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• The economics of carbon sequestration in South Australia were evaluated. • Results confirm active afforestation is a high-cost abatement option. • Conservative carbon accounting methods further limit incentives for land-use change. • Achievable abatement is likely small relative to emissions at recent carbon price. • Changes to Australian carbon accounting could incentivise more land-use change. Governments globally are developing increasingly ambitious carbon emissions reduction schemes that include significant emissions offset credits for forest-based carbon sequestration. Such strategies can present significant challenges in highly modified and intensively farmed regions where forest land use opportunity and establishment costs are high. This article evaluates the economics of land-use change via active afforestation for local carbon abatement in the Australian state of South Australia, a region with high supply costs representative of long-established temperate farming regions. We found that there is no economically viable abatement below $38 tCO 2 e−1, however up to 154 Mt CO 2 e of abatement could be available up to prices of $50 tCO 2 e−1. Variation in current Australian Emissions Reduction Fund (ERF) policy parameters related to permanence and crediting periods were also assessed. Recent ERF contracts involve a 100-year land-use change commitment (permanence period) and a 25-year crediting period where payments for growth in carbon from the land-use change is contracted. We compared outcomes of this arrangement to a scenario with equal 100-year permanence and crediting periods. We found substantial differences in carbon supply at some price points for a 25 rather than a 100-year crediting period. Under ERF parameters the first economically viable revegetation options occur at $42 tCO 2 e−1, however, we found a 69 percent reduction in economically viable supply at a carbon price of $50 tCO 2 e−1. The results highlight the role offset crediting policy can have on dis-incentivising land-use change and the need for landholders to be compensated fully for temporal opportunity costs. [ABSTRACT FROM AUTHOR]

Global change scenarios predict that precipitation regimes will become more variable in many parts of the world, extending drought periods and increasing rainfall intensity. Under these conditions, soil microbial community composition will likely change in ways that have implications for microbially-mediated nutrient cycling. Understanding these responses is key to predicting consequential changes in ecosystem functions. A 30 day incubation experiment was used to investigate the response of microbial community structure to three different soil moisture treatments, namely, constantly moist (CM), constantly dry (CD), and drying-rewetting (DRW), in soils of three different land condition types (Remnant, Restored, and Old-field) from Para Woodlands Nature Reserve, South Australia. Soil respiration and inorganic N transformations were approximately the same across soils, despite fundamental differences in physicochemical properties, vegetation communities, and land-use history. Soil microbial community structure changed in response to the different soil moisture treatments; responses of taxa was divergent among soils. These results demonstrate that changes to soil moisture regimes under climate projections will almost certainly have consequences for soil microbial communities and C and N dynamics. The results highlight the need for further research to understand the mechanisms driving divergent responses to soil moisture, particularly in areas of different land-use types. • C and N cycling, and microbial community response to soil moisture were examined. • Response of soil inorganic N pools and respiration were similar across soils. • Soil microbial community structure changed in response to moisture treatments. [ABSTRACT FROM AUTHOR]