PARENT SESSION
Contributed Oral Session 113: Forest Regeneration
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Spatial and temporal patterns in structure, regeneration, and mortality of old-growth ponderosa pine forests in the Colorado Front Range.
Bird, Suzanne*,1, Binkley, Dan 1, 2, Kaufmann, Merrill3, Shepperd, Wayne3, 1 Graduate Degree Program in Ecology, Fort Collins, CO, USA2 Natural Resource Ecology Laboratory, Fort Collins, CO, USA3 USDA Forest Service Rocky Mountain Research Station, Fort Collins, CO, USA
ABSTRACT- Effective management and restoration of ponderosa pine forests requires an understanding of the heterogeneity of contemporary and historical stand structures. We assessed spatial and temporal patterns of tree establishment, mortality and size structure over a thirty year period in an old-growth ponderosa pine stand in the mid-montane zone of the Colorado Front Range. We analyzed spatial patterns and spatial associations using Ripley's K(d) and K12(t) and then modeled the patterns using point process models. Forest age structure was estimated by aging a sub-sample of trees in the stand. Climate, and to a lesser extent fire, play a significant role in the timing of regeneration events. Stand structure (distribution of patches, light availability, and seed trees) influences the location and timing of more recent regeneration events. Patchy regeneration resulted in spatial independence and some segregation of size classes. The oldest trees in the stand (40-55 cm dbh) exhibited some regularity in their spatial distribution at short distances indicating that patterns of mortality had been historically clumped. Contemporary patterns of mortality were mostly patchy, and mountain pine beetles caused a significant amount of mortality in the 1970s and 1980s. Both establishment and mortality retained spatial patterns that were somewhat consistent with pre-settlement forests, despite changes in driving processes. We compare these results to the structural patterns of logged and unlogged pine stands in neighboring landscapes.
Key words: spatial pattern, ponderosa pine, stand structure