Sphagnum for dummies

The last couple of weeks I have been participating in a field course about peat moss, Sphagnum in Latin and ‘veenmos’ in Dutch. The course was lead by Klaas van Dort, an expert on mosses.

We started with some theory about the most common Sphagnum species in the Netherlands. We learned the key specifics: how we can determine which species we are looking at due to ecological preference, habitat conditions and specific details of the Sphagnum species itself, straight out in the field. Therefore we visited three locations to collect samples.

On Day 1 we started at Vragenderveen, close to Winterswijk in the Province of Gelderland, the Netherlands. Vragenderveen is a remnant of a swamp area, a bog habitat and peat swamp forests, which extends over the border to Germany. Farmers used to harvest peat to use as fuel. Peat is an accumulation of partly decomposed vegetation. One of the most important constituents is Sphagnum, although many other vegetation types may contribute to build layers of peat.

Sphagnum palustre, 'Gewoon veenmos', Gagelpolder

To maintain the precious area of Vragenderveen, Natuurmonumenten and the municipality of Winterswijk started to take measures. They mainly aim for an improvement of water levels in the bog. This requires dams and a division in compartments of the peat. Nowadays the rare peat is growing back and so we have experienced the rough terrain of the bog!

The bog is a no-go area for visitors. It can be very dangerous! The bog can only recover if it will be left at peace for most time of the year. We had the ultimate privilege to go there with a guide to extent our horizon of Sphagnum abundance…

Well, I should have known that my sprained ankle of last June would give me some trouble. Due to the fact that I didn’t know beforehand how hard the first day in the field would be, I carried my photographic equipment with me. This was not the right choice. We walked for 2-3 kilometers on a dam corresponding to a balance beam, reaching half a meter to higher off the ground. My ankle is still not strong enough to cope with difficult situations, which made my steps on the dam insecure. I did pull through eventually, though in my own pace. We inspected samples of Sphagnum through the magnifier while balancing on the dam. I felt like a heron on one leg strongly focused on its prey.

After the ‘balance beam act’ we crossed the bog and peat pits. Some people struggled to cope with the peat pits. You can actually fall in it till the neck if you are not careful. History recalls many incidents of armies crossing the bogs, leaving many soldiers behind that drowned in the peat pits. I sank in till my knees, leaving my rubber boot behind at first, and then I pulled the boot out slowly while sitting on a cushion of reed. Though the terrain made it hard for my ankle, I braced myself and enjoyed the kind of teambuilding that starts to appear in these kind of situations. Thanks guys!

Habitat of the Gagelpolder

 On Day 2 we enjoyed the scenery of the Gagelpolder and Molenpolder of Westbroek, just North of the city of Utrecht, the Netherlands.  We walked along the water edge to search for Sphagnum. We found species like Sphagnum palustre, in Dutch ‘Gewoon veenmos’, and Sphagnum squarrosum, in Dutch ‘Haakveenmos’. We took a short cut through the adjacent Gagel Forest where cushions of Sphagnum fimbriatum, in Dutch ‘Gewimperd veenmos’, adorned the tree roots. On our way back to the car parking, we found a rare Purple Fringed Riccia in the Ditch nearby, in Latin Ricciocarpos natans, in Dutch ‘Kroosmos’.

Ricciocarpos natans, 'Kroosmos', Gagelpolder

We left the Gagelpolder for a boat trip in the Molenpolder. In the marshes of the Molenpolder decayed vegetation has accumulated over thousands of years, leaving thick packages of peat. This is a different kind of peat as in Vragenderveen.  In Dutch we make a difference between ‘hoogveen’ and ‘laagveen’.

‘Hoogveen’ is created under the influence of rainwater and is called a raised bog. A raised bog continues to form peat in thick layers and is ombrotrophic: rain-fed for further development and accumulating under acidic conditions until a dome is created. Nutrients are obtained from whatever blows in and are therefore in short supply. A raised bog is formed above groundwater level. Vragenderveen, the location of Day 1, is a raised bog.

‘Laagveen’ appears below groundwater level and is called a fen. A fen accumulates vegetation into peat and is minerotrophic: it receives water and nutrients not only from precipitation, but also from inflowing streams and groundwater filtered through mineral soil. Nutrients are more abundant  and water is neutral or even alkaline. The conditions are suitable for a wide range of vegetation. Molenpolder consists of a combination of fens and quaking bogs, in Dutch ‘trilvenen’. Quaking bogs form a floating mat of vegetation on top of a water layer, like a raft. Sphagnum mosses are definitely in abundance in quaking bogs.

Habitat of Molenpolder

 A volunteer from Staatsbosbeheer arranged the boat trip through the Molenpolder, so we could visit the quaking bogs and fens. Wide stretched mats of Sphagnum were found, including small patches of Sphagnum subnitens, in Dutch ‘Glanzend veenmos’, and Sphagnum capillifolium, in Dutch ‘Stijf veenmos’. It was a relaxing boat trip through the abundance of vegetation of the Molenpolder.

I also tested the vegetation like Eurasian Watermilfoil, in Dutch ‘Aarvederkruid’, Common Bladderwort, in Dutch ‘Groot blaasjeskruid’, and different Sphagnum species on desmids. The samples were not as rich as I expected, though I did find some interesting species, like Tetmemorus laevis var. laevis and possibly Pleurotaenium archeri.

Tetmemorus laevis var. laevis

Tetmemorus laevis var. laevis is rather common, especially in sub-atmosphytic Sphagnum cushions, like quaking bogs. This desmid is characterized by fusiform cells and broadly rounded apices, with deep apical incisions and with pronounced ‘lips’. Cell dimensions: (70) 80-120 (-145) μm x (17) 20-30 (-38) μm.

I also found one possible specimen of the rare desmid Pleurotaenium archeri. I need to find more specimens to be absolutely sure of this identification. The phytoplankton expert Ton Joosten did sound quite convincing that he thought this really might be the rare species. Hopefully after my upcoming Holiday I can find another one in my sample. Here are the pictures.

cf Pleurotaenium archeri

Pleurotaenium archeri has subcylindric cells, only near the ends rather abrubtly tapering toward the truncately rounded apices. The semicells have a prominent basal inflation and a deep constriction immediately above it. The apices are provided with a twist of granules, though in my specimen these are hardly visible. The granules may be much reduced. Earlier specimens were found at least in some quaking fen hollows near Kortenhoef in the Province of Noord-Holland, the Netherlands. I also found my specimen in a quaking bog. Cell dimensions: 450-900 μm x 30-50 μm.

You can see the basal inflation and quite a
deep constriction above it in the center

Hardly visible granules at the apex

This will be the end of this very long Blog. In October I will participate in the microscopy session of the ‘Sphagnum for dummies’ course. To be continued…

Literature

Bouman AC (2002) De Nederlandse Veenmossen - Flora en verspreidingsatlas van de Nederlandse Sphagnopsida, Bryologische en Lichenologische Werkgroep van de KNNV, Stihcting KNNV Uitgeverij Utrecht.

Coesel PFM & Meesters KJ (2007) Desmids of the Lowlands - Mesotaeniaceae and Desmidiaceae of the European Lowlands, KNNV Publishing Zeist.

Van Dort K, Buter C & Horvers B (2010) Fotogids Mossen, KNNV Uitgeverij Zeist.