Biological Flora of the British Isles: Sorbus torminalis

Abstract

Summary This account presents information on all aspects of the biology of Sorbus torminalis (L.) Crantz (Wild Service‐tree) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. Sorbus torminalis is an uncommon, mostly small tree (but can reach 33 m) native to lowland England and Wales, and temperate and Mediterranean regions of mainland Europe. It is the most shade‐tolerant member of the genus in the British Isles, and as a result, it is more closely associated with woodland than any other British species. Like other British Sorbus species, however, it grows best where competition for space and sunlight is limited. Seedlings are shade tolerant but adults are only moderately so. This, combined with its low competitive ability, restricts the best growth to open areas. In shade, saplings and young adults form a sapling bank, showing reproduction and extensive growth only when released. Sorbus torminalis tolerates a wide range of soil reaction (pH 3·5–8·0) but grows best on calcareous clays and thin soils over limestone. Sorbus torminalis is a sexual, diploid, non‐apomictic species that has hybridised with a number of other Sorbus species to form microspecies. The hermaphrodite flowers are primarily insect pollinated. Seed production is reliable only in warm years, especially at the edge of its range, although even then seed viability is low. The fruits are primarily dispersed by carnivorous mammals. Seeds display embryo dormancy but most will germinate the first spring after falling. This tree is very tolerant of short droughts but only moderately tolerant of frost, hence its southerly and lowland distribution. It faces no particular individual threats although the small size of most populations makes it susceptible to habitat loss and fragmentation, particularly through the loss of open coppiced areas. As a consequence, it appears to be declining throughout Britain and Europe despite its wide range of historical uses and the high value of its timber. The extent to which these losses will be offset by increases due to climate change is unknown.