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Tough neighbourhood ? Density-dependent effects more important in old-growth forest than in recently burnt forest for saproxylic Coleoptera
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
(English)Manuscript (Other academic)
Abstract [en]

Resource competition is an important structuring mechanism in communities of insects living as larvae in ephemeral resource patches. Old-growth forest and recently burnt forest, two important boreal forest habitats, differ in several ways that could affect the intensity of resource competition in saproxylic (living in dead trees) Coleoptera. I studied the level of density-dependent effects in an experiment in two burnt-forest sites and two old-growth forest sites. A total of 140 bolts (0.5 m lengths of Norway spruce, Picea abies, bole) were exposed to colonization by saproxylic Coleoptera for increasingly longer times: 0.5, 1, 2, 4, and 8 weeks. Density (number of emerged Coleoptera per bolt) increased with increasing exposure time in a forest-type-specific manner. The increase showed concave-down linearity (the increase leveled off) in the old-growth sites, but a concave-up continuous increase in the burnt-forest sites. This showed that density-dependent effects, and possibly the intensity of resource competition, were more important for saproxylic Coleoptera in the old-growth-forest bolts than in the burnt-forest bolts.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:uu:diva-88759OAI: oai:DiVA.org:uu-88759DiVA: diva2:159024
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14
In thesis
1. Community Assembly and Spatial Ecology of Saproxylic Coleoptera
Open this publication in new window or tab >>Community Assembly and Spatial Ecology of Saproxylic Coleoptera
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Community assembly is the process deciding inclusion/exclusion of species in a developing community. Spatial ecology integrates spatial habitat factors with local biotic interactions within a given patch.

I used standardized tree bolts (0.35-1 m long) to sample saproxylic (wood living) beetles in natural and managed forest types.

Density-dependent effects were more intense in old-growth coniferous forest than in burnt forest. The final-state assemblages in these two forest types diverged regarding species composition but converged regarding community structure. The communities also followed forest-type specific assembly trajectories.

Order of arrival can influence the species assemblage, I found priority effects when comparing the reproductive success of two cerambycid species. A two-week head start had a positive effect on fitness in both species. Different fitness components were affected in the two species: offspring number in Acanthocinus aedilis and offspring quality in Rhagium inquisitor.

In birch-living Coleoptera a large part of variance in species composition could be explained by habitat variables (22.9 %), such as forest type, or spatial variables (15.8 %), such as distance apart. The assemblages in deciduous sites responded to distance apart and showed positive spatial autocorrelation up to a distance of 80 km. For assemblages in deciduous sites a metacommunity perspective is warranted – on a surprisingly large scale.

I compared two regions, one more fragmented and one less fragmented, (with 2.2 % more deciduous forest in the landscape). The effects of habitat fragmentation was primarily found in mature coniferous forest. Host-tree patches in this matrix forest were perceived as matrix by the Coleoptera in the more fragmented region but as habitat in the less fragmented region.

Some of my study sites consisted of protected old-growth forest. These were embedded in a landscape dominated by forestry. These protected areas were invaded by generalist species, thriving in managed forests.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 36 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 604
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88765 (URN)978-91-554-7427-0 (ISBN)
Public defence
2009-03-20, Zootissalen, EBC, Villavägen 18, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2009-02-27 Created: 2009-02-06 Last updated: 2009-03-31Bibliographically approved

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Victorsson, Jonas

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