Hydrologic Connectivity and Patch‐To‐Hillslope Scale Relations in Dryland Ecosystems

Abstract

In dryland ecosystems, the redistribution of rainfall runoff from bare soil to vegetated patches is fundamentally important to plant survival and the maintenance of hillslope functionality, sustaining vegetation in regions where annual rainfall alone would be insufficient (Dunkerley, 2002;Schlesinger et al., 1990). With soil infiltrability typically higher under vegetation cover than in bare soil areas (Assouline, 2004;Belnap, 2006), bare soil and vegetation patches create spatial mosaics of sources and sinks (see Figure 1a), where runoff generated in bare soil areas (sources) is trapped by downslope vegetated patches (sinks) (Dunkerley, 2002;Li et al., 2008;Moreno-de las Heras et al., 2012).More tortuous flowpaths that bypass vegetation can also form in drylands, for example, where plants grow on mounds (Michaelides et al., 2009;Parsons et al., 1996;Wainwright et al., 2000). The importance of vegetation resistance to flow in contributing to such tortuosity, however, is unclear, even though vegetated patches provide greater resistance to flow than bare areas (Dunne et al., 1991;Rossi et al., 2018). Higher infiltrability in vegetated patches relative to bare soil areas promotes "run-on" behavior (Thompson et al., 2011). Conversely, greater surface roughness-and thus greater resistance to flow-may divert runoff around vegetation, promoting "run-around" behavior and reducing the transport of resources to vegetated areas. On topographically smooth surfaces, the vegetation's effect on flowpaths must result from the interaction between its effects on the resistance and infiltration. Unraveling this interaction requires, at minimum, describing unsteady two-dimensional flows over spatially heterogeneous dryland hillslopes (Crompton et al., 2019).

Effect of Solar Farms on Soil Erosion in Hilly Environments: A Modeling Study From the Perspective of Hydrological Connectivity

“…This phenomenon might be related to the fact that higher HC often leads to shorter runoff time and larger runoff kinetic energy (Poesen et al, 2003), and thus is more likely to build connections between PV-caused erosion at local scales and sediment transfers at larger scales, in USFs with higher background HC (Holland et al, 2021;Smith et al, 2011). Similarly, increasing vegetation cover could lower the HC in USFs (Crompton et al, 2023), and thus significantly reduce the risk of erosion (Figure 5). The basic logic behind these measures is that they protect the surface by restricting the movement of sediment and increase the hydraulic conductivity of the soil, resulting in greater throughflow and less overland flow, thereby reducing HC and erosion (Phalane, 2021).…”