Structure and Composition of Juniperus Communities and Factors That Control Them

Abstract

Most Juniperus communities are savannas, evergreen woodlands, and, in some cases, evergreen forests. They are found above the arid deserts of the American West and Southwest or above the various grasslands found in this region (Coupland 1979; Sims 1988; West 1988, 1999; Van Auken 2000a). They are usually below the diverse high-elevation evergreen forests that are found here as well (West 1988, 1999). Rainfall in Juniperus woodland communities is usually 17 to 80 cm per year, and elevation is 200 to 2800 m, depending on latitude (West 1988, 1999; Jackson and Van Auken 1997; Gedney et al. 1999). In mountain ecosystems, lower-elevation Juniperus communities interdigitate with associated deserts and grasslands and are fairly open communities. At higher elevations, they grade into the evergreen forests and may have a closed canopy. In many grassland communities in central North America, Juniperus encroachment has converted large areas of contiguous grassland into savannas, woodlands, or closed-canopy forests (Briggs et al. 2002; also see Chapter 8, this volume).