Three-Dimensional Canopy Structure of an Old-Growth Douglas-Fir Forest

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In this study, the structurally heterogeneous canopy of a 12-ha plot in an old-growth Douglas-fir forest was analyzed using three-dimensional (3-D) canopy modeling, geographic information system (GIS), and spatial statistics. Using this approach, we were able to depict how species composition and spatial distribution affect the 3-D structure of canopies. We were also able to slice the canopy and calculate the canopy coverage at various heights, and therefore were able to calculate the cumulative canopy volume at individual crown bases. Information generated by GIS allowed us to calculate how much area canopies or canopy openings occupy. Total canopy volume (243,641 m3/ha) was dominated by western hemlocks (67.1%) and Douglas-firs (23.7%) in this plot. Western hemlocks and Douglas-firs also dominated the canopy coverage, with 65.7% and 25.5% average coverage, respectively. Average total canopy coverage was 84.3% with variations between 78.7% and 89.9% among the 12 1-ha subplots, implying that 15.7% of the stand consisted of canopy openings. Coverage of the canopy projection changed greatly from the lower to the upper canopy layers, with the maximum at about 20 m high. We also examined spatial relationships among groups of trees at different heights and at various scales using bivariate Ripley's K analysis. We found that different species of the understory layer showed different spatial relationships relative to the overstory canopy layer. Likewise the same species in the understory layer showed different spatial relationships when the overstory species differed. This approach provided a useful tool for characterizing 3-D forest canopies, and the results will be very helpful for examining leaf distribution, understory light environment, understory vegetation, and microclimate. FOR. SCI. 50(3):376–386.

Keywords: Canopy opening; GIS; Ripley's K analysis; environmental management; forest; forest management; forest resources; forestry; forestry research; forestry science; natural resource management; natural resources; vertical structure

Document Type: Regular Article

Affiliations: 1: Assistant Professor Belle W. Baruch Institute of Coastal Ecology and Forest Science Clemson University PO Box 596 Georgetown SC 29442-0596 Phone: (843) 545-5673;, Fax: (843) 546-6296, Email: 2: Professor Department of Earth, Ecological & Environmental Science University of Toledo Toledo OH 43606 Phone: (419) 530-2664, Email: 3: Associate Professor Department of Landscape Architecture University of Wisconsin Madison WI 53706 Phone: (608) 265-8093, Email:

Publication date: June 1, 2004

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