Microbial biomass and nitrogen transformations in surface soils strongly acidified by volcanic hydrogen sulfide deposition in Osorezan, Japan

Abstract

Volcanic acidification has created unique ecosystems that have had to adapt to the acidic environments in volcanic regions. To characterize the primary microbial properties of strongly acidified soils in such environments, we investigated microbial biomass, nitrogen transformations and other relevant chemical properties in the surface soils of solfatara and forests from Osorezan, a typical volcanic region in Japan, and compared the results to common Japanese forest soils. Soil microbial biomass C (MBC) and N (MBN) were determined using the chloroform fumigation–extraction method. Potential net N mineralization and net nitrification were measured in aerobic laboratory incubations. Long‐term acidification in the Osorezan soils by volcanic hydrogen sulfide deposition caused low soil pH (3.0–3.8), base cation deficiency and increased concentrations of toxic ions such as Al3+. The proportions of MBC to total carbon (MBC/TC ratio) and MBN to total nitrogen (MBN/TN ratio) were lower than those in common Japanese forest soils. The extreme acidic conditions may have inhibited microbial survival in the Osorezan acid soils. Net N mineralization occurred at rates comparable to those in common Cryptomeria japonica forest soils, probably because of the presence of acid‐tolerant soil microorganisms. Net nitrification was completely inhibited and autotrophic ammonia oxidizers were not detected by the MPN method. The inhibition of nitrification prevents nitrogen leaching from the soils, thus maintaining a nitrogen cycle in the volcanic acid region in which (and NH3) is recycled among microorganisms and plants.

Photosynthetic rate, needle longevity, and nutrient contents in Picea glehnii growing on strongly acidic volcanic ash soil in northern Japan

“…In addition, soils around solfataras contain high levels of aluminum (Al) (Kayama et al 2000, Hall et al 2003, Watanabe et al 2010. This is released from soil when pH falls below 5.5 (Marschner 1995, Kochian et al 2004.…”

Genetic consequences of plant edaphic specialization to solfatara fields: Phylogenetic and population genetic analysis of Carex angustisquama (Cyperaceae)

“…Volcanism also continues to disturb terrestrial ecosystems even after catastrophic eruptions, especially via volcanic gases often containing hydrogen sulphide and sulphur dioxide (Delmelle, Stix, Baxter, Garcia-Alvarez, & Barquero, 2002;Watanabe et al, 2010). The areas around fumaroles emitting these gases are called solfatara fields, and their soils have been acidified by long-term exposure to sulphide gases (Hara, 1983;Yoshitake, Sasaki, Uchida, Funatsu, & Nakatsubo, 2007).…”

Extreme low pH, not Al3+, is a key abiotic stressor for the extremophyte Carex angustisquama (Cyperaceae) in highly acidic solfatara fields

“…Therefore, C. angustisquama could offer novel insights into the molecular mechanisms of low pH tolerance in plants, on which little is currently known in vascular plants as compared to Al 3+ tolerance. On the other hand, there are other potential stressors in solfatara fields, such as extremely oligotrophic soils due to the strong leaching (Watanabe et al 2010) and the aboveground damage from volcanic gases (Baillie et al 2018). An examination of the impacts of these other potential stressors will be needed to fully comprehend the mechanisms of plant adaptation to volcanic environments.…”

“…On the other hand, there are other potential stressors in solfatara fields, such as extremely oligotrophic soils due to the strong leaching (Watanabe et al . 2010) and the aboveground damage from volcanic gases (Baillie et al . 2018).…”