Resource pulses of dead periodical cicadas increase the growth of American bellflower rosettes under competitive and non-competitive conditions
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This experiment investigates how pulsed nutrient resources interact with intraspecific competition to influence biomass production and nutrient use efficiency in the American bellflower (Campanulastrum americanum). The competitive environment of these plants was manipulated by growing plants alone or with neighboring conspecifics, and the occurrence of pulsed nutrient resources was manipulated through the addition of 17-year periodical cicada (Magicicada septendecim) carcasses in order to simulate naturally occurring pulsed resources in this system. The addition of cicada carcasses increased mean plant biomass by 61 % compared to non-supplemented plants, while competition decreased mean plant biomass by 44 % compared to plants grown without competition; these effects were additive. In comparison, nutrient use efficiency decreased in fertilized plants (cicada-supplemented plants showed 20 % greater foliage nitrogen concentrations compared to non-supplemented plants), but was not significantly affected by the plant’s competitive environment. In addition, cicada supplementation did not significantly increase the biomass asymmetry in competing pairs of plants. These results suggest that these plants increased their total nutrient uptake at a timescale commensurate with the pulsed increase in nutrient availability due to cicada carcass decomposition.
KeywordsResource pulses Competition Nutrient use efficiency Foliage nitrogen Periodical cicadas (Magicicadaseptendecim) American bellflowers (Campanulastrum americanum)
I thank the Mountain Lake Biological Station and Blandy Experimental Farm at the University of Virginia for field site assistance. Thanks to David Carr, T’ai Roulston, and Rick Karban for assistance in the field, and Rick Karban, Tom Schoener, Kevin Rice, Jonathan Levine and Tabatha Bruce for helpful comments on earlier versions of this manuscript. This research was supported by the Center for Population Biology and Section of Evolution and Ecology at the University of California, Davis and the National Science Foundation Graduate Research Fellowship Program.
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