1,721,025 research outputs found
Do tree-related factors mediate the response of lichen functional groups to eutrophication?
No full textIn the last decades, the pollution regime has been drastically changed in most industrialized countries, with a considerable decrease in sulphur dioxide (SO2) emissions and an increasing relevance of eutrophication compounds, such as nitrogen compounds and particulate matter. This situation hampers the interpretation of data in biomonitoring surveys, as high lichen diversity is not always associated with good air quality. The objective of this study was to test whether the effects of eutrophication on the abundance of different lichen functional groups varies according to some tree-related factors. We analysed the relationships between epiphytic lichen diversity, emissions of main atmospheric pollutants and tree characteristics (circumference and bark pH, light transmitted through the canopy). Hierarchical partitioning of variance and Generalized Linear Mixed Models (GLMM) confirmed that lichen functional groups with different nitrogen tolerances responded to several atmospheric pollutants, with both independent and joint effects, whereas they did not show significant differences depending on main tree-related factors. We demonstrated that, under high eutrophication levels, differences in bark pH did not significantly differentiated the composition of epiphytic lichen communities
Assessing photosynthetic biomarkers in lichen transplants exposed under different light regimes
No full texttThe present work is a methodological study testing alternative exposure conditions of lichen transplantsfor biomonitoring studies. We evaluated the effects of different light regime on the vitality of lichenby analysing the photosynthetic efficiency of transplanted thalli of the fruticose species Pseudeverniafurfuracea (L.) Zopf. var. furfuracea. In particular, we tested the hypothesis that shading lichen transplantsis necessary to ensure sufficient lichen vitality during the exposure time. Thalli of P. furfuracea wereexposed in a polluted area within the harbour of Genoa (N-Italy) for 4 weeks under two experimentalconditions: 5 thalli were covered with a shade cloth, whereas 5 thalli were kept in the light. We showedthat, under the same environmental conditions (i.e., climate and pollution regime), shading the thalliminimised the photoinhibition and prolonged the vitality of the lichen. Thus, we recommend shadinglichen transplants during biomonitoring surveys to better detect the effects of pollution on the lichens
Interaction of sea salt and atmospheric pollution alters the OJIP fluorescence transient in the lichen Pseudevernia furfuracea (L.) Zopf
No full textThis study investigated the effects of the interaction of sea salt and atmospheric pollution on the photosynthetic system of the lichen Pseudevernia furfuracea (L.) Zopf. v. furfuracea. Thalli of P. furfuracea were transplanted from remote area to different sites subjected to contrasting levels of atmospheric pollution and distance from the coast. Lichen chlorophyll a fluorescence was analysed weekly for one month by means of Handy PEA fluorometer. The effects of sea salt and atmospheric pollution were assessed by OJIP fluorescence transient and its derived fluorescence parameters. We showed that the response of the lichen to the single considered stressing factors was different and it could be detected in terms of variation of the electron flow at different steps of the OJIP fluorescence transient. Our data confirmed that the derived JIP-test parameters are good biomarkers to analyse different conditions of stress in lichens. In particular, we demonstrated that P. furfuracea is more sensitive to atmospheric pollution than to the proximity to the sea and to the interaction of these two factor
Discrimination between lichens according to their exposure to pollutants by NIR spectroscopy
No full textFunctional over-redundancy and vulnerability of lichen communities decouple across spatial scales and environmental severity
Get PDFAccording to the insurance hypothesis, high taxonomic diversity should ensure ecosystem stability because of functional redundancy, whereas reduced functional diversity that results from species loss should affect ecosystem sensitivity, resilience, and vulnerability. However, even in species-rich ecosystems, functional over-redundancy (FOR; i.e., the tendency of most species to cluster into a few over-represented functional entities) in some cases may result in under-representation of many functions, and the ecosystem might become highly vulnerable. Using a stratified random sampling design with nested spatial levels (nine land use strata, 70 plots, 435 trees/rock outcrops, and 9845 quadrats), we recorded the occurrence of over 350 species of epiphytic and rock-dwelling lichens in semi-arid ecosystems in western Sardinia, where solar radiation defines a wide environmental gradient. By accounting for species functional traits, such as growth form, photosynthetic strategies, and reproductive strategies, we obtained 43 functional entities (>60% of all possible combinations) and tested the scale-dependency of FOR and functional vulnerability (FV, i.e., the risk of losing functional entities) by generalized linear mixed models. We found that FOR increased and FV decreased with increasing spatial scale, which supports the hypothesis of a cross-scale functional reinforcement. Decoupling of FOR and FV was far more evident for rock-dwelling compared with epiphytic communities, which reflects differing environmental conditions associated with substrate type. Our results indicate that increased warming and climatic extremes could exacerbate species clustering into the most resistant functional entities and thus enhance FOR at the community level. Therefore, high taxonomic diversity may not ensure systematic buffering of climate change impacts
Human contribution to trace elements in urban areas as measured in holm oak (Quercus ilex L.) bark
No full textThe effect of human activities on the presence of trace elements in the atmosphere was evaluated by analyzing samples of holm oak bark, collected in Italy in a large city, in a small town, and in a reference area, scarcely inhabited. In all cases, point sources of pollution were excluded (e.g., industries and incinerators). The concentrations of As, Cd, Co, Cu, Fe, Mn, Ni, Pb, V, and Zn were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The element concentrations in the small town are not different from the reference area, except for Pb and Cu, while the samples collected in the large city show higher concentrations of Co, Cu, Fe, Ni, Pb, V, and Zn with respect to the rural area. In particular, the Pb levels in the large city are approximately 16 times higher than in the reference site, and five times higher than in the small town. Most element concentrations are correlated in the large city, while in the reference site, only a few significant correlations between elements were found. Even in the absence of specific sources of pollution, populations living in big cities are exposed to higher concentrations of trace elements than those living in rural environments or in small urban centers
Comparazione fra differenti metodi per la determinazione delle aree di endemismo e per gli elementi biotici: un esempio nelle Alpi Marittime e Liguri
No full textLo scopo di questo lavoro è quello di comparare differenti metodiche per la determinazione delle aree di endemismo e degli elemnti biotici analizzando gli endemismi vegetali dell'hotspot delle Alpi Marittime e Ligur
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
