Comparing fungal communities in Tsuga heterophylla seedling roots across nurse log decay stages and the forest floor

Nurse logs are fallen, decaying trees that have been shown to facilitate the survival, establishment, and growth of tree seedlings, therefore making vital contributions to forest regeneration. Plant-fungi interactions may play a role in influencing seedling survival across nurse log decay and the forest floor. We sought to examine how fungal communities in seedling roots change between nurse logs and forest floor as well as across nurse log decay stages. To study this, we collected western hemlock (Tsuga heterophylla) seedlings (5-10 cm) from nurse logs of each decay stage and the forest floor at three field sites on the Olympic Peninsula, WA. We then removed the root tips and sent them to Jonah Ventures lab for DNA extraction, PCR, and next generation sequencing. We preliminarily categorized fungal OTUs into ecological roles using the FunGuild database and literature search. Fungal community composition varied across substrates with forest floor composition being most similar to nurse log decay stage 3 and least similar to nurse log decay stage 1. No significant trend emerged across substrates for mycorrhizal and pathogenic OTUs, however saprotrophic OTUs increased in nurse logs of decay stages 1 and 2. Future analyses and further literature search may reveal a pattern in mycorrhizal and pathogenic OTUs, specifically when looking into T. heterophylla-specific symbionts and when incorporating distance to parent tree data. Overall, fungal communities change across nurse log decay and the forest floor, which could influence patterns of seedling abundance across these substrates