COS 87-2 - Small mammal activities decrease soil organic carbon storage in dryland ecosystems

Thursday, August 11, 2011: 8:20 AM
Ballroom F, Austin Convention Center
Jane G. Smith1, Heather L. Throop1, Thomas J. Valone2, S.K. Morgan Ernest3 and James H. Brown4, (1)Biology Department, New Mexico State University, Las Cruces, NM, (2)Department of Biology, Saint Louis University, St. Louis, MO, (3)Department of Biology, Utah State University, Logan, UT, (4)Department of Biology, University of New Mexico, Albuquerque, NM

Most of our what we know about the terrestrial carbon (C) cycle comes from research conducted in mesic systems and dryland C cycling dynamics are more poorly understood.  However, arid and semi-arid systems cover 40% of Earth’s land surface and may provide an important C sink that will help mitigate the accumulation of CO2 in the atmosphere.  In drylands small mammal disturbances such as digging and burrowing can affect a large proportion of the surface soil, and these disturbances have the potential to influence inputs to and stability of the soil organic carbon (SOC) pool.  We asked how small mammal activity affects SOC pools in dryland ecosystems.  We hypothesized that small mammals will enhance the quantity and stability of SOC by burying plant litter and increasing organic matter soil inputs and contact with soil minerals.  Alternately, small mammals may reduce the quantity and stability of SOC by disturbing stable soil aggregates and organo-mineral complexes.  We used the Portal Project’s long-term rodent manipulation experiment in southeastern Arizona to test our hypotheses.  We collected soil cores from plots where small rodents have been excluded for over 30 years and from non-exclusion control plots.  Soil was analyzed for SOC and total nitrogen (TN).  


Our results show that the removal of rodents leads to a significant increase in SOC and TN pools relative to control areas (P < 0.01) and that SOC and TN are greater beneath shrubs than in intercanopy spaces (P < 0.0001). These results support our second hypothesis and suggest that small mammal disturbances alter either the inputs to SOC pools or affect SOC stability. Future work will investigate differences in SOC stability between the two treatments.  In drylands, small mammal digging and burrowing may play an important role in C cycling dynamics.

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