Aspen Condition on Cedar Mountain, Utah: Ecological Indicators of Decline

The condition of quaking aspen (Populus tremuloides) ecosystems in the western United States is of rising concern with several studies reporting considerable loss of aspen from the landscape in the past 150 years. Potentially more alarming are accelerated losses, often termed \u27sudden aspen decline\u27, in recent decades. Although there is vigorous debate in the literature regarding region-wide aspen condition, local aspen loss can negatively affect individual stakeholders and local indicators of decline are poorly understood. We examined a large (~ 275 km2) landscape dominated by pure aspen communities in southern Utah with the goals of describing the existing stand structure in detail and determining if local indicators of decline exist. We sampled over 80 aspen-dominated forest plots on Cedar Mountain, Utah using standard forest health monitoring protocols. Major findings include: (1) uniform age of adults within the study area, (2) approximately 10% crown dieback on half of the plots sampled, (3) roughly 50% of the study plots had greater than 50% of the trees with damage to the bole, (4) about 25% of the adult basal area was dead, and (5) over half the plots had few sub-canopy individuals or inadequate regeneration. Physiographic variables including elevation, slope, and aspect were generally not strong indicators of aspen condition, typically explaining less than 15% of the variation in basal area, mortality, dieback, or damage. While healthy stands were rarely observed in the most drought prone physiographic settings, the inverse was not necessarily true; healthy and unhealthy stands were found in more mesic settings. Principle components analysis identified two clusters of plots, those with regeneration and those without; however, no other variables were found to differ between these groupings. We suggest exogenous factors such as land-use history or altered disturbance regimes influence aspen condition on Cedar Mountain, Utah