Greenhouse gas emission from soil Flashcards
Who is aiming for carbon neutrality?
Political agendas of individual countries and international initiatives
What year is the aim for carbon neutrality?
2050
How much carbon and nitrogen is stored in the soil? And which part?
1500 Pg of total carbon and 137Pg of total nitrogen in the uppermost meter of the global soil layer
What percentage of root respiration contributes towards total soil respiration?
Around 50%
How is methane produced in soil?
It is produced by methanogenesis under anaerobic conditions and is consumed by methanotrophic microorganisms that use oxygen and methane for their metabolism under aerobic conditions
What drives the release of Nitrous oxide and nitric oxide?
Nitrification and denitrification
What is nitrification?
Oxidation of ammonium (NH4+) to Nitrate (NO3-) via Nitrogen Dioxide (NO2-)
What is denitrification?
Reduction of Nitrate to Nitrogen Dioxide and dinitrogen
What 4 methods release greenhouse gases into the soil?
Microbial Activity.
Root Respiration.
Chemical Decay.
Heterotrophic Respiration.
What 6 things do emission flux rates depend on?
Soil water content, soil temperature, nutrient availability, distribution grain size, air pressure and pH-value
What does soil humidity control?
Microbial activity
What gases does not emit under low water conditions?
NitrIC oxide (NO) Methane (CH4)
When do Nitric Oxide (NO) emissions decrease in soils?
When soils have below 10% water-filled space due to inhibited nutrient supply
What conditions do Methane and nitrous oxide require?
Anaerobic conditions
What is anaerobic?
Without oxygen
What is Aerobic?
With oxygen
What gas produces well in fairly high water-filled space?
Nitrous oxide (N2O-)
When is N2O production optimal?
Around 60% Water filled pore space
When is N2O production lowest?
When water filled pore space is below 30%
What can significantly reduce soil emission?
Long periods of drought
What soil property can influence soil moisture?
Grain-size distribution. Soil with larger pools retain less water and therefore reduce emissions
What gas do coarse soil textures emit best?
NO (Nitric oxide)
What soils have larger NO emissions?
Coarse soil textures
What do soils with fine pores support?
The formation of CH4 and N2O produced under anaerobic conditions. CO2 emissions were encountered with fine soil textures
How does temperature affect emissions?
Higher temperature leads to higher emissions and higher respiration rates
What lack of gas can influence methane and nitrous oxide production?
Decreased O2 concentration
What does site exposure influence?
Increased temperature and moisture content
How does air pressure affect soil emissions? Why?
Lower air pressure supports higher soil emissions due to reduced counter pressure on the soil
What area shows lower CO2 and N2O fluxes?
Burned areas for around 1 month as root respiration is reduced in the absence of plant cover
What pH level results in lower soil emissions?
Acidic soils
What pH value does CO2 emit highest at?
A neutral pH value
What pH value does N2O emission decrease at?
At acidic pH levels
What is the optimal pH level for methanogenesis?
Between 4 and 7
