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International Journal of Wildland Fire International Journal of Wildland Fire Society
Journal of the International Association of Wildland Fire
RESEARCH ARTICLE

Structural and functional connectivity as a driver of hillslope erosion following disturbance

C. Jason Williams A B F , Frederick B. Pierson A , Peter R. Robichaud C , Osama Z. Al-Hamdan A D , Jan Boll B D and Eva K. Strand E
+ Author Affiliations
- Author Affiliations

A Northwest Watershed Research Center, Agricultural Research Service, USDA, 800 Park Boulevard, Plaza 4, Suite 105, Boise, ID 83712, USA.

B Environmental Science and Water Resources, University of Idaho, 875 Perimeter Drive, MS 1142, Moscow, ID 83844-1142, USA.

C Rocky Mountain Research Station, Forest Service, USDA, 1221 South Main Street, Moscow, ID 83843, USA.

D Department of Biological and Agricultural Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844-0904, USA.

E Department of Forest, Rangeland, and Fire Sciences, University of Idaho, 875 Perimeter Drive, MS 1133, Moscow, ID 83844-1133, USA.

F Corresponding author: Email: jason.williams@ars.usda.gov

International Journal of Wildland Fire 25(3) 306-321 https://doi.org/10.1071/WF14114
Submitted: 26 June 2014  Accepted: 9 April 2015   Published: 7 July 2015

Abstract

Hydrologic response to rainfall on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet cross-scale process connectivity is seldom evaluated in field studies owing to scale limitations in experimental design. This study quantified surface susceptibility and hydrologic response across point to hillslope scales at two degraded unburnt and burnt woodland sites using rainfall simulation and hydrologic modelling. High runoff (31–47 mm) and erosion (154–1893 g m–2) measured at the patch scale (13 m2) were associated with accumulation of fine-scale (0.5-m2) splash-sheet runoff and sediment and concentrated flow formation through contiguous bare zones (64–85% bare ground). Burning increased the continuity of runoff and sediment availability and yield. Cumulative runoff was consistent across plot scales whereas erosion increased with increasing plot area due to enhanced sediment detachment and transport. Modelled hillslope-scale runoff and erosion reflected measured patch-scale trends and the connectivity of processes and sediment availability. The cross-scale experiments and model predictions indicate the magnitude of hillslope response is governed by rainfall input and connectivity of surface susceptibility, sediment availability, and runoff and erosion processes. The results demonstrate the importance in considering cross-scale structural and functional connectivity when forecasting hydrologic and erosion responses to disturbances.

Additional keywords: ecohydrology, fire effects, infiltration, risk assessment, runoff, soil erosion, vegetation transition, wildfire, woodland encroachment.


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