[401]
MOUNTAIN
A NEW APPROACH
TO SCOTTISH
VEGETATION
BY M. E. D. POORE* AND D. N. MCVEAN
Edinburgh)
(The NatureConservancy,
(WithsevenFigures in theText)
CONTENTS
I.
II.
III.
IV.
V.
INTRODUCTION
.
REVIEW OF LITERATURE
THE
ECOLOGICAL
FRAMEWORK
A.
B.
C.
D.
E.
Altitudinal zonation .
.
Oceanicity
Snow cover
.
Base status
.
Moisture ..
A.
B.
C.
D.
E.
F.
G.
Dwarf shrub heaths .
.
Betula nana bogs
Lichen heaths
.
Moss heaths
.
Nardus snow beds
Vaccinium snow beds
Dryas heaths .
COMMUNITIES
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
DISTINGUISHED
.
.
I.
.
.
.
.
SUMMARY
ADDENDUM .
REFERENCES
.
.
.
.
.
.
.
.
.
.
401
402
.
.
PAGE
401
403
411
414
416
416
417
417
421
425
427
430
430
434
435
.
438
438
INTRODUCTION
Since Watt and Jones drew attention in 1948 to the scarcity of informationabout
vegetationat higheraltitudes in Britain therehave been several contributionsto this
subject (Metcalfe, 1950; Pearsall, 1950; Burges, 1951; Poore, 1955). As these are
either detailed regional studies, or parts of works of wider scope, there seems to be
room for a review of some of the general problems posed by Scottish mountain
vegetation. We hope to describe in this paper some of the variation whichis evident
over the whole of the Scottish Highlands, and discuss the factors responsible, at
the same time tryingto fitthe communitiesso distinguishedinto the knownpattern
of vegetation in north-westEurope.
II.
REVIEW
OF LITERATURE
In Smith's classification,reproducedin Tansley (1939), vegetationwhichis above the
potential tree-lineand rich in Arctic-Alpinespecies, is divided into two zones, the
Arctic-Alpineand the Upper Arctic-Alpine.The lowerlimitofthe formeris placed at
c. 2000 ft. (612 m.) in the central Highlands, but descends almost to sea level in the
west. It contains the climax association of Arctic-Alpinegrassland and certain
unspecifiedheath associations. In the Upper Arctic-Alpinezone are grouped the
Rhacomitriumheath association, the moss-lichenassocies of mountain-topdetritus,
and certain snow-patch communities, in addition to scree and chomophyte
* At present workingwith Hunting Aero Surveys, Elstree Way, Boreham Wood, Herts.
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402
A New Approach to ScottishMountain Vegetation
by maturity,by the exposure-snow
vegetation. The communitiesare differentiated
cover complex and by the chemical compositionofthe rock.
Pearsall (1950), in discussing the Arctic-Alpinezones, is mainly concerned with
soil characteristicsto which he attributesthe main differentiation
of communities.
He distinguishesfourtypes of vegetation; Rhacomitriumheath, montane grassland,
summit-heathvegetation and flushvegetation; and concludes 'the normal trend of
vegetational developmenton the mountain-topdetrituswith increasingstability of
surfacethus followsthe sequence: Rhacomitriumheath - summitgrassland - summit
heath (dryor wet) and is associated with the leaching of the humus whichfollowsthe
stabilization of the surface'.
Crampton (1911) distinguishesthree associations on the mountains of Caithness:
the Rhacomitriumcarpet association, the Calluna-lichen mat association, and the
Arctostaphylosmat association. In the geologically uniformterrain in which he
worked he consideredthat the plant associations were differentiated
chieflyby the
to
which
each
was
of
locality
subjected.
degree exposure
Watt and Jones (1948) are more systematicand detailed in theirtreatment. They
distinguishfourzones above the present tree-line:the Calluna zone, the EmpetrumVaccinium zone, the Juncus zone, and snow-patchvegetation. In Fig. 6 (p. 297) of
theirpaper, the relationshipsofthese zones, and ofthe associations occurringin them,
are representedin a diagram showingaltitude as one variable, and the exposure-snow
cover complex as the other.
Each of these contributionsrepresentspart of a system which might be applied
moregenerally,but in none ofthemis the scope wide enoughto relate the parts to the
whole. In particularit is unfortunatethat so littlereferenceis made to the extensive
and relevant Scandinavian publications.
The schemewhichis producedhereis completebut tentative. It is based on vegetation studies carried out by the methods described by Poore (1955a), supplemented
by extensive observations. In particular we have traced certain communitiesover
much of theirrange and have observed how theirfloristics,organizationand reaction
to habitat may change. From this, preliminaryhypotheseshave been formedabout
the principal causal influences. As the importance of some of the factors has not
previouslybeen stressed in the British literature,and as some of the communities
used in illustrationhave not previouslybeen described,some space is also devoted to
these topics.
III.
THE ECOLOGICAL FRAMEWORK
A general scheme for the arrangementof Scottish mountain vegetation should be
based on floristicsand synecology;for,although it is more convenientto distinguish
noda by floristics(Poore, 1955b), it is easier and more satisfactoryto arrange these
noda in ecological series. In the presentstate of our knowledgethis can best be done
by using the factor complexes which govern the main variation in vegetation, and
onlylater splittingthem into theircomponents.
Communities which are undoubtedly seral (e.g. screes) are omitted from the
scheme. We consider that most mountain communities(heaths, snow beds, flushes
and springs) are part of a climax mosaic, each being maintained by the action of
powerfulhabitat factors. Within each communitythere is oftencyclical change, or
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M. E. D. POORE AND D. N. MCVEAN
403
a small-scale pattern of micro-succession,as the work of the Cambridge Cairngorm
party has demonstratedabundantly; but the distributionof most of them and their
position relative to one another are so closely correlatedwith the presentpattern of
habitat factorsthat they are unlikelyto stand in a developmental relation to each
other. Alterations of the boundaries of communities caused by small climatic
fluctuationsare more evident than signs of seral development (contrast Pearsall,
1950).
Most of the Scottish mountain communitieswill fitinto a frameworkmade up of
the followingfivefactorcomplexes:
A. Altitudinalzonation
The climatic forestlimit, which is a convenient datum line in the zonation of
mountain vegetation, is difficultto employ in Scotland because of the general
scarcityof native forestand the modificationof its upper limitby grazing and burning. Some confusionarises in assigning to the correct category certain vegetation
types which may have been derived eitherfromthe upper forestor fromthe region
immediatelyabove (Fig. 1, a to c).
The scraps of evidence remaining(unpublished material - D. McV.) indicate that
the natural forestlimit in Scotland, if it could be realized, would be determined
largely by exposure and might,therefore,be expected to show considerable altitudinal variation and attain surprisinglyhigh levels locally in shelteredsites.
The highestnatural forestlimit (pine) to be seen at the presentday lies at 2100 ft.
(640 m.) on an exposed westernshoulder of the Cairngorms(Watt and Jones, 1948),
and it is borderedabove by a narrowband of juniper scrub. In Scandinavia the belt
of birch scrub (Betula tortuosa)above the upper limit of pine, spruce, or mixed
deciduous wood, is knownas the Sub-Alpinezone. Withinit thereare areas ofjuniper
and willow,or even of grassland wherethe establishmentof saeters has been followed
by clearing and grazing. Burning of scrub is not customaryhere. If the local topography is irregularthere may also be clearings caused by greater exposure or sustained snow cover.
The birch belt is fragmentaryin Scotland and the picturestill furtherconfusedby
the replacement of pine and oak by secondary birchwoods at lower altitudes. The
juniper scrub mentionedabove, some of the upper birchscrub in the west and central
Highlands and the most northernbirch woods of the mainland, beyond the limit of
oak and pine, may belong to the Sub-Alpine zone. The lower limit of the zone might
be set at 2300 to 2500 ft. (690 to 750 m.) in the east and central Highlands and about
ofthe presenttree-line
300 to 500 ft.(91 to 135 m.) in thewest,althoughthe artificiality
to fixwith any precision.
and ofthe communitiesimmediatelyabove make it difficult
Following Du Rietz (1925), Nordhagen (1943) has divided the Norwegian mountains above the birch-lineinto threeregions,*the Low Alpine, the Middle Alpine and
the High Alpine (Fig. 2). In Scandinavia the Low Alpine zone is predominantly
one of the dwarf shrubs, of which the most importantin continental Norway are
juniper (Juniperus commtunisssp. nana), dwarf birch (Betula nana) and various
Arctic willows (Salix glauca, S. hastata, S. lanata, S. lapponum, S. myrsinitesand
* The term
'region' is used in English translations of the Scandinavian literature. As this usage may
lead to confusion,we propose to use 'zone' instead.
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404
A New ApproachtoScottishMountainVegetation
~ACAIRNGORMS
3s.u-
from
Watl& Jones)
(Modified
c|
c_________
Salixherbacea
liverwort
4000snow
beds
CarexNardus
/
Juncus
rifidus
z
O
a
Nardus
&
Vaccinium
3000
snow /
beds
O
2000
Rhacooonum-
~Carex
cL
CALLUNALINE
with
ois uria
Calluna-Cladon
a
----
iper Scr_
TREE NE ----'pROBABLE POTENTIAL
(Yellowlichen)
--
PINE
/
now
CALUNA
wih
Trichophorum
wilh
Arclostaphylos
o<i
1000
INCREASING
SHELTER
AND SNOW COVER
INCREASING
EXPOSURE
Fig. la. Vegetation diagram - Cairngorms. ModifiedfromWatt and Jones.
|^'
~
lz~~
4
0
o
4000
4000
BREADALBANE
Salix-liverwort
snowb.e
[ .....Nardus
300
3000
ba'a
(Sibbaldia)
I
Vacc. /
Juncus
trifidus
mnomitrium)
Narus
Rhacomitrium
(Arcic-alpne
pioa
grassland)
_LienEmpelrum-Vaccinium
aichi lcaa
u
inV iim
(Nardus)
&Willow scrub
nabr
H
2-====
==_
2000 J-
Calluna
(Nardus)
t/
100
INCREASING
SHELTER
AND SNOW COVER
INCREASING_
EXPOSURE
Fig. lb. Vegetation diagram - Breadalbane.
NORTH-WEST
3000
2500
Snowbed
vegetation
[SibbaldiaAlchemilla
Hypnoid
mossheath
[Do.richin\
rareplants)
Rhacomitrium
withNardus
(J.trifidus)
2000
C
TrichophorumNardus
snow
beds
Juncuspavement
Calluna
with
Loiseleuria
and
c
[flush
grasslands]
1500
0A
Calluna withJuniperscrub
~Pine
~~~~~~~1000
1000
E^~t~~
<
~
:
[Specis rich
Rhacomitium
0
heath]
u
(wihJuniper,
Ilex,etc.)
[Oak-birchon leached brown earths]
- Calluna- Vacciniumand
~Derived
INCREASING
SHELTER& SNOW COVER
Calluna- Erica- Trichophorum
INCREASING
EXPOSURE
Fig. Ic. Vegetation diagram - North-westHighlands.
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M. E. D. POORE AND D. N. MCVEAN
405
S. phylicifolia).Juniperand birchfavourdry,poorsoilsand the willowsthriveon
wetteror richerspots,especiallywhereflushedfromabove by snowwater.
This is also the regionof dominanceof the ericoiddwarfshrubs(Vacciniumspp.,
and Calluna). In Sogn (Knaben, 1950)
Empetrumspp., Arctous,Arctostaphylos
at
and
the
ceases
about
900
m.
vegetationabove thisis composedof Empejuniper
and
Nardus
communities
Vaccinium,
trum,
up to about 1100m. where
Arctostaphylos
theLow AlpinepassesintotheMiddleAlpinezone,whichcontainssnow beds and
Festucaovinaand Carexbigelowii.
heathsofJuncustrifidus,
can
be
traced
betweenthe Scandinavianzones and thosedistinguishContinuity
able in themountainsofScotland(Fig. 2). The passagefromtheLow to theMiddle
Alpine zone correspondswell with the transitionin Scotland fromdwarfshrub
Vacciniumand Loiseleuriato snow-bed
heaths,withabundantCalluna,Empetrum,
or
communities
dominated
by grassesand grass-likehemicryptophytes
vegetation
1800
1800-
* HIGHALPINE
=I
_ MIDDLEALPINE
. eW
e? eOeLOWALPINE
o SUB-ALPINE
FORESTREGION
....:'
:.:.-.*.*.*.
:....:.
1600 -
I.
*.-.
o-
1400 1200
C
.....
10 000
800
600
::
0
400
200
.
SYLFJELLENE
MIDDLESOGN CAIRNGORMS
BEINNEIGHE CLISHAM
SIKILSDALH0
Fig. 2. Altitudinal variation in the alpine regions of Norway and Scotland.
Festucavivipara,Luzula spicata,Desclhampsia
such as Juncustrifidus,
fiexuosaand
whichare characteristic
of moderately
Carexbigelowii.In this zone communities
exposedgroundare virtuallysqueezed out (Fig. Ib). The divisionfalls at about
and at about3500ft.(1065m.) in
3800 to 4000ft.(1160to 1215m.) in theCairngorms
as communon
level
is
the
exact
but
Breadalbane;
dependent exposureand snow-lie,
whereeitheroftheseis excessive.
itiesoftheMiddleAlpinezone extenddownwards
In Scotlandthe Low Alpinezone may againbe subdividedintoa lowersub-zoneof
dwarfshrubheathsin whichCallunais themostimportantdominantand an upper
heathsor,wheresomeshelteris afforded
zoneofRhacomitrium
bysnow,ofEmpetrumVacciniumheaths.
Few mountainrangesin Scotlandhave largeareas ofvegetationassignableto the
MiddleAlpinezone, and it is doubtfulif any reachthe trueHigh Alpinezone althoughexposureon the highestScottishtops limitscontinuousvegetationin the
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406
A New ApproachtoScottishMountainVegetation
same way as raw soil parent material plus low temperaturein continentalregions,
and produces High Alpine conditionslocally in the Ben Nevis range,the Cairngorms
and elsewhere.
These zones can be schematizedas follows:
Sub-Alpine zone
Low Alpine
Middle Alpine
a. Dwarf shrub zone
b. Moss zone
(dwarfshrubs still
present)
(Potential birch wood)
Calluna moors, blanket bogs, TrichophorunMolinia, Nardus and Agrostis-Festucagrassland.
Ericoid dwarfshrub heaths.
Rarely willow, juniper and dwarf birch
scrub.
Rhacomitrium heaths. Nardus grassland.
Empetrum-Vacciniumcommunities.
Juncus trifidusheaths.
Festuca vivipara-Gymnomitrium communities.
Snow-bed communities.
As Empetrum-Vaccinium
communitiesare clearlylimitedto areas with slightsnow
cover, and as Rhacomitriumheaths are such a widespread and characteristicfeature
of the Upper Low Alpine zone, it is suggested that 'Rhacomitriumzone' should be
substitutedfor 'Empetrum-Vacciniumzone' as a term of general application to the
ScottishHighlands. In Fig. 2 the altitudinal distributionof these zones in a transect
fromcontinentalNorway to the west of Scotland is representeddiagrammatically.
The various stations are Sikilsdalho in the eastern Jotunheim,the Sylfjellenewest of
Trondheim,the mountains of middle Sogn, the Cairngorms,Beinn Eighe (Wester
Ross) and Clisham (Harris). No attempthas been made to maintain a firmdistinction
between the Sub- and Low Alpine zones in Scotland.
It can be seen that in Norway the boundaries of the various zones are steadily
depressed towards the more maritime stations and that there is a simultaneous
tendencyforthe zones to widen. The Cairngormscorrespondmore closely to Sylene
than to Sogn, their lower latitude perhaps compensatingfortheir probably greater
oceanicity (pp. 412-13). The vegetational parallels between the Cairngormsand the
moreacid parts of the Sylene national park are striking(Poore, 1955c). Within Scotland the lower position of all zones than that of their counterpartsin Norway is
evident. Particularly noteworthyis the much increased importance of the Low
Alpine zone. This is probably due to the depressionof the tree-linecaused by exposure, the great extensionof bog-coveredground,and to the relativelyhigheraltitude
at whichtemperaturebecomes criticalfordwarfshrubgrowth.
Juniper,willowand dwarfbirchscrub
The abundance of woodland and scrub in the Norwegian mountains affordsa
strikingcontrast to the typical landscapes of the Scottish Highlands. In Sikilsdal,
forinstance,Betula tortuosaextends to 1238 m. on south-facingslopes, and scrub continues foranother 200 m. (Nordhagen, 1943). In relativelycontinentalareas willow
and juniper scrub reach the lower limit of communitieswhich show the influenceof
exposure,while in the cold oceanic climate of Mjolfjell, below the Hardangervidda,
and Middle Sogn, on the westernside of the Jotunheim,snow-bedcommunitiesoccur
as enclaves in the birch wood. This scrub is partly primary,belongingto the Low
Alpine zone, and partlysecondary,derived frombirchwood by cuttingand grazing.
It is only in the neighbourhoodof the saeters that human interferenceis so intense
that the vegetation begins to look like the better Scottish mountain pasture.
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M. E. D. POORE AND D. N. MCVEAN
407
This profound contrast makes one consider how far the absence of a willowor to the absence
juniper-dwarfbirch belt in Scotland is due to climatic differences,
of suitable ecotypes,and how much it is due to the different
patternof land use in the
two countries. Evidence of relictscrub in Scotland, and of the course of degradation
in Scandinavia, is stronglyin favourof the latterview. It is to be expected,however,
that the Scottish scrub, although not identical with the Norwegian, would have
showed strongsimilaritiesto it as do some othercommunitieswhichhave escaped the
fullweightof man's activities (e.g. Carex saxatilis sociation,Poore, 1950c). With the
exception of Salix herbaceathe Arctic willows are rare in Scotland and such populations as do occur are mainly confinedto cliffs. That this is due to grazing is clear
fromthe absence of willows on suitable soils away fromthe cliffsand fromtheirundoubted palatability to animals. Occasional grazed specimensmay be foundin SubAlpine grassland as, for example, a 10 cm. high shrub of S. lappoinumin Nardus
grassland in Breadalbane. Poore (1955c) cites good indirect evidence for the
occurrenceof willow scrub in Scotland in discussingthe Carex saxatilis sociation in
Breadalbane, a sociation which shows close affinitiesin floristicsand habitat with
two sociations in Sylene and Sikilsdal but which differsprincipallyin the absence of
the willows. Other sociations show the same effect.
Where conditions are suitable small patches of 'willow scrub' do develop in
Scotland. The small groupsofSalix lapponumon screesand steep groundin Glen Doll
mightqualifyforthis term. These probably owe theirpresenceto the inaccessibility
of the ground togetherwith the relativelyhigh seeding potential of bushes on the
surroundingcliffs. Over most of the Highlands the number of individuals left is so
small, and the sexes oftenso widely separated, that reconstitutionof this vegetation
type in the absence of grazingwould be a long process.
The most remarkable area of willow scrub yet found in Scotland is on limestone
pavementin Inchnadamph. On a plateau lyingbetween700 and 900 ft.(210to274m.)
outcropsof the Durness limestonealternatewith peat-coveredhollows. The exposed
rock shows the characteristicclints and grikes of limestonepavement but there are
no large continuous areas of this formation. Blanket peat may formerlyhave
covered much of the limestonethat is now exposed, though suitable refugiaforbasiphilous species will always have existed on the steep sides of the nearby Traligill
burn. About 300 acres (121 ha.) of this ground are partially covered by low willow
scrub, mainly of S. myrsinites,but also containing S. repens, S. aurita and their
hybrids. Individual bushes are from6 in. (15 cm.) to 18 in. (46 cm.) tall and have a
prostrate habit. They are well established and are even invading thin peat over
limestone.
Five samples of the scrub (interveningareas of Callunetum on deep peat deliberately avoided) revealed considerablefloristicuniformity(Table 1), fivespecies being
constant. The mat of hypnoid mosses is usually co-extensive with the shoots of
willow, though it may extend beyond them in a few places, and contains the same
assemblage of species as certain low willow scrubs in Festuca ovina sociations of
centralNorway which also show this phenomenon. Tall Norwegian scrubs,however,
develop a different
groundand fieldlayer as lightintensitydecreases.
on thedrierlimestoneand thecreviceshave a florawhichhas some
is
abundant
Dryas
Trollius europaeus,
affinitieswith northernwoodland, e.g. Cirsium heterophyllum,
Sanicula europaea, Polystichumlonchitis,Primula vulgaris,Rubus saxatilis, Galium
boreale. The scrub is withinthe potential woodland zone (a fewsmall trees ofBetula
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408
A New ApproachtoScottishMountainVegetatiton
pubescensand Sorbusaucupariaare present)so that it may partlybe of secondary
the removalof the primarywoodlandand deep peat cover. It is,
originfollowing
therefore,
analogousto thesecondaryscruboftheSub-Alpinezone (p. 406).
This evidence,scantythoughit is, favoursthe viewthattherewas once a region
whichcontainedscrubofArcticwillowson the damperand more
abovethetree-line
scrub
Table 1. Salix myrsinites
1
4
2
4
Calluna vulgaris
Empetrum nigrum
Rubus saxatilis
Salix myrsinites
Vaccinium myrtillus
+
2
8
1
+8
Blechnum spicant
+
-
Agrostistenuis
Anthoxanthumodoratum
Festuca ovina
Deschampsia caespitosa
Nardus stricta
3
5
4
4
Plot area (sq. m.)
Carex binervis
Luzula campestris
3
-
-
Cirsiumheterophyllum
Galium hercynicum
Oxalis acetosella
Potentilla erecta
Primula vulgaris
Ranunculus acris
Thymus drucei
Trifoliumrepens
Viola riviniana
+
+
3
1
1
2
1
4
2
-
3
4
4
8
5
6
-
+
1
8
-
8
7
3
-
2
3
3
2
1
3
3
1
1
2
-
3
3
-
3
2
3
3
1
3
3
2
5
Breutelia chrysocoma
Ctenidium molluscum
Dicranum scoparium
Ditrichum flexicaule
Hylocomium splendens
Mnium undulatum
Pleurozium schreberi
Pseudoscleropodium purum
Rhytidiadelphus loreus
R. squarrosus
R. triquetrus
Thuidium tamariscinum
Tortella tortuosa
3
2
2
2
4
5
-
4
1
-4
1
4
1
3
2
1
1
3
1
-
-
8
5
3
3
1
-
Frullania tamarisci
-
+
-
Cladonia impexa
C. pyxidata
Peltigera aphthosa
P. canina
-
-
-
1
1
-
3
3
-
1
-
1
3
3
3
2
3
1
7
2
5
1
2
4
3
1
2
base-richsoils. It is likelythatwillowshave also playeda rolein the vegetationof
theSub-Alpinebirchwoods,and thata scrubofSalix atrocinerea
and S. auritamay
have replacedalderwoodat variousaltitudeson acid soilsofimpededdrainage,as it
stilldoesin suitablehabitatsin thenorthofScotland.
thereis a
Above the upperlimitofpine on CreagFhiaclach,alreadymentioned,
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M. E. D. POORE AND D. N. MCVEAN
409
discontinuous
band ofjuniperscrubwhichhas so farescapeddestruction
by moor
fires.This scrubis densein places and about 4 ft.(>1 m.) tall,formedofspreading
shrubswithlow brancheswhichturnupwardat the tips. In leaf charactersthis
thanto theprostratessp. nana.
juniperis morecloselyrelatedto thessp. communis
The scrubflorais different
fromthat of the surrounding
Calluna heaths and the
feature
of
the
is
the
continuous
principal
groundlayer
carpetof hypnoidmosses
Pleurozium
schreberi,
(Hylocomium
splendens,
Hypnumcupressiforme,
Rhytidiadelphus
undulatum
and Dicranumscoparium.
loreus,Thuidiumtamariscinum),
Plagiothecium
butthefollowing
Analyseshave notyetbeenmadeofthiscommunity,
specieshave
beenseenon different
occasions:Blechnum
Vaccinium
annotinum,
spicant,
Lycopodium
and
V.
Anthoxanthum
Holcus
Oxalis
acetosella,
vitis-idaea,
odoratum,
mollis,
myrtillus
Rumexacetosa,Veronicaofficinalis
Listeracordata,Pyrola?media,
and, occasionally,
Thalictrum
alpinumand Platysmalacunosum.
It is uncertainwhetherthe juniperscrubat the upperforestlimitin the eastern
ofbirch,but,whetherit did ornot,we can probably
Highlandscarrieda proportion
a.
b.
dwarf
Lichen-rich
shrubheath
Lichenheath
J~
Juniper
, Phyllodoco
-'"
Vaccinion
?
X
't
Juniper
Juncus
trifidus
islandica
& Cetraria
Salixherbacea
BESSHEIM
BESSHEIM
Exposed
Call,una
^call..
d
A,-~Brc
s>B^^
l~~rc~~h
\, Vaccinium
myrtillusun
ExposedCalluna
Callunainboulders
&
annotinum,
Callun4~__?Calluna, Lycopodium
Juniper
myrtillus
Vaccinium
\,-PhyllodoceNardus
Phyllodoce
Cassiope&
'
hepatics
MJ0LFJELL
'
Calluna
GLENFESHIE
Fig. 3. Relation of Sub-Alpine scrub to snow cover. 'For explanation see text.
assignmostofit to the Sub-Alpinezone. Evidencethatprimaryjuniperscrubwas
an important
constituent
oftheLow Alpinezoneis veryscanty,becausemostsuitable
burntforovera centuryand sporadically
groundat thesealtitudeshas beenregularly
are suggestive.
suchas thefollowing
fora muchlongerperiod. However,occurrences
NearthelimitofscrubinNorwayjuniperoftenformsan 'eyebrow'roundtheupper
above and thesnow-bedcomedgeofa snowbed betweenthe exposedcommunities
munities(usuallyPhyllodoco-Vaccinion)
below. Fig. 3 showstwosituationsobserved
nearBessheimin theeasternJotunheim,
and a similarzonationfromwithinthebirch
woods at Mjolfjellin westernNorway(Fig. 3, a, b and c); cf. also McVean (1955).
Traces ofthissituation,withjuniperoccupyingthe same place in thezonation,but
not forming
and centralPerthshirewhere
scrub,can be foundin the Cairngorms
listgives
borderVacciniumsnowbeds (Fig.3, d). The following
exposedcommunities
the compositionofsucha community:
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410
A New ApproachtoScottishMountainVegetation
Calluna vulgaris
Empetrum hermaphroditum
Juniperuscommunis
Sorbus aucuparia
Vaccinium myrtillus
V. vitis-idaea
6
5
4
+
5
3
Lycopodium annotinum
2
Carex bigelowii
Deschampsia flexuosa
Nardus stricta
1
2
1
Melampyrumpratense
1
Dicranum scoparium
Hylocomium splendens
Pleurozium schreberi
2
6
4
Cladonia rangiferina
C. sylvatica
1
3
Small patches of such juniper scrubs,at and above the tree-line,are frequentin the
Monadhliath to the west of Strathspey. Juniper scrub below the tree-lineis also
widespread in this part of the country,especially in Glen Dulnan and on the hills of
the Aberdeenshire-Banffshire
border. The Glen Dulnan scrub covers large areas of
alluvial flats as well as parts of the surroundingslopes.* Fire seems to be the main
enemy of the juniper, but where the scrub has once been opened up, grazing can
effectivelycheck regeneration. Many of the bushes are of great age, and the scrub
seems to be recedingalmost everywhere.
The extensive juniper scrub on headlands coming under the influenceof blown
shell sand near Bettyhill,Sutherland,can probably be assigned to this nodum also.
There is no evidence that mixed scrubs of juniper and dwarfbirch,such as can be
found in central Norway, ever occurred in Scotland. The somewhat differentbehaviour of Betula nana in the two countrieswould be sufficientto account for this
(p. 425).
A scrub of Juniperus nana, which undoubtedly belongs to the dwarfshrub communities of the Low Alpine zone, will be described below. We shall have to wait
for more detailed stratigraphicaland pollen analytical studies beforewe can know
forcertainwhetherthese scrubtypes did in factplay a part as importantas is assigned
to them here, although certain sub-fossil finds in the north-westHighlands are
significant(p. 421).
On the basis of vegetational evidence at presentat our disposal it seems reasonable
to suppose that a scrub zone succeeded the tree zone at higheraltitudes over much
of the Scottish Highlands. This scrub zone was probably of juniper on the welldrained and acid hills of east and central Scotland, of willows (Salix lanata, S.
lapponum. S. nigricans,S. myrsinites,S. repensand S. aurita) on the wetterand more
eutrophicsoils, and ofJuniperusnana on the Cambrian quartzite,Torridoniansandstone and granitesof the west.
Betula nana may have been an important constituentof scrub bogs in this zone,
but it is unlikelythat it has been a dominantwithinhistoricaltimes (p. 423).
At higher altitudes the effectof human activities becomes very much reduced
and the variation of vegetation can usually be explained in termsof physical factors
alone.
* Characteristic lichens
growingon the twigs of this juniper are Cetrariapinastri S. F. Gray and C.
sepincola Wain.
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M. E. D. POORE AND D. N. MCVEAN
411
B. Oceanicity
The notable differences,both in climate and vegetation, between the western
European seaboard and parts of the European continentdistant fromthe sea have
long been recognized by ecologists. Watt (1936), in his studies of the Breckland
regionof East Anglia, has drawn attentionto the continentalcharacteristicsof this
area. No attempthas been made so farto gauge the importanceof this factorin controllingthe communitiesof the Scottish mountains or in placing them in the series
from'oceanic' to 'continental' recognizedin the mountains of Scandinavia.
The communitieswhichmake the greatestcontributionto the vegetationabove the
potential tree-linein Scotland have already been mentioned(p. 406). It is onlyin the
coastal regions of Norway that the most important species of these communities,
Calluna and Rhacomitrium,
play any part. Instead, extensive areas are covered with
Betula
nana and lichen heath (Alectoria ochroleuca,A.
Empetrum,Arctostaphylos,
C.
Cetraria
nivalis,
islandica, C. cucullata and Cladonia alpestris). The
divergens,
dominated
communities
by juniper and willows have already been disNorwegian
cussed.
The trendfromoceanic to continentalclimate involves a numberof factorswhich
are important in the understandingof plant distribution. Various attempts have
been made to combine them in Indices of Oceanicity. Before consideringthese, what
are the climatic variables involved?
Precipitation is higherin oceanic regions,and there is a marked increase of the
precipitation/evaporationratio associated with the large number of wet days and
sustained highhumidity. Insolation is also reduced. This has the effectof increasing
the rate ofgrowthand the competitivepower of the bryophytes,especiallySphagnum,
and the hypnoid mosses, and there are also marked secondary effects
Rhacomitriutm
in the leaching of soils, and the developmentof impeded drainage.
Another important consequence for vegetation, and especially mountain vegetation, is the formof the annual temperaturecurve. Characteristicof a continental
climate are a highsummermaximumand low winterminimumwith rapid transitions
in springand autumn. The curve foran oceanic climate is flattened;in Poore (1955c)
a characteristiccurve for Scotland is compared with that froma relativelyoceanic
part of Norway.
The growth period is reduced in oceanic regions but the indirecteffectsmay be
even more important. Because of the continuously low winter temperatures in
continentalregions snow cover is both deeper and morepersistentfromyear to year.
removersof
Furthermore,low summerrainfalland hightemperaturesare less efficient
snow than low summertemperaturesand high rainfall. This was well illustratedin
Scotland by the late snow-lie in the hot dry summer of 1955, compared with the
early disappearance of snow in the cool wet summerof 1954.
One effectof this oceanic featuremay well have been the severe restrictionof the
range of frost-sensitivemontane species. In a continental climate snow melt is
usually rapid and followedby warm weather; in Scotland most of the snow may be
stripped fromthe hills in the middle of winteror early springby a warm air stream,
and this may be followedimmediatelyby hard frost(cf. Poore, 1955c).
Anotherfeatureof the oceanic climate is the prevalence of high winds. It cannot
fail to impressthe British ecologistin Norway that the evidences of wind cuttingof
trees and damage to mountainplants by high winds and blizzards are relativelyrare
compared with what he sees at home.
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412
A New ApproachtoScottishMountainVegetation
in Norwayof various Indices of
Godske (1944) has discussedthe distribution
measurements.He
Oceanicitywhichare calculablefromstandardmeteorological
findsthatthe best correlation
withbiologicalphenomenais givenby modifications
of Kotilainen'sIndex of Oceanicity. Kotilainen'soriginalindex is given by the
formula
N.dt
K =100 A
dt is thenumberofvernalor autumnal
whereN is theprecipitation
in millimetres,
with
mean
between
0? and 10?C.) and A is thedifference
temperature
days(i.e. days
of the warmestand coldestmonth. The various
betweenthe mean temperature
forN thevaluesNo.0,No.1
indices(Ko.o,Ko.1,K1.o)aremadeby substituting
modified
79
i
..*..
.
-
\100
12
164
/
156 .
203/
40
134
259
*58(
*53
261
0?
417=
347
23
*
25.
'
023
07_ 013 .
?47 ?sne17 270
39
032,.
0134
0222
240124
1990
227
024 \
*18 *44 022
44
38//
49
\15;20
^
/
'
56
Fig. 4. Indices of Oceanicity - Norway. ModifiedfromGodske.
and N..o whichare respectively
'measurable'
thenumberofdays withprecipitation,
or not,ofdayswithprecipitation
of 0.1 mm. and of 1.0 mm. The best correlation
withbiologicalphenomenawas obtainedwithKo0.. As exactequivalentscannotbe
calculatedfromBritishmeteorological
data forthesemodifiedindices,values have
been calculatedforK and the resultsare presentedin Figs. 4 and 5.
forGlenbranter
It can be seen fromthesemaps thathigherfiguresare registered
and Achnashellachthan forany stationon the west coast of Norway,wherethe
as one would
highestvalue is 417 at Floro,northof the Sognefjord.Furthermore,
the
index
is
lower
in
the
islands
Coll,
Shetlands,
expect,
Orkneys,
etc.) than
(Lewis,
it is on thewestcoastitself.It is significant
thatno valuesfortheindexofover100
are recordedfrominlandstationsin NorwayexceptfromSvandalsflonaat 1065m.
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M. E. D. POORE AND D. N. MCVEAN
413
and that stationsin the Jotunheimand Dovrefjell give low values (e.g. Dombas, 13),
while the lowest value in Scotland is at Nairn, 118 (cf. also Nordhagen, 1943, and
Knaben, 1950).
It is clear that these figuressupport the hypothesis that much of the difference
between Scottish and Norwegian mountain vegetation,where undisturbedby man,
is due to the very oceanic climate of the Scottish mountains. This is supported also
by data fromthe distributionof individual species. In a discussionof the floraof the
308
2. 2
f9
?"
t^
^
281r
1278
e
~3?
JA
^,3
269
~140
Fig. 5. Indices of Oceanicty- Scotland
n (1950), cites
of wes
Fig.5.
oceanicity
as the
InSogndistrict
following
Sogn district of western Norway Knaben (1950), cites as oceanic the following
species, which occur in our mountains:
Blechnum spicant
Carex pulicaris
Digitalis purpurea
Dryopteris oreopteris
Galium hercynicum
Holcus mollis
Hypericum pulchrum
Juncus squarrosus
Luzula sylvatica
Narthecium ossifragum
Of these,Carexpulicaris and Holcus mollisoccur veryrarely as fareast as Vik in the
Sognefjord. Luzula sylvatica and Hypericumpulchrumreach Balestrand (K, 256)
and only Blechnumand Dryopterisoreopterisstretchfartherto the east. In contrast
it is clear that there is no climatic restrictionon the general distributionof these
species in the Scottishmountains. Carexpulicaris, Hypericumm
pulchrum,Narthecium
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A New ApproachtoScottishMountainVegetation
414
and Juncussquarrosusoccurat considerablealtitudeswhereveredaphic
ossifragum
conditionspermit. Dryopteris
Luzula sylvatica,Galiumhercynicum
and
oreopteris,
Blechnumspicantshow a dependenceon snow cover in the centraland eastern
Highlands,but not in the west. The two last species,forinstance,are almostconfinedto snowbeds in the Cairngorms,
but Galiumhercynicum
occurson relatively
heaths
in
Rhacomitrium
Breadalbane.
More
evidence
of the oceanexposed
specific
of
the
Scottish
mountain
climate
will
be
with
dealt
later.
icity
C. Snowcover
Withina mountainarea whichis climatologically
and geologicallyuniformthe
local
in
causes
of
differences
are
the
snowcover-exposure
comprincipal
vegetation
1
7
2
3
4
5
8
9
10
II
12
Fig. 6. Snow depth records for some Breadalbane plant communities. For explanation see text.
The standsin questionwere:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Rhacomitrium-Carex
bigelowiisociation: Ben Ghlas: 3100 ft. (945 m.): ground level.
High altitude Nardus strictasoc.: Ben Ghlas: 3100 ft. (945 m.): N.E. aspect.
High altitude Nardus strictasoc.: Ben Lawers: 3250 ft. (990 m.): S.S.W. aspect.
Lichen-rich Vaccinium-Alchemillasoc.: Ben Lawers, 2550 ft. (777 m.): S. aspect.
Middle Alpine Festuca vivipara soc.: Ben Lawers: (provisional constants of this sociation are Festuca
Pohlia nutans, Polytrichumpiliferum,Rhacomitriumlanuginovivipara, Luzula spicata, Oligotrichum,
concinnatumand G. coralloides,Nardia scalaris and various
sum,Diplophyllumalbicans,Gymnomitrium
lichens includingCerania vermicularis).
Vaccinium-Alchermilla
grassland: Ben Lawers: 3250 ft. (990 m.): S.E. aspect.
Sibbaldia nodum: Ben Lawers: 3250 ft. (990 m.): S.E. aspect.
Sibbaldia nodum: Ben Lawers: 2800 ft. (853 m.): N. aspect.
Salix herbaceanodum: Ben Lawers: 3750 ft. (1143 m.): E. aspect.
Salix herbaceanodum: Ben Lawers: 3300 ft. (1006 m.): N.W. aspect.
Carex saxatilis sociation: Ben Lawers: 3000 ft. (914 m.): S.S.E. aspect.
Carex saxatilis sociation: Ben Lawers: 2800 ft. (853 m.): N. aspect.
below.
Fig. 6 showsthedepthin inchesofthesnowon thedatesmentioned
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M. E. D. POORE AND D. N. MCVEAN
415
plex and soil moisture. There are other factors which are locally important,but
broad trendscan be explained in termsof these two.
The scheme of Watt and Jones has drawn attention to the importance of snow
cover and exposure, but it has been less stressedthan it deserves,probably because
most vegetational studies are concentratedin the summer months. Poore (1955b
and c) has also mentioned its importance, and has predicted the probable snow
regimeof a numberof communities. These predictionshave been generallyjustified
by more intensivewinterobservations.
At the beginningof November 1954 twelve stands were chosen in representative
communitieson Ben Lawers and Ben Ghlas, and a graduated pole six feet (2 m.) long
was driveninto each. The depth ofthe snow was read on these posts at the beginning
of each month throughoutthe winter. Readings could not be made in May and all
snow had disappeared by June 1st.
These observationsconfirmthat the communitiesthoughtto be chionophobous (the
Rhacomitrium-Carex
bigelowiisoc. (1) and the Middle Alpine Festuca soc. (5) ), ununcovered
remain
except just aftersnow-fallon a windlessday, a sufficidoubtedly
rare
to
occurrence
be
ently
ignored. In exceptional circumstancessuch a fall may
thaw and freeze again before drifting. These conditions were found in February
1954 when a deep snow-fallwas followedby hail and sleet whichthen frozeto produce
a surfacelike frozensago pudding. Usually, however, these communities are blown
clear of snow and have only banners of rime on stones and projectingvegetation, or
a thinskinofverglas. The lichen-richVaccinium-Achemillasoc. (4) sometimescollects
a little snow, but usually remains clear. At the other extremeare communities(7),
(9), (10) and (11). All ofthesehad a cover ofover 5 ft. (152 cm.) fora period of at least
four weeks, but the cover is not necessarily so deep throughoutthe entire winter.
clear on the ground. Each deep driftis built up
The reason for this is sufficiently
round a centre of accumulation; even on November 1st there was a small patch of
driftedsnow less than 1 ft. (30.5 cm.) square near Post (9) which had already taken
on the hard compacted texture of neve. Later accumulation occurs round and over
initial centresof this kind, although of course the pattern may be farfromregular.
In the early stages the groundround the formingdriftis usually bare and exposed to
extremelysevere conditions.
Cornicesand deep driftsare usually formedin the lee of a ridge. Exposure reaches
its height immediatelyon the windward side, and the wind lashes back in violent
eddies just under the lee crest. To give some idea of the severityof weather experito say that on only one visit between November and April
enced it may be sufficient
was it physicallypossible, even on hands and knees, to cross the northridge of Ben
Lawers at Post (9).
At lower elevations and in less exposed situations deep driftsmay formwithout
such violent marginalconditions;here too the snow does not last so long, and a continuous cover of vascular plants helps to collect a small shelteringcover of rime and
snow. The distinctionbetween conditions in the snow bed and in its environs is
thus not so sharp.
The observations in the Carex saxatilis nodum (11 and 12) illustrate the same
point. Post (11) was nearer the centre of accumulation than (12), although neither
coincided with it exactly. These sites differfromthe othersbecause the firstsnow or
frostproduces a crust of ice an inch or two thick,which covers the whole flush,but is
G
J.E.
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416
A New ApproachtoScottishMountainVegetation
slightlyraised above the vegetation level, only the upper parts of the Carex leaves
being frozeninto the ice sheet. Driftingsnow accumulates over the ice but, because
this is an unfavourableholdingsurface,the centreof accumulation is usually slightly
upslope fromthe flush.
The Vaccinium-Alchemilla
grassland appears to be intermediatein its snow regime;
and the Nardus sociation is, as predicted,consistentlydifferentfromthe Rhacomi-
soc.
trium-Carex
bigelowii
Althoughthe exposure-snowcover factoris complex,and the ways in whichit may
influencethe vegetation are numerous and insufficiently
understood,yet its visible
effectsare consistentand effectivelydifferentiatethe communitieswithin the Low
and Middle Alpine regions. In any attemptto schematizethe variation in the vegetation of a mountain region,this is one of the key factors.
D. Base status
Enough has been writtenabout the influenceof the chemical composition, and
especially the base content, of soils on the distributionof vegetation to make it
unnecessaryto develop this theme. It is now accepted that base status is a fundamental factordifferentiating
plant communities,althoughits operationis once again
little known.
E. Moisture
A furtherfundamentaldistinctioncan be made on the water content of the soil
from well-drained to permanently waterlogged. Community variation can be
broadly explained in terms of variation in this factor,although smaller differences
may be due to additional variables such as oxygenationof the water supply,whether
it is perennial or seasonal, and so on.
It is true that the effectsof moistureand snow cover cannot be entirelyseparated.
Snow beds are often (although not always) in less well-drainedsituations; drifting
leads to a redistributionof winter precipitation,and irrigationby melt water is
important in determiningthe distributionof hygrophilouscommunities. In the
Middle Alpine zone and the Rhacomitriumzone thereis a close correlationbetween
the exposure-snowcover complex and drainage; but at lower altitudes they are more
independent.
Summary
Even if the numberof master factorsof a satisfactoryecological frameworkcan be
reduced to five (and this will necessarily exclude many specialized communities),
it is impossibleto representthewholesituationdiagrammatically.Nor is a hierarchical
classificationany more satisfactory,although the critical considerationrequired in
making such a classification,and the resultingclassificationitself,may be of the
greatest value, as has been shown by the use to Scottish vegetation studies of the
admirableworksofNordhagen. The onlycompleteanswerappears to be a vegetation
key as suggested by Gams (1917 and 1939).
Diagrams may, however, be invaluable forrepresentingparts of the variation in
vegetation. Thus, taking that reproduced in Watt and Jones (1948, Fig. 6) as a
model, Figs. 1, a-c, show the variation of vegetationwith altitude and with the exposure-snowcover complex in three areas, the continental Cairngorms,the Breadalbane hills, and the oceanic hills of north-westScotland. More base-rich variants
of common communities are inserted in square brackets. By using different
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M. E. D. POORE AND D. N. MCVEAN
417
variables in diagrams such as these, the whole situation may be simply presented.
If the diagrams forthese threeareas are compared,it can be seen that the situation
in Breadalbane is very similar to that in the Cairngorms, although there are
differencesin the composition of the various communitieswhich can only be seen
by inspection of tables; the main differencebetween these two lies in the presence
in Breadalbane of large areas of base-rich rock forming soils with larger silt
and clay fractions. The differencesbetween them and the third are more definite,
although the arrangementof the differenttypes follows much the same pattern.
Among the differencesare: the replacementof Nardus, Carex snow beds by hypnoid
moss heath; the presence of the species-richmoss heath in the base-richseries of the
Juncus trifiduszone, whichmay be due in part to the particularcharacteristicsof the
dolomitic mudstones, and in part to the greater solifluctioneffectsof the northwesternhills; the association of Nardus with the Rhacomitriumheaths; and the disappearance of the snow-bed communitiesbelow the potential tree-line.
IV. COMMUNITIES
DISTINGUISHED
The communitiesdescribedbelow have been chosen partlyfortheirintrinsicinterest,
and partlyto illustratehow the patternof variation of Scottish mountainvegetation
can be fittedinto the ecological framework.Two main groups can be distinguished;
those which,like the Rhacomitriumheaths,have part oftheirprincipaldistributionin
Britain, and those which are typicallyScandinavian, and are local in Scotland. The
localized communitiesmay be restrictedto relativelysmall areas withinwell-known
British vegetation types. It is thoughtthat the principle,usefulin autecology,that
the general distributionof the species can be valuable in interpretingits local behaviour,and viceversa,may be equally usefulin the fieldofphytosociology(cf.Boyko,
1947).
A. Dwarf shrubheaths
Within the Calluneta of the Sub-Alpine and Low Alpine zones, there is great
tolerances being included. The designation
diversity,communitiesof very different
of these by the name of the common dominant has helped to conceal interesting
details of distributionand of affinitiesto communitieselsewhere in which Calluna
plays only a subordinate part or is entirelyabsent. Although the two sociations
which follow,and the Betula nana bogs and lichen heaths of the next sections,might
all be classed as Calluneta, theyhave been named instead afterotherconstantspecies
whichare thoughtto give a betterexpressionoftheirecology.
Loiseleuria-Arctoussociation(Table 2)
Some exposed habitats of intermediatealtitude in the north-westof Scotland are
occupied by a dwarf shrub heath which is somewhat richer in species than the
Calluna heaths occupyingthis habitat elsewhere. Seven lists are set out in Table 1,
two fromBen Clibreck,two fromthe Coulin forest,Wester Ross, one fromBeinn
Dearg, east of Loch Broom, and one fromBeinn Eighe. The distributionof the community,as known at present,is a narrow discontinuousband stretchingfromLoch
Torridon in the south-westto Ben Clibreck in the north-east. The Arctostaphylosmat association described by Crampton (1911) fromMorven, Caithness, almost certainlybelongsto this sociation.
The communityformsa thick-setmat ofdwarfshrubsand lichensup to 5 cm. deep,
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418
A New ApproachtoScottishMountainVegetation
brokenoccasionallyby stones. In exceptionallyexposed places it may be banded and
interruptedby patches of erosion pavement liable to solifluction.From the data so
far available, it is distinguishedby the constancy ofLoiseleuria procumbens,Arctous
alpina, Calluna vulgaris (which usually has a cover of over 50 per cent), Empetrum
(both species), Rhacomitriumlanuginosum(small cover), Cetrariaislandica, Cladonia
sylvatica, C. uncialis, Ochrolechiatartarea,Platysma glaucum and Sphaerophorus
globosus. It is also distinguishedby the occurrenceof the lichenPlatysma lacunosum
and of certain species which are characteristicof exposed heaths in the north-west
Highlands, e.g. Solidago virgaurea,Antennaria dioica, Euphrasia frigida and Lotus
corniculatus.
Table 2. Arctous-Loiseleuria
nodum
Cover
Altitude (ft.)
Slope (deg.)
Aspect
Area of plot (sq. m.)
Arctostaphylosuva-ursi
Arctous alpina
Calluna vulgaris
Empetrum (both spp.)
Erica cinerea
Juniperuscommunis
Loiseleuria procumbens
Salix repens
Vaccinium myrtillus
V. uliginosum
V. vitis-idaea
1
100
1780
1
SW
4
5
6
100
100
2000
1800
2
2
E
W
1
4
3
4
2
95
100
100
1700 2000 2300
2-3
2
0
W
N
4
4
1
4
8
5
2
4
4
1
3
2
1
Lycopodium alpinum
L. selago
1
Agrostis tenuis
Deschampsia flexuosa
Festuca vivipara
4
8
4
4
7
4
+
5
7
3
1
4
6
4
5
7
2
4
4
+
+
1
+
2
+
3
4
-
3
-
+
1
+
+
-
-
3
2
3
2
1
1
2
3
-
Carex bigelowii
C. panicea
Juncus squarrosus
Luzula multiflora
Trichophorumcaespitosum
+
4
-
3
-
2
+
+
-
Antennaria dioica
Euphrasia frigida
Galium hercynicum
Hieracium alpinum
Lotus corniculatus
Pinguicula vulgaris
Potentilla erecta
Solidago virgaurea
Thymus drucei
2
1
1
+
+
+
+
+
++
-
+
+
-
3
Pleurozium schreberi
Rhacomitrium lanuginosum
2
--
1
3
1
+
3
3
1
2
-
1
+
-
1
1
1
1
5
2
2
1
Pleurozia purpurea
-
-
-
3
-
2
Alectoria nigricans
Cetraria aculeata
C. islandica
Cladonia bellidiflora
C. coccifera
C.-gracilis
1
2
2
2
1
-
1
3
1
-
2
1
1
1
-
1
-
1
1
1
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All use subject to JSTOR Terms and Conditions
M. E. D. POORE AND D. N. MCVEAN
C. pyxidata
C. subcervicornis
C. sylvatica
C.uncialis
Cerania vermicularis
Ochrolechia tartarea
Parmelia omphalodes
Platysma glaucum
P. lacunosum
Psoroma hypnorum
Sphaerophorus globosus
Stereocaulon vesuvianum
1.
2.
3.
4.
5.
6.
1
-
1
-
5
3
5
1
5
1
4
1
1
3
1
3
1
3
1
1
1
1
1
+
2
3
-
3
-
3
1
3
-
2
+
1
2
1
3
+
1
1
419
-
3
Map reference
Ben Clibreck
Ben Clibreck
Ben Dearg
Coulin
Coulin
Drum Grudie, Beinn Eighe
29/553270
29/550270
28/248780
18/975540
18/988545
18/971642
to exposedbluffs
and ridgesbetweenthealtitudesof1700
Thissociationis confined
and2300ft.(518to701m.) whereit maybe extensive.The parentmaterialis usually
morainicand composedof smallishstonesof Torridoniansandstoneor quartzite
mixed with Moine schistsor Serpulitegrits. It has not yet been foundon moraine of
a substratumto supportit.
pure quartzite, and this is probably too mineral-deficient
The soil is a thinskin ofpeat over sandy humus-richgravel and is shallow (20 to 30 cm.
in depth). The habitat is well drained and usually blown clear of snow in winter.
The communityis replaced at higheraltitudes in similar habitats by Rhacomitrium
heaths and at lower altitudes by the dry facies of the Calluna-Trichophorum-Molinia
complex of deforestedground. From its floristicsit would appear to be northern
and oceanic in affinity.Analogues in other parts of the Highlands are Callunaand Calluna-Loiseleuria communitiesin the easternand centralHighArctostaphylos
and
the
rare Calluna-lichen heaths (see below). On Beinn Eighe there is a
lands,
transitionto Nardus associated withincreasedsnow cover.
sociation(Table 3)
Juniperus-Arctostaphylos
Juniperscrub of the composition presented in Table 3 is very restrictedin distribution,having so farbeen foundonly on the northand north-eastslopes of Beinn
Eighe, and in the Coulin forest,both in Wester Ross. It is confinedto quartzite
morainic material, generallycoarser than that described forthe previous sociation,
betweenthe altitudesofabout 1200 and 1800 ft.(366 to 549 m.). Wherewelldeveloped
(lists 1 to 5) it survives as islands having total vegetative cover in a landscape of
quartziteerosionpavement withratherscantyvegetation. Lists 6 to 8 are examples of
semi-degradedjuniper scrub; complete degradation leaves only a few scattered individuals of the constantspecies with a cover of 5 to 10 per cent. Closed scrub forms
a carpet about 5 to 10 cm. deep ofJuniperusnana, Arctostaphylos,
Calluna, and sometimes Arctous and Empetrumhermaphroditum.Associated with these are various
sporadic herbs and grasses. A constant and notable featureis the abundance in the
ground layer of the liverwortsHerbertaadunca and Pleurozia purpurea, the former
sometimes attaining a cover of 20 to 25 per cent. Cladonia impexa and formsof C.
uncialis are also constant. In contrastslightlydegraded formshave a broken dwarf
shrub cover and a richerlichen flora;the alga Gloeocapsamagna (mountain dulse) is
oftenabundant.
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420
A New ApproachtoScottishMountainVegetation
Table 3. Juniperus-Arctostaphylos
nodum
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Area ofplot (sq. m.)
Arctostaphylos uva-ursi
Arctous alpina
Calluna vulgaris
Erica cinerea
Empetrum hermaphroditum
Juniperus communis
Sorbus aucupariaVaccinium myrtillus
V. uliginosum
Lycopodium selago
Deschampsia flexuosa
Festuca vivipara
Molinia caerulea
Carex bigelowii
Juncus trifidus
Trichophorumcaespitosum
Orchis ericetorum
1
2
3
4
100
100
100
100
1350 1350 1350 1650
2
2
2
2
N
N
N
SE
4
4
4
2
3
2
5
2
4
5
5
4
5
7
7
-
8
-
2
2
3
3
2
5
100
1850
2
W
4
6
90
1250
0
4
7
75
1400
0
2
8
80
1800
7
2
9
75
1500
5
NE
4
4
4
4
2
3
6
1
7
+
4
7
3
5
4
6
2
+
4
5
4
7
2
4
+
6
4
3
-
2
3
3
+
1
3
1
3
-
.
3
3
-
1
-
1
3
2
-
3
-
3
3
-
1
5
4
1
4
4
2
1
1
1
2
2
4
3
-
-
2
AntennariadioicaEuphrasia brevipila
Pedicularis sylvatica
Potentilla erecta
Solidago virgaurea
Succisa pratensis
Campylopus flexuosusHylocomium splendensHypnum cupressiforme
Pleurozium schreberiRhacomitrium lanuginosum
Sphagnum acutifoliumagg.
Diplophyllum albicans
Herberta adunca
Pleurozia purpurea
Frullania tamarisci
Ptilidium ciliare
Scapania gracilisvar. laxifolia
Cetraria aculeata
C. islandica
Cladonia bellidiflora
C. gracilisvar. chordalis
C.impexa
C. leucophaea
C. pyxidata
C. squamosa
C. subcervicornisC. sylvatica
C. tenuis
C. uncialis
Ochrolechia tartarea
Platysma glaucumSphaerophorusglobosus
Gloeocapsa magna1.
2.
3.
4.
5.
1
4
5
3
1
3
2
-
-
3
?
2
1
+
1
1
1
1
4
-
-
--
3
-
3
-
2
4
3
3
+
2
-
+
+
3
+
2
-
3
2
3
-
+
-
2
1
.1
3
+
3
2
+
+
2
2
-
1
2
2
3
-
3
-
3
1
+
+
+
+
-
1
2
2
1
-
4
-
2
.
2
-
-
2
2
.
2
-
+
1
1
3
1
3
2
-
Map reference
6. 18/995623
18/992618
7. 18/992626
18/992618
8. 18/990598
18/992618
9. 18/988530
18/973336
18/984615
This content downloaded on Tue, 5 Mar 2013 12:45:10 PM
All use subject to JSTOR Terms and Conditions
2
1
-
+
2
1
2
1
I
1
1
2
+
-
3
+
2
1
+
3
2
1
2
1
2
+
1
1
-
2
-
+
2
1
1
2
3
2
2
-
4
+
4
-
M. E. D. POORE AND D. N. MCVEAN
421
The soil consistsof a fewinchesof juniperand bryophytepeat over quartzite
rubble.The actualdepthofthepeat variesfromplace to place,and it is veryliable
to erosionwhenthe scrubmat is broken.As thereis no evidencethatthereis any
in habitatbetweentheareascoveredby juniperscruband thoseoferosion
difference
pavement,it seemsprobablethattheextensiveareasofquartzitemoraineabove the
forestlimiton BeinnEigheand Coulinonceboreclosedornearlyclosedscrubofthis
ofthistypeofgroundthroughout
in floristics
kind. Indeedthesimilarity
thewhole
that
the
area of quartzitein the north-west
Highlandssuggests
Juniperus-Arctoscrubmayoncehavebeena widespreadand commoncommunity.Its disstaphylos
appearancemay be attributedpartlyto the upwardextensionof thosefireswhich
havereducedtheformer
pinewoodsat loweraltitudesto an erosionpavementsparseand Trichophorum.
with
Molinia
ly vegetated
Sub-fossilstemsof dwarfjuniperare oftenexposedin deep peat by erosionand
theyalso are foundin abundancelyingloose on quartziteand Torridonsandstone
Maree area. It therefore
the Torridon-Loch
seems
erosionpavementthroughout
some
of
and
is
a
that
it
scrub
has
that
the
been
community
antiquity,
juniper
likely
in area by a periodofmoreactivebog growth.
restricted
and habitatthisscrubis verycloselyrelatedto the Calluna-Arctous
In floristics
in thepoorerand coarsersubstratum
and in
sociationdescribedabove,but it differs
reducedexposureindicatedby the absenceof,forexample,Loiseleuriaprocumbens
oflichensby hepatics.
and thereplacement
B. Betula nana bogs
It has been mentionedabove that the vegetationin southernNorwayin which
roleis essentiallycontinentaland that thisspecies
Betulanana plays a prominent
fromthecoastincreases.It is,therefore,
distance
as
ofgreat
Calluna
vulgaris
replaces
of certainbogs in the
interestto findthatBetulanana is an importantconstituent
northand centralHighlands.At present(December1955)exampleshavebeenfound
on Ben Clibreckand Ben Deargwhichcoverseveralhundredacres;buton Ben Wyvis
and the Monadhliathabove Dunachtonalmostall suitablegroundis coveredwith
has beenfoundis on thenorth
souththatthiscommunity
B. nana bog. The farthest
side of Cam Creag above Camghouran,Loch Rannoch. Relict patcheson deeply
erodedpeat occursouthofLoch Dromain theFannichforest.The floristic
composition is presentedin Table 4. The remainingconstantsare Eriophorum(either
Pleurozium
splendens,
Hylocomium
species),Calluna vulgaris,Vacciniummyrtillus,
and Sphagnumcapillaceum.
schreberi
fromordinary
Froma distancethesebogsareindistinguishable
Calluna-Eriophorum
theshootsrarelyreachingthesurtheBetulagrowsas an undershrub,
communities;
faceoftheCallunacanopywhenthe two are closelyassociated,althoughit may be
conspicuouswheretheCallunais sparse. Sphagnumgrowthis usuallyrapid,and the
branchesofthedwarfbirchspreadwidelywiththeirbasesburiedintheaccumulating
mossremains.
The community
appearson flator gentlyslopingterrainbetween1500ft.(457 m.)
itsrangeappearsto be ratherlower(1500to
and 2400ft.(731m.). In thenorth-west
1800 ft.) (457 to 550 m.) thanin the Monadhliath(2000to 2300ft.)(608 to 700 m.).
of exposedridges(Loiseleuria-Arctous
At its upperlimitit adjoinsthe communities
sociationon Beinn Dearg and Ben Clibreck,exposed Calluna at Rannoch and
belowit gradesintoerodedCalluna-Eriophorum
intheMonadhliath);
vaginatum
bogs.
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422
A New ApproachtoScottishMountain Vegetation
Table 4. Betula nana bogs
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Plot area (sq. m.)
Arctous alpina
Betula nana
B. pubescensB. verrucosa
Calluna vulgaris
Chamaepericlymenumsuecicum
Empetrum nigrum
E. hermaphroditumErica tetralix
Oxycoccus microcarpus
Rubus chamaemorus1
Vaccinium myrtillus
V. uliginosum
V. vitis-idaea-
1
100
1500
0
4
2
100
1700
3
E
4
4
4
2
3
6
+
3
2
Carex binervisEriophorumangustifolium
E. vaginatum
Juncus squarrosus
Trichophorumcaespitosum
5
7
2
Listera cordata
-
6
9
4
3
++
7
3
-
3
1
3
1
2
-.
-
1
3
3
2
1
1
3
3
-
-
2
3
4
+
-
6
-
4
3
6
1
+
7
-
-
+
-
-
6
6
4
4
3
-
Calypogeia trichomanisDiplophyllum albicans
Lepidozia setacea
Leptoscyphus taylori
Lophozia ventricosa
Mylia anomala
Ptilidium ciliareCladonia gracilis
C. impexa
C. leucophaea
C. rangiferina
C. sylvatica
C. uncialis
1.
2.
3.
4.
4
4
3
4
4
8
6
7
3
3
4
3
3
2
2
6
-
3
1
3
5
+- -
Pinguicula vulgaris
Potentilla erectaAulacomnium palustreCampylopus flexuosus
Dicranum scopariumEurhynchiumpraelongum
Hylocomium splendens
Hypnum cupressiforme
Plagiothecium undulatum
Pleurozium schreberi
Rhytidiadelphus loreus
R. squarrosus
Sphagnum palustre
S. fuscum
S. cf. capillaceum
4
3
6
5
7
100
100
80
70
70
1500 1800 1650 2300 2250
2
5
2-3
2
1
NE
W
SW
S
NE
4
4
4
4
4
1
1
3
1
3
3
1
1
1
1
1
1
5
1
3
2
3
2
+
4
-
3
++
2
2
4
4
-
1
2
2
-
2
3
5
1
1
+
4
-
8
9
1
-
-
+
1
1
1
3
2
-
1
1
-
1
3
1
3
-
-
1
-
3
6
2
6
1
7
1
1
-
-
1
1
Map reference
5. 27/550525
29/559271
6. 28/788090
28/250778
7. 28/790092
28/258778
28/448652
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M. E. D. POORE AND D. N. MCVEAN
423
The surfaceofthebogis gentlyundulating,
and showsno signsoflocalizedgrowth,
or 'regeneration
and
the
complex',
community,
exceptin its erodedform,may be
influenced
to someextentby groundwater.
Threedistinctfaciesare apparentin the Table. In the standsfromnorthof the
GreatGlen(1, 2, 3, and 4), Arctousis constant,whereasit is absentfromthoseto the
south,whichtendto be outsidethe rangeof the species. Lists 6 and 7 are froma
facieswidespreadin theMonadhliath.
lichen-rich
The community
occursalwayson whatappearto be 'flushed'areasofblanketbog,
and is absentfromthepoorerrocks. For instanceit doesnotappearon thequartzite
and TorridonsandstoneofRoss-shireand Sutherland,
and avoidsthegraniteofthe
and
Monadhliath
Charn
Geall
CharnBeag), althoughit is
Mor,
Cairngorms
(Geall
or
on
a
two
the
Moine
mile
schists.
The
away
present
countryrocksofthelistedsites
are quartziteschists,and, on Ben Wyvis,peliticschists. There is much suitable
groundadjacent to thesebogs,similarbut forthe absenceof the birch,and it is
was oncemuchcommoner
and thatits rangehas been
possiblethatthe community
reducedby burningand peat erosion.
Scandinavian affinities
The ScottishBetula nana bogs are so similarto the associationsdescribedby
Nordhagen(1928 and 1943), and placed in the provisionalAlliance Oxycoccothattheymay be assignedwithsome confidence
to this
Empetrionhermaphroditi,
of
alliance- but to an oceanicphase distinguished
the
such
by
presence
speciesas
Erica tetralix,Juncus squarrosus,Carex binervisand by the prominenceof Calluna.
This alliancehas beendividedintothreeassociations:
herm.- sphagnetosum
a. Oxycocco-Empetrum
b. Oxycocco-Empetrumherm.- cladinosum
c. Oxycocco-Empetrumherm.- hylocomiosum
of whichthe firsttwo have been describedfromSyleneand Sikilsdal,and the last
fromSylenealone. In contrastto ourbogstheyoccuras hummocksin fensor bogs
whichmaybe base-richand belongto theAllianceCaricionatrofuscae-saxatilis.
In
theRondanedistrictofcentralNorwaytheyforma smoothcarpetin wethollowsof
thelichenheath(Dahl,in press).
In Table 5 the constantsin thesevarioussociationsare comparedwiththeprovisionalconstantsin thetwofaciesoftheScottishbogs.
Sub-fossilevidence
The speciescompositionof the present-day
Betulanana bogsis strongly
reminiscentofthatofseveralpeat layersdescribedas 'Arcticbeds' by Lewis (1905-11)in
his studyoftheplantremainsin Scottishpeat mosses. A fulldiscussionmightwell
providethematerialfora separatepaper,but it seemsworthwhileto make one or
at thisstage. The floraofthelowestArcticbed is somewhatdifferent,
twocomments
and cannotbe discussedhere.
Lewis's recordofSalix arbusculafromthe upperofthe two mainbeds,and from
in the'UpperForestian',in associationwithSphagnumand
the 'Arctic'intercalation
Arctousalpina, is ecologicallyunlikely. Salix repensand S. aurita have been noted
on thebogs describedabove,althoughtheydo not occurin thefloristics
tables,but
Lewisdoesnotrecordanyofthemoreacid-tolerant
finds.
Salicesamonghissub-fossil
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424
A New ApproachtoScottishMountainVegetation
If it is accepted that these Upper Arcticbeds on Sphagnum-Trichophorumthat were substantiallythe same as the
Eriophorum
peat representcommunities
then
it
seems
unnecessaryto postulate,as Lewis does, a climatic
existingbogs
deterioration
ofsufficient
to bringaboutcorrieglaciationin theHighlands
magnitude
in orderto explaintheiroccurrence.
The lowestappearanceofLewis's secondArcticbed is at 150 ft. (46 m.) O.D. in
Shetland,at 500 ft. (150 m.) near Cape Wrath,at 750 ft.(228 m.) in thesouthern
Uplandsand at 1500ft.(457 m.) in east Sutherlandand the centralHighlands. His
Table 5. Comparison
between
Scottish
and ScandinavianBetula nana bogs
Lichen-Rich
1
2
3
100
100
0
Andromeda polifolia
100
0
100
Calluna vulgaris
100
100
100
Betula nana
100
100
Empetrum hermaphroditum 94
63
70
100
Vaccinium myrtillus
24
80
V. uliginosum
50
47
100
50
Oxycoccus microcarpus
100
100
100
Rubus chamaemorus
Sphagnum-Rich
4
5
6
100
100
0
4
0
100
100
100
100
100
100
100
52
8
100
100
100
0
92
100
20
100
96
80
PleuroziumRich
8
7
93
0
43
0
100
x
100
x
100
0
100
x
97
0
100
x
Carex pauciflorus
Eriophorum vaginatum
0
41
0
100
0
100
100
100
0
100
0
60
0
100
0
x
Dicranum bergeri
Hylocomium splendens
Pleurozium schreberi
Pohlia nutans
Polytrichumstrictum
Sphagnum angustifolium
S. capillaceum
S. fuscum
S. russowii
0
0
94
0
53
0
77
18
0
100
0
100
100
100
0
0
100
0
0
100
100
0
0
0
100
0
0
20
0
88
16
84
92
0
100
100
20
0
68
88
96
0
0
100
0
0
80
80
0
0
0
100
20
0
?100
0
100
100
97
73
0
87
97
0
x
0
0
0
0
0
0
0
Mylia anomala
94
100
100
100
100
100
97
0
0
65
59
94
0
100
100
100
100
100
100
0
100
100
0
0
0
0
0
100
100
8
0
0
0
0
20
28
12
40
12
0
0
52
64
0
0
0
0
60
20
40
27
3
23
47
0
70
97
0
0
0
0
0
0
0
Cetraria islandica
Cladonia alpestris*
C. coccifera
C. deformis
C. impexa
C. rangiferina
C. sylvatica
(Microhepatics are omitted: constancy - per cent.)
* The plant named as Cladonia impexa in these Scottish bogs is in many featuresintermediate
between lowland C. impexa and C. alpestris.
2, 5,
ey3, 6,
L8,
Sikilsdal.
Scotland.
Rondane ( x = presence only).
later intercalationin the upper forestlayer occurs at 300 ft. (91 m.) O.D. in
Sutherland,and at 2000ft.(608m.) in thecentralHighlands.
At thepresentdaytheBetzla-Arctous
bogsof Sutherlandextenddownto 1500 ft.
the
central
of the community
and
to just under2000 ft.
facies
Highland
(457 m.)
are
that
in
the
of
there
absence
indications
moor
(608 m.);
burningtheywouldbe
foundlowerstill. At anyratetheyextendto just above or a littlebelowthepresent
potentialforestlimit.
It shouldalsobe notedthattheSalixmyrsinites
scrubat Inchnadamph
canbe found
at 700 ft. (640 m.) above sea level.
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M. E. D. POORE AND D. N. MCVEAN
425
the profoundinfluence
thatman has had
Lewis appearsto have underestimated
local
the
of
and
also
Scottish
edaphicfactors,when
importance
upon
vegetation,
of
'In
short
the
distribution
statements:
the
pine and birchforest
making following
and thetwoassociationsare notnowfound
moorlandis welldefined,
and sub-arctic
underpreciselythesameclimaticconditions'and 'No changein drainage
intermixed
to replacea closegrowthof
wouldcause a forestofP. silvestris
orpeat characteristics
B. nana,etc.'. He also failsto appreciatetherapiddropin thelowerlimitofArcticAlpinespeciestowardsthenorthofScotland.
All thisleads to the conclusionthatthe UpperArcticbeds couldhave been laid
littledifferent
fromthoseoftoday;perhapssomewhat
downunderclimaticconditions
the tree-lineby severalhundredfeet,
coolerand wetterto the extentof depressing
but certainlynot 'Sub-Arctic'.The Betula nana-Salixhorizonscould thus be of
laterdate thanhe implies.
ofthepeatsbelowthepresent
to carryout an examination
It wouldbe instructive
Betulanana communities.
EcologyofBetulanana
in Scotlandand Norway. In the
The behaviourofBetulanana differs
considerably
continentaldistrictsof Norwayit is oftena dominanteven on well-drained
soils,
ofmorainicridgeswhereit mingleswithsuch
spreadingintoexposedcommunities
Knaben'sremarkson the ecology
speciesas Cetrarianivalisand Alectoriaochroleuca.
its scarcityin thisoceanic
She attributes
ofBetulanana in Sognmaybe significant.
to exposuresinceshefindsit only
and sensitivity
regionto itshighheatrequirement
in sheltered
localitieswithrelativelystronginsolation.
Its behaviourin Iceland is morelike that of the Scottishthan of the Norwegian
ofhabitatwouldbe
type,and the ecologicalor geneticalreasonsforthisrestriction
worthinvestigating.
C. Lichenheaths
Of somewhatsimilarinterestare the lichenheaths of the Scottishmountains.
and arefoundin muchthesame
heathsin composition,
TheyresembletheNorwegian
oftheScandinavianseries.
habitat,so thattheycan be consideredas extensions
heath(1 to 5), Vaccinium
In Table 6 are presentedlistsfromtheCalluna-lichen
whichis richin
of
the
former
and
an
to
facies
heath
exposed
10)
myrtillus-lichen (6
heathsalso occurin a habitatsimilarto
'yellowlichens'(11 and 12). Empetrum-lichen
thatofthe Vacciniumsociation.
In all of these the lichensare so abundantthat they can be describedas the
can readilybe distinguished
from
dominants,and the communities
physiognomic
and yellowcolour. The dwarfshrubs
somedistanceby thecharacteristic
grey-green
are in the same layer as the lichens,and hold the mat togetherso thatit can be
rolledoffthe groundlike a carpet. In wet weatherthe mat is slipperyunderfoot,
and in dryweatherthecrispand brittlelichensare easilydestroyed
by trampling.
in theirdistribution,
The lichenheathsare restricted
beingknownonlyfrombetween2400 ft.and 2600 ft.(731to 791 m.) on thewesternspursofGeallCharn,Cam
and fromthearea ofCam DeargMor
Ban Morand Cam Ban Beag above Glenfeshie
all localitiesbeingon thegranitealthough
and Geall CharnMorin theMonadhliath,
suitablehabitatsexistcloseat handon theschists.
apparently
From information
suppliedby Mr. A. Macdonaldit seemslikelythat a similar
district.
heathmayoccuron Moineschistin theGlenStrathfarrar
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426
A New ApproachtoScottishMountainVegetation
The sociationsare zoned accordingto exposure. That rich in yellowlichens
ochroleuca
and Cetrarianivalis)occursonlyin themostexposedsites,where
(Alectoria
is confined
Alectoriaochroleuca
the dwarfshrubis low (1 to 2 cm.),and intermittent.
to thesesitesalthoughit doesnotattainsuchluxurianceas in Scandinaviawhereits
Table 6. Lichenheaths
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Area of plot (sq. m.)
1
100
2500
20
N
1
3
4
5
6
100
2500
10
N
1
7
4
2
3
7
3
-
-
3
4
1
4
-
Calluna vulgaris
Empetrumhermaphroditum
Loiseleuria procumbens
Vaccinium myrtillus
V. vitis-idaea
7
4
7
2
7
4
2
-
1
3
Lycopodium alpinum
L. selago
1
1
-
1
-
Carex bigelowii
Deschampsia flexuosa
Juncustrifidus
1
3
-
Alicularia scalaris
Diplophyllumalbicans
Lophozia alpestris
Microhepatics
Dicranum scoparium
Hypnum cupressiforme
Pleurozium schreberi
Polytrichumpiliferum--?.
Rhacomitriumlanuginosum
Rhytidiadelphus loreus
Alectoria nigricans
A. ochroleuca
Cerania vermicularis
Cetraria aculeata
C. islandica
C. nivalis
Cladonia bellidiflora
C. floerkeana
C. gracilis
C. pyxidata
C. rangiferina
C. sylvatica
C. uncialis
Ochrolechia frigida
0. tartarea
f
Sphaerophorus globosus
2
1 ?
1
2
1
7
2
- 3
3
-?-
2
3
3
3
-
-
-
4
--
9
10
3
4
3
3
-
3
3
1
3
3
3
11
12
100 100
2600 2600
0
1
N
4
4
7
2
2
3
2
6
3
3
1
+
3
1
3
+
1
3
1
-1
1
2
2
2
1
3
-
2
-
1
1
.
-
2
3
3
1
-
2
2
2
1
-3
2
3
1
1
1
3
1
1
3
3
4
7
3
2
6
3
3
7
3
4
7
3
_
-
1
-
-
2
4
7
3
...
3
2
3
3
9
3
I
2
1
1
2
2
2
3
1
1
I1
2
-
2
3
-
--
2
-
3
-
1
2
4
9
3
3
+
+
2
-
1
-
2
3
8
3
9
3
9
1
3
9
-
1
+
3
3
1
4
2
2
3
1
3
1
2
2
3
1
5
4
4
2
4
3
4
3
4
Map reference
1-10. 28/888023
11, 12. 27/880976
tangledbranchesappearto suppressthedwarfshrubs.It maybe used as a differentialspeciesbetweenthisnodumand thosewhichfollow.(The otherspeciesofchionoand Cetrariacucullata,are not yetknownto us
phobouslichens,Alectoriadivergens
in the Scottishmountains,nor is trueCladoniaalpestris,whichis the chiefheath
ofScandinavia.)
former
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M. E. D. POORE AND D. N. MCVEAN
427
The lichens of these communitiescan be arrangedin order of increasingtolerance
to snow cover - Cetraria nivalis - Cladonia sylvatica - Cetraria islandica. The Norwegian order is - Cetraria nivalis - Cladonia alpestris - C. sylvatica - Cetraria islandica
(Nordhagen,1943, p. 211).
Because these lichen communitiesoccur under the same conditions of exposure
and on the same rock as similar communitiespoorer in lichens elsewhere in the
Cairngormstheirrange is unlikelyto be determinedby exposure and rock type; and,
as they representthe extension of a continental vegetation type into an oceanic
region, their distributionis probably controlledby microclimate. The explanation
is farfromestablished,but it may lie along the followinglines. At the junction of the
Low Alpine and Middle Alpine zones in Norway lichen heath covers extensive
exposed habitats at and above the altitude of our lichen heaths, i.e. much of their
potential range in the Cairngormsis occupied by Rhacomitriumheath and Juncus
trifiduscommunities. It seems possible that the greater force of the winterwinds,
and absence ofsnow cover,preventthe colonizationby lichensofthe groundoccupied
heath (scattered patches of lichen are present at this altitude); and
by J. trifiduts
where
that,
slight shelteris present,they are excluded by the competitivepower of
Rhacomitrium.Casual observationssuggestthat the lower limit of the Rhacomitrium
heath coincideswith the average cloud base.
The lichen-rich Vaccinium-Festuca sociation in Breadalbane (Poore, 1955c),
occupies similarhabitats at the same altitude,and is probably a parallel development
on morebasic rock.
D. Moss heaths
Rhacomitriumheaths are characteristicof moderatelyexposed plateaux and ridges
throughoutthe Scottish mountains,descendingto just under 3000 ft. (914 m.) in the
east and to somewhatlower elevations in the west.
Rhacomitrium-Carexbigelowiinodum
The Rhacomitrium-Carex
bigelowiinodum has been definedby Poore (1955b), but
other noda and theirvariants do occur, particularlyin north-westScotland, where
the moss heaths occupy vast areas of high ground as in the Fannich forestof Rossshire.
The moss heaths may be floristicallyimpoverished or surprisinglyspecies-rich,
according to the base status of the soil and the exposure of the site, so that the constants of the entirecomplex are few: Vacciniummyrtillus,Carex bigelowii,Rhacomitriumlanuginosumand Cetrariaislandica.
With increasingexposure they grade into the various open communitiesof erosion
pavements and solifluctionsoils, and with increasing snow cover they give way to
Nardus and Deschampsia caespitosa-dominatedsnow beds or to dwarf shrub heaths
at lower elevations. Abrupt transitionsfrom Callunetum to Rhacomitriumheath
occur at 2500 ft. (760 m.) on Ben Wyvis and fromCalluna-lichenheath to Rhacomitriumat 2900 ft. (882 m.) on Carn Ban Mor (Cairngorms.)These are not exposure
effectsbut may rather be related to increasing precipitation/evaporationratio
associated withincreasingmistcover at higheraltitudes.
Where the summit soils are deep and sandy, as on the Torridonian formationof
the north-west,thereoftenappears to be a cyclical alternationbetweenRhacomitrium
heath and erosionpavement accordingto the vagaries of the wind in producinglocal
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428
A New ApproachtoScottishMountainVegetation
erosionor deposition.All theScottishevidence,on theotherhand,is opposedto the
sequencesuggestedby Pearsall (1950,p. 90). An appearanceof successionalrelaofwintersnowcoverin favouring
peat developtionshipsmaybe givenby theeffect
mentand thegrowthofcertainspeciessuchas Nardusstricta,
Deschampsiacaespitosa
has immense
and Trichophorum
but in an oceanicclimateRhacomitrium
caespitosum,
and
its
over
the
favoured
communities
greatstability
competitivepower
rangeof
in
the
of
not
a
communities
erosion
It
does
open
part
play prominent
exposure.
to
the
extreme
and
frost
movement
in
the
soil,althoughit
exposure
pavementowing
or
scree
where
the
are large
colonize
rock
detritus
on
level
fragments
ground
may
of
the
on
this
subto
have
stability.Subsequentdevelopment
vegetation
enough
stratumwill dependon the exposureof the site and not on autogenoussuccession
alone.
heathshave been describedfromIceland (Hansen,1930;SteindorsRhacomitrium
son,1951;McVean,1955)and theFaeroes(Ostenfeld,
1908). Theyare also knownfor
in
and
are
thus
western.
oceanic
distribution.In continental
Norway,
markedly
are
flush
areasofthelichenheath
communities
Norwaythey hygrophilous
occupying
in
(Dahl, press).
In Table 7 the twelve examples of the Rhacomitrium-Carex
bigelowiinodum
describedby Poore (1955b),have been combinedwithsevenexamplesof the same
Scotlandand the constancyofthe speciesindicatedin col. 1.
nodumfromnorthern
thosespecieswhichoccuronlyin Breadalbanelists(B) orthe
Column2 distinguishes
northern
lists (N). The remainingcolumnsare devotedto analysesof othermoss
heathsfromnorthern
Scotland.
nodum(Table7; 3 and4)
Empetrumhermaphroditumfacies
oftheRhacomitrium-Carex
of
two
this
variant
have
so
far
been
examples
Only
analysedand its relationships
withEmpetrum-hypnoid
mossheathhave yetto be examined.
Nardusstrictafacies(Table7; 5, 6 and 7)
Nardus strictaheath is so farknownonlyfromthe north-west
whereit can be
Nardus-dominated
from
snow
beds
distinguished
by topographicalfeaturesand
the
almost
absence
of
floristically,
by
complete
hepatics. IsolatedcoloniesofNardus
in mossheath tend to encouragea littlesnow accumulationin theirvicinityand,
influence
the environment
in theirfavour;
throughthe extrashelterand moisture,
butlastingsnowbeds areneverbuiltup in thisway (seealso Poore,1955c,pp. 623-4).
Polygonum
viviparum-Salix
herbaceafacies
(Table7;10and 11)andhypnoid
mossfacies
12
and
7;
(Table
13)
Theseinteresting
variantsare againoflimiteddistribution
in Scotland,and so far
knownonlyfromthenorth-west
wheredolomiticmudstonesand shalesofthe Cambrianformation
outcropat about3000ft.(914m.).
Floristicaffinities
are withtheIcelandicRhacomitrium
heaths(McVean,1955)and
withthose of the Faeroes (Ostenfeld,1908) ratherthan with the Rhacomitriumnodum.
Carexbigelowii
The soilis a rich,brown,stonymud,circum-neutral
inreaction,and thecommunity
is a somewhatopenonebecauseofthemoderately
severeexposure.
In the anglesof the terraces,wherea littlesnow accumulates,Rhacomitrium
is
Pleuroziumand Rhytidiadelphus.
The
replacedby thehypnoidmossesHylocomium,
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M. E. D. POORE AND D. N. MCVEAN
429
exposedterraceflatsare neverprotectedby morethana coatingofrimeor verglas.
Cochlearia
viride,Selaginellaselaginoides,
micacea,Solidagovirgaurea,
Coeloglossumn
are
Luzula spicata and Aulacomniumturgidum
Sagina saginoides,
Juncustrifidus,
oftheRhacomitrium
while
Oxalis
characteristic
acetosella,
Saxifragahypnoides,
phase,
Rumex acetosa,Cerastiumvulgatum,Achilleamillefolium,
Plagiotheciumundulatumand
are
confined
to
the
moss
mat. This species-rich
hypnoid
Rhytidiadelphustriquetrus
the Rhytidiadelphusa
facies
of
also
be
as
moss
hypnoid
communitymay
regarded
nodum
described
below.
Deschampsia caespitosa
Juncustrifidus-Salixherbaceafacies (Table 7; 8 and 9)
The fewexamples ofthisvariant that have been analysed are closerintheiraffinities
to the Rhacomitrium-Polygonum-Salix
herbacea facies than to the RhacomitriumCarex bigelowiinodum itself. The Juncus trifidusvariant in Poore (1955) should be
compared with this. Soils are developed froma mixed parent material of mudstones
and quartzites so that they are probably of intermediatebase status.
HEATH (a)
RHACOMITRIUM
//
/ACTIVE SOLIFLUCTION (b)
HYPNOID MOSS HEATH (c)
_/
/(a)
(b)
/(bi
Fig. 7. Relationship of the moss heaths to exposure on the solifluctionterraces of Ruadh Stac Beag,
Beinn Eighe.
Rhytidiadelphus-Deschampsiacaespitosa nodum (Table 7; 14)
Small areas dominated by Hylocomium,Pleuroziumand Rhytidiadelphusare found
throughoutthe Rhacomitriumheaths of the northernHighlands. The relation of the
two types is well seen on Fionn Bheinn, a westernoutlieron the Fannich hills,where
deep
hypnoidmosses occupy all depressionsin the Rhacomitriummat not sufficiently
to encourage Nardus dominance. The status of the nodum is not yet certain but it
has been named provisionallyas above.
Soil profilesreveal a deeper and damper layer of surfacehumus under the hypnoid
mat than under the Rhacomitriumbut the extent of podzolization is variable in both
types.
On Ben Clibreck an Empetrum-hypnoidmoss community corresponds to the
heath
of Beinn Eighe. It formspatches in the Rhacomitrium
Empetrum-Rhacomitrium
and the change in moss dominance is abrupt and correspondsto the edge of the
Empetrummat and not to any variationin topography.
Hypnoid mosses sometimesdominate the Rhacomitriumin Icelandic moss heaths
(McVean, 1955, p. 334).
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430
A New Approach to ScottishMountain Vegetation
E. Nardus snow beds
Nardus
strictaare one of the commonestsigns of late
dominated
Depressions
by
snow-lie throughoutthe Scottish mountains between the altitudes of 2000 ft. and
3000 ft. (608 to 914 m.) although the lower limit in the central Highlands is 500 or
600 ft. (150 and 180 m.) higherthan in north-westScotland.
Poore (1955b) has already definedthe high altitude Nardus strictasociation as a
Carex bigeNardus-dominatedcommunitywhich also contains Galium hercynicum,
lowii,Pleurozium schreberiand Rhytidiadelphussquarrosus. Table 8 shows the compositionof this sociation in the Beinn Eighe districtof Ross-shire;and the combined
constancy of each species when these lists are added to Poore's Breadalbane and
Cairngormanalyses. Only R. squarrosus has had to be dropped from the list of
constants and R. loreus has almost replaced it there. Species limited to central or
northernHighlands are indicated as in the previous table.
It will be noticed immediately that the northernlists resemble the Cairngorm
Nardus grassland of the 'Empetrum-Vaccinium'zone (Burgess, 1951) in the presence
of Vaccinium uliginosum and Empetrumhermaphroditum.They are also richer in
species, particularlyhepatics, than any of the Scottish lists previously published,
and thus approach more closely the Nardus sociation of Scandinavia.
A notable feature of the Beinn Eighe lists is the abundance of Rhacomitrium
and scarcity of the hypnoid mosses, although R. loreus and Hypnum cupressiforme
are constants. This is rather surprisingin view of the fact that a small amount of
snow accumulation on the Rhacomitriumheath is sufficientto reverse moss dominance. No. 6, however, which is the only example fromthe summitridge of Beinn
Eighe, has Rhytidiadelphusmore abundant than Rhacomitrium.
In the north the soils are again podzolic with a tendency to peat accumulation,
and the Trichophorumvariant (Trichophorum-V.
uliginosumvariant of Beinn Eighe)
in wettersituations is even more distinctthan in Breadalbane; deep peat snow beds
on Beinn Eighe may be dominated by T. caespitosum.
The northernexamples of the Nardus sociation are associated with a maximum
period of snow cover of about five months,two months less than that of the most
permanentbeds.
The Nardus snow beds of Iceland, which occur at low altitudes on the coast, differ
in the abundance of forbsand grasses and the reduced role of the mosses,particularly
Rhacomitriumand Pleurozium (McVean, 1955).
F. Vaccinium snow beds
The effectsof winterand springsnow-lieon vegetation stretchdown into the SubAlpine zone and even below the potential altitudinal limit of pine forest. In the
centraland eastern Highlands these habitats are occupied by Vaccinium and Nardus
communities. The most characteristicof the Vaccinium snow beds has been pronodum and a few lists are
visionally named the Vaccinium-Chamaepericlymenum
as
a
basis
for
further
discussion,
presented
although
study is necessarybeforeit can
be definedaccurately. Lists 1 and 2 (Table 9) are taken at altitudes of2500ft.(750m.)
and 2400 ft. (720 m.) on Meall Dubhag and Craig an Dail Beag respectively;lists3 to 7
come froma large stand at 1800 ft. (540 m.) near the head of Loch Einich in the
Cairngorms. This is withinthe limit of historicalpine forestand representsthe lowest extension of the nodum, where the snow does not lie sufficiently
long to inhibit
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M. E. D. POORE AND D. N. MCVEAN
431
Table 7. Moss heaths
2
1
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Plot area (sq. m.)
Empetrum hermaphroditum
E. nigrum
Salix herbacea
Vaccinium myrtillus
V. vitis-idaea
V. uliginosum
25
10
20
75
35
Lycopodium alpinum
L. selago
15 -
Agrostiscanina
A. tenuis
Deschampsia caespitosa
D. flexuosa
Festuca ovina agg.
F. rubra
F. vivipara
Nardus stricta
25
35
5
40
70
15
55
15
-
9
11
3
8
4
6
7
10
12
13
5
14
90 100 100 100
100 100 100 100 99 100 100 90
2800 2800 2200 2300 2200 3100 2600 3000 2900 3100 2900 2800
3
0
0
0
2
1
2
10
2
5
3
3
-E
W
NW
E NW
E
NW
N
S
4
4
4
4
4
4
4
4
4
1
2
2
6
-
7
-
5
3
4
-
2
3
5
3
+
3
3
2
1
-
-
3
+.+
-
N
N
-
2
-
-2
2
1
-
1
-
3
Achillea millefolium
Alchemilla alpina
Armeria maritima
Cerastium vulgatum
Chamaepericlymenum
suecicum
Cochlearia micacea
Euphrasia frigida
Galium hercynicum
-???
Oxalis acetosella
Polygonum viviparum
Potentilla erecta
Ranunculus acris
Rumex acetosa
Saussurea alpina
Saxifraga hypnoides ?
Sedum roseum
Sibbaldia procumbens
Silene acaulis-?
Solidago virgaurea
Succisa pratensis
Thalictrum alpinum
Thymus drucei
-
-
-N
-1
--
-
60
3
6
5
6
3
+
2
2
4
2
-
+
5
1
-
1
--
-
2
-
-
3
-
2
--?---
+
N
N
5
N
Aulacomnium turgidum
60
Dicranum fuscescens
25 -+
D. scoparium
Oligotrichumhercynicum 10 B
Plagiothecium undulatum20
Pleurozium schreberi
H J.E.
2
1
4
-
2
-
-
-
-
1
-
-
-
6
4
6
3
2
2
2
3
4
4
2
+
3
+6
6
3
2
1
2
--
2
-
-
2
3
2
4
-
2
1
+
2
3
1
2
+-
3
3
-+
--
2
-
?1
-
-3
-
2
-1
- -2
--
4
.
-
-
3
2
-
6
2
3
-
-
1
-
-+
-
-
-
5
5
-
-
20 N
- --?-.+
-
3
-
1
2
-
20
5
-
1
1
4
3
3
100
Carex bigelowii
C. panicea
-5 N
C. pilulifera
Juncus squarrosus
5 J. trifidus
5 B
Luzula multiflora
10 B
L. spicata
Trichophorumcaespitosum
Coeloglossum viride
Narthecium ossifragum
3
1
-
-
-
-
2
2
1
2
-
1
1
3
1
-
2
3
+
+
2
+
+
+
4
-
-
1
-
1
1
3
1
1-
2
1
1
2-
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All use subject to JSTOR Terms and Conditions
2
-
2
3
+
-
-
432
A New ApproachtoScottishMountainVegetation
Pohlia ?annotina
Polytrichumalpinum
P. commune
P. gracile
P. urnigerum
Rhacomitrium
lanuginosum
Rhytidiadelphus loreus
R. triquetrus
1 2
5 B
65 5 N
-?100 10
-
Anastrepta orcadensis
?Aplozia sphaerocarpa
Diplophyllum albicans
Nardia scalaris
Lophozia alpestris
?
L. hatcheri
L. ?ventricosa
Ptilidium ciliare
-
Alectoria nigricans
Cerania vermicularis
Cetraria aculeata
C. islandica
Cladonia alpicola
C. bellidiflora
C. coccifera
C. crispata
C. furcata
C. gracilis
C. leucophaea
C. pyxidata
C. rangiferina
C. subcervicornis
C. sylvatica agg.
C. squamosa
C. tenuis
C. uncialis
Corisciumviride
Icmadophila ericetorum
Ochrolechia tartarea
Peltidea aphthosa var.
leucophlebia
Peltigera canina
Sphaerophorus globosus
Stereocaulon evolutoides
S. vesuvianum
3
-
7
--
1
8
9
10
11
12
13
14
1
1
-
1
--
3
2
2
2
2
3
7
3
9
8
1
-.
-
7
---
8
6
7
8
8
..
B
B
B
5
5
B
B
20
40
50
90
10
35
10
5
5
30
10
10
B
+
1
3
2
B
B
B
B
B
B
-
--
40
25
7010
5
35
B
-
1
3.
4.
5.
6.
7.
8.
8
1
1
8
1
1
-
1
--
1-
+
-
2
-
-+
2
3
1
1
2
3
1
-2
-
+
+-
1
3
+
3
2
-
1
1
--
-
-
-
-
1-
1
1
+
3
1
+
-
2
2
-
+2
1
1
2
2
-
1 1
-
25
5 N
-
?
1
5
15
5
B
B
--
6
5
4
1
2
-+
-
--
-
1
2
--
1
1
Map reference
9. 18/972618
18/975634
10. 18/955598
18/985604
11. 18/973617
18/902609
12. 18/953605
18/895580
13. 18/973618
18/973603
14. 28/148622
18/952599
thegrowthofCalluna. The firstpairshouldprobablybe regardedas thetypeand the
thereare a numberof constantsforthe entire
secondas a variant.Nevertheless,
whichshows high fidelityto this habitat,
suecicum,
group:Chamaepericlymenum
Blechnumspicant,Galiumhercynicum
Vacciniummyrtillus,
Empetrumhermaphroditum,
scarce.
and severalbryophytes.Lichensare comparatively
as a band belowthe crest
occur
These Vacciniumcommunities
characteristically
in Calluna
on thelee side ofridgesin theLow Alpinezone, or in small depressions
beds at
snow
to
the
in
which
habitats
longer-lasting
moors,
correspond topography
Nardus
be
of
the
centre
Vaccinium
The
altitudes.
by
occupied
patchesmay
higher
ifthesnowis persistent
lb,
(Figs. 3d).
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M. E. D. POORE AND D. N. MCVEAN
433
Table 8. Nardusstrictasnowbeds
1
2
Calluna vulgaris
Empetrum hermaphroditum
Juniperusnana
Vaccinium myrtillus
V. uliginosum
7
35
7
70
28
N
N
N
Lycopodium alpinum
L. selago
25
7
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Plot area (sq. m.)
-
N
N-
3
4
5
6
7
8
100
100
100
100
100
100
2300 2200 2200 3200 2700 2750
0
1
2
5
1
2
N
N
SW
SE
NW
4
4
4
4
4
4
+
1
4
3
+
3
1
3
7
56
7
49
7
35
100
B
N
-
B
B
-
8
100
7
7
28
14
35
N
B
N
N
7
N
Alchemilla alpina
Chamaepericlymenumsuecicum
Euphrasia frigida
Galium hercynicum
Melampyrumpratense
Potentilla erecta
Rumex acetosa
Solidago virgaurea
7
7
7
80
7
49
35
14
B
N
N
N
N
Dicranodontium unciatum
Dicranum fuscescens
D. scoparium
Hylocomium splendens
Hypnum cupressiforme
Plagiothecium undulatum
Pleurozium schreberi
Polytrichumalpinum
P. commune
P. formosum
P. gracile
P. juniperinum
Rhacomitrium lanuginosum
Rhytidiadelphus loreus
R. squarrosus
Sphagnum quinquefarium
S. tenellum
7
7
56
7
35
7
80
35
35
7
14
7
63
75
49
14
7
N
B
N
N
B
B
B
N
N
Anastrepta orcadensis
Anastrophyllumdonianum
Aplozia sphaerocarpa
Bazzania triangularis
Diplophyllumalbicans
Leptoscyphus taylori
Lophozia alpestris
Orthocaulis floerkii
Pleurozia purpurea
28
7
7
14
14
7
7
35
14
Agrostis stolonifera
A. tenuis
Deschampsia caespitosa
D. flexuosa
Festuca ovina agg.
F. vivipara
Nardus stricta
Carex bigelowii
C. flacca
C. pilulifera
Juncus squarrosus
Luzula sylvatica
Trichophorumcaespitosum
Narthecium ossifragum
-
B
N
N
N
N
N
-N
N
-N
--
4
2
3
1
2
3
9
-
3
+
-
8
1
1
2
5
2
-
-
-
-
-
-
-
4
1
-
11
3
-
-
1
3
2
21
+
1
-
5
2
5
1
2
2
-
-
-
-
2
1
2
1
1
-
---
4
1
4
1
3
+
-
5
1
-
2
+
1
5
1
4
1
1
--
-
3
3
-
1
3
3
4
-
4
2
+
2
1
1
3
2
-
2
1
-
2
+
9
-
-
3
8
+
+
1
4
9
3
-
2
4
+
+
+
4
3
-
3
3
4
2
2
3
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4
-
3
1
1
1
4
1
1
434
A New ApproachtoScottishMountainVegetation
Ptilidium ciliare
Scapania gracilis
S. nemorosa
1
63
7
14
2
N
N
Cerania vermicularis
Cetrariaaculeata
C. islandica
Cladonia bellidiflora
C. gracilis
C. impexa
C. leucophaea
C. pyxidata v. chlorophaea
C. rangiferina
C. sylvatica
C. tenuis
C. uncialis
Ochrolechia frigida
Sphaerophorus globosus
7
7
56
35
28
14
21
28
7
21
14
56
7
7
B
N
3
1
2
3
3
-
N
N
-
B
B
N
-
N
N
2
-
4
-
-
3
-
-
2
1
1
4
2
4
-
-
+
3
-
1
4
2
1
- +-
5
2
-
6
3
7
-
3
2
-
8
3
3
2
3
1
1
3
3
1
2
+
Map reference
6. 28/946600
3. 18/932639
7. 18/978635
4. 18/985598
8. 18/975636
5. 18/985598
to an extensionofthe ScandinavianalliancePhyllodocoThe nodumcorresponds
Vaccinionwithwhichit has a numberoffeaturesin commonin additionto habitat.
to the alliancein
The ScottishlocalitiesofPhyllodoce
caerulea,a speciesfaithful
exactlyto Nordhagen's
corresponds
Norway,lie withinthenodumwhosepreference
acidophilous,chionophilousand mesophilousto weakly
diagnosis'humus-loving,
xerophilous'.
Althoughthe alliance is representedin continentalNorway,it assumes most
ofthe high
in oceanicand sub-oceanicregionswherea largeproportion
importance
this
nodumin
small
areas
are
covered
That
as
snow.
falls
by
relatively
precipitation
Scotlandis probablydue to thewarmthofour oceanicclimateand theparticularly
erraticsnowcoverat low altitudes.It is notablethatthreeof the fourNorwegian
associationsof the allianceare coveredwithwood or scrubof juniper,Betulanana
orB. tortuosa.Sociationsanalogousto thesewereno doubtoncepresentin Scotland.
G. Dryas heaths
Base-richmountainheathsare rarein Scotlandpartlybecause ofthe scarcityof
limestoneor calcareousschistoutcropson fairlylevelterrainin Low and Sub-Alpine
rateofsoilleachingin an oceanicclimregionsand partlybecauseoftheformidable
ate. Anypotentialsitesofbase-richheathare exposedto strongleaching,and baseareconfined
to theslopesand cragledgesbelowas a varietyofflush
richcommunities
associations.On hardlimestonepeat mayformdirectlyon therock,and acid communitiesbecome dominantas at Loch Daimh, Perthshire,and at Durness and
Inchnadamphin Sutherland.Even in the east and centralHighlandstheonlylevel
habitatswhichhave a richvegetationare thoseon softrockswhere
andwell-drained
can keeppace withleaching,and wherethephysicalstructure
therateofweathering
ofthe soil favoursfrostmovement.This is even morepronouncedin the westand
north.(Cf.Coombeand White,1951.)
into two alliances,the
Nordhagen(1943) dividesthe Class Elyno-Seslerietalia
and the driermore
and
more
Potentillo-Polygonion
vivipari
chionophilous
damper
and someof
nodum
the
Sibbaldia
Poore
compares
(1955)
exposedElyno-Dryadion.
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M. E. D. POORE AND N. D. MCVEAN
435
the richercommunitiesof 'Arctic-Alpinegrassland' in Breadalbane with sociations
of the former. Well-drainedlocalities which might support Dryas in this region do
not do so, but the occurrenceof Dryas on the cliffsnearby suggeststhat this may be
in part a grazing effect. One fragmentof a communityallied to Dryas heaths has
been foundin Glen Lochay with the followingcomposition:
Salix reticulata
Selaginella selaginoides
Alchemilla alpina
Armeria maritima
Cerastium alpinum
Dryas octopetala
Polygonum viviparum
Saxifraga aizoides
S. oppositifolia
Silene acaulis
Thalictrum alpinum
Thymus drucei
Carex bigelowii
C. pulicaris
Festuca vivipara
Ditrichum flexicaule
Pleurozium schreberi
Tortella tortuosa
The nearest approach to the Scandinavian alliance is found on the Durness limestone and on the extensive deposits of blown shell sand along the north coast of
Sutherland. These areas naturally formexcellent grazings and have been used so
intensivelythat they are now covered with a close grass sward fromwhich many of
the more interestingspecies have been eliminated. Small patches of Dryas heath
have been preservedby theirinaccessibility.
Lists 1 and 2 (Table 10) were made on the shell sand at Druim Chuibhe near Bettyhill and list 3 fromlimestonenear Borralie. The second list is froman exposed site
and much poorer in species, but clearly belongs to the same nodum as the others,
(provisionallynamed Dryas-Carexflacca). All are probably primarycommunitiesalthough scrub woodland of birch,juniper and hazel may have been widespread along
this coast at one time.
Nordhagen (1943) expresses the view that the Irish Dryas communities on the
Burren do not belong to the same alliance as the mountain Dryas heaths. This is
arguable in view of the connectinglinks now established between them.
The Dryas-Carexrupestrisnodum (lists4 and 5) occursonlyonsteep (30 to60 degrees)
slopes on skeletal soils, and has been identifiedso far only at Durness and at Heilam
on the east shore of Loch Eriboll. It formsa close turfalternatingwith the DryasCarexflacca nodum on moistersites. Fragmentsalso occur at 1000 ft. (304 m.) above
Loch Mhaolach-Coirenear Inchnadamph, at Knockan and on epidioritein Breadalbane whereSesleria caeruleais added to the list of species.
V. SUMMARY
The methods of vegetation analysis and descriptiondeveloped in the Breadalbane
districtof Perthshire(Poore, 1955) have been applied more widely to the mountain
vegetation of the Highlands.
The principal ecological factorsat workin determiningvegetation developmentin
the Scottishmountainsare firstdescribed,with particular emphasis on hithertoneglected aspects such as the influenceof snow cover and the degree of oceanicity.
Comparisonsare also made withthe situationin Scandinavia. The inter-relationship
of altitude and exposure is shown in the formof diagrams forthree key areas of the
Highlands.
Examples of Sub-Alpine scrub, dwarfshrub heaths and bogs, moss heaths, Dryas
heaths and snow-bedcommunitiesare then describedin detail. These can be divided
into two categories; communitieswhich,like the Rhacomitriumheaths, have part of
theirprincipal range in Scotland, and which are well enough representedto show a
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436
A New ApproachtoScottishMountainVegetation
nodum
Table 9. Vaccinium-Chamaepericlymenum
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Area of plot (sq. m.)
2
1
- 70-90
2500 2400
45 10-15
N SSE
1
4
Calluna vulgaris
Chamaepericlymenum suecicum
Empetrum hermaphroditum
Rubus chamaemorus
Vaccinium myrtillus
V. uliginosum
V. vitis-idaea
3
3
3
2
5
7
7
Blechnum spicant
Dryopteris austriaca
Lycopodium annotinum
3
3
Agrostistenuis
Carex bigelowii
C. binervis
C. echinata
Deschampsia flexuosa
Molinia caerulea
Nardus stricta
3
3
+
-
-
5
2
4
2
1
-
2
2
2
3
2
+
1
+-
Alchemilla alpina
Galium hercynicum
Melampyrumpratense
Oxalis acetosella
Potentilla erecta
Trientaliseuropaea
Viola palustris
Dicranum scoparium
Hylocomium splendens
Hypnum cupressiforme
Leucobryum glaucum
Pleurozium schreberi
Polytrichum commune
Ptilium crista-castrensis
Rhytidiadelphus loreus
Sphagnum spp.
S. capillaceum
S. quinquefarium
Microhepatics
Cetraria islandica
Cladonia bellidiflora
C. gracilis
C. sylvatica
Icmadophila ericetorum
+
+
3
3
2
7
+
+
1
-
+
8
+
-
-
3
4
5
6
7
1
1
1
1
1
4
3
5
2
8
5
3
4
2
7
3
3
1
1
9
5
3
2
1
8
3
3
5
2
7
3
3
3
3
3
-
2
-
1
+
1
-
1
1
4
1
3
4
3
1
3
1
-
2
1
-
3
+
3
-
1
4
4
1
4
4
3
5
3
3
4
3
4
3
2
1
6
6
+
3
2
3
4
1
3
3
2
3
6
+
1
4
6
+
6
4
+
4
7
+
1
3
3
1
3
1
-
1
1
2
-
1
1
-
+
'Map reference
1. 28/883023
2. 37/154974
3.
4.
5, 27/90-977.J
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M. E. D. POORE AND D. N. MCVEAN
437
Table 10. Dryas heaths
1
100
200
5
N
4
2
100
175
2
S
4
9
3
9
3
3
3
2
3
3
6
4
4
1
3
Selaginella selaginoides
-
3
AgrostistenuisCarex cf.bigelowii+
C. flacca
C. paniceaC. rupestrisFestuca ovina
F. rubraHelictotrichonpratense
Sieglingia decumbensKoeleria gracilis
Luzula campestris
Schoenus nigricans
6
-
3
Cover (per cent)
Altitude (ft.)
Slope (deg.)
Aspect
Area of plot (sq. m.)
Arctostaphylosuva-ursi
Calluna vulgarisDryas octopetala
Empetrum nigrumand hermaphroditum
Juniperuscommunis
Salix repens
Thymus drucei
6
2
3
100
200
5
SE
4
2
1
2
-
+
2
-
1
-
1
2
1
1
+
1
2
1
+
1
3
2
1
+
+
+
+
2
3
-
+
-
3
6
5
2
4
2
-
1
1
2
-
+
3
3
2
2
3
3
3
1
-
4
5
5
2
3
-
+-
+
1
+
1
-
-
-
3
-
1
Antennariadioica
Anthyllisvulneraria
Bellis perennis
Campanula rotundifolia
Cerastiumvulgatum
Daucus carota
Euphrasia agg.
Galium hercynicum
G. verum
Gentianella amarella
Hieracium pilosella
Hypericum pulchrum
Hypochaeris radicata
Lathyrus montanusLinum catharticum
Lotus corniculatus
Plantago lanceolata
P. maritima
P. media+
Polygonum viviparum
Polygala cf.vulgaris
Potentilla erecta
Prunella vulgaris
Saxifraga aizoides
Senecio jacobaea
Succisa pratensis
Thalictrumalpinum
Viola riviniana
Camptotheciumlutescens
Ctenidium molluscumDitrichum flexicaule
Fissidens decipiens
Hylocomium splendens
Hypnum cupressiformeMnium sp.
1
8
3
6
1
2
4
-
-
-
5
85
100
30
W
4
-
5
+
Epipactis atrorubens
Listera ovata
Orchis mascula
4
80
50
40
W
4
2
1
+
3
1
2
3
1
2
2
2
3
3
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2
1
1
1
2
2
2
1
2
2
3
+
3
1
3
3
2
3
3
2
+
+
1
1
438
A New Approachto ScottishMountain Vegetation
Neckera crispa
Pleurozium schreberi
Pseudoscleropodiumpurum
Rhacomitriumlanuginosum
Rhytidiadelphus triquetrus
Thuidium sp.
Tortella tortuosa
1
1
4
3
Lochocolea sp.
Plagiochila asplenioides
Scapania undulata
1
+
Cladonia rangiformis
Peltigera canina
Solorina saccata
+
2
3
1
4
1
-
-
-
1
3
-
1
3
-
--
5
4
1
+
-
+
+
1
1
Map reference
1. 29/705605
2. 29/696612
3. 29/388652
4. 29/421676
5. 29/453604
responseto changein the ecologicalfactorsin different
parts of the country,and
thosesuchas Dryasheath,whichoccurin Scotlandonlyas the scatteredfragments
ofwell-known
vegetationtypesofScandinavia.
Salix myrsinites
scrub,Betulanana bog,lichenheath,Dryasheathand certainmoss
and dwarfshrubheathsare heredescribedforthefirsttimefromScotland.
ADDENDUM
Since thispaperwas submittedfurther
progresshas been made withthe surveyof
Scottishmontanevegetationcarriedout by the NatureConservancy,
Edinburgh.
The floristic
listspresentedabovehave beenincorporated
in themoreextensivedata
nowavailableso thatsomereshuffling
ofthecommunities
and nomenclatural
changes
have beennecessary.
In particular,further
examplesoflichenheath,Dryasheath,and the species-rich
faciesofRhacomitrium-Carex
heathhave been analysedand theirstatusis
bigelowii
nowbetterknown.A chionophilous
Athyrietum
alpestrishas beenrecognizedin the
centraland northern
oflate snowareas dominatedby
Highlandsand communities
Dicranumfalcatum,D. starkei,Polytrichum
Rhacomitrium
norvegicum,
spp. and
Gymnomitrium
spp. (Salix herbaceanodumofBreadalbane,Poore,1955c)have been
describedfromtheCairngorms,
Ben Wyvis,theFannichforestand Kintail.
The majorityof Poore's Breadalbanenoda have been foundto be widespreadin
the Highlandswithminor,but oftensignificant,
variationsin floristic
composition.
A finalclassification
mustawaitcompletion
oftheentiresurvey.
REFERENCES
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distribution. J. Ecol., 35, 138.
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271.
COOMBE,D. E. and WHITE, F. (1951). Notes on calcicolous communities and peat formationin Norwegian Lappland. J. Ecol., 39, 33.
CRAMPTON, C. B. (1911). The Vegetationof Caithness Consideredin Relation to theGeology. Edinburgh.
DAHL, E. (In press). Vegetation of Rondane.
Du RIETZ, G. E. (1925). Die regionaleGliederungder skandinavischenVegetation. Upsala.
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GODSKE, C. L. (1944). The geographical distribution in Norway of certain indices of humidity and
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i
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NORDHAGEN,R. (1943). Sikilsdalen og Norges Fjellbeiter,en PlantesosiologiskMonografi. Bergens Mus.
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OSTENFELD,C. H. (1908). The Land-Vegetationof theFaeroes. London.
PEARSALL,W. H. (1950). Mountains and Moorlands. London.
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STEIND6RRSON,S. (1941). Skrd um Islensk Grodurhverfi
(A list ofIcelandic Plantsociations examined and
defined).Akureyri.
TANSLEY,Sir A. G. (1939). The British Islands and their Vegetation. Cambridge University Press.
WATT,A. S. (1936). Studies in the ecology of Breckland. I. Climate, soil and vegetation. J. Ecol., 24,
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(ReceivedMarch 8th, 1956)
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