Jordao , Emilie Marques , Hippensteel, Christopher , Simons, Ashlie , Dannenhoffer, Joanne .
Populus tremuloides tree growth in grassland alvar and forest ecosystems on Drummond Island, MI.
Alvars are natural areas characterized by a discontinuous thin layer of soil over limestone/dolomite bedrock. Grassland alvars have sparse vegetative cover but only scattered shrubs and trees. Populus tremuloides (quaking aspen) is the primary tree invader from the surrounding woodlands into the Maxton Plains grassland alvar on Drummond Island, MI. We observed that these alvar aspens had an unusually rounded canopy and dwarfed stature instead of the typical pyramidal canopy and tall stature of nearby forest aspens. Therefore, we compared the growth patterns of quaking aspen individuals growing on the alvar to aspens growing in nearby forest ecosystems. In 2005, clones and individuals were chosen to measure both trunk and branch growth. Sixty trees were measured for the following tree variables: height and diameter at breast height (DBH). Branch growth variables measured were: branch diameter, average growth and number of leaves on twigs, and whether the branch tip lost apical dominance. Branch diameter of aspens was not different between the two ecosystems, but alvar aspens had fewer leaves per twig and shorter twig growth than forest aspens. The frequency of lateral buds replacing apical buds was higher for the alvar aspens than forest aspens. For trunk growth, the height of the aspens did not differ but the mean DBH of alvar aspens was double that of forest aspens. In 2010, an additional 60 individuals were analyzed for trunk variables including taller, more mature forest aspen trees. Height, DBH, and canopy area were measured. Aspens growing in forests were on average 2.4 times taller, and 1.5 times wider than aspens growing on alvars. Comparing trees of equal diameters, forest aspens were about twice as tall as alvar aspens. This may suggest that alvar aspens do not reach their growth potential in height but do continue to increase in diameter. Stunted Thuja occidentalis growing in a similarly adverse environment on cliff faces of the Niagara Escarpment are very old, exceeding 300 years in age. We are currently coring alvar and forest aspens in order to determine if alvar aspens are also unusually old, and if alvar conditions are allowing aspens to outlive their typical life expectancies. Alvars may provide insight into the effects of climate change on terrestrial ecosystems given aspens' abilities to respond to variable conditions such as high temperature regimes, drought, and a lack of nutrients and rooting space.
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1 - Central Michigan University, Biology, 217 Brooks Hall, Mount Pleasant, MI, 48859, USA
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:45 PM