Glossary
Abiotic Fixation
The conversion of atmospheric nitrogen gas (N2) into usable forms through non-biological processes, such as lightning or industrial combustion.
Example:
A powerful lightning strike can cause Abiotic Fixation, converting atmospheric nitrogen into nitrates that fall to Earth with rain.
Assimilation
The process by which plants absorb usable forms of nitrogen (primarily nitrate) from the soil and incorporate them into their tissues to synthesize organic molecules like proteins and DNA.
Example:
After a rain, plants rapidly undergo Assimilation, drawing dissolved nitrates from the soil into their roots to fuel new growth.
Biotic Fixation
The conversion of atmospheric nitrogen gas (N2) into ammonia (NH3) by living organisms, primarily nitrogen-fixing bacteria.
Example:
Rhizobium bacteria living in the root nodules of clover are responsible for significant Biotic Fixation in agricultural fields.
Denitrification
The final step in the nitrogen cycle where specialized bacteria convert nitrate (NO3-) back into nitrogen gas (N2) and nitrous oxide (N2O), returning nitrogen to the atmosphere.
Example:
In waterlogged soils with low oxygen, Denitrification can occur, leading to the release of nitrogen gas from agricultural fields.
Eutrophication
The excessive richness of nutrients, especially nitrogen and phosphorus, in a body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.
Example:
Agricultural runoff containing excess fertilizers can cause Eutrophication in nearby lakes, leading to harmful algal blooms and fish kills.
Limiting Nutrient
A nutrient that is essential for growth but is available in lower quantities than other nutrients, thereby restricting the growth of an organism or population.
Example:
In many terrestrial ecosystems, phosphorus can be a limiting nutrient, meaning its scarcity restricts plant growth even if other nutrients are abundant.
Macronutrient
An essential nutrient that organisms need in relatively large amounts for proper growth and development.
Example:
Nitrogen is a crucial macronutrient for plants, enabling them to build proteins and DNA.
Mineralization (Ammonification)
The process where decomposers break down organic nitrogen from dead organisms and waste products, converting it back into inorganic ammonium (NH4+).
Example:
When a leaf falls and decomposes, fungi and bacteria perform Mineralization, releasing nitrogen back into the soil for other plants.
Nitrification
A two-step process where ammonia (NH3) or ammonium (NH4+) is converted into nitrite (NO2-) and then into nitrate (NO3-) by specialized bacteria.
Example:
In a healthy aquarium, beneficial bacteria perform Nitrification to convert fish waste into less toxic forms of nitrogen.
Nitrogen Cycle
The complex biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems.
Example:
Understanding the Nitrogen Cycle is vital for managing agricultural runoff and preventing water pollution.
Nitrogen Fixation
The process by which atmospheric nitrogen gas (N2), which is unusable by most organisms, is converted into usable forms like ammonia (NH3) or nitrate (NO3).
Example:
Legumes like soybeans have symbiotic bacteria in their roots that perform Nitrogen Fixation, enriching the soil naturally.
Reduced Species Richness
A decrease in the number of different species present in an ecosystem, often due to environmental disturbances or imbalances.
Example:
Excess nitrogen deposition can favor fast-growing, nitrogen-loving plants, leading to Reduced Species Richness as native, less competitive plants are outcompeted.