Fen Management Handbook - Scottish Natural Heritage

10.3 Biological monitoring techniques – vegetation
Basic botanical survey methods, such as recording species presence and cover
in quadrats or transects, are usable in fens, given some adaptation and caution.
Suitable methods and some of the practical difficulties are described in the relevant
section of the Handbook of Biodiversity Methods (Hill et al, 2005). The plants
themselves are effectively sampling the environmental conditions continuously and
can provide good indications of the longer term hydrological, climatological and
geomorphological conditions.
10.3.1 The role of botanical surveying
Higher plants are the predominant primary producers in fenland habitat, forming the
structure and basis of the ecosystem. Habitat quality and diversity is reflected in the
plant diversity that supports the overall species diversity of the site. Management to
protect and enhance the most natural and diverse plant communities usually forms
the basis of the habitat management plan (see Section 5: Fen Management and
Restoration). Botanical survey will first define these communities, set the targets for
management, and then monitor them to measure the effect of management.
10.3.2 Indicator species
Knowledge of the various plant communities present in an area of fen help the
selection as positive indicators of species are strongly indicative of the extent and
quality of a community. If the selected species are reliable indicators, monitoring
can be based on surveys that plot their location, extent and abundance. A table
of suitable indicator species is given in Common Standards Monitoring (CSM)
Guidance for Lowland Wetland Habitats (JNCC, 2004), against the component
NVC communities of fen habitats (see Appendix IV). Negative indicator species
(listed in Table 6 of CSM Guidance) such as nettles or bracken are associated
with habitat deterioration, such as enrichment or drying out, while others such as
Himalayan balsam indicate their own undesirable presence.
Ellenberg indicator values, adapted for the British Isles, are another tool which can
be used to interpret the presence or absence of certain indicator species. This
system ranks most plant species on five scales for critical habitat factors, including
light, moisture, reaction (pH), nitrogen availability and salt tolerance. On the habitat
wetness scale, those species adapted to soils that are dry for long periods score
1, while submerged aquatic species score 12. Recording the species present
in a consistent area of habitat and calculating averages represents the physical
characteristics of the habitat and provides a quantitative index of change. A
description of the procedure and lists of values are available in Ellenberg’s Indicator
Values for British Plants (Hill et al., 1999), with revision and additional species
in Plantatt (Hill et al., 2004) and Bryoatt (Hill et al., 2007). All of these can be
downloaded from the Centre for Ecology and Hydrology website (www.ceh.ac.uk).
Advantages of the indicator species method include:
– In combination with measurement or assessment of other indicators it can
provide a body of negative or positive evidence that is readily understood by a
non-specialist audience.
– Results can be recorded in a simple format independent of data handling
software which minimises demand on time and resources.
– Spot checks at fixed locations can be combined with whole site ‘sweep up’
surveys using some of the same species, giving detailed observation of key
locations and an overview of the whole site.
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