assessment of changes in the phosphorus status of forest ...

2.3 Factors influencing the foliage P concentrations in trees
Species
Phosphorus concentrations in the foliage differ among various tree species, commonly
high P values are found in deciduous trees and low in coniferous species. For
example, using the data from stands which describe the optimum or sufficiency levels
of P in the foliage, Krauß and Heinsdorf (2005) suggested that the different species
can be grouped into the following the order:
(a) High range (>2 mg P/g) in Populus balsamifera, Tilia cordata, Carpinus betulus
and Betula pendula
(b) Medium range (1.5 to 2 mg/g) in Quercus robur, Pinus strobus, Larix decidua,
Pseudotsunga menziesii
(c) Low range (1.0 to 1.5 mg P/g) Quercus rubra, Fagus silvatica and Pinus nigra,
Picea abies, Pinus sylvestris
Thus the four species being considered more closely here could be ranked in the
following order of declining foliage P demand: Oak > Beech > spruce > pine, with
very little difference between spruce and pine in their P foliage concentrations.
If the median values given in Table 1 for the optimum range are considered (van den
Burg data), the four species follow the order: Oak = spruce > pine >beech with very
little difference among the species. In fact, while considering the forest foliar
chemistry surveys on level I sites of 16 European countries (1995 survey), an expert
panel decided to consider three classes for pine and spruce (2.0 mg
P/g), for beech (1.7 mg P/g) and for oak stands (1.8 mg
P/g) (Stefan et al 1997 (EC-UN/ECE)), which does not differentiate much between
the species. Interestingly, the expert panel decided not to assign specific names or
descriptions to these classes in order to avoid misinterpretations or wrong
conclusions.
Tree age
The data compiled by van den Burg (1985, 1990) differentiate between mature and
young stands and those from experiments, presumably seedlings or saplings from
greenhouse trials, for a large number of cases (Table 2). The range in the
concentration of P is very high for each group of trees with much overlap. However,
when the median and the mean values are compared, it shows that there are many
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