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Rien Aerts - One of the best experts on this subject based on the ideXlab platform.

Aerts R. - One of the best experts on this subject based on the ideXlab platform.

  • Arctic warming on two continents has consistent negative effects on lichen diversity and mixed effects on bryophyte diversity.
    2012
    Co-Authors: Lang S.i., Cornelissen J.h.c., Shaver G.r., Ahrens M., Callaghan T.v., Molau U., Ter Braak C.j.f., Holzer A, Aerts R.
    Abstract:

    Little is known about the impact of changing temperature regimes on composition and diversity of Cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9-16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other Cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that Cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by Cryptogams in high latitudes (e.g. carbon sequestration,

  • Arctic warming on two continents has consistent negativ effects on lichen diversity and mixed effects on bryophyte diversity
    'Wiley', 2012
    Co-Authors: Lang S.i., Cornelissen J.h.c., Shaver G.r., Ahrens M., Callaghan T.v., Molau U., Holzer A, Braak, Ter C.j.f., Aerts R.
    Abstract:

    Little is known about the impact of changing temperature regimes on composition and diversity of Cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9–16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other Cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that Cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by Cryptogams in high latitudes (e.g. carbon sequestration, N2-fixation, trophic interactions), these changes will have important feedback consequences for ecosystem functions and climat

  • An experimental comparison of chemical traits and litter decomposition rates in a diverse range of subarctic bryophyte, lichen and vascular plant species.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Klahn T., Van Logtestijn R.s.p, Broekman R.a., Schweikert W., Aerts R.
    Abstract:

    1. Climate change in the subarctic is expected to influence vegetation composition, specifically bryophyte and lichen communities, thereby modifying litter decomposition rates and carbon (C) dynamics of these systems with possible feedbacks to climate. 2. In a 2-year experiment, we investigated decomposition rates and chemical traits of 27 bryophytes, 17 lichens and 5 vascular plants in litter beds in subarctic Sweden. The majority of the sampled Cryptogam species are widespread at higher northern latitudes. 3. Average 2-year litter decomposition rates (exponential mass loss constant k) of lichen (0.44 ± 0.01) and vascular plant (0.56 ± 0.03) species were higher than that of bryophytes (0.11 ± 0.01), while within main Cryptogam taxa, species identity was an important determinant of mass loss rates. At Cryptogam group level, 2-year litter mass loss of Sphagnum was significantly lower than for non-Sphagnum mosses and liverworts. Within lichens,

  • Determinants of Cryptogam composition and diversity in Sphagnum-dominated peatlands: the importance of temporal, spatial and functional scales.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Ahrens M., Callaghan T.v., Holzer A, Braak, Ter C.j.f., Aerts R.
    Abstract:

    1. Changing temperature regimes and precipitation patterns in the Subarctic will impact on vegetation composition and diversity including those of bryophyte and lichen communities, which are major drivers of high-latitude carbon and nutrient cycling and hydrology. 2. We investigated the relative importance of such impacts at different temporal, spatial and plant functional scales in subarctic Sphagnum fuscum -dominated peatlands, comprising both an in situ warming experiment and natural climatic and topographic gradients in northern Sweden and Norway. We applied multivariate analyses to investigate the relationships among Cryptogam and vascular plant species composition and abiotic (temperature, moisture) and biotic ( Sphagnum growth) regimes at various scales. 3. At the short-term temporal scale (4-year warming experiment), increased temperature yielded no clear effect on Cryptogam or vascular plant species composition. Spatially, direct effects of temperature were decisive for overall species composition across regions (macro-scale) rather than within one region (meso-scale). Moisture and Sphagnum growth were drivers of species composition at all spatial scales, and Sphagnum growth itself depended on its position on the microtopographic gradient and on temperature. 4. Grouping of bryophytes and lichens at increasing scales of functional aggregation from species, growth form to the major higher taxon level ( Sphagnum , other mosses, liverworts, lichens) revealed mostly increasing correlation with climate regimes and Sphagnum growth. Excluding liverworts from the analysis tended to reduce the correlation. 5. Abundances of lichens, liverworts, non- Sphagnum mosses and (to a lesser degree) vascular plants were negatively related to Sphagnum abundance. Few Cryptogam and vascular plant species showed a positive relationship with Sphagnum abundance. Correspondingly, Cryptogam species richness and Shannon Index on peatlands strongly declined as Sphagnum abundance increased, while indices for vascular plants showed no significant relationship. 6. Synthesis . Scale, be it spatial or functional, strongly determined which environmental drivers showed the clearest relationships with vegetation composition and diversity. Our findings will help to optimize predictions about long-term effects of climate on peatland vegetati

  • Determinants of Cryptogam composition and diversity in Sphagnum-dominated peatlands: the importance of temporal, spatial and functional scales.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Ahrens M., Callaghan T.v., Ter Braak C.j.f., Holzer A, Aerts R.
    Abstract:

    Changing temperature regimes and precipitation patterns in the Subarctic will impact on vegetation composition and diversity including those of bryophyte and lichen communities, which are major drivers of high-latitude carbon and nutrient cycling and hydrology. 2. We investigated the relative importance of such impacts at different temporal, spatial and plant functional scales in subarctic Sphagnum fuscum-dominated peatlands, comprising both an in situ warming experiment and natural climatic and topographic gradients in northern Sweden and Norway. We applied multivariate analyses to investigate the relationships among Cryptogam and vascular plant species composition and abiotic (temperature, moisture) and biotic (Sphagnum growth) regimes at various scales. 3. At the short-term temporal scale (4-year warming experiment), increased temperature yielded no clear effect on Cryptogam or vascular plant species composition. Spatially, direct effects of temperature were decisive for overall species composition across regions (macro-scale) rather than within one region (meso-scale). Moisture and Sphagnum growth were drivers of species composition at all spatial scales, and Sphagnum growth itself depended on its position on the microtopographic gradient and on temperature. 4. Grouping of bryophytes and lichens at increasing scales of functional aggregation from species, growth form to the major higher taxon level (Sphagnum, other mosses, liverworts, lichens) revealed mostly increasing correlation with climate regimes and Sphagnum growth. Excluding liverworts from the analysis tended to reduce the correlation. 5. Abundances of lichens, liverworts, non-Sphagnum mosses and (to a lesser degree) vascular plants were negatively related to Sphagnum abundance. Few Cryptogam and vascular plant species showed a positive relationship with Sphagnum abundance. Correspondingly, Cryptogam species richness and Shannon Index on peatlands strongly declined as Sphagnum abundance increased, while indices for vascular plants showed no significant relationship. 6. Synthesis. Scale, be it spatial or functional, strongly determined which environmental drivers showed the clearest relationships with vegetation composition and diversity. Our findings will help to optimize predictions about long-term effects of climate on peatland vegetation composition, and subsequently its feedbacks to carbon and water cycles, at the regional scale. © 2009 British Ecological Society

Lang S.i. - One of the best experts on this subject based on the ideXlab platform.

  • Arctic warming on two continents has consistent negative effects on lichen diversity and mixed effects on bryophyte diversity.
    2012
    Co-Authors: Lang S.i., Cornelissen J.h.c., Shaver G.r., Ahrens M., Callaghan T.v., Molau U., Ter Braak C.j.f., Holzer A, Aerts R.
    Abstract:

    Little is known about the impact of changing temperature regimes on composition and diversity of Cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9-16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other Cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that Cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by Cryptogams in high latitudes (e.g. carbon sequestration,

  • Arctic warming on two continents has consistent negativ effects on lichen diversity and mixed effects on bryophyte diversity
    'Wiley', 2012
    Co-Authors: Lang S.i., Cornelissen J.h.c., Shaver G.r., Ahrens M., Callaghan T.v., Molau U., Holzer A, Braak, Ter C.j.f., Aerts R.
    Abstract:

    Little is known about the impact of changing temperature regimes on composition and diversity of Cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9–16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other Cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that Cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by Cryptogams in high latitudes (e.g. carbon sequestration, N2-fixation, trophic interactions), these changes will have important feedback consequences for ecosystem functions and climat

  • An experimental comparison of chemical traits and litter decomposition rates in a diverse range of subarctic bryophyte, lichen and vascular plant species.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Klahn T., Van Logtestijn R.s.p, Broekman R.a., Schweikert W., Aerts R.
    Abstract:

    1. Climate change in the subarctic is expected to influence vegetation composition, specifically bryophyte and lichen communities, thereby modifying litter decomposition rates and carbon (C) dynamics of these systems with possible feedbacks to climate. 2. In a 2-year experiment, we investigated decomposition rates and chemical traits of 27 bryophytes, 17 lichens and 5 vascular plants in litter beds in subarctic Sweden. The majority of the sampled Cryptogam species are widespread at higher northern latitudes. 3. Average 2-year litter decomposition rates (exponential mass loss constant k) of lichen (0.44 ± 0.01) and vascular plant (0.56 ± 0.03) species were higher than that of bryophytes (0.11 ± 0.01), while within main Cryptogam taxa, species identity was an important determinant of mass loss rates. At Cryptogam group level, 2-year litter mass loss of Sphagnum was significantly lower than for non-Sphagnum mosses and liverworts. Within lichens,

  • Determinants of Cryptogam composition and diversity in Sphagnum-dominated peatlands: the importance of temporal, spatial and functional scales.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Ahrens M., Callaghan T.v., Holzer A, Braak, Ter C.j.f., Aerts R.
    Abstract:

    1. Changing temperature regimes and precipitation patterns in the Subarctic will impact on vegetation composition and diversity including those of bryophyte and lichen communities, which are major drivers of high-latitude carbon and nutrient cycling and hydrology. 2. We investigated the relative importance of such impacts at different temporal, spatial and plant functional scales in subarctic Sphagnum fuscum -dominated peatlands, comprising both an in situ warming experiment and natural climatic and topographic gradients in northern Sweden and Norway. We applied multivariate analyses to investigate the relationships among Cryptogam and vascular plant species composition and abiotic (temperature, moisture) and biotic ( Sphagnum growth) regimes at various scales. 3. At the short-term temporal scale (4-year warming experiment), increased temperature yielded no clear effect on Cryptogam or vascular plant species composition. Spatially, direct effects of temperature were decisive for overall species composition across regions (macro-scale) rather than within one region (meso-scale). Moisture and Sphagnum growth were drivers of species composition at all spatial scales, and Sphagnum growth itself depended on its position on the microtopographic gradient and on temperature. 4. Grouping of bryophytes and lichens at increasing scales of functional aggregation from species, growth form to the major higher taxon level ( Sphagnum , other mosses, liverworts, lichens) revealed mostly increasing correlation with climate regimes and Sphagnum growth. Excluding liverworts from the analysis tended to reduce the correlation. 5. Abundances of lichens, liverworts, non- Sphagnum mosses and (to a lesser degree) vascular plants were negatively related to Sphagnum abundance. Few Cryptogam and vascular plant species showed a positive relationship with Sphagnum abundance. Correspondingly, Cryptogam species richness and Shannon Index on peatlands strongly declined as Sphagnum abundance increased, while indices for vascular plants showed no significant relationship. 6. Synthesis . Scale, be it spatial or functional, strongly determined which environmental drivers showed the clearest relationships with vegetation composition and diversity. Our findings will help to optimize predictions about long-term effects of climate on peatland vegetati

  • Determinants of Cryptogam composition and diversity in Sphagnum-dominated peatlands: the importance of temporal, spatial and functional scales.
    2009
    Co-Authors: Lang S.i., Cornelissen J.h.c., Ahrens M., Callaghan T.v., Ter Braak C.j.f., Holzer A, Aerts R.
    Abstract:

    Changing temperature regimes and precipitation patterns in the Subarctic will impact on vegetation composition and diversity including those of bryophyte and lichen communities, which are major drivers of high-latitude carbon and nutrient cycling and hydrology. 2. We investigated the relative importance of such impacts at different temporal, spatial and plant functional scales in subarctic Sphagnum fuscum-dominated peatlands, comprising both an in situ warming experiment and natural climatic and topographic gradients in northern Sweden and Norway. We applied multivariate analyses to investigate the relationships among Cryptogam and vascular plant species composition and abiotic (temperature, moisture) and biotic (Sphagnum growth) regimes at various scales. 3. At the short-term temporal scale (4-year warming experiment), increased temperature yielded no clear effect on Cryptogam or vascular plant species composition. Spatially, direct effects of temperature were decisive for overall species composition across regions (macro-scale) rather than within one region (meso-scale). Moisture and Sphagnum growth were drivers of species composition at all spatial scales, and Sphagnum growth itself depended on its position on the microtopographic gradient and on temperature. 4. Grouping of bryophytes and lichens at increasing scales of functional aggregation from species, growth form to the major higher taxon level (Sphagnum, other mosses, liverworts, lichens) revealed mostly increasing correlation with climate regimes and Sphagnum growth. Excluding liverworts from the analysis tended to reduce the correlation. 5. Abundances of lichens, liverworts, non-Sphagnum mosses and (to a lesser degree) vascular plants were negatively related to Sphagnum abundance. Few Cryptogam and vascular plant species showed a positive relationship with Sphagnum abundance. Correspondingly, Cryptogam species richness and Shannon Index on peatlands strongly declined as Sphagnum abundance increased, while indices for vascular plants showed no significant relationship. 6. Synthesis. Scale, be it spatial or functional, strongly determined which environmental drivers showed the clearest relationships with vegetation composition and diversity. Our findings will help to optimize predictions about long-term effects of climate on peatland vegetation composition, and subsequently its feedbacks to carbon and water cycles, at the regional scale. © 2009 British Ecological Society

Stef Bokhorst - One of the best experts on this subject based on the ideXlab platform.

Simone I Lang - One of the best experts on this subject based on the ideXlab platform.

  • an experimental comparison of chemical traits and litter decomposition rates in a diverse range of subarctic bryophyte lichen and vascular plant species
    Journal of Ecology, 2009
    Co-Authors: Simone I Lang, Thorsten Klahn, Wenka Schweikert, Richard S P Van Logtestijn, Rob Broekman, Johannes H C Cornelissen, Rien Aerts
    Abstract:

    Summary 1. Climate change in the subarctic is expected to influence vegetation composition, specifically bryophyte and lichen communities, thereby modifying litter decomposition rates and carbon (C) dynamics of these systems with possible feedbacks to climate. 2. In a 2-year experiment, we investigated decomposition rates and chemical traits of 27 bryophytes, 17 lichens and 5 vascular plants in litter beds in subarctic Sweden. The majority of the sampled Cryptogam species are widespread at higher northern latitudes. 3. Average 2-year litter decomposition rates (exponential mass loss constant k) of lichen (0.44 ± 0.01) and vascular plant (0.56 ± 0.03) species were higher than that of bryophytes (0.11 ± 0.01), while within main Cryptogam taxa, species identity was an important determinant of mass loss rates. At Cryptogam group level, 2-year litter mass loss of Sphagnum was significantly lower than for non-Sphagnum mosses and liverworts. Within lichens, N2-fixing versus non-N2-fixing lichens showed no variation in decomposability. 4. In a subset of the large species set, mass loss differed both among incubation environments (reflecting nutrient-rich and poor birch forest and Sphagnum peatlands, respectively) and species. The pattern of mass loss across incubation environments was not consistent among Cryptogam species. N2-fixing, in contrast to non-N2-fixing lichens with lower nitrogen (N) levels displayed similar decomposition rates across incubation environments. Mass loss of non-Sphagnum mosses was correlated with initial N irrespective of incubation environment. 5. Litter mass loss of Cryptogam taxa could be predicted very well from infrared spectra of the initial chemical composition of the species, by application of Fourier transform infrared using an attenuated total reflectance probe. The initial macronutrient concentrations (N, phosphorus, C and cations) and initial litter pH correlated less well. 6. Synthesis. We showed comprehensively that decomposition rates of bryophytes are generally lower than those of lichens and vascular plants. Among bryophyte or lichen species there is also great variation in litter decomposability which depends strongly on species-specific chemistry. Our data will help predict changing land surface feedback to C cycles and climate in cold biomes by understanding long-term climate effects on litter decomposability through shifting vegetation composition.

  • comparative Cryptogam ecology a review of bryophyte and lichen traits that drive biogeochemistry
    Annals of Botany, 2007
    Co-Authors: Johannes H C Cornelissen, Simone I Lang, Nadejda A Soudzilovskaia, Heinjo J During
    Abstract:

    †Background Recent decades have seen a major surge in the study of interspecific variation in functional traits in comparative plant ecology, as a tool to understanding and predicting ecosystem functions and their responses to environmental change. However, this research has been biased almost exclusively towards vascular plants. Very little is known about the role and applicability of functional traits of non-vascular Cryptogams, particularly bryophytes and lichens, with respect to biogeochemical cycling. Yet these organisms are paramount determinants of biogeochemistry in several biomes, particularly cold biomes and tropical rainforests, where they: (1) contribute substantially to above-ground biomass (lichens, bryophytes); (2) host nitrogen-fixing bacteria, providing major soil N input (lichens, bryophytes); (3) control soil chemistry and nutrition through the accumulation of recalcitrant polyphenols (bryophytes) and through their control over soil and vegetation hydrology and temperatures; (4) both promote erosion (rock weathering by lichens) and prevent it (biological crusts in deserts); (5) provide a staple food to mammals such as reindeer (lichens) and arthropodes, with important feedbacks to soils and biota; and (6) both facilitate and compete with vascular plants. †Approach Here we review current knowledge about interspecific variation in Cryptogam traits with respect to biogeochemical cycling and discuss to what extent traits and measuring protocols needed for bryophytes and lichens correspond with those applied to vascular plants. We also propose and discuss several new or recently introduced traits that may help us understand and predict the control of Cryptogams over several aspects of the biogeochemistry of ecosystems. †Conclusions Whilst many methodological challenges lie ahead, comparative Cryptogam ecology has the potential to meet some of the important challenges of understanding and predicting the biogeochemical and climate consequences of large-scale environmental changes driving shifts in the Cryptogam components of vegetation composition.