Soil Biogeochemistry of the Hawaiian Time-Climate Matrix:
The Hawaiian islands represent a powerful natural laboratory for studies of long term co-evolution of soils and ecosystems, and their biogeochemical consquences. We are using well-constrained climate and age gradients (established by our collaborators) to understand the changes in soil surface and redox chemistry that accompany pedogenesis in Hawaiian basalt. Recent work has focused on redox-driven dissolution and precipitation of soil Fe, which plays a central role in soil chemistry. In humid tropical forests, redox conditions can fluctuate between Fe-reducing and Fe-oxidizing conditions in association with the influx of labile NOM from the forest floor during leaching events. Using laboratory bioreactors and a range of microscopic and spectroscopic probes, we are examining specific linkages between redox active iron and carbon in tropical forest soils subjected to temporal redox fluctuations. The results are helping to elucidate mechanisms of C, N and P sequestration in humid, tropical forest soils.
Dr. Oliver Chadwick (UC Santa Barbara)
Dr. Peter Vitousek (Stanford University)
USDA National Research Initiative, Soil Processes Program
Selected Project References (click here for full publication list):
- Chadwick, O.A., and J. Chorover. 2001. The chemistry of pedogenic thresholds. Geoderma 100, 321-353.
- Chorover, J., M. K. Amistadi and O. A. Chadwick. 2004. Surface charge evolution of mineral-organic complexes during pedogenesis in Hawaiian basalt. Geochim. Cosmochim. Acta 68, 4859-4876.
- Thompson, A., O. A. Chadwick, D. G. Rancourt and J. Chorover. 2006. Iron-oxide crystallinity increases during soil redox oscillations. Geochim. Cosmochim. Acta 70, 1710-1727.
- Thompson, A., J. Ruiz, O. A. Chadwick, M. Titus, and J. Chorover. 2007. Rayleigh fractionation of iron isotopes during pedogenesis along a climate sequence of Hawaiian basalt. Chem. Geol. 238, 72-83.