Embed Size (px)
Citation preview
Nutrient Supply & Cycling
Photo from Wikimedia Commons
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
Rock-Derived Nutrients
Soil Horizons
Photo from Wikimedia Commons
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
Catchment / Drainage / Watershed Studies
Cain, Bowman & Hacker (2014), Fig. 22.13
Walker-Syers Model
Walker & Syers (1976), Fig. 1
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
Hawaiian Ecosystem Development
Cain, Bowman & Hacker (2014), Fig. 22.15
P limitation in oldest
ecosystem
N & P co-limitation in
intermediate-aged
ecosystem
N limitation in youngest
ecosystem
Metrosideros polymorpha
Plate tectonics
