Final report for GNC22-340
Project Information
Exploring the Effects of Prairie Restoration Management on Soil Microbial Carbon Storage
Integrating restored prairies into agricultural landscapes has emerged as a strategy for providing key ecosystem services like increasing biodiversity, reducing erosion and runoff, and supporting pollinator communities. These prairies can also act as valuable soil carbon sinks, though they often fall short of their carbon storage potential. This study aims to help farmers maximize carbon storage on their land by examining the influence of prairie management choices on soil microbial carbon dynamics, asking how prairie seed mix richness influences soil microbial carbon use efficiency and what this means for total soil carbon stores. Increasing soil carbon in agricultural systems has the potential to restore soil carbon stores lost through the transition to cropland and to offset ongoing agricultural greenhouse gas emissions. This work is particularly relevant with the Conservation Reserve Program’s recent addition of extra incentives for Climate-Smart Practices, including increasing carbon sequestration. By filling a key knowledge gap in managing for maximized soil carbon storage, this work can inform climate change mitigation efforts and thus contribute to increased environmental quality and quality of life in agricultural systems and beyond.
We sampled soils from a series of row crop agricultural fields planted to corn, oldfields abandoned from agriculture, prairies seeded with a low-richness seed mix of twelve plant species, and prairies seeded with a high-richness seed mix of seventy plant species. We compared carbon and microbial metrics across these soils to see how these different land management strategies affected soil carbon pools and microbial carbon use efficiency. We partnered with MiSTRIPS, the Kellogg Biological Station, Michigan State University Extension, the Osher Lifelong Learning Institute, and Western Michigan University to reach local stakeholders in 2023 and 2024. Informed by our research, we presented the results of our work to these groups and created a decision-making tool to share with managers. We will continue to disseminate our results by submitting articles to academic and farmer-focused publications and presenting at local and national scientific conferences.
We found that agricultural soils consistently had the lowest soil carbon stores, but the oldfields and both types of prairie were comparable to each other. Similarly, agricultural soils had the lowest microbial biomass and activity (as measured by respiration), while old fields and prairies were again similar. This indicates that taking land out of production and re-introducing perennial plants to the landscape has positive effects on soil carbon, regardless of whether land is managed as prairie or has a higher richness seed mix. Interestingly, when respiration was standardized to the amount of microbial biomass present, agricultural soils had significantly higher carbon respired per microbial biomass carbon, indicating that, while there were fewer microbes present in agricultural soils, the ones that were there were releasing carbon to the atmosphere at a higher rate, perhaps contributing to the lower carbon stores in agricultural soils.
We discussed our research at outreach events at the Kellogg Biological Station, created and distributed a decision aid pamphlet for blueberry farmers at a Michigan State Extension event, and reached the wider community through running courses with the Osher Lifelong Learning Institute and as part of Western Michigan University's Spring Into Action series. We were successful in distributing our materials about the benefits of prairies in agroecosystems, including distributing prairie seed to interested Osher Lifelong Learning Institute and Spring Into Action attendees who went on to plant backyard prairies.
Research Objectives: Compare soil carbon pools and soil microbial metrics across different land management types to determine how taking land out of active production (oldfield treatment) and converting formerly agricultural land to prairie (prairie treatments) affects soil carbon storage. Furthermore, we wanted to explore how the seed mix richness of the prairie restoration affected soil carbon storage, comparing low (12 species) and high (70 species) seed mix treatments. Through this work, we aim to provide farmers with actionable information about the level of management and financial investment needed to meet soil carbon storage goals.
Outreach Objectives: Leverage partnerships with Michigan State University Extension, MiSTRIPS, Kellogg Biological Station, Western Michigan University, and the Osher Lifelong Learning Institute to network with with local stakeholders and initiate two-way conversations about prairie establishment on Michigan farms, focusing on landowner needs and barriers they anticipate facing in these efforts. Then, informed by these conversations, present the results of our project and distribute our educational products to the groups.
Cooperators
- (Educator and Researcher)
Research
This work took place in 12 fields under conventional agricultural management (corn), 12 oldfields abandoned from agriculture, and an existing suite of 12 restored prairies at the Kellogg Biological Station in southwest Michigan. The prairies were restored from oldfields in 2015, and they range from 0.2-3.5 hectares. Each prairie is divided in half, one side planted with a 12-species seed mix (“low-richness”) and the other with a 70-species seed mix (“high-richness”). Each half-prairie and cornfield are hereafter referred to as “sites”, with 48 total sites for the project.
In August 2023, we collected fifteen 5cm soil cores to a depth of 10cm at each site. The cores were equally spaced from each other and the field edges to ensure a representative sample of the field area. Cores were composited and stored on ice until analysis. Once in the lab, samples were aseptically passed through a 2mm sieve and analyzed fresh or stored in the fridge until analysis, as appropriate. All analyses were performed in Dr. Kathryn Docherty’s lab at Western Michigan University unless otherwise noted.
I used the data collected in this effort to address the following research questions:
Q1: How does land management influence soil microbial communities and soil carbon pools?
Q2: How does land management influence how efficiently soil microbial communities use carbon?
Answers to these questions will help inform the overarching, applied question: "How do management choices influence soil microbial CUE and the potential for long-term soil carbon storage?"
We have completed a suite of standard soil physiochemical measurements (pH, water content, water holding capacity, bulk density, aggregate distribution, total phosphorous, nitrate, and ammonium). We have also measured several carbon-related metrics (microbial biomass carbon and nitrogen via chloroform fumigation extraction, total organic carbon and nitrogen, microbial respiration, and soil organic matter). We sent samples to Brookside Labs to analyze carbon-to-nitrogen ratios, and to RegenAg Labs to complete PLFA analysis. We will measure CUE using the 18O-water stable isotope tracing method.
Oldfields, low-richness prairies, and high-richness prairies all had larger soil carbon pools (as indicated by soil organic matter, % total carbon, and microbial biomass carbon) than agricultural fields. High-richness prairie soils also trended towards higher % total carbon than oldfields. When considering microbial respiration (the amount of carbon released as CO2 by soil microbes), agricultural soils had the lowest rate, while low-richness prairies had higher rates than oldfields, indicating more net CO2 is released by low-richness prairies. However, when respiration was standardized to the amount of microbial biomass present, agricultural soils had significantly higher µg C respired per µg C of microbial biomass, indicating that, while there were fewer microbes present in agricultural soils, the ones that were there were releasing carbon to the atmosphere at a higher rate, perhaps contributing to the lower carbon stores observed in agricultural soils.
Overall, while some weak trends in our data suggest it may provide more benefits to restore a prairie using a high-richness seed mix, our data indicate that stopping tillage and re-introducing perenniality to the landscape - in the form of either prairies or oldfields - can have positive effects on soil carbon storage goals. Despite weak evidence for an advantage to restoration over letting agricultural fields progress to oldfields where our measured soil health goals are concerned, prairie restoration remains a key tool for restoring native plant diversity to the landscape, reducing agricultural runoff, and supporting pollinator communities.
In the attached graphs, different letters indicate means are significantly different from each other at at least the p < 0.05 threshold, grayed letters indicate p values between 0.05 and 0.1.
Educational & Outreach Activities
Participation Summary:
In September 2023 and January 2024, I attended two outreach events at the Kellogg Biological Station, where I connected with local farmers and landowners on a one-on-one basis for relationship building and informal conversation about interest in questions raised by the funded work.
In June 2023 and July 2024, I taught workshops for the Osher Lifelong Learning Institute (OLLI) called "The Wild World of Prairies" which introduced participants to the prairie ecosystem and the benefits prairies provide, including some of the data from this project. I provided participants with guides for identifying prairie plants and starting backyard prairies, and I sent all participants home with seed to establish a small prairie plot of their own. The OLLI audience consists primarily of retired folks in the Kalamazoo, MI area. In April 2024, I taught this same workshop to the broader Kalamazoo community through Western Michigan University's Spring Into Action climate series.
In September 2024, Dr. Kathryn Docherty, Dr. Liz Schultheis, and I ran a booth at a Blueberry Farmer Field Day through Michigan State University Extension. The audience at this event was primarily blueberry growers, with some agronomy professionals present. We discussed the benefits of incorporating prairies in blueberry farm systems, including some of the results from this work. In preparation for this event, another grad student (Rachel Drobnak) and I developed a tri-fold informational pamphlet on the benefits of prairies in blueberry systems, including considerations for how and where to plant these prairies and local cost-share resources.
Also in September 2024, I tabled for MiSTRIPS at the Kellogg Biological Station LTER All-Scientist Meeting. I distributed this pamphlet and discussed the general benefits of prairie plantings in agricultural systems. The audience for this meeting was primarily scientists and agronomy professionals, though some farmers did attend.
Journal articles and presentations at scientific conferences are forthcoming.
Project Outcomes
Learning Outcomes: After presenting our results to local stakeholders and the larger scientific community, we expected both audiences would have an increased awareness of the benefits of establishing prairie plantings in agricultural systems and increased knowledge of the trade-offs associated with different prairie management techniques. We also anticipated that both audiences would have an increased appreciation for the importance of soil microbial communities to soil health – specifically, to soil carbon dynamics. Through conversations with farmers, land managers, and the general public during our outreach activities, we determined this outcome was successful.
Action Outcomes: After attending our summary presentation or reading our educational materials, I anticipate land managers will have increased openness to installing prairies on their farms and increased openness to considering belowground-minded management. Through conversations with farmers, land managers, and the general public during our outreach activities, we determined this outcome was successful. Specifically, while at the blueberry field day, we had a lot of interest from farmers and several folks left contact information in order to learn more about local resources for establishing prairies on their land. In addition, after the OLLI course, I have had several attendees submit photos of the backyard prairies they planted on their land.
We were surprised to see that the differences in measured soil characteristics between oldfields and the two prairie seed mix types were so minor or non-existent, particularly when plant communities are so clearly visually different between the site types. We have been considering several different explanations for these observations. Since these prairies were restored from oldfields, the oldfield land use history may be overwhelming any prairie effects. Perhaps sites had been abandoned from agriculture long enough prior to prairie planting that they were already nearing their maximum carbon storage potential. It also just could be that for our measured characteristics, which plants are present doesn't matter as much as whether you have stopped tilling and allowed perennial plants to move back into the landscape.