Soil seed bank
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The soil seed bank is the collective name for the store of seeds, often dormant, which are stored within the soil of many terrestrial ecosystems.
Soil seed banks of particular taxa have been classified according to the longevity of their seeds in species forming transient soil seed banks, for species whose seeds remain viable only to their next vegetation period and persistent meaning that the seeds can survive longer than to the next vegetation period i.e. often longer than one year. Species with relatively long viability of seeds in the soil ( > than 5 years) form long term persitent seed bank in opposition to those species generally germinating or dying from the soil seed bank earlier, which are called short term persistent. A typical long term persistent species is Chenopodium album (common name: Lamb's Quarters), a weed distributed in many temperate parts of the world, a species forming no soil seed bank at all (except the dry season between riping and the first autumnal rains) is Agrostemma githago a formerly widespread cereal weed species.
Longevity of seeds is very variable and depends on many factors, in "ordinary" moist soils the longevity of seeds can range from nearly zero (germination directly when reaching the soil or even before) to several hundreds of years. Some of the oldest C14 dated and still germinating seeds where those of Lotus (Nelumbo nucifera) buried in the soil of a pond.
Soil seed banks play an important role in many ecosystems, the rapid revegetation of burned or ploughed sites is in a big part due to a soil seed bank. But also forest ecosystems (gaps!), wetlands (drying of ponds, water erosion) contain a number of specialized plant species forming persistent soil seed banks. For the inclusion of non flowering plants the term soil diaspore bank can be used, including well known examples of ferns and bryophytes.
Soil seed banks are important in restoration of human influenced or destroyed ecosystems, their absence slows revegetation down e.g. in quarries (and thus lets the place to interesting other species?), or permits rapid developpement of species rich ecosystems e.g. fellow lands, some dry grasslands or even fens.
