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AN ABSTRACT OF THE THESIS OF Thomas Roy Rambo for the degree of Master of Science in General Science presented on December 2, 1997. Title: Ecology of Forest Floor Bryophytes in Pseudotsuga menziesii- Tsuga heterophvlla Stands of Western Oregon: Implications for Forest Management. Redacted for privacy Abstract approved: Patricia Muir Species richness and abundance of forest floor bryophytes, including epiphytes from incorporated litterfall, were assessed at two sites in western Oregon. Bryophyte diversity, abundance, and community composition were compared between sites, and between young forest stands (-55 yrs.) and old-growth stands (400+ yrs.) within each site. Relationships of stand structural features to diversity and community composition were assessed by stratifying sampling between "diversity" plots placed in areas of greater structural diversity, such as hardwood openings and remnant old-growth trees, and "matrix" plots situated within the remaining more homogeneous conifer-dominated forest matrix. Bryophyte relationships to substrate and stand age were quantified using the method of Dufrene and Legendre, which combines a species' relative abundance and relative frequency to calculate that species' importance in relation to environmental variables. The resulting "indicator value" describes a species' reliability for indicating the given environmental parameter. Ninety-three bryophyte species were found. Thirty-nine were indicative of either humus, a decay class of coarse woody debris, or stand age. A suite of bryophytes indicated old-growth forest. These were mainly either epiphytes associated with older conifers or liverworts associated with coarse woody debris. Hardwood-associated epiphytes mainly indicated young stands. Richness, particularly for liverworts, was significantly higher in old-growth than young stands, and the two ages differed significantly in community composition Substrate (ground versus coarse woody debris) and overstory (conifers versus hardwoods) were most strongly correlated with variation in bryophyte community composition. Composition changed along the continuum of coarse woody debris decomposition from recently fallen trees with intact bark to forest floor humus. Relatively open hardwood-dominated diversity plots differed in composition from matrix plots. Bryophyte abundance was lower in denser stands and plots, and positively correlated with canopy gaps, percentage of hardwoods, and incident solar radiation. The generality of inferences derived from results is limited by the number of stands studied. Landscape level factors such as topography and prevailing slope and aspect may influence results between sites and ages. However, results suggest that 1) availability of light may limit bryophyte productivity in these stands, 2) bryophyte richness increases with stand continuity, 3) older conifers, hardwoods, and coarse woody debris foster habitat complexity and diversity of bryophytes, and 4) diversity of forest floor bryophytes will be enhanced when a full range of coarse woody debris decay classes is present. Implementation of strategies to protect these biological legacies when thinning managed stands is consistent with an ecosystem approach to forest management. ©Copyright by Thomas R. Rambo December 2, 1997 All Rights Reserved Ecology of Forest Floor Bryophytes in Pseudotsuga menziesii-Tsuga heterophylla Stands of Western Oregon: Implications for Forest Management by Thomas Roy Rambo A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented December 2, 1997 Commencement June 1998 Master of Science thesis of Thomas Roy Rambo presented on December 2, 1997 APPROVED: Redacted for privacy Major professor, representing General Science Redacted for privacy Dean of theColleg/ofScience Redacted for privacy Dean of Gradifte School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Redacted for privacy Thomas Roy Rambo, Author ACKNOWLEDGMENTS The Bureau of Land Management, Eugene and Salem Districts, provided initial research funding in conjunction with their Density Management Studies. Nancy Wogen of the Eugene District was instrumental in making this possible. Peter O'Toole also of the Eugene District and Ed Hendricks of Longview Fiber assisted with logistics. The National Biological Service provided the majority of funding, and John Tappeiner of Oregon State University facilitated that support. Additional financial support came from Research Assistantships with Bruce McCune and Patricia Muir, and Teaching Assistantships at Oregon State University. Dan Norris, Wilf Schofield, and especially Bengt Jonsson, unselfishly contributed time and enthusiasm to aid in understanding bryophyte taxonomy and ecology. Peter Neitlich did much of the plot layout and characterization for this work. Bruce McCune contributed in innumerable behind the scene ways, helped elucidate multivariate analysis and cryptogam ecology, and reviewed these manuscripts. Julia Jones critiqued the thesis from a landscape ecology perspective, and Suzanne McAlister and Bengt Jonsson also provided helpful criticism of Chapter 2. TABLE OF CONTENTS Page Chapter 1. Introduction 1 Chapter 2. Forest Floor Bryophytes of Pseudotsuga menziesii-Tsuga heterophylla Stands in Oregon: Influences of Stand Age and Overstory 8 Abstract 9 Introduction 9 Study sites 11 Methods 12 Field 12 Analysis 14 Results 15 Comparisons between Sites 15 Comparisons between Ages 22 Comparisons between Diversity and Matrix Plots 23 Community analysis 23 Discussion 28 Comparisons between sites: influences of substrate and climate 28 Comparisons between sites: influence of overstory 29 Comparisons between sites: influence of air quality 30 Comparisons between ages: influence of stand continuity 31 Comparisons between ages: influences of substrate and climate 32 Comparisons between diversity and matrix plots 34 Conclusions 35 Chapter 3. Forest Floor Bryophytes as Indicators of Substrate and Stand Age 36 Abstract 37 Introduction 37 TABLE OF CONTENTS (continued) Page Study sites 39 Methods 41 Results 43 Decay Class II Wood 45 Decay Class III Wood 47 Decay Class IV Wood 48 Decay Class V Wood 48 Ecological groups across substrates 49 Stand Ages 49 Discussion 50 Substrate 50 Stand Age 53 Conclusions 55 Chapter 4. Conclusions 57 Bibliography 60 Appendices 70 LIST OF FIGURES Figure Page 2.1 Ordination of plots (n60) in species space across sites, using data relativized by species maxima 21 3.1 Indicator values (p <0.001) for Isothecium myosuroides and three ecological groups of bryophytes by substrates of coarse woody debris (CWD) decay class and humus. 46 LIST OF TABLES Table Page 2.1 Moss species inventory across sites 16 2.2 Liverwort species inventory across sites 18 2.3 Comparisons of site-level richness (7), plot-level richness (a), and Shannon diversity index for mosses, liverworts, and total bryophytes between sites (ANOVA) 19 2.4 Comparisons of site-level richness (-y), plot-level richness (a), and Shannon diversity index for mosses, liverworts, and total bryophytes between stand ages (ANOVA) 19 2.5 Comparisons of overstory basal area, % microplots on coarse woody debris, % bryophyte cover, and potential incident radiation between sites, between stand ages across and within sites, and between diversity and matrix plots 20 2.6 Comparisons of community composition across plots (n) between sites, ages across and within sites, and between diversity and matrix plots (types) across and within sites and ages (MRPP) 22 2.7 Strongest correlations of environmental variables and bryophyte species with ordination axes across sites and ages (NMS) 24 2.8 Strongest correlations of environmental variables and bryophyte species with ordination axes (NMS) for Lookout Point 24 2.9 Strongest correlations of Lookout Point young stand environmental variables and bryophyte species with ordination axes (NMS) 25 2.10 Strongest correlations of environmental variables and bryophyte species with ordination axes (NMS) for Bottomline, using untransformed data 26 3.1 Bryophyte species found on humus or decaying wood, categorized by ecological group according to their most usual habitat. 43 3.2 Bryophyte indicator values by substrate at each site and in stand ages across sites. 44 3.3 Bryophytes as indicators of stand age 47 LIST OF APPENDICES Appendix Page Approximate locations of adjacent young and old-growth stands at Lookout Point (T1S R5E S13) 71 Approximate locations of adjacent young and old-growth stands at Bottomline (T21S R5W Si, T2OS R5W S33, respectively) 72 Approximate locations of research plots in Lookout Point young stand 73 Approximate locations of research plots in Lookout Point old-growth stand 74 Approximate locations of research plots in Bottomline young stand 75 Approximate locations of research plots in Bottomline old-growth stand 76 Bryophyte indicator values for substrates within each stand 77 Data (see disk enclosed in pocket) 79 Ecology of Forest Floor Bryophytes in Pseudotsuga menziesii-Tsuga heterophylla Stands of Western Oregon: Implications for Forest Management Chapter 1. Introduction The Sustainable Biosphere Initiative names biological diversity as one of its three Research Priorities (ESA 1991). Elaborating upon this priority, more specific areas of concern are presented, including anthropogenic changes in patterns of genetic, species and habitat diversity;