N O Flashcards
Negative feedback
When new data produce a result in the opposite direction to previous results they are negative feedback, their effects stabilise the system. Neg fb halls to maintain stability in spite of external changes.
Net primary production NPP
The amount of carbon fixed by PS - respiration by the plant
Net ecosystem production NEP
The difference between total energy inputs and total energy outputs is the amount of energy stored in an ecosystem in the form of DOM in soil or sediments, or in living organisms.
Nitrification
The process in which ammonia or ammonium compounds are oxidised to nitrate and nitrite, yielding energy for decomposer organisms. Two groups of microorganisms are involved in Nitrification, nitrosomonas (oxidises ammonia to nitrate and water) and nitrobactor (oxidises nitrite ions to nitrate).
Nitrogen fixation
The conversion of gaseous nitrogen into ammonia or ammonium compounds, either through abiotic means such as lightening or biotic means, such as symbiotic and free living bacteria.
Nitrogenase
Enzymes involved in reactions leading to the formation of ammonium compounds from dinitrogen gas, as occurs in nitrogen fixation.
Non-equilibrium process
A mechanism of population regeneration in which population size is determined by stochastic events and not the availability of resources, competition or predation.
Numerical instability
Unrealistic, unstable behaviour in a computer model.
Nutrient limitation
Concept following liebigs law of the minimum, the main implications of which are that one key nutrient should be the primary limiting factor got plant growth in a given ecosystem, the growth of plants in a living ecosystem should be proportional to the rate of supply of this nutrient and that the control of eutrophication should be accomplished by restricting the loading of this key nutrient to the ecosystem.
Ocean-atmosphere General circulation models OAGCMs
A model of large scale atmosphere or ocean flow, often assumed to be complex and of high resolution.
Oligotrophic
A body of water with low nutrient inputs.
Open systems
Systems are are open to exchanges of materials and/or energy exchanges with other systems.
