Laura Breitsameter

Impact of climate change on weeds in agriculture: a review

Over the past decades, climate change has induced transformations in the weed flora of arable ecosystems in Europe. For instance, thermophile weeds, late-emerging weeds, and some opportunistic weeds have become more abundant in some cropping systems. The composition of arable weed species is indeed ruled by environmental conditions such as temperature and precipitation. Climate change also influences weeds indirectly by enforcing adaptations of agronomic practice. We therefore need more accurate estimations of the damage potential of arable weeds to develop effective weed control strategies while maintaining crop yield. Here we review the mechanisms of responses of arable weeds to the direct and indirect effects of climate change. Climate change effects are categorized into three distinct types of shifts occurring at different scales: (1) range shifts at the landscape scale, (2) niche shifts at the community scale, and (3) trait shifts of individual species at the population scale. Our main conclusions are changes in the species composition and new species introductions are favored, which facilitate major ecological and agronomical implications. Current research mainly considers processes at the landscape scale. Processes at the population and community scales have prevalent importance to devise sustainable management strategies. Trait-climate and niche-climate relationships warrant closer consideration when modeling the possible future distribution and damage potential of weeds with climate change.

Growth Responses to Elevated Temperature and Reduced Soil Moisture During Early Establishment of three Annual Weeds in Four Soil Types

We investigated the effects of simulated prospective increased temperatures and reduced soil moisture during the vegetation period on the early growth of three weed species that co-occur in spring crops and are currently spreading in Europe. Potted four-species crop-weed-communities of Abutilon theophrasti, Datura stramonium, Iva xanthiifolia, and maize were exposed to warming (ambient temperature + 2.5°C, treatment “warm”) and drought (soil water potential of -0.1 to -1.5 MPa, “dry”) versus ambient temperature (treatment “ambient”) and a soil water potential of −0.0036 MPa (“moist”), in four soil types (clay, loess, peat, sand based mixtures) in greenhouse settings. We determined the performance of the weeds in terms of total biomass accumulation as well as their morphological acclimation regarding root length, leaf size and root-to-shoot ratio at various combinations of the experimental factors. Warm-dry conditions had a significant negative effect on total weed biomass and also resulted in a higher proportion of maize in total aboveground biomass. In D. stramonium, aboveground vs. belowground allocation and leaf size responded more strongly to the experimental factors than in the other two species. Total biomass values of individual plants in warm-dry conditions on average were > 50%, 40 to 55%, and < 40% of those in ambient-moist conditions for A. theophrasti, I. xanthiifolia, and D. stramonium, respectively. Soil and its interaction with moisture and temperature additionally had a significant effect on various traits of the weed species which highlights the importance of considering this factor when investigating plant responses to altered climate conditions.