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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Nitrogen Fertilization on Tritrophic Interactions)

Author
item Chen, Yigen
item Olson, Dawn
item Ruberson, John

Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2010
Publication Date: 4/29/2010
Publication URL: http://www.springerlink.com/content/9757105777u36643/fulltext.pdf
Citation: Chen, Y., Olson, D.M., Ruberson, J. 2010. Effects of nitrogen fertilization on tritrophic interactions. Arthropod-Plant Interactions. 4:81-94. DOI:10.1007/s11829-010-9092-5.

Interpretive Summary: Plant—herbivore—natural enemy interactions are basic components of nearly all ecosystems. Nitrogen (N) can exert a variety of effects on plants and can significantly alter trophic interactions through various complex mechanisms. Here we describe and illustrate possible effects of N on tritrophic interactions. First, in plant—herbivore interactions, N availability can alter quality of the plant for herbivores. Plant’s direct defenses to herbivorous insects can also be changed by N fertilization through qualitative and quantitative alterations of defensive compounds such as digestibility reducers and toxins. Second, nitrogen effects can cascade to natural enemies through herbivores by changes in herbivore quality vis-à-vis the natural enemy and can provide herbivores with a defense against natural enemies. Nitrogen also may affect the plant’s indirect defenses, namely the efficacy of natural enemies that kill herbivores attacking the plant, through quantitatively and/or qualitatively changing herbivore-induced plant volatiles that are crucial for foraging success of natural enemies, modifying plant architecture that might affect natural enemy foraging efficiency, and altering the quality of plant-associated food and shelter for natural enemies.

Technical Abstract: Plant—herbivore—natural enemy interactions are basic components of nearly all ecosystems, and nitrogen can exert a variety of effects on plants which can significantly alter these interactions. We present a diagram illustrating the various ways that nitrogen can affect three trophic levels and review existing literature on these effects. We suggest that known variability within and among plant species in their response to nitrogen levels may be related to the three primary strategies that plants have evolved to deal with stress and disturbance. Namely, competitive-selected plants are typically found in good resource availability habitats and are predicted to minimize herbivory through selective spatial and temporal herbivore resistance factors. Ruderal-selected plants are are predicted to minimize herbivory through rapid completion of their life cycle and maximization of seed production. The selectivity of the response of both strategies in terms of space and time depends on the intensity of herbivory. Stress tolerant, or stress-selected plants, contrarily, are predicted to be less palatable overall, a trait likely to have evolved in response to sequestered N, slower growth rates and therefore, intensive natural selection for resistance to herbivores. These strategies can also differentially affect the responses of herbivores.

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