Concern and debate about the condition of quaking aspen in the intermountain West of North America have led to many studies examining aspen recruitment at local to landscape scales. Patterns of aspen mortality and recruitment may reflect local conditions, or may show broad synchrony if regional-scale drivers are important. This paper aggregates historical aspen establishment data from 12 case studies from nine locations in a meta-analysis of emergent patterns of aspen dynamics at sub-continental or mesoscales (104-106km2). Aspen establishment data were reported in multiple forms among studies, so the meta-analysis included two approaches (1) a quantitative analysis of percent aspen establishment in decadal time bins for 1820-1999 for six studies that reported data in a format suited for this approach and (2) a qualitative ranking of 19th and 20th century peaks in aspen establishment for all 12 studies. Aspen forests ranging from Wyoming to northern Arizona experienced two peaks in establishment between 1820 and the 1980s. The first peak began in the 1860s, reached its maximum in the 1880s, and gradually declined to an end the 1910s. The second peak began abruptly in the 1970s and continued through the 1980s. I speculate that the late-1800s peak in aspen recruitment was driven primarily by the occurrence of the last historical fires throughout the intermountain West and that the 1970s and 1980s peak was driven by improved moisture conditions brought about by a shift to a positive phase of the Pacific Decadal Oscillation and a persistent negative phase of the Atlantic Multidecadal Oscillation. The overarching implication of large-scale synchrony in aspen dynamics is that current aspen ecosystem condition is not solely the result of local-scale histories of browsing or fire, but is more likely the interwoven legacy of these local factors combined with broad factors such as climate and Euro-American settlement.
All Science Journal Classification (ASJC) codes
- Nature and Landscape Conservation
- Management, Monitoring, Policy and Law