Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Thorn, Greg

Abstract

A few species of boreal trees form symbiotic relationships with many ectomycorrhizal (ECM) fungi that allow trees to thrive on nutrient poor soils in Canada. A small number of ECM species grow on tree seedlings raised in nurseries for reforestation of clearcut sites. The native ECM fungal community composition of a mixed spruce-fir forest in Newfoundland was determined through next generation sequencing. With the introduction of nursery seedlings, the transfer of native ECM fungi to seedlings and nursery-established ECM fungi to roots was investigated over 20 months. ECM community composition was found to be similar to that of other boreal forests in Canada. Seven taxa likely transferred from roots to seedlings but none were transferred from seedlings to roots. Maintaining the composition of native ECM communities is key to forest health and this study suggests that reforestation practices in Canada do not alter native ECM community composition within the studied time-frame.

Summary for Lay Audience

Mutually beneficial relationships between fungi and plant roots, termed mycorrhizal associations, are found in over 90% of terrestrial plants. There are different types of mycorrhizal fungi, including ectomycorrhizal (ECM) fungi, which form underground connections with tree roots in forest stands and are of importance in Canada for their production of edible mushrooms such as chanterelles (Cantharellus) and supporting boreal tree species by performing functions such as nutrient and water uptake. The assemblage of ECM fungi in a given area is referred to as a community and the composition of a community may be influenced by the plant community, soil moisture, temperature, acidity, climate and other ecological factors. Previous studies have determined the ECM community composition of boreal forests in Canada, but there are currently no published studies of Newfoundland forests.

In Canada, tree seedlings raised in nurseries are often planted for the purpose of reforestation in forest sites that have been clearcut and have their own ECM community composition, with many of the same species found in nurseries globally. Little is known about the effect that ECM fungi established on nursery seedlings have on natural forest ECM fungi once the seedlings are planted.

By sequencing fungal DNA found on roots, my project determined the natural community composition of ECM fungi of a mixed spruce-fir forest in Newfoundland, and with the introduction of nursery seedlings to the same forest, the transfer of natural ECM fungi to seedlings and nursery-established fungi to natural roots was investigated over 20 months. ECM community composition was found to be similar to that of other boreal forests in Canada. Seven ECM fungi likely transferred from natural roots to seedlings, and no ECM fungi transferred from seedlings to natural roots. Due to the important role of ECM fungi in supporting forests, maintaining the composition of natural ECM communities is key and this study suggests that reforestation with nursery raised seedlings in Canada does not alter natural ECM community composition within a short time-frame.

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