Relationship Among Host Tree Species Diversity, Soil Fertility, and Carbon Availability in Maintaining Belowground Ectomycorrhizal Community Structure and Function

Montana State University, Bozeman MT

Investigators

Abstract

Integrated studies of interactions among plants, microbes, and the soils they inhabit are critical to our understanding of ecosystem function. We propose to use a combination of biochemical and molecular-genetic methods to determine effects of artificial defoliation of Pinus contorta (lodgepole pine) on structure and function of ectomycorrhizal (EM) communities in pure P. contorta and mixed P. contorta/Picea engelmannii (Engelmann spruce) stands. We will defoliate only the pine in both pure P. contorta and mixed P. contorta/P. engelmannii patches formed within mixed stands by small-scale disturbance. We will then determine how defoliation affects EM fungal community structure, activities of enzymes that break down litter, and enzymatic function of soil fungal communities. We will sample across a soil fertility gradient created by a transition from relatively nutrient-rich andesite, through a transition zone created by glacial activity, to nutrient-poor rhyolite. By doing so, we will determine how interactions among carbon flow to roots, tree species diversity, and soil fertility influence ectomycorrhizal fungal diversity and function, for the first time. Our preliminary data from this system indicate that defoliation of pine only in a patch of mixed pine/spruce can 1) significantly affect the EM community of mixed P. contorta/P. engelmannii stands, and 2) affect the EM of non-defoliated spruce. Our data also show that soil fertility plays a pivotal role in influencing EM community structure, and the work of others demonstrates that soil fertility can moderate effects of defoliation and insect herbivory. We will be the first to investigate how alteration of carbon flow to roots affects EM community structure, EM enzymatic function, and below-ground function in a mixed tree species forest, and the first to combine these factors with soil fertility. We will conduct this study in Yellowstone National Park, the centerpiece of the 11-million acre Greater Yellowstone Ecosystem, which includes several National Forests in three states. By using a combination of biochemical and molecular methods, we will provide the most comprehensive picture of these aspects of ecosystem function to date. Thus, we will add greatly to our understanding of a pristine, economically important, and geographically dominant ecosystem. Our education/outreach and broader impacts will be far-reaching. For example, Cullings is adjunct at a Hispanic-Serving Institution and will teach classes and seminars there, and students from that institution will be invited to participate in the study. In addition, Cullings is a member of the Ames Native American Advisory Council, an education/outreach organization within NASA dedicated to bringing science education to reservations. Henson has volunteered for 12 years as an ASM minority educator/lecturer, and has been a preceptor for NIH (Institutional Student Minority Development) and NSF (Minority Access Program, Science and Engineering for All) minority education grants. In addition, and for the past 10 years her lab has hosted Native American high school students and teachers through the American Indian Research Opportunities (AIRO) program on campus. Her group also assists YNP park personnel with their microbiology brochures and videotapes for the general public, and maintains a Web site about their work in Yellowstone (www.montana.edu.hotfungi). Henson also participates in ASMs on- line science mentoring project. Students from all programs will be recruited to participate in this project.