Impacts of earthworm species on soil acidification, Al fractions, and base cation release in a subtropical soil from China

Jialong Wu (1) , Chi Zhang (1) , Ling Xiao (1) , Mikael Motelica-Heino (2, 3) , Zongling Ren (1) , Ting Deng (1) , Jun Dai (1)

1 College of Natural Resources and Environment
2 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
3 Biogéosystèmes Continentaux - UMR7327

Soil-exchangeable aluminum (Al) has toxic effects on living organisms in acidic soils. Earthworm presence and activity can alter soil pH, which has a significant influence on Al toxicity. However, the effects of earthworms on soil Al toxicity and fractions are still largely unknown. This laboratory study focused on the effects of three earthworm species (endogeics Pontoscolex corethrurus and Amynthas robustus, anecis Amynthas aspergillum) on soil acidification, Al fraction distribution, and base cation release. Three native earthworm species and a soil (latosolic red soil) collected from a botanical garden in South China were incubated under laboratory conditions. After 40 days of incubation, six Al fractions in soil, namely exchangeable (AlEx), weakly organically bound (AlOrw), organically bound (AlOr), amorphous (AlAmo), Al occluded in crystalline iron oxides (AlOxi), and amorphous aluminosilicate and gibbsite (AlAag) fractions, were extracted using a sequential procedure. Soil pH; organic carbon; total nitrogen; total Al (AlTotal); exchangeable K, Na, Ca, Mg contents; and CEC were determined as well. Compared to control soil, pH values increased by 0.79, 0.41, and 0.57 units in casts in the presence of P. corethrurus, A. robustus, and A. aspergillum, and 0.70, 0.32, and 0.50 units in non-ingested soil, respectively. Compared to control soil, the 61.7%, 30.7%, and 36.1% of AlEx contents in casts and 68.5%, 25.9%, and 39.0% of AlEx in non-ingested soil significantly decreased with the addition of P. corethrurus, A. robustus, and A. aspergillum, respectively. Moreover, compared to control soil, the 78.7%, 37.7%, and 40.1% of exchangeable Ca2+ and 12.3%, 24.7%, and 26.8% of exchangeable Mg2+ contents in casts significantly increased with the presence of P. corethrurus, A. robustus, and A. aspergillum, respectively. Soil treated with P. corethrurus had higher soil pH values, exchangeable Ca2+ contents, and lower AlEx than those with A. robustus and A. aspergillum. Results of principal component analyses showed that P. corethrurus, A. robustus, and A. aspergillum casts and non-ingested soil differ for soil pH, Al fractions, and exchangeable base cations release. These results indicate that earthworms, especially P. corethrurus, can reduce soil Al toxicity, increase soil pH, and affect the release of exchangeable base cations.

Mots clés: Earthworms; Aluminum fractions; Soil pH; Exchangeable base cations; Latosolic red soil

Domaines: Planète et Univers [physics]; Interfaces continentales, environnement

Jialong Wu, Chi Zhang, Ling Xiao, Mikael Motelica-Heino, Zongling Ren, et al.. Impacts of earthworm species on soil acidification, Al fractions, and base cation release in a subtropical soil from China. Environmental Science and Pollution Research, 2020, 27, pp.33446-33457. ⟨10.1007/s11356-019-05055-8⟩. ⟨insu-02106413⟩