Project Number: 6235-11210-006-31
Project Type: Reimbursable

Start Date: May 11, 2004
End Date: May 10, 2009

Objective:
To quantify the relative resistance of dry and wet soils and associated vegetation to two types of disturbance associated with ground-troop trampling and wheeled vehicles on each of six nongypsic soil types in both dry and wet conditions.

Approach:
Treatments will be assigned using a randomized, complete block design with a minimum of six blocks with six treatment combinations each [3 disturbance levels (including control) X 2 soil moisture contents]. Wet soil plots will be wetted to at least 10 cm using a previously developed rainfall simulation device. The device allows relatively natural rainfall to be uniformly simulated throughout the long, narrow split-plots with minimum overspray. Buffer strips will be established between each split plot to further minimize potential overspray and to provide controlled corridors for foot traffic associated with soil and vegetation measurements. Soils at all sites will be thoroughly characterized. In order to control for soil variability, soil surface texture will be measured in each plot. Pre- and post-treatment measurements will be used to generate selected soil and vegetation indicators. These measurements were selected from a larger set included in the previous study based on the following criteria: (1) generate indicators sensitive to changes in soil erosion resistance, hydrology and plant community composition, (2) cost-effective (based on cost of collecting sufficient data to detect biologically and statistically significant differences). The following measurements will be completed pre- and post-treatment: line-point intercept (for vegetative and soil surface cover), soil stability in water (for soil erodibility) and soil pocket penetrometer and impact penetrometer and resistance (for surface and subsurface compaction). Line-point intercept will be used to monitor changes in vegetative cover and composition and in soil surface cover, including plant litter, rock and lichen. Soil stability in water will be measured using a field soil stability kit. This field method eliminates the introduction of bias associated with sample damage during transport. It is highly correlated with lab measurements and is sensitive to changes in soil surface condition in arid ecosystems. A standard pocket penetrometer will be used to monitor soil surface compaction, while an impact penetrometer developed specifically for noncultivated soils will be used do monitor changes in subsurface soil compaction.