If you have been an ardent follower of our Arctic escapades, you may have picked up on a strange sounding experiment we are carrying out across the tundra: the tundra tea bag experiment!
This is an international effort looking at how decomposition rates might change in a warming world.
We bury two types of tea (Green and Rooibos) at sites across the tundra biome – the cold environments found in the Arctic or the tops of mountains. After a few months we dig up the tea and look at how much it has decomposed. This helps us understand how rapidly it has broken down – and how fast the carbon and nutrients it contains move into the soils and air.
Normally when we look at decomposition we have to consider both what it is (how fast does it break down) and where it is (where does it break down fastest). But because all the tea we use is the same, we can be more confident that any differences are due to site conditions. This means we can look at how things like temperature, moisture and vegetation cover affect decomposition – which helps us make predictions about the future.
As the Arctic heats up, all the plant matter stored in cold and frozen soils will start to rot, releasing carbon to the atmosphere and speeding up global warming. This could cause a runaway positive feedback affecting the earth as a whole. The tundra tea bag experiment helps us understand if this will happen, and if so, how fast. It is one of many ways we can look at this, and we are working with scientists around the world – from Alaska to Australia, Sweden to Switzerland – to try to get as much data as we can. Similar experiments are also taking place all around the world, spearheaded by the dECOlab in Urtrecht in the Netherlands (http://www.decolab.org/tbi/).
And now the first results are now starting to come in! So far we have data for three-month burials from 14 sites, with more expected to come in over the next couple of months (see the map).
Initial results represent a gradient from European alpine to northern Arctic sites. As expected, there are large variations in decomposition rate (mass loss of tea bags) over the three-month period (see the figure below). This is more pronounced for Green tea than for Rooibos tea. However, the two types of tea display highly distinct decomposition rates despite the range of sites covered, with no overlap in distributions. This supports previous work suggesting that litter characteristics assert more influence over decomposition rate than site characteristics. The initial results are really exciting for our work looking at vegetation change and litter decomposition, as it greatly supports the idea that changes to plant traits and community composition are critical to understanding future rates of decomposition in tundra ecosystems.