nitrogen and phosphorus cycling

nitrogen is a key component of

amino acid and nucleic acids, making it a building block for both proteins and DNA in all living organisms

most of our atmosphere is made up of what

nitrogen gas, N2

why is nitrogen often a limiting resource

nitrogen must be fixed in order to be accessible to primary producers

what does nitrogen fixation consist of

atmospheric N2 been converted to ammonium (NH4+) or nitrate (NO3-), which is then dissolved in water and taken up through plant roots

nitrogen fixation occurs through 

• bacteria and cyanobacteria

• lightening strikes (N2 atoms split apart) 

  • fertilizer production 

what are root nodules

growths on the roots of some plants, such s bean and peas

what is the importance of root nodules

they can host Rhizobium bacteria that can convert atmospheric nitrogen to ammonium which can be used by the plant to build nucleic and amino acids

since plant cannot convert N2 to NH4+ themselves, the relationship between plants and rhizobium bacteria is

mutualistic

what is mineralization

the process by which microbes decompose organic N from manure, organic matter to ammonium (which is then often converted to nitrate, absorbed in water and taken up through plant roots- know as nitrification)

what does the rate of mineralization and nitrification depend on

soil temperature

t/F phosphorus is found in every living plant cell

true

what is phosphorus involved in

several key plant functions, including energy transfer and nutrient movement within the plant

why is the atmosphere not an important part of the phosphorus cycle

phosphorus does not have a gaseous phase

how does phosphorus enter the food web

through rock weathering (rocks breaking down)

following rock weathering, what happens to the phosphorus particles

they are dissolved in water and absorbed through plant roots

what are the two major limiting nutrients for net primary productivity in terrestrial environments

nitrogen and phosphorus

at high latitudes terrestrial land is highly what

nitrogen limited `

at lower latitudes terrestrial land is highly what

phosphorus limited

why has soils near the tropics been weathering for a long time

because they were not covered by ice during the last ice age

do tropical soils hold nutrients well

no

what is leibig’s law of the minimum

an organism’s growth is not determined by total nutrients available, but rather by the scarcest nutrients (i.e. the limiting factor)