Hillary Talbott

ABSTRACT

Meadows on the east slopes of the Cascade Mountains of Washington have been degraded by heavy grazing by elk herds and cattle.  In 1992, a grazing exclusion and fertilization study was initiated on four meadows in the Naches Ranger District of the Wenatchee National Forest to test rehabilitation strategies.   This study uses these existing meadow exclosures to observe how physical properties of compacted, degraded meadow soils may recover over time under different grazing and fertilization regimes.  Intact soil cores were used to determine bulk density, porosity, root biomass, and pore-size distribution.  Permeability was measured in situ.  Measurements were taken in three different grazing regimes (ungrazed, elk-grazed, and elk+cattle-grazed) in both fertilized and unfertilized plots.  Bulk density ranges from 0.66 g/cm3 to 1.36 g/cm3 with a mean of 1.01 g/cm3 .  Root biomass ranges from 0.00064 g/cm3 to 0.0079 g/cm3 with a mean of 0.0029 g/cm3.  Permeability ranges from 1.6x10-10cm to 5.7x10-8cm with a mean of 1.4x10-8cm.  Results indicate that both permeability and root biomass are highly spatially variable. Variability appears to be due, in part, to extensive gopher activity in these meadows.  Neither permeability, root biomass, bulk density, nor pore-size distribution was significantly different (p<0.05) across grazing and fertilizer treatments.  However, trends in the data suggest a slight decrease in bulk density in meadows with gopher activity and generally greater root biomass with decreasing grazing pressure.  Increases in root biomass were not statistically correlated with greater permeability or lesser bulk density.  There were no consistent trends in pore-size distribution.  These results suggest that 10 years is not a long enough recovery period to see significant changes in soil physical properties in these meadows, and that gophers may have a role in ameliorating compaction.