The National Science Foundation (NSF) recently announced ten new awards for its Critical Zone Collaborative Network (CZCN), and LTER sites will play a prominent role in four of them. The awards fund a wide range of investigations to better understand the ‘critical zone’, the area of our planet where water, air, soil, rock and living things interact. 

One of the $4.8M awards will support an urban environment study led by the Baltimore Ecosystem Study (BES) LTER’s Claire Welty, Peter Groffman, and Alan Berkowitz, focused on understanding how human influences, including construction, road salting, and polluted stormwater runoff, interact with natural weathering processes to affect water quality. The project includes data from a cluster of four cities – Philadelphia, Baltimore, Washington, DC, and Raleigh – that align along a north-south corridor called the Fall Zone, a geologic transition that lies between the low-lying Atlantic Coastal Plain and the rolling hills of the Piedmont. Including cities from across the Eastern Seaboard will also allow researchers to examine how climate affects the movement of sediment and dissolved materials through natural and urban environments. The age of cities also has implications for how “leaky” their infrastructure is expected to be. The northern cities in this cluster have older infrastructure that is more prone to leaking compared to southern cities with newer infrastructure.

“We have never been able to study this large, regional-scale of interaction before, and we can only do this because of the multi-city/multi-university collaboration funded by this new grant,” says Groffman. “The study is also unique because we are studying anthropogenic and geologic agents on an equal footing; this is truly ‘science for the anthropocene’.”

 The project builds on over two decades of BES research data on urban environments, and will include two BES study sites as well as several additional BES LTER researchers. While a great deal has been learned about the social and ecological interactions of Baltimore’s watershed, Welty says that “the subsurface has for the most part been ignored.” The team plans to leverage existing data to ask new questions about urban subsurface water flow and weathering. 

Says Welty, “None of the other awarded Critical Zone clusters focus on urban environments, so among the new CZ projects we are the only urban cluster.  What is unique about urban settings in terms of the subsurface is the extensive pipe system that pierces the subsurface, providing pathways for fluid exchange that differ greatly from natural systems.”

Berkowitz is on the team to help develop educational curricula based on the project’s research. “We’re really excited by the prospect of developing a module to teach about the critical zone – something most teachers and students aren’t familiar with even though it’s right beneath their feet and incredibly important for the functioning of ground and surface water systems,” he says. The Fall Zone is one of the most significant landforms in the region, historically determining where cities developed, how transportation evolved, and where ports were located. Berkowitz plans to roll out citizen science and educational initiatives to help people in the region connect to this hydro-geological and social history.

Matt Kirwan of the Virginia Coast Reserve LTER will co-lead another new Critical Zone cluster to study the transformation of important landscapes located at the intersection of land and sea, such as coastal marshes. The project will quantify the impacts of sea level rise on coastal ecosystems and communities, providing important knowledge to assist decision-makers in planning for future environmental change. Interdisciplinary field observations, experiments, and modeling will be fully integrated across three locations along the mid-Atlantic coast with paired marsh-forest and marsh-agriculture sites. The forested and agricultural sites at each location represent major differences in hydrology, geochemistry, and ecology, and are expected to respond differently to rising sea level, providing valuable information about the range of possible responses to climate change in the region.

The Jornada Basin and Sevilleta LTERs are integral to another Critical Zone cluster focused on ecological changes in arid and semi-arid drylands. Principle Investigator Lixin Jin and co-PI Anthony Darrouzet-Nardi of the Jornada LTER will lead a team of researchers to investigate how carbonate minerals in dryland soils control and impact water, nutrients, salts, and carbon moving in and out of the Critical Zone, and how global change is impacting these processes. This project builds on the rich historical data, knowledge, and models at the Jornada and Sevilleta LTER sites, the Reynolds Creek CZO, USDA-ARS Kimberly site in Idaho and irrigated agricultural sites along the Rio Grande Valley in Texas.

Finally, a CZ network cluster using Big Data approaches to study disturbance effects on ecohydrological resilience will merge data from multiple LTER sites, CZOs, and NEON observatories. Together, this new cohort of critical zone network clusters will build upon decades of important ecological data collected at LTER sites across the country, and take the next step toward understanding larger-scale processes. The CZCN is replacing the previous Critical Zone Observatory Program, and a focus on cross-cluster collaboration broader than single observatories is being emphasized from the start.

Observatories have served the bio-geoscience community well and will continue to do so,” says Jerad Bales, Director of NSF’s Consortium of Universities for the Advancement of Hydrologic Science (CUAHSI). “I think that CZCN Program will bring a unique perspective that will begin to help us understand how the same bio-geochemical processes may vary across landscapes and settings. A question being asked in the hydrologic science community is, for example, can a single hydrologic model work across the entire continental U.S.? How do we incorporate landscape variability in hydrologic processes into a forecast model? Or, how do we generalize from observatory-scale understanding to a broader regional to national scale?”

Bales says that the ecological focus of LTER sites will add an important component to helping Cluster scientists think about critical zone process. He also thinks that “the longer-term data sets available through many of the LTERs may be useful to supplement the shorter term data collection that will occur in the CZCN Clusters.”

The interdisciplinary nature of the Cluster programs, along with the breadth of expertise from LTER and beyond represented within them, will no doubt set the stage for many important and exciting discoveries about our earth’s ‘living skin’.  


-Kristen Weiss