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Part XII
Sampling and Analysis of Needles and Leaves
Table 2: Drying temperatures
Type of sample
A. Samples for the measurement of dry mass of 100 leaves
or 1000 needles
Drying temperature
105 °C
B1. Leaves / needles drying before grinding ≤ 70 °C
B2. Powder for moisture content determination (subsample
of B1), not chemically analysed
105 °C
5.1.2 Analysis
5.1.2.1 Pre-treatment of the samples
Before drying and further processing the samples it is recommended to record additional
information about colour, discolouration (e.g. symptoms of nutrient deficiency) and symptoms of
ozone injury, different diseases and insect attacks and other damage on the needle/leaf samples.
The method of this visual assessment should follow the procedures (methods and formats) used
in the Crown Condition Assessment, the Damage Cause Assessment and Symptoms of Ozone
Injury Assessment.
The determination of the dry mass of 100 leaves or 1,000 needles (by drying at 105ºC) is
recommended for Level II (Table 2). It is not necessary to cut the petioles of the leaves but in case
of compound leaves it may be advisable to detach the small leaves from the axis if this has not
been done in the forest. Use polyethylene gloves to avoid contamination. It is not necessary to
wash the samples regularly, but it may be advisable in regions with a high level of air pollution or
near the sea. The samples shall be washed with distilled water. Oven drying must be done at a
maximum of 70ºC for at least for 24 hours, and in any case till constant weight is achieved (Table
2). After drying the needles shall be removed from the twigs with the same precautions as for
detaching the small leaves from their axis. Dry samples shall be ground in order to obtain a fine
homogeneous powder. There will always remain some fibres, depending on the tree species; this
is not a major inconvenience if they are small and if the powder is mixed carefully before taking
samples for analysis. For Mn, Fe, Cu, Cd and Pb determination, it has to be assured that the grinder
does not contaminate the samples. The grinder should be tested for the release of contaminating
materials with dried fibrous cellulose. Before and after grinding the leaf/needle materials such test
should be carried out.
5.1.2.2 Digestion (or ashing) and analysis
The recommended methods for digestion or ashing and analysis are given in Table 3a and 3b.
Other methods may be allowed, but each country must validate the national method. To assure
the homogeneity of the sample a minimum sample amount of 100 - 200 mg depending on the
particle size for the analysis is recommended. It is necessary to compare the total element
concentrations obtained by national methods with those of reference standard samples and with
samples of the interlaboratory comparison tests (Fürst 2009, 2010).
10 www.icp-forests.org/Manual.htm