Plant-Soil Feedbacks and Subalpine Fir Facilitation In Aspen-Conifer Forests

This thesis includes two studies. First, changes in soil characteristics resulting from prolonged conifer dominance in successional aspen-conifer forests were studied. The primary objective of this paper was to identify how increasing conifer dominance that develops in later successional stages alters forest soil characteristics. Soil measurements were collected along a stand composition gradient, which includes the range of conditions that exists through the stages of secondary succession in aspen-conifer forests. Soil chemistry, moisture content, respiration, and temperature were measured. There was a consistent trend in which aspen stands demonstrated higher mean soil nutrient concentrations than adjacent meadows, mixed or conifer stands. Soil moisture was significantly higher in aspen stands and meadows in early summer. Soil respiration was significantly higher in aspen stands than conifer stands or meadows throughout the summer. The results indicate that soil resource availability and respiration peak within aspen dominated stands that are present during early succession and then decrease a