Table 1.

Correlations between annual data of δ¹⁵N and H⁺, , HNO₃, and over the entire record (1772–2006), and in the periods of 1850–1970, 1850–1950

	Period	Data type	[H+], μeq L−1	, μeq L−1	[HNO3], μeq L−1	, μeq L−1
			r (P1; P2)	r (P1; P2)	r (P1; P2)	r (P1; P2)
δ15N (‰)	1772∼2006	annual data	−0.78 (<0.01; <0.01)	−0.60 (<0.01; <0.01)	−0.78 (<0.01; <0.01)	−0.79 (<0.01; <0.01)
		detrended annual data	−0.09 (>0.05; >0.05)	0.04 (>0.05; >0.05)	−0.08 (>0.05; >0.05)	−0.14 (<0.05; <0.05)
δ15N (‰)	1850∼1970	annual data	−0.72 (<0.01; <0.01)	−0.63 (<0.01; <0.01)	−0.58 (<0.01; <0.01)	−0.59 (<0.01; <0.01)
		detrended annual data	−0.11 (>0.05; >0.05)	−0.01 (>0.05; >0.05)	−0.07 (>0.05; >0.05)	−0.03 (>0.05; >0.05)
δ15N (‰)	1850∼1950	annual data	−0.42 (<0.01; >0.05)	−0.37 (<0.01; >0.05)	−0.21 (<0.05; >0.05)	−0.18 (>0.05; >0.05)
		detrended annual data	−0.01 (>0.05; >0.05)	0.03 (>0.05; >0.05)	−0.04 (>0.05; >0.05)	0.01 (>0.05; >0.05)

Significant correlations are in bold. P₁, P value; P₂, adjusted P value taking into account the effective degree of freedom (autocorrelation).