"the State of Soil Streamlines Secondary Succession: Remediating Degrad" by Madeline Gregory

the State of Soil Streamlines Secondary Succession: Remediating Degraded Soils in a Post-agricultural Field

Date of Award

12-12-2024

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Ryan McEwan

Abstract

The abandonment of fields once used for industrial agriculture is a global phenomenon that is an increasing occurrence in the American Midwest. Fallow lands that were previously used for agriculture create both a challenge and an opportunity for ecosystem restoration and are an important goal for regional land management organizations. Management practices used in agriculture including large heavy equipment, intensive herbicide and pesticide use, and establishing monocultures of crops results in the loss of biodiversity and poor soil quality which creates obstacles for native reestablishment. In this thesis, I outline the results of a research project that aims to ameliorate the negative influences of industrial agriculture through Ecosystem Restoration. Specifically, I analyzed the influence of prairie seed mixes and soil amendments applied in a fully replicated, landscape scale, on the physicochemical and biological properties of the soil. These treatments were applied with the intent of facilitating succession in a post agricultural field by creating soil conditions that were more reflective of soils had not experienced the degradation associated with industrial agriculture. This project is in collaboration with the local conservation organization, the Five Rivers Metroparks, with a long-term goal of restoring the site to its historical state of a mature native forest. To assist with this transition, we applied one of four mixes of native prairie seeds, and one of four soil amendments (16 total treatments, each replicated 5 times). This study began in the summer of 2019 with the establishment of 20 (50 × 50 m) square plots in a former agricultural field, each of which received one of four native prairie seed treatments that varied by number of species present (diversity) and weight of legume (5% or 20%). These plots were then sub-divided into 4 subplots, each of which received one of four soil amendments which include a whole soil inoculation, a leaf compost treatment, a combination of whole soil and leaf compost, and a control. Soil samples were collected for the assessment of (a) nutrient levels and (b) activity of carbon cycling enzymes phenol oxidase, peroxidase & β-glucosidase. Samples were collected along two transects within each subplot in 2019 (pre-treatment), 2020, 2021, 2022 and 2023 to assess the state of the soil composition and microbial activity following intensive agriculture and to monitor how the trajectory changes over time and in relation to the treatments applied. I found that soil physical and chemical properties are significantly different in 2023 compared to 2019. We found that over time the soil is compositionally changing with an increase in organic carbon matter (C) and important nutrients crucial for plant growth such as Mg, K and Na. Over time there was a decrease in soil acidity, N content and heavy metals such as Mn and Al. Subplots which received the leaf compost treatment experienced a significant increase in % organic matter. There was no evidence to suggest that the whole soil treatment influenced microbial activity. My results suggest that number of species included in the seed mix played a role in % organic matter, N release and β-glucosidase activity with each of these variables being greater in plots which received a higher diversity seed mix. Plots treated with a higher % of legume weight didnot experience a significant increase in N content. Microbial analysis revealed that for all enzymes tested there was a significant decrease in plots treated with a lower diversity seed mix composed of 20% legumes. We believe this decline in activity is driven by microtopography and drainage rather than the content of the seed mix. My thesis research provides insight into ecosystem restoration in abandoned agricultural fields and provides impetus for further research about this ecological concern.

Keywords

ecosystem restoration, post agricultural soil, soil restoration, soil amendment, succession, secondary succession, native prairie, forest restoration, organic matter, plant diversity, oxidative enzyme, microtopography, abandoned agricultural field

Rights Statement

Copyright © 2024, author.

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