No abstract

Hillslope asymmetry is often attributed to differential eco‐hydro‐geomorphic processes resulting from aspect‐related differences in insolation. At midlatitudes, polar facing hillslopes are steeper, wetter, have denser vegetation, and deeper soils than their equatorial facing counterparts. We propose that at regional scales, the magnitude in insolation‐driven hillslope asymmetry is sensitive to variations in climate, and investigate the fire‐prone landscapes in southeastern Australia to evaluate this hypothesis. Patterns of asymmetry in soil depth and landform were quantified using soil depth measurements and topographic analysis across a contemporary rainfall gradient. Results show that polar facing hillslopes are steeper, and have greater soil depth, than equatorial facing slopes. Furthermore, we show that the magnitude of this asymmetry varies systematically with aridity index, with a maximum at the transition between water and energy limitation, suggesting a possible long‐term role of climate in hillslope development.

No abstract

Fire severity varies widely among and within wildfires. The objective of this work was to test the effectiveness of granular polyacrylamide (PAM) to reduce erosion in a Calcic Regosol exposed to different fire conditions. Three treatments were selected representing disturbances that coexist after a wildfire: unburned, low-moderate severity direct fire, and prolonged heating under moderate temperature [heated (HT)]. Granular PAM was spread on the surface of disturbed samples at two rates: (i) 0 (control) and (ii) 50 kg ha À1 . Additional application rates of 25 and 100 kg ha À1 were tested in HT. Three 80-mm rainstorms were applied with an intensity of 47 mm h À1 , separated by drying periods. PAM reduced soil loss in all storms in unburned and direct fire, although runoff increased during the first storm due to increased runoff viscosity. In the highly stable HT, soil loss was reduced only with an application rate of 100 kg ha À1 and after a drying period. In many cases, granular PAM could be effective to reduce post-fire erosion. In soils with high structural stability, a PAM dose should be selected to find a right balance between its stabilising effect on soil structure and its effect increasing runoff during the first storm.