Richard Bashford

Global decomposition experiment shows soil animal impacts on decomposition are climate-dependent

Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region- or biome-scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity.

Diversity and abundance of some ground-dwelling invertebrates in plantation vs. native forests in Tasmania, Australia

Land snails, millipedes, carabid beetles and velvet worms (Onychophora) were methodically hand-sampled at 46 localities on paired plots in conifer or eucalypt plantations and in nearby native forest in northwest Tasmania. Native land snails and millipedes were less diverse in plantations than in native forests, and introduced land snails were several times more abundant in plantations. Many taxa, however, including a velvet worm previously considered to be threatened by plantation development, and including almost half the taxa represented by 10 or more specimens, were found at least as commonly in plantations as in native forests. Invertebrate conservation may be assisted by specific forestry operations, including windrowing, mound ploughing, and leaving waste prunings and thinnings to rot. Plantation development on cleared farmland can allow invertebrates to re-invade from adjacent bush remnants, reducing the risk of local extinctions.

Sirex Woodwasp in Australia: Current Management Strategies, Research and Emerging Issues

It has been almost 60 years since Sirex noctilio (Sirex) was first detected in Australia, and it has now spread to all pine-growing states except Western Australia. Major outbreaks occurred soon after detection in both Tasmania and Victoria. However, in the Green Triangle region of western Victoria/south-eastern South Australia, only low numbers of Sirex were initially found. This led to reduced surveillance, which ultimately resulted in the largest recorded outbreak of Sirex in Australia, killing over five million trees between 1986 and 1989. Based on this outbreak, it was predicted that Sirex damage could result in losses of up to AU

The development of static trapping systems to monitor for wood-boring insects in forestry plantations

60 million per annum in the absence of control. This prediction resulted in the development of the National Strategy for Control of Sirex noctilio in Australia. There have been only a few, localised outbreaks of Sirex since, although several potential problems with the Sirex control strategy have recently been identified. In this Chapter we provide a synopsis of the Sirex Control Strategy in light of new developments and procedures that compliment the original strategy. We also describe current research activities and emerging issues, including reduced parasitism of nematode-inoculated trap trees; problems associated with Ips grandicollis attacking Sirex trap tree plots; determining whether temperature is limiting the northern spread of S. noctilio and Amylostereum areolatum, and its effect on the nematode, Deladenus siricidicola; and variation in nematode infectivity across south-eastern Australia.

Moving with the times: baseline data to gauge future shifts in vegetation and invertebrate altitudinal assemblages due to environmental change

Summary The effectiveness of combinations of panel and funnel static traps with lures in surveillance to detect wood-boring insects in softwood (Pinus) and hardwood (Eucalyptus) plantations was examined. Static trapping systems proved to be an effective tool for monitoring specific pest species such as the wood wasp Sirex noctilio, detecting their presence when more traditional surveillance methods did not. Traps can detect a broad range of wood-boring species, enabling detection of low (pre-outbreak) populations of pest species. The panel and funnel traps were found to be at least as effective as Malaise trapping, light trapping and insect rearing in determining the wood-boring insects present in a plantation. A strategy for the operational deployment of static traps for detecting developing outbreaks has still to be finalised — full deployment in all susceptible plantations is unlikely to be cost-effective, but sub-sampling susceptible plantations is feasible. The development of surveillance systems using static traps to detect exotic wood-borers is discussed.

The Use of Kairomone Lures for the Detection of Sirex noctilio in Susceptible Pinus radiata Plantations in Australia

Abstract A long-term monitoring program has been established in Tasmania, Australia, as a Satellite Project for the International Biodiversity Observation Year (IBOY). This program aims to monitor distributional change in vegetation and fauna assemblages along an altitudinal gradient (70–1300 m) in response to climate change and other environmental events. Baseline data collected over a two-year period will be available for comparison with data collected in future decades. The vegetation varies with altitude and fire history. The rate of change in vegetation is not continuous along the altitudinal gradient, but is most rapid above 700 m and below the treeline at 1000–1100 m. Most vascular plant species reach the limit of their distribution within this zone. Despite their preliminary nature, the invertebrate data also display altitudinal and seasonal patterns. The treeline and the 700–1000 m zone again appear to be notable in terms of invertebrate distribution. While the composition of ground-based taxa may be closely related to the floristic composition of the vegetation (or its environmental drivers), the airborne invertebrate fauna appears to be more closely related to structural characteristics such as height and density. Of all taxa, the Coleoptera appear to be the best potential indicators across most altitudes and times. Although the current data provide a wealth of inventory and distributional information over altitude, their greatest potential value lies in long-term comparative information. Future sampling should focus not only on changes at and above the treeline, but also on the zone below this where many species are at their altitudinal limits and may be particularly sensitive to climate change.

Biology of the bark beetle Ips grandicollis Eichhoff (Coleoptera: Scolytinae) and its arthropod, nematode and microbial associates: a review of management opportunities for Australia.

Exotic woodwasps can cause high levels of mortality in Pinus species plantations. One species, Sirex noctilio (Sirex), was first detected in Tasmania in 1952 and has subsequently spread into softwood plantations throughout southeastern Australia. Plantations aged 7 years or older are susceptible to Sirex attack. For several decades the method of detecting developing populations of Sirex has been through aerial and ground surveillance and the establishment of trap tree plots. Trap tree plots are sets of ten trees treated with a measured dose of herbicide sufficient to stress the tree and so render it attractive to Sirex. In Australia hundreds of trap tree plots are prepared each year in Sirex-infested plantations and in plantations entering the susceptible age bracket. Approximately half of all prepared plots are attacked by Sirex. The development of a novel method to detect Sirex in young plantations using static traps baited with pinene lures began in 2003 in Tasmania. The use of these traps for the Sirex detection is now a routine operation in Tasmania.

Pheromone and volatile lures for detecting the European house borer (Hylotrupes bajulus) and a manual sampling method

The five‐spined bark beetle, Ips grandicollis, is an exotic pest in Australia that preferentially attacks stressed pine trees, including Pinus radiata D. Don, but it can also attack healthy trees. The beetle has been present in Australia for 70 years, feeding principally on logging debris, with occasional outbreaks resulting in damage to plantations. Attack on trees stressed by drought, fire or storm damage leads to occasional significant losses. In recent years, I. grandicollis has been observed to attack ‘trap trees’ treated with herbicide to make them attractive to Sirex noctilio Fabricius as part of a successful biological control programme against this wood wasp. Ips grandicollis is able to tolerate a wide range of climatic conditions, and has an extensive geographical range (limited by host tree plantings). The economic impact of I. grandicollis is exacerbated by adults vectoring a fungus, Ophiostoma ips (Rumbold) Nannfeldt, which discolours the outer sapwood and contributes to tree death. Nematodes also are also associated with I. grandicollis, both in the body cavity and under the elytra. The dominant nematode is Contortylenchus grandicolli Massey, which is found internally, in haemocoel, the gut and the head region of the majority of adult beetles. Mites and bacteria are also associated with I. grandicollis but their biology is not well known. Since the first detection of I. grandicollis in Australia, various bio‐control and other management strategies have been tested. While a better understanding of the microbial and nematode associates of I. grandicollis may yield novel approaches for the management of this exotic pest, semiochemical‐based disruptants offer more immediate scope, particularly for protecting small areas of high value trees such as trap tree plots.

Relationships between annual rainfall, damage symptoms and insect borer populations in mid-rotation Eucalyptus nitens and Eucalyptus globulus plantations in Tasmania: can static traps be used as an early warning device?

Summary We evaluated commercially available cross-vane traps (‘Intercept’), loaded with either synthetic pheromone or a combination of (+)-ά-pinene and (−)-verbenone in terms of their ability to detect European house borer (Hylotrupes bajulus, ‘EHB’), and compared their effectiveness with a manual search method. We employed pairs of traps at 45 sites, 28 of which had previously been identified as infested using manual search methods. In a four-month trapping period, a total of only six female adult EHB were detected from three sites, all of which had previously been identified during the manual survey. We suggest that the general sedentary behaviour of the beetle and its tendency to reinfest the same individual host tree limits the probability of it being intercepted by chemical lure traps in the field. Although labour-intensive, manual search methods remain the most reliable means of identifying local EHB infestations.

The fungal matrices of Ophiostoma ips hinder movement of the biocontrol nematode agent, Deladenus siricidicola , disrupting management of the woodwasp, Sirex noctilio

Summary Routine forest health surveillance of Eucalyptus nitens and E. globulus plantations in Tasmania has detected more frequent borer-related mortality in mid-rotation plantations in drier areas of the state. Damaging borer populations are not usually detected using traditional health surveillance techniques until mortality has occurred. Appropriately baited static traps are known to attract a wide range of stem-boring insects and might provide a means of monitoring populations in at-risk plantations. The objectives of this study were to explore the relationships between rainfall, tree stress symptoms and stem-borer-related damage symptoms in plantation eucalypts, and the nature of the associated borer populations, to determine whether static traps might provide an effective early warning system. Trees from a number of mid-rotation plantations covering a range of rainfall categories were visually assessed for a wide range of damage symptoms, and two intercept panel traps baited with α-pinene and ethanol lures were deployed in each of 19 compartments between November 2006 and March 2007. All beetles caught in the traps were identified to species level and the numbers tallied. The incidence of damage symptoms tended to be negatively correlated with mean annual rainfall and was higher in plantations from lower-rainfall areas. There were no clear relationships between aggregated trap catches of borers and annual rainfall or the incidence of damage symptoms. However, a greater range of borer species was trapped in drier areas and the number of species trapped showed a strong negative correlation with annual rainfall. There were also strong positive correlations between damage levels and the range of borer species trapped. The size of the populations of some species, in particular some of the scolytids, increased substantially with decreasing rainfall and was strongly associated with the incidence of damaged trees. Cerambycids were the only group significantly correlated with borer-specific symptoms, but further work is required to determine their utility for monitoring purposes. In vulnerable plantations an increase in the range of borer species, scolytid populations or specific indicator species caught in static traps might provide useful early warning of unacceptable levels of mortality or stem damage. As such, static trapping has the potential to monitor populations and allow for timely silvicultural intervention to ameliorate stress.