Vegetation Structure in Eucalyptus salubris Woodlands Across Time Since Fire Chronosequence, Great Western Woodlands SuperSite, 2010-2012

Recurrent fire is a dominant disturbance in Mediterranean-climate landscapes. In infrequently-burnt communities, vegetation structure, habitat features and fuel availability can change over time-scales much longer than can be measured using contemporary remote-sensing approaches, creating challenges for conservation and fire management. The Great Western Woodlands (GWW) region of south-western Australia supports the world’s largest remaining area of Mediterranean-climate woodland, which in mosaic with mallee, shrublands and salt lakes cover an area of 160 000 km2. Eucalyptus woodlands in this region are typically fire-sensitive, and fire return intervals recorded over recent decades have been much shorter than the long-term average. This has led to considerable conservation concern regarding the loss of mature woodlands, and has highlighted a need to better understand how plant communities change with time since fire. To characterize longer-term patterns of vegetation structural change, we measured vegetation cover, ground cover, tree density and stand basal area across a multi-century time-since-fire sequence derived from growth ring-size relationships in fire-sensitive Eucalyptus salubris woodlands. The estimated time since fire range of the 76 sample sites ranged from 2 to 370+ years.