Presentation about the tea bag index given at the Netherlands Annual Ecology Meeting February 2014

1. The Tea Bag Index
Bas Dingemans
Joost Keuskamp
Judith Sarneel
Taru Lehtinen
Mariet Hefting
Abi Ashton
[Faculty of Science
Biology]

2. Soil Map
/Decomposition
At the Wageningen postgraduate 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 decomposition?
But how to obtain a
worldwide measured parameter for decomposition?
Faculty of Science
Biology

3. Experiments
/Litterbags
One method to analyse
decomposition rate in
the field is measuring litter mass loss using litter
bags.
Making litter bags
(weighing, sealing or
sowing) is time consuming.
Moreover, to get an overview of decomposition
rate and carbon sequestration, one has to do
various measurements in
time.
Photo: LogLife Experiment
Poster 103
[Faculty of Science
Biology]

4. 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 litter bags.
[Faculty of Science
Biology]

5. Tea Bags
/Decomposable
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 possible out of one harvest
in time.
1.0
Relative Mass Remaining (g g-1)
After extensive experimenting burying different
tea types, we chose two
tea types that differed in
decomposability: Green
tea and Rooibos tea.
Rooibos tea
0.8
0.6
0.4
Green tea
0.2
0.0
0
10
20
30
Time (days)
40
50
60
[Faculty of Science
Biology]

6. Tea bags
/C fractions
Green Tea
We used chemical composition analyses and
linked that to decomposability.
Compared to rooibos tea,
green tea contains a lot
of water soluble carbon,
while rooibos tea contains more acid insoluble
carbon.
Therefore Rooibos tea
is more recalcitrant and
decomposes slower than
the green tea.
0.15
Rooibos Tea
0.00 0.03
0.00 0.03
0.22
0.37
0.30
0.52
0.37
Non-polar extractables
Water solubles
Acid solubles
Acid insolubles
Mineral fraction
[Faculty of Science
Biology]

7. Tea Bag Index
/Calculations
From the weight loss
and the initial chemical
composition of the tea
we calculate two parameters, comprising the TBI:
Decomposition rate k
A measure for turnover
time of labile carbon
Stabilisation factor S
A measure for stabilisation potential of organic
carbon
[Faculty of Science
Biology]

8. Tea Bag Index
/Calculations
We modelled decomposition 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 decomposition rate of the labile
pool.
We assume that the mass
loss of the recalcitrant
pool is negligible.
Relative Mass Remaining (g g-1)
1.0
0.8
0.6
Rooibos tea
0.4
Green tea
0.2
0.0
0
20
40
60
80
Time (days)
100
120
140
[Faculty of Science
Biology]

9. Tea Bag Index
/Calculations
S is calculated from the
green tea results:
S = 1 - ag / Hg
where ag is the decomposable 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 environmental conditions
on decomposition of labile litter fraction
Relative Mass Remaining (g g-1)
1.0
0.8
ag
0.6
0.4
Green tea
0.2
0.0
20
0
0.15
40
60
80
Time (days)
120
140
0.00 0.03
Hg{
0.30
100
0.52
Non-polar extractables
Water solubles
Acid solubles
Acid insolubles
Mineral fraction
[Faculty of Science
Biology]

10. Tea Bag Index
/Calculations
Because the decomposable fraction of Red tea (ar)
cannot be determined in
the field in a short-term
incubation period, we estimated ar under the assumption that S is equal
for Green and Rooibos
tea:
Relative Mass Remaining (g g-1)
1.0
ar
0.8
0.6
Rooibos tea
0.4
0.2
0.0
ar = Hr (1 - S)
0
where Hr is the hydrolysable fraction of Red tea.
20
40
60
80
Time (days)
100
120
140
0.00 0.03
0.22
0.37
H r{
Non-polar extractables
Water solubles
Acid solubles
Acid insolubles
Mineral fraction
[Faculty of Science
Biology]
0.37

11. k is now calculated by
linearising and solving
the exponential decay
function for the labile litter pool:
Wr(t) = ar e + (1-ar)
-kt
ln(ar)-ln(Wr(t))-(1-ar)
k=
t
Decomposition rate (k)
Tea Bag Index
/Calculations
13*
0.03
14
0.02
0.01
5
16
9
10
15
17
6
11 4
2
12
3
1
7
US-FL mangrove-dwarf
US-FL mangrove-fringe
IE peat-disturbed
IE peat-undisturbed
IS grassland-warmed
IS grassland-ambient
CN desert-sandy
CN desert-loamy
NL forest
NL wet forest
NL pasture
NL peat
PA forest
AU mixed forest
AU birch forest
Lab 25°C
Lab 15°C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
8
0.00
0.00 .1 0.20 .3 0.40 .5 0.60 .7
Stabilisation factor (S)
Keuskamp, Dingemans et al. 2013, Methods in Ecology and Evolution
[Faculty of Science
Biology]

12. Iceland
Research
/Iceland
An example of successful implementation of the
TBI method is research
in Iceland.
In a geothermally heated valley with plots on
cold and heated soil with
comparable soil conditions.
Reykjavik
Hveragerdi
Land age
< 0.8 M j
0.8 - 3.3 M j
3.3 - 15 M j
[Faculty of Science
Biology]

13. Water flow
Research
/Iceland
Plots were placed in 2005
on warmed and ambient
soil and fertilised annually with N.
Between May and August
2011 we buried tea bags
to understand the effects
of warming and fertilisation and their interactive
effect on decomposition.
Control
Fertilised
25
Soil temperature (°C)
Plots consisted of two
adjacent subplots, a fertilised and an upstream
control.
Plot
Ambient
Warmed
20
15
10
5
0
Control
Fertilised
treatment
[Faculty of Science
Biology]

14. 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.
[Faculty of Science
Biology]

15. Research
/Iceland
Neither warming nor fertilisation had effect on
the decomposition rate,
however the stabilised
fraction of tea in warmed
plots was lower and, in
the ambient plots, fertilisation caused a lower
stabilised fraction of tea.
Decomposition rate (k)
0.03
UA
0.02
UW
FA
FW
0.01
0.00
0.0
0.1
0.2
Stabilised fraction (S)
0.3
Dingemans et al. 2014, in prep.
[Faculty of Science
Biology]

16. Tea Bag Index
/Application
Apart from using tea
bags as an estimator for
environmental effects
on organic carbon sequestration in scientific
experiments, TBI is very
suitable for:
Large scale/high density
measurements (crowdsourcing)
Global/european soil
map of decomposition
Education/ public awareness campaigns
[Faculty of Science
Biology]

17. Tea Bag Index
/Crowdsourcing
The simplicity and low
resource requirements
make the TBI suitable for
crowdsourcing.
We ask teadrinker worldwide to cooperate with
our experiment.
They just have to bury
two tea bags and weigh
them after 3 months.
@
decolab.org/tbi
production
weighing
harvest
tea bags
distribution
bury
tea bags
3 months in soil
[Faculty of Science
Biology]

18. Tea Bag Index
/Soil Map
The results from these
individual experiments
have the potential to result in a parameter for
decomposition in the
global soil map.
[Faculty of Science
Biology]

19. Tea Bag Index
/Education
The tea bag experiments
are suitable for various
types of teaching activities.
It visualises decomposition per se but also more
complex problems can
be addressed.
[Faculty of Science
Biology]

20. Tea Bag Index
/Future success
Method is accepted within the scientific community, but now...
We still aim to make
the method more userfriendly.
Continuation and constant quality of Lipton
tea and tea bags.
Global distribution
Implementing the parameter in a global soil map.
Faculty of Science
Biology

21. facebook.com/teabagindex
@TeaBagIndex
www.decolab.org/tbi
on behalf of the TBI team, thanks!
[Faculty of Science
Biology]