Dynamics of fine fuels in recurrently burnt eucalypt forests

Summary

Over a wide range of conditions fine fuel re-accumulation after fire in eucalypt forests is well described by equations of the form X_t = X_ss (l-e^−kt)

where X_t is the weight (t ha⁻¹) of litter accumulated at time t(yr), X_ss is the weight of accumulated litter under steady-state conditions, and k is a decomposition rate constant (yr⁻¹). Decomposition constants ranged from 0.11 to 0.31 yr⁻¹, and steady- state litter accumulations varied between 11.1 and 29.4 t ha⁻¹.

In many types of eucalypt forest, litter re-accumulates to dangerous (from a fire control point of view) weights in 3–6 years, thus severely limiting the period during which prescribed burning provides protection from wildfire. The rapid rate of litter re-accumulation is mostly due to a marked decrease in the total amount of litter decomposing (relative to rates of litter input), rather than to any fire-induced reduction in the rate of decomposition. The implications of these findings for fire management in eucalypt forests are briefly discussed.

More quantitative information on the relationships between fuel mass (and other fuel characteristics) and fire behaviour under high to very high fire danger conditions is required to enable better evaluation of the effectiveness of low intensity prescribed burning for fire control. The ecological impacts of prescribed burning regimes, which also need to be considered when devising burning programs, are briefly discussed.