Institut für Landschafts- und Pflanzenökologie

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/11

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Browsing Institut für Landschafts- und Pflanzenökologie by Journal "Journal of applied ecology"

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    Range‐wide population viability analyses reveal high sensitivity to wildflower harvesting in extreme environments
    (2021) Treurnicht, Martina; Schurr, Frank M.; Slingsby, Jasper A.; Esler, Karen J.; Pagel, Jörn
    1. The ecological effects of harvesting from wild populations are often uncertain, especially since the sensitivity of populations to harvesting can vary across species’ geographical ranges. In the Cape Floristic Region (CFR, South Africa) biodiversity hotspot, wildflower harvesting is widespread and economically important, providing an income to many rural communities. However, with very few species studied to date, and without considering range‐wide sensitivity to harvesting, there is limited information available to ensure the sustainability of wildflower harvesting. 2. We studied geographical variation in sensitivity to wildflower harvesting for 26 Proteaceae shrubs with fire‐driven life cycles using population viability analyses. We developed stochastic, density‐dependent population models that were parameterised from individual demographic rates (adult fecundity, seedling recruitment and adult fire survival) and local environmental conditions across the geographical ranges of the study species. We then simulated the effects of harvesting on populations in different environments across species ranges. Our model simulations predicted extinction risk per population, and we derived extinction probabilities over 100 years in response to different harvesting regimes. We used these population‐level extinction probabilities to quantify inter‐ and intraspecific variation in sensitivity to wildflower harvesting, and to explore how geographical variation in sensitivity depends on environmental conditions (climate, soil fertility and fire disturbance). 3. We detected considerable inter‐ and intraspecific variation in sensitivity to wildflower harvesting for the 26 study species. This held for both ‘nonsprouters’ and ‘resprouters’ (species with low and high fire persistence ability, respectively). Intraspecific variation in sensitivity to harvesting showed varying geographical patterns and associated with environmental variation. Notably, sensitivity was high towards range edges and at the climatic extremes of species ranges respectively. 4. Synthesis and applications. We show the importance of combining spatial demographic data, density‐dependent population dynamics and environmental variation when assessing sensitivity to harvesting across species' geographical ranges. Our findings caution against the application of general harvesting guidelines irrespective of species, geographical location or local environmental conditions. Our range‐wide population viability analyses provide insights for developing species‐specific, spatially nuanced guidelines for conservation management. Our approach also identifies species and areas to prioritise for monitoring to prevent the overexploitation of harvested species.
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    Simulating the spread and establishment of alien species along aquatic and terrestrial transport networks: A multi‐pathway and high‐resolution approach
    (2022) Bagnara, Maurizio; Nowak, Larissa; Boehmer, Hans Juergen; Schöll, Franz; Schurr, Frank M.; Seebens, Hanno
    The introduction and further spread of many alien species have been a result of trade and transport. Consequently, alien species are often found close to traffic infrastructure and urban areas. To contain and manage the spread of alien species, it is essential to identify and predict major routes of spread, which cannot be obtained by applying common modelling approaches such as species distribution models. Here, we present a new model called CASPIAN to simulate the dispersal of alien species along traffic infrastructure and the establishment of populations along these routes. The model simulates simultaneous spread of species of up to eight different modes of transport along roads, railways and waterways. We calibrated and validated the model using two species that spread within Germany as case studies: the terrestrial plant Senecio inaequidens and the freshwater clam Corbicula fluminea, and performed a shortest path analysis to quantify the relative importance of individual routes for spread. The application of the model yielded detailed predictions of dispersal and establishment for >600,000 segments of the traffic network throughout Germany. Once calibrated, the model captured the general spread dynamics of the two species with higher accuracy for the freshwater environment due to the higher quality of data available for the aquatic species. The quantification of spread routes using the shortest path analysis revealed a clear backbone of major routes of spread, which varied depending on the type of traffic network and the starting points considered. Major routes of spread aligned with high traffic intensities, but high traffic per se did not necessarily result in high spread intensities. Synthesis and application. By simulating the spreading dynamics of alien species along transport networks across multiple pathways, CASPIAN enables the identification of major spread routes along different dispersal pathways and quantification of their relative importance, which helps prioritising pathways of introduction as required by international biodiversity goals such as the CBD Aichi targets.