Soil seed bank

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.

Background

Soil seeds 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 persistent 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" (corncockle), which is a formerly widespread cereal weed species.

Seed longevity

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 and still germinating seeds were those of Lotus ("Nelumbo nucifera") buried in the soil of a pond.Fact|date=February 2008

Environmental significance

Soil seed banks play an important role in the natural environment and in many ecosystems. For example, the rapid revegetation of burned or ploughed sites is in a big part due to a soil seed bank. Additionally, 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, or permits rapid development of species-rich ecosystems e.g. fellow lands, some dry grasslands or even fens.clarifyme

Soil seed banks and population dynamics

The mortality of seeds in the soil is one of the key factors for the population persistence and size fluctuations of plants, especially for annual plants. A well studied example is the one of "Androsace septentrionalis".Studies on the genetic structure of populations in the seed bank compared to the those of established plants have shown that diversity within populations is higher below ground than above ground. In addition the differentiation of populations is higher above ground than below ground.There are indices that the accumulation of mutations is more important for species forming a persistent seed bank compared to those with only transient seeds.

Soil seed banks and diversity

The increase of species richness in a plant community due to a species rich and abundant soil seed bank is known as the 'storage effect'.