This article is an extract from Classic British Wildlife Sites –The Lizard Peninsula by Andrew Byfield in British Wildlife, 3 (2), pp. 92–105 (1991).
Travelling from north to south across the Peninsula one is immediately struck by the flat treeless nature of much of the landscape. The flatness is testimony to the force of wave action when the whole landmass was under water, forming a wave-cut platform of Pliocene–Pleistocene age.
The northern section, comprising softer sedimentary rocks (and termed `the Meneage`), has subsequently become eroded to form the gently rolling landscape crossed by numerous valleys that we see today. With relatively fertile, deep soils, the area is largely under dairy, arable or market garden crop production, except for areas of woodland on valley sides and marshy habitats in the valley bottoms.
In contrast, the southern half of the Peninsula, comprising the harder igneous/metamorphic geology, and termed the `Lizard District`, has not succumbed to the same levels of post-marine erosion and weathering, and is thus to all intents and purposes flat. It rises to a high point of 113m, sloping very gently to the coast with its precipitous sea cliffs (rising to 60m), and steep sided cove valleys on the west coast and less steep cliffs on the sheltered east coast.
Heathlands still dominate the substantial tracts of the serpentine and gabbro. It is perhaps only here and in the New Forest that it is still possible to witness not only an intact heathland flora, but also something of the wild spirit that so characterised this landscape type in the past.
In the New Forest, the remarkable survival of the commoning system has preserved the area: at The Lizard, the inherent infertility of the serpentine heaths, and the presence of extensive fields of `crusairs` – large gabbroic boulders – over the gabbro heaths, has mitigated against their destruction.
The heathland vegetation was first described by Coombe and Frost (1956) in their important Journal of Ecology paper, and has been refined, but not grossly altered by Marrs and Procter(1979), Hopkins (1983) and Hughes(1988).
Across much of the plateau the unenclosed heathlands take two basic forms, dictated by soil and drainage. Originally the whole of this area was covered with a fine soil deposit of wind-blown origin (a loess). Being of granite derivation, it is poor in minerals and strongly acidic. However, this loess `blanket` has subsequently been eroded in places, with the result that serpentine-derived soils have been exposed in the very shallow, broad valleys that intersect the plateau. These naturally tend to collect water and are generally wet through the year.
The granite loess `mounds` support `Agrostis curtsii Heath` which is dominated by the grasses Bristle-leaved Bent (Agrostis curtsii) and Purple Moor-grass (Molinia caerulea), and Heather (Calluna vulgaris), Bell Heather (Erica cinerea) and Cross-Leaved Heath (Erica tetralix). The latter gives this community a somewhat darkish hue. As the loessial soil is infertile and subject to temporary winter waterlogging and summer droughting (due to its fine particle size, consistent with its wind origin), this vegetation type is short and open in nature, with frequent open pans of bare soil. Field Gentian (Gentianella campestris), Fir Clubmoss (Huperzula selago) and Pale Heath Violet (Viola lactea) are scarce species characteristic of this heathland type and its wet variants.
Combining markedly with this short sombre coloured vegetation type is the `Erica vagans–Schoenus nigrans Heath`, which occupies the shallow valleys over permanently wet serpentine-derived soils of high pH and base status. The Black Bog-rush, with its tall bleached stems, gives a `fenny` appearance to this plant community, which also includes Cornish and Cross-leaved Heaths, Purple Moor-Grass and Saw-wort amongst its frequent members. Local species, often occurring in abundance in this community and its variants, include Bog Pimpernel (Anagallis tenella), the sedges Carex hostiana and C. Pulicaris, Early Marsh Orchid (Dactylorhiza incarnata ssp. incarnata and ssp. pulchella). Petty Whin (Genista anglica), Pale Butterwort (Pinguicula lusitanica) and Common Butterwort (Pinguicula vulgaris), Lesser Butterfly Orchid (Platanthera bifolia) and the mosses Campylium stellatum, Drepanocladus revolvens and Scorpidium scorpioides.
Criss-crossing these plateau heathlands is a series of trackway systems that provide some of the most fascinating microhabitats on the whole of the Peninsula. Created over centuries to provide access to remote farmsteads or serpentine quarries, they have developed a flora that is rich in rare, specialist species. The most important tracks are those that are deeply rutted and seasonally flooded. Here, ephemeral aquatics such as the Three-lobed Water Crowfoot (Ranunculus tripartatus), and the charophytes Chara fragifera and Nitella opaca are abundant, flowering and `fruiting` underwater during early spring, only to be replaced by a flora of exposed mud as the ruts dry out in early summer. The latter group includes fast declining species such as Yellow Centaury (Cicendia filiformis), Pillwort (Pilularia globulifera), Pigmy Rush and the liverwort Cephaloziella dentate, the latter two in their only known British localities.
Pools and quarries are of equal importance, and very varied. Peaty pools on the gabbro support `poor-fen` species such as Bog Bean (Menyanthes trifoliata), and Marsh Cinquefoil (Potentilla palustris), whilst the shallow watering pools, cob pits and serpentine quarries over the main heathlands include many of the species mentioned above, plus local species such as Shore-weed (Littorella uniflora), and Marshwort (Apium inundatum). The various water bodies within these heathland areas are also renowned for a rich charophyte flora: in total 13 species have been recorded with a high proportion of rare species including Chara aspera, C. baltica, C. canescens, C. desmacantha, C. fragifera, and Nitella translucens.
The coast together with the coastal valleys is of equal importance for rare habitat types and rich floras. Two further heathland types occur here: `Erica vagans–Ulex europaeus Heath` in the shelter of the valleys and on upper cliff slopes; and `Festuca ovina–Calluna vulgaris Heath` in more exposed conditions.
The `Erica vagans–Ulex europaeus Heath` community occurs on the deeper brown-earth soils to be found over the serpentine and more rarely gabbro in sheltered conditions. Whilst Cornish Heath and Common Gorse (Ulex europaeus) dominate this community, it is generally species-rich to the extent that Coombe and Frost coined the phrase `Mixed Heath` for this community. The rich flora includes species such as Dropwort, Bloody Cranesbill, Hairy Greenweed (Genista pilosa), Burnet Rose (Rosa pimpinellifolia) and Lesser Meadow Rue (Thalictrum minus).
These heathlands give way to a variety of Maritime Heaths variously dominated by heather, Sheep’s Fescue (Festuca ovina) and Spring Squill in more exposed situations. These develop on shallow soils over serpentine and in exposed situations, where the heather frequently takes on stunted, congested or hairy gowth forms in response to the exposure. Again the flora is rich, with rarer species such as Thyme Broomrape (Orobanche alba) and Spring Sandwort often occurring abundantly.
To complete this account of the Lizard`s most important vegetation types, mention must be made of the grasslands and erosion pan communities that are especially prevalent on the coast and on the rock outcrops along the valley sides. It is impossible here to enumerate the various types; suffice to say that they are extremely rich in rare species, some favouring winter-wet communities, all benefitting from high levels of summer droughting. It is here that many of the Lizard rarities grow : Chives (Allium schoenoprasum), Fringed Rupturewort, Land Quillwort, Dwarf Rush, Upright Chickweed (Moenchia erecta), Green-winged Orchid (Orchis morio), the rare clovers and many of the rarer ephemeral bryophytes are especially notable.
The above description paints only a part of the picture: lichen-rich screes and rocks, sandy coves, rush dominated valley marshes and extensive Sessile Oak coppice woodlands are amongst other species-rich habitats which merit description.