Kvetoucí pásy jako nástroj podpory opylovačů v agroekosystému

Ing. Anna Šrámková

Doctoral thesis

Abstract:

Declining trend in European pollinator populations is the most concerning in food specialists which species numbers decreased by 30% in the last 40 years. Throughout the European Union, sown flower strips are supported within agri-environment climate schemes (AECS) to mitigate pollinator declines and they are mostly focused on providing food resources for target pollinator groups on farmland. Our study tested pollinator occurrence in sown flower strips corresponding to Czech AECS 'Nectar-rich flower strips' as compared to nearby semi-natural habitats and intensively managed wheat fields. Aculeate Hymenoptera and Syrphidae as two target groups of the AECS with different ecology were chosen for our survey. The goal of our design was to determine whether there is a difference in the quality of pollinator support among habitats highly differing in their flowering plant species diversity as well as in the range of reproduction opportunities. The study was carried out on seven localities in Central Bohemia, Czech Republic, in 2016 and 2017. Each locality comprised three different habitat types (flower strips, semi-natural habitats and wheat fields) separated by at least 350 m, where occurrence of aculeate Hymenoptera and Syrphidae was sampled by yellow pan traps and transect walks in three summer terms in 2016. During each sampling term, all just flowering plant species were also recorded. Meanwhile, in 2016- 2017, a detailed sampling of flower strips (estimation of plant species cover, number of flowers for each plant species and transect walks) was done on all seven localities in three summer terms. Suitability of the two pollinator groups differing in their degree of philopatry within the pool of our study, sampled by yellow pan traps and transect walks, for local-scale biomonitoring was tested first. Philopatric group represented by aculeate Hymenoptera proved to be suitable for this purpose as it was detected in significantly different species numbers in two most contrasting habitat types (semi-natural habitats and wheat fields), regardless of sampling method used. In contrast, Syrphidae as a rather non-philopatric group within this study pointed to differences between habitats only in transect walks and thus, showed a mixed pattern. Nevertheless, affinity of Syrphidae towards non-philopatric behavior suggests that they may be a suitable indicator at a landscape scale.Comparison of the pollinator occurrence in three studied habitats (flower strips, semi-natural habitats and wheat fields) showed that Czech AECS 'nectar-rich flower strips' attracted most species of aculeate Hymenoptera and Syrphidae living at the studied sites despite a significantly lower plant species diversity in flower strips. However, bee food specialists prevailed significantly in semi-natural habitats. Sown flower strips attracted significantly higher abundances of all aculeate Hymenoptera comprising Apis mellifera, coming mostly from managed beehives. This potentially local benefit for beekeepers may be in conflict with conservation focus of the AECS as honeybees tend to suppress foraging of other bee pollinators in flowering patches. 'Nectar-rich flower strips' are conceived as a biennial to triennial simple 'pollen and nectar mix' composed of annuals, forbs and other perennials attractive to pollinators. They should be cut once in summer between July 1 and September 15. We tested the effect of early summer and late summer cutting in the establishment year on their development (plant species cover and number of flowers) and pollinator visitation rate of honeybees, bumble bees, other wild bees and hoverflies over a two-year period. It has been found that the date of mowing is not decisive for the subsequent visitation of the flower strips by target pollinator groups but it affects their botanical composition. However, there are other untested factors affecting pollinator visitation rate at least as much as flowering intensity. Early summer cutti

Abstract:

ng significantly supported sown species and simultaneously reduced weed species. Late summer cutting enhanced flowering of 'pollinator-friendly weeds' and their visitation by pollinators in mid-summer of the sowing year. In the tested seeding mix, there is a conflict between the conservation requirements for having as long of a flowering period in summer as possible and the support of perennial plant species in the flower strip requiring early cutting. A split mowing management could be a solution in weed-free flower strips. While all target pollinator groups were attracted mainly by Phacelia tanacetifolia in early summer of the establishment year, in the post seeding year, flower strips were attractive mainly for honeybees and bumblebees due to the flowering of Trifolium species. Therefore, plant species suitable for other wild bees and hoverflies (i.e. Asteraceae, Apiaceae) should be added in the seeding mix if the AECS is supposed to support wider pollinator species diversity.

Keywords

agricultural habitat, semi-natural habitat, aculeate Hymenoptera, biomonitoring, Syrphidae, bee, honeybee, biodiversity, flower strip, field margin

Language used: English

Date on which the thesis was submitted / produced: 22. 2. 2019

Thesis defence

• Supervisor: prof. RNDr. Ing. František Kocourek, CSc.
• Reader: Michal Knapp, Ph.D., Ing., Jiří Skuhrovec, externi, Hana Šefrová, externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Doctoral programme / field:
Agricultural Specialization / Agricultural and Forestry Phytopathology and Plant Protection