Linking spatial distributions of the patchy grass Achnatherum splendens with dynamics of soil water and salt using electromagnetic induction

The interactions between deep-rooted grass patches and soil hydrological processes are unclear. This study used the deep-rooted grass Achnatherum splendens as an indicator plant to evaluate the relationship between spatial distributions of A. splendens patches and dynamics of soil water and salt using electromagnetic induction (EMI) methods in Qinghai Lake watershed on Qinghai-Tibet Plateau in northwestern China. An experimental plot of size 60 m × 60 m was designed for collecting repeated apparent electrical conductivity (ECa) images. Vegetation and soil properties (e.g. soil water, salinity, hydraulic conductivity and particle composition) were investigated. Results showed that soils in A. splendens patches had greater macroporosity and higher unsaturated hydraulic conductivity compared to interpatch zones. Analysis of temporal stability of ECa images showed that locations near A. splendens patches had greater water and salt contents compared to interpatch zones, and these locations also showed the greater increasing magnitudes. This indicated that A. splendens patches acted as focal points for accumulating soil water since the high and dense crown could trap the aeolian sediments and then improve infiltration capacity of soils. Process of root water uptake of A. splendens promoted salt ions transporting into the root zone, which was thought to be the main reason for the salt accumulation. The deep-rooted A. splendens changed soil hydrological properties and affected the dynamics of soil water and salt, and these eco-hydrological processes were determined using the EMI. Our findings provide valuable insights in understanding the eco-hydrological processes of deep-rooted patchy vegetation.