Polyacrylamide application versus forest residue mulching for reducing post-fire runoff and soil erosion

Area of Science:

• Forestry
• Environmental Science
• Soil Science

Background:

• Forest fires are known to increase overland flow and soil erosion.
• Mitigation strategies for post-fire effects are understudied, particularly outside the USA.

Purpose of the Study:

• To quantify the effectiveness of two emergency treatments in reducing post-fire runoff and soil loss.
• To evaluate eucalyptus bark mulch and polyacrylamide (PAM) for post-fire erosion control in Portugal.

Main Methods:

• Microplot-scale study in a eucalyptus plantation in north-central Portugal.
• Application of eucalyptus bark mulch (10-12 Mg ha(-1)) and anionic polyacrylamide (PAM) (50 kg ha(-1)).
• Monitoring of overland flow and soil losses during the first year after a 2010 wildfire.

Main Results:

• Mulching significantly reduced overland flow by 52% and soil losses by 93%.
• PAM treatments showed no significant difference compared to control plots, with slightly lower runoff but higher soil erosion.
• Lower slope plots exhibited greater runoff and erosion than upper slope plots, potentially due to fire intensity and biomass differences.

Conclusions:

• Eucalyptus bark mulch is an effective treatment for mitigating post-wildfire runoff and soil erosion.
• Anionic polyacrylamide (PAM) is not effective for reducing runoff and soil erosion in this context.
• Site-specific factors like slope position and fire intensity influence the effectiveness of mitigation strategies.