Available water holding capacity of soil 0 Bulk density of soil 0 Carbon content of soil 0 Compound topographic index (relative wetness) 0 Day/night diurnal temperature difference 0 Integer number of consecutive months where Tavg >= 5 deg C (Length of potential growing season) 0 Nitrogen content of soil 0 Precipitation during the coldest quarter 0 Precipitation during the driest quarter 0 Precipitation during the hottest quarter 0 Precipitation during the wettest quarter 0 Ratio of precipitation to potential evapotranspiration 0 Solar interception 0 Sum of monthly Tavg where Tavg >=5 deg C 0 Temperature during the coldest quarter 0 Temperature during the hottest quarter 0