1. Nutrient Supply & Cycling
“Life is complex chemistry in a semipermeable bag” (pg. 24)
“Life… is the organized assembly and disassembly of stardust”
(pg. 138)
Mark Hunter
(2016)
The Phytochemical Landscape
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Wikipedia “Earthworm” page; accessed 18-XI-2014
Photo from Wikimedia Commons

2. Biogeochemistry
Nutrient availability is determined by biogeochemical processes
Nutrients are chemical elements required by organisms for metabolism and growth
Stoichiometry concerns the relative quantities of chemicals
E.g., Plant C:N = ~ 30
N:C = ~ 0.03
Human C:N = ~ 6
N:C = ~ 0.17
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Biogeochemistry – the study of the physical, chemical, and biological factors that influence the transformations of elements and their movements through the biosphere.
NOTE:
Plant N:C = ~ 0.03
Human N:C = ~ 0.17
Bowman, Hacker & Cain (2017), Table 22.1

3. Biogeochemistry
Nutrient availability is determined by biogeochemical processes
C often associated with
structural compounds
N largely found in enzymes
C:N can indicate relative concentrations of biochemical machinery in cells
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Biogeochemistry – the study of the physical, chemical, and biological factors that influence the transformations of elements and their movements through the biosphere.
NOTE:
Plant N:C = ~ 0.03
Human N:C = ~ 0.17
Bowman, Hacker & Cain (2017), Table 22.1

4. Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc.
Source for ecosystem input is inorganic minerals in Earth’s crust
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Ca(2+)
K(+)
Mg(2+)
PO4(3-)
Chemical weathering releases soluble forms of nutrients
Bowman, Hacker & Cain (2017), Fig. 22.4

5. Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc.
Source for ecosystem input is inorganic minerals in Earth’s crust
Organic matter
contains nutrients associated with C & H
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Ca(2+)
K(+)
Mg(2+)
PO4(3-)
Chemical weathering releases soluble forms of nutrients
Bowman, Hacker & Cain (2017), Fig. 22.4

6. Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc.
Source for ecosystem input is inorganic minerals in Earth’s crust
Organic matter
contains nutrients associated with C & H
Please do not use the images in these PowerPoint slides without permission.
Ca(2+)
K(+)
Mg(2+)
PO4(3-)
Chemical weathering releases soluble forms of nutrients
Bowman, Hacker & Cain (2017), Fig. 22.4

7. Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc.
Source for ecosystem input is inorganic minerals in Earth’s crust
Clays (– charge) determine cation (+ charge) exchange capacity
Organic matter
contains nutrients associated with C & H
Sedimentary parent material
can overlie bedrock parent material, e.g.:
Glacial till
Wind-blown loess
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Ca(2+)
K(+)
Mg(2+)
PO4(3-)
Particle sizes: sand > silt > clay
Chemical weathering releases soluble forms of nutrients
Bowman, Hacker & Cain (2017), Fig. 22.4

8. Rock-Derived Nutrients
Soil Horizons
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Wikipedia “High School Earth Science/Soils” page; accessed 18-XI-2014
[By HolgerK at en.wikipedia (Transferred from en.wikipedia) [Public domain], from Wikimedia Commons]
Photo from Wikimedia Commons

9. Atmosphere-Derived Nutrients
E.g., C, N
Source for ecosystem input is atmospheric gases
Earth’s atmosphere: 78% N (as N2); 21% O (as O2 & in H2O); 0.9% Ar; 0.04% C (mostly in CO2 & increasing!); plus other trace gases & aerosols (suspended solid, liquid & gaseous particles that can precipitate to Earth as atmospheric deposition)
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See also Ben Houlton’s work for an update: N is both atmosphere-derived and rock-derived!
Wikipedia “Atmosphere” page; accessed 18-XI-2014
[By NASA Earth Observatory [Public domain], via Wikimedia Commons]
Photo from Wikimedia Commons

10. Atmosphere-Derived Nutrients
E.g., C, N
Source for ecosystem input is atmospheric gases
Some bacteria (via nitrogenase), lightning &
the energy-demanding Haber-Bosch process fix N
Triple-bonded N2  ammonium (NH4+)
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Wikipedia “Rhizobia” page; accessed 18-XI-2014
[By Stdout [GFDL ( or CC-BY-SA-3.0 ( via Wikimedia Commons]
Wikipedia “Lightning” page; accessed 18-XI-2014
[By Fir0002 (Own work) [GFDL 1.2 ( via Wikimedia Commons]
Photos from Wikimedia Commons

11. Atmospheric Deposition Can Link Ecosystems
E.g., Dust originating in the Sahara Desert provides important atmospheric deposition of Fe to Atlantic Ocean & P to Amazon Basin
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Ecosystems are not entirely disconnected from one another…
Remotely sensed image from NASA -
saharan-dust-feeds-amazon-s-plants

12. Fragmentation by animals
Decomposition
A key nutrient recycling process within ecosystems (i.e., biochemical transformations that influence the movement & retention of nutrients in ecosystems)
Litter
Fragmentation by animals
Mineralization – bacteria & fungi release enzymes to transform organic macromolecules to small organic compounds & soluble nutrients
(e.g., ammonium)
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Bowman, Hacker & Cain (2017), Fig. 22.6

13. Climate Controls the Activity of Decomposers
How does temperature, water availability and oxygen availability each influence decomposition?
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Note that oxygen in the soil is generally related to how much water there is in the soil.
Bowman, Hacker & Cain (2017), Fig. 22.7

14. Lignin Decreases the Rate of Decomposition
Not all the C in litter is equally available as an energy source for decomposers
Lignin – a structural carbon compound in plant cell walls – does not break down readily
(Decomposition rate decreases as
biomass remaining increases)
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Note that oxygen in the soil is generally related to how much water there is in the soil.
Bowman, Hacker & Cain (2017), Fig. 22.8

15. Nutrient Cycling
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Like ammonium, nitrate can be taken up by plants or lost via leaching, etc.
Nitrification – certain chemoautotrophic aerobic bacteria convert mineralized ammonia (NH3) & ammonium (NH4+) into
nitrate (NO3-)
Bowman, Hacker & Cain (2017), Fig

16. Nutrient Cycling
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N2 & N2O can be lost from the ecosystem as gases.
Denitrification – certain anaerobic bacteria convert nitrate (NO3-) into N2 & nitrous oxide (N2O)
Bowman, Hacker & Cain (2017), Fig

17. Total pool of element (kg)
Nutrient Cycling
Elements vary in mean residence times in ecosystems
Total pool of element (kg)
Rate of input (kg/yr)
Mean residence time (yr) =
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Note: These are mean residence times for the soil pools of these ecosystems.
Bowman, Hacker & Cain (2017), Table 22.3

18. Catchment / Drainage / Watershed Studies
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Bowman, Hacker & Cain (2017), Fig – Longs Peak, Rocky Mtn. N. P., Colorado

19. Catchment / Drainage / Watershed Studies
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Bowman, Hacker & Cain (2017), Ecological Toolkit 22.1, Fig. B – weir; Fool Creek, CO

20. Catchment / Drainage / Watershed Studies
Pools
Total amount of an element found in a component of an ecosystem
Fluxes
Movement of an element into, out of, or between components of an ecosystem
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Bowman, Hacker & Cain (2017), Fig

21. Walker-Syers Model
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T. W. Walker & J. K. Syers The fate of phosphorus during pedogenesis. Geoderma 15:1-19.
In general, the model posits a decline in available P throughout
ecosystem development, as P is leached, lost, and becomes occluded
(soluble P combines with Al, Ca, Fe into insoluble secondary minerals
and is unavailable as a nutrient)
Walker & Syers (1976), Fig. 1

22. Hawaiian Ecosystem Development
Plate tectonics
P limitation in oldest ecosystem
N & P limitation in intermediate-aged ecosystem
N limitation in youngest
ecosystem
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Metrosideros polymorpha
Bowman, Hacker & Cain (2017), Fig

23. Hawaiian Ecosystem Development
Plate tectonics
P limitation in oldest ecosystem
N & P limitation in intermediate-aged ecosystem
N limitation in youngest
ecosystem
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Metrosideros polymorpha
Bowman, Hacker & Cain (2017), Fig

24. Hawaiian Ecosystem Development
Plate tectonics
P limitation in oldest ecosystem
N & P limitation in intermediate-aged ecosystem
N limitation in youngest
ecosystem
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Metrosideros polymorpha
Bowman, Hacker & Cain (2017), Fig

25. Hawaiian Ecosystem Development
Plate tectonics
P limitation in oldest ecosystem
N & P co-limitation in intermediate-aged ecosystem
N limitation in youngest
ecosystem
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Metrosideros polymorpha
Bowman, Hacker & Cain (2017), Fig