Field and laboratory studies on alpine soil erodibility, southern Rocky Mountains, Colorado

Abstract

Soil erodibility has been studied on the alpine tundra of Trail Ridge in the southern Rocky Mountains, Colorado. Field experiments were conducted using a portable rainfall simulator to estimate an erodibility index (grams of detached soil per unit area) at 71 sites. The index determined on eight soil types allowed discrimination of a high erodibility group (mean index of 18.9 g), moderate or transitional group (mean index of 10.1 g), and one low group (mean index of 4.5 g). Laboratory measurements of physical propertiesMdashtexture, water absorption capacity, organic carbon, and aggregationMdashwere compared with the erodibility index and results of simple and multiple regressions showed that 29 per cent of the variance in erodibility is explained by the measured variables, the strongest correlation (r=0.42) being associated with aggregation. Unexplained variability (71 per cent) may be due in part to unmeasured soil properties, non-linearity in the data, random processes, bias, and experimental error. These correlations represent a beginning in understanding factors influencing alpine soil erodibility. The results suggest that field measurement is still the most satisfactory method of estimating an erodibility index and that laboratory surrogates for this index are not readily applicable in this environment.