Collaborative Grant: RAPID: Capturing a critical transition in fungal wood endophyte communities by rapid-response sampling post-hurricane in Puerto Rico.

Endophytes are organisms that live inside plants. These inhabitants were long invisible to scientists studying plants, but with the advancement of DNA-based assessment tools, researchers have discovered an increasing diversity of organisms that reside inside healthy plants. Endophytes include hundreds of microbial species (bacteria and fungi) that live in healthy wood inside standing trees. Some provide benefits to the host tree, but others, particularly fungi, may attack and/or weaken trees (pathogens) or may try to get a head start decomposing wood (saprotrophs). In addition, there are many microbes present as endophytes with functions that have yet to be determined. Determining these functions is a critical need for predicting the risk of tree hazards, and for modeling rates of decomposition and carbon released once a tree dies. Accurately predicting wood decay is difficult and presents a significant uncertainty in carbon cycle models. To improve predictive power, it is necessary to model a key transition that occurs when a tree dies a natural death, killing many endophytes but exposing a payoff to others that rise to dominate these subsequent microbial communities, particularly saprotrophs. This research makes use of a natural disturbance event, the great deal of tree damage created by Hurricane Maria in Puerto Rico, to study how endophytes shape the fungal decomposition communities that develop post-disturbance. With this knowledge, it is possible not only to improve decomposition models but also better predict endophyte success, an asset for predicting tree hazard risks in future hurricanes. The project also offers opportunities for STEM training of several female team members, including Puerto Rican collaborators affected by Hurricane Maria. It will also lead to production of a public video describing the science, the scientists, and the role of endophytes in tree hazards and decomposition processes in nature.

The goals of this project are to track the development of tree endophyte fungi post-hurricane in Puerto Rico's Guanica Forest scientific area, and to correlate this process with environmental variables and wood traits (e.g. nitrogen content). There are three specific objectives to reach this goal, 1) rapid-response sampling to assess fungal communities present at time zero, 2) tracking communities at two additional time points to assess persistence of endophytes, and 3) matching outcomes over one year to site climate data (temperature, rainfall) and to wood substrate physiochemistry. This study includes wood sections from 14 tree species, either cut and left in ground contact to decay along a transect or remaining standing as a stump section. A key hypothesis is that endophyte saprotrophs will have a greater influence on decomposition in standing sections rather than in ground contact, but that the overall rates of decomposition will be influenced by climate and wood physiochemical variables, particularly wood nitrogen and heartwood content. The study design allows coupling of community structure and function with host traits over time.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.