Measurement Method Has a Larger Impact Than Spatial Scale For Plot‐Scale Field‐Saturated Hydraulic Conductivity ( K fs ) After Wildfire and Prescribed Fire in Forests

Wildfires raise risks of floods, debris flows, major geomorphologic and sedimentologic change, and water quality and quantity shifts. A principal control on the magnitude of these changes is field‐saturated hydraulic conductivity ( K fs ), which dictates surface runoff generation and is a key input into numerical models. This work synthesizes 73 K fs datasets from the literature in the first year following fire at the plot scale (≤ 10 m 2 ). A meta‐analysis using a random effects analysis showed significant differences between burned and unburned K fs . The reductions in K fs after fire, expressed by the ratio of K fs Burned / K fs Unburned , were 0.46 (95% confidence interval of 0.31‐0.70) combining wildfire and prescribed fire and 0.3 (95% confidence interval of 0.13‐0.71) for wildfire. No significant differences for K fs were observed between wildfire and prescribed fire or moderate and high fire severity. Both K fs magnitude and variability depended more on measurement method than measurement support area at the plot scale, with methods applying head ≥0.5 cm producing larger estimates of K fs . It is recommended that post‐fire efforts to characterize K fs for modeling or process‐based interpretations use methods that reflect the dominant infiltration processes: tension infiltrometers and simulated rainfall methods when soil matrix flow dominates and ponded head methods when macropore flow is critical. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.