Climate change and redoximorphosis in a soil with stagnic properties

Abstract In soils with perched water tables, frequent changes between reducing and oxidizing conditions result in the formation of redoximorphic features (RMF). Perched water tables are linked to the presence of a low water-permeable soil horizon and high water input by precipitation. Precipitation, however, is strongly affected by climate change. Hence, we postulate that soils with a perched water table are particularly vulnerable to climate change. To verify this hypothesis, we set up a monitoring campaign from April 2014 to October 2019 at a forested Planosol in North Rhine-Westphalia, Germany. On an hourly basis, the redox potential (EH) and air-filled pore volume (e) were measured in four soil depths. Furthermore, we calculated the CWB and employed two future climate scenarios for the years 2071–2100 to discuss the consequences for RMF formation. Reducing conditions were evident in the moist hydrological winter of 2015 and 2016, while oxidizing soil conditions (EH > 300 mV at pH 7) prevailed throughout the drier years (2017, 2018, 2019) for the whole soil profile. Concomitant with an increase in e during spring, we observed a switch from reducing to oxidizing soil conditions at low e of 0.01–0.03 cm3 cm−3 in the temporarily water-saturated soil horizons. At present, reducing soil conditions are limited during early spring during which manganese and iron can be mobilized from their oxides. Thus, RMF actively form but the CWB forecast until 2100 indicates a lower water input, which will diminish the period for redox-induced mineral dissolution. This study provided the essential information that soils with a perched water table are specifically vulnerable under progressing climate change. Presumably, RMF become more and more relictic that needs to be validated in the future.