Year of Award

2009

Document Type

Thesis

Degree Type

Master of Science (MS)

Other Degree Name/Area of Focus

Microbiology, Microbial Ecology

Department or School/College

Division of Biological Sciences

Committee Chair

James Gannon

Commitee Members

Matthias Rillig, Thomas DeLuca

Keywords

Arbuscular Mycorrhizal Fungi, Biochar, Black Carbon, Charcoal, Hyphal Abundace, Nutrient availabilities, Root Colonization

Abstract

The following thesis is a two-part study, investigating the influences of biochar (charcoal) on arbuscular mycorrhizal fungi (AMF). The first part of this study is a critical examination and conceptual overview of the literature regarding biochar and AMF available before July 2007. In the second part, I present three experiments all designed to evaluate the influences of biochar applications on AMF abundance in primarily temperate, neutral pH soils. This course of research was selected through an exstensive review of the literature suggesting that biochar presence can strongly affect both soil microbial populations, including mycorrhizal fungi, and biogeochemistry. As both biochar and mycorrhizal associations are subject to management, and because both components are potentially important in various ecosystem services provided by soils (e.g., sustainable plant production) understanding and exploiting interactions between them could be advantageous. After reviewing the experimental evidence for such effects, four mechanisms are proposed by which biochar could influence mycorrhizal abundance and/ or functioning. These mechanisms are: a) alteration of soil physico-chemical properties; b) indirect effects on mycorrhizae through effects on other soil microbes; c) plant-fungus signaling interference and detoxification of allelochemicals; and d) provision of refugia from fungal grazers. Through this overview, a roadmap for research is provided, which is aimed at testing these mechanistic hypotheses. Using this proposed framework as a template, three experiments were designed and implemented, incorporating three different soils, five different biochars, and eight different biochar application rates. Through these experiments, it was illustrated that five different types of biochar are all capable of significantly altering soil orthophosphate availabilities, with four of these biochars not significantly affecting soil pH. Overall, our results indicate that AMF abundances were either unchanged or decreased with biochar amendment across multiple treatments. These results also indicate that biochar, depending on the nature of the feedstock, the temperature attained during pyrolysis and amounts applied can significantly alter soil properties including phosphate availability. These findings may have implications for soil management where the goal is to increase the services provided by AMF.

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© Copyright 2009 Daniel Warnock