Soil carbon distribution and site characteristics in hyper-arid soils of the Atacama Desert: A site with Mars-like soils

https://doi.org/10.1016/j.asr.2012.03.003Get rights and content

Abstract

The soil carbon content and its relation to site characteristics are important in evaluating current local, regional, and global soil C storage and projecting future variations in response to climate change. In this study we analyzed the concentration of organic and inorganic carbon and their relationship with in situ climatic and geological characteristics in 485 samples of surface soil and 17 pits from the hyper-arid area and 51 samples with 2 pits from the arid–semiarid region from the Atacama Desert located in Peru and Chile. The soil organic carbon (SOC) in hyperarid soils ranged from 1.8 to 50.9 μg C per g of soil for the 0–0.1 m profile and from 1.8 to 125.2 μg C per g of soil for the 0–1 m profile. The analysis of climatic (temperature and precipitation), elevation, and some geologic characteristics (landforms) associated with hyper-arid soils explained partially the SOC variability. On the other hand, soil inorganic carbon (SIC) contents, in the form of carbonates, ranged from 200 to 1500 μg C per g of soil for the 0–0.1 m profile and from 200 to 3000 μg C per g of soil for the 0–1.0 m profile in the driest area. The largest accumulations of organic and inorganic carbon were found near to arid–semiarid areas. In addition, the elemental carbon concentrations show that the presence of other forms of inorganic carbon (e.g. graphite, etc.) was negligible in these hyperarid soils. Overall, the top 1 m soil layer of hyperarid lands contains ∼11.6 Tg of organic carbon and 344.6 Tg of carbonate carbon. The total stored carbon was 30.8-fold the organic carbon alone. To our knowledge, this is the first study evaluating the total budget carbon on the surface and shallow subsurface on ∼160,000 km2 of hyperarid soils.

Introduction

The Atacama Desert is located along the western coast of South America throughout the shore region of southern Peru and northern Chile covering about 3500 km, between 10°S to 35°S latitude, and 70°W to 72°W longitude. Because the average values of precipitation in the complete region are less than 200 mm/y, Houston and Hartley (2003) divided this desert according to the aridity index (AI) as semiarid (0.2 < P/PET < 0.5), arid (0.05 < P/PET < 0.2), and hyper-arid (P/PET < 0.05) regions (Fig. 1, Table 1, and Table 1S). This index was calculated as the ratio of precipitation and potential evapotranspiration (P/PET) using Thornthwaite’s equations as a function of mean monthly temperatures and mean monthly number of daylight hours (Thornwaite, 1948, UNEP, 1997). Hyper-arid areas emerge independent of human activities under a natural development and evolution of drier climates denominated “aridization”. This process takes place much more slowly than the processes of “desertification” (Kottek et al., 2006), which are defined as the land degradation in dry areas resulting from climatic variations and human activities (Houerou, 1996). Thus, hyper-arid lands are usually excluded from the consideration of desertification (Schlesinger, 1997). The combined effects of a high pressure system located on the western Pacific Ocean, the cold north-flowing Humboldt Current, and the rain shadow of the Andean Cordillera intercepting precipitation from the inter-tropical convergence are the main factors involved in the hyper-arid climate formation in this region (Arroyo et al., 1988, Houston and Hartley, 2003). These factors have been used in support of geological evidence that the Atacama Desert has remained hyper-arid between 9 and 25 Ma (Alpers and Brimhall, 1988, Dunai et al., 2005, Evenstar et al., 2005). Studies based on sedimentologic evidence estimate that the beginning of continuous hyper-aridity occurred until the Late Pliocene (Hartley and Chong, 2002, Hartley et al., 2005, Houston and Hartley, 2003), a conclusion supported by the end of supergene enrichment of copper deposits in the Atacama Desert (Arancibia and Matthews, 2006). However, this region seems to have had rainfall oscillations throughout its Quaternary history (Betancourt et al., 2000, Latorre et al., 2003). Currently, the mean values of mean annual precipitation recorded between 15°S and 27°S latitude are less than 100 mm/y, for this reason this particular area is considered one of the driest regions on the world (Dillon and Hoffmann, 1997, McKay et al., 2003), and is the object of our principal analysis in this study.

Soil carbon concentrations to a specified depth are needed for calculating current soil C stores (Feng et al., 2002, Kern, 1994, Schlesinger et al., 1990). A shift towards a greater area of arid land potentially represents a permanent loss in the productive capacity of the biosphere (Schlesinger et al., 1990). In addition, relating soil carbon to site characteristics may help in formulating and evaluating static and dynamic models of pedogenic processes (Burke et al., 1989), and in assessing the effect of land use and climate change on soil C stores (Bon, 1982, Feng et al., 2002, Grigal and Ohmann, 1992, Plante et al., 2006, Turner et al., 1993). In this context, few analyses have been made showing the relationship between soil carbon and environmental site characteristics for hyper-arid soils, and even for arid–semiarid regions. Indeed, although other authors have calculated the organic or inorganic carbon concentrations in samples of soils from the Atacama Desert (e.g. Navarro-González et al., 2003, Navarro-González et al., 2006, Ewing et al., 2006, Ewing et al., 2008, Lester et al., 2007), the importance of the total carbon distribution and its relationship with in situ characteristics have not been completely evaluated, perhaps due to the small number of samples used in those works (Ewing et al., 2008, Ewing et al., 2006).

The purpose of this study determines the surface and subsurface soil carbon concentration until one meter deep in the hyper-arid soils of the Atacama Desert in order (a) to evaluate the distribution and deposition of organic and inorganic forms of carbon present there, (b) to compare to arid and semiarid deposits in surrounding areas, (c) to analyze any relationship between carbon concentrations and some geomorphological and climatological variables “in situ”, and (d) to seek differences between the driest areas of Yungay and Pampas de La Joya located in Chile and Peru respectively, which have showed the lowest levels of organic carbon in previous studies (Ewing et al., 2008, Navarro-González et al., 2009, Navarro-González et al., 2006, Navarro-González et al., 2003, Valdivia-Silva, 2009b). Additionally, the predominant abiotic geochemical processes and eolic transportation observed in this region could be used as an excellent analogue in order to understand the carbon cycle present in other hyper-arid environments on Earth and/or Mars.

Section snippets

Site description

The Atacama Desert is located between 10°S and 35°S latitude in Peru and Chile, bounded on the east by the front ranges of the Andes and on the west by the Coast Range. Hyper-arid areas considered in this study were focused between 15°S and 27°S latitude because this encompasses the driest areas of the desert. Chilean and Peruvian areas, Yungay region and Pampas de La Joya respectively, present interesting geomorphological differences caused by variations on the tectonic uplift of the desert

Soil organic carbon (SOC)

Table 2 and Fig. 3 show the soil organic carbon concentrations in the surface and the first meter of depth from three different climatic regions in the Atacama Desert, respectively. For 485 samples of hyper-arid soils, SOC ranged from 1.8 μg C to 50.9 μg C per g of soil in the 0–0.1 m profile and from 1.8 μg C to 125.2 μg C per g of soil in the 0–1 m layer. Interestingly, the lowest values on surface SOC (2.14 ± 0.8 μg C) were found on the site named “Mar de Cuarzo”, located in the Peruvian region (16° 44′

Mars-like soils and perspectives

The role of the geochemical cycle of carbon into processes which have extremely limited amounts of water on Earth and Mars remain poorly studied and understood. The recent identification of calcium carbonate (∼3–5 wt.%) in the soils around the Phoenix landing site (Boynton et al., 2009) has increased interest in understanding these processes and has led, as the present study, to seek a better explanation of the carbon geochemistry on hyper-arid soils and environments considered analogues to the

Conclusions

The purpose of this study was to determine the surface and subsurface soil carbon concentration until one meter deep in the hyper-arid soils of the Atacama Desert in order (a) to evaluate the distribution and deposition of organic and inorganic forms of carbon present there, (b) to compare to arid and semiarid deposits in surrounding areas, (c) to analyze any relationship between carbon concentrations and some geomorphological and climatological variables “in situ”, and (d) to seek differences

Acknowledgments

Funding for this research comes from Grants from the Universidad Nacional Autónoma de México (DGAPA IN107107, IN109110), Consejo Nacional de Ciencia y Tecnología de México (CONACyT 45810-F, 98466, 121479), fellowship from NASA Postdoctoral Program, and by the National Aeronautics and Space Administration Astrobiology Science and Technology for Exploring Planets Program.

References (97)

  • C.P. McKay et al.

    High-frequency rock temperature data from hyper-arid desert environments in the Atacama and the Antarctic Dry Valleys and implications for rock weathering

    Geomorphology

    (2009)
  • G. Michalski et al.

    Long term atmospheric deposition as the source of nitrate and other salts in the Atacama desert, Chile: new evidence from mass-independent oxygen isotopic compositions

    Geochemica et Cosmochemica Acta

    (2004)
  • K. Nishiizumi et al.

    Remnants of a fossil alluvial fan landscape of Miocene age in the Atacama Desert of northern chile using cosmogenic nuclide exposure age dating

    Earth Planet. Sci. Lett.

    (2005)
  • J.A. Rech et al.

    Isotopic evidence for the source of Ca and S in soil gypsum, anhydrite and calcite in the Atacama Desert, Chile

    Geochim. Cosmochim. Acta

    (2003)
  • D.S. Schimel et al.

    Soil organic matter dynamics in paired rangeland and cropland topo-sequences in North Dakota

    Geoderma

    (1985)
  • J.E. Valdivia-Silva et al.

    Thermally evolved gas analysis (TEGA) of hyperarid soils doped with microorganisms from the Atacama Desert in southern Peru: implications for the Phoenix mission

    Adv. Space Res.

    (2009)
  • J.E. Valdivia-Silva et al.

    Multidisciplinary approach of the hyperarid desert of Pampas de La Joya in southern Peru as a new Mars-like soil analogue

    Geochim. Cosmochim. Acta

    (2011)
  • J.E. Valdivia-Silva et al.

    Decomposition of Sodium formate and L- and D- alanine in the Pampas de La Joya soils: Implications as a new geochemical analogue to Martian regolith

    Adv. Space Res.

    (2012)
  • A.P. Zent et al.

    The chemical-reactivity of the Martian soil and implications for future missions

    Icarus

    (1994)
  • C.N. Alpers et al.

    Middle Miocene climatic change in the Atacama Desert, northern Chile: evidence from supergene mineralization at La Escondida

    Geol. Soc. Am. Bull.

    (1988)
  • R. Amundson

    The carbon budget in soils

    Annual Rev Earth Planetary Sci.

    (2001)
  • R. Amundson et al.

    Pedogenic evidence for climate change and aridification on Mars

    Geochim. Cosmochim. Acta

    (2006)
  • R. Amundson et al.

    The climatic and biotic thresholds on soil elemental cycling along an arid and to hyperarid rainfall gradient

    Geochim. Cosmochim. Acta

    (2007)
  • G. Arancibia et al.

    K–Ar and 40Ar/39Ar geochronology of supergene processes in the Atacama Desert, Northern Chile: tectonic and climatic relations

    J. Geol. Soc.

    (2006)
  • M.T.K. Arroyo et al.

    Effects of aridity on plant diversity in the northern Chilean Andes: results of a natural experiment

    Ann. Mo. Bot. Garden

    (1988)
  • S.K. Atreya et al.

    Oxidant enhancement in martian dust devils and storms: implications for life and habitability

    Astrobiology

    (2006)
  • J.L. Betancourt et al.

    A 22,000-year record of monsoonal precipitation from northern Chile’s Atacama Desert

    Science

    (2000)
  • K. Biemann

    Implications and limitations of the findings of the Viking Organic-analysis experiment

    J. Mol. Evol.

    (1979)
  • K. Biemann

    On the ability of the Viking gas chromatography–mass spectrometer to detect organic matter

    Proc. Natl. Acad. Sci. USA

    (2007)
  • H.L. Bon

    Estimate of organic carbon in world soils (II)

    Soil Sci. Soc. Am. J.

    (1982)
  • Biemann, K., Bada, J.L. Comment on “Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes...
  • W.V. Boynton et al.

    Evidence for calcium carbonate at the Mars phoenix landing site

    Science

    (2009)
  • I.C. Burke et al.

    Texture, climate, and cultivation effects on soil organic matter content in US grassland soils

    Soil Sci. Soc. Am. J.

    (1989)
  • M.B. Burkins et al.

    Origin and distribution of soil organic matter in Taylor Valley, Antarctica

    Ecology

    (2000)
  • M.B. Burkins et al.

    Organic carbon cycling in Taylor Valley, Antarctica: quantifying soil reservoirs and soil respiration

    Global Change Biol.

    (2001)
  • J.N. Butler

    Carbon Dioxide Equilibria and Their Applications

    (1982)
  • Davila, A.F., Gomez-Silva, B., de los Rios, A., Ascaso, C., Olivares, H., McKay, C.P., Wierzchos, J., Facilitation of...
  • Dijkerman, J.C., Field description, morphology and sampling of soils. Course in soil science and water management...
  • M.O. Dillon et al.

    Lomas formations of the Atacama Desert, northern Chile

  • K.P. Drees et al.

    Bacterial community structure in the hyperarid core of the Atacama Desert, Chile

    Appl. Environ. Microbiol.

    (2006)
  • T.J. Dunai et al.

    Oligocene-Miocene age of aridity in the Atacama Desert revealed by exposure dating of erosion-sensitive landforms

    Geology

    (2005)
  • J.W. Einax et al.

    Chemometrix in Environmental Analysis

    (1997)
  • G.E. Ericksen

    Geology and Origin of the Chilean Nitrate Deposits, Geological Society Professional Paper 1188

    (1981)
  • G.E. Ericksen

    The Chilean nitrate deposits

    Am. Sci

    (1983)
  • Evenstar, L., Hartley, A.J., Rice, C., Stuart, F., Mather, A., Chong Díaz, G., Miocene-Pliocene climate change in the...
  • Ewing, S.A., Macalady, J.L., Warren-Rhodes, K., McKay, C.P., Amundson, R., Changes in the soil C cycle at the...
  • L.E. Fletcher et al.

    Determination of low bacterial concentrations in hyper-arid Atacama soils: comparison of biochemical and microscopy methods with real-time Quantitative-PCR

    Can. J. Microbiol.

    (2011)
  • G.J. Flynn

    The delivery of organic matter from asteroids and comets to the early surface of Mars

    Earth Moon Planet.

    (1996)
  • Cited by (28)

    • Dust and aerosols in the Atacama Desert

      2022, Earth-Science Reviews
    • The Atacama Desert: a window into late Mars surface habitability?

      2021, Mars Geological Enigmas: From the Late Noachian Epoch to the Present Day
    View all citing articles on Scopus
    View full text