TY - JOUR

T1 - Chemistry and microbiology of the Critical Zone along a steep climate and vegetation gradient in the Chilean Coastal Cordillera

AU - Oeser, Ralf A.

AU - Stroncik, Nicole

AU - Moskwa, Lisa Marie

AU - Bernhard, Nadine

AU - Schaller, Mirjam

AU - Canessa, Rafaella

AU - van den Brink, Liesbeth

AU - Köster, Moritz

AU - Brucker, Emanuel

AU - Stock, Svenja

AU - Fuentes, Juan Pablo

AU - Godoy, Roberto

AU - Matus, Francisco Javier

AU - Oses Pedraza, Rómulo

AU - Osses McIntyre, Pablo

AU - Paulino, Leandro

AU - Seguel, Oscar

AU - Bader, Maaike Y.

AU - Boy, Jens

AU - Dippold, Michaela A.

AU - Ehlers, Todd A.

AU - Kühn, Peter

AU - Kuzyakov, Yakov

AU - Leinweber, Peter

AU - Scholten, Thomas

AU - Spielvogel, Sandra

AU - Spohn, Marie

AU - Übernickel, Kirstin

AU - Tielbörger, Katja

AU - Wagner, Dirk

AU - von Blanckenburg, Friedhelm

N1 - Funding information: Special thanks to CONAF for giving us the opportunity to work in the national parks of Pan de Azúcar, La Campana, and Nahuelbuta. We also thank CEAZA for facilitating access to the Reserva Natural Santa Gracia. We thank Anja Schleicher at GFZ Section 3.1 Inorganic and Isotope Geochemistry for support of XRF analyses. We are grateful for the comments of two anonymous reviewers that helped to improve this paper. This project is funded by the German Science Foundation DFG-SPP 1803 (EarthShape; www.earthshape.net ).

PY - 2018/11

Y1 - 2018/11

N2 - The Chilean Coastal Cordillera features a spectacular climate and vegetation gradient, ranging from arid and unvegetated areas in the north to humid and forested areas in the south. The EarthShape project (“Earth Surface Shaping by Biota”) uses this natural gradient to investigate how climate and biological processes shape the Earth's surface. We explored the Critical Zone, the Earth's uppermost layer, in four key sites located in desert, semidesert, Mediterranean, and temperate climate zones of the Coastal Cordillera, with the focus on weathering of granitic rock. Here, we present first results from 16 approximately 2 m-deep regolith profiles to document: (1) architecture of weathering zone; (2) degree and rate of rock weathering, thus the release of mineral-derived nutrients to the terrestrial ecosystems; (3) denudation rates; and (4) microbial abundances of bacteria and archaea in the saprolite. From north to south, denudation rates from cosmogenic nuclides are ~10 t km−2 yr−1 at the arid Pan de Azúcar site, ~20 t km−2 yr−1 at the semi-arid site of Santa Gracia, ~60 t km−2 yr−1 at the Mediterranean climate site of La Campana, and ~30 t km−2 yr−1 at the humid site of Nahuelbuta. A and B horizons increase in thickness and elemental depletion or enrichment increases from north (~26°S) to south (~38°S) in these horizons. Differences in the degree of chemical weathering, quantified by the chemical depletion fraction (CDF), are significant only between the arid and sparsely vegetated site and the other three sites. Differences in the CDF between the sites, and elemental depletion within the sites are sometimes smaller than the variations induced by the bedrock heterogeneity. Microbial abundances (bacteria and archaea) in saprolite substantially increase from the arid to the semi-arid sites. With this study, we provide a comprehensive dataset characterizing the Critical Zone geochemistry in the Chilean Coastal Cordillera. This dataset confirms climatic controls on weathering and denudation rates and provides prerequisites to quantify the role of biota in future studies.

AB - The Chilean Coastal Cordillera features a spectacular climate and vegetation gradient, ranging from arid and unvegetated areas in the north to humid and forested areas in the south. The EarthShape project (“Earth Surface Shaping by Biota”) uses this natural gradient to investigate how climate and biological processes shape the Earth's surface. We explored the Critical Zone, the Earth's uppermost layer, in four key sites located in desert, semidesert, Mediterranean, and temperate climate zones of the Coastal Cordillera, with the focus on weathering of granitic rock. Here, we present first results from 16 approximately 2 m-deep regolith profiles to document: (1) architecture of weathering zone; (2) degree and rate of rock weathering, thus the release of mineral-derived nutrients to the terrestrial ecosystems; (3) denudation rates; and (4) microbial abundances of bacteria and archaea in the saprolite. From north to south, denudation rates from cosmogenic nuclides are ~10 t km−2 yr−1 at the arid Pan de Azúcar site, ~20 t km−2 yr−1 at the semi-arid site of Santa Gracia, ~60 t km−2 yr−1 at the Mediterranean climate site of La Campana, and ~30 t km−2 yr−1 at the humid site of Nahuelbuta. A and B horizons increase in thickness and elemental depletion or enrichment increases from north (~26°S) to south (~38°S) in these horizons. Differences in the degree of chemical weathering, quantified by the chemical depletion fraction (CDF), are significant only between the arid and sparsely vegetated site and the other three sites. Differences in the CDF between the sites, and elemental depletion within the sites are sometimes smaller than the variations induced by the bedrock heterogeneity. Microbial abundances (bacteria and archaea) in saprolite substantially increase from the arid to the semi-arid sites. With this study, we provide a comprehensive dataset characterizing the Critical Zone geochemistry in the Chilean Coastal Cordillera. This dataset confirms climatic controls on weathering and denudation rates and provides prerequisites to quantify the role of biota in future studies.

KW - Chile

KW - Climate

KW - Denudation

KW - Microbial abundance

KW - Weathering

UR - http://www.scopus.com/inward/record.url?scp=85048768594&partnerID=8YFLogxK

U2 - 10.1016/j.catena.2018.06.002

DO - 10.1016/j.catena.2018.06.002

M3 - Article

AN - SCOPUS:85048768594

VL - 170

SP - 183

EP - 203

JO - Catena

JF - Catena

SN - 0341-8162

ER -