Fen Management Handbook - Scottish Natural Heritage

plastic bags (e.g. freezer bags). Nutrient concentrations can alter rapidly so samples
should be sent for analysis as soon as possible, or refrigerated if unavoidable delays
arise. The laboratory will indicate how much water or soil sample is required to
complete an analysis. Soil samples should be collected using volumetric sampling
techniques which are more appropriate to the spongy organic soils often found in
fens than techniques which express results by weight.
Sample locations should track the pathway of nutrient input to the fen, and nutrient
migration through the fen. Once the sample points have been chosen they should
be mapped, using GPS if available, so that sampling can be repeated. The first set
of samples will form the baseline for subsequent monitoring and it is a good idea to
take as many as practically and financially possible. This may show that there is little
variation across the fen and, if so, fewer samples could be taken during the next
round of monitoring. The baseline may also detect variations and nutrient ‘hotspots’
where the number of sampling points needs to be increased.
The timing of sampling should be consistent; frequency will depend on available
resources and reason for monitoring. Annual sampling should include both spring
and autumn where possible to allow for seasonal variations. Monthly sampling for
one year may be sufficient to measure change across a year, but to detect longerterm
variations twice yearly sampling over five years is more appropriate. The
frequency could temporarily be increased, for example, to examine the affect of a
new land management prescription being introduced.
232
Nutrient monitoring in soils and water – a basic approach
What to test? Available-phosphorus and available-nitrogen in soil and
water
When? Minimum two times (spring and autumn) per year
Where? Inlet water source(s)
Key habitat compartments, e.g. reedbed, wet woodland,
open water
Why? To identify key areas with high nutrients and nutrient
sources
To monitor changes in nutrients over time
For how long? Ongoing sampling is highly recommended, or a minimum of
three years
Given the potential pitfalls of conventional measurements of nutrient concentration
in water and soils, other techniques have been developed to provide more accurate
information on the degree to which vegetation has become, or has the potential to
become, enriched. These more complex methods of gauging the nutrient status may
be necessary where initial assessment has revealed or demonstrated a problem
requiring external specialist advice or support from conservation or environmental
regulators, or outside organisations such as a university or research programme.
Examples of such detailed techniques are:
– Measuring the N and P content of vegetation: e.g. mosses. Changes in moss
nutrient contents are usually the most sensitive measure, but very little data
is available on the values that might be expected of unpolluted systems, and
comparison is therefore difficult.