Speaker
Description
(1) Cropping practices shape the weed species community. Intensive mechanical and chemical weed control measures favour species that can adapt to these conditions while species that cannot adapt disappear, leading to lower species diversity (Albrecht et al., 2016) and potentially making the weed species community more similar to the crop (Fried et al., 2009) and thereby more difficult to control with traditional weed control measures. Moreover, mechanical and chemical weed control also negatively affect organisms in the soil (Torppa and Taylor, 2022) and in water bodies (DeLorenzo et al., 2001), reduce soil structural stability (Montgomery, 2007) and can lead to herbicide resistance (Peterson et al., 2018). Adapting to weed control measures with a weaker selection pressure on the weed community is therefore of interest both for farmers and society at large. Many factors affect the weed species community and over a long time, but annual management methods have a direct impact on which species are favoured and not. We assessed the effects of crop competition and mechanical disturbance on the weed species trait composition over one growing season. (2) Data on weed species numbers were collected at species level from six field experiments running over three years. RLQ-analysis was used to connect species traits, obtained from two data bases (Bàrberi et al., 2018; Tyler et al., 2021), with the environmental characteristics (biomass of oats and intercropped legume service crop, row-hoeing intensity, and sampling location in relation to the crop row). (3) The analysis showed that intermediate to high crop competition, mainly from the main crop, reduced the occurrence of tall-growing, perennial, competitive species, according to Grime’s life strategies, and additional competition from the service crop in the main crop row reduced the number of tall-growing, shade tolerant, competitive-stress tolerant species. In both cases, a more diverse group of low-growing ruderal species with lower moisture requirements were favoured. Furthermore, with increased disturbance, the weed species community shifted from being associated with competitive-stress tolerant species to ruderal species, except from the most disturbed environments that were more associated with competitive species. Clustering the data according to how commonly the species occur together confirmed the pattern described. The cluster analysis further showed that the cluster with the perennial competitive species scored highest on a set of diversity traits (number of associated species, nectar production and myccorhiza association). (4) The findings reflected quite well the expected environmental conditions. The most surprising finding was the negative association between high disturbance and the trait of disturbance requirement. However, in the case of this within-season study, it mainly shows that perennials recover better from in-season mechanical disturbance than do annuals, which could be expected due to their under-ground storage organs. Moreover, the effect of management was greater on species level than on trait level, with species being more dispersed over the ordination space than traits. This indicates an already quite homogeneous weed species community, but also that only assessing the weed community based on species composition might indicate larger differences in functions than what is actually present. (5) High crop competition, especially from contrasting species, as well as intermediate disturbance reduced the in-season occurrence of the most competitive species according to Grime´s life strategies.
References
Albrecht et al. (2016). Management options for the conservation of rare arable plants in Europe. Botany Letters, 163(4), 389–415.
Bàrberi et al. (2018). Linking species traits to agroecosystem services: A functional analysis of weed communities. Weed Research, 58(2), 76–88.
DeLorenzo et al. (2001). Toxicity of pesticides to aquatic microorganisms: A review. Environmental Toxicology and Chemistry, 20(1), 84–98.
Fried et al. (2009). A functional analysis of large-scale temporal shifts from 1970 to 2000 in weed assemblages of sunflower crops in France. Journal of Vegetation Science, 20(1), 49–58.
Montgomery (2007). Soil erosion and agricultural sustainability. Proceedings of the National Academy of Sciences, 104(33), 13268–13272.
Peterson et al. (2018). The challenge of herbicide resistance around the world: a current summary: Herbicide resistance around the world. Pest Management Science, 74(10), 2246–2259.
Torppa and Taylor (2022). Alternative combinations of tillage practices and crop rotations can foster earthworm density and bioturbation. Applied Soil Ecology, 175, 104460.
Tyler et al. (2021). Ecological indicator and traits values for Swedish vascular plants. Ecological Indicators, 120.
| Keywords | agroecology; biodiversity; ecological weed management |
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