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Maize-dominated landscapes reduce bumblebee colony growth through pollen diversity loss

Hass, Annika Louise ; Brachmann, Lara ; Batáry, Péter ; Clough, Yann LU ; Behling, Hermann and Tscharntke, Teja (2019) In Journal of Applied Ecology 56(2). p.294-304
Abstract

Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well-known that semi-natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear. We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff-tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central... (More)

Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well-known that semi-natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear. We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff-tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central Germany. We found that augmenting maize cover had a detrimental effect on pollen diversity collected by bumblebees, probably due to intensive management resulting in low plant diversity. This low pollen diversity translated into reduced colony growth, since colonies with high pollen diversity gained more weight than colonies with low pollen diversity. In contrast, OSR cover and configurational and compositional heterogeneity did neither affect colony growth nor pollen diversity. However, for OSR, the timing of the flowering period was important. When OSR fields had a high flower cover at the end of the OSR blooming period, colonies showed increased growth rates. Synthesis and applications. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass-flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
bumblebee, colony growth, configurational heterogeneity, crop diversity, landscape heterogeneity, oilseed rape, pollen diversity, pollinator
in
Journal of Applied Ecology
volume
56
issue
2
pages
294 - 304
publisher
John Wiley and Sons
external identifiers
  • scopus:85056768606
ISSN
0021-8901
DOI
10.1111/1365-2664.13296
language
English
LU publication?
yes
id
4e345a39-87f9-4621-bf2c-de69546aad8c
date added to LUP
2018-11-28 14:10:23
date last changed
2021-01-19 02:53:24
@article{4e345a39-87f9-4621-bf2c-de69546aad8c,
  abstract     = {<p>Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well-known that semi-natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear. We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff-tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central Germany. We found that augmenting maize cover had a detrimental effect on pollen diversity collected by bumblebees, probably due to intensive management resulting in low plant diversity. This low pollen diversity translated into reduced colony growth, since colonies with high pollen diversity gained more weight than colonies with low pollen diversity. In contrast, OSR cover and configurational and compositional heterogeneity did neither affect colony growth nor pollen diversity. However, for OSR, the timing of the flowering period was important. When OSR fields had a high flower cover at the end of the OSR blooming period, colonies showed increased growth rates. Synthesis and applications. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass-flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services.</p>},
  author       = {Hass, Annika Louise and Brachmann, Lara and Batáry, Péter and Clough, Yann and Behling, Hermann and Tscharntke, Teja},
  issn         = {0021-8901},
  language     = {eng},
  number       = {2},
  pages        = {294--304},
  publisher    = {John Wiley and Sons},
  series       = {Journal of Applied Ecology},
  title        = {Maize-dominated landscapes reduce bumblebee colony growth through pollen diversity loss},
  url          = {http://dx.doi.org/10.1111/1365-2664.13296},
  doi          = {10.1111/1365-2664.13296},
  volume       = {56},
  year         = {2019},
}