Please log on to access EcoTrends content

Log On

EcoTrends

Glossary

Abundance
Biogeochemistry
Biomass
Cover
Decomposition
Density
Fire disturbance
Human population density
Human population size
Ice duration
Landuse
Litter
Net primary production
Palmer drought severity index
Plant phenology
Precipitation
Precipitation chemistry
Primary production
Sea level
Secchi disk
Soil moisture
Soil temperature
Solar radiation
Species diversity
Storm disturbance
Streamflow
Surface water chemistry
Water table
Water temperature
Water turbidity
Wind speed




Abundance

Back to top

The number of individuals or the representation of the number of individuals of a species in a particular ecosystem. Unit: number of individuals/sampling area or sampling effort.

Biogeochemistry

Back to top

The biogeochemistry of ecosystems involves the movement or cycling of elements (e.g., sulfur, carbon, nitrogen) and compounds (e.g., water) through the biotic (e.g., plants, animals, microbes) and abiotic (e.g., soils, atmosphere) components of an ecosystem.

Biomass

Back to top

The mass per unit area of living material (plants, animals, microbes). Unit: g/m2 or kg/ha.

Cover

Back to top

The amount or proportion of surface area occupied by plants or animals. Unit: %.

Decomposition

Back to top

The breakdown of organic matter (e.g., litter) accompanied by the release of carbon dioxide and other inorganic compounds. It is a key process in nutrient cycling.

Density

Back to top

The number of individuals found in an area. Unit: #/m2 or #/ha.

Fire disturbance

Back to top

Area burned by a fire. Unit: ha, or % of area.

Human population density

Back to top

Number of people per unit area.

Human population size

Back to top

Number of people living in a specified geographic area at a specified time.

Ice duration

Back to top

The number of days in a year when a water body (e.g., lake, a part of an ocean) is covered by ice. Unit: days/year.

Land use

Back to top

Land use is the human modification of natural environment or wilderness into built environment such as farmland, pastures, and settlements.

Litter

Back to top

Recently fallen plant material that is only partially decomposed. Unit: %.

Net primary production

Back to top

The amount of carbon or energy (usually measured as biomass) fixed by primary producers (e.g., plants, algae) minus their respiratory loss. It can be used for growth and reproduction of primary producers, and is available for consumption by herbivores. Unit: g/m2/yr.

Palmer drought severity index

Back to top

Developed by Wayne Palmer in the 1960s and uses temperature and rainfall information in a formula to determine dryness. It uses a 0 as normal, and drought is shown in terms of minus numbers; for example, minus 2 is moderate drought, minus 3 is severe drought, and minus 4 is extreme drought.

Plant phenology

Back to top

The timing of life history events, such as initiation of growth, flowering and dormancy.

Precipitation

Back to top

The amount and pattern of rainfall and snowfall. Unit: cm

Precipitation chemistry

Back to top

Concentration or total amount of an element (e.g., nitrogen, sulfur, calcium, chloride, phosphate) in precipitation. It can be expressed as volume-weighted concentration or deposition. Volume-weighted concentration is concentration per unit volume of precipitation (mg/L). It is measured on a subsample of precipitation and then converted to total volume of precipitation collected. Deposition is total amount of an element per unit of land area (kg/ha). It is converted from volume-weighted concentration based on the area receiving precipitation.

Primary production

Back to top

The amount of carbon or energy (usually measured as biomass) transformed from CO2 to organic carbon by primary producers (e.g., plants, algae) per unit area in a specified time period, usually seasonally or annually. Unit: g/m2/yr. Unit: cm

Sea level

Back to top

Annual mean sea level is defined as the annual arithmetic means of hourly heights relative to the National Tidal Datum Epoch (i.e., the most recent mean sea level datum established by CO-OPS currently the mean sea level 1983-2001). Unit: m.

Secchi disk

Back to top

A circular disk created in 1865 by Pietro Angelo Secchi. It is used to measure water transparency in oceans and lakes. The disc is mounted on a pole or line, and lowered slowly down in the water. The depth at which the pattern on the disk is no longer visible is taken as a measure of the transparency of the water.

Soil moisture

Back to top

The total amount of water, including the water vapor, in an unsaturated soil. Unit: % by volume.

Soil radiation

Back to top

The visible and near visible (ultra violet and near infrared) radiation emitted from the sun received per unit area. Unit: MJ/m2 The temperature of soil at a specified depth. Unit: oC

Species diversity

Back to top

Species diversity is a measure of the diversity within an ecological community that incorporates both species richness and the evenness of species' abundances.

Species richness

Back to top

The number of species in a community. Unit: number of species/sampling area or sampling effort.

Storm disturbance

Back to top

Number of major storms or hurricanes per year.

Stream flow

Back to top

Measured as stream discharge here, which is the volume of water moving down a stream or river per unit of time. Unit: L/s

Surface water chemistry

Back to top

Concentration of an element (e.g., nitrogen, sulfur, calcium, chloride, phosphate) per unit volume of water in surface water (e.g., stream, lake, coastal water). Unit: mg/L.

Water table

Back to top

The underground depth at which point the ground is totally saturated with water. Unit: m.

Water temperature

Back to top

Unit: oC

Water turbidity

Back to top

A measure of the degree to which the water looses its transparency due to the presence of suspended particulates. It is commonly measured by using a Secchi disk. Unit: m.

Wind speed

Back to top

Unit: m/s