Every spring, prescribed burns are conducted in the forest of the Pine Barrens of New Jersey, United States. These operations have been carried out on an average of roughly 12000 acres per year over the past 10 years. Historically, fire is a natural occurrence in the Pine Barrens and is an integral part of maintaining the ecosystem. Such prescribed burns are also used as a type of ‘fuel treatment’ aimed at reducing the fuel loading, the quantity of vegetation biomass, in the forest. The intent is that, by managing the accumulation of fuel, accidental wildland fires will have a lower, more manageable intensity, thus reducing both the potential risks to the community and the costs of firefighting operations. This is particularly important in an area like New Jersey, which lies in the middle of the densely populated coastline of the Northeast United States.
In a three year project, researchers from the Fire Group, in collaboration with the United States Forest Service, Rochester Institute of Technology (U.S.), and Tomsk State University (Russia) are attempting to better understand the effectiveness of such fuel treatment, as well as general aspects of fire behaviour and firebrand generation. The approach involved experimental measurement of the fire during two high-intensity prescribed burns in the Pine Barrens.
Members of the team from left to right: Chris Thomas, Mohamad El Houssami, Alex Filkov (Tomsk State Uni.), Denis Kasimov (Tomsk State Uni.), Albert Simeoni, Nick Skowronski (US Forest Service), Eric Mueller, Ross Galloway, Michal Krajcovic, Rory Hadden
Fire behaviour in these experiments was measured in a number of ways, including temperatures within the flames and plume, total and radiant heat fluxes, and wind speed and direction - all at various locations throughout the burn block. A series of aerial images, taken from an IR camera mounted on an airplane, also provided a progression of the footprint of the fire. To relate this information to the pre-fire vegetation distribution and the consumption during the fire, measurements of fuel loading were made both before and after the burn. This was done through a combination of field sampling and aerial, georeferenced Light Detection And Ranging (LiDAR) measurements.
Earlier this year, our team of seven travelled to the United States to help set up instrumentation and observe the second of these two fires. Unfortunately, the late-winter weather in this region is quite chaotic. After two days under the snow, forcing us to stay in the lab to work on the experimental set up and survive on pizza and beer, part of the team had to fly back to Edinburgh. A reduced team was left to conduct the burn with our partners.
Instrument preparations at the Pine Barrens field station
To add an extra level of complexity when gambling on the weather, the IR aircraft must be ordered in advance and can’t be refunded. The experimental site was also located under the highly restricted airspace of a local bombing range and we are subject to their scheduling whims, making things even more difficult to organize. In the end, with the allowed season for burning quickly coming to a close, it was an enormous relief to finally manage a fire on the 11th of March – with ignition occurring just as a pair of fighter jets cleared the airspace.
Experimental prescribed fire on 11/3/14
As with any large scale experimental collaboration, it is nearly impossible to avoid a myriad of small complications which arise at the last minute. In this case, we were actually quite fortunate. With a combination of expertise from past experiences and good luck (not necessarily in that order), we ended up with a promising set of measurements from some rather exciting fire behaviour. Not to mention a number of smaller successes – the expensive FLIR camera did not melt (much to Michal’s relief), and we managed to survive an axe-wielding Rory without incident.
Pre- and post-fire conditions
Such experiments are a somewhat rare opportunity, and it is a great asset to be able to draw from the impressive and varied expertise found in the Fire Group. Though the experimental aspect proposed at the outset of this project has come to a close, we are working to maintain a strong relationship with our collaborators in the U.S. It is our hope that this will be far from the last time the group is involved in such an undertaking. Beyond this, the results have already yielded a number of interesting questions which present and future researchers can investigate here in the laboratory. With the amount we have learned over the last two experiments, from both our successes and failures, we are excited by the prospect of what we can accomplish in the future.
All photos copyright of Eric Mueller