An unprecedented amount of road, trail, and other infrastructure development is currently occurring or planned for many arid and semiarid ecosystems nationally.  This is due to a variety of factors, including energy resources development (oil, gas, wind, solar, coalbed methane, and others), recreational off-road vehicle activity, exurban development and military training.  Planning and mitigation necessary to protect these ecosystems require accurate identification of highest resilience areas, including those most resistant to degradation and those that have the greatest capacity to recover quickly following degradation. The objective of this study was to develop a strategy for assessing the long-term effects of different types of roads on adjacent soil and vegetation properties in a southern New Mexico grassland.  To accomplish this objective, 110 plots selected within a 63,418 acres study area using a stratified random sampling scheme.  Plots were stratified by soil type (5 levels) and road type (3 levels: no road, major road and minor road).  Additionally, to maximize detection of problem areas, we further stratified our base set of road points based on apparent impact as determined by qualitative aerial photo interpretation.  Vegetation cover, soil cover, and soil aggregate stability data were collected along three 25-m transects at each plot.   

Results/Conclusions

Overall, roads had significant, negative impacts on adjacent soils and vegetation when compared to non-road areas.  The severity of impacts varied with soil type suggesting that road and trail development should be carefully planned to avoid more sensitive soils.  Results indicate that most negative impacts due to road and trail development in the study area occurred in map units dominated by fairly coarse, low water holding capacity soils.  Differences were primarily driven by reduced plant productivity in road corridors as indicated by increased bare ground and decreased canopy cover.   In some soil types, loss of soil stability in unprotected locations also appears to be an issue.  Few significant differences in plant community composition were detected between road and non-road areas.  The level of road development did not consistently affect results, suggesting that concentration of activity along a smaller set of major roads may be one strategy to reduce cumulative impacts.  For some soil types, the qualitative stratification technique was important for detecting rare but important negative impacts.  This study illustrates the importance of integrated soil and ecological inventory data for incorporating site specific resilience knowledge into planning processes.