The Black Wood of Rannoch - October 2016

I had briefly visited the Black Wood of Rannoch, back in May and decided then, that it warranted a return visit(s). Events conspired to present an opportunity to further explore the woodland, during a weeks stay in Kinloch Rannoch, in late October with the potential for autumnal colour.

Surprisingly for a woodland, there is plenty of literature on the Black Wood of Rannoch and the surrounding area. Through documents, surveys and maps, woodland historians have pieced together a history of the wood, identifying major timber felling events and periods of regeneration. Archaeologists have recorded iron working sites, charcoal platforms, lime kilns, saw pits, saw mills and occupation sites, to provide an indication of the level of natural resource exploitation. Scientists have published papers and reports on numerous aspects of the ecology and species that inhabit the woodland. Judging by the number of old painted stakes, marker posts denoting transect lines and new orange spray painted stakes, the Black Wood is an area of ongoing scientific research and monitoring activities.

Granny Pines and regeneration, in the Black Wood

Geology, Glaciation, Climate and Soils

The geology underlying the Black Wood is predominantly Dalradian metasedimentary rocks, though away from streams, bedrock exposures are limited.  The area has been repeatedly inundated by glacial ice during the Quatenary, the last time during the Loch Lomond stadial. The littoral of Loch Rannoch provides evidence for the origin of glacial debris, as amongst the metasedimentary rocks of local origin, are pale speckled granite rocks that originate from the Moor of Rannoch granite pluton to the west of Loch Rannoch. Analysis of glacial landforms has allowed Geomorphologist to hypothesise that an Ice Cap ~1 Km thick, formed over Rannoch Moor during the Loch Lomond stadial, with outlet glaciers spreading out across the landscape. The study of glacial landforms has led some to hypothesise that there were areas of cold and warm based Ice and that the cold based Ice may have preserved relict landforms from previous episodes of glaciation.  When the climate ameliorated, the Loch Lomond stadial glaciers retreated and the Ice Cap down wasted, leaving behind an extensive assemblage of glacial till, morainic debris and glaciofluvial deposits, mantling the land.

Stream exposure of inclined bedrock and riparian woodland

The metamorphic bedrock underlying the woodland is relatively impermeable and rainfall drains through the superficial deposits and soil layers. The Loch Rannoch area receives a mean annual rainfall of ~1.5 metres and higher amounts over adjacent elevated ground. Away from forestry tracks and wandering along animal track ways that contour the slopes, there are a surprising number of spring lines and flushes encountered.

Flush mosses 

The nature and topography of the woodland floor has generated a range of soils: mainly podzols, gleys and peats. The diverse nature of the ground topography and soils has created a mosaic of micro-habitats within the Black Wood of Rannoch, exploited by flora to produce vegetation communities in ground and field layers of: mosses, rushes, sedges, grasses, herbs, shrubs and bracken.

Woodland history

The general consensus amongst woodland historians is that once upon a time the Black Wood extended further west, east and south. The combination of over grazing and unsustainable tree felling, reduced the wood to a core area, with Gaelic place names, Old maps, remnant Scots Pines, hinting at the former extent of the wood. Matters could be far worse, if it wasn't for enlightened individuals in times past, initiating programs of woodland regeneration, but on the whole it has been a case of gradual decline. From 1947 the Black Wood, has been managed by the Forestry Commission and what exists today reflects the good and not so good aspects of the Forestry Commissions management of the woodland, that they in turn took ownership of. Conservation areas, regeneration and expansion of the Caledonian Forest are the good aspects and Management plans are in place to underpin a number of objectives and ambitions.

Scots Pines and Birch

The not so good aspects of the FC's management are being revisited, non native trees removed and native trees of local provenance planted. A significant area of the Black Wood has also been designated as a Special Area of Conservation and Site of Special Scientific Interest, legally protected and specific management plans cover these areas.


Granny Pines

Granny Pine and Birch

The Granny Pines define the special nature of the Caledonian Forest, their size and morphology, adding presence and a visual indicator of a woods age. The Granny Pines in the Black Wood have been dated by dendrochronology to the late 17th C. To my eyes, some of the Granny Pines have a form akin to pollarded Oaks, with large spreading crowns and as with Oak woodlands there is also Wood Sorrel growing beneath then amongst the needle litter. The survival of Granny Pines has been attributed to their unsuitability for timber.

Woodland floor under a Granny Pine

Hummocks

Anyone wandering 'off piste' in native Pinewoods will encounter 'hummocks' and the Black Wood of Rannoch is no exception, with 'Hummocks' covered in bilberry and heather, sometimes with a Scots Pine or Birch tree growing on them. Some hummocks are of a substantial size, others are in an embryonic state, with a blaeberry/moss cushion colonising a pine stump.

Hummock forming on pine stump

As far as I could tell, the majority of 'hummocks' in the Black Wood, do not appear to be erratic boulders blanketed in vegetation and instead are most likely formed from relict pine tree stumps, although a case could be made for wood ants nests also making a contribution. Conventional wisdom suggests the formation of a 'hummock' takes some time and they are a feature of Caledonian Pine woods with a long history of continuous woodland cover.

Hummocks

Bones of the Forest and windthrow

Foresters indoctrinated in 'modern' forestry at the old Forest schools, would no doubt be aghast at the scruffy nature of the Black Wood, there are a visible number of snags and fallen deadwood in the conservation areas within the Black Wood. The snags and windblow are a positive development for biodiversity and the organisms who are dependent on deadwood for habitat. Standing deadwood is a particularly important resource as the decay rate is slower than fallen material on the ground. The slower decay rate in standing deadwood is exploited by different organisms, to those that breakdown fallen wood on the ground, which in turn means increased biodiversity.

The deciduous woodland

A feature of the Black Wood is the prevalence of Birch, Rowan and Willow trees, that add diversity and a welcome splash of autumnal colour. Whilst Birch dominate some woodland areas, it seems that the Rowan trees are good indicators of the grazing level, in one enclosure where deer have been excluded for some while, it is now dominated by Rowan, in stark contrast to the numbers of Rowan trees in the wider woodland. Having typed that there are numbers of Rowan seedlings on the ground under trees where birds have roosted and this might indicate a further reduction in grazing animals/pressure. With very little imagination, it is easy to extrapolate how Highlands woods and the wider landscape might appear with a reduction in grazing of herbivores, to conservation levels.

During the visits, significant numbers of Fieldfares were seen feeding on Rowan berries and blaeberries, plants that rely on avian dispersal and the reason why Rowan saplings, Blaeberry and Cowberry. can be seen growing as epiphytes on Granny Pines.

Fungi

I had anticipated some native Pine woodland specialists and was not disappointed.

Scaly Tooth fungus (Sarcodon squamosus)

Gypsy mushroom (Cortinarius caperatus) and Ostrich-plume Feather-moss (Ptilium crista-castrensis)

Fly agaric (Amanita muscaria)

Unidentified solitary Amanita fungus and Five-ranked Bog-moss (Sphagnum quinquefarium)

I thoroughly enjoyed my visits to the Black Wood of Rannoch, although only exploring a small fraction of its extent, there was still plenty of subject matter to photograph, much to ponder and the unique atmosphere of a native Pinewood in autumn to savour. Definitely a place to return to again.

Native Pinewoods of Scotland

I was conducting some research into native pinewoods in Scotland and this post is a summary of the information on native pinewoods.  The distribution of native Scots pinewoods is illustrated on the Joint Nature Conservation Committee website, elsewhere the Forestry Commission maintain a Native Pinewood Inventory of sites.

Distribution of Caledonian Forest
http://jncc.defra.gov.uk/publications/JNCC312/habitat_comparison.asp?FeatureIntCode=H91C0 

The conservation numbers are as follows

• 84 locations are currently attributed as sites of native pinewoods.
• 10 of the most notable areas with native pinewoods have been designated as Special Areas of Conservation (SAC), 
• The remainder mostly designated as Sites of Special Scientific Interest (SSSI)
• An inventory of Caledonian Pinewoods has been drawn up by the Forestry Commission and the inventory contains all the known pinewoods with more than 30 individual trees where the balance of probability is that they are genuinely native (semi-natural), that is, descended from one generation to another by natural seeding.
• In 1998 the inventory stated that there was a Pinewood (core) area 17,882 ha, Regeneration zone 25,399 ha and Buffer zone 92032 ha.
• For a Pinewood to be accepted as a registered source of native scots pine seed it needs to be isolated from pine of non-local origins, normally at least 400 m.

Ballochbuie Forest SAC, 2014

Information that relates to the native pinewoods of Scotland

Early observations

• Stephens and Carlisle record in their 1959 publication Native Woods Pinewoods of Scotland that there was some controversy and speculation about the quality of native Scots Pine in the 18th C. Timber merchants and tree growers were adamant that there were two distinct species of Scots Pines producing vastly different timber quality. Others disputed that there wasn't two species and instead observed that climate and site determined the quality. Another point of view was that the Scots Pine needed time to mature before being assessed for timber quality and that 30 year plantations were not a reliable guide to mature tree timber quality. Another view was that some planting had been undertaken with 'superior' continental pine seeds, mixed in native seeds. And someone else pointed out that native Scots Pines in the highlands, do not grown in regimented plantations, but in exposed locations upon ground unfit for anything else and when mature demonstrably produce high quality timber.
• With the issue of timber quality highlighted, there then ensued a concentrated effort starting in the late 18th C to  determine every conceivable physical characteristic of Scotland's Scots Pines; morphology, cone size and shape, seed weight, seed colour, bark character, needle length ...
• Scots Pines were also characterised from Switzerland, Sweden, Finland, France, Germany and Scotland. Numerous species/varieties of Pinus Sylvestris were proposed/named based on morphology, habit, bark or combinations thereof.
• Bark studies showed distinct varieties on trees with numerous designations of ridge, mussel, flake, plate and intermediaries. Someone inconveniently pointed out that the character of bark also changes over the course of a tree's lifespan ... Nonetheless, in Scotland's native pinewoods there appeared to be a regional flavour of bark characters.
• 18th and 19th Century plantings of known continental provenanced Scots pines in Scotland proved disappointing. The ferocity of a 'heelan hooley' was too much for some plantations and the combination of exposure to rain/wind/hail/freeze thaw conditions, affliction from disease/pests produced inferior sub optimal growth in continental trees.

Plate and flake bark, Glen Affric ~ 2013

• Forestry Commission provenance trials 1929 - 1942 indicated that Scots Pine from continental Europe were superior to Scottish provenanced Scots Pines in southern England and were inferior in Scottish trial locations. Southern England has more of a continental climate, Scotland has an oceanic climate. There was no record on the soil/bedrock geology of the trial sites.
• When researchers and conservationist arrived at the new Nature Conservancy Council purchased Beinn Eighe National Nature Reserve (NNR) during the 1950's they commented on the differences between the west coast pines and the Highland/Cairngorms pines.
• Limited trials at an exposed site Glen Trool in 1965 determined that Scots Pines from Loch Maree coped better with Winter Blast than other trees.

Coulin native pinewood, Glen Torridon ~ 2012

Genetic diversity and consequences

• In the late 20th and early 21st Century genetic research has indicated that the Native Scots Pines are genetically diverse from the European Scots Pine populations and there is also a regional genetic diversity amongst the native pinewoods of Scotland.
• The genetic diversity continues down at the local level in Wester Ross, with the West Coulin pines being distinct from the East Coulin pines and Loch Maree pines, despite being less than 2 and 4 miles away respectively. 
• Beinn Eighe National Nature Reserve (NNR) started a tree nursery in the 1953 from seed collected in the reserve, to grow seedlings that would regenerate the native pinewoods on the reserve.
• In the 1970 the Beinn Eighe NNR closed its tree nursery and the Forestry Commission supplied the Beinn Eighe National Nature Reserve with seed instead from its Black Isle nursery.
• A shortage of seedlings from the nursery meant the Forestry Commission supplied Glen Affric originated Scots Pine seedlings to the Beinn Ejghe NNR, which were planted.
• When the genetic studies of the native pinewoods were made available, the Beinn Eighe NNR had to remove Glen Affric sourced Scots Pines to preserve the genetic diversity of the Coulin Pinewoods and also remove Glen Affric sourced Scots Pines plantations adjacent to Coille na Glas Leitire to preserve the genetic diversity of Loch Maree pines.
• In 1987 Beinn Eighe NNR restarted a tree nursery growing its own local origin seedlings. 

Glen Affric ~ 2013

Dates and pinewood dynamics

• The oldest living native Scots pine trees date from the 1450's AD in Glen Loyne and Glen Derry.
• Palynologists declared Scots Pine colonised Scotland around 8,000 years before present from the north west and slowly spread south.
• Sub fossil Scots Pine retrieved from lochs in the Cairngorms have been dated to just before 8,000 years before present.
• Dendrochronologists are cautiously optimistic of eventually establishing a sequence of 8,000 years of tree ring chronology data for the Highlands of Scotland from subfossil pine material retrieved from lochs and peat.
• The East end of Glen Affric has seen a continuous presence of Scots Pine woodland for the last 8,000 years, whilst the West end of Glen Affric has an entirely different history of Scots Pine woodland with very little Scots Pine woodland for the last 4,000 years. Ecologists speculate that the difference is due to a shifting ecotone due to the steep climatic gradient down the glen or blanket peat and hydrology or a combination of both.
• Historical research has identified a small number of Pinewoods that are recorded in the 17th and 18th Centuries but have either disappeared or are are no longer considered as viable woodland. Some of those pinewoods were already in decline at the time of recording.
• There is a general consensus that the decline of native pinewoods are a combination of mismanagement and climate.
• Palynology studies have been suspect in identifying the physical presence of Scots Pines at sites.
• Climate change is believed to have influenced the ability of Scots Pine to colonise and regenerate on blanket peat.

Screenshot from Forestry Commission