DISSERTATION RESEARCH: Scaling Plant Physiology to Ecosystem Ecology: Assessing the Role of the Plant Community in Preventing Nitrogen Losses Following Fire

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DEB-1601279 Wright, Justin P., Duke University: DISSERTATION RESEARCH: Scaling Plant Physiology to Ecosystem Ecology: Assessing the Role of the Plant Community in Preventing Nitrogen Losses Following Fire.The availability of soil resources, such as nutrients and water, influence the diversity of plants at local and global scales. Disturbances such as fires can drastically change resource availability to plants. For example, ecosystems that experience frequent fires also experience surges of nitrogen availability after the fire. Although nitrogen is a crucial resource for all plants, nitrogen not captured by plants can be washed away and contribute to the pollution of streams and lakes. As such, it is important to understand how plant diversity might change if nitrogen availability changes, and subsequently how the ability of the plant community to retain nitrogen might also change. Investigators will examine whether plant communities that have experienced frequent pulses of nitrogen are better able to capture nitrogen and prevent it from leaving the ecosystem than are plant communities that have not experienced nitrogen pulses. This research will help to predict how plant communities respond to changes in nitrogen availability, and how patterns of nitrogen retention and loss are affected by fire frequency. As part of this project, one undergraduate student will gain hands-on experience in field ecology and laboratory chemical analyses. In addition, the investigators will develop teaching activities to improve understanding of N cycling at local and global scales by undergraduate students. Data from this study will be added to a database used to estimate the global carbon cycle. The findings of the study will be disseminated in peer-reviewed journals and at national conferences.This project is an empirical field test of patterns identified in greenhouse studies of interspecific differences in pulsed nitrogen assimilation. The researchers will trace the fate of nitrogen into different ecosystem compartments in a longleaf pine (Pinus palustris) forest, using isotope analysis in sites with contrasting historical fire frequencies (annual burns or fire suppression). Researchers will measure the amount of isotope stored in microbial biomass, aboveground and belowground biomass of dominant plant species, and the bulk soil pool. By comparing the amount of nitrogen stored in different compartments between sites under annual burn or fire suppression regimes, they will assess the extent to which plant communities exposed to frequent nitrogen pulses are adapted to capturing this ephemeral resource. Further, they will test whether these interspecific differences in the capacity to capture pulsed nitrogen scale up to influence ecosystem-level nitrogen retention patterns in the field. The researchers predict that shifts in community composition favoring species adapted to assimilating ephemeral nitrogen will result in increased nitrogen retention in frequently burned sites, as compared to fire-suppressed sites.