- Infiltration, soil erosion, nitrogen loss and soil profile
characteristics were measured on 36 sites representing land occupied
by Artemisia tridentata ssp. tridentate, wyomingensis, and vaseyana.
Infiltration, soil erosion, and nitrogen loss were strongly correlated
but highly variable. Soil loss, but not infiltration or nitrogen
loss was significantly different between subspecies. At
Frenchglen infiltration rates were higher and soil erosion and nitrogen
loss rates were lower for A.t. ssp. vaseyana sites than for A.t.
ssp. wyomingensis sites. Infiltration rate decreased between plots
as mean soil particle size decreased, organic ground cover decreased,
bulk density increased, and extractable sodium increased.
Infiltration rate was especially low on sites with vesicular porosity
in the surface soil. Soil loss, and for the most part, percent
nitrogen in the runoff water increased between plots as bare ground
increased, and vesicular porosity in the surface soil increased, but
soil and nitrogen loss was negatively correlated with medium and
coarse sand and coarse fragments in the surface soil, and with organic
ground cover. Aridisols lost more soil than Mollisols, but only
if sites dominated by surficial tephra were omitted from the analysis,
did Aridisols show significantly lower infiltration rates. The
nitrogen lost in the simulation does not appear to be large in comparison
with either capital or yearly flux. Nearly all characteristics
of the soil profile show either no significant differences
between subspecies or they show a significant interaction between
location and subspecies. The Frenchglen location had the greatest
elevational differences between subspecies and most of the significant
physical and chemical differences between subspecies, including
greater depth of maximum illuviation, greater rooting depth, and in
the surface soil, lower ph, higher organic matter, higher cation
exchange capacity, lower base saturation and lower percent
exchangeable sodium on higher elevation A.t. ssp. vaseyana sites
than on A.t. ssp. wuomingensis sites and/or A.t. ssp. tridentata
sites. In the deeper soil horizons at Frenchglen, A.t. ssp.
vaseyana sites had lower ph and lower base saturation than A.t. ssp.