Introduction
Trees do not just die; there is always a primary cause, and often contributing factors. Trees need adequate quantities of water, heat, light, nutrients, carbon dioxide, oxygen, and other abiotic resources to sustain life, growth, and reproduction. When these factors are deficient or excessive, they cause mortality. According to the concept of baseline mortality (Chapters 1, 2, and 3), a certain number of trees must die as a forest ages to maintain a healthy condition. Abiotic factors kill trees in different ways, e.g., starvation, desiccation, uprooting, or stem breakage. The patterns of mortality and how the forest responds determine how changing stand structures impact sustainability and productivity. Here, we discuss abiotic factors, and how they influence diameter and age class distributions. We conclude this chapter by suggesting general principles about the impacts of abiotic disturbances on stand structures within forest ecosystems.
Weather events
Weather is the set of all phenomena occurring in a given atmosphere at a given time. Weather phenomena include wind, clouds, rain, snow, fog, dust storms, ice storms, hurricanes, tornadoes, and others. Some weather events can reset forest succession directly by killing trees. Weather events also can influence the rate and direction of forest succession indirectly by increasing fuels to enhance fire risk or by predisposing trees to other stresses.