Assistant Professor, Simon Fraser University
PhD, Earth and Planetary Science, University of California, Berkeley
Process linkages between geology, topography, and life: Vegetation distribution in the Eel River watershed appears to be controlled principally by lithologic variation across accreted terrains. For example, coniferous forests are often absent from the central mélange belt, but the mechanisms inhibiting these forests are poorly understood. A complementary area of interest is to better understand how tectonic forcing, biota, and geomorphic processes produce unique landscape forms across different rock types. For example, hillslopes are steep and convexo-planar in the greywackes and argillites of the ER CZO, relative to the gently undulating nearby mélange, but the processes responsible for hillslope sediment transport (and ultimately landscape form) in both rock types are not well understood. One way to explore a process inferred from field observation is to cast it in the form of a geomorphic transport law, which can be coupled with continuity in a model landscape.
CZO Research Groups
Digging deeper: what the critical zone perspective adds to the study of plant ecophysiology. Dawson, T.E., Hahm, W.J., & Crutchfield-Peters, K. (2020): New Phytologist 226 (3): 666-671
Arrested development: Erosional equilibrium in the southern Sierra Nevada, California, maintained by feedbacks between channel incision and hillslope sediment production. Callahan, R.P., Ferrier, K.L., Dixon, J., Dosseto, A., Hahm, W.J., Jessup, B.S., Miller, S.N., Hunsaker, C.T., Johnson, D.W., Sklar, L.S., Riebe, C.S. (2019): GSA Bulletin Cross-CZO
Low Subsurface Water Storage Capacity Relative to Annual Rainfall Decouples Mediterranean Plant Productivity and Water Use From Rainfall Variability. Hahm, W.J., Dralle, D.N., Rempe, D.M., Bryk, A.B., Thompson, S.E., Dawson, T.E., and Dietrich, W.E. (2019): Geophysical Research Letters
Lithologically Controlled Subsurface Critical Zone Thickness and Water Storage Capacity Determine Regional Plant Community Composition. Hahm, W.J., Rempe, D.M., Dralle, D.N., Dawson, T.E., Lovill, S.M., Bryk, A.B., Bish, D.L., Schieber, J. & Dietrich, W.E. (2019): Water Resources Research 55
Quantification of the seasonal hillslope water storage that does not drive streamflow. Dralle, D.N., Hahm, W.J., Rempe, D.M., Karst, N.J., Thompson, S.E., Dietrich, W.E. (2018): Hydrological Processes
Controls on the distribution and resilience of Quercus garryana: ecophysiological evidence of oak's water‐limitation tolerance. Hahm, W.J., Dietrich, W.E., and Dawson, T.E. (2018): Ecosphere 9 (5)
Drainage from the Critical Zone: Lithologic Controls on the Persistence and Spatial Extent of Wetted Channels during the Summer Dry Season. Lovill, S.M., Hahm, W.J. & Dietrich, W.E. (2018): Water Resources Research 54(8)
In-situ nuclear magnetic resonance detection of fracture-held water in variably saturated bedrock. Rempe, D.M., Schmidt, L.M. & Hahm, W.J. (2018): SEG Technical Program Expanded Abstracts 2018
Testing for supply limited and kinetic limited chemical erosion in field measurements of regolith production and chemical depletion. Ferrier, K. L., Riebe, C. S. and Hahm, W. J. (2016): Geochemistry, Geophysics, Geosystems. 17 (6), 2270-2285.
Landscape response to tipping points in granite weathering: The case of stepped topography in the Southern Sierra Critical Zone Observatory. Jessup, BS; Hahm, WJ; Miller, SN; Kirchner, JW; Riebe, CS. (2011): Applied Geochemistry
Papers and books that explicitly acknowledge a CZO grant are highlighted in PALE ORANGE.
Critical Zone Ecohydrology of the Northern California Coast Ranges. Hahm, W.J. (2019): University of California, Berkeley
Investigating Hillslope Self-Similarity: Field Observations of Weathering Profiles Across a Sequence of Repeating Ridges and Valleys. Pedrazas, M., Hahm, W.J., Huang, M.-H., Nelson, M.D., Bryk, A.B., Dralle, D., Fauria, K., Dietrich, W.E., and Rempe, D.M. (2019): American Geophysical Union 2019 Fall Meeting, San Francisco, CA, 9-13 December 2019 Abstract #EP53F-2213
The influence of Critical Zone structure on runoff paths, seasonal water storage, and ecosystem composition. Hahm, W.J., Dietrich, W.E., Rempe, D.M., Dralle, D., Dawson, T.E., Lovill, S.M., and Bryk, A.B. (2017): American Geophysical Union 2017 Fall Meeting, New Orleans, Louisiana, 11-15 December 2017 Abstract #U13B-37
Comprehensive seismic surveys suggest that subsurface water-holding capacity is secondary to bedrock nutrient content as a regulator of vegetation productivity in the Sierra Nevada Batholith, California. Taylor, N.J.; Riebe, C.S.; Dueker, K.G.; Goulden, M.; Flinchum, B.A.; Pasquet, S.; Callahan, R.P.; Hahm, W.J.; Keifer, I.S.; Holbrook, W.S. (2016): Fall Meeting, American Geophysical Union, December 2016. Abstract EP43C-0964.
Testing for supply-limited chemical erosion in field measurements of soil production and chemical depletion. Ferrier, K.; C. Riebe; W.J. Hahm; J. Kirchner (2014): American Geophysical Union, Fall Meeting 2014, abstract #EP13E-04
Strong Lithologic Control on Mountain Ecosystem Productivity and Landscape Evolution. Hahm, W.J., C.S. Riebe, C.E. Lukens, and S. Araki. (2013): The Geological Society of America annual meeting
Bedrock composition limits mountain ecosystem productivity and landscape evolution. Riebe, C.S. W.J. Hahm; and C. Lukens (2013): American Geophysical Union, Fall Meeting 2013, abstract #B13L-02
25 Jun 2019 - Eel River CZO research findings from Hahm et al. 2019 are featured on the UC Berkeley News website.
31 May 2019 - Scientists link vegetation mosaics in California to patterns of weathered bedrock.