CAREER: Quantifying environmental impacts in a community context: indirect effects of climate mediated through multiple species interactions

About This Grant

Environmental effects on plant and animal populations can be mediated via both direct effects on individuals, such as water stress, and/or indirect effects, such as a reduction in the densities of competing species. Quantifying the strength of direct vs. indirect effects is critical to accurately predicting responses to a variable climate. If direct effects are strong, responses in one community will accurately predict responses in another community with different interacting species. If indirect effects are strong, effects in novel communities cannot be accurately predicted because the net effect depends strongly on the community of interacting species. In spite of their importance, a unifying framework for understanding the strengths of direct and indirect effects is lacking for primary producers, particularly for species interactions besides competition, or when multiple indirect effects operate simultaneously. This research will quantify the strengths of direct and indirect effects mediated through three species interactions (competition, and two herbivore guilds) for more than 120 plant species. In addition, this project will fund ~20 undergraduates to engage in a structured mentoring and training program designed to improve quantitative skills, provide training in modeling to up to 75 graduate students, and increase scientific literacy for 200 Kansas residents annually. The project addresses three questions that are central to ecological predictions: (1) What fraction of net precipitation effects are direct and how does this vary across species?, (2) How often are indirect effects of precipitation mediated through different species interactions simultaneously?, and (3) How general is the strength and direction of direct vs. simultaneous indirect effects across taxa? The project will unite data from three sources: 1) new experimental work manipulating indirect effects for three focal species at the Konza Prairie Long-Term Ecological Research site (KNZ); 2) an ongoing long-term (4 years to date) and multi-site observational demographic study conducted at KNZ on these three species; and 3) long-term (40 years to date) observational data on changes in percent cover collected at KNZ for 128 species. For the three focal species, the work will use both observational and experimental data to quantify the strength of direct vs. indirect effects on population growth rate. This approach will provide insights into the particular demographic rates that tend to drive direct vs. indirect effects. The less-detailed data on many more species will be analyzed using a common framework that allows fair comparison across disparate species, allowing generalities concerning when and where indirect effects are important. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.