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Scientists & Staff

Ken Clark

Research Forester
Climate, Fire, and Carbon Cycle Sciences
501 Four Mile Road
New Lisbon, NJ, 08064
Phone: 609-894-0325

Contact Ken Clark


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

Publications & Products

Research Datasets

  • Skowronski, Nicholas S.; Simeoni, Albert A.; Clark, Kenneth L.; Mell, William E.; Hadden, Rory M.; Gallagher, Michael R.; Mueller, Eric V.; Kremens, Robert L.; El Houssami, Mohamad; Filkov, Alexander I.; Thomas, Jan Christian. 2018. New Jersey fuel treatment effects: Leaf-off airborne LiDAR data. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2017-0059.
  • Kremens, Robert L.; Skowronski, Nicholas S.; Simeoni, Albert A.; Clark, Kenneth L.; Mell, William E.; Hadden, Rory M.; Gallagher, Michael R.; Mueller, Eric V.; El Houssami, Mohamad; Filkov, Alexander I.; Thomas, Jan Christian. 2017. New Jersey fuel treatment effects: Wildfire Airborne Sensor Program - orthorectified long-wave infrared and visible data images. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2017-0063.
  • Skowronski, Nicholas S.; Simeoni, Albert A.; Clark, Kenneth L.; Mell, William E.; Hadden, Rory M.; Gallagher, Michael R.; Mueller, Eric V.; Kremens, Robert L.; El Houssami, Mohamad; Filkov, Alexander I.; Thomas, Jan Christian. 2017. New Jersey treatment effects: Burn units. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2017-0062.
  • Gallagher, Michael R.; Clark, Kenneth L.; Thomas, Jan Christian; Mell, William E.; Hadden, Rory M.; Mueller, Eric V.; Kremens, Robert L.; El Houssami, Mohamad; Filkov, Alexander I.; Simeoni, Albert A.; Skowronski, Nicholas S. 2017. New Jersey fuel treatment effects: Pre- and post-burn biometric data. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2017-0061.
  • Clark, Kenneth L.; Skowronski, Nicholas S.; Simeoni, Albert A.; Mell, William E.; Hadden, Rory M.; Gallagher, Michael R.; Mueller, Eric V.; Kremens, Robert L.; El Houssami, Mohamad; Filkov, Alexander I.; Thomas, Jan Christian. 2017. New Jersey fuel treatment effects: 3-dimensional turbulence and temperature data. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2017-0060.

National Research Highlights

Favorable fire behavior in mixed conifer and brush during a burn operation near Jerseydale; Ferguson Fire, Sierra NF, CA, 2018.

Understanding Wind Gusts During Fire can Help Fire and Smoke Managers

Year: 2018

Wind fields in the vicinity of wildland fires can be highly variable or turbulent, exhibiting significant gusts that can lead to erratic fire behavior and enhanced mixing of smoke into the atmosphere. Northern Research Station scientists are examining the properties of turbulent circulations in forested wildland fire environments to ultimately improve predictive tools for fire and smoke management.

Figure 1. (a) A low intensity surface fire; and (b) a high intensity fire starting to transition to the forest canopy in the Pinelands National Reserve, New Jersey. Figure 2. One of the towers used to quantify turbulence and heat fluxes from wildland fires in the Pinelands National Reserve, New Jersey.

Forest Service scientists disentangle some of the complexity associated with wildland fires

Year: 2017

Land mangers conduct planned wildland fires with the goals of reducing hazardous fuels and the severity of future wildfires and to create desired conditions of forest structure and composition. How do fire managers optimize desired outcomes while reducing the impacts of smoke emissions and ember transport?

Figure 1. (a) Dead and down pitch pines killed by southern pine beetle in the Pinelands National Reserve of New Jersey, and basal area of (b) live trees and (c) live saplings separated into pines (Pinus rigida, P. echinata, P. virginiana), oaks (Quercus alba, Q. prinus, Q. marlandica, Q. velutina, Q. stellata, Q. falcata, Q. bicolor), and other hardwoods (Acer rubra, Nyssa sylvatica, Carya glabra, Magnolia virginiana, Sassifrass albicaulis) in control, natural, and treated plots.

Impacts of southern pine beetle on pine-dominated forests in New Jersey and New York

Year: 2017

Invasive insects can kill trees, alter forest structure, impact hazardous fuel loads, and modify the trajectory of forest succession. Forest Service scientists and their partners investigated how invasive insects alter forest structure and composition in pine-dominated forests of the northeastern United States and how forest resilience to wildfire and other disturbances is affected.

Examples of mixedwood types in eastern North America: A) shortleaf pine – oak forest in southern Missouri (credit: Missouri Department of Conservation); B) white pine – red oak forest in southern Maine (credit: Justin Waskiewicz); C) spruce – fir – hardwood forest in Quebec (credit: Patricia Raymond); D) hemlock – hardwood forest in northern Wisconsin. Kate Gerndt.

Hardwood-Softwood Mixtures for Future Forests in Eastern North America: Assessing Suitability to Projected Climate Change

Year: 2016

Despite growing interest in management strategies for climate change adaptation, there are few methods for assessing the ability of stands to endure or adapt to projected future climates. Forest Service scientists developed a means for assigning climate “compatibility” and “adaptability” scores to stands for assessing the suitability of tree species for projected climate scenarios. They used these scores to determine if mixed hardwood-softwood stands or “mixedwoods” were better suited to projected future climates than pure hardwood or pure softwood stands.

A low-intensity backing fire in a pine-oak stand with relatively low fuel loading in 2012, and initiation of a head fire in a pitch pine-scrub oak stand with relatively high fuel loading in 2014. Michael Gallagher and Nick Skowronski, U.S. Department of Agriculture Forest Service.

Scientists Untangle Relationships Among Firing Technique, Fuel Consumption, and Turbulent Transfer in Forests

Year: 2016

Forest Service research indicates that relatively low-intensity prescribed fires can be effective at reducing hazardous fuels in forests while minimizing impacts on local air quality.

A prescribed fire in a pitch pine stand in the Pinelands of New Jersey. Prescribed fires consume primarily forest floor and understory vegetation, resulting in rapid recovery following burns. USDA Forest Service

Fire Management and Carbon Sequestration in Pine Barrens Ecosystems

Year: 2015

Forest Service scientists quantified consumption and accumulation of the forest floor and understory vegetation during and following prescribed fires in upland forest stands in the New Jersey Pinelands. Their findings suggest that prescribed burning in upland pine-dominated forests has little effect on long-term forest carbon dynamics at the landscape scale.

A prescribed fire burning in the New Jersey Pinelands. Recovery following prescribed fires is rapid, and over a ten-year period burned stands sequestered twice the amount of carbon compared to stands defoliated by invasive insects. Michael Gallagher, USDA Forest Service

Contrasting Effects of Invasive Insects and Fire on Forest Carbon Dynamics

Year: 2014

Forest Service scientists quantified rates of carbon sequestration and water use by forests before and after invasive insect defoliation and prescribed burns in the Pinelands of New Jersey. Ecosystem Water Use Efficiency (WUEe), a measure of the amount of water used to sequester carbon by forests, was reduced in oak-dominated and mixed stands during defoliation, whereas, prescribed fire had little effect on WUEe. Long-term data indicated that even when consumption losses from fires are considered, insect-defoliated stands were only half as productive compared to burned stands, while water use was less affected.

A March 2013 prescribed fire burning at the Cedar Bridge carbon flux tower in the New Jersey Pinelands. Recovery following prescribed fires is rapid, and stands can replace released carbon within 2-3 years. Kenneth Clark, USDA Forest Service

Scientists Study Fire Management and Carbon Sequestration in Forests

Year: 2013

Forest Service scientists quantified rates of carbon sequestration by forests before and after prescribed burns were conducted by the New Jersey Forest Fire Service. Uptake of carbon dioxide during the summer following spring burns averaged 79 percent of pre-burn levels; and, it takes treated forests only 2 to 3 years to accumulate the amount of carbon released from the litter layer and understory during the fire.

A prescribed fire burning in the New Jersey Pinelands. Michael Gallagher, Forest Service

Impact of Invasive Insects and Fire on Forest Water Resources

Year: 2012

Minor disturbances in forests that do not significantly alter biomass can reduce water use and increase ground water recharge to aquifers

Instrumented towers set up within and in the vicinity of prescribed fires in the New Jersey Pine Barrens provide critical meteorological and air quality data for validating smoke prediction tools. Nicholas Skowronski, Forest Service

Fireflux Experiments Improve Safety of Prescribed Burns in the New Jersey Pine Barrens

Year: 2011

Predicting the effects of smoke from low-intensity prescribed fires on local air-quality is being made easier by new tools developed by Forest Service scientists. These tools are now being validated through data collected from fuels, meteorological, and air quality monitoring networks set up near and within prescribed fires in the New Jersey Pine Barrens. The tools and observational data from this project help fire and forest managers in planning for prescribed burns to minimize adverse air-quality impacts in the vicinity of the burns.

Light detection and ranging (LIDAR) data showing the cover of understory vegetation a 1 to 2 meter height before and after prescribed fire in the Pine Barrens of New Jersey. <b>Green</b> indicates < 10 % cover, and <b>red</b> indicates > 40% cover. The area covered by the figures is 9 km<sup>2</sup>. Forest Service

Hazardous Fuel Assessments Using LIDAR and Field Measurements

Year: 2010

Lasers, in what is termed Light Detection and Ranging (LiDAR) systems, are being used by NRS researchers Nicholas Skowronski and Kenneth Clark to measure forest structure and canopy fuel loading at the Silas Little Experimental Forest in the New Jersey Pine Barrens.

A prescribed fire conducted in the Pine Barrens of New Jersey. NRS-06 researchers are measuring the recovery of carbon and water cycling following fire and insect defoliation in forests in the Pine Barrens. Forest Service

Carbon and Water Cycle Recovery Patterns After Disturbance in Forest Ecosystems

Year: 2010

The recovery of carbon and hydrologic cycling following two major disturbances in pine and oak-dominated stands in the New Jersey Pine Barrens---invasive insect defoliation and fire---are being measured by NRS scientists Kenneth Clark and Nicholas Skowronski.

Last modified: Wednesday, June 29, 2022