The effect of plant nitrogen levels on insect herbivory in northern Michigan sand dunes

General EcologyNitrogen is a limiting factor for plant and animal growth. Some herbivores have illustrated dietary preferences in regard to nitrogen, choosing some foodstuffs over others in order to get the highest possible levels of nitrogen in their diet. Nitrogen is especially low in particular environments, including the sand dunes at Sturgeon Bay of Lake Michigan, which may make selective feeding of herbivores there more common. Nitrogen levels in plants on dunes have been shown to increase with distance from shore, as moisture and amount of vegetation increase. At Sturgeon Bay, we tested the ideas both of increasing nitrogen with increasing distance from shore and the idea that herbivory increases at higher nitrogen levels, with insects showing a preference for the more nutritious plants. We looked at the dune grass Ammophila, analyzing percent nitrogen and amount of herbivory at 6 distances from shore, ranging from 0 to 125 m. We found that nitrogen levels did increase at increasing distances from shore, but there was no significant relationship between herbivory and nitrogen levels. There was a slight trend which appeared in graphs of increasing herbivory on the dune grass at increasing distance from shore. Further research is suggested on this relationship.http://deepblue.lib.umich.edu/bitstream/2027.42/61514/1/Dengate_Clune_Foster_Kiel_2008_GE.pd