Abstract
Abstract Increasing landscape heterogeneity by restoring semi‐natural elements to reverse farmland biodiversity declines is not always economically feasible or acceptable to farmers due to competition for land. We hypothesized that increasing the heterogeneity of the crop mosaic itself, hereafter referred to as crop heterogeneity, can have beneficial effects on within‐field plant diversity. Using a unique multi‐country dataset from a cross‐continent collaborative project covering 1,451 agricultural fields within 432 landscapes in Europe and Canada, we assessed the relative effects of compositional and configurational crop heterogeneity on within‐field plant diversity components. We also examined how these relationships were modulated by the position within the field. We found strong positive effects of configurational crop heterogeneity on within‐field plant alpha and gamma diversity in field interiors. These effects were as high as the effect of semi‐natural cover. In field borders, effects of crop heterogeneity were limited to alpha diversity. We suggest that a heterogeneous crop mosaic may overcome the high negative impact of management practices on plant diversity in field interiors, whereas in field borders, where plant diversity is already high, landscape effects are more limited. Synthesis and applications. Our study shows that increasing configurational crop heterogeneity is beneficial to within‐field plant diversity. It opens up a new effective and complementary way to promote farmland biodiversity without taking land out of agricultural production. We therefore recommend adopting manipulation of crop heterogeneity as a specific, effective management option in future policy measures, perhaps adding to agri‐environment schemes, to contribute to the conservation of farmland plant diversity.
Highlights
We suggest that a heterogeneous crop mosaic may overcome the high negative impact of management practices on plant diversity in field interiors, whereas in field borders, where plant diversity is already high, landscape effects are more limited
Our study provides the first multi-country evidence that heterogeneity of the crop mosaic itself can provide additional benefits to semi-natural elements for the maintenance of plant diversity within agricultural fields
Our findings support the importance of adopting a landscape perspective in policy measures, perhaps adding to agrienvironmental schemes, to preserve within-field plant diversity and by extension, associated ecosystem services (Tscharntke et al, 2005)
Summary
Sirami et al, 2019 for details). The landscape selection process used the most recent remotely sensed data or land cover map available for each agricultural region (see Table S1). Compositional and configurational crop heterogeneity (SHDI and TBL), and their interaction with within-field position (field border vs field interior, POS) and the proportion of semi-natural cover types (SemiNatCover) were included as fixed effects. TA B L E 2 Model-averaged standardized estimates, standard errors and p values from linear mixed-effects models of alpha, beta and gamma within-field plant diversity in relation to compositional and configurational crop heterogeneity, within-field position and the amount of semi-natural cover. 0.025 ns Abbreviations: ns, not significant; POS, within-field position; SemiNatCover, proportion of semi-natural cover types in the landscape; SHDI, Shannon crop diversity index; TBL, total length of crop borders. The only landscape variable to have a significant effect on beta diversity was configurational crop heterogeneity (TBL), through an interaction with within-field position (POS) (Figure 4). SemiNatCover, alone or in an interaction with POS, had a significant and positive effect on gamma diversity (Table 2; Appendix S3)
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