Temporal trends in the foliar nutritional status of the French, Walloon and Luxembourg broad-leaved plots of forest monitoring

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Table II

Mean leaf mass and foliar nutrient concentrations of the various plot groups (standard deviation). Groups without common letters are significantly different (ff = 0.05, Tukey multiple comparison test). Threshold values are given for comparison (Bonneau, 1995; Croisé et al., 1999; Van den Burg, 1985; 1990).

	n	Mass of 100 leaves (g)	N (mg · g⁻¹)	S (mg · g⁻¹)	P (mg · g⁻¹)	Ca (mg · g⁻¹)	Mg (mg · g⁻¹)	K (mg · g⁻¹)
Pedonculate oak acid soils	9	21.8 (3.1) ^b	25.8 (1.5) ^a	1.60 (0.06) ^ab	1.36 (0.22) ^a	7.5 (1.1) ^a	1.7 (0.20) ^b	9.4 (1.3) ^b
Sessile oak acid soils	22	30.1 (2.5) ^c	24.5 (1.9) ^a	1.47 (0.15) ^a	1.27 (0.19) ^a	6.6 (1.1) ^a	1.6 (0.27) ^b	8.5 (1.0) ^ab
European beech acid soils	18	13.3 (1.7) ^a	25.5 (2.0) ^a	1.60 (0.15) ^b	1.21 (0.19) ^a	6.2 (1.9) ^a	1.0 (0.25) ^a	7.5 (1.5) ^a
European beech eutrophic soils	8	13.4 (2.6) ^a	25.2 (1.9) ^a	1.57 (0.15) ^ab	1.20 (0.20) ^a	12.9 (2.0) ^b	1.4 (0.18) ^b	7.4 (1.1) ^a

Deficiency			15	1.0–1.3	0.8	3	0.8–0.9	4–5
Critical			20	1.3–1.5	1.1	5	1.2	6–7
Optimum			22-23		1.5–2.0		1.4–1.5	8–9