the 21st century, with the widespread application of computer technology, network technology, "3S" technology and geostatistics, the visualization and digitization of grassland classification has entered a stage of rapid development. the

At present, there are many researches on the visualization and digitalization of grassland types, subtypes, and types at the large-scale level. Digital grassland distribution maps and their attribute databases at the level of types, subtypes, and types have been established. There is no reliable digital method for the composition of vegetation subtypes and plant dominance information, and there is a lack of clear principles and methods for naming vegetation subtypes. If the distribution of vegetation subtypes and the plant composition and distribution of each subtype can be displayed intuitively and quantitatively on a regional distribution map, and the visualization and digitization of vegetation subtype distribution and plant composition can be realized, the layer information can be used for people. It provides rich subtypes and their vegetation information, which can provide simple, intuitive, accurate and scientific support for grassland resource assessment, scientific research and decision-making of agricultural and animal husbandry departments. the

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a grassland vegetation subtype establishment and digital representation method that can reflect the distribution of grassland vegetation subtypes, the plant composition of each vegetation subtype and the information of plant dominance. the

In order to achieve the above object, the present invention adopts the following technical solutions: a kind of establishment and digital representation method of grassland vegetation subtype, which includes the following steps: 1) mark the survey area, and carry out vegetation survey to the survey sample points obtained; 2) Calculate the plant species dominance of the vegetation in each survey sampling point; 3) judge whether it is the same vegetation subtype according to the plant species and species dominance of each survey sampling point, and when the vegetation subtype changes, the actual measurement of different vegetation subtypes Input the boundary coordinates of each vegetation subtype into Google Earth and ENVI4.7 programs to obtain the vector base map of each vegetation subtype in the survey area; 4) Construct the attribute data table of each vegetation subtype, with different The colors represent different dominant species of plants, and the colors are assigned according to the dominance of different dominant species of plants, and the distribution layer of each dominant plant is generated on the vector base map of each vegetation subtype, and the transparency of each distribution layer is adjusted and superimposed to obtain each vegetation The vector distribution map of the subtype; 5) Put together the digitized vector diagrams of each vegetation subtype obtained in step 4), and finally generate and display the distribution of vegetation subtypes in the survey area and the composition and composition of dominant species in each vegetation subtype. Vector profile of the distribution. the

Described step 2) in, the dominance degree SDR of plant species is:

SDR＝[(Y'+C'+D')/3]×100％;

Among them, Y' is the relative biomass of a certain plant, C' is the relative coverage of a certain plant, D' is the relative density of a certain plant; the relative biomass Y' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; Y</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; ;</span>$

Among them, y is the biomass of a certain plant; Y is the total biomass of vegetation in the survey sample point;

The relative coverage C' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; ;</span>$

Among them, c is the coverage of a certain plant; C is the total coverage of vegetation in the survey sample point;

The relative density D' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; D.</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ;</span>$

Among them, d is a certain plant density, and D is the total density of vegetation in the survey sample point. the

In said step 3), the method for judging whether each survey sample point is the same vegetation subtype includes: 1) if there is a plant species dominance > 50% in a certain survey sample point, then it has the same dominance as the survey sample point The survey sampling points of each plant species belong to the same vegetation subtype, and the vegetation subtype is named after a plant; The survey sample points with the same dominant plant species belong to the same vegetation subtype, and the survey sample points are named after the two plants according to the order of the species dominance of the two plants; 3) In other cases, the plant species dominance From large to small, the survey sample points with the same plant species dominance were classified into the same vegetation subtype, and the vegetation subtype was named after the first three dominant plants. the

Described step 4) in, the drawing method of the digitized vector distribution map of each vegetation subtype comprises: 1) make the attribute data table of each vegetation subtype; , the different colors that are easy to distinguish represent the dominant species in each vegetation subtype, and the representative colors of the same dominant species in different vegetation subtypes in the entire survey area are consistent; Assignment, quantitatively express the dominance of the dominant species in different survey sampling points in the vegetation subtype with the depth of the color, and use the Krigging interpolation method to generate the dominant species in each vegetation subtype on the vector base map of the vegetation subtype 3) Adjust the transparency of the distribution layer of each dominant plant: the distribution layer of the plant with the largest species dominance in each vegetation subtype does not adjust the transparency; the transparency of the distribution layer of the remaining dominant plants according to Its average species dominance within this vegetation subtype make adjustments, transparency Among them, the average species dominance is the average value of the dominance degree of the dominant species in all surveyed sampling points in the vegetation subtype; 4) According to the order of transparency from small to large, the distribution layers of different dominant species in each vegetation subtype are superimposed, That is, the less transparent ones are placed in the inner layer, and the more transparent ones are placed in the outer layer, so that the distribution of dominant species in the inner layer can be observed through the outer layer.

Because the present invention adopts the above technical scheme, it has the following advantages: 1. The present invention can intuitively and quantitatively observe the distribution of grassland vegetation subtypes and each vegetation because it realizes the digital representation of grassland vegetation subtype distribution on a vector distribution map. Composition and distribution of dominant species within subtypes. 2. The present invention introduces a method of naming different vegetation subtypes according to the degree of dominance of plants, which makes up for the current deficiency in naming vegetation subtypes. 3. In the present invention, because the vegetation survey method is not limited by the size of the required survey area, the latitude and longitude interval unit of the survey sample point can be flexibly selected according to the survey area area and manpower, financial resources, and material resources conditions, which greatly improves the investigation of the survey sample point. efficiency. 4. The present invention represents different plants by adjusting the RGB values of the three primary colors. There are many types of colors, and the selection is flexible. The representative colors of plants are easy to distinguish. The selected color can be obtained by adjusting the RGB value (or HSV value) of the color, and the operation is simple. 5. Since the attribute database information established by the present invention can provide various data information as required, such as geographical features, meteorological factors, pest and rodent information, etc., its application value is greatly increased. 6. The digitization process of the present invention is simple and flexible, and can be realized through the basic operation of ArcGIS. Therefore, the present invention can be widely used in practical applications such as grassland vegetation evolution research, agricultural production and grassland vegetation resource monitoring. the

Description of drawings

Fig. 1 is vegetation subtype investigation area and vegetation investigation sampling point of the present invention

Fig. 2 is the Stipa type distribution area and the Stipa distribution figure of the present invention

Fig. 3 is alfalfa Leymus chinensis type region and alfalfa distribution map of the present invention

Figure 4 is a commonly used partial RGB color table

Fig. 5 is alfalfa, Leymus chinensis type region and Leymus chinensis distribution figure of the present invention

Fig. 6 is a distribution map of alfalfa, Leymus chinensis type area and Leymus chinensis after the transparency is adjusted in the present invention

Fig. 7 is alfalfa, Leymus chinensis type region and distribution map of alfalfa and Leymus chinensis of the present invention

Fig. 8 is the distribution map of Artemisia frigidi, Cryptospermia, Stipa type area and Artemisia frigidi, Cryptospermia, Stipa in the present invention

Fig. 9 is the vegetation subtype distribution and each subtype plant composition and distribution diagram in the survey area of the present invention

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments. the

The establishment of grassland vegetation subtype of the present invention and digital representation method, comprise the following steps:

1) Mark the survey area, and conduct vegetation survey on the obtained survey sample points. the

As shown in Figure 1, the survey area was marked by Google Earth (Google Map), and the vector map of the survey area was obtained by using ENVI4.7 (The Environment for Visualizing Images, a complete remote sensing image processing platform) software, and marked on the vector map Survey sample points, obtain vegetation survey sample points by ArcGIS (Geographic Information System) with latitude and longitude 2 "(only as an example, but not limited to this). Each dot in Fig. 1 represents a survey sample point, its area It is 1m ² , and the type, coverage, height, density and biomass of the vegetation are investigated in the survey sample point.

2) Calculate the plant species dominance of the vegetation in each survey sample point. the

The species dominance degree SDR of a certain plant in the survey sample point is expressed in percentiles, and the calculation method of SDR is:

SDR＝[(Y'+C'+D')/3]×100％

Among them, Y' is the relative biomass of a certain plant, C' is the relative coverage of a certain plant, and D' is the relative density of a certain plant. The relative biomass Y' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; Y</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}$

Among them, y is the biomass of a certain plant; Y is the total biomass of vegetation in the survey sample point;

The relative coverage C' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}$

Among them, c is the coverage of a certain plant; C is the total coverage of vegetation in the survey sample point;

The relative density D' of a certain plant in the survey sample point is:

${\mathrm{<span\; class="notranslate">\; D.</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}$

Among them, d is a certain plant density, and D is the total density of vegetation in the survey sample point. the

3) Determine the boundary coordinates of each vegetation subtype, and draw the vector base map of each vegetation subtype in the survey area. the

According to the plant species and species dominance of each survey sample point to judge whether it is the same vegetation subtype, the methods for judging whether each survey sample point is the same vegetation subtype include:

① If there is a species dominance of a plant species in a survey sample point > 50%, then the survey sample points with the same dominant plant species as the survey sample point belong to the same vegetation subtype, and the vegetation subtype is classified as a plant species Naming, such as: Stipa type (as shown in Figure 2);

② If the sum of the species dominance of two plants in a survey sample point is >75%, then the survey sample points with the same dominant plant species as the survey sample point belong to the same vegetation subtype, and the species of the two plants The order of dominance degree is named this investigation sample point with two kinds of plants, as: alfalfa, Leymus chinensis type (as shown in Figure 3);

③ In other cases, according to the degree of plant species dominance from large to small, the survey sample points with the same degree of plant species dominance were classified into the same vegetation subtype, and the vegetation subtype was named after the first three dominant plants. the

When the vegetation subtype changes, the boundary coordinates of different vegetation subtypes are actually measured, and the boundary coordinates of each vegetation subtype are input into Google Earth and ENVI4.7 programs to draw the vector basemap of each vegetation subtype in the survey area. the

4) Construct the vector distribution map of dominant species in each vegetation subtype, including the following steps:

① Make the attribute data table of each vegetation subtype. the

② After determining the composition of dominant species of different vegetation subtypes, select colors with large differences, and different colors that are easy to distinguish represent the dominant species in each vegetation subtype, and the same dominant species in different vegetation subtypes in the entire survey area The representative colors of should be consistent. As shown in Figure 4, the selected color can be obtained by adjusting the RGB values (or HSV values) of the three primary colors. the

③Assign the selected color with the dominance degree SDR of the dominant species, and quantitatively express the dominance of the dominant species in different survey sampling points within the vegetation subtype (as shown in Figure 2). The Kriging (Kriging) interpolation method with high accuracy of ArcGIS was used to generate the distribution layer of each dominant plant species in each vegetation subtype on the subtype vector base map (as shown in Figure 3 and Figure 5). the

③ Adjust the transparency of the distribution layer of each dominant plant species: the distribution layer of the plant with the largest species dominance in each vegetation subtype does not adjust the transparency; average species dominance within Adjust (as shown in Figure 6), transparency mean species dominance It is the average value of the species dominance of the dominant species in all surveyed sampling points in the vegetation subtype.

④According to the order of transparency from small to large, superimpose the distribution layers of different dominant species in each vegetation subtype, that is, the ones with less transparency are placed in the inner layer, and the ones with greater transparency are placed in the outer layer, so that the outer layer can be observed The distribution of dominant species in the inner layer (as shown in Figure 6). the

5) Put together the vector distribution diagrams of each vegetation subtype obtained in step 4), and finally generate a vector distribution diagram showing the distribution of vegetation subtypes in the survey area and the composition and distribution of each dominant species in each vegetation subtype (such as Figure 9). the

Taking the vegetation survey in the substation area of the western suburbs of Xilinhot City, Xilin Gol League, Inner Mongolia as an example in 2014, the establishment of grassland vegetation subtypes and the digital representation method of the present invention are described in detail below. the

1) Mark the survey area, and conduct vegetation survey on the obtained survey sample points. the

As shown in Figure 1, the survey area is marked by Google Earth (Google Map), and the vector map of the survey area is obtained through ENVI4.7 software registration, and the survey sample points are marked on the vector map. Obtain vegetation survey sample points. Each dot in Figure 1 represents a survey sample point with an area of 1m ² , and investigate the type, coverage, height, density and biomass of vegetation in the survey sample point.

2) Calculate the plant species dominance of the vegetation in each survey sample point. the

3) Through data investigation and observation, it is obtained that the survey area is divided into five vegetation subtypes, namely Stipa type, Leymus chinensis type, Artemisia grandis type, Medicago clover, Leymus chinensis type, Artemisia frigidiosa, and Cryptospermia , Stipa type. According to the changes of vegetation subtypes, the geographical coordinates of the boundaries of different vegetation subtypes were actually measured, and input into Google Earth and ENVI4.7 programs to obtain the vector basemap of each vegetation subtype in the survey area. the

4) Construct vector distribution maps of dominant species within each vegetation subtype. the

According to the division and naming principles of different vegetation subtypes, the acquisition of vector distribution maps can be divided into the following three situations:

① Draw the vector distribution map of the vegetation subtypes of Stipa, Leymus chinensis and Artemisia grandis. the

Taking the subtype of Stipa vegetation as an example, first establish its attribute database (as shown in Table 1). Due to the large number of sampling points, only some sampling points are listed in Table 1. The content of the table can be adjusted according to the needs of the user's application field to increase. Stipa is represented by [RGB, (0,255,0)]; as shown in Figure 2, the color is assigned by the dominance of Stipa, and the dominance of Stipa in each survey sample point is quantitatively expressed by the depth of the color , through the high-precision Krigging interpolation method in ArcGIS, the distribution layer of Stipa is generated on the vector base map of the Stipa vegetation subtype; the distribution layer of Stipa is not treated with transparency, and the Stipa vegetation can be obtained Vector distribution map of subtypes. After establishing the attribute database of Artemisia grandis and Leymus chinensis, [RGB, (255,0,0)] represents Leymus chinensis and [RGB, (255,225,0)] represents Artemisia grandis, and the same method is used to The vegetation subtypes of Artemisia chinensis and Leymus chinensis were processed, and the vector distribution maps of the subtypes of Artemisia grandis and Leymus chinensis were obtained. the

Table 1 Attribute table of Stipa grassland

②Draw the vector distribution map of alfalfa and Leymus chinensis type vegetation subtypes. the

Establish the attribute database of alfalfa and Leymus chinensis type vegetation subtypes (as shown in Table 2). Due to the large number of sampling points, only some of the sampling points are listed in Table 2. The content of the table can be added according to the needs of the user's application field. Use [RGB, (160,32,240)] to represent alfalfa, and use [RGB, (255,0,0)] to represent Leymus chinensis (the same color as Leymus chinensis in step ①). As shown in Figure 3 and Figure 5, the distribution layer of Medicago sativa and the distribution layer of Leymus chinensis were generated in the vector basemaps of Medicago sativa and Leymus chinensis respectively. The distribution layer of alfalfa is not treated with transparency, according to the average dominance of alfalfa and Leymus chinensis type vegetation subtype Adjust the transparency of the Leymus distribution layer That is, P=61% (as shown in Figure 6). As shown in Figure 7, the distribution layer of alfalfa and the distribution layer of Leymus chinensis are superimposed, the distribution layer of alfalfa without transparency treatment is placed in the inner layer, and the distribution layer of Leymus chinensis with transparency adjusted is placed in the outer layer Layer overlay is performed, and the composition and distribution of plants in the subtypes of Medicago clover and Leymus chinensis can be visually and quantitatively observed through Figure 7.

Table 2 Attributes of alfalfa and Leymus chinensis

③Draw the digital vector distribution map of subtypes of Artemisia fragrans, Cryptospermia, and Stipa type vegetation. the

Establish the attribute database (as shown in Table 3) of subtypes of Artemisia frigidi, Cryptospermia, and Stipa type vegetation. Because there are many sampling points, only some sampling points are listed in Table 3. The content in the table can be determined according to the user's The fields of application need to be increased. Use [RGB, (255, 97, 0)] to represent Artemisia fragrans, [RGB, (0, 0, 255)] to represent cryptophylla, and [RGB, (0, 255, 0)] to represent Stipa (color Same color as Stipa in step ①). The Artemisia frigidiosa distribution layer, the Cryptospermia distribution layer and the Stipa distribution layer were respectively generated in the vector basemaps of Artemisia frigidiosa, Cryptogonia and Stipa type vegetation subtypes. The distribution layer of Artemisia fragilis with the greatest degree of dominance is not treated with transparency, and the transparency adjustment is performed on the distribution layer of cryptic grass (P=65%)) and the distribution layer of Stipa (P=77%). The adjustment method is the same as in step 2. The adjustment method of Leymus chinensis distribution layer is the same. As shown in Figure 8, the layers are superimposed outward in order of transparency from small to large, that is, the distribution layer of Artemisia fragrans is in the innermost layer, the distribution layer of Cinnamon grass is in the middle layer, and the distribution map of Stipa Layers are superimposed on the outermost layer to obtain the vector distribution map of subtypes of Artemisia militaris, Cryptospermia, and Stipa type vegetation. From Figure 8, we can intuitively and quantitatively observe the subtypes of Artemisia militaris, Cryptospermia, and Stipa type vegetation Composition and distribution of dominant species Artemisia frigidi, Cryptospermia and Stipa. the

Table 3 Attributes of Artemisia frigidiosa, Cryptospermia, and Stipa type grassland

5) Put together the vector distribution maps of each vegetation subtype obtained in step 4), and finally generate a digitized vector distribution map showing the distribution of subtypes and the composition and distribution of dominant plants of each subtype in the survey area. As shown in Figure 9, it can be visually and quantitatively observed that the grassland vegetation in the survey area can be divided into five subtypes: A area is Stipa type, with Stipa as the dominant plant species; , Stipa type, and the degree of plant dominance is Artemisia frigidi > Cryptospermia > Stipa; Area C is Artemisia grandis type, with Artemisia grandis as the dominant plant species; Area D is Medicago sativa, Leymus chinensis type, and the plants The degree of dominance is alfalfa > Leymus chinensis; area E is Leymus chinensis type, Leymus chinensis is the dominant plant species. the

The above-mentioned embodiments are only used to illustrate the present invention, and all equivalent transformations and improvements based on the technical solutions of the present invention should not be excluded from the protection scope of the present invention. the

Claims (4)

1. A method for establishing and digital representation of grassland vegetation subtypes, comprising the following steps: 1) Mark the survey area, and conduct vegetation survey on the acquired survey sample points; 2) Calculate the plant species dominance degree of vegetation in each survey sample point; 3) According to the plant species and species dominance of each survey sample point, judge whether they are the same vegetation subtype; when the vegetation subtype changes, actually measure the boundary coordinates of different vegetation subtypes, and input the boundary coordinates of each vegetation subtype Google Earth and ENVI4.7 program to get the vector base map of each vegetation subtype in the survey area; 4) Construct the attribute data table of each vegetation subtype, use different colors to represent different dominant plants, assign colors according to the dominance of different dominant plants, and generate the distribution map of each dominant plant on the vector base map of each vegetation subtype layer, adjust the transparency of each distribution layer and superimpose to obtain the vector distribution map of each vegetation subtype; 5) Put together the digitized vector diagrams of each vegetation subtype obtained in step 4), and finally generate a vector distribution map showing the distribution of vegetation subtypes in the survey area and the composition and distribution of each dominant plant species in each vegetation subtype. 2. the establishment and digital representation method of a kind of grassland vegetation subtype as claimed in claim 1, is characterized in that: in described step 2), the species dominance degree SDR of plant is: SDR=[(Y'+C'+D')/3]×100%; Among them, Y' is the relative biomass of a certain plant, C' is the relative coverage of a certain plant, D' is the relative density of a certain plant; the relative biomass Y' of a certain plant in the survey sample point is: ${\mathrm{<span\; class="notranslate">\; Y</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; ;</span>$ Among them, y is the biomass of a certain plant; Y is the total biomass of vegetation in the survey sample point; The relative coverage C' of a certain plant in the survey sample point is: ${\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; ;</span>$ Among them, c is the coverage of a certain plant; C is the total coverage of vegetation in the survey sample point; The relative density D' of a certain plant in the survey sample point is: ${\mathrm{<span\; class="notranslate">\; D.</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ;</span>$ Among them, d is a certain plant density, and D is the total density of vegetation in the survey sample point. 3. the establishment of a kind of grassland vegetation subtype as claimed in claim 1 and digital representation method, it is characterized in that: in described step 3), the method for judging whether each investigation sample point is same vegetation subtype comprises: 1) If there is a species dominance of a plant in a certain survey sampling point > 50%, then the survey sampling points with the same dominant plant species as the survey sampling point belong to the same vegetation subtype, and the vegetation subtype is classified as one botanical naming; 2) If the sum of the species dominance of two plants in a certain survey sample point is >75%, then the survey sample points with the same dominant plant species as the survey sample point belong to the same vegetation subtype, and according to the species dominance of the two plants The order of species dominance is named after two plants; 3) In other cases, according to the order of plant species dominance from large to small, survey sample points with the same plant species dominance are classified into the same vegetation subtype, and the vegetation subtype is named after the first three dominant plants. 4. the establishment and digital representation method of a kind of grassland vegetation subtype as claimed in claim 1, it is characterized in that: in described step 4), the drawing method of the digitization vector distribution map of each vegetation subtype is: 1) Make the attribute data table of each vegetation subtype; after determining the composition of dominant species of different vegetation subtypes, select different colors with large differences, which are easy to distinguish, to represent the dominant species in each vegetation subtype, and in the whole investigation The representative colors of the same dominant species in different vegetation subtypes in the region are consistent; 2) Use the dominance degree SDR of the dominant species to assign a value to the color, and use the depth of the color to quantitatively express the dominance of the dominant species in different survey sampling points within the vegetation subtype, and use Krigging on the vector base map of the vegetation subtype The interpolation method generates the distribution layer of each dominant plant species in each vegetation subtype; 3) Adjust the transparency of the distribution layer of each dominant plant: the distribution layer of the plant with the largest species dominance in each vegetation subtype does not adjust the transparency; average species dominance within a type make adjustments, transparency mean species dominance is the average value of the dominance of the dominant species in all surveyed sampling points in the vegetation subtype; 4) According to the order of transparency from small to large, the distribution layers of different dominant species in each vegetation subtype are superimposed, that is, the less transparent ones are placed on the inner layer, and the more transparent ones are placed on the outer layer, so that the outer layer can be observed to the distribution of dominant species in the inner layer.