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Seed mobility and connectivity in changing rural landscapes
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. (Landscape Ecology)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The success or failure of many organisms to respond to the challenges of habitat destruction and a warming climate lies in the ability of plant species to disperse between isolated habitats or to migrate to new ranges. European semi-natural grasslands represent one of the world's most species-rich habitats at small scales, but agricultural intensification during the 20th century has meant that many plant species are left only on small fragments of former habitat. It is important that these plants can disperse, both for the maintenance of existing populations, and for the colonisation of target species to restored grasslands. This thesis investigates the ecological, geographical and historical influences on seed dispersal and connectivity in semi-natural grasslands, and the mobility of plants through time and space. Seed dispersal by human activity has played a large role in the build-up of plant communities in rural landscapes, but patterns have shifted. Livestock are the most traditional, and probably the most capable seed dispersal vector in the landscape, but other dispersal methods may also be effective. Motor vehicles disperse seeds with similar traits to those dispersed by livestock, while 39% of valuable grasslands in southern Sweden are connected by the road network. Humans are found to disperse around one-third of available grassland species, including several protected and red-listed species, indicating that humans may have been valuable seed dispersers in the past when rural populations were larger. Past activities can also affect seed mobility in time through the seed bank, as seeds of grassland plant species are shown to remain in the soil even after the grassland had been abandoned. Today however, low seed rain in intensively grazed semi-natural grasslands indicates that seed production may be a limiting factor in allowing seeds to be dispersed in space through the landscape.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University , 2013. , 38 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 37
Keyword [en]
Biodiversity, Conservation, Functional connectivity, Historical ecology, Human-mediated dispersal, Invasive species, Landscape Ecology, Long-distance dispersal, Restoration, Seed bank, Seed dispersal, Seed rain, Structural connectivity
National Category
Physical Geography Ecology
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-89105ISBN: 978-91-7447-692-7 (print)OAI: oai:DiVA.org:su-89105DiVA: diva2:616412
Public defence
2013-06-05, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Formas, 2006-2130
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Accepted. Paper 4: In press. Paper 5: Manuscript.

Available from: 2013-05-14 Created: 2013-04-11 Last updated: 2013-05-03Bibliographically approved
List of papers
1. Can seed dispersal by human activity play a useful role for the conservation of European grasslands?
Open this publication in new window or tab >>Can seed dispersal by human activity play a useful role for the conservation of European grasslands?
2011 (English)In: Applied Vegetation Science, ISSN 1402-2001, E-ISSN 1654-109X, Vol. 14, no 3, 291-303 p.Article in journal (Refereed) Published
Abstract [en]

Objective: To review the recent research into human-mediated dispersal (HMD) in the European rural landscape, and explore the potential positive aspect of HMD for grassland conservation, in contrast to it's common association with the spread of invasive species. Methods: A literature search was undertaken to identify HMD vectors in the rural landscape for discussion regarding dispersal potential past and present, implications for management, and the identification of future research needs. Results: Grazing animals are important propagule dispersers, but the reduced movement of livestock through the landscape has also meant a reduction in seeds dispersed in this way. Other, non-standard human-mediated dispersal vectors such as clothing and motor vehicles can also transport seeds of many species, and HMD vectors often transport seeds with a variety of dispersal specialisations. Recommendations: There should be a greater movement of grazing animals throughout the landscape, either within larger grazing areas or between existing grasslands. Where this is not possible, other, more directed dispersal of propagules from species-rich communities to target sites should be considered. The potential of non-standard HMD vectors to make a positive contribution to biodiversity should be considered, but more research into all types of HMD vectors is important if we are to fully understand their role in the dispersal of plant species in fragmented landscapes.

Keyword
Anthropochory, Conservation, Grassland, Long-distance dispersal, Restoration, Zoochory
National Category
Environmental Sciences Ecology Botany
Identifiers
urn:nbn:se:su:diva-69228 (URN)10.1111/j.1654-109X.2011.01124.x (DOI)000292339800001 ()
Note

authorCount :1

Available from: 2012-11-19 Created: 2012-01-11 Last updated: 2017-12-08Bibliographically approved
2. Past and present management influences the seed bank and seed rain in a rural landscape mosaic
Open this publication in new window or tab >>Past and present management influences the seed bank and seed rain in a rural landscape mosaic
2011 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 48, no 5, 1278-1285 p.Article in journal (Refereed) Published
Abstract [en]

1. Seed bank and seed rain represent dispersal in time and space. They can be important sources of diversity in the rural landscape, where fragmented habitats are linked by their histories. 2. Seed bank, seed rain and above-ground vegetation were sampled in four habitat types (abandoned semi-natural grassland (ABA), grazed former arable field (FAF), mid-field islet (MFI) and grazed semi-natural grassland (SNG)) in a rural landscape in southern Sweden, to examine whether community patterns can be distinguished at large spatial scales and whether seed bank and seed rain are best explained by current, past or intended future vegetation communities. 3. We counted 54 357 seedlings of 188 species from 1190 seed bank and 797 seed rain samples. Seed bank, seed rain and above-ground vegetation communities differed according to habitat. Several species characteristic of managed grassland vegetation were present in the seed bank, seed rain and vegetation of the other habitats. 4. The seed banks of SNGs and the seed rain of the FAFs were generally better predicted by the surrounding above-ground vegetation than were the other habitat types. The seed rain of the grazed communities was most similar to the vegetation in the FAFs, while the seed banks of the abandoned grasslands most resembled the vegetation in SNGs. 5. Gap availability and seed input could be limiting the colonisation of target species in FAFs, while remnant populations in the seed bank and the presence of grassland specialists in the above-ground vegetation indicate that abandoned grasslands and mid-field islets could be valuable sources of future diversity in the landscape after restoration. 6. Synthesis and applications. SNG communities are able to form seed banks which survive land-use change, but their seed rain does not reflect their above-ground communities. It is important that grassland plants set seed. By connecting existing grasslands with restoration targets, increased disturbance in the target habitats would allow for colonisation via the seed bank or seed rain, while decreased grazing intensity would benefit seed production in the source grasslands. Otherwise, landscape-wide propagule availability might increase with a more varied timing and intensity of management.

Keyword
abandonment, biodiversity, co-correspondence analysis, conservation, dispersal, former arable fields, land-use history, mid-field islet, restoration, semi-natural grassland
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-69879 (URN)10.1111/j.1365-2664.2011.02019.x (DOI)000295095100024 ()
Funder
Formas
Available from: 2012-11-19 Created: 2012-01-15 Last updated: 2017-12-08Bibliographically approved
3. Grassland connectivity by motor vehicles and grazing livestock
Open this publication in new window or tab >>Grassland connectivity by motor vehicles and grazing livestock
2013 (English)In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 36, no 10, 1150-1157 p.Article in journal (Refereed) Published
Abstract [en]

In addition to habitat loss and fragmentation, agricultural change has led to a change in seed dispersal processes in therural landscape through a loss of structural and functional connectivity. Here, human-mediated dispersal vectors areprevalent, and we explored whether the loss of connectivity via free-ranging livestock could be mitigated by the increasein roads and motor vehicles. We found that structurally, 39% of all valuable semi-natural grassland habitats in southernSweden are adjacent to public road verges, which in the rural landscape are often considered to be suitable habitat forgrassland species. Additionally, by collecting mud attached to cars and farming machinery and manure from livestock(cattle, horse, sheep) grazing semi-natural grassland pasture, we found that motor vehicles are also capable seed dispers-ers. A similar number of species were dispersed by both vectors, although the composition of samples was quite different.Motor vehicles dispersed more grassland specialists than invasive species, although in much lower abundances than didgrazing livestock. Despite these differences, motor vehicles were found to be able to disperse species with the same kindsof dispersal traits as livestock. A high number of seeds, species and specialists in manure samples means that greater move-ment of livestock is desirable to increase functional grassland connectivity. However, effective management could improvethe suitability of roadsides as grassland corridors and increase the availability of seeds for long-distance human-mediateddispersal via cars and tractors. Our results suggest that in many rural landscapes, connectivity by road networks couldhelp mediate habitat loss and fragmentation of grasslands. However, such effects can be context dependent, and the con-nectivity provided by roads could have serious negative consequences in other regions.

National Category
Ecology
Identifiers
urn:nbn:se:su:diva-89133 (URN)10.1111/j.1600-0587.2013.00185.x (DOI)000325114500011 ()
Funder
Formas
Available from: 2013-04-12 Created: 2013-04-12 Last updated: 2017-12-06Bibliographically approved
4. Humans as long-distance dispersers of rural plant communities
Open this publication in new window or tab >>Humans as long-distance dispersers of rural plant communities
2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 5, e62763- p.Article in journal (Refereed) Published
Abstract [en]

Humans are known for their capacity to disperse organisms long distances. Long-distance dispersal can be important for speciesthreatened by habitat destruction, but research into human-mediated dispersal is often focussed upon few and/or invasive species.Here we use citizen science to identify the capacity for humans to disperse seeds on their clothes and footwear from a knownspecies pool in a valuable habitat, allowing for an assessment of the fraction and types of species dispersed by humans in analternative context. We collected material from volunteers cutting 48 species-rich meadows throughout Sweden. We counted 24354 seeds of 197 species, representing 34% of the available species pool, including several rare and protected species. However, 71species (36%) are considered invasive elsewhere in the world. Trait analysis showed that seeds with hooks or other appendageswere more likely to be dispersed by humans, as well as those with a persistent seed bank. More activity in a meadow resulted inmore dispersal, both in terms of species and representation of the source communities. Average potential dispersal distances weremeasured at 13 km. We consider humans capable seed dispersers, transporting a significant proportion of the plant communities inwhich they are active, just like more traditional vectors such as livestock. When rural populations were larger, people might havebeen regular and effective seed dispersers, and the net rural-urban migration resulting in a reduction in humans in the landscapemay have exacerbated the dispersal failure evident in declining plant populations today. With the fragmentation of habitat andchanges in land use resulting from agricultural change, and the increased mobility of humans worldwide, the dispersal role ofhumans may have shifted from providers of regular local and landscape dispersal to providers of much rarer long-distance andregional dispersal, and international invasion.

National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:su:diva-89134 (URN)10.1371/journal.pone.0062763 (DOI)000321200500037 ()
Available from: 2013-04-12 Created: 2013-04-12 Last updated: 2017-12-06Bibliographically approved
5. Dispersal geography: a new concept for managing seed dispersal in rural landscapes
Open this publication in new window or tab >>Dispersal geography: a new concept for managing seed dispersal in rural landscapes
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:su:diva-89135 (URN)
Available from: 2013-04-12 Created: 2013-04-12 Last updated: 2013-04-17Bibliographically approved

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