Marie-Anne de Graaff, Ph.D.

Summary: My research is focused around two themes: (1) plant-soil-microbe interactions as controllers of the carbon cycle, and (2) biodiversity impacts on ecosystem functioning.

The amount of carbon stored in soils controls atmospheric CO₂ concentrations and climate change. It also affects soil quality and has direct implications for sustainable agriculture. To better understand the mechanisms that control soil carbon storage, we study the interactions between the chemical composition of carbon deposited in soil through plants, and the soil microbial community metabolizing this carbon. We study these interactions in a variety of ecosystems, including bioenergy cropping systems in IL, in ancient soils in NE and in the semi-arid desert in ID.

Unprecedented contemporary species losses have reduced biodiversity across many ecosystems throughout the world. While threats to aboveground organisms have been quantified extensively, risks for belowground species diversity and consequences for ecosystem functioning have been explored to a much lesser extent. This knowledge gap persists even as evidence accumulates that belowground biodiversity appears to play an important role in regulating aboveground diversity, ecosystem processes, and their response to changing environmental conditions. Our lab studies the impacts of environmental changes (e.g. land use change, invasions, climate change) on belowground species diversity and the consequences for the functioning of ecosystems.

Minimum Classes: N/A

Projects:

Desert Detrital Input and Removal Treatment Experiment (D-DIRT): Despite the critical role played by litter in the global carbon cycle, and in the Earth’s climate system, its control on soil organic matter dynamics remains poorly understood. The DIRT (Detrital Input and Removal Treatments: https://dirtnet.wordpress.com/) experiments were started in 1956 at the University of Wisconsin Arboretum by Dr. Francis Hole, a soil scientist who wanted to examine the effects of changing litter inputs on soil organic matter dynamics. This launched the international DIRT network which aims to assess how rates and sources of plant litter inputs control the long-term stability, accumulation, and chemical nature of soil organic matter in ecosystems over decadal time scales. Originally, the majority of DIRT sites in the US were established in mesic forests. To increase the diversity of ecosystems included in the network, we established a desert (D-) DIRT experiment in Idaho in 2013, at the Reynold’s Creek Experimental Watershed (RCEW). Student working in the lab will contribute to research in this project by analyzing soil samples for C and N, and by applying treatments in the field.

Impacts of root structure and chemical composition of exudates on soil carbon stabilization: Root traits, the chemical composition of root exudates and interactions with the soil microbial community are critically important in regulating soil carbon inputs and stabilization, but highly uncertain and poorly represented in global carbon cycling and modeling. This research aims to elucidate how root structure, rhizosphere chemistry and microbial community structure interact to affect soil carbon accumulation. Students will help analyze the structure of plant roots, and will assist with measuring soil carbon and nitrogen contents.