A preliminary investigation of gully edge effect on the distribution pattern of soil moisture across a permanent gully

• Published in: Journal of hydrology (Amsterdam) 2020-11, Vol.590, p.125288, Article 125288
• Main Authors: Jia, Yu-Hua, Li, Tong-Chuan, Shao, Ming-An
• Format: Article
• Language: English
• Subjects: Gully edge effect; Permanent gully; Slope–gully system; Soil erosion; Soil water content; Spatial pattern
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2020.125288

•Soil moisture has a bilateral asymmetry pattern across the permanent gully.•The effect of distance to the gully was stronger than that of soil depth.•Gully edge effect is proposed for the fragmented landscape.•Gully edge effect is adverse for soil water conservation. Describing and mapping soil water content (SWC) distribution are required to understand and explain the hydrological phenomena at various spatial scales. Soil drought in the hilly and gully regions of Loess Plateau reduces agricultural production and plants biomass, which has attracted great attention but few studies associated it with the gullied terrain. To understand the SWC distribution pattern in the slope–gully system, we established a cross-section transect for SWC observation across a permanent gully and acquired 23 occasions of SWC data in the periods from October 2014 to September 2018. The standardized beta coefficient in stepwise multiple linear regression was employed to determine the strength of the effect of the selected variables (soil textural separates, soil depth, relative height, distance to the gully and saturated hydraulic conductivity) on SWS distribution. Spectral and cross-spectral analysis were performed on the time series of SWC to evaluate the cyclical behavior and the similarity for adjacent sites, respectively. The following results were obtained: First, the SWC distribution had a bilateral asymmetrical pattern across the gully, which constituted a specific and detailed content of spatial variability of SWC. Second, soil water storage in the slope–gully system was primarily affected by soil texture, meanwhile, the effect of distance to the gully was stronger than that of soil depth. Third, the SWC of the adjacent pair sites presented consistent periodic behavior. The cross-spectral analysis indicated a dissimilar pattern for soil layer of 0–60 cm and deep synchrony for the other depth layers. In conclusion, the gully edge effect aggravated the SWC status in the south bank and caused a bilateral asymmetrical pattern in the slope–gully system. These results improved our knowledge on the complicated distribution of SWC in the gullied region. Moreover, the results indicate that ignoring the nearby areas of a permanent gully in a catchment is inappropriate when investigating soil water resources.