Transcript Composition and ecology of bryophyte communities on oak

Composition and Ecology of Bryophyte Communities on Oak (Quercus spp.)
Woody Debris in a Mixed-oak Forest of Southern Ohio, USA
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
Methods and Materials
•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
Northeast
Results
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•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)
•Cover correlated with various plot- and log-level
parameters (Table 1)
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
15
10
0
20
40
60
80
100
120
140
Log
Figure 1. Species-area curve of bryophytes collected from
165 Quercus spp. logs. The curve was constructed with the
first log as the smallest and the last log as the largest.
12
10
8
0.5
Percent Solid
Log Volume
Pylaisiadelpha
tenuirostris
Platygyrium repens
Slope Aspect
Landform Index
4
2
-0.5
Dicranum
flagellare
Hypnum
imponens
Percent
Fragmented
Dicranum montanum
Nowellia
curvifolia
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Axis 1
Solid log
Small log
Southwest slope
Ridge
Fragmented log
Large log
Northeast slope
Valley
Results
0
1-5
5-10
10-25
25-50
50-75
75-100
Figure 2. Frequency of bryophyte species
occurrences on 165 Quercus spp. logs.
Platygyrium repens is common and
widely distributed on logs, stumps
and tree trunks. Despite its small
size, it is distinctive because it forms
spreading patches that have a
peculiarly oily-looking, shiny, darkgreen sheen. Many of the branches
are terminated by dense clusters of
asexual reproductive structures.
Lichen Cover
Figure 3. CCA biplot of bryophyte species and environmental
variables (blue). Note: Individual logs not shown for clarity.
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Commonly Encountered Bryophytes*
Hypnum imponens is a distinctive,
relatively large pleurocarp that often
covers logs. It is pinnate, and its
shiny tapered leaves are swept to
opposite sides of the branches
(secund). Three other Hypnum
species were also found in this
study.
Plot CWD Volume
Hypnum curvifolium
160
Percentage of logs
Dicranum flagellare is a narrowleaved acrocarp that occurs mainly
on coarse woody debris at the study
site. In addition to producing spores,
this species reproduces by means
of asexual brood branchlets.
Thuidium delicatulum
0.0
5
0-1
Thuidium delicatulum is aptly
termed the “fern moss” due to its
bipinnate growth form. It commonly
covers stumps and logs. The leaf
cells have projecting points
(papillae), and the stem is clothed
with minute filiform appendages
(paraphyllia).
1.0
0
Southwest
Northeast- and southwest-facing slopes showing the
change in microsite conditions related to topographic
gradients. (Note: photos taken seconds apart).
20
Small woody debris load
Elevated lichen cover
Study Site
Steerecleus serrulatus
Axis 2
Large woody debris load
Low lichen cover
1.5
Number of species
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 < 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.
Number of bryophyte species
Abstract
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
Table 1. Plot and study log parameters and correlation with
percent bryophyte cover and Platygyrium repens cover. Only
significant correlation coefficients (P < 0.05) are reported.
Correlation Coefficients
Parameter
Mean (± SE)
All
Bryophytes
P. repens
Plot:
Percent slope
23.5 ± 1.7
Landform index†
16.2 ± 0.8
Slope aspect (˚)
180.9 ± 13.3
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
Sapling density (stems ha-1)
2702.8 ± 120.3
Sapling basal area (m2 ha-1)
1.7 ± 0.1
-0.299
0.237
0.194
Study log:
Aerial (%)
14.5 ± 1.7
Volume (m3)
1.0 ± 0.1
Litter cover (%)
6.7 ± 0.7
Lichen cover (%)
5.1 ± 0.7
•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)
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
0.332
0.291
0.383
Surface structure (%):
Examples of moderately decayed woody debris
Goals
•Determine the bryophyte community composition
on woody debris
•Identify factors that influence bryophyte species
distribution and community composition
Data Analysis
•Correlation analysis to investigate possible
relationships between bryophyte cover and
measured parameters
•Canonical Correspondence Analysis (CCA) used
to simultaneously study environmental variables
and community response
•Stepwise variable selection used to select
important environmental parameters for
analysis
•Only species present on 5% of logs included
in analysis (9 species)
Nowellia curvifolia is a common
leafy liverwort found almost
exclusively on decorticated logs.
The leaves are deeply concave,
giving the slender stems a tubular
appearance.
Bark
8.6 ± 1.7
Solid
11.1 ± 1.6
0.256
Punky
67.0 ± 2.1
-0.228
Fragmented
13.2 ± 1.4
†Landform
index is a measure of slope position; small values = ridges,
and large values = valleys.
*Moss line drawings from Crum and Anderson 1981; Nowellia from Hicks 1992.
Casehardened log lacking sapwood and exhibiting a dry, gray
rind. Bryophytes growing on log are Platygyrium repens and
Dicranum sp.
Acknowledgements
Ohio Department of Natural Resources (Dave Swanson)
Hanover College Faculty Development Committee
Barbara Andreas
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