Future challenge for endangered arable weed species facing global warming: Low temperature optima and narrow moisture requirements

- Impact of temperature and water availability on germination of arable weeds.
- Differences in germination requirements between endangered and common arable weeds.
- Endangered species are more vulnerable to global warming.
- Scenarios based on IPCC suggest that common but not endangered weeds may profit from climate change.

As a result of the intensification of agriculture in Central Europe, many arable weed species have declined. Global climate change may further challenge the adaptability of arable weeds since plants may be more often subjected to higher temperatures and lower soil moisture during the germination period.A climate chamber experiment analysed the response of four familial pairs of common and endangered arable weeds from Germany. To this end we used a large range of temperatures and water potentials to assess specific traits defining their germination requirements. Using a simple response surface approach, we predicted germination response under three climate change scenarios.Results supported our expectation that endangered species, owing to their narrow germination requirements, may be more negatively affected by global warming than common species. Endangered species germinated significantly less than the common arable weeds, except at very low temperatures (3 °C and 5 °C). The preference of endangered arable weed species for low germination temperatures was confirmed by their low optimal germination temperature (15.8 °C ± 0.4). In contrast, common species germinated at significant higher temperatures (optimal temperature 18.4 °C ± 0.2), had a significantly wider range of germination temperature (endangered: 24 °C ± 3.5, common: 31 °C ± 0.5) and were also more flexible towards changes in water potential.Calculations based on response surfaces for three climate change scenarios indicated that endangered arable weed species may benefit less from climate warming than common species.