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Fen Management Handbook - Scottish Natural Heritage

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Old trees and<br />

dead wood<br />

Continuous and<br />

near-continuous<br />

scrub/woodland<br />

with shaded wet<br />

conditions<br />

<strong>Fen</strong>-edge<br />

transitions<br />

Seasonally<br />

exposed marginal<br />

sediments<br />

Temporary pools<br />

and areas of<br />

seasonal flooding<br />

Seepages and<br />

surface flow<br />

Saproxylic beetles of a range of families;<br />

also saproxylic flies, including hoverflies,<br />

craneflies, Tipuloidea, and a range of other<br />

groups; solitary bees and wasps nesting in<br />

dead wood, especially old beetle holes; and<br />

a good range of phytophagous species,<br />

with the varied structure of older trees<br />

providing a range of hibernation sites.<br />

Diptera, especially craneflies, but also a<br />

range of other families; species associated<br />

with foliage and timber will be similar to<br />

those of more scattered trees and shrubs;<br />

they will be generally less diverse, but will<br />

include specialist species not found in more<br />

open conditions.<br />

A wide scatter of species in varied groups,<br />

with phytophagous beetles, bugs and<br />

moths key amongst them. <strong>Fen</strong>-edge<br />

grassland shares some species with<br />

calcareous grassland; the marsh moth<br />

(Athetis pallustris) and the marsh fritillary<br />

(Eurodryas aurinia) are both found in<br />

relatively dry grassland.<br />

Surface-active beetles, especially ground<br />

beetles and rove beetles; many flies with<br />

larvae which develop in the sediments or<br />

stranded snails.<br />

There are temporary pool specialists in<br />

a number of groups, especially including<br />

a number of uncommon water beetles;<br />

a wider range of species tolerant of<br />

seasonality may benefit from the absence of<br />

fish and the oxidation of organic sediments<br />

in temporary waters.<br />

Various groups of flies, especially soldierflies<br />

at unshaded seepages and craneflies<br />

at shaded seepages.<br />

Standing living trees with dead wood provide<br />

the best resource, but dead standing trees<br />

and fallen wood may be valuable. Fallen wood<br />

on shaded seepages has a particular fauna.<br />

Permanently or near-permanently wet<br />

conditions are critical for high interest,<br />

because many larvae develop in the surface<br />

layers. All conditions from sheltered but sunny<br />

areas amongst scrub to densely shaded wet<br />

leaf litter support interesting species.<br />

Transitional habitats may be anything from<br />

open grassland to woodland. Open grassland<br />

and grass/scrub mosaics are generally the<br />

richest in uncommon and characteristic<br />

species.<br />

Bare sediments in a mosaic with or wellstructured<br />

transition to wetland vegetation are<br />

usually richest.<br />

The richest specialist faunas are in unshaded<br />

pools, but those amongst taller vegetation<br />

or beneath shade of woody vegetation have<br />

uncommon species of their own.<br />

Continuous seepages over a substantial<br />

area are best; seepages are long-lasting but<br />

often isolated and of limited area, so historical<br />

continuity of conditions may be critical to their<br />

interest.<br />

35

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