Vegetation of the Santa Catalina Montains Arizona USA community types and dynamics.

Niering, W.; Lowe, Charles

This paper interprets plant community dynamics within 3 major vegetation regions, the Sonoran desert, the Encinal and coniferous forest, which extend from 700 m to the summit (2766 m) on the south slope of the Santa Catalina Mt., Arizona. On the bajada, Larrea tridentata and disturbed desert scrub communities have been degraded by overgrazing and Carnegieae gigantea reproduction is failing on many sites. In the Spinose, suffrutescent desert scrub on protected lower mountian slopes Carnegiea is reproducing but mature populations are periodically decimated by freezing temperatures. In the desert grassland, graminoids or Agave chottii dominate, the former favored by fire, the latter by fire protection. In the Encinal above 1220 m an open oak woodland dominated by Quercus oblongifolia is transitional to the pine, oak woodland where fire and drought result in several community segrates. A relict Cupressus arizonica forest is restricted to certain canyons. Above the Encinal (2100 m) a Pinus ponderosa Q. hypoleucoides forest is replaced by a less xeric P. ponderosa forest. In the latter a dense pine understory develops with fire protection and savana-like pine stands are favored by fire. At higher elevations a mature Pseudotsuga menziesii, Abies concolor forest dominates the north-facing slopes where fire plays a signficant factor in its perpetuation. An even aged subalpine Abies lasiocarpa stand on the north slope below the summit suggests post-fire origijn. In the pinaleno Mt. to the northeast, mixed conifer and spruce, fir forest complete the vegetation grandient typical of theses southwest mountain ranges. Here fire and windthrows interact in maintaining a. of pure or mixed even or uneven-aged stands. Although Shreve's description of this mountian vegetation is still valid after more than half a century, the role of grazing and freezing at lower elevations and fire at higher elevations adds a new dimension to those factors operative in this series of relatively stable yet highly dynamic communities.

Vegetation of the Santa Catalina Montains Arizona USA community types and dynamics.

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