The effect of groundwater depth on topsoil organic matter mineralization during a simulated dry summer in northwestern Europe

作者：Astrid Françoys, Orly Mendoza, Junwei Hu, Pascal Boeckx, Wim Cornelis, Stefaan De Neve, Steven Sleutel · 发表于：SOIL · 年份：2025 · DOI：10.5194/soil-11-121-2025 · 被引用次数：2 · 研究领域：Soil Carbon and Nitrogen Dynamics、Soil and Unsaturated Flow、Geology and Paleoclimatology Research

Abstract. With climate change expected to intensify the occurrence and severity of droughts, the impacts of the groundwater table (GWT) depth and capillary rise on topsoil moisture may become critical drivers of biological activity. Consequently, the GWT depth could influence topsoil carbon (C) mineralization. In this study, undisturbed 200 cm long soil columns with three different textures (loamy sand, sandy loam and silt loam) were subjected to two artificial GWT depths (−165 and −115 cm) in the laboratory. We examined (1) upward moisture flow by capillary action along the soil profile, specifically into the top 20 cm of soil, and (2) the effect of the GWT on the decomposition of an added 13C-enriched substrate (ryegrass) over a period of 10 weeks, with limited wetting events representing a dry summer. A 50 cm difference in the GWT depth (−165 vs. −115 cm) resulted in different topsoil moisture values for the sandy loam (31 % vs. 38 % water-filled pore space – WFPS) and silt loam (33 % vs. 43 % WFPS) soils. In the loamy sand soil, GWT-induced moisture differences appeared only up to 85 cm above the GWT. The expected acceleration of the mineralization of the added ryegrass under a shallower GWT was not confirmed. In contrast, CO2 efflux pulses after some of the wetting events were even higher for the drier −165 cm GWT than for the −115 cm GWT across all three soil textures. Additionally, a model fitted to cumulative ryegrass mineralization showed a lower mineralization rate ...