Project 17:
Saguaros are experienced high mortality in their Sonoran Desert homes due to unprecedented heat waves and wildfires for which they are not adapted. Efforts to replace saguaros with young plants are challenging because we know little about the more efficient strategies to maximize their success in fire affected landscapes. We know that nurse plants are important for young saguaros but we don’t know if particular nurseplants would be more helpful post-fire. The student will use soils from different saguaro nurse plants to grow saguaros from seed and determine which nurse plants promote saguaro growth the best. In particular, we are interested in nurses that associate with nitrogen fixing bacteria and those that do not as our preliminary work with saguaros in the greenhouse suggests that lack of nitrogen can severely limit saguaro growth. The project relates to NASA goals because saguaros are some of the most stress tolerant plants as they can survive high temperatures and drought. However, it unclear how important soil microbes are to this stress tolerance and to reestablishment after an additional stressor they are not used to – fire.
The student would help the PIs collect soil in the desert from five different species of nurseplants. They would plant saguaro seeds in the soil and growth them in the NAU Research Greenhouse. During the first semester the student would monitor germination and seedling growth. They would also characterize the soils for soil nutrients and texture. During the second semester the student would harvest some of the small saguaros to measure their biomass and rates of root colonization by beneficial microorganisms that our previous studies suggest are important for saguaro seedling establishment. This procedure involves clearing and staining root samples and observing them under the light microscope to count fungal structures. During the second semester the student would also analyze the germination, size, biomass and root colonization data and prepare a poster and presentation on their results. Ideally, the student would work 8 hours per week during the academic year.
The work adds to research efforts by Gehring, Rowe and Dr. Nancy Johnson on the conditions required for saguaro cactus reestablishment following disturbance. The data collected by the student would be added to citizen science generated nurse plant surveys in a paper for the journal Restoration Ecology. The student would be an author and could be the lead author if they have time for that in addition to their coursework. The student would also present a talk or poster at NAU’s undergraduate expo and at the NASA Space Grant symposium.