4 Ecosystem Decomposition and Lab Practices

Flashcards based on the Introduction to Decomposition lecture, covering laboratory experiments, decomposition scales, and regulatory factors.

Ocean Acidification

The process by which oceans absorb $CO_2$ which dissociates into carbonic acid, leading to a decrease in seawater pH.

Anthropogenic Carbon Dioxide

Carbon dioxide produced by human activities, of which approximately one third is estimated to end up in seawater.

Carbonic Acid

An acid formed when carbon dioxide ends up in seawater, leading to a measured decrease in pH from $8.2$ to $8.1$ since preindustrial times.

Logarithmic Scale (pH)

The scale used for pH whereby a small numerical change, such as $0.1$ units, represents a large physical change, such as a $26\%$ increase in acidity.

Calcareous Organisms

Organisms with shells or structures made of carbonates, such as corals, which are eroded and degraded as seawater pH decreases.

Titration

A chemical analysis method used in the lab to determine the amount of carbonates and bicarbonates in seawater or to measure potassium hydroxide levels.

Net Ecosystem Exchange (NEE)

The calculation of how much carbon dioxide is either taken up by plants via photosynthesis or respired from the soil.

Infrared Gas Analyzer (IRGA)

An instrument used to measure the fluxes or concentrations of $CO_2$ within a contained environment.

Mesocosms

Contained experimental environments, such as cores with or without plants, used to measure carbon dioxide exchange.

Soil Respiration

A critical ecosystem process involving the release of carbon dioxide from the soil as a result of energy movement.

Potassium Hydroxide (KOH) Trap

A method to measure soil respiration where liberated $CO_2$ is trapped in a solution to form potassium carbonate.

Potassium Carbonate ($K_2CO_3$)

The compound formed when $CO_2$ is liberated from soil and reacts with a potassium hydroxide solution.

V max ($V_{max}$)

The maximum velocity or rate of respiration reached when increasing organic carbon in the soil no longer acts as a limiting factor.

Algal Balls

Small spheres created by immobilizing freshwater algae to measure rates of photosynthesis and respiration.

Gross Primary Production (GPP)

The total amount of carbon that is assimilated into an ecosystem.

Net Primary Production (NPP)

The amount of carbon left in primary producers after they have undergone respiration.

Net Ecosystem Productivity (NEP)

The amount of carbon left in an ecosystem after accounting for respiration by producers, consumers, and decomposers.

Heterotrophic Respiration

The release of carbon and energy by consumers and decomposers as they process organic material.

Decomposers

The community of organisms in the environment that regulates the process of decomposition and energy release.

Macro Scale Decomposition

The conversion of organic matter from large physical forms into smaller particles, soluble compounds, and gases.

Molecular Scale Decomposition

The conversion of complex organic molecules into simpler forms and eventually into inorganic compounds like ammonium and $CO_2$.

Inorganic Compounds

The final, simple products of decomposition, such as ammonium and carbon dioxide, which offer little additional energy recovery.

Carbon Fixation

The process of producing organic compounds from inorganic materials and sunlight; considered the opposite of decomposition.

Biogeochemical Cycles

The movement of elements through an ecosystem driven by the release of nutrients from organic material during decomposition.

Nitrate ($NO_3^-$)

An essential plant nutrient released from organic material during the decomposition process.

Litter Bag Model

A method of studying decomposition by placing organic material in mesh bags and measuring degradation over time.

Recalcitrant Material

Organic material that is highly resistant to decomposition and remains after easily broken down parts are gone.

Leaching

The initial phase of decomposition involving the rapid removal of easily broken down material.

First Order Models

Decomposition models where the rate of mass loss is proportional to the mass still present.

k

The mathematical term representing the decomposition rate of material over a period of time.

Broadleaf Trees (Decay Rate)

Terrestrial plants with a slow decomposition rate, often measured at approximately $k = 0.001$ per day.

Microalgae (Decay Rate)

Aquatic organisms that decompose very rapidly, often measured at approximately $k = 0.1$ per day.

Lignin

A complex structural component of terrestrial plants that is highly resistant to decomposition and lacks a repeating unit structure.

Carbon to Nitrogen (C:N) Ratio

The ratio of carbon to nitrogen in organic matter, which is generally higher in terrestrial plants than in aquatic plants.

Carbon to Phosphorus (C:P) Ratio

The balance of carbon and phosphorus in plant material, influencing decomposition rates.

Herbaceous Plants

Plants that lack woody stems and typically decompose faster than evergreen or deciduous trees.

Evergreens

Plants whose litter is relatively resistant to decay, often losing only $20\%$ biomass in the first six months.

Leaf Shredding Organisms

Invertebrates found in water systems that physically break down leaves into smaller particles.

Microorganisms

Bacteria, archaea, and fungi that are primarily responsible for the molecular scale of decomposition.

Invertebrates

Animals such as earthworms that contribute to the macro scale of decomposition by fragmenting organic matter.

Bacteria

Microbes efficient at nutrient acquisition in low concentrations, often performing the final stages of decomposition.

Archaea

A broad category of microorganisms involved in the breakdown of organic matter at the ecosystem level.

Fungi

Microbes primarily involved in the initial degradation of wood and recalcitrant polymers like lignin.

Fine Particulate Organic Matter (FPOM)

Small fragments of organic material produced when invertebrates break down larger organic litter.

Net Growth Efficiency (NGE)

The proportion of assimilated carbon incorporated into biomass rather than lost as respiration.

Assimilated Carbon

The total carbon taken up by an organism that is available for growth or respiration.

Syntrophy

A process where different organisms, like fungi and bacteria, work as a consortium to degrade organic matter.

Complex Polymers

Large organic molecules like lignin, proteins, and cellulose that require multiple steps to decompose.

Monometric Units

Individual units like sugars and amino acids produced by the initial breakdown of complex organic polymers.

Aerobic Decomposition

The breakdown of organic matter in the presence of oxygen, typically resulting in higher biomass production.

Anaerobic Decomposition

The breakdown of organic matter without oxygen, resulting in lower biomass production and various redox products.

Redox Reactions

Chemical reactions involving the transfer of electrons, typical of anaerobic breaking down of compounds.

Exclusion Experiments

Studies that remove specific organisms from an environment to measure their impact on decomposition rates.

Humid Grasslands

Ecosystems where decomposer organisms have been shown to play a particularly large role in the rate of decomposition.

Deciduous Forests

Forests where the removal of decomposers has a measurable but smaller effect on decomposition rates compared to grasslands.

Earthworms

Invertebrates whose presence increases decomposition and causes a preferential removal of nitrogen-rich organic matter.

Intrinsic Factors

Factors related to the internal composition of the material being decomposed, such as its lignin or nutrient content.

Extrinsic Factors

Environmental factors that regulate decomposition, such as temperature, moisture, and pH.

Secondary Metabolites

Chemical compounds produced by plants, such as alkaloids or phenolics, that can decrease the palatability of litter.

Palatability

The degree to which organic matter is attractive or digestible to decomposers.

Peat Bogs

Ecosystems that serve as major carbon stores, where decomposition is highly sensitive to temperature and moisture.

Vascular Plants

Plants with conducting tissues that contain structural lignin, making them more resistant to decay than nonvascular plants.

Nonvascular Plants

Plants without specialized conducting tissues that generally decompose more easily due to a lack of lignin.

Microbial Biomass C:N Requirement

The ratio of approximately $5$ carbons to $1$ nitrogen needed for a microbe to increase its biomass.

Respiration Carbon Loss Ratio

The concept that for every carbon molecule incorporated into biomass, another is typically lost to respiration.

Ideal Substrate C:N Ratio

A ratio of approximately $10:1$ in organic matter, allowing microbes to fully decompose the material for growth.

Alkaloids

Secondary metabolites in plants that can act as anti-herbivory agents and slow decomposition.

Phenolics

Plant compounds that alter the digestibility of organic material to protect against decomposition.

Terpenes

Organic compounds produced by plants that influence the rate of decomposition by affecting palatability.

Temperature (Decomposition Factor)

An extrinsic factor where increases generally lead to higher microbial activity and faster decomposition.

Moisture Content (Decomposition Factor)

An extrinsic factor where wetter soils typically increase decomposition until saturation limits oxygen.

Saturated Soils

Conditions where soil is water-logged, leading to decreased decomposition due to lack of oxygen.

Acid Mine Drainage

An environmental problem where very low pH water enters a system, potentially slowing decomposition rates.

Science Teaching Hub

The university facility where the student lab sessions and mesocosm experiments are conducted.

My Aberdeen

The online platform where the lecture protocols, worksheets, and experiment data are hosted.

Primary Producers

Organisms like plants and algae that assimilate carbon into the ecosystem via photosynthesis.

Carbon Sink

A part of the environment, such as the ocean or peat bogs, that absorbs and stores substantial amounts of carbon.

Carbonated Seawater

Seawater for the lab experiment that has been treated with $CO_2$ to simulate acidification.

Soil Organic Carbon

The amount of carbon available in the soil, which can be a limiting factor for microbial respiration.

Freshwater Algae

Organisms used in the lab to study the rates of photosynthesis and respiration relative to environmental factors.

Consumers

Organisms in the ecosystem that act on primary production to release carbon and energy.

Particular Organic Matter (POM)

Organic material in the form of particles that serves as a substrate for decomposition.

Carbohydrates

Complex organic molecules that are broken down into individual sugars during the molecular scale of decomposition.

Proteins

Complex organic molecules that are broken down into amino acids during decomposition.

Amino Acids

The building blocks of proteins released during the molecular breakdown of organic matter.

Energy Recovery

The capture of energy stored in organic compounds as they are broken down into inorganic forms.

Leaching Rate

The speed at which soluble materials are removed from litter at the start of the decomposition process.

Polymeric

A characteristic of complex molecules like lignin that are made of many repeating units, making them hard to break.

Heterogeneous

The characteristic of lignin being made of different units in various orders, hindering enzymatic degradation.

Oxidation (Lignin)

The state of parts of the lignin molecule that results in low energy recovery during its catabolism.

Enzymatic Degradation

The process by which microbes use enzymes to break down organic structures, often limited by a lack of water solubility in the substrate.

Cellulose

A complex polymer found in plants that, like lignin and protein, requires initial processing by fungi.

Ammonium ($NH_4^+$)

An inorganic form of nitrogen produced at the end of the molecular scale of decomposition.

Microbial Consortia

Groups of different microorganisms working together to achieve the full decomposition of complex materials.

Physical Stresses

Environmental forces that, along with organisms, contribute to the initial breaking down of litter.

Fragility

The physical property of original organic material that influences how easily it is broken into smaller fragments.

Substrate Composition

The specific makeup of the organic material, including nutrients and carbon types, that dictates its decay rate.

Incubation

The two-week period during which the soil respiration experiment is left to run in the lab.

Harvesting (Experiment)

The process of collecting the potassium hydroxide traps at the end of the two-week soil respiration study.