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Geographical range and distribution – overlapping, wide of narrow?


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2007 Course Paper—Calluna vulgaris and Erica ciliaris (Dorset/Ciliated Heath (Webb, 1986))
Geographical range and distribution – overlapping, wide of narrow?
Comparisons



Erica ciliaris



Rose et al.

(p. 617)


Narrow, restricted—SE Dorset, W Cornwall, single cites in Devon and W Galway. Others sites in Hampshire – may be planted, may be ‘recent native’ spread from Dorset.

Classified as Rate in GB by British Red Data Book (Perring & Farrell 1983)

‘In Dorset the main populations of the plant are confined to the wet heaths and valley mires of the Poole Basin to the south of Poole Harbour, small pop and isolated plants outside.’

(p. 618) Dorset – Continuous, Truro area of Cornwall—disjunct fragments (may have been a larger single populations, drier than Dorset.

(p.619) ‘There are other heathlands in southern Britain with apparently suitable wet heath and valley mire habitats from which the plant is absent.

(p. 622)


‘In Dorset, the E. ciliaris-dominated communities occur mainly on the wet heath and valet mires, with the drier heath sites containing only scattered plants. Isolated plants tend to occur at the edge of the range of the species in Dorset and it is likely that these plants are colonists. (Chapman 1975)’
(Webb 1986)

Found in Dorset, Devon, Cornwall (p.108)

Dorset: south of Poole Harbour—extensive stands (p.118)

Three 10km2 in Dorset, ten in Devon and Cornwall. But more abundant in Dorset.

‘Distribution of Dorset Heath extends from north-west Morocco to the western coast of Portugal. Spain and France, and reaches the very northern limits of its range in southern Britiain.
Q: Expanding/ reach its limits?

Moore (1962, cited in Webb p.119) – Dying out in the periphery of its range

Chapman (1975, cited in Webb p.119) – expanding, remained absent from apparently-suitable habitats.
Hybridity Expanding/Contracting range (Webb, p.619)

Calluna vulgaris



Gimingham

(p.456)


Throughout Bristish Isles.

(p.457)


Locally absent from the more intensively cultivated districts of calcareous or base-rich soils.
Webb(1986)

‘The range of Calluna covers most of western Europe from Iceland and Norway in the north, southwards through France and Spain to Morocco and the Azores. Eastwards, its range extends to just beyond the Ural Mountains in Russia.’ (p.108)

Sea level to 1040m (p.109)



Performance –

Optimal conditions for growth,

Limiting factors,

Physiological stress and

Sub-optimal conditions
Comparisons

(Rose et al. p.623)

Erica ciliaris—slightly more calcicolous (high con of ions, esp. ca and magnesium) (C. v. more acidophilous)

(But E.c. still grow less well on calcareous soils (Marrs and Bannister 1978) and ‘showed a high concentration of calcium and reduced amounts of iron and phosphorus in their green shoots in contrast to the more calcicolous species’. C. V.—similar reactions, but more extreme

Erica ciliaris



Rose et al. 617,

Why distribution is restricted


(p.619)

Climatic:

Present distribution in the British Isles-- Northern limit

Can be cultivated at higher latitudes but winter damage (Bannister 1981)

Intolerant of salt spray (Underhill 1990), negative asso. w/ exchangeable sodium content of the soil in Dorset locations (Marrs and Bannister 1979)
Substratum:

Permanently or frewuently waterlogged

Gelyed podsols and peats

Cornwall—drier locations + 1 case on turf-clad stone walls

Dorset—most prolific in the wet heath zone where there is shallow peat. ‘as the wet heath grades into valle t mire and the peat depth becomes greater, plabts occur less abundantly and grow less vigorously with only occasional specimens being present where the peat depth is > 2m.’

pH: table 2 (Cornwall > Dorset )

Organic content – seems no limit (Cornwall < Dorset)

Dorset: sandy; Cornish: higher silt fraction

Small clay friction Implication?
Gregariousness

(Rose et al. 622)

‘The plant occurs in almost pure stands, as scattered plants and as isolated individuals growing several 100m from any other Erica ciliaris plants. In Dorset, the E. ciliaris-dominated communities occur mainly on the wet heath and valet mires, with the drier heath sites containing only scattered plants. Isolated plants tend to occur at the edge of the range of the species in Dorset and it is likely that these plants are colonists. (Chapman 1975)’
Performance in Various habitats

(Rose et al. 622)

Grows best in moist mineral soils and on shallow peats. Drier habitat- less robust

‘Can survive on deeper peats that are often dominated by taller plants (> 0.5m ) of Molinia caerulea or Phragmites australis and create a shaded environment. In afforested sites E.c. has been observed to persist without flowering. ‘


Frost and Drought

p.622


Not sensitive

Pls refer to text.


Calluna vulgaris



Height

Gimingham, 457

Ascends in Britain from sea level to about 1036m. isolated plant 1095m
Climatic

Gimingham, 457

Wide ecological amplitude—lowland and upland heaths, moors, and bogs etc.

‘Widely tolerant in respect of temperature range and length of growing season, extending from latitude 360N to 7105’ N (Hegi). Widespread in oceanic or sub-oceanic climatic regimes (ecological optimum…. E Britain…)

‘Becoming restricted to forests, or other habitats with relatively high atmospheric humidity…’

458


‘tolerant of severe exposure on mountain in Britain,…, than in the more sheltered areas were snow lies longer (Watts and Jones, 1948)’

‘In woodland,…, correlated largely with variations in light intensity…..(Johnson 1957)’

‘Maximum development and abundance only in the open.’
Substratum

Gimingham, 458

Oligotrophic, ‘calcifuge’ species

Occurs on sand, gravel, leached soils from a variety of parent materials. On mainly organic substrata, and even on saturated peat..

‘Freely drained soils carrying Calluna communities usually show erll-developer podsolic profiles, with a litter layer more than 2cn thick, below which F and H layers may be distinguished.

‘The range of water content in Calluna soils is wide, but growth is best where the soil is at least moderately well drained. Mechanical analyses of mineral soils supporting vigorous Calluna often shows high proportions of the coarser particles.


pH

‘Approximate limits of pH at the surgace fro the occurrence of Calluna are 3.2-7.0, but it is most usually found within the range 3.5-6.5’

‘Found surviving at a pH of 7.4 on serpentine soils in west Aberdeenshire an the Lizard. (Ferreira)

‘Calluna soils are ysyally of poort fertility and low base status (Ratcliffe 1959), deficient especially in available phosphate and calcium, and have a high baic ration (K +NA)/ Ca usually > 1.5 (Pearsall 1922)


Gregariousness

Gimingham, 470

Normally large patches or extensive, dense stands. More or less continuous cover may be achieved by dense initial colonization or rapid sprouting after fire.

‘Repeated regrowth after fire often leads to the development of more or less even-aged populations which, if allowed to mature, sometimes dies out simultaneously over a wide area (Gram, 1929)


Performance in various habitats

Gemingham, 470

Optimum development--- where a distinct layer of moist humic material overlies well-drained horizons of sandy or gravelly mineral material; or whole root region consists of drained peat.
Mean number of flowers per stem are fry weight of shoots per unit area of ground, was superior on podsolized oils to that on wet hill peat in east Scotland.

471


Moist moss stratum—promote abundance adventitious rooting and vigorous growth, but tall stems tend to become decumbent.
Waterlogged, substrata, wet hill peat, bogs—weak sprawling form results, with buried prostrate stems, flowering poorly.
Poor stony ground, clays—height may be restricted, stem twisted etc

Terraced slopes—tall Calumna in the shelter of the ‘step’ to very short on the ‘brow’

Severely exposed regions—dwarf, procumbent for occurs, <8cm.

Widespread on the mountain

Increasing shade under trees—a gradation in form occurs
Frost and Drought

Experiment—failed

Extensive patchy fie-back observed.

Young calluna is less winterhardy than old, though it sprouts again from the bas more readily than older plants similarly affected

Susceptible to summer drought, especially on shallow soils with low organic content.

Pot—humus-rich soil.. may survive a period of drought, even when mildly calcareous.

Pure mineral substrata—die
(Webb, 1986)

‘In winter, reddening and death of Calluna foliage occurs. This so-called frosting is in fact not caused by low temperatures but bu the low atmospheric humidities which may occur during cold weather.’(p.111)

Similar results during summer drought

(Webb, 1986)

‘The germination rate is affected by the wetness and composition of the osil, and is generally greater on wet soil and peat than on either dry soil or humus. In the driest conditions, full germination does not take place and remaining seeds only germinate when the soil is re-moistened.’ ( Bannister, 1964) (p.109)
Biejerinck, 1940 optimal conditions


  1. Soils with small quantities of assimilable plant nutrients (oligotrophy)

  2. Soil acidity in the range pH 3.5 to pH 6.7

  3. small seasonal fluctuations in the humidity of the soil and air

  4. Protection fomr low temperatures by snow cover at high altitudes or on mountains

  5. Adequate levels of light.


Competition –

Do species niches overlap?

Do species appear to compete of co-exist?

What factors explain competition or co-existence?
Comparisons

Rose et al.

p. 621 table 3

p. 619 ‘but departs from the floristic table given by Rodwell (1991( in having a decreased constancy of Calluna vulgaris and Erica cineria…….that indicates a trend towards wetter community types

p. 622 ‘ growth in drear Calluna vulgaris-dominated habitats is less robust but E ciliaris appears to tolerate such conditions better that E. tetralix (Chapman 1975)


Webb 1986

‘Better seedling establishment than bell heather (e. cinerea) and cross-leaved heather ( e. tetralix)


Erica ciliaris



Rose et al.

(p.619)


Communities

Dorset: ranging from dry heath and acid grassland to peatland (Chapman 1975)

Cornwall: drier communities; absent from the serpentine soils of the Lizard (Coombe & Frost 1956)

Rare in H3, H4, M16, M21

M16- humid and wet heath vegetation types (chapman 1975); most common vegetation type E. c. occurs in Dorset.
(Webb, 1986)

Grow in same habitat as cross-leaved heath (Erica tetralix) (p.118)

Hybridise with it since flowering season overlap

Calluna vulgaris



Rose et al.

p. 620


‘M16c stands tend to have a lower proportion of the dry heath species such as Calluna vulgaris’
Communities

Gimingham, 460

‘occurs in a wide range of plant communities’ (example p. 461-468)



Disturbance –

How does each species respond to particular disturbance factors such as climatic change, nutrient enrichment, grazing, or fire?

Do species exhibit differing life strategies?
Comparisons

Rose et al.

p. 620


Burning:

‘typically, a burnt area will initially be dominated by grasses, E. ciliaris with or without E. tetralix,, taking over after two or three yers. On the drier heaths, the slower-growing Calluna vulgaris will form a large proportion of the vegetation from five years onwards. Where they occur together, the regrwoth of Ulex minor from rootstocks is more rapid than that of E. ciliaris (Foregeard 1990..)


Grazing:

(Rose et al., p.622)

‘Under high intensities all dwarf shrubs may be eliminated and replaced by hemicryptophytes (Fenton 1949). Observations suggest that animals may find E. c less palatable than C. v.’ Selective Grazing? NO.(p. 625)

Parasites:

(Rose et al. p. 625)

‘Cuscuta epithymum has been observed on plants on E. c. in Dorset growing in association with infected plans of Calluna v. and Ulex minor.’



Erica ciliaris



Chapman & Rose (1994), cited at Rose et al., 617

‘The reduction in the number of localities where the plant occurs has been associated with changes in land use such as afforestation, agricultural reclamation and urban development.’


Rose et al.

(p.620)


Burning:

‘Regeneration from surviving rootstocks after a fire is rapid. Some plant s will flower in the summer following a managed spring burn.’

‘Seedling germination occurs more readily on open ground after a fire than amongst established vegetation. However, mortality rates are high in the initial stages of establishment (Clement & Touffet 1990).
Mowing and Cutting

(Rose et al., 620)

‘Cut material left as a mulch will restrict re-growthbut, if it is removed, regeneration form rootstocks follows the same pattern as that following burning.’
Trampling

(Rose et al., 621)

easily damaged by trampling and vehicle movements, by breaking setms or soil compaction or physical damage to the soil surface (Gimingham 1960; Harrison 1981; Beije 1986; Webb 1986)
Grazing

(Rose et al., 621-622)

‘In recent times few Erica ciliaris sites in Britain have been subject to grazing by domestic animals. Changes in heathland management policy have resulted in grazing being re-introduced to some Dorset heaths Justified, but the areas where the plant occurs do not appear to have been grazed for long enough or a great enough intensity to have had a significant effect on the composition of the vegetation.’
(p. 625)

‘Both cattle and horses graze, although it is not grazed selectively’


Ploughing and Rotovating

(Rose et al. 622)

‘Where areas are ploughed or rotovated such as on firebreaks, regeneration will occur from root fragments where soils are wet enough to prevent desiccation of the regrowth. Cultivars do not transplant well (Underhill 1990). Seed germination and seedling establishment are less prolific than after a fire, as some seed is buried and drier conditions break up the soil surface structure.’
Reduction of habitat.

(Rose et al. 622)

‘Conversion to forestry, agriculture and urban development has lad to a reduction in the area of habitat in both Cornwall and Dorset. Both the general loss of heathland in Dorset (Moore 1962; Webb ad Haskins 1980; Webb 1990) and the specific loss of E. ciliaris heathland (Chapman & Rose 1994) have been documented. Afforestation has been the main cause of habitat loss in areas where E. ciliaris occurs. Plants can survive for 15-20 years after planting under productive forest but persist only in the wider rides and on the side of tracks as the plantation matures.
Peat Cutting

(Rose et al. 622)

‘Dorset’

‘It is likely that the cur areas would favour recolonization by seedling establishment’


Calluna vulgaris



Fire

Gimingham, 469

‘Fire is one of the chief factors responsible for the maintenance of extensive tracts of Calluna-dominated heath, by the prevention of tree regeneration. Burning of Calluna is a regular practice to encourage new growth for the benefit of both sheep and grouse.’

‘An exceptionally fierce fire will completely kill plants of all ages, but controlled burning kills only the mature and defenerate phases which have grown tall and straggly at ages exceeding 18-20 years. Younger individuals normally regenerate abundantly from the stem bases (Lovat 1911….)’

‘Under favourable conditions, cover may be restored in 2- 3 years, but the effects of fire vary greatly depending upon the amount of hear generated and its duration.’

‘successful recovery if plants aged < 15yrs’


(Webb 1986:110) Must take reference!!!!
Peat cutting

Gimingham, 469

‘since the newly exposed surface is normally closer to a water table and may be saturated, the result is usually the disappearance of Calluna…..however, where the new peat level is not waterlogged, abundant seedlings of Calluna may be found.
Grazing

Gimingham 469

‘Substantial part of diet of hill sheep throughout the year, of particular importance in winter.’

Summer preference—tips of growing shoots

Winter preference—larger portions, including woody shoots up to 2in long.

‘Young Callune ( up to 6 yrs in age), while being extensively grazed in summer, is largely avoided in winter.’(Hunter, 1954)

470

Calluna is also a valuable grazing plant for hill cattle, especially in winter (Thomas 1956)



‘Considerable damage may by inflicted on the plants by these grazing animals. Fairly heavy stocking by sheep may in some areas cause disappearance of Calluna as a dominant. Seedling establishmenr may also be reduced by sheep, which uproot many seedlins before they are firmly anchored. Under milder grazing intensities, in the absence of more resistant competitors such as…….., Calluna may persist and increase its cover-value.

‘Calluna may be killed by severe rabbit pressure’

‘Calluna may also succumb to trampling by grazing animals, but on the other hand consolidation of the surface of the substratum improves conditions for reestablishment from seed (Wallace 1917). Much animal manuring affects heather adversely.’
Parasites

Gemingham, 478


(Webb, 1986)

‘Not all seeds shed by Calluna germinate in the first season; they may remain in the soil, forming a seed-bank which may persist for up to forty years (Gimingham, 1972; Hill and Stephens, 1981) (p.110)


Light stimulates germination. No germination in complete darkness (p.110)

Seeds buried in the upper layers of the soil will not germinate unless removal of cover.




Webb (1986) Heathlands, Collins, London.


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