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Ecological and biogeochemical implications of the recovery of Eurasian beavers

Levanoni, Oded (2016). Ecological and biogeochemical implications of the recovery of Eurasian beavers. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2016:93
ISBN 978-91-567-8688-6
eISBN 978-91-567-8689-3
[Doctoral thesis]

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Abstract

In pre-industrial times beavers, ecosystem engineers, inhabited most of the Holarctic. Intensive exploitation over the last millennium, particularly in Europe during the 18th and 19th centuries, led to a dramatic decline in beaver populations. By the end of the 19th century the Eurasian beaver (Castor fiber) was at the verge of extirpation in many regions of Eurasia. However, during the 20th century, changes in management policy and reintroductions have resulted in a fast recovery of the species. Presently, Eurasian beavers are colonizing large parts of their former distribution range, and their population is still growing. Once again, beaver engineering and its outcomes are becoming prominent features of many streams in the boreal landscapes.

The goal of this thesis was to investigate how the reintroduction and population recovery of Eurasian beavers might affect ecosystem functioning at local and landscape scales. The work was based on measurements from 12 beaver systems of various colonization histories (pioneer and recolonized) in Swedish boreal forests. Based on water chemistry measurements together with field and lab experiments, I evaluated the effect of beavers on processes of mercury methylation, litter decomposition, and the growth and respiration of benthic biofilms. I also investigated how beavers alter the nutrient limitation of biofilm activity. To assess the environmental effects of the reintroduction of beavers at the landscape scale, this empirical approach was complemented by a meta-analysis of 76 published studies on a total of 16 environmental factors. The results showed that beavers increased MeHg concentrations, decreased algal biomass accrual, and sometimes increased litter decomposition rates downstream compared to upstream beaver systems. However, distinct contrasting patterns were observed in pioneer and recolonized systems: While all the above effects were prominent in pioneer systems, they were moderate or absent in recolonized systems. Albeit algal accrual and community respiration were nutrient limited, beaver systems had no effect on the degree of limitation. Based on the meta-analysis, this thesis demonstrates that, when compared to a reference site, beavers can potentially affect all studied factors. The meta-analysis also identified gaps in knowledge regarding the dependency of beaver effects on different stages of age and colonization history.

In conclusion, this thesis highlights: a) the importance of incorporating the successional stage and the colonization history of beaver systems when considering the effects of reintroducing beavers into stream ecosystems; and b) the lack of knowledge regarding these issues.

Authors/Creators:Levanoni, Oded
Title:Ecological and biogeochemical implications of the recovery of Eurasian beavers
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :20 September 2016
Depositing date:3 October 2016
Volume:2016:93
Number of Pages:59
Papers/manuscripts:
NumberReferences
ILevanoni, O., Bishop, K., McKie, B., Hartman, G., Eklöf, K. & Ecke, F. (2015). Impact of beaver pond colonization history on methylmercury concentrations in surface water. Environmental Science & Technology, 49(21), pp. 12679-12687.
IILevanoni, O., Ecke, F., Hartman, G. & Mckie, B. G. Responses of stream ecosystem functioning to the recovery of Eurasian beaver (Castor fiber). (Manuscript).
IIILevanoni, O., Sponseller, R., Hartman, G., Ecke, F. & Mckie, B. G. Nutrient limitation of autotrophic and heterotrophic biofilms in boreal streams colonized by Eurasian beaver (Castor fiber). (Manuscript).
IVEcke, F., Levanoni, O., Audet, J., Carlsson, P., Eklöf, K., Hartman, G., McKie, B. G., Ledesma, J.L.J., Segersten, J., Truchy A. & Martyn Futter. Meta-analysis of environmental effects of beaver and artificial dams. (Manuscript).
Place of Publication:Uppsala
Publisher:Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-567-8688-6
ISBN for electronic version:978-91-567-8689-3
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L20 Animal ecology
P Natural resources > P01 Nature conservation and land resources
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Zoology
Agrovoc terms:beavers, population dynamics, habitats, ponds, rivers, ecosystems, environmental impact, mercury, methylation, algae, plant litter, biodegradation, nutrient availability, europe, asia, eurasia
Keywords:beaver, beavers, reintroduction, castor fiber, ecosystem functioning, nutrient limitation, decomposition
URN:NBN:urn:nbn:se:slu:epsilon-e-3706
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3706
ID Code:13696
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Aquatic Sciences and Assessment
External funders:FORMAS
Deposited By: Oded Levanoni
Deposited On:03 Oct 2016 08:58
Metadata Last Modified:03 Oct 2016 08:58

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