The Experts below are selected from a list of 26976 Experts worldwide ranked by ideXlab platform

Farkas E. - One of the best experts on this subject based on the ideXlab platform.

Johan Asplund - One of the best experts on this subject based on the ideXlab platform.

  • how Lichens impact on terrestrial community and ecosystem properties
    Biological Reviews, 2017
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Lichens occur in most terrestrial ecosystems; they are often present as minor contributors, but in some forests, drylands and tundras they can make up most of the ground layer biomass. As such, Lichens dominate approximately 8% of the Earth's land surface. Despite their potential importance in driving ecosystem biogeochemistry, the influence of Lichens on community processes and ecosystem functioning have attracted relatively little attention. Here, we review the role of Lichens in terrestrial ecosystems and draw attention to the important, but often overlooked role of Lichens as determinants of ecological processes. We start by assessing characteristics that vary among Lichens and that may be important in determining their ecological role; these include their growth form, the types of photobionts that they contain, their key functional traits, their water-holding capacity, their colour, and the levels of secondary compounds in their thalli. We then assess how these differences among Lichens influence their impacts on ecosystem and community processes. As such, we consider the consequences of these differences for determining the impacts of Lichens on ecosystem nutrient inputs and fluxes, on the loss of mass and nutrients during lichen thallus decomposition, and on the role of lichenivorous invertebrates in moderating decomposition. We then consider how differences among Lichens impact on their interactions with consumer organisms that utilize lichen thalli, and that range in size from microfauna (for which the primary role of Lichens is habitat provision) to large mammals (for which Lichens are primarily a food source). We then address how differences among Lichens impact on plants, through for example increasing nutrient inputs and availability during primary succession, and serving as a filter for plant seedling establishment. Finally we identify areas in need of further work for better understanding the role of Lichens in terrestrial ecosystems. These include understanding how the high intraspecific trait variation that characterizes many Lichens impacts on community assembly processes and ecosystem functioning, how multiple species mixtures of Lichens affect the key community- and ecosystem-level processes that they drive, the extent to which Lichens in early succession influence vascular plant succession and ecosystem development in the longer term, and how global change drivers may impact on ecosystem functioning through altering the functional composition of lichen communities.

  • the impact of secondary compounds and functional characteristics on lichen palatability and decomposition
    Journal of Ecology, 2013
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Summary There has been much recent interest in understanding how functional traits of vascular plant species drive ecological processes such as herbivory and litter decomposition. In plants, these two processes are often driven by the same or similar suites of traits and therefore correlate across species. However, few studies have considered how traits of plant-like life forms such as Lichens determine species differences in their effects on ecological processes. This is despite the significant contribution of Lichens to carbon and nutrient cycling in many environments. We collected 28 lichen species that differed in their growth form, substrate type and capacity to fix N, and determined key traits for each species. For each species, we performed a feeding bioassay using the generalist snail Cepaea hortensis and carried out a laboratory bioassay to assess decomposability. We did these tests both with intact lichen material containing natural concentrations of carbon-based secondary compounds (CBSCs), and material that had been acetone rinsed to reduce concentrations of CBSCs, to evaluate the effect of CBSC on palatability and decomposability. We found that reducing CBSC concentrations greatly increased palatability for 17 species, and decomposability of 10 species. However, decomposability was correlated with several lichen traits while palatability was not, regardless of whether or not CBSCs were removed, and we therefore found no relationship between decomposability and palatability across species. Decomposability and palatability both varied, but in contrasting directions, among N-fixing vs. non-fixing Lichens, Lichens with different growth forms and those from contrasting substrate types. As such, N-fixing Lichens had higher decomposition rates but lower consumption rates than non-fixing Lichens, while foliose species had higher decomposition rates but lower consumption rates than fruticose species. Synthesis: We have shown that lichen CBSCs regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.

  • Contrasting changes in palatability following senescence of the lichenized fungi Lobaria pulmonaria and L. scrobiculata
    Fungal Ecology, 2012
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Epiphytic Lichens can contribute significantly to ecosystem nutrient input because they efficiently accumulate atmospheric mineral nutrients and, in the case of cyanoLichens, also fix nitrogen. The rate at which carbon and other nutrients gained by Lichens enters the ecosystem is determined by lichen litter decomposability and by invertebrate consumption of lichen litter. In turn, these processes are driven by the secondary compounds present in senesced Lichens. Therefore, we explored how lichen palatability and concentrations of secondary compounds change with tissue senescence for Lobaria pulmonaria, a green-algal lichen with cyanobacterial cephalodia, and Lobaria scrobiculata, a cyanobacterial lichen. During senescence both Lichens lost 38–48 % of their stictic acid chemosyndrome, while m-scrobiculin and usnic acid in L. scrobiculata remained unchanged. Snails preferred senesced rather than fresh L. pulmonaria, while senesced L. scrobiculata were avoided. This provides evidence that species with labile secondary compounds will have higher turnover rates, through consumption and decomposition, than those producing more stable secondary compounds.

  • Mollusc grazing limits growth and early development of the old forest lichen Lobaria pulmonaria in broadleaved deciduous forests
    Oecologia, 2008
    Co-Authors: Johan Asplund
    Abstract:

    This study aims: (1) to quantify mollusc grazing on juvenile and mature thalli of the foliose epiphytic lichen Lobaria pulmonaria , and (2) to test the hypothesis inferring a herbivore defensive role of lichen depsidones in forests with indigenous populations of lichen-feeding molluscs. Lichens were transplanted in shaded and less shaded positions in each of two calcareous broadleaved deciduous forests, one poor in Lichens, one with a rich Lobarion community. Preventing the access of molluscs significantly reduced the loss of juvenile L. pulmonaria , particularly in the naturally lichen-poor forest. Molluscs also severely grazed mature thalli in the lichen-poor forest, especially thalli placed under the more shading canopies. Furthermore, reducing the natural concentration of depsidones by pre-rinsing with acetone increased subsequent grazing significantly, showing that lichen depsidones function as herbivore defence in natural habitats. Our results suggest that mollusc grazing may play important roles in shaping the epiphytic vegetation in calcareous deciduous forests, and that recently established juvenile L. pulmonaria thalli seem to be particularly vulnerable.

David A. Wardle - One of the best experts on this subject based on the ideXlab platform.

  • how Lichens impact on terrestrial community and ecosystem properties
    Biological Reviews, 2017
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Lichens occur in most terrestrial ecosystems; they are often present as minor contributors, but in some forests, drylands and tundras they can make up most of the ground layer biomass. As such, Lichens dominate approximately 8% of the Earth's land surface. Despite their potential importance in driving ecosystem biogeochemistry, the influence of Lichens on community processes and ecosystem functioning have attracted relatively little attention. Here, we review the role of Lichens in terrestrial ecosystems and draw attention to the important, but often overlooked role of Lichens as determinants of ecological processes. We start by assessing characteristics that vary among Lichens and that may be important in determining their ecological role; these include their growth form, the types of photobionts that they contain, their key functional traits, their water-holding capacity, their colour, and the levels of secondary compounds in their thalli. We then assess how these differences among Lichens influence their impacts on ecosystem and community processes. As such, we consider the consequences of these differences for determining the impacts of Lichens on ecosystem nutrient inputs and fluxes, on the loss of mass and nutrients during lichen thallus decomposition, and on the role of lichenivorous invertebrates in moderating decomposition. We then consider how differences among Lichens impact on their interactions with consumer organisms that utilize lichen thalli, and that range in size from microfauna (for which the primary role of Lichens is habitat provision) to large mammals (for which Lichens are primarily a food source). We then address how differences among Lichens impact on plants, through for example increasing nutrient inputs and availability during primary succession, and serving as a filter for plant seedling establishment. Finally we identify areas in need of further work for better understanding the role of Lichens in terrestrial ecosystems. These include understanding how the high intraspecific trait variation that characterizes many Lichens impacts on community assembly processes and ecosystem functioning, how multiple species mixtures of Lichens affect the key community- and ecosystem-level processes that they drive, the extent to which Lichens in early succession influence vascular plant succession and ecosystem development in the longer term, and how global change drivers may impact on ecosystem functioning through altering the functional composition of lichen communities.

  • the impact of secondary compounds and functional characteristics on lichen palatability and decomposition
    Journal of Ecology, 2013
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Summary There has been much recent interest in understanding how functional traits of vascular plant species drive ecological processes such as herbivory and litter decomposition. In plants, these two processes are often driven by the same or similar suites of traits and therefore correlate across species. However, few studies have considered how traits of plant-like life forms such as Lichens determine species differences in their effects on ecological processes. This is despite the significant contribution of Lichens to carbon and nutrient cycling in many environments. We collected 28 lichen species that differed in their growth form, substrate type and capacity to fix N, and determined key traits for each species. For each species, we performed a feeding bioassay using the generalist snail Cepaea hortensis and carried out a laboratory bioassay to assess decomposability. We did these tests both with intact lichen material containing natural concentrations of carbon-based secondary compounds (CBSCs), and material that had been acetone rinsed to reduce concentrations of CBSCs, to evaluate the effect of CBSC on palatability and decomposability. We found that reducing CBSC concentrations greatly increased palatability for 17 species, and decomposability of 10 species. However, decomposability was correlated with several lichen traits while palatability was not, regardless of whether or not CBSCs were removed, and we therefore found no relationship between decomposability and palatability across species. Decomposability and palatability both varied, but in contrasting directions, among N-fixing vs. non-fixing Lichens, Lichens with different growth forms and those from contrasting substrate types. As such, N-fixing Lichens had higher decomposition rates but lower consumption rates than non-fixing Lichens, while foliose species had higher decomposition rates but lower consumption rates than fruticose species. Synthesis: We have shown that lichen CBSCs regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.

  • Contrasting changes in palatability following senescence of the lichenized fungi Lobaria pulmonaria and L. scrobiculata
    Fungal Ecology, 2012
    Co-Authors: Johan Asplund, David A. Wardle
    Abstract:

    Epiphytic Lichens can contribute significantly to ecosystem nutrient input because they efficiently accumulate atmospheric mineral nutrients and, in the case of cyanoLichens, also fix nitrogen. The rate at which carbon and other nutrients gained by Lichens enters the ecosystem is determined by lichen litter decomposability and by invertebrate consumption of lichen litter. In turn, these processes are driven by the secondary compounds present in senesced Lichens. Therefore, we explored how lichen palatability and concentrations of secondary compounds change with tissue senescence for Lobaria pulmonaria, a green-algal lichen with cyanobacterial cephalodia, and Lobaria scrobiculata, a cyanobacterial lichen. During senescence both Lichens lost 38–48 % of their stictic acid chemosyndrome, while m-scrobiculin and usnic acid in L. scrobiculata remained unchanged. Snails preferred senesced rather than fresh L. pulmonaria, while senesced L. scrobiculata were avoided. This provides evidence that species with labile secondary compounds will have higher turnover rates, through consumption and decomposition, than those producing more stable secondary compounds.

Alessandra Di Tullio - One of the best experts on this subject based on the ideXlab platform.

  • investigation by solid phase microextraction and gas chromatography mass spectrometry of secondary metabolites in Lichens deposited on stone monuments
    Rapid Communications in Mass Spectrometry, 2003
    Co-Authors: Francesco De Angelis, Roberta Ceci, R Quaresima, Samantha Reale, Alessandra Di Tullio
    Abstract:

    Lichens are ubiquitous organisms formed by symbiotic associations of fungal hyphas and algae that also grow under often extreme environmental conditions. They produce secondary metabolites, the so-called lichen substances, whose structural characterization can give an important contribution to lichen taxonomy. Lichens are also widely employed as biomonitors of atmospheric pollution; being epiphyte organisms they tend, in fact, to accumulate exogenous compounds. Moreover, it could be questioned if the environmental stress alters their secondary metabolites production. Therefore, a new strategy for the analysis of the organic substances absorbed or metabolized by Lichens has been developed. This method exploits the dry solid-phase microextraction (SPME) headspace technique coupled with gas chromatography/mass spectrometry (GC/MS). Lichens coating the stone surfaces of monuments, located in small towns between high mountains and far away from urban environments, have been investigated. In the field of cultural heritage, this study can contribute to the knowledge of the state of conservation of outdoor exposed historical monuments. Copyright © 2003 John Wiley & Sons, Ltd.

Pekka Niemela - One of the best experts on this subject based on the ideXlab platform.

  • growth of reindeer Lichens and effects of reindeer grazing on ground cover vegetation in a scots pine forest and a subarctic heathland in finnish lapland
    Ecography, 2003
    Co-Authors: Michael Den Herder, Minnamaarit Kytoviita, Pekka Niemela
    Abstract:

    Reindeer Lichens are an important component of northern ecosystems. The aim of this study was to measure the growth rate of terricolous Lichens as it is a key parameter involved in productivity of these ecosystems and an important part of lichen tolerance to reindeer grazing. Furthermore, the natural succession and the long-term effects of reindeer grazing on lichen community characteristics in two contrasting habitats were investigated as well as the interactions between lichen cover and mosses and vascular plants. Biomass and coverage measurements were conducted in a lichen woodland and in a subarctic heath with grazed and ungrazed areas in northern Finland. Measurements spanning over 13 yr of undisturbed development show that the growth rate of Cladina stellaris can be as high as >0.17 g g−1 produced annually, although in average growth rates were much lower. During the succession of ground vegetation, C. stellaris, C. rangiferina, C. mitis and Cetraria nivalis increased in biomass in fenced areas and were reduced most in biomass by reindeer in unprotected areas. Reindeer grazing and trampling seem to change the vegetation towards a type that is dominated by small dwarf shrubs, bare soil and minute-cup Lichens (Cladonia spp.). Removing the lichen layer by reindeer may reduce natural regeneration of pine trees as implied by increasing numbers of pine seedlings with increasing lichen cover.