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The Southern Sierra Critical Zone Observatory is a community platform for research on critical zone processes, with ongoing investigations and measurements at several sites along a 2300-m elevation gradient on the western slope of the southern Sierra Nevada.

We encourage the research community to utilize our intesively studied field sites.

Observatory research is framed by multiple spatial and temporal scales.

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.

Learn more about our field areas and instrumentation -->
 

Our integrated research is centered on several interdisciplinary questions and goals:

 

Critical Zone researchers are currently investigating a tightly linked set of research questions at our Observatory, including:

  • How do soil moisture and topographic variability interact to influence soil-formation and weathering?
  • How is the response of soil moisture to snowmelt and rainfall controlled by variability across the landscape, and how do these responses both reflect and constrain streamflow and ET?
  • How does vegetation, and ecosystem distribution and function (species, plant functional type, production), vary with climate (elevation); and what physiological mechanisms regulate these interactions?
  • How does vegetation influence land-atmosphere exchange of water, energy, and CO2?
  • How do soil/landscape heterogeneity and water fluxes influence nutrient cycling and retention?
  • What is the role of aeolian fluxes in controlling nutrient availability and NPP?

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.

Explore examples of current research topics in detail -->
 

Initial research focus and findings

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:

  • How does landscape variability control how soil moisture, evapotranspiration and stream flow respond to snowmelt and rainfall?
  • How is soil moisture linked to topographic variability, soil formation and weathering?
  • What physiological mechanisms are controlling how vegetation distribution and function vary with climate
  • How do vegetation attributes influence cycling of water, energy, and CO2?
  • What is the link between soil heterogeneity, water fluxes and nutrient availability?


Among the many results to date at our CZO, four key findings stand out:

  • A strategically distributed measurement suite provides the data needed to close the water balance at multiple scales, providing a foundation for further process research. At the headwater catchment scale our estimates of evapotranspiration (ET) using a water-balance approach are in good agreement with flux-tower measurements. Similarly, our estimate of the water balance across the entire Upper Kings River basin also matches observations.
  • Mid-montane forests have a year-round growing season, avoiding summer water-stress shutdown through deep rooting and avoiding winter shutdown cold tolerance, explaining high productivity and biomass in the mid-montane belt.
  • In contrast to high rates of evapotranspiration (ET) at mid-elevation, we observed reduced ET and productivity at lower elevations owing to summer moisture stress and at high elevations due to cold stress. This confirms the inverse drought and energy limitation conceptual model, with implications for effects of warming on ET.
  • Deep rooting and soil development are important for sustaining high rates of net primary productivity (NPP). At our main instrumented headwater catchment, we found that over one-third of the ET came from depths below 1 m.
For more information on our activities and findings, view our annual reports and publications.

 

© SSCZO

© SSCZO

© SSCZO

© University of California, Merced

© Sierra Nevada Research Institute

Through late September, the stream at the Providence subcatchment 301 was muddy but had no running water, even after a few small storms. Now, enough rain and snow has fallen to start flow again.  © SSCZO

The forest around Soaproot Saddle is showing extreme water stress. At the end of the water year, the eddy covariance flux tower was only showing respiration and decay, no water usage! © SSCZO

This view from a helicopter above Soaproot Saddle shows the patchy nature of the tree death. As more trees are impacted by insects, these patches are growing. © M Meadows

Observatory research is framed by multiple spatial and temporal scales.

Major questions and goals of current research at the Southern Sierra Critical Zone Observatory


Research News

FEATURED NATIONALLY

UCTV: Southern Sierra CZO researchers featured on Sustainable California channel

21 Jun 2017 - University of California Television (UCTV) features Bales, Conklin, Glaser, Safeeq, and others on the new Sustainable California channel

FEATURED

Southern Sierra CZO Videos

04 May 2017 - Onward California - University of California television spots showcase Southern Sierra CZO research

FEATURED NATIONALLY

The frontier beneath our feet — an AGU commentary on the critical zone

21 Apr 2017 - AGU has published a collection of commentaries highlighting the important role Earth and space science research plays in society.

FEATURED NATIONALLY

2017 CZO Webinar Series: Critical Zone and Society

06 Apr 2017 - 2017 CZO Webinar Series: Critical Zone and Society.

FEATURED

NSF: Dust contributes valuable nutrients to Sierra Nevada forest ecosystems

28 Mar 2017 - NSF Press Release: New research finding provides insight into role dust may play as ecosystems change

FEATURED

NY Times: Sierra Nevada Snow Won’t End California’s Thirst

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...

FEATURED

Critical Zone Profiles - Meet the people doing CZO science (Southern Sierra CZO)

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.


New SSCZO comic artfully communicates research

19 Jul 2017 - Wonder what soils and sponges have in common? Or why some trees in the Sierra Nevada are dying while others are surviving? Find out in our new comic.

Gobi Desert Dust Helps Sustain California’s Sierra Nevada

28 Mar 2017 - A team of researchers found that dust provides a much greater amount of nutrients to vegetation in the Sierra Nevada than previously thought.

Pushing the Limits on Water Isotope Measurement:  Lawrence Livermore and UC Merced

20 Dec 2016 - Lawrence Livermore and UC Merced researchers are tracking water through the critical zone using cutting-edge technology and new collection methods.

CZOs at AGU 2016

22 Nov 2016 - CZOs at AGU 2016: Agenda and award recipients

Critical Zone Q&A with researcher Adrian Harpold

19 Oct 2016 - University of Nevada Reno's Adrian Harpold reflects on his past and present time researching at Critical Zone Observatories.

More News >


Example Publications

FEATURED

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

FEATURED NATIONALLY

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

FEATURED

Controls on deep critical zone architecture: a historical review and four testable hypotheses. Riebe, C. S., Hahm, W. J., Brantley, S. L. (2017): Earth Surface Processes and Landforms, 42 (1): 128–156 Cross-CZO National

FEATURED

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

FEATURED

Variation of organic matter quantity and quality in streams at Critical Zone Observatory watersheds. Miller, Matthew P., Boyer, Elizabeth W., McKnight, Diane M., Brown, Michael G., Gabor, Rachel S., Hunsaker, Carolyn T., Iavorivska, Lidiia, Inamdar, Shreeram, Johnson, Dale W., Kaplan, Louis A., Lin, Henry, McDowell, William H., Perdrial, Julia N. (2016): Water Resources Research, 52 (10): 8202–8216 Cross-CZO

FEATURED

Influence of terrain aspect on water partitioning, vegetation structure, and vegetation greening in high elevation catchments in northern New Mexico. Zapata-Rios X., Brooks P.D., Troch P.A., McIntosh J. and Guo Q. (2016): Ecohydrology 9(5): 782-795 Cross-CZO National

FEATURED

Hydrological partitioning in the critical zone: Recent advances and opportunities for developing transferable understanding of water cycle dynamics. Brooks P.D., Chorover J., Fan Y., Godsey S.E., Maxwell R.M., McNamara J.P., and Tague C. (2015): Water Resources Research 51 (9): 6973-6987 Cross-CZO


Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes. Uhlig, D., Schuessler, J.A., Bouchez, J., Dixon, J.L., von Blanckenburg, F. (2017): Biogeosciences 14, 3111-3128

Technical report: The design and evaluation of a basin-scale wireless sensor network for mountain hydrology. Zhang, Z.; Glaser, S.D.; Bales, R.C.; Conklin, M.; Rice, R.; Marks, D.G. (2017): Water Resources Research.

The problem of predicting the particle size distribution of sediment supplied by hillslopes to rivers. Sklar, L. S., Riebe, C. S., Marshall, J. A., Genetti, J., Leclere, S., Lukens, C. L., Merces, V. (2017): Geomorphology. 277 31.

Simulations of energy balance components at snow-dominated montane watershed by land surface models. Kim, D.; Ray, R.L.; Choi, M. (2017): Earth Environmental Sciences. 76 337.

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth. Brantley, S.L., McDowell, W.H., Dietrich, W.E., White, T.S., Kumar, P., Anderson, S., Chorover, J., Lohse, K.A., Bales, R.C., Richter, D., Grant, G., and Gaillardet, J. (2017): Earth Surface Dynamics Cross-CZO National

Reviews and syntheses: On the roles trees play in building and plumbing the Critical Zone. Brantley, Susan L., David M. Eissenstat, Jill A. Marshall, Sarah E. Godsey, Zsuzsanna Balogh-Brunstad, Diana L. Karwan, Shirley A. Papuga, Joshua Roering, Todd E. Dawson, Jaivime Evaristo, Oliver Chadwick, Jeffrey J. McDonnell, Kathleen C. Weathers (2017): Biogeosciences Discussions Cross-CZO National

Dust outpaces bedrock in nutrient supply to montane forest ecosystems. Aciego, S.M.; Riebe, C.S.; Hart, S.C.; Blakowski, M.A.; Carey, C.J.; Aarons, S.M.; Dove, N.C.; Botthoff, J.K.; Sims, K.W.; Aronson, E.L. (2017): Nature Communications

More Publications >