2.1. Study area
The experiment was conducted on
riparian slopes of the lower Yellow River, Zhongmu County, Henan
Province, China (Fig. 1a, b), from September to October
2015.
Zhongmu
County is located at the south bank of the Yellow River (N
34°26′–34°56′, E 113°46′–114°12′) with a total area of 1406
km2. The climate in Zhongmu County is a typical warm
temperate continental monsoon
climate, characterized by mild
windy springs (April–June), hot rainy summers (July–September), and
cool dry autumns and winters (October–March). The mean annual
temperature is 14.2ºC, and the
maximum and minimum monthly temperatures occur in July and January
respectively (Geng et al., 2012; Zhao et al., 2016; Zhao et al., 2015b).
The mean annual precipitation is 616 mm, with significant seasonality;
most precipitation occurs during the rainy season (Geng et al., 2012;
Zhao et al., 2016; Zhao et al., 2015b). Influenced by historical floods
of the Yellow River, sedimentary rocks in Zhongmu County are mainly
alluvium and diluvium, and soils contain much sub-sand and silt-sand
(Zhao et al., 2015b). Vegetation in Zhongmu County is limited by the
climatic characteristics and soil and water conditions. The dominant
plant species in this area include Salix babylonica ,Populus L. , and grass (Setaria viridis ). The families
Gramineae, Compositae, Leguminosae, and Brassicaceae occupy an important
position in the lower Yellow River riparian flora. While the main
agricultural crops in this area are wheat (Triticum aestivum L. )
and maize (Zea mays L. ) (Zhao et al., 2015b).
[Insert Figure 1]