eDissertationen: Search
Now showing items 1-7 of 7
The impact of socio-economic development and climate change on livestock management in Benin
(2008)
Livestock management is a rapidly changing sector in developing countries due to increasing demand for animal products and changes in the availability of common resources. Moreover, livestock management is important as it ...
Water productivity in medium and small reservoirs in the Upper East Region (UER) of Ghana
(2008)
Improving water productivity (WP) is one important strategy for addressing future water scarcity, which is driven particularly by population growth and potential climate changes. Although an understanding of WP is required ...
Resource utilization and sustainability of conservation-based rice-wheat cropping systems in Central Asia
(2011-08-26)
Excessive and inefficient water use, intensive soil tillage and decreasing soil fertility have caused land degradation and desertification, which are threatening the sustainability of rice-wheat systems in the irrigated ...
Carbon Stocks and Ecological Implications of Open Spaces: A Case Study in Recife - Brazil
(2011-07-14)
The aim of this work is to evaluate the ecological implications of the whole range of urban and rural land use systems from a common perspective focused on carbon stocks and land use change (LUC) in urbanizing areas of ...
Climate Volatility and Change in Central Asia: Economic Impacts and Adaptation
(2013-07-08)
Central Asia is projected to experience a significant climate change, combined with increased weather volatility. Agriculture is a key economic sector and a major source of livelihoods for Central Asia’s predominantly rural ...
Zur tierökologischen Bedeutung der Elsbeere (Sorbus torminalis L. CRANTZ)
(2018-06-14)
Mit der vorliegenden Dissertation soll das ökologische Beziehungsgeflecht der Elsbeere (Sorbus torminalis) erfasst werden, einer in Deutschland seltenen, in zerstreuten, kleinen Populationen vorkommenden Baumart (Fam. Rosaceae). In den Jahren 2011 bis 2013 wurden Versuche zur Blüten- und Fortpflanzungsbiologie durchgeführt; auch wurden erstmalig die Tiere erfasst, welche die Ressourcen Blüten, Blätter und Früchte nutzen. Hauptziel dieser Arbeit ist es, die wechselseitigen Beziehungen zwischen Fortpflanzungssystem und Morphologie der Elsbeere einerseits und den Blütenbesuchern, Frugivoren und Herbivoren andererseits zu erfassen. Die Tiere wurden taxonomisch und autökologisch kategorisiert. Bei den Untersuchungsstandorten bei Bonn handelt es sich um eine Baumsamen-Plantage mit unbedrängten, gepfropften Elsbeeren und um einen seit Jahrzehnten forstlich nicht mehr genutzten Berghang des FFH-Gebiets Siebengebirge.<br /> Durch ihr generalisiertes Blütensyndrom sichert sich die konkurrenzschwache Elsbeere in allen für sie besiedelbaren Habitaten den größtmöglichen und von Umwelteinflüssen weitgehend unabhängigen Bestäubungserfolg. Die morphologischen und quantitativen Ausprägungen ihrer generativen Organe unterschieden sich signifikant je nach Standort. <br /> Die Bestäubungsversuche ergaben, dass durch Fremdbestäubung die höchste Anzahl an Samen je Frucht produziert wurde und somit die erfolgreichste von allen Bestäubungsvarianten war. Es gab Hinweise auf ein nicht vollständig funktionierendes gametophytisches Selbstinkompatibiltäts-System (GSI), welches zu einer Erhöhung des Homozygotiegrades führen kann, und entgegen früherer Erkenntnisse scheinen Apomixis und Autogamie bei der Elsbeere möglich zu sein. An der Plantage mit einer weitaus höheren Blütendichte wurden 78 Arten als Blütenbesucher dokumentiert, im Siebengebirge 37 Arten. <br /> Die Klopfschirmproben ergaben eine Phytophagen-Dominanz an beiden Standorten. Im Siebengebirge deutete der hohe Anteil parasitischer Hymenopteren auf eine höhere Spezialisierung dieser Gruppe hin sowie auf stabilere ökologische Verhältnisse und eine höhere strukturelle und floristische Biodiversität. In Folge des starken Befalls wurde die Elsbeerlaus (Dysaphis aucupariae) als sekundäre Nutzungsressource identifiziert, mit deren Auftreten die Zoodiversität in der Baumkrone erhöht wird. Durch die Züchtung von Schmetterlingsraupen mit Elsbeerlaub wurde ermittelt, dass 17 Lepidoptera-Arten die Elsbeere als Raupenfutterpflanze nutzen. <br /> Bei den frugivoren Vögeln konnten Stare und Drosseln als Haupt-Samenausbreiter bestätigt werden. Bei den Säugetieren wurden als potenzielle Samenverbreiter Rehe, Wildschweine und der Steinmarder mit einer Wildkamera eindeutig identifiziert. Die vorliegenden Untersuchungen führen zu einer für den Naturschutz positiven Erkenntnis: Die Elsbeere kann einen wertvollen Beitrag zu Arterhalt und Diversität einer Vielzahl von Insekten und frugivoren Vertebraten leisten und beim prognostizierten Klimawandel zur ökologischen Stabilisierung und Diversifizierung künftiger Forste beitragen....
<strong>The Significance of the Wild Service Tree (Sorbus torminalis L. Crantz) in Regard to Animal Ecology</strong><br /> This thesis aims to document the ecological web of the wild service tree (Sorbus torminalis) – a rare species of the Rosaceae family which in Germany occurs in scattered and small populations. During the years 2011 to 2013 research on flower visitors and reproduction biology were conducted and, for the first time, those animals were documented which use the tree´s annual resources flowers, leaves, and fruits. The main objective of this thesis is to record the mutual relationships between the reproductive system and the morphology of S. torminalis on the one hand and the flower visiting, frugivorous, and herbivorous animals on the other. These animals were classified taxonomically and autecologically. Both research sites are located near Bonn; one is a tree seedling plantation with grafted and generously spaced trees; the other is a slope on a hill in the nature reserve Siebengebirge (FFH, Flora-Fauna-Habitat-Directive) which has been taken out of forestry management for several decades.<br /> With its generalistic flower syndrome, the competitively weak service tree manages to ensure the greatest possible pollination success in all its suitable habitats. Due to the strong tree competition in the Siebengebirge, the two locations showed significant differences in the morphologies and quantities of the tree´s reproductive organs. <br /> Experiments proved that cross-pollination yielded the highest numbers of seeds per fruit which translated into the greatest reproduction success. There were signs pointing to a sometimes failing gametophytic self-incompatibility system (GSI) which can increase the degree of homozygosity. Contrary to literature, S. torminalis seems capable of apomixis and autogamy. On the plantation with its far greater flower density, 78 flower visiting species were recorded whereas the Siebengebirge location yielded 37 species.<br /> The beating tray results showed that the feeding guilds in both locations were dominated by phytophagous invertebrates. The high percentage of parasitic hymenoptera species in the Siebengebirge pointed to a higher specialization of this group and a more stable ecological situation as well as a higher structural and floral biodiversity there. As a consequence of a massive infestation with Dysaphis aucupariae, this aphid proved to be an abundant secondary food resource for many animals. The aphids increased canopy zoodiversity considerably. Rearing caterpillars exclusively with service tree leaves showed that also 17 butterfly species used the tree as a food resource.<br /> Starlings and thrushes were identified as main seed dispersers; a scouting camera captured roe deer, wild boars, and stone marten as potential seed dispersing mammals.<br /> The evaluation of the collected animal data leads to a positive insight for nature conservation: Wild service trees can considerably improve species conservation success and enrich the numbers and diversity of many invertebrate species as well as frugivorous vertebrates. And, last but not least, during a climate change, S. torminalis could help to ecologically stabilize and diversify future managed forests....
<strong>The Significance of the Wild Service Tree (Sorbus torminalis L. Crantz) in Regard to Animal Ecology</strong><br /> This thesis aims to document the ecological web of the wild service tree (Sorbus torminalis) – a rare species of the Rosaceae family which in Germany occurs in scattered and small populations. During the years 2011 to 2013 research on flower visitors and reproduction biology were conducted and, for the first time, those animals were documented which use the tree´s annual resources flowers, leaves, and fruits. The main objective of this thesis is to record the mutual relationships between the reproductive system and the morphology of S. torminalis on the one hand and the flower visiting, frugivorous, and herbivorous animals on the other. These animals were classified taxonomically and autecologically. Both research sites are located near Bonn; one is a tree seedling plantation with grafted and generously spaced trees; the other is a slope on a hill in the nature reserve Siebengebirge (FFH, Flora-Fauna-Habitat-Directive) which has been taken out of forestry management for several decades.<br /> With its generalistic flower syndrome, the competitively weak service tree manages to ensure the greatest possible pollination success in all its suitable habitats. Due to the strong tree competition in the Siebengebirge, the two locations showed significant differences in the morphologies and quantities of the tree´s reproductive organs. <br /> Experiments proved that cross-pollination yielded the highest numbers of seeds per fruit which translated into the greatest reproduction success. There were signs pointing to a sometimes failing gametophytic self-incompatibility system (GSI) which can increase the degree of homozygosity. Contrary to literature, S. torminalis seems capable of apomixis and autogamy. On the plantation with its far greater flower density, 78 flower visiting species were recorded whereas the Siebengebirge location yielded 37 species.<br /> The beating tray results showed that the feeding guilds in both locations were dominated by phytophagous invertebrates. The high percentage of parasitic hymenoptera species in the Siebengebirge pointed to a higher specialization of this group and a more stable ecological situation as well as a higher structural and floral biodiversity there. As a consequence of a massive infestation with Dysaphis aucupariae, this aphid proved to be an abundant secondary food resource for many animals. The aphids increased canopy zoodiversity considerably. Rearing caterpillars exclusively with service tree leaves showed that also 17 butterfly species used the tree as a food resource.<br /> Starlings and thrushes were identified as main seed dispersers; a scouting camera captured roe deer, wild boars, and stone marten as potential seed dispersing mammals.<br /> The evaluation of the collected animal data leads to a positive insight for nature conservation: Wild service trees can considerably improve species conservation success and enrich the numbers and diversity of many invertebrate species as well as frugivorous vertebrates. And, last but not least, during a climate change, S. torminalis could help to ecologically stabilize and diversify future managed forests....
Gender roles in Agriculture and natural resources management in upper east region, Ghana
(2019-11-08)
The Upper East region is one of the poorest regions in Ghana with an estimated 90% of the people living in rural areas being peasant farmers. In many instances, farmers use their land unsustainably thus worsening the already ...