Event Title

Environmental and Physiological Drivers of Aspen to Conifer Succession

Event Website

http://www.nafew2009.org/

Start Date

23-6-2009 11:30 AM

End Date

23-6-2009 11:50 AM

Description

An important knowledge gap in aspen ecology is a poor understanding of factors that define aspen to conifer succession dynamics. Environmental conditions in the understory change dramatically as conifers establish in aspen stands. Light levels decrease and soil chemistry (reductions in soil N and C) and structure are modified. These two changes likely have important impacts on regeneration success of aspen suckers and conifer seedlings, the outcome of which will influence shifts in stand composition. We conducted a field and greenhouse study to examine how changes in light environment and soil chemistry that occur along aspen-conifer overstory transition zones (pure conifer, aspen-conifer mix, pure aspen, gap) affect the growth, photosynthesis and leaf defense chemistry of regenerating aspen and subalpine fir. Results from the greenhouse and the field study were consistent. Aspen had substantially greater reductions (>50%) in photosynthesis and growth rates than subalpine fir when grown under low light or on conifer modified soils. Maintenance of subalpine fir growth and photosynthesis on conifer modified soils was a function of greater nitrogen acquisition resulting from an increase in their root:shoot ratio. Leaf defense chemistry of aspen was significantly reduced under mixed and pure conifer stands as a result of reduction in light levels. The results suggest that subalpine fir seedlings have higher fitness than aspen suckers as conifer establishment in aspen stands modify light and soil conditions.

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Jun 23rd, 11:30 AM Jun 23rd, 11:50 AM

Environmental and Physiological Drivers of Aspen to Conifer Succession

An important knowledge gap in aspen ecology is a poor understanding of factors that define aspen to conifer succession dynamics. Environmental conditions in the understory change dramatically as conifers establish in aspen stands. Light levels decrease and soil chemistry (reductions in soil N and C) and structure are modified. These two changes likely have important impacts on regeneration success of aspen suckers and conifer seedlings, the outcome of which will influence shifts in stand composition. We conducted a field and greenhouse study to examine how changes in light environment and soil chemistry that occur along aspen-conifer overstory transition zones (pure conifer, aspen-conifer mix, pure aspen, gap) affect the growth, photosynthesis and leaf defense chemistry of regenerating aspen and subalpine fir. Results from the greenhouse and the field study were consistent. Aspen had substantially greater reductions (>50%) in photosynthesis and growth rates than subalpine fir when grown under low light or on conifer modified soils. Maintenance of subalpine fir growth and photosynthesis on conifer modified soils was a function of greater nitrogen acquisition resulting from an increase in their root:shoot ratio. Leaf defense chemistry of aspen was significantly reduced under mixed and pure conifer stands as a result of reduction in light levels. The results suggest that subalpine fir seedlings have higher fitness than aspen suckers as conifer establishment in aspen stands modify light and soil conditions.

http://digitalcommons.usu.edu/nafecology/sessions/aspen/4