Why conifers are encroaching into rangeland and what we can do to prevent it from happening.
The western landscape of today’s world looks different than it did just 200 years ago. I am not referring to more people, cities or roads; I am talking about the natural landscape. As the landscape has changed so has the public opinion and with change typically comes the attainment of knowledge. As land managers we at Ranch Resources are always on the forefront of the latest scientific research, trying to further our knowledge of natural systems and how to apply that to real world situations so that we can best manage our client’s properties. Without getting too deep into an ecology lesson I would like to briefly touch on some of the major factors that shape our landscape.
Disturbance is the main force that changes the way natural landscapes look and work. By disturbance I am referring to events such as: wildfire, wind, flooding, earthquakes, erosion… and the list goes on. Certainly disturbance cannot only be associated with natural events; we must also consider mans role in shaping the landscape through various acts such as: development, farming, mining…etc. Landscapes may also change by suppressing disturbance events from happening.
Prior to the Louisiana Purchase and Lewis and Clark’s famous transcontinental exploration, the west experienced frequent wildfires. In fact we have scientific evidence that several landscapes were burned quite frequently. Fires were often lightening caused and would burn in regular intervals. There is also strong evidence that Native Americans used fire for many different purposes. The natives used fire to create fresh grass for their horses and to attract bison, they understood that in forested systems huckleberries typically follow fire, and they also used it as a weapon against rival tribes.
Frequent low intensity fire across the landscape has resulted in the evolution of species with adaptations to the frequent fire. Ponderosa pine trees have extremely thick bark which is a result of centuries of fire adaptation. Other species such as Lodgepole pine have unique adaptations to live with fire. Lodgepole grow in thick stands and typically burn in stand replacing fires. This means that every 200-300 years a fire will burn with high intensity and kill the entire stand of timber. Lodgepole’s adaptation is in its cone. The cones are small and closed, filled with a resin that will only expand when exposed to serious heat; this adaptation is called a Serotinous cone. Thus when a high intensity fire kills a section of Lodgepole the cones open and new seeds are distributed to begin a new stand; in another 200-300 years when the moisture content of the stand is dry enough a fire will replace that stand and the cycle continues.
As Americans expanded west and civilization followed, the idea of wildfires was not accepted. When a fire was started it was all hands on the scene to extinguish the fire. This attitude carried forward and in 1935 became an official rule of the United States Forest Service in the form of the 10 AM policy. This being that all wildfires were to be contained and controlled by no later than 10 AM of the following morning.
With over a century of fire suppression our forested landscapes changed in many ways. Stands became denser with more stems per acre. Some fire resistant species were outcompeted and were not able to reproduce with aggressive less fire resistant species blanketing their understory.
Where the prairie meets the forest is called an interphase, and this area was usually easy to define when regular wildfires would burn the understory and kill the young less fire resistant conifers. Because wildfire has been suppressed on the landscape the aggressive conifers have made headway encroaching into the rangeland. Cattlemen often refer to this as green slime because it results in the loss of grazeable range.
There are a couple of solutions to the problem. The first option is to put fire back on the landscape and restore the natural process. There are several issues with this idea. Most landowners do not wish to use wildfire as a tool to manage their range and forest. There are numerous risks involved with prescribed burns the first being the liability if it gets out of control. Grass fires can travel quickly and be difficult to contain especially under certain weather conditions. Second, the encroaching conifers are of an age and size that makes them somewhat tolerant to low intensity fire. Meaning it takes a fairly intense fire to accomplish the goal of killing the problem conifers on the interphase. To kill the cambium of a tree the cells must be heated to 60 degrees Celsius (140 Fahrenheit) for at least one minute. The larger the diameter the tree, the thicker the bark, and the longer it will take to heat the cambium to the threshold temperature.
We have found that by sawing and hand piling the trees we can effectively reclaim the range ground. We burn the slash during the wetter months of the year. Of course this requires a commitment to continually remove the trees, but there is considerably less liability than using wildfire. By committing to treating conifer encroachment we are able to maintain the range-forest interphase similar to it was before fire suppression.