Table 1.

Scaling of leaf nitrogen concentration N_L in relation to leaf phosphorus concentration P_L for all data pooled, for plants grouped by phylogeny (angiosperm, gymnosperm), by four functional groups within the angiosperms and by three different biomes within the angiosperms. (All relations were significant (p < 0.0001). All equations were fit using the log–log version of the equation: Y = β X^α. Reduced major axis intercepts and slopes (exponents) are shown, as well as the lower and upper 95% CI of the exponent, and r². n, the number of observations, i.e. unique species-site combinations with data for N_L and P_L obtained from same individuals. Significant differences (p < 0.05) in exponents among groups (for appropriate contrasts separated by blank lines) are shown by the lack of shared letters. Intercepts were not standardized to a common slope, and thus are not contrasted among groups. Biomes were broadly defined, such that temperate includes temperate and boreal; and moist tropical is both wet and moist tropical and subtropical.)

plant group	n	intercept	exponent	low CI	high CI	r2
all	9356	1.113	0.676	0.658	0.694	0.37
divisions
angiosperm	6466	1.166	0.637 a	0.621	0.653	0.48
gymnosperm	2890	1.002	0.696 a	0.650	0.746	0.22
angiosperm functional groups
graminoid	699	1.105	0.688 a	0.631	0.751	0.42
forb	1072	1.127	0.664 a	0.595	0.742	0.23
shrub	1518	1.155	0.652 a	0.624	0.682	0.56
trees	2878	1.195	0.633 a	0.610	0.658	0.48
biomes
temperate	3147	1.134	0.686 a	0.641	0.734	0.21
Mediterranean	714	1.143	0.655 a	0.623	0.689	0.68
moist tropical	1866	1.203	0.651 a	0.614	0.690	0.38