Snow removal and ambient air temperature effects on forest soil temperatures in Northern Vermont

We measured deciduous forest soil temperatures under control (unmanipulated) and snow-free (where snow is manually removed) conditions for four winters (at three soil depths) to determine effects of a snow cover reduction such as may occur as a result of climate change on Vermont forest soils. The four winters we studied were characterized as: 'cold and snowy', 'warm with low snow', 'cold with low snow', and 'cool with low snow'. Snow-free soils were colder than controls at 5- and 15-cm depth for all years, and at all depths in the two cold winters. Soil thermal variability generally decreased with both increased snow cover and soil depth. The effect of snow cover on soil freeze-thaw events was highly dependent on both the depth of snow and the soil temperature. Snow kept the soil warm and reduced soil temperature variability, but often this caused soil to remain near 0degreesC, resulting in more freeze-thaw events under snow at one or more soil depths. During the 'cold snowy' winter, soils under snow had daily averages consistently >0degreesC, whereas snow-free soil temperatures commonly dropped below -3degreesC. During the 'warm' year, temperatures of soil under snow were often lower than those of snow-free soils. The warmer winter resulted in less snow cover to insulate soil from freezing in the biologically active top 30 cm. The possible consequences of increased soil freezing include more root mortality and nutrient loss, which would potentially alter ecosystem dynamics, decrease productivity of some tree species, and increase sugar maple (Acer saccharum Marshall) mortality in northern hardwood forests.