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)
Key Elements of Biogeochemical Cycles picture emerges than with the energy cycle – e.g., phosphorous in a food chain within a small pond.
Three major categories of biogeochemical cycles based on slowest-changing pool(=reservoir):
Sedimentary Cycles rates per day shown.
Major Components of Nitrogen Cycle rates per day shown.
Root nodules on ? rates per day shown.Cassia fasciculata
NO from lightning rates per day shown.
Lightning + N2 + O2 NO + O2 Nitrate (NO3)
Phosphorous Cycle rates per day shown.
Phosphate – PO4-3
Potassium rates per day shown.
Sources of Nutrients rates per day shown.
CO2 or CH4
CO2 versus CH4 production
CO2 or CH4
k is the microbial respirationfraction of
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)
H nutrients:2O - Precipitation
Upper mineral soil
Lower mineral soil
Leaching, run off
Forest Type nutrients:
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.