Epiphytic Lichen Vegetation Research Articles

Recalibration and validation of the Swiss lichen bioindication methods for air quality assessment

The aim of this study was to recalibrate the Swiss lichen bioindication methods, developed and calibrated with air pollution data 30years ago. Since then, levels of air pollution have considerably decreased, and the mix of pollutants has changed due to successful emission control in Switzerland and neighboring countries. In particular, there has been a change from a sulfur- and acid-dominated to a more nitrogen-dominated pollution mix of NH3/NOx and ozone, resulting in increased pH levels. This allowed a recolonization and change in abundance and composition of the epiphytic lichen vegetation, indicating an improved air quality in Switzerland. The existing indices of atmospheric pollution or purity IAP18 and IAPBR developed 30years ago showed good longitudinal correlations with air pollutant levels until the end of the last century, but a growing drift was observed in some regions over the last 15years. This called for a method recalibration with more recent air pollution data. Data from a total of 7178 trees from 22 Swiss regions grouped into 1331 homogenous plots and covering the period 1994 to 2017 were averaged by year within plots. Three pollutant-specific lichen indices were newly established, one for primary pollutants (NO2, PM10, SO2), one for ozone (AOT40f), and one for ammonia (NH3). These pollutant-specific lichen indices were derived from linear regression models with lichen variables and a linear time trend variable as predictors, using time-dependent coefficients. Parameters were selected using the Lasso method. The primary pollutant lichen index showed a coefficient of determination R2 of 0.86 in the model with NO2, PM10, and SO2 as predictor variables, whereas corresponding models with other predictor variables (i.e., NH3, AOT40f, and meteorological variables) were of considerably lower fit. Regionalized lichen models for three larger Swiss regions revealed even better results, compared with the unified Swiss models. The best regionalized ozone and ammonia lichen indices reached an R2 of 0.88 and 0.71, respectively.

Characterization of the epiphytic lichen vegetation in a riparian forest in southern Brazil

Characterization of the epiphytic lichen vegetation in a riparian forest in southern Brazil

Forest edge-interior differentiation in the epiphytic lichen diversity of the forest steppe in the Khangai Mountains, Mongolia

The effects of traditional land use by mobile livestock keepers on biodiversity in forest steppe ecotones are insufficiently studied. Epiphytes are an important part of forest plant diversity. Here we analyze differences in the diversity and composition of the epiphytic lichen vegetation between the edge and the interior of Siberian larch forests in the Khangai Mountains, western Mongolia, which are highly subdivided into patches. We asked whether the epiphytic lichen vegetation at the forest edge differs significantly from that in the interior, whether the edge is inhabited by more nitrophilous species than the interior and whether the density of nomad camps around the forest affects epiphytic lichen diversity. Cover percentages of epiphytic lichen species were recorded from 20 trees per plot on 6 plots in the interior and 6 plots at the edge of Larix sibirica forests. The position of nomad summer camps was surveyed using Global Positioning System. Data were analyzed with pairwise significance tests, analysis of similarities, nonmetric multidimensional scaling and canonical correspondence analysis. The composition of the epiphytic lichen vegetation clearly differed between the two habitats, with more species being more frequent at the edge than in the interior. However, there was no difference in species richness (α-diversity). The epiphyte vegetation at the edge was more uniform and characterized by lower variation of tree-level α-diversity and lower β-diversity than in the interior. At the edge, only nitrophytic lichens were dominant, whereas in the interior, nitrophytes and acidophytes were among the dominant species. This pattern is probably attributable to the spatial heterogeneity of the intensity of forest grazing and was shown to be influenced by the density of nomad summer camps in the vicinity of the forests. Tree-level α-diversity increased with stem diameter, but high-diameter trees were rare. The results suggest that the present level of forest patchiness and the effect of forest grazing increases the diversity of epiphytic lichens on the landscape level, while logging of high-diameter trees reduces lichen diversity.

Epiphytic lichens as indicators of grazing pressure in the Mongolian forest-steppe

The ecological impact of the traditional land use by pastoral nomads on forest ecosystems is little studied. We analyzed the influence of livestock density on epiphytic lichen diversity in larch forests of the Mongolian forest-steppe, which we selected as a case example because pastoral nomadism is here most widespread within Central Asia. Canonical correspondence analysis showed that the epiphytic lichen vegetation was strongly influenced by the livestock density within a radius of 1km around the sampled forests. Goats together with horses were most significant at shaping lichen vegetation in the forest edges as were horses alone in the forest interiors. This result matches with the results of interviews with 169 herder families and own field observations, which substantiate that goats preferably graze at the edges, whereas horses often browse the interiors. The livestock impact is thought to be primarily exerted through fertilization by the animals and mechanical abrasion. Based on an indicator species analyses, we propose to use epiphytic lichens as indicators of the grazing impact at different livestock densities in the Mongolian forest-steppe. The proposed indication system can be used as a tool for the rapid assessment of the livestock grazing impact. It has the advantage that it is thought to average the livestock impact of several years, which is important with regard to the nomadic style of livestock husbandry. The use of lichens as indicator species can at least partly substitute the time-consuming interviewing of the herder families to assess livestock densities and their impact on forest biodiversity. The proposed indicator system could thus be used as a planning tool for purposes of nature conservation.

Monitoring H 2S air pollution caused by the industrial exploitation of geothermal energy: The pitfall of using lichens as bioindicators

This study showed that NH 3 emitted from geothermal power plants affects the surrounding epiphytic lichen vegetation and diversity, confounding the interpretation of lichen diversity counts in terms of air pollution by H 2S. The presence of nitrophytic lichen species around geothermal installations, determined by NH 3, caused relatively high diversity values that were not related with the levels of air pollution by H 2S. It is recommended that in the presence of NH 3 emission, nitrophytic species are excluded from the calculation of lichen diversity values.

Effects of reduced nitrogen compounds on epiphytic lichen communities in Mediterranean Italy

The effects of reduced nitrogen compounds on epiphytic lichen vegetation have been largely investigated in northern Europe. This paper reports for the first time results of a study carried out on pine trees in the Mediterranean basin. Contrary to the usual acidophytic lichen colonization of pine bark, in this case a nitrophytic lichen vegetation was found, suggesting that the study area is characterized by a diffuse eutrophication. Tree circumference, distance from the stock farms, bark pH and bark electrical conductivity emerged as the main factors influencing the distribution and abundance of epiphytic lichens in the study area. Both Hyperphyscia adglutinata and Xanthoria parietina were suitable local indicator species of high pine bark pH values. However, while X. parietina indicated high nitrogen dust pollution, H. adglutinata occurred also where there was an additional increase in bark pH caused by the release of high amounts of ammonia. The increased nitrogen availability caused by ammonium apparently had no effect on the occurrence of nitrophytes.

Long-term changes of epiphytic lichen species composition over landscape gradients: an 18 year time series

Abstract:The study aimed to determine how the response of the epiphytic lichen vegetation to sulphur air pollution is affected by interaction with other factors (distance from pollution sources, habitat, altitude, initial eutrophication of the tree bark). It was based on a series of four successive recordings taken over a period of 18 years with increasing pollution levels and on the same set of 139 solitary trees. Relationships between habitat variables and lichen community composition are assessed using canonical correspondence analysis. The data set comprised 69 lichen species. Ordination of initial species composition on trees revealed two major gradients: eutrophication and acidity.The species composition significantly changed with time, with a general decrease of the total number of lichen species per tree. In general, species sensitive to air pollution decreased, while tolerant species increased in number. Change over time differed depending on the position of the tree within the landscape (relative to one major source of pollution, the town of Tábor, whereas the distance to the other source, Sezimovo Ústí, was not significant) and on the initial species composition found on the tree. Trees under the effect of eutrophication changed their species composition less, indicating that the effect of eutrophication (mainly increased bark pH) may ameliorate the effects of air pollution; a local effect of eutrophication also seems to play an important role. Distance to pollution sources had only a small impact on the rate of change and perhaps other local conditions (sheltered or humid position, altitude) play a role in this interaction. There was a decrease of the overall heterogeneity of the data set over time. This means that the gradients in species composition attributable to these variables became less important over time. Therefore, one of the effects of air pollution is also a general homogenization of the lichen vegetation of the solitary trees.

Epiphytic lichens indicate recent increase in air pollution in the Mongolian capital Ulan Bator

Mongolia is one of the least densely populated countries of the world with 2·6 million people occupying an area of 1·5 million km2. A high proportion of the population and economy is concentrated in the capital Ulan Bator, which has 1 million inhabitants. Ulan Bator is characterized by its high elevation (1350 m), low precipitation (300 mm), high annual sunshine duration, and its location in a basin. The city is surrounded by mountain ranges to the north and to the south. Furthermore, it is the coldest capital of the world with an annual mean temperature of −3·7°C (Hilbig et al. 2004). Outside Ulan Bator and a few industrial areas, including a large copper plant near the second-largest city Erdenet, Mongolia’s air is extremely pure (ADB 2006). Therefore, Mongolia’s forests, which cover 10% of the country (Erdenechuluun 2006) harbour a rich epiphytic lichen vegetation (Cogt 1995). Most of these woodlands are conifer stands that form the southernmost range of the continuous Siberian taiga forests (Gunin et al. 1999). Eighty percent of the forest area of Mongolia is covered by Larix sibirica (Savin et al. 1978), while other important tree species in the taiga include Pinus sibirica, P. sylvestris, Picea obovata, Abies sibirica, and Betula platyphylla (Hilbig 1995; Dulamsuren et al. 2005). Dominant epiphytic lichen species in the larch-dominated taiga include Bryoria fuscescens, B. nadvornikiana, Evernia mesomorpha, Flavopunctelia soredica, Hypogymnia bitteri, H. physodes, Lecanora symmicta, Melanohalea septentrionalis, Parmelia sulcata, Usnea sp., and Vulpicida pinastri (Biazrov 1974; Hauck et al. 2007).

Epiphytic lichen vegetation on Larix in the Italian Alps

A synthesis of the epiphytic lichen vegetation on larch in the Italian Alps is presented. Vegetation types are described on the basis of a numerical classification of 291 relevés. They can be compared to a few well-known phytosociological unions found in other parts of the Alps. Some communities are restricted to subalpine areas with continental climate. Despite the homogeneity of the substrate, the flora is rich, with 98 species, several of which are rare, and hence of interest from a conservational point of view.

The significance of precipitation and substrate chemistry for epiphytic lichen diversity in spruce-fir forests of the Salish Mountains, northwestern Montana

The relevance of chemical site factors for the abundance of epiphytic lichens was studied in Picea engelmannii- Abies lasiocarpa forests of the Salish Mountains, northwestern Montana, USA. The Salish Mountains are an area with relatively low atmospheric pollutant load and low precipitation. Canonical correspondence analysis (CCA) suggests that cover of several lichen species was limited by high Mn concentrations of bark or by high ratios of Mn to Ca, Mg and Fe. Mn in the bark is known primarily to derive from the soil. An effect of Mn concentration or Mn/Ca and Mn/Mg ratios was not found on A. lasiocarpa. This suggests that A. lasiocarpa deposits Mn in the bark in a physiologically inactive form as already known from A. balsamea. Precipitation chemistry was apparently less relevant for epiphytic lichen distribution in the Salish Mountains, as no correlations between element concentrations in stemflow and cover values were found and as amounts of stemflow were small. However, precipitation in the study year was less than average. The lacking significance of precipitation chemistry is probably the cause why epiphytic lichen vegetation differed less between living and dead trees in the Salish Mountains than in highly polluted coniferous forests studied by our group in Germany; in Germany, the difference between living and dead trees was attributed to reduced interception of pollutants from the atmosphere by trees with reduced crown surface. The result of the present study that small-scale variation of epiphytic lichen abundance is only partly explainable by chemical parameters gives rise to the assumption that microclimate (e.g., moisture), which has not been systematically explored, could be an important site factor for epiphytic lichens in the Salish Mountains. Furthermore, tree age was identified by CCA as a relevant site factor for lichens on P. engelmannii.

Epiphytic lichen diversity on dead and dying conifers under different levels of atmospheric pollution

Based on literature data, epiphytic lichen abundance was comparably studied in montane woodlands on healthy versus dead or dying conifers of Europe and North America in areas with different levels of atmospheric pollution. Study sites comprised Picea abies forests in the Harz Mountains and in the northern Alps, Germany, Picea rubens– Abies balsamea forests on Whiteface Mountain, Adirondacks, New York, U.S.A. and Picea engelmannii– Abies lasiocarpa forests in the Salish Mountains, Montana, U.S.A. Detrended correspondence analysis showed that epiphytic lichen vegetation differed more between healthy and dead or dying trees at high- versus low-polluted sites. This is attributed to greater differences in chemical habitat conditions between trees of different vitality in highly polluted areas. Based on these results, a hypothetical model of relative importance of site factors for small-scale variation of epiphytic lichen abundance versus atmospheric pollutant load is discussed.

Recovery of the Epiphytic Lichen Flora Following Air Quality Improvement in South-West Sweden

The development of the epiphytic lichen vegetation on tree trunks inside and nearby twelve towns and industrial areas in south-west Sweden was investigated 1986/88 and 1997 using a photographic technique. The lichen vegetation studied in terms of area cover as well as the air pollution sensitivity and preference for nitrogen of the individual lichens. During both surveys the lichen flora was strongly impoverished in urban areas compared to suburban areas and especially to the countryside (reference) areas nearby. The air pollution situation has improved in the area both before and during the study period. This holds especially for SO2, to a lesser extent also for NO2. Following the improvement of the air quality, an increased lichen area cover on the tree trunks was observed. Also the cumulative pollution sensitivity of the lichens present was higher in 1997 compared to 1986/88 in suburban and countryside areas. For the nitrogen impact, the increase from 1986/88 to 1997 was smaller than for pollution sensitivity, but still statistically significant. The trends are interpreted as signs of a normalisation of the lichen flora. It is concluded that the observed pattern of lichen recovery reflects the fact that the reduction of the air pollution level in the central parts of the towns is still not large enough to permit a large-scale recovery of the lichen flora, while in the suburban areas and the countryside next to the towns, the air quality has now improved to an extent, which permits the reinvasion of a number of lichens.

Epiphytic Lichen Diversity and Forest Dieback: The Role of Chemical Site Factors*

Montane coniferous forests in Europe affected by pollutant-caused forest dieback often have a well-developed epiphytic lichen vegetation, including pollution-sensitive species. This phenomenon, apparently contradicting the assumption that acid air pollution is the cause for forest dieback, has been discussed controversially since the 1980s. Studies in Picea abies forests of the Harz Mountains, northern Germany suggest that the high lichen diversity on dieback-affected trees is due to reduced pollutant levels in bark and stemflow. Pollutant-caused needle loss reduces the interception of pollutants from the atmosphere and thus, reduces their concentrations in stemflow. Lower concentrations in stemflow result in lower concentrations in the bark because of reduced absorption. In the Harz Mountains, lower S concentrations in the stemflow of dieback-affected trees are thought to be the main cause for an even higher epiphytic lichen diversity on affected versus healthy trees. In one out of three spruce stands, high Cu concentrations in bark apparently have an additional limiting effect on lichen diversity. In all spruce stands studied in the Harz Mountains, high Mn concentrations in bark and partly also in stemflow limit lichen abundance. In contrast to S and Cu, Mn in bark and stemflow is primarily soil-borne. Lower Mn concentrations found in bark and stemflow of damaged and dead trees are attributed to reduced or lacking element uptake by the tree roots. Experiments to Mn uptake and toxicity in epiphytic lichens support the hypothesis that high Mn levels limit the abundance of epiphytic lichens. Decreasing lichen abundance with increasing Mn concentrations in bark or stemflow found in polluted and remote areas of western and eastern North America suggests that Mn may be an important site factor for epiphytic lichens in coniferous forests in general. Microclimate (including light and water conditions) is apparently of subordinate importance for the high epiphytic lichen diversity in dieback-affected spruce forests of the Harz Mountains. On dieback-affected Picea rubens on Whiteface Mountain, Adirondacks, New York, epiphytic lichen diversity was also found to be higher than on healthy trees. This cannot be attributed to S concentrations in stemflow, as the atmospheric deposition is much lower than in Germany. While Mn concentrations are apparently relevant for a limited number of lichen species on Whiteface Mountain, it is unclear whether lichen diversity might be limited by toxic effects of NO3− from stemflow. On dieback-affected Acer saccharum in Québec more acidophytic and less subneutrophytic lichen species were observed. This suggests that chemical site factors also control epiphytic lichen abundance in this case, however, the mechanisms leading to this effect are not known.

Lichens as bioindicators of environmental quality in dry Mediterranean areas: A case study from northern Greece

In dry Mediterranean areas, the scarcity of substrates for epiphytic lichens is a serious limiting factor in biomonitoring studies. In the present study, the epiphytic lichen vegetation of Quercus coccifera bushes was investigated in northern Greece, complementary to and compared with that of Pinus brutia trees. By combining the lichen data from these two quite different phorophytes, sampling versatility was greatly improved, and much better zonal mapping of the area was obtained.

Correlations between the Mn/Ca ratio in stemflow and epiphytic lichen abundance in a dieback-affected spruce forest of the Harz Mountains, Germany

Summary Dieback-affected trees of a boggy stand of Picea abies in the Harz Mountains, northern Germany, bore a richer epiphytic lichen vegetation than healthy trees. Cover of the foliose epiphytic lichen Hypogymnia physodes decreased with increasing Mn/Ca ratio in stemflow. The total of lichen species per tree decreased both with the Mn/Ca ratio in stemflow and with the Mn concentration in bark. The results agree with experimental tests of Mn toxicity to H. physodes . Comparison with other dieback-affected spruce stands of the Harz Mountains revealed that Mn attained unusually high concentrations in the study site because of high Mn concentrations in the soil. Mn concentrations in soil, bark, stemflow, and incident precipitation suggest that Picea abies removes excess Mn taken up from the soil by the root system by transferring it into the bark. Mn in stemflow is supposed to derive primarily from leaching of Mn from bark and needles. SO 4 2– concentration that was found to be decisive for epiphytic lichen distribution in other dieback-affected spruce stands of the Harz Mountains was of subordinate significance to lichen vegetation in the present case.

Epiphytic lichen vegetation of the Cedrus atlantica forests (Morocco)

L’activité humaine et la dégradation sont en train de transformer la végétation forestière du Maroc. Pour étudier les communautés de lichens épiphytes qui présentent encore leur structure originale, nous avons entrepris une étude sur trois ans (1998-2000) de la végétation lichénique des forêts à Cedrus atlantica du Rif et de l’Atlas central. Les données marocaines ont été comparées aux unités syntaxonomiques des forêts à Larix decidua et Pinus cembra des montagnes européennes et, en particulier, aux communautés acidophyles épiphytiques de l’Hypogymnietea physodis Follm. 1974. Malgré une certaine similitude floristique, les communautés des lichens des cédraies marocaines diffèrent de celles des montagnes européennes : les différences dépendent surtout des facteurs climatiques, écologiques et phytogéographiques qui marquent les limites de la végétation épiphytique oroboréale avec la végétation oroméditerranéenne. La spécificité des communautés épiphytiques des cédraies du Maroc est représentée par le Pseudevernio-Hypogymnietum laminisorediatae ass. nov., vicariante du Pseudevernietum furfuraceae des montagnes européennes.

Applicability of the lichen biodiversity method (L.B.) to a Mediterranean area (Liguria, nw Italy)

This study is part of the work aimed to standardise air quality biomonitoring methods in Italy. Some practical problems of the application of the lichen biodiversity (L.B.) method to a coastal area of the eastern Ligurian Riviera are analysed. In the first phase we studied the influence of variability on the parameters of the phorophytic substrata, on which we carried out the relevés. We considered the inclinations and circumferences of the tree trunks, and the exposure and height from the ground of the sampling grid. In the second phase, the study deals with the influence of the great geomorphologic variability on the microclimate and epiphytic lichen vegetation. The L.B. values were considered in relation to versant exposure, height above sea level and distance from the coast. We have suggested the use of less restrictive parameters for the L.B. sampling protocol. Furthermore, the distribution of two of the principal types of epiphytic lichen vegetation of the area, Xanthorion and Parmelion, were analysed in relation to the microenvironmental conditions.

Relevance of element content of bark for the distribution of epiphytic lichens in a montane spruce forest affected by forest dieback

Element content in the bark of Norway spruce ( Picea abies) was measured in a montane forest heavily affected by forest dieback and compared to that in a nearby intact stand. Bark contained less S, K, Fe, Mn, Pb, Cu, and H + and more N, Ca, Mg, and Zn in the dieback-affected stand than in the intact one. Diversity of epiphytic lichen vegetation was higher in the dieback-affected stand than in the intact one. Cover of the foliose lichen Hypogymnia physodes was negatively correlated with Mn and Cu content of bark. Cover of the extremely acidophytic species Lecanora conizaeoides decreased with increasing Mg and increased with increasing Cu content of bark. The measurements support the hypothesis that chemical site factors are decisive for the high lichen diversity in dieback-affected montane spruce forests.

EFFECT OF DUST ON EPIPHYTIC LICHEN VEGETATION IN THE MEDITERRANEAN AREA (ITALY AND GREECE)

The epiphytic lichens around limestone and sandstone quarries were investigated in northern Greece and central Italy to study the effect of alkaline and acid dust on epiphytic lichen vegetation in the Mediterranean area. The results showed that the main factor influencing the diversity of the epiphytic lichen vegetation studied is the distance from quarries, and that the chemistry of dust is not an important parameter. The fact that all but a few resistant lichen species die when subjected to high dust concentrations suggests that epiphytic lichens could be usefully employed for monitoring dust fallout and the effects of dust contamination.

Lichens as bioindicators of temporal variations in air quality around Thessaloniki, northern Greece

The epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia, northern Greece) surveyed in 1987 was sampled again in 1997 to monitor any changes in lichen communities and consequently in air quality. A general impoverishment in lichen communities was recorded in the 10‐year period, presumably chiefly due to changes in the air pollution status. A small increase in lichen species diversity was recorded in some stations, probably as a result of the buffering capacity of airborne dust.