Hydrological and thermal properties of moss and lichen species on rock barrens: Implications for turtle nesting habitat

Abstract In central Ontario, Canadian Shield rock barrens are a dominant geographic feature supporting at‐risk reptiles near their northern range limit. To better understand the characteristics of the organic soil that make Canadian Shield rock barrens suitable turtle nesting habitat, we measured moisture retention and evaporative potential and calculated the thermal properties of lichen ( Cladonia ) mats and moss ( Sphagnum and Polytrichum ) cushions, as well as their underlying mineral–organic soils. The upper soil profile consisted almost entirely of low density (14–49 kg m −3 ), high porosity (72–98%) organic matter (loss on ignition [LOI] of 84–99%), which transitioned rapidly to comparatively high density (304–815 kg m −3 ) mineral–organic soil (LOI of 10–85%). In contrast to Sphagnum and Cladonia , under laboratory conditions, Polytrichum was able to maintain an evaporation rate well above the open‐water potential for several days during a drying experiment. Overall, contrasts in composition and water retention between soil layers are likely to dampen diurnal temperature fluctuations. However, differences in potential water loss between species will have a direct impact on soil thermal dynamics, particularly if substantial water loss occurs in the mineral–organic layer. Because soil depth and temperature regulation by moisture content and soil composition are an important component of nesting habitat, this research provides evidence for the need to conserve moss/lichen ‐ dominated habitats within turtle species' home ranges. Understanding the ecohydrological controls and limits to how these key moss/lichen species develop and influence primary peat formation represents a critical research need for habitat restoration strategies.