<center>![Millennium_Seed_Bank_at_Wakehurst_Place_-_geograph.org.uk_-_836739.jpg](https://steemitimages.com/DQmbfGzZx5W497pxfYiXnFZa6D74dbb1jp2HqP1R3t6iMU6/Millennium_Seed_Bank_at_Wakehurst_Place_-_geograph.org.uk_-_836739.jpg)</center>
<center><sup>By Elliott Simpson, <a title="Creative Commons Attribution-Share Alike 2.0" href="https://creativecommons.org/licenses/by-sa/2.0">CC BY-SA 2.0</a>, <a href="https://commons.wikimedia.org/w/index.php?curid=13517588">Link</a></sup></center>

Good day to my readers and welcome to another session of blogging after a little unavoidable break. I recently started a series on the soil seed bank of vegetation and today’s article is still going to be along the same line. In order to fully understand what today’s article is all about, I will implore my readers, especially those that have not read my previous posts on the same topic to do so. The links to the articles are listed below.

* [Introduction to soil seed bank]( https://steemit.com/stemng/@gentleshaid/introduction-to-soil-seed-bank)
* [understanding the dynamics of soil seed banks]( https://steemit.com/stemng/@gentleshaid/understanding-the-dynamics-of-the-soil-seed-bank)
* [components of fire and the soil seed banks]( https://steemit.com/stemng/@gentleshaid/components-of-fire-and-their-effects-on-the-soil-seed-bank)
* [seasonal variation, seed bank and extant vegetation]( https://steemit.com/stemng/@gentleshaid/seasonal-variation-seed-bank-and-extant-vegetation)

As a form of quick revision, the seed bank of a vegetation refers to the amount of seeds stored in the soil which has the potential of replacing the above ground or extant vegetation in the case of vegetation disturbance or removal. The study of seed bank is important in order to estimate the potentials of the stored soil seeds to replace extant vegetation as well as been able to biologically conserve species that might be going or have gone into extinction. As we might have known, plant species represent a major source of food, drugs and materials for human and livestock uses.

Two important characteristics are considered as far as the study of the soil seed bank is concerned; the species composition and density of the soil seed bank. While the species composition refers to the different species of plants whose seeds are present in the soil, the density refers to the number of seeds of individual species present in the soil per square of a meter.

### How is the soil seed bank studied?
From past researches, there are two main methods that have been employed in the study of soil seed banks. These are
* The seedling emergence method; and
* Seed extraction method.

The seedling emergence method is the more popular of the two methods due to the fact that it is less laborious and can be applied when large volume of soil samples are to be considered. However, the method requires a large amount of space in the green house where seedling emergence experiment is carried out in order to exclude external influences. Soil seed bank researchers have opined that the seed extraction method generally detects more seed density and species richness as compared to the seedling emergence study. Also, the seedling emergence study is time consuming requiring three to twenty months of observations.

### Seedling Emergence Study

In order to carryout soil seed bank study using the seedling emergence method, sampling plots are measured out within the study area, usually with a dimension of 50 x 50 m and soil samples are randomly collected within this sample plots using a soil auger of known dimension. Thereafter, the collected soils are carefully spread out on flat plates while aggregates are gently broken. The plates are then set up in the screen house where they are watered and monitored daily for seedling emergence. Emerged seedlings are counted and identified appropriately before being removed from the soil to ensure that double enumeration does not occur. 

<center>![2017-03-15-10-44-28.jpg](https://steemitimages.com/DQmPuNar5dVjNAHswW9UcDyZqvxAL4VW83D2Y3Q6BzAPCXv/2017-03-15-10-44-28.jpg)</center>
<center><sup>source: [pixnio](https://pixnio.com/flora-plants/greenhouse-seedlings-sprouting-plants-plastic-pots)</sup></center>

Data on the number of emerged seedlings and species are collected for a period ranging from 3 to 20 months as the case may be. At the end of the experiment, seed density of the soil seed bank is calculated as the number of emerged seedlings per square meter of soil while species richness of the soil seed bank is calculated as number of unique species that emerged per square meter of soil.

### Seed Extraction

This method is kind of similar to seedling emergency method in the ways the research plots are selected and soil samples collected. After soil sampling, seeds are extracted from the soil by mixing the soil with saturated sodium chloride solution, a solution that separates the various seeds present in the soil from the mineral soil fraction. Saturated sodium chloride solution is prepared by dissolving 35 g of the salt per 100 ml of distilled and deionised water. The soil/salt solution is then allowed to settle for about thirty minutes after which the supernatants is filtered through standard filter paper and dried in an hot air oven at 35<sup>O</sup>C. Thereafter, seeds of different plant species are separated from the supernatant through the use of binocular stereomicroscope, counted and then recorded as number of seeds per square meter of soil.

<center>![Flax_seeds.jpg](https://steemitimages.com/DQmSkdSLsfLjmyCbkQLHQsZFe2VwrUTvT6RiiaBc1BUgWbM/Flax_seeds.jpg)</center>
<center><sup>By <a href="https://en.wikipedia.org/wiki/User:Bdevel" class="extiw" title="en:User:Bdevel">Bdevel</a>, <a title="Creative Commons Attribution-Share Alike 2.5" href="https://creativecommons.org/licenses/by-sa/2.5">CC BY-SA 2.5</a>, <a href="https://commons.wikimedia.org/w/index.php?curid=245429">Link</a></sup></center>

One of the challenges with seed extraction is that not all extracted seeds are viable and will readily germinate given the necessary conditions. The viability of the extracted seeds can be determined by the pressure test or seed crush test, a method that involves visual inspection and application of little pressure using forceps to the seeds in order to detect embryo’s presence. The efficiency of the extraction method can be determined by mixing seeds of different sizes with soil in a saturated sodium chloride solution and then extracting normally by following the same process.

### Summary
There are varieties of methods used in carrying out soil seed bank study. Method used may vary depending on location, equipment available, the cost of research as well as the time-frame available for the research. The two major methods used in the study are seedling emergence study and seed extraction study. Each of the methods has its merits and demerits of use. Overall, seed bank study enables the indicator components of the seed bank such as seed density and species richness to be calculated.

Thank you for reading.
### References
* [Colby.edu]( http://www.colby.edu/biology/BI131/Lab/Lab09CalcBiodivers.pdf)
* [research gate](https://www.researchgate.net/profile/Sofia_Gonzalez6/publication/270535141_Comparison_of_methods_to_estimate_soil_seed_banks_The_role_of_seed_size_and_mass/links/54da107b0cf246475820478c/Comparison-of-methods-to-estimate-soil-seed-banks-The-role-of-seed-size-and-mass.pdf)
* [edepot](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwib8f2k4d3ZAhXkJsAKHWiFD9kQFgg-MAM&url=http%3A%2F%2Fedepot.wur.nl%2F154378&usg=AOvVaw3EJLrDSzMcT9BHILAZi-BE)
* [nrc research press](http://www.nrcresearchpress.com/doi/abs/10.1139/b92-202)
* [online library](http://onlinelibrary.wiley.com/doi/10.1111/j.2041-210X.2010.00011.x/full)
*All images are labeled for reuse under the creative common license*

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