Ronald Amundson

Professor
Ph.D.  
  

317 Hilgard Hall
Berkeley, California 94720
earthy@nature.berkeley.edu
office: 510-643-7890   lab: 510-643-7890   fax:  510-643-5438

     Recent publications      People

The Earth has entered the Anthropocene, a geologic epoch where humans are altering the face of the planet on a scale rivaled only by past meteor impacts or glacial cycles. These are therefore exciting and important times for earth scientists, a period requiring multidisciplinary research to understand the functioning of the present global system, a need to project the Earth’s future, and the skill to conveying this message effectively and clearly to the public.

Chile is a natural long running outdoor experiment, where rainfall declines continuously from the south to the north. My research in Chile follows a series of sites stretched along the northern end of the country, sites ranging from semi-arid, to nearly lifeless, climate zones. We have discovered that soil and ecological processes change non-monotonically as rainfall declines and life disappears, and the dry, abiotic region attains properties unexpected from extrapolations from the rest of our largely biotic planet.

For example, soil chemical processes shift from net chemical losses to large chemical gains (from retention of atmospheric solutes) with this decline in rainfall (Ewing et al. 2006). We discovered that the vast accumulations of nitrate in the Atacama desert are the result of the cessation of the soil nitrogen cycle due to aridity and a lack of microbial activity (Ewing et al. 2007), and that without microbial processes that reduce N back to nitrogen gas in soils and sediments , the Earth’s atmospheric composition would (Capone et al. 2006) be largely different than today.

We discovered that variations in the stable isotopes of the element calcium, recently considered to be largely a mark of biology, undergo large changes do to entirely abiotic processes, as do isotopes of sulfur and oxygen in sulfate (Ewing et al. 2008). These fascinating observations, combined with a provocative recent paper by Dietrich and Perron (Dietrich and Perron 2006), have provided a unique insight into how profoundly different how planetary processes behave without the stamp of life. The role of life on geological processes is a question at the forefront of modern earth science. Yet establishing the experimental abiotic “controls” in field studies is exceedingly challenging since most of the Earth’s surface has been exposed to life since the Precambrian.

In a similar vein, we are also studying the role of burrowing animals on the formation of soils and the vernal pools of the Merced River region of California. The formation of vernal pools, and adjoining Mima mounds, is a long standing question in California geomorphology and ecology. This project, part of the PhD of Sarah Reed, combines the use of natural radioactive isotopes, and GIS modeling, to understand the rates at which animals can reconfigure the land surface (Reed and Amundson, 2007).

One of the important, and poorly integrated, parts of the soil N cycle is the impact of climate on the production of N₂O, a trace gas with more greenhouse gas strength than CO₂. Additionally, an even lesser understood feature is the N and O isotope composition of N₂O from soils (and its geographical distribution), a chemical signature important to determine the present and past sources of N₂O in the atmosphere. We are presently developing numerical models to allow us to understand how variations in different soil processes affect both the quantity and isotope composition of soil N₂O. Additionally, we are planning field studies to examine the geographical and temporal variations in California ecosystems.



We have just begun a large collaborative project to examine the climate effect on the S cycle. Unlike C and N, the soil S cycle is much less studied, yet it is an important ecosystem nutrient, and an important pollutant from the burning of coal. We are presently in the very initial stages of our work on this problem, one that involves 4 PIs and numerous students and post docs. The research sites in this project extend from the wet tropics of Puerto Rico to the dry limits of the Atacama Desert.

In 2004, we began to analyze the growing data of set of Martian soil chemical analyses using geochemical models commonly used on Earth. These calculations suggested that the Mars soils had lost significant quantities of water-soluble elements relative to the rock from which they formed. This loss, on Earth, can be achieved only by rain/snowfall and the subsequent downward movement of this water and the reaction products. The well-known accumulation of sulfate and chloride salts in Martian soils then appears to have been overlain on this earlier stage of chemical weathering by downward moving water.

This interpretation of the soil chemistry suggests a much wetter (in a relative sense) earlier Mars climate, with a long and protracted aridification. We have recently published the results of this work, and have discussed the nature of Mars soils, in a recent paper (Amundson et al. 2008), This initial foray into planetary geochemistry is part of a larger interest in Mars research. I am an associated earth scientist involved in the development of the “Urey instrument”, a proposed amino acid and organic compound analyzer that is projected to be on the payload of an upcoming European Space Union mission to Mars (Aubrey et al. 2008).

The longest running theme in my research is the impact of humans on soil and ecological processes. My concern now extends, like most scientists, to the global climate system and to the earth as a whole. I have discussed the role and impact of humans in two recent articles/essays (Amundson et al. 2007)(Amundson 2008).


The polar regions are being preferrentially impacted by climate change relative to equatorial regions.

Amundson, R. (2008) Exhibition - The ends of the Earth. Nature Geoscience, 1, 5-6.

Amundson, R., S. Ewing, W. Dietrich, B. Sutter, J. Owen, O. Chadwick, K. Nishiizumi, M. Walvoord & C. McKay (2008) On the in situ aqueous alteration of soils on Mars. Geochimica Et Cosmochimica Acta, 72, 3845-3864.

Amundson, R., D. D. Richter, G. S. Humphreys, E. G. Jobbagy & J. Gaillardet (2007b) Coupling between biota and earth materials in the Critical Zone. Elements, 3, 327-332.

Aubrey, A. D., J. H. Chalmers, J. L. Bada, F. J. Grunthaner, X. Amashukeli, P. Willis, A. M. Skelley, R. A. Mathies, R. C. Quinn, A. P. Zent, P. Ehrenfreund, R. Amundson, D. P. Glavin, O. Botta, L. Barron, D. L. Blaney, B. C. Clark, M. Coleman, B. A. Hofmann, J. L. Josset, P. Rettberg, S. Ride, F. Robert, M. A. Sephton & A. Yen. 2008. The Urey instrument: An advanced in situ organic and oxidant detector for Mars exploration. 583-595.

Capone, D. G., R. Popa, B. Flood & K. H. Nealson (2006) Follow the nitrogen. Science, 312, 708-709.

Dietrich, W. E. & J. T. Perron (2006) The search for a topographic signature of life. Nature, 439, 411-418.

Ewing, S. A., G. Michalski, M. Thiemens, R. C. Quinn, J. L. Macalady, S. Kohl, S. D. Wankel, C. Kendall, C. P. McKay & R. Amundson (2007) Rainfall limit of the N cycle on Earth. Global Biogeochemical Cycles, 21.

Ewing, S. A., B. Sutter, J. Owen, K. Nishiizumi, W. Sharp, S. S. Cliff, K. Perry, W. Dietrich, C. P. McKay & R. Amundson (2006) A threshold in soil formation at Earth's arid-hyperarid transition. Geochimica Et Cosmochimica Acta, 70, 5293-5322.

Ewing, S. A., W. Yang, D. J. DePaolo, G. Michalski, C. Kendall, B. W. Stewart, M. Thiemens & R. Amundson (2008) Non-biological fractionation of stable Ca isotopes in soils of the Atacama Desert, Chile. Geochimica Et Cosmochimica Acta, 72, 1096-1110.

REED, SN AND R AMUNDSON 2007. Sediment, gophers and time: a model for the origin and persistence of mima moundVvernal pool topography in the Great Central Ralley. Pages "15-27 in R A Schlising and D G Alexander Editors, Vernal Pool Landscapes. Studies from the Herbarium, Number 14 California State University, Chico, CA.

1. Stern, L., T. Baisden, and R. Amundson. 1999. Processes controlling the oxygen isotope ratio of soil CO2: analytic and numerical modeling. Geochemica et Cosmochimica Acta 63:799-814.

2. Wang, Y., R. Amundson, and S. Trumbore. 1999. The impact of land use change on C turnover in soils. Global Biogeochemical Cycles 13:47-57.

3. Wang, Y., R. Amundson, and X-F. Niu. Seasonal and altitudinal variation in decomposition of soil organic matter inferred from radiocarbon measurements of soil CO2 flux. Global Biogeochemical Cycles 14:199-211.

4. Arens, N.A., A.H. Jahren, and R. Amundson. 2000. Can C3 plants faithfully record the carbon isotope composition of atmospheric carbon dioxide? Paleobiology 26:137-164.

5. Davidson, EA., S.E. Trumbore, and R. Amundson. 2000. Soil warming and the organic carbon budget. Nature. 408:789-790.

6. Gadbury, C. L. Todd, A.H. Jahren, and R. Amundson. 2000. Spatial and temporal variations in the isotopic composition of bison tooth enamel from the Early Holocene Hudson-Meng Bone Bed, Nebraska. Palaeogeography, Palaeoclimatology, and Palaeoecology. 157(1-2):79-93.

7. Jahren, A.H., N.C. Arens, G. Sarmiento, J. Guerero, and R. Amundson. 2001.Terrestrial record of methane hydrate dissociation in the early Cretaceous. Geology 29:159-162..

8. Amundson, R. 2001. The Soil Carbon Cycle. Annual Reviews of Earth and Planetary Sciences. 29:535-562.

9. Stern, L., R. Amundson, and T. Baisden. 2001. The influence of soils on oxygen isotope ratio of atmospheric CO2. Global Biogeochemical Cycles 15:753-759.

10. Jahren, A.H., R. Amundson, C. Kendall, and P. Wigand. 2001. Paleoclimate reconstruction using the correlation in d18O of hackberry carbonate and environmental water, North America. Quaternary Research 56:252-263.

11. Brenner, D.L., R. Amundson, W.T. Baisden, C. Kendall, and J. Harden. 2001. Soil N and 15N variation with time in a California annual grassland ecosystem. Geochimica et Cosmochimica Acta 65:4171-4186.

12. Baisden, W.T., R. Amundson, D.L. Brenner, A.C. Cook, C. Kendall, and J. Harden. 2002. A multi-isotope C and N modeling analysis of soil organic matter turnover and transport as a function of soil depth in a California annual grassland. Global Biogeochemical Cycles 16(4):1135. doi:10.1029/2001GB001823, 2002.

13. W.T. Baisden, R. Amundson, A.C. Cook, and D.L. Brenner. 2002. Turnover and storage of C and N in five density fractions from California annual grassland surface soils. Global Biogeochemical Cycles 16(4):1117, doi 10.1029/20001GB001822, 2002.

14. Sharp, W.D., K.L. Ludwig, O.A. Chadwick, R. Amundson, and L. Glaser. 2003.Datin fluvial terraces by 230Th/U on pedogenic carbonate. Wind River Basin, Wyoming . Quaternary Research 59:139-150.

15. Baisden, W.T. and R. Amundson. 2003. An analytical approach to ecosystem biogeochemistry modeling. Ecological Applications 13(3):649-663.

16. Sanderman, J., R. Amundson, and D. D. Baldocchi. 2002. Application of eddy covariance measurements to the temperature dependence of soil organic matter mean residence time. Global Biogeochemical Cycles 17(2):1061, soi:10.1029/2001GB1833,2003.

17. Amundson, R., Y. Guo, and P. Gong. 2003. Soil diversity and land use in the United States.Ecosystems 6:470-482.

18. Guo, Y., R. Amundson, P. Gong, and R. Ahrens. 2003. Taxonomic structure, distribution, and abuance of the soils in the USA. Soil Science Society of America Journal 67:1507-1516.

19. Y. Guo, P. Gong, and R. Amundson. 2003. Pedodiversity in the United States of America. Geoderma 117:99-115.

20. Amundson, R., A.T. Austin, E.A.G. Schuur, V. Matzek, A. Uebersax, D. Brenner, W.T. Baisden, and C. Kendall. 2002. Global patterns of the isotopic composition of soil and plant nitrogen. Global Biogeochemical Cycles 17(1):1031, doi:10.1029/2002GB001903, 2003.

21. Osher, L.J., P.A. Matson, and R. Amundson. 2003. Effect of land use change on soil carbon in Hawaii. Biogeochemistry 65(2):213-232.

22. Miller, A.J., R. Amundson, I.C. Burke, and C. Yonker. 2004. The effect of climate and cultivation on soil organic C and N. Biogeochemistry67(1):57-72.

23. Hoppe, K.A., R. Amundson, M. Vavra, M.P. McClaren, and D.L. Anderson. 2004. Isotopic analysis of tooth enamel carbonate from modern North American feral horses: implications for paleoenvironmental reconstructions. Palaeogeography, Palaeoclimatology, and Palaeoecology. 203(3-4):299-311.

Book Chapters etc.

1. Hoosbeek, M.R., R.G. Amundson, and R.B. Bryant. 1999. Pedological modeling. Chapter 3. In: (L.P. Wilding, Associate Editor) Handbook of Soil Science; Section V. Pedology. CRP Press. (in press).

2. Amundson, R. 2000. Are soils endangered? p, 144-153. In: (J. Schneiderman, ed) The Earth Around Us. W.H. Freeman and Co.

3. Amundson, R. 2000. Are soils endangered? California Geology July/Aug:4-13 (illustrated reprint of citation above).

4. Amundson, R. and W.T. Baisden. 2000. Stable isotope tracers and models in soil organic matter studies. pp. 117-137 In: O. Sala, H. Mooney, B. Howarth, and R.B. Jackson (eds), Methods in Ecosystem Science. Springer Verlag.

5. Mermut, A.R., R. Amundson, and T. Cerling. 2000. The use of stable isotopes in studying carbonate dynamics in soils. p. 65-86 In: R. Lal, J.M. Kimble, H. Eswaren, and B.A. Stewart (eds), Global Climate Change and Pedogenic Carbonates. Lewis Publishers, Washington, DC.

6. Amundson, R. 2002. Pedological Modeling. In: R. Lal (ed). Encyclopedia of Soil Science.

7. McFadden, L. and R. Amundson. 2002. Soil inorganic carbon modeling. In: R. Lal (ed). Encyclopedia of Soil Science.

8. Amundson, R. 2002. Donath Medal citation for Hope Jahren. GSA Today. 12(2):17-18.

9. Amundson, R. 2004. Soil Formation. Chap. 5.01, pp. 1-35. In: Treatise on Geochemistry, H.D. Holland and K.K. Turekian (Eds in Chief). Elsevier Press, Amsterdam.

10. Sanderman, J. and R. Amundson. 2004. Biogeochemistry of decomposition and detrital processing. Chap. 8.07, pp. 249-316. In: Treatise on Geochemistry, H.D. Holland and K.K. Turekian (Eds in Chief). Elsevier Press, Amsterdam.