CONTROL OF VEGETATION MICROCLIMATES ON SHALLOW GROUND TEMPERATURES ABOVE CONTINUOUS PERMAFROST

The Arctic is warming at four times the rate of the global average, altering Arctic vegetative regimes. Tundra vegetation is responding rapidly to this warming, and shrubs are becoming more prevalent farther north in the Arctic. Vegetation is known to affect ground temperatures and seasonal thaw depths, and thus can influence permafrost stability. As Arctic vegetation can increase ground temperatures through processes such as snow-trapping and decrease temperatures through sun-reflectance, Arctic vegetation can contribute to the degradation of continuous permafrost and eventual ground subsidence. The strength of these effects varies greatly across vegetation types with larger-stature vegetation (>45cm), such as shrubs in the salix and betula genera, having the greatest effect. Due to some vegetation canopies being quite dense, microclimates can exist in patches of dense shrub beneath the vegetation canopy but above the ground. Temperatures in these microclimates are separated from air temperatures that exist above the canopy, and can act as a buffer between these air temperatures and shallow ground temperatures. This study measured temperatures both within vegetation microclimates at a height of 5 to 7 centimeters and in the ground beneath both shrub and grass-type vegetation at five centimeters depth using thermocouple wire and a CR1000 datalogger. Study sites were located on one south facing hillslope and one north facing hillslope located on the North Slope of Alaska, separated by a distance of roughly 23 kilometers. Preliminary results suggest a maximum summer temperature difference of eight degrees Celsius between the two study sites in soil temperatures beneath similar shrubs, indicating that shrub type may not have a direct control on microclimate temperatures. Instead, potential controls on the difference of temperature between the two study locations may be due to topographic or environmental controls such as slope, aspect, topographic exposure, snow cover duration, or vegetation height and density. Ongoing research will examine these predictive parameters, and attempt to find relationships between field observations and remotely-sensed values and shallow soil temperatures beneath Arctic vegetation.