Forest plantations can access water from some unconfined aquifers that also contain nitrate at concentrations that could support hydroponic culture, but the separate effects of such additional water and nitrogen availability on tree growth have not hitherto been quantified. We demonstrate these effects using simulation modelling at two contrasting sites supporting Eucalyptus globulus Labill. or Pinus radiata D.Don plantations. The APSIM Eucalyptus and Pinus models simulated plantation growth within 2% of observed growth where the water table was at 4 m depth for eucalypts (height 28 m, MAI 32 m3 ha−1 year−1) and at 23 m for pines (height 37 m, MAI 20 m3 ha−1 year−1). In simulations without an aquifer, observed growth could only be matched using unrealistically high surface soil nitrogen (N) supply, suggesting this is an unlikely mechanism. Simulated aquifer N concentrations, evapotranspiration, and net N mineralization and leaching (emergent properties of modelling) were similar to measured values. These results strengthen the plausibility that aquifer N uptake by plantations could be contributing to tree growth. This hypothesis warrants further research that quantifies these processes at multiple sites. Simulations included growth of herbaceous and tree weed species, and pasture, which demonstrated the utility of the process-based APSIM modelling framework for dynamically simulating carbon, water and N of plantations and other mixed-species systems.

Over half of the large African mahogany plantation estate in northern Australia has reached the mid-point of the target rotation length of 20 to 25 years. As such, there is increasing interest in understanding the potential volume and grade qualities recovered from these young trees using different processing methods. The objective of this study was to compare the recovery rates and product grade quality for rotary veneer using spindleless lathe technology and sawn boards using traditional sawing techniques. Net veneer recovery ranged between 42% and 55% of log volume, with most veneers being limited to D-grade. Compression, surface roughness, and grain breakout were the most prominent defects limiting veneer grade. The sawn-dried-dressed recovery was low, with less than 20% of the log volume representing a potential saleable product. The small log diameter combined with defects including wane, heart shake, pith, and knots reduced the potential recovery. A high presence of sawn board distortion was observed that negatively impacted the efficiency of sawn timber processing along with product recovery. While low, the recovery of veneers and sawn timber from young African mahogany was like other young plantation grown hardwoods.

As the global population increases and becomes more affluent, biomass demands for food and biomaterials will increase. Demand growth is further accelerated by the implementation of climate policies and strategies to replace fossil resources with biomass. There are, however, concerns about the size of the prospective biomass demand and the environmental and social consequences of the corresponding resource mobilization, especially concerning impacts from the associated land-use change. Strategically integrating perennials into landscapes dominated by intensive agriculture can, for example, improve biodiversity, reduce soil erosion and nutrient emissions to water, increase soil carbon, enhance pollination, and avoid or mitigate flooding events. Such "multifunctional perennial production systems" can thus contribute to improving overall land-use sustainability, while maintaining or increasing overall biomass productivity in the landscape. Seven different cases in different world regions are here reviewed to exemplify and evaluate (a) multifunctional production systems that have been established to meet emerging bioenergy demands, and (b) efforts to identify locations where the establishment of perennial crops will be particularly beneficial. An important barrier towards wider implementation of multifunctional systems is the lack of markets, or policies, compensating producers for enhanced ecosystem services and other environmental benefits. This deficiency is particularly important since prices for fossil-based fuels are low relative to bioenergy production costs. Without such compensation, multifunctional perennial production systems will be unlikely to contribute to the development of a sustainable bioeconomy. This article is categorized under: Bioenergy > Systems and Infrastructure Bioenergy > Climate and Environment Energy Policy and Planning > Climate and Environment

Current forest industries in south-western Australia are based on regrowth natural eucalypt forests and Pinus and Eucalyptus spp. plantations, and restricted to areas with >600 mm y(-1) annual rainfall. Dryland farming systems have been developed across 20 million ha in a zone with 300-600 mm y(-1) annual rainfall and a Mediterranean climate. This zone is beset with land degradation problems, such as salinity and wind erosion, and there has been considerable effort in the last three decades to develop reforestation options to stabilise the landscapes. Traditional forestry approaches using pulp wood or sawlog production in this zone have been limited by unfavourable economics driven by modest tree growth rates, large transport costs to processing and export facilities, and high labour costs. Given that salinity results from a disruption of the landscape water balance, reforestation has represented a major component in attempts to tackle the problem. Issues with reforestation include (1) obtaining sufficient scale of activity to impact watershed water balances, (2) obtaining a hydrological response without displacing farm production and rural communities and (3) gaining payment for non-forest benefits. This paper reviews the approaches that have been used to integrate trees into the dryland farming (300-600 mm y(-1) annual rainfall) systems of south-western Australia, and have resulted in at least 113 286 ha of reforestation. These included both traditional (pine and eucalypt sawlogs) and new (sandalwood, biodiversity restoration and carbon mitigation through bioenergy and carbon sequestration) projects. Ongoing investment has centred on carbon sequestration as this represents one of the few profitable options for the management of dryland salinity in this region. Approaches developed in this region to encourage farmland reforestation will be applicable in other dryland regions, particularly with the interest in using the land-sector to meet climate mitigation targets.

A synthesis of work on integrating short‐rotation biomass plantings into existing mixed crop and livestock farming regimes with the biomass being converted to biofuels, including aviation fuel, is provided. This agroforestry system, based on mallee eucalypt species native to Australia, provides broader environmental benefits, including biodiversity protection. These species are suited to the edaphic and climatic conditions of rainfed farming systems in southern Australia. The study focused on the Great Southern region of Western Australia, with an average annual rainfall of 400–600 mm. Compared to other locations in Australia, significantly more research and development has been conducted in this region, with a mallee biomass‐to‐jet fuel business case and farmer cooperation providing reliable data for assessing the viability and sustainability of commercial supply chain development. The limited capacity of Australian agricultural systems to produce biomass due to the relatively dry climate means that the available biomass resources should be directed to strategically important energy uses such as aviation fuel. Technical, economic, and environmental insights gained from these long‐term studies have demonstrated that it is feasible to integrate this new production system into the overall farming enterprise and indicate strong prospects for a biomass industry in this region should political and economic uncertainties currently facing the renewable energy industry in Australia be resolved. WIREs Energy Environ 2017, 6:e221. doi: 10.1002/wene.221 This article is categorized under: Bioenergy > Science and Materials Bioenergy > Economics and Policy Bioenergy > Systems and Infrastructure

Mallee plantations have been integrated into wheat farms in Western Australia as a large-scale and multi-purpose woody crop since the 1990s. Mallee describes the growing habit of certain eucalypt species that grow with multiple stems shooting from an underground crown root (lignotuber), usually to a height of up to 10 meters. These types of plantations could be a considerable source of biomass to produce renewable energy. In this project the supply chain of Mallee was modelled using BIOPLAN's linear programming model to investigate the im- pact of tree size, extraction distance and transport distance on supply chain costs. The harvest- ing system included a feller-buncher, front end loader, in-field chipper and truck. The mobile Bruks chipper was found to be more efficient than Peterson Pacific to chip Mallee trees. The results indicated that harvesting larger tree sizes can slightly diminish chipping cost. Extrac- tion cost was very sensitive to the extraction distance in this case study. Long transport dis- tances in larger management area (to meet higher energy demands) will highly increase the transport cost. From optimised supply chain cost and sensitivity analysis, the best practice for efficient Mallee biomass supply chain was suggested as following: harvesting Mallee trees when reaching larger size (about 0.3 m 3 for a tree consisting of multiple stems with an average DBH of 5 cm to 10 cm per each stem), planning average extraction distance to be shorter than 1000-1500 m, establishing the Mallee plantations closer to energy plant with transport dis- tance shorter than 100 km (with a radius of 50-75 km providing an effective compromise between cost and distance) or alternatively installing new bioenergy plants no farther than 100 km from existing Mallee plantations.

Jet fuel made from mallee biomass can be sustainable and can reduce carbon emissions, according to a new report produced by Future Farm Industries CRC.

This paper tests the hypothesis that thinning and nitrogen fertiliser can increase the mass of wood produced per volume of water used (evapotranspiration) by plantations of Eucalyptus globulus. We have called this plantation water productivity (PWPWOOD) and argue that, for a given genotype, this term integrates the effects of management, site and climate on both production and evapotranspiration. This is done using annual estimates of wood production and evapotranspiration from age three years to harvest age (similar to age 10 years) in three E. globulus stocking density by nitrogen experiments. The ratio of annual rainfall to potential evaporation at these three sites varied from 0.85 to 0.45.Plantation water productivity (PWPWOOD) was calculated as the ratio of annual growth to annual evapotranspiration. In this study, the PWPWOOD of E. globulus varied from 0.2 to 3.1 g kg(-1) and was significantly increased by the application of nitrogen at two sites where growth was nitrogen limited. In fertilised stands, soil stored water was depleted early in the summer while in contrast, unfertilised stands used the water more slowly, thereby extending the growth season to late summer when average daily evaporation was much higher. Increased PWPWOOD in response to nitrogen was associated with an increase in water stress that could be mitigated by reducing stocking density without affecting either production or PWPWOOD.Plantations are managed at the compartment scale while water resources are monitored and managed at the catchment scale or larger. At the compartment scale, growth and PWPWOOD are correlated with evapotranspiration; managing plantations to maximise water use can also minimise the impact of wood production on water resources. (C) 2014 Elsevier B.V. All rights reserved.

Salinization threatens up to 17 million hectares of Australian farmland, major fresh water resources, biodiversity and built infrastructure. In higher rainfall (>600 mm/year) areas of south-western Australia a market based approach has resulted in the reforestation of over 280,000 ha of farmland with Eucalyptus globulus plantations. This has had significant collateral environmental benefits in terms of reducing salinity in several watersheds. This model has not been replicated in the lower (300–600 mm/year) rainfall areas of this region, which is a global biodiversity hotspot. In this area, conventional forestry species have lower wood yields and longer rotations, compromising profitability, and reinforcing land-holder preference to maintain existing agricultural activities. Two complementary strategies are being used to restore landscape function across this drier region, through increased reforestation. The first is to shift from the paradigm of forestry comprising tall trees grown in relatively long rotations and producing timber to one based on the production of a range of biomass products (bioenergy, chemicals, sequestered carbon), and environmental services such as providing fresh water. As a consequence of breaking this paradigm, silvicultural practices such as stand densities and rotation length can also be redefined. The second strategy is to integrate these new systems into the existing dryland farming systems. Four broad approaches are being assessed viz. (a) belts of trees with farming maintained in inter-row alleys, (b) blocks of trees located on areas of water accumulation or of high recharge, (c) adjusting species selection to soil conditions, such as those that are shallow or saline, and (d) alternating short phases (3–5 years) of trees with farming. These systems offer the prospect of sequestering carbon, and producing wood or biofuels from farmland without displacing food production.

Eucalyptus globulus plantations are thought to use stored soil water when planted on ex-agricultural sites, and we hypothesized that this is likely to affect productivity of 2nd and later rotation plantations because the next rotations have access to less stored soil water. We used a combination of experiments and modeling to understand the impact of E. globulus plantations on soil water stores over the first rotation and early second rotation. The experiments were conducted at 3 contrasting sites in southwestern Australia, and modeling was used to extrapolate the results to other climatic zones. Soil water dynamics were assessed to 8 m depth under a range of management options, including spacing and nitrogen addition in the first rotation, and coppice or seedling re-establishment in the 2nd rotation. We found that soil water stores declined over the course of the first rotation at all sites, with some (incomplete) annual replenishment evident at the higher rainfall sites, but less replenishment at depth, especially in the lower rainfall sites. Only the wettest of the 3 sites fully replenished with soil water after harvest of the 1st rotation. Plots with higher stocking rates had higher soil water depletion early in the rotation, although by the end of the first rotation, most treatments had similar soil water deficits of around 800 mm at all of the sites. Of the sites that were responsive to N fertilizer, there was a strong differential in the degree of soil water deficit between N treatments, with N fertilized trees using more of the soil water store each year, but also producing more wood. A process-based plantation growth model, CABALA, was found to be adequate for predicting soil water dynamics under the range of management options that we explored, and we applied it to understanding the potential replenishment of soil under 2nd rotation plantations in a range of climatic zones within the E. globulus estate in south-western Australia. This modeling showed that most sites with soil depths of more than 4 m (i.e., most of the estate) are unlikely to be fully replenished in the 2nd rotation, and that this is likely to have a significant impact on the capacity of sites to achieve similar productivity levels in the second rotation as the first unless the sites are given an opportunity for soil water replenishment between rotations. The results from this study suggest that plantation managers will need to understand soil water dynamics at any given site to be able to predict productivity in 2nd and later rotations, and may need to explore novel management options like fallowing between rotations to allow for soil water replenishment. (C) 2011 Elsevier B.V. All rights reserved.

This paper reports on variation in leaf area index (L) in five Eucalyptus globulus Labill. plantations in response to application of nitrogen, thinning at age 2 years and variation in climate wetness index (the ratio of rainfall to potential evaporation). Observed L is compared with: (i) L predicted to optimize net primary productivity for a given average annual temperature, annual water use and potential evaporation (L(opt)) and (ii) L calculated as a linear function of climate wetness index (L(eq)). L peaked in fertilized plots at between 4 and 5 years of age or immediately after canopy closure. The value of L from canopy closure to age 8 years was not strongly related to annual rainfall or climate wetness index. At two sites with total soil nitrogen <1.2 mg g(-)(1), L in fertilized plots was about two units greater than in unfertilized plots. This difference persisted until measurements ended in 2004 when the trees were 8 years old. The L of plots thinned to 300 and 600 stems ha(-)(1) at age 2 years recovered quickly and was not significantly different from L in unthinned plots when the trees were 8 years old. L(opt) was a good predictor of the leaf area index of 8-year-old plots of E. globulus when nitrogen and phosphorus were non-limiting (model efficiency (EF) was 0.5). For the same plots, L(eq) underestimated observed L by an average of two units, and the model efficiency was low (-3.25). Data from two nitrogen-limited sites demonstrated that for fertilized plots L(opt) (EF = 0.6) was a much better predictor of L than L(eq) (EF = -3.36). At the same sites, L(eq) (EF = 0.42) was a better model for predicting L of unfertilized plots than L(opt) (-3.59). These results provide evidence that comparing observed L with L(opt) can identify stands limited by factors other than growing climate.

We conducted a comprehensive modelling study to estimate future stem wood production and net ecosystem production (NEP) of Pinus radiata D. Don plantations in south-western Australia, a region that is predicted to undergo severe rainfall reduction in future decades. The process-based model CenW was applied to four locations where it had previously been tested. Climate change scenarios under four emission scenarios for the period from 2005 to 2066 were considered, in addition to simulations under the current climate. Results showed that stem wood production and NEP were little affected by moderate climate change. However, under the most pessimistic climate change scenario (Special Report on Emission Scenarios A2), stem wood production and NEP decreased strongly. These results could be explained by the trade-off between the positive effect of rising atmospheric CO(2) on plant water use efficiency and the negative effects of decreasing rainfall and increasing temperatures. Because changes in heterotrophic respiration (R(H)) lagged behind changes in plant growth, and because R(H) rates were increased by higher temperatures, NEP was more negatively affected than stem wood production. Stem wood production and NEP also strongly interacted with location, with the site currently having the wettest climate being least affected by climatic change. These results suggest that realistic predictions of forest production and carbon sequestration potential in the context of climate change require (1) the use of modelling tools that describe the important feedbacks between environmental variables, plant physiology and soil organic matter decomposition, (2) consideration of a range of climate change scenarios and (3) simulations that account for a gradual climate change to capture transient effects.

The occurrence of tree deaths in young, 3 to 6 year old Eucalyptus globulus plantations established on farmland in south-western Australia was found to be strongly related to factors indicative of poor soil water storage capacity. Seven years after planting tree survival was significantly less on soils <2 m deep compared to >2 m deep (22% vs 70%). This is due to the limited ability of some soils to store a sufficient proportion of the annual rainfall within the root-zone to meet the plant water demand in a region with a recurrent annual summer drought. There are practical difficulties in routinely surveying soils to depths in excess of 2 m over broad areas, to predict the likelihood of tree death. On the granitic basement rocks of south-west Western Australia, the occurrence of ferricrete gravels provides a useful surrogate indicator for the presence of deeper soils. In this region the distribution of soil depth and soil fertility has a geomorphic basis, being related to previous patterns of deep weathering and regolith stripping. Soils have developed on various horizons of deeply weathered profiles, formed from granites and gneisses. These materials have been stripped to a variable extent by erosion, leading to a range of soil depths. The original weathered profiles, which correspond to the soils with ferricrete gravels, comprise the deepest soil/regolith materials (~30-50 m deep); whereas along drainage lines the regolith has been completely stripped, the soils are shallow and plantations are most susceptible to drought. Knowledge of the relationship between soil depth and plantation performance allows regional indications of drought risk to be developed from regional soil mapping and the production of more efficient sampling designs for site assessment.

More than 2.5 million ha of Eucalyptus globulus are now planted across the globe including approximately 500 000 ha in southern Australia. In this region average annual rainfall has declined since 1960 and this trend is predicted to continue in the coming decades. E. globulus is a premium species for paper manufacture and grows well under moderate seasonal water stress. The traits that underpin this rapid early growth also make the species vulnerable to prolonged water stress. We established nitrogen rate and nitrogen-by-stocking experiments in five 2-year-old E. globulus plantations along a climatic gradient in south-western Australia. We measured volume growth, predawn leaf water potential and leaf area index over 7 years or until the plantations were 9 years old. These data were used to explore the relationship between growth and water stress, to understand the mechanistic basis for the relationship and to identify best-bet management strategies for E. globulus plantations in southern Australia.Nearly all of the variation in volume growth rate between sites could be explained by a combination of climate wetness index and soil depth. There was a significant growth response to nitrogen at two low rainfall and one high rainfall site. There was no growth response to nitrogen on sites where total soil nitrogen in the top 0.1 m of soil was more than 1.9 mg g(-1) and a very rapid increase in relative growth response below this threshold. The observed growth response to nitrogen was associated with an increase in water stress and on at least one site increased mortality. Matching the supply of nutrients to demand will maximise the growth at any site but this may increase the risk of drought death at water-limited sites. This will be exacerbated if forecasted changes in the climate of southern Australia are realised. Thinning to 600 stems ha(-1) significantly reduced the level of water stress experienced by E. globulus in Western Australia without significantly affecting end of rotation stand volume compared to unthinned stands. These results indicate that for a range of sites in south-western Australia a final stocking density of 600 stems ha(-1) coupled with application of fertiliser to maximise growth will minimise risk without sacrificing any of the site potential. (C) 2009 Elsevier B.V. All rights reserved.

Over much of south-western Australia there was a rapid decrease in rainfall of around 20% in the mid-1970s. Further declines in rainfall are predicted along with increases in temperature and atmospheric CO2 concentration. This study focused on the implications of such a change for wood production and net ecosystem carbon exchange of pine plantations in that region.The process-based model CenW was evaluated using measurements of basal area and soil moisture in Pinus radiata plantations at seven sites in south-western Australia, encompassing a range of climatic conditions and silvicultural treatments (fertiliser application and thinning). The model predicted basal area very well and soil moisture reasonably well, except for one site where a water table may have provided additional water supply to trees.The model was then applied to assess the effects of the climatic changes that have occurred since 1975 by running the model for whole 30-year rotations, using observed climate data from either the 1945-1975 or 1975-2005 periods. The simulations showed that out of the six sites considered, wood production and net ecosystem carbon exchange were increased in the latter period at three sites, remained almost unchanged at two sites, and decreased at one site. Analysis of the model outputs, aided by additional simulations revealed that the response to the climate shift was determined by soil type (i.e. decreased growth rate was confined to the site with a sandy soil), and by the interaction between rising CO2 levels (positive effect) and changes in rainfall (positive or negative depending on the direction of the change in rainfall). (C) 2007 Elsevier B.V. All rights reserved.

ABSTRACT

HUNT, S., STUART, G., MCGRATH, J. and HOSSAIN, S., 2007. Improvements to Integrated Coastal Zone Management on Australia's Gold Coast. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 25 - 28.Gold Coast, Australia, ISSN 0749.0208 Gold Coast City Council is one of the largest local governments in Australia with a staff of approx 2800. The City includes over 50 km of open coastline and over 600 kin of waterways. Given the city's position as an international coastal destination it is important that the values of these environments that attract residents and tourists are managed and protected.Integrated Coastal Zone Management requires people that can work across many disciplines. Recent projects and roles developed within Gold Coast City Council are presented as an example of ways that one local government is addressing the complexity of ICZM.Case studies exploring the Gold Coast Ocean Beaches and Foreshores Strategy and the role of the Beaches and Waterways Development Officer describe the ways in which the local coastal management issues are being integrated across a large organisation, across varying disciplines and different levels of government.Both examples are measured against the barriers to successful coastal policy making as described in a theme report following the Coast to Coast Conference (Australia's national coastal conference) in 2002. The major barriers discussed include; lack of integration, lack of adequate monitoring of policy implementation and review, lack of resources for both policy making and the information base is either inadequate or drawn from a narrow range of sources.