Detection of flying-foxes using automated audio recorders

Flying-foxes are little understood in Australia largely due to their extreme mobility. This mobility is particularly evident in the two species (spectacled and little red) found across the north of Australia, where huge numbers of animals will suddenly converge on a region and then leave a few weeks later. To improve management of these species we need to understand the movement and ecology of the animals and this is not straightforward as the camps are often remote and inaccessible. In this project we aimed to test the viability of using automated acoustic recorders for determining the presence of spectacled flying-foxes at camp locations. A Song Meter SM4 recorder was used to record flying-foxes in a number camps around South East QLD/Northern Rivers (black and grey-headed flying-foxes) and Cairns (spectacled flying-fox). A total of 35 hour of flying-foxes calls were recorded over a period of 8 weeks from August to October 2017. The recordings were processed using a Binary Winnow classifier and Hidden Markov Model in Kaleidoscope Software (Wildlife Acoustics). Tagged one-minute recordings were used to train the Hidden Markov Model in Kaleidoscope which was subsequently used in classifying the remaining recordings. Using this approach, we were able to quickly and easily detect the presence of flying-foxes in the acoustic recordings. In this way, ecologists can easily implement projects for long-term monitoring of flying-fox populations using remotely deployed acoustic recorders. It may also assist management agencies for urban planning in northern Australia. For future work, we will be investigate advanced machine learning algorithms coupled with flying-fox behavioural call patterns to attempt to distinguish the species of flying-fox from acoustic recordings

Similar patterns of leaf temperatures and thermal acclimation to warming in temperate and tropical tree canopies

As the global climate warms, a key question is how increased leaf temperatures will affect tree physiology and the coupling between leaf and air temperatures in forests. To explore the impact of increasing temperatures on plant performance in open air, we warmed leaves in the canopy of two mature evergreen forests, a temperate Eucalyptus woodland and a tropical rainforest. The leaf heaters consistently maintained leaves at a target of 4 °C above ambient leaf temperatures. Ambient leaf temperatures (Tleaf) were mostly coupled to air temperatures (Tair), but at times, leaves could be 8–10 °C warmer than ambient air temperatures, especially in full sun. At both sites, Tleaf was warmer at higher air temperatures (Tair > 25 °C), but was cooler at lower Tair, contrary to the ‘leaf homeothermy hypothesis’. Warmed leaves showed significantly lower stomatal conductance (−0.05 mol m−2 s−1 or −43% across species) and net photosynthesis (−3.91 μmol m−2 s−1 or −39%), with similar rates in leaf respiration rates at a common temperature (no acclimation). Increased canopy leaf temperatures due to future warming could reduce carbon assimilation via reduced photosynthesis in these forests, potentially weakening the land carbon sink in tropical and temperate forests

Fluvial dynamics of dissolved and particulate organic carbon during periodic one-flood events in a steep tropical rainforest catchment

In small catchments with rapid flood pulses, detailed temporal data is essential as high discharge events can be measured in hours and days, rather than weeks and months. Using high resolution (15 minutes) sampling procedures, we studied the dynamics of aquatic dissolved and particulate\ud organic carbon (DOC and POC) export through episodic discharge events in a small pristine rainforest catchment in north-east Australia between November 2009 and March 2010. The concentration of DOC and POC peaked during times of high stream discharge, reflecting an increased mobilisation of soil water carbon stocks. DOC was the major form of organic carbon in the stream, over 70% of the total carbon export. 84% of the total organic carbon exported from\ud the catchment occurred during significant discharge events (discharge >50 L s-l) measured during 9% of the study. Export of DOC and POC totalled 195 and 68 kg km-2 month-1, respectively. with a DOC:POC ratio of 2.9 ± 0.9. If this sub-catchment was sampled at weekly intervals the lateral export of carbon would have been underestimated by between 49% and 78% for DOC and POC, respectively. Preliminary 613C and molar C:N values of the dissolved and particulate matter which suggested that during discharge events less microbially processed material from the upper soil\ud layers dominated organic matter export, with the opposite being true in non-flood conditions. Not only will the quantities of organic matter exported change in different discharge conditions, but the source and quality may also shift

Fluvial dynamics of dissolved and particulate organic carbon during periodic discharge events in a steep tropical rainforest catchment

In small catchments with rapid flood pulses, detailed temporal data is essential as high discharge events can be measured in hours and days, rather than weeks and months. Using high resolution (15 minutes) sampling procedures, we studied the dynamics of aquatic dissolved and particulate\ud organic carbon (DOC and POC) export through episodic discharge events in a small pristine rainforest catchment in north-east Australia between November 2009 and March 2010. The concentration of DOC and POC peaked during times of high stream discharge, reflecting an increased mobilisation of soil water carbon stocks. DOC was the major form of organic carbon in the stream, over 70% of the total carbon export. 84% of the total organic carbon exported from\ud the catchment occurred during significant discharge events (discharge >50 L s-l) measured during 9% of the study. Export of DOC and POC totalled 195 and 68 kg km-2 month-1, respectively. with a DOC:POC ratio of 2.9 ± 0.9. If this sub-catchment was sampled at weekly intervals the lateral export of carbon would have been underestimated by between 49% and 78% for DOC and POC, respectively. Preliminary 613C and molar C:N values of the dissolved and particulate matter which suggested that during discharge events less microbially processed material from the upper soil\ud layers dominated organic matter export, with the opposite being true in non-flood conditions. Not only will the quantities of organic matter exported change in different discharge conditions, but the source and quality may also shift

Detection of flying-foxes using automated audio recorders

Flying-foxes are little understood in Australia largely due to their extreme mobility. This mobility is particularly evident in the two species (spectacled and little red) found across the north of Australia, where huge numbers of animals will suddenly converge on a region and then leave a few weeks later. To improve management of these species we need to understand the movement and ecology of the animals and this is not straightforward as the camps are often remote and inaccessible. In this project we aimed to test the viability of using automated acoustic recorders for determining the presence of spectacled flying-foxes at camp locations. A Song Meter SM4 recorder was used to record flying-foxes in a number camps around South East QLD/Northern Rivers (black and grey-headed flying-foxes) and Cairns (spectacled flying-fox). A total of 35 hour of flying-foxes calls were recorded over a period of 8 weeks from August to October 2017. The recordings were processed using a Binary Winnow classifier and Hidden Markov Model in Kaleidoscope Software (Wildlife Acoustics). Tagged one-minute recordings were used to train the Hidden Markov Model in Kaleidoscope which was subsequently used in classifying the remaining recordings. Using this approach, we were able to quickly and easily detect the presence of flying-foxes in the acoustic recordings. In this way, ecologists can easily implement projects for long-term monitoring of flying-fox populations using remotely deployed acoustic recorders. It may also assist management agencies for urban planning in northern Australia. For future work, we will be investigate advanced machine learning algorithms coupled with flying-fox behavioural call patterns to attempt to distinguish the species of flying-fox from acoustic recordings

Tropical rainforest canopies and climate change

There is less certainty about the impact of climate change on tropical rainforests than on temperate forests because of the comparative lack of background data and because few large scale experiments have been, and are being, carried out in tropical rainforests. Many of the factors critical to the future of tropical rainforests concern canopies, the key processes that take place there, and the roles and interactions of canopy biodiversity. In particular there are almost no data on how forest canopies and processes are changing with increased carbon dioxide levels. The implications of elevated carbon dioxide, climatic stress and related changes in water-use efficiency, nutrient availability and other such changes are discussed particularly with references to Australia's tropical rainforests

Similar patterns of leaf temperatures and thermal acclimation to warming in temperate and tropical tree canopies

As the global climate warms, a key question is how increased leaf temperatures will affect tree physiology and the coupling between leaf and air temperatures in forests. To explore the impact of increasing temperatures on plant performance in open air, we warmed leaves in the canopy of two mature evergreen forests, a temperate Eucalyptus woodland and a tropical rainforest. The leaf heaters consistently maintained leaves at a target of 4 °C above ambient leaf temperatures. Ambient leaf temperatures (Tleaf) were mostly coupled to air temperatures (Tair), but at times, leaves could be 8–10 °C warmer than ambient air temperatures, especially in full sun. At both sites, Tleaf was warmer at higher air temperatures (Tair > 25 °C), but was cooler at lower Tair, contrary to the ‘leaf homeothermy hypothesis’. Warmed leaves showed significantly lower stomatal conductance (−0.05 mol m−2 s−1 or −43% across species) and net photosynthesis (−3.91 μmol m−2 s−1 or −39%), with similar rates in leaf respiration rates at a common temperature (no acclimation). Increased canopy leaf temperatures due to future warming could reduce carbon assimilation via reduced photosynthesis in these forests, potentially weakening the land carbon sink in tropical and temperate forests