The Bunchgrass biogeoclimatic zone in British Columbia is critical rangeland habitat, but its health has been threatened by the invasion of exotic plant species for several decades. Invasives can reduce the abundance of important native grasses and forbs.

The objective of this study was to quantify and summarize relationships between soil properties, vegetation, and topography in order to identify critical areas for the future movement of invasive plant species.

Data were collected on 38 sites in Lac du Bois Provincial Park near Kamloops, BC over the period 2006-2010. The area surveyed ranges from approximately 400 m to 1000 m in elevation and encompasses 3 distinct plant/climate/soil communities. Vegetation cover was estimated on each site along 4, 30-m long transects laid out 5 meters apart. Soil samples were collected at 0 – 7.5 cm depth for determination of bulk density, aggregate stability, total C and N, pH, and available P at each site. In addition, slope, aspect, elevation and lat/long coordinates were recorded.

Total plant species richness for all sites was 135, 20% of which were exotics. The proportion of exotic species and abundance of invasive species increased with elevation. The increase in elevation was also associated with an increase in soil fertility and stability, and a decrease in bulk density. Insight was gained through multivariate statistical methods about the relative influence of soils and topography in determining plant community composition. This analysis approach may be useful as part of a proactive management plan to predict the most at-risk zones in native rangelands.