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Effects of Dominant Grasses on Microbial ProcessesRobert 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

TreatmentsSoil (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