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what is a seed bank

Seed Bank

A seed bank is the reservoir of viable seeds present in a plant community. Seed banks are evaluated by a variety of methods. For some species , it is possible to make careful, direct counts of viable seeds. In most cases, however, the surface substrate of the ecosystem must be collected and seeds encouraged to germinate by exposure to light, moisture, and warmth. The germinating seedlings are then counted and, where possible, identified to species.

In most cases, the majority of seeds are found in surface layers. For example, the organic-rich forest floor contains almost all of the forest’s seed bank, with much smaller numbers of seeds present in the mineral soil .

The seeds of some plant species can be remarkably long-lived, extending the life of the seed bank. For example, in northeastern North America, the seeds of pin cherry (Prunus pensylvanica ) and red raspberry (Rubus idaeus ) can persist in the forest floor for perhaps a century or longer. This considerably exceeds the period of time that these ruderal species are present as mature, vegetative plants during the initial stages of post-disturbance forest succession . However, because these species maintain a more-or-less permanent presence on the site through their persistent seed bank, they are well placed to take advantage of temporary opportunities of resource availability that follow disturbance of the stand by wildfire , windstorm, or harvesting.

The seeds of many other plant species have only an ephemeral presence in the seed bank. In addition to some tropical species whose seeds are short-lived, many species in temperate and northern latitudes produce seeds that cannot survive exposure to more than one winter. This is a common trait in many grasses, asters, birches, and most conifers, including pines, spruces, and fir. Often these species produce seeds that disperse widely, and can dominate the short-lived seed banks during the autumn and springtime. Species with an ephemeral presence in the seed bank must produce large numbers of well-dispersed seeds each year or at least frequently, if they are to successfully colonize newly disturbed sites and persist on the landscape.

Although part of the plant community, seed banks are much less prominent than mature plants. In some situations, however, individual plants in the seed bank can numerically dominate the total-plant density of the community. For example, in some cultivated situations the persistent seed bank can commonly build up to tens of thousands of seeds per square meter and sometimes densities which exceed 75,000 seeds per square meter. Even natural communities can have seed banks in the low tens of thousands of seeds per square meter. However, these are much larger than the densities of mature plants in those ecosystems.

The seed bank of the plant community is of great ecological importance because it can profoundly influence the vigour and species composition of the vegetation that develops after disturbance.

[Bill Freedman Ph.D. ]

RESOURCES

BOOKS

Harper, J. L. Population Biology of Plants. San Diego: Academic Press, 1977. Grime, P. Plant Strategies and Vegetation Processes. New York: Wiley, 1979.

Seed bank A seed bank is the reservoir of viable seeds present in a plant community. Seed banks are evaluated by a variety of methods. For some species , it is possible to make careful, direct counts of viable seeds. In most cases, however, the surface substrate of the ecosystem must be collected and seeds encouraged to germinate by exposure to light, moisture, and warmth. The germinating seedlings are then counted and, where possible, identified to species. Source for information on Seed Bank: Environmental Encyclopedia dictionary.

How Seed Banks Work

Plants are crucial for the welfare of human society. They help our ecosystem function. They provide us with oxygen to breath, medicine, clothing fiber and, importantly, food. Out of the 7,000 species of plants currently used for agriculture around the planet, only 30 crops make up the world’s diet. Wheat, corn and rice alone account for more than half of the world’s food consumption [source: Diverseeds].

Did you ever stop to think about what might happen if these crops disappeared? Right now, for example, our wheat supply is dwindling. The world’s stockpiles are at their lowest numbers in thirty years. Consumption is exceeding production, and farmers are having a tough time keeping up. Experts predict this trend is temporary [source: Streitfeld].

But what if it’s not? Or, what if a natural disaster wipes out the majority of wheat and other important crops? Scientists think they have hit upon a solution — seed banks.

Think of a seed bank as a savings account. Seeds are “deposited” into secure storage with the intention of “withdrawing” them in the future when they are needed. Just as you might keep money saved for an unforeseen emergency, scientists are saving up seeds to use for replanting in case certain crops die out or are destroyed. When stored correctly, seeds can remain viable for decades or even centuries [source: Minister of Agriculture and Food].

There are currently about 1,400 seed banks around the world, but the most famous is the Svalbard Global Seed Vault, which opened on Feb. 26, 2008. Also known as the Doomsday Vault, it functions as a global repository and backup for all other seed banks [source: Mellgren].

Seed banking is a complicated concept. This article will touch upon all of its facets — why we need seed banks, who’s responsible for the seeds, and how they are stored. Read on to find out why seed banking is an investment in the future of the human race.

The 1972 sci-fi film Silent Running depicts a barren future where humans have destroyed all plant life. Only a few plant species survive, sealed in a domed greenhouse that orbits in space. The keeper of this preserved forest, played by Bruce Dern, winds up battling his own crew to save his beloved trees. Will he — and a couple of robots — wind up drifting in space alone? Rent the movie to find out.

Seed banks store our world's seeds, in case disaster wipes out a plant species. Find out how seed banks protect our future.