Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Contributed Poster

Session: Biogeochemistry

PS 40-120 - The potential role of termites in neotropical Nitrogen cycling

Wednesday, August 9, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Abstract: Nitrogen availability influences the growth and function of neotropical forests, and has led to decades of research to understand what controls nitrogen inputs. Much of this work has focused on the symbiosis between trees of the Fabaceae family and nitrogen-fixing bacteria, with little understanding of the other symbioses these bacteria form with other organisms (Cleveland et al. 2022). Termites, accounting for 10% of all biomass in the tropics (Bignell 2006) and around 40% of the soil biomass (Rosenberg et al. 2023), and many contain nitrogen-fixing bacteria in their gut that convert atmospheric dinitrogen (N2) into a form that is readily available for use (NH3). Given their ability to fix nitrogen (N) and their pervasiveness in many Neotropical rainforests, termites may have an important influence on the nitrogen cycling of these ecosystems. Other research has identified termite mounds (Sarcinelli et al. 2009) and various other types of nests (Amelung et al. 2002) as significant sources of organic nitrogen in other ecosystems. However, this hypothesis has yet to be explored in Neotropical rainforests. To understand this symbiosis and its ecosystem impacts, we assessed N fixation from five nests of the arboreal termite Nasutitermes corniger at La Selva Biological Station. From each nest we collected nest material and 50 termites (25 workers-25 soldiers) to determine the N and C content. We measured N-fixation rates using isotopically enriched 15N2 gas incubation on termites and their frass. Based on estimates of N. corniger termites found per m2 (Vasconcellos, 2010), we calculated with isotopically-enriched 15N2 incubations of workers and soldiers fixed on average 0.9 Kg of N ha-1 year-1 and 0.37 Kg of N ha-1 year-1, respectively. We found that on average the C:N ratio for the nests (50.7) was significantly higher than frass, soldiers and workers (19.0, 5.20, and 12.3, respectively). Nitrogen made up ~1% of nests in our study, or about 29.8 g of N per nest. Assuming 15 nests per hectare (Vasconcellos, 2010), these nests represent a standing pool of 447 gN ha-1. Our data suggest that termites make up ecologically meaningful N inputs in Neotropical rainforests. This termite-fixed N cycles directly through termite bodies, and is not stored long-term in the nest biomass before being incorporated into the soil. Understanding the impact of these termites in the Neotropics enhances our understanding of the N and carbon cycles by highlighting another potentially important symbiosis fueling N inputs -- termites and N-fixing bacteria.