Abstract
Abstract Bumble bees fill an important function in temperate, boreal and alpine ecosystems as pollinators of wild plants and cultivated crops. Global declines in population size of many bumble bee species call for knowledge about how habitats influenced by human land use can be managed to accommodate diverse bumble bee communities. We carried out a field experiment to study effects on bumble bee communities in power‐line clearings in response to different vegetation clearing practices: (i) cutting, (ii) cutting and removing, and (iii) not cutting the woody vegetation, whilst simultaneously assessing the effect of environmental variables, both individually and in interaction with treatment. Cutting the woody vegetation improved habitat quality for bumble bees relative to the uncut treatment, whereas removal of woody debris provided no additional benefit. The treatment effect on bee richness, diversity, abundance, and the abundance of generalist bees depended on local forb species richness. Increasing functional variation of forbs and cover of forbs with nectar tubes were positively related to species richness and abundance of bees, irrespective of treatment. The abundance of specialized long‐tongued and late emerging bumble bees – which are of special conservation interest – were higher in the cut and cut‐remove treatments and increased with functional variation of forb species irrespective of treatments. Management to improve habitat conditions for bumble bees in power‐line clearings does not require costly removal of woody debris after cutting, but more frequent cutting can benefit specialized bumble bee species of particular conservation interest.
Highlights
Bumble bees have an important function in natural and humandominated ecosystems as pollinators of wild plants and agricultural crops (Biesmeijer et al, 2006; Klein et al, 2007; Ollerton et al, 2011)
We found that average richness and abundance of bumble bees was higher in the cut and cut-remove treatment plots, compared to the uncut plots (Table 2)
We found that the power-line clearings did support typical forest dwelling species such as, Bombus jonellus, B. hypnorum or B. cingulatus, and several species associated with flowerrich natural or semi-natural grasslands, and other open habitats (e.g. B. ruderarius, B. humilis, B. sylvarum, B. wurflenii, and B. sylvarum) (Supporting Information Table A2)
Summary
Bumble bees have an important function in natural and humandominated ecosystems as pollinators of wild plants and agricultural crops (Biesmeijer et al, 2006; Klein et al, 2007; Ollerton et al, 2011). Maintenance clearing creates open habitats facilitating insect-pollinated plants (Steinert et al, 2018), and plants associated with semi-natural landscapes (Eldegard et al, 2017). This provides potential foraging resources and nesting substrate for bumble bees (Goulson et al, 2008). Removing the woody debris in power-line clearings have been found to promote a sustained positive effect on solitary bee communities (Steinert et al, 2020). No previous studies have assessed the potential habitat enhancement effect of experimentally removing the woody debris in power-line clearings on bumble bee communities
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