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Background: Understanding the influence of fires on terrestrial carbon stocks is important for informing global climate models and underpinning land management-based carbon markets. Aims: To quantify biomass carbon in south-western Australia's Great Western Woodlands – the world's largest extant Mediterranean-climate woodland – with time-since-fire and prior fire interval. Methods: Plot-based measurement of live and dead tree and shrub size, woody debris volume and litter mass across a ~400-year chronosequence to calculate biomass carbon. Key results: Biomass carbon increased with time-since-fire, reaching >65 Mg C ha−1, although the rate of increase declined in mature woodlands. Biomass carbon decreased after fire in these obligate-seeder woodlands, while a longer prior fire interval buffered carbon fluxes through retained large standing dead trees and fallen woody debris. Conclusions: The current age class distribution of the ~95,000 km2 of eucalypt woodlands in the region may support ~0.453 Pg C. Further refinement of carbon estimates explicitly considering variation in woodland type and climate, a continuous woodland age distribution and soil carbon are required to underpin a carbon methodology. Implications: Biomass carbon would be maximised by reducing the extent of bushfires impacting woodlands, focussing on existing mature stands that support the greatest carbon stocks. Fire regimes can have a significant bearing on terrestrial carbon stocks, with carbon markets potentially providing a mechanism to support land management activities. We quantify the effect of time-since-fire and prior fire interval on biomass carbon in the world's largest extant Mediterranean-climate woodland, located in south-western Australia. Photographs by C. Gosper. [ABSTRACT FROM AUTHOR]

Optimal conservation approaches have been proposed to differ for biota with contrasting evolutionary histories. Natural selection filters the distribution of plant traits over evolutionary time, with the current expression of traits mediating susceptibility to contemporary and often novel threats. We use old, climatically buffered, infertile landscape (OCBIL) theory to compile predictions regarding differences in exposure and susceptibility to key threats between OCBIL and young, often disturbed, fertile landscape (YODFEL) flora. Based on literature and existing data from the Southwest Australian Floristic Region (SWAFR), we evaluate evidence in support of our predictions, finding strong theoretical and empirical support for the proposition that exposure and/or impact of many threats differs between OCBILs and YODFELs. OCBILs have more exposure to land clearance from mining, whereas many YODFELs have greater exposure to land clearance from agriculture, and urban and industrial land uses, and greater overall levels of habitat loss and fragmentation. OCBIL flora are more susceptible to pathogens and extremes of fire interval than YODFEL flora, but conversely may have a greater capacity to persist in smaller populations if small populations featured in the evolutionary history of the species prior to anthropogenic fragmentation, and have substantial resistance to weed invasion. We argue that consideration of evolutionary history has an important role in informing conservation management. [ABSTRACT FROM AUTHOR]

The flora of the Southwest Australian Floristic Region (SWAFR) is characterized by remarkable richness, endemism, spatial turnover and numbers of threatened taxa. Increasingly, evolutionary history is recognized as contributing to SWAFR biogeographical patterns, culminating in the theory of old, climatically buffered, infertile landscapes (OCBILs) [and their counterpoint: young, often disturbed, fertile landscapes (YODFELs)]. For the SWAFR, we: (1) developed a spatially explicit distribution of OCBILs and YODFELs; (2) analysed the spatial distribution of Threatened and Priority (Data Deficient) flora; and (3) tested the hypotheses that Threatened and Priority flora will be most strongly represented in OCBILs and will have small geographical ranges. We found that OCBILs and YODFELs dominated spatially distinct portions of the SWAFR. Threatened and Priority flora were not uniformly or randomly distributed and were more strongly characterized by narrow-range endemics than the non-Threatened flora. The occurrence of Threatened and Priority flora was positively correlated with the age of surface exposure of landscape features and unique geological features of limited extent (if not YODFELs). The concentration of Threatened flora in OCBILs provides the opportunity to improve conservation management through investigations of how plant traits favoured by evolution in OCBILs might increase or decrease the susceptibility of the flora to anthropogenic threats. [ABSTRACT FROM AUTHOR]