Table 1. Summary of optimal models for plant species richness in relation to N deposition and climate variables.

	Model 1 (Total N deposition + environmental variables)									Model 2 (oxidized/reduced N + environmental variables)
Response variable	All sites	d.f.	P	Uplands	d.f.	P	Lowlands	d.f.	P	All sites	d.f.	P	Uplands	d.f.	P	Lowlands	d.f.	P
Total species	(−) N	51	***	(−) N	23	***	(−) N	26	**	(−) NOy	51	**	(−) NOy	24	***	(−) NOy	26	**
	(−) gdd		***				(−) gdd		**	(−) gdd		***	(−) NHx		*	(−) gdd		**
	N x gdd		*							(−) NHx		***
Total lichen species	(−) N	51	**	(−) N	24	**	-	-	-	(−) NHx	51	***	(−) NOy	24	**	(−) NHx	24	*
	N x gdd		*	N x gdd		**				(−) NOy		**	(−) NHx		*
										(−) gdd		***	NHx x gdd		**
													NHx x rain		*
Total bryophyte species	(−) gdd	51	***	-	-	-	(-) gdd	26	**	(-) gdd	51	***	-	-	-	(−) NOy	26	**
																(−) gdd		*
																(−) rain		*
Total graminoid species	(−) N	51	**	(−) N	24	*	(−) N	26	*	(−) NOy	51	*	(−) NHx	24	*	(−) NOy	26	*
	(−) gdd		**				(−) gdd		**	(−) NHx		*				(−) gdd		***
										(−) gdd		**				NHx x gdd		*
Total forb species	(−) N	51	***	(−) N	24	**	(−) N	26	**	(−) NOy	51	***	(−) NOy	24	***	(−) NOy	26	***
				N x rain		*				(−) NHx		*	(−) NHx		*	NOy x rain		*
										(−) gdd		*				NHx x rain		*

(+/−)  =  direction of response; x  =  interaction; P values  =  * <0.05, **<0.001, ***<0.001; gdd  =  growing degree days.