SPATIALLY-EXPLICIT SIMULATION OF THE EFFECT OF PRESCRIBED BURNING ON FIRE REGIMES AND PLANT EXTINCTIONS IN SHRUBLANDS TYPICAL OF SOUTH-EASTERN AUSTRALIA

A spatial model was used to simulate plant extinction in relation to p rescribed burning in fire-prone shrublands. Prescribed burning may be used to manipulate fuel to levels that are sub-critical for fire-sprea d in extreme weather. Effects of variation in area of annual prescribe d burning on area of unplanned fires occurring under severe weather an d the probability of extinction in three functional groups of shrubs ( serotinous and leguminous obligate seeders and serotinous resprouters) were examined. Results of 200 year simulations indicated that restric tion of the size of unplanned fires occurred when large (>30%) areas o f the landscape were burnt annually. Risk of extinction in obligate se eders was high at such levels of prescribed burning. Extinction probab ility was also positively related to frequency of unplanned fires. In resprouters, risk of extinction was unaffected by prescribed fire. The model predicts that passive restriction of unplanned fires in extreme weather, by prescribed burning, is incompatible with floristic conser vation objectives. (C) 1998 Elsevier Science Ltd. All rights reserved.