Browsing by Subject "Pflanzenart"

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Die Bedeutung städtischer Gliederungsmuster für das Vorkommen von Pflanzenarten unter besonderer Berücksichtigung von Paulownia tomentosa (Thunb.) Steud. - dargestellt am Beispiel Stuttgart
(2002) Richter, Matthias; Böcker, Reinhard
The relevance of urban landuse patterns and ecological factors for the occurrence of spontaneously and subspontaneously growing plant species is the subject of this doctoral thesis. First a model of scales for urban ecological research is introduced in order to structure the different hypotheses. This model distinguishes between the agglomeration Stuttgart, separated in main ?landuse types? (forest, agricultural area, settlement), the central city of Stuttgart, "building structure/free space types" and ?types of soil use?. The types of soil use (e.g. lawns, bushes, flower-beds or pavements) are characterised by the most frequent plant species. Moreover their soils are analysed and they are described climatically. In cities average types of soil use (concerning the chemical characterisation of soils) are wide-spread. Some plant species (e.g. Paulownia tomentosa) are described more in detail, concerning their ecological traits and their preferential occurrence on each spacial scale. The hypothesis is tested: If there is a dependence - of plant species and phytocoenoses on types of soil use - and of types of soil use on building structure/free space types - and of building structure/free space types on their location within the city centre, - then there is a dependence of plant species and their phytocoenoses on the location within the city. To test this hypothesis, some building structure/free space types and types of soil use were selected at random and there vegetation relevés were collected. An attempt is made to construct an improved model of a big city, representing an agglomeration. On the spatial level of the agglomeration Stuttgart Paulownia tomentosa can be found neither in forests nor in agricultural area. It is growing within settlements only, namely within the central built-up areas of Stuttgart, Feuerbach and Bad Cannstatt. The city centre of Stuttgart can be divided into three zones: the central business district with big department stores and banking houses, bordering on old apartment houses and detached houses (especially at the slopes). Other building structure/free space types (like villas, graveyards, parks, or industrial areas) are mingled in these zones. A scheme is outlined which shows how the different building structure/free space types are scattered over the central city. Paulownia tomentosa can be detected most frequently within the zone of old apartment houses. Historical and climatological reasons are important for this result, too. More than 90% of the sites where Paulownia tomentosa is growing are cracks: cracks along the bottom of buildings, gravelled area and urban wasteland. The sites are characterised by a low level of nutrients, high pH-values and soils which extremely dry out in summer. So the occurrence of the species depends on the presence of special types of soil use. A low intensity of gardencare is a further important factor for its presence. Paulownia tomentosa is an exemplification showing how the ecological traits of a species and its dependence from the presence of structural types can be used to find the places where it is growing. In the case of Paulownia this attempt can be used to forecast the expected further spread.
The performance of and interactions between multiple co-occurring alien and native plant species
(2023) Ferenc, Viktoria; Sheppard, Christine
This thesis focuses on investigating species interactions in the context of alien species establishment, which poses severe threats to species, communities, and ecosystems due to climate change and globalization. The study emphasizes the need to understand the effects of multiple co-occurring alien species and their potential explanations, such as niche or fitness differences. The outcome of competition can also be influenced by priority effects, where earlier emerging species affect later emerging species in a given environment. Positive interactions, like facilitation, are often overlooked but play a significant role in species interactions. Legumes, known for their ability to fix atmospheric nitrogen, can facilitate alien species, leading to both severe negative effects on natives and reduced resource competition. The research conducted three common garden pot experiments to address various aspects of alien species interactions. The first experiment examined pairwise combinations of 20 alien annual plant species in Germany to identify the mechanisms driving these interactions. It tested the prevalence of competition versus facilitation and assessed the effectiveness of individual traits, hierarchical or absolute trait distances, multivariate trait or phylogenetic distance, and trait plasticity in explaining plant performance. Results indicated that while interspecific competition was more common, interspecific facilitation occurred in 24% of cases. Hierarchical trait distances provided better explanations for interactions than phylogenetic or multivariate trait distances. Accounting for trait plasticity did not necessarily improve plant performance predictions. Notably, taller individuals with lower specific leaf area than their alien neighbours exhibited increased biomass and seed production when growing together. The second experiment focused on interactions between five pairs of alien and native species. It evaluated the impact of growing with one or two alien neighbour species on native plants and manipulated the arrival time of alien or native neighbours. Generally, native species performed worse when surrounded by two alien species compared to one, although the effect varied among species. Both native and alien species experienced significant performance decreases when arriving second in the pot, while alien species tended to benefit more from early arrival. However, further studies are required to generalize these findings across multiple alien and native plants regarding neighbour species and arrival time responses. The third experiment delved into legume facilitation in more detail. It involved growing 30 annual Asteraceae species (neophytes, archaeophytes, and natives) in communities with or without legume presence. The study measured functional traits, fitness, and nitrogen characteristics to understand how legume presence affected Asteraceae fitness and the relationship between traits, nitrogen concentration, and fitness. Using the δ15N natural abundance method, the research explored whether facilitation mechanisms differed among native phytometer, neophyte, and archaeophyte Asteraceae. Specific leaf area negatively affected aboveground biomass and seed production, with a stronger effect in the absence of legumes. Nitrogen concentration was positively correlated with biomass but did not significantly increase seed production. The results suggested direct legume facilitation for the native grass phytometer Festuca rupicola when growing alongside archaeophytes but not neophytes. This indicated varied mechanisms of competition for nitrogen between natives and alien species of different residence times and deepened understanding of altered facilitative leguminous effects in the presence of alien species. Overall, this research demonstrates the application of community ecology concepts and theories to investigate alien species interactions, particularly when multiple co-occurring alien species are involved. As the rate of alien species arrival in new habitats continues to increase, understanding their combined impact on native species, communities, and ecosystems becomes increasingly crucial.