Characteristics of deep soil layer water deficit under different
vegetation types of the Loess Plateau, China
Abstract
Soil water is a crucial factor for the growth of vegetation and
sustainable development in water-limited areas. After large-scale
vegetation restoration on the Chinese Loess Plateau, understanding the
relationship between vegetation and deep soil moisture has become a
crucial focus in current research. In this study, we selected artificial
forest ( Pinus tabulaeformis, Robinia pseudoacacia, and
Platycladus orientalis), apple orchard, secondary forest and
farmland as the research objects, and native grassland as the control,
using soil drilling techniques, we systematically monitored the soil
water content of 0-10 m soil layer over two hydrological years, and
explore the effects of different vegetation types on soil water
deficiency. The results showed that: (1) The deep soil water various
significantly among different vegetation types, which indicating the
depth of the influence of vegetation on soil water has reached 10 m. (2)
The mean deficit size values of P. tabulaeformis (0.14), R.
pseudoacacia (0.17), P. orientalis (0.07), apple orchard (0.15)
and secondary forest (0.10) and farmland (0.27) were positive in 0–1 m,
indicating that surface soil water had accumulated during more than half
of the sampling periods. In the 2–10 m soil layer, the mean deficit
size was negative in all vegetation types except in farmland, leading to
soil desiccation. The deficit size was found to fluctuate with soil
depth. (3) Soil water deficit degree was affected by a combination of
soil properties and vegetation growth. Altitude, soil bulk density and
canopy density had a significant impact on soil water deficit. Our
results indicate that the current afforestation model could lead to the
deficiency of deep soil water. Therefore, in planning future vegetation
allocation and management, it is imperative to make reasonable
vegetation structure according to the available local soil and water
resources.