What makes a weed a weed? A large‐scale evaluation of arable weeds through a functional lens

Abstract

Premise of the Study Despite long‐term research efforts, a comprehensive perspective on the ecological and functional properties determining plant weediness is still lacking. We investigated here key functional attributes of arable weeds compared to non‐weed plants, at large spatial scale. Methods We used an intensive survey of plant communities in cultivated and non‐cultivated habitats to define a pool of plants occurring in arable fields (weeds) and one of plants occurring only in open non‐arable habitats (non‐weeds) in France. We compared the two pools based on nine functional traits and three functional spaces (LHS, reproductive and resource requirement hypervolumes). Within the weed pool, we quantified the trait variation of weeds along a continuum of specialization to arable fields. Key Results Weeds were mostly therophytes and had higher specific leaf area, earlier and longer flowering, and higher affinity for nutrient‐rich, sunny and dry environments compared to non‐weeds, although functional spaces of weeds and non‐weeds largely overlapped. When fidelity to arable fields increased, the spectrum of weed ecological strategies decreased as did the overlap with non‐weeds, especially for the resource requirement hypervolume. Conclusions Arable weeds constitute a delimited pool defined by a trait syndrome providing tolerance to the ecological filters of arable fields (notably, regular soil disturbances and fertilization). The identification of such a syndrome is of great interest to predict the weedy potential of newly established alien plants. An important reservoir of plants may also become weeds after changes in agricultural practices, considering the large overlap between weeds and non‐weeds.

Which Traits Make Weeds More Successful in Maize Crops? Insights from a Three-Decade Monitoring in France

“…These traits can be divided in two categories. The first category of frequent and abundant weeds in maize shares rapid resources acquisition capacities through high SLA and high Ellenberg-N values. This is consistent with a recent study that showed that weeds were distinguished from other herbaceous species in open habitats by high values of SLA and Ellenberg-N, and that among crop weeds, those most specific to the cultivated environment also had high values of these indices [28]. The second category of frequent and/or abundant weeds have a strong colonization capacity with a low seed weight combined with a high fecundity.…”

Which Traits Make Weeds More Successful in Maize Crops? Insights from a 3-Decade Monitoring in France

“…The first category of frequent and abundant weeds in maize shares rapid resources acquisition capacities through high SLA and high Ellenberg-N values. This is consistent with a recent study that showed that weeds were distinguished from other herbaceous species in open habitats by high values of SLA and Ellenberg-N, and that among crop weeds, those most specific to the cultivated environment also had high values of these indices [25]. The second category of frequent and/or abundant weeds have a strong colonization capacity with a low seed weight combined with a high fecundity.…”

Untitled

“…This study indicated that except three geophytes (Cyperus esculentus, Ledebouria sudanica and Stylochaeton hypogaeus) the flora is largely dominated by therophytes, which includes 95% of the recorded species. According to Bourgeois et al (2019), therophytes were the mostly weeds because of some adaptability among them higher specific leaf area, earlier and longer flowering, sunny and dry environments. Higher number of small sedge (Cyperus amabilis, Cyperus esculentus, Fimbristylis hispidula, Mariscus squarrosus and Kyllinga squamulata) found in this study is a characteristic of degraded land and showed the effect of rotation with others rainy crop mainly Groundnut and Maize.…”