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

Authors :
Mirjam Schaller
Francisco Matus
Rafaella Canessa
Dirk Wagner
Friedhelm von Blanckenburg
Leandro Paulino
Maaike Y. Bader
Thomas Scholten
Todd A. Ehlers
Michaela A. Dippold
Roberto Godoy
Kirstin Übernickel
Sandra Spielvogel
Svenja Stock
Yakov Kuzyakov
Liesbeth van den Brink
Katja Tielbörger
Peter Kühn
Juan Pablo Fuentes
Ralf A. Oeser
Nicole Stroncik
Lisa-Marie Moskwa
Jens Boy
Pablo Osses Mc-Intyre
Peter Leinweber
Oscar Seguel
Emanuel Brucker
Rómulo Oses Pedraza
Marie Spohn
Moritz Köster
Nadine Bernhard
Source :
Catena
Publication Year :
2018

Abstract

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 Azucar 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.

Details

Database :
OpenAIRE
Journal :
Catena
Accession number :
edsair.doi.dedup.....65f2fc29614b8ab31a7b0d6157c85a9a