Howard Springs Research Articles

Quarantine Facility Model of Care Toolbox

Introduction:The COVID-19 pandemic public health strategy to reduce community transmission in Australia included unprecedented use of quarantine facilities to separate those at risk and those with the infection from the rest of the community. No standardized approach to quarantine facilities existed resulting in different models of care emerging across the country. The Northern Territory Howard Springs Quarantine Facility was a large-scale quarantine and isolation operation which hosted over 33,000 domestic and international arrivals with zero COVID-19 transmission recorded from residents to staff for the duration of its operation. The facility was deemed the gold standard model of care and the aim of this project was to distill the important elements of that model of care into an evidence-based tool kit for future use as an open access, online resource. The toolkit was a result of intense data and information analysis including resident, staff and leadership surveys, policies and procedures and results of audits of the facility during its operation.Method:This project to develop an online, open access evidence-based toolkit forms part of the Translational Research to Improve Health Outcomes project funded by the Australian Government’s Medical Research Future Fund. The methodology included mixed methods with an underpinning grounded theory approach to analyze de-identified audit data and information from the quarantine and isolation facility operational period. Staff and leadership team surveys were conducted to explore experiences of site functions and infrastructure. A (non-experimental) descriptive design allowed collation and statistical analysis of information recognizing the variables in the data and information.Results:The toolbox includes a resident centered quarantine care model, infection, prevention and control strategies for health professionals and non-health staff, quarantine communication model and presentation of core challenges (rapid recruitment, environmental factors, workforce resilience).Conclusion:The resulting online web resource presents evidence-based core strategies and resources for implementation in future pandemics.

Building a safety culture for infection prevention and control adherence at Howard Springs: A workplace survey.

Building a safety culture is essential to facilitate infection prevention and control (IPC) adherence in workplaces. We aimed to explore perceptions, barriers and facilitators to IPC procedures by the Australian Medical Assistance Team (AUSMAT) at Howard Springs International Quarantine Facility (HSIQF). We performed a descriptive analysis of a cross-sectional survey administered to the AUSMAT employed at HSQIF from October 2020 to April 2021. We described motivation, training and compliance to IPC adherence and Likert scales described the level of agreement to the success of IPC procedures across the domains of communication, risk, trust, safety and environment, from the individual, team and organisational perspective. There were 101 participants (response rate 59%, 101/170) and 70% (71/101) were clinical. There was strong agreement to the success of IPC procedures, with a median 4 (agree) or 5 (strongly agree) across each domain and perspective of the 67 Likert items. Clinical staff reported slightly higher agreement than non-clinical staff across Likert items. To improve IPC compliance, most reported that daily training should be provided (77/97, 79%) and daily training was very or extremely effective (91/97, 93%). Participants were motivated by protecting self, friends, family and the community rather than workplace pressures. Barriers to IPC compliance were the ambient environment and fatigue. A safety culture was successfully built at HSQIF to optimise IPC adherence whilst managing multiple hazards including prevention of COVID-19 transmission. Strategies implemented by AUSMAT at the quarantine facility may inform the development of safety culture in other settings.

Telehealth for Comprehensive Care to Quarantine Residents: A Novel Approach and Lessons Learned.

Proactive engagement and care with regular and timely information are required to manage the health and well-being of people in quarantine. At Australia's Howard Springs International Quarantine Facility, a telehealth model was rapidly established using trained non-clinical Customer Service Officers (CSO's) with the aim to provide comprehensive care to residents, maximize staff safety, and reduce clinical workforce capacity pressures. We describe this model, whereby CSO's provided residents with daily COVID-19 symptom and well-being screening, weekly psychological screening, and ongoing linkage to additional clinical and administrative services. In addition, CSO's went beyond these duties to deliver personalized care through delivery of care packages and attendance of the departure point to farewell residents. From October 2020 to May 2021, across 7105 residents, we estimated that CSO's prevented over 75 000 face-to-face resident visits, which reduced workforce requirements and preserved staff safety through minimizing potential COVID-19 transmission and time spent in personal protective equipment in the challenging ambient environment. We share key lessons learned which may inform future telehealth models and guide a positive experience for quarantine residents.

An outdoor hotel quarantine facility model in Australia: best practice with optimal outcomes

ObjectiveTo describe the operationalisation of a novel outdoor quarantine facility managed by the Australian Medical Assistance Team, the Howard Springs International Quarantine Facility (HSIQF) at the Centre for National Resilience in the Northern Territory, Australia. MethodsWe collated documentation and data from HSIQF to describe policies and procedures implemented and performed a descriptive analysis of key procedures and outcomes. ResultsFrom 23 October 2020 to 31 March 2021, 2.2% (129/5,987) of residents were confirmed COVD‐19 cases. On average per day, 82 [Interquartile Range (IQR): 29‐95] staff completed personal protective equipment (PPE) training, 94 [IQR: 90‐104] staff completed antigen testing and 51 [IQR: 32‐136] staff completed polymerase chain reaction testing. The operation focused on building a safe environment with infection prevention and control adherence and workforce sustainability. There was no leakage of SARS‐CoV‐2 to staff or the community and no PPE compromises requiring staff to quarantine for 14 days. ConclusionHSIQF demonstrates the operationalisation of an effective, safe and replicable quarantine system. Implications for public healthQuarantine is a critical public health tool for pandemic control. The HSIQF operations may be useful to inform the establishment and management of quarantine facilities for future and current disease outbreaks.

Electronic monitoring of doffing using video surveillance to minimise error rate and increase safety at Howard Springs International Quarantine Facility

BackgroundSafe donning and doffing of personal protective equipment (PPE) are critical to prevent transmission of infectious diseases. Novel strategies to improve infection prevention and control (IPC) adherence can optimise safety. We describe and quantify video surveillance of doffing at an outdoor hotel quarantine facility led by the Australian Medical Assistance Team in the Northern Territory, Australia.MethodsMotion-activated video cameras were installed in seven areas where personnel doffed PPE upon exit from an area dedicated to quarantined residents. Video footage was reviewed daily and compliance issues were identified using a standardised checklist and risk graded to initiate feedback. We collated audit data from 1 February to 18 April 2021 to describe trends by month, staff group, doffing component and risk.ResultsIn 235 h of video footage, 364 compliance issues were identified, of which none were considered high-risk compromising to PPE integrity. Compliance issues were low risk (55/364, 15%) or moderate risk (309/364, 85%) and the most common issue was missed or inadequate hand hygiene (156/364, 43%). Compliance issues per minute of video footage reviewed decreased following introduction of the activity, from 24 per 1000 in February to 7 per 1000 in March and April.ConclusionVideo surveillance with feedback supported rapid response to improve IPC adherence in a challenging ambient environment. The activity focused on perfection to identify compliance issues that would go unreported in most healthcare settings and contributed to a suit of activities that prevented any high-risk PPE breaches or compromises to safety.

Avoiding Catastrophe in a High-Risk Environment: AUSMAT at Howard Springs

The Australian Medical Assistance Team (AUSMAT) led the implementation, establishment and management of Howard Springs International Quarantine Facility at the Centre for National Resilience from October 2020 to May 2021. The operation is internationally renowned for its success to mitigate leakage of the coronavirus disease from the quarantine facility to the community during a national policy of virus elimination or suppression. The operations success led to other Australian jurisdictions seeking to replicate the quarantine model. Here, we use three theoretical frameworks to describe AUSMATs approach to risk mitigation at the quarantine facility.

Heat Health Management in a Quarantine and Isolation Facility in the Tropics.

The Howard Springs Quarantine Facility (HSQF) is located in tropical Northern Australia and has 875 blocks of four rooms (3,500 rooms in total) spread over 67 hectares. The HSQF requires a large outdoor workforce walking outdoor pathways to provide individual care in the ambient climate. The personal protective equipment (PPE) required for the safety of quarantine workers varies between workgroups and limits body heat dissipation that anecdotally contributes to excessive sweating, which combined with heat stress symptoms of fatigue, headache, and irritability, likely increases the risk of workplace injuries including infection control breaches. The purpose of this study was the description of qualitative and quantitative assessment for HSQF workers exposed to tropical environmental conditions and provision of evidenced-based strategies to mitigate the risk of heat stress in an outdoor quarantine and isolation workforce. The study comprised two components - a cross-sectional physiological monitoring study of 18 workers (eight males/ten females; means: 41.4 years; 1.69m; 80.6kg) during a single shift in November 2020 and a subjective heat health survey completed by participants on a minimum of four occasions across the wet season/summer period from November 2020 through February 2021. The physiological monitoring included continuous core temperature monitoring and assessment of fluid balance. The mean apparent temperature across first-half and second-half of the shift was 34.7°C (SD = 0.8) and 35.6°C (SD = 1.9), respectively. Across the work shift (mean duration 10.1 hours), the mean core temperature of participants was 37.3°C (SD = 0.2) with a range of 37.0°C - 37.7°C. The mean maximal core temperature of participants was 37.7°C (SD = 0.3). In the survey, for the workforce in full PPE, 57% reported feeling moderately, severely, or unbearably hot compared to 49% of those in non-contact PPE, and the level of fatigue was reported as moderate to severe in just over 25% of the workforce in both groups. Heat stress is a significant risk in outdoor workers in the tropics and is amplified in the coronavirus disease 2019 (COVID-19) frontline workforce required to wear PPE in outdoor settings. A heat health program aimed at mitigating risk, including workplace education, limiting exposure times, encouraging hydration, buddy system, active cooling, and monitoring, is recommended to limit PPE breaches and other workplace injuries in this workforce.

Influence of modifications (from AoB2015 to v0.5) in the Vegetation Optimality Model

Abstract. The Vegetation Optimality Model (VOM, Schymanski et al., 2009, 2015) is an optimality-based, coupled water–vegetation model that predicts vegetation properties and behaviour based on optimality theory rather than calibrating vegetation properties or prescribing them based on observations, as most conventional models do. Several updates to previous applications of the VOM have been made for the study in the accompanying paper of Nijzink et al. (2022), where we assess whether optimality theory can alleviate common shortcomings of conventional models, as identified in a previous model inter-comparison study along the North Australian Tropical Transect (NATT, Whitley et al., 2016). Therefore, we assess in this technical paper how the updates to the model and input data would have affected the original results of Schymanski et al. (2015), and we implemented these changes one at a time. The model updates included extended input data, the use of variable atmospheric CO2 levels, modified soil properties, implementation of free drainage conditions, and the addition of grass rooting depths to the optimized vegetation properties. A systematic assessment of these changes was carried out by adding each individual modification to the original version of the VOM at the flux tower site of Howard Springs, Australia. The analysis revealed that the implemented changes affected the simulation of mean annual evapotranspiration (ET) and gross primary productivity (GPP) by no more than 20 %, with the largest effects caused by the newly imposed free drainage conditions and modified soil texture. Free drainage conditions led to an underestimation of ET and GPP in comparison with the results of Schymanski et al. (2015), whereas more fine-grained soil textures increased the water storage in the soil and resulted in increased GPP. Although part of the effect of free drainage was compensated for by the updated soil texture, when combining all changes, the resulting effect on the simulated fluxes was still dominated by the effect of implementing free drainage conditions. Eventually, the relative error for the mean annual ET, in comparison with flux tower observations, changed from an 8.4 % overestimation to an 10.2 % underestimation, whereas the relative errors for the mean annual GPP remained similar, with an overestimation that slightly reduced from 17.8 % to 14.7 %. The sensitivity to free drainage conditions suggests that a realistic representation of groundwater dynamics is very important for predicting ET and GPP at a tropical open-forest savanna site as investigated here. The modest changes in model outputs highlighted the robustness of the optimization approach that is central to the VOM architecture.

Impact of elevated atmospheric CO2 on aleurone cells and starch granule morphology in domesticated and wild rices

Wild rice species represent valuable germplasm for breeding of elite genotypes with enhanced resistance to biotic and abiotic stresses. However, differences in endosperm morphology between wild and cultivated rice, and how these are affected by enhanced levels of atmospheric CO2 (eCO2) predicted for later this century, are largely unknown. Accessions of native rice species from northern Australia, Oryza australiensis and O. meridionalis, and a local cultivar, O. sativa cv. Doongara, were grown to maturity in glasshouses at ambient (aCO2, 400 ppm) and eCO2 (700 ppm). Endosperm morphology was studied from transverse sections of mature grains using scanning electron microscopy. Aleurone cell length and width were higher in eCO2 than in aCO2 in the O. meridionalis accession Howard Springs, but lower in Doongara. The average starch granule size in Doongara was greater than in the wild genotypes in both CO2 treatments. The area and length of the starch granule images were larger in eCO2 than in aCO2 in the O. meridionalis accession Cape York but smaller in Doongara. Responses of rice endosperm morphology to eCO2 were dependent on genotype. We conclude that endosperm morphology responds differentially to eCO2, both between and within rice species. Contrasts in these responses can be exploited by breeders.

Wastewater surveillance demonstrates high predictive value for COVID-19 infection on board repatriation flights to Australia

Controlling importation and transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from overseas travelers is essential for countries, such as Australia, New Zealand, and other island nations, that have adopted a suppression strategy to manage very low community transmission. Wastewater surveillance of SARS-CoV-2 RNA has emerged as a promising tool employed in public health response in many countries globally. This study aimed to establish whether the surveillance of aircraft wastewater can be used to provide an additional layer of information to augment individual clinical testing. Wastewater from 37 long-haul flights chartered to repatriate Australians was tested for the presence of SARS-CoV-2 RNA. Children 5 years or older on these flights tested negative for coronavirus disease 19 (COVID-19) (deep nasal and oropharyngeal reverse-transcription (RT)-PCR swab) 48 h before departure. All passengers underwent mandatory quarantine for 14-day post arrival in Howard Springs, NT, Australia. Wastewater from 24 (64.9 %) of the 37 flights tested positive for SARS-CoV-2 RNA. During the 14 day mandatory quarantine, clinical testing identified 112 cases of COVID-19. Surveillance for SARS-CoV-2 RNA in repatriation flight wastewater using pooled results from three RT-qPCR assays demonstrated a positive predictive value (PPV) of 87.5 %, a negative predictive value (NPV) of 76.9 % and 83.7% accuracy for COVID-19 cases during the post-arrival 14-day quarantine period. The study successfully demonstrates that the surveillance of wastewater from aircraft for SARS-CoV-2 can provide an additional and effective tool for informing the management of returning overseas travelers and for monitoring the importation of SARS CoV-2 and other clinically significant pathogens.

Estimation of latent heat flux using satellite land surface temperature and a variational data assimilation scheme over a eucalypt forest savanna in Northern Australia

In this study, the performance of the combined-source variational data assimilation scheme (CS-VDA) is assessed in detail using in situ heat fluxes (i.e. sensible heat (H) and latent heat (LE)) collected at a Eucalypt forest savanna of Northern Australia (Howard Springs). The CS VDA scheme estimates surface turbulent heat fluxes via assimilation of sequences of land surface temperature (LST) and meteorological data into a surface energy balance model and a dynamic model. The main objectives of this paper were to extend previous studies to a semi-arid ecosystem and to evaluate the potential of using global meteorological forcing data (GMD) to drive the CS VDA model (rather than in-situ meteorological observations). In order to study the new errors associated with the use of GMD, the effects on LE of the uncertainty in air temperature and wind speed (the two key meteorological factors that controls the total estimation error) was quantitatively characterized. Using hourly in-situ measurements as inputs, the daily-averaged LE RMSEdaily was 54 W/m2, which agrees with the errors previously reported in the literature. As expected, replacing local meteorological data with GMD reduces the performance of the LE estimation (GMA: RMSEdaily = 82 W/m2, GLDAS: RMSEdaily = 151 W/m2). However, LE RMSE values at 8-day temporal scale for GMA are RMSE8-days = 32 W/m2, similar to those reported in this area for other models (MODIS (MOD16A2) and Breathing Earth System Simulator (BESS)). The error propagation analysis indicate that the CS VDA model is very sensitive to uncertainties in wind speed measurements. Moreover, there are large discrepancies between in situ and GMD wind speed. These two factors combined can explain the degradation in LE estimations. In this context, our study is a first step towards the characterization of an operational daily LE estimation scheme using hourly LST observations.

Leaf canopy architecture determines light interception and carbon gain in wild and domesticated Oryza species

Oryza sativa has many wild relatives that exhibit a wide range of canopy architectures. Two fast-growing ecotypes of an Australian wild rice (O. meridionalis) were compared with cultivated O. sativa to analyze the efficiency of light interception in mature vegetative canopies and how well light capture predicts biomass production. Canopies of individual plants were digitized and analyzed with YplantQMC. Plants were also grown at 700 ppm CO2 as a means of increasing the canopy density and assessing the relative impact of rising CO2 levels on photosynthesis, light interception and biomass. Simulations of light interception for these morphologically diverse canopies were combined with photosynthetic light response curves to estimate theoretical carbon gain. Both O. meridionalis genotypes had more tillers and leaves, and denser canopies, than O. sativa but one (‘Howard Springs’) intercepted more light than the other two genotypes, resulting in the highest simulated carbon gains. Photosynthesis per unit leaf area (Amax) was enhanced by 20–50% in 700 ppm CO2 in all genotypes but the proportion of total leaf area intercepting light decreased as a result of denser leaf canopies in these plants. Estimated total shoot carbon gain increased strongly at elevated CO2 despite these denser canopies and increased self-shading, reaching a peak in ‘Howard Springs’ at 700 ppm CO2. Thus, while high crown density and low leaf dispersion reduced the efficiency of light interception by the canopy, elevated CO2 still enhanced growth through consistently higher assimilation rates. Simulations showed that during the Summer Solstice, carbon gain was predicted to be greater than at the Equinox through superior light capture, particularly in ‘Howard Springs’. However, the relationship between light interception and carbon gain was broadly maintained, regardless of genotype, CO2 concentration and season.

Tree–grass phenology information improves light use efficiency modelling of gross primary productivity for an Australian tropical savanna

Abstract. The coexistence of trees and grasses in savanna ecosystems results in marked phenological dynamics that vary spatially and temporally with climate. Australian savannas comprise a complex variety of life forms and phenologies, from evergreen trees to annual/perennial grasses, producing a boom–bust seasonal pattern of productivity that follows the wet–dry seasonal rainfall cycle. As the climate changes into the 21st century, modification to rainfall and temperature regimes in savannas is highly likely. There is a need to link phenology cycles of different species with productivity to understand how the tree–grass relationship may shift in response to climate change. This study investigated the relationship between productivity and phenology for trees and grasses in an Australian tropical savanna. Productivity, estimated from overstory (tree) and understory (grass) eddy covariance flux tower estimates of gross primary productivity (GPP), was compared against 2 years of repeat time-lapse digital photography (phenocams). We explored the phenology–productivity relationship at the ecosystem scale using Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices and flux tower GPP. These data were obtained from the Howard Springs OzFlux/Fluxnet site (AU-How) in northern Australia. Two greenness indices were calculated from the phenocam images: the green chromatic coordinate (GCC) and excess green index (ExG). These indices captured the temporal dynamics of the understory (grass) and overstory (trees) phenology and were correlated well with tower GPP for understory (r2 = 0.65 to 0.72) but less so for the overstory (r2 = 0.14 to 0.23). The MODIS enhanced vegetation index (EVI) correlated well with GPP at the ecosystem scale (r2 = 0.70). Lastly, we used GCC and EVI to parameterise a light use efficiency (LUE) model and found it to improve the estimates of GPP for the overstory, understory and ecosystem. We conclude that phenology is an important parameter to consider in estimating GPP from LUE models in savannas and that phenocams can provide important insights into the phenological variability of trees and grasses.

Yet Alive? Methodists in British Fiction since 1890

David Dickinson's exploration of the treatment of Methodists in British fiction since the end of the nineteenth century focuses on nine authors and ten novels. One novel was written by a Methodist, Joseph Hocking; some of the others came from the pens of authors with Methodist antecedents or sympathies (Sir Arthur Quiller-Couch, Howard Spring, and George Eliot); the rest emanated from people with little first hand knowledge of Methodism, or, in the case of Arnold Bennett, a deep animosity toward it. It is not clear whether the chosen authors and titles are to be regarded as representative or typical, or as especially significant, but the list is evidently not comprehensive, either of Methodist writers or of the appearance of Methodists in fiction, and it would be helpful to know the rationale for the selection. The chapters are partly chronological and partly thematic, and they include summaries of the plots under consideration, as well as some reflection and analysis. Overall, Dr Dickinson finds that there is a lot of nostalgia for an imagined Methodism of yesteryear in the novels, and he suggests that contemporary authors may find Methodism unpromising territory for fiction because it lacks the sort of ecclesiastical hierarchy, dogmatic belief system, and social breadth which feed plots. Surely there is plenty of scope here for further investigation!

Exploring the link between clouds, radiation, and canopy productivity of tropical savannas

The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (α), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0–0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR>80%), which caused increases in α by 24% and 62% compared to thin clouds (fDPAR between 30% and 80%) and clear sky (fDPAR<30%) conditions respectively. The influence of environmental conditions shows that under similar vapour pressure deficit, temperature and soil water content classes, α values were significantly higher under thick clouds compared to thin clouds or clear skies. This indicates the importance of diffuse radiation in enhancing LUE even within similar environmental conditions. However, the enhanced LUE under cloudy skies is insufficient to increase GPP due to the dramatic decline in total radiation. Therefore, it can be concluded that the quantity of solar radiation is more critical than the quality of radiation in savannas. However, savanna ecosystems appear to be well adapted to the environment where a 63% decrease in PAR only reduced GPP by 26%. These findings highlight the importance of clouds as a critical factor in determining savanna productivity that has implications for savannas carbon cycle.

Using weaver ants Oecophylla smaragdina to control two important pests on African mahogany Khaya senegalensis in the Northern Territory of Australia

African mahogany, Khaya senegalensis, is a high-value timber tree species. Pilot plantings showed that the species performed well in the wet–dry tropical areas of northern Australia, but the yellow looper, Gymnoscelis sp., and the bush cricket, Myara yabmanna, caused severe damage to the trees. The weaver ant, Oecophylla smaragdina, is an effective bio-control agent of a range of insect pests in tropical tree crops and forest trees. To determine whether the ants control these mahogany pests, field experiments were conducted from April 2006 to January 2009 at two sites near Darwin, Australia. The fraction of the total number of trees damaged per year was 4.2–32.4% by yellow loopers and 0–10.4% by bush crickets on trees with weaver ants, but 25–70.4% by yellow loopers and 25–100% by bush crickets on trees without the ants. The damaged trees with weaver ants were attacked on fewer occasions than damaged trees without the ants. Significantly fewer trees with weaver ants were damaged per monitoring occasion (2.1–8.4% at Berrimah Farm and 0.5% at Howard Springs by yellow loopers; 0–2.2% by bush crickets) than trees without the ants (24.2–51.3% at Berrimah Farm and 5.0% at Howard Springs by yellow loopers; 18.1–40.7% by bush crickets). Data suggested that weaver ants were effective bio-control agents of the two pests.

Biological control of the fruit‐spotting bug Amblypelta lutescens using weaver ants Oecophylla smaragdina on African mahoganies in Australia

African mahogany Khaya senegalensis is a high‐value timber tree. Pilot plantings showed that the fruit‐spotting bug Amblypelta lutescens causes severe damage of the tree in the wet–dry tropics of northern Australia. The weaver ant Oecophylla smaragdina is an efficient biocontrol agent in some horticulture crops. To investigate whether the ants control this pest, field experiments were conducted from April 2006 to January 2009 at two study sites in the Darwin area, Australia. A laboratory experiment was carried out in March 2007 at Berrimah Farm. During the experimental period, in the weaver ant treatments, the overall percentage of trees damaged by the pest was 0–8% at both sites, and the damaged trees were attacked once only. In the treatments without weaver ants, however, the damage level was &gt; 80% at Berrimah Farm and 31–100% at Howard Springs, and the damaged trees were attacked more than once. The mean percentage of trees damaged per monitoring occasion was 0–2.6% in the weaver ant treatments at both sites, whereas, in the treatments without the ants, the damage percentages were 14.2–27.0% at Howard Springs and 28.2–48.6% at Berrimah Farm. Extrafloral nectar of African mahoganies is attractive to weaver ants. Fruit‐spotting bugs only damage the tender parts of flushing shoots and growing tips. Weaver ants live on sugar solution and meat, and they frequently harvest extrafloral nectar on growing shoots, on which they catch nymphs of the pest for their meat supply. The aggressive behaviour of the ants also repels the pest away from flushing shoots. The data suggest that weaver ants were effective biocontrol agents of fruit‐spotting bugs, and the ants can be used to manage the pest on African mahoganies. The present study demonstrates that the introduced African mahogany comprises another major host of the fruit‐spotting bug.

Environmental controls on the spatial variability of savanna productivity in the Northern Territory, Australia

Gross Primary Productivity (GPP) is a critical measure of the health and sustainability of natural ecosystems. Understanding the magnitude, spatial patterns and processes of GPP will underpin predictions of the impact of climate change on the carbon cycle. In Australia, savannas account for one third of the terrestrial carbon stores and therefore, estimating the magnitude of savanna GPP and studying the spatial relationship between GPP and environmental determinants at the regional scale is essential in understanding ecosystem responses to increasing atmospheric CO2 concentrations and climate change. In this study we employed an integrated approach combining in situ measurements, eddy covariance based flux tower data and remote sensing techniques to examine the role of environmental drivers in controlling the spatial variation in GPP of savannas in the Northern Territory (NT), Australia. We used field based light use efficiency (LUE), regional specific meteorology and Moderate Resolution Imaging Spectro-radiometer (MODIS) based fraction of absorbed Photosynthetically Active Radiation (fPAR) data to estimate GPP. The estimated GPP agreed quite well (only a 6% error) with GPP estimated from flux tower at the Howard Springs site. The spatial pattern of GPP along the Northern Australian Tropical Transect (NATT) was calculated and showed a strong gradient in GPP from the coast (12.50°S where rainfall was 1622mmyear−1) to inland (17.73°S where mean rainfall was 643mmyear−1) with a decrease of 77%. A decreasing trend in GPP with rainfall is noticed especially at the dry end of the transect studied. However, in the wet end and middle part of the transect (e.g. dominated by different Eucalyptus species), the response of GPP to changes in rainfall is reduced. This finding suggests that the influence of rainfall on various Eucalyptus species may be dampened by biotic factors. Our results suggest that future changes in precipitation driven by climate change may affect the future distribution and dynamics of GPP in northern Australia.

The Importance of Termites to the CH4 Balance of a Tropical Savanna Woodland of Northern Australia

Termites produce methane (CH4) as a by-product of microbial metabolism of food in their hindguts, and are one of the most uncertain components of the regional and global CH4 exchange estimates. This study was conducted at Howard Springs near Darwin, and presents the first estimate of CH4 emissions from termites based on replicated in situ seasonal flux measurements in Australian savannas. Using measured fluxes of CH4 between termite mounds and the atmosphere, and between soil and the atmosphere across seasons we determined net CH4 flux within a tropical savanna woodland of northern Australia. By accounting for both mound-building and subterranean termite colony types, and estimating the contribution from tree-dwelling colonies it was calculated that termites were a CH4 source of +0.24 kg CH4-C ha−1 y−1 and soils were a CH4 sink of −1.14 kg CH4-C ha−1 y−1. Termites offset 21% of CH4 consumed by soil resulting in net sink strength of −0.90 kg CH4-C ha−1 y−1 for these savannas. For Microcerotermes nervosus (Hill), the most abundant mound-building termite species at this site, mound basal area explained 48% of the variation in mound CH4 flux. CH4 emissions from termites offset 0.1% of the net biome productivity (NBP) and CH4 consumption by soil adds 0.5% to the NBP of these tropical savannas at Howard Springs.

Seasonal variation and fire effects on CH4, N2O and CO2 exchange in savanna soils of northern Australia

Tropical savanna ecosystems are a major contributor to global CO2, CH4 and N2O greenhouse gas exchange. Savanna fire events represent large, discrete C emissions but the importance of ongoing soil-atmosphere gas exchange is less well understood. Seasonal rainfall and fire events are likely to impact upon savanna soil microbial processes involved in N2O and CH4 exchange. We measured soil CO2, CH4 and N2O fluxes in savanna woodland (Eucalyptus tetrodonta/Eucalyptus miniata trees above sorghum grass) at Howard Springs, Australia over a 16 month period from October 2007 to January 2009 using manual chambers and a field-based gas chromatograph connected to automated chambers. The effect of fire on soil gas exchange was investigated through two controlled burns and protected unburnt areas. Fire is a frequent natural and management action in these savanna (every 1–2 years). There was no seasonal change and no fire effect upon soil N2O exchange. Soil N2O fluxes were very low, generally between −1.0 and 1.0μg Nm−2h−1, and often below the minimum detection limit. There was an increase in soil NH4+ in the months after the 2008 fire event, but no change in soil NO3−. There was considerable nitrification in the early wet season but minimal nitrification at all other times.Savanna soil was generally a net CH4 sink that equated to between −2.0 and −1.6kg CH4ha−1y−1 with no clear seasonal pattern in response to changing soil moisture conditions. Irrigation in the dry season significantly reduced soil gas diffusion and as a consequence soil CH4 uptake. There were short periods of soil CH4 emission, up to 20μg Cm−2h−1, likely to have been caused by termite activity in, or beneath, automated chambers. Soil CO2 fluxes showed a strong bimodal seasonal pattern, increasing fivefold from the dry into the wet season. Soil moisture showed a weak relationship with soil CH4 fluxes, but a much stronger relationship with soil CO2 fluxes, explaining up to 70% of the variation in unburnt treatments. Australian savanna soils are a small N2O source, and possibly even a sink. Annual soil CH4 flux measurements suggest that the 1.9million km2 of Australian savanna soils may provide a C sink of between −7.7 and −9.4 Tg CO2-e per year. This sink estimate would offset potentially 10% of Australian transport related CO2-e emissions. This CH4 sink estimate does not include concurrent CH4 emissions from termite mounds or ephemeral wetlands in Australian savannas.