Abstract: 119 investigated Quercus trunks and 67 species of lichens, 23 bryophytes and 3 non-lichenized fungi are arranged by means of the Minimum Spanning Tree analysis, resulting in four Lobarion communities and one Parmelion community. Lobarion is restricted to bark with pH > 5.0 in old forests. pH and Ca-content in the bark are strongly correlated; Ca seems to originate from Ca-uptake through the roots of the phorophyte. Within a single site the soil also seems to be responsible for the variation in the Mg-content of the bark, being correlated with Ca. The dominating source of the regionalvariationinMg, however, seems to be marine aerosols. Parmelion caperatae occurs on acid bark of young trees. The bark is, however, rich in Mg. Soluble tannins in the bark decrease with increasing age of the phorophyte, but are probably of minor significance for the epiphytic vegetation.

Abstract: The seasonal and annual variation in the litter fall of epiphytic lichens and tree litter was studied over a period of 2 to 3 years at two forested hills in the eastern part of central Sweden. Litter fall was measured using traps and for one species, Usnea longissima, by collecting specimens present on the ground. Total litter fall amounted to 2.5 and 2.8 tons ha−1 year−1 of which lichens constituted 4.6 and 5.7% at the two sites. Lichen litter fall was highest during the period from late autumn to the beginning of summer. Both the lichens and the tree litter showed significant between-year differences. Usnea longissima had an annual turnover of 7.0 and 10.0% of the standing crop at the two sites. The thallus length distribution of U. longissima was positively skewed. It is concluded that dispersal of thallus fragments by wind evidently plays an important role for many of the filamentous lichens studied. It is suggested that U. longissima disperses over a much shorter distance than Alectoria sarmentosa an...

Abstract: Cryptogam-covered, sandy soils of the Big Sand Mound prairie in southeastern Iowa are significantly more aggregated than bare soils. Soil particles covered by moss are intertwined by rhizoids, whereas cyanobacteria and lichen fungal hyphae adhere to the particles and glue them together. Lichen-covered samples that were tested and oven dried, then retested 2 yr later, retain their aggregation, indicating that the aggregating material is stable even after the death of the

Abstract: At Birthday Ridge, a small ice free area in northern Victoria Land (70°48′S, 167°00′E), cryptogamic vegetation is mostly confined to gaps between granitc rocks. The sheltering effect on lichens and mosses was analyzed by continuous measurements of the microclimate at various levels between the rocks. Although warming by solar radiation was favourable for the existence of cryptogams, rocks strongly insolated were mostly devoid of lichens and mosses. Lichens in the soaked active state were heated to above air temperature but did not reach more than 10°C. The presence of lichens was dependent on the moisture conditions of the habitat. It was observed that snow, the only source of moisture, accumulated in summer only in deeper levels between rocks, and that the snow rapidly melted on contact with the lichens. After a snow shower,Usnea sulphurea gained 67% andUmbilicaria decussata 94% of their maximum water capacity. During one quarter of the time period of 7 days the lichens were soaked and therefore capable of carrying out photosynthesis. The lichens in soaked state had always less than optimum temperatures for net photosynthesis. The rock gaps at Birthday Ridge form oases, the only localities where moisture is provided, and temperature is high enough to enable growth of lichens and mosses.Bryum is also able to exist in the upper 3 cm of soil.

Abstract: Synthetic thalli of Usnea strigosa produced the same fibril morphology and secondary compounds as natural thalli. The outer cortex of synthetic lichens was covered with crystals of usnic acid and compounds related to norstictic acids. The common presence on the fibrils of lichen acids suggests that these compounds have a functional role in the symbiosis. During alcohol dehydration, crystals of usnic acid dissolved and left impressions in the mucilage around the symbionts. The impressions were valuable indicators of the position of crystals in the lichen thallus. Crystal impressions of usnic acid were common on the cortical hyphae and were seen also on the surface of algal cells. The crystal impressions were larger in the synthetic lichen than in natural thalli. Impressions of norstictic acid and related compounds were not seen.

Abstract: Many different groups of fungi became independently and at various times lichenized. As they are symbiotic with a wide range of distantly related phyco- and cyanobionts with structurally and compositionally distinct cell walls, it is not surprising that many different types of symbiotic relationships can be found among lichens. Extensive comparative light microscopic studies of the mycobiont-phyco- or cyanobiont interface in distantly related lichens were carried out by Tschermak (1941) and Plessl (1963) who, respectively, first observed a correlation between the anatomical organisation or evolutionary stage of a lichen and the type of mycobiont-phycobiont relationship. Their data were largely confirmed by different transmission electron microscopic (TEM) studies (reviewed by Honegger, 1984)

Abstract: Our knowledge of the ecophysiology of photosynthetic production of Antarctic lichens is based on separate investigations made with species from the maritime Antarctic or species from the continental Antarctic, but no studies have yet been made comparing the same or similar species in both areas. Many data have been published from field and laboratory measurements on Signy Island, although much less about lichens (Lindsay, 1978; Hooker, 1980a,b,c) than about bryophytes (Baker, 1972; Collins, 1977; Collins and Callaghan, 1980; Fenton, 1980). With respect to the continental Antarctic there are more studies on lichens (Gannutz, 1970; Lange and Kappen, 1972; Schofield and Ahmadjian, 1972; Kappen 1983a; Kappen and Friedmann, 1983) than on mosses (Rastorfer, 1970; Longton, 1974; Ino, 1983). Climate and ecological conditions are very different in the two areas, particularly the winter conditions. In the maritime Antarctic, as the author has seen on King George Island, the abundance and variety of lichens is remarkable. In continental Antarctica, even near the coast of northern Victoria Land (Kappen, 1983b) lichens may be considered to be extremely resistant representatives of a pioneer vegetation in a polar desert. Consequently, the aim of this study was to evaluate whether lichens show adaptive physiological differences or whether they have the same physiological and ecological requirements in the polar desert and the maritime Antarctic due to presumably convergent habitat conditions.

Abstract: macrolichens, including 12 new records, are reported for cool temperate rainforests in Tasmania. These species belong mainly to the austral cool temperate element. A descriptive account of the lichen floras from five major rainforest communi- ties is given. Field observations suggest that substrate and light are the most important ecological factors affecting the distribution of lichens in rainforest. Although most species are widespread in Tasmania, large-scale disturbance and the fragmentation of rainforest stands is seen as a threat to their survival. Abundance 'subjectively assessed) and presence-absence data for macrolichens were obtained from over 300, 20 x 20 m quadrats examined during a survey of higher plant communities in cool temperate rain- forest in Tasmania. The quadrats were located subjectively to include a broad range of geographical, altitudinal and topographical situations within rainforest vegetation. Lichen data were recorded from the lower levels of the forest (to 3—4 m above the ground surface) and included epiphytic, saxicolous and terricolous species. Due to their inaccessibility, canopy lichens were incompletely surveyed but limited information was derived from litter, fallen branches and, more rarely, from fallen trees. Supplementary data from previous work (Kantvilas & James, unpublished) and from numerous spot- checks in a range of vegetation types provided a general overview for the lichen survey.

Abstract: The acetylene reduction assay was used to examine biological nitrogen fixation in the high arctic tundra at Sarcpa Lake, Northwest Territories (68°32′ N, 83°19′ W). The highest rates of acetylene reduction (9.37 ± 3.19 μmol C2H4 m−2 h−1) were in habitats that had a high density of the legumes Oxytropis maydelliana, O. arctobia, and Astragalus alpinus. Nitrogen fixation in the wet soils along the shore of a small lake was similar (8.87 ± 4.35 μmol C2H4 m−2 h−1) because of the blue-green alga Nostoc, which associates with mosses. Free-living blue-green algae and lichens made insignificant contributions to the total nitrogen fixation budget because they were uncommon and fixed nitrogen at a slower rate. Nitrogen-fixing lichens in the area included Stereocaulon arenarium and S. rivulorum. It is concluded that legumes have a significant input to the biological nitrogen fixation budget at Sarcpa Lake.

Abstract: Using published data on the integrated deposition of fallout 90Sr (137Cs) until 1975 and current measurements of the,137Cs activity in plant communities along the latitudinal gradient north of 50° N, an estimate has been made of the 137Cs effective half-life, Teff, in the composite vegetation of the Canadian Arctic. The lichens Alectoria nigricans, Alectoria ochroleuca, Cladonia rangiferina, Cornicularia divergens, and Umbilicaria muhlenbergii were studied, as well as a moss, Polytrichum juniperinum, and the vascular cushion plants Dryas integrifolia, Saxifraga oppositifolia, and Silene acaulis. In all cases, the effective half-life increased with increasing latitude, the longest Teff (10–12 years) being exhibited by dry-habitat lichens at 80° N.

Abstract: There has been considerable interest over the last 15 years in the carbon metabolism of a range of lichen species and particularly in the movement of the products of photosynthesis from the algal component across to the fungal symbiont. This work has largely been developed by Smith and his co-workers and has been summarised in a series of reviews by Smith (1974, 1975, 1980).

Abstract: The sulphur content was studied in the epiphytic lichens Hypogymnia physodes (L.) Nyl. and Pseudevernia furfuracea (L.) Zopf, in the terricolous lichens Cladonia sp. and Pehigera aphthosa (L.) Willd. (inch some Nephroma arcticum (L.) Torss.), and also in pine and birch bark and in the layer below the birch bark in 31 sites in Finland. Sulphur was determined by the isotope excited X-ray fluorescence method, using a semiconductor detector. The total sulphur content of the lichens appeared to depend closely upon the species and to vary considerably due to several factors. In H. physodes and P. furfuracea it had a highly significant correlation with the wet and dry sulphate deposition. In P. aphthosa (and N. arcticum) the sulphur content also correlated with the sulphate deposition. In Cladonia, however, there was no correlation between the sulphur content and the sulphate deposition, which indicates that the sulphur uptake mechanism is different in this lichen. The sulphur contents of H. physodes and P. furfuracea in different parts of Finland showed statistically significant regional variation. The microclimatic factors were considered, account being taken of the sources and chemical form of the sulphur, and the phorophyte species and their habitats.

Abstract: The determination and interpretation of patterns in photosynthetic primary production which are characteristic of different lichen species within their respective habitats may lead to a better understanding of habitat preferences and species distributions. However, the necessary photosynthetic CO2 exchange measurements are difficult to accomplish in the field. Thus, only a few examples of diurnal courses of photosynthetic CO2 uptake by poikilohydric organisms may be found in the ecophysiological literature. Recently mathematical models have been developed which have been used to simulate the net photosynthetic performance of lichens under natural conditions. Because such models are usually based upon physiological parameters obtained from laboratory experiments, their validity can only be established by comparing simulated rates of photosynthesis with rates actually measured in the field. Thus, the development of instrumentation and methods which allow accurate determination of CO2 exchange of lichens under natural conditions is essential.

Abstract: Lichens have certain features which have resulted in their intensive use as indicators of air quality and as monitors of the atmospheric deposition of various elements. These salient features include the lack of roots or structures which have the absorptive function of roots and thus some lichens are dependent for their mineral nutrients to a large extent on material landing on the lichen thallus as the result of wet and dry deposition from the atmosphere. Also, lichens unlike higher plants, do not have a well-developed cuticle and hence there is no comparable physical barrier to impede exchange with the environment. Consequently, lichens can accumulate mineral elements to levels far greater than their expected physio-logical needs. Lichens are perennial and this feature together with the other characteristics has led to the use of these plants as longterm integrators of deposition from the atmosphere of elements originating from both natural and man-made sources.

Abstract: Initial investigations of the weathering effects of crustose lichens on mica-schist rock from Signy Island show considerable mechanical disruption of the rock surface, and penetration of the thallus into the rock. SEM studies show the presence of fungal propagules attached to the rock, and the growth form of the lichen thallus in colonizing bare rock.

Abstract: Lichens are slow growing and the lichen component of ecosystems is usually small. Lichens have, however, ecological and biogeochemical significance in some types of boreal heaths, forests and bogs (Wein and Speer, 1975; Rencz and Auclair, 1978), and as epiphytes in humid, subtropical-temperate swamps (Bosserman and Hagner, 1981). Furthermore, species of Cladonia (generally = Cladina*) have been used as monitoring organisms in order to survey the deposition of atmospheric metals in northern woodlands, bogs and tundra (Tomassini et al., 1976; Pakarinen et al., 1978; Puckett and Finegan, 1980; Glooschenko et al., 1981; Pakarinen, 1981a).

Abstract: Cyanobacteria are 02-evolving photosynthetic prokaryotes, many species of which fix N2. Most cyanobacteria are exclusively free- living forms but a few occur in symbiotic association with a variety of eukaryotes. Those which occur in symbiotic association are, almost invariably, N2-fixing heterocystous forms (see Stewart et al., 1980; 1983 for recent reviews). In this paper we will consider aspects of the fixation, transfer and assimilation of nitrogen in the lichensPeltigera aphthosa andPeltigera canina.