Environmental Engineering Reference
In-Depth Information
addition to light and heat energy from the sun. Two types of nutrient cycle provide the
many nutrients necessary to plants. Gaseous cycles provide carbon, oxygen, nitrogen
and sulphur to the biosphere through fixation. Sedimentary cycles provide elements
such as potassium, phosphorus and calcium through the weathering of rock minerals.
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Living plant material (biomass) and dead organic matter (litter and humus) contain a
great reservoir of nutrients. This reservoir is released through decomposition by
micro-organisms. Individual species (e.g. coniferous trees) and ecosystems (e.g.
tropical rain forests) have evolved many mechanisms for cycling nutrients efficiently,
with a minimum of loss from the system. The efficiency of nutrient cycling is perhaps
the hallmark of climax vegetation. Understanding of nutrient cycles is vital in the
management of renewable resources such as agriculture, forestry and water systems.
