Ecology Terms Starting With K
Ecology Glossary: K
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K-Strategist
/ KAY-STRAT-uh-jist / · From K representing carrying capacity in logistic growth equations, first proposed by ecologists MacArthur and Wilson in 1967
K-strategist is an organism with life history traits that favor survival and competitive ability in stable, resource-limited environments where populations remain near carrying capacity.
K-strategists typically produce few offspring with high parental investment, delay reproduction until relatively late in life, and maintain stable population sizes near the environmental carrying capacity. These traits evolved in predictable, competitive environments where resources are limited and population density stays high, favoring larger body size, longer lifespan, and greater competitive ability over rapid reproduction. African elephants (Loxodonta africana) exemplify this strategy with a 22-month gestation period, single calves born every four to six years, and intensive maternal care lasting up to 16 years.
Because slow reproductive rates prevent rapid population recovery, K-strategists face elevated extinction risk from habitat loss, and many large mammals require decades to rebound from population declines. Unlike r-strategists that reproduce prolifically in unstable environments, K-strategists invest energy in maintenance and competitive dominance rather than maximizing offspring number.
The wandering albatross (Diomedea exulans) does not breed until age 11 and produces only one egg every two years, yet individuals regularly live past 50 years. Population stability in this species depends on adult survival rates exceeding 95 percent annually, meaning even modest increases in adult mortality from longline fishing bycatch can push populations into decline.
Body size predicts reproductive strategy, but small organisms can be K-strategists too. The tuatara Sphenodon punctatus of New Zealand weighs only about one kilogram but reaches sexual maturity at age 13, reproduces only every four years, and lives past 100 years, fitting the K-strategy profile despite its modest size.
Giant sequoias (Sequoiadendron giganteum) in California's Sierra Nevada demonstrate K-strategy through longevity exceeding 3,000 years and delayed reproduction that begins around age 175. These trees invest heavily in thick, fire-resistant bark and chemical defenses, persisting in stable forest communities where competitive ability and long-term survival matter far more than rapid seed output.
Keystone Species
/ KEE-stohn SPEE-sheez / · Old English cysten (related to stone arch) + Latin species
Keystone species is a species whose effect on its ecosystem is disproportionately large relative to its abundance or biomass.
A keystone species shapes ecosystem structure through predation, herbivory, mutualism, or physical habitat modification, and its removal triggers trophic cascades that ripple through multiple food web levels. Sea otters (Enhydra lutris) along the Pacific coast control sea urchin populations through predation; without otters, urchin numbers surge and overgrazing destroys kelp forests, eliminating habitat for hundreds of associated species. Robert Paine coined the term in 1969 after his experiments on rocky intertidal shores in Washington State showed that removing the sea star Pisaster ochraceus caused mussels to monopolize the substrate and species richness to collapse.
Prairie dogs (Cynomys spp.) modify grassland structure by excavating burrow systems that provide nesting sites for burrowing owls, shelter for black-footed ferrets, and grazing patches that attract bison and pronghorn.
Wolves reintroduced to Yellowstone National Park in 1995 triggered a cascade that altered river channel morphology. By reducing elk browsing pressure on willows and aspens along stream banks, wolf predation allowed riparian vegetation to recover, stabilizing stream banks and changing the physical course of rivers, a process researchers call a trophic cascade extending to geomorphology.
Keystone species are always the most abundant species in their community. Their ecological importance comes from the strength and reach of their interactions, not their numbers; a keystone species may represent less than one percent of total community biomass.
Sea otters along the Aleutian Island chain were hunted nearly to extinction by the early twentieth century, and kelp forest coverage collapsed across large stretches of coastline as urchin populations exploded. When otter populations recovered in protected areas, urchin densities dropped from hundreds per square meter to fewer than ten, and kelp canopy returned within a few years.
What Do Otters Eat? →Krummholz
/ KRUM-holts / · From German krumm meaning crooked or bent, and holz meaning wood
Krummholz describes the zone of stunted, wind-deformed trees growing at the treeline boundary where severe environmental conditions prevent normal upright forest development.
Krummholz formation occurs at high elevations or latitudes where persistent winds, freezing temperatures, and ice crystal abrasion prevent vertical growth, forcing trees into horizontal, twisted forms rarely exceeding two meters in height. These stunted stands mark the ecotone between subalpine forest and alpine tundra, typically appearing between 3,000 and 3,700 meters elevation in the Rocky Mountains. Species forming krummholz include subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii), and whitebark pine (Pinus albicaulis), which survive by growing flagged shapes with branches only on the leeward side or adopting prostrate mat forms pressed against the ground.
Winter desiccation kills exposed buds and shoots while snow-covered portions survive, producing the characteristic asymmetrical growth patterns visible on any Rocky Mountain treeline. Krummholz thickets provide critical winter shelter for snowshoe hares and white-tailed ptarmigan, whose survival depends on the dense, low canopy that the harsh conditions themselves create.
Some krummholz spruces less than three meters tall are more than 400 years old, with annual diameter increments sometimes below one millimeter. Dendrochronologists have used these slow-growing trees to reconstruct centuries of climate history at high elevations, because even tiny ring-width variations record temperature anomalies that lower-elevation trees do not register.
Krummholz trees are a genetically distinct dwarf variety of their species. These stunted forms result entirely from environmental stress; seedlings transplanted from krummholz zones to lower elevations develop normal upright growth within a few growing seasons.
Mount Washington in New Hampshire displays classic krummholz zones near 1,400 meters elevation, where black spruce (Picea mariana) and balsam fir (Abies balsamea) form dense, wind-sculpted thickets. Wind speeds on the summit have exceeded 370 kilometers per hour, and temperatures drop below negative 40 degrees Celsius in winter, creating some of the most severe treeline conditions recorded outside polar regions.
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