| Tayside Biodiversity - Tayside
Biodiversity Action Plan - Farmland - Stone
Dykes |
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DEFINITION
Dykes, whether dry stone or mortared, are found throughout Tayside. The great
dyke-building period in Scotland was from 1750 -1850 following the Enclosure
Acts. Many of these linear features have lasted 200 years. Primarily of landscape
and stockholding importance, dykes also have a role to play in terms of wildlife
conservation particularly for invertebrates and small mammals. Drystone dykes
were, historically, the dominant field boundaries where rocky outcrops, thin
soils and climate made the use of hedgerows impractical. Lowland, more fertile
regions also contain a
significant number of drystone walls.
CURRENT STATUS AND EXTENT OF HABITAT
Many dykes are in poor or very poor condition. Whilst some have the potential
to be restored there are many that are beyond repair. In central Scotland it
is estimated that only 14% of dykes are in good stockproof condition. 49% are
in the advanced stages of dereliction and are unlikely to be rebuilt. The remaining
37% are in poor condition but have the
potential to be restored. |
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KEY SPECIES
P = UK Priority species C = UK species of conservation concern
| Mammals |
Stoat |
Mustela erminea |
C |
| Weasel |
Mustela nivalis |
C |
| Birds |
Wheatear |
Oenanthe oenanthe |
C |
| Stonechat |
Saxicola torquata |
C |
| Whinchat |
Saxicola rubetra |
C |
| Amphibians and Reptiles |
Slow-worm |
Anguis fragilis |
C |
| Common Frog |
Rana temporaria |
C |
| Common Toad |
Bufo bufo |
C |
| Common Lizard |
Lacerta vivipera |
C |
| Invertebrates |
a mason bee |
Osmia parietina |
P |
| Bumble bees |
Bombus spp |
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| Plants |
Saxifrage spp. |
Saxifraga spp |
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| Maidenhair spleenwort |
Asplenium trichomanes |
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| Lichen spp. |
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| Liverworts and Mosses spp. |
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NATURE CONSERVATION
IMPORTANCE
Dykes contain numerous holes and
cracks that provide growth, shelter and nest sites for a variety
of plants and animals. Pioneer plants such as lichens and mosses
colonise walls in unpolluted areas, these in turn providing rooting
for the Saxifrage species and ferns such as Maidenhair spleenwort
Asplenium trichomanes. Insects (spiders, woodlice, bees and wasps
for example) utilise walls and species such as the Stoat Mustela
erminea can use them as cover and hunting ground. Wheatear Oenantte
oenantte often nest in dykes.
In terms of nature conservation importance fallen or derelict dykes can often
be equally important as standing dykes. This is particularly the case in the
more intensively farmed areas where fallen dykes and their associated grassy
margins provide cover and habitat for a wide range of species. |
The
Slow Worm
Anguis fragilis is a common inhabitant of drystone dykes.
Though often mistaken for a snake the slow-worm is, in fact
a legless lizard - and it can move
quite fast if disturbed. Slow-worms like warmth and live
on sunny banks and hillsides where there is good cover such
as grass, scrub or stones. |
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NATIONAL BIODIVERSITY
CONTEXT
Although there is no UK Action Plan
for dykes the National Habitat Statement suggests that targets
similar to those for hedges should be aspired to.
Owing
to the specialist knowledge needed to record the many lichen, moss
and fern species in Tayside, their
distribution and status is not generally known.
There are, however, a number of factors affecting the many species
found on stone dykes - air pollution, for instance, especially
from diffuse sources such as motor vehicles which raise concentrations
of ammonia in the air. This can subsequently result in the decline
of the rarer lichens that depend on nutrient-poor conditions. Localised
nutrient enrichment can also occur where livestock concentrate
in one area or where dung or fertilisers are spread.
Excess shade from shrubs and trees can affect some mosses and lichens
on drystone dykes. Recreational use can also cause local damage,
i.e. by indiscriminate climbing on to walls or trampling of lichens
and ferns. |
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