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

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?

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

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.

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.

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.

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

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

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.

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…..

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

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

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?

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

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

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

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

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

Environmental gradients Topography Climate Lithology Time Biology Disturbance

CZO Network (2017): criticalzone.org RC 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)

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

Jenny Parks, artist