Measuring warfare in wood: linking competition among wood-degrading fungi of northern forests to its ecological consequences

Abstract

Competition between distinctive groups of fungi determines the pattern of wood decomposition in forests, but the outcome of these battles may shift in a changing climate. With more than 70% of Earth's biotic carbon stored in woody tissues, understanding the processes that unlock this carbon and release the greenhouse gas CO₂ is critical. For my thesis research, I am addressing several key questions about how fungi colonize and dominate wood on the forest floor. Quantitative PCR was developed to measure biomass of specific fungi from a community in Chapter one. This technique was coupled with ergosterol, dilute alkali solubility, pH and carbon component analysis to measure biotic and abiotic dynamic during wood decomposition. With these comprehensive tools, factors that may influence fungal competition and decomposition outcomes were studied in the following chapters. In Chapter two, wood type was shown not to influence the competition between a brown rot fungus and a white rot fungus. It is contrary to the observations on wood preferences in nature, but reflected different foraging strategies by fungi. This led to the study of Chapter three on priority effect. By increasing the inoculum potential either inside or outside wood substrate, I have shown evidence that a weak competitor fungus can outcompete its more aggressive opponents, thus achieving co-existence. Another two factors, temperature and endophytes, along with priority effect were studied in Chapter four. Endophytes showed a much larger effect in influencing wood decomposition than temperature, mostly through antagonisms against soil fungi. Studies on these factors reveals potential for a more comprehensive model for wood decomposition. Emphasis on the role of microbial components, especially the often neglected endophytic communities, is possible to explain the variability in wood decomposition that can not be explained by abiotic factors, alone.