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Article

Hot Spots and Hot Moments of Soil Moisture Explain Fluctuations in Iron and Carbon Cycling in a Humid Tropical Forest Soil

1
Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA
2
Department of Environmental Science, Policy, and Management, University of California-Berkeley, Berkeley, CA 94720, USA
3
Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA
*
Author to whom correspondence should be addressed.
Soil Syst. 2018, 2(4), 59; https://doi.org/10.3390/soilsystems2040059
Received: 30 September 2018 / Revised: 26 October 2018 / Accepted: 27 October 2018 / Published: 1 November 2018
(This article belongs to the Special Issue Iron and Manganese Biogeochemical Cycling in Soils)
Soils from humid forests undergo spatial and temporal variations in moisture and oxygen (O2) in response to rainfall, and induce changes in iron (Fe) and carbon (C) biogeochemistry. We hypothesized that high rainfall periods stimulate Fe and C cycling, with the greatest effects in areas of high soil moisture. To test this, we measured Fe and C cycling across three catenas at valley, slope, and ridge positions every two days for a two-month period in a rainforest in Puerto Rico. Over 12 days without rain, soil moisture, FeII, rapidly reducible Fe oxides (FeIIIRR), and dissolved organic C (DOC) declined, but Eh and O2 increased; conversely, during a 10-day period of intense rain (290 mm), we observed the opposite trends. Mixed-effects models suggest precipitation predicted soil moisture, soil redox potential (Eh), and O2, which in turn influenced Fe reduction/oxidation, C dissolution, and mineralization processes. The approximate turnover time for HCl-extractable FeII was four days for both production and consumption, and may be driven by fluctuations in FeIIIRR, which ranged from 42% to 100% of citrate–ascorbate-extractable FeIII (short-range order (SRO)-FeIII) at a given site. Our results demonstrated that periods of high precipitation (hot moments) influenced Fe and C-cycling within day-to-week timescales, and were more pronounced in humid valleys (hot spots). View Full-Text
Keywords: iron reduction; dissolved organic carbon; soil moisture; redox processes iron reduction; dissolved organic carbon; soil moisture; redox processes
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MDPI and ACS Style

Barcellos, D.; O’Connell, C.S.; Silver, W.; Meile, C.; Thompson, A. Hot Spots and Hot Moments of Soil Moisture Explain Fluctuations in Iron and Carbon Cycling in a Humid Tropical Forest Soil. Soil Syst. 2018, 2, 59. https://doi.org/10.3390/soilsystems2040059

AMA Style

Barcellos D, O’Connell CS, Silver W, Meile C, Thompson A. Hot Spots and Hot Moments of Soil Moisture Explain Fluctuations in Iron and Carbon Cycling in a Humid Tropical Forest Soil. Soil Systems. 2018; 2(4):59. https://doi.org/10.3390/soilsystems2040059

Chicago/Turabian Style

Barcellos, Diego, Christine S. O’Connell, Whendee Silver, Christof Meile, and Aaron Thompson. 2018. "Hot Spots and Hot Moments of Soil Moisture Explain Fluctuations in Iron and Carbon Cycling in a Humid Tropical Forest Soil" Soil Systems 2, no. 4: 59. https://doi.org/10.3390/soilsystems2040059

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