Microenvironment of Lake Huron sand dunes

Abstract

Measurements were obtained of relative abundance of vegetation, edaphic properties, and microclimate characteristics of some initial stages of the Lake Huron sand-dune sequence at Pinery Provincial Park, Ont. Of the five dune habitats sampled, the oldest (transition zone) was distinguishable from the rest on the basis of greater diversity and abundance of vegetation, higher organic matter content, higher moisture-retaining capacity, enhanced concentrations of available K+ and Mg2+, depleted levels of Ca2+ in the surface soil, reduced air turbulence, and slightly higher air temperatures. The midsummer microclimate of the open dune habitat was characterized by extremely high day temperatures at the soil surface (5 cm) with large diurnal temperature fluctuations. Soil moisture content was generally low in the surface layers of the soil, but at depths greater than 10 cm, it was always plentiful (> 2.5% of soil by weight). Canonical variates analysis showed that the transition zone habitat (800 years old) was separated from younger ones (first dune ridge, slack, high beach) on the first canonical variate (V1), which accounted for about 50% of the total dispersion in the data. The discrimination of the transition zone microclimate on V1 was best characterized by difference in soil moisture content at shallow depths (5 and 10 cm) and wind velocity at 50 and 150 cm above the soil surface.