Pioneer plant
A pioneer plant or pioneer species is a type of plant that has special adaptive abilities to colonize new, still vegetation-free areas. Pioneer species are therefore species that occur more frequently in newly created habitats than in old (“mature”) habitats. Species are enabled for successful colonization through special adaptations in physiology and life cycle.
- Species with effective long-distance distribution mechanisms. Since pioneer habitats emerge unpredictably and in isolation, species with a high number of seeds are preferred. The seeds should have transport mechanisms. Most of the pioneer species are wind spread ( anemochory ). Animal spreading is also possible, v. a. by birds ( ornithochory ).
- Pioneer species usually endure more extreme environmental conditions than other species. Established vegetation stands dampen maxima z. B. the temperature and the soil water. The underdeveloped soils of a pioneer habitat often show nutrient deficiencies or imbalances.
Typical pioneer species are weak competitive and are displaced by other species in the course of biological succession . This can be explained by the fact that advantages in one area, such as particularly high or rapid seed production, with limited resources by disadvantages in other areas, e.g. B. with the height, must be "bought" (eng .: trade-offs ). They compensate for (local) extinction by colonizing newly created habitats faster than other species. In order to survive, they are therefore dependent on constantly new pioneer habitats. Due to the loss of extreme locations (due to the deposition of nutrients (especially nitrogen) and cultivation by humans), some pioneer species in rare locations are threatened with extinction or become extinct.
Typical pioneer habitats can arise naturally during volcanic eruptions (lava areas), large fires (cf. Karrikine ), landslides (rubble and rubble), changes in the coastline and floods after a glacier has retreated . On a small scale, they are constantly created by the influence of animals (feeding, burrowing activity). Such small gaps can be very important for the establishment of numerous species. Today, extensive pioneer habitats are created by human impact: after artificial soil movements, in pits and opencast mines and on fallow land.
Pioneer vegetation comprises plant communities in which pioneer species dominate. Typical companies are e.g. B.
- Dwarf rush corridors of dry pond floors (Nanocyperion). Typical species: toad bulrush , brown sedge
- Riverside corridors and stagnant waters (Bidention, Chenopodion rubri). Typical species: three-part two-tooth , red goosefoot , poison buttercup
- short-lived ruderal corridors (rubble corridors, from the Latin "rudus" = rubble) (Sisymbrietalia). These include a variety of e.g. T. species-rich societies. Some typical species are: compass lettuce , rocket , pigeon trespe , Canadian fleabane , adder's head , evening primrose
Forest communities that consist of fast-growing pioneer tree species that are dispersed in the wind are referred to as pre-forest . Typical tree species are white willow , aspen and sand birch .
A special case of pioneer vegetation in recent history was ruderal vegetation on the urban rubble and debris created by air raids and ground fighting during World War II. The term rubble flowers , which was created for unusual plants or plants previously unknown in urban areas , was transferred to the narrow-leaved willowherb in particular .
