4.3 ~ Carbon cycling

Peat formation

Peat formation

1. Forms when organism matter is not fully decomposed because of acid and/or anaerobic conditions in waterlogged soil

2. Dead organic matter is usually broken down by saprotrophic bacteria and fungi

3. Acidic conditions tend to develop in waterlogged soil, which further inhibits saprotrophs and methanogenic bacteria that would breakdown the organic matter

4. Over time, large quantities of partially decomposed organic matter accumulates and compresses into a dark brown acidic substance called peat

5. Around 3% of the earth’s surface is covered in peat

Reservoires

• A pool or store of an element

• With C, it can be in an inorganic form, or it can be organic, such as the biomass of the autotrophs

  • Not static entities

• When C moves from one reservoir or sink to another, it is called a flux

Flux

• The process that moves an element from one reservoir or sink to another

• Through a process that moves the carbon from one reservoir to another

  • E.g. the conversation of atmospheric CO2 into glucose and other carbon compounds by autotrophs

  • E.g. photosynthesis turning inorganic C into organic biomass

    • Sink in this example is the autotroph because now the C is locked up in the organism itself

Sinks

• One of the largest carbon sinks is the earth’s crust or lithosphere, where C is found as sedimentary rocks and fossil fuels

• Other C sinks include the biota (living organisms), the hydrosphere (aquatic environment), and the atmosphere (as CO2)

  • Much of the C on earth is in flux, meaning that it is in movement from one sink to another

Lithosphere

The portion of the earth that consists of the crust and upper mantle

Hydrosphere

The portion of the earth that consists of water including oceans, lakes, ponds, and rivers

Biota

the portion of the earth that consists of the living organisms

Atmosphere

The layer of gases surrounding the earth

Fluctuation of carbon

• Atmospheric carbon is bound to keep increasing over the years as humans continue to burn fossil fuels with a high amount of uncertainty

  • Impossible to measure the exact amount of C at each flux and sink; estimated with a high amount of high uncertainty

• Certain factors will alter the C flow per year

  • Maybe due to human activity such as deforestation or an increase in the burning of fossil fuels

• May be natural, such as in the case of volcanic activity

  • C in the atmosphere can also change with the seasons when there is more CO2 in the atmosphere during winter months (in northern hemisphere) because there is less photosynthesis

• C can also change as ecosystems grow and develop into climax communities

Environmental

• Strong link between the concentration of certain gases and the climate

  • Two of these gases, CO2 and CH4 have had a major impact on the average global temperature which, in turn, has led to climate change

• Strong correlation has been established between the atmosphere CO2 conc- and the avg. global temperature

  • Atmospheric CO2 had been steadily increasing since the beginning of the Industrial Revolution in the 19th century

  • At the same time, atmospheric CO2 was around 300 ppm (now stands at around 400 ppm)

Fluctuation due to seasons

• A closer look at the CO2 fluctuations within each years shows that it varies with the seasons

• CO2 is a raw material for photosynthesis, and thus the level of atmosphere CO2 decreases as there is an increase in the rate of photosynthesis in summer

  • During spring, trees and other autotrophs tend to grow and increase their foliage, which is where photosynthesis takes place

  • In winter, the rate of photosynthesis is much lower due to lower temperatures and shorter days with less light; therefore an increase in atmospheric CO2 is recorded

Human activity and fluctuation

• Increased concentration of CO2 and methane due to an increase in fossil fuel combustion and an increase in livestock farms

  • Both are strong contributors to the greenhouse effect

• Because of this connection and the possible negative effects on the climate, it is important to have accurate reliable data

• Several research stations have been established to measure atmospheric gases

  • One of the best known with a long record is the Maura loa observatory in Hawaii