Fen Management Handbook - Scottish Natural Heritage

– Phytometric tests measure how well a standard plant species grows in a
substrate, giving an indication of relative fertility of that substrate, but are of
limited use with regard to setting limits to the nutrient pressure on a fen because
of the high cost and difficulties in repeating tests. This technique is therefore
best suited to one-off comparisons of soil fertility between locations within a site,
or between sites.
– Identifying if the fen is N or P limited: Small (1-2 m 2 ) experimental plots of
fen vegetation can be chosen in the field and treated monthly with (20 kg P h -1
y -1 +/- 50 kg N h -1 y -1 ) over two to three years, using dilute solutions. Vegetation
monitoring could include species composition, total biomass/unit area, N and
P content of vegetation, total N and P in vegetation per unit area. Very clear
changes in these parameters have been observed with N and P addition even
where the overall changes in plant tissue nutrient concentrations were small.
Mosses in particular show a strong response to P under conditions where higher
plants are often still N limited.
– Atmospheric N inputs: measurements require large data sets to be meaningful,
and in general the modelled data provided by www.apis.ac.uk for the 5 km
square will provide the most useful data. Exceptions to this would include
circumstances where the inputs to the site were likely not to be representative
of the area generally, e.g. point sources such as major roads (NO x) or intensive
livestock units (NH 3). In such cases NO 2 or ammonia diffusion tubes could
provide useful information.
10.11 Weather
Key weather parameters such as rainfall and temperature can be monitored using
commercially available individual pieces of equipment, or multiple parameters can
be measured using weather stations. In the UK, the Meteorological Office (www.
metoffice.gov.uk) maintains an extensive programme of weather monitoring. Of
interest in relation to understanding the inputs and outputs of water to fen sites
are rainfall and potential evaporation data. Some monitoring data, usually at a low
spatial and temporal resolution, is available from their website, and higher resolution
data can be purchased.
10.12 Site Diary
In executing a monitoring strategy, it is important to keep a diary of events which
may influence the ecological and physical condition of the site. When read in
conjunction with formal monitoring data, information from a site diary can be the
key to understanding how a fen functions. Recording methods can include narrative
description (with notebook prompts on subjects) or fixed point photography, and
might include:
– Site management activities: for example, activities to control non-native
species, raising or lowering of a water control structure, ditch clearance,
mowing, movement of grazing animals, etc.
– The effects of natural events on the site: for example, the extent and depth
of surface water flooding, the direct effects of an intense rainfall or flooding
event, the effects of a prolonged dry period on spring flows and river flows,
geomorphological changes, etc.
– Off-site events: for example ditch clearance, whether a local groundwater or
surface water abstraction has been used or not used for a specific period, etc.
233