Mycorrhizal Abundance and Diversity: Factors Determined by Forest Succession

Abstract

Mycorrhizae are fungus that generally form symbiotic relationships on the roots of 90% of all terrestrial plant species. There are the two main categories of mycorrhizae: Arbuscular mycorrhizae typically grow on herbaceous plants, while ectomycorrhizae grow on woody plants. Forest succession in Wisconsin has recognized shifts in dominant tree species as outlined by Curtis and McIntosh (1951). Soils in temperate forests have been shown to increase in N and P during these shifts. Mycorrhizal growth is affected by soil nutrient levels, as median N and P results in highest mycorrhizal growth. This study assessed how mycorrhizae and soil nutrients change throughout forest succession in Wisconsin forests. Four forests that fall along a successional gradient were examined by both surveying and soil core samples to determine the abundance of both types of mycorrhizae. Three 20x20m plots in each forest were visited once per month to extract soil cores. Results show that soil nutrients showed no large changes with succession. Overall ectomycorrhizal abundance tended to be highest in intermediate stage forests, and lowest in early stages of succession. Arbuscular mycorrhizae showed peaks in mid succession, but results varied. Findings suggest that although mycorrhizae may show broad successional patterns, they tend to level off when moving into mid and late stages of succession. Additionally, the amount of water in the soil likely plays a very prominent role in the mycorrhizal community.