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Friday Philosophicals - Fall Semester 2021

Friday Philosophicals featuring Tyler Watson and Erica Stroud on December 3, 2021

Tyler Watson: Investigating mycelial-crop residue mat application to reduce early-colonizing weeds in row-crop agriculture
Erica Stroud:
Short-term vs. long-term responses of soil carbon and microbial activity to warming and nitrogen addition in a temperate old field

Friday Philosophicals run most Fridays by Zoom (check the schedule). Seminars start at 3:30 pm and are expected to end by 4:20 pm.

Each week a Zoom invite will be distributed to bioseminar-ee@uwo.ca. Contact thain@uwo.ca if you are not on this list and need the Zoom login details.

December 3, 2021

Tyler Watson: Investigating mycelial-crop residue mat application to reduce early-colonizing weeds in row-crop agriculture

Tyler Watson photo Supervisor: Dr. Greg Thorn

Herbicide use within conventional agriculture has contributed to greatly increased crop yields since its widespread adoption, however environmental concerns regarding overuse and reliance on selective herbicides continue to mount. Using five fungal species and two crop residues in a factorial design, I created a novel slurry to control weeds through inhibition by the mycelial mat formed after application to soil. I monitored weed stem counts and the strength of the mycelial mat under the treatments. Additionally, as a proxy for crop yield, I measured the wet and dry weight of crop plant grown under application treatments. Weed prevalence was significantly reduced when compared to a bare soil control, but not when compared to a substrate only control without fungal inoculum. Similar strength values were recorded between treatments and control, suggesting poor colonization of the substrate under greenhouse or field conditions. No significant weed reduction was achieved in field trials.

Erica Stroud:  Short-term vs. long-term responses of soil carbon and microbial activity to warming and nitrogen addition in a temperate old field

Erica Stroud photoSupervisor: Dr. Hugh Henry

Climate warming and atmospheric nitrogen deposition are two global change drivers expected to exert strong effects on northern temperate ecosystems over the next century. I added new nitrogen addition and warming plots to a pre-existing nitrogen addition and warming field experiment in London, Ontario to compare the short-term (1-2 year; new plots) versus long-term (14-15 year; old plots) treatment effects on soil carbon and microbial activity. I used soil density fractionation and size fractionation to separate soil carbon fractions and analyzed carbon quality using FTIR. I used extracellular enzyme assays to assess microbial responses. The soil organic matter free light fraction increased in response to nitrogen addition in the old plots but decreased in the new plots. Interactions between warming and plot age were significant for some hydrolase enzymes. These results confirm short-term responses of soil carbon and microbial activity differed from long-term responses in this global change field experiment.

November 26, 2021

Dariusz Wojtaszek: Applying stable isotope techniques to evaluate origins of northern pintails (Anas acuta) harvested in Canada

Dariusz Wojtaszek photo Supervisors: Drs. Keith Hobson and Ben Rubin

The Northern Pintail (Anas acuta) is a waterfowl with population levels consistently below long-term management goals. Conversion of native habitat agriculture limits recruitment and population growth. My objective is to provide a proof-of-concept of how stable isotope ratios can complement existing pintail management. I used hydrogen isotope ratios (δ2H) in feathers to determine that the most likely origins of harvested pintails are in the northern boreal region of Canada, despite long-term population estimates attributing most of the pintail population being supported by the Canadian prairies. I used carbon and nitrogen stable isotope ratios (δ13C, δ15N) to differentiate individuals originating in boreal biomes, rather than agricultural-influenced prairie habitats. These findings can be used by wildlife managers to inform adaptive harvest management protocols and population models of pintails.

Noor Saeed Cheema:  Manipulating the root mycobiome of corn (Zea mays) to enhance plant performance and reduce pathogen pressure

Noor Saeed Cheema photoSupervisor: Dr. Greg Thorn

Manipulating the root mycobiome of crops could potentially increase yield by reducing pathogen pressure and improving access to soil water and nutrients. However, identifying organisms that can induce these effects remains a challenge. My objective is to investigate how selected fungal isolates affect plant performance and the root mycobiome when applied to soil in which corn seedlings are grown under growth room conditions. In previous studies, A&L Biologicals observed major productivity differences within fields of corn, soybean, and wheat rotations. Root-associated fungi from corn were identified and isolated in culture. Comparing the fungal communities in high- versus low-yielding sites may help identify key fungal isolates that could improve crop productivity. Corn seeds were sown into soil from low-yielding sites inoculated with potentially beneficial fungal strains, with or without a co-inoculated soilborne fungal pathogen of corn, to quantify if different inoculation regiments affect crop health, productivity, and the soil mycobiome.

November 19, 2021

Matt Meehan: From individuals to communities: The effect of climate change on ectothermic predators

Matt Meehan photo Supervisor: Dr. Zoë Lindo

In my PhD, I used feeding and mesocosm experiments to examine how climate change affects ectothermic predators at the individual-, population-, and community-level, using mesostigmatid mites (Arachnida: Parasitiformes) as my model predator. With feeding experiments, I showed that predator mites increasingly fed on small-bodied but not large-bodied prey under warming, which lowered their energy intake. I hypothesize predators lowered their handling costs associated with smaller prey, rather than maximize energy gain by feeding on larger prey to offset higher metabolic demands. Furthermore, with predator mite and collembolan prey populations, I found that greater exposure of predators (and prey) to warmer temperatures increased the average size of their prey and strengthened predator-prey interactions, suggesting predators increasingly fed on smaller prey. Finally, I observed that short-term intensive warming shifted soil Mesostigmata assemblages, which was primarily due to the increased abundance of a single asexual species, Veigaia mitis.

Katarina Kukolj:  Investigating the effects of the Blewit Mushroom Lepista nuda on the community composition of its soil environment

Katarina Kukolj photoSupervisor: Dr. Greg Thorn

This study will investigate the effects of the edible Blewit mushroom (Lepista nuda) on the community composition of its soil environment in coastal regions of Newfoundland, Canada. Previous studies on Blewits have discovered antimicrobial properties in the lab, but there have been no field studies to observe how the soil and the organisms in it could change by growth of Blewit mycelium in their natural environments. Therefore, this study includes sampling soil at various time points from known natural Blewit patches and nearby treatment plots inoculated with Blewit mycelium. Arthropod, nematode, bacterial and fungal members of the soil community will be identified, and their relative abundance determined by DNA metabarcoding analyses. These results will tell us if potential crop pests and plant pathogens are significantly reduced by the growth of Blewit mycelium, which could lead to use of Blewits as an environmentally friendly biopesticide and potential co-crop.

November 12, 2021

Simone Miklosi: Evaluating the ability of nuclear environmental DNA (eDNA) to determine number of individuals and biomass of Atlantic salmon

Simone Miklosi photo Supervisor: Dr. Bryan Neff

Environmental DNA (eDNA) is an emerging population assessment tool with considerable potential for fishes. Current eDNA approaches largely focus on mitochondrial genes, which are used to determine the presence or absence of a species of a fish in a particular habitat. Nuclear genes, and microsatellites in particular, have the potential to provide increased population-level information about abundance. Microsatellites are commonly used in population genetics because they typically have considerable standing genetic variation. Despite the potential use of microsatellites for eDNA, the reliability and consistency of the microsatellite genetic information obtained from water samples remains uncertain. My research will capture and extract eDNA from water samples collected from tanks and streams containing differing numbers of Atlantic salmon to compare the microsatellite genotypes inferred from the water samples to those of the individuals. Preliminary work has established four working microsatellite primer pairs and the successful recovery of microsatellite alleles from water samples.

Alicia Banwell:  At the root of it: The introduction of nursery seedlings and their fungi into conifer forests

Alicia Banwell photoSupervisor: Dr. Greg Thorn

Ectomycorrhizae (ECM), a type of association between fungi and plants, are of importance in Canada for their role in supporting boreal tree species and are of interest for their production of valuable edible mushrooms such as chanterelles (Cantharellus). ECMs are present in a wide range of habitats, including natural forest stands, forest stands that have experienced severe disturbances, and seedlings reared in nurseries for reforestation efforts. Little is known about the effect that nursery established ECMs have on forest environments once seedlings are planted. My project will investigate whether ECMs established on nursery seedlings continue to persist once planted in forests, or if existing ECMs in forests, such as Cantharellus, form associations with seedlings. This knowledge can be used to improve reforestation practices by protecting existing valuable ECMs in forests, or to provide the forestry industry with the ability to form associations of valuable mushrooms, such as Cantharellus, on seedlings.