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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 25 •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. 6 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 1.2