Thesoil seed bank is the natural storage ofseeds, often dormant, within thesoil of mostecosystems.^[1] The study of soil seed banks started in 1859 whenCharles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake. The first scientific paper on the subject was published in 1882 and reported on the occurrence of seeds at different soil depths.^[2] Weed seed banks have been studied intensely inagricultural science because of their important economic impacts; other fields interested in soil seed banks includeforest regeneration andrestoration ecology.

Henry David Thoreau wrote that the contemporary popular belief explaining thesuccession of a logged forest, specifically to trees of a dissimilar species to the trees cut down, was that seeds eitherspontaneously generated in the soil, or sprouted after lying dormant for centuries. However, he dismissed this idea, noting that heavy nuts unsuited for distribution by wind were distributed instead by animals.^[3]

The seed bank is one of the key factors for the persistence and density fluctuations of plant populations, especially forannual plants.^[4]Perennial plants have vegetativepropagules to facilitate forming new plants, migration into new ground, or reestablishment after being top-killed, which are analogous to seed bank in their persistence ability under disturbance. These propagules are collectively called the 'soil bud bank', and include dormant and adventitiousbuds onstolons,rhizomes, andbulbs. Moreover, the termsoildiaspore bank can be used to include non-flowering plants such asferns andbryophytes.^{[citation needed]}

Soil seed bank is significant breeding source for vegetation restoration^[5] and species-rich vegetation restoration,^[6] as they provide memories of past vegetation and represent the structure of future population.^[6] Moreover the composition of seed bank is often more stable than the vegetation to environmental changes,^[7] although a chronic N deposition can deplete it.^[8][9] In many systems, the density of the soil seed bank is often lower than the vegetation,^[4] and there are a large differences inspecies composition of the seed bank and the composition of the aboveground vegetation.^[10][11][12] Additionally, it is a key point that the relationship between soil seed bank and original potential to measure the revegetation potential.^[13][14] In endangered habitats, such as mudflats, rare and critically endangered species may be present in high densities, the composition of the seed bank is often more stable than the vegetation to environmental changes[7][7],^[15]

Soil seed banks are a crucial part of the rapid re-vegetation of sites disturbed by wildfire, catastrophic weather, agricultural operations, and timber harvesting, a natural process known assecondary succession. Soil seed banks are often dominated bypioneer species, those species that are specially adapted to return to an environment first after a disturbance.^[16]Forest ecosystems andwetlands contain a number of specialized plant species forming persistent soil seed banks.^{[citation needed]}

The absence of a soil seed bank impedes the establishment of vegetation duringprimary succession, while presence of a well-stocked soil seed bank permits rapid development of species-rich ecosystems duringsecondary succession.^{[citation needed]}

Manytaxa have been classified according to the longevity of their seeds in the soil seed bank. Seeds oftransient species remain viable in the soil seed bank only to the next opportunity togerminate, while seeds ofpersistent species can survive longer than the next opportunity—often much longer than one year. Species with seeds that remain viable in the soil longer than five years form thelong-term persistent seed bank, while species whose seeds generally germinate or die within one to five years are calledshort-term persistent. A typical long-term persistent species isChenopodium album (Lambsquarters); its seeds commonly remain viable in the soil for up to 40 years and in rare situations perhaps as long as 1,600 years.^[17] A species forming no soil seed bank at all (except the dry season between ripening and the first autumnal rains) isAgrostemma githago (Corncockle), which was formerly a widespread cereal weed.^{[citation needed]}

Longevity of seeds is very variable and depends on many factors. Seeds buried more deeply tend to be capable of lasting longer.^[18] However, few species exceed 100 years.^[19] In typical soils the longevity of seeds can range from nearly zero (germinating immediately when reaching the soil or even before) to several hundred years. Some of the oldest still-viable seeds were those ofLotus (Nelumbo nucifera) found buried in the soil of a pond; these seeds were estimated bycarbon dating to be around 1,200 years old.^[20] Onecultivar ofdate palm, theJudean date palm, successfully sprouted in 2008 after accidental storage for 2,000 years.^[21]

One of the longest-running soil seed viability trials was started inMichigan in 1879 byJames Beal. The experiment involved the burying of 20 bottles holding 50 seeds from 21 species. Every five years, a bottle from every species was retrieved and germinated on a tray of sterilized soil which was kept in a growth chamber. Later, after responsibility for managing the experiment was delegated to caretakers, the period between retrievals became longer. In 1980, more than 100 years after the trial was started, seeds of only three species were observed to germinate:moth mullein (Verbascum blattaria),common mullein (Verbascum thapsus) andcommon mallow (Malva neglecta).^[22] Several other experiments have been conducted to determine the long-term longevity of seeds in soil seed banks.

Species ofStriga (witchweed) are known to leave some of the highest seed densities in the soil compared to other plantgenera; this is a major factor that aids their invasive potential.^[28] Each plant has the capability to produce between 90,000 and 450,000 seeds, although a majority of these seeds are not viable.^[29] It has been estimated that only two witchweeds would produce enough seeds required to refill a seed bank after seasonal losses.^[30]Before the advent of herbicides, a good example of a persistent seed bank species wasPapaver rhoeas, sometimes so abundant in agricultural fields in Europe that it could be mistaken for a crop.^{[citation needed]}

Studies on the genetic structure ofAndrosace septentrionalis populations in the seed bank compared to those of established plants showed that diversity within populations is higher below ground than above ground.^{[citation needed]}

• Plant reproduction
• Seeds
• Gene banks
• Ecological restoration
• Biology terminology
• Habitat
• Environmental terminology
• Biorepositories

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