14 (1): 81-91 (2007)

The diversity of epiphytic lichens is affected by a mul-titude of factors inherent to the host tree, as well as char-acteristics of the surrounding landscape. Numerous studies have shown the effects of, e.g., tree species identity, light, humidity, and bark chemistry on lichen communities, as well as of mesoclimate, land use history, and landscape con-figuration (Culberson, 1955; Edwards, Soos & Ritcey, 1960; Adams & Risser, 1971; Rose, 1976; Halonen, Hyvärinen & Kauppi, 1991; Bates, 1992; Dettki & Esseen, 1998; McCune

et al., 2000; Johansson & Ehrlén, 2003; Mistry & Berardi, 2005). Tree age, commonly estimated as trunk diameter, has also often been examined in this context, demonstrat-ing lichen species turnover from young to old tree trunks and the importance of old trees for rare or red-listed spe-cies (Almborn, 1948; Yarranton, 1972; Rogers, 1988; Thor, 1998; Uliczka & Angelstam, 1999; Boudreault, Gauthier & Bergeron, 2000; Kantvilas & Jarman, 2004). However, it is difficult to separate the effect of tree age from that of tree size (Rolstad & Rolstad, 1999; Snäll, Ribeiro & Rydin, 2003; Kantvilas & Jarman, 2004). While physical and chemical bark conditions may be functions of both age and size, there are other factors that specifically relate to either

Tree age relationships with epiphytic lichen diversity and lichen life history traits on ash in southern Sweden1

Per JOHANSSON2, Department of Ecology, Swedish University of Agricultural Sciences, Box 7002, SE-750 07 Uppsala, Sweden, e-mail: per.johansson@nvb.slu.se

Håkan RYDIN, Department of Plant Ecology, Evolutionary Biology Centre, Uppsala University, Villavägen 14, SE-752 36 Uppsala, Sweden.

Göran THOR, Department of Ecology, Swedish University of Agricultural Sciences, Box 7002, SE-750 07 Uppsala, Sweden.

Abstract: We examined the influence of tree- and stand-level conditions on lichen diversity on 143 ash trees, varying in age from 11 to 140+ y, in 5 deciduous stands in southern Sweden. The number of lichen species per tree varied from 2 to 30 and was primarily explained by tree trunk diameter and to a lesser extent by tree age, crown cover, lichen cover, and stand identity. The positive relationship between species richness and lichen cover seems compatible with a random placement of species and suggests that similar factors affect both lichen growth and establishment. Species richness did not increase on trees above 65 y of age, while species composition changed with tree age. Together with the positive linear effect of trunk diameter, these results suggest a slight overall positive effect of area, but that species richness over time depends more on species turnover. In addition, we examined if lichens occurring on trees of different ages differed in life history traits, e.g., spore size, thallus height, and pH preference. The results indicate that lichens that most frequently occurred on old trees had larger spores and thicker thalli than other species, suggesting that lichen species’ response to tree age can be understood to some extent from their life history traits. However, in this respect lichen ecology is still in its infancy.Keywords: crustose lichens, deciduous forest, Fraxinus excelsior, NMS ordination, spore size.

Résumé : Nous avons étudié l’influence des caractéristiques de l’arbre et du peuplement sur la diversité des lichens pour 143 frênes âgés de 11 ans à plus de 140 ans dans 5 peuplements feuillus du sud de la Suède. Le nombre d’espèces de lichens sur chaque arbre variait de 2 à 30. Le diamètre du tronc était le facteur qui expliquait le plus cette variabilité ainsi que, dans une moindre mesure, l’âge de l’arbre, la couverture de la cime, la couverture de lichens et le type de peuplement. La relation positive entre la richesse en espèces et la couverture de lichens semble compatible avec une distribution au hasard des espèces et suggère que les mêmes facteurs affectent à la fois la croissance des lichens et leur établissement. La richesse en espèces n’augmentait plus avec l’âge de l’arbre au delà de 65 ans alors que la composition en espèces variait avec l’âge de l’arbre. En combinaison avec l’effet linéaire positif lié au diamètre du tronc, ces résultats suggèrent un léger effet positif de la surface quoique la richesse en espèce dans le temps soit plus attribuable au renouvellement des espèces. Nous avons aussi examiné si les lichens retrouvés sur des arbres d’âges différents avaient des traits d’histoire de vie tels que la taille des spores, la hauteur des thalles et la préférence au niveau du pH qui différaient. Les résultats indiquent que les lichens retrouvés plus fréquemment sur les vieux arbres avaient des spores plus gros et des thalles plus épais que les autres espèces ce qui suggère que la réponse des espèces de lichens à l’âge de l’arbre peut être expliquée en partie par leurs traits d’histoire de vie. Cependant, sur ce point, l’étude de l’écologie des lichens est encore à ses débuts.Mots-clés : forêt feuillue, Fraxinus excelsior, lichens crustacés, ordination CMN, taille des spores.

Nomenclature: Santesson et al., 2004.

Introduction

1Rec. 2005-10-24; acc. 2006-02-13. Associate Editor: Johannes Kollmann.2Author for correspondence.

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age or size. Stem diameter should correlate with number of species because of the simple species–area effect, while greater age also means a longer time for colonization.

As trees grow, the epiphytic lichen community changes due to both allogenic factors such as bark texture and autogenic factors such as competition and facilitation (Topham, 1977; Rogers, 1988; Stone, 1989; Ruchty, Rosso & McCune, 2001). It could be expected that lichen traits related to establishment and performance will dif-fer between lichens occurring on young versus old trees, just as life history traits generally differ between early and late successional vascular plant species (Huston & Smith, 1987). Therefore, examining physiological and life history traits of species along tree age gradients may reveal, e.g., causes of rarity among rare and red-listed lichens confined to old trees.

In southern Sweden, ash (Fraxinus excelsior) is a com-mon tree of high value as substrate for rare and red-listed lichens (Thor, 1998). In conservation and management schemes it would therefore be valuable to have simple models to assess lichen diversity on ash trees. Parameters in such models could include tree diameter and rapid estimates of light conditions, such as crown and understory cover, as well as factors operating at larger spatial scales than the individual host tree. In this study we examine how lichen diversity on ash relates to tree parameters such as tree age and diameter, light conditions, and stand identity. We dis-

cuss the separate effects of tree size and age for the diversity of lichens and also examine lichen life history traits along the tree age gradient. The specific questions we address in this study are: How do lichen cover, species richness, and community composition on ash trees (Fraxinus excelsior) relate to tree age, tree diameter, and light conditions? What is the relative importance of these tree-level conditions compared to stand-level factors for lichen diversity? Do lichen species occurring on trees of different ages differ in life history traits?

MethodssTudy siTes

The field survey was carried out by P. Johansson in 1997 at 5 sites in the hemiboreal zone (Ahti, Hämet-Ahti & Jalas, 1968) in the province of Uppland in southern Sweden (60° n, 18° e). The sites were selected to include deciduous stands with a high proportion of ash (Fraxinus excelsior) and few conifers. In all stands except at Ekebyholm, a part of a larger forest stand was delimited based on these crite-ria. The size of the delimited stands (hereafter referred to as the stands) was 0.5–2.0 ha, and the proportion of ash trees ≥ 6 cm in diameter at breast height ranged from 30% to 65% (Table I). The actual number of ash trees ranged from 80 to 412, and the age of the sample trees varied from 50 to 140+ y (Table I). Kungsträdgården and Riddersholm were

TabLe i. Descriptive statistics of stands and sampled trees of Fraxinus excelsior within each stand. Mean values for sampled trees are given with standard error (SE).

Biskops Arnö Ekeby holm Kungsträdgården Riddersholm VällensTandsArea (ha) 0.5 1.9 0.8 1.2 0.5Total stem number (≥ 6 cm ) 220 824 244 629 388Total number of Fraxinus excelsior 132 249 80 412 215Proportion (%) Fraxinus excelsior 60 30 33 65 55 Acer platanoides 0 7 14 < 1 < 1 Alnus glutinosa 0 2 1 21 11 Betula spp. < 1 4 2 3 15 Crataegus spp. 0 < 1 4 1 0 Malus spp. <1 0 5 0 0 Picea abies 3 1 1 3 < 1 Pinus sylvestris < 1 0 0 0 < 1 Populus tremula 1 27 0 0 5 Prunus padus 0 < 1 7 3 6 Quercus robur 15 13 7 0 1 Salix spp. 0 < 1 1 < 1 1 Sorbus spp. 0 2 2 2 4 Ulmus glabra 19 11 23 0 0

sampLed TRees Number of Fraxinus excelsior 16 31 29 41 26 Mean tree diameter (cm) 20.2 ± 1.7 20.1 ± 2.0 26.0 ± 3.0 23.8 ± 2.3 21.1 ± 2.1 Mean tree age (y) 44.6 ± 0.8 59.5 ± 4.8 65.5 ± 7.6 68.5 ± 4.9 37.0 ± 3.5 Maximum tree age (y) 50 122 140 140 63 Mean depth of bark crevices (mm) 2.3 ± 0.2 2.2 ± 0.3 3.3 ± 0.6 2.7 ± 0.4 1.9 ± 0.2 Mean stem inclination (°) 3.2 ± 0.8 5.1 ± 0.8 6.2 ± 1.0 10.6 ± 0.8 7.0 ± 1.1 Mean crown cover (%) 83.1 ± 1.8 93.5 ± 1.9 94.5 ± 2.0 93.2 ± 1.2 93.1 ± 2.1 Mean understory cover (%) 14.4 ± 3.8 77.7 ± 2.8 34.8 ± 4.6 31.5 ± 2.8 65.4 ± 4.7 Total number of lichen species recorded on the sampled trees 47 60 80 74 65 Mean number of lichen species/tree 15.5 ± 1.1 12.1 ± 0.8 18.7 ± 0.9 22.0 ± 0.6 13.8 ± 1.1 Mean lichen cover/tree (%) 35 ± 4 39 ± 2.6 38 ± 2.6 47 ± 1.9 39 ± 3.2

managed by grazing, whereas the other stands were unman-aged. The maximum and minimum distances between 2 stands were 87 and 1 km, respectively.

sampLing of TRees and descRipTion of TRee condiTions

In each stand, all trees ≥ 6 cm DBH (diameter at breast height 130 cm above ground) were recorded by species and DBH (220 to 824 trees per stand; Table I). In each stand, 5 ashes in each size class (6–10, 11–20, 21–30, 31–40, and > 40 cm) were then selected by random sampling. In some stands there were fewer than 5 ashes in the largest or next-largest size classes; in these cases, all ashes in the size class were sampled. Parallel to field work, lichen collections were identified in the lab in order to compile accumulated species lists for each stand. After sampling 5 trees in each DBH size class, additional trees were sampled in each stand by random selection among the remaining ash trees, irrespec-tive of DBH class, until the accumulated lichen species list reached an asymptote. In all, we sampled 143 trees (16 to 41 per stand; Table I).

For each tree, age was determined from increment cores taken at 130 cm above ground level. Depth of bark crevices was measured with a vernier caliper and averaged over 16 systematically positioned locations on the tree trunk from 0 to 130 cm above ground (in each corner of the sample plots, see Lichen sampling). The inclination of the tree trunk was measured as degree deviation from vertical. Crown cover around each sampled tree was estimated visually in 10% classes within a 10–m radius around the tree trunk (as tree crown projections to the sky). The cover of the understory vegetation layer less than 5 m high was estimated in 10% classes within a 5–m radius around each sampled tree. Both crown and understory cover can be seen as indirect mea-sures of light, moisture, and temperature conditions (Sillett & Antoine, 2004; Mistry & Berardi, 2005).

Lichen sampLing

For each sampled tree we recorded all lichen species occurring on the tree trunk up to 130 cm above ground level. In addition, we recorded all lichen species occurring in 4 sample plots, 8 × 16 cm (horizontal × vertical), placed on each tree on the north and the south side, at ground level and 130 cm above ground level. In these plots we also mea-sured the total lichen cover: each plot was divided into 18 subplots and cover was measured as the proportion of sub-plots with 100% lichen cover. Species-wise cover was not measured.

Species that could not be identified in the field were collected and identified by microscopy and thin layer chro-matography (HPTLC, Arup et al., 1993) by P. Johansson and G. Thor. Cladonia spp. refers to unidentified phyllo-cladia. Lecanora carpinea coll. may also include L. lepty-rodes. Lecanora subfusca grp. refers to field observations only and may include L. allophana, L. argentata, and L. pulicaris. Lepraria spp. refers to specimens not collected and analyzed by HPTLC. Physcia spp. refers to small and unidentified specimens of either P. adscendens or P. tenella. Physconia sp. refers to small and unidentified specimens. When summing up the species number per tree these collec-tive groups were not included if any of the possible species

within the groups were also identified on that tree. Voucher specimens were deposited in the herbarium at the Museum of Evolution at Uppsala University (UPS).

Life hisToRy TRaiTs

For all species recorded on at least 3 trees, 84 species in total, we compiled data on life history traits (Table II). We included spore length, spore size, dispersal mode, growth form, and thallus height as estimates of species competitive ability and traits that may affect colonization and persis-tence on ageing trees. Dispersal mode was given only as either by spores (sexual) or soredia (vegetative dispersal propagules that disperse algal cells together with fungal hyphae; Table II). For species that develop both soredia and spores, the dispersal mode given was the most commonly observed mode in southern Sweden. Species with isidia, another type of vegetative dispersal propagules, were few and were excluded from the analyses. Photobiont associa-tion was included since it may be important for explaining lichen species occurrence (cf. Wolseley & Aguirre-Hudson, 1997; Lücking, 1999; Sillett & Antoine, 2004), e.g., in Sweden a higher proportion of lichens with Trentepohlia algae are red-listed than species with other green algae (Hallingbäck, 1995). We also tested for associations with overall abundance and distribution in Sweden, and with pH preference, although these characteristics may not be true life history traits but rather consequences of inherent life history traits. Overall abundance and distribution can affect local abundance through, e.g., colonization, however, and there is often a positive relationship between these mea-sures (Gaston, Blackburn & Lawton, 1997). Data on spore length, spore width, dispersal mode, growth form, thallus height, and photobiont were gathered mainly from Purvis et al. (1992) and Foucard (2001), while data on abundance, distribution range, and pH preference were compiled from Hallingbäck (1995) and Foucard (2001). Substrate pH pref-

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TabLe ii. Description of life history traits compiled for all species recorded on at least 3 trees, and tested for associations with species occurrence on trees of various age.

Life history traits DescriptionSpore length average length (mm)Spore size average length × width × thickness (mm3)Dispersal mode sexual versus vegetative dispersal (spores - soredia)Growth form crustose; foliose; fruticoseThallus size six classes: 1) immersed crustose thalli; 2) thin crustose; 3) thick crustose; 4) small foliose (Melanelia spp., Parmeliopsis, Phaeophyscia, Xanthoria polycarpa); 5) large foliose (Hypogymnia physodes, Parmelia sulcata); 6) fruticosePhotobiont Trentepohlia or “other green algae” (there were no species with cyanobacteria)Overall abundance in Sweden given in scale 1–5 (very rare–common) Swedish distribution range given as number of provinces with known occurrence (ranging from 4–29)pH preference given as both minimum and maximum

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erence was taken from a compilation in Hallingbäck (1995), who reported the range in pH preference values for a large number of the species observed in this study.

daTa anaLyses

In a preliminary analysis we examined stand-wise cor-relations among all variables, which revealed variable and opposite relationships among the stands (Table III). Both lichen cover and species richness were correlated with inde-pendent variables, and there were also correlations among the independent variables. Stand-wise linear multiple regres-sions for lichen cover and species richness, including all independent variables, in 4 cases showed a high (> 10) vari-ance inflation factor for bark crevices, and this variable was therefore excluded from further analyses. Stand-wise regres-sions were then repeated, including two-way interaction terms and the quadratic terms of DBH, tree age, and crown and understory cover. Trunk inclination was excluded from these regressions because of its weak overall influence in the linear regressions. Next, we included all 143 trees in one model for lichen cover and one for species richness, simul-taneously evaluating the effects of stand identity, tree age, DBH, and crown and understory cover, with general and stand-wise specific slope coefficients for these variables to account for stand-dependent relationships (y = stand + var. a + var. a(stand) + var. b + var. b(stand) + etc.). Quadratic terms of age and understory cover, and interaction terms of understory cover × age and understory cover × crown cover, were included since the stand-wise regressions indicated significance of these terms. Backward elimination was used to select the final models for each lichen cover and species richness. At each step the variable with the highest P-value was removed, and all variables at P < 0.10 were kept in the final model. For all models we checked the residuals, which were independent and did not show deviation from normal-ity. The stand-wise regressions were performed in Proc reg in SAS (SAS Institute, 2000), while SAS Proc glm was used for the final models.

nms oRdinaTion

Tree-level species composition was examined using non-metric multidimensional scaling NMS (McCune, Grace & Urban, 2002) performed in PC-Ord (McCune & Mefford, 1999). We used a species presence–absence matrix with only species recorded at least on 3 trees, and we also includ-ed unidentified Cladonia spp., Lecanora subfusca 8 grp., and Lepraria spp. when none of the possible species within the respective group were also identified on the tree. In all, 88 taxa and 142 trees were included in the ordination. One

tree at Vällen was excluded due to a very low number of species (2), providing for better resolution in the ordination.

We used the autopilot mode provided in PC-Ord, which performs 40 runs with the real dataset compared with 50 randomized runs, each run with 400 iterations. The dimensionality (number of axes) is automatically selected and added until additional dimensions do not reduce the stress level by at least 5%. The autopilot ordination was repeated using both the Jaccard and the Sørensen distance measures, and the results were very similar among the runs. Stress level did not decrease after 2 dimensions and was 22%, which differed significantly from the random-ized runs (P < 0.05). The final instability was close to 0.0005 in all cases. In this paper we present an ordination based on the Jaccard distance measure. Compositional differences among the stands were examined visually in the ordination graph and also formally tested by Multi-response permutation procedures (MRPP) in PC-Ord using the Jaccard distance measure (Mielke & Berry, 2001; McCune, Grace & Urban, 2002).

Indicator species analysis (ISA), also provided in PC-Ord, was used to identify species that were over-represented in a particular stand, and in a particular tree age class: 18–50 y (72 trees), 51–87 y (51), and 96–140 y (19). The ISA combines, in this case, species relative frequencies and faithfulness to a particular stand or tree age class to calculate indicator values for stands and tree age classes. Monte Carlo randomizations were then used by PC-Ord to test whether species occurred more often than expected by chance in a particular stand or tree age class. Species that were statistically over-represented (at P < 0.05-level) in a particular stand or tree age class were identified as “indica-tor species” for that stand or tree age class.

anaLyses of species Life hisToRy TRaiTs

Relationships between species life history traits and species occurrence at trees of various age were examined for all species with at least 3 records. For each species, the relationship with tree age was given from the param-eter estimate for tree age in a univariate logistic regression with all 143 trees, performed in Proc genmod in SAS (SAS Institute, 2000). Using the overall estimate for tree age was justified by the overall strong influence of tree age and DBH on both species richness and composition. We then used the parameter estimate for tree age as the dependent variable. For the categorical life history variables (growth form, thal-lus height, dispersal mode, and photobiont), we compared the age parameter estimates among the trait categories (e.g.,

TabLe iii. Range of Pearson correlation coefficients among the 5 study sites for the independent variables, lichen cover, and lichen species richness. Correlations with |r| < 0.31 (critical value for n = 41) are non-significant, and all correlations with |r| > 0.50 (critical value for n = 16) are significant at the P < 0.05 level.

Tree age Bark crevices Crown cover Understory cover Inclination Species richness Lichen coverDBH 0.68 – 0.84 0.65 – 0.92 0.13 – 0.43 –0.26 – 0.25 –0.37 – 0.25 0.17 – 0.75 –0.11 – 0.55Tree age 0.53 – 0.91 0.06 – 0.31 –0.20 – 0.12 –0.25 – 0.39 –0.12 – 0.86 –0.25 – 0.77Bark crevices –0.03 – 0.39 –0.19 – 0.49 –0.34 – 0.37 0.07 – 0.72 –0.15 – 0.56Crown cover –0.58 – 0.62 –0.26 – 0.16 –0.50 – 0.60 –0.20 – 0.36Understory cover –0.19 – 0.22 –0.30 – 0.43 –0.37 – 0.03Stem inclination –0.24 – 0.13 –0.21 – 0.27Species richness 0.27 – 0.80

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crustose, foliose, fruticose) in ANOVAs using Proc glm in SAS (SAS Institute, 2000). With continuous traits we used linear regression.

To account for phylogeny we tested for the same relationships between the age estimates and life history traits within phylogenetic groups, i.e., within orders or families with at least 6 species: Arthoniales (11 species), Lecanoraceae (12), Parmeliaceae (6), Pertusariales (8), Physciaceae (8), and Ramalinaceae (15). The systematic classification follows Eriksson (2004) (Appendix I). For most categorical traits we could not test for differences within the phylogenetic groups due to a limited number of species in each trait category. Since all analyses of life his-tory traits were exploratory we did not correct for multiple tests. Spore length, spore size, and distribution range were log transformed before analyses.

ResultsIn total, we found 113 lichen species (Appendix I),

ranging from 47 to 80 per stand, with an average spe-cies number per tree ranging from 12 to 22 among stands (Table I). The lowest number of species on one tree was for an 11-y-old ash tree at Vällen, which hosted Lecania cyrtella and Lecanora sambuci. Two trees hosted 30 spe-cies: one tree at Riddersholm (age 117 y) and one tree at Kungsträdgården (age 130 y). There were consistent posi-tive correlations between lichen cover and species number (Table III). Therefore, lichen cover was included as a pre-dictor variable in the model for species richness.

Lichen coveR

The average tree trunk lichen cover was rather similar among stands, ranging from 35% to 47% (Table I). The correlations between lichen cover and the independent variables showed large variation among stands (Table III). Besides stand identity, tree age and understory cover were the only variables included in the final model for lichen cover, which explained ca 25% of the variation (model adjusted r2 = 0.26). This model included stand, the stand-wise coefficients for tree age, and the quadratic term of understory cover (Table IV). Tree age showed a strong posi-tive relationship with lichen cover at Vällen (Table IV), but a weaker relationship at the other sites. The overall effect of the quadratic term for understory cover indicated that lichen cover was highest at intermediately shaded trees. A scatter-plot for lichen cover against understory cover (not shown) also indicated maximum values for lichen cover at 30–40% of understory cover.

species Richness

For species richness on the tree trunk, the final model explained almost 70% of the variation in the data (adjusted r2 = 0.68). Besides stand identity, there was an overall strong positive effect of tree size (DBH), as well as a stand-specific effect of tree age (Table V). The quadratic term of age gave a slightly better model fit (Figure 1a), and that trend was similar at all 3 stands with trees older than 65 y: Ekeby, Kungsträdgården, and Riddersholm (stand-wise scatterplots not shown). Crown cover had a

stand-dependent positive or negative effect on species richness, while the estimate of understory vegetation cover did not explain species richness (Table V).

For trees up to 65 y old, species richness showed a stronger relationship with tree age (r2 = 0.45) than with DBH (r2 = 0.23). Thus, in this case, it appears that tree age is a better predictor of species richness than trunk diameter for young trees.

The best model for species richness in the sample plots was very similar to the model for the total tree trunk, but with weaker relationships with tree age and DBH (Figure 1a,b).

species composiTion

The axes in the final NMS accounted for 72% of the variance in species composition, which was equal-ly partitioned between the uncorrelated axes (r = –0.01; r2 axis 1 = 0.38; r2 axis 2 = 0.34). The ordination graph indicated most separation between trees at Riddersholm and Vällen along axis 1, while the trees at Vällen and Biskops Arnö separated from trees at Ekeby along axis 2 (Figure 2).

TabLe iv. The final multiple regression model for lichen cover, with the effect size of each significant variable and the coefficient esti-mates for these variables; intercept estimate for each stand, stand-specific slopes for age, and overall slope for the quadratic term of understory cover.

Effect Type III Sum of squares df FStand 1 623.1 4 5.09***Age (stand) 2 315.9 5 5.81***Understory cover2 1 088.7 1 13.66***Error 10 120.9 127 Stand Constant Age Understory cover2

Biskops Arnö 31.4 –0.1264 Ekeby 41.2 –0.0757 Kungsträdgården 34.1 –0.0619 –0.0014Riddersholm 33.6 0.0297 Vällen 15.9 0.5301

*** P < 0.001.

TabLe v. The final multiple regression model for lichen species ri-chness, with the effect size of each significant variable and the coef-ficient estimates for these variables, the intercept estimate for each stand, the overall slope for lichen cover and DBH, and the stand-specific slopes for age (the quadratic term) and crown cover.

Effect Type III Sum of squares df FStand 191.9 4 4.10**DBH 418.2 1 35.71***Age2 (stand) 364.1 5 6.22***Crown cover (stand) 320.5 5 5.47***Lichen cover 144.0 1 12.29**Error 1 417.0 121

Stand Constant Lichen cover DBH Age2 Crown coverBiskops Arnö –3.4 –0.0059 0.2825Ekeby 26.2 –0.0004 –0.2102Kungsträdgården –5.6 0.1157 0.2101 –0.0002 0.1787Riddersholm 4.5 –0.0005 0.1216Vällen 7.0 0.0014 –0.0341

** P < 0.01, *** P < 0.001.

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The compositional differences among stands were also confirmed by MRPP which showed significant within-stand agreement for all stands (A = 0.074, P < 0.001), as well as for all comparisons between any 2 stands. Tree age was clearly correlated with axis 2, and only the older trees at Ekeby, Kungsträdgården, and Riddersholm were found in the lower half of the ordination graph (Figure 2; Table VI). The other descriptive variables showed weak or no correla-tions with species composition (Table VI). Species richness, on the other hand, was positively correlated with axis 1, while lichen cover only showed a weak positive correlation with the same axis (Table VI).

The indicator species analysis showed 60% (53) of all species included in this analysis to be statistically over-rep-resented in a particular stand (Appendix I). Most indicator species were found at Riddersholm (20), while only one spe-cies was over-represented at Ekeby, Anisomeridium polypori. The indicator species lists for Riddersholm and Vällen include several species typical for somewhat shaded or smooth bark, such as Arthonia ruana, A. spadicea, Biatora ocelliformis, B. sphaeroidiza, Buellia disciformis, Dimerella pineti, Lecania cyrtella, Ochrolechia arborea, Opegrapha

atra, and Schismatomma pericleum (Appendix I). In con-trast, the species list for Kungsträdgården indicated a nitrophilous profile, with species such as Candelariella xan-thostigma, Phaeophyscia spp., Physcia tenella, Ramalina farinacea, and Xanthoria polycarpa.

In the ISA for species preference for tree age, 6 of the indicator species for Kungsträdgården and 4 for Riddersholm were typical also of old trees, above 95 y old (Appendix I). In addition to these species, Acrocordia gem-mata, Bacidia rubella, Cladonia chlorophaea, Chrysothrix candelaris, Eopyrenula leucoplaca, Lecanora allophana, L. argentata, Lepraria lobificans, Pertusaria albescens, P. amara, and P. coccodes were significant for the oldest tree age class, without being over-represented at any site. Only 5 species were identified as indicator species for the youngest tree age class, 18–50 y: Arthonia dispersa, A. radiata, Naetrocymbe punctiformis, Lecanora carpinea, and Xanthoria polycarpa.

figuRe 1. a) Lichen species richness versus tree age for whole tree trunks up to 130 cm above ground (circles, y = –0.002x2 + 0.32x + 5.70, adjusted r2 = 0.18) and for sample plots (squares, y = –0.001x2 + 0.18x + 6.33, adjusted r2 = 0.07). b) Lichen species richness versus tree diameter at breast height (DBH) for whole tree trunks up to 130 cm above ground (circles, y = 0.18x + 12.94, r2 = 0.15) and for sample plots (squares, y = 0.06x + 10.91, r2 = 0.03). All sampled trees (143) at the 5 study sites are included.

figuRe 2. NMS ordination of 142 ash trees in species space (black diamonds, Biskops Arnö; black squares, Ekeby; white diamonds, Kungsträdgården; crosses, Riddersholm; white squares, Vällen). The size width of the symbols represents tree age (from 18 to 140 y).

TabLe vi. Pearson correlation coefficients between the ordination axes in Figure 2, lichen cover, species richness, and the tree condi-tion variables.

Axis 1 Axis 2Lichen cover 0.317 0.027Species richness 0.666 0.073Tree age 0.382 –0.690DBH 0.298 –0.579Depth of bark crevices 0.239 –0.638Stem inclination 0.132 0.019Crown cover 0.029 –0.200Understory cover –0.325 –0.322

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Lichen Life hisToRy TRaiTs

Across all species, spore length and spore size were the only life history traits that were significantly related to the species’ relationships with tree age (r2 = 0.34 and 0.32, respectively, P < 0.01). These results indicate that lichens that occurred more frequently on old trees had larger spores. Similar results were also found when examining the life history relationships within orders and families. Spore length was related to the tree age estimate for Physciaceae (P = 0.048) and Ramalinaceae (P = 0.011), and the same trend was found for Arthoniales and Pertusariales (P = 0.079 and P = 0.08, respectively). Spore size was, however, signif-icantly related to species relationships with tree age only for Physciaceae (P = 0.014). For Arthoniales and Ramalinaceae there were also significant differences among species with varying thallus height. For Arthoniales, species with immersed thalli more often occurred on younger trees than species with thin thalli (P = 0.03). For Ramalinaceae, spe-cies with a thick crustose thalli more often occurred on older trees than species with immersed or thin thalli (P = 0.019).

DiscussionThis study suggests that lichen diversity on ash trees,

Fraxinus excelsior, in deciduous forests in southern Sweden is mainly related to tree conditions such as tree age and light exposure. Stand identity, reflecting location, history, and local conditions, had less influence on the tree-level diversity, but was important for species composition. This conclusion fits with the study by Boudreault, Gauthier, and Bergeron (2000) who found that epiphytic species richness on trembling aspen most of all was correlated with tree age, while species composition and the occurrence of certain species were associated with stand history.

Both tree diameter and tree age were included in our model for species richness, and it is difficult to separate the effects of bark conditions (which may be a function of age), area per se, and the longer time for colonization in old trees (Snäll, Ribeiro & Rydin, 2003; Kantvilas & Jarman, 2004). For species richness at tree-level there is often a positive correlation with tree age, but there are also stud-ies showing negative or no tree age–diversity relationships (Culberson, 1955; Pedersen, 1980; Gauslaa, 1985; Bates, 1992). One reason for these conflicting results may be that the relationship is affected by the studied tree age range. In our data, richness levelled out after around 65 y and even showed a slight decrease for the oldest trees, similar to the peaked diversity–tree age relationship described by Adams and Risser (1971). Like in our study, other studies have also shown how species composition changes with increasing tree age (Yarranton, 1972; Degelius, 1978; Rogers, 1988; Stone, 1989; Hilmo, 1994). Thus, at some intermediate age, there could be species present from both early and late successional stages, leading to the highest species richness. For trees up to 65 y of age, we found a stronger effect of age than of tree diameter on species richness, which would suggest that richness is limited by colonization rates instead of area per se. The species richness recorded in a fixed area (the sample plot data) showed a very similar relationship with tree age as for the whole tree trunks, while DBH only showed a weak relationship with sample plot species rich-

ness. Together this suggests that there is a slight overall posi-tive effect of area, but that species richness over time depends more on species turnover (cf. Löbel, Snäll & Rydin, 2006).

The positive relationship between lichen cover and species richness implies that similar factors, such as light conditions, affect both lichen growth and establishment, and that no superior competitors dominate when cover is high (cf. Bergamini et al., 2001). It also seems compatible with a random placement of species; the more individuals that are encountered, the more species are found (Arrhenius, 1921). This is in accordance with the study by Löbel, Snäll, and Rydin (2006) which indicated an area per se effect for epi-phytic bryophytes, whereas for lichens the random sampling model was more appropriate. This has practical applica-tions. Lichen cover is easy to estimate and together with tree diameter explained 30% of the variation in tree-level species richness. Therefore, a simple model with lichen cover and tree diameter could be useful for, e.g., biodiver-sity assessments and management decisions when time and resources are limited.

With our 5 stands we can establish that stand-level factors are important, but more stands would be required to test which stand conditions are most influential on our results. For both tree- and stand-level species richness, the highest values were encountered at Kungsträdgården and Riddersholm, which hosted the oldest trees and the greatest number of large trees. The occurrence of old trees and the tree age distribution is a function of stand history, but there may also be other site factors that affect tree-level diver-sity. Local climate and landscape configuration, as well as stand history, have been shown to correlate with epiphytic cryptogam communities (Halonen, Hyvärinen & Kauppi, 1991; Dettki & Esseen, 1998; Hedenås & Ericson, 2000; Johansson & Ehrlén, 2003; Snäll et al., 2004). Landscape configuration can affect stand-level colonization rates, while local climate that favours lichen growth and produc-tion should lead to higher diversity through random place-ment. As a result, more species colonizing a particular stand means more species that can colonize any given tree, which should result in a positive relationship between stand- and tree-level diversity (cf. regional and local diversity, Loreau, 2000; He et al., 2005).

For species composition at tree-level, stand identity was important, especially among younger trees. Almost two-thirds of all lichen species included in the ordination were over-represented at one of the sites. Few of these were also associated with old trees, which further suggests that factors other than the tree age distribution contributed to the stand-specific profiles. It is intuitive that species composition varies among geographically separated sites that differ in many environmental variables (cf. Brown, Mehlman & Stevens, 1995).

Lichen Life hisToRy TRaiTs

We found few associations between life history traits and species occurrence along the tree age gradi-ent. However, the results suggest that species with large spores occur to a greater extent on old trees. This relation-ship was found among related species within Arthoniales, Pertusariales, Physciaceae, and Ramalinaceae, which indi-

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cates that it is not biased by phylogeny. The positive spore size–tree age relationship can be viewed as support for a general increase in propagule size during succession, as sug-gested both for lichens (Topham, 1977) and plants (Huston & Smith, 1987).

Spore size can be assumed to affect dispersal ability: large spores should be less widely distributed than small spores in the atmosphere (see Pentecost, 1981). Along the same line, it can be assumed that the longer that a tree is available, the higher is its probability of receiving large spores. Tibell (1994) argued that small spores resulted in wider species distributions within the order Caliciales. At smaller and shorter spatial and temporal scales there are, how-ever, few studies of lichen spore size distributions. Pentecost (1981) did not find differences in spore size between lichens preferring rough versus smooth bark, and Lücking (1999) concluded that spore size among foliicolous lichens was not an adaptation to microsite conditions, although species with large spores were over-represented in light gaps.

Spore size may also affect the establishment process. Like seeds (Silvertown, 1989), large spores may have more resources (Pentecost, 1981), which in turn could affect their ability to establish in a closed community, survive during unfavourable conditions, etc. However, knowledge about spore size effects on colonization and establishment is limited. For mycorrhizal fungi there appears to be no cor-relation between spore size and hyphal growth (Demiranda & Harris, 1994), and for Sphagnum bryophytes, Sundberg and Rydin (2002) even found a weak negative relation-ship between spore size and establishment success, which provides an alternative hypothesis for the observed spore size–tree age relationship in this study.

For dispersal mode, growth form, type of photobiont, frequency, distribution, and pH preference, we did not find any associations with tree age. Several of these character-istics have been shown to correlate with age gradients in other studies, although the photobiont is likely most sensi-tive to stronger light and moisture gradients than in this study. Comparing pH preference values may be irrelevant if the variation with tree age is small. Further, population size (frequency) and distribution range estimates are often good predictors of species occurrence (Brändle et al., 2003) but may first of all be linked with stand-level incidence rates, while tree- and stand-level factors determine the tree-level species occurrence.

For growth form, the analysis was limited by the low number of foliose and fruticose species that actu-ally occurred on ash trees in this study (85% were crus-tose). Among the crustose lichens within Arthoniales and Ramalinaceae, however, the results indicated a successional sequence on ageing trees, from species with immersed or thin thalli on young trees to species with a thick thalli on old trees. Possible explanations could be that thicker thalli need more time to develop, and that they are superior competitors that can persist on old trees.

ConclusionIn conclusion this study suggests that tree-level lichen

diversity is mainly determined by tree age and local light

conditions, while species composition is strongly influenced by both tree age and overall site conditions. To some extent species response to tree age could be understood from their life history traits, but in this respect lichen ecology is still in its infancy.

AcknowledgementsWe are grateful to L. Hansson and the two anonymous review-

ers for helping us improve the manuscript. We also wish to thank S. Ekman, R. Moberg, and C. Printzen, who verified or identified some of our lichen samples, and L. Norell for statistical advice. The work was partially funded by the WWF Sweden.

Literature citedAdams, D. B. & P. G. Risser, 1971. Some factors influencing the

frequency of bark lichens in north central Oklahoma. American Journal of Botany, 58: 752–757.

Ahti, T., L. Hämet-Ahti & J. Jalas, 1968. Vegetation zones and their sections in north-western Europe. Annales Botanici Fennici, 5: 169–211.

Almborn, O., 1948. Distribution and ecology of some South Scandinavian lichens. Botaniska Notiser, Supplement, 1(2): 1–254.

Arrhenius, O., 1921. Species and area. Journal of Ecology, 9: 95–99.

Arup, U., S. Ekman, L. Lindblom & J.-E. Mattsson, 1993. High performance thin layer chromatography (HPTLC), an improved technique for screening lichen substances. Lichenologist, 25: 61–71.

Bates, J. W., 1992. Influence of chemical and physical factors on Quercus and Fraxinus epiphytes at Loch Sunart, western Scotland: A multivariate analysis. Journal of Ecology, 80: 163–179.

Bergamini, A., D. Pauli, M. Peintinger & B. Schmid, 2001. Relationships between productivity, number of shoots and number of species in bryophytes and vascular plants. Journal of Ecology, 89: 920–929.

Boudreault, C., S. Gauthier & Y. Bergeron, 2000. Epiphytic lichens and bryophytes on Populus tremuloides along a chrono-sequence in the southwestern boreal forest of Québec, Canada. Bryologist, 103: 725–738.

Brändle, M., W. Durka, H. Krug & R. Brandl, 2003. The assembly of local communities: Plants and birds in non-reclaimed mining sites. Ecography, 26: 652–660.

Brown, J. H., D. W. Mehlman & G. C. Stevens, 1995. Spatial variation in abundance. Ecology, 76: 2028–2043.

Culberson, W. L., 1955. The corticolous communities of lichens and bryophytes in the upland forests of northern Wisconsin. Ecological Monographs, 25: 215–231.

Degelius, G., 1978. Further studies on the epiphytic vegetation on twigs. Botanica Gothoburgensia, 7: 1–58.

Demiranda, J. C. C. & P. J. Harris, 1994. Effects of soil-phos-phorus on spore germination and hyphal growth of arbuscular mycorrhizal fungi. New Phytologist, 128: 103–108.

Dettki, H. & P.-A. Esseen, 1998. Epiphytic macrolichens in man-aged and natural forest landscapes: A comparison at two spatial scales. Ecography, 21: 613–624.

Edwards, R. Y., J. Soos & R. W. Ritcey, 1960. Quantitative obser-vations on epidendric lichens used as food by caribou. Ecology, 41: 425–431.

Eriksson, O., 2004. Myconet, Outline of Ascomycota – 2004. [Online] URL:http://www.umu.se/myconet/asco/indexASCO.html

Écoscience, voL. 14 (1), 2007

89

Foucard, T., 2001. Svenska skorplavar och svampar som växer på dem. Interpublishing, Stockholm [in Swedish].

Gaston, K. J., T. M. Blackburn & J. H. Lawton, 1997. Interspecific abundance-range size relationships: An appraisal of mecha-nisms. Journal of Animal Ecology, 66: 579–601.

Gauslaa, Y., 1985. The ecology of Lobarion pulmonariae and Parmelion caperatae in Quercus dominated forests in south-west Norway. Lichenologist, 17: 117–140.

Hallingbäck, T., 1995. The Lichens of Sweden and Their Ecology. ArtDatabanken SLU, Uppsala [in Swedish].

Halonen, P., M. Hyvärinen & M. Kauppi, 1991. The epiphytic lichen flora on conifers in relation to climate in the Finnish middle boreal subzone. Lichenologist, 23: 61–72.

He, F., K. J. Gaston, E. F. Connor & D. S. Srivastava, 2005. The local–regional relationship: Immigration, extinction, and scale. Ecology, 86: 360–365.

Hedenås, H. & L. Ericson, 2000. Epiphytic macrolichens as con-servation indicators: Successional sequence in Populus tremula stands. Biological Conservation, 93: 43–53.

Hilmo, O., 1994. Distribution and succession of epiphytic lichens on Picea abies branches in a boreal forest, central Norway. Lichenologist, 26: 149–169.

Huston, M. & T. Smith, 1987. Plant succession: Life history and competition. American Naturalist, 130: 168–198.

Johansson, P. & J. Ehrlén, 2003. Influence of habitat quantity, quality and isolation on the distribution and abundance of two epiphytic lichens. Journal of Ecology, 91: 213–221.

Kantvilas, G. & S. J. Jarman, 2004. Lichens and bryophytes on Eucalyptus obliqua in Tasmania: Management implications in production forests. Biological Conservation, 117: 359–373.

Löbel, S., T. Snäll & H. Rydin, 2006. Species richness patterns and metapopulation processes: Evidence from epiphyte communi-ties in boreo-nemoral forests. Ecography, 29: 169–182.

Loreau, M., 2000. Are communities saturated? On the relationship between α, β and g diversity. Ecology Letters, 3: 73–76.

Lücking, R., 1999. Ecology of foliicolous lichens at the ‘Botarrama’ trail (Costa Rica), a neotropical rainforest. IV. Species associations, their salient features and their dependence on environmental variables. Lichenologist, 31: 269–289.

McCune, B. & M. J. Mefford, 1999. Multivariate Analyses of Ecological Data. MjM Software, Gleneden Beach, Oregon.

McCune, B., J. B. Grace & D. L. Urban, 2002. Analysis of Ecological Communities. MjM Software Design, Gleneden Beach, Oregon.

McCune, B., R. Rosentreter, J. M. Ponzetti & D. C. Shaw, 2000. Epiphyte habitats in an old conifer forest in western Washington, USA. Bryologist, 103: 417–427.

Mielke, P. W. & K. J. Berry, 2001. Permutation Methods: A Distance Function Approach. Springer Verlag, New York, New York.

Mistry, J. & A. Berardi, 2005. Effects of phorophyte determinants on lichen abundance in the cerrado of central Brazil. Plant Ecology, 178: 61–76.

Pedersen, I., 1980. Epiphytic lichen vegetation in an old oak wood, Kaas Skov. Botanisk Tidsskrift, 75: 105–120.

Pentecost, A., 1981. Some observations on the size and shape of lichen ascospores in relation to ecology and taxonomy. New Phytologist, 89: 667–678.

Purvis, O. W., B. J. Coppins, D. L. Hawksworth, P. W. James & D. M. Moore (eds.), 1992. The Lichen Flora of Great Britain and Ireland. Natural History Museum Publications, London.

Rogers, R. W., 1988. Succession and survival strategies in lichen populations on a palm trunk. Journal of Ecology, 76: 759–776.

Rolstad, J. & E. Rolstad, 1999. Does tree age predict the occurren-ce and abundance of Usnea longissima in multi-aged submon-tane Picea abies stands? Lichenologist, 31: 613–625.

Rose, F. 1976. Lichenological indicators of age and environmental continuity in woodlands. Pages 279–307 in D. H. Brown, D. L. Hawksworth & R. H. Bailey (eds.). Lichenology: Progress and Problems. Academic Press, London.

Ruchty, A., A. L. Rosso & B. McCune, 2001. Changes in epiphyte communities as the shrub, Acer circinatum, develops and ages. Bryologist, 104: 274–281.

Santesson, R., R. Moberg, A. Nordin, T. Tønsberg & O. Vitikainen, 2004. Lichen-forming and lichenicolous fungi of Fennoscandia. Museum of Evolution, Uppsala University, Uppsala.

SAS Institute, 2000. SAS/STAT User’s Guide, Version 8. SAS Institute Inc., Cary, North Carolina.

Sillett, S. C. & M. E. Antoine, 2004. Lichens and bryophytes in forest canopies. Pages 151–174 in M. D. Lowman & H. B. Rinker (eds.). Forest Canopies. Elsevier Academic Press, San Diego, California.

Silvertown, J., 1989. The paradox of seed size and adaptation. Trends in Ecology and Evolution, 4: 24–26.

Snäll, T., P. J. Ribeiro Jr. & H. Rydin, 2003. Spatial occurrence and colonisations in patch-tracking metapopulations: Local condi-tions versus dispersal. Oikos, 103: 566–578.

Snäll, T., A. Hagström, J. Rudolphi & H. Rydin, 2004. Distribution pattern of the epiphyte Neckera pennata on three spatial scales: Importance of past landscape structure, connectivity and local conditions. Ecography, 27: 757–766.

Stone, D. F., 1989. Epiphyte succession on Quercus garryana bran-ches in the Willamette valley of western Oregon. Bryologist, 92: 81–94.

Sundberg, S. & H. Rydin, 2002. Habitat requirements for esta-blishment of Sphagnum from spores. Journal of Ecology, 90: 268–278.

Thor, G., 1998. Red-listed lichens in Sweden: Habitats, threats, protection, and indicator value in boreal coniferous forests. Biodiversity and Conservation, 7: 59–72.

Tibell, L., 1994. Distribution patterns and dispersal strategies of Caliciales. Botanical Journal of the Linnean Society, 116: 159–202.

Topham, P. B., 1977. Colonization, growth, succession and compe-tition. Pages 31–68 in M. R. D. Seaward (ed.). Lichen Ecology. Academic Press, London.

Uliczka, H. & P. Angelstam, 1999. Occurrence of epiphytic macro-lichens in relation to tree species and age in managed boreal forest. Ecography, 22: 396–405.

Wolseley, P. A. & B. Aguirre-Hudson, 1997. The ecology and dis-tribution of lichens in tropical deciduous and evergreen forests of northern Thailand. Journal of Biogeography, 24: 327–343.

Yarranton, G. A., 1972. Distribution and succession of epiphytic lichens on black spruce near Cochrane, Ontario. Bryologist, 75: 462–480.

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appendix i. Total species list with number of records (no. of trees) for each species at each site. The total number of sampled trees at each site is given in parentheses in the heading. Systematic classification in order or family for species tested for associations with life history traits according to Eriksson (2004). Bold font indicates species that were over-represented in a particular stand in the Indicator Species Analysis. Species that were significant indicators for trees in the 96–140 y age class are indicated by *.

Biskops Arnö Ekebyholm Kungsträdgården Riddersholm Vällen Order/Family (16) (31) (29) (41) (26) Acrocordia gemmata* 0 5 7 5 2 Agonimia allobata 0 0 1 0 0 Amandinea punctata 6 3 9 2 3 PhysciaceaeAnaptychia ciliaris 0 0 1 0 0 Anisomeridium polypori 6 19 3 6 11 Arthonia didyma 0 2 5 10 2 ArthonialesArthonia dispersa 3 3 3 6 4 ArthonialesArthonia mediella 5 2 10 12 0 ArthonialesArthonia radiata 8 13 18 22 16 ArthonialesArthonia ruana 0 0 0 13 8 ArthonialesArthonia spadicea 1 0 0 12 0 ArthonialesArthonia vinosa 0 0 1 1 0 Bacidia arceutina 0 0 0 2 2 RamalinaceaeBacidia beckhausii 0 4 3 2 6 RamalinaceaeBacidia fraxinea* 0 0 0 8 3 RamalinaceaeBacidia polychroa 0 0 0 0 1 Bacidia rubella* 0 7 8 8 0 RamalinaceaeBacidia subincompta 0 9 4 7 6 RamalinaceaeBacidina caligans 0 0 0 0 1 Biatora efflorescens 4 11 10 29 8 RamalinaceaeBiatora helvola 0 1 0 0 0 Biatora ocelliformis 0 0 0 0 4 RamalinaceaeBiatora sphaeroidiza 0 0 0 10 0 RamalinaceaeBiatoridium monasteriense* 0 4 7 3 1 Buellia disciformis 1 0 1 20 1 PhysciaceaeBuellia griseovirens 7 12 12 31 15 PhysciaceaeCaloplaca flavorubescens 0 0 0 0 1 Caloplaca obscurella 0 0 1 0 0 Candelariella xanthostigma* 0 1 7 0 0 LecanoraceaeCatillaria nigroclavata 0 0 0 0 1 Catinaria atropurpurea 1 1 0 0 1 Chrysothrix candelaris* 0 0 2 1 0 ArthonialesCladonia chlorophaea* 0 3 2 7 2 Cladonia coniocraea 3 4 3 10 4 Cladonia spp. 5 10 8 19 5 Cliostomum griffithii 0 0 0 22 2 RamalinaceaeDimerella pineti 0 0 0 7 1 Eopyrenula leucoplaca* 0 0 1 3 0 Evernia prunastri 4 0 16 23 0 ParmeliaceaeFuscidea arboricola 8 5 2 34 4 Graphis scripta 0 0 2 25 11 Hypogymnia farinacea 0 0 0 1 0 Hypogymnia physodes 9 9 20 37 8 ParmeliaceaeHypogymnia tubulosa 1 0 0 0 0 Lecania cyrtella 2 6 6 2 12 RamalinaceaeLecania cf. cyrtellina 0 2 1 5 10 RamalinaceaeLecania hyalina 1 4 9 12 0 RamalinaceaeLecania naegelii 0 0 1 0 5 RamalinaceaeLecanora allophana* 0 1 1 4 0 LecanoraceaeLecanora argentata* 1 2 1 6 4 LecanoraceaeLecanora carpinea coll. 14 12 15 26 15 LecanoraceaeLecanora chlarotera 10 15 20 11 4 LecanoraceaeLecanora expallens 11 7 14 29 7 LecanoraceaeLecanora impudens 0 0 1 0 0 Lecanora pulicaris 4 1 2 8 0 LecanoraceaeLecanora sambuci 0 1 2 0 5 LecanoraceaeLecanora symmicta 6 3 0 2 4 LecanoraceaeLecanora subfusca grp 8 7 3 28 12 Lecidea erythrophaea 0 0 1 1 4 Lecidea nylanderi 6 3 1 4 2 Lecidella elaeochroma* 11 26 28 28 25 LecanoraceaeLepraria eburnea 0 0 0 1 1 Lepraria elobata 1 1 5 3 1 Lepraria incana 0 1 2 2 0 Lepraria lobificans* 0 2 4 1 3

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appendix i. Concluded.

Biskops Arnö Ekebyholm Kungsträdgården Riddersholm Vällen Order/Family (16) (31) (29) (41) (26) Lepraria spp. 0 0 0 7 0 Leptogium lichenoides 0 0 1 0 0 Melanelia exasperatula 0 1 0 0 0 Melanelia fuliginosa 12 15 24 41 15 ParmeliaceaeMelanelia subaurifera 1 0 3 0 1 ParmeliaceaeMicarea cf. nitschkeana 0 0 0 2 0 Micarea prasina 3 2 0 7 1 Mycoblastus fucatus 3 2 2 0 0 Naetrocymbe punctiformis 4 2 6 7 10 Ochrolechia androgyna 2 0 0 6 1 PertusarialesOchrolechia arborea 0 0 0 8 2 PertusarialesOchrolechia turneri 0 2 0 1 0 PertusarialesOpegrapha atra 0 0 0 0 5 ArthonialesOpegrapha ochrocheila 0 0 0 1 0 Opegrapha rufescens* 0 13 23 27 11 ArthonialesOpegrapha varia* 0 1 5 2 0 ArthonialesPachyphiale fagicola 1 1 1 0 1 Parmelia saxatilis 1 0 0 0 0 Parmelia sulcata 10 18 22 32 10 ParmeliaceaeParmelina tiliacea 0 0 1 0 0 Parmeliopsis ambigua 6 3 1 8 4 ParmeliaceaePeltigera canina 0 0 1 0 0 Peltigera praetextata 0 0 0 2 0 Pertusaria albescens* 0 4 3 0 0 PertusarialesPertusaria amara* 1 18 17 26 7 PertusarialesPertusaria coccodes* 0 6 2 4 1 PertusarialesPertusaria coronata 0 0 1 0 0 Pertusaria flavida 0 1 1 0 0 Pertusaria leioplaca 8 19 23 29 11 PertusarialesPertusaria pupillaris 9 3 3 8 1 PertusarialesPhaeophyscia endophoenicea 0 0 4 0 0 PhysciaceaePhaeophyscia orbicularis 0 0 14 0 0 PhysciaceaePhlyctis agelaea* 0 0 8 21 4 Phlyctis argena* 9 26 28 39 16 Physcia adscendens 0 0 1 0 0 Physcia tenella 0 0 4 0 0 PhysciaceaePhyscia spp. 0 1 0 0 0 Physconia enteroxantha 0 0 2 0 0 Physconia spp. 0 0 3 1 0 Ramalina farinacea 8 10 22 27 8 RamalinaceaeRamalina fastigiata 0 0 1 0 0 Rinodina efflorescens 2 1 1 0 0 PhysciaceaeRinodina pyrina 1 2 0 0 0 PhysciaceaeRopalospora viridis 12 7 6 31 2 Schismatomma pericleum* 0 0 0 4 0 ArthonialesSclerophora pallida* 0 0 5 0 0 Scoliciosporum chlorococcum 8 0 4 4 0 LecanoraceaeScoliciosporum sarothamni 1 0 3 0 3 LecanoraceaeTephromela atra* 0 0 0 4 0 RamalinaceaeThelenella pertusariella 0 0 0 0 1 Vulpicida pinastri 0 0 0 2 0 Xanthoria parietina 0 0 1 0 0 Xanthoria polycarpa 6 6 18 16 3