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Abstract: Historical fire regimes in the semi-arid shrublands of southern Western Australia are poorly understood, largely owing to a lack of quantitative historical data. We sought to determine the dendroecological potential of fire-sensitive Callitris preissii Miq. trees to date historical fires and extend the length of fire-history data available from remotely sensed imagery. We sampled C. preissii trees from known fire areas in the Lake Johnston region in southern Western Australia. Our objective was to assess the capacity to date historical fires using stand establishment date as a proxy measure of time since fire. We measured stem basal diameter and height and collected stem sections of C. preissii trees and saplings from five areas that were burnt on known dates between 1974 and 2001. We also sampled older trees (>35 years), which were used to create a master chronology to assist with dating of seedlings and saplings. Tree age could not be reliably estimated from stem basal diameter and tree height, with 95% prediction intervals of more than 17 years. However, we were able to successfully determine tree age and develop a ring-width chronology using standard dendrochronological techniques. The cross-dated chronology showed a relatively high inter-series correlation in ring width (r=0.63) indicating consistency in growth rate among samples and sites, while mean sensitivity (0.39) signified high inter-annual variability in ring width. The age structure of C. preissii stands revealed consistent recruitment within 1 year of fire occurrence and maximum intra-stand variation in tree age of 4 years. Our results confirm that C. preissii has significant dendroecological potential to accurately date past fire events and that this approach will assist in extending fire-history records beyond recent decades for much of southern semi-arid Australia. [Copyright &y& Elsevier]

Australia's Great Western Woodlands are the largest intact temperate woodland ecosystem on Earth, spanning an area the size of the average European country. These woodlands are part of one of the world's biodiversity hotspots and, despite subsisting on just 200–400 mm of rainfall a year, can store considerable amounts of carbon. However, they face growing pressure from a combination of climate change and increasingly frequent and large wildfires, which have burned over a third of these slow-growing, fire-sensitive woodlands in last 50 years alone. To develop conservation strategies that bolster the long-term resilience of this unique ecosystem, we urgently need to understand how much old-growth woodland habitat remains intact and where it is distributed across this vast region. To tackle this challenge, we brought together data from an extensive network of field plots distributed across the region and combined this with information on vegetation 3D structure derived from drone, airborne and spaceborne LiDAR. Using this unique dataset, we developed a novel modelling framework to generate the first high-resolution maps of woodland tree size and age structure across the entire region. We found that 41.2% of the woodland habitat is covered by old-growth stands, equivalent to an area of approximately 39,187 km2. Only 10% of these old-growth woodlands fall within current protected areas managed by the state government. Instead, most remaining old-growth woodlands are found either within the Ngadju Indigenous Protected Area (26.9%) or outside of formal protected areas on leaseholds and privately owned lands (57.2%). Our maps of woodland size and age structure will help guide the targeted management and conservation of the Great Western Woodlands. Moreover, by developing a robust pipeline for integrating LiDAR data from multiple platforms, our study paves the way for mapping the 3D structure and carbon storage of open and heterogeneous woodland ecosystems from space. • Novel framework fusing drone, airborne and satellite LiDAR for large-scale mapping. • Fires have burned 39% of the world's largest temperate woodland in just 50 years. • Old-growth woodlands still cover 41% the region, equivalent to 38,715 km2. • Only 10% of old-growth woodlands are in protected areas managed by the government. [ABSTRACT FROM AUTHOR]