Fen Management Handbook - Scottish Natural Heritage

A small quadrat size (e.g. 0.5 m2) can be used, and only important or indicator
species need to be recorded if the aim is simply to identify change between years.
In order to link back to NVC, a full species list is required. Abundance values can
be included, which may help to determine the extent of a community. Common reed
at high cover values is characteristic of some fen communities (S24, S25, S26),
but also occurs at low cover values in other communities (S17, S27). Ellenberg
values for the species included in a survey can also be used to relate the quadrat
records to environmental factors, tracking changes in conditions. Repeat surveys do
not have to use the same quadrat locations but should achieve the same density of
samples.
Whilst vegetation sampling can be done by anyone with good botanical knowledge
or survey skills, provided that suitably accurate GPS equipment is used for position
fixing, data processing for geo-statistical vegetation mapping demands a high level
of training and practise. As a new and evolving technique, there are risks that the
particular method used for analysing baseline survey results may be superseded
and in-house skills may become outdated, while academic help may no longer be
available.
10.3.5 Quadrats and transects linked to hydrological monitoring
This method combines the traditional tools of quantitative botanical surveying with
the hydrological model, by using fixed quadrats and transects as described in
Wheeler, Shaw and Hodgson (1999). Species presence and cover values in semifixed
quadrats around locations of ecological and hydrological significance are
recorded at fixed intervals of three to five years, providing quantitative data that can
be subjected to statistical analysis. Transects along hydrological gradients or other
lines of change can tie botanical change to changing physical conditions.
Advantages include:
– Strong linkage of botanical monitoring results to hydrological monitoring.
– Results can be presented graphically.
– Recording can be based on a limited range of species, so that there is no need
to identify all species in a quadrat.
– Good position fixing of the survey stations.
– Direct comparison of the survey results from repeat recording of the same
locations.
Disadvantages include:
– Bias introduced with the initial selection of survey locations will persist through
the monitoring events.
– Large numbers of survey stations are needed for analysis.
– Assumptions about the likely nature and direction of change have to be made, so
other processes may then be missed because the survey locations do not relate
to them.
– Changes to the survey site locations, to monitor unpredicted processes,
effectively set a new baseline and year zero for data analysis.
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