Decomposition is an important process for life on earth and global change as it produces the greenhouse gas carbon dioxide (CO2). Changes in the balance between soil carbon storage and release can significantly amplify or attenuate global warming.
Although a lot of progress has been made in determining potential drivers of carbon release through large-scale decomposition experiments, climate predictions are still hampered by data limitation at a global scale as a result of high effort and measurement costs of comparative litter decomposition studies.
To measure decomposition, researchers from Sweden’s Umea University, the Austrian Agency for Health and Food Safety Ltd. And Utrecht University in The Netherlands have come up with an innovative, cost-effective, well-standardised method to gather data on decomposition rate and litter stabilisation using ordinary tea bags.
Red tea in red sand: burying roobios at Ethabuka Reserve, Simpson Desert, Australia (image courtesy Tamara Potter)
Two types of plastic tea bags (green and rooibos) with contrasting decomposability are placed in the soil and weight loss is determined after three months. Their decomposition is indicative for a two-phased decomposition model called the Tea Bag Index (TBI), consisting of two parameters describing decomposition rate (k) and litter stabilisation factor (S).
The standardisation and simplicity of the method make it possible to collect comparable, globally distributed data through crowdsourcing. TBI can further provide an excellent decomposition reference and has the potential to increase reliability of soil carbon flux estimates based on extrapolations of decomposition data.
The project has two main goals: 1) to make a soil map of decomposition; and 2) to use the data obtained from scientific networks and crowdsourcing experiments worldwide, to compare effects of climate.
The TBI-project has inspired many researchers all over the world to do their own experiments using tea bags to test the effects of climatological gradients and experimental treatments on decomposition. Some of them have amended the TBI method to fit their specific decomposition questions.
TERN is inspired by this worldwide experiment and we’ve been busy burying tea bags at many of our research sites around the nation.
Tea bags have been planted at most of TERN’s environmental monitoring SuperSites, including Great Western Woodlands in WA, Litchfield Savanna in the NT, FNQ Rainforest and SEQ Peri-urban in QLD, Cumberland Plain in NSW, Warra Tall Eucalypt in Tasmania, and Calperum Mallee in SA.
Dr Mirko Karan, of James Cook University and TERN’s Australian SuperSite Network, is utilising the suite of research infrastructure at the SuperSites to gather supplementary data during the TBI experiments.
“We have located the tea bags near soil sensors installed at the sites so that we will have chemistry, soil moisture and temperature data for the incubation periods,” says Mirko.
Decomposition data together with this additional soil data represent a comprehensive dataset for complex ecological analyses and is expected to facilitate new ecosystem research when it becomes openly available via TERN’s data infrastructure.
“I think the tea bag index (TBI) will get more interesting over time,” adds Mirko. “In future I expect we’ll repeat the Tea Bag Index experiment in different seasons. We’re also looking at co-locating further TBI experiments with our monitoring transects that measure decomposition by termites so we can link the two experiments.”
Tea bags have been planted at most of TERN’s environmental monitoring SuperSites, including Great Western Woodlands in WA (left and middle), and FNQ Rainforest (right) (images courtesy Georg Whiehl and Mirko Karan).
The Teatime4science project itself has grown to roughly 1700 locations and researchers from numerous other (global) networks started decomposing tea alongside their own standard protocol, many also involving TERN sites.
For instance, Professor Glenda Wardle’s team from the Desert Ecology Research Group (DERG) at The University of Sydney has, with TERN support, deployed over 1100 teabags across multiple international experiment networks.
Over 300 tea bags have been buried at the Desert Ecology Plot Network, part of TERN’s Long Term Ecological Research Network (LTERN) in Queensland’s Simpson Desert to look at differences in decomposition across desert landscapes and vegetation types.
A further 360 bags have been deployed for the international BioDesert project, which is investigating how simultaneous changes in climate and grazing pressure affect both the biology and functionality of global dryland ecosystems.
TERN’s Cumberland Plain’s SuperSite, as well as DERG, have also deployed teabags in two other experiments. The global Nutrient Network experiment studies the additions of nutrients (nitrogen, phosphorus, and potassium) and the DroughtNet project seeks to understand the responses of ecosystems to drought by reducing rainfall using custom-built shelters.
“It’s fantastic that the same standard protocol has been picked up by several very important international distributed experiment networks and used as an add-on method to quantify decomposition,” says Glenda.
“Control plots allow comparison to the other sites in the global soil map of decomposition, as well as the extra dimension of the manipulations of nutrients, drought and grazing. And, additionally, all these activities link the Desert Ecology Research Group, as part of TERN, to global efforts.”
The Tea Bag Index is a global citizen science experiment and you’re invited to take part. Whether you’re a budding science student, accomplished professor, or just an interested citizen keen to lend a hand, head to the TBI website and you can find a stack on information on how to get involved.
There are no costs associated and you will be provided with tea bags. Plant your tea bags at the start of summer (December 2016) and dig them up in March 2017 then dry and weigh them. Then share your data on simple environmental characteristics such as GPS location, vegetation information and soil type.
You can read more about the Tea Bag Index in a paper published in the journal Methods in Ecology and Evolution and keep an eye out in future editions of TERN eNewsletter to stay up with TERN’s involvement in the project.
Published in TERN newsletter November 2016