Wildfire 2009


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  • Double or treble the sediment loss from the ‘road’ compared with the burnt area of the catchment.
  • Wildfire 2009

    1. 1. Paper presented at Wildfire 2009 Conference, June 16-17th2009, Lyndhurst, UK<br />
    2. 2. Wildfires in Portugal: characteristics, soil degradational impacts and mitigation measures<br />Rick Shakesby<br />In collaboration with<br />A.J.D. Ferreira, C.S.S. Ferreira, C.R. Stoof, E. Urbanek, R.P.D. Walsh<br />Photo of Coimbra, 2005: António Ferreira<br />“A global initiative to combat desertification”<br />
    3. 3. High fire frequency since early 1980s<br />Reasons:<br />1. Summer dry period<br />2. Highly flammable tree plantations<br />3. Poor litter and timber waste management<br />4. Improved access to forest areas<br />Insurance claims, feuds, vandalism<br />
    4. 4. Reduction in sediment yield<br />caused by increasing cover of stones, vegetation and litter<br />Post-wildfire soil erosion<br />From: Shakesby & Doerr (2006)<br />
    5. 5. Study sites in Portugal<br />Águeda Basin<br />Vale Torto<br />
    6. 6. Water drops <br />Águeda Basin, 1988 – 2 years after wildfire<br /><ul><li> Thin stony soils
    7. 7. Steep slopes (up to 20-30°)
    8. 8. Fast-growing Eucalyptus globulus and Pinus pinaster plantations
    9. 9. High rainfall (c.1600 mm)
    10. 10. Summer dry period, with pronounced soil water repellency</li></li></ul><li>Pasture with mixed woodland<br />Pre- 1920s<br />Pine <br />1920s<br />Eucalyptus <br />1940s<br />Fire<br />1986<br />Rip-ploughed & planted eucalyptus seedlings<br />Pine seedlings<br />Eucalyptus<br /> regrowth<br />‘Mature’ eucalyptus<br />Mature pine<br />Águeda Basin – land use change<br />Post 1986<br />
    11. 11. ‘Mature’ Eucalyptus (c. 12 years old)<br />Large quantity of highly flammable undergrowth and litter<br />
    12. 12. Management responses to fire - Eucalyptus<br />Plough and plant Eucalyptus seedlings<br />Allow regrowth from stumps<br />
    13. 13. Machinery used to rip-plough before planting Eucalyptus seedlings<br />
    14. 14. Terraces - preferred preparation for planting Eucalyptus seedlings<br />
    15. 15. Stone armouring<br />Preferential loss of fine sediment, organic matter and nutrients<br />Wildfire – effect on soil erosion<br />
    16. 16. Large loss of a range of particle sizes<br />Rip-ploughing – effect on soil erosion<br />Rip-ploughing disturbs quasi-stable soil, moves soil downslope and dislodges large bedrock slabs <br />
    17. 17. Rip-ploughing & Eucalyptus seedling regrowth<br />Wildfire & regrowth<br />Ploughing<br />Fire<br />Post-fire soil erosion: schematic <br />Soil erosion <br />‘Background’ soil erosion<br />Time<br />
    18. 18. Post-fire changes, Águeda Basin<br /><ul><li> Increased stone cover in one year from 17 to 42%
    19. 19. Preferential loss of organic matter
    20. 20. Losses of N, K and P increased by 3-4 orders of magnitude (in eroded sediment)
    21. 21. Losses of P for 2 years after fire represent 19-55% of soil nutrient reserves
    22. 22. Similarly large losses of orthophosphate and potassium in solutes</li></li></ul><li>Research design for testing post-wildfire mitigation measures<br />Different treatments applied 9 months after wildfire<br />Eucalyptus<br />Low <br />Burnt control<br />Medium<br />High<br />Unburnt<br />Pine needles removed<br />Pine<br />Bare soil<br />Burnt control<br />Medium<br />High<br />Unburnt<br />
    23. 23. Post-fire mitigation - pine<br />Pine needlefall<br />Pine salvage waste<br />
    24. 24. Salvage logging waste applied to erosion plots<br />Soil loss reduced by 95%<br />Eucalyptus: high amount of salvage waste <br />Soil loss reduced by 55%<br />Eucalyptus: low amount of salvage waste <br />
    25. 25. Prescribed fire as a soil conservation tool<br />Vale Torto catchment, February 20th 2009<br />
    26. 26. Vale Torto – ‘experimental’ fire<br /><ul><li> Catchment = 10 ha
    27. 27. Scrub vegetation (fuel load = 23 t/ha)</li></li></ul><li>Fire characteristics<br />Fire started at the catchment boundary<br />Measuring flame temperatures<br /><ul><li>Relatively ‘hot’ for a controlled fire
    28. 28. Flame temperatures up to > 800°C, but relatively little soil heating (soil temperatures < 100°C)</li></ul>Temperature-sensitive paints<br />Paint strips on metal bars <br />
    29. 29. Spatial variation in fire severity<br />Near the main drainage line<br />Higher impact on vegetation and litter<br />Near to the watershed<br />Lower impact on vegetation and litter<br />
    30. 30. Use of sediment fences to monitor soil erosion<br />
    31. 31. Fire break/access road on catchment boundary<br />Higher soil losses than on burnt land <br />
    32. 32. Camelo site – wildfire on July 3rd 2008<br />Soil losses up to 2 orders of magnitude higher than at Vale Torto<br /><ul><li>Similar geology, soil, vegetation and relief to Vale Torto
    33. 33. Higher fuel load (65 t/ha) compared to Vale Torto</li></li></ul><li>Conclusions<br />Wildfire causes ‘modest’ soil losses versus some agricultural practices. However…<br />Fine sediment, organic matter and nutrients are preferentially removed<br />Post-fire ploughing and terracing cause very large downslope soil transfers<br />Even an atypically ‘hot’ prescribed fire causes far less soil loss than a wildfire <br />Timing of prescribed fire may be critical to limit soil losses <br />We still can only guess at the soil renewal rate!<br />
    34. 34. Thank you<br />‘Desire’ is an EU-funded project, 2007-12<br />“A global initiative to combat desertification”<br />