U.S. Joint Fire Science Program


Date of this Version


Document Type



Project ID: 05-2-1-98


US government work.


Pinyon-juniper woodlands are a dominant vegetation type throughout the Interior West on lands managed by the U.S. Forest Service and the USDI Bureau of Land Management. The woodlands have traditionally been viewed as having a low risk of wildfires because of the lack of a continuous and dense ground cover and low tree stand densities. However, stand densities are often high and are increasing in many areas and wildfires, often resulting in loss of lives and property, will occur under conditions of low humidity, high temperatures and wind speeds, and an ignition source. Woodlands commonly surround or are adjacent to many towns in the region; however, in recent years, people have moved into the woodlands to construct individual homes and housing developments. In this decade, the ecology and fire risk in pinyon-juniper woodlands have changed dramatically because of the continuing drought and the region-wide infestation of the pinyon engraver beetle, Ips confusus, which have resulted in high pinyon mortality, increased fuel loadings, and risks of severe wildfires. Managers are attempting to reduce fire hazards and create defensible spaces in the wildland-urban-interface (W.U.I.). They have commonly used hand thinning-piling-burning prescriptions in the W.U.I. but have recently turned to mechanical mastication to accomplish stand reduction goals, especially where slope and soil surface conditions permit the safe operation of heavy equipment. In most situations the goal is to create a mosaic of open and wooded conditions on the landscape. These has advantages of maintaining wildlife habitats, tree and shrub growth, an esthetic landscape, and increasing herbaceous production while improving fire suppression opportunities and reducing fire hazards. However, managers do not know the consequences of mastication on soil nutrient and microbiological populations and on the residual tree, shrub, and herbaceous vegetation. While the number of research studies of the effects mastication on ecosystem components has increased recently, there still are many questions.