Collaborators: Steve Pennings and Angela Laws
This project is funded by NSF (see here).
Relatively little is known about the relative importance of factors controlling the abundance and diversity of insect herbivores compared to plant communities. Understanding these factors, however, is important because herbivores both eat plants and serve as food for higher trophic levels. Additionally, many herbivores are pests that eat agricultural plants or compete with livestock for food. Research has largely focused on three canonical factors that are known to control herbivore communities: 1) plant biomass (food availability), 2) plant diversity (the diversity of food options), and 3) plant quality (namely the nitrogen and phosphorus content of leaves). Collectively, however, these three factors explain a relatively small amount of variability in herbivore community structure.
Recent research has suggested that micronutrients (particularly calcium, potassium, and sodium) may help explain how herbivore communities are structured. At our field site at the University of Houston Coastal Center, a coastal tallgrass prairie in Texas, we have seen that foliar micronutrients were better predictors of herbivore community structure than were any of the 3 canonical factors. Additionally, we found that grasshoppers selective feed on plants based on soil micronutrient concentrations. With recent NSF funding, We have begun a large, multi-factorial field experiment to rigorously test the importance of micronutrients in mediating herbivore abundance and diversity. This study will be the first to manipulate macro- and micronutrients in concert, and will do so in the field at an unprecedented scale. We will determine if the importance of micronutrient depends on macronutrients, and varies among herbivore feeding modes and guilds. Complementary mesocosm and laboratory experiments will test if mechanisms of micronutrient effects are direct (via plant food quality) or indirect (via plant composition).
See below for footage of these large-scale plots in the summer of 2015 before fertilization experiments were implemented.