Global Biochemical Cycles

Flashcards covering the phosphorus, sulphur, nitrogen, and carbon cycles, including human influences and anthropogenic disturbances. Also covers related vocabulary.

Biogeochemical cycle

• complex systems that involve the atmosphere, hydrosphere, geosphere through a series of inputs and outputs - Dahlgren, 2006 

• how nutrients are moved

Phosphorus Cycle

• Heavily increased since the agricultural revolution in the 1950s. - fertiliser

• The main source of phosphorus is the Bodele Depression, which deposits 50 million tonnes of dust loaded with phosphorus in South America per year.

• Filippelli, 2008

why is phosphorous important ?

• role in biological systems

• weathering relates more phosphorus

• Filippelli, 2008

Inputs of phosphorus

• rate of phospherous flow now 3x more than before agricultural and industrial revolution - Begon et al., 2021

• rapid uplift of Himalayan - Tibet Plateau - increased chemical weathering - more phosphorus in oceans - Filippelli, 2008

Outputs of phosphorus

• loss of phosphorus through leaching and runoff into water bodies, affecting aquatic ecosystems - Filippelli, 2008.

• rivers transports P to oceans - unaltered the oceans - Filippelli, 2008

• related during decomposition - Knoops et al., 2002

Impacts from phosphorus cycle

• freshwater eutrophication - from runoff and erosion

• marine dead zones

• loss of plant diversity

• P tends to stay in one place - excessive

• Filippelli, 2008

Sulphur Cycle

• Atmospheric sulphur is coming from smelting and fossil fuel combustion.

• Heavily connected to acidification of the ocean. Though volcanoes are a natural source, their emissions are tiny compared to human emissions.

• Changes in soil pH due to sulphur levels can drive massive changes in plant community composition.

• Begon et al., 2021

why is sulphur useful

• most organisms need a small amount

• high sulphur = major changes

• humans now use it for fuels to produce energy

• Begon et al., 2021

Sulphur inputs

• originated from burning coal + volcanoes

• Begon et al., 2021

Sulphur outputs

• occurs as acid rain

• Begon et al., 2014

impacts from sulphur

• freshwater acidification

• forest dieback

• loss of plant diversity

• reduced sulphur emissions have led to an increase in PH

• Higher PH = lower plant diversity

• Begon et al., 2021

Nitrogen Cycle

• The most active cycle, with most nitrogen coming from fertilizers.

• Human nitrogen fixation is twice as much as natural fixation.

• Fowler et al., 2021

Why is nitrogen important

Nitrogen inputs

• elevation and topography have an impact on soil characteristics - affects nitrogen cycling - Bohlen et al., 2001

• Acacia invasions influence nitrogen cycling - Knoops et al., 2002

• herbivores slow down nitrogen cycling by eating plants - Knoops et al., 2002\

• Fixation - N enters the soil

• Fowler et al., 2013

Nitrogen outputs

• Denitrification - nitrogen leaves as nitrogen oxide

• Ammonification - debris proteins get broken and metabolised to ammonium

• Nitrification - ammoinia —> nitrogen dioxide —> Nitrate

• Fowler et al., 2013

Nitrogen stores

• in biomes - wetlands and soils that are waterlogged - Begon et al., 2021

• higher litter fall of nitrogen may increase nutrient cycling

• Most nitrogen in decomposition not released - in soil - Knoops et al., 2002

• Forests 70% of terrestrial nitrogen - Townsend et al., 2011

• Geologic nitrogen store - 20% - Dahlgren, 2006

Nitrogen impacts

• ocean dead zones with loss of biotic diversity

• stream and lake eutrophication - agal blooms

• nitrogen deposition that changes community deposition

• toxic nitric oxide compounds in atmosphere with carcinogenic effects

• Fowler et al., 2013

Nitrogen deposition changes biotic communities

• N deposits soil PH increases affecting plant community diversity and composition

• Field et al., 2014

Carbon Cycle

• When productivity is higher than respiration, an ecosystem acts as a carbon sink.

• Increased CO2 in the atmosphere can lead to CO2 fertilization, allowing plants to grow more.

• Mycorrhizal fungi provide nitrogen and phosphorus to plants. The growing season is becoming earlier each year, allowing plants to store more carbon.

• Luyssaert et al., 2008

Why is carbon important

• for plant growth - photosynthesis - Huggett, 2004

carbon inputs

• higher plant diversity - increases C input - Lange et al., 2015

• concentration increase due to burning of fossil fuels ( combustion) - Begon et al., 2021

• deforestation - Begon et al., 2021

• terrestrial ecosystems as carbon sinks

• Land abandonment increases carbon sequestration

• forests grow —> primary productivity exceeds ecosystem respiration

• respiration may = primary productivity

• poorter et al., 2016

carbon outputs

• warm ocean water releases C, cold absorbs it - Begon et al., 2021

Carbon storage

• soils store most of it - Lange et al., 2015

• C soluble in water - Begon et al., 2021

• warming temperatures increase C storage - Keenan et al., 2014

• sink dynamics affect C storage more N or P = higher primary productivity = more Caron storage

• Old growth forests accumulate C

• Luyssaert et al., 2008

Carbon impacts

• co2 has fertilising effect

• higher concentration - increases rates of primary productivity

• response varies in magnitude

• Terrer et al., 2016

• more C02 = warmer temperatures - Keenan et al., 2014

Water and nutrient cycling

• water solvent - transport agent

• nutrient cycling large impacts on lake productivity

• lake metamophic features reduce nutrient losses

• streams - cycling - controlled by the ability of particulates to sequester nutrients + dissolved nutrients to travel downstream

• lakes - controlled by processes of remineralisation from particulates

• Essignton and Carpenter, 2000

Eutrophication

• Excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land

• causes a dense growth of plant life and death of animal life from lack of oxygen.

• fowler et al., 2013

Mycorrhizal fungi

• help plants grow

• terrer et al., 2016