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Lichen Communities (lichen + community)

Distribution by Scientific Domains
Earth and Environmental Science54%
Life Sciences45%

Selected Abstracts

Photobiont Selectivity and Interspecific Interactions in Lichen Communities.

PLANT BIOLOGY, Issue 4 2003

Abstract: Lichen communities are characterised by interspecific interactions that not only include interactions between different lichen species but also between the symbionts within a single lichen species. The community "Bunte Erdflechtengesellschaft", growing on weathered calciferous rocks known as Gravel Alvar on Gotland (Baltic Sea, Sweden), shows a high complexity of inter- and intraspecific interactions, including Fulgensia bracteata, F. fulgens, Toninia sedifolia, Squamarina cartilaginea, Psora decipiens and Lecidea lurida. F. bracteata and F. fulgens are the dominant species of this community, showing a tendency to overgrow the other species involved and even parasitic behaviour. Culture experiments have been performed to investigate the selectivity of the mycobiont of F. bracteata towards a variety of potential photobionts. The results provide evidence for the selectivity of the mycobiont and varying compatibility of the respective symbionts that can be interpreted as a cascade of interdependent processes of specific and non-specific reactions of the symbionts involved. [source]

Aspen succession and nitrogen loading: a case for epiphytic lichens as bioindicators in the Rocky Mountains, USA

JOURNAL OF VEGETATION SCIENCE, Issue 3 2009
Paul C. Rogers
Abstract Question: Can lichen communities be used to assess short- and long-term factors affecting seral quaking aspen (Populus tremuloides) communities at the landscape scale? Location: Bear River Range, within the Rocky Mountains, in northern Utah and southern Idaho, USA. Method: Forty-seven randomly selected mid-elevation aspen stands were sampled for lichens and stand conditions. Plots were characterized according to tree species cover, basal area, stand age, bole scarring, tree damage, and presence of lichen species. We also recorded ammonia emissions with passive sensors at 25 urban and agricultural sites throughout an adjacent populated valley upwind of the forest stands. Nonmetric multidimensional scaling (NMS) ordination was used to evaluate an array of 20 variables suspected to influence lichen communities. Results: In NMS, forest succession explained most variance in lichen composition and abundance, although atmospheric nitrogen from local agricultural and urban sources also significantly influenced the lichen communities. Abundance of nitrophilous lichen species decreased with distance from peak ammonia sources and the urban center in all aspen succession classes. One lichen, Phaeophyscia nigricans, was found to be an effective bioindicator of nitrogen loading. Conclusions: Lichen communities in this landscape assessment of aspen forests showed clear responses to long-term (stand succession) and short-term (nitrogen deposition) influences. At the same time, several environmental factors (e.g. tree damage and scarring, distance to valley, topography, and stand age) had little influence on these same lichen communities. We recommend further use of epiphytic lichens as bioindicators of dynamic forest conditions. [source]

Photobiont Selectivity and Interspecific Interactions in Lichen Communities.

PLANT BIOLOGY, Issue 4 2003

Abstract: Lichen communities are characterised by interspecific interactions that not only include interactions between different lichen species but also between the symbionts within a single lichen species. The community "Bunte Erdflechtengesellschaft", growing on weathered calciferous rocks known as Gravel Alvar on Gotland (Baltic Sea, Sweden), shows a high complexity of inter- and intraspecific interactions, including Fulgensia bracteata, F. fulgens, Toninia sedifolia, Squamarina cartilaginea, Psora decipiens and Lecidea lurida. F. bracteata and F. fulgens are the dominant species of this community, showing a tendency to overgrow the other species involved and even parasitic behaviour. Culture experiments have been performed to investigate the selectivity of the mycobiont of F. bracteata towards a variety of potential photobionts. The results provide evidence for the selectivity of the mycobiont and varying compatibility of the respective symbionts that can be interpreted as a cascade of interdependent processes of specific and non-specific reactions of the symbionts involved. [source]

Aspen succession and nitrogen loading: a case for epiphytic lichens as bioindicators in the Rocky Mountains, USA

JOURNAL OF VEGETATION SCIENCE, Issue 3 2009
Paul C. Rogers
Abstract Question: Can lichen communities be used to assess short- and long-term factors affecting seral quaking aspen (Populus tremuloides) communities at the landscape scale? Location: Bear River Range, within the Rocky Mountains, in northern Utah and southern Idaho, USA. Method: Forty-seven randomly selected mid-elevation aspen stands were sampled for lichens and stand conditions. Plots were characterized according to tree species cover, basal area, stand age, bole scarring, tree damage, and presence of lichen species. We also recorded ammonia emissions with passive sensors at 25 urban and agricultural sites throughout an adjacent populated valley upwind of the forest stands. Nonmetric multidimensional scaling (NMS) ordination was used to evaluate an array of 20 variables suspected to influence lichen communities. Results: In NMS, forest succession explained most variance in lichen composition and abundance, although atmospheric nitrogen from local agricultural and urban sources also significantly influenced the lichen communities. Abundance of nitrophilous lichen species decreased with distance from peak ammonia sources and the urban center in all aspen succession classes. One lichen, Phaeophyscia nigricans, was found to be an effective bioindicator of nitrogen loading. Conclusions: Lichen communities in this landscape assessment of aspen forests showed clear responses to long-term (stand succession) and short-term (nitrogen deposition) influences. At the same time, several environmental factors (e.g. tree damage and scarring, distance to valley, topography, and stand age) had little influence on these same lichen communities. We recommend further use of epiphytic lichens as bioindicators of dynamic forest conditions. [source]

Reproductive strategies, relichenization and thallus development observed in situ in leaf-dwelling lichen communities

NEW PHYTOLOGIST, Issue 3 2002
William B. Sanders
Summary ,,Suppositions about lichen reproductive strategies were investigated and elusive early stages of lichen ontogeny documented in a foliicolous lichen community. ,,Plastic coverslips attached to supportive netting were placed among foliicolous lichen communities within a neotropical lowland forest. The germination and development of diverse lichen propagules colonizing the coverslips were studied with light microscopy. ,,Foliicolous lichens were observed to begin development from lichenized vegetative propagules, aposymbiotic fungal spores, fungal spores dispersed together with attached phycobionts, and diahyphae. Aposymbiotically dispersed spores and diahyphae were capable of associating with compatible phycobionts encountered upon the substratum, following germination. ,,Many developing thalli produced characteristic structures (discoid isidia, thalline setae, pycnidia, etc.) which permitted their recognition as typical members of the foliicolous lichen community. Thalline setae in Tricharia were produced upon the prothallus, and subsequently incorporated into the thallus proper by advance of the lichenized thallus margin. Tricharia and other members of the Gomphillaceae showed a distinctive organization of symbionts in thallus growth, whereby the unicellular green phycobiont cells were positioned at the tips of advancing fascicles of mycobiont hyphae. In Coenogonium sp., branching filaments of the phycobiont Trentepohlia grew along prothallic paths initiated by the mycobiont. [source]

Effects of forest management on epiphytic lichen diversity in Mediterranean forests

APPLIED VEGETATION SCIENCE, Issue 2 2010
Gregorio Aragón
Abstract Question: What are the responses of epiphytic lichens to the intensity of management along a large environmental gradient in Mediterranean Quercus forests? Location: Central Spain. Methods: This study was carried out on 4590 trees located in 306 forest stands dominated by Quercus faginea or Quercus ilex ssp. ballota. The effect of forest management and other predictor variables on several species diversity indicators were studied. Variables modelled were total species richness, cyanolichen richness and community composition. A large number of predictor variables were included: forest fragmentation (patch size, stand variability), climate and topographic (altitude, slope, sun radiation, annual rainfall and mean annual temperature) and intensity of management. General linear models and constrained ordination techniques were used to model community traits and species composition, respectively. Results: Total richness and especially cyanolichens richness were significantly and negatively affected by the intensity of management. Lichen composition was influenced by management intensity, climatic and topographic variables and stand variability. Conclusions: In Mediterranean forests, human activities related to forestry, agricultural and livestock use cause impoverishment of lichen communities, including the local disappearance of the most demanding species. The conservation of unmanaged forests with a dense canopy is crucial for lichen diversity. [source]

Spatial scale of GIS-derived categorical variables affects their ability to separate sites by community composition

APPLIED VEGETATION SCIENCE, Issue 3 2008
Emily A. Holt
Abstract. Questions: How well do GIS-derived categorical variables (e.g., vegetation, soils, geology, elevation, geography, and physiography) separate plots based on community composition? How does the ability to distinguish plots by community composition vary with spatial scale, specifically number of patch types, patch size and spatial correlation? Both these questions bear on the effective use of stratifying variables in landscape ecology. Location: Arctic tundra; Bering Land Bridge National Preserve, northwestern Alaska, USA. Methods: We evaluated the strength of numerous alternative stratifying variables using the multi-response permutation procedure (MRPP). We also created groups based on lichen community composition, using cluster analyses, and evaluated the relationship between these groups and groupings within categorical variables using Mantel tests. Each test represents different measures of community separation, which were then evaluated with respect to each variable's spatial characteristics. Results: We found each categorical variable derived from GIS separated lichen communities to some degree. Separation success ranged from strong (Alaska Subsections) to weak (Watersheds and Reindeer Ownership). Lichen community groups derived from cluster analysis demonstrated statistically significant relationships with 13 of the 17 categorical variables. Partialling out effects of spatial distance had little effect on these relationships. Conclusions: Greater number of patch types and larger average patch sizes contribute to optimal success in separating lichen communities; geographic distance did not appear to significantly alter separation success. Group distinctiveness or strength increased with more patch types or groups. Alternatively, congruence between lichen community types derived from cluster analysis and the 17 categorical variables was inversely related to patch size and spatial correlation. [source]

Changing climate and historic-woodland structure interact to control species diversity of the ,Lobarion' epiphyte community in Scotland

JOURNAL OF VEGETATION SCIENCE, Issue 5 2007
Christopher J. Ellis
Abstract Question: How will changing climate and habitat structure interact to control the species diversity of lichen epiphytes? Location: Scotland. Method: Species richness (=diversity) of the epiphyte lichen community known as Lobarion (named after Lobaria pulmonaria) was quantified for 94 Populus tremula stands across Scotland, and compared in a predictive model to seven climate variables and eight measures of woodland structure. An optimum model was selected and used to project Lobarion diversity over the geographic range of the study area, based on IPCC climate change scenarios and hypothetical shifts in woodland structure. Results: Species diversity of the Lobarion community was best explained by three climate variables: (1) average annual temperature; (2) autumn and winter precipitation; in combination with (3) historic-woodland extent. Projections indicate a positive effect of predicted climate change on Lobarion diversity, consistent with the physiological traits of cyanobac-terial lichens comprising the Lobarion. However, the general response to climate is modified significantly by the effect on diversity of historic-woodland extent. Conclusions: Historic-woodland extent may exert an important control over local climate, as well as impacting upon the metapopulation dynamics of species in the Lobarion. In particular, a temporal delay in the response of Lobarion species to changed woodland structure is critical to our understanding of future climate change effects. Future Lobarion diversity (e.g. in the 2050s) may depend upon the interaction of contemporary climate (e.g. 2050s climate) and historic habitat structure (e.g. 1950s woodland extent). This is supported by previous observations for an extinction debt amongst lichen epiphytes, but suggests an extension of simple climate-response models is necessary, before their wider application to lichen epiphyte diversity. [source]

Reproductive strategies, relichenization and thallus development observed in situ in leaf-dwelling lichen communities

NEW PHYTOLOGIST, Issue 3 2002
William B. Sanders
Summary ,,Suppositions about lichen reproductive strategies were investigated and elusive early stages of lichen ontogeny documented in a foliicolous lichen community. ,,Plastic coverslips attached to supportive netting were placed among foliicolous lichen communities within a neotropical lowland forest. The germination and development of diverse lichen propagules colonizing the coverslips were studied with light microscopy. ,,Foliicolous lichens were observed to begin development from lichenized vegetative propagules, aposymbiotic fungal spores, fungal spores dispersed together with attached phycobionts, and diahyphae. Aposymbiotically dispersed spores and diahyphae were capable of associating with compatible phycobionts encountered upon the substratum, following germination. ,,Many developing thalli produced characteristic structures (discoid isidia, thalline setae, pycnidia, etc.) which permitted their recognition as typical members of the foliicolous lichen community. Thalline setae in Tricharia were produced upon the prothallus, and subsequently incorporated into the thallus proper by advance of the lichenized thallus margin. Tricharia and other members of the Gomphillaceae showed a distinctive organization of symbionts in thallus growth, whereby the unicellular green phycobiont cells were positioned at the tips of advancing fascicles of mycobiont hyphae. In Coenogonium sp., branching filaments of the phycobiont Trentepohlia grew along prothallic paths initiated by the mycobiont. [source]