Fen Management Handbook - Scottish Natural Heritage

with appropriate training. Providing clear, concise and ‘user friendly’ data or
monitoring schemes ensures that site management utilises the data to its fullest
extent, and does not become overwhelmed by the technical complexities of data
or results.
– Actions and/or contingencies for malfunction or loss of a monitoring point
or installation. Where monitoring data is critical, for example for designated site
assessment, it is useful to detail the contingency actions which would be taken
to restore or replace a lost monitoring point or installation.
– The required accuracy and precision of measurement. Accuracy is the
closeness of a measurement to the actual value of the parameter. Precision is
the repeatability of a measurement. An introduction to error analysis (Taylor,
1997) provides an excellent introduction to the treatment of uncertainties in
physical measurements.
10.2.4 When and for how long
Complex statistical techniques can be used to decide optimal monitoring
frequencies, but understanding why you want to monitor - for example to prove a
link between a nutrient source and enriched vegetation, or evaluating the success
of current fen management – generally determines monitoring frequency and
duration. For example, increased grazing aiming to micro-diversify vegetation
structure, requires monitoring of the vegetation structure before, during and after
the management, and the impact of the increased grazing on target species such
as invertebrates. Key considerations are:
What is the smallest time unit for the particular interest? In the context of a fen, this
varies between one day (for example, short term fluctuations in water recharge) and
several years (if the response of the site to longer-term climatic variation was the
aspect being scrutinised). A time unit smaller than one day, is of interest for specific
testing, e.g. a groundwater pumping test.
Is the parameter to be monitored ‘noisy’, i.e. does it vary significantly? As a rule of
thumb, short term variations, around a tenth or greater than the expected variation
during the time of interest will normally cause problems. If the parameter response
is noisy, choose a monitoring frequency which is sufficiently high to capture the
variations. For example if we monitor water level in the soil and the expected change
due to management is a seasonally average increase of 25cm, but daily fluctuations
are 5cm due to evapotranspiration, then we need to monitor frequently to separate
the management effect from the natural variation.
If the temporal variability of a parameter is unknown, it is appropriate initially to
monitor at a high frequency to obtain a scoping level understanding of temporal
variability and then reduce the frequency accordingly.
Include both pre-management and post management measurements, for the length
of the expected impact. Be prepared as this could be several years! Where the
impact is unknown ‘pilot’ or ‘trial’ management can provide data to inform the further
roll out of larger scale management.
If a protracted monitoring is likely, sturdy monitoring equipment and installations,
although initially expensive are a good investment, as the information gathered is the
basis for future project spending.
215