Hello again guys,
How are your doing? I hope you are doing great. Here I am starting to feel sad. That's close to finish. In four days I will be back in Spain, and my USA learning experience will arrive to its end. Actually, only the face part, because there are still many things to think about, to "ferment" in my brain. Therefore, the learning part will be always with me.
I have many things to speak about, so I don't know where to start. Let's see a couple of photos showing fire effects:
I took those only two days after doing FF80 prescribed burn, in Lakeland, GA. As you can see, Serenoa repens is fully fire adapted. Besides being really flamable, it starts to resprout in only a few duys after the burn. The trunk is horizontaly-oriented and it's really fire-resilient. That species recolonizes fastly burned plots.
In this other pictures, you can see some fire severity visual indicators:
They are not the most accuratest ones, but they are useful and fast to see and interpret. You can pay attention to the scorching height, to the ground cover consumption and to the soil impacts. Also, you can make a overall rating of the impacts in the landscape. It is really impresive how much we can learn only taking a look over a recently burned area. In two photos we have enough information for being speaking two days. Even though this is a little plot and not the best example, you can find some interesting things.
Let's go ahead and talk about the firing techniques. That is one of the most important things when planing a burn
in situ. I mean, not making the plan, but deciding how to implement it. There are some statements that you shouldn't include in your plan; you have to write those by and large. For example, the firing techniques. You have to ve flexible, because the field conditions may differ from forecasted ones. Therfore, adapting firing techniques is essential. While it is true that in the same plot, with the same conditions, and the same crew, you can expecto to use the same techniques, you should not be tempted not to reassess continuously your plan. Hence, you have to know all the firing techniques and its safe way of implementation.
(*) remember: 1 chain = 66 feet = 22 meters.
1.- Backing fire:
A backing fire is started along a baseline (anchor point),
such as a road, plow line, stream or other barrier, and allowed to back
into the wind. Variations in windspeed have little effect on the rate of
spread of a fire burning into the wind. Such fires proceed at a speed
of 1 to 3 chains per hour. Backing fire is the easiest and safest type
of prescribed fire to use, provided windspeed and direction are steady.
It produces minimum scorch and lends itself to use in heavy fuels and
young pine stands.
2.- Strip-Heading fire:
In strip-headfiring, a series of lines of fire are set
progressively upwind of a firebreak in such a manner that no individual
line of fire can develop to a high energy level before it reaches either
a firebreak or another line of fire. A backing fire is generally used
to secure the base line and the remainder of the area then treated with
strip-heading fires. Strips are often set 1 to 3 chains apart. The
distance between ignition lines is determined by the desired flame
length. This distance can be varied within a fire to adjust for
slight changes in topography, stand density, weather, or the type,
amount or distribution of fuel.
3.- Flanking fire:
The flanking-fire technique consists of treating an area
with lines of fire set directly into the wind. The lines spread at right
angles to the wind. This technique requires considerable knowledge of
fire behavior, particularly if used by itself. It is used quite often to
secure the flanks of a strip-heading fire or backing fire as it
progresses. It is sometimes used to supplement a backing fire in areas
of light fuel or under more humid weather conditions. It is useful on a
small area or to facilitate burning a large area in a relatively short
time when a line-heading fire would be too intense.
This method of firing can stand little variation in wind direction and requires expert crew coordination and timing. For safety,
all lines of flank fire should be ignited simultaneously and all torch
people should keep abreast of one another.
4.- Point Source fires:
A prudent burning boss will often switch from strip-heading
fires to point source fires as the day progresses and continuous lines
of fire become too intense. When properly executed, a grid of spot
ignitions will produce a fire with an intensity much greater than that
of a line-backing fire but somewhat less than that of a line-heading
fire. Timing and spacing of the individual ignition spots are the keys
to the successful application of this method. First a line backing fire
is ignited across the downwind side of the block and allowed to back 10
to 20 feet into the block to increase the effective width of the control
line. A line of spots is then ignited at some specified distance upwind
of the backing fire and the process continued until the whole block has
been ignited.
To minimize crown scorch, ignition-grid spacing is selected
to allow the spots along a line to head into the rear of the spots along
the downwind line before the flanks of the individual spots merge to
form a continuous flame front. The merger of successive ignition lines
thus takes place along a moving point rather than along a whole line at
the same time. Merger along a moving point can be ensured by beginning
with a closely spaced square grid (2 chains by 2 chains is recommended).
It is important to say that this is a general and generical description. That means that you can combine techniques and that you MUST adapt them to your own conditions. Also that each of them can be built using another one. For example, you can do a backing fire control line/black area using strip-heading fire to make it wider. Also, if doing ignitions Fire Boss realises that strip-heading fire generates too much intense fire behavoir and point-source ignitions are not enough, he/she can ask the ligthers to use dashes (that means: dash of X meters on fire, hole of Y meters without fire,...). You have to be flexible and always pay atention to the changes in weather!
Those are the main firing techniques you'll use in most of the prescribed burns. However, there are more. Even though they are not as usual as the previous ones, they're sometimes useful, so we have to know them.
5.- Aerial Ignition:
When ground ignition techniques are used, the downwind spots
will usually coalesce and burn out before the whole block has been
ignited. In contrast, aerial firing permits ignition of a block to be
completed before the downwind spots have burned out. This does not
present a problem at the damp end of the prescribed burning window when
actual fine-fuel moisture is near 20 percent. Rapid ignition of a block
reduces both flying time and the time needed to complete the burn.
However, when using aerial ignition techniques under "traditional" ideal
burning conditions for line-backing fires with actual fine-fuel
moisture near 10 percent, rapid ignition of the entire area can result
in an increase in fire intensity to unacceptable levels. You would then
have little recourse except to let the area burn out and hope that
damage is limited to just a loss in overstory growth.
Some experienced burners start firing early in the day,
before the fuel is dry enough to carry fire well. They reduce the
distance between spots within a line to less than 2 chains by 2 chains.
The increased number of ignitions creates more heat and helps dry the
surface fuels, especially when a helitorch is used. The distance between
spots must be expanded as the morning progresses and burning conditions
improve. Otherwise, the spots will merge laterally forming lines of
heading fire that get too intense before reaching the next downwind line
of ignition points. The distance between lines can also be increased as
necessary to maintain a square ignition grid.
6.- Center and Circular (Ring) firing:
This technique is useful on
cutover areas where a hot fire is needed to reduce or eliminate logging
debris prior to seeding or planting. It works best when winds, if any,
are light and variable. This procedure should never be used for
underburning because of the likelihood of severe tree damage as the
flame fronts merge.
7.- Pile and Windrow burning:
The objective of piling logging debris before burning it is
to prolong fire residence time on a restricted area so that larger
materials have time to be consumed. Some areas will contain an
unacceptable amount of large, scattered debris that must be concentrated
to ensure consumption. This material should be piled and not windrowed.
Windrowing can reduce site quality by removing topsoil. Piedmont soils
are also susceptible to compaction from the heavy equipment used,
especially during wet weather. Full exposure of the soil to the sun and
rain bakes the top layer. Furthermore, the direct force of raindrops
will clog soil pores and often results in erosion on steep slopes. The
area beneath the windrows is lost to production because the debris is
rarely consumed completely and what remains makes planting difficult or
impossible. Even when windrows contain breaks spaced every couple of
chains, they still present a barrier to firefighting equipment and
wildlife.
If you want to read more about that techniques (all of them), there are many prescribed burning guides which explain them. I've took that information from a Forest Service Southern Region technical publication (USDA).
Besides both having a good weather forecast and paying attention to changes in weather, you can improve your planning and implementation by being used to your fuels. The more you know about them, the more accurate will be your burn and the less unwanted results you'll have. That's why I recommend you to use, in adittion to Rothermel's thirteen, the Standard Fire Behavior Fuel Models:
I hope you enjoy!
