Nutrient Cycling: The Ash-bed
Despite the losses (which may be as high as 400 kg/ha for N in eucalypt forests) during fire,
nutrient availability in topsoils is, at least temporarily, increased.
In addition to the nutrients added in ash, surface soils are heated, which releases nutrients from soil organic matter.
Heating also 'sterilises' the soil, resulting in a changed soil microflora.
Each of these changes contributes to increased plant growth following fire.
These mountain ash seedlings have been grown for the same length of time in the glasshouse under identical conditions. The seedlings on the left were grown on soil collected from a recently burnt site. The seedlings on the right were grown on soil collected from an adjacent unburnt area.