Learning from spatial variability: Aspen persistence in the Centennial Valley, Montana

Quaking aspen (Populus tremuloides) is commonly believed to be declining throughout western North America. A literature review of recent local-scale aspen studies, however, indicates that regional-scale spatial variability in aspen dynamics is greater than previously recognized and there are areas of successful aspen regeneration and recruitment. This study examines 20th century aspen recruitment and regeneration patterns along a 15 km long lower forest-grassland ecotone in the Centennial Valley, Montana to determine if the Centennial Valley ecotone aspen stands support the observation that there are areas of successful recruitment and regeneration and provide another example of such areas. A total of 525 adult aspen stems were cored and 8924 aspen suckers were counted and mapped in 106 rectangular plots randomly distributed along the ecotone. Aspen-age distribution was constructed at a decadal time scale to examine 20th century recruitment patterns. Sucker density was examined to evaluate aspen regeneration. The tree-age distribution patterns indicated successful aspen recruitment during the 20th century, while the sucker density assessment suggested successful regeneration. The Centennial Valley ecotone aspen stands appear to support the observation that aspen recruitment and regeneration are spatially variable and there are areas of aspen persistence. Learning about the underlying factors that enable successful aspen regeneration and recruitment in such areas can help management and restoration activities at other locales. Recognizing the regional-scale spatial variability in aspen dynamics can inform regional-level policy and management.