In the Western Australian wheatbelt, the restoration of native eucalypt forests for managing degraded agricultural landscapes is a critical part of managing dryland salinity and rebuilding biodiversity. Such reforestation will also sequester carbon. Whereas most investigative emphasis has been on carbon stored in biomass, the effects of reforestation on soil organic carbon (SOC) stores and fertility are not known. Two 26 year old reforestation experiments with four Eucalyptus species (E. cladocalyx var nana, E. occidentalis, E. sargentii and E. wandoo) were compared with agricultural sites (Field). SOC stores (to 0.3 m depth) ranged between 33 and 55 Mg ha(-1), with no statistically significant differences between tree species and adjacent farmland. Farming comprised crop and pasture rotations. In contrast, the reforested plots contained additional carbon in the tree biomass (23-60 Mg ha(-1)) and litter (19-34 Mg ha(-1)), with the greatest litter accumulation associated with E. sargentii. Litter represented between 29 and 56% of the biomass carbon and the protection or utilization of this litter in fire-prone, semi-arid farmland will be an important component of carbon management. Exch-Na and Exch-Mg accumulated under E. sargentii and E. occidentalis at one site. The results raise questions about the conclusions of SOC sequestration studies following reforestation based on limited sampling and reiterate the importance of considering litter in reforestation carbon accounts. (C) 2012 Elsevier B.V. All rights reserved.

Summary Carbon forestry is part of a suite of land-based activities that can be used to mitigate carbon emissions, and also provide a range of other environmental co-benefits. Components are included in the Carbon Credits (Carbon Farming Initiative) Act 2011. There is large divergence in Australian estimates of the areas of land that may be used for carbon forests and there has been a vigorous public debate about carbon forestry, partly based on concerns about displacement of food-producing land. We identify four distinct afforestation or reforestation (AR) activities that involve carbon mitigation and suggest a terminology based on these. These are (1) ‘plantations’ that also produce timber and wood products, (2) ‘carbon-focused’ sinks, (3) ‘environmental’ or natural resource management plantings and (4) ‘bioenergy’ plantings for use either as a feedstock for stationary energy production or transport fuels. After accounting for AR projects established for other purposes (e.g. timber and pulpwood), we estimate that the current area of carbon forests in Australia is 65000 ha. Despite the national Renewable Energy (Electricity) Act 2000 and its 2010 amendments there are few extant biomass projects. However this may change with the development of new technologies and the imposition of a carbon price on electricity production. The reasons for the gulf between actual and potential carbon AR activity are proposed to include (1) the absence of a formal carbon compliance scheme, (2) challenges in managing carbon through an entire product cycle, (3) the degree of understanding of carbon forestry by financiers, (4) landholder preference, (5) technical barriers and (6) regulatory uncertainty. We suggest an extension of the National Plantation Inventory from traditional plantations to carbon forestry, so that future policy can be developed on the basis of good-quality underpinning information that can be disaggregated to analyse trends in AR for different purposes. To encourage innovation in the sector, we also suggest either the extension or establishment of research and development funding arrangements, similar to those already existing for other rural industries.

The current agricultural systems of broad areas of Australia are unsustainable, with large projected increases in salinization, decreases in water quality, wind erosion, and losses of biodiversity. It is well known that these problems can be partially resolved by farmland reforestation; however, a major issue is financing the scale of activity required. The international response to global warming, the United Nations Framework Convention on Climate Change and its Kyoto Protocol, includes provisions that enable greenhouse sinks (sequestration of carbon in soils and vegetation) to be used by parties to fulfil their obligations. The Kyoto Protocol also allows for trading in emission reductions, and this opens the possibility that investment in carbon sinks may help underwrite broader natural resource management objectives. This paper examines the possibilities for improved land management in Western Australia arising from the development of carbon sinks by considering: (a) the likelihood of a carbon market developing and the likely depth of that market as a result of current national and international policies, (b) the data available to provide estimates on different types of sinks, and (c) the likely benefits of wide-scale sink investment.It was estimated that the total amount of carbon that could be sequestered by reforesting 16.8 Mha of cleared farmland is 2200 Mt CO2 -e, and between 290 and 1170 Mt CO2-e by destocking 94.8 Mha of rangelands. There were insufficient data to produce estimates of sequestration following changes in tillage practice in cropping systems or the revegetation of already salinized land. We conclude that carbon sinks are only likely to become profitable as a broad-scale stand-alone enterprise when carbon prices reach AUD$15/t CO2-e, with this threshold value varying with carbon yield and project costs. Below this price, their value can be significant as an adjunct to reforestation schemes that are aimed at providing other products (wood, pulp, bioenergy) and land and water conservation benefits. Irrespective of this, carbon sinks provide an opportunity to both sequester carbon in a least-cost fashion and improve soil and watershed management. (c) 2006 Elsevier B.V. All rights reserved.