Table 2.

Regressions of tissue N concentrations of selected species on species number. ((a) The tissue N of two forbs (L. perennis, a leguminous forb, and S. rigida, a non-leguminous forb) significantly decreased with increasing diversity. (b) The tissue N of two grasses (P. pratensis, a C3 grass, and S. scoparium, a C4 grass) significantly increased with increasing diversity. The species identity term shows how much greater, on average, tissue N concentration is for L. perennis compared to S. rigida and for P. pratensis compared to S. schizachyrium, for the forb and the grass regressions, respectively. For both regressions, a model including an interaction term between species identity and species richness showed no significant effect (p>0.4).)

	per cent N of two forb species			per cent N of two grass species
parameter	estimate	standard error	p	estimate	standard error	p
intercept	1.23	0.04	<0.0001	0.902	0.03	<0.0001
species number	−0.0074	0.0034	0.029	0.0054	0.0020	0.010
species identity	0.237	0.019	<0.0001	0.082	0.011	<0.0001

overall model
R2		p		n
0.60		<0.0001		107
0.37		<0.0001		109