Table 2.

Effects of increased soil N availability on total biomass, growth indices, inorganic and organic N net uptake capacity, and N metabolite levels on (A) seedlings growing single and (B) seedlings growing in competition of Fagus sylvatica, Quercus robur, Pinus sylvestris, Prunus serotina, and Robinia pseudoacacia.

	Biomass and growth indices					N net uptake capacity				N metabolites
										Total soluble		Total soluble
										amino acid-N		protein-N
	Total	Root:shoot	RGR	SLA	SRL	${\mathrm{N}\mathrm{H}}_{\mathrm{4}}^{\mathrm{+}}$	${\mathrm{N}\mathrm{O}}_{\mathrm{3}}^{\mathrm{-}}$	Gln-N	Arg-N	Leaves	Fine	Leaves	Fine
	biomass	ratio									roots		roots
(A) Seedlings growing single
Fagus	n.s.	n.s.	n.s.	n.s.	n.s.	↑	↑	n.s.	↑	n.s.	n.s.	n.s.	↑
Quercus	n.s.	n.s.	n.s.	n.s.	n.s.	↑	n.s.	n.s.	↑	↓	n.s.	n.s.	n.s.
Pinus	n.s.	n.s.	n.s.	n.s.	n.s.	↑	↑	↑	↑	n.s.	n.s.	n.s.	n.s.
Prunus	n.s.	n.s.	n.s.	n.s.	n.s.	↑	n.s.	n.s.	↑	n.s.	n.s.	n.s.	n.s.
Robinia	n.s.	↓	n.s.	n.s.	n.s.	↑	n.s.	n.s.	↑	n.s.	n.s.	n.s.	n.s.
(B) Seedlings growing in competition
Fagus	n.s.	n.s.	n.s.	n.s.	↓	↑	n.s.	n.s.	↑	↓	↓	n.s.	n.s.
Quercus	n.s.	n.s.	↓	n.s.	n.s.	↑	n.s.	↑	↑	n.s.	↓(b)	n.s.	↓
Pinus	n.s.	n.s.	↓	n.s.	n.s.	↑	n.s.	n.s.	↑	↓	n.s.	n.s.	n.s.
Prunus	n.s.	n.s.	n.s.	n.s.	↓	↑	n.s.	↑	↑	↓	↓	↓	n.s.
Robinia	n.s.	n.s.	n.s.	n.s.	n.s.	↑	↑	↑(a)	↑	↓	↓(c)	n.s.	↓

↑, significant increase with increased soil N availability; ↓, significant decrease with increased soil N availability; n.s., no significant differences between high and low soil N availability. Total biomass (g), root:shoot ratio, ratio of belowground biomass to aboveground biomass; RGR, relative growth rate (g dw g^-1 dw d^-1); SLA, specific leaf area (cm² g^-1 dw); SRL, specific root length (cm g^-1 dw); N net uptake capacity (nmol N g^-1 fw h^-1); ${\mathit{N}\mathit{H}}_{\mathit{4}}^{\mathit{+}}$, ammonium; ${\mathit{N}\mathit{O}}_{\mathit{3}}^{\mathit{-}}$, nitrate; Gln-N, glutamine; Arg-N, arginine; total soluble amino acid-N (mg amino acid-N g^-1 dw); total soluble protein-N (mg protein-N g^-1 dw). (a) Only in competition with Fagus and Pinus. (b) Only in competition with Prunus. (c) Only in competition with Fagus and Quercus. No letter: effect of soil N availability regardless of competitor identity.