The New Jersey Forest Fire Service is actively involved in furthering fire science with numerous partner groups to better understand the effects that fire, both prescribed and naturally occurring, have on the landscape.
For over 90 years, New Jersey Forest Fire Service and the US Forest Service Northern Research Station have worked as partners in wildfire and prescribed fire science. This partnership has largely taken place in the New Jersey Pinelands, a place that serves as a model landscape for globally relevant wildland fire research. This is due to the rich and well-documented wildfire and prescribed fire history, along with the simple topography and tractable vegetation characteristics, and close proximity to numerous research opportunities and public and private land managers.
At the core of this research is the US Forest Service’s Silas Little Experimental Forest, a long-standing natural laboratory collocated with the Rutgers Pinelands Field Station in Brendan T. Byrne State Forest, just up the road from NJ Forest Fire Service’s Division B Headquarters. Initially tasked with conducting science to guide the use of prescribed burning to reduce fire danger and restore forest structure and composition that had been degraded by centuries of industrial forestry and rampant wildfires. With its inception in 1927, following legislation to create experimental forests, this program is among earliest in the country to study wildland fire and fuels management. This work has continued to evolve with the needs of management and for nearly 100 years has informed forest management in New Jersey and beyond. Experimental fuel treatments of this program have even saved the research station from large wildfires in 1946, and again 1963.
Today the program takes a strong, interdisciplinary focus on prescribed fire science, utilizing state-of-the-art tools and methods along with a global team of research partners to answer key questions that inform management, training, and policy. The first theme of the program is understanding vegetation as a complex matrix of fuels and developing improved approaches for measuring these fuels. The second theme is fire behavior and smoke which builds upon the knowledge of fuels by incorporating fire physics, meteorology, and climate. Fire effects are the third key theme, particularly how the effects of fire, like needle consumption or stem mortality, vary spatially and relate to specific ecological changes of interest, such as reducing tick populations. The fourth theme is physical experimentation to drive refinement and testing of fire behavior models. This theme synthesizes the knowledge developed through the first 3 themes and employs it to develop tools that can predict complex prescribed fire scenarios with high precision.
A USFS researcher monitors tree and shrub layer mortality in 1930 after the Bass River Fire.
A researcher collects data for a new physics-based fire behavior simulator with a custom sensor array in 2019.
New Jersey Forest Fire Service Section B2 and B3 crew members with researchers from the USFS Silas Little Experimental Forest and University of Edinburgh, UK after working together to collect research data during a prescribed burn.
The “fire triangle” is a concept often used to illustrate the three essential components that make up fire: fuel, oxygen, and heat. Of these components, fuel is the only component that managers can control preventatively. Fuel in a forest is the live and dead plant matter available for combustion, however different materials like leaves and fine dead branches on the forest floor, shrubs, and the forest canopy and its attributes largely influence how a fire will burn. In forests, these fuels change through time as they naturally grow and are disturbed and are intentionally modified through prescribed burning and forest thinning. These fuels are the same biological structures that provide key ecological functions in forests such as habitat and carbon cycling. The properties of forest fuels, such as moisture content or structure, can also change dramatically with the changing of the seasons as plants progress through annual phenological cycles and this impacts how a fire may burn.
Measuring forest fuels and how they change relative to seasons, prescribed burning, and wildfire has been a major focus of the research program at the Experimental Forest. At the core of this work is a technology called “lidar”, standing for light detection and ranging, which uses a pulse of energy to detect objects like sonar or radar, but instead of sound uses light. This light can be emitted either from a plane to collect data across large areas, like a county, or with a portable device to measure forest structure and fuel loading. Using lidar in the Pine Barrens researchers have demonstrated the importance of fuel hazards to homes on adjacent properties, how prescribed fire can increase landscape-scale forest heterogeneity and rare forest structures while reducing hazardous fuels, and how long-term repeated prescribed burning leads to a forest structure over time with more gap space and reduced crown fire potential.
Beyond fuel large scale fuel structure, the researchers have also studied the small fuels that comprise firebrands. Firebrands are small, hot or flaming, particles generated by some fires that manifest in intense “showers” during wind-driven fires and are the leading ignition source of structure fires during wildfires. Field research on firebrands is limited, so over multiple operational prescribed fires, the research team has created a method for capturing firebrands during fires (emberometer)to better understand how fire, fuel, and weather conditions can be used to estimate when and where ember showers could occur. This work revealed that the majority of firebrands in Pine Barrens fires are actually bark flakes from pine trees, a finding that has been found to be consistent in other coastal plain forests. More recent work has revealed that the structure of pine bark itself can change (peel) over the course of a day as it dries with changing solar exposure to become more easily detached during fires, and have led to the hypothesis that phenomena may align with seasonal winds to produce intense spotting conditions (especially in the spring wildfire season).
A lidar scan of a research plot collected with a terrestrial laser scanner.
Lidar image illustrating how frequent prescribed burning (left) and fire exclusion have divergent outcomes for forest fuel hazard and structure.
The peeling action of a bark flake during a single day.
a) schematic of emberometer, used to record information about firebrands during fires, and b) deployment of emberometer in the field.
Fire managers carefully choose the fuel conditions, weather, and ignition patterns for prescribed fires as an effective means of controlling fire behavior and mitigating smoke problems. Understanding how these factors interact to drive fire behavior and smoke is complex and can help further improve prescriptions for burning and our understanding of how smoke dispersion will occur under different forest and meteorological conditions. Answering these questions requires experimentation at multiple scales ranging from small laboratory experiments to prescribed fires in the forest. These experiments drive a mechanistic understanding of fire behavior based in the physical conditions and processes.
Laboratory fire experiments are used to explore combustion characteristics of fuels in controlled conditions that can be easily repeated to examine phenomena. Working with partners at the University of Edinburgh and Worcester Polytechnic Institute, we explore combustion properties of key live and dead fuels using specially equipped laboratories. These combustion experiments have helped understand differences in the volatility of pitch pine needles in the canopy and at the forest floor, and how energetic outputs of combustion would contribute to combustion at broader scales. We explored the combustion of complex fuel as matrices with other laboratory equipment.
Because of the complexity of the natural environment, which can be controlled in the laboratory, field experiments are more challenging to study. The smallest size of our experiments is in plots that are 100m2. This small size allows us to control fuel loading and structure while deploying complex equipment that allows us to measure the properties of the fire and the environment. In these experiments, outdoor conditions can be repeatedly explored while fuels and ignitions are changed. Sensors in and above the burns measure temperature and radiative energy of the fire as well as fire induced flows and turbulence. Larger field experiments, which can be 100s of acres, can be difficult to instrument and measure, but enable researchers to apply and test what has been learned at smaller scales under complex conditions typical of management. These projects also allow the exploration of how fuels drive fire behavior, and the study of how forest canopies interact with combustion, flow, and smoke dispersion. Ultimately the physical relationships determined through these experiments are numerically represented to be later incorporated as components of complex models that predict fire behavior and smoke dispersion.
Field experiments also allow unique opportunities to test new equipment. In 2019, the research team worked with Dr. Matthew Hoehler of NIST to field test a new 360-degree camera apparatus that could withstand the temperatures of a forest fire. The camera functions as a 360-degree waterproof video camera, housed in a custom glass globe that is charged with cold water via a pumping water through a dry ice chamber. Not only did these experiments successfully test the setup, but they collected informative videos that highlight some of the variability in fire behavior that can be achieved during prescribed burns.
Laboratory fire experiments with Pine Barrens fuels.
Large-scale experiment during a prescribed burn. The tower is collecting wind and temperature data throughout the vertical air column, as well as radiative heat flux from the fire at the forest floor.
Understanding how fire affects fuels has been a core component of the fire research program since its beginnings. Dr. Silas Little conducted experiments that showed gains in fuel reduction from repeated burning and demonstrated that these fire effects could stop or slow wildfires. More recently, the program has been able to evaluate fuel consumption over many burns to evaluate general patterns for how much fuel is reduced during typical dormant season prescribed fires, and how long it can take for those fuels to reaccumulate.
Satellite data can provide a rich and valuable picture of how fire effects might vary across burns and landscapes. Using data from Landsat 7 and Worldview 3, the team has illustrated different patterning between prescribed fire and wildfire effects based on the change in reflectance between pre- and post-burn states. With the additional incorporation of Lidar data, which quantifies three-dimensional forest structure, the team has further shown how applying different burn strategies , forest structural diversity can be enhanced, which is has a large ecological benefit Finally, by combining these results with fire history information, the team has identified how repeated prescribed fire versus repeated wildfire produce divergent trajectories for forest structure.
Most recently, the team has been exploring how prescribed fire may have be an effective tool for reducing tick populations. We have highlighted how fire effects of wildland or prescribed fires maintain a harsher environment for ticks. For instance, areas that have been prescribed burned tend to have shorter and more spaced apart vegetation that would reduce ticks’ potential for encountering a host, as they typically must climb vegetation to accomplish that. However, these changes also tend to permit more sunlight to the forest floor, which has been darkened from burning, and likely has greater air flow because of the more open conditions. These factors reduce the availability of moisture at the forest floor, which is required to prevent desiccation. An ongoing monitoring effort in numerous burned and unburned area supports this concept that prescribed fire can reduce a significant reduction in ticks and maintain that reduction for at least two years following burns. Working with partners from Penn State University and the Rutgers Center for Vector Biology, we are also investigating if the ticks in burned areas carry less disease than those in fire excluded areas.
Reaccumulation of forest fuel with time since burn. Note how shrub and litter components reaccumulate at different rates.
An Amblyomma americanum (lone star tick) captured at a tick survey plot.
To combine the knowledge developed under the other three research themes, we develop and test new, physics-based, wildland fire models These models are much more complex than older fire behavior models and provide much more realistic estimates of fire spread and behavior using actual inputs of fuels, weather, and topography. These models present a way to investigate management inputs to the landscape, investigate fire suppression tactics and strategies, and generally improve our ability to understand and simplify the complex interactions that happen in the fire environment.
Currently the team is engaged with researchers at the Tall Timbers Research Station and Los Alamos National Lab to test a next-generation physics-based fire behavior model called QUIC-fire. QUIC-fire is advantageous in that it requires less computing time than other emergent simulators and can make predictions faster than real-time. The team has been working to reconstruct the 2019 Spring Hill Wildfire that burned over 10,000 acres in Burlington and Ocean Counties, NJ, and to use the model to explore how alternate fuel conditions might have led to alternate fire outcomes. The research team has worked with researchers at University of Edinburgh and the USFS Pacific Northwest Research Station to test a wildland fire simulator called WFDS and has found favorable comparisons between model predictions and actual observations of fire behavior in the field.
The model refinement and testing effort has also included smoke modeling, with meteorologists from the Northern Research Station’s Lansing, MI office, and collaboration with Michigan State University. This effort has involved using field data collected during burns in the New Jersey Pinelands to test model predictions and explore the use of new coupled models, which combine smoke emission models with smoke transport models. Most recently, the team has performed three-dimensional simulations of smoke transport from prescribed fires in Brendan T. Bryne State Forest, based on fuels, meteorology, and fire behavior data collected during the burns. These efforts help identify where these models need improvement, to become operationally available to fire managers.
Simulated fire footprint and smoke plume for the 2019 Spring Hill Wildfire.
Research is most useful when people know about it and how to use it. The USFS and New Jersey Forest Fire Service have been key partners in the North Atlantic Fire Science Exchange (NAFSE) since 2014, a regional network of practitioners, scientists, and students who share new information through trainings, webinars, research briefs, field trips, and workshops. The USFS and NJFFS have partnered often to provide events and science transfer through this organization, enabling the dissemination of research to an international audience, as well as New Jersey and the Region. Webinars and coverage of events focused on the research developed through the partnership can be found on the NAFSE website.
The work of each of these themes has been possible due to substantial financial support from the US Forest Service Northern Research Station, as well as many competitive grants from the US Department of Defense Strategic Environmental Research and Development Program and the Joint Fire Sciences Program.
The Center for Environmental Studies at Raritan Valley Community College is investigating the effects of prescribed burning as a tool for forest management and restoration in northern New Jersey.
Priorities for forest restoration in these areas include the dramatic declines (70-80%) in tree regeneration and native understory cover that have taken place since the mid-Twentieth Century due primarily to overabundant deer, as well as the observed increase in exotic invasive plant species, especially in younger, post-agricultural forests, which have a greater history of soil disturbance and degradation (Kelly 2019).
Working in partnership with the NJDEP Forest Fire Service, Morris and Mercer County Parks, and the NJ Natural Lands Trust, among others, our research was initiated to determine the effectiveness of prescribed burning at a) reducing the cover of invasive plant species, b) stimulating tree regeneration, and c) enhancing the abundance and diversity of native shrub, herb and woody vines. Data are being collected from 60 forest stands, recording the variation in vegetative responses from one to ten years after the initial burn, as well as the cumulative effects of multiple burns (two to three) in the same time frame.
The results, we hope, will help inform the use of prescribed burning as a tool for forest management in northern New Jersey and elsewhere in the future.