Citation. Burrows, R. 2001. Plant biodiversity impacts on arbuscular-mycorrhizal fungi. Ph.D. Thesis, University of Minnesota.

Abstract. The effect of increasing plant diversity (1, 2, 8, or 16-species) of tallgrass prairie species on the associated arbuscular-mycorrhizal fungi (AMF) communities was assessed as part of a larger biodiversity experiment at the Cedar Creek Long Term Ecological Research site at East Bethel, Minnesota, from 1997-1999.

Spore density in 16-species plots was 30 to 150% greater than in monocultures, and total spore volumes of 16-species plots were 40 to 70% greater than in monocultures. Plant diversity was a better predictor than plant cover of spore numbers, especially as cover increased over the three years. Sporulation by larger-spored, but not smaller-spored AMF species increased consistently with increasing plant diversity. Spore numbers of several AMF species were consistently correlated with the percent cover of several legumes and C 4 grasses. Despite low (0 to 1.98 mg/kg) soil nitrate concentrations, correlations between spore production by individual AMF species and soil nitrate ranged from non-significant to consistently negative, demonstrating the sensitivity of these species to nitrate.

Fabric strips were used to trap glomalin, a unique glycoprotein produced by AMF hyphae that serves as an indicator of hyphal growth. Monocultures had consistently lower production of glomalin compared to higher diversity plots. Glomalin levels were more closely correlated with plant diversity than with percent plant cover. Mycorrhizal infection potentials of monocultures were also lower compared with more diverse plots in 1998 and 1999. Infectivity was positively correlated with spore production, but not with glomalin or plant cover.

Increasing source-plot plant diversity caused significant increased ability of the associated mycorrhizae to enhance growth of Lespedeza capitata , but not of Schizachyrium scoparium or Liatris aspera . Plots containing Lespedeza and Liatris had increased AMF species richness and spore numbers with increased plant diversity; this was not true in plots with Schizachyrium . Inoculum from Schizachyrium monocultures led to increased growth of both Schizachyrium and Lespedeza compared with soil from Lespedeza monocultures.