Wytham Woods: A Carbon Cycle Perspective
Yadvinder Malhi, Nathalie Butt, Mike Morecroft, Katie Fenn
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
Source
Sink
CO2 flux (PgC y-1)
10
5
deforestation
5
10
1850
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
1.1±0.7
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
10
Source
Sink
CO2 flux (PgC y-1)
fossil fuel emissions
7.7±0.5
5
deforestation
5
10
1850
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
1.1±0.7
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
10
Source
Sink
CO2 flux (PgC y-1)
fossil fuel emissions
7.7±0.5
5
deforestation
5
10
1850
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
1.1±0.7
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
10
Source
7.7±0.5
5
deforestation
atmospheric CO2
Sink
CO2 flux (PgC y-1)
fossil fuel emissions
5
10
1850
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
1.1±0.7
4.1±0.1
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
10
Source
7.7±0.5
5
deforestation
atmospheric CO2
Sink
CO2 flux (PgC y-1)
fossil fuel emissions
1.1±0.7
4.1±0.1
5
ocean
ocean
10
1850
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
2.3±0.4
(5 models)
Human Perturbation of the Global Carbon Budget
2000-2009
(PgC)
10
Source
7.7±0.5
5
deforestation
atmospheric CO2
Sink
CO2 flux (PgC y-1)
fossil fuel emissions
land
5
ocean
2.4 (Residual)
2.3±0.4
(5 models)
10
1850
1.1±0.7
4.1±0.1
1900
1950
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
2000
So there is a large carbon sink in the land biosphere
Where is it?
What does it mean for climate change?
What is causing it?
Why is it so unstable?
Will it persist?
The 18 ha long term monitoring plot
Wytham
Woodland in the Upper
Thames Basin
0
T. Riutta, unpublished
10
20
30
40
50 km
Smithsonian
18 ha plot
Network of small
plots, 0.3 - 1ha
Flux tower
Canopy walkway
The CTFS, Smithsonian Institute, the world’s largest tropical forest programme.
• First census plot set up in Panama in 1980
• Global network monitoring 4.5 million individual tropical trees; 8,500 species
• Long term, large scale research
• Collaboration with 75 institutions – 42 plots, 21 countries
Extension into non-tropical systems as The Smithsonian Institution Global Earth
Observatories (SIGEO)
The census
• Laying out plots & subplots
(450 subplots)
• Tagging
• Identifying
• Measuring
• Marking
• Mapping
• Recording
• …of every stem >1cm dbh
• More than 20, 000 stems!
N
All stems mapped
across the whole plot
300 m
SIGEO Wytham carbon budget
Carbon stock value
Woody debris
3.6 MgC/ ha-1
Above-ground biomass (trees)
97 MgC/ha-1
(Estimated) below-ground
biomass
19 MgC/ha-1
Soil
140 MgC/ha-1
Total
256 MgC/ha-1
Data collected by Earthwatch
volunteers
The net carbon balance
Forests both absorb and release carbon dioxide every day
Measuring forest-atmosphere carbon flows
Example of annual CO2 cycle
source
Dry summer 
smaller CO2 sink
Warm autumn 
bigger CO2 source
sink
Aurela et al. 2007, Tellus B
The Breath of
Wytham Woods
2010
2009
2008
Thomas et al. 2010
Biogeosciences
Forest Survey Plots
The carbon balance of Wytham Woods
1.8
Carbon Flux (t C/ha /year
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
Tree Growth Tree Death
What is causing this carbon sink?
How long will it persist?
Net Balance
Tower Net
Flux
The forest carbon cycle
GPP
The Carbon Cycle of a
Forest
NPP VOC
NPP leaves,flowers,fruit
R leaf
NPP wood (Branch + Stem)
DFine litterfall
R stem
R soil
R CWD
DCWD
R roots
NPP coarse roots
R soil het
DRoot
NPP fine roots
Fdoc
Stem and leaf respiration
Weather station
Soil respiration
Growth
Litterfall trap
Soil core
Ingrowth Cores
Rhizotron
The carbon cycle of Wytham Woods
GPPB = 20.3 ± 1.0
RECO B = 19.3 ± 0.9
NPPTotal = 6.93 ± 0.84
GPPT = 21.1
RECO T = 19.8
NPPAg
= 3.88 ± 0.31
RAut
= 13.9 ± 0.6
NPPBg
= 2.51 ± 0.78
RHet
= 5.4 ± 0.8
NPP leaves,flow ers = 2.77 + 0.22
R leaf = 4.17 + 1.87
Rstem = 8.79 + 0.00
Fine litterfall = 2.77 + 0.21
NPPstem = 1.11 + 0.22
Rsoil = 4.10 + 0.09
RCWD = 0.03 + 0.01 *
M = 0.04 + 0.02
Rlitter = 2.08 + 0.69 *
Rroot+rhiz. = 0.9 + 0.2
Rmycorrhiza = 0.3 + 0.1
NPPcoarseroot = 0.22 + 0.17
RSOM = 3.0 + 0.3
Fenn et al., in review
NPPfineroot
= 2.29 + 0.76
The influence of fragmentation
0
0
0
1
0
2
1
2
4 Km
1
2
1
2
4 Km
4 Km
4 Km
Distance to the
edge from within
the woodland, m
0 - 20
20 - 40
40 - 60
60 - 80
80 -100
100 - 120
120 - 140
140 - 160
160 - 180
180 - 200
>200
0 01 12 2
4 Km
4 Km
Earthwatch fragmented woodland objectives
To quantify how the woodland carbon cycle varies
– Between forest core areas and edges and between large and
small fragments
– In current and changing climatic conditions
>60% of the forest area in this region
can be classified as edge
Forest edges and small fragments are
more sensitive to changes in weather
conditions, especially moisture-related
Climate change impacts are larger in these habitats
Trees near the forest edge use more water and have
a different microclimate
Water loss at forest edge
Herbst et al. 2007. Forest Ecology and Management 250.
Woodlice, edges and forest biogeochemistry
Watering experiment
• Watering once a week from
the beginning of June until
the beginning of September.
• The amount of water added
corresponds to 200 mm
extra rainfall.
Litter decomposition experiment
• Two mesh sizes: large
mesh allows soil
macrofauna access to the
leaves, small mesh
excludes them.
• Three months of
decomposition, from the
beginning of June to the
beginning of September.
Soil macrofauna
• Approximately 80% of the leaf
litter in a woodland is consumed
by the soil fauna
• In Britain, woodlice and millipedes
• Initial breakdown of leaf litter,
mixing into a homogeneous state
• The presence of soil macrofauna
enhances microbial decomposition
• Soil fauna is sensitive to
temperature and moisture
conditions
Ash
Interior Watered
Interior Control
Ash
Edge Watered
1.0
Edge Control
Interior Watered
Interior Control
Edge Watered
Edge Control
Mass loss, proportion of initial mass
Results
Oak
Macrofauna
Microbes, microfauna
and mesofauna
Oak
0.8
0.6
0.4
0.2
0.0
Error bars
±1 SE
Future prospects
Thank you!
Katie Fenn, Martha Crockatt, Michele Taylor, Nigel Fisher, Toby Marthews,
Terhi Riutta, Paul Eddowes, Kate Barker, Sara Banning, Emma Bush, Kate
Grounds, Ben Cjiffers, Richard Sylvester, Sam Armenta Butt, Luke Sherlock,
Youshey Zakiuddin, Dan Gurdak, Arthur Downing, Dominic Jones, Jay Varney,
Leo Armenta Butt, Jeremy Palmer, HSBC volunteers.