Whole soil acidification and base cation reduction across subtropical China

• Published in: Geoderma Vol. 361; p. 114107
• Main Authors: Yu, Zaipeng, Chen, Han Y.H., Searle, Eric B., Sardans, Jordi, Ciais, Philippe, Peñuelas, Josep, Huang, Zhiqun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2020; Elsevier
• Subjects: acid deposition; acidity; altitude; Base cations; calcium; chemical bases; China; Continental interfaces, environment; Deep soil; exchangeable calcium; exchangeable magnesium; global change; magnesium; meadows; Nitrogen deposition; nutrients; Ocean, Atmosphere; Sciences of the Universe; shrublands; soil acidification; Soil pH; soil profiles; soil surface layers; terrestrial ecosystems; topsoil; tropical forests; uncertainty; Warming; Whole soil acidification; China; Warming; Base cations; Soil pH; Deep soil; Nitrogen deposition; Whole soil acidification
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2019.114107

•Soil pH decreased over the last 60 years across the whole soil profile.•Exchangeable Ca2+ and Mg2+ decreased similarly or greater in deep soil as compared to topsoil.•The magnitudes of acidification varied among ecosystems and elevations.•Multiple global change drivers contributed to the soil acidification. Soil acidity plays a central role in the diversity and function of terrestrial ecosystems. Recent studies have revealed that acid deposition has acidified topsoil over time. However, uncertainties relating to how the acidity of the entire soil profile, including deep soil, responds to multiple global change drivers make it challenging to predict the effects of the ongoing global change on soil functions. Using data from 2952 observations of 200 montane sites in subtropical China, we show that the soil pH decreased over the last 60 years across the whole soil profile (0–150 cm), though there was less reduction in deep soils. The contents of exchangeable Ca2+ and Mg2+ decreased at the same rate, or more quickly, in the deep soil than topsoil. Soil pH and base cations decreased more in forests and shrublands at low elevations, but less in mountain meadows at high elevations. Our sensitivity analysis indicated that regional N deposition, S deposition, warming, and decreasing water availability have contributed to the temporal decreases in pH and base cations in natural ecosystems across tropical and subtropical China. The results extend the previous findings of changes in acidity in surface soil layers and demonstrate that deep soils of natural systems across a large area can be acidified over a few decades. Our results suggest that ongoing global changes are reducing the base nutrients across the entire soil profile, and thus, the diversity and functionality of subtropical forests.