Andreas Dahlkamp

People may be exposed to questing Ixodes ricinus ticks in urban settings, e.g. residential gardens. Little is known about the garden characteristics that support a tick population. To determine which features in and around residential gardens support or limit the occurrence and abundance of questing I. ricinus ticks, we sampled them in residential gardens in the Braunschweig region that differed in various intrinsic and extrinsic parameters. We recorded the number of questing nymphal and adult ticks on transects, and by using mixed-effects generalized linear regression models, we related their occurrence and abundance to garden characteristics, meteorological covariates, and landscape features in the vicinity. We detected questing I. ricinus ticks in about 90% of the 103 surveyed gardens. Our occurrence model (marginal R² = 0.31) predicted the highest probability of questing ticks on transects with hedges or groundcover in gardens, which are located in neighborhoods with large proportions of forest. The abundance of questing ticks was similarly influenced. We conclude that I. ricinus ticks are frequent in residential gardens in Northern Germany and likely associated with intrinsic garden characteristics on a small scale, such as hedges, as well as extrinsic factors on a local scale, such as the proportion of nearby woodland.

Knowledge about the distribution of species along rivers and estuaries is the basis for decisions in nature conservation, but also for nature-based coastal and shore protection. Along rivers and estuaries, abiotic conditions affect plant traits, especially close to the marsh edge, and thus determine the distribution of plant species. Phragmites australis and Phalaris arundinacea occur along the German Elbe in the inland river and in the estuary, but the distribution of both species is locally and regionally inhomogeneous. We therefore simulated abiotic conditions of respective Elbe sections in a mesocosm experiment and investigated the influence of soil type, salinity, water level, and plant provenance on plant traits of P. australis and P. arundinacea. We compared growth-related and mechanical plant traits of both species. Productivity of P. arundinacea was less affected by sandy soil than that of P. australis. P. australis was insensitive to salinity and water level fluctuations, while traits of P. arundinacea responded to these factors. Furthermore, mechanical properties within a species were mainly dependent on plant growth. P. arundinacea was more flexible than P. australis, which can be attributed to morphological differences and differences in plant tissue. Plant provenance did not affect the response of plant traits to abiotic conditions. Our study provides clues for understanding the distribution patterns of P. australis and P. arundinacea.