Nutrient Cycles. Nutrient requirements Biogeochemical cycles Rates of decomposition Plant adaptations in low nutrient conditions. Nutrient Requirements for Plant Growth. Taken up in gaseous form, Oxygen (O 2 ), Carbon CO 2 , and from roots - Water (H 2 O).
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The cycling of nutrients through ecosystems via food chains and food webs, including the exchange of nutrients between the biosphere and the hydrosphere, atmosphere and geosphere (e.g., soils and sediments)
Ecosystems produce and process energy primarily through the production and exchange of carbohydrates which depends on the carbon cycle.
When we look at other nutrients, a somewhat different picture emerges than with the energy cycle – e.g., phosphorous in a food chain within a small pond.
Example of changes in the amounts of tracer phosphorous being exchanged within an aquatic food web
Model of phosphorous cycle for an aquatic ecosystem – flux rates per day shown.
Three major categories of biogeochemical cycles based on slowest-changing pool(=reservoir):
Lightning + N2 + O2 NO + O2 Nitrate (NO3)
Phosphate – PO4-3
CO2 or CH4
CO2 versus CH4 production
CO2 or CH4
a material that decomposes
in a given year
Decomposition as a Function of Lignin Content
Coniferous forests have longer residence times than deciduous
Boreal forests have longer residence times than temperate forests
The answer is no –
NUE = A / L
A – the nutrient productivity (dry matter production per unit nutrient in the plant)
L – nutrient requirements per unit of plant biomass
A common pattern found in ecosystem productivity is saturation curve.
Productivity increases linearly with N availability, up to a certain point, when other resources become limiting (e.g., light, water, temperature, other nutrients)
Upper mineral soil
Lower mineral soil
Leaching, run off
Boreal forest has the largest available nutrient pool in soil, but lowest rates of production, where as tropical forest has lowest soil pool, and highest production.