Epiphytic Lichen Communities Research Articles

Hot-spots of epiphytic and epixylic lichens in fragmented temperate forests are underpinned by microhabitat heterogeneity and spatiotemporal habitat continuity

Habitat loss, fragmentation and degradation are major causes of the ongoing decline of epiphytic and epixylic lichen species in temperate forests throughout Europe. We investigated how extant species richness and composition of epiphytic and epixylic lichen communities in ten hot-spots of lichen diversity in the Czech Republic reflected the occurrence and properties of potentially suitable microhabitats and habitats. At each hot-spot, we surveyed a pair of 1-ha square plots, one in (over-)mature managed and the second in unmanaged forest. In total, we recorded 513 epiphytic and epixylic lichen species which represent a substantial part of lichen biota in Central Europe. Species richness and composition of lichen communities were explained by microhabitat heterogeneity, and also by the area of near-natural forest habitats (habitat extent) at the landscape scale. In addition, lichen species richness and number of red-listed species were explained by a categorial variable distinguishing mature managed and unmanaged plots, used as a proxy of temporal continuity of natural succession. This finding illustrates that temporal continuity of natural succession in unmanaged forests likely had an extra stimulus for lichen communities that may not be reflected by observed aspects of forest habitats. Hence, we confirmed indispensable positive effects of (micro)habitat heterogeneity, and spatial and temporal continuity for preserved hot-spots of lichen diversity in Central Europe. Due to generally slow colonization-extinction dynamics of epiphytic and epixylic lichens we call for strengthening microhabitat heterogeneity, and the spatial and temporal continuity of European temperate forests at the landscape scale.

The combined effects of habitat fragmentation and life history traits on specialisation in lichen symbioses

Abstract Interactions between organisms are determined by life‐history traits. Ecological strategies regarding species specialisation range from generalist to highly specialised relationships. Although it is expected that habitat fragmentation's effect on species abundance and survival depends on their degree of specialisation and life‐history traits, few studies have delved into the interplay between interaction specialisation, life‐history traits and habitat fragmentation. Here, we investigate the combined effect of habitat fragmentation, forest structure and life‐history traits (growth form and reproductive mode) on the specialisation of lichen‐forming fungi (mycobionts) toward their photosynthetic partners (photobionts) in lichen symbioses. We studied mycobiont specialisation in epiphytic lichen communities present in 10 fragments of Quercus rotundifolia forest embedded in an agricultural matrix. Both mycobionts and photobionts were identified DNA barcoding and mycobiont specialisation was measured through interaction parameters calculating the relative number of interactions (normalised degree; ND) and the specialisation of each species based on its discrimination from a random selection of partners (d'). Phylogenetic generalised linear mixed models were used to analyse the effect of patch size as well as the life history traits growth form (crustose, foliose, fruticose) and reproduction mode (sexual vs. asexual) on mycobiont specialisation. Both mycobiont and photobiont richness along the patch size gradient followed a hump‐back pattern, which was more pronounced in photobionts. Mycobionts forming crustose thalli established the largest number of interactions. Mycobiont specialisation (d') was larger for fruticose and foliose forms and species with vegetative reproduction. Along the gradient of fragment size, the relative number of interactions decreased and the specialisation of mycobionts with vegetative reproduction increased. Synthesis. The study of mycobiont specialisation towards their photobionts in epiphytic lichen communities in a fragmented Mediterranean forest revealed a complex interaction between species' life history traits and habitat fragmentation. In particular, this interplay had a significant impact on the specialisation of mycobionts. The results show the ability of some species to modulate their specialisation according to habitat conditions, suggesting that some species may be more resilient to abiotic changes than expected.

The response of epiphytic lichens on living and dead Pinus sylvestris to prescribed fires of varying severity

Prescribed burning can be used to restore forest ecosystems degraded by anthropogenic pressures. However, some species such as epiphytic lichens may be vulnerable to fire. We studied the effects of fire on epiphytic lichens on living and dead Pinus sylvestris (Scots pine) by surveying lichens up to two meters on the trunks 21 years after experimental and replicated prescribed burnings in pine-dominated boreal forests in Finland. We investigated three types of stands that had faced different levels of fire severity: 1) unburned semi-natural mature stands (i.e., control sites), 2) burned semi-natural mature stands, and 3) burned retention groups on clearcut sites. In the semi-natural mature stands, the fires were low-severity surface fires and induced negligible mortality in P. sylvestris. In the retention groups, the fires induced high tree mortality and made fresh deadwood the dominant substrate type. Low-severity fires reduced the occurrence of several species, but usually did not eliminate them. High-severity fires eliminated some species, but the abundant deadwood frequently hosted some species that were absent or infrequent on the unburned sites. Thus, the fires had only small effects on total species richness. However, fires substantially changed species composition: they reduced the occurrence of species associated with late-successional habitats, while increasing the occurrence of early-successional species. We also found fires to decrease the occurrence of microlichens and increase that of macrolichens. The magnitude of the compositional changes increased with fire severity. Our findings indicate that the high quantities of fresh deadwood in post-disturbance forests provide habitat only to a limited portion of deadwood-associated lichens. Fire can increase landscape-scale variation in epiphytic lichen communities, but we observed negative effects, which increased with fire severity, on lichen flora of conservation concern. Thus, we recommend prescribed burning to be applied primarily in sites with a history of intensive management. Fire should be avoided in sites with substrates that are fire-sensitive and important to lichen diversity.

Natura 2000 network enhances the protection of rare epiphytic lichens: evidence from forest sites of Central Italy

AbstractAlthough epiphytic lichens are widely adopted as environmental indicators, they are not yet included among the target species listed in Annex II of the Habitats Directive, to which the system of protected areas of the Natura 2000 network refers. In this work, we aim to test the effectiveness of this system, mainly designed for the conservation of other groups of species, in protecting lichen species richness. For this purpose, we considered a case study (Central Italy) with half of the territory included in protected areas. Statistical differences in species richness and lichen communities were tested between sites located in 16 Protected Areas (PA) and 11 Non-Protected Areas (NPA) using non-parametric tests, multi-response permutation procedures (MRPP), non-metric multidimensional scaling (NMDS) and Indicator Species Analysis (ISA). Despite the broad overlap between epiphytic lichen communities of NPAs and PAs and a similar number of total and common species, PAs contain a significantly higher number of nationally rare and extremely rare species, including cyanolichens. These results are also confirmed by the indicator analysis. Although the Natura 2000 network does not explicitly address the conservation of lichens, the protected areas in our study can play a role in protecting the diversity of epiphytic lichens, especially nationally rare and endangered species. However, the future inclusion of red-listed epiphytic lichens among the target species of Annex II of the Habitats Directive would be welcome to better protect these organisms on a European level.

Remote sensing in mapping biodiversity – A case study of epiphytic lichen communities

In boreal forests, European aspen (Populus tremula L.) is a keystone species that hosts a variety of accompanying species including epiphytic lichens. Forest management actions have led to a decrease in aspen abundance and subsequent loss of suitable habitats of epiphytic lichens. In this study, we evaluate the environmental responses of epiphytic lichen species richness and community composition on aspen, focusing on the potential of remote sensing by combined hyperspectral imaging and airborne laser scanning to identify suitable habitats for epiphytic lichens. We measured different substrate and habitat parameters in the field (e.g., aspen diameter and bark pH) and by remote sensing (e.g., mean canopy height and tree species composition of the surrounding forest) in the study area in Southern Finland that includes protected and non-protected forest. We used linear regression and the Hierarchical Model of Species Communities (HMSC) to compare how the different parameters explain and predict lichen species richness and community composition, respectively. We show that coarse predictions of epiphytic lichen community composition can be made using parameters extracted from remote sensing data. Estimated mean canopy height, tree density, dominant tree species and tree species diversity of the stand predicted the species community on aspens slightly better than field parameters. Remote sensing variables calculated over a larger area (30 m radius) always outperformed the same variables calculated over a smaller area (10 m radius) in predicting community composition, highlighting the cost-efficiency of remote sensing compared to covering a similar area with on-ground measurements. These results are encouraging for the prospects of using remote sensing data to direct field inventories and to map potential high-biodiversity habitats. Aspen bark pH was the only parameter affecting species richness regardless of whether the forest was protected or not, whereas, interestingly, the effects of tree diameter, height and furrow depth were only significant in protected areas. Our results also underline the importance of protected areas, since they hosted a higher tree-specific number of epiphytic lichen species, and red listed species, than non-protected areas.

Composition and Conservation Value of Epiphytic Lichen Communities on Common Ash in North-Western Alps: A First Assessment

In the western sector of the Alps, and particularly in the Aosta Valley, lichenological communities on broad-leaved trees have received very little attention, and information about lichen species associated with common ash (Fraxinus excelsior L.) are still scanty. Therefore, in this study, we analyzed epiphytic lichen communities of ash trees to estimate their composition, their conservation value, and their association with some key environmental variables. Our results show that lichen communities appear to be different in terms of occurrence and frequencies in different sampling sites. The tested environmental variables contribute to shape the lichen communities, which are significantly different (p < 0.05) in sites characterized by different elevation, solar radiation, and source vicinity. The conservation value of lichen species was assessed by comparing distributional data at the national and local level. Our findings show that, in the Italian Alps, ash trees represent an important substrate for locally, or even nationally, rare lichens: 14 recorded species were not previously known in the study area, and some (Lecanora impudens and Rinodina polyspora) were included in the red list of Italian epiphytic lichens.

Conifer tree species and age as drivers of epiphytic lichen communities in northern European production forests

AbstractThe epiphytic lichen species richness and community composition was compared for 600 living trees distributed within the interior of 60 Scots pine and Norway spruce monoculture stands in southern Sweden. A higher species richness, and more unique species, was found on trees of Scots pine than of Norway spruce, and distinctive communities were associated with the two tree species. Lichen species composition also shifted between the 30-, 55- and 80-year-old stands, although there was no significant difference in species richness between the different age classes. Tree species and age of the stand explained most of the variation in community composition (41%), with additional variance explained by lichen proximity to the ground (6%) and aspect (1%) (northern/southern side of trunk). Scots pine and Norway spruce share many attributes, such as both being conifers with acidic bark properties and having a similar geographical distribution in Fennoscandia. However, our study showed that species richness and community composition can nevertheless diverge in stands dominated by these two tree species. Since the occurrence of red-listed species was low in these stands, we suggest that 80-year rotations are not long enough for the occurrence of the many rare and specialized lichen species that require old forest structures and long forest continuity in this region.

NO2 air pollution drives species composition, but tree traits drive species diversity of urban epiphytic lichen communities

Lichens serve as important bioindicators of air pollution in cities. Here, we studied the diversity of epiphytic lichens in the urban area of 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. Our study moreover highlights the importance of large urban green spaces for species diversity. City planners need to include large green spaces when designing urban areas, both to improve biodiversity and to promote human health and wellbeing.

Functional traits of epiphytic lichen communities in a Temperate-Mediterranean fragmented landscape: Importance of patch size, tree diameter and summer rainfall

Functional traits have become important tools for evaluating the response of epiphytic lichens to environmental changes. In this study, we evaluated which predictors related to fragmentation, habitat quality and climate were driving the richness and cover of lichen growth form, type of photobiont and reproduction traits, at both fragment and plot levels in a Temperate-Mediterranean area dominated by Quercus forests. At fragment level, patch size and summer rainfall positively contributed to richness in most of the traits, while tree diameter and slope were the most important drivers, especially for the type of reproduction and growth form at plot scale. High coverage of growth forms especially sensitive to fragmentation were indicative of high values of total species richness, while early-colonizers indicated the opposite. These results provide important information on how lichen traits respond to environmental conditions in an ecotone area where a shift towards a drier climate is more likely to occur.

Do the natural dynamics of West Carpathian forests affect the diversity of epiphytic lichens on Norway spruce?

Over the last decades the West Carpathian spruce and mixed forests with a share of Picea abies, have been undergoing intensified dynamic changes, determined by windstorms and European spruce bark beetle outbreaks. Those changes should have a decisive effect on the survivability of species and shifts in epiphytic lichen communities on this phorophyte. Research conducted in the Gorce Mts (West Carpathians, Poland) in 1993, 2013 and 2018, on the same 186 spruce trees at 33 sites, revealed an increase in the species diversity of lichen communities in a long-term perspective (25 years). At the same time, there was a decrease in the coverage of the dominant species. Such changes are a result of long-term tree composition processes: the natural thinning of upper mountain spruce forests and the increase of lower mountain forests density after a decrease in the share of Norway spruce. The former prefers photophilous epiphytes, and the latter leads to an increase in the share of shade-tolerant species. The analysis of lichen communities by means of the principal components analysis (PCA) method for all three study periods combined showed that long-term changes were the most significant for this lichen biota, and short-term changes had no considerable effect. The conducted Redundancy Analysis (RDA) revealed, that the forest plant association was a stronger factor affecting the lichen community composition and coverage than tree stand density and saplings density in each observation term. The changes taking place in stands under bark beetle and wind disturbances should be treated differently in different types of forest associations, but in both, they cause differentiation of niches used by more specialized species of epiphytic lichens.

Little time left. Microrefuges may fail in mitigating the effects of climate change on epiphytic lichens

Climate change is already causing considerable reductions in biodiversity in all terrestrial ecosystems. These consequences are expected to be exacerbated in biomes that are particularly exposed to change, such as those in the Mediterranean, and in certain groups of more sensitive organisms, such as epiphytic lichens. These poikylohydric organisms find suitable light and water conditions on trunks under the tree canopy. Despite their small size, epiphytic communities contribute significantly to the functionality of forest ecosystems.In this work, we surveyed epiphytic lichen communities in a Mediterranean area (Sardinia, Italy) and hypothesized that 1) the effect of microclimate on lichens at tree scale is mediated by the functional traits of these organisms and that 2) micro-refuge trees with certain morphological characteristics can mitigate the negative effects of future climate change.Results confirm the first hypothesis, while the second is only partially supported, suggesting that the capability of specific trees to host specific conditions may not be sufficient to maintain the diversity and ecosystem functionality of lichen communities in the Mediterranean.

Climate and epiphytic macrolichen communities in the Four Corners region of the U.S.A.

We used data on epiphytic lichen communities in 1215, 0.4-ha plots in the Southwest U.S.A. collected by the Forest Inventory and Analysis (FIA) program to analyze relationships with climate. We sought the climate variables most strongly associated with differences in epiphytic macrolichen communities and described the nature of those relationships, including diversity, community composition, and patterns in individual species. Five lichen community groups were strongly related to temperature and elevation gradients, overall moisture, and summer rain. Lichen abundance was highest in the wettest groups and lowest in the hottest and driest groups. Warm summer monsoonal climates supported the greatest number of species across all plots and within plots. The monsoonal pattern did not occupy a discrete geographic area, but instead formed a gradient, strongest in the southern part of our study area, diminishing to the north and west. In contrast, hot summer monsoonal climates had much lower within-plot richness. Hot, dry climates had the most variation in species composition among plots, but the fewest species within each plot and across all plots. Lichen community gradients had nonlinear relationships with combinations of climate variables rather than strong linear relationships with any single variable, including those derivative climate variables meant to have direct biological relevance. Relationships between air quality and community gradients were weak, potentially overwhelmed by regional climatic variation and complex topographic gradients. Richness of particular functional groups was more strongly related to climate than was overall species richness; functional groups have their own climatic tolerances, owing to the physiological consequences of growth form and photobiont. Presumably species in different functional groups have experienced their own evolutionary tradeoffs, developing peak performance in different climates. On the other hand, overall richness was driven by an even more complex combination of performances relative to climate and was in some functional groups more strongly related to geographic coordinates than to climate variables. Because climatic variables are themselves geographically structured, stronger model fit for geographic coordinates than for climate implies some influence of large-scale historical factors (i.e., factors not clearly expressed in modern climates, such as past climates, vegetation structure, or disturbance regimes).

Genetic variation in the symbiont partners in the endangered macrolichenSeirophora villosa(Teloschistaceae: Ascomycota)

AbstractThe decline observed in many populations of highly sensitive lichens has led to the inclusion of some species on regional Red Lists, but this has seldom been accompanied by an examination of the genetic variation of the fungal and algal symbiotic partners. Here, the red-listed epiphytic lichen Seirophora villosa was surveyed in 14 Mediterranean coastal populations to examine the genetic diversity of both partners. The geographical distribution of four-locus haplotypes followed the same trend in mycobiont and photobiont data sets, some being widespread and others restricted to single localities. The fungus showed a moderate selectivity in its photobiont choice, associating with two undescribed Trebouxia microalgae with a biased distribution across the western Mediterranean. One alga species occurred exclusively in the Italian Peninsula. This region also hosted the highest number of haplotypes for both symbionts. The use of 454-pyrosequencing revealed no clear signs of algal coexistence within selected thalli. The phylogenetic reconstruction for the mycobiont showed uncertain limits among Seirophora spp., stressing the need for further taxonomic evaluation. Additionally, we found that Ramalina lacera, a co-occurring epiphytic lichen in the studied area, shared photobiont genotypes with S. villosa. Our results thus suggest that the protection not only of the red-listed species S. villosa, but also of the whole epiphytic lichen community investigated here might be advisable.

Tree species identity and composition shape the epiphytic lichen community of structurally simple boreal forests over vast areas.

Greatly simplified ecosystems are often neglected for biodiversity studies. However, these simplified systems dominate in many regions of the world, and a lack of understanding of what shapes species occurrence in these systems can have consequences for biodiversity and ecosystem services at a massive scale. In Fennoscandia, ~90% of the boreal forest (~21Mha) is structurally simplified with little knowledge of how forest structural elements shape the occurrence and diversity of for example epiphytic lichens in these managed forests. One form of structural simplification is the reduction of the number and frequency of different tree species. As many lichen species have host tree preferences, it is particularly likely that this simplification has a huge effect on the lichen community in managed forests. In a 40-70 years old boreal forest in Sweden, we therefore related the occurrence and richness of all observed epiphytic lichens to the host tree species and beta and gamma lichen diversity at the forest stand level to the stand's tree species composition and stem diameter. Picea abies hosted the highest lichen richness followed by Pinus sylvestris, Quercus robur, Alnus glutinosa, Betula spp., and Populus tremula. However, P. tremula hosted twice as many uncommon species as any of the other tree species. Stand level beta and gamma diversity was twice as high on stands with four compared to one tree species, and was highest when either coniferous or deciduous trees made up 40-50% of the trees. The stem diameter was positively related to lichen richness at the tree and stand level, but negatively to beta diversity. For biodiversity, these findings imply that leaving a few trees of a different species during forest thinning is unlikely as effective as combining life-boat trees for endangered species with an even tree species mixture.

Lichen communities on Populus tremula are affected by the density of Picea abies

AbstractQuestionsAspen (Populus tremula) is declining in the old‐growth forests of boreal Fennoscandia. This threatens the numerous taxa that are dependent on old aspens, including many epiphytic lichens. Potential methods to aid epiphytic lichens on aspen are centered around treatments which affect the density of Norway spruce (Picea abies). In this study, we investigated how epiphytic lichen communities on aspen are affected by the variation of spruce density in the immediate vicinity of the focal aspen.LocationSouthern boreal forests in Finland.MethodsWe recorded the occurrence of lichens from 120 aspens in 12 semi‐natural forest sites. We used spruce basal area as the measure for spruce density. The selected aspens represented a gradient in spruce basal area in the vicinity of the aspen from 0 to 36 m2/ha. We also measured other tree‐ and stand‐level variables that are known to influence lichen occurrence.ResultsLichen communities on aspen were affected by spruce density, stand age and bark pH. Both lichen species richness and the richness of red‐listed species were highest at an intermediate spruce density, and both increased with stand age. Lichen species richness was higher when bark pH was lower. Additionally, community composition was influenced the most by spruce density, followed by bark pH.ConclusionsOur study highlights the detrimental effects of high spruce density on lichen diversity on aspens. This is caused by high spruce density resulting in low light availability. Lichen diversity on aspens was highest when spruce density was intermediate. Spruce thinning in aspen‐rich old‐growth forests can be helpful in ensuring the long‐term persistence of old‐growth lichens on aspen in protected forests.

Phylogenetic structure of lichen metacommunities in Amazonian and Northeast Brazil

AbstractAmazon, Atlantic forest, Brejos de Altitude, Caatinga, Carrasco, Cerradão and Restinga are major vegetation units in North and Northeast Brazil. Little is known about lichen metacommunity structure in these habitats. While species richness and composition generally depend on climatic factors, in azonal vegetation edaphic factors may have a filtering effect on tree bark structure and hence the composition of epiphytic lichen communities. We hypothesized that climatic stress and a tree bark filtering effect would result in reduced richness and phylogenetic clustering in Caatinga, Carrasco, Cerradão and Restinga, whereas high richness and phylogenetic overdispersion were predicted for Amazon and Atlantic Forest. To test this, we analyzed 2,090 lichenized species in the study area, with a supertree to assess phylogenetic metacommunity structure. Amazon and Atlantic forest exhibited high richness and phylogenetic diversity, with phylogenetic overdispersion only in the Amazon. The zonal Caatinga with drought stress and the extrazonal Brejos both exhibited phylogenetic clustering. Among the azonal, edaphic vegetation units, Cerradão exhibited phylogenetic overdispersion, whereas Restinga showed phylogenetic clustering. Nearest taxon phylogenetic distance indicated a close relationship between Amazon and Atlantic forest, Atlantic forest and Brejos and Atlantic forest and Caatinga. Carrasco was mostly closely related to Cerradão, and Restinga was distantly related to any other unit. These findings indicate more complex patterns in the phylogenetic structure of lichen metacommunities, partly reflecting those of plant metacommunities, as a result of concurrent macroecological evolutionary histories. Our data supported floristic evidence that Carrasco is part of the Cerrado complex and not related to Caatinga.

Weak recovery of epiphytic lichen communities in Sweden over 20 years of rapid air pollution decline

AbstractEpiphytic lichens are sensitive to deteriorating air quality, but levels of nitrogen and especially sulphur deposition have been in decline over most of Europe in recent decades. We assessed the response of epiphytic lichens to this decline, using data from long-term monitoring sites in Sweden. We analyzed 20 years of data to investigate temporal trends in lichen communities’ sensitivity to sulphur, nitrogen preference, species richness and alpha and beta diversity. We found only limited and partial evidence of recovery in the area that previously had high levels of deposition, and a decline in mean sulphur sensitivity at a northern site with low deposition levels throughout the monitoring period. The slow recolonization of sensitive species, even where environmental conditions are now suitable, is probably a result of impoverished regional species pools and the inherent limited dispersal capacity of many lichen species. We suggest due consideration of these factors in the use of epiphytic lichens as environmental indicators in a period of improving air quality.

Challenges characterizing N deposition to high elevation protected areas: A case study integrating instrument, simulated, and lichen inventory datasets for the Devils Postpile National Monument and surrounding region, USA

Excess N deposition is a common stressor of ecological health. Sensitive biota, including many lichens, respond to small differences in atmospheric N deposition. For lands with a conservation mandate, obtaining sufficient N data to evaluate risks is a challenge, especially in Mediterranean or arid landscapes. Managers in the Western U.S. commonly use epiphytic (“tree-dwelling”) lichens to supplement N assessments, although options for higher elevations lacking epiphytes are poorly developed. Managers instead rely on broad-scale air quality simulations like the Total Deposition Model (TDEP). The Sierra Nevada Range is an example where anthropogenic N reaches mid-to-high elevation protected areas but managers lack tools for monitoring at ecologically relevant spatial-scales. Our main goals were to demonstrate how well-studied epiphytic bioindicators can supplement N assessments and recommend saxicolous (“rock-dwelling”) candidates for similar development to improve coverage in higher elevations. As a case study, we characterized N deposition at a small (323 ha) protected area, Devils Postpile National Monument (DEPO), by integrating data from TDEP, air instruments, and assays of %N in the epiphyte Letharia vulpina. We used the regional N threshold associated with detrimental effects to epiphytic lichen communities, 2.9 kg N ha−1 yr−1 in throughfall (i.e. under a tree canopy), as a provisional critical load (CL) for indicating areas at risk of ecological impacts. Results clearly showed the need for empirical, diverse, and finer-scaled information, even for an area as small as DEPO. Importantly, simulations from TDEP overestimated dry deposition of oxidized N, making total N estimates nearly twice measured values (6.0 vs 3.03 – 3.66 kg N ha−1 yr−1, respectively). While small, our L. vulpina dataset (n = 5) from the Monument indicated highly variable N in throughfall (1.7 – 4.44 kg N ha−1 yr−1), with small-scale drivers, like proximity to the river canyon and the Central Valley, tipping the scale towards CL exceedance. Regional L. vulpina assays (n = 355) showed a distinct north-to-south gradient in California where N deposition at DEPO was highly similar to the nearby protected area, Yosemite National Park, where ecological impacts of excess N are well-documented. To expand N bio-monitoring into higher elevation areas, we recommend vetting five widespread saxicolous species, Rhizoplaca melanophthalma, Umbilicaria phaea, U. polaris, Xanthoparmelia coloradoënsis, and X. cumberlandia.

The response of lichen growth forms to fire frequency: a case study in oak forests of the southern Russian Far East

Epiphytic lichens are used as sensitive indicators of environmental changes. Lichen growth forms are related to biotic and abiotic factors. In the present study, we investigate the response of lichen growth form diversity to fire frequency. In the oak forests of the southern Primorsky Krai, we established 43 sampling plots of 25 m x 25 m each. All plots were assigned to four fire history regimes defined by the combination of fire marks. A total of 168 epiphytic lichen species were recorded. They were classified into 12 groups of growth forms. The linear regression model demonstrated that the taxonomic diversity of epiphytic lichens and the growth form diversity were highly and positively correlated. Increasing fire frequency resulted in limited damage to growth form diversity of the epiphytic lichen communities, whereas species diversity drastically decreased with increasing fire frequency. The diversity of most growth form groups were connected with the gradient of fire frequency. Diversity of growth forms tolerant to a wide environmental variety, such as foliose species with narrow lobes, crustose granular verrucose, and compact crustose, drastically decreased under regular fire events. In contrast, growth forms adapted to sheltered and humid environments, such as foliose gelatinous, foliose inflated, and foliose with broad lobes, were absent on the plots with regular and frequent fire events. Thus, due to the close relationship between morphological traits and specific environmental conditions, certain groups of growth forms can be used as indicators of fire regimes of forests.

Evaluación de los cambios en una comunidad de líquenes epífitos después de 45 años, un caso de estudio en álamos blancos del norte de la península ibérica (jaca, Aragón)

Los líquenes epífitos se usan generalmente como bioindicadores, debido a que son organismos sésiles de crecimiento lento y las diferentes especies muestran un gran rango de sensibilidad ambiental. La mayoría de los estudios sobre líquenes epífitos se centran en utilizarlos como indicadores de las condiciones ambientales actuales, pero hay pocos analizando cambios temporales. La escasez de datos antiguos y la poca persistencia de los substratos, árboles en su mayoría, hacen que los estudios que incluyen una comparación temporal más o menos larga sean bastante raros. Sin embargo, en 1973 uno de nosotros (X. Llimona) describió la comunidad de líquenes de Populus alba de la parte urbana de Jaca, y esos árboles aún siguen vivos. El objetivo de este estudio es conocer la comunidad de líquenes de epífitos del 2018 y comparar con el estudio de 1973. La riqueza de especies disminuyó ligeramente durante estos 45 años. Sólo el 36% de las especies encontradas en 1973 persistían en 2018, aunque las persistentes se observaron con alta frecuencia en el muestreo de 2018. La sensibilidad ambiental de la comunidad de líquenes no cambió a lo largo de los años, así como, la localidad y sus alrededores no han cambiado de uso de suelo durante décadas. Los cambios en la composición de los líquenes entre ambos muestreos podrían explicarse por la sucesión autógena o limitación en la dispersión más que por filtraje ambiental. Nuestros datos sugieren que, en entornos estables, el ensamblaje de las comunidades de líquenes epífitos durante décadas depende de otros rasgos como la competencia y no de la sensibilidad ambiental de los líquenes.