Ponderosa Pine, Mixed Conifer, and Spruce-fir Forests

Before European settlement of the interior west of the United States, coniferous forests of this region were influenced by many disturbance regimes, primarily fires, insects, diseases, and herbivory, which maintained a diversity of successional stages and vegetative types across landscapes. Activities after settlement, such as fire suppression, grazing, and logging significantly altered these disturbance regimes. As a result, forest structure and species composition have departed from historical conditions on many landscapes and this has led to increased forest densities, forest type conversions, and greater contiguity of many western forests. These forests are now more susceptible to large-scale insect infestations, disease outbreaks, and severe wildland fires than in the past, possibly endangering overall forest ecosystem health. The purpose of this paper is to address the historical and current conditions of coniferous forests of southern Utah to aid in the development of treatments to restore the ecological composition, structure, and function of these ecosystems. The distribution of coniferous forests in southern Utah is mainly influenced by both climate and disturbance regime. Climatic factors, such as temperature and precipitation, determine where certain forest types can grow. Ponderosa pine (Pinus ponderosa) forests are the lowest elevation coniferous forest type in southern Utah occurring just above the warmer, drier Colorado pinyon-Utah juniper (Pinus edulis-Juniperus osteosperma) woodlands (Youngblood and Mauk 1985). As elevation increases, mixed conifer forests consisting of ponderosa pine, white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), blue spruce (Picea pungens), limber pine (Pinus flexilis), Engelmann spruce (Picea engelmannii), and subalpine fir (Abies lasiocarpa) occur. Species dominance in these mixed conifer forests is mainly determined by disturbance history and micro climate. Chapter 2