AUTHORS: Brian Buma*, University of Alaska; Sarah Bisbing, University of Nevada Reno; John Krapek, University of Alaska Southeast; Greg Wiles, Wooster College; Allison Bidlack, Alaska Coastal Rainforest Center; Glenn Wright, University of Alaska Southeast
ABSTRACT: Understanding the drivers and patterns of primary and secondary succession are among the oldest questions in ecology, and integral to the study of landscape change, modeling, and ecosystem response to climate change. These processes are often examined via chronosequences, which carry the assumption that space can, in fact, be substituted for time. This assumption is rarely checked due to a lack of long-term data. In this study, we expanded the longest running primary succession study in the world (the William S. Cooper plots in Glacier Bay, Alaska, now running for 101 years) to examine successional trajectories and the role of spatial factors and stochasticity in community composition from both a regional and local perspective. After approximately 140 years since initiation, the ecological communities and dominant cover types better reflect variation in early (1916-1935) community composition rather than plot age. General cover type and richness appears to be primarily driven by location rather than time, and significant spatial structuring at the plot scale reflect exclusion of potential “later” successional species. The current communities appear stable, reflecting multiple generations and little to no establishment of other canopy species, despite available seed and ample time. At the plot scale, variation in species is related to stochastic establishment in the early landscape. Soil development, carbon, and nitrogen stocks are spatially consistent, with little spatial structure. These results indicate that space and stochastic effects early in a plot's history shape community composition for at least 140 years, and that alternate, apparently stable regimes can persist for long-periods of time in the early successional environment driven by stochastic establishment and spatial constraints.
