Gambel Oak Shrubland

Abstract

Gambel Oak Shrubland is the second-most abundant shrubland on the mountains and plateaus of the American Southwest. It is more extensive in the northern half of the region. It is bounded at high elevation by forest, primarily Ponderosa Pine Forest in the south and Mixed Conifer Forest in the north. At low elevation, it is bounded by Pinyon-Juniper vegetation or sagebrush shrubland. It is dominated by Gambel oak and other deciduous shrubs. Stands are divided into southern and northern shrublands. Fire is a primary driver of Gambel Oak Shrubland, and the fire regime is dominated by infrequent, high-severity fires that occur during drought. Anthropogenic disturbances include livestock grazing, fire management, modern climate change, invasive species, recreation, and nearby land use. Vegetation dynamics are dominated by rapid regrowth from sprouts following disturbance. Some stands appear to be a seral stage in forest or woodland succession; other stands are more stable in structure and composition. Historical conditions are poorly known, but the regional distribution of southwestern Gambel Oak Shrubland is generally unchanged and stands in many areas have increased in both size and density. Vegetation dynamics are illustrated in a nested, three-tiered set of conceptual models. Key conclusions and challenges for researchers and land managers are summarized.