Zane Ashford - July 2018

The past few weeks in the Zabinski lab have been incredibly busy. We have finally finished extracting the potentially mineralizable nitrogen (PMN) from the soil and have analyzed the three hundred samples in the Environmental Analytical Lab in order to detect ammonium concentration before and after the growing season. A preliminary analysis of the data yielded promising results that there is a significant amount of nitrogen available to plants, indicating that the soils are not nitrogen deficient; however, I have yet to look at species specific differences in ammonium content.

Soil enzyme extractions have proven to be incredibly time consuming. For each of the enzymes that we are looking for activity of – nitrogen, phosphorus (under both acid and alkaline conditions), and carbon – we have performed 100 extractions, duplicates for each sample. The extractions are both light and time sensitive, therefore we have spent many hours in the dark while working with these samples in order to preserve their color. And as can be expected with analytical equipment, our spectrophotometer has been quite finicky and has been the source of much grief over the past few weeks. When it is reading that water has negative absorbance of color, you know something must be wrong. But as soon as the extractions are completed, we will use a series of formulas to convert the absorbance of the color into numerical enzymatic activity that can be compared between different species.

Image 1 and 2. Soil enzyme extractions filtering in order to separate all soil from the extraction. The absorbance of the color was then measured using a spectrophotometer at a specified wavelength.

After enzymes, we will begin scanning the roots separated from the soil cores. Root scanning will allow me to address one of my hypothesized questions, that belowground root traits can potentially predict soil quality. Of the four invasive weeds and the mixed native community, I have found vastly differing root traits already. Some are tap-rooted, such as Sulphur cinquefoil and knapweed, with one dominant woody root and many smaller roots extending from the main stem. Other species, such as cheatgrass, have very fibrous root systems, with hundreds of tough smaller roots creating a network. The mixed native community has a variety of root traits from the multiple species present. These varying root traits have had a great effect on belowground biomass. One question I hope to address is how the belowground biomass alone affects soil parameters; however, this may pose to be a difficult question because it is hard to compare woody roots to fibrous roots, in terms of biomass.

Image 3. Knapweed roots being separated from the soil during the sieving process. The remnant soil was analyzed for biological parameters and the roots will be scanned for surface area.

Image 4. The taproot system of leafy spurge separated from soil.

Image 5. The expansive taproot and fibrous root network of sulphur cinquefoil.

My research will continue over the summer and likely into the fall semester, especially when considering the time it will take to analyze all of the data. This experience has really enlightened me to the beauty of research: the good, the bad, and the ugly. But I have loved every minute of it. I expect to graduate this upcoming fall and having this opportunity as an undergraduate has been fundamental in my decision to pursue graduate school, and I cannot wait to continue my education.

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