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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

How thick is the skin of the earth?

26 Aug 2018 (Reynolds) - A team of Idaho State University researchers working at the Reynolds Creek Critical Zone Observatory in partnership with the USDA Agricultural...

FEATURED NATIONALLY

CZOs at AGU 2018

23 Aug 2018 (National, Boulder, Calhoun, Catalina-Jemez, Eel, IML, Luquillo, Reynolds, Shale Hills, Sierra) - The 2018 AGU Fall Meeting will be held December 10-14 in Washington, D.C.

FEATURED NATIONALLY

Call for proposals: Research Coordination Networks (RCNs) Driving Convergent CZ Science

12 Jul 2018 (National, Boulder, Calhoun, Catalina-Jemez, Eel, IML, Luquillo, Reynolds, Shale Hills, Sierra) - NSF Dear Colleague Letter: Research Coordination Networks (RCNs) for Driving Convergent Science in the Critical Zone

FEATURED NATIONALLY

IPBES: Biodiversity & Nature’s Contributions Continue Dangerous Decline, Scientists Warn

21 May 2018 (National) - IPBES released the outcome reports on the regional assessment of biodiversity and ecosystem services.

FEATURED NATIONALLY

NSF News Release: Billions of gallons of water saved by thinning forests

11 May 2018 (Sierra) - Too many trees in Sierra Nevada forests stress water supplies, scientists say

FEATURED NATIONALLY

NSF Discovery articles focus on the CZOs.

10 May 2018 (National, Boulder, Calhoun, Catalina-Jemez, Christina, Eel, IML, Luquillo, Reynolds, Shale Hills, Sierra) - The Discoveries section of the National Science Foundation's website on Critical Zone Observatories (CZOs).

FEATURED NATIONALLY

NSF Discovery: On World Water Day, scientists study spawning salmon through a riverbed lens

22 Mar 2018 (Sierra) - NSF Southern Sierra CZO researchers peer into North America’s West Coast salmon rivers

FEATURED NATIONALLY

Recent paper by Rempe and Dietrich on rock moisture featured by NSF and others

02 Mar 2018 (Eel) - A recent paper on rock moisture by Danielle Rempe and Bill Dietrich of the Eel River CZO is been featured on NSF News site, SF Chronicle, others


FEATURED

Multiple postdoc and grad student opportunities at UC Merced

12 Sep 2018 (Sierra) - Two postdoctoral scholar positions and multiple MS or PhD research assistantships are currently available at the University of California, Merced....

Research Program Update: September 2018

07 Sep 2018 (Sierra) - Recent activities and findings, funding opportunities, upcoming events, and other updates

FEATURED

In drought and heavy rains, ecosystems function like information communication networks

29 Aug 2018 (IML) - Connectivity explains ecosystem responses to extreme events

Research Program Update: July 2018

17 Jul 2018 (Sierra) - Recent activities and findings, funding opportunities, upcoming events, and other updates

REU students with the Visualizing Forest Futures (ViFF) program visit the CZO

16 Jul 2018 (Shale Hills) - Trail walks on the Menominee Indian Reservation and through Pennsylvania Forestlands around the CZO (Penn State Stone Valley Forest, Rothrock State...

More News >


Example Publications

FEATURED NATIONALLY

Clays in the Critical Zone. Paul A. Schroeder (2018): Cambridge University Press (National, Calhoun) Cross-CZO National

FEATURED NATIONALLY

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 (National, Boulder, Calhoun, Luquillo, Reynolds, Shale Hills, Sierra) Cross-CZO National

FEATURED NATIONALLY

A net ecosystem carbon budget for snow dominated forested headwater catchments: linking water and carbon fluxes to critical zone carbon storage. Perdrial J., Brooks P.D., Swetnam T., Lohse K.A., Rasmussen C., Litvak M., Harpold A.A., Zapata-Rios X., Broxton P., Mitra B., Meixner M., Condon K., Huckle D., Stielstra C., Vázquez-Ortega A., Lybrand R., Holleran M., Orem C., Pelletier J., Chorover J. (2018): Biogeochemistry 138{3): 225–243 (Boulder, Catalina-Jemez, Luquillo, Reynolds, Shale Hills) Cross-CZO

FEATURED NATIONALLY

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 (Eel)

FEATURED NATIONALLY

Humidity determines snowpack ablation under a warming climate. Harpold A.A. and Brooks P.D. (2018): PNAS 115(6): 1215-1220 (Boulder, Catalina-Jemez) Cross-CZO


Carbon and oxygen isotope composition in soil carbon dioxide within deep Ultisols at the Calhoun CZO, South Carolina, USA. Cherkinsky A., Brecheisen Z , Richter D. (2018): Radiocarbon (Calhoun)

Unified representation of the C3, C4, and CAM photosynthetic pathways with the Photo3 model. Hartzell, Samantha, Mark S. Bartlett, and Amilcare Porporato (2018): Ecological Modelling 384: 173-187 (Calhoun)

Similarities in the evolution of plants and cars. Hartzell, Samantha, Mark Bartlett, Jun Yin, Amilcare Porporato (2018): PLoS ONE 13(6): e0198044 (Calhoun)

State dependent jump processes: Ito–Stratonovich interpretations, potential, and transient solutions. Bartlett, M.S., and A. Porporato (2018): arXiv:1807.01848 (Calhoun)

Evaluating the effect of nutrient redistribution by animals on the phosphorus cycle of lowland Amazonia. Buendía, Corina, Axel Kleidon, Stefano Manzoni, Björn Reu, and Amilcare Porporato (2018): Biogeosciences 15: 279-295 (Calhoun)

Ecohydrological model for the quantification of ecosystem services provided by urban street trees. Revelli, Roberto, and Amilcare Porporato (2018): Urban Ecosystems 21(3): 489-504 (Calhoun)

A class of exact solutions of the Boussinesq equation for horizontal and sloping aquifers. Bartlett, M.S., and A. Porporato (2018): Water Resources Research 54 (2): 767-778 (Calhoun)

More Publications >