Muirburn for Grazing Management

See Supplementary Information – Muirburn for Grazing Management

 

Key Issues:

Application

  • Anyone who uses muirburn to manage vegetation for grazing of domestic livestock or deer.

Objectives

  • In grassland, to remove old or dead grasses, encourage new growth, and create a varied structure.  Burning can be used to provide an “early bite”.
  • In heather moorland, to encourage regeneration of young heather, and to create a mix of patches of different age and structure to provide a balance between feeding and shelter.
  • Burning or cutting may also provide improved access for stock amongst taller vegetation to areas that can be grazed.
  • Burning should not be used in an attempt to eliminate heather and replace it with grassland, either where heather is dominant or where there is a grass-heather mixture.  This usually produces grasslands of low forage and biodiversity value.

Frequency

  • Carrying out muirburn too frequently damages heather and blaeberry, which provide winter feed.  It results in poor quality grassland (for example Purple moor-grass Molinia caerulea), and a loss of winter grazing and biodiversity.
  • The minimum recommended muirburn frequency in grassland ranges from four to ten years, depending on growing conditions and the type of grassland.  In heather-dominated vegetation, muirburn frequency should be determined by the rate of growth of the heather, and should not take place until the heather is 20-30cm tall.  In the most productive situations, this will take at least 8 years and it may take much longer in other areas.

Size of fire

  • Fires should not be bigger than can be controlled by the available people and equipment.
  • Large fires burn indiscriminately, including areas that are suitable for burning and those that are not.
  • Large fires carried out without due care are a significant cause of wildfire.
  • Large fires are less likely to create the mosaic of habitats and vegetation ages that provide forage through the year and increase the biodiversity value.
  • Fires in excess of 50m wide can be difficult to control.

Risks:

  • Grass fires have a fast rate of spread and react quickly to changes in wind direction or wind speed.
  • Grass fires can breach firebreaks through direct heat transfer, flying embers (spotting) or by creeping across short vegetation.
  • Dead grass is a fine fuel that can dry out quickly, often in less than one hour, and this can lead to significant increases in the rate of spread and fire intensity.
  • Insufficient preparation of firebreaks, staff or equipment creates a significant risk of wildfires.  Fires of this type can destroy large areas.
  • Burning in a small area, in a single year, may result in a ‘honeypot effect’, causing local overgrazing and poaching.

Benefits:

  • Greater short-term grazing capacity for domestic stock and deer.
  • Fires can be used to distribute grazing more widely, to encourage movement through areas avoided by livestock, or to attract deer to specific areas.