Method for determining the threshold value of ecological carrying capacity in arsenic sandstone areas

Abstract

The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention includes: judging the type of the area to be determined, judging whether the area to be determined is a soil-covered area, a sand-covered area or an exposed area; obtaining the mean value x of the vegetation coverage of several detection points in the area to be determined; according to the type of the area to be determined and the value of x, selecting a formula to calculate the ecological carrying capacity threshold y of the sandstone area, the soil-covered arsenic sandstone y=1.9668x-0.2514, the sand-covered arsenic sandstone y=1.3731x-0.0496, and the exposed arsenic sandstone y=1.0142x+0.0863. The technical scheme of the present invention can more accurately determine the ecological carrying capacity threshold of the arsenic sandstone area, and according to the ecological carrying capacity threshold of the arsenic sandstone area, the density of afforestation (grass planting) can be reasonably controlled, and the economy and scientificity of the ecological governance of the arsenic sandstone area can be improved, which can not only quickly increase the vegetation coverage and reduce soil erosion, but also enhance the stability and sustainability of vegetation.

Description

Technical Field

[0001] The present invention relates to the field of environmental governance, and in particular to a method for determining an ecological carrying capacity threshold value in an arsenic sandstone area. Background Art

[0002] Pisha sandstone is a loose rock formation, specifically referring to the interbedded rocks composed of thick sandstone, sandstone shale and mudstone in the Permian Period of the Paleozoic Era and the Triassic, Jurassic and Cretaceous Period of the Mesozoic Era. Pisha sandstone is a continental clastic rock system. Due to the small thickness and low pressure of its overlying rock layers, it has a low degree of diagenesis, poor cementation between sand grains and low structural strength.

[0003] Due to its low degree of diagenesis, poor cementation between sand particles and low structural strength, it becomes mud when it comes into contact with water and sand when it comes into contact with wind, causing very serious soil erosion. The rock layer is extremely susceptible to weathering and erosion, and the people suffer greatly from it. They regard the poison as arsenic, so they call it "arsenic sandstone."

[0004] The assessment of the ecological carrying capacity of the arsenic sandstone area is very important for the management of the arsenic sandstone. In the ecological engineering of afforestation (grass planting), in addition to selecting plant types suitable for the local growth environment, the threshold conditions of the ecological carrying capacity of the arsenic sandstone area must be fully considered. Only by reasonably controlling the density of afforestation (grass planting) according to the maximum ecological carrying capacity threshold of different arsenic sandstone types under terrain differences such as altitude, slope, and slope direction, can the ecological management of the arsenic sandstone area be effectively carried out. Summary of the invention

[0005] The purpose of the invention is to provide a method for determining the threshold value of ecological carrying capacity in arsenic sandstone areas.

[0006] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises:

[0007] Determine the type of the area to be determined, and determine whether the area to be determined is a soil-covered area, a sand-covered area, or a bare area;

[0008] Obtain the mean value x of vegetation coverage of several detection points in the area to be determined;

[0009] According to the type of area to be determined and the value of x, the formula is selected to calculate the threshold value y of the ecological carrying capacity of the sandstone area.

[0010] Overburden arsenic sandstone y=1.9668x-0.2514,

[0011] Overlying sandstone y=1.3731x-0.0496,

[0012] Exposed arsenic sandstone y=1.0142x+0.0863.

[0013] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises the following steps: dividing the area to be determined into a plurality of sub-areas with different altitudes according to the altitude, setting a plurality of detection points in each sub-area, calculating the value of vegetation coverage of each detection point, and dividing the sum of the values ​​of vegetation coverage of the detection points by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined.

[0014] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention, wherein obtaining the mean value x of the vegetation coverage of several detection points in the area to be determined comprises:

[0015] According to the slope, the area to be determined is divided into multiple sub-areas with different slopes. Several detection points are set in each sub-area, and the vegetation coverage value of each detection point is calculated. The sum of the vegetation coverage values ​​of the detection points is divided by the number of detection points to obtain the mean value x of the vegetation coverage of several detection points in the area to be determined.

[0016] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises the following steps: dividing the area to be determined into a plurality of sub-areas with different slope directions according to the slope directions; setting a plurality of detection points in each sub-area; calculating the value of vegetation coverage of each detection point; and dividing the sum of the values ​​of vegetation coverage of the detection points by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined.

[0017] The technical solution of the present invention can more accurately determine the ecological carrying capacity threshold of the arsenic sandstone area. According to the ecological carrying capacity threshold of the arsenic sandstone area, the density of afforestation (grass planting) can be reasonably controlled, thereby improving the economy and scientificity of ecological management in the arsenic sandstone area. It can not only quickly increase vegetation coverage and reduce soil erosion, but also enhance the stability and sustainability of vegetation. DETAILED DESCRIPTION

[0018] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises:

[0019] Determine the type of the area to be determined, and determine whether the area to be determined is a soil-covered area, a sand-covered area, or a bare area;

[0020] Obtain the mean value x of vegetation coverage of several detection points in the area to be determined;

[0021] According to the type of area to be determined and the value of x, the formula is selected to calculate the threshold value y of the ecological carrying capacity of the sandstone area.

[0022] Overburden arsenic sandstone y=1.9668x-0.2514,

[0023] Overlying sandstone y=1.3731x-0.0496,

[0024] Exposed arsenic sandstone y=1.0142x+0.0863.

[0025] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises the following steps: dividing the area to be determined into a plurality of sub-areas with different altitudes according to the altitude, setting a plurality of detection points in each sub-area, calculating the value of vegetation coverage of each detection point, and dividing the sum of the values ​​of vegetation coverage of the detection points by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined.

[0026] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention, wherein obtaining the mean value x of the vegetation coverage of several detection points in the area to be determined comprises:

[0027] According to the slope, the area to be determined is divided into multiple sub-areas with different slopes. Several detection points are set in each sub-area, and the vegetation coverage value of each detection point is calculated. The sum of the vegetation coverage values ​​of the detection points is divided by the number of detection points to obtain the mean value x of the vegetation coverage of several detection points in the area to be determined.

[0028] The method for determining the ecological carrying capacity threshold of the arsenic sandstone area of ​​the present invention comprises the following steps: dividing the area to be determined into a plurality of sub-areas with different slope directions according to the slope directions; setting a plurality of detection points in each sub-area; calculating the value of vegetation coverage of each detection point; and dividing the sum of the values ​​of vegetation coverage of the detection points by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined.

[0029] In terms of determining the threshold indicators of ecological carrying capacity of the arsenic sandstone area, the first-level indicator divides the arsenic sandstone area into three types: soil-covered area, sand-covered area, and exposed area according to the surface material coverage of the arsenic sandstone; the second-level indicator divides it into three categories according to the altitude; the third-level indicator divides it into three levels according to the slope gradient, namely ≤15°, 15°-25°, and >25°; the fourth-level indicator divides it into four slope directions, namely semi-sunny slope, sunny slope, semi-shady slope, and shady slope.

[0030] In the ecological project of afforestation (grass planting), in addition to selecting plant types suitable for the local growth environment, it is necessary to fully consider the threshold conditions of the ecological carrying capacity of the arsenic sandstone area, and reasonably control the density of afforestation (grass planting) according to the maximum ecological carrying capacity threshold under different arsenic sandstone types and terrain differences such as altitude, slope, and slope direction, so as to improve the economy and scientificity of ecological management in the arsenic sandstone area.

[0031] The fractional vegetation cover, or FVC, refers to the percentage of the vertical projection area of ​​vegetation on the ground to the total area of ​​the statistical area.

[0032] According to the correlation fitting calculation between the FVC mean value (independent variable x) and the FVC threshold value (dependent variable y) under different indicators of elevation, slope, and slope direction, the fitting equations of the FVC threshold values ​​of the soil-covered arsenic sandstone area, sand-covered arsenic sandstone area, and exposed arsenic sandstone area were obtained (Table 1). It can be seen that the complex correlation coefficient R of the FVC threshold fitting formula of different types of arsenic sandstone areas is 2 The multiple correlation coefficient R of the fitting formula in the overburden arsenic sandstone area is relatively high. 2 It reached 0.9561, and the multiple correlation coefficients of the sand-covered arsenic sandstone area and the exposed arsenic sandstone area were 0.8499 and 0.8332, respectively.

[0033] Table 1 FVC threshold fitting equation

[0034]

[0035] Where y is the FVC threshold value in the arsenic sandstone area, and x is the mean FVC in the arsenic sandstone area.

[0036] To further verify the actual estimation accuracy of the FVC threshold fitting equation, 5 sample plots (15 sample plots in 3 categories) were randomly collected in the soil-covered area, sand-covered area, and exposed area as test points (Table 2). Sample plots S1-S5 were selected in the soil-covered arsenic sandstone area. Under the altitude index, S1 and S2 were 1200-1300m, S3 was ≤1200m, and S4 and S5 were >1300m; under the slope index, S1, S2, and S3 were ≤15°, S4 was 15°-25°, and S5 was >25°; under the slope index, S1-S5 were shady slope, semi-sunny slope, sunny slope, sunny slope, and semi-shady slope, respectively. In the sand-covered arsenic sandstone area, sample plots S6-S10 were selected. Under the altitude index, S6 and S8 were 1000-1500m, S7 was ≤1000m, and S9 and S10 were >1500m; under the slope index, S6 and S7 were 15°-25°, S8 was >25°, and S0 and S10 were ≤15°; under the slope aspect index, S6-S10 were shady slope, semi-sunny slope, sunny slope, semi-sunny slope, and semi-shady slope, respectively. In the soil-covered arsenic sandstone area, sample plots S11-S15 were selected. Under the altitude index, S11, S12, S13, and S15 were 1000-1500m, and S14 was >1500m; under the slope index, S11, S13, and S14 were ≤15°, S12 was 15°-25°, and S15 was >25°; under the slope index, S1-S5 were shady slope, shady slope, semi-sunny slope, sunny slope, and semi-shady slope, respectively. In terms of vegetation type, the vegetation types of S1-S5 in the soil-covered arsenic sandstone area are mainly fruit trees, caragana shrubs, Stipa grandis, and grass steppes; the vegetation types of S6-S10 sample plots in the sand-covered arsenic sandstone area are mainly caragana shrubs, wormwood, and grass steppes; the vegetation types of S11-S15 sample plots in the exposed arsenic sandstone area are mainly long silver grass steppes.

[0037] 15 sample plots were used as test points to analyze the determination error and accuracy evaluation of the evaluation model (Table 3). The results showed that the relative error between the FVC threshold determined by the FVC threshold fitting equation and the actual threshold in different arsenic sandstone types was relatively small (all <13%), among which the relative error in the soil-covered arsenic sandstone area was between 6.54% and 11.22%, the relative error in the sand-covered arsenic sandstone area was between 6.04% and 11.01%, and the relative error in the exposed arsenic sandstone area was between 12.90% and 8.05%. The fitting accuracy of the FVC threshold of the test plots in different arsenic sandstone types was mainly concentrated in 87% to 94%, and the average fitting accuracy of the FVC threshold in the soil-covered arsenic sandstone area, the sand-covered arsenic sandstone area and the exposed arsenic sandstone area was 90.93%, 91.52% and 90.54%, respectively. It can be seen that the use of a FVC value with a cumulative percentage of 90% as the vegetation coverage threshold has good credibility, and the FVC threshold fitting equation can maintain a high determination accuracy in practical applications.

[0038] Table 2 Characteristics of test samples

[0039]

[0040] Table 3 FVC threshold model determination error

[0041]

[0042] The altitude of the arsenic sandstone area is relatively high, and irrigation technology cannot be used directly in most areas. Plant growth mainly depends on atmospheric precipitation. In the sand-covered arsenic sandstone type area, precipitation is relatively small and the water holding capacity of sand is relatively poor. A survey of 8-year-old poplar plantations in the southeast of Ejin Horo Banner found that fast-growing poplars with faster growth were selected in the artificial forest construction without much consideration of the local ecological carrying capacity. The row spacing of poplars is relatively small (about 3m×3m), which can maintain a high FVC in the early stage of afforestation. However, with the rapid growth of poplars, the demand for soil moisture gradually increases, and the local atmospheric precipitation and groundwater content cannot meet the soil moisture demand for the normal growth of poplars. In the end, the planting density of fast-growing poplars exceeded the local ecological carrying capacity threshold, resulting in the unsustainable development of artificial forests, which manifested as the tops of many poplars drying up or dying as a whole. Therefore, according to the ecological carrying capacity threshold of the sand-covered arsenic sandstone area, in future artificial forest reconstruction projects in the area, in addition to considering the types of afforestation plants, for example, using Larix gmelinii to replace large water-consuming poplars, planting shrubs such as Caragana korshinskii and Tamarix chinensis, or semi-shrubs such as Artemisia ordosica, it is also necessary to comprehensively consider the reasonable reduction of afforestation density so that the vegetation coverage of artificial forests does not exceed the ecological carrying threshold.

[0043] In the soil and water conservation and ecological management of the arsenic sandstone area, seabuckthorn is widely used as a plant with strong adaptability and high economic value. Since 1986, the Yellow River Conservancy Commission has listed Ordos City, Inner Mongolia, where the arsenic sandstone is most concentrated, as a seabuckthorn trial planting project area. In 1990, Inner Mongolia implemented the "Special Seabuckthorn Management Project in the Inner Mongolia Arsenic Sandstone Area". In 1997, the United Nations Development Program began to implement the "China Seabuckthorn Assistance Project". In 1998, the "Seabuckthorn Ecological Project in the Arsenic Sandstone Area of ​​Shanxi, Shaanxi and Inner Mongolia" construction project was carried out. In 1998, Jungar Banner focused on the development of seabuckthorn ecological management projects and formed a Jungar Banner seabuckthorn planting area circle, forming a benign development industry chain of "planting seabuckthorn-restoring ecology-industrial development-increasing farmers' income". The rapid implementation of a series of seabuckthorn projects has enabled seabuckthorn afforestation to be carried out in the arsenic sandstone area. However, due to the lack of consideration of the local ecological carrying capacity and the inadequate management of artificial forests, some seabuckthorn forests have degraded and died.

[0044] Through the survey of seabuckthorn plantations in Dahonggou, a soil-covered arsenic sandstone area in Jungar Banner conducted in 2019, it was found that although the terrain in the area is flat and the soil covering conditions are good, the problem of large-scale death of seabuckthorn forests is relatively serious. The seabuckthorn forest was established 10 years ago, and the seabuckthorn planting density was too large (1m×1m), with a planting density of 10,000 plants / ha. Since then, with the growth and rapid reproduction of seabuckthorn, large-scale death problems have occurred. In terms of seabuckthorn planting density, the density of seabuckthorn forests in the top of the Shibultaigou slope adjacent to Dahonggou was 3,000 plants / ha in the stability survey. The precipitation in 2018 was 336.8mm, and the average water consumption of seabuckthorn forests was 619,740kg / ha. The density of 9-year-old seabuckthorn forest in Wuqi County in the northern part of the Loess Plateau is 4,200 plants / ha. Studies have shown that the precipitation in Wuqi County in 2007 was 350.00 mm, the transpiration of the seabuckthorn forest was 1,032,832 kg / ha, the soil evaporation was 1,775,986 kg / ha, and the stable density of the seabuckthorn forest was 1,586 plants / ha. Compared with Wuqi County, Jungar Banner, located in the overburden arsenic sandstone area, has less precipitation, a thinner soil layer, and higher soil evaporation, so the stable density should be lower. In addition, for the planting of seabuckthorn on the top of the slope, in order to reduce the aging and degradation of seabuckthorn such as stagnation of growth or even drying, in addition to reasonably arranging the planting density according to the local ecological carrying capacity threshold, the seabuckthorn forest should also be slashed or rotated every 5-6 years in terms of seabuckthorn per kilometer management.

[0045] In terms of ecological restoration, the local government and people have carried out a series of economic forest construction work in recent years in the spirit of combining afforestation and ecological benefits. Taking the soil-covered arsenic sandstone as an example, according to the characteristics of the ecological carrying capacity threshold, in the top area of ​​the slope, due to the flat terrain, economic tree species such as Scots pine, wild peach, and wild apricot are mostly planted in the ecological management of the arsenic sandstone, as well as mixed forests of trees and shrubs such as wild peach, wild apricot, caragana and sea buckthorn. The planting density of wild peach and wild apricot is 4m×5m, which is a more reasonable solution.

[0046] In slope ditches, sea buckthorn and caragana are good plant types for preventing soil erosion. Sea buckthorn ditch sealing has also been proven to be a successful solution. In sea buckthorn and caragana afforestation, considering the rapid reproduction ability of sea buckthorn and caragana after survival, in order to quickly achieve ditch mouth vegetation closure, they can be planted at 2m×2m. In relatively flat areas on the slope, Stipa krylovii and Stipa benthamiana (measured 40-50 plants / m 2 ) As the dominant grass species in the local area, it plays an important role in preventing and controlling soil erosion.

[0047] The bottom of the slope has relatively good water and nutrients. The survey found that in addition to the good growth of seabuckthorn and grass in the bottom area, the seabuckthorn forest coverage is high in the Erlaohugou ditch bottom survey, and the height of a single seabuckthorn can reach more than 2.5m. In order to maintain the stability and sustainable growth of seabuckthorn, the density of seabuckthorn afforestation at the bottom of the slope can be appropriately reduced, and the general spacing can be controlled at 3m×2.5m. Trees such as willows and poplars are also distributed in large numbers in the ditch bottom area and grow well. In the prevention and control of soil and water loss at the ditch bottom, afforestation adopts a combination of trees (willows) and shrubs (seabuckthorn) according to the actual situation of relatively more water. Willow afforestation is mixed with shrubs such as seabuckthorn according to the afforestation standards for water conservation forests, and the spacing is determined to be 4m×5m. This can not only quickly increase the vegetation coverage at the bottom of the slope and reduce soil and water loss, but also enhance the stability and sustainability of the vegetation at the bottom of the slope.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the threshold value of ecological carrying capacity in arsenic sandstone areas, characterized in that: include: Determine the type of the area to be determined, and determine whether the area to be determined is a soil-covered area, a sand-covered area, or a bare area; Obtain the mean value x of vegetation coverage of several detection points in the area to be determined; According to the type of area to be determined and the value of x, the formula is selected to calculate the threshold value y of the ecological carrying capacity of the sandstone area. Overburden arsenic sandstone y=1.9668x-0.2514, Overlying sandstone y=1.3731x-0.0496, Exposed arsenic sandstone y = 1.0142x + 0.0863, the mean value x of vegetation coverage of several detection points in the area to be determined includes: The area to be determined is divided into multiple sub-areas with different altitudes according to the altitude, and a number of detection points are set in each sub-area. The value of vegetation coverage of each detection point is calculated, and the sum of the values ​​of vegetation coverage of the detection points is divided by the number of detection points to obtain the mean value x of vegetation coverage of the multiple detection points in the area to be determined. Obtaining the mean value x of vegetation coverage of the multiple detection points in the area to be determined includes: According to the slope, the area to be determined is divided into a plurality of sub-areas with different slopes, a plurality of detection points are set in each sub-area, the value of vegetation coverage of each detection point is calculated, and the sum of the values ​​of vegetation coverage of the detection points is divided by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined; according to the slope direction, the area to be determined is divided into a plurality of sub-areas with different slope directions, a plurality of detection points are set in each sub-area, the value of vegetation coverage of each detection point is calculated, and the sum of the values ​​of vegetation coverage of the detection points is divided by the number of detection points to obtain the mean value x of vegetation coverage of the plurality of detection points in the area to be determined; The y is the FVC threshold in the arsenic sandstone area.

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