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The Calhoun CZO presents an important opportunity to evaluate CZ resilience, and to test a scientifically and socially significant hypothesis

"That the Southern Piedmont’s impressive post-agricultural reforestation masks persisting alterations in geomorphic, hydrologic, and biogeochemical processes of the region’s CZ that have important implications for ecosystem services today."

In support of this central hypothesis, five supporting hypotheses are being tested...

Ecohydrological Recovery:

"In CZs altered by land degradation and soil erosion, restoration of hydrologic functions depends on recoveries of macropore networks, biodiversity, and biogeochemical processes."

 

Calhoun researchers are bringing back to life gauged watersheds built by the U.S. Forest Service over 50 year ago. Re-instrumentation of the catchments is necessary to forecast changes in hydrologic functioning of the Calhoun CZ, and thereby test the Ecohydrological Recovery Hypothesis.

Archived stream and rain data housed at Coweeta Hydrologic Laboratory contain a detailed record of hydrologic response of eroded watersheds from the 1940s to present. The ability to hindcast will contribute to testing the Ecohydrological Recovery, Erosion-induced Carbon Dynamics, and Dynamic Persistence of Alternative States Hypotheses.

Biogeochemical Decoupling:

"In CZs altered by land degradation and soil erosion, biogeochemical processes in surficial components CZs become decoupled from those in deep layers."

In cooperation with Mr. Steve Stone, a local landowner, Dan Richter and Allan Bacon hired an engineering firm in 2010 to drill to a depth of nearly 70m.

Soil and unweathered granitic gneiss collected at regular intervals for comprehensive chemical analysis has established valuable measures of pedogenesis essential to testing the Biogeochemcial Decoupling Hypothesis.

The installation of an inverted tower at the Calhoun CZO will give reserachers access to deep soil, gas, and water samples. In conjunction with a eddy-covaraince flux tower to provide atmospheric data, direct observations from the uppermost to lowermost CZ will allow testing of the Decoupling Hypothesis, e.g. differences in carbon parameters between pristine hardwood and eroded plots.

Erosion-induced Carbon Dynamics:

"Delayed oxidation of eroded soil organic carbon (SOC) buried in oxygen-deficient alluvial sediments represents a substantial fraction of erosion-induced alterations of soil C cycling."

Holcombe's Branch will be intensively sampled to quantify soucres and sinks of SOC. Using numerous approaches to the characterization of soil C, researchers will have a detailed history of carbon mobilization and stabilization in the watershed.

Quantifying the potential for Fe and Al-oxide rich subsoils to stabilize SOC relative to surface horizons is central to testing the Erosion-induced Carbon Dynamics Hypothesis.

Human-CZ Interactions:

"Within a physiographic region, historic and contemporary human-forced alterations of the CZ fundamentally shape present and future management and livelihood options."

The legacy of cotton cultivation fundamentally altered the landscape of the Southern Piedmont. While the Calhoun LTSE has traced biogeochemical changes that accompanied forest growth on old fields, socio-economic changes in the region have been remarkable as well.

The Gist family cemetery is a sober reminder of the area's plantation history. William Henry Gist was Governor of South Carolina from 1858-1860 and a strong advocate of secession. Today, the former Gist property, known as Rose Hill State Park, has reference hardwood stands and gullied old fields that are being studied as part of the Calhoun CZO.

Dynamic Persistence of Alternative States:

"In CZs altered by land degradation and soil erosion, loss of surficial horizons, and reductions in infiltration, deep rooting, macroinvertebrates, and aggregation, impede redevelopment of forests and CZs with high productivity, standing biomass, and environmental services characteristic of forests never converted to cultivation agriculture."

Critical zone structure and function are being compared between remnant uncultivated hardwood forests, and directly adjacent old fields and pastures.

In cooperation with Mr. Steve Stone, a local landowner, Dan Richter and Allan Bacon hired an engineering firm in 2010 to drill to a depth of nearly 70m.

 

Soil and unweathered granitic gneiss collected at regular intervals for comprehensive chemical analysis has established valuable measures of pedogenesis essential to testing the Biogeochemcial Decoupling Hypothesis.

 

Archived stream and rain data housed at Coweeta Hydrologic Laboratory contain a detailed record of hydrologic response of eroded watersheds from the 1940s to present.  The ability to hindcast will contribute to testing the Ecohydrological Recovery, Erosion-induced Carbon Dynamics, and Dynamic Persistence of Alternative States Hypotheses.

 

 

Calhoun researchers are bringing back to life gauged watersheds built by the U.S. Forest Service over 50 year ago.  Re-instrumentation of the catchments is necessary to forecast changes in hydrologic functioning of the Calhoun CZ, and thereby test the Ecohydrological Recovery Hypothesis.

 

 

 

 

 

The installation of an inverted tower at the Calhoun CZO will give reserachers access to deep soil, gas, and water samples.  In conjunction with a eddy-covaraince flux tower to provide atmospheric data, direct observations from the uppermost to lowermost CZ will allow testing of the Decoupling Hypothesis, e.g. differences in carbon parameters between pristine hardwood and eroded plots.

 

 

Calhoun researchers are bringing back to life gauged watersheds built by the U.S. Forest Service over 50 year ago.  Re-instrumentation of the catchments is necessary to forecast changes in hydrologic functioning of the Calhoun CZ, and thereby test the Ecohydrological Recovery Hypothesis.

 

Holcombe's Branch will be intensively sampled to quantify soucres and sinks of SOC.  Using numerous approaches to the characterization of soil C, researchers will have a detailed history of carbon mobilization and stabilization in the watershed.

 

Quantifying the potential for Fe and Al-oxide rich subsoils to stabilize SOC relative to surface horizons is central to testing the Erosion-induced Carbon Dynamics Hypothesis.

 

The installation of an inverted tower at the Calhoun CZO will give reserachers access to deep soil, gas, and water samples.  In conjunction with a eddy-covaraince flux tower to provide atmospheric data, direct observations from the uppermost to lowermost CZ will allow testing of the Decoupling Hypothesis, e.g. differences in carbon parameters between pristine hardwood and eroded plots.

 

 

The legacy of cotton cultivation fundamentally altered the landscape of the Southern Piedmont.  While the Calhoun LTSE has traced biogeochemical changes that accompanied forest growth on old fields, socio-economic changes in the region have been remarkable as well.

Critical zone structure and function are being compared between remnant uncultivated hardwood forests, and directly adjacent old fields and pastures.

The Gist family cemetery is a sober reminder of the area's plantation history.  William Henry Gist was Governor of South Carolina from 1858-1860 and a strong advocate of secession.  Today, the former Gist property, known as Rose Hill State Park, has reference hardwood stands and gullied old fields that are being studied as part of the Calhoun CZO. 


Research News

FEATURED

X-ray Diffraction for Clay Minerals at Calhoun

01 May 2017 - Anna Wade (visiting from Duke University) and Jay Austin (based at the University of Georgia) are collaborating by using X-ray Diffraction (XRD) to...

FEATURED

Zach Brecheisen wins the Frederick K. Weyerhaeuser Forest History Fellowship

27 Apr 2017 - The Forest History Society announces that Zachary Brecheisen is the 2017-18 recipient of the F. K. Weyerhaeuser Fellowship! The fellowship consists...

FEATURED NATIONALLY

The frontier beneath our feet — an AGU commentary on the critical zone

21 Apr 2017 - AGU has published a collection of commentaries highlighting the important role Earth and space science research plays in society.

FEATURED NATIONALLY

2017 CZO Webinar Series: Critical Zone and Society

06 Apr 2017 - 2017 CZO Webinar Series: Critical Zone and Society.

FEATURED

Bruno Latour talks about the Calhoun CZO in Munich

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

FEATURED

CZOs at AGU 2016

22 Nov 2016 - CZOs at AGU 2016: Agenda and award recipients

FEATURED

Four soil pits installed in new Research Area 8!

21 Nov 2016 - 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.

FEATURED

Eight new soil pits dug at the Calhoun!

17 Oct 2016 - Eight soil pits were installed at the Calhoun CZO on 17-18 October 2016 for easy access for soil sampling down to 2 meters. Photo: Will Cook.

FEATURED

First flux tower erected at the Calhoun CZO

17 Aug 2016 - On August 17, 2016 a crew from Georgia Tech led by graduate student Yao Tang and professor Jingfeng Wang, with a little help from the folks at Duke,...

FEATURED

Going deep! Gas wells installed at 8.5 m

14 Jul 2016 - Another Calhoun CZO record - gas reservoirs installed at 8.5m depth! Jay Austin, Zach Brecheisen, and Dan Richter only stopped at 8.5m because they...

FEATURED

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

15 Nov 2015 - Get a sense of the people and the work. Several members of the Calhoun CZO are profiled here, including students and professors.

FEATURED

New study suggests bedrock weathering based on topography

30 Oct 2015 - St. Clair et al. suggest tectonic stresses interact with topography to influence bedrock weathering.

FEATURED

Sino-USA CZO scientists meet to discuss future collaborations

09 Oct 2015 - About 60 Chinese and American critical zone scientists met in Guiyang, China for two days of discussions and presentations on the significance of...


TDR probes installed to monitor soil moisture

13 Jul 2016 - On July 13, 2016, Duke PhD candidate Zach Brecheisen, with assistance from his advisor Dan Richter and Jay Austin, installed TDR probes at 25-cm...

Critical Zone Profile - Diego Barcellos

09 Jun 2016 - PhD Student, Soil Science, University of Georgia

Historic Legacy Sediments Examined at 2016 Summer Science Meeting

03 Jun 2016 - The Calhoun CZO held its third annual Summer Science Days meeting.  In the photo, Calhoun researchers discuss a 18th-19th century pine root...

EOS: Taking the Pulse of the Earth’s Surface Systems

04 Dec 2015 - Taking the Pulse of the Earth's Surface Systems In September of 2014, Laurel Larsen (UC Berkley), Elizabeth Hajek (Penn State), and others...

Critical Zone Profile - KYUNGJIN (KJ) MIN (soil ecologist, PhD student)

15 Nov 2015 - PhD Student, Department of Ecology and Evolutionary Biology, University of Kansas

More News >


Example Publications

FEATURED

Historical land use dynamics in the highly degraded landscape of the Calhoun Critical Zone Observatory. Coughlan, Michael R., Donald R. Nelson, Michael Lonneman, and Ashley E. Block (2017): Land 6(2), 32

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

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 Cross-CZO

FEATURED

Hydro-geomorphic perturbations on the soil-atmosphere CO2 exchange: How (un)certain are our balances?. Dialynas, Y. G., R. L. Bras, and D. deB. Richter (2017): Water Resources Research, 53

FEATURED

Special issue of The Earth Scientist about the Critical Zone and the US NSF Critical Zone Observatory (CZO) program. CZO Education/Outreach team (2016): The Earth Scientist, Volume XXXII, Issue 3, Fall 2016 Cross-CZO National

FEATURED

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

FEATURED

Topographic variability and the influence of soil erosion on the carbon cycle. Dialynas, Y. G., S. Bastola., R. L. Bras, S. A. Billings, D. Markewitz, and D. deB. Richter (2016): Global Biogeochemical Cycles 30(5): 644-660

FEATURED

Geophysical imaging reveals topographic stress control of bedrock weathering. St. Clair, J., S. Moon, W. S. Holbrook, J. T. Perron, C. S. Riebe, S. J. Martel, B. Carr, C. Harman, K. Singha, D. deB. Richter (2015): Science, 30 October 2015, Vol. 350, no. 6260, pp. 534-538 Cross-CZO National

FEATURED

Chapter 2 – The Role of Critical Zone Observatories in Critical Zone Science. White T., Brantley S., Banwart S., Chorover J., Dietrich W., Derry L., Lohse K., Anderson S., Aufdendkampe A., Bales R., Kumar P., Richter D., McDowell B. (2015): Developments in Earth Surface Processes 19: 15–78 Cross-CZO National

FEATURED

'One Physical System': Tansley's ecosystem as Earth's critical zone. Richter, D. deB., and S.A. Billings (2015): New Phytologist 206 (3): 900-912

FEATURED

Diachronous beginnings of the Anthropocene: The lower bounding surface of anthropogenic deposits. Edgeworth, M., D.deB. Richter, C. Waters, P. Haff, C. Neal, S.J. Price (2015): The Anthropocene Review 2 (1): 33-58

FEATURED

Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development. Mobley, Megan L., Kate Lajtha, Marc G. Kramer, Allan R. Bacon, Paul R. Heine and Daniel deB. Richter (2015): Global Change Biology 21(2): 986-996

FEATURED

Evolution of Soil, Ecosystem, and Critical Zone Research at the USDA FS Calhoun Experimental Forest. Richter, D. deB., A.R. Bacon, S.A. Billings, D. Binkley, M. Buford, M.A. Callaham, A.E. Curry, R.L. Fimmen, A. S. Grandy, P.R. Heine, M. Hofmockel, J.A. Jackson, E. LeMaster, J. Li, D. Markewitz, M.L. Mobley, M.W. Morrison, M.S. Strickland, T. Waldrop, and C. G. Wells (2014): In: USDA Forest Service Experimental Forests and Ranges: Research for the Long Term, Chapter: 18, Publisher: Springer Verlag, Editors: D.C. Hayes, S.L. Stout, R.H. Crawford, A.P. Hoover, pp. 405-433


A model of three-dimensional topographic stresses with implications for bedrock fractures, surface processes, and landscape evolution. Moon, S., J.T. Perron, S.J. Martel, W.S. Holbrook, and J. St. Clair (2017): Journal of Geophysical Research: Earth Surface 122 (4): 823-846 Cross-CZO

Multiple outflows, spatial components, and nonlinearities in age theory. Calabrese, S., and Porporato, A. (2017): Water Resources Research, 53 (1): 110-126

On the dynamic smoothing of mountains. Bonetti, S., and Porporato, A. (2017): Geophysical Research Letters, in press

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth. Brantley, S.L., McDowell, W.H., Dietrich, W.E., White, T.S., Kumar, P., Anderson, S., Chorover, J., Lohse, K.A., Bales, R.C., Richter, D., Grant, G., and Gaillardet, J. (2017): Earth Surface Dynamics Cross-CZO National

Aging exo-enzymes can create temporally shifting, temperature-dependent resource landscapes for microbes. Billings, S., K. Min, F. Ballantyne IV, Y. Chen, M. Sellers (2016): Biogeochemistry 131:163-172

Carbon availability modifies temperature responses of heterotrophic microbial respiration, carbon uptake affinity, and stable carbon isotope discrimination. Min, Kyungjin, Christoph A. Lehmeier, Ford Ballantyne IV, and Sharon A. Billings (2016): Frontiers in Microbiology 7, Article 2083

The Anthropocene is functionally and stratigraphically distinct from the Holocene. Waters, C.N., and 23 co-authors, including D.deB. Richter (2016): Science 351(6269): 137

More Publications >