This study examined how the presence of two dominant tall grass species, Andropogon gerardii and Sorgastrum nutans, affected soil microbial processes in prairie restorations. Soil samples were taken from 48 plots that included grass only, soil only, combined grass and soil, and control treatments. Microbial enzyme assays showed that the presence of the grasses significantly increased N-acetyl-glucosaminidase (NAG) activity, indicating effects on nitrogen cycling, but did not affect phosphatase, xylosidase, or cellobiohydrolase activity. Elevation also influenced all enzyme activities, with microbial processes varying across sites. The findings provide insight into how dominant grasses impact soil

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Effects of Dominant Grasses on Microbial Processes
Robert Harris III, Dan Hernandez, Corina Perez, Laura Freymiller, and Julia Reich
Biology Department, Carleton College, Northfield, MN USA
Abstract
• Restoration of prairies throughout the Midwest of the United
States has become a major topic of interest in recent years. The
major question that has arisen is: What species should be
included in restorations? In this study, we look at how dominant
tall grass, Andropogon gerardii and Sorgastrum nutans, affect
microbial processes. Previous studies have shown that the
presence of dominant grasses can influence ecological
processes. Soil cores were taken from 48 plots with a grass
treatment, a soil treatment, a combination of grass and soil
treatment and a control plot. We conducted microbial enzyme
assays on soil samples to evaluate the effects. The findings of
this study can influence future decisions about prairie
restorations.
Background
• Previous studies have shown that the presence of dominant
grasses can influence microbial ecological processes
• Changes in vegetation can affect soil chemistry thus effects
of dominant grasses should show up in microbial enzyme
activity
• Enzyme assays show the maximum activity of the tested
enzyme
• Each enzyme acquires a different nutrient thus can tell a
different story about microbial soil processes
Study Area
Methods
Grass treatment affected NAG activity, but not other
enzymes
Elevation affected enzyme activity
Conclusions
• Elevation is significant across all the enzyme activities
• The grass treatment has a statistically significant effect on NAG
activity
• PHOS, XYL, and CELLO show no significant differences among
treatments
• Other data taken during vegetation surveys also showed no effect
Plot design
• Each plot has 4 subplots with a different treatment (refer to Table 1 for
treatments)
• The grass treatment includes the two dominant grasses during planting
• The subplots are divided into a grid like pattern for vegetation
surveying
• Soil cores were taken arbitrarily in the middle of each plot. The green
line demarcates the sample area
Treatments
Soil (S) Grass (G) GS (Grass+ Soil) Control (C)
Table 1. The four treatments used across each plot
Subplot
Acknowledgements
Figure 1. Shows the arithmetic mean of each enzyme activity across the four treatments. Grass
treatment is significant for NAG activity. Refer to table 1 for treatment codes.
Enzyme activities across elevations
Figure 2. Shows the mean activity of each enzyme across the three elevations. Elevation is significant
across all four enzyme activities. None of the other treatments are significant.
• Summer Science Fellowship
• North Star Alliance
• Carleton Arb staff
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Andropogon gerardii Sorghastrum nutans