Research

Mycorrhizal associations, plant-fungal assembly, & human land use

ecm-root-tip-smallMycorrhizal fungi form symbiotic relationships with >90% of all plant species. The nature of the symbiosis is such that the fungi provide limiting soil nutrients to their associate plants in exchange for photosynthetically derived carbon. In tropical rain forests, the majority of tree species form arbuscular mycorrhizal (AM) associations. However, there is a striking correlation between tropical tree dominance and the formation of ectomycorrhizal (ECM) associations. Understanding the mechanisms by which ECM associations contribute to tropical tree diversity and dominance, and how these mutualisms are altered by human land use is a major focus of our work. Currently, we are exploring these relationships in the forests of SE Asia, in which the dominant tree family is the Dipterocarpaceae. There are >600 species of dipterocarp trees, all of which depend on ECM associations. Our work is examining the basic ecology of how ECM fungi are assembled and function in this ecosystem, while simultaneously evaluating the role of anthropogenic drivers in such as selective logging and oil palm agriculture in altering these communities.

Microbial assembly and function in vineyard agricultural landscapes

IMG_4324Agricultural landscapes comprise more than 50% of all land area, so understanding ecological patterns and processes across the matrix of managed and unmanaged systems is important for an integrated understanding of contemporary terrestrial ecosystems. We are currently using a network of vineyard agroecosystems across Oregon to evaluate the biotic and abiotic factors structuring microbial communities within and across vineyards, in addition to relating microbial composition to ecosystem functions that enhance sustainability. We are also exploring the consequences of feedbacks between microbial mutualists and plant natural enemies on vine health. With over 1000 vineyards composed of 72 grape varietals spanning 16 distinct viticulture areas, this system is an important part of the coupled human and natural landscape across Oregon. Results of this research will not only answer basic questions in ecology, but will also have implications for informing management practices that minimize chemical inputs and facilitate biodiversity conservation.

Linking soil microbial composition and function

coral-fungus-from-brfSoil microbes play critical roles in the cycling of most nutrients, but inferring the function of a soil community from the composition of bacteria and fungi has been challenging. Molecular tools have enabled us to make substantial progress in the last several decades and our lab has been utilizing some of these techniques to understand how shifts in microbial composition can be linked to shifts in ecosystem functions such as decomposition. A more mechanistic understanding of how changes in the composition of specific functional groups of microbes lead to altered ecosystem functions will greatly improve management strategies in human-altered environments and will aid in the development of predictive models of global nutrient cycling under future global change scenarios.

Microbial ecology in the urban environment

central-park-samplingMore than half of the world’s population currently resides in urban centers. This increase in urbanization has led to a variety of environmental problems such as the urban heat island effect, habitat fragmentation, and storm water runoff that combines with sewage into surrounding water bodies. Current sustainability initiatives include increasing the quantity and quality of vegetated areas such as parks and green roofs to alleviate some of the problems associated with urbanization, which has led to renewed interest in asking ecological questions about the role of these vegetation islands in community assembly and the maintenance of biodiversity. Soil microbes are integral components to the functioning of urban vegetation, as they are responsible for the majority of nutrient cycling, contribute to plant tolerance of disturbed environments, and can degrade a variety of organic pollutants. However, few surveys of soil microbes have been done in urban environments, despite the theoretical and practical information that can be gained from such studies. Across the green infrastructure of New York City and in urban to rural landscapes, we are investigating the ecological processes that shape microbial composition and function, and how plant-microbial feedbacks facilitate the ecosystem services that green infrastructure is valued for.