Our lab investigates how plants and soil microbes mediate energy flow and nutrient dynamics in forests. Plants and microbes perform vital ecosystem services (e.g., carbon storage, water filtration, nutrient retention), and reduce the impacts of some of society’s greatest environmental threats. We use a complementary suite of approaches that integrate field observations with controlled environmental systems to address questions that intersect plant physiological ecology and soil microbial ecology in an ecosystem context.
Much of our work focuses in the role of roots, "the hidden half" of plants. Roots are often considered to be passive portals for soil resources. However, there is an emerging view that roots, through their activities and interactions with soil microbes, actively alter ecosystem processes. The consequences of root-microbe interactions are critical, as these processes link the carbon, nutrient, and water cycles in ecosystems, and have the potential to influence ecosystem dynamics and global climate change.
The mycorrhizal associated nutrient economy: We're investigating how the traits of trees and their associated microbes influence biogeochemical processes in forests. We hypothesize that trees that associate with arbuscular mycorrhizal (AM) fungi alter nutrient and carbon cycling differently than trees that associate with ectomycorrhizal (ECM) fungi. We refer to this as the Mycorrhizal-Associated Nutrient Economy framework, and have been investigating whether AM and ECM trees contribute to unique “biogeochemical syndromes” in terms of energy transformations and nutrient cycling.
Drought impacts on carbon dynamics: Many climate models predict increases in the frequency and intensity of droughts in temperate biomes. Droughts reduce carbon uptake by vegetation, and thus reduce the potential of forests to slow climate warming. Droughts are also likely to impact soil microbes, which control nutrient availability and greenhouse gas fluxes. Our group is investigating the carbon consequences of drought in forests, and the degree to which species-specific adaptations to water stress (trees and soil microbes) influence the magnitude of this effect.
Biogeochemical impacts of understory invaders: Biological invasions are known to have highly variable impacts on ecosystem processes. We’re investigating the biogeochemical impacts of one of the most widespread invasive plant species in the eastern US, Microstegium vimineum (Japanese stiltgrass), in order to develop a framework to explain how and why invasion impacts differ across the landscape. Specifically, we’re examining whether species have the largest impacts where they are in greatest abundance, or where they function most differently from the resident vegetation with respect to nutrient cycling.
Plant-microbial feedbacks to global change: Forests slow global climate change by absorbing and storing CO2, but the extent to which these ecosystems will persist as carbon sinks is unknown. We are currently investigating the mechanisms by which trees and soil microbes mediate carbon retention and loss in forests. Specifically, we’re testing the hypothesis that roots play a critical role in stimulating microbes to release nutrients from soil organic matter - a process that increases plant growth, alters long-term soil carbon storage, and potentially affects feedbacks to climate.
Volatile organic carbon fluxes from soil: We are investigating the biotic and abiotic controls of volatile organic compound (VOC) emissions from forest soils. VOCs emitted from forests contribute significantly to the production of ozone in urban and regional environments, and represent the primary source of VOCs at the global scale. Aboveground plant tissues have long been considered the primary emitters of VOCs in forests, but recent studies suggest that roots and soil microbial emissions represent an important yet under-appreciated flux in these systems.
Climatic controls on carbon balance: We're investigating how intra- and inter-annual variation in climate influence carbon storage at the Morgan-Monroe State Forest. We're coupling micrometeorological (eddy co-variance) and ground-based approaches, including intensive measurements of belowground processes. Our research seeks to quantify and better understand 1) how much atmospheric CO2 is removed by forests, 2) what factors regulate productivity, and 3) how will the ability of the forest to store C respond to drought, warming, and rising atmospheric CO2?
Director of Research, IU Research and Teaching Preserve
Department of Biology
247 Jordan Hall
1001 E. Third St.
Indiana University, Bloomington, IN 47405
December, 2016: Busy year in 2016: Steve published his first chapter in Oecologia, Matt won best student talk in Biogeosciences at ESA, and is getting to submit two manuscripts, Adrienne completed her pulse labeling experiment, and is preparing her first manuscript, Andrea finished harvesting her massive mesocosms and is writing up the results, Quan and Loic are about to submit their first pd manuscripts, and Katie Beidler joined the lab.