Ecosystem response to climate change: the importance of long term investigations

Predicting exactly how climate change is going to affect our planets diverse ecosystems is inherently difficult. No two ecosystems function in the same way due to complex variations of interacting features. This is especially true in the world of plants [3]. Research indicates plants show a range of different responses to climatic features including warmer temperatures, extreme rainfall patterns and elevated carbon dioxide (CO2) concentrations [2]. These responses can include increases or decreases in growth, different methods of nutrient utilization and alternative strategies in water usage [3].

Associate Professor Sally Power is one ecosystems ecologist interested in exactly this topic. Broadly, her research explores how human induced climate change affects leaf, plant and vegetation community functioning and how these effects ultimately impact ecosystem sustainability [3].

While Power is currently working with the University of Western Sydney her dedication to plant ecology did not begin in Australia.  After obtaining her PHD from the Imperial College of London, she became involved in the DIRECT experiment (Diversity, Rainfall & Elemental Cycling in a Terrestrial system) located in the United Kingdom [3]. This experiment investigated drought effects on British grasslands [1]. Since her move to Sydney, Australia a few years ago, her research has focused on the interactive effects of a variety of co-occurring drivers of global change, including biodiversity loss, climate variations, pollution, habitat management and climate change [3]. As a member of the Hawkesberry Institute of the Environment, Powers has specifically been working on two projects, DRI-grass project and the Euc-FACE project [3]. In addition, Power is passionate about involving the public in the importance of science, leading many outreach activities with local community members and engaging school children in “hands on” experiments (see her website: http://www.uws.edu.au/hie/people/researchers/associate_professor_sally_power).

In a recent seminar, Power, discussed three of her long term experimental studies looking at how plants and their ecosystems respond to features of human induced climate change.

DIRECT Experiment

The DIRECT experiment specifically investigates the impacts of rainfall change on grassland ecosystem functioning [1]. Prior to this study, climate models (IPCC) predicted that between 2080-2100 rainfall in South East England would be approximately 30% lower in summer and 15% higher in winter [3]. For this reason, Power wanted to assess how grasslands would respond to these different rainfall patterns and how various plant traits are affected [3]. Traits included features like leaf area and leaf nitrogen content [1,3].

This continuing experiment involved setting up transparent roofs on a series of plots, which allow rainfall amount and frequency control (see image 1). All plots include a specific variety of native grasses, while weeds are removed [1]. Control plots include roof holes, allowing natural rainfall [1]. Overall, a reduction in species richness in response to rainfall frequency, not rainfall amount was found [3]. Mostly affected were perennial species, suggesting they will be most drought sensitive [1].

 

Image 1. Roof structures used in DIRECT and DRI grass experiments. Image from;https://workspace.imperial.ac.uk/climatechange/public/pdfs/CAPER_poster.pdf

Image 1. Roof structures used in DIRECT and DRI grass experiments. Image from;https://workspace.imperial.ac.uk/climatechange/public/pdfs/CAPER_poster.pdf

DRI- grass Experiment

After moving to Australia, Power became involved in a similarly designed experiment looking at drought and root herbivore interactions in an Australian grassland ecosystem [3]. Climate change models have also been simulated for Australia, predicting a highly variable climate with extreme drought and rainfall events in the future [3]. By artificially simulating these predicted differences in rainfall, Power and colleagues began measuring the responses of native plants as well as root herbivores, like scarab beetles and weevils [3]. While this experiment in still in progress, it will undoubtingly assist future management plans for Australian grasslands ecosystems.

 

EucFACE Experiment

Increases in atmospheric CO2 emissions form human activities such as burning fossil fuels, has been the largest driver of global warming since the early 1900’s [2]. Carbon, along with nitrogen, is critical to many aspects of plant and herbivore metabolism, ultimately having a large effect on ecosystem functioning [4]. Therefore, long term experiments investigating the impacts of elevated CO2 levels is vital to our understanding of how climate change and global warming will affect ecosystems in the future [4]. The truly impressive cutting edge Free Air CO2 Enrichment facility set up by the Hawkesberry Institute of Environment in the Cumberland Plain forest, allows researchers like Power to investigate such effects [3]. Specifically, this facility consists of six rings, three release CO2, while three release nothing (controls) into massive circular plots, 25m in diameter [3] (see image 2).

Image 2. Carbon- fibre rings used in the EucFACE experiments. Image from; http://www.uws.edu.au/hie/facilities/face

Image 2. Carbon- fibre rings used in the EucFACE experiments. Image from; http://www.uws.edu.au/hie/facilities/face

Powers EucFACE experiments specifically look at soil nutrient cycling and how plants process nutrients in a higher CO2 world [3]. Powers early results indicate CO2 increases cause almost instant releases in phosphate. The continuation of her work will undoubtingly be significant by adding to the important understanding of how plants and ecosystems will respond to rising CO2 levels [3].

 

References

  1. Fry, E. L., Manning, P., Allen, D. G., Hurst, A., Everwand, G., Rimmler, M., & Power, S. A. (2013). Plant functional group composition modifies the effects of precipitation change on grassland ecosystem function. PloS one, 8(2), e57027.

 

  1. Kauwe, M. G., Medlyn, B. E., Zaehle, S., Walker, A. P., Dietze, M. C., Hickler, T., … & Norby, R. J. (2013). Forest water use and water use efficiency at elevated CO2: a model‐data intercomparison at two contrasting temperate forest FACE sites. Global change biology, 19(6), 1759-1779.

 

  1. Power, S. (2014, May 14). Drought, deluge and elevated CO2; a two hemisphere look at ecosystem responses to climate change. Biology seminar series, Macquarie University, North Ryde, NSW.

 

  1. Reich, P. B., Hungate, B. A., & Luo, Y. (2006). Carbon-nitrogen interactions in terrestrial ecosystems in response to rising atmospheric carbon dioxide. Annu. Rev. Ecol. Evol. Syst., 37, 611-636.

 

Interesting links

Associate Professor Sally Power website;

http://www.uws.edu.au/hie/people/researchers/associate_professor_sally_power

EucFace Experiment video

https://www.youtube.com/watch?v=7jz4WI7NQ2k

 

 

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