Fire Management

Volunteer Fire Crew Participation

Volunteers are welcome on Arboretum burns if they have the appropriate training. Training is important in order to keep all members of the crew safe and to ensure proper implementation of the fire plan. 

The Arboretum provides offers training to volunteers every two or three years. If you are interested in being informed of our next volunteer training opportunity, contact Arboretum Director Nancy Braker (nbraker@carleton.edu).

Alternatively, if you have received prescribed fire training from another source, please contact us to see if your training is considered adequate for our purposes. NWCG courses S130/S190/L180 taken within the past five years, or current NWCG qualification of Firefighter Type 2 or above, will serve for qualification. We also accept training provided by other organizations that have fire management programs.

Volunteers work alongside our staff and student workers to implement prescribed fires. Fires are typically conducted during the weekday, although occasional weekend dates may be considered if enough volunteers are available. Our prescribed burn seasons typically run April 1-May 15, and October 15 – November 15, depending on seasonal variations.

It may seem surprising, but natural fire has coexisted with American landscapes long before the interaction of fire with humans. Fire is one of the oldest natural phenomena. Fossil evidence of fire dates back to the coal beds of the Carboniferous period (360-300 million years ago) and its true origin likely dates back to the advent of lightning, plant based fuels, and the evolution of Earth’s oxygen rich atmosphere.  

The influence of natural fire is incredibly common to American landscapes. From 2001-2010 15% of 760,000 reported fires were caused by lightning, but these fires resulted in 64% of the 65 million acres burned. Every year fires reach out over huge swaths of land as they have for eons. Before human fire suppression efforts began it is it doubtful that any temperate ecosystem evolved free from the influence of such a widespread natural phenomena.  

Midwest grasslands in particular were affected by natural lightning and Native American fire disturbance as often as every 2 years. It might seem strange that if fires occurred so frequently and across such diverse landscapes that plants could thrive at all. But an important lesson in fire ecology teaches that many ecosystems evolved to coexist with routine exposure to fire. Plants native to fire prone areas were constantly adapting, as nature selected those with later growing seasons, sub-soil growth points, extensive root systems, and woody, fire resistant bark. The Bur Oaks, tall grasses, and prairie flowers one might see in the native Minnesota landscape have all adapted over thousands of years to fire. For most native plants the presence of fire is natural and as ordinary as snow in the winter, or rain in the spring.  

Humans as Part of Fire’s Story

Another misunderstanding in fire history involves the role humans played before European colonization. Human-caused fire first reached North America with the migration of humans across the Bering Strait, and fire has been used as a valuable tool in North America ever since. Especially in the Midwest, human fire practices went hand in hand with the development of the native plant communities that dominate the landscape. Of course fire was used for domestic purposes such as cooking, or canoe carving, but lighting fire to the American landscape was also a practice that was quite widespread. Native American fire coverage on the continent was so extensive that it isn’t any stretch to think of Indigenous people as architects of the landscape, using fire to achieve very specific goals.  

Fire was commonly used by Native Americans to hunt, control, and promote wild game.  Fire was used in hunting bison on the plains, for rabbits along the Colorado River, and for alligators in the Everglades. Forest smoke was used to kill moth caterpillars for harvest, or attract deer pestered by flies. Small, barren tracts of land were maintained as deceptive sanctuaries for animals trying to escape hunting fires. When enough were trapped on these pockets of sparse vegetation the animals were hunted with ease.   

More intriguing than the fire that was used for individual hunts was the fire used by Native Americans to change the ecology of the landscape. Native Americans were well aware that the fresh growth occurring the year after a fire was attractive to all manners of small and large game. Burning for such purposes was used to attract bison to lands favorable for hunting. Also, burning forests increased the amount of border between forest and grassland, augmenting the amount of game the land could support. Native Americans made a conscious effort in using fire to maintain favorable conditions for hunting and persisting in Midwest landscapes. As their territories were reduced and American agriculture moved west, policies of fire suppression replaced the loose system of Native American fire management that North American habitats once benefited from.  

History of Fire Suppression

Suppression of fire as policy in American forest has a long history, but received more attention and support in the aftermath of larger fires in the late 19th Century. Initial support can be traced to two major causes, the expansion of settlements and homesteading in the west, as well as the westward expansion of the forestry industry. Before the turn of the century as settlers continued moving west, natural landscape were slowly claimed for human development. Prairies were tilled for agriculture, and in these cases suppression was considered favorable by the settlers. As farms and settlements moved into expansive prairies and forests, humans came into contact with wildfire more often. Wildfires were increasingly affecting (and often devastating) American settlements, solidifying public opinion in favor of complete fire suppression. One of the most devastating fires was the Great Peshtigo fire of 1871. Part of a larger regional fire complex that included the Great Chicago fire, the Great Peshtigo fire resulted in an estimated 1500 deaths in Wisconsin alone.  

More support for suppression came from the timber and forestry industries taking advantage of western expansion. It hardly made sense to set aside a forest reserve, or purchase tracts of Timber for future harvest if they ran the risk of being damaged by future fire. Foresters and Timber companies alike saw the need for an active fire policy to manage the immense swaths of land accessible to settlements. By the early 20th century these ideas and suppression policies policy had gone international. It was widely accepted as an essential method of preserving forests, and Henry Graves, Forest Service Chief from 1910-1920, said fire suppression comprised 90% American Forestry.  

The problem with these policies that fire ecologists have since learned is that suppression isn’t altogether healthy for the ecology of native prairies and forests. In fact the suppression of fire in the short term can lead to harsh ecological consequences in the long term. The reasons aren’t entirely obvious, but they are the basis for using controlled fire disturbance in maintaining the health of land in conservation.

Why Fire isn’t Fatal

Many people approach the idea of prescribed fire with the understandable view that because fire is a destructive force it can only serve to harm the prairies and forests where it is implemented. In reality fire is a natural phenomena that native prairie and forest ecosystems, like those in the arboretum, have adapted to over thousands of years.

In a limited sense, the destructive force of fire seems obvious. As a fire burns through a prairie dry thatch is completely consumed, and living plants die. During fires rodents scurry to find their burrows, and a number will inevitably perish. Fire leaves the forest floor bare and trees blackened. Visually it is quite striking how quickly fire can consume and affect an entire landscape. 

These potentially damaging aspects of fire are what the public knows and can see, but from the perspective of a land manager, fire ecologist, or naturalist they represent only the surface effects of fire. We can watch in an instant as fire removes thatch on the prairie, but we can’t see that the native plants’ deep roots are unaffected, and in coming months they’ll grow taller and more vigorously with recycled nutrients and no thatch to impede early growth. They are adapted to survive the fire, and flourish when the nutrients released by the fire are recycled into the soil. We see rodents scurrying around near the fire line, but we don’t see that the majority of rodents that darted into their burrows will outlast the fire and colonize an adjacent patch of prairie. We see the forest floor cleared and the bark of trees singed, but we can’t visualize the nutrients being returned to the soil in ash, or that the native trees have thick fire resistant bark, and will grow just as robustly the coming year, if not more so. The bare and blackened prairie appears to be a wasteland, but this betrays the true health and vitality that it will see in coming seasons.

Nutrients and the Prairie

It might sound surprising, but an important reason to use prescribed fire is because of its powerful effect on the soil. Prescribed fire results in soils that are full of with nutrients, rich in beneficial microbes, warmed for an earlier growing season, and are more accessible for the seeds of annual and biennial plants. These conditions allow existing native plants to thrive and new ones to reestablish. 

The added nutrients come from the act of burning itself. The ash from a fire is incredibly rich in phosphorus, nitrogen, and even minerals like calcium. Fire takes all of the nutrients from the dead plant material above ground and converts them back to elementary forms. These nutrients are all recycled back into the soil to be used by the roots of the plants, which sprout much more vigorous shoots in the following year. 

Burned soil also allows a slightly earlier growing season because the blackened soil absorbs heat more quickly in the early spring sun. This means that the soil warms sooner, and plant growth begins earlier. This in combination with the powerful nutrient releasing effect of fire enable post-fire growing seasons to be among the most productive in terms of biomass produced and flowering. 

Lastly, once a fire burns through an area the soil is exposed, which opens up mineral soil to new seeds. Certain native plants are annuals or biennials, meaning that they only live one or two years. They greatly benefit from having exposed soil where their seeds can germinate as opposed to built up thatch that often prevents them from reaching it. 

Species Balance/ Invasives

Another very important reason to use prescribed fire is to maintain a balanced species composition in the prairie, forests and savanna. Though it might seem counterintuitive, the regular disturbance of fire promotes a sort of homeostasis among native plant populations. 

If you observe a native savanna over long periods of time you notice that a war is constantly being fought. The forest contains many types of woody plants constantly trying to pass their seed into the prairies, and colonize more land area, shading the prairie out. The prairie has little to defend itself against this onslaught, except of course for fire. Though the plants of the prairie, as well as mature ash, and elm, and especially oak species can survive the effects of fire, younger offspring of these woody plants cannot. The bark of seedlings or trees just starting to establish themselves isn’t yet thick enough to resist the destructive effect of fire. Thus the young progeny of these woody plants are killed if a prairie fire does indeed overtake them. In this sense fire itself and the fire adaptation of prairie plants is a critical defense against the incursion of the forests in to the savanna and prairie. If you remove fire the forests have a much better chance of establishing new trees in the prairie, shading the prairie plants out, and taking over.

This relationship however isn’t restricted to the prairie and woody plants of the upland forest. For example, certain invasive species such as buckthorn that otherwise would quickly colonize forests can be kept at bay through fire management. Burning forest floors of leaf-litter and other accumulated biomass severely damages buckthorn sprouts attempting to establish themselves in the open spaces of the forest. Managers regard the use of prescribed fire as the most effective long-term tool to be used against the incursion of buckthorn into the arboretum. It can easily invade drier habitats like prairies, oak savanna and oak forests if fire is excluded from those areas. Though there do exist invasive species that are resistant to fire, it remains an important method of reducing populations of invasive plants, halting their progress, or even keeping them from establishing themselves in the first place.