The author(s) chose to restrict access to this thesis to current Whitman students, faculty, and staff. Please log in to view it.
Effects of golf course fungicide applications on beneficial soil biota
Louisa Irene Lehua Rogers
December 11, 2015
Department or Program
Heidi E. M. Dobson
Arbuscular mycorrhizal fungi (AMF) form symbioses with most species of land plants, aiding the nutrient and water uptake of their hosts in exchange for sugars produced during photosynthesis. In addition to their host plants, AMF interact with many other soil organisms, whether being grazed on by fungivorous Collembola and oribatid mites or releasing compounds into the soil to change the community of decomposing microbes living there. Fungicides have been shown to inhibit AMF, and as golf courses rely heavily on fungicides in their management of turfgrass, this study aimed to determine the effects of these fungicide applications on the turfgrass-AMF symbiosis and identify any downstream effects. This was done by quantifying differences in AMF root colonization and spore density, activity of extracellular microbial enzymes involved in carbon and nutrient cycling, and Collembola and oribatid mite density between fungicide-treated and untreated golf courses, as well as in an undisturbed grassy meadow. AMF colonization of roots was significantly lower in fungicide-treated turfgrass, though spore abundance was not affected by treatment type and was higher in the meadow than in all golf courses. Microbial enzyme activity was not sensitive to fungicide application, but activity of several enzymes varied significantly by site. Six Collembola and oribatid taxa were found across the sites sampled. The mite superfamily Oppioidea was denser in the meadow, and the Collembola family Tomoceridae was found exclusively in the meadow. Decreased AMF root colonization due to long-term fungicide applications may decrease turfgrass water and nutrient uptake in the long run, the but full ecological effects of suppression of the AMF symbiosis merit further exploration.