NASA Astrobiology Institute (NAI)

1. Hindcasting Ecosystems

   Project Investigators: Hector D' Antoni, Jay Skiles

   Other Project Members

   Seth Burgess (Research Staff)

   Lidia Burry (Collaborator)

   Nora Madanes (Collaborator)

   Cynthia Schultz (Research Staff)

   Matilde Trivi (Collaborator)

   Jeanette Zamora (Research Staff)

   Ignigo Aguirre de Carcer (Collaborator)

   Virgilio Correcher (Collaborator)

   Jorge Frangi (Collaborator)

   William Swearson (Research Staff)

   Summary

   Using the vegetation of South America as an analog to the biosphere of an earth-like planet, this project links Earth Science to Astrobiology. A past-ecosystem-process model was created to predict the history of the carbon cycle in terms of Net Primary Production (NPP). Proxy data were used to reconstruct the past sea surface temperature (SST) of the last 754 years at 1-year resolution. Based upon the high correlation between SST and the vegetation index (NDVI), soil types, potential evapotranspiration, water retention capacity, and nitrogen concentration in soils, the model predicted past NPP for most continental ecosystems of South America.

   Astrobiology Roadmap Objectives:

   • Objective 6.1: Environmental changes and the cycling of elements by the biota, communities, and ecosystems

   Project Progress

   Our contribution to Astrobiology Roadmap Objective 6.1, is entitled, “Environmental changes and the cycling of elements by the biota, communities, and ecosystems” and is a past-ecosystem-process model. The Hindcasting Ecosystems Model (HEMO) uses proxy data to predict past net primary production (p-NPP), as follows,

   p-NPP= LGS/p-NDVI * (PET/ p-NDVI) * p-NDVI * (N in soil/p-NDVI)

   Climate is represented by the length of the growing season (LGS), soil by concentration of nitrogen in soils (N in soil) and Potential Evapotranspiration (PET), and vegetation by the vegetation index (NDVI). SST holds high correlation with NDVI and hence, our tree-ring based reconstruction of past SST was used to infer past NDVI. With these predictions we reconstructed past NPP at 1-year resolution (Figures 1, 2, and 3). In order to validate our assumptions on changes in NDVI related to changes in the forcings of climate during the Holocene (volcanic, orbital, and solar) we explored the history of these forcings over the last 754 year. While the orbital and solar forcing could account for changes of a few calories in the solar energy received at the surface of the Earth, the volcanic forcing produced a maximum cooling of SST starting in 1453 when the Kuwae volcano erupted explosively in the New Hebrides and elevated the concentration of non-marine sulfates to 1380 μg per liter of ice in Antarctica. The aerosols of this eruption shaded the Earth and lowered the SST of the South Atlantic and the Western Pacific for several years. This and other volcanic eruptions have affected terrestrial vegetation of South America and hence the carbon cycle in the period 1246-2000. The project produced an SST reconstruction cross referenced with the record of volcanic eruptions in Antarctica, 754 maps of past NDVI, 754 maps of NDVI deviations from the average value for the period 1246-2000, and 41 reconstructions of past NPP (as those shown in Figures 1, 2 and 3). These data will be available to users at the Earth Science Division website.

   
   

   Lago do Caju (Brazil): Reconstruction of past NPP by HEMO model.

   
   

   Resistencia, Chaco (Argentina): Reconstruction of past NPP by HEMO model.

   
   

   Semidesert of Patagonia (Argentina): Reconstruction of past NPP by HEMO model.

   
   

   Solar UV spectral irradiance measured with a CCD high-resolution spectroradiometer in Madrid, at 7:38 AM on June 4, 2008.

   
   

   Thermoluminiscence detection of solar UV-C excitation by a specific alkaline halide dosimeter. (30 seconds exposure simultaneous with the spectral measurement shown in Figure 4).

   Field Expeditions

   Name

   Solar measurements in Tierra del Fuego

   Dates

   November 17, 2007 - November 21, 2007

   Location

   54 degrees 43' South 68 degrees 18' West

   Description

   Spectral recording.

   Name

   Solar Irradiance Measurements

   Dates

   November 25, 2007 - December 2, 2007

   Location

   La Plata 34°55' S; Punta del Este 34° 58' S La Plata 57° 38' W; Punta del Este 54° 58' W

   Description

   Spectral recording

   Name

   Solar UV-C irradiance at ground level I

   Dates

   May 4, 2008 - May 12, 2008

   Location

   40° 24' North 3° 47' West

   Description

   Cross-checking photo- and thermo luminescence of alkaline halides doped with Europium 2+ and CCD spectrometers in the detection of UV-C. Choice of methods.

   Name

   Solar UV-C irradiance at ground level II

   Dates

   May 31, 2008 - June 30, 2008

   Location

   40° 24' North 3° 47' West

   Description

   Simultaneous measurements of Solar UV-C radiation with dosimeters and CCD spectrometers.

Publications

Aguirre de Carcer, I., D'Antoni, H.L., Correcher, V., Barboza-Flores, M. & Jaque, F.  (2008).  KCl: Eu2+ as a solar UV-C radiation dosimeter. Optically Stimulated Luminescence and Thermoluminescence analysis. [Abstract].  REMAT2008 (International Conference on Rare Earth Materials. Karpacz, Poland. (Accepted, July 2008)..

Burry, L.S., Trivi de Mandri, M.E. & D’Antoni, H.L.  (2007).  Modern Analogues and Past Environments in Central Tierra del Fuego, Argentina.  Anales del Instituto Patagonico (Chile), 35(2):5-14.

D'Antoni, H., Rothschild, L., Schultz, C., Burgess, S. & Skiles, J.W.  (2007).  Extreme environments in the forests of Ushuaia, Argentina.  Geophysical Research Letters, 34(L222704, doi:10.1029 / 2007GL031096, 2007):1-5.

D'Antoni, H.L.  (2008).  Arqueoecología Sistémica y Caótica (Systemic and Chaotic Archeo-ecology): Textos Universitarios (University textbooks).  Consejo Superior de Investigaciones Científicas, Madrid, Spain.

D'Antoni, H.L., Rothschild, L.J. & Skiles, J.W.  (2008).  Reply to comment by Stephan D. Flint et al. on "Extreme environments in the forests of Ushuaia, Argentina".  Geophysical Research Letters, 35(L13711 doi: 10.1029 / 2008GL033836).