Configurational crop heterogeneity increases within-field plant diversity

1. 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. 2. Using a unique multi-country dataset
from a cross-continent collaborative project covering 1451 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. 3. 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. 4. 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.