Predictor Importance Values for river birch (Betula nigra)

Predictor Name	Importance Score	Rank
Annual precipitation (mm)	10.4	25
Mean May-September precipitation (mm)	14.59	12
Mean annual temperature (°C)	8.49	35
Mean May-September temperature (°C)	7.99	39
Mean temperature of coldest month (°C)	8.16	37
Mean temperature of warmest month (°C)	7.16	42
Annual aridity index	14.94	11
Minimum elevation	11.05	21
Maximum elevation	10.58	23
Average elevation	7.48	41
Median elevation	9.16	30
Range of elevation	4.16	44
Elevation coefficient ofvariation	15.18	10
Elevation standard deviation	8.38	36
Annual daylength coefficient of variation	12	18
Total available water capacity (cm, to 150 cm)	15.36	9
Total available water supply (cm, to 150 cm)	13.18	16
Depth to water table (cm)	19.19	1
Soil permeability rate (cm/hr)	16.73	6
Soil calcium carbonate (% by weight)	11.04	22
Soil cation-exchange capacity	10.35	26
Soil pH	17.79	4
Soil bulk density (g/cm3)	14.45	14
Organic matter content (% by weight)	14.39	15
Potential soil productivity	8.97	31
Soil erodibility factor, rock fragment free	15.48	8
Soil erosion by wind (tons/acre/year)	8.86	33
Percent soil passing sieve No. 10 (coarse)	8.1	38
Percent soil passing sieve No. 200 (fine)	14.52	13
Percent clay (< 0.002 mm size)	16.81	5
Percent sand (< 0.002 mm size)	17.94	3
Percent silt (< 0.002 mm size)	8.93	32
Percent of texture clayey	11.78	19
Percent of texture loamy	10.19	27
Percent of texture sandy	7.95	40
Percent of texture other	11.11	20
Alfisol (%)	10.55	24
Aridisol (%)	0	45
Entisol (%)	12.25	17
Histosol (%)	10	28
Inceptisol (%)	18.91	2
Mollisol (%)	15.77	7
Spodosol (%)	6.01	43
Ultisol (%)	8.5	34
Vertisol (%)	9.41	29