The theme of my research is the functioning of nutrient-limited ecosystems. At the heart of it all is understanding plant roots: how they are built, how they work, and how long they live. It's not glamorous work, but it's important. With the offhand observation once that I could predict root nitrogen concentrations pretty well by measuring the leaf angle of grassland plants, the linkages between root and leaf traits soon became clear. This led to studies of the evolution of suites of plant traits associated with low nutrient supplies. From Terry Chapin and Dave Wedin, I learned early on to seek to integrate multiple aspects of nutrient-limited ecosystems. The nitrogen cycle, plant defenses, and herbivory soon became favorite topics to learn more about. Of late, I've been exploring the differences in N- and P-limited ecosystems, reconstructing past N cycles with natural abundance 15N, and the mechanisms by which plants compete for nutrients.

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