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The location of lichen surveying sites in Epping Forest with an additional map inset showing the location of Epping Forest within Great Britain. Ó Crown copyright. All rights reserved. (100023243) (2010).
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The relationship between different features of lichen communities in Quercus robur canopies and environmental variables, including concentrations of NO(2) and NH(3) was investigated. NO(2) concentration was the most significant variable, it was positively correlated with the proportion of lichen cover comprising nitrophytes and negatively correlate...
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... sites were chosen as representative 'background' (non-roadside) sites located more than 100 m from the nearest road (Fig. 1). These sites formed a 19 km transect through the Forest, at distances from 14 to 30.5 km from central London. The minimum distance between two sites was 200 m. The transect was located in a northesouth orientation, in the direction of the prevailing wind, and directly downwind of London. Seven further sites were located close to ...
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Citations
... In our study, the number of plots, in which L. conizaeoides was identified with eDNA in 2021, has halved in relation to the floristic study in 2007/2008. Today, nitrogen pollution is more important in shaping lichen communities than SO 2 pollution (Purvis et al. 2003;Hultengren et al. 2004;Pinho et al. 2008;Gadsdon et al. 2010). Temperate forests experience increased deposition of nitrogen, for example, through ammonia fertilisers or nitric oxides from fuel combustion, and nitrophytic species have increased in the recent past (Carter et al. 2017). ...
... Temperate forests experience increased deposition of nitrogen, for example, through ammonia fertilisers or nitric oxides from fuel combustion, and nitrophytic species have increased in the recent past (Carter et al. 2017). In the present study, two species regarded as nitrophytes, Physcia adscendens and P. tenella (Gadsdon et al. 2010), have been found more frequently in the eDNA sampling than in the earlier floristic survey (Fig. 3). Interestingly, other nitrophytic species, such as Xanthoria parietina, Phaeophyscia orbicularis or Candelariella reflexa (Gadsdon et al. 2010), were found less frequently or not at all in the eDNA sampling (Suppl. ...
... In the present study, two species regarded as nitrophytes, Physcia adscendens and P. tenella (Gadsdon et al. 2010), have been found more frequently in the eDNA sampling than in the earlier floristic survey (Fig. 3). Interestingly, other nitrophytic species, such as Xanthoria parietina, Phaeophyscia orbicularis or Candelariella reflexa (Gadsdon et al. 2010), were found less frequently or not at all in the eDNA sampling (Suppl. material 1). ...
Lichens are an important part of forest ecosystems, contributing to forest biodiversity, the formation of micro-niches and nutrient cycling. Assessing the diversity of lichenised fungi in complex ecosystems, such as forests, requires time and substantial skills in collecting and identifying lichens. The completeness of inventories thus largely depends on the expertise of the collector, time available for the survey and size of the studied area. Molecular methods of surveying biodiversity hold the promise to overcome these challenges. DNA barcoding of individual lichen specimens and bulk collections is already being applied; however, eDNA methods have not yet been evaluated as a tool for lichen surveys. Here, we assess which species of lichenised fungi can be detected in eDNA swabbed from bark surfaces of living trees in central European forests. We compare our findings to an expert floristic survey carried out in the same plots about a decade earlier. In total, we studied 150 plots located in three study regions across Germany. In each plot, we took one composite sample based on six trees, belonging to the species Fagus sylvatica , Picea abies and Pinus sylvestris . The eDNA method yielded 123 species, the floristic survey 87. The total number of species found with both methods was 167, of which 48% were detected only in eDNA, 26% only in the floristic survey and 26% in both methods. The eDNA contained a higher diversity of inconspicuous species. Many prevalent taxa reported in the floristic survey could not be found in the eDNA due to gaps in molecular reference databases. We conclude that, currently, eDNA has merit as a complementary tool to monitor lichen biodiversity at large scales, but cannot be used on its own. We advocate for the further development of specialised and more complete databases.
... Moreover, few studies have investigated the recovery of lichen communities once disturbance ceased (Edmondson et al. 2013;Benvenutto-Vargas & Ochoa-Hueso 2020). While variation in the composition of lichen communities under atmospheric pollution and different climatic gradients is well documented (Gadsdon et al. 2010), little is known about potential changes in the interactions between mycobiont and photobiont; this is surprising as adaptation of lichens to different environmental conditions is highly dependent on their photobiont (Peksa & Skaloud 2011). The ability of mycobionts to establish associations with several lineages of photobionts is considered an adaptive strategy to tolerate a wider range of environmental conditions (Fern andez-Mendoza et al. 2011;Jüriado et al. 2019). ...
Atmospheric pollution containing soil‐nitrifying ammonium sulfate ((NH₄)₂SO₄) affects semi‐natural ecosystems worldwide. Long‐term additions of (NH₄)₂SO₄ to nitrogen (N)‐limited habitats, including heathlands, increase climate stress affecting recovery from wildfires. Although heathland vegetation largely depends on ericoid mycorrhizal fungi (ErM) to access soil N, we lack detailed understanding of how prolonged exposure to (NH₄)₂SO₄ may alter ErM community composition and host plants' reliance on fungal partners following wildfire and affect recovery. Simulation of atmospheric pollution ((NH₄)₂SO₄) occurred bi‐weekly for 5 years after a 2006 wildfire in a UK heathland. Ten years after treatments ceased, we measured vegetation structure, lichen and lichen photobiont composition, soil characteristics, ErM colonization, ErM diversity in roots and soil, and assessed ErM potential as novel recovery indicators. Heather height and density, and moss groundcover, were greater in N‐enriched plots. Lichen community indices showed significant treatment effects, but without differences in photobionts. Soil pH and Mg were significantly lower in treated plots while soil cation exchange capacity was significantly higher. There were no detectable differences in ErM composition and keystone ErM taxa between control and treated plots. Soil carbon stock measures were variable. Our results indicate atmospheric pollution following fire can have significant lingering effects above‐ and belowground. ErM diversity and root colonization were not assessed in the original N‐addition experiment; we advocate for their inclusion in future studies as an integral part of the recovery assessment toolkit. We show that mycorrhizal fungi diversity is a viable ecological tool and summarize key steps for ErM identification.
... The association rules found for the genera Pyxine and Physcia identified them as tolerant to heavy pollution, most especially SO 2 and NO 2 , thus indicating their relevance as bioindicators of poor air quality. These genera have been reported to be tolerant to heavy pollution as found in urban environments (Gadsdon et al. 2010;Sujetovienė 2010;Lewis 2012;Manninen 2018;Yatawara and Dayananda 2019). The genus Diorygma was found to be tolerant to poor ambient conditions with high levels of SO 2 and NO 2 . ...
There are significant gaps in air quality monitoring across many low- and middle-income countries, which can be filled by bioindicators like lichen. This study examined the links between lichen and air quality across urban environments in Nigeria. Lichen surveys and air quality monitoring were carried out across four major cities focusing on NO2, SO2, PM2.5, and PM10. Association rule mining was used to identify robust rules defining the association between lichen and air quality categories. For the maximal frequent set with Lichen in the antecedent, 9 and 5 rules were identified by A priori and Eclat, respectively. These indicated that three genera: Diorygma, Pyxine, and Physcia are the most commonly associated lichen with poor air quality particularly NO2 and SO2. This showed that these lichens are viable indicators of long-term air quality due to their consistent occurrence across the rules from different algorithms.
... Moreover, few studies have investigated the recovery of lichen communities once disturbance ceased (Edmondson et al. 2013;Benvenutto-Vargas & Ochoa-Hueso 2020). While variation in the composition of lichen communities under atmospheric pollution and different climatic gradients is well documented (Gadsdon et al. 2010), little is known about potential changes in the interactions between mycobiont and photobiont; this is surprising since adaptation of lichens to different environmental conditions is highly dependent on their photobiont (Peksa & Škaloud 2011). The ability of mycobionts to establish associations with several lineages of photobionts is considered an adaptive strategy to tolerate a wider range of environmental conditions (Fernandez-Mendoza et al. 2011;Jüriado et al. 2019). ...
Atmospheric pollution containing soil-nitrifying ammonium sulphate is affecting semi- natural ecosystems worldwide. Long-term additions of ammonium sulphate on nitrogen (N)-limited habitats such as heathlands increase climate stress affecting recovery from wildfires. Yet although heathland vegetation largely depends on ericoid mycorrhizal fungi (ErM) to access soil N, we lack a detailed understanding of how prolonged exposure to ammonium sulphate may alter ErM community composition and host plants’ reliance on fungal partners following wildfire and substantial reductions in ammonium sulphate pollution. Effects on ecosystem processes, particularly carbon stores, also remain uncertain. Ammonium sulphate additions occurred bi-weekly for five years after a 2006 wildfire burnt a UK heathland. Ten years after the treatments ceased (2021), we measured vegetation structure, lichen and lichen photobiont composition, soil characteristics, ErM colonisation, ErM diversity in roots and soil, and assessed their potential as recovery indicators. We found heather height and density, and moss groundcover, were greater in N-enriched plots. Lichen community indices showed significant treatment effects without photobiont differences. Soil pH and Mg, and the proportion of putative ErM fungi in soil were significantly lower in treated plots while soil cation exchange capacity was significantly higher. Increases in soil pH were positively correlated to soil ErM abundance. Soil carbon stock measures were variable and negatively related with soil ErM. Our results indicate that atmospheric pollution following fire can have significant lingering effects and mycorrhizal fungi diversity are a novel and effective ecological tool to assess ecosystem recovery on heathlands.
IMPLICATIONS FOR PRACTICE
Recovery of heathlands from wildfire and atmospheric pollution may require decadal scales. Conventional restoration assessment tools lack critical understanding of belowground soil and mycorrhizal fungi interactions and nutritional feedback loops with aboveground hosts.
Given that ericoid mycorrhizal fungi (ErM) communities are key nutrient regulators of resilient heathlands, we recommend baseline measurements of ErM diversity and abundance in both soil and dominant plant roots be added to the recovery assessment toolkit prior to commencing restoration or management plans.
What defines ErM recovery, and disentangling effects of ammonium sulphate pollution and fire, remain open questions which only long-term field experiments across pollution gradients will address.
... NO 2 pollution levels were found to determine the species composition of epiphytic lichen communities on deciduous trees in the urban area of Munich in Germany, and all common species except one were nitrophilic (Sebald et al. 2022). In regions with depositions of NO 2 and ammonia, acidophilic lichens have been largely replaced by nitrophilic ones (de Bakker 1989;van Dobben & de Bakker 1996;van Herk 2001;Gadsdon et al. 2010). For example, the nitrophilic Xanthoria parietina (L.) Th. ...
Microsatellite markers can provide valuable information about gene flow and population history. We developed and tested new microsatellites for the nitrophilic lichenized fungus Xanthoria parietina and studied its genetic diversity and structure within the urban area of Munich, Bavaria. We compared its local genetic pattern with that of its photobiont partner Trebouxia decolorans , for which existing microsatellites were applied. For comparison, a reference site with clean air was included in the sampling. We found support for three genetic clusters in the fungus X. parietina , which occurred intermingled in collecting sites. There was a high degree of admixture within fungal populations and individuals, and analysis of molecular variance revealed a lack of population structure in the mycobiont. The Trebouxia photobiont, in contrast, exhibited structured populations which grouped into two to five genetic clusters, and individuals showed less admixture than in the mycobiont. This indicates that the two lichen partners differ in their ability to move around in the landscape. The microsatellite markers we report are polymorphic and are suitable for population genetic studies.
... Many studies have provided interesting biomonitoring results regarding the relationships between lichen communities' compositions and modeled or measured values of nitrogen and sulfur deposition within forest national monitoring networks in several different European countries (Estonia [44,50], the UK [45], Portugal [46,55], Finland [47], Italy [51], and the USA [40,41,48,49,52,54]). Forests are remote ecosystems of less interest from a risk assessment point of view because of their low population density. However, studying the effects of atmospheric pollution in forest environments may be a good approach for obtaining a reference for the background values in remote areas. ...
... Monitoring of the functional traits of animals, plants, and fungi has increased considerably in recent decades [60]. Concerning epiphytic lichens, functional traits such as growth forms, photosynthetic partners, reproductive strategies, and sensitivity to pollutants (e.g., oligotrophic and nitrophytic species) have been extensively studied in the context of forest monitoring (e.g., [16,44,45,48,50,55]). Here, we consider for discussion only some of the relevant papers on the topic ranging from 1999 to 2021 (Table 2). ...
... One example is the composition and ratio of oligotrophic and nitrophytic species in the lower trunks of forest trees. Several studies suggest that the proportions of the two functional groups may be a suitable indicator of the impact of oxidized and reduced nitrogen compounds [31,33,45,46,68]. ...
Currently, forest ecosystems are often located in remote areas, far from direct sources of air pollution. Nonetheless, they may be affected by different types of atmospheric deposition, which can compromise their health and inner balance. Epiphytic lichens respond to air pollution and climate change, and they have been widely adopted as ecological indicators, mainly in urban and industrial areas, while forest ecosystems are still underrepresented. However, in recent years, their use has become increasingly widespread, especially in the context of long-term monitoring programs for air pollution in forests. In this review, we provide a critical analysis of the topic from the point of view of the different methodological approaches based on lichen responses adopted in forest ecosystems. Further, we discuss the main challenges posed by the current global change scenario.
... The association rules found for the genera Pyxine, Physcia and Lecanora identified them as tolerant to heavy pollution (PM, SO 2 and NO 2 ), thus relevant as bioindicators of poor air quality. This was in agreement with the findings of Conti and Cecchetti [9], Lewis [16], Davies, Bates [21], Yatawara and Dayananda [44], Wolseley and Aguirre-Hudson [47], Gadsdon, Dagley [48], Sujetovienė [49], Manninen [50], Asta, Erhardt [51] which identified them as tolerant to heavy pollution found across heavily disturbed sites e.g., urban centres and roadsides. The genera Candelaria, Diorygma and Parmotrema were also found to be N-tolerant and PM-tolerant, thus indicative of poor air quality. ...
Urban environments represent the most intense human-environment interaction. This interaction can result in negative outcomes like air pollution and its health implications. There is a significant data deficit in air quality monitoring across many developing nations, which prevents effective policies and measures from being taken to promote the accomplishment of sustainable development. Around the world, lichens have been used to track environmental changes due to their sensitivity to changes and concentration of atmospheric pollutants. This study investigated the relationships between lichen and air quality across some Nigerian cities. Lichen surveys were conducted in four cities. At various periods during the day, NO2, SO2, PM2.5, and PM10 levels were measured. Association rule mining was carried out to investigate the relationship between lichen found and air quality categories. Results showed that the most prevalent lichen Genera are Pyxine in Abuja and Kano, Diorygma in Lagos, and Dirinaria in Port Harcourt. Out of the 40 rules found from the rule mining, 17 are important (lift values ≥ 1.1), capturing six of the fourteen lichen genera identified in the field. The findings indicated that there are important relationships between lichens and air quality indices, suggesting that some lichen species in Nigeria may serve as indicators of long-term air quality. To develop a network of urban environmental quality bioindicators across Nigerian cities, surveying and transplanting are advised. The use of lichen for air quality monitoring can provide information for sustainable management of air quality and environmental quality in Nigeria.
... Ammonium toxicity arises as the algal uptake exceeds its assimilation capacity. When the transformation of NH 3 to NH 4 + occurs in (Davies et al., 2007), e= (Pinho et al., 2008), f= (Manninen, 2018), g= (Watmough et al., 2017), h= (Watmough et al., 2014), i= (Gadsdon et al., 2010), j= (Gibson et al., 2013), k= (Perlmutter et al., 2018), l= (Jovan et al., 2012). LOEC levels are indicated by circles, and bars represent the range of NO 2 exposures observed in the study. ...
... If photosynthesis increases in response to N additions a positive feedback loop might be created, in which conversion of the NH X to amino acids could then be used to increase chlorophyll concentration and further increase photosynthetic capacity. A comparison of lichen exposed to NH 3 , NH 4 + and NO 3 − , found exposure to dry deposition of NH 3 caused the (Pitcairn et al., 2004), b= (Leith et al., 2005), c= (Pinho et al., 2009), d= (Wolseley et al., 2006), e= (Rihm et al., 2009), f= (Frati et al., 2007), g= , h= , i= , j= (Watmough et al., 2014), k= (Pinho et al., 2012), l= (Aguillaume et al., 2017), m= (Gadsdon et al., 2010), n= (Sparrius, 2007), o= (van Herk, 2001), p= (Jovan et al., 2012), q= (Pinho et al., 2011). LAN = Lichen Diversity index, LDVnitro = Lichen diversity index nitophytic species, LDVoligo = Lichen diversity index oligotrophic species, *study from Canada, ** study from the United States. ...
... Atmospheric Environment 292 (2023) 119396 not report the p-value (Gibson et al., 2013;Watmough et al., 2017). Results from the study examining lichen cover show decreasing total lichen cover (Gadsdon et al., 2010) was offset by increasing cover of eutrophs. It is important to note that declines in species richness are likely due to a decline in oligotrophic species and may be partially offset by gains in eutrophic species, however the one study that evaluated species richness of eutrophs showed no significant effect of NO 2 (Pinho et al., 2008). ...
The dominant chemical form of nitrogen pollution in the atmosphere in the U.S. is shifting from oxidized nitrogen, primarily from combustion of fossil fuels, to reduced nitrogen from agricultural animal waste and fertilizer applications. Does it matter to lichens? In this synthesis, we characterize U.S. air concentrations of the most ubiquitous gaseous forms of reduced and oxidized nitrogen, NO2 and NH3, respectively, and their direct effects on lichens. In the U.S., the 3-year average (2017–2019) of the annual mean for each monitoring site ranges up to 56.4 μg NO2 m−3 (∼30 ppb) and 6 μg NH3 m−3 (∼9 ppb). The spatial coverage of current routine monitoring of NO2 and NH3 likely does not accurately represent exposures of NO2 to ecosystems in rural areas or capture spikes of NH3 concentrations proximal to intensive agriculture, which are documented to exceed 700 μg NH3 m−3 (∼1000 ppb) for short durations. Both NO2 and NH3 can act as nutrients to lichens, but as exposures rise, both can cause physiological stress and mortality that then change community composition and diversity. There is a growing body of evidence that lichen community composition is altered at current levels of exposure in the U.S. with estimated no effect or lowest effect concentrations from <1 to 3 μg m−3 NO2 and <1 μg m−3 NH3. Better spatial characterization of both NO2 and NH3 concentrations, especially near intensive agriculture, would help to characterize the extent of the impacts across the U.S. These findings are discussed in the context of U.S. air pollution policy.
... They were mostly matching to the class Gammaproteobacteria (54%, phylum Proteobacteria) and the family Chitinophagaceae (77%, phylum Bacteroidetes), respectively (Table S2). The sequential reduction of nitrogen oxides during denitrification may be crucial since these oxides could decrease the photosynthetic rates in lichens (Hauck, 2010;Gadsdon et al., 2010), so bacteria in the thalli removing these damaging compounds could be beneficial for the lichen symbiosis. Predicted markers related to denitrification mainly matched the phyla Proteobacteria and Bacteroidota (Fig. S1), which were two of the most abundant phyla in the bacterial microbiome of P. frigida lichens (Leiva et al., 2021). ...
... By limiting sulphurous fuels in "first world" countries, global SO 2 pollution has decreased over the last 20 years (Baumbach, 1994), whereas nitrogen dioxide pollution has remained constant. This has caused increases in the abundance of nitrophilous species (Gadsdon et al., 2010). ...
... Studies of epiphytic foliose lichens in Ontario found a decline of lichen richness with increasing nitrogen pollution (McDonough and Watmough, 2015;Watmough et al., 2014). Similarly, a study that sampled lichens in Quercus robur canopies in the UK showed that NO 2 concentrations are negatively correlated with total lichen cover (Gadsdon et al., 2010). Nitrogen pollution has a direct negative influence on lichen physiology, influencing nitrophobic species more than nitrogen tolerant species (Munzi et al., 2014). ...
Lichens serve as important bioindicators of air pollution in cities. Here, we studied the diversity of epiphytic lichens in an urban area in Munich, Bavaria, southern Germany, to determine which factors influence species composition and diversity. Lichen diversity was quantified in altogether 18 plots and within each, five deciduous trees were investigated belonging to on average three tree species (range 1–5). Of the 18 plots, two were sampled in control areas in remote areas of southern Germany. For each lichen species, frequency of occurrence was determined in 10 quadrats of 100 cm² on the tree trunk. Moreover, the cover percentage of bryophytes was determined and used as a variable to represent potential biotic competition. We related our diversity data (species richness, Shannon index, evenness, abundance) to various environmental variables including tree traits, i.e. bark pH levels and species affiliation and air pollution data, i.e. NO2 and SO2 concentrations measured in the study plots. The SO2 levels measured in our study were generally very low, while NO2 levels were rather high in some plots. We found that the species composition of the epiphytic lichen communities was driven mainly by NO2 pollution levels and all of the most common species in our study were nitrophilous lichens. Low NO2 but high SO2 values were associated with high lichen evenness. Tree-level lichen diversity and abundance were mainly determined by tree traits, not air pollution. These results confirm that ongoing NO2 air pollution within cities is a major threat to lichen diversity, with non-nitrophilous lichens likely experiencing the greatest risk of local extinctions in urban areas in the future.
