Ecological - Second Order
Fire Intensity / Burn Severity
Fire is a key ecological process within most ecosystems in the United States and Canada. An understanding of factors controlling the initial response of vegetation to fire is essential to its management. Fire effects on plants can vary significantly among fires on different areas of the same fire. Fire behavior, fire duration, the pattern of fuel consumption, and the amount of subsurface heating all influence injury and mortality of plants, and their subsequent recovery. Postfire responses also depend upon the characteristics of the plant species on the site, their susceptibility to fire, and the means by which they recover after fire. This chapter describes the key elements that explain fire effects on vascular plants, those plants with specific- structures for gathering and transporting water and nutrients. Effects on mosses, lichens, liverworts, algae, and fungi are not discussed. The chapter addresses plant survival, resprouting, and seedling establishment in the initial stages of postflre recovery. Factors that affect a species presence or presence or absence in the immediate postflre community will be described, but not those that affect productivity, such as changes in soil nutrient availability. The adaptations that allow survival, and the methods by which plants recover, are common to species found in almost all of the ecosystems discussed in this volume. The chapter describes principles in a general way, and provides specific examples from different ecosystems, although no attempt has been made to present examples from every system. Mechanisms operate in the same way no matter where they occur.