New paper: 75 years of dryland science

Authors: Aaron C. Greenville, Chris R. Dickman and Glenda M. Wardle

Published in: Plos One

Abstract:

Research gaps in global dryland literature: Research gap distance matrix heat-map (red = high, clear = low) on global dryland literature. The greater the metric the higher the dissimilarity between topics.

Growth in the publication of scientific articles is occurring at an exponential rate, prompting a growing need to synthesise information in a timely manner to combat urgent environmental problems and guide future research. Here, we undertake a topic analysis of dryland literature over the last 75 years (8218 articles) to identify areas in arid ecology that are well studied and topics that are emerging. Four topics — wetlands, mammal ecology, litter decomposition and spatial modelling, were identified as ‘hot topics’ that showed higher than average growth in publications from 1940 to 2015. Five topics — remote sensing, climate, habitat and spatial, agriculture and soils-microbes, were identified as ‘cold topics’, with lower than average growth over the survey period, but higher than average numbers of publications. Topics in arid ecology clustered into seven broad groups on word-based similarity. These groups ranged from mammal ecology and population genetics, broad-scale management and ecosystem modelling, plant ecology, agriculture and ecophysiology, to populations and paleoclimate. These patterns may reflect trends in the field of ecology more broadly. We also identified two broad research gaps in arid ecology: population genetics, and habitat and spatial research. Collaborations between population genetics and ecologists and investigations of ecological processes across spatial scales would contribute profitably to the advancement of arid ecology and to ecology more broadly.

Reference:

Greenville A.C., Dickman C.R. & Wardle G.M. (2017). 75 years of dryland science: trends and gaps in arid ecology literature. Plos One, 12: e0175014.

Posted in Ecology, Publications | Tagged , , , , | Leave a comment

New paper: Science on a micro-budget

What happens when one of your hobbies and work collide? A short article in Science!

I am sort of obsessed with astrophotography and try to obtain the best quality and quantity of data I can to make my images of some faint and distant object in the night sky. This results in me fine-tuning my equipment and spending long nights imaging under the stars. However, I need to find time to sleep as well. After all, I have a day job as an ecologist. So I have been semi-automating my system in order to let it run for the entire night on its own and while I get some sleep.

IMG_20160514_145537

Arduino-based cloud sensor, with infrared thermometer to measure the sky temperature and ambient temperature sensor (black cable).

I stumbled across a user group that make their own cloud sensors (amongst other equipment) and thought this could be an interesting project to try. If clouds are detected, an alarm could be sent to my mobile phone and wake me up in time to pack or cover up my gear before getting wet and damaged. The cloud sensor is based on the Arduino, an open-source micro-controller and electronics platform. By combining temperature sensors and some coding, I can monitor for clouds. It works by measuring the sky and ambient temperature and at some threshold, the different between the two indicates cloud. You can find my code on GitHub.

There are many environmental sensors that are available for the Arduino and user-friendly groups to get you started. This is also true for the Raspberry Pi, an open-source micro-computer platform. Both the Arduino and Raspberry Pi run open-source software, which is easy to learn and already familiar to some scientists (e.g. Python). Nathan (aka @ecotechnica) had experience with the Raspberry Pi, so we teamed up to explore how open-source hardware and software could be used in science to help reduce research costs.

Fig-1-Two-Micro-controllers

The two leading open-source hardware platforms: (A) The Arduino Uno (US$23), which has 16 MHz micro-controller with 32 kb of memory, plus 14 digital input/output pins and six analog pins to connect it to sensors and other components. (B) The first generation Raspberry Pi model B board included Ethernet and USB ports for connectivity. The current (2016) model B board (US$35) now includes integrated Bluetooth (v4.1) and wireless networking (802.11n).

We found that a wide range of devices can be made, such as weather stations, automatic watering systems for crops, high-altitude balloons for astronomy, remote camera systems, GPS tracking systems and laboratory automation equipment. All systems could be built at a fraction of the cost of their commercial equivalents. There was another advantage. Designs and code can be easily shared and even published along-side scientific reports or as separate publications, further improving transparency and repeatability of experiments.  Imagine been able to build the same piece of research equipment, with the exact components and run the same code that collects data in previous experiments! This is all possible with open-source hardware platforms, such as the Arduino and Raspberry Pi.

This all may sound a bit complicated and hard, but remember I was able to build a cloud sensor from instructions already published and modify the code to suit my needs. I also was able to write a driver in Visual Basic to interface the the cloud sensor to my imaging software. I have very little soldering, electronics or even coding experience. Now for the next open-hardware project!

Reference:

Greenville, A.C. and Emery, N.J. (2016). Gathering lots of data on a small budget. Science, 353: 1360-1361.

See Nathan’s blog post for more.

Posted in Publications | Tagged , , , , , , , | Leave a comment

New paper: Spatial and temporal synchrony in reptile population dynamics in variable environments

Authors: Aaron C. Greenville, Glenda M. Wardle, Vuong Nguyen and Chris R. Dickman.

Published in: Oecologia

Abstract:

Resources are seldom distributed equally across space, but many species exhibit spatially synchronous population dynamics. Such synchrony suggests the operation of large-scale

The panther skink (Ctenotus pantherinus) from the Simpson Desert, Australia.

The panther skink (Ctenotus pantherinus) from the Simpson Desert, Australia.

external drivers, such as rainfall or wildfire, or the influence of oasis sites that provide water, shelter, or other resources. However, testing the generality of these factors is not easy, especially in variable environments. Using a long-term dataset (13–22 years) from a large (8000 km²) study region in arid Central Australia, we tested firstly for regional synchrony in annual rainfall and the dynamics of six reptile species across nine widely separated sites. For species that showed synchronous spatial dynamics, we then used multivariate follow a multivariate auto-regressive state–space (MARSS) models to predict that regional rainfall would be positively associated with their populations. For asynchronous species, we used MARSS models to explore four other possible population structures: (1) populations were asynchronous, (2) differed between oasis and non-oasis sites, (3) differed between burnt and unburnt sites, or (4) differed between three sub-regions with different rainfall gradients. Only one species showed evidence of spatial population synchrony and our results provide little evidence that rainfall synchronizes reptile populations. The oasis or the wildfire hypotheses were the best-fitting models for the other five species. Thus, our six study species appear generally to be structured in space into one or two populations across the study region. Our findings suggest that for arid-dwelling reptile populations, spatial and temporal dynamics are structured by abiotic events, but individual responses to covariates at smaller spatial scales are complex and poorly understood.

Reference:

Greenville A.C., Wardle G.M., Nguyen V. & Dickman C.R. (2016). Spatial and temporal synchrony in reptile population dynamics in variable environments. Oecologia, 182: 475–485.

Posted in Ecology, Publications | Tagged , , , , , , , , , | Leave a comment

New paper! Population dynamics of desert mammals: similarities and contrasts within a multi-species assemblage

Authors: Aaron C. Greenville, Glenda M. Wardle, Vuong Nguyen and Chris R. Dickman.

Published in: Ecosphere

Abstract:

A mulgara from the Simpson Desert, Qld, Australia.

A mulgara from the Simpson Desert, Qld, Australia.

Understanding the temporal and spatial dynamics of species populations remains a key focus of population biology, providing vital insight into the drivers that influence demography and into sub-populations that are vulnerable to extinction. Across regional landscapes, spatially separated sub-populations may fluctuate in synchrony, or exhibit sub-structuring due to subtle differences in local intrinsic and extrinsic factors. Using a long-term dataset (17‑22 years) obtained from a large (8000 km²) study region in arid central Australia, we tested firstly for regional synchrony in annual rainfall and the dynamics of five small mammal species across nine widely separated sites. Using Moran’s theorem, we predicted that the spatial correlation between the regional sub-populations of these species would equal that between local density-independent conditions (annual rainfall).

For species that showed synchronous spatial dynamics, we then used multivariate state-space (MARSS) models to predict that regional rainfall would be positively associated with their populations, whereas species with asynchronous sub-populations would be influenced largely by other factors. For these latter species, we used MARSS models to test four hypotheses. These were that sub-population structures: 1) were asynchronous and governed by local site-specific factors, 2) differed between oasis and non-oasis sites, 3) differed between burnt and unburnt sites, and 4) differed between three sub-regions with different rainfall gradients. We found that the spatial population dynamics of our study small mammals differed between and within families. Two species of insectivorous dasyurid marsupials showed asynchronous dynamics that most likely tracked local conditions, whereas a larger carnivorous marsupial and two species of rodents had strongly synchronous dynamics. These latter species exhibited similar spatial correlations to local and regional rainfall events, providing evidence that the Moran effect operates for some, but not all, species in this arid system.

Our results suggest that small mammal populations do not respond in similar ways to shared environmental drivers in arid regions, and hence will vary in their responses to climate change. As arid lands globally are predicted to face climatic shifts that will exacerbate rainfall-drought cycles, we suggest that future work focuses on exploring these responses at different spatial scales across multiple dryland taxa.

 

Reference:

Greenville, A. C., G. M. Wardle, V. Nguyen, & C. R. Dickman. 2016. Population dynamics of desert mammals: similarities and contrasts within a multi-species assemblage. Ecosphere 7:e01343. 10.1002/ecs2.1343.

Posted in Ecology, Publications | Tagged , , , , , , , , , | Leave a comment

New paper: Long-term patterns of invertebrate abundance and relationships to environmental predictors factors in arid Australia

Authors: Alan B.C. Kwok, Glenda M. Wardle, Aaron C. Greenville, Chris R. Dickman.

Published in: Austral Ecology

This paper represents the first published study from the Desert Ecology Research Group on the invertebrates that occur in our study region in the Simpson Desert. Even though we have been surveying invertebrates for over two decades for various projects, Alan was able to collate all the data and get it (and us) organsied!

ScorpionAG

Abstract:

Resource pulses are a key feature of semi-arid and arid ecosystems, and are generally triggered by rainfall. While rainfall is an acknowledged driver of the abundance and distribution of larger animals, little is known about how invertebrate communities respond to rain events or to vegetative productivity. Here we investigate Ordinal-level patterns and drivers of ground-dwelling invertebrate abundance across six years of sampling in the Simpson Desert, central Australia. Between February 1999 and February 2005, a total of 174,381 invertebrates were sampled from 32 Orders. Ants were the most abundant taxon, comprising 83% of all invertebrates captured, while Collembola at 10.3% of total captures, were a distant second over this period. Temporal patterns of the six invertebrate taxa specifically analysed (Acarina, ants, Araneae, Coleoptera, Collembola and Thysanura) were dynamic over the sampling period, and patterns of abundance were taxon-specific. Analyses indicate that all six taxa showed a positive relationship with the cover of non-Triodia vegetation. Other indicators of vegetative productivity (seeding, flowering) also showed positive relationships with certain taxa. Although the influence of rainfall was taxon-dependent, no taxon was affected by short-term rainfall (up to 18 days prior to survey). The abundance of Acarina, ants, and Coleoptera increased with greater long-term rainfall (up to 18 months prior to survey), whilst Araneae showed the opposite effect. Temperature and dune zone (dune crest vs. swale) also had taxon-specific effects. These results show that invertebrates in arid ecosystems are influenced by a variety of abiotic factors, at multiple scales, and that responses to rainfall are not as strong or as predictable as those seen for other taxa. Our results highlight the diversity of invertebrates in our study region, and emphasize the need for targeted long-term sampling to enhance our understanding of the ecology of these taxa and the role they play in arid ecosystems.

Reference:

Kwok, A. B. C., G. M. Wardle, A. C. Greenville, and C. R. Dickman. (2016). Long-term patterns of invertebrate abundance and relationships to environmental factors in arid Australia. Austral Ecology 41: 480-491.

Posted in Ecology, Publications | Tagged , , , , , , , , , | Leave a comment

New paper: Cattle removal in arid Australia benefits kangaroos in high quality habitat but does not affect camels

Authors: Anke S. K. Frank, Glenda M. Wardle, Aaron C. Greenville and Chris R. Dickman

Published in: The Rangeland Journal

Abstract:

Removing cattle as a management tool to conserve biodiversity may not necessarily alter grazing impacts on vegetation if other introduced or native herbivores move in and replace the cattle after removal. This study investigated whether there was a difference in the abundance of native red kangaroos (Osphranter (Macropus) rufus) and introduced feral camels (Camelus dromedarius) on arid rangelands where cattle had been recently removed compared with where cattle remained. Activity was measured by clearing and weighing dung, and by counting animal sightings. Kangaroos were encountered more frequently in high quality habitat (gidgee woodland) where cattle had been recently removed. However, kangaroo dung in newly cattle-free areas comprised only ~1.5% of the weight of cattle dung in this habitat where cattle still grazed, indicating no grazing compensation by the native herbivore. Camels showed no clear preference for particular habitat types but used dune tops usually avoided by kangaroos and cattle. There was no indication of camels using habitats differently in areas where cattle were removed. Camel dung collected across all habitats comprised less than a tenth the weight of cattle dung, but almost five times as much as kangaroo dung. As cattle removal had occurred relatively recently, further monitoring is needed to determine its impact over longer periods,  especially through low and high rainfall cycles. Methods to improve the monitoring of large herbivores in the presence and absence of livestock and to assess whether anticipated conservation goals are achieved are discussed.achieved.

Reference:

Frank A. S. K., Wardle G. M., Greenville A. C. & Dickman C. R. (2016). Cattle removal in arid Australia benefits kangaroos in high quality habitat but does not affect camels. The Rangeland Journal 38: 73-84.

 

Posted in Conservation, Ecology, Publications | Tagged , , , , , , , , , | Leave a comment

2014 ‘Ecology in Action’ Photographer of the Year

The Ecological Society of Australia “Ecology in Action” Photographic Competition is an annual event attracting amazing images celebrating the diversity of landscapes and ecosystems within Australia and New Zealand. In 2014, a new award was added for Best Portfolio and attracted a cash prize as well as the opportunity for an online photographic exhibition of the winner’s work. The inaugural prize was shared by Dr Aaron Greenville from the University of Sydney and Richard Wylie, based at Monash University, Victoria.

Head to the society’s webpage to see my online exhibition featuring the images which won me best portfolio in the 2014 competition, as well as some additional images showcasing  my photographic interests.

A mulgara from the Simpson Desert, Qld, Australia.

A mulgara from the Simpson Desert, Qld, Australia.

 

Posted in Conservation, Ecology, Photography | Tagged , , , , , , | Leave a comment