Agroecology in Southern IL: Field Notes from July

Roosevelt University Sustainability Studies major Allison Breeding was awarded a National Science Foundation-funded Research Experience for Undergraduates (REU) fellowship this summer at Southern IL University. This is the fifth installment of weekly blogs this summer from Allison on the work she is doing for her research fellowship.

For July, we had a variety of planned field trips and activities earlier in the month:

  • Ecological Measurement sessions on soil carbon storage and sequestration, animal population ecology and aquatic community ecology
  • Readings on offsetting global carbon change, noninvasive sampling techniques for studying animal populations, and long-term monitoring of biological communities in aquatic ecosystems
  • Checking grassland traps for small mammals, trapping demonstration for local mesocarnivores (bobcats and coyotes), introduction to tracking wild turkeys using radio telemetry
  • Electrofishing and aquatic community assessments in the Campus Lake—we mostly caught large-mouth bass during electrofishing, but there were a few bluegill and croppie as well.
  • Off-trail tour of three ecological areas in Shawnee (Caney Branch Barrens, Fink Sandstone Barrens, Burden Falls) with IDNR employee Chris Evans. These sites were just lovely—the ground was covered in splotches of moss, lichens, prickly pear, etc.
  • Lecture on agricultural practice impacts on watersheds, by Maria Lemke of the Nature Conservancy—Maria is working with local farmers on a series of paired watershed projects along the Mackinaw River
  • Lecture on grassland bird population benefits from the Conservation Reserve Program’s (CRP) grassland restoration efforts, by Dr. Jim Herkert (director of office of resource conservation at IDNR)
  • Lecture on the Illinois Wildlife Action Plan to Conserve Freshwater Mussels, by Ann Holtrop of IDNR. Ann is a stream ecologist currently serving as head of IDNR’s Watershed Protection Section
  • Lecture on three wildlife conservation case studies by Dr. Clay Nielsen of SIU: Jaguars, Pumas and Prey in Sonora, Mexico; Wildlife Conservation and Biodiversity Assessments in Panama; and the Human-Big Cat Conflict in Central India—tensions and fatalities from the proximity of dense village populations to the Tadoba-Andhari Tiger Reserve

But final lab tests, data analysis and developing our presentations took precedence during the middle and end of July:

Fumigating samples

Fumigating samples

I used chloroform to fumigate 18 of my serum bottle subsamples in a desiccator, where they remained for 24hrs before I evacuated and incubated them for 10 days. Afterwards, I ran air samples from these 18 Fumigated samples and the 18 Non-Fumigated samples through the gas chromatograph (GC) to compare carbon and nitrogen concentrations and calculate microbial biomass for each treatment group (i.e., CT, NT and ORG).

I injected air samples from my 18 intact cores through the GC four more times over a span of 20 days (for a total of five readings). I used the data from these tests to determine rates and amounts of CO2 respiration and N2O flux for each of my treatment groups.

The ~20g soil subsamples I previously ground and dried in the oven were weighed, compacted into tin packets, and then analyzed using dry combustion elemental analysis—where a lab machine essentially combusts all contents of the tin packet, separates each element, and then produces readings for each element. From this I obtained how much total carbon and nitrogen were present among my treatment groups.

The 18 additional 10cm Giddings cores I collected at the end of June were weighed whole, then broken apart at their natural aggregate seams until they could be passed through an 8mm sieve, and picked over for large roots and debris. I then collected ~20g of soil each from the 18 broken-down cores, weighed it and dried it (the soil’s fresh weight and dry weight were used to calculate soil bulk density). I separated an additional ~100g from each broken-down core to use for aggregate tests.

Wet sieving samples

Wet sieving samples

Wet sieving to determine soil aggregation was the most time-consuming lab test I conducted. My 18 dried ~100g subsamples were individually soaked in deionized water for five minutes, then gently agitated in water through a large macroaggregate sieve (>2000 micro meters), a small macroaggregate sieve (250-2000mm), and a microaggregate sieve (53-250mm). At each sieving stage I deposited what the sieve collected into aluminum pans by rinsing the sieves out with deionized water, and then placed the filled pans in an oven to dry out. The smallest soil remnants (<53mm), or the silt and clay particles, that passed through the microaggregate sieve were also deposited with water into aluminum pans. Once the pans were dried, they were weighed and compared against the whole sample’s fresh weight to calculate the percentages of different-sized aggregates within each sample.

This wet-sieving process could be tedious and slow-going because I had to be careful not to spill or lose any of the sample at any stage—if the percentage of soil recovery was found to be too low after totaling a sample’s dry weights, the sample would be compromised and I wouldn’t be able to determine aggregation. Fortunately, my anal-retentiveness paid off here; my lowest soil recovery rate across all 18 samples was 97.11%! 🙂

Once I obtained all of my data and compiled them into a spreadsheet, I began running calculations with my mentor to determine my soil moisture content, bulk density, and means and standard errors, etc to start graphing my data sets. For me, this was the most intimidating and difficult part of my fellowship experience. Considering I’ve only taken intro to stats in the past (and that was years ago), and I had never worked with this type of data, formulas or graphing software (Sigmaplot and SAS) before, none of this was intuitive to me. But thanks to the dedication (and patience!) of my mentor and others, I was able to gain a better grasp of how these pieces fit together. With that, it was time to tie everything together for my project presentation!

In my final note from the field, I’ll reflect on my summer’s overall experience and provide info on my project’s presentation.

Allison BreedingAllison Breeding is a senior Sustainability Studies major at Roosevelt University. She was awarded an agroecology research fellowship through a National Science Foundation-funded Research Experience for Undergraduates (REU) fellowship this summer at Southern IL University. This summer she is writing from the field as a SUST at RU guest blogger.

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