Soil microclimate and chemistry of spruce-fir tree islands in Northern Utah

The objective was to investigate differences in soil properties in high-ele vation tree islands composed of subalpine fir [Abies lasiocarpa (Hook.) Nut t.] and Engelmann spruce [Picea engelmannii Parry ex Engelm.] relative to s emiarid meadows in Northern Utah. We compared snow depths, surface soil tem perature and moisture, and soil chemical properties (0-30 cm) between tree islands and the surrounding meadow. Snow accumulated evenly around the tree islands. Snow depth differences developed during snowmelt when shaded area s to the north of the islands retained snow longer. Less snow accumulated i nside and at the edge of the tree islands. In summer, canopy shading inside the islands slowed soil moisture loss and decreased the magnitude and fluc tuation of soil temperatures relative to the exposed meadow. Tree islands a ffected O horizon mass and chemistry: 6 to 10 kg m(-2) of O material, with higher macronutrient concentrations and lower C/N ratio, had accumulated un der tree cano pies; 3 kg m(-2) in the island interior; and <1 kg m(-2) in t he meadow. Surface soils inside the free islands had significantly higher C and N soil concentrations and higher C/N ratio. The pH of meadow soils was constant with depth (6.22-5.95). Below the trees, the pH in the upper soil was 0.1 to 0.3 units higher than in the meadow and decreased 0.8 to 0.9 pH units with depth. The presence of tree islands significantly modified the soil microclimate and nutrient distribution relative to the surrounding mea dows.