Vegetatio vol. 41, 2: 121-128, 1979

VEGETATION AND SOIL STUDIES OF THE ENCLOSED HEATHLANDS OF THE LIZARD PENINSULA,

CORNWALL*

Robert H. MARRS** & John PROCTOR***

Department of Biology, University of Stirling, Stirling FK9 4LA, Scotland **Now at: Institute of Terrestrial Ecology, Monks Wood Experimental Station, Abbots Ripton, Huntingdon, Cambs.

PE17 2LS, England

Keywords: Enclosure, Heathlands, Management, Ordination, Serpentine, Soils, Vegetation

Introduction

Plant ecological studies on the heathlands of the Lizard Peninsula, SW Cornwall, have concentrated on the areas which have never been enclosed (Coombe & Frost 1956a, b, Marrs & Proctor 1978). The unenclosed heathlands overly- ing both serpentine and non-serpentine bedrock can be classified into four main types, 'Short', 'Tall', 'Mixed' and

'Rock Heath'. These heath types are quite distinct, and can be recognised in the field from a consideration of the dominant species; in 'Rock Heath' Calluna vulgaris and

Festuca ovina; in 'Mixed Heath' Erica vagans and Ulex europaeus (sometimes also U. galliO, in 'Tall Heath' Erica vagans; Molinia caerulea and Schoenus nigricans; in 'Short Heath' Agrostis setacea, Calluna vulgaris , Erica cinerea, E. tetralix, Molinia caerulea and Ulex gallii. There

are, however, on the Lizard Peninsula, a number of enclosed areas, formerly farmed, which have reverted to a heathland vegetation. The vegetation of these enclosed heaths was known to be complex (D.E. Coombe, pers. comm.) partly as a result of past management practices, and no comparison with the unenclosed areas had been attempted.

* Species nomenclature follows Clapham, Tutin & Warburg (1962) for higher plants and Watson (1968) for bryophytes. *** We would like to thank Drs. D.E. Coombe and LC. Frost for considerable assistance throughout this work. Professor P. Bannister and Mr. M.O. Hill assisted with numerical analysis, and Dr. D.F. Chamberlain confirmed the identification of bryophytes. Professor A.D. Bradshaw kindly allowed one of us (R.H.M_) the facilities of his department to complete this work. N.E.R.C. are thanked for financial support.

A study of these enclosed heathlands is desirable for a number: of reasons. They represent (on the Lizard) an important habitat type which is, at the present time, being gradually destroyed by ploughing and a return to agriculture. It was felt that a descriptive study would draw attention to their special qualities and enable a stronger case to be made for their conservation. Since the enclosed heathlands are the result of a relatively recent succession they might provide information of value for the manage- ment of Lizard heaths in general.

Unfortunately, little detailed information is available on the management of the Lizard heathlands, although there is evidence of peat being removed for fuel (Johns 1848) and of sporadic burning of both enclosed and unenclosed areas (Coombe & Frost 1956a). Vegetation patterns similar to 'ridge and furrow' marks can be found in many enclosed areas indicating that ploughing had taken place. The present reclamation practice involves a combination of drainage, ploughing and sowing an agricultural seed mixture with additions of both fertilizer and lime.

It is also extremely difficult to determine when these heathlands were enclosed, since there is evidence of prehistoric circles and enclosures and some degree of disturbance may have taken place as early as the Bronze Age (L_C. Frost pers. comm.). From an inspection of both the Tithe Maps of 1840 and the Ordnance Survey six-inch maps of 1888 it was ascertained that the majority of enclosures surveyed in this study were enclosed after 1840, although three large enclosures were used for arable farming or as pasture prior to 1840. Lake (1976)] on the other hand, considered that heathland vegetation covered its maximum area in 1888, which suggests that the enclosu-

121

res had been abandoned by this time. If this is true, the ma- jority of enclosures might only have been used for a maxi- mum of fifty years between 1840-1888, coinciding with the start of the decline of agricultural production between 1875-1885 (Orwin & Whetham 1964). It is possible, howe- ver, that some of the enclosures have been subsequently used for short periods. At the time of the present study all of the enclosures had reverted to heathland.

Materials and methods

Sampling methods

All sampling sites are located in the South of the Lizard Peninsula; further information is provided in Table 1. In June 1976 12 areas of unenclosed 'Rock', 'Mixed', 'Tall" and 'Short Heath' vegetation, overlying both serpentine and non-serpentine substrata, were sampled from at least 10 quadrats at each site. In April 1977 20 enclosed fields,

surrounded at least partly by earth banks, overlying both serpentine and non-serpentine rock were sampled with between 4 and 16 quadrats from each. Quadrats were

regularly spaced and the number of quadrats from each enclosure was dependent on the size of the enclosure.

Only the data from the 'Tall' and the 'Short Heath' from

the enclosed study were selected for numerical analysis with the enclosed data as the vegetation of the enclosed areas most closely resembled these heath types. Moreover, all of the enclosed heath samples, with the exception of one quadrat, contained Molinia caerulea and this species had

been shown to separate 'Rock' and 'Mixed Heath' ( -

Table 1. Description of sampling sites on the Lizard.

M. caerulea) from "Short' and "Tall Heath' ( + M. caerulea) in a normal association analysis (Marrs & Proctor 1978).

Although there may be some difficulties in comparing the two sets of data because of seasonal effects, all species found in the unenclosed examples of 'Short' and 'Tall Heath' were also found in the enclosed areas.

At each sampling point the cover-abundances of all higher plants, bryophytes and lichens in a 1 m 2 quadrat were recorded using the Domin scale.

From each of the quadrats sampled a soil sample was collected, from 0-19 cm depth, using an Eijelkamp standard auger. Soil samples were air-dried within 2 weeks of collection.

Soil analysis

The air-dried soil was lightly ground and sieved to pass a 2 mm sieve prior to analysis. The pH of the soil was measured in a 1 : 2 slurry of soil: deionized water that had been allowed to equilibriate for 2 hr. For exchangeable analysis 10 g of soil was shaken for approximately 24 h

with 95 ml of I M ammonium acetate adjusted to pH 7.0. The solutions were filtered through a Watman No 44 filter paper and made up to 100 ml with deionized water.

All cations were measured on a Perkin-Elmer 103 atomic absorption spectrophotometer.

Soils were wet ashed in a mixture of nitric: perchloric: sulphuric acids (5 : 1 : 1) for phosphorus analysis. Phos- phorus was analysed colorimetrically using ammonium molybdate, potassium antimony tartrate and ascorbic acid to develop the blue coloration.

Total soil nitrogen was analysed using techniques described by Dancer (1975).

SITE GRID REFERENCE

SUBSTRATE

Bray's Cot SW 727183 Serpentine Bray's Cot SW 727183 Serpentine Bray's Cot SW 727183 Serpentine Predannack SW 687153 Serpentine Predannaek SW 689184 Serpentine Crousa Downs SW 763188 Gabbro Crousa Common SW 771198 Crousa Gravels Main Dale SW 785200 Gabbro

Kynance/Predannack SW 685145 Serpentine Traboe Cross SW 736206 Serpentine Crousa Downs SW 763195 Gabbro Polcoverack SW 770192 Gabbro

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VEGETATION QUADRAT NUMBERS

Unenclosed 'Short Heath' Unenclosed 'Short/Tall Heath' Unenclosed 'Tall Heath' Unenclosed 'Short Heath' Unenclosed 'Tall Heath' Unenclosed 'Tall Heath' Unenclosed 'Short Heath' Unenclosed 'Short Heath'

Enclosed (12 fields) Enclosed (1 field) Enclosed (3 fields) Enclosed (3 fields)

41450 3140 61-80

1-10 91-100 81-90 21-30 11-20

101-177 211 220 178-197 198-210

Analysis of vegetation data 100,--

One of the major problems associated with an extensive study of closely-related vegetation types is that there is a large number of stands with a similar vegetation. In an attempt to simplify the siabsequent interpretation of these

data the 220 stands were grouped using a nearest neighbour technique (cf. Williams, Lambert & Lance 1966)_ Fusions were carried out until 20 stand groups remained, which was thought sufficient to cover most of the heath types found in both the enclosed and unenclosed surveys. The mean value of the transformed Domin number (Bannister 1966) was calculated for each species in each stand group and reciprocal averaging used to ordinate the stand groups (Hill 1973).

This approach was used to aid the interpretation of large numbers of quadrats containing similar vegetation

types and proved successful in summarizing a large body of ecological information.

Results

Vegetation analysis

In general (the exceptions are recorded in Table 2), the species observed in the enclosed heaths were also present in the unenclosed 'Short' and 'Tall Heath'. It is noteworthy, in view of the past management of these areas, that several Pasture species, Agrostis canina, A. stolonifera, Lolium perenne, Lotus cornieulatus, Poa pratensis and Ranuneulus aeris should be found, albeit rarely, in enclosed heathland vegetation.

The 20 stand groupings arrived at are listed in Table 3_ All of the unenclosed 'Short Heath' (except stands 26 and

60) were placed in group 3 and the unenclosed 'Tall Heath'

Table 2. Species recorded in enclosed heath but not from the unenclosed 'Short Heath' or 'Tall Heath' (Marrs & Proctor 1978).

HIGHER PLANTS

Agrostis canina A. stolonifera Cirsium palustre Galium mollugo Hypericum pulchrum Lotus corniculatus Poa pratensis Prunella vulgaris Ranunculus acris Sieglingia decumbens Ulex europaeus

BRYOPHYTES

Archidium alternifohum Dicranurn scoparium Eurynchium praelongurn Fissidens bryoides F. taxifolius Pseudoscleropodium purum Riccardia pinguis

AXIS 2

(

50'--

[ ]

® &,

Tall ( Heath

Enclosed ) Heath

[] ®

I 50

AXIS 1

I lOO

Fig. 1. Ordination by reciprocal averaging of the stand groups ; the major unenclosed stand groups are surrounded by circles, whereas the enclosed stand groups are surrounded by a square.

were placed mainly in groups 16, 17 and 19. Few of the enclosed stands were grouped with the unenclosed exam- ples of 'Short Heath' and 'Tall Heath' except in group 16 which contained both 'Tall Heath' and several enclosed stands. The enclosed stands were placed into 5 main groups (groups 6, 10, 12, 13 and 16; all being groups which

contained more than 5 stands). Ordination of these stand groups by reciprocal averaging (Fig. 1) showed that the enclosed groups occupy an intermediate position to the unenclosed 'Short' and 'Tall Heaths'. There appears to be no correlation between the stand groups and either geographical position or geological substrate (Table 4); all of the main enclosed groups were found at the three main areas sampled and overlying both serpentine and non-serpentine rock.

The mean cover-abundance of the most common plant species is shown in each of the major stand groups ranked along the first ordination axis (Fig. 2) and three main types Of distribution can be observed:

(1) Agrostis setaeea, Calluna vulgaris, Eriea cinerea, E.

tetralix!and~Ulex:galliLThesespecies although abundant in 'Short Heath' show a reduced cover-abundance in the intermediate stands. This is most noticeable in Agrostis

setacea, a constant and dominant species of 'Short Heath' which has a very low abundance in the intermedi- ate groups.

(2) Carex pulicaris, Erica vagans, Schoenus nigricans and

Succisa pratensis_ These species are most abundant in

123

Table 3. Stand groupings derived from the fusion analysis show- ing component stands.

GROUP STAND

1 26 2 163 164 3* 1-25, 27-59, 130, 179, 198, 200, 208 4 101 5 155, 184 6* 102, 104, 11(~112, 114-118, 123, 128, 129, 188 192,

201,211,213 7 168 8 146 9 162, 169, 170 10" 108, 117, 122, 127, 148, 150, 159, 165, 167, 171-173,

175, 176, 178,181, 193, 217, 219 11 207 12' 60, 105, 113, 132, 133, 136-138, 140, 144, 147, 149,

151-154, 156, 158, 166, 177, 182, 185, 194-197, 206, 212, 220

13" 71, 109, 121, 139, 141, 145, 157, 160, 161, 174, 180 14 218 15 183,186,187,202 16" 64,74,83,85,93,94,99,106,107,143,199,203,205,

214-216 17" 65, 67-69, 79, 97 18 142 19" 61-63, 66, 70, 72, 73, 75-78, 80 82, 87-89, 90-92, 95,

96,98,100 20 84

*Main stand groupings, containing more than five stands, used for further analysis.

(3) Betonica officinalis, Carex flacca, C_ panicea, Festuca ovina, Molinia caerulea, Polygala serpyllifolia, Potentilla erecta and Sanguisorba officinalis. These species were at

least as abundant in the enclosed heaths as in the

unenclosed heaths.

It should also be noted that the cover of bare ground was

highest in the 'Short Heath', intermediate in the enclosed

stand groups and lowest in the 'Tall Heath' (Fig. 2). These vegetation analyses imply that the enclosed

groups are vegetation types intermediate between the

unenclosed 'Short ' and 'Tall Heaths'. The results indicate

a vegetation gradient between the two main unenclosed

vegetation types, possibly reflecting the different tolerances

and preferences of the component species. For example,

Agrostis setacea and Schoenus nigricans are more restricted

to the unenclosed 'Short ' and 'Tall Heaths' respectively

than the other dominant species. In group 16, the only

group with many stands of both unenclosed 'Tall Heath'

and enclosed vegetation, there is a lower cover abundance

of Schoenus nigricans than in Group 17 and 19 which

include most of the unenclosed 'Tall Heath ' stands.

Soils

'Tall Heath" vegetation and show a reduced cover-

abundance in the intermediate vegetation types. Schoe- nus nigricans has a very low abundance in the intermedia-

te groups.

Table 4. The distribution of the major stand groupings in the different sampling areas.

Results of some soil analyses of the main stand groups are

shown in Fig. 3.

Soil pH was lowest in the unenclosed 'Short Heath'

soils, intermediate in the enclosed heaths and highest in the

unenclosed 'Tall Heath ' soils. There appeared to be no

significant relationships between the stand groups and both

loss-on-ignition and the total nitrogen concentration of the

soil, except that groups 6, 17 and 19 tended to have higher

soil nitrogen concentrations than the other stand groups.

SITE SAMPLING AREA STAND GROUPS 3 6 10 12 13 16 17 19

(A) SERPENTINE Bray's Cot Unenclosed 'Short Heath' + Bray's Cot Unenclosed 'Short/Tall Heath' + Predannack Unenclosed 'Tall Heath' + Bray's Cot Unenclosed 'Tall Heath' Predannack Unenclosed 'Tall Heath' Kynance Enclosed + Traboe Cross Enclosed

+

+ + + + + + +

+ + + + + + + + +

(B) NON-SERPENTINE Crousa Common Main Dale Crousa Downs Crousa Downs (1) Zoar (2) Polcoverack

Unenclosed 'Short Heath' Unenclosed 'Short Heath' Unenclosed 'Tall Heath'

Enclosed + + + + + Enclosed + + + + +

+ +

124

,00 \ .-"\... / \ , •

LLI 300 40C ~ ~ •

U") lOOh X • 20 , - -e - - - - -e / ~ " ' - ' - - ° ' ~ l ~, ' /"

_z o L ~ - - - " ' ' " - ' ' " . . . . ,oc- / I G~ o .............o...,~ /

eoor / " i 5°°~-~i)Sch°enus ,.O 4oo[-- n igr icans f / (j)Bare ground z! El (k)Car._~ex./~°~""'~oPanicea I (I) Carex f l a c c a

~ 2o0~-- /J~.---" / " lie ~ carex I , I,~ pulicaris/~. ~11~ Sa nguisorbaofficinalis ,,, , g o t - : _

g , , ~ / " ~ ' % %.o. ~ . ~ , . e,s,,,,,,s ° - ' - ' e o L ~ . / - - , • . / \ . _ _ . i " < D Z 30.(o) Polygal a s e r p y l l i f o l i a _(p) Potentilla erecta __(q)Betonica officinalis _(r)Suc~sa i~ 'a tensis

'I-..° .,-, . . . . . . . . I-":" .... \L /, I ," • . . . - - _ . . . . . . _ _ u I I I I l I I I I I I l I I 1 I t I J I I I I i I ] - " i ' l l 1 1 J

3 6 10 12 13 11 17 19 3 II le 12 13 11 17 11 3 II Ill 12 13 11 17 I I i I i l 11 I i 14 17 II STAND GROUPS

Fig. 2. The mean cover-abundance of the dominant higher plants and bare ground in the main stand groups (n > 5) ranked along the first ordination axis from the reciprocal anveraging.

Both total phosphorus and exchangeable potassium It seems that the majority ofheathland areas on the Lizard, concentrations were higher in the enclosed groups than the including the more complex and disturbed enclosed unenclosed groups. The enclosed stands tended to have areas, can be adequately characterised using the abstract intermediate concentrations of exchangeable sodium, noda erected by Coombe & Frost (1956a). A variant of magnesium and calcium, the unenclosed 'Short Heath' 'Tall Heath' lacking Schoenus nigricans was also noted by having the lowest and the unenclosed 'Tall Heath' the these authors, and this variant appears similar to some of highest concentrations, the enclosed heaths described in this paper.

In the unenclosed areas 'Tall Heath' tends to occur in depressions which must be seasonally waterlogged, and the

Discussion soils under 'Tall Heath' are rich in exchangeable bases (Marrs & Proctor 1978). The unenclosed 'Short Heath' on

It is clear that the majority of the enclosed Lizard heath- the other hand belongs to raised areas on deeper loessic

lands sampled in the survey are intermediate between two deposits and the soils are acidic and base-poor (Marrs 1977; of the main unenclosed heathland types found on the Marrs & Proctor 1978). The enclosed heaths were generally Lizard, 'Short' and 'Tall Heath'. The effect of enclosure found on raised areas where one would have expected the with subsequent abandoning of management has left a vegetation before enclosure to be of a 'Short Heath' type. distinct group of vegetation types, not found in abundance The enclosed heath had higher concentrations of outside the enclosed areas, and apparently representing a exchangeable potassium and total phosphorus than either gradient between the unenclosed 'Short' and 'Tall Heaths'. the unenclosed 'Short' or 'Tall Heath', perhaps indicating

125

a) pH

7'0 f " ~ ~ ' ~ i ' ~ t / 22

" ; ' - - t ,o

/ . 0-0 I % , ,

$'0 14

12

4.0 10

b) Loss On Ignition

c) Nitrogen

"'F 1'0 TOTAL SOIL

mo 0"1 40l'--

j i g , - I I I I I I l I 3 0 10 12 13 10 17 10

STAN D GROUPS

0-3~ d) Phosphorus

0'1

° - I I I l l I I l 3 8 10 12 13 10 17 19

126

300 - -

20I

101

EXCHANGEABLE CATJONS 2O0@ i~g g-1

1000

e) Potassium

_

g) Magnesium ( S - t

/

- - _ r . ~

I I i I I I I [ 3 0 10 12 13 10 17 10

STAND GROUPS

3001 ~ f) Sodium -~

200~ J I

10

1000

h) Calcium

- I I I I ~ 1 I 1 3 6 10 12 13 10 17 10

Fig. 3. The results for the soil analyses of the main stand groups (n > 5) ranked along the first ordination axis from the reciprocal averaging; mean values and standard errors are given.

a residual effect of fertilizer addition. No similar effect was

shown for total soil nitrogen, and it might be expected that

fertilizer nitrogen would be rapidly lost from the ecosystem

in an area of high rainfall and on soils derived from porous

loessic material (Dancer 1975). The increased potassium

and phosphorus indicate that some fertilization of these

areas was carried out, and indeed the intermediate con-

centrations of exchangeable calcium, magnesium and

sodium of the enclosed soils indicate either an element

input from fertilizer sources or in the case of magnesium by

the contamination of the surface soils by serpentine-rich

subsoil during ploughing. It is unlikely that these element

increases are derived entirely from the high deposition of

sea spray on the Lizard Peninsula (Malloch 1972) since

areas of 'Short Heath' vegetation in the same locality show

no increase in these elements.

It is interesting that one of the main differences between

the soils of the unenclosed 'Short' and 'Tall Heath' are

the higher concentrations of exchangeable bases, especially

magnesium and calcium in the 'Tall Heath' (Marrs &

Proctor 1978), and it is possible that the intermediate

concentrations of these elements in the soils of the enclosed

heaths are at least partly responsible for the intermediate

vegetation.

It is worth speculating on the mode of succession of these

enclosed vegetation types once they were abandoned.

These enclosures still have evidence of disturbance after

almost a century of neglect (although they will still be

subject to grazing by cattle, and to heath fires at least

as frequently as in the unenclosed areas). In view of the lack

of enclosed stands which were similar to the pure 'Short'

and 'Tall Heath' communities it appears that the enclosed

heaths are relatively stable vegetation types. It is possible,

however, that the enclosed heaths represent plant com-

munities during a successional phase reverting to 'Short

Heath'. No evidence is as yet available to indicate whether

a pure 'Tall Heath' vegetation preceded the present

enclosed vegetation.

There has been a substantxal increase in the reclamation

of heathland on the Lizard for agricultural purposes

since 1963 (Lake 1976), especially on the more fertile non-

serpentine Crousa Common. The problems for conserving

these unusual heathland areas are great. Basically there are

five major heathland variants overlying both serpentine and non-serpentine rock on the Lizard Peninsula; these

include 'Short Heath', 'Tall Heath' 'Mixed Heath', 'Rock

Heath' and the more complex enclosed heaths. Examples of

each of these interesting and unique vegetation types

should be conserved, especially some of the enclosures.

Perhaps some of the newly reclaimed heathland will soon

be abandoned and provide the opportunity to study the

population dynamics and time scale of the re-invasion and

regeneration of these enclosed plant communities.

Summary

The heathland vegetatxon of the Lizard Peninsula, Corn-

wall, which had been formerly enclosed for agricultural

purposes and allowed to revert to heathland, was compared

with unenclosed areas. The enclosed vegetation tended to

be more complex and intermediate between two of the

main heath types found on the Lizard, 'Short' and 'Tall

Heath' (sensu Coombe & Frost 1956a). The concentrations

of exchangeable calcium, sodium and magnesium in the

soils of the enclosed heaths were also intermediate between

those of the two unenclosed vegetation types, whilst

exchangeable potassium and total phosphorus concentra-

tions were higher, perhaps a relic of past management. The

enclosed heaths are therefore distinctive entities in their

own right, although they are related to the unenclosed

vegetation types. The relevance to heathland conservation

on the Lizard Peninsula is discussed.

References

Bannister, P. 1966. The use of subjective estimates of cover- abundance as the basis for ordination. J. Ecol. 54:665 674.

Clapham, A.R., T.G. Tutin & E.F. Warburg. 1962. Flora of the British Isles. 2nd Edn. Cambridge University Press, London.

Coornbe, D.E. & L C_ Frost. 1956a. The heaths of the Cornish serpentine. J. Ecol. 44: 226-256.

Coombe, D.E. & UC. Frost, 1956b. The nature and origin of the soils of the Cornish serpentine J. Ecol. 44: 605-615.

Dancer, W.S. 1975. Leaching losses of ammonium and nitrate in the reclamation of sand spoils in Cornwall. J. Envir. Qual. 4: 499-504.

Hill, M.O. 1973. Reciprocal averaging: an eigenvector method of ordination. J. Ecol. 61 : 237 250.

Johns, C.A. 1848. A week at the Lizard. The Society for Pro- moting Christian Knowledge, London.

Lake, W.G. 1976. Report of historical biogeographical survey of the Lizard Peninsula to identify heathland changes. Nat. Conserv. Council Rep., Tavistock.

Malloch, A.J.C. 1971. Salt spray deposition on the maritime cliffs of the Lizard Peninsula. J. Ecol. 60: 103-112.

127

Marrs, R.H. 1977. Ecological aspects of the mineral nutrition of several members of the Ericaceae. Ph.D. thesis, University of Stirling.

Marrs, R_H. & J. Proctor, 1978. Chemical and ecological studies of heath plants and soils of the Lizard Peninsula, Cornwall. J. Ecol. 66: 417-432.

Orwin, C.S_ & E.H. Whetham, 1964. History of British Agri- culture 1846-1914, Longmans, London.

Watson, E.V. 1968. British Mosses and Liverworts. Cambridge University Press, London.

Williams, W.T., J.M. Lambert, & G.N. Lance, 1966. Multivari- ate methods in plant ecology. V Similarity analyses and information analysis. J. Ecol. 54: 427445.

Accepted 7 November 1979

128