Fire regimes in mountain ash forests: evidence from forest age structure,extinction models and wildlife habitat.

The mean interval between tree-killing fires in mountain ash (Eucalyptus regnans F. Muell.) forest was inferred from information on the age structure of unlogged forest, the prevalence of mountain ash trees in the landscape, and on the abundance of live and dead hollow-bearing trees. The analyses were based on models of the local extinction and recolonization of forest patches by mountain ash trees and of the development of hollow-bearing trees in response to time since fire. The results of the analyses suggested that the mean interval between tree-killing fires was between ≃75 and 150 years in mountain ash forest. Data on mortality of mountain ash trees suggest that approximately half the trees survive fire, making the mean interval between all fires equal to 37-75 years. The model predicts that the proportion of the landscape occupied by mountain ash will decline sharply as the mean fire interval decreases, suggesting that changes in the fire regime may have abrupt and major effects on ecosystem properties