BSBI Species Accounts Archive

It occurs in three main habitats: ancient woodland on calcareous soils; limestone and other rock outcrops; and hedges. This mirrors the distribution of other species of Sorbus. Given that these are very widespread habitats, it is perhaps surprising that it is so uncommon. Rodwell (1991-2000) gives just two vegetation communities for it: W5 Alnus glutinosa and W8 Fraxinus excelsior woodlands. W8 is the typical climax community on drier calcareous soils in England & Wales, and presumably accounts for the majority of sites. W5, however, is an acid wet woodland type and seems somewhat incongruous.

In North-east England at least, Ribes spicatum has a narrow and distinctive habitat niche. It occurs mostly in upland areas, but at low altitudes (rarely above 200 m) in native woodland within 50 m of shallow, rocky rivers and streams, usually in ‘denes’ (steep declivities in sandstone country). It is usually rooted amongst water-borne boulders in areas where the water course regular changes position, either in raised islands or on steep banks, often in considerable shade, most usually from alders (Alnus glutinosa). It appears to compete poorly with comparable life-forms, and persists in a tension zone between the erosive powers of flooding, and the establishment of a dense, shrubby ground layer. It has a wide range of associates, but seedling sycamore (Acer pseudoplatanus), Geum urbanum, Chrysosplenium oppositifolium, Dryopteris dilatata, D. filix-mas, Allium ursinum, Urtica dioica and Luzula sylvatica are amongst the most typical. Most localities classify as W6 Alnus glutinosa-Urtica dioica woodlands (Rodwell 1991). It is noteworthy that this habitat bears little relationship to that cited in Warburg (1962) ‘Woods on limestone’ or that in Preston et al. (2002) ‘a shrub of limestone woods.......’, and although it does occur rarely in this habitat (including grikes in limestone woods) in Lancashire and Yorkshire, nevertheless, it nearly always occupies a streamside position, and is much more commonly met with in the sandstone denes of Northumberland and Durham

Ribes spicatum typically forms clonal individuals, varying from one to more than 100 stems. Large plants may cover 10 m or more and are considered to be of a considerable age. They are deep-rooted and capable of withstanding considerable flooding, although it seems that repeated flooding and root erosion can eventually lead to the death of large parts of the clone, and many individuals tend to be partially senescent. Many plants, especially those in deep shade, flower rarely, and fruit-set is usually very poor. Flowers are visited by bees, especially queen Bombus spp., but plants are probably self-incompatible. It is notable that fruit-set is best where several flowering individuals occur within a relatively small area (<100m). Seeds are presumably dispersed by birds, but in most populations evidence of regeneration by seed is absent.

Q. cerris has a fast growth habit, and seemingly tolerates a range of soil types; most common on free draining, sandy and acidic soils, but is also known on calcareous soils (Sterry 2007; Preston et al. 2002). Four non-native cynipid gall wasps, Andricus kollari, A. lignicola, A. quercuscalicis and A. corruptrix, have become established in the British Isles since the introduction of Quercus cerris. Their interesting lifecycles involve host-alternating generations, with a sexual generation on the male flowers of Q. cerris in spring, and an agamic (asexual) generation on the acorn cups of British native oaks, (Q. robur, Q. petraea and their hybrid Q. x rosacea) in autumn, (Schonrogge et al. 2002). Infection results in a reduction in the acorn crop of the British Oaks as development of a sexual gall replaces an acorn, but galling rates have been shown to vary between the gall wasp species over time, and differ greatly between individual trees, (Collins et al. 1983; Schonrogge et al. 2002)

A rhizomatous mycorrhizal evergreen perennial woody herb of well drained, mildly acidic to slightly basic soils in woods and heaths, Pyrola media occurs in the mossy dwarf-shrub field layer in W18 Pinus sylvestris – Hylocomium splendens woodland (Rodwell 1991). It also grows occurs in the H16 Calluna vulgaris – Arctostaphyllos uva-ursa heath.

In the Burren, Western Ireland, it occurs on the summits of limestone hills where there is sufficient peat development to support dwarf-shrub heath.

The decline in Pyrola media in woodlands has been attributed to unfavourable management, with some populations lost to afforestation. Heathland populations have variously been affected by changing grazing practices and decreased muirburn. There is over-grazing in some areas and no grazing in others, leading to a very short turf in which some herbaceous species are grazed out, or a rank growth of heather which shades them out (SNH 2007). In some cases heavy grazing has even led to the conversion of heather moorlands to grassland. Burning may also have lead to losses, although this may be less of an issue now with a reduction in muirburn in recent years.

Under-grazing may also result in populations going undetected and unrecorded. An additional factor in the apparent decline of Pyrola media is that there is thought to have been some previous confusion with P. minor, with which it often grows. The situation is further complicated by the reluctance of some P. media populations to flower (especially in N. Ireland and northern Scotland).

Monotropa contains no chlorophyll, and was until recently thought to be saprophytic (deriving nutrients from decaying leaf litter) but recent research shows that it is actually epiparasitic, using Tricholoma fungi to extract nutrients from living trees in its vicinity (Leake et al. 2004). It is usually found in woods or in scrub. Rumsey (in the New Atlas, op. cit.) describes it as most frequent under Beech and Hazel on calcareous soils, and under pines on more acid substrates. It is sometimes also found in dune slacks, where it is associated with Creeping Willow, Salix repens. It is not listed by Rodwell (1991-2000) as a component of any NVC community. The maps show that in the past it was strongly associated with limestone and chalk soils in the south of England, but that seems a less obvious association in the more recent data. It is a rather transient plant, sometimes appearing in large numbers (hundreds of flowering spikes) at a site, only to disappear within a few years. Sometimes it is found in secondary woodland. It is a lowland plant - the maximum recorded altitude is 395 m, at Buxton, Derbyshire.

Hyacinthoides non-scripta is typically a woodland plant, occurring in calcareous and mildly acid woodlands of all types except the very wettest (Rodwell 1991a). It is sometimes overwhelmingly abundant in the ground flora in the spring, although it dies down by mid-summer and even dead fruiting spikes can be difficult to find towards the end of the season. The most characteristic communities for it are W8 Fraxinus excelsior and W10 Quercus robur woodlands, which are the climax communities over much of lowland Britain. It is often found in grassland, presumably long after woodland is cleared, and under bracken, most typically in U20 Pteridium aquilinum-Galium saxatile grassland (Rodwell 1992, Taylor, ibid.) and in coastal grassland in the MC12 Festuca rubra - Hyacinthoides non-scripta community (Rodwell 2000). Rodwell (1991b) does not list it as a component of any heathland community. The ecology of H. hispanica and H. x massartiana is not well studied. They are rarely seen far from habitation or where garden soil has been tipped on roadsides, and although patches increase in size, they do not appear to spread much from their original planting site (pers. obs.). This raises questions about the fertility and dispersal of the hybrid. Their ability to outcompete native bluebells is often quoted but has yet to be demonstrated empirically.

Nearly all sites are in old, often largely undisturbed primary woodland. Restricted to difficult terrain, which has resulted in restricted forest clearance. Consequently, most habitats are not threatened. However, F. altissima almost invariably coexists with Luzula sylvatica which tends to be much more successful, aggressive and catholic in its requirements and appears to outcompete it. I suspect that warmer summers have allowed the latter to disperse into and survive in niches previously occupied by the grass. Typically inhabits horizontal joints in near vertical cliffs above rivers, under deciduous trees in partial or complete, often deep, shade. Mostly commonly found on rather calcareous sandstones. Associated species suggest that absence from large areas of apparently suitable habitat can be explained by the low carbonate content of the sandstone, giving rise to soils of too acidic a reaction. Also grows in hard limestone and dolerite. Invariably occurs within 50 m of water, and is often found only just above flood level and not higher up the cliff. Undoubtedly needs continuous levels of high humidity at all times, and the observation in Cope & Gray (2009) that it is shallow-rooted may explain its very stringent habitat requirements, and vulnerability to competition, as well as dislodging. Subsidiary habitats include vegetated talus below cliffs if above flood level, and wooded limestone pavement. To associated species listed in Cope & Gray (Galium odoratum, Luzula sylvatica, Melica spp., Polystichum spp., Sanicula europaea) can be added Dryopteris dilatata, D. filix-mas, Deschampsia cespitosa, Bromus ramosus, Schedonorus giganteus and Brachypodium sylvaticum. Typically the woodland (NVC W8) is dominated by Quercus spp., but may include Fraxinus excelsior and the cliff scrubby Ulmus glabra and Corylus avellana. In many sites it flowers rarely, or few inflorescences are produced. It suffers from the usual problems experienced by chasmophytes, so that establishment may depend upon seeds being caught in spiders webs, and seedlings are unusual. Most populations consist of mature tussocks which may be a considerable age. Consequently, attrition from competition and erosion may exceed the regenerative power of the population.

Rodwell (1991) lists only W10 Quercus robur and W16 Quercus petraea woodland types for this species. Ecological accounts for it are difficult to find. One of the most authoritative available is given by Sinker et al. (1985) in their account of it in Shropshire: ‘Open woodland and edges of dry peat mosses, persisting in grassland on previously wooded sites, on dry to damp sandy or peaty soils, PN poor base poor, acid, usually sheltered and half shaded to shaded but tolerates some exposure to sun. Poor competitor but sometimes abundant in disturbed parts of recently cleared plantations or woods, scrambling over tree stumps.’

The ecology of C. elongata is perhaps its most interesting attribute. It is most typically a plant of W5 Alnus glutinosa woodland on scrubbed-over mires that are inundated by surface water. Jermy et al. (2007) say it also occurs in W2 Salix-Betula woodland and C.R. Hall (pers. comm.) considers that it grows in W6 Alnus glutinosa woodland in Hampshire. David (1994) describes how it often occurs on floating wood, and Mallabar (1998) takes this one step further, suggesting that seeds tend to germinate on rotting wood, due to some association that has not yet been defined. This might explain why David (op. cit.) considered seeds to have low viability. In the past, C. elongata was found on the rotting wooden piles of canals, but it appears to have completely gone from canals now as wood is no longer used in their construction. C. elongata populations fluctuate enormously in size, being most successful in late-successional sites as they start to dry out. Hencott Pool in Shropshire was considered one of the best sites for it in the 1980s, with hundreds of plants, but it had almost gone from there twenty years later (Lockton & Whild 2003) as the pool dried out and the canopy closed. Hill et al. (1999) give it an Ellenberg L value of 5, which is for half shade, and it presumably cannot thrive under a very dense woodland canopy.