Post on 24-Feb-2016
description
Coupled Biogeochemical Cycles
William H. Schlesinger
Millbrook, New York
1. Some basic stoichiometry for life―in biomass
First articulated by Liebig (1840)and later advanced by Redfield (1958), Reiners (1986), Sterner and Elser (2002), and Cleveland and Liptzin (2007)
Complementary Models for Ecosystems
Reiners, W.A. 1986
145
100 + ?Δ
121
40
The Global Nitrogen Cycle - Modern
48-59
18
<5
IF NPP = 60 x 1015 g C/yr
60 X 1015 g C x 1 N = 1.2 x 1015 g N 50 C
= 1200 x 1012 g N/yr
From: Magnani et al. 2007
Townsend et al. 1996. Ecological Applications 6(3):806-814.
Spatial Distribution of the 1990 Carbon Sink Resulting from Fossil-fuel N Deposition between 1845 and 1990
Coupling of biogeochemical cycles, due to:
2. The flow of electrons in the oxidation/reduction reactions―
First articulated by Kluyver (1926),and later advanced by Morowitz, Nealson, Falkowski, and many others
Schlesinger, W.H. 1997
H2O/O2 C N S FeH
2O/O
2
X
PhotosynthesisCO2 CH2O O2
C
RespirationC CO2O2 H2O X
DenitrificationC CO2NO3 N2
Sulfate reductionC CO2SO4 H2S
Iron reduction- organic C oxidation4a or
AOM4b
C CO2FeIII FeII
N
Heterotrophic nitrification
NH4 NO3O2 H2O
Chemoautotrophy(nitrification)
NH4 NO3CO2 C
AnammoxNH4 + NO2N2+H2O
Sulfate reduction7
NH4 N2/ NO3SO4 H2S
Feammox 5a,b,c
NH4 NO2/N2/NO3FeIII FeII
S
Sulfur oxidationS SO4
O2 H2O
Chemoautotrophy(sulfur-based
photosynthesis)S SO4CO2 C
Autotrophic DenitrificationS SO4
NO3 N2/NH4
X
Iron reducing and sulfur oxidizing
bacterial consortium 6
S SO4FeIII FeII
Fe
Chemolithotrophic(Iron oxidizing
bacteria) 1
FeII FeIIIO2 H2O
Autotrophic or mixotrophic (iron
oxidizing bacteria) 2
FeII FeIIICO2 C
iron oxidizing archaeum3a or nitrate-
reducing, Fe(II)-oxidizing bacteriums3b
FeII FeIIINO3 N2/NH4
X X
Oxidized ReducedO
xidi
zed
R
educ
ed
Table 1. Matrix of redox reactions via microbial metabolisms as updated and modified from Schlesinger et al (2011).
Mikucki et al. 2009
Coupled Metabolism & The Sulfur Wars
Howarth and Teal 1979report 75 moles/m2of sulfate reduction annually
2H+ + SO4= + 2CH2O 2CO2 + H2S + 2H2O
implies 150 moles of C is oxidized
150 mols C = 1800 g C/m2/yr
Howes et al. 1984
NPP nowhere near that high!
145
100 + ?Δ
121
40
The Global Nitrogen Cycle - Modern
48-59
18
<5
Denitrification
5CH2O + 4H+ + 4NO3- →
2N2 + 5CO2 + 7H20
Intermediates include NO and N2O
Hirsch et al. 2006Hirsch et al. 2006
∆ N20= TOTAL
N20 __________________
N2 + N20
Schlesinger 2009
Calculation of change in denitrification from N2O
124 Tg (0.37) + 110 Tg (0.082) = 234 Tg (0.246)
4 TgN2O/yr / 0.25 = 17 TgN/yr
145
116-124
121
40
The Global Nitrogen Cycle - Modern
48-59
18
150+9
<5
Land-sea Transport48
3. Coupling of biogeochemical cycles to carbon through chelation
Fig. 2. The fractional amount of Pb loss calculated over the study period is significantly correlated with the thickness (cm) of the forest floor at each site. A logarithmic fit to these data give r2 = 0.65.
Kaste et al. 2006.
Principles of coupled biogeochemical cycles apply to geo-engineering
For example, if we wanted to sequester a billion metric tons of C in the oceans by enhancing NPP with Fe fertilization
Current marine NPP = 50 x 1015 g C/yr
F-ratio of 0.15 means that 7.5 x 1015 g C/yr sinks through the thermocline
An additional 1 x 1015 g C/yr sinking would require ~7 x 1015 g C/yr additional NPP, so
7 x 1015 g C x 23 x 10-6 Fe/C = 1.6 x 1011 g Fe (Lab uptake), or x 6 x 10-4 = 4.2 x 1012 (Field observation) Buesseler & Boyd (2003)
Versus, the global production of Fe annually (1900 x 1012 g Fe/yr)
For example, to provide a sink for 1 x 1015 gC/yr in the world’s soils by
fertilizing them:
Current terrestrial NPP = 50 x 1015 g C/yr
Preservation ratio of 0.008; i.e., global NEP – 0.4 g C/yr (Schlesinger 1990)
To store an additional 1.0 x 1015 g C in soils would require adding125 x 1015 g C/yr to terrestrial NPP
125 x 1015 g C/yr x 1 N/50 C = 2.5 x 1015 g N as fertilizer each year
2.5 x 1015 g C @ 0.857 g C released as CO2 per g N = 2.14 x 1015 g C/yr released in fertilizer production
The Global Phosphorus Cycle
Natural Biogeochemical Cycle in Surface Biosphere (terrestrial & oceanic)Element Flux (1012 g/yr) Biospheric Flux/Sedimentary Flux
C 107000 446N 9200 368P 1000 500S 450 5.6Cl 120 0.46Ca 2300 3.7Fe 40 5.3Cu 2.5 23.6Hg 0.003 4.3
Comparison of Biogeochemical Cycle to Anthropogenic Cycle (Flux in 1012 g/yr)
Element Biospheric Flux Anthropogenic Flux Anthro/Sedimentary Anthro/Biospheric
C 107000 8700 36.3 0.081
N 9200 221 8.8 0.024
P 1000 25 12.5 0.025
S 450 130 1.6 0.29
Cl 120 170 0.65 1.42
Ca 2300 65 0.10 0.028
Fe 40 1.1 0.14 0.028
Cu 2.5 1.5 14.3 0.60
Hg 0.003 0.0023 3.3 0.77
My final message today:
There is an increasing role for biogeochemists
to contribute to the understanding and fruitful
solutions to global environmental problems.
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