Plant community relationships to soil properties and topography in a southern interior BC grassland : a refinement

• Main Author: Lee, Robert N.
• Language: English
• Published: University of British Columbia 2011
• Online Access: http://hdl.handle.net/2429/39437

The grasslands of British Columbia, Canada are an asset to the province’s biodiversity, economy, natural beauty, and recreation. Since the late 1800s, these areas have been largely modified and reduced, and they are currently threatened by climate change and exotic plant invasions. The ability of land managers to adapt to the effects of climate change and plant invasion depends on having the best possible understanding of these systems; however, little quantitative information is available on the strength of relationships between topography, soil properties, and plant community composition. I collected data on plant communities, selected soil properties, and topography on 31 sites in Lac du Bois Provincial Grasslands Park in southern interior British Columbia during May-July 2010. Cluster analysis (UPGMA) and multi-response permutation procedures (MRPP) of my data produced more homogeneous groups of sites by vegetation (A=0.29, p=0.001) and soil properties (A=0.22, p=0.001) than for two currently used grassland classification systems that are based on elevation ranges (A=0.17, p=0.001; A=0.15, p=0.001). Non-metric multidimensional scaling (NMS) confirmed the distinctiveness in overall species composition and main environmental correlates for the three main plant communities: bluebunch wheatgrass/big sage, bluebunch wheatgrass/rough fescue, and rough fescue/Kentucky bluegrass. The Mantel (multivariate) correlation between plant community composition and soil properties was stronger on north-facing sites (0.58) than on south-facing sites (0.19), while the Mantel correlation between topography and soil properties was stronger on south-facing sites (0.38) than on north-facing sites (n.s.). These correlations indicate stronger plant-soil feedbacks on north-facing slopes, while on south-facing slopes the effect of slope angle on heat and desiccation stress is the most important factor shaping plant communities. The highest occurrences of invasive species in the study area were at the higher elevations, likely in response to increasing precipitation, lower temperatures, and higher soil fertility at the higher elevations. The information provided in this thesis can aid land managers by adding to current knowledge about the relationships between plant communities, soil properties, and topography, which is important for predicting effects of future climate change and the spread of invasive plant species.