User: | Open Learning Faculty Member:
My hypothesis (that the community structure of forb species changes as elevation increases within a riparian environment) is likely related to several underlying processes within my study area (located on the Eastern bank of the South Saskatchewan River in Saskatoon). The underlying processes that (appear to) impact the types of forbs and their abundance along the elevation gradient are soil moisture/type, cover, competition, and disturbance.
I have soil-sampled (through hand texturing) each of my quadrats and it seems that the soil moisture content is related to the types of forbs that I find at various elevations. I initially expected to see a steady decline in soil moisture as elevation increased; however, soil moisture was not directly related to elevation in all locations. Areas with dense shrub cover appear to have higher soil moisture than areas without cover at similar elevations. In addition, the quadrats shaded by heavy shrub cover do not appear to have the same community structure as quadrats with similar soil moisture and are not shaded. Therefore, this has led me to believe that competition from shrubs and canopy cover may also influence the community structure of forbs in the area.
Finally, it is notable that some transects have an elevation difference of 25 meters (from the lowest quadrat to the highest quadrat). The study area maintains a (relatively) consistent river depth throughout the year because of its close proximity of a weir (which was constructed for the purpose of maintaining a consistent water level within the city). Therefore, flood disturbance does not likely play a major part in community structure at higher elevations. However, the modest fluctuations in river depth do submerge the lowest quadrats when the river is high. Therefore, flooding may also be an influence on forb community structure within my study location.
On a broader, theoretical level: different species of forb within my study area are likely to have a wide variety of adaptations to deal with disturbance, water submergence, drought, and shade. While these adaptations remain unknown to me at the moment, I can speculate on several adaptations that some of the forb species may have. For example: it is possible that drought tolerant species (found closer to the uplands) have deeper roots (that can penetrate lower in the soil to access groundwater) than the forb species that exhibit a preference for areas with higher levels of water saturation. Conversely, species that exhibit a high preference for low elevations may have adaptations to prevent them from becoming waterlogged by high levels of water saturation.
Keywords: Riparian vegetation, forb community structure, elevation gradient
