The Carbon Cycle: Global to local

Ruth Varner, PhD

Atmospheric CO2 at Mauna Loa

Keeling, C.D. and T.P. Whorf. 2004. Atmospheric CO2 records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

An Impeccable Record of our AtmosphereAn Impeccable Record of our Atmosphere

The Earth System

• The Earth is a system made up of components.

• There are feedbacks between these components.

• These relationships can be used to predict past and future changes in the environment.

• The Carbon cycle is an important Earth System.

Formation of Fossil Carbon

• Coal: from the remains of plants (mainly from Carboniferous period)

• Oil: from marine organisms that were buried under ocean or river sediments

• Natural Gas: was originally oil; higher temperature and pressure converted it to primarily methane

Combustion

Burning hydrocarbons produces CO2 and CO:

CxHx + O2 CO2 + H2O(if enough O2) Complete combustion

 Hydrocarbon + oxygen = carbon dioxide and water

CxHx + O2 CO2 + CO + H2O(if not enough O2) incomplete combustion

 Hydrocarbon + oxygen = carbon dioxide and carbon monoxide and water

Photosynthesis – carbon fixed from inorganic CO2 to organic molecules (sugars)

6 CO2 + 6 H2O C6H12O6 + 6 O2

chlorophyll, sunlight

Respiration – sugar is “burned” as part of a metabolic process that consumes oxygen and produces energy (ATP) – decomposition results in respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

Biological uptake/release of CO2

From the Atmosphere: Inorganic C in the Ocean

CO2 (atm) ↔ CO2 (aq) ↔ HCO3- + H+ ↔ CO32- + H+ ↔ CaCO3 ↔ seds

Carbon dioxide in the oceans

Calcareous skeleton carbon – can be dissolved or deposited

Figure 7.10

UNH/NOAA-PMEL CO2 Buoy in Gulf of Maine

In sea water

In overlying atmosphere

Terrestrial Carbon

• Soil carbon is released through respiration : root and microbial (decomposition)

• Plants respire CO2

• Plants also fix carbon through photosynthesis

Terrestrial Carbon

Biological uptake/release of CO2

Photosynthesis – carbon fixed from inorganic CO2 to organic molecules (sugars)

6 CO2 + 6 H2O C6H12O6 + 6 O2

chlorophyll, sunlight

Respiration – sugar is “burned” as part of a metabolic process that consumes oxygen and produces energy– decomposition

results in respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

•Global network of flux towers used to measure COGlobal network of flux towers used to measure CO22 exchange between exchange between ecosystems and the atmosphereecosystems and the atmosphere•Sites also include measurements on vegetation, soils, hydrology and Sites also include measurements on vegetation, soils, hydrology and meteorology. meteorology. •Information available to researchers, students and educators.Information available to researchers, students and educators.

FLUXNET

Wind direction

Turbulent eddiesWind direction

Turbulent eddies

http://www.fluxnet.ornl.gov/fluxnet/index.cfm

Total ecosystem respiration =Rsoil + Rleaf + Rstem + Rcwd

Rsoil

Rstem

Rleaf

Rcwd

Rsoil = Rroot + Rdecomp

Soil CO2 efflux is a measurement of the Rsoil that reaches the atmosphere

Measuring Soil CO2 EffluxManual chamber measurements

Autochamber measurements

Volcanic CO2

Subduction of limestone at plate boundariesCarbonotype: watery low temperature lava

Oceans +2 Pg yr-1

Atmosphere +2 Pg yr-1

FACE Duke Forest, Chapel Hill, NC

Carbon Fertilization ?

FACE site locations

Carbon cycling in temperate ecosystems

Role of peatlands in global carbon cycle

CARBON EMISSION

CARBON SINK

Modified from Brown, 1998; and Moore et al, 1998

PLANTS

PEAT

anaerobic decomposition

aerobic decomposition

oxidation

CO2

CH4

CH4

CO2

DOC

photosynthesisCO2

c1c2c3c4

c5

c6c7

c8

c9

c10c11

•Temperate poor fen in southeastern Temperate poor fen in southeastern New Hampshire (43 12.5’N, 71 New Hampshire (43 12.5’N, 71 3.5’W)3.5’W)

•Area: 1.7 haArea: 1.7 ha

•Peat depth: 2-4.5mPeat depth: 2-4.5m

•Mean annual precipitation: 1100 mmMean annual precipitation: 1100 mm

•Mean annual temperature: 8.1 CMean annual temperature: 8.1 C

•Mean growing season T: 14.9 CMean growing season T: 14.9 C

•Biologically active season from April-Biologically active season from April-OctoberOctober

•Sphagnum dominatedSphagnum dominated

•Other important species are Other important species are leatherleaf, blueberry, sedgeleatherleaf, blueberry, sedge

Select from chamber

IRGALI6262

Pump

MFC

Select to chamber

Control System

Box

Clear Lexan Boxes

0.07 – 0.08 m3 (5)0.14 – 0.16 m3 (5)

Automated Chamber Fluxes

Distributed Return Manifold

Fans mix headspace

A flux every 20 minutes

96 fluxes per day

Manual Chamber Fluxes– CH4: Grab samples taken during

chamber measurements; analyzed on an GC-FID

– CO2: IRGA (LiCor 6200) analyzes air from chamber headspace; calculates NEE

June 8, 2005

minutes

0 2 4 6 8 10 12

CH

4, p

pm

v

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

1110

1995 2007

Vegetation survey maps of Sallie’s Fen from 1995 and 2007.

Research Questions?