© 2000 Heron Publishing—Victoria, Canada
Spatial and temporal variability of foliar mineral concentration in beech (Fagus sylvatica) stands in northeastern France
A. Duquesnay (1), J. L. Dupouey (1, 4), A. Clement (1), E. Ulrich (2) and F. Le Tacon (3)
1. Ecophysiology Unit, INRA-Nancy, 54280 Champenoux, France / 2. O.N.F., Department of Technical Research, Boulevard de Constance, 77300 Fontainebleau, France / 3. Microbiology Team, INRA-Nancy, 54280 Champenoux, France / 4. Author to whom correspondence should be addressed (dupouey@nancy.inra.fr) / Received September 3, 1998
Summary
Foliar mineral concentration may provide a basis for monitoring the consequences of long-term environmental changes, such
as eutrophication and acidification of soils, or increase in atmospheric CO2 concentration. However, analytical drifts and inter-tree and year-to-year variations may confound environmental effects on
long-term changes in foliar mineral concentration. We have characterized the relative effects of these potentially confounding
factors on foliar carbon, nitrogen, phosphorus, calcium, potassium, magnesium and manganese concentrations in 118 pure beech
(Fagus sylvatica L.) stands, sampled in 1969–71 and 1996–97. Interannual fluctuations of these elements were quantified in a subset of six
beech stands monitored for 5 years.
Intercalibration between the methods used at each sampling period for nitrogen and phosphorus analyses showed significant,
but low, relative differences (0.8 and 3.3% for N and P, respectively). Based on inter-tree variability, elements could be
arranged in four groups: C (constant), N and P (low variability), K and Ca (medium variability), Mn and Mg (high variability).
Inter-tree coefficients of variation were 2, 6, 8, 15, 18, 22 and 27%, respectively. Year-to-year fluctuations increased in
the order N, P, Mg, K, Ca, and Mn coefficients of variation of 4, 4, 7, 9, 11, 15 and 29%, respectively).
Between the two sampling periods, foliar N concentration increased 12%, whereas decreases were observed for P (–23%), Mg (–38%)
and Ca (–16%). Ratios of N/P, N/K and N/Mg increased by 42, 19 and 77%, respectively. These changes were larger than the interannual
variations for P, Mg, N/P, N/Mg and Mg/Ca. Decreasing concentrations of P and cations were particularly marked for trees growing
on acidic soils, whereas the positive N trend did not depend on soil type. Both increasing atmospheric CO2 concentrations and acidification of forest soils could contribute to decreasing P and cation concentrations in foliage. The
increase in foliar N concentration with time suggests a nitrogen deposition effect. Whatever the causes of these changes,
the large shift in element ratios indicates an accelerating imbalance between nitrogen and cation status.
Keywords:
calcium, cations, foliar analysis, long-term trend, magnesium, manganese, mineral analysis, nitrogen, nutrition, phosphorus,
potassium, sampling strategy.
