Spring and fall are when the smell of smoke may tickle your nose around Whiterock Conservancy. Many of us are familiar with burning parts of our garden annually which involves standing watch over the fire with a rake or a shovel for a short while.  Prescribed burns for the natural lands of Iowa have some commonalities. For example, I helped my Dad bun his asparagus patch a couple weekends back – a couple of minutes with a rake and match and the show was over. But, burning a prairie or a savanna is a bigger time commitment. Both activities can be done with a rake, but water equipment makes bigger burns a whole lot easier and safer. Either way, being safety conscious and producing the ecological benefit desired determines the outcome of the burn.

Good burns are all about preparation. At Whiterock we put a lot of time into preparing burn lines to make sure that crew members and the public are safe during and after a burn. Removing excess grass and leaves from the burn line makes it not only safer but easier as well. This also means that the crew can be more confident in moving more quickly. Burning should always be a little stressful with a healthy respect for fire, but good preparation definitely helps put everyone on the crew at ease.

Prairie burn in the spring. Notice that the grass has greened up in the well-maintained burn line which makes it easy to control the spread of fire along the line.

After preparation, good burns depend on the weather. Weather conditions affect how and when a burn is conducted, specifically the relative humidity and wind. Relative humidity should be below 50% to have a good prescribed burn (note that it is important to pay attention to the relative humidity that adjusts actual humidity for temperature and atmospheric pressure). Wind speed and direction are the next things to consider in anticipating the behavior of the fire and smoke. Be kind and let your neighbors know if you plan to burn and if the smoke may impact their activities. Wind speed is a big concern but different types of prescribed burns have different goals. High winds for prairie burns are just dangerous. But, 30 mph winds in a woodland burn can be great! Woodlands can drop wind speed by up to 90% within yards of the stand edge, which in the case of 30 mph winds in the open may mean that you only feel 3 mph in the woodland. Even with high winds in the open areas, in the woods you should be able to literally walk across the burn with proper personal protective equipment as flames are commonly only 12” in height.

Prescribed burn in a woodland with approximately 12” flame height. Flames will kill undesirable shrubs and stimulate the growth of the herbaceous layer (not common in many overgrown timbers across Iowa).

Good burns also take into account a balanced approach to protect the ecosystem. Fire is good for prairie and oak ecosystems such as savanna, but too much of a good thing can be bad for the system as a whole. There are a couple of rules we abide by when planning a burn: don’t burn everything at once, don’t burn at the same time of the year all the time, don’t relight in order to burn every last inch in the unit, and don’t rely just on fire. Fire is just one tool in the toolbox.

Burning at the same time of the year frequently gives one species an advantage so it can out-compete other species. Grazing or mowing a woodland or prairie can stimulate growth and doesn’t remove all the thatch as fire can. It’s easy to keep on doing the same thing after seeing the benefits once, but good management requires variety.

A variety of management practices across the landscape means that the habitat varies through an area. One area may not have burned for whatever reason and that’s just fine. These areas are refugia for wildlife and may be up to 50% of a burn unit. That being said, anyone that likes turkey hunting knows that turkeys like to peruse recently burned woodlands as the leaves no longer hide all the good stuff. Deer are similar; it’s not uncommon to see deer go right back to a woodland that was burned within hours and continue browsing shrubs. However, not all species benefit from fire, so when planning a burn we pay attention to soil temperatures though to avoid impacting turtles or snakes that may be out early in the year. Burn when soil temperatures are cool and cold-blooded wildlife is still hibernating. The wildlife of Iowa dealt with fires for millennia, they will continue to deal with it but not when activities are highly out of sync.

All prescribed burn materials have to have a fun fire photo so I’ll end on that note. About 80% of a burn should be boring and babysitting the backfire (letting the fire burn against the wind and controlling downwind spread) and then you wrap up with the fun part – the head fire (burning in the same direction as the primary wind direction). When you get to the last 20% or so of a burn enjoy the flames that leap and dance for those too short a period of time. But, it’s well worth it to keep everyone safe and to know you’ve helped to restore the natural lands of Iowa.

Head fire at the end of a prescribed burn with a modest headwind. The head fire is lit in the ring-fire technique once the unit edges on the downwind side, or backfire, have been safely burned out.