Fig. 1 Geographical
location of the study area, including political borders and main
topographic features.
The temperature, precipitation, wind speed, and other meteorological
data used in this study were all derived from the Global Surface of
Daily Meteorological Data produced by the National Centers for
Environmental Information (NOAA, https://www.ncdc.noaa.gov/). More than
200 meteorological stations in southern Africa and its surrounding areas
were selected. The data covered 1991–2015 and ANUSPLIN 4.3
(https://fennerschool.anu.edu.au/research/products/anusplin) was used to
spatially interpolate the information. The Digital Elevation Model (DEM)
was provided by the Shuttle Radar Topography Mission and has a
resolution of 90 m (http://srtm.csi.cgiar.org/srtmdata/); the soil
properties were determined using 250 m resolution raster data from the
International Soil Reference and Information Center and included sand,
clay, silt, and organic matter contents (https://soilgrids.org/); the
CaCO3 data came from the Harmonized World Soil Database
(HWSD v1.2) with a resolution of 1 km
(http://www.fao.org/soils-portal/soil-survey/); the vegetation data were
obtained from the standard normalized vegetation index (NDVI) in GIMMS
3g and covered 1991–2015 with a spatial resolution of 8 km; and the
vegetation coverage was calculated by the maximum synthesis method
(https://ecocast.arc.nasa.gov/data/pub/gimms/). The land use/cover data
came from the European Space Agency and its Climate Change Initiative
(CCI-LC) project provided global land use data with a resolution of 300
m (http://maps.elie.ucl.ac.be/CCI/viewer/). All data were uniformly
resampled to a spatial resolution of 8 km.
2.2 Revised wind erosion equation
The
RWEQ model is an empirically-based model developed by the United States
Department of Agriculture to estimate soil loss in farmland at a height
of 2 m (Fryrear et al., 2000). When the wind force is greater than the
resistance, the soil particles will move, and when the wind force is
less than the resistance, the soil will not be eroded by wind. The RWEQ
model is based on the WEQ and includes its experience and process
components. It can predict and simulate wind erosion processes by
combining existing data sets and computer models (Jarrah, Mayel,
Tatarko, Funk, & Kuka, 2020). Compared to other complexity models that
have more parameters, the RWEQ model has a relatively simple structure
and has been widely used to estimate the transport capacity of long-term
and large-scale aeolian sediments (Borrelli et al., 2017; Guo et al.,
2013; Youssef et al., 2012; Zobeck et al., 2000). The model calculation
is as follows: