Composition and Ecology of Bryophyte Communities on Oak (Quercus spp.) Woody Debris in a Mixed-oak Forest of Southern Ohio, USA

1
Composition and Ecology of Bryophyte Communities
on Oak (Quercus spp.) Woody Debris in a Mixed-oak
Forest of Southern Ohio, USA

• Darrin L. Rubino1, Robert A. Klips2, Brian C.
  McCarthy3
• 1Department of Biology, Hanover College, Hanover,
  IN 2Department of Evolution, Ecology, and
  Organismal Biology, The Ohio State University at
  Marion, Marion, OH 3Department of Environmental
  and Plant Biology, Ohio University, Athens, OH

Abstract Bryophytes are a ubiquitous component of
forested ecosystems, but little is known about
their community composition and the factors that
influence their distribution in many forest
types. The goals of this investigation were to
identify the members of the bryophyte community
found on woody debris in topographically
dissected mixed-oak forests and to identify
parameters that influence community composition
and species distributions. In a southern Ohio
forest, 50 plots were constructed across slope
aspects and slope positions throughout the
landscape to maximize microsite variability 165
oak (Quercus spp.) logs were selected for
analysis. Twenty-five bryophyte species (24
mosses 1 liverwort) were collected. Total moss
cover was significantly (P lt 0.05) positively
correlated with slope aspect, log volume, and
lichen cover. Cover of Platygyrium repens, the
most commonly encountered species, was
significantly correlated with tree basal area
(), lichen cover (), percent of the log that
was solid (), percent of the log that was
fragmented (-), and landform index (a
quantitative measure of slope position-).
Canonical correspondence analysis revealed that
slope aspect, landform index, log volume, plot
woody debris volume, percent lichen cover, and
the percentages of the log that were fragmented
or solid explained a significant amount of
variation in the bryophyte community. Species
separated along a proposed moisture and decay
gradient suggesting that dry, casehardened logs
and moist, friable logs support unique bryophyte
communities. Ultimately, bryophyte distribution
and abundance is influenced by factors that vary
at the landscape, plot, and log scales.

• Methods and Materials
• Study Site
• Waterloo Wildlife Research Station, Southeast
  Ohio (Athens County)
• Mixed-oak forest
• Second growth (150 yr-old)
• Allegheny Plateau
• Highly dissected topography
• Much microsite variability related to daily
  insolation and moisture
• Complex mixture of microhabitats throughout the
  landscape
• Xeric conditions steep slopes, ridges,
  southwest-facing slopes
• Mesic conditions gentle slopes, valleys,
  northeast-facing slopes

• Results
• 165 logs studied
• 13,591 sampling points
• Twenty-five bryophyte species collected
• 24 mosses
• 1 liverwort
• Species area curve does not reveal asymptote
  (Fig.1)
• Species richness and distribution
• Range 0 7 species log-1
• 1.7 0.1 species log-1 (mean SE )
• Great among species variability in commonness
  (Fig. 2)
• Bryophyte cover
• 16.7 1.3 (mean SE)
• Range 0 81.8
• Cover correlated with various plot- and log-level
  parameters (Table 1)
• Platygyrium repens
• Most commonly encountered bryophyte
• 70 of logs
• Cover 10.7 1.0 (mean SE)

Figure 3. CCA biplot of bryophyte species and
environmental variables (blue). Note Individual
logs not shown for clarity.

• Results
• Canonical correspondence analysis (Fig 3)
• Seven of the 20 environmental parameters
  explained a significant amount of variation in
  species distribution
• Environmental parameters explained 15.6 of
  variation in species data on Axes 1 and 2
• Axes 1 and 2 strongly correlated with various
  parameters (Fig. 3 see trends in red)

• Introduction
• Bryophytes
• Mosses, liverworts, and hornworts
• Distribution influenced by microhabitat
• Substrate (decaying wood, rock, soil, etc.)
• Light quantity and quality
• Moisture availability
• Represent a unique and diverse community
• Approximately 535 bryophytes in Ohio
• All too often understudied ecosystem component
• Coarse Woody Debris
• Dead and downed tree limbs and boles ( 10 cm
  diameter 0.5 m length)
• Ubiquitous and conspicuous in forested systems
• Serves many roles
• Nutrient reservoir
• Important microhabitat for a wide range of
  organisms
• Maintains biodiversity

• Field Methods
• Fifty 500 m2 plots created across various slope
  aspects, slope positions, and aspect-position
  combinations
• Measured variety of plot and log characteristics
  (Table 1)
• Woody debris
• Identified to lowest possible taxonomic level
• Assigned decay classes (low to high)
• Up to five moderately decayed oak (Quercus spp.)
  logs in each plot selected for bryophyte study
• Moderately decayed logs characterized by
• Little to no bark
• Moderate to complete sapwood degradation
• Pockets of punky and fragmented wood
• No twigs or fine branches
• Transect created across the top of each study log
  from butt to tip
• Every 10 cm along the transect, the surface
  structure of the log was noted
• Bark bark cover
• Solid unfragmented, sound wood
• Punky wood easily dented with fingernail
• Fragmented loose wood fragments that could be
  dislodged with a flicking motion friable
• At each 10 cm point, the presence or absence of
  bryophyte cover was recorded and a collection was
  made if a bryophyte was present

Table 1. Plot and study log parameters and
correlation with percent bryophyte cover and
Platygyrium repens cover. Only significant
correlation coefficients (P lt 0.05) are reported.

• Discussion Conclusions
• Distribution of individual species, like vascular
  plants, are influenced by factors that vary at
  both micro- and macroscales
• Overall moisture and decay gradients likely
  influences bryophyte species distributions
• Bryophyte community consists of mesic and xeric
  specialists
• Platygyrium repens found mainly on solid,
  casehardened logs (photos below) found in xeric
  microhabitats (e.g., ridges)
• Nowellia curvifolia prefers larger (slower to
  dry), fragmented logs in valleys and on mesic
  slope aspects
• Future work
• Explore relationships between relative importance
  of individual species and environmental variables
• Identify bryophyte community composition of other
  species of woody debris

Correlation Coefficients Correlation Coefficients
Parameter Mean ( SE) All Bryophytes P. repens
Plot
Percent slope 23.5 1.7
Landform index 16.2 0.8 -0.299
Slope aspect () 180.9 13.3 0.237
Dominant tree age (yr) 145.9 4.0
Dominant tree height (m) 29.4 0.7
Canopy cover () 80.8 0.8
CWD volume (m3 ha-1) 42.0 5.1
CWD density (pieces ha-1) 282.8 19.3
Tree density (stems ha-1) 320.8 11.7
Tree basal area (m2 ha-1) 31.1 1.3 0.194
Sapling density (stems ha-1) 2702.8 120.3
Sapling basal area (m2 ha-1) 1.7 0.1

Study log
Aerial () 14.5 1.7
Volume (m3) 1.0 0.1 0.332
Litter cover () 6.7 0.7
Lichen cover () 5.1 0.7 0.291 0.383
Surface structure ()
Bark 8.6 1.7
Solid 11.1 1.6 0.256
Punky 67.0 2.1 -0.228
Fragmented 13.2 1.4

• Goals
• Determine the bryophyte community composition on
  woody debris
• Identify factors that influence bryophyte species
  distribution and community composition

Landform index is a measure of slope position
small values ridges, and large values
valleys.
Acknowledgements Ohio Department of Natural
Resources (Dave Swanson) Hanover College Faculty
Development Committee Barbara Andreas