Fig. 2: Field monitoring schema and biogeochemical proxy variation as a function of soil depth.
From: Mineral weathering is linked to microbial priming in the critical zone
a Field monitoring of soil temperature, moisture and gas partial pressure, as well as soil porewater sampling. Soil temperature and moisture were monitored at depths of 2, 10, 30, 60, and 135 cm, and soil O2 and CO2 at 2, 10, 30, and 60 cm. Porewaters were sampled at 10, 30, 60, and 135 cm. Data and depth trends of (b) dissolved organic carbon (DOC) flux (fDOC), dissolved inorganic carbon (DIC) flux (fDIC) and organic C:N ratio of dissolved organic matter (DOM), (c) DOM composition-related parameters including specific ultraviolet absorbance at 254 nm (SUVA254), humification index (HIX) and fluorescence index (FI), (d) SO42− flux (fSO4) and Cl− flux (fCl), (e) proxies for mineral weathering intensity including Si flux (fSi), total cation charge flux, and Sr/Ba ratio, (f) proxies for weathering congruency including [Si]/[Na]norm and [Al]/[Na]norm, and (g) saturation indices (SI) for secondary minerals ferrihydrite and gibbsite. Proxies for mineral weathering intensity show overall similar depth trends, confirming the predominance of silicate weathering in the soil profile and validating the use of these proxies for analysis of mineral weathering intensity. Weathering has the highest intensity at 60 cm, consistent with the trends of SI of secondary minerals. The data are from all three instrumented pedons. Shaded areas represent 95% confidence intervals. **denotes significant data fit at p < 0.01 and *significant data fit at p < 0.05.
