Relationships of Soils to Mountain and Foothill Range Habitat Types and Production in Western Montana

Abstract

AbstractSoils at 23 sites representing eight western Montana mountain and foothill range habitat types were characterized and classified in accordance with Soil Taxonomy. The soils ranged from Borollic Calciorthids at the dry end of a moisture and soil development gradient to Pachic Cryoborolls on the moist end. Corresponding vegetation was a Stipa comata‐Bouteloua gracilis community on the dry end and a Festuca idahoensis‐Agropyron caninum community on the moist end. Soil taxonomic units and vegetation habitat types were ordered along the moisture gradient. Multiple linear regression analysis was used to model above‐ground dry‐matter productivity of the sampled sites. Eighteen significant variables were identified including thickness of the mollic epipedon, total soil organic matter, total N content, elevation, depth to free carbonates, estimated annual precipitation, aspect, solum thickness, summer soil temperature at 50 cm, percent coarse fragments in the A horizon, and extractable K. The thickness of the mollic epipedon was the variable most highly correlated with productivity (r=0.89**) and the best regression model accounted for 90% of the variability in total productivity between sites (based on 2 years' productivity data). Soil morphological characteristics proved more useful in models of site productivity than estimated climatic data or site nutrient data.