Fire effects on ectomycorrhizal diversity, community structure, and function in the New Jersey Pine Barrens

Wildfires are an inherent part of the system in the New Jersey pine barrens. Consequently, prescribed burning has been conducted regularly since the 1940's to reduce the risk of wildfire. Regions within the pine barrens are subjected to varying frequencies and intensities of prescribed burning, depending on management objectives for each region. Fluxes and exports of nutrients and changes in vegetation have been documented following fire. I was interested in how those changes affected ectomyocorrhizal diversity, community structure and function, since ectomycorrhizae are important to plant function. Therefore, I proposed alternatives to Connell's Intermediate Disturbance Hypothesis and related changes in ectomycorrhizal diversity and community structure to function. I predicted that the most nutrients would be available at intermediate levels of disturbance. Since plants tend to have fewer ectomycorrhizae in environments with more nutrients available, I predicted that ectomycorrhizal diversity would be lowest at intermediate levels of disturbance. Thus, there would be an inverse relationship between diversity and function for these symbiotic mutualists.; To test the above concepts, with the help of the New Jersey Forest Fire Service, I manipulated short-term fire frequency and intensity along a gradient. I also investigated short-term recovery and annual variation. In other locations, identified from burn histories, I studied long-term effects of varying frequencies of prescribed burning. I used morphological traits to describe 120 ectomycorrhizal types. Ectomycorrhizal function was assessed using nutrient uptake bioassays for nitrogen, phosphorus, and potassium.; In all studies, ectomycorrhizal function readily shifted to accommodate increased nutrient availability following fire, regardless of community structure or diversity. There were small shifts in community structure, but no change in diversity in the short-term intensity and short-term frequency studies. There was a large amount of annual variation in nutrient uptake but not in ectomycorrhizal diversity. There was only a significant correlation between ectomycorrhizal diversity and function in the long-term frequency study, with an inverse relationship between ectomycorrhizal diversity and function. Overall, ectomycorrhizal diversity followed the pattern for Connell's Intermediate Disturbance Hypothesis, but ectomycorrhizal function was lowest at intermediate levels of disturbance, so ectomycorrhizal diversity is inversely related to ectomycorrhizal function.