Anoxic Conditions Maintained High Phosphorus Sorption in Humid Tropical Forest Soils

Authors

Yang Lin, University of California - Berkeley
Avner Gross, University of California - Berkeley
Christine S. O'Connell, Chapman UniversityFollow
Whendee L. Silver, University of California - Berkeley

Document Type

Article

Publication Date

1-7-2020

Abstract

The strong phosphorus (P) sorption capacity of iron (Fe) and aluminum (Al) minerals in highly weathered, acidic soils of humid tropical forests is generally assumed to be an important driver of P limitation to plants and microbial activity in these ecosystems. Humid tropical forest soils often experience fluctuating redox conditions that reduce Fe and raise pH. It is commonly thought that Fe reduction generally decreases the capacity and strength of P sorption. Here we examined the effects of 14 d oxic and anoxic incubations on soil P sorption dynamics in humid tropical forest soils from Puerto Rico. Contrary to the conventional belief, soil P sorption capacity did not decrease under anoxic conditions, suggesting that soil minerals remain strong P sinks even under reducing conditions. Sorption of P occurred very rapidly in these soils, with at least 60 % of the added P disappearing from the solution within 6 h. Estimated P sorption capacities were much higher, often by an order of magnitude, than the soil total P contents. However, the strength of P sorption under reducing conditions was weaker, as indicated by the increased solubility of sorbed P in NaHCO₃ solution. Our results show that highly weathered soil minerals can retain P even under anoxic conditions, where it might otherwise be susceptible to leaching. Anoxic events can also potentially increase P bioavailability by decreasing the strength, rather than the capacity, of P sorption. These results improve our understanding of the redox effects on biogeochemical cycling in tropical forests.

Comments

This article was originally published in Biogeosciences, volume 17, issue 1, in 2020. https://doi.org/10.5194/bg-17-89-2020

Recommended Citation

Lin, Y., Gross, A., O'Connell, C. S., and Silver, W. L.: Anoxic conditions maintained high phosphorus sorption in humid tropical forest soils, Biogeosciences, 17, 89–101, https://doi.org/10.5194/bg-17-89-2020, 2020.

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The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.