Fen Management Handbook - Scottish Natural Heritage

The Common Standards Monitoring (CSM) Guidance for Lowland Wetland Habitats
(JNCC, 2004) is a useful aid to broad scale assessment of fens. The guidance
provides descriptions of the different hydrological and topographical situations
associated with different fen types, allowing the main fen type(s) on a site to be
identified. Knowing the main fen type and the key hydrological inputs of a site along
with some general information on catchment land use allows an evaluation as to
whether a fen feature is likely to be associated with high or low nutrient regimes and
therefore whether it may be at risk of enrichment.
Summary of the broad fen types and their likely risk of enrichment
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Fen type
Floodplain
fen
Susceptibility/
Risk of
enrichment
Key sources of
enrichment
Medium / High Floodwaters and groundwater
especially in intensively farmed
landscapes.
Basin fen High / High Groundwater and run-off
especially in intensively farmed
landscapes.
Open water
transition
fen
Medium / Medium Vulnerable to enrichment if
associated lake/open water also
enriched.
Valley fen High / Medium Groundwater and run-off,
especially in intensively farmed
landscapes.
Springs,
flushes
Fen
woodland
Fen
meadow
High / Medium Variable depending on situation
in the landscape.
Low / Medium Usually tolerant to higher
nutrients therefore less at risk of
enrichment.
High / Medium Close proximity to improved
fields places fen meadow at risk
to enrichment. Management can
reduce build up of nutrients.
4.6.2 What can the vegetation tell you about nutrient enrichment?
Additional comments
May have naturally eutrophic vegetation
types due to regular sediment inputs
into system from river flooding.
Small size and situation in the landscape
makes them particularly vulnerable.
Often associated with naturally
eutrophic vegetation (swamps and tall
herb fen).
Can have elements of naturally
eutrophic habitat types, such as fen
woodland.
Often found within another fen/bog
type.
Increasing woody cover might suggest
the fen is drying out and undergoing
internal enrichment.
Maintain management to remove
nutrients.
Once the broad fen type, in terms of its hydrological and topographical status,
is identified then the variation in vegetation on that fen can offer further clues to
nutrient status. Plant species have different nutrient requirements and the presence
of particular plants or group of plants can indicate nutrient enrichment might be
occurring, especially if they are nutrient- demanding species. Such plants are often
termed ‘negative indicators. Clues as to the origin of enrichment are indicated by
gradients in height/vigour of some of these indicators.