Forests, Lands, and NR Operations

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Effect of Time Trends in Tree Dominance on Site Height and Site Index

Author(s) or contact(s): G.D. Nigh
Source: Forests, Lands, and NR Operations
Subject: Growth and Yield, Site Index
Series: Extension Note
Other details:  Published 2016. Hardcopy is available.


Data from the Site Index - Biogeoclimatic Ecosystem Classification (SIBEC) project show that estimated site index declines with breast height age for some species. Since the true site index should be independent of age, this trend requires some investigation. This project looks at the effect of time trends in tree dominance (based on tree diameter) on site height and site index. Experiment EP1065 provided Douglas-fir (Pseudotsuga menziesii var. menziesii) data and a young stand monitoring sample provided data for lodgepole pine (Pinus contorta var. latifolia) and interior spruce (Picea glauca P. engelmannii). Site height and site index both declined slightly as the stand aged, but not enough to cause the amount of decline noted with these data and elsewhere. As this analysis is not definitive, further work on this issue should be considered.

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Updated August 23, 2016