presentation naem 2014

The Tea Bag IndexBas Dingemans

Joost KeuskampJudith SarneelTaru Lehtinen

Mariet HeftingAbi Ashton

[Faculty of ScienceBiology]

Soil Map/Decomposition

At the Wageningen post-graduate soil ecology course in 2010, we were asked to come up with an interesting parameter missing from the global soil map.

We thought: What’s more interesting for soil functioning and climate change than decomposi-tion? But how to obtain a worldwide measured pa-rameter for decomposi-tion?

Faculty of ScienceBiology

Experiments/Litterbags

One method to analyse decomposition rate in the field is measuring lit-ter mass loss using litter bags.

Making litter bags (weighing, sealing or sowing) is time consum-ing.

Moreover, to get an over-view of decomposition rate and carbon seques-tration, one has to do various measurements in time.


Photo: LogLife ExperimentPoster 103

Tea Bags/Litterbags

To collect data on decomposition at a large scale and density, a much easier, cheaper and better standardised method is needed.

Some brands of tea use nylon bags, very similar to litter bags.The tea inside the bags resembles dried plant material used in litter bag studies.

These tea bags can be used as prefabricated lit-ter bags. [Faculty of Science

Biology]

Tea Bags/Decomposable

After extensive experi-menting burying different tea types, we chose two tea types that differed in decomposability: Green tea and Rooibos tea.

Green tea decomposed faster than rooibos tea and reached the fase where decomposition stagnates faster than rooibos tea.

Our goal was to get as much information as pos-sible out of one harvest in time.

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Rooibos tea

Green tea


Tea bags/C fractions

We used chemical com-position analyses and linked that to decompos-ability.

Compared to rooibos tea, green tea contains a lot of water soluble carbon, while rooibos tea con-tains more acid insoluble carbon.

Therefore Rooibos teais more recalcitrant and decomposes slower than the green tea.


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Non-polar extractablesWater solublesAcid solublesAcid insolublesMineral fraction

Rooibos TeaGreen Tea


Tea Bag Index/Calculations

From the weight loss and the initial chemical composition of the tea we calculate two parame-ters, comprising the TBI:

Decomposition rate k

A measure for turnover time of labile carbon

Stabilisation factor S

A measure for stabilisa-tion potential of organic carbon



We modelled decompo-sition after Brock et al. (1985) as an exponential decay curve operating at two pools: a labile and a recalcitrant carbon pool.

W(t)=a e-kt + (1-a)

where W(t) is the mass fraction remaining at time t, a is labile pool fraction and k is initial decompo-sition rate of the labile pool.We assume that the mass loss of the recalcitrant pool is negligible.

Rooibos tea

Green tea

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S is calculated from the green tea results:

S = 1 - ag / Hg

where ag is the decom-posable fraction of Green tea based on the mass loss in the field and Hg is the hydrolysable fraction of Green tea.

S can be interpreted as the inhibiting effect of en-vironmental conditions on decomposition of la-bile litter fraction

Green tea

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Because the decomposa-ble fraction of Red tea (ar) cannot be determined in the field in a short-term incubation period, we es-timated ar under the as-sumption that S is equal for Green and Rooibos tea:

ar = Hr (1 - S)

where Hr is the hydrolysable fraction of Red tea.

Rooibos tea

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Hr{

ar



k is now calculated by linearising and solving the exponential decay function for the labile litter pool:

Wr(t) = ar e-kt + (1-ar)

ln(ar)-ln(Wr(t))-(1-ar) k = t

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US-FL mangrove-dwarfUS-FL mangrove-fringe

IE peat-disturbedIE peat-undisturbed

IS grassland-warmedIS grassland-ambient

CN desert-sandyCN desert-loamy

NL forestNL wet forest

NL pastureNL peat

PA forestAU mixed forestAU birch forest

Lab 25°CLab 15°C

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Stabilisation factor (S)

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Keuskamp, Dingemans et al. 2013, Methods in Ecology and Evolution

Research/Iceland

An example of success-ful implementation of the TBI method is research in Iceland.

In a geothermally heat-ed valley with plots on cold and heated soil with comparable soil condi-tions.


Reykjavik Hveragerdi

Iceland

< 0.8 M j

Land age

0.8 - 3.3 M j

3.3 - 15 M j

Research/Iceland

Plots consisted of two adjacent subplots, a fer-tilised and an upstream control.

Plots were placed in 2005 on warmed and ambient soil and fertilised annu-ally with N.

Between May and August 2011 we buried tea bags to understand the effects of warming and fertilisa-tion and their interactive effect on decomposition.


Control FertilisedPlot

Water flow

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Research/Iceland

We buried a pair of green and rooibos tea bags in 80 plots and I was very happy to find most of them back after 3 months.


Research/Iceland

Neither warming nor fer-tilisation had effect on the decomposition rate, however the stabilised fraction of tea in warmed plots was lower and, in the ambient plots, ferti-lisation caused a lower stabilised fraction of tea.


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Stabilised fraction (S)D

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UA

UW FA

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Dingemans et al. 2014, in prep.

Tea Bag Index/Application

Apart from using tea bags as an estimator for environmental effects on organic carbon se-questration in scientific experiments, TBI is very suitable for:

Large scale/high density measurements (crowdsourcing)

Global/european soil map of decomposition

Education/ public aware- ness campaigns


Tea Bag Index/Crowdsourcing

The simplicity and low resource requirements make the TBI suitable for crowdsourcing.

We ask teadrinker world-wide to cooperate with our experiment.

They just have to bury two tea bags and weigh them after 3 months.


@

production

distribution

bury tea bags

3 months in soil

decolab.org/tbi

weighing

harvest tea bags

Tea Bag Index/Soil Map

The results from these individual experiments have the potential to re-sult in a parameter for decomposition in the global soil map.


Tea Bag Index/Education

The tea bag experiments are suitable for various types of teaching activi- ties.

It visualises decomposition per se but also more complex problems can be addressed.


Faculty of ScienceBiology

Tea Bag Index/Future success

Method is accepted with-in the scientific commu-nity, but now...

We still aim to make the method more user-friendly.

Continuation and con-stant quality of Lipton tea and tea bags.

Global distribution

Implementing the param-eter in a global soil map.


facebook.com/teabagindex

@TeaBagIndex

www.decolab.org/tbi

on behalf of the TBI team, thanks!

presentation naem 2014

Education

tea bagslitterbagsto

green tea results

different tea types

brands of tea use nylon

litter bags

rooibos teais

mass fraction

rooibos teagreen tea01