Climate change results in alterations in the environment. Changing conditions such as rising temperatures and different precipitation directly affect the bio- logy and ecology of plants. Arable ecosystems are shaped by agriculture and the cultivated crops and associated weeds are a part of them. Here, climate change influences crops and weeds also indirectly by enforcing adaptations of agricultural methods, land use and policy. This cumulative thesis covers the direct and indirect effects of climate change on weeds. In order to face the challenges of future climate change, agriculture is in need of more accurate estimations about potential weed interference to develop effective and sustainable weed control while maintaining crop yield. Whereas conservation needs accurate projections in order to develop strategies to preserve rare species and to prevent their extinction in the long-term. This thesis covers some open questions and knowledge gaps and, furthermore, focuses on the underlying biological and ecological mechanisms of climate induced changes on weeds in arable ecosystems at different scales.
The review paper as first part of this cumulative thesis reveals that the most important outcome of climate change in arable ecosystems are shifts that occur at different scales. Whereas range shifts cover processes at the landscape scale, niche shifts involve ecological processes at the community scale and trait shifts involve biological processes at the population scale. Subsequently, three original research paper, including two semi-field experiments and one climate chamber experiment, reveal that weeds realise species-specific biological strategies in response to altered climate conditions.
The theoretical framework, the findings and data as a result of this thesis provide insights into some underlying biological processes that weeds realise in or- der to respond to climate change at different scales. Predictions within agriculture and conservation rely on original research data in order to develop sustainable and successful strategies with climate change. These data can be used to increase the accuracy of bioclimatic models further. This thesis also presents proposals to assure harvest and prevent further biodiversity loss in arable ecosystems.