Summary
The amount of ferric hydroxide plaque deposited on Typha latifolia roots varied between wetlands submerged throughout the growing season. Plaque formation was positively correlated with extractable iron in the substrate and pH, and negatively correlated with the percent organic matter and percent inorganic carbonates in the soil. All the above correlations were significant but weak, and in a stepwise regression analysis these four soil factors accounted for 72% of the variation in plaque deposition. Plaque formation was unrelated to soil texture.
Methodology
Seven southern Ontario wetlands, exhibiting a wide range of physical characteristics, were chosen for this study (Fig. 1). They had populations of T. latifolia with markedly different levels of iron plaque on their roots (Macfie, 1986). The wetlands were visited during mid-September when the maximum level of plaque deposition on T. latifolia roots occurs (Crowder and Macfie, 1986).
A 20-m transect was established in each wetland in areas which remained submerged year round. In the marsh-like wetlands, transects ran from within 1 m of the water's edge, through the T. latifolia stand. In the ditch-like wetlands, the transects ran through the cattails parallel to the water's edge. Ten sampling points were marked along each transect (2-m intervals). Soil and plant roots were collected from each point.