Surface soil physical and hydrological characteristics in Bromus tectorum L. (cheatgrass) versus Artemisia tridentata Nutt. (big sagebrush) habitat

Limited information exists of the differences in soil physical and hydrologic properties in invasive Bromus tectorum L. (BT) (cheatgrass) habitats versus native Artemisia tridentata Nutt. (AT) (big sagebrush) habitats. Our objective was to assess differences in soil physical and hydrological properties by comparing measures of soil particle size; aggregate stability; hydrophobicity; bulk density; penetration resistance; surface roughness; and infiltration (double-ring and mini-disk tension infiltrometer) between habitats. BT sites were sampled following AT stand replacing fires that resulted in near continuous BT establishment. Sites characterized by AT, and not burned, were sampled as controls. Significantly lower infiltration rates and surface roughness ratios in conjunction with statistically significant higher aggregate stability and penetration resistance suggest that BT sites have different surface physical characteristics from AT sites. Lower surface roughness and higher penetration resistance on BT sites may yield greater runoff, subsequently providing less available water for plant growth. However, higher aggregate stability and plant cover on BT sites may negate this effect. Higher percentage coarse sand fractions and lower percentage fine fractions, in conjunction with smoother, less permeable surfaces on BT sites, suggest the potential for soil erosion on BT sites. Further research is needed to elucidate the specific mechanisms responsible for the differences seen between AT and BT sites and whether post fire BT occupation, fire, or landscape differences are responsible.