Ngugi M.R.,Innovation and the Arts |
Neldner V.J.,Innovation and the Arts |
Ecological Management and Restoration | Year: 2015
The standard rehabilitation objective for open-cut mines in Queensland is to establish a self-sustaining native forest ecosystem. Consequently, mine regulators and managers need tools to project whether sites are likely or not to meet agreed completion criteria and to ensure timely remedial interventions. The Ecosystem Dynamics Simulator (EDS) is such a tool capable of modelling forest dynamics and projecting long-term growth of woody species only. Here, the model was applied to rehabilitation sites aged between 5 and 22 years in Meandu open-cut coal mine in southeast Queensland. EDS projected structural characteristics for trees (height, diameter, basal area, foliage projective cover and stem density) and tree species composition as a function of rehabilitation age. Projected stand growth attributes were assessed against BioCondition benchmarks developed from eucalypt (Eucalyptus/Corymbia) remnant forests adjacent to the mine. Growth trajectories indicated that sites with >30% eucalypt basal area composition were more likely to develop into eucalypt-dominated self-sustaining ecosystems compared with sites that were initially dominated by acacias (Acacia spp.). Projections suggested that some benchmark attributes such as number of large eucalypt trees would take more than 70 years to be met. The application of EDS provided a framework to support decisions on early remedial intervention and assess the risk associated with lease relinquishment. © 2015 Ecological Society of Australia and Wiley Publishing Asia Pty Ltd.
Liu X.,Griffith University |
Chen C.R.,Griffith University |
Wang W.J.,Innovation and the Arts |
Hughes J.M.,Griffith University |
And 3 more authors.
Soil Biology and Biochemistry | Year: 2013
Production of nitrous oxide (N2O) by anaerobic denitrification is one of the most important processes in the global nitrogen (N) cycle and has attracted recent attention due to its significant impacts on climatic change. Fire is a key driver of many ecosystem processes, however, how fire drives the shift in microbial community and thus alters nutrient cycling is still unclear. In this study, a 35-year-old repeated prescribed burning trial, with three treatments (no burning, 2 yearly burning and 4 yearly burning), was used to explore how the long-term repeated prescribed burning affects N2O flux, key soil properties (inorganic N, dissolved organic carbon (DOC) and N, pH, electrical conductivity (EC), moisture), denitrification gene abundance and their interactions. Soil samples were collected in January and April 2011. Quantitative real-time PCR was employed to quantify the gene copy number of target genes, including narG, nirK, nirS and nosZ. In situ N2O fluxes ranged from 0 to 8.8 g N2O-N ha-1 h-1 with an average of 1.47 g N2O-N ha-1 h-1. More frequent fire (2 yearly burning) significantly reduced soil N2O fluxes, availability of C and N substrates and moisture, but increased soil pH and EC compared with no burning and 4 yearly burning treatments. Fire treatments did not significantly affect the abundance of most denitrification genes. There were no significant differences in most parameters measured between the 4 yearly burning and no burning treatments, indicating microbial community function is not affected by less frequent (4 year interval) burning. Variation in the N2O fluxes among the treatments can largely be explained by soil substrate (NO3-, DOC and total soluble nitrogen (TSN)) availability and soil environmental factors (pH, EC, and moisture), while the abundance of most denitrification genes were not related to the N2O fluxes. It is concluded that soil environmental factors rather than denitrification gene abundance control N2O fluxes in this wet sclerophyll forest in response to long-term repeated fires. © 2012 Elsevier Ltd.
Bradshaw C.J.A.,University of Adelaide |
Bradshaw C.J.A.,South Australian Research And Development Institute |
Bowman D.M.J.S.,University of Tasmania |
Bond N.R.,Griffith University |
And 28 more authors.
Biological Conservation | Year: 2013
Pricing greenhouse gas emissions is a burgeoning and possibly lucrative financial means for climate change mitigation. Emissions pricing is being used to fund emissions-abatement technologies and to modify land management to improve carbon sequestration and retention. Here we discuss the principal land-management options under existing and realistic future emissions-price legislation in Australia, and examine them with respect to their anticipated direct and indirect effects on biodiversity. The main ways in which emissions price-driven changes to land management can affect biodiversity are through policies and practices for (1) environmental plantings for carbon sequestration, (2) native regrowth, (3) fire management, (4) forestry, (5) agricultural practices (including cropping and grazing), and (6) feral animal control. While most land-management options available to reduce net greenhouse gas emissions offer clear advantages to increase the viability of native biodiversity, we describe several caveats regarding potentially negative outcomes, and outline components that need to be considered if biodiversity is also to benefit from the new carbon economy. Carbon plantings will only have real biodiversity value if they comprise appropriate native tree species and provide suitable habitats and resources for valued fauna. Such plantings also risk severely altering local hydrology and reducing water availability. Management of regrowth post-agricultural abandonment requires setting appropriate baselines and allowing for thinning in certain circumstances, and improvements to forestry rotation lengths would likely increase carbon-retention capacity and biodiversity value. Prescribed burning to reduce the frequency of high-intensity wildfires in northern Australia is being used as a tool to increase carbon retention. Fire management in southern Australia is not readily amenable for maximising carbon storage potential, but will become increasingly important for biodiversity conservation as the climate warms. Carbon price-based modifications to agriculture that would benefit biodiversity include reductions in tillage frequency and livestock densities, reductions in fertiliser use, and retention and regeneration of native shrubs; however, anticipated shifts to exotic perennial grass species such as buffel grass and kikuyu could have net negative implications for native biodiversity. Finally, it is unlikely that major reductions in greenhouse gas emissions arising from feral animal control are possible, even though reduced densities of feral herbivores will benefit Australian biodiversity greatly. © 2013 Elsevier Ltd.
Rotstayn L.D.,CSIRO |
Collier M.A.,CSIRO |
Chrastansky A.,CSIRO |
Jeffrey S.J.,Innovation and the Arts |
Luo J.-J.,Center for Australian Weather and Climate Research
Atmospheric Chemistry and Physics | Year: 2013
All the representative concentration pathways (RCPs) include declining aerosol emissions during the 21st century, but the effects of these declines on climate projections have had little attention. Here we assess the global and hemispheric-scale effects of declining anthropogenic aerosols in RCP4.5 in CSIRO-Mk3.6, a model from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results from this model are then compared with those from other CMIP5 models. We calculate the aerosol effective radiative forcing (ERF, including indirect effects) in CSIRO-Mk3.6 relative to 1850, using a series of atmospheric simulations with prescribed sea-surface temperatures (SST). Global-mean aerosol ERF at the top of the atmosphere is most negative in 2005 (-1.47 W m -2). Between 2005 and 2100 it increases by 1.46 W m−2, i.e., it approximately returns to 1850 levels. Although increasing greenhouse gases (GHGs) and declining aerosols both exert a positive ERF at the top of the atmosphere during the 21st century, they have opposing effects on radiative heating of the atmosphere: increasing GHGs warm the atmosphere, whereas declining aerosols cool the atmosphere due to reduced absorption of shortwave radiation by black carbon (BC). We then compare two projections for 2006-2100, using the coupled atmosphere-ocean version of the model. One (RCP45) follows the usual RCP4.5; the other (RCP45A2005) has identical forcing, except that emissions of anthropogenic aerosols and precursors are fixed at 2005 levels. The global-mean surface warming in RCP45 is 2.3° C per 95 yr, of which almost half (1.1° C) is caused by declining aerosols. The warming due to declining aerosols is almost twice as strong in the Northern Hemisphere as in the Southern Hemisphere, whereas that due to increasing GHGs is similar in the two hemispheres. For precipitation changes, the effects of declining aerosols are larger than those of increasing GHGs due to decreasing atmospheric absorption by black carbon: 63% of the projected global-mean precipitation increase of 0.16 mm per day is caused by declining aerosols. In the Northern Hemisphere, precipitation increases by 0.29 mm per day, of which 72% is caused by declining aerosols. Comparing 13 CMIP5 models, we find a correlation of-0.54 (significant at 5%) between aerosol ERF in the present climate and projected global-mean surface warming in RCP4.5; thus, models that have more negative aerosol ERF in the present climate tend to project stronger warming during 2006-2100. A similar correlation (-0.56) is found between aerosol ERF and projected changes in global-mean precipitation. These results suggest that aerosol forcing substantially modulates projected climate response in RCP4.5. In some respects, the effects of declining aerosols are quite distinct from those of increasing GHGs. Systematic efforts are needed to better quantify the role of declining aerosols in climate projections. © 2013 Author(s).