Decomposition and Nutrient Cycling Flashcards

Vocabulary flashcards covering key concepts, processes, and organism classifications in decomposition and nutrient cycling based on lecture notes.

Liebig's Law of the Minimum

The ecological principle stating that plant growth is limited by the essential nutrient available in the smallest amount relative to its requirement.

Retranslocation

The internal recycling of nutrients within a plant prior to leaf senescence, calculated as the difference between green leaf and senescent leaf nitrogen content expressed as a percentage of green leaf nitrogen content.

Decomposition

The breakdown of chemical bonds formed when organic molecules and tissues are built, releasing energy, carbon dioxide, and water while converting organic compounds into mineral nutrients.

Microfauna and Microflora

Decomposer organisms with a body width less than $100\,\mu m$, including soil protists and nematodes living in water within soil pores.

Mesofauna

Soil invertebrate decomposers with a body width ranging between $100\,\mu m$ and $2\,mm$, such as mites and springtails.

Macrofauna

Invertebrate decomposers with a body width ranging between $2\,mm$ and $20\,mm$, including millipedes and earthworms.

Megafauna

Invertebrate decomposers with a body width greater than $20\,mm$.

Trametes versicolor

A species of white-rot fungus commonly known as Turkey tail.

Fomitopsis pinicola

A species of brown-rot fungus commonly known as Red-belt conk.

Microbivores

Organisms that feed on bacteria and fungi, including protists, springtails, nematodes, beetle larvae, and mites.

Litterbag

A synthetic mesh bag with $1\text{--}2\,mm$ holes used in field experiments to examine plant litter decomposition rates while allowing decomposer entry.

Leaf packs

Areas of active deposition and accumulation of leaf litter in stream ecosystems, often replicated with mesh bags in research to measure aquatic decomposition.

Lignin

A complex plant cell wall component composed of large molecules with a three-dimensional structure that decomposes very slowly and yields almost no net energy gain to microbes.

Mineralization

The process through which microbial decomposers convert nitrogen and other organic elements into inorganic mineral forms.

Immobilization

The uptake and assimilation of inorganic mineral nutrients from soil or water by microbial decomposers.

Net mineralization rate

The rate of nutrient release calculated as total mineralization rate minus total immobilization rate.

Humus

Dark, homogenous organic matter produced as plant litter is broken down and degraded during decomposition.

Soil organic matter

Humus embedded directly within the soil matrix.

Rhizosphere

The active region of soil directly surrounding plant roots where plant processes and root functions occur.

Soil microbial loop

The process where carbon exudates from plant roots supplement rhizosphere microbes, driving the breakdown of low-quality soil organic matter and subsequent nutrient release via microbivores.

Epilimnion

The warm, low-density, oxygen-rich surface water layer in stratified open-water aquatic ecosystems where photosynthesis occurs.

Thermocline

The intermediate layer in stratified aquatic ecosystems characterized by a steep vertical temperature gradient.

Hypolimnion

The cold, dense deep-water layer in stratified open-water aquatic ecosystems where decomposition primarily occurs.

Nutrient spiraling

The process of nutrient cycling in flowing water ecosystems where continuous downstream displacement causes nutrients to recycle across both time and space.

Estuary

A coastal aquatic ecosystem located where freshwater from rivers and streams meets and mixes with saltwater from the ocean.

Pycnocline

The water layer in an estuary or ocean defined by the maximum vertical rate of change in water density.

Aquatic microbial loop

A cycling pathway in aquatic ecosystems where dissolved organic matter (DOM) is absorbed by bacteria, which are subsequently consumed by ciliates and zooplankton to return carbon to the food web.

Retranslocation

The internal recycling of nutrients within a plant prior to leaf senescence, calculated as the difference between green leaf and senescent leaf nitrogen content expressed as a percentage of green leaf nitrogen content.

Decomposition

The breakdown of chemical bonds formed when organic molecules and tissues are built, releasing energy, carbon dioxide, and water while converting organic compounds into mineral nutrients.

Microfauna and Microflora

Decomposer organisms with a body width less than $100\,\mu\text{m}$, including soil protists and nematodes living in water within soil pores.

Mesofauna

Soil invertebrate decomposers with a body width ranging between $100\,\mu\text{m}$ and $2\,\text{mm}$, such as mites and springtails.

Macrofauna

Invertebrate decomposers with a body width ranging between $2\,\text{mm}$ and $20\,\text{mm}$, including millipedes and earthworms.

Megafauna

Invertebrate decomposers with a body width greater than $20\,\text{mm}$.

Microbivores

Organisms that feed on bacteria and fungi, including protists, springtails, nematodes, beetle larvae, and mites.

Litterbag

A synthetic mesh bag with $1\text{--}2\,\text{mm}$ holes used in field experiments to examine plant litter decomposition rates while allowing decomposer entry.

Leaf packs

Areas of active deposition and accumulation of leaf litter in stream ecosystems, often replicated with mesh bags in research to measure aquatic decomposition.

Lignin

A complex plant cell wall component composed of large molecules with a three-dimensional structure that decomposes very slowly and yields almost no net energy gain to microbes.

Mineralization

The process through which microbial decomposers convert nitrogen and other organic elements into inorganic mineral forms.

Immobilization

The uptake and assimilation of inorganic mineral nutrients from soil or water by microbial decomposers.

Net mineralization rate

The rate of nutrient release calculated as total mineralization rate minus total immobilization rate.

Humus

Dark, homogenous organic matter produced as plant litter is broken down and degraded during decomposition.

Soil organic matter

Humus embedded directly within the soil matrix.

Rhizosphere

The active region of soil directly surrounding plant roots where plant processes and root functions occur.

Soil microbial loop

The process where carbon exudates from plant roots supplement rhizosphere microbes, driving the breakdown of low-quality soil organic matter and subsequent nutrient release via microbivores.

Carbon-to-Nitrogen ratio of plant litter

The relative proportion of carbon to nitrogen in fresh plant detritus, typically ranging from $50:1$ to $100:1$.

Carbon-to-Nitrogen ratio of decomposer microbes

The relative proportion of carbon to nitrogen in bacterial and fungal biomass, typically ranging from $10:1$ to $15:1$.

Leaching phase of decomposition

The initial stage of decomposition where water-soluble organic and inorganic nutrients are washed out of plant litter into the surrounding soil or water.

Shredders

Aquatic invertebrate detritivores that fragment coarse organic particles like leaf litter while consuming the attached bacteria and fungi.

Upwelling

The wind- and Coriolis-driven vertical movement of deep, cold, nutrient-rich water to the ocean surface.

Seasonal turnover

The vertical mixing of surface and deep waters in temperate lakes caused by seasonal temperature changes and density shifts, which restores nutrients to the photic zone.

Salt marsh detrital system

A coastal ecosystem where most primary production enters the food web as dead organic matter, with around $75\%$ broken down by microbes and $20\text{--}45\%$ exported to estuaries.

Soil nitrogen feedback loop

A positive feedback mechanism where high soil nitrogen availability increases plant leaf nitrogen and productivity, leading to high-quality litter that rapidly mineralizes and further enhances soil nutrients.