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

The mean interval between tree-killing fires in mountain ash (Eucalyptus re gnans 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 we re based on models of the local extinction and recolonization of forest pat ches by mountain ash trees and of the development of hollow-bearing trees i n response to time since fire. The results of the analyses suggested that t he mean interval between tree-killing fires was between approximate to 75 a nd 150 years in mountain ash forest. Data on mortality of mountain ash tree s suggest that approximately half the trees survive fire, making the mean i nterval 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 re gime may have abrupt and major effects on ecosystem properties. (C) 1999 El sevier Science B.V. All rights reserved.