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Recent landscape‐scale wildfires in eastern Australia have made apparent the need for a greater understanding of the flammability dynamics of forested ecosystems. Fire severity is a measure of the impact of a fire on vegetation, but little is known about the landscape‐scale response of the fire‐prone dry sclerophyll forests of eastern Australia to different levels of fire severity. Species in these forests have multiple responses to fire, which can be dependent on the fire severity. In this study, we aimed to determine the effect of fire severity on the vegetation structure, and therefore flammability, of these forests. We addressed two hypotheses that 1) High severity fire would result in a denser understory than low severity fire after 5 years and that 2) High severity fire would reduce the vertical separation between understory and canopy after 5 years. Field surveys of 38 forest sites with differing fire severity but standardised time since fire and forest type, in Sydney region of New South Wales, Australia, were used to test these hypotheses. We found lower canopy cover and greater understory cover (0.5–4 m height) after high severity fire compared with sites which burnt at low severity. Vertical separation was less between the canopy and understory at sites after high severity fire than after low severity fire. The greater quantity of understory fuel and greater vertical continuity in fuel structure observed suggests a potential increase in forest flammability after high severity fire compared with lower severity fires in these forest types. [ABSTRACT FROM AUTHOR]

Abstract: Identifying and quantifying attributes that help predict rates of heterotrophic soil respiration is a key issue. Similarly, assessing the temperature sensitivity (Q10) of soil C is critical to establishing if increases in Mean Annual Temperature will serve to further increase atmospheric CO2. Using organic soils from three sub-alpine communities that differ significantly in structure, species composition and productivity, we measured the respiratory quotient (RQ = rates of CO2 efflux/rates of O2 uptake) and temperature sensitivity of heterotrophic respiration during long-term (120 days) incubation. As a directly measurable parameter, RQ is free of empirical assumptions and provides an additional tool that can be used in conjunction with constants derived from fitted Arrhenius or exponential equations, to help understand shifts in microbial use of C substrates and how changes in vegetation might affect soil processes. Q10 did not change significantly over the course of a 120-day incubation for any of our studied soils. RQs varied with vegetation type and were consistently lower in grassland soils than woodland soils. RQs also varied during long-term incubations and declined consistently with time for grassland soils. RQs declined towards the end of the 120-day incubation for woodland soils. The generally low E a for these soils from sub-alpine vegetation types in Australia, and the fairly rapid decline in RQ during incubation, suggest the likely greater temperature sensitivity of recalcitrant C relative to labile C could provide a strong positive feedback to increases in Mean Annual Temperature. [Copyright &y& Elsevier]