Document Type
Article
Publication Title
Ecology
Publisher
The Ecological Society of America
Publication Date
8-2014
Volume
95
Issue
8
Disciplines
Forest Management | Forest Sciences | Life Sciences
Abstract
Mortality processes in old-growth forests are generally assumed to be driven by gap-scale disturbance, with only a limited role ascribed to density-dependent mortality, but these assumptions are rarely tested with data sets incorporating repeated measurements. Using a 12-ha spatially explicit plot censused 13 years apart in an approximately 500-year-old Pseudotsuga–Tsuga forest, we demonstrate significant density-dependent mortality and spatially aggregated tree recruitment. However, the combined effect of these strongly nonrandom demographic processes was to maintain tree patterns in a state of dynamic equilibrium. Density-dependent mortality was most pronounced for the dominant latesuccessional species, Tsuga heterophylla. The long-lived, early-seral Pseudotsuga menziesii experienced an annual stem mortality rate of 0.84% and no new recruitment. Late-seral species Tsuga and Abies amabilis had nearly balanced demographic rates of ingrowth and mortality. The 2.34% mortality rate for Taxus brevifolia was higher than expected, notably less than ingrowth, and strongly affected by proximity to Tsuga. Large-diameter Tsuga structured both the regenerating conspecific and heterospecific cohorts with recruitment of Tsuga and Abies unlikely in neighborhoods crowded with large-diameter competitors (P , 0.001). Densitydependent competitive interactions strongly shape forest communities even five centuries after stand initiation, underscoring the dynamic nature of even equilibrial old-growth forests.
Keywords
Abies amabilis, long-term data sets, Pseudotsuga menziesii, Taxus brevifolia, tree mortality, Tsuga heterophylla, Wind River Forest Dynamics Plot
DOI
10.1890/14-0157.1
Rights
© 2014 by the Ecological Society of America
Recommended Citation
James A. Lutz, Andrew J. Larson, Tucker J. Furniss, Daniel C. Donato, James A. Freund, Mark E. Swanson, Kenneth J. Bible, Jiquan Chen, and Jerry F. Franklin 2014. Spatially nonrandom tree mortality and ingrowth maintain equilibrium pattern in an old-growth Pseudotsuga–Tsuga forest. Ecology 95:2047–2054. http://dx.doi.org/10.1890/14-0157.1
