Image by Mayur Ankushe from Pixabay

Many plant species have become endangered in the last few decades as a result of human activities with some plant species already thought to be extinct. However, a recent study has shown that many of these threatened, rare, and in some cases, extinct species may simply be hiding in the soil, and may be more common then previously suspected.

Within the soil of most ecosystems, the seeds of many plant species are stored in what is called a soil seed bank. Here, the seeds remain dormant until environmental conditions are suitable for them to germinate, such as during rainy or warmer periods that are more favorable for their growth and survival. These seed banks are critical for the re-vegetation of areas frequently devastated by natural fires and extreme weather. Many seeds can remain dormant for decades in this state, and for some species even centuries. In the case of the sacred lotus flower, seeds have been found to still be viable 1,300 years later! It is this capacity for seeds to remain under the soil surface for long periods of time that could be their secret weapon for making a comeback from the brink of extinction, or beyond.

Image by Benjamin Balazs from Pixabay

The potential use of soil seed banks for conservation efforts has been demonstrated by Peter Poschlod and Sergey Rosbakh of the University of Regensburg. In their study, they investigated the seed bank of 100 mudflats in Germany, one of the most endangered habitats in Central Europe, where over 60 % of plant species are listed as endangered. From these soil banks, they were able to germinate some 30,000 seeds, including those of species considered endangered or nearly extinct. The seeds of these rare plants were not only viable, but were found in very high density within the soil (up to 3,000 seeds/liter). Many species were also found in study sites without any records of their presence despite being consistently surveyed for over 50 years.

The authors conclude that many seeds of mudflat plants have the potential survive around 50 years in a dormant state, with some species able to lay dormant for more than a century. They also suggest that plant species lists be revised so that rare and extinct species with the capacity for long-term seed dormancy be considered as not rare or extinct but perhaps merely hidden. This study not only highlights the hidden diversity of plants present within the soil, but also shows the importance of preserving soil samples of endangered plant communities so they could potentially be used for future re-population efforts.

Written by Jose Valdez

Research article:

Poschlod P, Rosbakh S. 2018. Mudflat species: Threatened or hidden? An extensive seed bank survey of 108 fish ponds in Southern Germany. Biological conservation. 225:154-63. https://doi.org/10.1016/j.biocon.2018.06.024