| Abstract |
Vernal ponds experience hydrologic changes throughout the year that cause heterogeneity in soil redox conditions which alter nutrient bioavailability in the soil. During flooded conditions, minerals such as iron (Fe) remain in a dissolved state, unable to sorb nutrients like phosphate (PO43-). As vernal ponds dry out, oxygen diffuses through the soil causing iron oxides to precipitate. These minerals can sorb PO43-, making it unavailable to organisms. Additionally, seasonal changes within temperate vernal pond soils can affect PO43- concentrations depending on precipitation, temperature and organic matter quality. Generally, as soils thaw, PO43- bioavailability increases due to microbial cell lysis in which nutrients are expelled from cells. Further, fresh leaf litter during autumn can also provide an input of PO43- to these soils. Therefore, I predict that there will be higher concentrations of PO43- in microbial biomass during the autumn and spring seasons. To assess changes in PO43- concentrations in microbial biomass as a function of seasonal variations, we obtained soil samples from lowland soils within a vernal pond and upland soils adjacent to the pond in Northeast Ohio during spring, summer, autumn and winter months. We measured microbial biomass P using traditional chloroform fumigation followed by a salt extraction. Preliminary results show that upland soils have a higher concentration of PO43- in microbial biomass compared to lowland soils. Additionally, upland soils have a higher percentage of organic matter than lowland soils. Further investigation of microbial biomass P will determine how significant seasonal events like thawing and leaf litter additions contribute to PO43- bioavailability in vernal pond soils.
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| Modified Abstract |
Vernal ponds experience hydrologic changes throughout the year that cause heterogeneity in soil redox conditions which alter nutrient bioavailability in the soil. During flooded conditions, minerals such as iron (Fe) remain in a dissolved state, unable to sorb nutrients like phosphate (PO₄³¯). As vernal ponds dry out, oxygen diffuses through the soil causing iron oxides to precipitate. These minerals can sorb PO₄³¯, making it unavailable to organisms. I predict that there will be higher concentrations of PO₄³¯ in microbial biomass during the autumn and spring seasons. To assess changes in PO₄³¯concentrations in microbial biomass during seasonal variations, we obtained soil samples from lowland soils within a vernal pond and upland soils adjacent to the pond in Northeast Ohio within the 4 seasonal changes. We measured microbial biomass P using traditional chloroform fumigation followed by a salt extraction. Preliminary results show that upland soils have a higher concentration of PO₄³¯in microbial biomass compared to lowland soils.
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