2.4. Vegetation Index in the Test Area

The test area is dominated by the subfamily of temperate desertification, and the main soil types are brown calcium soil and sandy soil. From the perspective of vegetation, the main group building species and dominant species are Artemisia giraldii pamp, Astragalus tataricus, Suaeda glauca and so on, and the main companion species is ice grass. Artemisia giraldii pamp has obvious main roots and many lateral roots, so it grows vigorously. It is the dominant plant species in the test area, has a diameter of 4~10 mm, and the flowering and fruit period is from July to October. On the hillside grassland and parts of sandy land, there are small fruits of Astragalus and Suaeda, which belong to the annual Chenopodiaceae plant that are rich in nutrients and loved by sheep.

The remote sensing images of the Landsat 8 satellite are selected to extract vegetation parameters. The satellite has a total of 11 bands, with a spatial resolution of 30 m for bands 1~7 and 9~11, and a panchromatic band for band eight with a resolution of 15 m. Vegetation data analysis was carried out on the remote sensing image data on 16 October 2020. In order to ensure the accuracy of the data, radiometric correction and atmospheric correction were performed on the image data. The normalized vegetation index (NDVI) value of the test area was calculated by using the band operation method as follows:

where ρNIR is the spectral value of near infrared band, ρR is the spectral value of red band. The NDVI value is between 0 and 1. The NDVI value is proportional to the vegetation coverage in the study area, and the NDVI value distribution in the test area is shown in Figure 5.

The NDVI map of the test area.