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Löbel, Swantje
Publications (10 of 11) Show all publications
Löbel, S., Snäll, T. & Rydin, H. (2012). Epiphytic bryophytes near forest edges and on retention trees: reduced growth and reproduction especially in old-growth-forest indicator species. Journal of Applied Ecology, 49(6), 1334-1343
Open this publication in new window or tab >>Epiphytic bryophytes near forest edges and on retention trees: reduced growth and reproduction especially in old-growth-forest indicator species
2012 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 49, no 6, p. 1334-1343Article in journal (Refereed) Published
Abstract [en]
  1. Epiphytes are an important component in many forest ecosystems. The proportion of threatened epiphyte species is high, and the impact of clearcuts on key demographic processes via edge-influence is still poorly understood. There are few studies on epiphyte growth, and even less is known about how reproduction is affected by proximity to forest edges. For retention trees, demographic studies are even scarcer.
  2. Based on the results from a 6-month transplant experiment and a 3-year study of natural colonies, we modelled growth and reproduction of epiphytic bryophytes used as indicators of old-growth forests and widespread epiphytes in relation to distance from the forest edge. We also modelled growth and reproduction on retention trees within the clearcut. Species responses were linked to variation in canopy openness.
  3. Unlike the widespread species, the old-growth-forest indicators grew exponentially with distance from the edge, and this response was more pronounced at the south-east than north-west forest edge. In one red-listed species, reproduction was thoroughly inhibited near the edge, whereas the reproductive rate of the widespread species tended to increase. However, the widespread species also showed reduced shoot lengths on the retention trees.
  4. Reduced growth and inhibited reproduction of sensitive epiphytes near edges decrease the number of dispersing diaspores and may, in combination with lower local connectivity and increased tree fall rates close to edges, increase the risk of metapopulation extinction.
  5. Synthesis and applications. Two general management implications for boreal forests are drawn. First, retention trees may not have the capacity to act as a ‘lifeboat’ for epiphytic bryophytes and support their populations during the regeneration phase. Second, the creation of buffer zones is a useful conservation strategy for bryophytes. The exact width of zones depends on the forest structure and should be orientated in relation to the requirements of the most sensitive species. For the rather dense experimental forest, a width of at least 30 m was required for the south-facing buffer, whereas for the north-facing buffer 10 m was sufficient.
Keywords
buffer zones, canopy openness, edge effect, edge orientation, edge-influence, growth, reproduction, transplantation experiment, tree retention, vitality
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-190128 (URN)10.1111/j.1365-2664.2012.02201.x (DOI)000311855000015 ()
Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2019-02-01Bibliographically approved
Löbel, S. & Rydin, H. (2010). Trade-offs and habitat constraints in the establishment of epiphytic bryophytes. Functional Ecology, 24(4), 887-897
Open this publication in new window or tab >>Trade-offs and habitat constraints in the establishment of epiphytic bryophytes
2010 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 24, no 4, p. 887-897Article in journal (Refereed) Published
Abstract [en]

1. Diversity of patch-tracking epiphyte metacommunities depends on successful colonization of new habitats. Habitat constraints and critical stages in the establishment have gained little attention in metacommunity studies, but a trade-off between dispersal ability and establishment rate is often assumed. This assumption remains largely untested, and alternative dispersal and reproductive strategies offer several trade-offs to be explored.

2. We used in vitro experiments to identify critical stages in the establishment of obligate epiphytic bryophytes with contrasting dispersal strategies [sexual via small (< 20 mu m) or large (> 20 mu m) spores, asexual via gemmae or gemmae-like branchlets], and to identify habitat constraints of diaspore establishment and trade-offs among species traits.

3. Across all stages of the establishment process, large asexual diaspores performed better than small sexual ones. Asexual species also had a higher ability to establish from fragments than sexual species. Germination of all diaspore types was limited by pH with highest germination rates at intermediate pH. Large moss spores showed a higher desiccation tolerance than small ones, but lower germination and protonemal growth rates. Liverwort spores had the lowest desiccation tolerance, germination and protonemal growth rates, but rapidly developed gametophytic shoots once they had germinated.

4. Combining the results with earlier studies on dispersal distances in epiphytes, our study demonstrated a trade-off between dispersal distance and establishment ability, which may be central for the evolution of asexual dispersal in epiphytes. The evolution of spore size may additionally involve trade-offs between high germination and protonemal growth rates, desiccation tolerance, and a rapid development from protonema to shoots. We suggest that trade-offs in epiphytes are shaped by conflicting selection pressures imposed by habitat patchiness, landscape dynamics and irregular water supply.

Keywords
desiccation, germination, life-history trade-offs, metacommunity, pH, patch-tracking, protonema, reproductive strategies
National Category
Biological Sciences
Research subject
Ecological Botany
Identifiers
urn:nbn:se:uu:diva-107315 (URN)10.1111/j.1365-2435.2010.01705.x (DOI)000279837700022 ()
Note
Part of PhD-thesis which will be defended the 26th of September 2009Available from: 2009-08-05 Created: 2009-08-05 Last updated: 2019-02-01Bibliographically approved
Löbel, S. & Rydin, H. (2009). Dispersal and life-history strategies in epiphyte metacommunities: alternative solutions to survival in patchy, dynamic landscapes. Oecologia, 161(3), 569-579
Open this publication in new window or tab >>Dispersal and life-history strategies in epiphyte metacommunities: alternative solutions to survival in patchy, dynamic landscapes
2009 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 161, no 3, p. 569-579Article in journal (Refereed) Published
Abstract [en]

Host trees for obligate epiphytes are dynamic patches that emerge, grow and fall, and metacommunity diversity critically depends on efficient dispersal. Even though species that disperse by large asexual diaspores are strongly dispersal-limited, asexual dispersal is common. The stronger dispersal limitation of asexually reproducing species compared to species reproducing sexually via small spores may be compensated by higher growth rates, lower sensitivity to habitat conditions, higher competitive ability or younger reproductive age.

We compared growth and reproduction of different groups of epiphytic bryophytes with contrasting dispersal (asexual vs sexual) and life-history strategies (colonists, short- and long-lived shuttle species, perennial stayers) in an old-growth forest stand in the boreo-nemoral region in Eastern Sweden.

No differences were seen in relative growth rates between asexual and sexual species. Long-lived shuttles had lower growth rates than colonists and perennial stayers. Most groups grew best at intermediate bark pH. Interactions with other epiphytes had a small, often positive effect on growth. Neither differences in sensitivity of growth to habitat conditions nor differences in competitive abilities among species groups were found. Habitat conditions, however, influenced the production of sporophytes, but not of asexual diaspores. Presence of sporophytes negatively affected growth, whereas presence of asexual diaspores did not. Sexual species had to reach a certain colony size before starting to reproduce, whereas no such treshold existed for asexual reproduction.

The results indicate that the epiphyte metacommunity is structured by two main trade-offs: dispersal distance vs reproductive age, and dispersal distance vs sensitivity to habitat quality. There seems to be a trade-off between growth and sexual reproduction, but not asexual. Trade-offs in species traits may be shaped by conflicting selection pressures imposed by habitat turnover and connectivity rather than by species interactions.

Keywords
Growth, Local processes, Metapopulation, Reproduction, Trade-offs
National Category
Biological Sciences
Research subject
Ecological Botany
Identifiers
urn:nbn:se:uu:diva-107314 (URN)10.1007/s00442-009-1402-1 (DOI)000269010300012 ()
Available from: 2009-08-05 Created: 2009-08-05 Last updated: 2019-02-01Bibliographically approved
Löbel, S., Snäll, T. & Rydin, H. (2009). Mating system, reproduction mode and diaspore size affect metacommunity diversity. Journal of Ecology, 97(1), 176-185
Open this publication in new window or tab >>Mating system, reproduction mode and diaspore size affect metacommunity diversity
2009 (English)In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 97, no 1, p. 176-185Article in journal (Refereed) Published
Abstract [en]

1. Metapopulation persistence and metacommunity diversity in patchy dynamic landscapes critically depend on efficient dispersal. Dispersal strategies could involve trade-offs that result in different species responses to habitat fragmentation, alteration in habitat quality and changes in landscape dynamics. 2. We studied spatial structuring in species richness of obligate epiphytic bryophytes in 135 deciduous forest patches in a largely coniferous landscape in Sweden. We tested the effects of forest patch size (0.01-15 ha), patch quality and present and historic connectivity (as revealed by air photographs) on species richness of species groups with different mating systems, reproduction modes and diaspore sizes. 3. Present connectivity to other deciduous forest patches had positive effects on richness of dioecious species with predominant asexual reproduction, whereas richness of monoecious species with predominant sexual reproduction was affected by historic connectivity only. The scale of spatial structuring in species richness increased with decreasing diaspore sizes. Forest patch quality affected richness of monoecious species reproducing sexually but not of dioecious species reproducing asexually. 4. Our results suggest shorter dispersal distances, but higher establishment rates, of large asexual diaspores than of small sexual ones. In monoecious species with sexual reproduction, it may take several decades from establishment to first spore production, and this may explain the strong effect of historic, but not present, forest patch connectivity on species richness of this group. This suggests a trade-off between dispersal distance and age at first reproduction, which may explain the parallel evolution of asexual reproduction and monoecism in species inhabiting patchy, transient habitats. 5. Synthesis. We conclude that dispersal success of metacommunity members is influenced both by species traits and habitat characteristics. In patch-tracking metacommunities, trade-offs in species traits may have evolved as a consequence of conflicting selection pressures imposed by habitat patchiness and dynamics. Syndromes of interrelated species traits imply that fairly small changes in habitat conditions may lead to distinct changes in metacommunity diversity: Species reproducing asexually may drastically decline with increasing distances among patches, whereas sexually reproducing species may decline with increasing patch dynamics.

Keywords
asexual reproduction, bryophytes, dispersal strategies, epiphytes, habitat fragmentation, landscape dynamics, life-history trade-offs, metapopulation, patch-tracking, species richness
National Category
Biological Sciences
Research subject
Ecological Botany
Identifiers
urn:nbn:se:uu:diva-107313 (URN)10.1111/j.1365-2745.2008.01459.x (DOI)000261684400020 ()
Available from: 2009-08-05 Created: 2009-08-05 Last updated: 2019-02-01Bibliographically approved
Löbel, S. (2009). Metapopulation and metacommunity processes, dispersal strategies and life-history trade-offs in epiphytes. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Metapopulation and metacommunity processes, dispersal strategies and life-history trade-offs in epiphytes
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to increase knowledge about metapopulation and metacommunity processes in patchy, dynamic landscapes, using epiphytic bryophytes as a model system. Host trees and deciduous forest stands in the coniferous landscape are patchy, temporal and undergo changes in habitat quality during succession. Epiphytes must track this dynamic habitat network for their long-term survival. Community patterns at different spatial scales were explored and linked to regional metapopulation processes and local population dynamics.

Spatial structuring in species richness both at a local and regional scale indicated stronger dispersal limitation but lower sensitivity to habitat quality in species with large asexual than in species with small sexual diaspores. In sexually dispersed species, a strong rescue effect was indicated by a bimodal frequency distribution of the species and by increasing local abundance with increasing patch connectivity. Present connectivity to other deciduous forest patches had positive effects on richness of asexually dispersed species, whereas richness of sexually dispersed species was instead related to the landscape connectivity 30 years ago. A study of local growth and reproduction suggested that this is caused by delayed sexual, but not asexual, reproduction. Habitat conditions affected the production of sporophytes, but not of asexual diaspores. No differences in either growth rates or competitive abilities among species with different dispersal and life-history strategies were found. In vitro experiments showed that establishment is higher from large asexual diaspores than from small sexual. Establishment of all diaspore types was limited by pH. There were indications of trade-offs between high germination and protonemal growth rates, desiccation tolerance and a rapid development of shoots from protonema.

The results indicated that the epiphyte metacommunity is structured by two main trade-offs: dispersal distance (diaspore size) versus age at first reproduction, and dispersal distance versus sensitivity to habitat quality. Trade-offs in species traits may have evolved as a consequence of conflicting selection pressures imposed by habitat turnover, connectivity and irregular water supply rather than by species interactions. Syndromes of interrelated species traits imply that fairly small changes in habitat conditions can lead to distinct changes in metacommunity diversity: the results indicate that increasing distances among patches cause most harm to asexually dispersed species, whereas cuttings of forests of high age and quality as well as increasing patch dynamics are most harmful to sexually dispersed species.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. p. 37
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 661
Keywords
asexual, biodiversity, bryophytes, dispersal limitation, establishment, evolution of reproductive traits, germination, growth, habitat fragmentation, landscape dynamics, local processes, patch-tracking, pH, reproduction, species richness, species interactions
National Category
Other Biological Topics
Research subject
Ecological Botany
Identifiers
urn:nbn:se:uu:diva-106847 (URN)978-91-554-7578-9 (ISBN)
Public defence
2010-05-20, Lindahlsalen, EBC, Norbyvägen 18B, 752 36, Uppsala, 10:00 (English)
Opponent
Supervisors
Note
Senarelagd disputation från: 2009-09-26, Lindahlsalen, EBC, Villavägen 9, 75236 Uppsala, Uppsala, 10:00 Available from: 2010-03-09 Created: 2009-07-06 Last updated: 2011-03-02Bibliographically approved
Löbel, S. & Dengler, J. (2008). Dry grassland communities on southern Öland: phytosociology, ecology, and diversity. Acta Phytogeographica Suecica, 88, 13-31
Open this publication in new window or tab >>Dry grassland communities on southern Öland: phytosociology, ecology, and diversity
2008 (English)In: Acta Phytogeographica Suecica, ISSN 0084-5914, Vol. 88, p. 13-31Article in journal (Refereed) Published
Abstract [en]

We studied dry grassland vegetation on southern Öland, both within and outside the Great Alvar, using the Braun-Blanquet approach. We were able to distinguish 15 associations or equivalent units belonging to three major syntaxa. Dry grasslands on sandy soils (class Koelerio-Corynephoretea; subclass Koelerio-Corynephorenea) occurred along the east and west coasts. Weathered rock and outcrop communities (class Koelerio-Corynephoretea; subclass Sedo-Scleranthenea) inhabited shallow skeletal soils, mainly on the Great Alvar. Semi-dry basiphilous grasslands of the class Festuco-Brometea occurred on moraine soils, which were the least extreme in terms of soil moisture and nutrient availability. Whereas the first category comprises impoverished variants of widely distributed syntaxa, all Sedo-Scleranthenea and Festuco-Brometea communities lack direct counterparts in central Europe. The alvar communities proved to be floristically well separated from the others. Species density on 4 m2 was highest in the Sedo-Scleranthenea (that of the Gypsophilo fastigiatae-Globularietum vulgaris with 80 taxa being one of the highest known), intermediate in the Festuco-Brometea, and lowest in the Koelerio-Corynephorenea. Harsh and variable conditions, small plant sizes, and a large local species pool are considered possible causes.

Keywords
Alvar, Biodiversity, Environmental condition, Festuco-Brometea, Koelerio-Corynephorenea, Sedo-Scleranthenea, Species richness, Syntaxonomy
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-17200 (URN)10.3170/2008-12-18541 (DOI)
Available from: 2008-06-17 Created: 2008-06-17Bibliographically approved
Dengler, J. & Löbel, S. (2006). Dry grassland communities of shallow, skeletal soils (Sedo-Scleranthenea) in northern Europe. Tuexenia, 26, 159-190
Open this publication in new window or tab >>Dry grassland communities of shallow, skeletal soils (Sedo-Scleranthenea) in northern Europe
2006 (English)In: Tuexenia, Vol. 26, p. 159-190Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-24124 (URN)
Available from: 2007-02-03 Created: 2007-02-03 Last updated: 2011-01-11
Löbel, S., Snäll, T. & Rydin, H. (2006). Metapopulation processes in epiphytes inferred from patterns of regional distribution and local abundance in fragmented forest landscapes. Journal of Ecology, 94, 856-868
Open this publication in new window or tab >>Metapopulation processes in epiphytes inferred from patterns of regional distribution and local abundance in fragmented forest landscapes
2006 (English)In: Journal of Ecology, Vol. 94, p. 856-868Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-24128 (URN)
Available from: 2007-02-03 Created: 2007-02-03 Last updated: 2019-02-01
Löbel, S., Dengler, J. & Hobohm, C. (2006). Species richness of vascular plants, bryophytes and lichens in dry grasslands: The effects of environment, landscape structure and competition. Folia Geobotanica, 41(4), 377-393
Open this publication in new window or tab >>Species richness of vascular plants, bryophytes and lichens in dry grasslands: The effects of environment, landscape structure and competition
2006 (English)In: Folia Geobotanica, ISSN 1211-9520, E-ISSN 1874-9348, Vol. 41, no 4, p. 377-393Article in journal (Refereed) Published
Abstract [en]

We studied the relative importance of local habitat conditions and landscape structure for species richness of vascular plants, bryophytes and lichens in dry grasslands on the Baltic island of Oland (Sweden). In addition, we tested whether relationships between species richness and vegetation cover indicate that competition within and between the studied taxonomic groups is important. We recorded species numbers of vascular plants, bryophytes and lichens in 4 m(2) plots (n = 452), distributed over dry grassland patches differing in size and degree of isolation. Structural and environmental data were collected for each plot. We tested effects of local environmental conditions, landscape structure and vegetation cover on species richness using generalized linear mixed models. Different environmental variables explained species richness of vascular plants, bryophytes and lichens. Environmental effects, particularly soil pH, were more important than landscape structure. Interaction effects of soil pH with other environmental variables were significant in vascular plants. Plot heterogeneity enhanced species richness. Size and degree of isolation of dry grassland patches significantly affected bryophyte and lichen species richness, but not that of vascular plants. We observed negative relationships between bryophyte and lichen species richness and the cover of vascular plants. To conclude, effects of single environmental variables on species richness depend both on the taxonomic group and on the combination of environmental factors on a whole. Dispersal limitation in bryophytes and lichens confined to dry grasslands may be more common than is often assumed. Our study further suggests that competition between vascular plants and cryptogams is rather asymmetric.

Keywords
alvar, biodiversity, dispersal limitation, environmental heterogeneity, fragmentation, soil pH, spatial autocorrelation
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-24127 (URN)10.1007/BF02806555 (DOI)000242230200002 ()
Available from: 2007-02-03 Created: 2007-02-03 Last updated: 2017-12-07Bibliographically approved
Löbel, S., Snäll, T. & Rydin, H. (2006). Species richness patterns and metapopulation processes evidence from epiphyte communities in boreo-nemoral forests. Ecography, 29, 169-182
Open this publication in new window or tab >>Species richness patterns and metapopulation processes evidence from epiphyte communities in boreo-nemoral forests
2006 (English)In: Ecography, Vol. 29, p. 169-182Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-24126 (URN)
Available from: 2007-02-03 Created: 2007-02-03 Last updated: 2019-02-01
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