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Climate warming has been linked to shrub expansion in alpine regions and the decomposition of shrub leaf litter and subsequent release of nutrients has been proposed as a mechanism to facilitate shrub growth. We quantified the rate of alpine shrub leaf litter decomposition (measured as mass loss) over the course of a year in four locally occurring alpine shrub species that grow across four alpine summits. We measured a range of environmental attributes at the study sites, and via a standard litter bag approach, we evaluated the effects of site elevation, the depth of litter bag deployment, the removal time, the species‐specific leaf area (SLA) and the accumulated growing degree days at each site on the total per cent and rate of litter decomposition (as mass loss). The higher elevation sites were cooler with more snow days than the lower sites. Soil moisture was higher early in the snow‐free season at the higher elevation sites. Linear mixed effect models indicated no significant effects of elevation on total and rate of litter decomposition, but there were significant positive effects of deployment depth and removal time and a significant negative effect of species SLA. There were significant negative relationships between the rate of decomposition and growing degree days, as decomposition slows through time. The modelled mean rates of shrub litter decomposition for each species indicated that there would be more and faster decomposition if winter and early spring conditions were to persist for a whole year, compared with the modelled rates of average annual conditions persisting for a whole year. Our results indicate that Australian alpine shrub litter decomposes readily, with the highest rates of decomposition occurring soon after deployment, which in this study was after a snowy winter at the start of the growing season in spring. [ABSTRACT FROM AUTHOR]

Peatlands are globally significant carbon sinks, but when disturbed, have the potential to release carbon back to the atmosphere as greenhouse gases. Feral horse populations in the Australian Alps degrade Sphagnum peatlands, which are highly sensitive to disturbance. However, the link between this degradation and peatland carbon cycling is not understood. Here, we compared the autumn daytime carbon dioxide (CO 2) and methane (CH 4) fluxes of 12 alpine and subalpine Sphagnum peatlands in Kosciuszko National Park, Australia. The presence of feral horses at these sites was correlated with higher carbon loss: sites with horses were losing carbon to the atmosphere (4.83 and 8.18 g CO 2 -e m−2 d−1 in areas of Sphagnum moss and bare soil, respectively), whereas sites without horses were removing carbon from the atmosphere (−6.39 g CO 2 -e m−2 d−1). Sites with feral horses also had higher soil bulk density, temperature, and electrical conductivity (EC), and higher water pH, EC, and turbidity, than sites without horses. Our findings suggest that excluding feral horses from peatland areas could reduce rates of carbon loss to the atmosphere, in addition to improving overall site condition, peat soil condition, and water quality. We discuss potential management applications, further research, and restoration opportunities arising from these results. • Horse-present peatlands were net carbon sources; horse-absent peatlands were net carbon sinks. • Net carbon emission was 91% higher at bare soil areas than Sphagnum -covered areas. • Soil bulk density, temperature, and EC were higher at peatland sites with feral horses. • Water pH, EC, and turbidity were higher at peatland sites with feral horses. [ABSTRACT FROM AUTHOR]

Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management. [ABSTRACT FROM AUTHOR]

Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.