Refining rare weed trait syndromes along arable intensification gradients

Abstract

Question How does the conservation (rarity) value of arable weed communities differ along intensification gradients? Which functional traits best distinguish the weed communities of more and less extensively managed fields? Can the same traits predict the rarity of individual weed species? Location Hungary. Methods Using relevé data from 60 cereal and 70 stubble fields, together with weed trait data, we characterized community responses to arable intensification using functional trait analyses based on trait‐convergence and trait‐divergence assembly patterns. We also examined how well the broad‐scale rarity status of species predicts their occurrence along intensification gradients, and how it maps onto our functional classifications describing intensification responses. Results The response of weeds to intensification in cereal fields was best described by a functional classification based on species' flowering duration, maximum height and seed weight: weeds of extensively managed fields have short flowering seasons (2–5 mo) and particularly large or small seeds. The highest proportions of rare species also happen to be found in these groups. The rarest weeds among these species tend to be late‐winter and early‐summer annuals, while the rare species of stubble fields tend to be broad‐leaved with low nitrogen requirements, small seeds and short height. Stubble fields showed a decline in weed cover with increasing application of fertilizer and distance from the field edge, but we could detect no strong associations of management factors with trait composition, perhaps because the intensification gradient across these fields was shorter. Conclusions Many rare Hungarian weeds are associated with traditional extensive farming practices. They are particularly characterized by short, midsummer flowering periods and by preference for low nitrogen levels, but a range of trait syndromes must be considered to understand their ecology and conservation. Analyses based on trait‐divergence patterns, rather than trait‐convergence patterns, provide better insights into the functional composition of weed communities, emphasizing the importance of disruptive filters in weed community assembly and the need for improved methods to detect such effects.

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

“…Higher Ellenberg indices for nitrogen among arable weeds revealed their adaptation to the nutrient‐rich environment of arable fields resulting from fertilization. Plants with low nitrogen requirements are indeed rare in arable fields (Pinke and Gunton, ; Wagner et al., ) because agricultural intensification generally selects for nitrophilous plants (Fried et al., ; Storkey et al., ; Moreau et al., ).…”

“…In arable fields, early and long flowering can also be interpreted as a potential strategy to escape weed control and crop competition (Bagavathiannan and Norsworthy, ). Arable weeds with a short or late flowering period are indeed often rare in agroecosystems (Storkey et al., ; Pinke and Gunton, ).…”

Management options for the conservation of rare arable plants in Europe

“…Otte, Bissels, and Waldhardt (2006) found that the species which increased in arable habitats in recent decades tend to be characterized by relatively high temperature optima for germination. Similarly, Pinke and Gunton (2014) ascribe the rarity of late-winter and early-summer annuals to the fact that the timing of their emergence may make them more susceptible to early-season herbicide application, characteristic of intensive cereal farming.…”

Using the response–effect trait framework to quantify the value of fallow patches in agricultural landscapes to pollinators

“…These habitats generally have lower fertility than fertilized arable fields and are more likely to harbour legumes, a plant morphology which is predicted to increase under these conditions (van Elsen, ); in our study, legume species of the Coronilla , Medicago or Retama genera were found at higher frequency in landscapes with a larger proportion of semi‐natural habitat. The relative ecological stability of semi‐natural areas is also reflected in the presence of species with late time of first flowering (Pinke & Gunton, ) or autochory seed dispersal. Autochory is a short‐distance dispersal mechanism, and the low colonizing capacity over space suggests that species are in an optimal area.…”