2018 ESA Annual Meeting (August 5 -- 10)

COS 100-1 - Positive demographic feedbacks at the level of mycorrhizal guilds in a temperate forest

Thursday, August 9, 2018: 8:00 AM
238, New Orleans Ernest N. Morial Convention Center
Cassandra Allsup and Richard Lankau, Plant Pathology, University of Wisconsin, Madison, WI
Background/Question/Methods

Climate change is altering tree species distributions, but these responses may vary among functional guilds of tree species. Temperate forest trees are typically associated with either arbuscular mycorrhizal fungi (AMF) or ectomycorrhizal fungi (EMF). Higher functional diversity, impacts on N cycling, and common networks of their symbionts may enable EM hosts to tolerate novel climates better than AM hosts. Furthermore, these traits may create positive feedbacks at the level of mycorrhizal guilds. We hypothesized that tree seedlings will survive better in neighborhoods of their own guild, and that this positive feedback will be modified when seedlings are under drought stress.

We quantified the effects of mycorrhizal guild (EM vs. AM recruitment under EM vs. AM canopy trees) and drought conditions in a field experiment in a temperate forest in central Illinois. In the spring of 2017, we grew seedlings in a split-plot design, where we established 12 large plots with a gradient of AM and EM canopy tree basal area. In each block, we planted six subplots, where three were covered with throughfall reduction shelters, while the others had sham shelters. Each sub-plot had one each of twelve tree species – six AM and six EM species.

Results/Conclusions

In ambient conditions, seedlings showed relatively equal survivorship when growing in plots dominated a matched or mismatched mycorrhizal guild. However, in throughfall reduction subplots, EM seedling significantly increased their survival when under EM canopy trees, and vice versa for AM seedlings. Independently, seedlings tended to survive less well in plots dominated by their own congeners, potentially reflected shared natural enemies.

Climate change is expected to lead to dramatic changes to the species composition of forests. However, unexpected resiliency may emerge at higher functional levels, such as mycorrhizal guilds. Understanding whether the dominant mycorrhizal guild of forests remains stable, independent of species level changes within guilds, may have important implications for future forest functioning.