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Impacts of insect herbivory and nitrogen eutrophication on grassland ecosystems

Borgström, Pernilla (2017). Impacts of insect herbivory and nitrogen eutrophication on grassland ecosystems. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2017:22
ISBN 978-91-576-8817-0
eISBN 978-91-576-8818-7
[Doctoral thesis]

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Nitrogen (N) eutrophication causes severe species richness declines in grassland ecosystems worldwide. Species interactions, for example between plants and herbivores, are likely to mediate the grassland’s response to increased N availability. However, attempts to investigate how herbivores might modify ecosystem-level N impacts have so far focused near-exclusively on the aboveground subsystem. Such approaches overlook the importance of the great number of belowground interactions that occur among plants, herbivores and other organisms. A great challenge in global change ecology is to understand how the above- and belowground subsystems interact to determine the ultimate, ecosystem-level impact of N eutrophication and other global change drivers. In this thesis, I present controlled experiments that were carried out to explore the role of above- and belowground insect herbivory in mediating interactions among plant species, and how the interaction between above- and belowground herbivory determines the response of the grassland to N eutrophication.

In a field experiment, I found that above- and belowground herbivory determined the impact of N eutrophication on the grassland ecosystem, in terms of plant community composition, ecosystem functioning, and the soil food web. N and herbivory synergistically conferred a competitive advantage to forbs over grasses, as the former strongly benefited from the presence of both herbivory types at elevated N. Nutrient turnover displayed inverted responses to above- and belowground herbivory at contrasting N levels. Additionally, the shifts in the plant community extended to shifts in the functional composition of the soil nematode community. In a parallel plant competition experiment, I found that belowground herbivory mitigated an increased competitive asymmetry caused by aboveground herbivory.

I conclude that insect herbivores can be important mediators of the impact of N
eutrophication on grasslands, and that their mediating role will depend on whether both above- and belowground herbivores are present. Therefore, the ecosystem-level impact of herbivory above ground should, whenever possible, be studied alongside that of herbivory below ground, as the omission of either herbivory type could lead to erroneous conclusions about the role of the other.

Authors/Creators:Borgström, Pernilla
Title:Impacts of insect herbivory and nitrogen eutrophication on grassland ecosystems
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2017
Depositing date:24 February 2017
Number of Pages:51
IBorgström, P., Strengbom, J., Marini, L., Viketoft, M., Bommarco, R. (2017). Above- and belowground insect herbivory modifies the response of a grassland plant community to nitrogen eutrophication. Ecology 98:545-554.
IIBorgström, P., Strengbom, J., Viketoft, M., Bommarco, R. (2016). Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect. PeerJ 4:e1867.
IIIBorgström, P., Bommarco, R., Viketoft, M., Strengbom, J. Nitrogen eutrophication inverts the interaction between above- and belowground insect herbivory effects on grassland ecosystem functioning. (manuscript).
IVBorgström, P., Bommarco, R., Strengbom, J., Viketoft M. Above- and belowground insect herbivory mediates the impact of nitrogen eutrophication on soil nematode communities in a grassland ecosystem. (manuscript).
Place of Publication:Uppsala
Publisher:Department of Ecology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8817-0
ISBN for electronic version:978-91-576-8818-7
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:H Protection of plants and stored products > H10 Pests of plants
P Natural resources > P01 Nature conservation and land resources
P Natural resources > P34 Soil biology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Ecology
Agrovoc terms:eutrophication, nitrogen, herbivores, insects, grasslands, ecosystems, soil fauna, climate change, biodiversity
Keywords:global change ecology, above-belowground linkages, foliar herbivory, root herbivory, grassland plant communities, ecosystem functioning, soil nematodes
Permanent URL:
ID Code:14096
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Ecology
(S) > Dept. of Ecology
Deposited By: Pernilla Pernilla Borgstrom
Deposited On:27 Feb 2017 09:34
Metadata Last Modified:10 Sep 2020 13:41

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