Abstract
Concentrated patches of recent trembling aspen (
Populus tremuloides) mortality covered 56,091 ha of Colorado forests in 2006. Mortality has progressed rapidly. Area affected increased 58% between 2005 and 2006 on the Mancos-Dolores Ranger District, San Juan National Forest, where it equaled nearly 10% of the aspen cover type. In four stands that were measured twice, incidence of mortality increased from 7-9% in 2002/2003 to 31-60% in 2006. Mortality generally decreased with increasing elevation over the primary elevation range of aspen and occurred on less steep slopes than healthy aspen. Slope-weighted mean aspects of aspen cover type were northern at low elevations and generally southern at high elevations. Relative frequency of mortality was generally highest on southern to western aspects. In 31 stands measured in detail, mortality ranged from 0 to 100% (mean 32%) and was negatively correlated with stand density (P = 0.033). Size of trees affected was strongly correlated with amount of current mortality (P < 0.001), and current mortality was skewed toward larger diameter classes. Density of regeneration was in a low range typical of undisturbed stands and did not increase with overstory mortality.
Keywords
disturbance,
decline,
dieback
Citation
Worrall, James J.; Egeland, Leanne; Eager, Thomas; Mask, Roy A.; Johnson, Erik W.; Kemp, Philip A.; Shepperd, Wayne D. 2008. Rapid mortality of
Populus tremuloides in southwestern Colorado, USA. Forest Ecology and Management. 255(3-4): 686-696.
