PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Growth and abundance of buckthorn (Rhamnus cathartica) and bur oak (Quercus macrocarpa) saplings in a west central Minnesota forest as a function of light availability and soil moisture.
Patten, Ruth*,1, Wyckoff, Peter1, 1 University of Minnesota-Morris, Morris, MN, USA
ABSTRACT- In a prior study we reported that invasive European buckthorn (Rhamnus cathartica) is the most abundant tree species at five forested sites along the prairie-forest border in western Minnesota. Here we compare growth and microsite utilization for European buckthorn and bur oak (Quercus macrocarpa) saplings at one of those sites, a forest near Herman, Minnesota. The canopy layer at the site is dominated by bur oak, green ash (Fraxinus pennsylvanica), basswood (Tilia americana) and hackberry (Celtis occidentalis), while buckthorn dominates the subcanopy. Buckthorn and bur oak are the only two tree species at the site with substantial seedling and sapling pools. We assessed light conditions for 60 buckthorn and 40 bur oak saplings using both fish-eye photographs and the ratio of above canopy to open site PAR for target individuals. Soil moisture for the same saplings was measured repeatedly using TDR. After measuring height and diameter of our target saplings, we sacrificed them and assessed growth by measuring annual rings. Compared to bur oak, buckthorn saplings are found in significantly darker microsites with higher soil moisture. Light and soil moisture explain approximately half of the variation in growth seen among buckthorn saplings. The relationship between growth and microsite condition is less clear for bur oak. Limited success of buckthorn in light, dry microsites suggests that the invasive European tree will not lead the charge as forest moves out into the prairies of western Minnesota, but may subsequently follow as a new forest develops.
Key words: Rhamnus cathartica, Quercus macrocarpa