Prescribed Burn

Prescribe burn at Asylum Lake

Why burn the prairie?

Asylum Lake Preserve is an isolated remnant of what once was a much larger landscape that was maintained by fire, grazing and other natural disturbances. Fire is one of the more useful land restoration techniques. Prescribed fire is used as a management tool not only for its historically good track record, but because of its low relative cost when compared to mowing and herbicide use. It's important to remember that the plants of the tallgrass prairie did not simply adapt to growing with fire, they evolved with fire over the course of tens of thousands of years.

Consider the following benefits of prescribed fire:

  • More native plants flower, produce seed and are more robust when prescribed fire is used in the management plan.
  • Fire lengthens the growing season for native plants and shortens the growing season for Eurasian weeds.
  • After a spring fire, the dark soil warms quickly to the benefit of prairie plants and to the detriment of weeds.
  • Cool-season Eurasian weed grasses such as the blue grasses (Poa sp.), quack grass (Agropyron repens) and many bromes (Bromus sp.) stop growing as the soil warms.
  • Late spring fires can burn off 3 to 8 inches of weeds before the prairie plants even begin growing. Most prairie plants are warm-season forbs, legumes and grasses.
  • Microbial activity in the soil is stimulated by fire and the nutrients released by ash. More than 40 species of arthropods are attracted to burned sites because of smoke, increased soil temperatures and higher carbon dioxide levels.
  • Invasive woody weeds are at a disadvantage due to the formation of the dense prairie sod that prevents seedlings from germinating.

What is prescribed fire?

Prairie Prescribed fire is a very carefully planned and controlled burn. Before prescribed fire is used at Asylum Lake Preserve, a document known as a "burn prescription" is prepared. The document identifies the acceptable conditions under which a burn will take place. Some of these conditions include expected fire intensity, relative humidity, wind speed and direction, air temperature and fuel moisture. Also contained in the burn prescription is a plan for how the fire will be ignited and contained.

It is difficult to predict good burn weather more than a few hours ahead of time. If any of the conditions identified in the burn prescription is unacceptable or "out of prescription," the burn is postponed.

WMU's 1st prescribed burn:

Fires lit along prairie edges

Fires are lit along prairie edge

After allowing a full growing season for the plantings in 2002, it was time to plan a burn. In the spring of 2003, a trained and experienced burn crew was hired by the University to conduct the first prescribed burn on the reconstructed prairie. Assisting the "burn boss" and his crew were staff members from Landscape Services. Fire crews from both the Oshtemo and Kalamazoo Fire Departments were on hand in case they were needed.

On April 24, 2003 our burn boss, Jim Bruce, decided that conditions in the burn prescription were satisfied. Wind speed was 6-8 mph from the SSW and would keep smoke from blowing over Drake Road. Air temperature and relative humidity were predicted to be such that smoke would rise aloft rather than blowing closer to the ground. Fuel moisture was excellent; however, we experienced a lack of fuel. In all but two of the burn units, there was insufficient vegetation to carry a fire.

This, however, was not the case with burn units 2 and 3, which consist of the switchgrass (Panicum virgatum) plots immediately south of the dirt path which divides the savanna and prairie. Here, the dry grasses waved 6 feet in the air and promised a spectacular burn.

Trees within the burn units were first protected by spot-firing around them. A "black line" of burned vegetation was formed by back-firing the lee side of the grasses. Finally, the head-fires were ignited which raced across the plots, meeting the back-fires in the middle. Standing in a safe location up-wind, the roar of the head fire was so loud that several simply put down their tools to enjoy the spectacle.

A prescribed burn in full force

When will the next burn take place?

The next burn has yet to be determined. The prairie has been divided into burn units and, as of spring 2007, each of the units has been burned at least once. During summer 2008, a floristic inventory was performed on the property. Based on the results of this inventory, we will be able to create an effective burn schedule. Once the conservative prairie plants are firmly established and weeds are under control, we will limit burns to only 1 or 2 burn units each year. This will provide refuges for insects, birds and a myriad of other forms of wildlife. The goal of fire management at Asylum Lake Preserve is to establish a biologically diverse habitat and increase the educational and aesthetic experience for visitors. The most recent burn took place March 18, 2018

Related links:

Michigan Prescribed Fire Council
The Nature Conservancy—Maintaining fire's natural role
The Northern Prairie Wildlife Research Center
Society for Ecological Restoration International