Hydrological response of a small catchment burned by experimental fire

摘要

Fire can considerably change hydrological processes, increasing the risk ofextreme flooding and erosion events. Although hydrological processes arelargely affected by scale, catchment-scale studies on the hydrologicalimpact of fire in Europe are scarce, and nested approaches are rarely used.We performed a catchment-scale experimental fire to improve insight into thedrivers of fire impact on hydrology. In north-central Portugal, rainfall,canopy interception, streamflow and soil moisture were monitored in smallshrub-covered paired catchments pre- and post-fire. The shrub cover wasmedium dense to dense (44 to 84%) and pre-fire canopy interception was onaverage 48.7% of total rainfall. Fire increased streamflow volumes 1.6times more than predicted, resulting in increased runoff coefficients andchanged rainfall-streamflow relationships – although the increase instreamflow per unit rainfall was only significant at the subcatchment-scale.Fire also fastened the response of topsoil moisture to rainfall from 2.7 to2.1 h (p = 0.058), and caused more rapid drying of topsoils after rain events.Since soil physical changes due to fire were not apparent, we suggest thatchanges resulting from vegetation removal played an important role inincreasing streamflow after fire. Results stress that fire impact onhydrology is largely affected by scale, highlight the hydrological impact offire on small scales, and emphasize the risk of overestimating fire impactwhen upscaling plot-scale studies to the catchment-scale. Finally, theyincrease understanding of the processes contributing to post-fire floodingand erosion events.