Spatial differences along the elevation gradient characterizing our Critical Zone Observatory's field areas - from forest ecology to preciptation phase to bedrock composition - create a natural laboratory to study changes in critical zone characteristics and processes across the landscape. While this elevation transect experiences rapid seasonal changes, from snow cover to wet soil to dry soil in a 1-2 month period, climate warming will shift this transition to an earlier time and a higher elevation. Researchers can also use the gradient then as a substitution of space for time to research how critical zone processes respond to natural and anthropogenic environmental changes, including warmer average temperatures and forest thinning.
Our growing community of critical zone scientists from multiple institutions and areas of research expertise are carrying out investigations in the Sierra National Forest, Kings River Experimental Watershed, San Joaquin Experimental Range, and Sequoia National Park.
Critical Zone researchers are currently investigating a tightly linked set of research questions at our Observatory, including:
While some research is centered on a single discipline, many questions require a multi-disciplinary approach. Our measurements and monitoring efforts overlap with other observatories in the National Science Foundation's U.S. Critical Zone Observatory Network in order to rapidly improve Earth systems models.
Since it was initiated in 2007, the Southern Sierra CZO has become a platform for a wide variety of research. Much of the research during the first five years addressed these questions:
Among the many results to date at our CZO, four key findings stand out:
11 May 2018 - Too many trees in Sierra Nevada forests stress water supplies, scientists say
10 May 2018 - The Discoveries section of the National Science Foundation's website on Critical Zone Observatories (CZOs).
22 Mar 2018 - NSF Southern Sierra CZO researchers peer into North America’s West Coast salmon rivers
21 Jun 2017 - University of California Television (UCTV) features Bales, Conklin, Glaser, Safeeq, and others on the new Sustainable California channel
04 May 2017 - Onward California - University of California television spots showcase Southern Sierra CZO research
11 Apr 2016 - New York Times reporter, Henry Fountain spoke with Southern Sierra CZO PIs Roger Bales and Martha Conklin and investigtor Mohammad Safeeq as they...
07 Sep 2015 - Get a sense of the people and the work. Several members of the Southern Sierra CZO are profiled here, including students and professors.
19 Nov 2018 - The 2018 AGU Fall Meeting will be held December 10-14 in Washington, D.C.
14 Nov 2018 - Say 'Hello!' to biogeochemist Morgan Barnes! Morgan specializes in the study of soil nutrient biogeochemistry, focusing on phosphorus in the Sierras
06 Nov 2018 - Marshall Receives 2018 Luna B. Leopold Young Scientist Award
24 Oct 2018 - Meet forest ecologist Jeff Lauder! Lauder's research focuses on Sierra Nevada Conifers and how they have been responding to stress during drought!
12 Sep 2018 - Two postdoctoral scholar positions and multiple MS or PhD research assistantships are currently available at the University of California, Merced....
Southern Sierra Critical Zone Observatory and Kings River Experimental Watersheds: A Synthesis of Measurements, New Insights, and Future Directions. O'Geen, A.; Safeeq, M.; Wagenbrenner, J.; Stacy, E.; Hartsough, P.; Devine, S.; Tian, Z.; Ferrell, R.; Hopmans, J.W.; and Bales, R. (2018): Vadose Zone Journal, 17:180081
Reevaluating growing season length controls on net ecosystem production in evergreen conifer forests. Barnard, D.M., Knowles, J.F., Barnard, H.R., Goulden, M.L., Hu, J., Litvak, M.E., Molotch, N.P. (2018): Scientific Reports 8(1): 17973 Cross-CZO
Mercury sourcing and sequestration in weathering profiles at six Critical Zone Observatories. Richardson, Justin B., Arnulfo A. Aguirre, Heather L. Buss, A. Toby O'Geen, Xin Gu, Daniella M. Rempe, and Daniel deB. Richter (2018): Global Biogeochemical Cycles, doi: 10.1029/2018GB005974 Cross-CZO National
Ideas and perspectives: Strengthening the biogeosciences in environmental research networks. Richter, D.D., S.A. Billings, P.M. Groffman, E.F. Kelly, K.A. Lohse, W.H. McDowell, T.S. White, S. Anderson, D.D. Baldocchi, S. Banwart, S. Brantley, J.J. Braun, Z.S. Brecheisen, C.W. Cook, H.E. Hartnett, S.E. Hobbie, J. Gaillardet, E. Jobbagy, H.F. Jungkunst, C.E. Kazanski, J. Krishnaswamy, D. Markewitz, K. O’Neill, C.S. Riebe, P. Schroeder, C. Siebe, W.L. Silver, A. Thompson, A. Verhoef, G. Zhang (2018): Biogeosciences 15: 4815-4832 Cross-CZO National
Controls on Soil Organic Carbon Partitioning and Stabilization in the California Sierra Nevada. Rasmussen C., Throckmorton H., Liles G., Heckman K., Meding S., and Horwath W.R. (2018): Soil Systems 2(3): 41 Cross-CZO
Beyond clay: towards an improved set of variables for predicting soil organic matter content. Rasmussen C., Heckman K., Wieder W.R., Keiluweit M., Lawrence C.R., Berhe A.A., Blankinship J.C., Crow S.E., Druhan J.L., Hicks Pries C.E., Marin-Spiotta E., Plante A.F., Schädel C., Schimel J.P., Sierra C.A., Thompson A., Wagai R. (2018): Biogeochemistry 137(3): 297–306 Cross-CZO
Regional sensitivities of seasonal snowpack to elevation, aspect, and vegetation cover in western North America. Christopher J. Tennant, Adrian A. Harpold, Kathleen Ann Lohse, Sarah E. Godsey, Benjamin T. Crosby, Laurel G. Larsen, Paul D. Brooks, Robert W. Van Kirk, Nancy F. Glenn (2017): Water Resources Research 53 Cross-CZO National
Prevalence and magnitude of groundwater use by vegetation: a global stable isotope meta-analysis. Jaivime Evaristo and Jeffrey J. McDonnell (2017): Scientific Reports 7 Cross-CZO National
Special issue of The Earth Scientist about the Critical Zone and the US NSF Critical Zone Observatory (CZO) program. CZO Education/Outreach team (2016): The Earth Scientist, Volume XXXII, Issue 3, Fall 2016 Cross-CZO National
Topographic controls on the extension and retraction of flowing streams. Prancevic, J.P.; Kirchner, J.W. (2019): Geophysical Research Letters
Bayesian inference of hydraulic properties in and around a white fir using a process-based ecohydrologic model. Massoud, E.C.; Purdy, A.J.; Christoffersen, B.O.; Santiago, L.S.; Xu, C. (2019): Environmental Modelling & Software
Cosmogenic Isotopes Unravel the Hydrochronology and Water Storage Dynamics of the Southern Sierra Critical Zone. Visser, A.; Thaw, M.; Deinhart, A.; Bibby, R.; Safeeq, M.; Conklin, M.; Esser, B.; van der Velde, Y. (2019): Water Resources Research
Climate, snow, and soil moisture data set for the Tuolumne and Merced river watersheds, California, USA. Roche, J.W.; Rice, R.; Meng, X.; Cayan, D.R.; Dettinger, M.D.; Alden, D.; Patel, S.C.; Mason, M.A.; Conklin, M.H.; Bales, R.C. (2019): Earth System Science Data
Aeolian dust deposition and the perturbation of phosphorus transformations during long-term ecosystem development in a cool, semi-arid environment. Gu, C.; Hart, S.C.; Turner, B.L.; Hu, Y.; Meng, Y.; Zhu, M. (2019): Geochemica et Cosmochimica Acta, 246, 498-514
More than climate? Predictors of tree canopy height vary with scale in complex terrain, Sierra Nevada, CA (USA). Fricker, G.A.; Synes, N.W.; Serra-Diaz, J.M.; North, M.P.; Davis, F.W.; Franklin, J. (2019): Forest Ecology and Management, 434, 142-153
Emulation of environmental models using polynomial chaos expansion. Massoud, E.C. (2018): Environmental Modelling & Software