ESPM 116B: Midterm 1

Flashcards for the first unit test in Grassland & Woodland Ecology

Primary productivity

The rate at which photosynthetic organisms convert sunlight into chemical energy stored in organic compounds.

Ecological site

A conceptual division of a landscape defined by recurring soil, landform, hydrology, geology, and climate characteristics.

Rangeland

Grasslands, savannas, shrublands, and prairies that provide important ecological, economic, and social services.

Carbon stock

The amount of carbon stored in an ecosystem at a given time.

Carbon sink

An ecosystem in which carbon inputs exceed carbon losses over a given period.

Carbon source

An ecosystem in which carbon losses exceed carbon inputs over a given period.

GPP

Gross primary productivity; total carbon/energy captured through photosynthesis before autotrophic respiration.

NPP

Net primary productivity; carbon gained by vegetation after autotrophic respiration.

ANPP

Aboveground net primary productivity; production of aboveground plant biomass.

BNPP

Belowground net primary productivity; carbon allocated to production of roots and associated belowground compounds.

Autotrophic respiration

Respiration by plants that releases CO2 and uses some of the carbon fixed through photosynthesis.

Heterotrophic respiration

Respiration by decomposers and other organisms that breaks down organic matter and releases carbon.

Root exudates

Carbon-containing compounds released by plant roots into the soil that provide resources to belowground organisms.

Primary productivity equation

NPP = GPP − autotrophic respiration.

NPP components

NPP = ANPP + BNPP.

Sequential coring

A method for estimating root production by comparing root mass in soil cores at different times.

Ingrowth core

A root-production method that places root-free soil into the ground and measures roots that grow into it.

Minirhizotron

A nondestructive method that allows direct observation of root growth and death through time.

Niche complementarity

A biodiversity mechanism in which species use different resources or occupy different niches, allowing mixtures to use resources more completely.

Sampling effect

A biodiversity mechanism in which high-diversity communities are more likely to contain a particularly high-performing species.

Facilitation

An interaction in which one species improves the presence or performance of another species.

Portfolio effect

Stabilization caused by averaging fluctuations among species whose productivity varies differently through time.

Ecosystem stability

The degree to which ecosystem functioning resists or recovers from environmental disturbance.

Resistance

The ability of an ecosystem to maintain its structure and processes during a disturbance.

Resilience

The ability of an ecosystem to recover toward previous conditions after disturbance.

Coefficient of variation

CV = σ/μ; a measure of relative variability, with higher values indicating less stability.

Stability ratio

μ/σ; the reciprocal of CV, with higher values indicating greater stability.

Propagule pressure

The number of individuals arriving, number of introduction events, and duration of introductions that influence establishment probability.

Non-native species

A species occurring outside its natural biogeographic range.

Introduced species

A population transported by humans.

Naturalized species

A non-native population that becomes self-sustaining in the wild.

Invasive species

A population that spreads widely in its introduced range; in policy contexts, the term may additionally imply harm.

Release

A deliberate pathway of species introduction into the wild.

Escape

A species escaping from a place where humans kept it.

Contaminant

A species transported unintentionally with a traded commodity.

Stowaway

A species transported unintentionally on transportation such as ships, vehicles, or cargo.

Corridor

A human-built pathway such as roads, canals, or railways that facilitates species spread.

Unaided spread

Spread from a nearby region where a species was previously introduced without direct human transport.

Biotic resistance

The ability of an established community to resist establishment of introduced species.

Plant functional traits

Characteristics such as biomass allocation and litter quality that can alter ecosystem pools and fluxes.

Disturbance regime

The frequency, intensity, and type of disturbances such as fire, flood, or grazing.

Trophic structure

The pattern of feeding relationships describing who eats whom in an ecosystem.

Ecosystem engineer

A species that changes the physical environment.

Keystone species

A species whose ecological effect is disproportionately large relative to its abundance.

Foundation species

A species that is abundant and provides much of the structure of an ecosystem.

Woody plant encroachment

Increases in the abundance and distribution of woody plants in grassland and savanna ecosystems.

MAP

Mean annual precipitation.

Fertile island

A nutrient-rich area beneath or around shrub canopies compared with surrounding intershrub areas.

Woody plant rooting depth

Shrubs generally have deeper maximum rooting depths than grasses, allowing greater access to deep soil water.

Hydrologic mass balance

PPT = ET + Q + ΔS; precipitation equals evapotranspiration plus runoff plus change in storage.

Nutrient limitation

The gap between what the soil can supply and what plant growth requires.

Diffusion

Passive movement of nutrients from areas of high concentration toward areas of low concentration.

Mass flow

Movement of nutrients through flowing water, including water associated with transpiration or rainfall.

Root interception

Physical encounter between roots and nutrients as roots grow through soil; relatively unimportant as a direct nutrient-acquisition mechanism.

Root:shoot ratio

The amount of root biomass relative to shoot biomass; increasing it can increase belowground resource acquisition.

Mycorrhizae

Symbiotic fungi associated with plant roots that increase soil volume explored in exchange for plant carbohydrates.

Ectomycorrhizae

A type of mycorrhizal association found in about 10% of plant families and common among woody plants.

Arbuscular mycorrhizae

A type of mycorrhizal association found in about 85% of plant families.

Active nutrient transport

Energy-requiring movement of ions across membranes, including movement against concentration gradients.

Carboxylates

Compounds released by roots that can help release bound phosphate from soil surfaces.

Phosphatases

Enzymes that help release phosphate from organic compounds.

Nitrate

An inorganic form of nitrogen that generally must be reduced before assimilation.

Ammonium

A reactive form of nitrogen that plants can directly assimilate.

Reactive nitrogen

Nitrogen compounds other than atmospheric N2 that are biologically or chemically reactive.

N2

Atmospheric nitrogen gas; highly abundant but relatively unreactive and unavailable to most organisms directly.

Nitrogen fixation

The conversion of atmospheric N2 into biologically usable reactive nitrogen by specialized organisms.

Nitrogen mineralization

The release of inorganic nutrients as organic matter decomposes.

Nitrogen immobilization

The uptake of nutrients by plants or microbes into organic matter.

Phosphorus weathering

The release of phosphorus as rock material is chemically or biologically broken down.

Phosphorus cycle

A largely unidirectional nutrient cycle without a major atmospheric gas pool.

Liebig's Law of the Minimum

The principle that biological activity is limited by the nutrient in shortest supply relative to biological demand.

Carbon sequestration

The storage of carbon in biomass, soil, or other ecosystem pools.

Nutrient supply

The amount of a nutrient that the soil can deliver to plants.

Nutrient demand

The amount of a nutrient required by plants for growth and function.