Response and Effect Traits of Arable Weeds in Agro‐
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DOI: 10.1111/wre.12245 Response and effect traits of arable weeds in agro-ecosystems: a review of current knowledge S GABA* , R PERRONNE*†,GFRIED‡, A GARDARIN§¶, F BRETAGNOLLE**, L BIJU-DUVAL*, N COLBACH*, S CORDEAU*, M FERNANDEZ-APARICIO*, C GAUVRIT*, S GIBOT-LECLERC*, J-P GUILLEMIN*, D MOREAU*, N MUNIER-JOLAIN*, F STRBIK* & X REBOUD* *Agroecologie, AgroSup, INRA, Universite Bourgogne Franche-Comte, Dijon, France, †UMR GQE – Le Moulon, INRA, Universite Paris-Sud, CNRS, AgroParisTech, Universite Paris-Saclay, Paris, Gif-sur-Yvette, France, ‡ANSES-LSV, CBGP, Montferrier-sur-Lez cedex, France, §AgroParisTech, UMR 211 Agronomie, Thiverval-Grignon, France, ¶INRA, UMR211 Agronomie, Thiverval-Grignon, France, and **UMR5561 Biogeosciences, Universite de Bourgogne, Dijon, France Received 30 January 2016 Revised version accepted 13 January 2017 Subject Editor: Jonathan Storkey, Rothamsted Research, UK traits to cropping systems and (iii) weed functional Summary effect traits affecting agro-ecosystem functioning. For Integrating principles of ecological intensification into each functional trait, we explicitly present the assump- weed management strategies requires an understanding tions and evidence on the linkage between trait values of the many relationships among weeds, crops and other and ecological functions, in response to either manage- organisms of agro-ecosystems in a changing context. ment practices, for example tillage, sowing and herbi- Extensively used during the last two decades in weed cides, or biotic interactions, for example crop–weed science, trait-based approaches have provided general competition and pollination. Finally, we address and insights into weed community response to agricultural discuss major research avenues that may significantly practices, and recently to understanding the effect of improve the use of traits and the knowledge of func- weeds on agro-ecosystem functioning. In this review, we tional diversity in weed science for the future, especially provide a holistic synthesis of the current knowledge on to design and implement more environmentally sustain- weed response and effect functional traits. Based on the able weed management strategies. literature and recent advances in weed science, we review current knowledge on (i) weed functional groups Keywords: agro-ecology, ecological intensification, and ecological strategies, (ii) weed functional response functional ecology, cropping system, biodiversity. GABA S, PERRONNE R, FRIED G, GARDARIN A, BRETAGNOLLE F, BIJU-DUVAL L, COLBACH N, CORDEAU S, FERNANDEZ -APARICIO M, GAUVRIT C, GIBOT-LECLERC S, GUILLEMIN J-P, MOREAU D, MUNIER-JOLAIN N, STRBIK F, REBOUD X (2017). Response and effect traits of arable weeds in agro-ecosystems: a review of current knowledge. Weed Research. doi: 10.1111/wre.12245 environments and have been associated with crop produc- Introduction tion since the origin of agriculture (Mazoyer & Roudart, Arable weeds comprise the set of wild plants found in 1997; further references cited in Supporting Information agro-ecosystems that are well adapted to disturbed S1). The ecological role of weeds can be seen in very Correspondence: Sabrina Gaba, INRA UMR1347 Agroecologie, 17 rue Sully, 21065 Dijon cedex, France. Tel: (+33) 3 80 69 31 87; Fax: (+33) 3 80 69 32 62: E-mail: [email protected] © 2017 European Weed Research Society 2 S Gaba et al. different ways, depending on one’s perspective. On the one However, managing weeds based on these ecological hand, weeds are perceived as noxious because they com- intensification principles is far from straightforward. pete with the crop for resources and can favour a set of Although weeds commonly share several ecological crop pests, thus causing yield losses (reviewed in Oerke, attributes, they are by no means a homogeneous group 2006) exceeding $33 billion per year (Pimentel et al., of species. Weed floras comprise hundreds of weed spe- 2005). On the other hand, weeds are valuable agro-ecosys- cies, making impossible a detailed analysis of the eco- tem components that provide ecosystem functions and ser- logical properties of each weed species in varying vices that may, to a certain extent, support crop environmental and management conditions. To partly production, for example by maintaining pollinators (Bre- overcome this issue, the response–effect traits approach tagnolle & Gaba, 2015). Weeds can also reduce soil erosion (Lavorel & Garnier, 2002; Fig. 1) is a promising (Ruiz-Colmenero et al., 2013) and provide food and shel- framework for quantifying weed responses to environ- ter for rodents, insects and birds (Marshall et al., 2003). mental factors (sensu lato) and evaluating weed effects Concerns over herbicide resistance (Delye et al., on the ecosystem functioning. This conceptual 2013), environmental and health hazards of herbicides approach describes species by their biological charac- (Waggoner et al., 2013) and the decline in agricultural teristics through the measurement of functional traits, biodiversity (Tilman & Lehman, 2001), are challenging that is features measurable at the individual level that the existing paradigm of weed management strategies contribute to fitness either directly (performance traits based solely or mainly on herbicide use. Nowadays, sev- sensu Violle et al., 2007) or indirectly (functional traits eral alternatives co-exist. Integrated weed management sensu Violle et al., 2007). One major contribution of combines herbicides with other agricultural practices this conceptual approach to wider plant ecological the- (e.g. tillage, mechanical weeding, diversified crop ory is the definition of the worldwide leaf economics sequences and modified sowing dates, adapted sowing spectrum (LES), which describes strong correlations densities and inter-row widths, competitive cultivars) to between multiple leaf functional traits (e.g. leaf lifespan prevent crop yield losses while reducing negative envi- or leaf mass per area) underlying resource allocation ronmental impacts (Liebman & Gallant, 1997; Lechenet and fluxes in plants (Wright et al., 2004). The trait- et al., 2014). Another commonly used alternative is based approach also provides an integrated method to organic farming, where synthetic agrochemical inputs determine the influence of community assembly mecha- are excluded. Many studies have assessed the potential nisms, such as environmental filtering, niche differenti- benefits of organic farming relative to conventional ation and competitive hierarchies (Kraft et al., 2015). farming, and showed an overall positive effect of Under this community assembly framework, manage- organic farming on agricultural biodiversity (Hole et al., ment practices and biological interactions can be con- 2005; Henckel et al., 2015), but this is generally associ- sidered as filters limiting or allowing the establishment, ated with a reduction in crop yield (Gabriel et al., 2013; growth and persistence of distinct weed species that Tuck€ et al., 2014). More recently, ecological intensifica- may disperse from a reference species pool to a specific tion has been proposed that optimises the natural func- site (Booth & Swanton, 2002). Extensively used during tionality provided by ecosystems to maintain crop the last two decades in weed science, trait-based production while reducing chemical inputs (Bommarco approaches have provided general insights into weed et al., 2013). One key assumption of this concept is that community response to agricultural practices (Storkey, agriculture could benefit from an enhancement of eco- 2006; Fried et al., 2009a; Gardarin et al., 2010a; Stor- logical processes and functions to protect crops against key et al., 2010; Gunton et al., 2011; Fried et al., 2012; pests, such as weeds, while reaching environmental, Colbach et al., 2014; Perronne et al., 2015; Armengot social and economic objectives. The transition from con- et al., 2016), to environmental properties characterising ventional cropping systems to these alternatives requires field boundaries (Cordeau et al., 2012; Perronne et al., a shift from strategies considering the effects of manage- 2014) and to landscape heterogeneity (Fried et al., ment techniques on weeds viewed as noxious species, to 2009b; Alignier et al., 2012). A deeper understanding strategies considering webs of relationships among of how weed traits shift across climatic and manage- weeds, between weeds and organisms at the field and ment intensity gradients, at both global and local landscape scales. Emphasis is therefore placed on scales, however requires the appropriate ‘core’ traits to knowledge and understanding of the relationships be identified as well as the translation of management between weed species, weed and crop species, weed spe- practices into gradients of resources and disturbances. cies and others organisms in the agro-ecosystems (e.g. Weed plants differ from other herbaceous plants by parasites, pollinators, seed-eating organisms), and weed being more likely to have an annual life cycle with a species dynamics in response to cropping systems and fast growth rate, high seed production, fruits that per- agricultural landscapes. sist on the plant, widely dispersed seed, high seedling © 2017 European Weed Research Society Weed functional traits: review and challenges 3 Fig. 1 Response–effect conceptual framework adapted to weed ecology in agro-ecosystems. Weed traits are affected by local pedocli- matic conditions, the cropping systems and the biotic interactions with the crop (effect traits). Resource levels and disturbances