Table 2.

Comparison of local and global models predicting fine root intersect densities (number of fine root intersects per 25 cm² grid cell) across soil profiles, stand ages, and soil types.

Soil profile	Stand age (yr)	Soil type	Local models	R2	RMSE	Global models	R2	RMSE	Fobs
P0	1	20% clay	FRD = 1.4677 − 0.2960D + 6.7027exp(−19.0512D)	0.91	0.23	FRD = 1.3307 − 0.2587D + 5.3375exp(−19.3729D)	0.83	0.28	15.4****
P1			FRD = 1.1931 − 0.2213D + 3.9528exp(−19.7684D)	0.78	0.26
P0	2	20% clay	FRD = 1.9000 − 0.3504D + 3.7492exp(−4.0025D)	0.83	0.24	FRD = 1.6917 − 0.3118D + 3.6078exp(−3.4614D)	0.94	0.25	9.4****
P1			FRD = 1.4520 − 0.9407D − 0.1275exp(−0.6502D)	0.95	0.22
P0	3.5	20% clay	FRD = 2.7974exp(−0.7111D)	0.90	0.21	FRD = 2.7168exp(−0.7178D)	0.88	0.22	2.7 NS
P1			FRD = 2.6385exp(−0.7262D)	0.87	0.22
P0	6	20% clay	FRD = 1.4419 − 0.1743D + 18.1805exp(−14.7543D)	0.92	0.36	FRD = 1.4221 − 0.1726D + 17.1942exp(−13.1137D)	0.92	0.36	2.2 NS
P1			FRD = 1.4023 − 0.1709D + 16.4777exp(−11.8440D)	0.93	0.35
All	1	20% clay	FRD = 1.3307 − 0.2587D + 5.3375exp(−19.3729D)	0.83	0.17	FRD = 1.2318 − 0.1649D + 6.9213exp(−9.0045D)	0.69	0.54	330.0****
	2		FRD = 1.6917 − 0.3118D + 3.6078exp(−3.4614D)	0.94	0.25
	3.5		FRD = 2.7168exp(−0.7178D)	0.88	0.22
	6		FRD = 1.4221 − 0.1726D + 17.1942exp(−13.1137D)	0.92	0.36
All	6	40% clay	FRD = 1.8160 − 0.2120D + 11.4810exp(−8.0817D)	0.91	0.38	FRD = 1.6472 − 0.1964D + 14.7334exp(−11.3966D)	0.90	0.40	39.9****
		20% clay	FRD = 1.4221 − 0.1726D + 17.1942exp(−13.1137D)	0.92	0.36

F-tests compare local models with a global model.

Only parameters significantly different from 0 (P < 0.05) are shown. D is soil depth in meters. NS, ^*, ^**, ^*** and

^****indicate non-significant differences at P < 0.05 and significant differences at the thresholds of 0.05, 0.01, 0.001, and 0.0001, respectively.