Lab 7: Soil Respiration and the Carbon Cycle Flashcards
What are the three main steps that carbon goes through in the carbon cycle?
Assimilation, stored and respired
What happens during the assimilation phase of the carbon cycle?
CO2 is assimilated by plants during the process of photosynthesis, and is converted to organic compounds such as simple sugars (glucose) or complex carbohydrates (cellulose and lignin)
What happens during the storage phase of the carbon cycle?
Carbon is stored in these plant structures until it is respired
What happens during respiration step of the carbon cycle?
These simple sugars and complex carbs are broken down, when plants die/ are eaten/decompose, into CO2 and H2O which releases CO2 back into the atmosphere and water
What are the 4 major reservoirs of carbon in the world?
Rock
Ocean
Atmosphere
All life
Was the atmospheric carbon content higher in the Paleozoic or now? What does this mean for the climate back then?
It was much higher in the Paleozoic, and because it acts as an insulating barrier and traps solar heat in the atmosphere this means that temperatures were much higher all over earth
As plants evolved this CO2 decreased and increased in oxygen levels
What effect did the industrial revolution have on atmospheric CO2?
Dramatically increased it due to burning coal, wood, oil, gas at a high rate to support the growing demand for energy
Where is the rate of warming the greatest?
Greatest in the arctic regions, and therefore the arctic permafrost is thawing at a high rate. This releases more carbon back into the atmosphere as it released trapped methane gas, and previously frozen soil is accessible to decomposers
What is soil respiration? What are its three steps?
The use of oxygen or the release of carbon dioxide by living organisms in the soil. Primary means in which CO2 is returned to the atmosphere, and occurs when microorganisms decompose detritus, especially leaf litter
1. Leaching of water-soluble minerals and simple sugars, such as glucose, from the material
2. Fragmentation of the litter into smaller pieces by mechanical or biological means
3. Mineralization, the conversion of large organic compounds to smaller and simpler forms
What are 4 factors that effect the rate of soil respiration?
Temperature (increase in temp results in increase in metabolism of microbes)
Oxygen (direct effect, increase and increase)
Water availability (more water leads to faster respiration
Composition of decomposing mattter
How does composition of leaf litter affect the rate of soil respiration?
Simple sugars such as glucose are small and soluble in water therefore are quickly lost by leaching or consumed by microbes
Cellulose is a big/complex carb that is hard to decompose and requires specific enzymes to break the chemical bonds to microbes can metabolize it, and breakdown occurs extracellularly
Lignin is even larger and more complex and in woody plants, usually only broken down by fungi in extracellular decomp, and slows it down
Why does C:N ratio matter for soil respiration?
Low C:N ratio are higher in nutrients and softer, therefore decompose faster
High C:N ratio means that they are tough and hard to break down
