**3.1 Three sand binding shrubs in Mu Us Sandy Land**

This study was conducted in Ordos Sandy Land Ecological Station, Institute of Botany, Chinese Academy of Forestry, which located in Ejin Holo Banner, Ordos

*Water Source of Six Woody Plants in Different Habitats on Desertified Land of Ordos Plateau… DOI: http://dx.doi.org/10.5772/intechopen.99658*

City, Inner Mongolia. The banner has a temperate continental climate, which mean air temperature varies from 5.0°C to 8.5°C, mean annual precipitation is 350 mm, potential evapotranspiration is 2300 mm and forest free days are 136 d [28]. The natural vegetation is sandy land dominated by *Sabina vulgaris*, *Artemisia ordosica*, *Salix psammophila* and *Caragana intermedia*, and steppe dominated by *Stipa bungeana* and *Iris lactea* var. *chinensis*.

*Sabina vulgaris* is an evergreen shrub with height of 0.3–1.0 m. It is a drought resistant species and widely used as sand binding and soil and water conservation shrub. It mainly inhabits on rocky slope, mixed coniferous and broad-leaf forest or sand dune, which distributes in Tianshan Mountain, Altai Mountain, Helanshan Mountain, Inner Mongolia, Northeast Qinghai, Gansu and North Shaanxi [22].

*Artemisia ordosica* is a small shrub with mean height of 0.5–1.0 m. It is resistant to sand burial and was widely used as a good sand-binding plant with air seeding. It mainly inhabits in moving, semi-fixed and fixed sand dunes in desert and slope in steppe, which distributes in Inner Mongolia, North Hebei and North Shanxi [29].

*Salix psammophila* (sand willow) is a shrub with mean height of 3–4 m. It is resistant to wind and sand burial, which was widely used as a sand-binding and afforestation species. It mainly distributes in Shaanxi, Inner Mongolia, Ningxia and Shanxi [30].

In the study site, the mean height of *S. vulgaris*, *A. ordosica* and *S. psammophila* were 0.78, 0.92 and 3.33 m, respectively. The semi-shrub *Hedysarum fruticosum* var. *laeve* was the associated species in *A. ordosica* and *S. psammophila* community. The main water source of four shrubs was measured by comparing their xylem water with different water sources, e.g. soil water in 10, 25, 50, 75, 100 and 150 cm for *A. ordosica*, whereas soil water in 10, 25, 50, 100, 150 and 200 cm for other two shrubs. The sample and extraction of soil water and xylem water was shown in 2.1. Groundwater was not sampled because shallow groundwater was depleted after coal mining in 2012. Deep groundwater table was 70 m at the study site, which is unavailable for vegetation. Meteorological data was obtained from Ordos Ecological Station. The contribution of different water sources to their total water use was analyzed by Iso-source 1.3.1 software [24].

#### **3.2 Precipitation in Ordos Ecological Station in the growing season of 2018**

The total precipitation of Ordos Ecological Station was 367.00 mm in the growing season of 2018 (**Figure 3**), which was slightly higher than the annual mean precipitation of 350 mm. The maximal daily precipitation was 34.4 mm and occurred on August 30, the next value was 32.2 mm on July 19, and 31.8 mm on July 16. The monthly precipitation were 25.6, 47.6, 11.4, 144.2, 92.2 and 46.0 mm from April to September.

#### **3.3 Stable oxygen isotope of xylem water of four shrubs, soil water and rainwater in sandy land**

On May 13, stable oxygen isotope ratio of *S. vulgaris* xylem water were closer to soil water in 10–25 cm, stable oxygen isotope ratio of *A. ordosica* and *H. fruticosum* var. *laeve* xylem water were closer to soil water in 10–150 cm, whereas stable oxygen isotope ratio of *S. psammophila* and *H. fruticosum* var. *laeve* xylem water was closer to soil water in 10 cm and 50–200 cm. On July 13, stable oxygen isotope ratio of 10 cm soil water was closer to rainwater on July 11. Stable oxygen isotope ratio of *S. vulgaris* was closer to soil water in 25 cm and 100–200 cm, stable oxygen isotope ratio of *A. ordosica* and *H. fruticosum* var. *laeve* xylem water were closer to soil water in 10 cm and 150 cm, whereas stable oxygen isotope ratio of *S. psammophila*

#### **Figure 3.**

*Daily precipitation at Ordos Ecological Station from April to September of 2018.*

and *H. fruticosum* var. *laeve* xylem water was closer to soil water in 10–25 cm and 100–200 cm. On September 22, stable oxygen isotope ratio of 10 cm soil water was closer to rainwater on September 11. Stable oxygen isotope ratio of *S. vulgaris* xylem water was closer to soil water in 25–200 cm, stable oxygen isotope ratio of *A. ordosica* and *H. fruticosum* var. *laeve* xylem water were closer to soil water in 10–150 cm, whereas stable oxygen isotope ratio of *S. psammophila* and *H. fruticosum* var. *laeve* xylem water were closer to soil water in 25–200 cm (**Figure 4**).
