DHBlog034 · A Dorset Flora Group field trip report from a unique site
On 9th May, Bryan Edwards (Ecologist, Dorset Environmental Records Centre) and Tom Smith (DFG Programme Coordinator) led a well-drilled group of 12 DFG members on a botanical visit to the Ministry of Defence's fuel depot at West Moors. Access to the site is tightly controlled so we were grateful to Defence Support for welcoming us and to our former chairman, Jon Crewe, for brokering the visit last year. We were also pleased to be joined by Maisie Barrell (Environmental Protection Officer for the site) and, later in the day, by Jenny Bennett (Defence Infrastructure Organisation Senior Ecologist).
The Operational Energy Authority premises at West Moors form a key part of the Holt and West Moors Heaths Site of Special Scientific Interest (SSSI). They comprise 400 acres and include valuable areas of unspoilt heathland with a host of specialist wildlife including all six UK reptile species. Our aim was trained as much on associated acidic and industrial habitats as the prime heathland and we were not disappointed by what we found. To reduce the risk of fire, large areas of the site are kept tightly clipped or mown throughout the year; much of the land is unimproved and the resulting flora is highly distinctive and of exceptional conservation interest.
The catalyst for our visit was Bryan's recent discovery of a large population of the nationally rare Dwarf Rush (Juncus capitatus), as reported by Robin Walls in his Vice-county Recorder's Review of 2022. Our main objective was to count the population, but our route to and from its location took us across several different types of terrain where we had good opportunities to botanise. Early on, we passed through a large expanse of short, dry acid grassland where we found two Dorset rarities: Pale Dog-violet (Viola lactea) and Heath Dog-violet (Viola canina). The two species are quite similar but are usually distinguishable on leaf shape (lanceolate or ovate-lanceolate with a cuneate to truncate base in Pale Dog-violet; roughly triangular with a truncate to shallowly cordate base in Heath Dog-violet) and flower colour (white to milky violet in Pale Dog-violet; slatey blue in Heath Dog-violet).
Bryan led us on until we arrived at what appeared at first glance to be a sparsely-vegetated area. Evidently waterlogged in winter, disturbed by vehicles and droughted in summer, we were faced with a plain of stoney, drying mud – and on closer inspection, an abundance of Dwarf Rush.
We were able to see that Dwarf Rush is a small, tufted annual around 5cm in height. Its stems and leaves are bristle-like, and its inflorescence is clustered with pointed outer tepals and a long, pointed bract at the base that gives the species its alternative name, Leafybract Dwarf Rush.
We counted approximately 2000 Dwarf Rush plants in this area – a considerable number. This is good news for a species that is on the Red List as Vulnerable in Great Britain and Endangered in England. The only other examples in Great Britain are found in the Channel Islands, Cornwall and Anglesey, and none of these populations are sited as far inland as West Moors. The mud also supported other notable species including Coral-necklace (Illecebrum verticillatum) and Heath Pearlwort (Sagina subulata), which we were pleased to find albeit in lesser quantities.
During the day, we passed through several dry areas with light or gravelly soils. These were also a rich source of notable species including Mossy Stonecrop (Crassula tillaea), Bird's-foot Clover (Trifolium ornithopodioides), Hairy Bird's-foot-trefoil (Lotus subbiflorus), Rue-leaved Saxifrage (Saxifraga tridactylites) and Wall Bedstraw (Galium parisiense). The latter is a particularly rare find in Dorset, the only other recent example being at Bovington Camp – also at the hands of the Dorset Flora Group.
Wetter areas also yielded a good range of species. These included Marsh Pennywort (Hydrocotyle vulgaris), Carnation Sedge (Carex panicea), Star Sedge (Carex echinata) and Lousewort (Pedicularis sylvatica).
On our way back, one of the grassier areas also provided a head-scratching moment when curiously, we found a small, isolated patch of American Blue-eyed-grass (Sisyrinchium montanum). Being a garden escape, its presence in this location was something of a mystery, although it is known to spread freely by seed. Perhaps it is only fitting that a site that underwent major development by American Forces during World War II should host such a species.
It didn't escape our attention that several of the rare species seen during the day most likely arrived at the West Moors fuel depot by way of military vehicles. Species falling into this category include Dwarf Rush, Coral-necklace and Wall Bedstraw. Nationally, the Ministry of Defence's estate includes some of the UK’s most important wildlife sites and is remarkable in both its size and the diversity of habitats and species that it supports. Trying to work out what came from where might be a fairly speculative exercise but it's clear that connections between these sites have a role to play in the distribution of some of the UK's scarcer botanical species.
Our thanks go to both Maisie and Jenny for making our trip to this unique site possible and for sparing the time to accompany us on the day.
A list of selected species observed is available here:
This article contains contributions from Daniel Holloway, Tom & Jean Smith and Maisie Barrell, and was edited by Daniel Holloway. Content was approved by Charlotte Jupp, Communications Manager, Defence Support.