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• Presentations: next week Thursday
Global Change:
Biogeochemistry #1:
the Carbon cycle
Global Change Lecture #9, S. Saleska, Sept 28. 2010
I.
Biogeochemistry
Example: the long-term global carbon cycle
(Geology, Oceanography, & Ecosystem Ecology)
II. Ecosystem Ecology and the Carbon Cycle
A.
B.
Carbon is the currency of Life
What does it take to make a plant?
Next lectures: Terrestrial:
Marine (Julie):
- Ecosys. Development /N-cycle - ocean carbon/acidification
- the terrestrial H2O cycle
- ocean productivity
-Microbial biogeochemistry (Virginia)
I. What is Biogeochemistry?
Biogeochemistry = the study of how the cycling of
elements through the earth system (water, air, living
organisms, soil and rock) is governed by physical,
chemical, geological and biological processes
hydrosphere
atmosphere
biosphere
pedosphere
lithosphere
Key Names
Vladimir Vernadsky (1863-1945): Russian scientist
known as the “father of biogeochemistry”, invented the
terms geosphere, biosphere, and “noosphere”
G. Evelyn Hutchinson (1903-1991): famous limnologist
(considered to be founder of limnology) (also studied
the question of how biological species coexist)
Example: the global carbon cycle
through time
What controls atmospheric CO2?
Trends
Controlled by:
A. Geology
B. Oceanography
C. Ecosystem Ecology
Timescale:
(millions of yrs)
(thousands yrs)
( days to 100s yrs)
Stocks of Carbon in the Earth
System
Location
Lithosphere
• carbonate in rocks
• organic C in rocks
ocean HCO-3 + CO-23
Biosphere/Atmosphere
• soil carbon
• Living organic matter
• atmospheric CO2
Mass, Pg C (=GtC)
(=1015 g)
60,000,000
15,000,000
42,000
1,500
600
750
Chemistry of Carbon Dioxide
• Long-term atmospheric CO2 is the balance of
volcanism (input) and chemical weathering/
transfer to oceans/subduction (removal):
CO2 + {Ca,Mg}SiO3  {Ca,Mg}CO3 + SiO2
(Silicate rock)
(Carbonate,
as sediment)
• Shorter-term is the balance between
Photosynthesis and Oxidation:
H2O + CO2  CH2O + O2
Weathering of rock
• Weathering = physical and chemical
decomposition of rock material
• Weathering
(in situ
decomposition)
≠
erosion
(physical
removal)
• Weathering + erosion = denudation
CO2 – Carbonate cycle
CO2 from
Volcanism
(~ 0.1 Pg/yr)
CaSiO3 + 2CO2 + H2O
 Ca2+ + 2HCO-3 +SiO2
(weathering +
erosion of
silicate rocks,
 riverine
transport to
oceans)
Ca2+ + 2HCO3-  CaCO3
(e.g. organisms build seashells)
Subduction
CaCO3 + SiO2  CaSiO3 + CO2
Schlesinger 1997
A. Long-term trends in atmospheric CO2
(geology controls)
With a big assist from evolutionary ecosystem ecology!
The rise of
vascular plants
with roots
Ratio of
ancient to
modern
preindustrial
CO2
Present day
Berner, 1997
A. Long-term trends in atmospheric CO2
(geology controls)
With a big assist from evolutionary ecosystem ecology!
The rise of
vascular plants
with roots
Ratio of
ancient to
modern
preindustrial
CO2
Amt of
carbon in
plant
biomass
Present day
Berner, 1997
Stocks of Carbon in the Earth
System
Location
Lithosphere
• carbonate in rocks
• organic C in rocks
ocean HCO-3 + CO-23
Biosphere/Atmosphere
• soil carbon
• atmospheric CO2
• Living organic matter
Mass, Pg C
(=1015 g)
60,000,000
15,000,000
42,000
1,500
750
600
geology dominates
(only in long-term)
Ocean controls
(medium-term)
B. Medium-term trends in atmospheric CO2
(ocean circulation controls)
Large scale ocean circulation (timescale ~1,000s of yrs) driven by density
changes, caused by fluxes of heat and salt (i.e. the “thermohaline
circulation”)
Atm:
750 Pg C
Ocean:
40,000 Pg C
Ocean currents carry dissolved CO2 between deep ocean and surface
mixed layer (where it can exchange readily with the atmosphere)
Variations in thermohaline circulation (probably forced by solar
Milankovich cycles) drive variations in CO2 – temperature pattern across
glacials and interglacials
B. Medium-term trends in atmospheric CO2
(ocean circulation controls)
Data from Vostok and Dome C Ice cores, Antarctica
Atmospheric CO2 (ppm)
Temperature Anomaly (°C)
Ice Cores Preserve the History of Atmospheric CO2
and climate over recent ice ages
EPICA. 2004, 2005.
Ice Cores Preserve the History of Atmospheric CO2
and climate over the recent ice ages
Doubled pre(Ocean circulation controls)
Atmospheric CO2 (ppm)
Temperature Anomaly (°C)
industrial CO2
(~560 ppm)
Current CO2
(390 ppm)
Ice cores + instruments record the recent (~100 yr) record
of atmospheric CO2
Why biogeochemistry
matters to Global Change!
Uptake by
= land and
oceans
ecosystem
ecology
…and (surface
ocean)
oceanography
Study the mechanisms of
terrestrial and marine
biogeochemistry
Ecosystem Ecology determines the
Terrestrial Uptake of excess atmospheric CO2
(a) What mechanisms cause it?
• Long-term forest regrowth?
(e.g., IPCC 2001; Goulden et al, 1996)
(not a feedback)
• CO2 fertilization effect? (Bazzaz, Field)
(a negative feedback)
• N-deposition fertilization effect? (partial negative feedback)
(probably not, say Nadelhoffer, et al. 1999)
(b) Where is it and what kind of ecosystems?
• Northern mid-lattitude forests?
(atmospheric inversion models: e.g. Tans et al., 1990; Fan et al., 1998)
• Tropical forests?
(forest surveys: Phillips et al., 1998; plant physiological models of CO2
enrichment: Lloyd & Farquhar, 1996; Tian et al, 1998)
More details in later lecture on fate of anthropogenic CO2
C. What is Ecosystem Ecology?
• Ecosystem - all organisms in an area and the
physical environment in which they interact
– (abiotic and biotic characteristics of an area)
• Ecosystems are characterized by energy flow
and structural linkages (trophic structure)
• Ecosystem ecology is the study of
interactions among organisms and their
physical environment as an integrated
system
C. What is Ecosystem Ecology?
“The ecosystem stands as a basic unit
of ecology, a unit that is as important
to this field of natural science as the
species is to taxonomy and
systematics.”
Francis Evans (1956)
Ecosystems as the Basic Unit in Ecology, Science, 123: 1127-28
Ecosystem are important because carbon (in the form of
organic matter) is the currency of life, and carbon (in the
form of CO2) is also a key greenhouse gas
Carbon is the currency of life:
photosynthesis
H2O + CO2  CH2O + O2
Carbon in
atmospheric
CO2
respiration
Reduced Carbon
in organic matter
(plant biomass & energy
supply)
Ecosystem Ecology and terrestrial
ecosystem development
What ingredients are needed to build
a terrestrial ecosystem?
On average, plants are
made (roughly) of:
CH2O
or, more precisely:
C106H263O110N16P1
+ 21 other elements
(of which element 53,
Iodine, is heaviest)
95% of
biosphere
Ecosystem Ecology and terrestrial
ecosystem development
What ingredients are needed to build
a terrestrial ecosystem?
On average, plants are
made (roughly) of:
CH2O
or, more precisely:
C106H263O110N16P1
+ 21 other elements
(of which element 53,
Iodine, is heaviest)
Plants need:
• Carbon
• Nutrients
95% of
biosphere
– (N, P, in inorganic forms)
– Cations (Ca+, Mg+, K+ , ...)
– Trace metals (Fe, Cu, Mn,
Zn, …)
• Water
Ecosystem Ecology and terrestrial
ecosystem development
How do necessary ecosystem ingredients
get assembled?
Plants need:
• Carbon
• Nutrients
–
–
–
–
Ultimate source
Atmosphere (CO2)
(via biological photosynthesis)
Atmosphere (N2 is 80%)
(via biological fixation)
N
P
Underlying
+
+
+
Cations (Ca , Mg , K , ...)
Rock material
Trace metals (Fe, Cu, Mn,
(via chemical weathering)
Zn, …)
(via evaporation & reconOcean densation as precip.)
• Water
Ecosystem Ecology and terrestrial
ecosystem development
How do necessary ecosystem ingredients
get assembled?
Plants need:
• Carbon
• Nutrients
–
–
–
–
Ultimate source
Atmosphere (CO2)
(via biological photosynthesis)
Atmosphere (N2 is 80%)
(via biological fixation)
N
P
Underlying
+
+
+
Cations (Ca , Mg , K , ...)
Rock material
Trace metals (Fe, Cu, Mn,
(via chemical weathering)
Zn, …)
(via evaporation & reconOcean densation as precip.)
• Water
Biological flows of Carbon
photosynthesis
H2O + CO2  CH2O + O2
Atmospheric
carbon
dioxide
respiration
Gross
Primary
Production
(GPP)
Photosynthesis,
summed to
ecosystem
scale
Fraction of carbon
Autotrophic
devoted to metabolic
Respiration
respiration (energy of life)
Net Primary
Production (NPP)
Ecosystem carbon cycling
Plants play major role:
- C inputs to
ecosystem (GPP)
(Gross Primary
Production)
- C transfers to
soil (litterfall)
- C losses to
atmosphere
(respiration)
NPP: Who is in charge?
Photosynthesis, NPP, or
respiration?
• NPP = GPP - Respiration
• Control probably depends on time scale
Global patterns of NPP vary with climate
Increases with ppt (up to max at 2 m/yr)
Increases exponentially with temperature
High variance due to variation in soils, etc.
(very dry
systems
excluded)
Warm wet
(e.g. tropics)
highest
What is NPP?
Components of NPP
% of NPP
New plant biomass
40-70
Leaves and reproductive parts (fine litterfall)
Apical stem growth
Secondary stem growth
New roots
Root secretions
20-40
Root exudates
Root transfers to mycorrhizae
Losses to herbivores, mortality, and fire
1-40
Volatile emissions
0-5
What do we usually measure?
Litterfall
Sometimes stem growth
10-30
0-10
0-30
30-40
10-30
10-30
Global distribution of terrestrial biomes,
their total carbon, and NPP
Area
(106 km2)
Biome
Tropical forests
Temperate forests
Boreal forests
Mediterranean shrublands
Tropical savannas and
grasslands
Temperate grasslands
Deserts
Arctic tundra
Crops
Ice
Total
a
Total C pool
(Pg C)
Total NPP
(Pg C yr-1)
17.5
10.4
13.7
2.8
340
139
57
17
21.9
8.1
2.6
1.4
27.6
15.0
27.7
5.6
13.5
15.5
79
6
10
2
4
--
14.9
5.6
3.5
0.5
4.1
149.3
652
62.6
--
Data from [Roy, 2001]. Biomass in units of carbon, assuming biomass is 50% carbon.
What is the fate of NPP?
Biological flows of Carbon
photosynthesis
H2O + CO2  CH2O + O2
Atmospheric
carbon
dioxide
respiration
Gross
Primary
Production
(GPP)
Photosynthesis,
summed to
ecosystem
scale
Fraction of carbon
Autotrophic
devoted to metabolic
Respiration
respiration (energy of life)
Net Primary
Production (NPP)
Biological flows of Carbon
Atmospheric
carbon
dioxide
Atmospheric
carbon
dioxide
Rauto
Gross
Primary
Production
(GPP)
Rhet
Autotrophic
Respiration
Net Primary
Production (NPP)
Plant Heterotrophic
Biomass Respiration
NPP - Rhet
Net Ecosystem
= Production (NEP)
What is Net Ecosystem
Production (NEP)?
• Rate of carbon accumulation in an
ecosystem (if no other loss processes)
NEP = NPP - Rheterotr
= GPP - (Rplant+ R heterotr )
= GPP - (R ecosyst )
NEP is the balance between two large fluxes:
GPP and ecosystem respiration
NEP is what ultimately matters for carbon storage
– and, hence, ecosystem feedbacks to climate
Typical Seasonal pattern of biological carbon fluxes
in temperate zone
Conclusion: things to take away
from this lecture
• Definitions: Biogeochemistry, Ecosystem
Ecology, and weathering
• The basics of the long vs. short term carbon
cycle
• Ingredients for a terrestrial ecosystem
• Terrestrial carbon cycling: GPP, NPP, NEP
– GPP is photosynthesis
– NPP is production of plant matter
– NEP is carbon storage (and feedback to climate)
Global Change:
Biogeochemistry #1:
the Carbon cycle
Global Change Lecture #10, S. Saleska, Oct. 6. 2009
I.
Biogeochemistry
Overview: the long-term global carbon cycle
II. Ecosystem Ecology and the Carbon Cycle
A.
B.
Carbon is the currency of Life
What does it take to make a plant?
Next lectures: Terrestrial:
Marine (Julie):
- Ecosys. Development /N-cycle - ocean carbon/acidification
- the terrestrial H2O cycle
- ocean productivity
-Microbial biogeochemistry (Virginia)