Wildfires

• wildfire

  an uncontrolled rural fire
• crown fires

  spreads across canopies and affects forested areas
• ground fires

  burns beneath the ground in layers of organic peat
• Ladder effect

  describes the process of fires from the forest floor spreading to the tree canopy
• flash point

  the temperature which everything has when it will burst into flames
• fuel triangle

  combination of heat, oxygen and fuel which are required for a fire to form
• Santa Ana winds

  role in development and path of wildfires in Southern California

  1. desert winds originate clockwise from air around high pressure systems east of Sierras
  2. air from mountains is compressed and warmed becoming less humid and drying out vegetation
  3. wind squeezes through canyons
  4. strong winds create turbulence
• affect of topography on wildfires

  • wildfires travel faster uphill than downhill
  • the steeper the slop the faster the fire travels
  • fires travel in the direction of the ambient wind
  • fire can can preheat the fuel uphill as the smoke and heat is rising in that direction
  • the fire struggles to travel backdown as it cant preheat the fuel downhill as well
• benefits of wildfires

  • can burn underbush of a forest which can prevent a large fire if the bush accumulates
  • can benefit plant growth by reducing disease spread, releasing nutrients from burned plants into the ground to encourage new growth
• fire brands

  burning fragments of vegetation which can be carried ahead of the fire front by convection currents and strong winds to ignite isolated spot fires which gravity is responsible for so they can roll downhill
• Indian Ocean Dipole (IOD)

  • difference in sea surface temperature between western pole in the Arabian sea and an eastern pole in the Indian ocean
  • affects the climate and precipitation of Australia and surrounding countries
  • In a positive phase, warm waters are pushed to the Western part of the Indian Ocean, while cold deep waters are brought to the surface in the Eastern Indian Ocean
  • This pattern is reversed during the negative phase of the IOD
• Wildfires and global systems

  • local ecosystems affected - soil nutrients depleted
  • toxic ash can enter water sources affecting aquatic ecosystems
  • loss of vegetation affects water cycle by reducing humidity so less runoff, evaporation and infiltration
  • nutrient cycles will be impacted as biomass and litter stores are burned
  • burning will release carbon stores in trees, plants and peat increasing atmospheric co2
  • affects vegetation development causing secondary sucession to be initiated in forests and scrublands
  • human systems affected