A regional coastal Douglas-fir index of site quality for young stands in western Washington, USA

Document Type

Article

Publication Date

11-15-2025

Abstract

Site index is frequently used for deciding how to manage stands, however, it often omits or fails to accurately characterize the site-dependent growth of young (ages ≤8 years) trees. This early stage of development is a critical period in a rotation during which important management decisions with the potential to influence all future growth are made. To address this, we developed a new index of site quality for young, coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stands in western Washington, USA. We used high-density light detection and ranging (LiDAR) scans for 161 stands between 3 and 8 years old, in conjunction with Soil Survey Geographic Database information to identify site characteristics that were associated with productivity in young Douglas-fir sites. We utilized individual-tree detection algorithms to measure tree heights and developed a linear model for correcting LiDAR-derived heights in young Douglas-fir stands based on field-measured heights. Our findings indicated that Douglas-fir growth tended to be greatest on sites that were low in elevation, high in precipitation, and had fine-textured soils. We provide an index of site quality for young Douglas-fir based on elevation, precipitation, and soil textural classes to guide early stand management.

Publication Title

Forest Ecology and Management

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