Current Research

My current research at the Silas Little Experimental Forest in the New Jersey Pine Barrens focuses on quantifying and modeling factors driving fire danger and fire behavior. Severe wildfires in the Pine Barrens are strongly driven by weather, especially episodes of low relative humidity and high windspeeds associated with the passage of strong cold fronts, such as before and during the 18,000 acre Warren Grove fire of May 2007. Delivery of high quality weather data measured from our network of fire weather towers, and accurate, validated fire weather predictions by the EAMC for the region provide wildland fire managers with tools to detect and plan for these events. EAMC model predictions are evaluated using extensive field measurements in the Pine Barrens, including three eddy flux towers to measure turbulence and energy exchange, and a SODAR to measure windspeed and direction up to 700 meter height.

Fire weather interacts with complex fuel beds, and much of my collaborative research is focused on fuel mapping, quantification of complex fuel bed structure, and measuring the effects of prescribed fires on fuels and forest structure. The interactions of weather and fuel beds drive fuel moisture dynamics, and these are key elements of wildfire risk and fire behavior. Thus, fuel moisture dynamics and ecosystem scale characterization of energy and hydrologic fluxes are important parts of my research. I am also interested in tech-transfer, or how to best provide this information to wildland fire and other land managers.

My other research interests are the physical and biological processes that drive the carbon and nutrient dynamics of terrestrial ecosystems. This research addresses two major questions: 1) How do environmental factors, substrate quality and disturbances interact to control short-term carbon and nutrient dynamics, and 2) How do processes linked to global environmental change, such as forest and fire management, land use change, and climate change affect the long-term dynamics of these systems? Understanding the effects of forest management, fire, invasive insects, and land use change on carbon dynamics at landscape and regional scales is essential, because these human-induced changes are impacting the composition of the atmosphere, further driving climate change. My research approach involves the complementary use of measurements and models of land-atmosphere exchanges of energy, water, and CO2. For example, I use eddy covariance to quantify net CO2 exchange, and evaluate flux measurements against models and carbon budgets constructed from field measurements of biomass accumulation, litterfall and decomposition.

The integration of these disciplines, from operational fire danger rating and complex fuel bed characterization to landscape level measurements of forest productivity result in a synthetic framework to solve many of the complex questions assigned to the Silas Little Experimental Forest. My research also has included investigations of landscape-scale carbon dynamics in a mosaic of intensively-managed and naturally-regenerated forests in Florida, regional linkages in the nitrogen cycle between lowland and montane forests in Costa Rica, and the role of native herbivores in carbon and nitrogen dynamics of semiarid scrub in Argentina and Longleaf Pine forests in Florida.

Research Interests

• A validated fuel moisture model for complex fuel beds driven by MM5 fire weather predictions
• Development and delivery of a drought stress index based on eddy covariance measurements
• Impacts of disturbances on hydrologic and nutrient cycles in the Pine Barrens

Why This Research is Important

Wildfire risk is real in the Pine Barrens. This landscape is dominated by highly flammable forests consisting of Pitch Pine and dense understory shrubs and oaks, and it continues to be flammable despite repeated wildfires and/or fuel reduction treatments. These forests are adjacent to extensive wildland urban interface (WUI) and key transportation corridors, making suppression activities complicated. The need for accurate fire weather, fuel loading, and fuel moisture information is obvious.

My current research in the Pine Barrens also has important policy implications, because it focuses on the carbon dynamics of fire management, and how prescribed fire, wildfire, and other disturbances control rates of carbon sequestration by forests. By placing forest harvesting, prescribed fire treatments, and other disturbances in the context of forest productivity measurements and models, we have advanced an understanding of how these activities and processes affect long-term C dynamics. We are incorporating this information in a synthetic, predictive framework to assist State and Federal fire and forest managers optimize the reduction of wildfire risk and emissions while maintaining rates of C sequestration by forests.

Education

• University of Florida, Gainesville, FL, Ph.D. Forest Ecology 1994
• Humboldt State University, Arcata, CA, M.A. Biology 1985
• Humboldt State University, Arcata, CA, B.A. Botany 1981

Professional Organizations

• Ecological Society of America
• American Association for the Advancement of Science (AAAS)
• Association of Tropical Biology and Conservation
• Wilderness Society
• Pinelands Preservation Alliance

Featured Publications & Products

• Skowronski, Nicholas S.; Clark, Kenneth L.; Duveneck, Matthew; Hom, John. 2011. Three-dimensional canopy fuel loading predicted using upward and downward sensing LiDAR systems.
• Clark, Kenneth L.; Skowronski, Nicholas; Hom, John. 2010. Invasive insects impact forest carbon dynamics.
• Schafer, Karina V.; Clark, Kenneth L.; Skowronski, Nicholas; Hamerklynck, Erik P. 2010. Impact of insect defoliation on forest carbon balance as assessed with a canopy assimilation model.
• Hollinger, D.Y.; Ollinger, S.V.; Richardson, A.D.; Meyers, T.P.; Dails, D.B.; Martin, M.E.; Scott, N.A.; Arkebauer, T.J.; Baldocchi, D.D.; Clark, K.L.; Curtis, P.S.; Davis, K.J.; Desai, A.R.; Dragoni, D.; Goulden, M.L.; Gu, L.; Katul, G.G.; Pallardy, S.G.; Paw U, K.T.; Schmid, H.P.; Stoy, P.C.; Suyker, A.E.; Verma, S.B. 2010. Albedo estimates for land surface models and support for a new paradigm based on foliage nitrogen concentration.
• Clark, Kenneth L.; Skowronski, Nicholas; Hom, John; Duveneck, Matthew; Pan, Yude; Van Tuyl, Stephen; Cole, Jason; Patterson, Matthew; Maurer, Stephen. 2009. Decision support tools to improve the effectiveness of hazardous fuel reduction treatments in the New Jersey Pine Barrens.

Publications

• Charney, Joseph J.; Kiefer, Michael T.; Zhong, Shiyuan ; Heilman, Warren E.; Nikolic, Jovanka ; Bian, Xindi ; Hom, John L.; Clark, Kenneth L.; Skowronski, Nicholas S.; Gallagher, Michael R.; Patterson, Matthew ; Liu, Yongqiang ; Hawley, Christie . 2019. Assessing Forest Canopy Impacts on Smoke Concentrations Using a Coupled Numerical Model.
• Heilman Warren E., ; Clements Craig B., ; Zhong, Shiyuan ; Clark, Kenneth L.; Bian, Xindi . 2019. Atmospheric turbulence.
• Heilman, Warren E.; Bian, Xindi ; Clark, Kenneth L.; Zhong, Shiyuan . 2019. Observations of Turbulent Heat and Momentum Fluxes during Wildland Fires in Forested Environments.
• Helliker, Brent R.; Song, Xin ; Goulden, Michael L.; Clark, Kenneth ; Bolstad, Paul ; Munger, J. William; Chen, Jiquan ; Noormets, Asko ; Hollinger, David ; Wofsy, Steve ; Martin, Timothy ; Baldocchi, Dennis ; Euskirchenn, Eugenie ; Desai, Ankur ; Burns, Sean P. 2018. Assessing the interplay between canopy energy balance and photosynthesis with cellulose 18O: large-scale patterns and independent ground-truthing.
• Clark, Kenneth L.; Branch, Lyn C.; Farrington, Jennifer . 2018. Bioturbation by mammals and fire interact to alter ecosystem-level nutrient dynamics in longleaf pine forests.
• Clark, Kenneth L.; Renninger, Heidi J.; Skowronski, Nicholas; Gallagher, Michael; Schäfer, Karina V.R. . 2018. Decadal-Scale Reduction in Forest Net Ecosystem Production Following Insect Defoliation Contrasts with Short-Term Impacts of Prescribed Fires.
• Mueller, Eric V; Skowronski, Nicholas ; Thomas, Jan C.; Clark, Kenneth ; Gallagher, Michael R.; Hadden, Rory ; Mell, William ; Simeoni, Albert . 2018. Local measurements of wildland fire dynamics in a field-scale experiment.
• Butler-Leopold, Patricia R.; Iverson, Louis R.; Thompson, Frank R.; Brandt, Leslie A.; Handler, Stephen D.; Janowiak, Maria K.; Shannon, P. Danielle; Swanston, Christopher W.; Bearer, Scott ; Bryan, Alexander M.; Clark, Kenneth L.; Czarnecki, Greg ; DeSenze, Philip ; Dijak, William D.; Fraser, Jacob S.; Gugger, Paul F.; Hille, Andrea ; Hynicka, Justin ; Jantz, Claire A.; Kelly, Matthew C.; Krause, Katrina M.; La Puma, Inga Parker; Landau, Deborah ; Lathrop, Richard G.; Leites, Laura P.; Madlinger, Evan ; Matthews, Stephen N.; Ozbay, Gulnihal ; Peters, Matthew P.; Prasad, Anantha ; Schmit, David A.; Shephard, Collin ; Shirer, Rebecca ; Skowronski, Nicholas S.; Steele, Al ; Stout, Susan ; Thomas-Van Gundy, Melissa ; Thompson, John ; Turcotte, Richard M.; Weinstein, David A.; Yáñez, Alfonso . 2018. Mid-Atlantic forest ecosystem vulnerability assessment and synthesis: a report from the Mid-Atlantic Climate Change Response Framework project.
• Chu, Housen ; Baldocchi, Dennis D.; Poindexter, Cristina ; Abraha, Michael ; Desai, Ankur R.; Bohrer, Gil ; Arain, M. Altaf; Griffis, Timothy ; Blanken, Peter D.; O'Halloran, Thomas L.; Thomas, R. Quinn; Zhang, Quan ; Burns, Sean P.; Frank, John M.; Christian, Dold ; Brown, Shannon ; Black, T. Andrew; Gough, Christopher M.; Law, Beverly E.; Lee, Xuhui ; Chen, Jiquan ; Reed, David E.; Massman, William J.; Clark, Kenneth ; Hatfield, Jerry ; Prueger, John ; Bracho, Rosvel ; Baker, John M.; Martin, Timothy A. 2018. Temporal dynamics of aerodynamic canopy height derived from eddy covariance momentum flux data across North American flux networks.
• Simeoni, Albert; Owens, Zachary C.; Christiansen, Erik W.; Kemal, Abid; Gallagher, Michael; Clark, Kenneth L.; Skowronski, Nicholas; Mueller, Eric V.; Thomas, Jan C.; Santamaria, Simon; Hadden, Rory M. 2017. A preliminary study of wildland fire pattern indicator reliability following an experimental fire.
• Heilman, Warren E.; Bian, Xindi; Clark, Kenneth L.; Skowronski, Nicholas S.; Hom, John L.; Gallagher, Michael R. 2017. Atmospheric turbulence observations in the vicinity of surface fires in forested environments.
• Clark, Kenneth L.; Ayres, Matthew; Aoki, Carissa; Wengrowski, Emily; Peterken, Jane. 2017. Impact of Southern Pine Beetle on Forest Structure and Fuel Loading in a Wildfire-prone Landscape.
• Thomas, Jan C.; Mueller, Eric V.; Santamaria, Simon; Gallagher, Michael; El Houssami, Mohamad; Filkov, Alexander; Clark, Kenneth; Skowronski, Nicholas; Hadden, Rory M.; Mell, William; Simeoni, Albert. 2017. Investigation of firebrand generation from an experimental fire: Development of a reliable data collection methodology.
• Kabrick, John M.; Clark, Kenneth L.; D'Amato, Anthony W.; Dey, Daniel C.; Kenefic, Laura S.; Kern, Christel C.; Knapp, Benjamin O.; MacLean, David A.; Raymond, Patricia; Waskiewicz, Justin D. 2017. Managing hardwood-softwood mixtures for future forests in eastern North America: assessing suitability to projected climate change.
• ​Clark, Kenneth L.; Gallagher, Michael; Heilman, Warren E.; Skowronski, Nicholas; Mueller, Eric; Simeoni, Albert. 2017. Relationships between firing pattern, fuel consumption, and turbulence and energy exchange during prescribed fires.
• Mueller, Eric V.; Skowronski, Nicholas; Clark, Kenneth; Gallagher, Michael; Kremens, Robert; Thomas, Jan C.; El Houssami, Mohamad; Filkov, Alexander; Hadden, Rory M.; Mell, William; Simeoni, Albert. 2017. Utilization of remote sensing techniques for the quantification of fire behavior in two pine stands.
• Clark, Kenneth L.; Branch, Lyn C.; Hierro, Jose L.; Villarreal, Diego. 2016. Burrowing herbivores alter soil carbon and nitrogen dynamics in a semi-arid ecosystem, Argentina.
• El Houssami, Mohamad; Mueller, Eric; Filkov, Alexander; Thomas, Jan C; Skowronski, Nicholas; Gallagher, Michael R; Clark, Ken; Kremens, Robert; Simeoni, Albert. 2016. Experimental procedures characterizing firebrand generation in wildland fires.
• Carlo, Nicholas J.; Renninger, Heidi J.; Clark, Kenneth L.; Schäfer, Karina V.R. 2016. Impacts of prescribed fire on Pinus rigida Mill.
• Zscheischler, Jakob; Fatichi, Simone; Wolf, Sebastian; Blanken, Peter D.; Bohrer, Gil; Clark, Ken; Desai, Ankur R.; Hollinger, David; Keenan, Trevor; Novick, Kimberly A.; Seneviratne, Sonia I. 2016. Short-term favorable weather conditions are an important control of interannual variability in carbon and water fluxes.
• Clark, Kenneth L.; Skowronski, Nicholas; Gallagher, Michael. 2015. Fire management and carbon sequestration in Pine Barren Forests.
• Mueller, Eric; Skowronski, Nicholas; Clark, Kenneth; Kremens, Robert; Gallagher, Michael; Thomas, Jan; El Houssami, Mohamad; Filkod, Alexander; Butler, Bret; Hom, John; Mell, William; Simeoni, Albert. 2015. Initial results from a field experiment to support the assessment of fuel treatment effectiveness in reducing wildfire intensity and spread rate.
• Heilman, Warren E.; Clements, Craig B.; Seto, Daisuke; Bian, Xindi; Clark, Kenneth L.; Skowronski, Nicholas S.; Hom, John L. 2015. Observations of fire-induced turbulence regimes during low-intensity wildland fires in forested environments: implications for smoke dispersion.
• Renninger, Heidi J.; Carlo, Nicholas J.; Clark, Kenneth L.; Schäfer, Karina V.R. 2015. Resource use and efficiency, and stomatal responses to environmental drivers of oak and pine species in an Atlantic Coastal Plain forest.
• Skowronski, Nicholas S.; Haag, Scott; Trimble, Jim; Clark, Kenneth L.; Gallagher, Michael R.; Lathrop, Richard G. 2015. Structure-level fuel load assessment in the wildland-urban interface: a fusion of airborne laser scanning and spectral remote-sensing methodologies.
• Skowronski, Nicholas S.; Clark, Kenneth L.; Gallagher, Michael; Birdsey, Richard A.; Hom, John L. 2014. Airborne laser scanner-assisted estimation of aboveground biomass change in a temperate oak-pine forest.
• Clark, Kenneth L.; Skowronski, Nicholas; Renninger, Heidi; Scheller, Robert. 2014. Climate change and fire management in the mid-Atlantic region.
• Clark, K.L.; Skowronski, N.S.; Gallagher, M.R.; Renninger, H.; Schäfer, K.V.R. 2014. Contrasting effects of invasive insects and fire on ecosystem water use efficiency.
• Schäfer, K.V.R.; Renninger, H.J.; Clark, K.L.; Medvigy, D. 2014. Hydrological responses to defoliation and drought of an upland oak/pine forest.
• Lucash, Melissa S.; Scheller, Robert M.; Kretchun, Alec M.; Clark, Kenneth L.; Hom, John. 2014. Impacts of fire and climate change on long-term nitrogen availability and forest productivity in the New Jersey Pine Barrens.
• Song, Xin; Clark, Kenneth S.; Helliker, Brent R. 2014. Interpreting species-specific variation in tree-ring oxygen isotope ratios among three temperate forest trees.
• Renninger, Heidi J.; Carlo, Nicholas; Clark, Kenneth L.; Schäfer, Karina V.R. 2014. Modeling respiration from snags and coarse woody debris before and after an invasive gypsy moth disturbance.
• Kiefer, Michael T.; Heilman, Warren E.; Zhong, Shiyuan; Charney, Joseph J.; Bian, Xindi; Skowronski, Nicholas S.; Hom, John L.; Clark, Kenneth L.; Patterson, Matthew; Gallagher, Michael R. 2014. Multiscale simulation of a prescribed fire event in the New Jersey Pine Barrens using ARPS-CANOPY.
• Kretchun, Alec M.; Scheller, Robert M.; Lucash, Melissa S.; Clark, Kenneth L.; Hom, John; Van Tuyl, Steve; Fine, Michael L. 2014. Predicted effects of gypsy moth defoliation and climate change on forest carbon dynamics in the New Jersey Pine Barrens.
• Clark, Kenneth L.; Skowronski, Nicholas; Gallagher, Michael. 2014. The fire research program at the Silas Little Experimental Forest, New Lisbon, New Jersey.
• Cole, Jason A.; Johnson, Kristopher D.; Birdsey, Richard A.; Pan, Yude; Wayson, Craig A.; McCullough, Kevin; Hoover, Coeli M.; Hollinger, David Y.; Bradford, John B.; Ryan, Michael G.; Kolka, Randall K.; Wieshampel, Peter; Clark, Kenneth L.; Skowronski, Nicholas S.; Hom, John; Ollinger, Scott V.; McNulty, Steven G.; Gavazzi, Michael J. 2013. Database for landscape-scale carbon monitoring sites.
• Renninger, Heidi J.; Clark, Kenneth L.; Skowronski, Nicholas; Schäfer, Karina V.R. 2013. Effects of a prescribed fire on water use and photosynthetic capacity of pitch pines.
• Medvigy, David; Jeong, Su-Jong; Clark, Kenneth L.; Skowronski, Nicholas S.; Schäfer, Karina V. R. 2013. Effects of seasonal variation of photosynthetic capacity on the carbon fluxes of a temperate deciduous forest.
• Schneider, Maximilian P. W.; Pyle, Lacey A.; Clark, Kenneth L.; Hockaday, William C.; Masiello, Caroline A.; Schmidt, Michael W.I. 2013. Toward a "molecular thermometer" to estimate the charring temperature of wildland charcoals derived from different biomass sources.
• Scheller, Robert M.; Kretchun, Alec M.; Van Tuyl, Steve; Clark, Kenneth L.; Lucash, Melissa S.; Hom, John. 2012. Divergent carbon dynamics under climate change in forests with diverse soils, tree species, and land use histories.
• Clark, Kenneth L.; Skowronski, Nicholas; Gallagher, Michael; Renninger, Hedi; Schafer, Karina. 2012. Effects of invasive insects and fire on energy exchange and evapotranspiration in the New Jersey pine lands.
• Medvigy, D.; Clark, K.L.; Skowronski, N.S.; Schäfer, K.V.R. 2012. Simulated impacts of insect defoliation on forest carbon dynamics.
• Scheller, Robert M.; Van Tuyl, Steve; Clark, Kenneth L.; Hom, John; La Puma, Inga. 2011. Carbon sequestration in the New Jersey Pine Barrens under different scenarios of fire management.
• Kiefer, Michael T.; Heilman, Warren E.; Zhong, Shiyuan; Charney, Joseph J.; Bian, X.; Shadbolt, Ryan P.; Hom, John; Clark, Kenneth; Skowronski, Nicholas; Gallagher, Michael; Patterson, Matthew. 2011. Development of a fine scale smoke dispersion modeling system. Part II: Case study of a prescribed burn in the New Jersey Pine Barrens.
• Hierro, Jose L.; Clark, Kenneth L.; Branch, Lyn C.; Villarreal, Diego. 2011. Native herbivore exerts contrasting effects on fire regime and vegetation structure.
• Miao, Zewei; Lathrop, Richard G.; Xu, Ming; La Puma, Inga P.; Clark, Kenneth L.; Hom, John; Skowronski, Nicholas; Van Tuyl, Steve. 2011. Simulation and sensitivity analysis of carbon storage and fluxes in the New Jersey Pinelands.
• Clark, Ken; Skowronski, Nicholas; Michael, Gallagher; Heilman, Warren E.; Hom, John. 2010. Fuel consumption and particulate emissions during fires in the New Jersey Pinelands.
• Scheller, Robert M.; Van Tuyl, Steve; Clark, Kenneth; Hayden, Nicholas G.; Hom, John; Mladenoff, David J. 2008. Simulation of forest change in the New Jersey Pine Barrens under current and pre-colonial conditions.
• Skowronski, Nicholas; Clark, Kenneth; Nelson, Ross; Hom, John; Patterson, Matt. 2007. Remotely sensed measurements of forest structure and fuel loads in the Pinelands of New Jersey.
• Clark, Kenneth; Skowronski, Nick; Pan, Yude; Van Tuyl, Steve; Heilman, Warren. 2006. Fire research in the pine barrens of New Jersey.
• Pan, Yude; Birdsey, Richard; Hom, John; McCullough, Kevin; Clark, Kenneth. 2006. Improved estimates of net primary productivity from MODIS satellite data at regional and local scales.
• Powell, Thomas L.; Starr, Gregory; Clark, Kenneth L.; Martin, Timothy A.; Gholz, Henry L. 2005. Ecosystem and understory water and energy exchange for a mature, naturally regenerated pine flatwoods forest in north Florida.
• Clark, Kenneth L.; Nadkarni, Nalini M.; Gholz, Henry L. 2005. Retention of inorganic nitrogen by epiphytic bryophytes in a tropical montane forest.
• Clark, Kenneth L.; Gholz, Henry L.; Castro, Mark S. 2004. Carbon dynamics along a chronosequence of slash pine plantation in north Florida.

Research Highlights

Highlight	Title	Year
NRS-2010-002	Carbon and Water Cycle Recovery Patterns After Disturbance in Forest Ecosystems The recovery of carbon and hydrologic cycling following two major disturbances in pine and oak-dominated stands in the New Jersey Pine Barrens-- ...	2010
NRS-2014-073	Contrasting Effects of Invasive Insects and Fire on Forest Carbon Dynamics Forest Service scientists quantified rates of carbon sequestration and water use by forests before and after invasive insect defoliation and pre ...	2014
NRS-2015-150	Fire Management and Carbon Sequestration in Pine Barrens Ecosystems Forest Service scientists quantified consumption and accumulation of the forest floor and understory vegetation during and following prescribed ...	2015
NRS-2011-07	Fireflux Experiments Improve Safety of Prescribed Burns in the New Jersey Pine Barrens Predicting the effects of smoke from low-intensity prescribed fires on local air-quality is being made easier by new tools developed by Forest S ...	2011
NRS-2017-71	Forest Service scientists disentangle some of the complexity associated with wildland fires Land mangers conduct planned wildland fires with the goals of reducing hazardous fuels and the severity of future wildfires and to create desire ...	2017
NRS-2016-84	Hardwood-Softwood Mixtures for Future Forests in Eastern North America: Assessing Suitability to Projected Climate Change Despite growing interest in management strategies for climate change adaptation, there are few methods for assessing the ability of stands to en ...	2016
NRS-2010-001	Hazardous Fuel Assessments Using LIDAR and Field Measurements Lasers, in what is termed Light Detection and Ranging (LiDAR) systems, are being used by NRS researchers Nicholas Skowronski and Kenneth Clark t ...	2010
NRS-2012-26	Impact of Invasive Insects and Fire on Forest Water Resources Minor disturbances in forests that do not significantly alter biomass can reduce water use and increase ground water recharge to aquifers	2012
NRS-2017-42	Impacts of southern pine beetle on pine-dominated forests in New Jersey and New York Invasive insects can kill trees, alter forest structure, impact hazardous fuel loads, and modify the trajectory of forest succession. Forest Ser ...	2017
NRS-2013-059	Scientists Study Fire Management and Carbon Sequestration in Forests Forest Service scientists quantified rates of carbon sequestration by forests before and after prescribed burns were conducted by the New Jersey ...	2013
NRS-2016-133	Scientists Untangle Relationships Among Firing Technique, Fuel Consumption, and Turbulent Transfer in Forests Forest Service research indicates that relatively low-intensity prescribed fires can be effective at reducing hazardous fuels in forests while m ...	2016
NRS-2018-95	Understanding Wind Gusts During Fire can Help Fire and Smoke Managers Wind fields in the vicinity of wildland fires can be highly variable or turbulent, exhibiting significant gusts that can lead to erratic fire be ...	2018