Nutrient Cycling Notes

Nutrient Cycling

Nutrient cycling is a vital aspect of understanding how ecosystems function.

Nutrients and Matter

• Nutrients are a form of matter, possessing mass and occupying space.

• Nutrients differ from energy; they flow through ecosystems following matter flow principles, not energy flow.

• Tracing the movement of nutrients (matter) between biotic (living) and abiotic (non-living) components is central to understanding nutrient cycling.

• Matter is anything that has mass and takes up space.

Matter Flow vs. Energy Flow

• Matter flow is cyclical, unlike energy flow, which is one-way due to the second law of thermodynamics.

• Matter flow follows cycles, moving through different forms and locations.

Law of Conservation of Matter

• Matter is neither created nor destroyed; it transforms and moves within a closed system (like Earth).

• The total amount of matter on Earth remains constant; it only changes in form as it cycles through the environment.

Definition of Nutrients

• A nutrient is any substance required by a living organism to sustain life.

• Examples include oxygen and water.

• The ecological definition of nutrients differs from the dietary context.

Essential Nutrients and Biogeochemical Cycles

• Essential nutrients are those necessary for life and are cycled through biogeochemical processes or cycles.

• Biogeochemical Breakdown:

  • Bio refers to life, indicating that nutrients are found in living organisms (biosphere). Examples: water in animals and plants, oxygen in plants and animals.

  • Geo refers to geological components like rocks, soil, water, and the atmosphere (abiotic structures of Earth).

  • Chemical indicates that nutrients undergo chemical reactions as they move between living organisms and the environment. Examples: oxygen in the air, water vapor in clouds, water in soil/oceans.

• Biogeochemical cycles involve nutrients cycling through both biotic and abiotic components of ecosystems.

Processes Common to All Nutrient Cycles

Nutrient cycles, whether for water, carbon, nitrogen, or other essential nutrients, share common processes.

Absorption by Roots

• Plant roots absorb nutrients from the soil, acting as the crucial interface between the abiotic (soil) and biotic (plants) components.

Assimilation

• Assimilation occurs when a living organism incorporates a nutrient into its body to build its structures. Plant roots absorb nutrients and use materials to build leaves, flowers, fruit, and so on

• Plants absorb nutrients through their roots and assimilate them to build new tissues and structures (leaves, stems, etc.).

• Animals also assimilate nutrients to build their bodies. For example, when a cow eats grass, it uses the nutrients to build muscle, store fat, and develop bones.

Consumption

• Consumption is the process by which nutrients move from one living organism to another. An animal eating a plant passes nutrients into the animal, moving the nutrients from living thing to living thing.

• Nutrients transfer from plants to animals when animals consume plants (e.g., deer eating plants).

• Nutrients can also move from animal to animal when a predator consumes prey.

• Consumption is how nutrients are transferred into the body - by eating plants and animals.

Decomposition

• Decomposition returns nutrients from dead organisms (plants and animals) back into the environment.

• When a tree dies, decomposition releases carbon and nitrogen back into the soil.

• Decomposition is essential for cycling nutrients, regardless of the specific nutrient (nitrogen, phosphorus, etc.).

The Water Cycle

The water cycle demonstrates all the universal processes.

Unique Vocabulary

Key processes include:

• Precipitation: Water falling from the atmosphere to the Earth in the form of rain, snow, sleet, or hail.

• Runoff: Water flowing over the land surface.

• Groundwater: Water located beneath the Earth's surface in soil and rock formations.

• Infiltration: The process by which water seeps into the soil and becomes groundwater.

• Transpiration: The process by which plants release water vapor into the atmosphere through their leaves.

• Evaporation: The process by which water changes from a liquid to a gas and enters the atmosphere.

Reservoirs/Sinks

• Reservoirs or sinks are locations where nutrients accumulate or are stored for extended periods.

• Water reservoirs include glaciers, oceans, lakes, and groundwater.

Processes

• Evaporation: Transformation of liquid water into water vapor, entering the atmosphere.

• Condensation: Water vapor in the atmosphere turns into liquid water.

• Precipitation: Condensed water falls back to Earth (rain, snow, etc.).

• Infiltration: Water seeps into the ground, replenishing groundwater.

• Runoff: Water flows across the land surface into bodies of water.

• Transpiration: Water loss from plants during photosynthesis.

The Carbon Cycle

The carbon cycle includes all the universal processes.

Unique Processes

• Photosynthesis: A vital process in the carbon cycle in which plants absorb carbon dioxide and assimilate that carbon in their structures.

• Respiration: Another key process to the carbon cycle where living things release carbon dioxide back into the atmosphere.

Reservoirs/Sinks

• Oceans: Absorb and store significant amounts of carbon.

• Living things: Organisms store carbon throughout their lives.

• Fossil fuels: Coal, oil, and natural gas are significant carbon reservoirs.

Processes

• Carbon dioxide ($CO_2$) in the atmosphere.

• Photosynthesis: Plants absorb $CO_2$ to create energy and store carbon.

• Respiration: Living organisms release $CO_2$ back into the atmosphere.

• Fossil Fuels - compacted, fossilized carbon that remains, used for fuel

Fossil Fuels Detail

• Fossil fuels are formed from the fossilized remains of plant matter over millions of years.

• Burning fossil fuels (coal, oil, natural gas) releases stored carbon back into the atmosphere as $CO_2$.

• Coal is used for electricity, oil for gasoline, and natural gas for heating.

• Burning fossil fuels increases atmospheric $CO_2$ levels.

The Nitrogen Cycle

Nitrogen cycle involves the same universal processes as carbon and water cycles.

Unique Processes

• Nitrogen fixation: The process of converting nitrogen in the atmosphere into forms usable by plants.

• Denitrification: The process of converting nitrates in the soil back into atmospheric nitrogen. Bacteria is very important in these processes.

Reservoirs/Sinks

• Atmosphere: The primary reservoir of nitrogen.

• Soil: Contains nitrogen compounds.

• Living things: Plants and animals contain nitrogen.

• Water: Bodies of water can store nitrogen compounds.

Processes

• Nitrogen fixation converts atmospheric nitrogen to ammonia.

• Bacteria are involved in both nitrogen fixation and denitrification processes.

• Denitrification returns nitrogen to the atmosphere.

The Phosphorus Cycle

Phosphorus cycle features same universal processes as other nutrient cycles.

Unique Aspects

• The phosphorus cycle does not include the atmosphere. Phosphorus is not part of the atmosphere.

• Cycling from rocks to soil and back to rocks.

Reservoirs/Sinks

• Rocks: The primary reservoir, where phosphorus can remain for millions of years.

• Living things: Store phosphorus during their lifetime.

• Soil: Contains phosphorus compounds available to plants.

• Water: Can store phosphorus, but to a lesser extent.

Processes

• Phosphorus is released from rocks through weathering. Weathering involves breaking rocks part further and further until the rock becomes smaller and smaller pieces until it becomes soil.

• Plants absorb phosphorus from the soil.

• Sedimentation compacts soil layers into rock, trapping phosphorus.

Nutrient cycling is a vital aspect of understanding how ecosystems function. Nutrients are a form of matter, possessing mass and occupying space, and they flow through ecosystems following matter flow principles, unlike energy flow which is one-way due to the second law of thermodynamics. Tracing the movement of nutrients between biotic (living) and abiotic (non-living) components is central to understanding nutrient cycling. Nutrient cycling is essential for maintaining ecosystem health, as it involves processes such as absorption by roots, assimilation, consumption, and decomposition, allowing for the transfer and transformation of nutrients within ecosystems.

• Nutrients: Substances required by living organisms to sustain life. Examples include oxygen, water, carbon, nitrogen, and phosphorus.

• Biogeochemical Cycles: Processes that describe the cycling of nutrients through both biotic (living) and abiotic (non-living) components of ecosystems.

• Decomposition: Process through which dead organisms are broken down, returning nutrients to the environment.

• Photosynthesis: Process by which plants convert carbon dioxide into organic compounds using sunlight, playing a critical role in the carbon cycle.

• Respiration: Process where living organisms release carbon dioxide back into the atmosphere.

• Nitrogen Fixation: Conversion of atmospheric nitrogen into forms usable by plants, essential for the nitrogen cycle.

• Denitrification: Process of converting nitrates in soil back into atmospheric nitrogen.

• Weathering: The breaking down of rocks, releasing nutrients into the soil.

• Infiltration: The process by which water seeps into the soil, contributing to groundwater.

• Evaporation: Transformation of liquid water into vapor, part of the water cycle.

• Transpiration: Release of water vapor from plants into the atmosphere.

• Carbon Dioxide (CO₂): A key component of the carbon cycle, absorbed by plants and released by animals.

• Reservoirs/Sinks: Locations where nutrients accumulate or are stored for long periods (e.g., oceans, soil, rocks).

• Assimilation: The incorporation of nutrients into living organisms' bodies to build structures and perform functions.