Crop rotation and agri‐environment schemes determine bumblebee communities via flower resources

Abstract

In many parts of the world, farmland pollinators decreased significantly during the last half of the 20th century mainly due to land‐use changes and agricultural intensification. We studied the effect of different typical crop rotations and agri‐environment schemes (AES) on bumblebee diversity in Estonia. We compared species abundances between four crop rotation types (cereal rollover [no change from 1 year to the next], cereal to mass‐flowering crops [hereafter MFC], MFC rollover and MFC to cereal fields) where all counts were conducted in the second year and in three farming types (conventional farming, organic farming and environmentally friendly management). We surveyed bumblebees and flower cover along 401 field margins in five consecutive years and recorded 20 species and more than 6,000 individuals. Abundances of long‐tongued and threatened bumblebee species were higher at the field margins of cereal rollover fields than for the other three crop rotation types. In addition, cereal rollover field margins had higher abundances of medium colony species, generalists and forest‐scrub species than MFC rollover and MFC to cereal or cereal to MFC field margins. Bumblebee species richness was higher at the field margins of both AES types than those of conventional farming. However, in general, the strongest driver of bumblebee presence was flower cover. Higher bumblebee abundances in cereal rollover field margins were probably owing to a concentration effect there and/or a dilution effect into MFC fields. Both AES schemes supported increasing flower cover in field margins and thereby diversity of bumblebees, indicating positive AES impacts upon wild pollinators. Synthesis and applications. Crop rotation and agri‐environment schemes determine bumblebee richness and abundance via the availability of flower resources, but crop rotation constrains bumblebees differently based on their traits. Therefore, future agri‐environmental policy should account for these management options. Crop rotation could be a simple, but efficient solution to increase the biodiversity of agricultural landscapes.

Effectiveness of agri‐environmental management on pollinators is moderated more by ecological contrast than by landscape structure or land‐use intensity

“…; Marja et al . ). Therefore, effective AEM, which is targeted to enhance pollinator diversity, should be determined first of all by the availability of food resources.…”

“…Our interaction model results indicated that large ecological contrast had in all cases (except when sample size was too small) significant positive effects on pollinator species richness. We determined in most cases ecological contrast by the difference between AEM and control sites in the amount of suitable flower resources providing energy and food for pollinators (Wood et al 2015;Marja et al 2018). Therefore, effective AEM, which is targeted to enhance pollinator diversity, should be determined first of all by the availability of food resources.…”

“…; Marja et al . ), resulting in large ecological contrasts between margins with and without such strips. However, delayed mowing of intensively managed grasslands only produces small ecological contrasts, because it results in negligible increases in floral resources compared to conventional management (Kleijn et al .…”

“…Kleijn et al (2011) hypothesized that landscape structure and land-use intensity, together with the implemented management, are ultimately expressed in the ecological contrast that is created between fields with AEM and conventional control fields. For instance, the increase in floral resources produced by the establishment of wildflower strips on conventionally managed cereal field margins is relatively high (Scheper et al 2015;Marja et al 2018), resulting in large ecological contrasts between margins with and without such strips. However, delayed mowing of intensively managed grasslands only produces small ecological contrasts, because it results in negligible increases in floral resources compared to conventional management .…”

Plant damage in urban agroecosystems varies with local and landscape factors

“…, Marja et al. ). Agroecological practices grounded in ecological theory have potential to minimize crop plant damage and enhance crop production through on‐farm management of habitat structure (Garibaldi et al.…”