TY - JOUR
T1 - Contingency in the direction and mechanics of soil organic matter responses to increased rainfall
AU - Berhe, Asmeret Asefaw
AU - Suttle, K. Blake
AU - Burton, Sarah D.
AU - Banfield, Jillian F.
N1 - Funding Information:
Acknowledgements The authors wish to thank Carsten Mueller for comments on an earlier version of this manuscript, and Karelyn Cruz and Anna Rosling for their helpful discussions. We wish to extend our sincere thanks to two anonymous reviewers and the section editor for their constructive comments. We also thank Peter Steel and the University of California Natural Reserve System for protection and stewardship of the study site, as well as Bill Dietrich and Mary Power for their useful discussions regarding the site. This project was supported by National Research Initiative Competitive Grant No. 2007-35107-17893 from the USDA Cooperative State Research, Education, and Extension Service, the NSF Science and Technology Center National Center for Earth-Surface Dynamics; and a University of California President’s Postdoctoral Fellowship to A.A.B. A portion of this research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.
PY - 2012/9
Y1 - 2012/9
N2 - Background and Aims: Rainfall is expected to show greater and more variable changes in response to anticipated rising of earth surface temperatures than most other climatic variables, and will be a major driver of ecosystem change. Methods: We studied the effects of predicted changes in California's rainy season for storage and stabilization mechanisms of soil organic matter (SOM). In a controlled and replicated experiment, we amended rainfall over large plots of natural grassland in accordance with alternative scenarios of future climate change. Results: We found that increases in annual rainfall have important consequences for soil carbon (C) storage, but that the strength and even direction of these effects depend critically on seasonal timing. Additional rainfall during the winter rainy season led to C loss from soil while additions after the typical rainy season increased soil C content. Analysis of MIneral-Organic Matter (OM) associations reveals a potentially powerful mechanism underlying this difference: increased winter rainfall greatly diminished the role of Fe and Al oxides in SOM stabilization. Dithionite extractable crystalline Fe oxides explained more than 35% of the variability in C storage under ambient control and extended spring rainfall conditions, compared to less than 0. 01% under increased winter rainfall. Likewise, poorly crystalline Fe and Al oxides explained more than 25 and 40% of the variability in C storage in the control and extended spring rainfall treatments, respectively, but less than 5% in the increased winter rainfall treatment. Conclusions: Increases in annual precipitation identical in amount but at three-month offsets produced opposite effects on soil C storage. Such clear differences in the amount and chemical composition of SOM, and in the vertical distribution of oxides in the soil profile in response to treatment timing carry important implications for the C sequestration trajectory of this ecosystem.
AB - Background and Aims: Rainfall is expected to show greater and more variable changes in response to anticipated rising of earth surface temperatures than most other climatic variables, and will be a major driver of ecosystem change. Methods: We studied the effects of predicted changes in California's rainy season for storage and stabilization mechanisms of soil organic matter (SOM). In a controlled and replicated experiment, we amended rainfall over large plots of natural grassland in accordance with alternative scenarios of future climate change. Results: We found that increases in annual rainfall have important consequences for soil carbon (C) storage, but that the strength and even direction of these effects depend critically on seasonal timing. Additional rainfall during the winter rainy season led to C loss from soil while additions after the typical rainy season increased soil C content. Analysis of MIneral-Organic Matter (OM) associations reveals a potentially powerful mechanism underlying this difference: increased winter rainfall greatly diminished the role of Fe and Al oxides in SOM stabilization. Dithionite extractable crystalline Fe oxides explained more than 35% of the variability in C storage under ambient control and extended spring rainfall conditions, compared to less than 0. 01% under increased winter rainfall. Likewise, poorly crystalline Fe and Al oxides explained more than 25 and 40% of the variability in C storage in the control and extended spring rainfall treatments, respectively, but less than 5% in the increased winter rainfall treatment. Conclusions: Increases in annual precipitation identical in amount but at three-month offsets produced opposite effects on soil C storage. Such clear differences in the amount and chemical composition of SOM, and in the vertical distribution of oxides in the soil profile in response to treatment timing carry important implications for the C sequestration trajectory of this ecosystem.
KW - Changes in rainfall
KW - Mechanisms of SOM stabilization
KW - MIneral-Organic Matter (OM) associations
KW - Soil carbon
UR - https://www.scopus.com/pages/publications/84865739312
U2 - 10.1007/s11104-012-1156-0
DO - 10.1007/s11104-012-1156-0
M3 - Article
AN - SCOPUS:84865739312
SN - 0032-079X
VL - 358
SP - 371
EP - 383
JO - Plant and Soil
JF - Plant and Soil
IS - 1-2
ER -
