Nora Flower

Date of Award

2020

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Oberle, Brad

Area of Concentration

Environmental Science

Abstract

Plant biogeography is a key driver of plant-microbe dynamics in soil. For this reason, it is important to better understand the effects of plant biogeography on soil health parameters. Essentially, the amount of time that a given plant species has been living in a certain region determines the length of time it has had to develop symbiotic relationships with different microbes. These relationships have notable effects on plant and soil health. To study this dynamic, plant biogeography can be categorized in different ways, and determining the best way to categorize it in terms of effects on soil health is an important step toward developing an understanding of these dynamics. 2 potential ways to categorize biogeography are through distinguishing temperate versus tropical and native versus introduced plants. While these binary systems oversimplify complex dynamics, they are still useful for studying the effects of plant biogeography in a concrete and replicable way and may provide a readily applicable index for predicting soil health based on plant-microbe dynamics. This study aims to answer two questions for an urban landscape in Sarasota, Florida: (1) Does plant biogeography impact soil health? (2) Does season impact soil health? To evaluate soil health, I measured microbial activity (respiration rate, bacterial and fungal diversity based on Shannon Diversity Indexes) and soil macronutrients (phosphorus, potassium and magnesium). I characterized plant biogeography in two ways: (1) temperate versus tropical and (2) native versus introduced. I evaluated seasonal impact by comparing bacterial diversity across summer and winter samples. My results indicate that soils of native plants have significantly lower phosphorus and magnesium content than introduced soils, but plant geographic range made no discernable difference. Respiration rate did not differ across soils of different plant biogeographic categories, suggesting that differences in nutrient levels were likely not due to differences in microbial diversity but rather differences in management practices that this study did not account for. Bacterial diversity was significantly higher in summer samples compared to winter samples based on an analysis of Shannon Diversity Indexes, indicating an effect of seasonality. This study demonstrates that season should be taken into account when evaluating soil health. It also suggests the need for further investigation into the effects of management practices on soil health at the Florida House Institute, as well as more research on the effects of plant native status on soil health independent from management-related factors.

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