Wytham Woods: A Carbon Cycle Perspective Yadvinder Malhi, Nathalie Butt, Mike Morecroft, Katie Fenn

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) 5 deforestation 1.1

± 0.7

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

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) fossil fuel emissions 7.7

± 0.5

5 deforestation 1.1

± 0.7

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

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) fossil fuel emissions 7.7

± 0.5

5 deforestation 1.1

± 0.7

5 10 1850 1900 Time (y) 1950 Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS 2000

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) fossil fuel emissions 7.7

± 0.5

5 deforestation atmospheric CO 2 1.1

± 0.7

4.1

± 0.1

5 10 1850 1900 Time (y) 1950 Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS 2000

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) fossil fuel emissions 7.7

± 0.5

5 deforestation atmospheric CO 2 1.1

± 0.7

4.1

± 0.1

5 10 1850 1900 1950 Time (y) ocean ocean 2000 2.3

± 0.4

(5 models) Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS

Human Perturbation of the Global Carbon Budget

10 2000-2009 (PgC) fossil fuel emissions 7.7

± 0.5

5 5 deforestation atmospheric CO 2 land ocean 1.1

± 0.7

4.1

± 0.1

2.4

(Residual) 2.3

± 0.4

(5 models) 10 1850 1900 Time (y) 1950 2000 Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS

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

T. Riutta, unpublished 0 10 20 30 40 50 km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!

300 m N All stems mapped across the whole plot

SIGEO Wytham carbon budget

Woody debris Above-ground biomass (trees) (Estimated) below-ground biomass Soil

Total Carbon stock value

3.6 MgC/ ha -1 97 MgC/ha -1 19 MgC/ha -1 140 MgC/ha -1

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 CO 2 cycle

source Dry summer  smaller CO 2 sink Warm autumn  bigger CO 2 source sink Aurela et al. 2007, Tellus B

The Breath of Wytham Woods 2010 2009 Thomas et al. 2010

Biogeosciences

2008

Forest Survey Plots

The carbon balance of Wytham Woods 0,2 0 -0,2 -0,4 1 0,8 0,6 0,4 1,8 1,6 1,4 1,2 Tree Growth Tree Death Net Balance What is causing this carbon sink?

How long will it persist?

Tower Net Flux

The forest carbon cycle

GPP

The Carbon Cycle of a Forest

NPP

leaves,flowers,fruit R leaf R soil R soil het R roots R stem R CWD

NPP

wood (Branch + Stem) D CWD D Fine litterfall

NPP NPP

coarse roots fine roots D Root F doc NPP VOC

Stem and leaf respiration Weather station Soil respiration Rhizotron Growth Litterfall trap Soil core Ingrowth Cores

The carbon cycle of Wytham Woods

GPP B = 20.3 ± 1.0

GPP T = 21.1

R EC O B = 19.3 ± 0.9

R EC O T = 19.8

R Aut R Het = 13.9 ± 0.6

= 5.4 ± 0.8

NPP leaves,flow ers = 2.77 + 0.22

R leaf = 4.17 + 1.87

NPP Total = 6.93 ± 0.84

NPP Ag = 3.88 ± 0.31

NPP Bg = 2.51 ± 0.78

R soil = 4.10 + 0.09

R root+rhiz.

= 0.9 + 0.2

R mycorrhiza = 0.3 + 0.1

R SOM = 3.0 + 0.3

R stem = 8.79 + 0.00

NPP stem = 1.11 + 0.22

R CWD = 0.03 + 0.01 *

M

Fine litterfall = 2.77 + 0.21

= 0.04 + 0.02

R litter = 2.08 + 0.69 * NPP NPP coarseroot fineroot = 0.22 + 0.17

= 2.29 + 0.76

Fenn et al., in review

The influence of fragmentation

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 1 0 2 1 2 4 Km 4 Km 0 1 2 0 1 2 4 Km 4 Km 0 0 1 1 2 2 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

0.4

0.2

0.0

1.0

0.8

0.6

Results

Ash Ash Macrofauna Microbes, microfauna and mesofauna Oak Oak 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.