Spores, Sphagnum Moss and Peatlands

Sphagnum moss- an introduction

Sphagnum is a flowerless genus of moss with some quite remarkable properties.

Sphagnum moss soft, Craig Meagaidh National Nature Reserve, Scotland

Click for slide show

There are 125 moss species in the Sphagnum genus.

spagnum moss growing on boggy moorland Peak district national Park© alexhyde.photoshelter.com

Different species of Sphagnum moss often form low lying living ‘carpets’….

sphagnum moss at Fiordland National Park, Te Anau, South Island, Southland, New Zealand,

…and thrive in boggy, damp conditions.

Sphagnum-moss-bog-Aviemore-Scotland

Sphagnum moss also flourishes on damp forest floors…

Spruce trees and sphagnum moss on the boreal forest floor, Denali National Park, Alaska

…and even at the bottom of volcanic craters.

Caldera ilha do Faial, Açorescommons.wikimedia.org/wiki/File:Caldeira_faial_3.JPG 

  • So what is so remarkable about Sphagnum moss? Read on!!

How Sphagnum moss reproduces

The reproductive spores of Sphagnum moss develop inside capsules. These capsules rise on stalks above the leaves.

sphagnum-in-bog showing reproductive headspomona.edu/news/2010/07/22-whitaker-mushroom-cloud.aspx

Each capsule contains up to 30,000 microscopic spores.

Capsule of a Sphagnum moss containing microscopic spores© University of Nijmegen, Holland

The capsules containing the spores are sometimes different in shape.

  • Why is this?

Three capsules from Sphagnum henryeuse. Two are round (unexploded) and one that has alreadypomona.edu/news/2010/07/22-whitaker-mushroom-cloud.aspx

In the summer months the spherical capsules start to dry out. As they dry out the capsules dehydrate….

Sphagnum stalk with spores inside spherical shape

… and shrink. They then become compressed which leads to a build up in air pressure.

Sphagnum moss capsule shrinks and air inside is compressed

Eventually the internal air pressure becomes so great that the lid of the capsule blows open. The spores escape from inside the capsule and rapidly accelerate upwards and outwards.

Sphgnum moss capsule explodes open producing vortex ring and releasing spores

The whole sequence is summarized below:

capsule of sphagnum moss exploding forming a vortex ring

The escaping spores, accelerating incredibly fast, then form a mushroom shaped cloud.

The formation of a mushroom shaped cloud is recorded in this sequence of images below. Each image represents 1/10,000th of a second. The whole process, from explosion to formation of mushroom shaped cloud, takes only 9/10,000th of a second!

sphagnum-series-lgpomona.edu/news/2010/07/22-whitaker-mushroom-cloud.aspx

The spores accelerate with a gravitational force (G-force) of 36,000 g!

By way of comparison the maximum rate of acceleration of a Bugatti Veyron is 1.55g…

bugatti-veyron-super-sport-17

…the rate of acceleration of an ejector seat is 15 g ….

Ejector seat fired out of aircraf

….while the rate of acceleration of a 9mm bullet fired from a handgun is ‘only’ 31,000 g.

Lahti L-35 pistol fires bulets which accelerate at 31000g

Even Superman doesn’t accelerate as fast as Sphagnum moss spores!

faster than a speeding bullet but slower than sphagnum moss spores

The rapid acceleration of the spores has been captured in this slow motion video:

  • Why have Sphagnum moss spores evolved to accelerate so fast?

Exploding out of their capsules allow the spores to escape the windless zones near ground level and reach the faster more turbulent airflows located 10 centimeters above the ground.

sphagnum moss with capsules at a higjh elevation in Costa Ricamy.chicagobotanic.org/science_conservation/finding-the-perfect-match/

These turbulent airflows help disperse millions of microscopic spores to new habitats often many kilometers away.

If the spores land somewhere where they can grow they will germinate and produce the next generation of plants.

The circulation of spores in mushroom shaped vortex rings enables the spores to stay in the air longer and travel further.

Sphagnum moss spores circulate in mushroom shaped vortex rings

This very successful method of reproduction has led to the formation of vast Sphagnum peatlands throughout the world.

Sphagnum peatlands (also known as peat bogs, mires and wetlands) What are they?

As old plants die new plants grow on top. Slow rotting, dead plant material accumulates under this new growth.

Leptostomum macrocarpum showing accumulation of dead material

This accumulation of dead plant material produces a type of soil called peat. Over time the peat soil becomes deeper and deeper until peatlands are formed.

A thick layer of peat soil can be seen in this image where it has been excavated.

peat-bog outer herbrides virtualhebrides.com/articles/peat-cutting/peat-bank.htm

On average, peatlands increase in depth by one centimeter every 10 years. So that makes this peatland over 1000 years old!

peat bog in highlandswalkhighlands.co.uk/news/scotlands-ghostly-trees/0010851/

The accumulation of peat soil is greatest in areas where temperatures are high enough for plant growth but low enough to slow down the rate at which plant matter decays. There also needs to be high rainfall and ….

Buachaille Etive Mor Rain Over lochsplus.com/2013/03/

….low levels of evapo transpiration.

evapotranspiration diagram showing precipitation, transpiration and evaporation

Such conditions, ideal for the growth of Sphagnum peatlands, are found in vast regions of North America, northern Europe and Russia.

Map of peat in world

In these northern regions Sphagnum moss is the foremost peat forming species.

Permafrost peatbog Large Flaket, Abisko, Sweden.Dentren at English Wikipedia

  • So what is so special about Sphagnum peatlands?

Features of Sphagnum peatlands

Individual Sphagnum moss plants can store large quantities of water inside leaves, branches and stems.

Sphagnum flexuosum demonstrates how much water casn be stored in the leaves “Sphagnum flexuosum” by James Lindsey at Ecology of Commanster

The cumulative effect is that millions of individual Sphagnum plants, both dead and alive, contribute to an eco-system that remains permanently waterlogged.

Sphagnum peat bog - St-Daniel sector - Frontenac National Park (Québec, Canada)“Bog 03 – Frontenac Park – July 2008” by Boréal Wikimedia Commons

In such waterlogged conditions subsurface layers of peat soils are deprived of oxygen. This lack of oxygen slows down the rate of decomposition of dead Sphagnum found below the surface.

peat dug up showing high water contentgardeningattheedge.wordpress.com/2012/04/14/building-a-peat-wall/

The soils of Sphagnum peatlands are incredibly acidic and are of a similar acidity to vinegar.vinegar in bottle has a similar ph acidity to peat bogs of sphagnum moss

These unique soil conditions (very acidic and lacking in oxygen) mean that anything dropped in peatlands often remains very well preserved.

Many ancient artefacts have been found in peatlands including this wooden wheel; it was found in Holland and has been dated at around 2700 BC making it more than 4,700 years old!

wooden wheel found in sphagnum peat bog in Holland

Sphagnum peatlands- effects on other organisms

Sphagnum moss removes vital plant nutrients, such as potassium and magnesium, from the soil. This makes it impossible for many plant species to grow.

Those plant and animal species that can survive in Sphagnum peatlands have had to adapt to living in conditions in which there are few nutrients.

The Common Sundew (Drosera rotundifolia) is one plant that can survive in Sphagnum peatlands. It extracts all the nutrients it needs from the bodies of insects that it captures.

Using a glue- like substance this Common Sundew has captured a yellow and brown colored butterfly.

common sundew (Drosera rotundifolia) has captured a butterlfy

Wildlife commonly found in Sphagnum peatlands includes red grouse of Scotland….

Red-Grouse Lagopus lagopus scotica inhabits acidic solis and peat bog mire wetlandsPeter Cairns/Northshots -wild-scotland.org.uk/species/21/red-grouse/

…dragonflies of northern China….

Yellow winged darter Sympetrum flaveolum inhabits peat lands

 …and Corroboree frogs of Australia.

Northern Corroboree Frog, Pseudophryne pengilleyi, on a bed of Sphagnum.

Different types of Sphagnum Peatland

The two main processes by which Sphagnum peatlands develop are called terrestrialization and paludification.

  • What are terrestrialization and paludification?

terrestrialization and paludification in a diagram

1) Terrestrialization

This is the process by which peatlands grow over water.

In the initial stages Sphagnum moss grows near the shore of a lake or pond as a floating bog mat.

This floating bog mat of Sphagnum moss also contains sedge grasses and Sundew carnivorous plants.

floating bog mat of sphagnum moss and sedge grass with carnivorous plant sundew

Over time peat soil in the floating bog mat starts to infill the lake. The lake slowly becomes smaller….

terrestrialization and in filling of a lake by sphagnum mossJoshua G. Cohen  at mnfi.anr.msu.edu/

…and smaller….

terrestrialization of lake to produce sphagnum wetlandsaquatic.uoguelph.ca/wetlands/chapter2/bogpage2.htm

….until the lake completely silts up. This peatland in Slovenia has developed out of several silted up lakes.

Lovrenška Lake, Slovenia, peat bogs have infilled the lake through process of terrestrialization geocaching.com/geocache/GC3MMYV_bog-of-lovrenc-lakes

2) Paludification

This is the process by which peatlands grow over land. There are two main types of paludificationblanket bog diagram

a) Blanket bogs

These can be found in cooler climates in which rainfall is consistently high. The surface  of the land remains waterlogged, providing ideal conditions for the growth of Sphagnum moss.

In such circumstances peat soils “blanket” much of the land, including hilltops and slopes.

Gribun cliffs in Western Mull, Scotland, showing blanket bogwildfuture.co.uk/index.php/western-mull-places-to-go

Blanket bogs can also be found in mountainous regions. This blanket bog is in northern Spain.

Peat Bogs in the Xistral Mountains, northwestern Spainpubs.acs.org/cen/news/87/i50/8750notw4.html

b) Raised Peat Bog

Some peat bogs, such as this one in Scotland, are raised above the level of the surrounding countryside.

  • How does this happen?

Cranley moss raised peat bog

Before a raised peat bog can be formed, colonised by Sphagnum Moss, a process of terrestrialization needs to take place.

Following the retreat of the last ice age in Europe 10,000 years ago…

Earth showing maximum extent of the last ice age 10 000 years ago“Ice Age Earth” by Ittiz – Own work. Wikipedia

…lakes formed in the shallow depressions that were left by the retreating ice. Trees and plants grew beside these lakes and aquatic plants grew on the surface of the lakes.

Over time dead plant material infilled the lake. The plant material sitting at the bottom of the lake formed a thick layer of peat soil that, over time, grew upwards towards the surface.

lake deposits and build up of fen peat

These peat soils, unlike the more acidic Sphagnum peat soils, were either alkaline or only mildly acidic.

Conditions were not yet acidic enough for Sphagnum moss to grow.

Eventually these peat soils infilled the lake until it completely disappeared. The peat soils were fed by mineral rich groundwater and surface water forming what is known as a fen.

Diagram of fen wetlands containing alkaline soils

The mineral rich water feeding the fen ensured that the peat soils remained alkaline or only mildly acidic.

As the fen peat thickened, the roots of plants growing on the surface could no longer feed off any mineral-rich groundwater.

formation of a Raised peat bog and sphagnum wetlands

The only source of minerals for plants was now rainwater, which contains few minerals. Such conditions favored the growth of Sphagnum moss which soon turned the soil acidic.

The more Sphagnum moss that grew, the more acidic the soil became.

You can view the whole process, from lake to raised peat bog, in this video.


Benefits to the environment

Sphagnum peatlands capture and store vast amounts of atmospheric carbon dioxide. This helps prevent the accumulation of greenhouse gases in the atmosphere and helps slow down the rate of global warming.

Carbon Exchange in sphagnum peatlands

Consider this amazing statistic: 3% of the earth’s land surface is covered by peatlands but peatlands have captured 33% of all the carbon in all the soils of the world.

peatlands as carbon stores

Peatlands lock away VAST amounts of carbon.

This carbon storage is threatened by human activity….

modern-peat-cuttingPhoto courtesy of Killofin Home Genuine Irish Peat

….which sometimes takes place  on an industrial scale.

harvesting peat on industrial scale with picture of a tractor alongside a pile of peat whisky.com/information/knowledge/tasting/flavor/peat-and-its-significance-in-whisky.html

  • Why do humans harvest peat?

Peat has traditionally been used for cooking and heating  for thousands of years. Burning peat releases stored carbon back into the atmosphere as carbon dioxide gas.

feu de tourbe or peat fire

Peat is also widely used in agriculture and gardening. When mixed with soil, peat helps improve mineral and water retention.

Sphagnum moss peat in a bag

Further reading

Information about Irish peat in Natures way- the Wonder of Peatlands 

Some great water color paintings illustrating the different stages of Raised Bog development.

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One Response to “Spores, Sphagnum Moss and Peatlands”

  1. The effect of horses walking on Sphagnum moss seems to be considered essential to retain the peat moss in Dartmoor, England. The pug marks stop surface water running off by pooling in the pug hoof prints and slowly being absorbed by the moss (Dartmoor National Park website) BUT Koscuizsko National Park says the pug hoof marks dry out the moss and it blows away.
    Can you explain why there are these two seemingly opposing views and the benefits or not of horses imprints in the moss.
    Thanks, Jill Pickering

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