Variability of Stand Structures and Development in Old-Growth Forests in the Pacific Northwest, USA

• Published in: Forests Vol. 6; no. 9; pp. 3177 - 3196
• Main Authors: Pil Sun Park, Chadwick D. Oliver
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-09-2015
• Subjects: cluster analysis; correlation; diameter distribution; Douglas-fir; shade tolerant species; species composition
• ISSN: 1999-4907
• DOI: 10.3390/f6093177

The forest stand structure class “old-growth” has previously been qualitatively described as having several distinct “sub-structures.” Species composition, diameter distribution, and other structural features commonly associated with old-growth in the Pacific Northwest are quite variable. We determined which quantitative stand structure variables are commonly found together using the Spearman correlation and non-metric multidimensional analysis. Some features were more commonly found together than others, indicating different old-growth stand types, or sub-structures. Cluster analysis classified the old-growth forests into four groups: Douglas-fir dominance, shade tolerant species dominance, and intermediate groups. The intermediate groups were split by the density of large logs and large shade tolerant trees. The old-growth sub-structures appear to change from one to another as the old forest develops.