Current research projects

TESTING A UNIFIED HYPOTHESIS OF MYCORRHIZAL FUNCTION, National Science Foundation DEB: 0316136

Read more
Collaborators:

Gail Wilson, Kansas State University

R. Michael Miller, Argonne National Laboratory

Catherine Gehring, NAU faculty

Andrea Redman, NAU technician

Jack Shapiro, NAU graduate student

The goal of this research program is to help link field-based measurements of AM structure with mutualistic function. Previous research indicates that resource availability (specifically soil P, soil N, and light), relative allocation to fungal structures, and evolutionary legacies are important controllers of the mutualistic function of arbuscular mycorrhizal (AM) symbioses. These patterns have been articulated in the trade balance, the functional equilibrium, and the co-adaptation models of mycorrhizal function. This proposal will test predictions of these three conceptual models and help develop a unified hypothesis of mycorrhizal function. The primary goal of this research program is to identify principles that will help predict AM function in natural and human-managed ecosystems.

In this research program we are measuring mycorrhizal structure as it relates to mutualistic function at three grasslands: Konza Prairie Long Term Ecological Research (LTER) site in Kansas, Cedar Creek LTER site in Minnesota, and FermiLab Department of Energy (DOE) site in Illinois. These sites form a natural gradient of available soil N:P ratios. Impacts of soil fertility and light availability on relative allocation to AM structures and mycorrhizal function within "co-adapted" plant-fungus-soil complexes are studied in field and greenhouse studies. Mycorrhizal structure is assessed from root colonization, spore communities, lipid, and DNA analyses. Mycorrhizal function is assessed from AM affects on plant biomass allocation, tissue nutrients, and reproductive effort. Through this work, we will seek ways to predict mycorrhizal function based upon structural measurements. 

INTERACTING RESPONSES OF C AND N CYCLES TO ALTERED BIODIVERSITY, ELEVATED CO2, AND N ENRICHMENT, National Science Foundation DEB: 0322057 

Read more

Collaborators:

Peter Reich, University of Minnesota

Shahid Naeem, Columbia University

Donald Zak, University of Michigan

Anita Antoninka, NAU graduate student

This collaborative work is being conducted at the BioCON facility at Cedar Creek Minnesota. The first goal of this research is to study the affects of plant diversity and enrichment of atmospheric CO2 and soil N on the structure of AM fungal communities. We are assessing AM structure by measuring hyphal lengths, glomalin production, and spore community composition in experimental field plots at BioCON. The second goal is to examine the affect of "soil organism feedbacks" on the composition of plant communities. To do this we are studying field mesocosms inoculated with soil organisms from BioCON plots that contain monocultures or polycultures and are either enriched or un-enriched with nitrogen. 

NARROWING THE GAP BETWEEN THEORY AND PRACTICE IN MYCORRHIZAL MANAGEMENT, National Center for Ecological Analysis and Synthesis

Read more
Collaborators:

Jason Hoeksema, University of California, Santa Cruz

James Umbanhower, University of Guelph

Lynette Abbott, University of Western Australia

Mike Amaranthus, Mycorrhizal Applications

James Bever, Indiana University

Catherine Gehring, Northern Arizona University

John Klironomos, University of Guelph

R. Michael Miller, Argonne National Laboratory

John Moore, University of Northern Colorado

Mark Schwartz, University of California, Davis

Suzanne Simard, University of British Columbia

William Swenson, University of California, Riverside

Gail Wilson, Kansas State University

Catherine Zabinski, Montana State University

Research on interactions between plants and their symbiotic mycorrhizal fungi has increased dramatically during the last decade, generating a confusing body of theoretical and empirical results. Simultaneously, there has been an explosion in commercial applications of mycorrhizal fungi in agriculture, horticulture, forestry and ecosystem restoration. Considering the unexpected consequences of many human introductions of non-native plants and animals, and our current lack of understanding of the factors controlling mutualistic performance of mycorrhizas, it is alarming that so little caution is being used in commercial applications of mycorrhizal fungi. Jason Hoeksema, James Umbanhower, and I are co-organizing a working group at the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara California to help narrow the gap between theory and practice in mycorrhizal management. Our working group is: 1) performing meta-analyses to synthesize the currently disparate body of empirical and theoretical work on mycorrhizal function within communities and ecosystems, 2) summarizing current theories of mycorrhizal performance with regard to environmental conditions and plant and fungal phenotypes, and 3) generating recommendations and precautions regarding the commercial use of mycorrhizal inoculum. In addition to contributing to the development of principles to guide mycorrhizal management, our efforts will help generate better theories for understanding the roles of mutualisms in population and community dynamics. 

EVALUATING THE ROLE OF ARBUSCULAR MYCORRHIZAL FUNGI IN ARSENIC UPTAKE BY PLANTS, Department of Energy

Read more
Collaborators:

Richard Foust, NAU faculty

Andrea Redman, NAU technician

Grant Evans, NAU graduate student

Monica Markley, NAU graduate student

Rebekka Rieder, NAU undergraduate student

Sadie Iverson, REU undergraduate student

High levels of arsenic compounds in soils, sediment, and water poses a serious health threat in many parts of the world. Living organisms can be managed to sequester and transform toxic compounds in the environment. Consequently, bioremediation of arsenic contaminated sites may be an effective and economical method to ameliorate contamination. More studies are needed to identify potential organisms that can be managed for remediation purposes. The goal of this research is to identify species of plants and mycorrhizal fungi that show promise for bioremediators of arsenic. 

SOLVING THE MYSTERY OF YIELD DECLINE IN CROPS BY MEASURING 13C ASSIMILATION INTO MYCORRHIZAL DNA AND RNA, Merriam Powell Center for Environmental Research

Read more

Collaborators: 

Maribeth Watwood, NAU faculty

Egbert Schwartz, NAU faculty

Catherine Gehring, NAU faculty

Jack Shapiro, NAU graduate student

Matthew Lau, NAU graduate student

Ted Martinez, NAU graduate student

Most crop plants form symbiotic associations with arbuscular mycorrhizal (AM) fungi. These root-inhabiting fungi usually help plants get nutrients from the soil, but this benefit is greatly reduced by fertilization. There is correlative evidence supporting the hypothesis that, over time, agriculture selects species of AM fungi that can reduce crop productivity in highly fertilized systems. It is necessary to develop new research methods to more effectively test this hypothesis. Species of AM fungi are currently distinguished by the morphology of their soil-borne spores and it is very difficult or impossible to identify which AM fungi are present inside plant roots and in the soil. We are working to develop new methods to identify AM fungi that assimilate 13Carbon atoms from 13CO2 into their nucleic acids. This data will provide compelling evidence that the fungus is directly engaged in a symbiotic association with the plant and may provide insight into the quantity of carbon the fungus receives from the plant. Development of this method would revolutionize the way that mycorrhizal studies are done. 

A QUANTITATIVE TEST OF RANGELAND HEALTH SOIL STABILITY INDICATORS: DO THEY REFLECT IMPACTS TO MYCORRHIZAL FUNGAL INOCULUM AND PLANT ESTABLISHMENT? Bureau of Land Management

Read more

Collaborators: 

Thomas O'Dell, National Park Service

Bala Chaudhary, NAU graduate student

Andrea Redman, NAU technician

The Bureau of Land Management Rangeland Health standards mandate assessment of grazing allotments by evaluating a standard set of qualitative indicators, including several indicators of soil and site stability. However, the ecological implications of rating sites high or low in the assessment have not been experimentally tested so we can not substantiate the value of the assessment protocol for determining impacts on ecological processes. One consequence of soil loss (an indicator assessed in the protocol) is that propagules (spores, hyphae, and colonized root fragments) of mycorrhizal fungi may be reduced. Because most perennial plants require mycorrhizal symbioses for water and nutrient acquisition, a reduction in mycorrhizal fungal propagules could lead to lower recruitment of native plants on sites with poor soil stability.

This study compares sites with low, medium and high ratings for soil and site stability at Grand Staircase Escalante National Monument. One experiment measures plant, fungal, and soil properties at 219 sites throughout the monument. Another experiment examines survival rates of seedlings planted into each of the sites. The results of these experiments will help indicate whether our qualitative ratings of soil and site stability relate to the structure and function of mycorrhizal fungal communities, and in turn, if detectable changes in these fungi affect seedling establishment. Additionally, this study contributes to quantitative testing of the rangeland health assessment protocol by measuring variables that are not currently assessed in the protocol. 

BIOLOGICAL SOIL CRUST SURVEY AND HABITAT CHARACTERIZATION

Read more

Collaborators: 

Jayne Belnap, National Park Service, Moab Utah

Matthew Bowker, NAU graduate student

Learn more about the biological soil crust survey and habitat characterization project.