To what extent do mycorrhizal fungi account for the overall contribution of fungi to the forest ecosystem?

By Jess Windram

Abstract

This project will assess to what extent mycorrhizal fungi account for the overall contribution of fungi to the forest ecosystem. The origins and classification of fungi will be considered, before delving in to the three ecological roles which fungi play in forest ecosystems: mycorrhizal, saprotrophic, and parasitic. It will then look at reasoning and evidence to suggest that mycorrhizal fungi do contribute the most to forest ecosystems.

Next it will look at evidence and reasoning to suggest that in fact saprotrophic and parasitic

fungi contribute more to forest ecosystems, and come to an overall conclusion that overall,

saprotrophic fungi contribute more to forest ecosystems.

Introduction

There are an estimated 2.2 to 3.8 million species of fungi in the world (Sheldrake, 2023), putting them second in abundance to only invertebrates, and well ahead of plants and vertebrates.

However, despite their abundance, they have been significantly overlooked for centuries in

terms of their contribution to forest ecosystems.

There are three main ecological roles of fungi: mycorrhizal, saprotrophic and parasitic.

Mycorrhizal fungi engage in a symbiotic relationship with their plant counterparts, saprotrophic break down dead organic matter, and parasitic feed o􀆯 their live hosts.

These fungi each play important roles in forest ecosystems. For example, the ‘wood wide web’ theorem, published by Suzanne Simard in 1997, has recently gained media and public

attention.

This describes how the trees in a forest are interlinked by fungi ‘threads’, allowing

trees to communicate and share resources with one another. Saprotrophic fungi play major

roles in nutrient cycling and decomposition, as they are the main way dead organic matter gets decomposed into soil, allowing for new growth. Finally, the contribution of parasitic fungi to the forest ecosystem is mostly negative, with fungal diseases such as Ash Dieback and White Pine Blister Rust having devastating impacts on the forest ecosystem.

This project will examine each type of the ecological functions of fungi. It will then delve into

case studies and reasoning to back up each argument, before coming to a final conclusion that saprotrophic fungi contribute the most to forest ecosystems. This is because without them, it is arguable that the ecosystem simply wouldn’t exist.

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