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Ca:Al ratio effects on competition between arbuscular
mycorrhizal and ectomycorrhizal forest trees
POSTER OR TALK: Biodiversity and Ecology or
Mycorrhizae in Stressed Ecosystems
DECKER, KELLY L.M, SHERRI J. MORRIS, and RALPH E.J. BOERNER
Department of Plant Biology, Ohio State University, Columbus,
OH 43210 USA
ICOM1 Abstract
In the deciduous forest of eastern North America, the
abundance of species of trees dependent on ectomycorrhizae,
such as oaks (Quercus spp.) and hickories (Carya spp.) has
declined over the last two decades while the abundance of
species dependent on arbuscular mycorrhizae, such as maples
(Acer spp.) and yellow-poplar (Liriodendron tulipifera) has
increased. We hypothesize that this shift in dominance is
the consequence of the effects of heavy N deposition and
decreasing soil Ca:Al ratio on both plants and fungi. In
this study, we examine the effect of lowering the Ca:Al ratio
from 100 to 4 under high N conditions on growth and
competitive interactions between second year seedlings of
ectomycorrhizal red oak (Quercus rubra) and arbuscular
mycorrhizal yellow-poplar (Liriodendron tulipifera).
Overall, the relative growth rate of yellow-poplar seedlings
exceeded that of red oak seedlings, although the difference
was greater at the higher Ca:Al ratio. When in interspecific
competition, yellow-poplars outgrew red oaks at both Ca:Al
ratios. The relative growth rate of red oak seedlings was
relatively insensitive to competition, whereas yellow-poplar
plants grew faster when in inter- than intraspecific
competition. Under these high N conditions, yellow-poplars
were competitively superior to red oaks regardless of Ca:Al
ratio. We will also discuss the impact of Ca:Al ratio on N
uptake, C and N allocation to leaves, stems, and roots and
the effects of Al on the fine structure of ectomycorrhizal
roots.