Both farming practices and landscape characteristics determine the diversity of characteristic and rare arable weeds in organically managed fields

Abstract

AbstractQuestionsDo both current and past (short‐term) farming practices and landscape characteristics have an effect on the diversity of characteristic and rare arable plant communities in organic fields? What is the role of farm management strategies, apart from farm spatial configuration, in determining the diversity components of these species sets?LocationThirty‐two farms scattered across NE Spain (Catalonia).MethodsSpecialist species of arable fields, belonging to the Secalietalia cerealis Br‐Bl. 1936, were surveyed at the edges of organically managed fields. We assessed the effects of farm management and landscape characteristics at the field and farm scales on α‐, β‐ and γ‐diversity values of these characteristic arable species. Analyses were also conducted on a subset of Secalietalia species that are considered to be rare. Statistical analyses were performed using multimodel inference determined on the basis of all possible models from an a priori set.ResultsField variables, such as years since conversion to organic management, proportion of cereal crops in the rotation and autumn sowing, had a positive effect, whereas growing non‐cereal crops and fertilization had a negative effect on the richness of characteristic species. The field area had a positive effect on the species richness of characteristic and rare arable plants. At the farm level, the proportion of cereal crop fields to the total amount of fields affected both β and γ characteristic diversity. The landscape variables at the farm level only influenced the β‐diversity of rare species.ConclusionsThe effects of management and landscape on arable weed diversity depended on whether the field or the farm is the focus of the analysis. Characteristic and rare arable species were more affected by factors operating at local scales. Characteristic species richness responded positively to sowing cereal crops, autumn sowing and periodic soil disturbances but was negatively affected by slurry fertilization. Thus, policies promoting some of the former practices should favour characteristic arable species and mitigate the decline of the rare arable species.