Abstract
Questions: Studies in functional biogeography have mostly focused on unmanagedecosystems, and neglected testing how management intensity affects community-levelresponse of plant traits to bioclimatic gradients. We hypothesize that trait–climaterelationships for arable weeds spontaneously establishing in croplandssubject to intensive management should differ from the relationships characterizingless intensively managed grassland ecosystems.Location: France.Methods: We computed community-weightedmeans (CWM) and variances (CWV) of954 and 5,619 cropland and grassland plant assemblages, respectively, for three fundamentalleaf traits (specific leaf area, SLA; leaf dry matter content, LDMC; leaf nitrogencontent, LNC). Based on growing season length accounting for both temperatureand soil water limitations (GSLtw), we compared trait–climaterelationships betweenherbicide-freecroplands and grasslands, and between herbicide-freeand herbicide-sprayedcropland assemblages. The contribution of beta-diversityto the trait–climaterelationships was then evaluated using multiple regression on distance matrices.Results: Distinct trait–climaterelationships characterized herbicide-freecropland andgrassland plant assemblages. CWM of all traits showed weaker relations with GSLtwin cropland relative to grassland assemblages. CWV of LDMC and LNC respondedmore sharply in croplands. Furthermore, no herbicide effect on trait–climaterelationshipswas detected within cropland assemblages. These results seem to be explainedby a greater taxonomic beta-diversityalong the GSLtw gradient for grasslands.Conclusions: Specific trait–environmentrelationships characterize croplands, underliningthat management intensity greatly affects trait–climaterelationships for plantassemblages. Deciphering the interplay between land use intensification and climateis critical to accurately forecast functional vegetation changes in response to globalchanges, and hence to foster actions enhancing ecosystem resilience.