TU Darmstadt / ULB / TUbiblio

The contribution of sheep zoochory to the conservation and restoration of target plant communities in isolated sand ecosystems

Wessels, Saskia Cornelie (2008):
The contribution of sheep zoochory to the conservation and restoration of target plant communities in isolated sand ecosystems.
Darmstadt, Technische Universität, TU Darmstadt,
[Ph.D. Thesis]

Abstract

The dispersal of seeds is crucial for the survival of many plant species. Fragmentation of the European cultural landscape and changes in land management, e.g. decrease of livestock numbers and lower mobility of livestock between different areas, have severely limited spatial dispersal processes, and thereby made a major contribution to the reduction of species richness of cultural landscapes. Reintroduction of extensive grazing regimes involving large domestic herbivores is often claimed to restore the connectivity between separated populations via endo- and epizoochorous dispersal of seeds. This thesis aimed to investigate sheep-induced seed dispersal over long distances and its contribution to the recruitment of especially target species. The use of a sheep grazing regime which involves consecutive grazing of well-developed target communities, as a seed source, followed by less-developed sinks, could increase the quality of dispersed seeds (more target species). If recruitment takes place successfully, spatially isolated populations can be functionally re-connected or new sites colonised. The study was carried out in three inland sand ecosystems, relatively isolated from each other in the landscape (Darmstadt region, Germany). The two larger areas “Ehemaliger August-Euler-Flugplatz von Darmstadt” and “Griesheimer Düne und Eichwäldchen” are both nature protection areas, grazed by sheep since 1999/2000. Animals walk a 3-km distance when transferring from one area to the other. Recently, for restoration purposes an abandoned agricultural field “Streitgewann” was also included in the grazing system. “Streitgewann” is situated between the first two areas and could function as a “stepping stone”. Dispersal and post-dispersal processes within and between the above-mentioned areas were analysed. As seed sources mostly well-developed target communities Koelerion glaucae (Kg), Armerio-Festucetum trachyphyllae (AF) and Allio-Stipetum capillatae (AS) were used. All investigations employed three or four tamed male sheep. First of all, species compositions of grazing sources and epizoochorously dispersed seeds (both intra- and inter-area transfers) were determined. The quantities and species composition of seeds detected in sheep coats before and after walking from one area to another were compared to test for potential seed losses. Additionally, the impact of seed surface structure, seed mass and plant seed-releasing height on attachment was tested. Naturally attached seeds of Stipa capillata and Agrimonia procera were used to study retention times and detachment rates during different herbivore activities (long-distance walking, grazing). In total, 56 seed species were detected in investigated sheep coats. Half of the species in the three vegetation types were target species. In sheep coats target species were slightly over-represented; among them were seven Red List species. Quantitatively, most transported seeds belonged to target species, whereas almost no graminoid competitors were detected. No significant numbers of epizoochorously transported seeds dropped out of the sheep coats during 3-km inter-area transfers, whereas many seeds of S. capillata and A. procera detached in the sink area. Longer duration of the grazing period and grooming behaviour probably stimulate seed detachment. Furthermore, it was shown that attachment is determined by seed mass and seed morphological appendages. Seeds without well-developed seed structures are probably negatively affected by seed mass, whereas seeds with structures (e.g. hooks) seem to have an equal attachment probability, regardless of mass. The fate of epizoochorously dispersed seeds was studied for 14 seed species. Most of them were endangered target species of inland sand ecosystems, for which epizoochorous dispersal was already shown in our previous investigations. Three 10 m x 10 m sand fields were established at a former agricultural field. Per field two sheep were present for 24 h; seeds were experimentally attached to their coats. The impact of sheep trampling on seedling emergence was also tested for two threatened species: Jurinea cyanoides (EU Fauna-Flora-Habitat directive species) and Koeleria glauca. Sheep trampling patterns, seed detachment rates and spatial dispersal patterns of the three largest-seeded species (Stipa capillata, Medicago minima and Cynoglossum officinale) were studied. Also, seedling emergence and survival of all included species were recorded over an 8-month period. The relatively brief sheep presence at the sand fields resulted in high detachment rates. Seedlings of almost all species emerged (up to 40 % of original seed number). Analysing the patterns of sheep trampling, seed shadow, and seedling emergence by use of Spatial Analysis by Distance Indices (SADIE), showed non-random distributions. Generally, a positive correlation between sheep abundance and the number of relocated seeds and emerged seedlings was found, whereas individual species showed a variable trampling response. The seedling emergence of J. cyanoides increased after trampling, whereas K. glauca showed no effect. Estimation of the potential contribution of herbivores to plant species dispersal via the endozoochorous pathway has mostly been based on results of seedling emergence tests. To check the reliability of such estimates, a comparison of viable seed contents in sheep dung by use of two methods was conducted. Dung was collected after a 6-day grazing period in one of the target communities (Allio-Stipetum). Following the Ter Heerdt method (TH), samples were concentrated and kept under controlled conditions (glasshouse or climate room, duration experiment 5 months). In the second seedling emergence test (common garden method, CG) unconcentrated samples were kept outdoors (15 months). Qualitative and quantitative similarities between the two methods were calculated by use of Sørenson similarity index (QS). Detected seeds showed a highly similar species composition (QS = 0.81) and content (QS = 0.69). Some more seedlings emerged via TH, and especially several small-seeded winter annuals (Veronica arvensis, Arenaria serpyllifolia, Arabis glabra) showed a higher emergence. More species and higher quantities of hard-coated seed species of Fabaceae and Cistaceae emerged outdoors (CG). In relation to each other, both methods offer a valuable means of estimating the potential seed input via dung deposition. If the main research interest is the species composition, CG should be used. TH, on the other hand, better estimates the overall viable seed content and uses less space and time. Finally, the impact of endozoochorously transported seeds, the deposition of dung, disturbance by removal of the moss layer (Hypnum cupressiforme), and dung removal by the dung beetle Typhaeus typhoeus (Linnaeus, 1758) on fine-scale species richness was investigated (factorial experiment).. Sheep dung was collected after the same source paddocks used for epizoochory investigations were grazed (Kg, AF, AS). The species composition and viable seed content of dung-embedded seeds were analysed by use of seedling emergence tests. Treatments were established in the field in stands having different productivity (Kg < semi-ruderalised AF < ruderalised AF). From the three dung types (referring to vegetation types), viable seeds of 59 taxa were found, whereas under field conditions, 23 dung-borne taxa were detected (60 % target species). Quantitatively, most seedlings belonged to target species (e.g. Helianthemum nummularium, previously absent in the sink area), whereas competing graminoids emerged only within more productive AF plots. Despite a lower seedling emergence, dung deposition did promote species richness in Kg and semi-ruderalised AF plots. The impact of dung deposition can be modified when dung beetles transport dung pellets into larvae chambers, situated below-ground (> 40 cm). As a result, several disturbance species, e.g. Oenothera biennis and Polygonum aviculare, emerged at high rates from the dung beetle-disturbed topsoil. Disturbance of the moss layer promoted seedling emergence from dung and soil seed bank in semi-ruderalised AF plots, and the emergence of especially herbs resulted in increased fine-scale species richness. The vegetation of the most productive AF plots responded differently to the two treatments (disturbance of moss layer and dung deposition) in comparison with semi-ruderalised AF plots. Phytodiversity and plant density were initially suppressed in both treatments and additionally dung deposition decreased the abundance of graminoid competitors Carex hirta and Cynodon dactylon. Nevertheless, the reduced competition and soil fertilising effect of dung presumably promoted those same competitors in a later stage. Increased competition probably limited species diversity. The effect of herbivore-induced disturbance and endozoochorously transported seeds on fine-scale species richness probably depends at least partly on the productivity of the established vegetation. The present study has shown that a regime of sheep grazing, the use of well-developed target communities as seed sources and inter-area transfers between isolated habitats offers a good management measure for conservation and restoration of open inland sand ecosystems in fragmented landscapes. A large sheep flock (around 600 animals) and the presence of a high proportion of habitat-typical species in the selected grazing sources promote epi- and endozoochorous dispersal of millions of seeds of target species over long distances. Additionally, herbivore activity can increase the availability of micro-sites. By altering main determinants of recruitment (especially seed and micro-site availability), sheep play an important role in the establishment of target species and promote species-richness, especially in early and mid-successional stages.

Item Type: Ph.D. Thesis
Erschienen: 2008
Creators: Wessels, Saskia Cornelie
Title: The contribution of sheep zoochory to the conservation and restoration of target plant communities in isolated sand ecosystems
Language: English
Abstract:

The dispersal of seeds is crucial for the survival of many plant species. Fragmentation of the European cultural landscape and changes in land management, e.g. decrease of livestock numbers and lower mobility of livestock between different areas, have severely limited spatial dispersal processes, and thereby made a major contribution to the reduction of species richness of cultural landscapes. Reintroduction of extensive grazing regimes involving large domestic herbivores is often claimed to restore the connectivity between separated populations via endo- and epizoochorous dispersal of seeds. This thesis aimed to investigate sheep-induced seed dispersal over long distances and its contribution to the recruitment of especially target species. The use of a sheep grazing regime which involves consecutive grazing of well-developed target communities, as a seed source, followed by less-developed sinks, could increase the quality of dispersed seeds (more target species). If recruitment takes place successfully, spatially isolated populations can be functionally re-connected or new sites colonised. The study was carried out in three inland sand ecosystems, relatively isolated from each other in the landscape (Darmstadt region, Germany). The two larger areas “Ehemaliger August-Euler-Flugplatz von Darmstadt” and “Griesheimer Düne und Eichwäldchen” are both nature protection areas, grazed by sheep since 1999/2000. Animals walk a 3-km distance when transferring from one area to the other. Recently, for restoration purposes an abandoned agricultural field “Streitgewann” was also included in the grazing system. “Streitgewann” is situated between the first two areas and could function as a “stepping stone”. Dispersal and post-dispersal processes within and between the above-mentioned areas were analysed. As seed sources mostly well-developed target communities Koelerion glaucae (Kg), Armerio-Festucetum trachyphyllae (AF) and Allio-Stipetum capillatae (AS) were used. All investigations employed three or four tamed male sheep. First of all, species compositions of grazing sources and epizoochorously dispersed seeds (both intra- and inter-area transfers) were determined. The quantities and species composition of seeds detected in sheep coats before and after walking from one area to another were compared to test for potential seed losses. Additionally, the impact of seed surface structure, seed mass and plant seed-releasing height on attachment was tested. Naturally attached seeds of Stipa capillata and Agrimonia procera were used to study retention times and detachment rates during different herbivore activities (long-distance walking, grazing). In total, 56 seed species were detected in investigated sheep coats. Half of the species in the three vegetation types were target species. In sheep coats target species were slightly over-represented; among them were seven Red List species. Quantitatively, most transported seeds belonged to target species, whereas almost no graminoid competitors were detected. No significant numbers of epizoochorously transported seeds dropped out of the sheep coats during 3-km inter-area transfers, whereas many seeds of S. capillata and A. procera detached in the sink area. Longer duration of the grazing period and grooming behaviour probably stimulate seed detachment. Furthermore, it was shown that attachment is determined by seed mass and seed morphological appendages. Seeds without well-developed seed structures are probably negatively affected by seed mass, whereas seeds with structures (e.g. hooks) seem to have an equal attachment probability, regardless of mass. The fate of epizoochorously dispersed seeds was studied for 14 seed species. Most of them were endangered target species of inland sand ecosystems, for which epizoochorous dispersal was already shown in our previous investigations. Three 10 m x 10 m sand fields were established at a former agricultural field. Per field two sheep were present for 24 h; seeds were experimentally attached to their coats. The impact of sheep trampling on seedling emergence was also tested for two threatened species: Jurinea cyanoides (EU Fauna-Flora-Habitat directive species) and Koeleria glauca. Sheep trampling patterns, seed detachment rates and spatial dispersal patterns of the three largest-seeded species (Stipa capillata, Medicago minima and Cynoglossum officinale) were studied. Also, seedling emergence and survival of all included species were recorded over an 8-month period. The relatively brief sheep presence at the sand fields resulted in high detachment rates. Seedlings of almost all species emerged (up to 40 % of original seed number). Analysing the patterns of sheep trampling, seed shadow, and seedling emergence by use of Spatial Analysis by Distance Indices (SADIE), showed non-random distributions. Generally, a positive correlation between sheep abundance and the number of relocated seeds and emerged seedlings was found, whereas individual species showed a variable trampling response. The seedling emergence of J. cyanoides increased after trampling, whereas K. glauca showed no effect. Estimation of the potential contribution of herbivores to plant species dispersal via the endozoochorous pathway has mostly been based on results of seedling emergence tests. To check the reliability of such estimates, a comparison of viable seed contents in sheep dung by use of two methods was conducted. Dung was collected after a 6-day grazing period in one of the target communities (Allio-Stipetum). Following the Ter Heerdt method (TH), samples were concentrated and kept under controlled conditions (glasshouse or climate room, duration experiment 5 months). In the second seedling emergence test (common garden method, CG) unconcentrated samples were kept outdoors (15 months). Qualitative and quantitative similarities between the two methods were calculated by use of Sørenson similarity index (QS). Detected seeds showed a highly similar species composition (QS = 0.81) and content (QS = 0.69). Some more seedlings emerged via TH, and especially several small-seeded winter annuals (Veronica arvensis, Arenaria serpyllifolia, Arabis glabra) showed a higher emergence. More species and higher quantities of hard-coated seed species of Fabaceae and Cistaceae emerged outdoors (CG). In relation to each other, both methods offer a valuable means of estimating the potential seed input via dung deposition. If the main research interest is the species composition, CG should be used. TH, on the other hand, better estimates the overall viable seed content and uses less space and time. Finally, the impact of endozoochorously transported seeds, the deposition of dung, disturbance by removal of the moss layer (Hypnum cupressiforme), and dung removal by the dung beetle Typhaeus typhoeus (Linnaeus, 1758) on fine-scale species richness was investigated (factorial experiment).. Sheep dung was collected after the same source paddocks used for epizoochory investigations were grazed (Kg, AF, AS). The species composition and viable seed content of dung-embedded seeds were analysed by use of seedling emergence tests. Treatments were established in the field in stands having different productivity (Kg < semi-ruderalised AF < ruderalised AF). From the three dung types (referring to vegetation types), viable seeds of 59 taxa were found, whereas under field conditions, 23 dung-borne taxa were detected (60 % target species). Quantitatively, most seedlings belonged to target species (e.g. Helianthemum nummularium, previously absent in the sink area), whereas competing graminoids emerged only within more productive AF plots. Despite a lower seedling emergence, dung deposition did promote species richness in Kg and semi-ruderalised AF plots. The impact of dung deposition can be modified when dung beetles transport dung pellets into larvae chambers, situated below-ground (> 40 cm). As a result, several disturbance species, e.g. Oenothera biennis and Polygonum aviculare, emerged at high rates from the dung beetle-disturbed topsoil. Disturbance of the moss layer promoted seedling emergence from dung and soil seed bank in semi-ruderalised AF plots, and the emergence of especially herbs resulted in increased fine-scale species richness. The vegetation of the most productive AF plots responded differently to the two treatments (disturbance of moss layer and dung deposition) in comparison with semi-ruderalised AF plots. Phytodiversity and plant density were initially suppressed in both treatments and additionally dung deposition decreased the abundance of graminoid competitors Carex hirta and Cynodon dactylon. Nevertheless, the reduced competition and soil fertilising effect of dung presumably promoted those same competitors in a later stage. Increased competition probably limited species diversity. The effect of herbivore-induced disturbance and endozoochorously transported seeds on fine-scale species richness probably depends at least partly on the productivity of the established vegetation. The present study has shown that a regime of sheep grazing, the use of well-developed target communities as seed sources and inter-area transfers between isolated habitats offers a good management measure for conservation and restoration of open inland sand ecosystems in fragmented landscapes. A large sheep flock (around 600 animals) and the presence of a high proportion of habitat-typical species in the selected grazing sources promote epi- and endozoochorous dispersal of millions of seeds of target species over long distances. Additionally, herbivore activity can increase the availability of micro-sites. By altering main determinants of recruitment (especially seed and micro-site availability), sheep play an important role in the establishment of target species and promote species-richness, especially in early and mid-successional stages.
Place of Publication: Darmstadt
Publisher: Technische Universität
Uncontrolled Keywords: Epizoochorie, Endozoochorie, Samenausbreitung, Binnenland-Sandökosystem, Herbivore, Keimlingsemergenz, Pionier- Sukzessionsstadium, Ziel-Planzengemeinschaft
Divisions: 10 Department of Biology
10 Department of Biology > Vegetation ecology - Restoration
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Date Deposited: 17 Oct 2008 09:22
Official URL: urn:nbn:de:tuda-tuprints-9482
License: only the rights of use according to UrhG
Referees: Scheu, Prof. Dr. Stefan
Refereed / Verteidigung / mdl. Prüfung: 18 January 2008
Alternative keywords:
Alternative keywordsLanguage
Epizoochory, endozoochory, seed dispersal, inland sand ecosystem, herbivores, seedling emergence, spatial patterns, target plant community, restoration, conservationEnglish
Alternative Abstract:
Alternative abstract Language

Die Ausbreitung von Diasporen ist entscheidend für das Überleben vieler Pflanzenarten. Die Fragmentation europäischer Kulturlandschaften und Änderungen im Land-Management, z.B. der Rückgang von Weidetier-Abundanzen und deren geringere Mobilität zwischen Gebieten, haben entscheidend die räumlichen Ausbreitungsprozesse gemindert und trugen zur Verminderng des Artenreichtums von Kulturlandchaften bei. Die Wiedereinführung eines extensiven Beweidungsregimes mit Haustieren und die dadurch bedingte endo- und epizoochore Ausbreitung von Diasporen von Fläche zu Fläche wird oft als entscheidend angesehen, um den Verbund (“connectivity”) zwischen separierten Populationen zu gewährleisten. Diese Arbeit hat zum Ziel, die Schaf-induzierte Ausbreitung von Diasporen über längere Distanzen und den Beitrag zur Etablierung insbesondere von Zielarten zu untersuchen. Die Etablierung eines Systems der Schafbeweidung, das die aufeinander folgende Beweidung gut entwickelter Leitbildflächen (Diasporen-„Source“) mit anschließender Beweidung weniger entwickelter Flächen („Sink“) verbindet, kann die Qualität der ausgebreiteten Diasporen (mehr Zielarten) steigern. Wenn die Etablierung erfolgreich war, können räumlich separierte Populationen wieder funktionell verbunden oder neue Flächen kolonisiert werden. Die Untersuchungen wurden in Binnenland-Sandökosystemen durchgeführt, die relativ isoliert voneinander liegen (Region Darmstadt). Die zwei größeren Gebiete „Ehemaliger August-Euler-Flugplatz von Darmstadt” und „Griesheimer Düne und Eichwäldchen” sind beides Naturschutzgebiete, die seit 1999/2000 mit Schafen beweidet werden. Die Weidetiere legen eine Strecke von ca. 3 km zurück, wenn sie von einem Gebiet in das andere ziehen. Im Zusammenhang mit Restitutionsmaßnahmen wurde ein brach liegender Acker („Streitgewann”) in das Beweidungsregime integriert. Die Fläche liegt zwischen den beiden zuerst genannten Naturschutzgebieten („Trittstein”). Ausbreitungs- und Nach-Ausbreitungsprozesse in und zwischen den oben genannten Gebieten wurden analysiert. Als „source” wurden gut entwickelte Zielgesellschaften des Koelerion glaucae (Kg), Armerio-Festucetum trachyphyllae (AF) und Allio-Stipetum capillatae (AS) genutzt. Für alle Untersuchungen wurden drei bis vier gezähmte Hammel verwendet. Zunächst wurden die Arten-Zusammensetzung der “Source”-Gebiete und die epizoochor ausgebreiteten Diasporen determiniert, sowohl für den Intra- als auch für den Inter-Gebietstransfer. Um mögliche Diasporen-Verluste zu quantifizieren, wurden die Mengen und Arten-Zusammensetzungen der Diasporen im Schaffell vor und nach dem Gebietstransfer bestimmt. Zusätzlich wurden die Oberflächenstruktur der Diasporen, das Diasporen-Gewicht und die Expositionshöhe der Diasporen auf der Pflanze (Höhe auf der Pflanze) mit der Anheftung im Schaffell korreliert. Durch natürliche Prozesse angeheftete Diasporen von Stipa capillata und Agrimonia procera konnten genutzt werden, um Rententionszeiten und Raten des Diasporen-Verlustes während verschiedener Aktivitäten (Fortbewegung bei Gebietswechsel bzw. bei Koppelbeweidung, Abfressen der Vegetation) zu berechnen. Insgesamt sind Diasporen von 56 Pflanzentaxa im Schaffell nachgewiesen worden. Die Hälfte der Taxa in den drei untersuchten Vegetationstypen waren Zielarten. Im Schaffell waren die Zielarten leicht überrepräsentiert; unter ihnen gab es sieben Rote-Liste-Arten. Quantitativ gehörten die meisten der transportierten Diasporen zu Zielarten, wohingegen praktisch keine konkurrenzstarken Graminoiden nachgewiesen wurden. Während der 3-km Gebietstransfers kam es nicht zu signifikanten Verlusten an epizoochor ausgebreiteten Diasporen, wohingegen viele Diasporen von S. capillata und A. procera im „Sink“-Gebiet ausgebreitet wurden. Eine längere Dauer der Weidezeit und Fellpflege mit Maul und Klauen fördern wahrscheinlich die Lösung von Diasporen aus dem Fell. Des weiteren wurde gezeigt, dass die Anheftung im Fell durch Diasporen-Gewicht und Diasporen-Strukturen (Anhänge) bestimmt wird. Der Erfolg der Anheftung wird bei Diasporen ohne gut entwickelte Strukturen (Anhänge wie Klettenstrukturen u.a.) wahrscheinlich durch das Diasporen-Gewicht bestimmt; bei solchen Diasporen mit gut entwickelten Anhangsstrukturen ist die Anheftungswahrscheinlichkeit nicht abhängig vom Diasporen-Gewicht. Für 14 verschiedene Pflanzenarten wurde das Schicksal nach erfolgter epizoochorer Ausbreitung untersucht. Die meisten dieser Arten waren gefährdete Zielarten der Sandökosysteme, für die epizoochore Ausbreitung bereits in unseren vorherigen Untersuchungen gezeigt werden konnte. Drei 10 m x 10 m große Sandflächen wurden auf einer Ackerbrache etabliert. Pro Fläche hielten sich zwei Schafe mit experimentell im Fell angehefteten Diasporen für 24 h auf. Außerdem wurde der Effekt des Schaftritts auf die Samenkeimung für zwei gefährdete Arten analysiert: Jurinea cyanoides (Art der EU Fauna-Flora-Habitat Direktive) und Koeleria glauca. Das räumliche Trittmuster, die Ausbreitungsrate der Diasporen und die räumliche Verteilung von drei Arten mit großen Diasporen (Stipa capillata, Medicago minima und Cynoglossum officinale) wurden untersucht. Das Keimlingsaufkommen und die Überlebensrate aller untersuchten Arten konnte für eine Periode von 8 Monaten verfolgt werden. Die relative kurze Präsenz der Schafe auf den Sandflächen führte trotzdem zu hohen Raten des Diasporen-Eintrags. Diasporen von fast allen Arten kamen zur Keimung (bis zu 40 % der ursprünglichen Diasporen-Anzahl). Die Analyse der räumlichen Verteilung des Schaftritts, der Diasporen-Verteilung und -Keimung auf der Fläche mit Hilfe von „Spatial Analysis by Distance Indices (SADIE)“, zeigte eine nicht-randomisierte Verteilung. Generell konnte eine positive Korrelation zwischen der Abundanz der Weidetiere und der Zahl lokalisierter Diasporen auf dem Boden sowie dem Keimlingsaufkommen gefunden worden. Die Effekte des Schaftritts waren Arten-abhängig verschieden: J. cyanoides wurde gefördert, wohingegen K. glauca keine Effekte zeigte. Die Abschätzung des potenziellen Beitrags von Herbivoren zur Ausbreitung von Pflanzenarten über den endozoochoren Pfad basiert zumeist auf Untersuchungen mit verschiedenen Keimungsmethoden. Um die Zuverlässigkeit dieser Methoden zu prüfen, wurde ein Vergleich von zwei Methoden zur Quantifizierung des Gehalts an lebensfähigen Diasporen im Schafdung durchgeführt. Der Dung wurde gesammelt nach einer Weideperiode von sechs Tagen in einer der Leitbildgesellschaften (Allio-Stipetum). Nach der Ter Heerdt-Methode (TH, 5 Monate) werden die Proben konzentriert und unter kontrollierten Bedingungen gehalten (Gewächshaus oder Klimaraum). Bei der zweiten Methode werden nicht-konzentrierte Proben unter Freilandbedingungen exponiert („common garden“ CG, 15 Monate). Qualitative und quantitative Ähnlichkeiten zwischen den Methoden werden mit dem Sørenson-Index (QS) dargestellt. Die nachgewiesenen Diasporen zeigten für beide Methoden eine ähnliche Artenkombination (QS = 0.81) und Abundanz (QS = 0.69). Quantitativ keimten mehr Individuen bei TH; insbesondere einige kleinsamige Winterannuelle (Veronica arvensis, Arenaria serpyllifolia, Arabis glabra) zeigten hohe Abundanz. Bei CG keimten mehr Arten (auch mit höheren Abundanzen), die hartschalige Diasporen haben (Fabaceae und Cistaceae). Im Vergleich sind beide Methoden sehr gut anwendbar, um die potenzielle Diasporenausbreitung via Dung zu quantifizieren. Wenn das Hauptinteresse einer Untersuchung die Artenzusammensetzung ist, ist CG eine optimale Methode; TH ermöglicht die beste Quantifizierung der Individuendichte und benötigt weniger Platz und Zeit. Schließlich wurden die Einflüsse von endozoochor ausgebreiteten Diasporen, der Dung-Deposition, Störung in Moosbeständen (Hypnum cupressiforme), und Dung-Entnahme durch den Stierkäfer Typhaeus typhoeus (Linnaeus, 1758) auf die lokale Artenvielfalt untersucht. Schafdung wurde in den Habitaten gesammelt, die auch für die Epizoochorie-Untersuchungen genutzt wurden (Kg, AF, AS). Die Artenstruktur und die Abundanz im Dung wurde mit Keimungsmethoden analysiert. In einem feldökologischen Ansatz wurden faktorielle Experimente in einem Produktivitätsgradienten etabliert (Kg < semi-ruderalisiertes AF < ruderalisiertes AF). In den drei Dungtypen (bezogen auf die Vegetationseinheiten) konnten keimfähige Diasporen von 59 Taxa nachgewiesen werden, unter feldökologischen Bedingungen nur 23 Taxa (60 % Zielarten). Quantitativ waren die meisten Taxa Zielarten (z.B. Helianthemum nummularium, das im “Sink”-Gebiet nicht vorkommt), wohingegen konkurrenzstarke Graminoide nur in den produktiveren AF-Flächen keimten. Trotz eines geringeren Aufkommens an Keimlingen, förderte die Dung-Deposition den Artenreichtum in Kg und in semi-ruderalisierten AF-Untersuchungsflächen. Der Effekt der Dung-Deposition kann modifiziert werden, wenn Dungkäfer die Kotpillen in die Larven-Brutkammern transportieren (> 40 cm tief im Boden). Als ein Ergebnis stellten sich nach der Störung durch den Dungkäfer Störung-anzeigende Arten ein, z.B. Oenothera biennis und Polygonum aviculare, die mit hohen Individuenzahlen keimten. Die Störung der Moosdecke förderte das Aufkommen von Keimlingen aus dem Dungsubstrat und aus der Diasporen-Bank in den semi-ruderalisierten AF-Untersuchungsflächen; die Keimung insbesondere von krautigen Arten bedingte höheren Artenreichtum. Die produktivsten AF-Untersuchungsflächen zeigten im Vergleich zu den semi-ruderalisierten Flächen andersartige Reaktionen auf die beiden Behandlungen (Moos-Entfernung und Dung-Deposition). Phytodiversität und Individuenzahl wurden in beiden Behandlungen reduziert, und die Dung-Deposition führte außerdem zu einer Abnahme der Abundanz der konkurrenzstarken Arten Carex hirta und Cynodon dactylon. Schließlich förderte wahrscheinlich die geringere Konkurrenz auf den Untersuchungsflächen bzw. der düngende Effekt der Faeces dieselben konkurrenzkräftigen Arten in einem späteren Stadium der Vegetationsentwicklung; letzteres führte zu einer geringeren Phytodiversität. Es zeigt sich, dass wahrscheinlich Störung und Dung-Applikation und ihre Auswirkung auf die Mikroskala-Phytodiversität zum Teil durch das Produktivitätsniveau der etablierten Vegetation bedingt werden. Die vorliegende Arbeit hat gezeigt, dass ein extensives Beweidungsregime mit Schafen, die Nutzung gut entwickelter Leitbild-Flächen als Diasporen-Quellen und Inter-Gebietstransfers zwischen separierten Lebensräumen eine gute Management-Maßnahme für den Schutz und die Restitution von offenen Sandökosystemen in fragmentierten Landschaften sind. Eine große Schafherde (etwa 600 Tiere) und das Vorkommen eines hohen Anteils Habitat-spezifischer Arten in den “Source”-Gebieten fördern die epi- and endozoochore Ausbreitung von Millionen von Diasporen. Zusätzlich kann die Aktivität der Herbivoren die Verfügbarkeit von Kleinstandorten erhöhen. Durch die Änderung wichtiger Determinanten für die Etablierung von Pflanzenarten, insbesondere der Diasporen- und Mikrohabitat-Verfügbarkeit, spielen Schafe eine bedeutende Rolle für die Etablierung von Zielarten der Sandvegetation, insbesondere in frühen und mittleren Sukzessionsstadien.

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