Mycorrhizal fungi are ubiquitous and influential symbionts of most terrestrial plants, and their communities have been observed to replace each other over time in predictable successional order. Ecologists have no understanding how successional suites of mycorrhizal fungi differ functionally or how changes in functional traits relate to effects of mycorrhizae on plants. Changes in the conditions of such an important symbiosis must have broad consequences for plant community and ecosystem-level dynamics. Thus, establishing an experimental and theoretical basis for understanding consequences and causes of trait variation in distinct, successional mycorrhizal communities is the central theme of the work proposed.
Coastal California pine forests harbor the best-studied examples of mycorrhizal succession in the world. In them a very different suite of mycorrhizal species colonize seedlings in burned areas and open dunes compared to mature forest settings, where seedlings are linked to adult trees in common mycorrhizal networks (CMNs). Experiments have shown that recruiting seedlings in forests respond very differently to these two guilds of mycorrhizal fungi; however, ecologists do not understand why these ectomycorrhizal fungal communities change over time, or how successive functional traits of successive fungi relate to their effects on plants. Growth chamber experiments, along with the results of a three-year field experiment in a coastal California Monterey pine (Pinus radiata) forest, wil establish differences in the mechanisms by which early- and late-stage fungi influence seedling performance in the forest understorey.
The proposed work will have broad implications for conservation and silviculture. In its native range of California and Mexico, Monterey pine is limited to five small populations, some of which are at risk of extinction. Outside this range, it is one of the most widely planted timber species in the world, covering millions of acres on multiple continents. As an exotic, it is both a valuable commodity that preempts the need to harvest native timber and an aggressive invader, often naturalizing in ecosystems. Three undergraduate students, a graduate student and a postdoctoral research will receive research training as part of this research.
