Figure 1 Study area.
Prior to the commencement of underground mining, the study area was
characterized by a diverse distribution of species and some grazing
vegetation communities, consisting mostly of sandy plant communities
with perennials and shrubs (Liu et al., 2020; Zhang et al., 2022). The
dominant trees were poplar, and the dominant shrubs were Salixcheilophila , Artemisia desertorum , and Caragana
korshinskii ; the dominant herbaceous included Stipa capillat.,
Bothriochloa ischaemum and Setaria viridis . A total of six
dominant vegetation species and bare land were selected for this study,
including Poplar, Artemisia, Salix, Caragana, Herb, Corn and Bare
ground. Grass was not specifically classified since it occurred under
tree canopies and shrubs or was very sparsely distributed on bare land,
making it challenging for UAVs to detect or identify specific grass
species. Therefore, all types of grass were classified as ‘Herb’ without
detailed evaluation.
2.2 UAV Surveying
A DJI P4-Multispectral UAV equipped with six 1/12.9 inch CMOS image
sensors collected spectral data in five bands (blue, green, red, red
edge, and near-infrared). The data collection occurred during the peak
growth period of vegetation in the Ordos region, from 10:00-14:00 on
September 10, 2020. Data were acquired during three separate flights
covering a flight area of 38.57ha. Twelve ground control points were
used to ensure accurate geopositioning of the data. Standard reference
whiteboard correction with a reflectance value of 50% was performed
before each flight to avoid overexposure or underexposure due to cloud
changes. Flight planning included capturing photos with a 75% forward
and side overlap ratio, evenly spaced intervals, a flight height of
120m, a pixel resolution of 6.4cm, and a speed of 9.8m/s.
Pre-processing, including image stitching and radiometric correction,
was performed by Agisoft PhotoScan (Figure 2).