Predictor Importance Values for gray birch (Betula populifolia)

Predictor Name	Importance Score	Rank
Annual precipitation (mm)	13.92	5
Mean May-September precipitation (mm)	15.02	3
Mean annual temperature (°C)	11.2	13
Mean May-September temperature (°C)	12.78	8
Mean temperature of coldest month (°C)	8.99	28
Mean temperature of warmest month (°C)	15.44	1
Annual aridity index	6.09	41
Minimum elevation	15.25	2
Maximum elevation	9.92	21
Average elevation	13.5	7
Median elevation	13.94	4
Range of elevation	10.09	18
Elevation coefficient ofvariation	9.37	26
Elevation standard deviation	8.35	34
Annual daylength coefficient of variation	11.69	11
Total available water capacity (cm, to 150 cm)	9.38	25
Total available water supply (cm, to 150 cm)	7.32	37
Depth to water table (cm)	9.5	24
Soil permeability rate (cm/hr)	4.78	42
Soil calcium carbonate (% by weight)	4.05	43
Soil cation-exchange capacity	9.53	23
Soil pH	8.78	29
Soil bulk density (g/cm3)	11	14
Organic matter content (% by weight)	10.87	15
Potential soil productivity	7.75	36
Soil erodibility factor, rock fragment free	8.12	35
Soil erosion by wind (tons/acre/year)	13.54	6
Percent soil passing sieve No. 10 (coarse)	11.75	10
Percent soil passing sieve No. 200 (fine)	10.22	16
Percent clay (< 0.002 mm size)	8.74	31
Percent sand (< 0.002 mm size)	11.59	12
Percent silt (< 0.002 mm size)	8.69	32
Percent of texture clayey	10.05	19
Percent of texture loamy	6.11	40
Percent of texture sandy	8.74	30
Percent of texture other	7.22	38
Alfisol (%)	8.54	33
Aridisol (%)	0	45
Entisol (%)	11.81	9
Histosol (%)	9.84	22
Inceptisol (%)	10.19	17
Mollisol (%)	9.27	27
Spodosol (%)	10.02	20
Ultisol (%)	6.25	39
Vertisol (%)	1.14	44