Publications
Zeiner, C. A., Kisch, M. N., Lynch, E. D., Shrestha, P., & Small, G. E. (2024). Soil microbial activity profiles associated with organic compost fertilizers in an urban garden. Urban Agriculture & Regional Food Systems, 9, e20059. https://doi.org/10.1002/uar2.20059
Abstract:
Biological soil health is recognized as an important component of sustainable agriculture due to microbial biomineralization of nutrients. However, soil health can be difficult to assess consistently across urban agricultural systems due to diverse land use histories, soil heterogeneity, and lack of mechanistic links to agricultural management practices (e.g., recycled compost addition) and crop outcomes. In this study, we characterized soil microbial activity profiles in an urban agriculture system in Minnesota, USA, including microbial abundance, soil respiration, extracellular enzyme activity, and crop yield. Garden plots were fertilized with recycled organic compost (either manure or municipal) at high or low rates (ranging from 2.6 to 39 tons ha−1) targeted to crop N and P demands. Control plots received inorganic fertilizer or no fertilizer. We found that a high application rate of manure compost supported 6–10x higher basal respiration than municipal compost or inorganic fertilizer. Enzyme activity data demonstrated that soil microbial communities exhibited unique profiles of biochemical function that varied among fertilizers of different compositions. Microbial biochemical function predicted 50% of the variability in bell pepper (Capsicum annuum) yield, while soil microbial community size alone was a poor predictor of yield. Yield was highest in plots fertilized with municipal compost, outperforming inorganic fertilizer by threefold. High-yield plots exhibited higher ratios of N to P enzyme activity compared to those with lower yield. Our findings demonstrate that “more is better” may not necessarily be true regarding soil microorganisms in biological soil health, and that measures of soil microbial biochemical function may be more important.
Summary:
This is a report of findings from the 2019 sediment coring of Bone Lake and School Lake completed as a collaborative project between the St. Croix Watershed Research Station and the University of St. Thomas. Each core was analyzed for Lead-210 activity to develop a dating model for each lake and determine the sediment accumulation rate over the past 150-200 years. Sediments were analyzed for inorganic, organic, and carbonate components using loss-on-ignition analysis. Geochemical analyses also included sediment phosphorus and biogenic silica. Subfossil diatoms and algal pigments were analyzed to reconstruct changes in lake ecology and trophic state. The full summary of the report can be found through the citation link below. My contribution was in data curation; formal analysis; funding acquisition; and investigation with Bone Lake. Refer to the "presentations" section of this page for more details on the analysis of Bone Lake.
Ramstack Hobbs, J.M., M.B. Edlund, K.M. Theissen, T. Edmundson, E. Lynch, and J. Wallick. 2020 A Paleolimnological Study in the Comfort Lake Forest Lake Watershed District: Phase II. Final report submitted to Comfort Lake Forest Lake Watershed District. St. Croix Watershed Research Station, Science Museum of MN, 55047. https://www.clflwd.org/document/2020-paleolimnology-report/
Projects
Cellobiohydrolase Enzyme Activity Predicts Ascomycete Fungal Growth Rate
This paper summarizes the research completed in an undergraduate capstone Biology research project. Fungal enzymatic activity was investigated for potential predictive applications on growth rate.
Link to the document here
Current Metallocentric Paradigms for Mitochondrial ROS Dismutation and Utilization
This paper summarizes the current understanding of the utility of mitochondrial reactive oxygen species (ROS), the role of metals in biochemical redox mechanisms for ROS dismutation and speciation.
Link to the document here
Southern Great Basin Paleohydrology Report
This report summarizes describes climatological trends in the southern great basin and range area in the Lake Mead area in Southwest United States.
Link to the document here
Brownie Lake Geochemical Report
This report summarizes the Geochemical trends in Brownie Lake, MN, 2020 using data from the water column, a collected sediment core, historical imaging and records.
Link to the document here
Manganese Nodules Synthesis Presentation
This presentation recording describes what Manganese Nodule are before exploring our understanding of the processes that drive the synthesis of manganese nodule formation
See the presentation by clicking below
A Hydrogeological Characterization of the Hazardous Waste Site at Seymour, IN
This report investigates the town of Seymour, IN, through a hydrogeological lens to understand the spread of Tetrahydrofuran chemical pollutants from a closed recycling plant in the local environment.
Link to the document here
Presentations
Urban Garden Soil Microbial Community CO2 Respiration Correlated with Fertilizer Input
Lynch ET, Anderson GR, Kisch MA, Paulsen RH, Zeiner CA. Stewardship Garden Soil Microbial Community CO2 Respiration Correlated with Fertilizer Input. Undergraduate Research Symposium, Oct 2021.
Ethan Lynch using the LiCOR to measure microbial CO2 respiration
While urban gardening is an increasingly common suggested solution for food deserts in urban communities, urban ecosystems are hot spots of inefficient internal biogeochemical cycling of nutrients. Although urban garden biogeochemical budgeting studies have identified systemic inefficiencies, the mechanistic pathways describing how ecosystem structure affects the flow of nutrients through systems remains poorly understood. Since microbial soil communities drive soil nutrient fluxes, the Zeiner Lab seeks to better inform best management practices by characterizing the effects of microbial soil communities on biogeochemical systems between various fertilizer treatments in urban garden plots. Here we determine whether soil moisture and pH parameters are significant predictors of in-lab CO2 respiration measurements of six different fertilizer treatments across a three bi-weekly sampling dates beginning in July 2021. Conclusions from this work show that pH is not a significant environmental predictor of CO2 respiration rate. However, while the soil moisture data is shown to describe some variability in the data, the soil moisture data also positively correlates with the organic carbon content in the soil. This correlation motivates future analysis to better understand these overlapping trends and make a more definitive statement regarding the impact of soil moisture on CO2 respiration. Since CO2 respiration is a well supported proxy for microbial nutrient scavenging which increases the bioavailability of nutrients such as nitrogen, phosphorus, and minerals for crops, we suggest that fertilizer treatments accounting for the existing carbon availability in soils are better poised to promote plant growth, regardless of the impact of soil moisture on CO2 respiration. Future works seeks to add proteomics data to temporally correlate soil biogeochemical changes with the microbial activity.
The Role of Manganese in Carbon Degradation by Ascomycete Fungi
In the summer of 2019, Ethan Lynch and the Zeiner Lab researched the role manganese plays in carbon degradation by Ascomycete Fungi. Our experiment tested the impact the presence of manganese has on the ability of four Ascomycete Fungi to grow on three carbon sources. The carbon sources varied from recalcitrant to more labile. We used three carbon sources to vary recalcitrance- from left to right in order of most to least recalcitrant: Tannic Acid (TA), a 50/50 by weight mix of TA and Carboxymethylcellulose (CMC), and CMC. Through image analysis, we were able to discover that manganese causes a statistically significant increase in the growth rate of less competitive Ascomycete Fungi species (Pyrenochaeta, Staganospora, and Paraconiothyrium) on the most recalcitrant carbon source we tested. The competitive generalist species, Alternaria Alternata, did not show a correlation between presence of manganese and growth rate. We concluded that the utility of manganese correlates with increased recalcitrance in less competitive species. Future work will focus on understanding mechanisms and the reasons for variance in the utility and tolerance of manganese among Ascomycete Fungi.
Ethan Lynch presenting his summer research at the 2019 Fall Inquiry Research Symposium
Lynch ET and Zeiner CA. Presence of Manganese (II) Confers Growth Benefit to Litter-Degrading Ascomycete Fungi on Recalcitrant, but not Labile, Carbon Sources. Ecological Society of America Annual Conference, Virtual, Aug 2020.
Ethan Lynch presenting his work in an artistic interpretation at the 2019 Sidewalk Symposium
Bone Lake: Evaluating Past and Present Ecosystem Health
Lynch ET and Theissen KE. Bone Lake: Evaluating Past and Present Ecosystem Health.
2020 Scholars at the Capitol, St. Paul, March 2020.
Dr. Mark Edlund (left) and Ethan Lynch (right) working on extracting a sediment core
Ethan Lynch and Dr. Kevin Theissen partnered with Dr. Mark Edlund and other scientists at the St. Croix Watershed Research Station to complete a geochemical record for one of several lakes selected in the Comfort Lake Forest Lake Watershed District. This project was completed to understand how the lake ecosystem has changed since European settlement in order to efficiently allocate limited financial resources for ecosystem rehabilitation. For this project, a sediment core was collected from Bone Lake and split at the University of Minnesota's LacCore Facility. Then three techniques (Loss on Ignition, Carbon to Nitrogen Analysis, and Pb-210 age dating) were used to paleolimnological history. Four significant events were shown. Between 1860-1900, a doubling of sedimentation occurred as the area became settled. Then, in 1920, a dramatic increase in sedimentation, potentially due to clearing of forested area and local farmland development. CaCO3 became significant and continued an upward trend suggesting increased algal growth due to excess nutrient runoff. The third event, beginning around 1960, was driven by inorganic sediment likely due to housing development. Current trends suggest that Bone Lake is eutrophic.
Ethan Lynch (left) and Dr. Kevin Theissen (right) at the Minnesota 2020 Scholars at the Capitol