<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="311" name="ecology" parent="650" scope="Study of the relations between living plants and animals and their environment."/><uf><usefor name="bionomics"/></uf><bt><term thcode="2" code="650" name="life sciences" parent="1019" scope="Branches of science that study living and fossil organisms."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><rt><term thcode="2" code="40" name="animal behavior" parent="921" scope="The way animals act or react to conditions in the environment and to other organisms, including life patterns such as migration, hibernation, and nocturnal living."/><term thcode="2" code="53" name="aquatic biology" parent="650" scope="The scientific study of organisms living in or near water.  This term is to be used for the science of 'aquatic biology' and for  biological studies in fresh and brackish water. For marine biological studies, use 'marine biology'."/><term thcode="2" code="54" name="aquatic ecosystems" parent="319" scope="Communities of interdependent organisms living primarily in or on water."/><term thcode="2" code="85" name="benthic ecosystems" parent="54" scope="Biologic communities and habitats at the bottom of lakes, streams, or oceans."/><term thcode="2" code="88" name="bioaccumulation" parent="310" scope="The biological sequestering of a substance at a higher concentration than that at which it occurs in the surrounding environment or medium.  Also, the process whereby a substance enters an organism through the gills, epithelial tissues, dietary, or other sources."/><term thcode="2" code="92" name="biodiversity" parent="921" scope="The variety in form, genetics, and ecological roles of organisms within a specific geographic area."/><term thcode="2" code="93" name="biogeochemical cycling" parent="310" scope="The cycling of chemical constituents through a biological system."/><term thcode="2" code="96" name="biogeography" parent="921" scope="The study of the geographic distributions of plants and animals."/><term thcode="2" code="108" name="biological productivity" parent="310" scope="The rate at which primary producers in the ecosystem utilize solar energy to produce food for consumption by other organisms. Do not use this term for productivity of organisms related to studies of the reproduction rates of a species."/><term thcode="2" code="113" name="bioremediation" parent="980" scope="Use of biological methods, usually involving microorganisms, to break down or neutralize contaminants in soil, water, and wastes."/><term thcode="2" code="141" name="carbon cycling" parent="93" scope="The circulation of carbon in the biosphere, atmosphere, and hydrosphere through a series of processes that include photosynthesis, consumption, and respiration."/><term thcode="2" code="145" name="carnivores" parent="194" scope="Flesh-eating animals."/><term thcode="2" code="174" name="coastal ecosystems" parent="1156" scope="Biological communities and habitats within the narrow zones of land between the margin of oceans or seas and large landmasses."/><term thcode="2" code="187" name="community ecology" parent="921" scope="Study of the relationships of species that interact in a common area."/><term thcode="2" code="194" name="consumers (organisms)" parent="841" scope="Organisms unable to produce food from nonliving matter and dependent on ingesting other animals, plants, or particulate organic matter."/><term thcode="2" code="238" name="decomposers" parent="841" scope="Organisms, chiefly microorganisms and invertebrates, that feed on dead plant or animal matter breaking it down and recycling the resulting elements and compounds in the environment."/><term thcode="2" code="245" name="desert ecosystems" parent="1156" scope="Biological communities and habitats in arid areas with little precipitation, sparse, highly adapted vegetation, and extreme temperatures."/><term thcode="2" code="246" name="desertification" parent="168" scope="The alteration of arable land to dry, barren land due to prolonged drought or the deleterious effects of human intervention including overgrazing, overpopulation, or destructive agricultural practices."/><term thcode="2" code="268" name="dispersal (organisms)" parent="310" scope="The dissemination or geographic spread of individuals of a plant or animal population."/><term thcode="2" code="308" name="ecological competition" parent="310" scope="The struggle between members of two or more species for scarce environmental resources."/><term thcode="2" code="310" name="ecological processes" parent="101" scope="Dynamic biogeochemical interactions that occur among and between biotic and abiotic components of the biosphere."/><term thcode="2" code="315" name="ecosystem functions" parent="310" scope="The total life activities of organisms in habitats and the effects of those activities on the nonliving components of the environment."/><term thcode="2" code="317" name="ecosystem monitoring" parent="375" scope="Recording, evaluating, and actively intervening over time in the interaction of living and nonliving elements in a specific environment."/><term thcode="2" code="319" name="ecosystems" parent="921" scope="The interacting populations of plants, animals, and  microorganisms occupying a certain area, and their relationship to the environment."/><term thcode="2" code="320" name="ecotoxicology" parent="650" scope="Scientific study of causes, dispersal, and effects of contaminants on the environment."/><term thcode="2" code="485" name="effects of climate change" parent="1174" scope="Characteristics and behaviors of organisms and earth systems that are modified as a result of changes in global, regional, or local climate."/><term thcode="2" code="332" name="endangered species" parent="841" scope="Any species that is in danger of extinction throughout all or a significant portion of its range."/><term thcode="2" code="333" name="endemic species" parent="768" scope="Plant and animals species native to and confined to specific geographic areas."/><term thcode="2" code="358" name="estuarine ecosystems" parent="54" scope="Biological communities and habitats within sea inlets or the zones where rivers meet the seas which are subject to tidal effects and the mixture of fresh and saltwater."/><term thcode="2" code="359" name="eutrophication" parent="310" scope="The process by which water becomes enriched with plant nutrients, most commonly phosphorus and nitrogen."/><term thcode="2" code="365" name="extinction and extirpation" parent="310" scope="Extinction is the complete disappearance of a species from the earth.  Extirpation is the complete disappearance (elimination) of a species from a given region, island, or area."/><term thcode="2" code="384" name="fires" parent="101" scope="Combustion, marked by flames or intense heat, in natural settings, often ignited by lightning or human activities.  For fires set as part of natural resource management, use 'controlled fires'."/><term thcode="2" code="407" name="food web" parent="807" scope="The complex intertwining of the interrelated food chains in an ecosystem."/><term thcode="2" code="410" name="forest ecosystems" parent="1156" scope="Biological communities and habitats in geographic areas with dense growths of trees and associated vegetation."/><term thcode="2" code="411" name="forest resources" parent="777" scope="Trees and associated vegetation available for human use.  Use for timber and other forest resources with economic value."/><term thcode="2" code="419" name="freshwater ecosystems" parent="54" scope="Biological communities and habitats that exist in lakes, rivers, ponds, and other bodies of water that are not salty."/><term thcode="2" code="499" name="grassland ecosystems" parent="1156" scope="Biological communities and habitats with ground cover of grasses and other herbaceous plants, but few trees.  Examples include prairies, meadows, and savannas."/><term thcode="2" code="522" name="habitat alteration and disturbance" parent="310" scope="Changes in the environments where plants and animals live.  Includes natural changes as well as results of human actions, deliberate or accidental."/><term thcode="2" code="537" name="herbivores" parent="194" scope="Animals that eat chiefly plants or their products, such as seeds, nectar, and fruit."/><term thcode="2" code="548" name="human impacts" parent="1174" scope="The effects, intentional or unintentional, beneficial or harmful, direct or indirect, which human activities have upon the environment and living things."/><term thcode="2" code="602" name="invasive species" parent="797" scope="Plant, animal, or microbe species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm, or harm to human health."/><term thcode="2" code="629" name="land use change" parent="548" scope="Effect of changing land use patterns on ecological systems."/><term thcode="2" code="672" name="long-term ecological monitoring" parent="317" scope="Data collection over a period of years or decades to assess changes in selected biological communities and habitats."/><term thcode="2" code="704" name="marine ecosystems" parent="54" scope="Biological communities composed of plants and animals living primarily in or on seawater."/><term thcode="2" code="720" name="mercury contamination" parent="1181" scope="Biological disturbances caused by mercury compounds that have entered the environment."/><term thcode="2" code="743" name="migration (organisms)" parent="310" scope="The movement of animals, often periodical, from one area to another due to seasonal changes, availability of food, or climatic conditions."/><term thcode="2" code="744" name="migratory species" parent="841" scope="Species that have a pattern of moving from one geographical area to another, primarily according to the seasons, and usually traveling long distances along established routes."/><term thcode="2" code="768" name="native species" parent="841" scope="Organisms originating in the area where they live."/><term thcode="2" code="797" name="nonindigenous species" parent="841" scope="Organisms accidentally or intentionally introduced into areas where they did not previously originate or live."/><term thcode="2" code="807" name="nutrient cycling" parent="93" scope="The exchange of elements or compounds essential for the nourishment of organisms in an ecosystem."/><term thcode="2" code="832" name="omnivores" parent="194" scope="Animals that eat both plant and animal materials."/><term thcode="2" code="879" name="pesticide and herbicide contamination" parent="769" scope="Pollution resulting from chemical agents applied to crops, rights of way, lawns, or residences to control weeds, insects, fungi, nematodes, rodents or other pests (pesticides) or kill undesirable plants (herbicides)."/><term thcode="2" code="911" name="plot sampling" parent="379" scope="Outlining small areas of land within a larger area to use as samples to study biological populations or ecosystems."/><term thcode="2" code="916" name="pollinators" parent="841" scope="Organisms that aid in the growth and distribution of plants by transferring pollen as a byproduct of their feeding activities."/><term thcode="2" code="921" name="population and community ecology" parent="1174" scope="Interactions of a single species (population) or an association of different species (community) occupying a particular region, including their biotic and abiotic environments."/><term thcode="2" code="922" name="population dynamics" parent="921" scope="Changes in the size, composition, or structure of aggregates of single or multiple species in a specific area over time."/><term thcode="2" code="935" name="producers (organisms)" parent="841" scope="Organisms, chiefly green plants, which use inorganic elements, compounds, and light to produce their food (photosynthesis). They are a source of food for animals."/><term thcode="2" code="971" name="reef ecosystems" parent="704" scope="Biological communities formed by the skeletons of calcareous seawater organisms, usually corals."/><term thcode="2" code="980" name="remediation" parent="776" scope="Methods for decontaminating, reclaiming, and restoring natural resources or reducing the effects of hazards."/><term thcode="2" code="1059" name="shrubland ecosystems" parent="1156" scope="Biological land communities and habitats with sparse, low-growing vegetation."/><term thcode="2" code="1123" name="succession (biological)" parent="310" scope="Gradual replacement of one species in an area by another."/><term thcode="2" code="1156" name="terrestrial ecosystems" parent="319" scope="Communities of living organisms in a specific geographical location which exist primarily on land and not in water."/><term thcode="2" code="1196" name="tundra ecosystems" parent="1156" scope="Biological communities and habitats located in the treeless plains of Arctic regions where the subsoil is permanently frozen."/><term thcode="2" code="1266" name="vegetation" parent="841" scope="Plant life or general plant cover in an area."/><term thcode="2" code="1293" name="waste treatment and disposal" parent="548" scope="The chemical and physical methods to recycle or dispose of materials which, without treatment, are deemed to have no further value or are too contaminated to be used."/><term thcode="2" code="1326" name="wetland ecosystems" parent="319" scope="Ecosystems whose soil is saturated for long periods seasonally or continuously, including marshes, swamps, and ephemeral ponds.  More detailed terms for wetlands can be selected from the FGDC Wetland Classification &lt;http://fgdc.gov/standards/status/sub3_4.html&gt;."/><term thcode="2" code="1327" name="wetland functions" parent="315" scope="Processes related to wetlands such as support of ecosystems, evaporation effects on weather, nutrient cycles, etc."/></rt></descriptor>