Nutrient cycling

Nitrogen-fixing organisms convert atmospheric nitrogen into ammonia and ammonium (forms of nitrogen that plants can utilize).

Some are free living (soil and water), while others form symbiotic relationships with plants (Root nodules in legumes) 

Nitrogen fixers are fungi, bacteria or cyanobacteria.

Rhizobium

• 1- Spend nrg to break N2 bonds
• 2- nitrogenase (enzyme in N fixers) reduces N2 to ammonia (NH3)
• 3- N further reduced to ammonium (NH4), plants can now use

Plants and microorganisms convert fixed N (inorganic) into organic compounds.

process by which nutrients are converted from inorganic to organic forms.

opposite of mineralization.

process by which nutrients are converted from organic to inorganic forms.

 decomposition as microbes break down dead and decaying organic matter.

opposite of immobilization.

The ratio of carbon to nitrogen

indicator of litter quality and soil fertility.

The lower the ratio (higher proportion of nitrogen), the higher the litter quality and the more fertile the soil

low ratio: quicker decomposition of litter (releases N quicker)

process in the nitrogen cycle in which microorganisms convert ammonium into nitrates and nitrites.

most commonly performed by free-living bacteria.

Done bc it makes nitrogen more usable to broader range of plants (more soluable)

process in the nitrogen cycle in which denitrifying bacteria convert nitrates and nitrites back into gaseous forms of nitrogen such as nitric and nitrous oxides.

Convert what plants don't use back into gas

an atom of a nutrient travels through a cycle, but is displaced downstream by the current as it goes. The faster the current, the more elongated the spiral.

pH of 4.5 or lower

caused by the release of acid-forming gases, primarily sulfur dioxide (SO2) and nitrous oxides (NOx).

acidification of water habitats 

initial harm to standing trees, effects forest nutrient cycling over time

exists in sediments and mineral deposits.

Weathering slowly releases phosphorus to terrestrial and aquatic ecosystems. Since rock weathering is a slow process, most undisturbed terrestrial ecosystems are normally phosphorus-limited.

>99% of Earth's carbon = rocks, particularly limestone, and cycles very slowly.

major fluxes of carbon involve less than 1% of the total. most involve CO2.

• Phosphorus is an integral part of energetics (ATP),
• genetics (RNA and DNA) and cellular structures (cell membranes)

key element in amino acids, which form structural proteins and enzymes.

forms nucleic acids and the porphyrin rings of chlorophyll and hemoglobin

CyanoBacteria - Blue-green alga -freshwater, marine, soil

Free-living soil bacteria

bacteria associated w/legume roots (Rhizobium most common)

Acinomycetes fungi associ8d with roots of some plants

occurs in anoxic environments

N acts as electron acceptor and is reduced to N2

May be one of primary reasons N is limiting in Marine systems

Hydrolysis of Protein and Oxidation of amino acids produces ammonia. 

we all do this

• found in all organic molecules including sugars,
• proteins, nucleic acids, etc.

atmospheric CO2

Largest source = oceans

Large stores in fossil fuels and carbonate rocks, but not actively cycled

• 1- plants bring it in w/photosynth
•  and in aquatic systems, it readily combines with carbonate ions = calcium carbonate.(shells)

2) plants take up about as much as is put back with respiration of plants and animals