Characterization of preferential flow in saline-alkali soils under different vegetation types

Background To investigate the preferential flow of soil water in the Yinbei Plain. Methods In this paper, five vegetation types Echinochloa crus-galli (A1), Phragmites australis (A2), Sesbania cannabina (A3), Suaeda salsa (A4), Atriplex spp. (A5) saline soils in the Yinbei Plain were taken as the research objects, use bare ground (CK) as a blank control. and the preferential flow characteristic parameters were determined through field dyeing tracer test, combined with the image processing software technology, to analyze the preferential flow characteristics of saline soils of different vegetation types and the influencing factors. The results showed that: Results1) Differences in preferential soil flow patterns existed across vegetation types, with uniform staining patterns in S. salsa, E. crus-galli and Atriplex spp., shallower staining depths in bare ground and P. australis, and poorer regularity of staining patterns in S. cannabina.2) E. crus-galli and S. salsa exhibited the largest stained areas, reaching 35.71% and 34.70% respectively. Their stained regions were concentrated, showing good connectivity between upper and lower soil layers without distinct, narrow preferential flow paths. Compared to Bare land, the dye-stained area ratios (DAR) of E. crus-galli, S. salsa, Atriplex spp., S. cannabina, and P. australis increased by factors of 4.04, 3.9, 2.97, 2.75, and 2.08, respectively. Compared to S. salsa, the matrix flow depths (UniFr) under E. crus-galli, Atriplex spp., P. australis, S. cannabina, and Bare land decreased by 20%, 25%, 56%, 65%, and 82.5%, respectively. The preferential flow ratios (PF-fr) increased in the following order: P. australis < Atriplex spp. < S. salsa < E. crus-galli < bare land < S. cannabina, indicating that S. cannabina had the highest degree of preferential flow development. 3) The preferential flow ratio (PF-fr) was positively correlated with soil bulk density. Redundancy analysis identified soil bulk density as the dominant factor, demonstrating its strong explanatory power for preferential flow variation. Conclusions The highest development of preferential flow of S. cannabina in saline soils of different vegetation types, E. crus-galli, Atriplex spp. and S. salsa with a high percentage of substrate flow may be better adapted to drought-stressed environments, and their homogeneous water transport patterns are more conducive to improving regional water ecology.