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Nutrient availability is determined by biogeochemical processes
Biogeochemistry
Nutrients are chemical elements required by
organisms for metabolism and growth
Stoichiometry concerns the relative quantities of
chemicals
E.g.Plant C:N = ~ 30Human C:N = ~ 6
Cain, Bowman & Hacker (2014), Table 22.1
Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc. Source for ecosystem input is minerals in Earth’s crust
Cain, Bowman & Hacker (2014), Fig. 22.4
Chemical weathering releases soluble forms of nutrients
Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc. Source for ecosystem input is minerals in Earth’s crust
Cain, Bowman & Hacker (2014), Fig. 22.4
Chemical weathering releases soluble forms of nutrients
Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc. Source for ecosystem input is minerals in Earth’s crust
Cain, Bowman & Hacker (2014), Fig. 22.4
Chemical weathering releases soluble forms of nutrients
Rock-Derived Nutrients
E.g., Ca, K, Mg, P, etc. Source for ecosystem input is minerals in Earth’s crust
Cain, Bowman & Hacker (2014), Fig. 22.4
Chemical weathering releases soluble forms of nutrients
Clays (– charge) determine cation (+ charge) exchange capacity
Particle sizes: sand > silt > clay
Sedimentary parent material can overlie bedrock parent material, e.g.: Glacial till Wind-blown loess
E.g., C, NSource for ecosystem input is atmospheric gases
Atmosphere-Derived Nutrients
Photo from Wikimedia Commons
Earth’s atmosphere: 78% N (as N2); 21% O (as O2 & in H2O); 0.9% Ar; 0.04% (mostly in CO2 &
increasing!); plus other trace gases & aerosols (suspended solid, liquid & gaseous particles that can
precipitate to Earth as atmospheric deposition)
E.g., C, NSource for ecosystem input is atmospheric gases
Atmosphere-Derived Nutrients
Photos from Wikimedia Commons
Some bacteria (via nitrogenase), lightning & the energy-demanding Haber-Bosch process fix N
Triple-bonded N2 ammonium (NH4+)
A key nutrient recycling process within ecosystems
(i.e., biochemical transformations that influence the movement & retention of
nutrients in ecosystems)
Decomposition
Cain, Bowman & Hacker (2014), Fig. 22.6
Litter
Fragmentation by animals
Mineralization – bacteria & fungi release enzymes to
transform organic macromolecules to small
organic compounds & soluble nutrients
(e.g., ammonium)
Nutrient Cycling
Cain, Bowman & Hacker (2014), Fig. 22.10
Nitrification – certain chemoautotrophic aerobic bacteria convert mineralized ammonia (NH3)
& ammonium (NH4+) into
nitrate (NO3-)
Nutrient Cycling
Cain, Bowman & Hacker (2014), Fig. 22.10
Denitrification – certain anaerobic bacteria convert nitrate (NO3
-) into N2 & nitrous oxide (N2O)
Nutrient Cycling
Elements vary in mean residence times in ecosystems
Cain, Bowman & Hacker (2014), Table 22.3
Mean residence time (yr) = Total pool of element (kg)
Rate of input (kg/yr)
Catchment / Drainage / Watershed Studies
Cain, Bowman & Hacker (2014), Fig. 22.12 – Longs Peak, Rocky Mtn. N. P., Colorado
Hawaiian Ecosystem Development
Cain, Bowman & Hacker (2014), Fig. 22.15
P limitation in oldest
ecosystem
N & P limitation in
intermediate-aged
ecosystem
N limitation in youngest
ecosystem
Metrosideros polymorpha
Plate tectonics
Hawaiian Ecosystem Development
Cain, Bowman & Hacker (2014), Fig. 22.15
P limitation in oldest
ecosystem
N & P limitation in
intermediate-aged
ecosystem
N limitation in youngest
ecosystem
Metrosideros polymorpha
Plate tectonics
Hawaiian Ecosystem Development
Cain, Bowman & Hacker (2014), Fig. 22.15
P limitation in oldest
ecosystem
N & P limitation in
intermediate-aged
ecosystem
N limitation in youngest
ecosystem
Metrosideros polymorpha
Plate tectonics