My study was conducted to understand tree community
structure and how soil moisture and fire frequency
influence them. Eighteen plots were placed in the Edge of
Appalachia Nature Preserve of unglaciated southern Ohio:
nine within a prescribed burn site and nine control sites
outside the burn. Sites were stratified in triplicate
across GIS-derived integrated soil moisture index (IMI)
classes. Burning was done in 1996. Overstory species dbh
and sapling species were sampled 1997, 2001, and 2008.
Overstory stems were located in 2009 using range finders.
Stem locations were loaded into GIS using novel techniques
to quantify individual stem IMI values.
Nonmetric multi-dimensional scaling identified greater
heterogeneity among intermediate and mesic sites than xeric
sites. Multi-response permutation procedures did not detect
community differences between burned and unburned sites,
but did detect strong (A=0.3 to 0.2, T=-3.6 to -4.1)
distinct community differences that were statistically
significant (P < 0.05) among xeric, intermediate, and mesic
IMI classes. Analysis of variance identified significant
initial effects of burning on Carya saplings and overstory
Sassafras albidum stems, as well as lasting effects
significant on Carpinus caroliniana.
ANOVA detected significant differences across all
sampling years in sapling relative number for Acer rubrum,
Sassafras albidum, and Carpinus caroliniana saplings, as
well as Quercus prinus, and Liriodendron tulipifera
overstory stems between IMI classes. Bonferroni adjusted
Kolmogorov-Smirnov tests were used to identify and quantify
IMI habitat restrictions of species. Quercus prinus
dominated xeric sites (IMI quartiles 18-24), Carya occupied
intermediate sites (IMI quartiles 22-44), Acer saccharum
occupied intermediate to mesic sites (IMI quartiles 33-44),
Sassafras albidum (IMI quartiles 20-40, IMI median 43) and
Liriodendron tulipifera (IMI quartiles 39-45) were
restricted to mesic sites. My results suggest that greater than one prescribed burn is needed to influence tree
community structure; however, some species can be affected
by a single burn. Tree communities within a continuous
forest region appear to segregate along an IMI gradient.
Xeric regions present greater homogeneity than intermediate
or mesic regions. However, my results also suggest that
specialization does not occur just at the extremes of the
gradient, but also in intermediate sites. This finding
presents interesting avenues for future research of
potential species-specific landscape genetic structures
that would be reflective of moisture regimes within a
continuous forest. One other possible future application is
the use of these novel techniques to resolve and quantify
environmental and spatial variables for individual stem
with a high degree of accuracy in other study systems.