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Goal 1
DEVELOP A UNIFYING THEORETICAL FRAMEWORK of critical zone evolution that integrates physical, chemical, and biological processes.


The CZOS are working toward a holistic conceptual model of critical zone evolution that couples hydrological, geochemical, geomorphic, and biological processes. Such a model must consider many spatial and temporal scales.

Conceptual Models >


Goal 2
DEVELOP COUPLED SYSTEMS MODELS to explore how critical zone services respond to anthropogenic, climatic, and tectonic forcings.


The CZOs are building systems models that quantitatively combine multiple processes, often spanning an entire watershed. These models typically track fluxes and storage of energy, water, carbon, sediments, and/or other materials.

Numerical Models >


Goal 3
DEVELOP INTEGRATED, EXTENSIVE DATASETS that document a wide range of critical zone settings, including geology and climate.


The CZOs are assembling the needed infrastructure for an integrated data/ measurement foundation. This foundation will inform our theoretical framework, constrain our models, and help test hypotheses across CZOs.

Data >


Fundamental Questions

Despite the Critical Zone's importance to terrestrial life and many environmental issues, it remains poorly understood. Key questions include:

  • How does the Critical Zone form?
  • How does it operate?
  • How does it evolve?

There are many followup questions as well. For example:

  • How will the Critical Zone respond to projected climate and land use changes?
Specific Questions

Each Critical Zone Observatory is helping work on these fundamental questions along with numerous others. Some questions are specific to the unique characteristics of their field site and the talents of their collaborative research team. Some examples:

  • What is the legacy of climate and geologic history in critical zone architecture?
     - Boulder
  • How does variability in energy input and related mass flux influence critical zone structure and function?
      - Jemez-Catalina
  • How does saprolite advance vary with regolith thickness and landscape position?
     - Luquillo
  • How does water sculpt a landscape on shale bedrock?
     - Shale Hills
  • How does landscape variability control how soil moisture, evapotranspiration and streamflow respond to snowmelt and rainfall?
     - Southern Sierra
Cross-CZO Questions

A key advantage of the coordinated system of Critical Zone Observatories is that it can address the biggest questions by leveraging differing environments and histories.  More specifically, cross-CZO science can begin to answer questions such as:

  • How do processes that nourish ecosystems change over human and geologic time scales?
  • How do biogeochemical processes govern long-term sustainability of water and soil resources?
  • What processes control fluxes of carbon, particulates, and reactive gases over different timescales?
  • How do variations in and perturbations to chemical and physical weathering processes impact the Critical Zone?

An expressed goal of the CZO program is to catalyze transformative Earth surface science in the coming decade by developing cross-site science that helps to establish: 1) a unifying theory of CZ evolution; 2) coupled systems models to explore how CZ services respond to anthropogenic, climatic, and tectonic forcing; and 3) data sets that document differing CZ geologic and climatic settings, inform the theoretical framework, constrain conceptual and coupled systems models, and test model-generated hypotheses.

Cross-CZO studies >


Our Approach

Answering fundamental questions requires much better knowledge of how physical, chemical, and biological processes in the Critical Zone are coupled and at what spatial and temporal scales. Many of these processes are highly non-linear and can range across vast scales - from atomic to global, and from seconds to eons.

Interdisciplinary & Multidisciplinary

To better understand how the complex processes of the Critical Zone are linked, the U.S. NSF National CZO Program employs a systems approach across a broad array of sciences. This interdisciplinary and multidisciplinary approach integrates many disciplines, especially in the geological and biological sciences. Examples include hydrology, ecology, biogeochemistry, and geomorphology.

Multiple Disciplines >


A Common Infrastructure

Our systems approach across disciplines is well supported via our infrastructure. Our nine observatories span a range of climatic, geologic, and physiographic environments, from California to Puerto Rico. Each CZO is working toward a common set of resources, which will enable comparison of whole-watershed energy and mass balances across a variety of settings.

Infrastructure >


  Community & Collaboration

Within each CZO, scientific collaborations are common, often bringing together researchers from different institutions and crossing disciplinary boundaries.  This team-based approach helps foster a strong community, which is further strengthed by graduate student involvement.  Similar collaborations occur between investigators and students at different CZOs as well as with members of other US science programs.  Moreover, the US CZO program also works with an international network of Critical Zone investigators and research sites.

Partner Organizations >


Predictive Ability

An immediate challenge is to develop a robust predictive ability for how the structure and function of the Critical Zone evolves, including how it will respond to projected climate and land-use changes. This predictive ability must be founded on:

  • Broad knowledge of the complex physical, chemical, and biological processes of the Critical Zone
  • The ability to describe interactions between the varied climatic and geologic factors that distinguish different regions.
  • Advances in theory, modeling, and measurement.

Over the next decade, the CZO program will produce a fundamental understanding and four-dimensional data sets that will stimulate, inspire, and test the resulting predictive models. 

Read: Future Directions for CZO Science >

Models >



See Multiple Disciplines

See Infrastructure

See Partner Organizations


Research News

FEATURED NATIONALLY

2017 CZO Webinar Series: Critical Zone and Society

09 Mar 2017 (National, Boulder, Calhoun, Catalina-Jemez, Christina, Eel, IML, Luquillo, Reynolds, Shale Hills, Sierra) - 2017 CZO Webinar Series: Critical Zone and Society.

FEATURED NATIONALLY

CZO SAVI Summer Interns Program 2017

17 Jan 2017 (National) - Applications are being accepted for 2017 CZO SAVI Summer Interns until March 24.

FEATURED NATIONALLY

BIOGEOMON 2017: International Symposium on Ecosystem Behavior

06 Jan 2017 (National) - The 9th International Symposium on Ecosystem Behavior BIOGEOMON 2017 will be held August 20-24, 2017 in Litomyšl, Czech Republic.

FEATURED NATIONALLY

AGU-SEG Hydrogeophysics Workshop: Imaging the Critical Zone

05 Dec 2016 (National) - This workshop will be held July 24-27, 2017 at Stanford. Abstract submission deadline: February 23, 2017.

FEATURED NATIONALLY

CZOs at AGU 2016

22 Nov 2016 (National, Boulder, Calhoun, Catalina-Jemez, Christina, Eel, IML, Luquillo, Reynolds, Shale Hills, Sierra) - CZOs at AGU 2016: Agenda and award recipients

FEATURED NATIONALLY

Critical Zone Profiles - Meet the people doing CZO science (Shale Hills CZO)

26 Sep 2016 (National, Shale Hills) - Get a sense of the people and the work. Several members of the Shale Hills CZO are profiled here, including students and professors.


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

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

FEATURED

Southern Sierra CZO Videos

15 Dec 2016 (Sierra) - Onward California - University of California television spots showcase Southern Sierra CZO research

FEATURED

Bruno Latour talks about the Calhoun CZO in Munich

08 Dec 2016 (Calhoun) - Bruno Latour, anthropologist and philosopher of science, gave a talk on Critical Zone science and the Anthropocene entitled "From the Anthropocene...

FEATURED

Soybean plants with fewer leaves yield more

23 Nov 2016 (IML) - Scientists predict that modern soybeans produce more leaves than they need to the detriment of yield—made worse by rising atmospheric CO2.

FEATURED

Four soil pits installed in new Research Area 8!

21 Nov 2016 (Calhoun) - Four soil pits were installed in new Research Area 8 at the Calhoun CZO on 21-22 November 2016 for easy access for soil sampling down to 2 meters.

More News >


Example Publications

FEATURED NATIONALLY

Enhancing Interoperability and Capabilities of Earth Science Data using the Observations Data Model 2 (ODM2). Hsu, Leslie, Emilio Mayorga, Jeffery S. Horsburgh, Megan R. Carter, Kerstin A. Lehnert and Susan L. Brantley (2017): Data Science Journal, 16: 4, pp. 1–16 (National, Shale Hills) Cross-CZO National

FEATURED NATIONALLY

Expanding the role of reactive transport models in critical zone processes. Li Li, Kate Maher, Alexis Navarre-Sitchler, JennyDruhan, Christof Meile, Corey Lawrence, Joel Moore, Julia Perdrial, Pamela Sullivan, Aaron Thompson, Lixin Jin, EdwardW. Bolton, Susan L. Brantley, William E. Dietrich, K. Ulrich Mayer, Carl I. Steefel, Albert Valocchi, John Zachara, Benjamin Kocar, Jennifer Mcintosh, Benjamin M. Tutolo, Mukesh Kumar, Eric Sonnenthal, Chen Bao, Joe Beisman (2017): Earth-Science Reviews, 165:280-301 (Calhoun, Catalina-Jemez, Eel, Shale Hills) Cross-CZO

FEATURED NATIONALLY

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 (National, Luquillo, Shale Hills, Sierra) Cross-CZO National

FEATURED NATIONALLY

Clays in the Critical Zone: An Introduction . Paul Schroeder (2016): Clays and Clay Minerals 65 (5): 586-587 (Calhoun)

FEATURED NATIONALLY

Decreasing, not increasing, leaf area will raise crop yields under global atmospheric change. Srinivasan, V., Kumar, P., and Long, S.P. (2016): Global Change Biology (IML)

FEATURED NATIONALLY

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 (Boulder, Christina, Luquillo, Shale Hills, Sierra) Cross-CZO

FEATURED NATIONALLY

Designing a suite of measurements to understand the critical zone. Brantley, S. L., DiBiase, R. A., Russo, T. A., Shi, Y., Lin, H., Davis, K. J., Kaye, M., Hill, L., Kaye, J., Eissenstat, D. M., Hoagland, B., Dere, A. L., Neal, A. L., Brubaker, K. M., and Arthur, D. K (2016): Earth Surface Dynamics 4: 211-235 (Shale Hills)


Weathering of rock to regolith: The activity of deep roots in bedrock fractures. Hasenmueller, E. et al. (2017): Geoderma (Shale Hills)

FEATURED

Weather whiplash in agricultural regions drives deterioration of water quality. Loecke, T.D., Burgin, A.J., Riveros-Iregui, D.A., Ward, A.S., Thomas, S.A., Davis, C.A., and St. Clair, M.A. (2017): Biogeochemistry Letters (IML)

FEATURED

Using Magnetic Fly Ash to Identify Post-Settlement Alluvium and its Record of Atmospheric Pollution, Central USA. Grimley, D., Anders, A., Bettis, E.A., Bates, B., Wang, J. Butler, S., and Huot, S (2017): Anthropocene (IML)

FEATURED

A service-oriented architecture for coupling web service models using the Basic Model Interface (BMI). Jiang, P., Elag, M., Kumar, P., Peckham, S.D., Marini, L., and Rui, L. (2017): Environmental Modelling & Software (IML)

FEATURED

Integration of fuzzy logic and image analysis for the detection of gullies in the Calhoun Critical Zone Observatory using airborne LiDAR data. Noto, L. V., S. Bastola, Y. G. Dialynas, E. Arnone, and R. L. Bras (2017): ISPRS Journal of Photogrammetry and Remote Sensing 126: 209-224 (Calhoun)

Controls on solute concentration-discharge relationships revealed by simultaneous hydrochemistry observations of hillslope runoff and stream flow: The importance of critical zone structure. Kim, H., W. E. Dietrich, B. M. Thurnhoffer, J. K. B. Bishop, and I. Y. Fung (2017): Water Resour. Res., 53 (Eel, Shale Hills) Cross-CZO

Critical zone properties control the fate of nitrogen during experimental rainfall in montane forests of the Colorado Front Range. Hinckley, E. S., Ebel, B. A., Barnes, R. T., Murphy, S. F., Anderson, S. P. (2017): Biogeochemistry (2017) 132: 213. doi:10.1007/s10533-017-0299-8 (Boulder)

More Publications >