Peat-coring on Kirkconnell Flow

Kirkconnell Flow, South of Dumfries and West of the River Nith, is one of those valuable and unusual peat-bogs known as raised mires or, more poetically, Mosses. There are several around the edges of the Solway Firth, all protected in various ways and by various organisations.

Kirkconnell Flow is a Scottish National Nature Reserve (NNR), a UK Site of Special Scientific Interest (SSSI) and an EU Special Area of Conservation (SAC) – but don’t be put off by all the conservation acronyms. It’s a special place, with a complicated history and, as is already apparent, a place with optimism, and insights, about the future.

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Dr Lauren Parry and some of the Borderlands#2 group

 

At the end of April this year a group of artists, poets and fiction-writers, scientists of various sorts, sound-artists and composers wandered out onto the Flow as part of the Borderlands#2 gathering – not only to experience what being on a Moss or Flow or Mire might mean, but for a more practical purpose, too: to get our hands dirty – to go peat-coring.

 

Like all the other raised mires around the Upper Solway, Kirkconnell Flow is a dome of peat. I’ve borrowed Scottish Natural Heritage’s beautifully visual description of its origin: “When the glaciers retreated from Scotland 10,000 years ago, the landscape was littered with many pits, often within a layer of watertight glacial debris or till. These basins formed lochs and were colonised by a fringe of fen plants, which slowly spread across the lochs until no open water was left. A combination of loch sediment and plant material eventually led to many lochs completely infilling. As the loch basin filled with fen peats and sediments, the plants could no longer root in the mineral soils below.

Plants in the outer fringes of the swamp soaked up all of the nutrients flowing in from the surrounding ground, leaving the centre of the swamp waterlogged and nutrient-poor – just the right conditions to encourage a bog to form. Sphagnum bog mosses thrive in these conditions and started to dominate the vegetation. The steady upward growth of the living Sphagnum layer and the slow accumulation of the dead vegetation below combined to produce peat.

As peat accumulated, it began to rise above the level of the former loch surface. Once a layer half a metre or more in thickness had formed above the old surface, the peat became isolated from groundwater. The bog therefore became dependent on rainwater alone, deriving all its nourishment from the atmosphere, and as a result is poor in nutrients [my italics].

In other words, it’s ‘ombrotrophic’: a new word, one of many that I learnt that afternoon from Dr Lauren Parry, of Glasgow University, who had come to lead us through the heather to the central dome. An ombrotrophic , literally ‘cloud-fed’, bog is one that is wetted only by rain, not by springs or burns, and is isolated from the surrounding landscape. Rain is poor in nutrients, so only those plants that tolerate acid, low-nutrient conditions live there: the richly-coloured Sphagnum mosses; the berry-bearing plants such as blaeberry and crowberry; bog-myrtle and bog rosemary with their crushed-leaf scents; pale ‘reindeer moss’ lichen; and the white fluffy flags of the bog-cottons. It was early in the year when we visited, but the hints of past and future were there – even wizened last-season crowberries amongst the cotton-buds.

To reach the dome of peat we had walked a woodland path ringing with the descending chromatic scales of competing willow-warblers, and waded through knee-deep tangles of heather. The Flow had for decades been gnawed and battered by humans: first by peat-cuttings, then by heather-burning for grouse-moors. Birch carr and pine forest encroached as the water-table dropped and the peat dried out; the trees themselves transpired water and hastened the drying and destabilisation of the mire.

The SNH document describes well the history of the Flow and the damage inflicted upon it. But in 1998 they purchased the Reserve and – as is the case with conservers of the Solway’s other Mosses – are attempting to restore the raised bog’s hydrology. One of the first, and major, tasks, has been to cut down and remove the trees from the central area of the Flow

As Lauren Parry said, “Removing the trees has been an ‘encroachment issue’ which is different from a ‘plantation issue’” (which would have involved probably lengthy discussions about ownership of the plantation, and compensation).

Lauren’s PhD research related to the composition of peat; since then she has concentrated on carbon sequestration – the ways in which peatlands store carbon and how the carbon levels relate to changes in the climate.While very well-practised in the technique of peat-coring, she’s now also exploring less ‘dirty’ techniques such as ground-penetrating radar to get information about the ‘bulk density’, the relative amount of solid, organic material within the peat. I hadn’t realised that a peat-bed may be riddled with ‘pipes’ and cavities and cracks.

And now, out on the Flow proper, there are more words, too; hard-edged words and musical words with a cadence: acrotelm and catotelm, the lagg fen and the haplotelm; the ‘Russian’ corer, proxies, testate amoebae.

“We really love taking cores and looking at them under a microscope,” Lauren says. “The peat’s a wonderful archive.”

Why “an archive”?  Vegetation growing on the thin ‘living’ top layer of the bog (the acrotelm) responds in different ways to the environmental conditions – the amount of rain, warmth, nutrients, pollution. Different species – of plants and of microscopic animals – grow more slowly or out-compete others depending on their favourite conditions. Pollen, even radioactive particles (remember Chernobyl)  blown in from surrounding areas is deposited or incorporated amongst the stems.

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The acrotelm and catotelm: diagram from Richard Lindsay’s document for the RSPB (see below for link)

And as plants die and are replaced, they are grown over by new individuals. The combination of new plant growth and water-logging means that oxygen diffuses into the lower layers so slowly that the decomposition of dead plants uses it faster than it can be supplied, and so the lower layers (the catotelm) are anaerobic. Layers of only partly-decomposed plant matter build up in an ‘active mire’.

Dr Richard Lindsay, of the Sustainable Research Unit, University of East London, has written a long, but delightfully easy-to-read and very informative discussion document for the Scottish RSPB on Peat bogs and Carbon, a critical synthesis (2010) – what he calls his ‘Big Bogs Report’ (unfortunately it’s only available online).

‘Peatbogs are responsive systems with homoeostatic mechanisms that are not far removed from those found in living organisms … features having many similarities to tree-rings can be found in the equally-thin layers of peat which are successively deposited in a bog over millenia. These narrow bands of peat tell the same tale as tree-rings but over a much longer time-scale.’

And the peat (or ‘turf’ as it’s called in Ireland – but then, in County Mayo they call herons, ‘storks’) is ‘a direct product of the vegetation which created it. Consequently the characteristics of this peat soil reflect the nature of the vegetation which created it, while the vegetation itself reflects the prevailing hydrological and nutrient conditions.’

So, an archive: which can be examined by drilling down and taking a core, slices of which can undergo a battery of chemical, spectroscopic, radiological and microscopical examination in the lab for the range of minerals and isotopes, for types of pollen, for the hard cases of the unicellular testate amoebae, and more. Amoebae, pollen – these are ‘proxies’, different species flourishing or dying out according to prevailing conditions and therefore acting as indicators. All these measurements provide clues as to what climatic conditions prevailed at the time that ‘peat-ring’ was laid down.

Taking a core doesn’t need a drilling-rig, just patience, organisation, and some brute manual force. It required the help of ‘the Russian’ – ‘who’ turned out to be type of metal corer, a side-filling sampler with a sharpened edge; when rotated clockwise the blade cuts a core which is then held in the chamber by a plate. Back on the surface, the corer is rotated in the opposite direction and the undisturbed sample is slid out into a plastic ‘gutter’ which is marked with felt pen for ‘top’ and depth, and the whole is then wrapped in cling film and kept horizontal.

The first core, from the acrotelm, was fibrous with roots and decaying grass and other plants. Fifty-centimetre lengths were gradually added as the Russian penetrated deeper; each time it was then pulled back to disgorge its sample.

The core from 150-200 cms represented life about 2000 years ago.

Gloop-gloop. The corer made wet, sucking sounds as it was pulled free. Deeper cores became smoother and sloppier.

More rods were added: taller, able-bodied men were co-opted to help lift the rod vertically into place. An artist was taking photos of cranberries; someone was watching skylarks through his binoculars; others were sitting on the ground chatting; someone was making notes in a tiny ring-bound book; three of us bounced on the mire’s surface several metres away from the group, and startled faces turned towards us as the quake spread out in waves.

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The final, clay, core – from 6.5metres

And then, at 6.5 metres’ depth, the bottom of Kirkconnell Flow was reached! The sample chamber of the corer revealed a glossy grey cylinder of clay, formed by the friction of glaciers against rocks, and deposited around 9000 years ago.

At that time, there would have been forest growing each side of the Firth, birch, hazel, oak and pine. But as the climate became wetter and freshwater drained down towards the Firth, sphagnum mosses formed blanket-bogs in these low-lying areas, the tree-roots became waterlogged, trees died; the remains of this mighty ‘submerged forest’ were preserved in the peat-beds that are occasionally revealed on the Cumbrian shore. Further inland, though, the peat domes of Kirkconnell, Drumburgh, Wedholme and the other raised mires grew and developed, becoming isolated ecosystems with their own special character.

As for ‘our’ peat core, the sections have been frozen and await investigation by Lauren Parry with the help of the creative practitioners of Borderlands#2

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  1. There is a very good and useful BBC video of Natural England’s Alasdair Brock explaining about peat-coring and the restoration of Wedholme Flow, in the South Solway Mosses.

2. Since I wrote this blog-post, Kate Foster – artist, writer and organiser of the Borderlines#2 event – has written a lovely piece about how peat, and what it contains, including the proxies of testate amoebae, are inspiring her art.

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