Dissertationes Biologicae Universitatis Tartuensis 131
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DISSERTATIONES BIOLOGICAE UNIVERSITATIS TARTUENSIS 131 DISSERTATIONES BIOLOGICAE UNIVERSITATIS TARTUENSIS 131 DIVERSITY OF LICHEN SPECIES IN ESTONIA: INFLUENCE OF REGIONAL AND LOCAL FACTORS INGA JÜRIADO TARTU UNIVERSITY PRESS Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Estonia The dissertation is accepted for the commencement of the degree of Doctor philosophiae in botany and mycology at the University of Tartu on May 23, 2007 by the Council of the Faculty of Biology and Geography of the University of Tartu. Supervisors: Assoc. Prof. Tiina Randlane and Prof. Jaanus Paal Opponent: Prof. Dr. Christoph Scheidegger, Swiss Federal Research Institute for Forest, Snow and Landscape Research, WSL, Birmensdorf, Switzerland Commencement: Room 218, Lai 40, Tartu, on September 12, 2007, at 10.15 The publication of this dissertation is granted by the Institute of Ecology and Earth Sciences, University of Tartu. ISSN 1024–6479 ISBN 978–9949–11–685–0 (trükis) ISBN 978–9949–11–686–7 (PDF) Autoriõigus Inga Jüriado, 2007 Tartu Ülikooli Kirjastus www.tyk.ee Tellimus nr 290 CONTENTS LIST OF ORIGINAL PUBLICATIONS ....................................................... 6 1. INTRODUCTION .................................................................................... 7 1.1. General introduction .......................................................................... 7 1.2. The objectives of the thesis ............................................................... 9 2. MATERIAL AND METHODS ............................................................... 11 2.1. Study area .......................................................................................... 11 2.2. Study sites ......................................................................................... 12 2.3. Data collection .................................................................................. 13 2.3.1. Lichen sampling ...................................................................... 13 2.3.2. Environmental variables ......................................................... 14 2.4. Data processing ................................................................................. 16 3. RESULTS ................................................................................................ 17 3.1. Effect of area, number of biotopes and isolation on the diversity of lichen species on the islets (Paper I) ........................................... 17 3.2. Factors influencing the diversity of lichen species in forests ........... 19 3.2.1. Stand level (Papers II–III) ...................................................... 19 3.2.2. Tree level (Paper IV) .............................................................. 21 3.3. Distribution and habitat ecology of the forest lichen Lobaria pulmonaria (Paper V) ....................................................................... 23 4. DISCUSSION ........................................................................................... 25 4.1. Biogeographical determinants of the diversity of lichen species on the islets (Paper I) ....................................................................... 25 4.2. Factors influencing the diversity of lichen species in forests (Papers II–V)..................................................................................... 27 CONCLUSIONS ........................................................................................... 31 REFERENCES .............................................................................................. 32 SUMMARY IN ESTONIAN ........................................................................ 42 ACKNOWLEDGEMENTS .......................................................................... 45 PUBLICATIONS ........................................................................................... 47 5 2 LIST OF ORIGINAL PUBLICATIONS The thesis is based on the following publications which are referred to in the text by the Roman numerals: I. Jüriado, I., Suija, A. & Liira, J. 2006. Biogeographical determinants of lichen species diversity on islets in the West-Estonian Archipelago. Journal of Vegetation Science 17: 125–134. II. Jüriado, I., Liira, J. & Paal, J. 2003. Epiphytic and epixylic lichen species diversity in Estonian natural forests. Biodiversity and Conservation 12: 1587–1607. III. Meier, E., Paal, J., Liira, J. & Jüriado, I. 2005. Influence of tree stand age and management to the species diversity in Estonian eutrophic alvar and boreo-nemoral Pinus sylvestris forests. Scandinavian Journal of Forest Research 20: 135–144. IV. Jüriado, I., Liira, J., Paal, J. & Suija, A. Ecological conditions influencing the diversity of epiphytic lichens on temperate broad-leaved trees in Estonian floodplain forests. Manuscript submitted to Applied Vegetation Science. V. Jüriado, I. & Liira, J. Distribution, habitat ecology and conservation impli- cations of the epiphytic forest lichen Lobaria pulmonaria in Estonia. Manuscript submitted to Annales Botanici Fennici. Published papers are reproduced with due permission from the publishers. The author was primarily responsible for data collection and identification of lichens, for surveying and examining the literature, and for the writing of Papers I–II, IV and V. The author substantially contributed to analysing data in Papers I–II, IV and V. In Paper III, the author was responsible for the identification of lichens and participated in writing. 6 1. INTRODUCTION 1.1. General introduction The patterns of species diversity are influenced by factors functioning at different levels of spatial and temporal scales (Ricklefs 1987; Loreau 2000). On a small scale the processes such as biotic interactions (e.g. competition, parasitism), small-scale disturbance, resource availability, and niche differen- tiation predominate in the formation of community structure and diversity (Mouquet et al. 2003; Cottnie & Meester 2004; Ricklefs 2004; He et al. 2005). Factors operating on a large scale cover a variety of ecological and evolutionary processes, historical events and geographical aspects (Ricklefs 1987; Zobel 1992, 1997; Ricklefs & Schluter 1993). The relative importance of local and regional factors in structuring local communities varies among different geographical regions and on the time scale (McCune 2000; Mouquet et al. 2003; Ricklefs 2004; Will-Wolf et al. 2006). The delimiting of scales and processes is difficult as factors acting on a multitude spatial and temporal scales are intercorrelated (Jesberger & Sheard 1973; McCune 1993; Loreau 2000; Ricklefs 2004; Giordani 2006). The main discriminates of diversity patterns are known to depend also on the taxonomical group of organisms (e.g. Nilsson et al. 1988; Ricklefs & Lovette 1999). Most studies deal with vascular plants and vertebrates (Ricklefs & Schluter 1993; Rosenzweig 1995), and less attention has been paid on cryptogams (bryophytes, fungi, algae) and other less conspicuous organism groups. Lichenized fungi (lichens) are symbiotic organisms consisting mainly of two components, fungi (the mycobiont) and algae or cyanobacteria (the photobiont), living in close symbiotic association (Nash 1996). Due to the poikilohydric nature of lichens, they are more dependent on the atmosphere, regarding their metabolic processes, than vascular plants. As the periods of the metabolic activity of lichens are determined mainly by the precipitation and conditions of evaporation, they are generally slow-growing organisms (Armstrong 1988; Nash 1996). Lichens do not have a cuticule which effectively protects the living cells of vascular plants from the free admission of solutions and gases to the living tissues; thus lichens are more sensitive to the chemical content of the atmosphere than terrestrial vascular plants (Gries 1996). Nevertheless, as lichens have no roots and are much smaller in size than most plants, they have an advantage of colonizing a wide range of substrates (Armstrong 1988; During 1992). Owing to these peculiarities of the physiology and morphology of lichens, some factors determining the diversity of lichen communities are more pronounced, or, on the contrary, less important than those crucial for the diver- sity of vascular plant species (Buckley 2002; Löbel et al. 2006a; Paltto et al. 2006). 7 Many epigeic and epilithic lichens can colonize open habitats in the early stages of succession (Lawrey 1984; Longton 1992), e.g. terricolous and saxicolous lichens on islands. Environmental conditions on small islands and on the seashore are rather harsh and unsuitable for most organisms. Yet, many lichens are able to tolerate salinity, repeated drying and wetting, high light intensity, and the destructive effect of the winds and waves (Fletcher 1973a, b; Lawrey 1984). Habitat conditions in forest are much more stable and many of the forest-dwelling lichens favour the balanced light and moisture regime of a climax stand (e.g. old-growth forests) (Esseen et al. 1992; Rose 1992; Will- Wolf et al. 2002). However, occurrence of epiphytes depends first of all on the distribution of host trees, while the chemical and physical properties of the bark are considered more important than the fact to what species a tree belongs (Barkman 1958; Kuusinen 1996b). Species interactions (e.g. competition and facilitation) between lichen species and between lichens and other organisms (e.g. bryophytes) as well as small-scale disturbances also affect the structure of lichen communities (During & van Tooren 1990; Lawrey 1991a). Forest management