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Discipline: Ecology Environmental and Earth Sciences
Subcategory: Biochemistry (not Cell and Molecular Biology and Genetics)
Odemaris Carrasquillo Quintana - University of Puerto Rico Mayaguez Campus
Co-Author(s): Shaquetta Johnson, Jackson State University, Jackson, MS Thomas C. Harmon and Angel S. Fernandez Bou, University of California, Merced, CA
Leaf-cutter ants (LCA) play an important role in carbon dynamics, especially in America’s lowland rainforests. Analyzing and understanding the controls on carbon fluxes into and out of soils helps address critical uncertainties in the global carbon cycle. In this work, we focused on Atta cephalotes, the most abundant LCA species in Mesoamerica, and its contribution to the carbon cycle. This research was conducted during the summer period at La Selva Biological Station, a lowland tropical rainforest located in northeast Costa Rica. Our focus was to quantify A. cephalotes nest CO2 emissions under variable weather conditions (rain, temperature and wind). Our hypothesis was that rain events will result in decreasing soil effluxes and compensating increases in vent/entrance fluxes. The secondary hypothesis was that the soil effluxes from nest areas will be generally greater than those for undisturbed soils due to soil structural modifications by the ants. With this aim in mind, many measurements were made after rain events in order to analyze their impact on soil effluxes. We observed that after a rain event the soil efflux tended to decrease as a results of reduction or blockage of the diffusion pathway. However, vent fluxes increased, a result we attributed to wetness or saturation of the surrounding soils causing CO2 diffusion to occur mainly through vent openings. For the three sites tested, analysis of variance revealed a significant difference for nest and control soil fluxes for several sampling events of site 1 and several marginally significant differences for site 2. In addition, analysis of variance for the response surface demonstrated a significant linear model of nest 3 fluxes as function of drain time (i.e., time following rain event). Overall, our studies point to the important link between soil CO2 emissions and precipitation in wet neotropical forests. However, key factors such as soil porosity/bulk density, soil texture, micro-topography and drainage time play important roles in CO2 soil diffusion, and vary significantly in time and space. For this reason, these factors merit further consideration in terms of contributions to the global carbon cycle by dominant herbivores like leaf-cutting ants.
Funder Acknowledgement(s): This research was conducted under the National Science Foundation - Luis Stocks Alliance for Minority Participation (LSAMP) fund. The investigation was developed as part of the Research Experience for Undergraduates (REU) program that took place at La Selva Biological Station in Costa Rica, in collaboration with the Organization of Tropical Studies (OTS).
Faculty Advisor: Thomas C. Harmon, tharmon@ucmerced.edu
Role: I was responsible of the development of the research questions, the work plan, data collection and analysis of results. In order to collect the data, I focused in the use of CO2 chambers in order to complete flux measurements on the nest soil and vents.
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