1. Introduction to Critical Zone science and CZ Observatories (CZO)
Dr. Tim White
Earth and Environmental Systems Institute
The Pennsylvania State University

2. Critical Zone:
• Term published by the U.S. National
Research Council in 2001 Basic Research
Opportunities in the Earth Sciences report
= Thin veneer at Earth’s surface spanning
from the top of vegetation canopy through
soil to deep in the subsurface where fresh groundwater circulates.
= Critical Zone –v- critical zones?

3. Soil exists at the “heart” of the Critical Zone
Important for:
- agriculture
- water filtration
- C sequestration
- biodiversity
But degraded by humanity.

4. Societal relevance:
The zone within which most terrestrial
life exists and depends on.
Ongoing climate and land use changes
to the zone may stress terrestrial life
including humanity – thus a better understanding of CZ processes and
function may aid adaptation to change.

5. Critical Zone Services
* Pollination
* Fulfillment of cultural, spiritual/intellectual needs
* Regulation of climate
* Insect pest control
* Maintenance and provision of genetic resources
* Maintenance and regeneration of habitat
* Provision of shade and shelter
* Prevention of soil erosion
* Maintenance of soil fertility
* Maintenance of soil health
* Maintenance of healthy waterways
* Water filtration
* Regulation of river flows and groundwater levels
*Waste absorption and breakdown
If we allow natural assets to decline, so do the benefits.
But if we care for and maintain natural assets, we will reap greater returns.

6. A primary goal of the CZOs is to gather interdisciplinary scientific information from diverse landscapes that can be more broadly applied, or scaled up, to understand and manage the effects of ongoing land use and climate change at regional, continental, and global scales.

7. State of CZ Science: Nine CZOs represent an array
of geologic, climatologic, and ecologic settings in
which a variety of Critical Zone processes can be
studied from the vegetation canopy into bedrock. ER RC
IML CH
- SC
Base map from the National Atlas of the United States; no longer online. Reuse information is public domain. 7

8. The sites promote site-specific research and
education activities and are beginning to create
community among a diverse group of CZ scientists
(hydrology, geomorphology, geochemistry, ecology….) ER RC
IML CH
- SC
Base map from the National Atlas of the United States; no longer online. Reuse information is public domain. 8

9. To the CZ community, the sites represent the initial
steps toward building a network that can attract
a diverse group of Earth scientists to advance
CZ science by answering questions like: How has
the CZ changed and how will it change in the future? ER RC
IML CH
- SC
Base map from the National Atlas of the United States; no longer online. Reuse information is public domain.

10. Critical Zone science and Observatories (CZOs)
evolved from the recognition that many similar
scientific questions were being asked by diverse
groups of Earth surface scientists who did not
typically collaborate.
For example…..

11. Societal and Scientific Questions from the Water and
Environmental Research Systems (WATERS)
Network Science Plan:
How are human pressures and climate trends changing the
water cycle?
(2) How will fresh water availability change and how can we
better predict the change?
(3) How can we predict and better manage water availability
and quality for future generations and ecosystems? 11

12. Geobiological hypotheses developed during
Geobiology of Weathering and Erosion meeting, 2009
How does biology shape the topography of the CZ?
(2) How will increasing global temperatures change carbon
losses and chemical weathering fluxes from the CZ?
(3) Will land use change impact CZ processes and exports
compared to climate change? 12

13. Fundamental Geomorphologic considerations in CZ science
What controls the depth to bedrock? to regolith? the land surface itself?
How do biological agents affect the CZ?
How do the processes (and rates) of processes that govern landscape evolution change as climate changes?

14. Four Driving Questions of CZ Science
Atmosphere
What processes control fluxes of carbon, particulates, and reactive gases over different timescales?
How do processes that nourish ecosystems change over human and geologic time scales?
Landform
Evolution
Nutrients
How do biogeochemical processes govern long-term sustainability of water and soil resources?
How do variations in and perturbation to chemical and physical weathering processes impact the Critical Zone?
Chemistry
of Water

15. CZOs bring diverse interdisciplinary
communities together to build cross-science alliances to answer these complex interdisciplinary questions.
But…… How?

16. CHALLENGES:
Critical Zone is a complex system(s)
CZ is global in extent, therefore requires
international cooperation and funding
Deeply interdisciplinary, requires new
cadre of scientists

17. Network Approach
To explore one environmental variable with other variables constant
To compare data measured in the same way at multiple sites
To understand broad patterns of behavior
To create community among scientists and generate interdisciplinary understanding

18. Soil formation, or pedogenesis, is
controlled by five variables in nature,
the so-called state factors:
1. parent material
2. climate
3. topography
4. biota
5. time
6. humans

19. Environmental gradients
Topography
Climate
Lithology
Time
Biology
Disturbance

21. CZO Network (2017): criticalzone.orgRC ER
IML CH
- SC
Base map from the National Atlas of the United States; no longer online. Reuse information is public domain.
SS Southern Sierra CZO (California) BC Boulder Creek CZO (Colorado)
SH Susquehanna-Shale Hills CZO (Pennsylvania) LM-Luquillo CZO (Puerto Rico)
Jemez River Basin – Sta. Catalina CZO (NM/AZ) ER Eel River CZO (California)
RC Reynolds Creek CZO (Idaho) CH Calhoun CZO (South Carolina)
IML Intensively Managed Landscapes CZO (Illinois/Iowa)

22. CZO Timeline National Research Council report, 2001
NFS funds 3 CZO’s, 2007 (SS, BC, SH)
Elements special issue, 2007
Germany funds 4 CZOs, 2008 (TERENO network)
European Union funds 4 CZOs, 2009 (SoilTrEC)
NFS funds 3 CZOs, 2009 (J-C, CR, LQ)
Vadose Zone J special issue, 2011
All Hands Meeting, Biosphere 2, 2012
NFS funds 4 CZOs, 2014 (ER, RC, IML, CH)
All Hands Meeting, SS host, 2014

23. Jenny Parks, artist