Biogeochemical cycles: Cycling of energy and elements essential for plant and animal growth

Reservoirs are where elements are held in quantities for periods of time
Exchange pool is a part of a nutrient cycle where element is held for a period of time
Residence time is how long an element is held in a or pool
Energy for nutrient cycles provided by either energy or force, are the only extra-terrestrial sources of elements.

Bioremediation is using microbes to soils by degrading organic or changing toe of a pollutant.

Soil organic matter is a complex mixture of both plant and animal at various stages of . It contains root and soil .
% of soil is solid made up of minerals, % air, % water and % living organisms. Water, air and organisms make up space.

Soil pores and law: pores that have a diameter than a critical value will be filled with at a given water .

Soil is strongly influenced by presence of water, root and soil . Oxygen diffuses times slower in than air in soil. Types of soil organisms present depends on soil .

Soil organic and soil activity have a role in soil . Specific produced by soil microbes promote . Example: Fungi produce which coats preventing loss of water and . Soil aggregation has a key role in microbial and organic matter and turn over

Occurrence and distribution of microbes in soil:

Bacteria and algae are considered as they require and nutrients to be in water for their nutrition. Bacteria prefer to live in pores only slightly than them for protection against and predation. Bacteria can be free living or attached to the surface of . When attached they may be cells, micro- or bio-.

Less than % of available pore space is occupied by microbes. of pore is determined by size. occupy the same size and larger pores as bacteria, with extending through pores. Soil microhabitats are not always .

In clay soil % and in sandy soil % of pores inaccessible to microbes due to size being smaller than microns. Large pores of microns are filled with . There is a limited of oxygen, nutrients and and less protection from . Water content and Oxygen diffusion affects .

Pore size also affects the ability of microbes to around and their ability to on soil which then affects the transfer of bacterial to other levels.

The interior if aggregates is and colonised by anaerobic bacteria while aerobic bacteria colonise the of aggregates. Microbe numbers as depth of soil increases. Different groups of microbes are found at different of soil.

Rhizosphere

Soil region under immediate influence of . Rhizosphere include amino acids, organic acids, sugars, vitamins, and proteins and the rhizosphere and roots from pathogen . The exudates also attract microbes, retains , obtains and stabilises . Rhizosphere has a high microbe population and is from soil.

Water and root affects soil levels and microbial . Rhizodeposits are used as a source by soil microbes. Release of my microbes modifies soil , and secretion or uptake of modifies nutrient availability

cycle is the driving force behind other nutrient cycles and are critical to the cycle.

of carbon can be physically or chemically , but or transfer between reservoirs can occur.

Carbon reservoir in the warms the planet due to fossil fuel and cement . Terrestrial and ocean mitigate some of the CO2 in the atmosphere.

The temperature of Earth is much colder than the sun. The infra red radiation emitted by the sun has a wavelength, and a wavelength when emitted by earth. Some interact with earth's wavelength and vibrate.

Silicate-Carbonate cycle:

rocks + soil or organic acids form rocks and oceans. the plant and forms and fossil fuels.
is fixed by photosynthesis and the of organic matter

Mineral weathering: of rocks, soil or minerals
Plants accelerate mineral weather process by secreting acids. Warm temperatures also promote weathering, formation and growth if nit inhibited by or nutrient availability.

Burial of Organic Matter: During periods with rainfall accumulates in poorly areas creating soils dominated by vegetation. In conditions large amounts of organic form which become under mineral sediments during periods when occurs.

Photosynthesis carbon and respiration carbon. Energy sourced from is transferred through the . On land photosynthesis mainly by plants and by and algae in the ocean. The ocean is largely unproductive for carbon fixation due to limitations, especially . Less than of solar energy is used during photosynthesis.

Oxic respiration: Sugar is the carbon and energy source and is oxidised by

Anoxic respiration: Sugar is the carbon and energy source but is oxidised by -,4+, 3+ or 2-

Methanogenesis: CO2 or CH3COOH oxidises H2 to form under conditions

Photosynthesis: CO2 oxidised by O2 in presence of light to form

Methanotrophs: Bacteria and archaea that consume and live oxic and anoxic environments where both and methane are present. Their contribution to the carbon cycle is due to their environment.

Decomposition of organic

Most litter compounds are too for microbes to digest, some are digested by released by microbes. Some biomass of detritus is .

During decomposition Carbon is lost as and organic matter becomes . Not all carbon is lost, some is retained in the and protected by both and chemical barriers.

Starch is a polymer of and is hydrolysed by . Most organisms can digest starch.

Cellulose is a polymer of and is energy. It is surrounded by chains of and forms cell . Digestion by enzyme. Few organisms can digest cellulose, only those with symbionts. Hemicellulose is to digest. Microbes must use to produce free radicles to digest to reach cellulose and hemicellulose. Oxidation releases .

surrounds cellulose and hemicellulose. It is a structure that is hard to . Usually only decomposed by that use free radicles. Brown rot and soft rot fungi digest the associated with lignin, but rot fungi digests lignin completely and associated polysaccharides, not digested.

Protein digested via enzymes and fat by . Fat is harder to digest as it is so decomposition is .

Physical protection of organic matter

Pore spaces are not so organic matter is not always accessible to . Degradation requires between the substrate and microbe. Pores which contain organic matter may have a size too small for microbes , such as soil, and microbes only occupy a proportion of soil volume and are distributed.

very hard to digest as composed of benzene which is very high energy, requires .

Interaction of organic compounds with and ions decreases their , such as in volcanic soils, they have a composition of organic matter.

In clay soil, oxides precipitate on clay molecules the surface area and organic matter attaches to the iron oxide . Soil in compounds with a surface area have more organic matter, and microbes require energy to digest the organic matter.

Organic matter is . The hydrophobic region faces the , and the exposed hydrophilic region attracts , which attracts more of the mineral.

Properties of organic matter in soil

Binds soil particles to form , reduces , increases holding capacity and increases .

Required for cycles, retains , buffers soil and filters .

Organic matter provides a source of and energy to soil microbes, to plants, inactivates some and enhances degradation of pesticide .