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

Douglas fir which suffered from absolute and relative P deficiencies. According to
Van den Burg (1990) the increasing N deposition in the south-eastern part of the
Netherlands is largely responsible for the present absolute and relative phosphorus
deficiencies in current needles of Douglas firs, whereas in pine needles the
calcium and absolute and relative magnesium contents were mostly affected. This
contrasting behaviour among Douglas fir and pines was related to the preference
of nitrate uptake by Douglas fir suppressing the uptake of P.
• U.K.
Harrison et al. (1999) studied the effects of pollutants on beech, Scots pine and
Sitka spruce stands growing on a range of comparable soils in the UK. They
investigated the canopy conditions of the stands in relation to the possible role of
P limitation. Use of a root bioassay and a resin-extraction procedure to assess the
availability of P in surface soil indicated that a higher level of P stress in stands
with the thinner canopy was observed in eight out of the nine paired stands of
Sitka spruce, Scots pine and beech suggesting the need to monitor the acid inputs
on affected plots;
• Canada
For an area in central Ontario with high atmospheric N depositions, Grawdoski
and Thomas (2006) reported that the annual stem growth of sugar maple (last 5
year average) was limited by available P levels measured by using the Bray 1
method. Variations in this measure of P availability in the surface soils explained
74% of variance in growth. Low P values were associated with low soil pH in the
root zone.
• Germany
Polle et al. (1992) found that foliar P in 3 Norway spruce stands growing at
different altitudes in calcareous Alps of Bavaria were in the deficient range.
Thomas and Büttner (1998) reported limiting values of P in the leaves of Quercus
petraea. Heinsdorf and Branse (2002) followed element concentrations in pine
stands growing in Brandenburg, Germany, between 1964 and 1999 and found no
clear decrease of P in needles. Similarly Mellet et al. (2004) in their review of
foliar concentrations in the context of the RECOGNITION project found no clear
evidence of P decrease in the foliage of conifer stands, especially that of pine.
(b) Field and laboratory studies under controlled conditions.
There are a number of case studies in the literature, where acidifying substances were
applied to forests either under field conditions or under controlled laboratory
conditions in order to determine the changes in the nutrition of trees and/or soil P
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