We provide geochemical data for three sites that define a gradient of erosion rates – an “erodosequence”. These sites are the Swiss Central Alps, a rapidly-eroding post-glacial mountain belt; the Southern Sierra Nevada, USA, eroding at moderate rates; and the slowly-eroding tropical Highlands of central Sri Lanka.
Specifically, we provide silicon isotope ratios and germanium/silicon ratios and the major element composition of 1) rock, 2) saprolite, 3) soil, 4) plants, 5) river dissolved loads, 6) the soil and saprolite amorphous silica fraction (accessed with a NaOH leach), and 7) the soil and saprolite clay-size fraction (isolated with a differential settling protocol). These data serve two purposes. First, they allow us to improve understanding of the controls on silicon isotopes and germanium/silicon ratios in the 'Critical Zone'. Specifically, we can quantify the fractionation factors (for silicon isotopes) and the exchange coefficients (for germanium/silicon ratios), for secondary mineral precipitation and for biological uptake. Secondly, we can use mass-balance approaches to quantify the partitioning of silicon - a nutrient, and a major rock-forming element - among secondary minerals, plant material, and solutes.
All samples are assigned with International Geo Sample Numbers (IGSN), a globally unique and persistent Identifier for physical samples. The IGSNs are provided in the data tables and link to a comprehensive sample description.
This data set contains chemical and Mg isotope analyses of time-series creek water, subsurface flow (0-15cm and 15-150cm), vegetation, regolith, clay-sized fraction and exchangeable fraction of regolith from a catchment of the Black Forest, Germany. This dataset is a following work of “Uhlig, D., & von Blanckenburg, F. (2019)", in which major and trace elements concentrations and 87Sr/86Sr isotope data was reported on the same batch of samples. With the new Mg isotope analyses, we investigated the potential controlling factors on water Mg isotopic composition, and we found exchange reactions in our catchment are a primary control on water chemistry. To further interrogate this finding, a batch of adsorption and desorption experiments using soil samples from our study site were carried out. The adsorption and desorption experiment results are also included here. This combination of field research and lab experiments informs about processes fractionating Mg in the critical zone – with the role of the exchangeable pool highlighted as particularly important – and further verifies the potential of Mg isotopes as a tool in tracing continental weathering process. Samples are assigned with International Geo Sample Numbers (IGSN), a globally unique and persistent Identifier for physical samples.
We provide geochemical background data on the partitioning and cycling of elements between rock, saprolite, soil, plants, and river dissolved and solid loads from at three sites along a global transect of mountain landscapes that differ in erosion rates – an “erodosequence”. These sites are the Swiss Central Alps, a rapidly-eroding post-glacial mountain belt; the Southern Sierra Nevada, USA, eroding at moderate rates; and the slowly-eroding tropical Highlands of Sri Lanka.
The backbone of this analysis is an extensive data set of rock, saprolite, soil, water, and plant geochemical data. This set of elemental concentrations is converted into process rates by using regolith production and weathering rates from cosmogenic nuclides, and estimates of biomass growth. Combined, they allow us to derive elemental fluxes through regolith and vegetation. The main findings are: 1) the rates of weathering are set locally in regolith, and not by the rate at which entire landscapes erode; 2) the degree of weathering is mainly controlled by regolith thickness. This results in supply-limited weathering in Sri Lanka where weathering runs to completion, and kinetically-limited weathering in the Alps and Sierra Nevada where soluble primary minerals persist; 3) these weathering characteristics are reflected in the sites’ ecosystem processes, namely in that nutritive elements are intensely recycled in the supply-limited setting, and directly taken up from soil and rock in the kinetically settings; 4) contrary to common paradigms, the weathering rates are not controlled by biomass growth; 5) at all sites we find a deficit in river solute export when compared to solute production in regolith, the extent of which differs between elements but not between erosion rates. Plant uptake followed by litter erosion might explain this deficit for biologically utilized elements of high solubility, and rare, high-discharge flushing events for colloidal-bound elements of low solubility. Our data and the new metrics have begun to serve for calibrating metal isotope systems in the weathering zone, the isotope ratios of which depend on the flux partitioning between the compartments of the Critical Zone. We demonstrate this application in several isotope geochemical companion papers with associated datasets from the same samples.
All samples are assigned with International Geo Sample Numbers (IGSN), a globally unique and persistent Identifier for physical samples. The IGSNs are provided in the data tables and link to a comprehensive sample description in the internet.
The data herein were used to assess the importance of geogenic-derived nutrients on long-term forest ecosystem nutrition in two mountainous temperate forest ecosystems in southern Germany (Conventwald/Black Forest and Mitterfels/Bavarian Forest). Presented are element concentrations of various forest ecosystem compartments along with the soil pH, chemical depletion fractions (CDF), mass transfer coefficients (τ_(X_i)^X), radiogenic Sr isotope ratio (87Sr/86Sr) of soil and saprolite as well as in situ 10Be concentrations of bedload sediment.Element concentrations measured by X-ray fluorescence (XRF) are provided for drilling core samples (depth: 20 m, site Conventwald (CON), and 30 m, site Mitterfels (MIT)) including unweathered parent bedrock (paragneiss) and regolith comprising soil, saprolite and weathered bedrock but also for bedload sediment. Element concentrations were also measured by ICP-OES to determine the element composition of the soil´s and saprolite´s water-soluble, easily exchangeable, carbonate and organic-bound fraction. In addition, ICP-OES derived element concentrations are reported for plant tissues such as needles, leaves, and stem wood comprising heartwood (dead part of wood) and sapwood (living part of wood) of the two tree species European beech (Fagus sylvatica) and Norway spruce (Picea abies).Along with the chemical composition of soil and saprolite calculated weathering indices such as the chemical depletion fraction (CDF) and the mass transfer coefficient (τ_(X_i)^X) are reported for regolith and bedrock. Further, the dataset contains phosphorus (P) concentrations measured by ICP-OES and UV spectrometry from various P fractions obtained by sequential extractions following the Hedley fractionation method. Additionally, the pH of soil and saprolite measured by a pH meter as well as the radiogenic Sr isotope ratio, namely 87Sr/86Sr measured by MC-ICP-MS for bulk bedrock and regolith are reported in the dataset. Finally, to estimate the landscapes lowering rate (total denudation) in situ 10Be concentrations were measured by accelerator mass spectrometry (AMS) on bedload sediment at the outlet of the catchment.The data presented here stem from sampling campaigns described in Uhlig et al. (2019) to which they are supplementary material to. Samples were mainly processed in the Helmholtz Laboratory for the Geochemistry of the Earth Surface (HELGES) and the GFZ section of Inorganic and Isotope Geochemistry (XRF analyses), the University of Bonn (P Hedley fractionation), and the University of Cologne - Centre for Accelerator Mass Spectrometry (AMS) (10Be measurements).This dataset represents the supplementary material to Uhlig et al. (2019). Tables (including data quality control) supplementary to the article are provided in pdf and xls formats. In addition, data measured in the course of the study is given in machine readable ASCII files. All samples are indexed with an International Geo Sample Number (IGSN). Sample metadata can be viewed by adding the IGSN to the “http://igsn.org/” URL (e.g. igsn.org/GFDUH00LT).