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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 4 weathering and denudation rates and provides prerequisites to quantify the role of biota in future studies.

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Andisols present exceptional physical properties, making up < 1% of the world's soils. While there is a lot of information about non-volcanic soil properties, research about soils of volcanic origin is limited. Specifically, no major studies have been carried out to improve our knowledge of these soils' hydrological behavior, which is relevant due to the impact of climate change on water resources and to the soil's role in the hydrological cycle. Thus, the aim of this work was to analyze the water content dynamics of a soil slope derived from volcanic ashes under different land covers. We hypothesized that land cover, rainfall, and air temperature, in addition to the hydraulic properties of the volcanic ash soil, regulate the slope's water content dynamics. Our study was conducted in S Chile, in a fluvial terrace covered by pastures in the uplands, a native forest in the adjacent slope, and a hygrophilous forest in the floodplain at the base of the slope, surrounding a stream. Soil physical properties, such as bulk density (Db), volume of macropores (wCP), plant available water (PAW) and saturated hydraulic conductivity (Ks) were studied. Rainfall, air temperature, volumetric water content ( Field ) and soil temperature were continuously measured with data loggers. The groundwater level was also measured. Water content dynamics reflect the behavior of rainfall and air/soil temperatures under different land covers, as well as, revealing the specific behavior of volcanic soil's pore system (e.g., Db < 0.9 Mg m -3 ). Soil depths exposed to more intensive and dynamic wetting and drying cycles presented well-defined water release ranges as compared to the pore system of deeper soil horizons. Soils present large water holding capacities (PAW > 24%), however, during summer they can reach volumetric water contents near to the permanent wilting point quickly at a depth of 5 cm. The water table altitude was directly related to the temporal changes of Field measured at a depth of 50 cm, highlighting the fact that the saturated and unsaturated zones are connected.