SG: Connecting root foraging strategies to competitive outcomes and community structure

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Up to 80% of the plant mass in a grassland is belowground, in the form of roots. Roots play a substantial role in determining the composition and diversity of species in plant communities. Competition among plants for resources is a driving force in shaping plant communities, and root competition often has stronger effects than aboveground competition. A recent review of root competition research concludes that to understand plant community structure we need to know more about the mechanisms by which plants interact belowground. This project investigates mechanisms of root interactions by determining how root growth responds to two important cues that plants encounter in the soil: nutrient availability and the presence of the roots of competitors. How root growth responses influence competition and community structure will be investigated with this research. A graduate student and three undergraduates will contribute to the research, and this project will be used to introduce non-science majors to the principles of scientific research.Roots encounter many cues in the soil which may trigger changes in growth patterns to maximize plant fitness. This research focuses on two cues that are well studied but still not fully understood: nutrient-rich patches, and roots of neighbors. Responses to these cues will be studied for a set of eight co-occurring grassland plant species. Individuals will be grown in soil with even or patchy distribution of resources and in the presence or absence of neighbors, to determine whether species differ in response to neighbors and whether responses to resources depend on the presence of neighbors. The species identity and relative abundance of roots in samples from two-species pots will be determined using a set of species-specific DNA markers. In a second experiment, communities of seven or eight species will be grown in greenhouse microcosms to determine whether species' response traits influence community structure or the ability of seedlings to establish in existing vegetation. In addition, methods will be developed for classroom investigations of root growth, with plants grown in clear plastic containers so that roots can be readily observed and measured. Students in an ecology class for non-science majors will use this system to practice the scientific method while asking questions about root growth of native and non-native species.