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Opposing effects of elevated CO2 and N deposition on Lymantria monacha larvae feeding on spruce trees

Opposing effects of elevated CO2 and N deposition on Lymantria monacha larvae feeding on spruce... The effects of elevated atmospheric CO2 and increased wet N deposition on leaf quality and insect herbivory were evaluated in nine model ecosystems composed of 7-year-old spruce trees (Picea abies) and three understorey species established on natural forest soil. Each model ecosystem was grown in a simulated montane climate, and was exposed to one of three CO2 concentrations (280, 420, and 560 μl l−1), and to one of three levels of N deposition (0, 30, and 90 kg ha−1 year−1) for 3 years. In the 3rd year of the experiment second to third instars of the nun moth (Lymantria monacha) were allowed to feed directly on current-year needles of top canopy branches of each tree for 12 days. Specific leaf area (SLA), water content, and N concentration decreased in needles exposed to elevated CO2, whereas the concentrations of starch, condensed tannins, and total phenolics increased. Increased N deposition had no significant effect on SLA, and water content, but the concentrations of starch, condensed tannins, and total phenolics decreased, and sugar and N concentrations increased. Despite higher relative consumption rates (RCRs) larvae consumed 33% less N per unit larval biomass and per day at the two high CO2 treatments, compared to those feeding on 280 μl l−1-needles, but they maintained similar N accumulation rates due to increased N utilization efficiencies (NUE). However, over the 12-day experimental period larvae gained less N overall and reached a 35% lower biomass in the two high-CO2 treatments compared to those at 280 μl l−1. The effects of increased N deposition on needle quality and insect performance were generally opposite to those of CO2 enrichment, but were lower in magnitude. We conclude that altered needle quality in response to elevated CO2 will impair the growth and development of L. monacha larvae. Increasing N deposition may mitigate these effects, which could lead to altered insect herbivore distributions depending on regional patterns of N deposition. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Oecologia Springer Journals

Opposing effects of elevated CO2 and N deposition on Lymantria monacha larvae feeding on spruce trees

Oecologia , Volume 118 (2) – Feb 23, 1999

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References (50)

Publisher
Springer Journals
Copyright
Copyright © 1999 by Springer-Verlag Berlin Heidelberg
Subject
Life Sciences; Ecology; Plant Sciences; Hydrology/Water Resources
ISSN
0029-8549
eISSN
1432-1939
DOI
10.1007/s004420050720
Publisher site
See Article on Publisher Site

Abstract

The effects of elevated atmospheric CO2 and increased wet N deposition on leaf quality and insect herbivory were evaluated in nine model ecosystems composed of 7-year-old spruce trees (Picea abies) and three understorey species established on natural forest soil. Each model ecosystem was grown in a simulated montane climate, and was exposed to one of three CO2 concentrations (280, 420, and 560 μl l−1), and to one of three levels of N deposition (0, 30, and 90 kg ha−1 year−1) for 3 years. In the 3rd year of the experiment second to third instars of the nun moth (Lymantria monacha) were allowed to feed directly on current-year needles of top canopy branches of each tree for 12 days. Specific leaf area (SLA), water content, and N concentration decreased in needles exposed to elevated CO2, whereas the concentrations of starch, condensed tannins, and total phenolics increased. Increased N deposition had no significant effect on SLA, and water content, but the concentrations of starch, condensed tannins, and total phenolics decreased, and sugar and N concentrations increased. Despite higher relative consumption rates (RCRs) larvae consumed 33% less N per unit larval biomass and per day at the two high CO2 treatments, compared to those feeding on 280 μl l−1-needles, but they maintained similar N accumulation rates due to increased N utilization efficiencies (NUE). However, over the 12-day experimental period larvae gained less N overall and reached a 35% lower biomass in the two high-CO2 treatments compared to those at 280 μl l−1. The effects of increased N deposition on needle quality and insect performance were generally opposite to those of CO2 enrichment, but were lower in magnitude. We conclude that altered needle quality in response to elevated CO2 will impair the growth and development of L. monacha larvae. Increasing N deposition may mitigate these effects, which could lead to altered insect herbivore distributions depending on regional patterns of N deposition.

Journal

OecologiaSpringer Journals

Published: Feb 23, 1999

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