Ptyxis Ecology - Our Botany Blog

Sunday, 4 May 2008

Hummocks of brown Sphagnum

Yesterday was a very satisfying day in the field. I went up to Kielder to check out a site that had old records for Sphagnum austinii. This is a special species for several reasons. It is very uncommon nationally and has only been recorded at 4 sites in Northumberland. It always grows only in the best quality bog habitat and in bogs that have not been mis-managed. And it used to be our most abundant peat-forming Sphagnum species in the past. Estimates reckon it formed about 80% of our peat and sometimes it is still possible to identify its leaves (due to the distinctive lamellae on the green cells) at the bottom of the peat. Here is a close-up image of the surface of a hummock:Sphagnum austinii

In the few sites where it is found nowadays it can form very big hummocks which are very hard. Some people say you can sit on it and leave no impression behind but maybe that's exaggerating slightly! You can imagine how it would be a good peat-former when you see those big hummocks. I found two hummocks of it yesterday in a very wet bog. These hummocks were not very big but they were easy to find as most of the bog was incredibly flat. The few hummocks of Sphagnum that were there really stood out.

Low hummock of Sphagnum austinii in wet bog at Kielder

In the picture above you can see a lot of surface water in the background . This is the kind of bog where it would be useful to have snow shoes. The extensive wet part of the bog had about 50% surface water interspersed with flat carpets of Sphagnum rather than hummocks. Most of the Sphagnum was papillosum, magellanicum, capillifolium and tenellum. There was also lots of sundews, cranberry and bog rosemary. In the NVC this vegetation is known as M18a. This is known to be one of the wettest types of bog communities, described as 'saturated' and this example was probably towards the wetter end of this normally wet community.

The brown of Sphagnum austinii contrasting with the red of Sphagnum magellanicum on the left.

From the pictures above you can see it is a very brown species and this is a good way of initially recognising it in the field. Where you find Sphagnum austinii it is always worth looking for another uncommon brown species Sphagnum fuscum. This differs in having much more narrow branch leaves - like a brown version of Sphagnum capillifolium. It is a bit more common than austinii in the north of Scotland but it is even more rare than austinii in Northumberland.

Surface of Sphagnum fuscum hummock.

Before yesterday it had only ever been recorded at one site in Northumberland - the famous Muckle Moss. Sure enough, after a bit of searching I was able to find a single hummock.

Prominent hummock of Sphagnum fuscum in flat area of bog.

Both of these species are indicators of really good quality habitat and both have suffered massive declines. If one of these wet bogs is drained or burnt even once these species quickly dissapear, usually never to return. Yesterday the way the tiny number of hummocks of these two species stood out from the flat bog surface was quite melancholy as it made them look very isolated!



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