Soil organic matter regulates molybdenum storage and mobility in forests

Biogeochemistry
By: , and 

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Abstract

The trace element molybdenum (Mo) is essential to a suite of nitrogen (N) cycling processes in ecosystems, but there is limited information on its distribution within soils and relationship to plant and bedrock pools. We examined soil, bedrock, and plant Mo variation across 24 forests spanning wide soil pH gradients on both basaltic and sedimentary lithologies in the Oregon Coast Range. We found that the oxidizable organic fraction of surface mineral soil accounted for an average of 33 %of bulk soil Mo across all sites, followed by 1.4 % associated with reducible Fe, Al, and Mn-oxides, and 1.4 % in exchangeable ion form. Exchangeable Mo was greatest at low pH, and its positive correlation with soil carbon (C) suggests organic matter as the source of readily exchangeable Mo. Molybdenum accumulation integrated over soil profiles to 1 m depth (τMoNb) increased with soil C, indicating that soil organic matter regulates long-term Mo retention and loss from soil. Foliar Mo concentrations displayed no relationship with bulk soil Mo, and were not correlated with organic horizon Mo or soil extractable Mo, suggesting active plant regulation of Mo uptake and/or poor fidelity of extractable pools to bioavailability. We estimate from precipitation sampling that atmospheric deposition supplies, on average, over 10 times more Mo annually than does litterfall to soil. In contrast, bedrock lithology had negligible effects on foliar and soil Mo concentrations and on Mo distribution among soil fractions. We conclude that atmospheric inputs may be a significant source of Mo to forest ecosystems, and that strong Mo retention by soil organic matter limits ecosystem Mo loss via dissolution and leaching pathways.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Soil organic matter regulates molybdenum storage and mobility in forests
Series title Biogeochemistry
DOI 10.1007/s10533-015-0121-4
Volume 125
Issue 2
Year Published 2015
Language English
Publisher Springer
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description 17 p.
First page 167
Last page 183
Time Range Start 2012-06-01
Time Range End 2014-10-18
Country United States
State Oregon
Other Geospatial Oregon Coast Range
Online Only (Y/N) N
Additional Online Files (Y/N) N