Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Alexander Smart

Second Advisor

Lan Xu

Abstract

Research was conducted in 2019 and 2020 on rangelands located in south-central South Dakota assessing a number of physical, chemical, and biological properties of mineral ustepts and ustents soils associated with eastern redcedar (ERC) (Juniperus virginiana) afforestation and prescribed fire. ERC afforestation appeared to be associated with significantly higher field-condition soil aggregate stability, cation exchange capacity (CEC), soil pH, and fungi:bacteria (F:B) as well as significantly lower soil moisture, nitrate-N, phosphorus, bacteria biomass, and Gram-positive:Gram-negative (GP:GN) bacteria compared to native grassland conditions, while other mineral soil properties appeared relatively unaffected. Compared to soil conditions under dense, living ERC canopies, prescribed fire over ERC-afforested areas appeared to be associated with significant decreases in soil aggregate stability, ERC duff, magnesium, potassium, and F:B as well as significant increases in field-saturated infiltrability, sediment yield, soil water content, soil pH, calcium, sulfate, and GP:GN bacteria. Fire also appeared to facilitate a number of soil chemical and biological properties to increase (although not always significantly) and trend toward mineral soil conditions resembling more of native grasslands as time progressed post-fire including soil calcium, CEC, nitrate, total nitrogen, organic carbon, phosphorus, pH, soil organic matter (SOM), sulfate-S, actinomycetes biomass, arbuscular mycorrhizal fungi biomass, and bacteria biomass. In particular, land managers should consider how potentially higher soil pH and the indefinite persistence of ERC duff over affected areas may affect land management decisions over these areas post-fire as well as the role of fire and secondary succession of herbaceous vegetation in being successful components to retaining and/or restoring some important properties of native grassland soils. Future investigations around these topics may consider plant-root and soil-cover (duff, litter, living-plant canopies) dynamics on the soil environment (soil temperature, moisture, and structure) and on SOM, the potential impacts that high soil pH may have on succession of plant and microbial communities, the influence of microbial-community composition on plant-species composition and plant biomass in areas undergoing secondary succession, as well as the functional roles that F:B and GP:GN bacteria have under different plant communities and on nutrient cycling.

Publisher

South Dakota State University

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Rights Statement

In Copyright