Size distribution of unharvested redwood forests in Mendocino County
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Late-seral conditions in redwood forests are becoming a management goal on some timberlands. However, published information is rare regarding the structure of late-seral forests upon which silvicultural prescriptions can be guided, or upon which to measure success. Old-growth forests—those perceived to be near or at the successional climax—are the ultimate model. Yet, old-growth forests are a rare commodity in Mendocino County, limited mostly to state parks and small stands on private lands. Their rarity yields a poor sampling of the variation among stands, making historic sources of information valuable. Despite often incomplete information relative to ecologically important but non-commercial vegetation such as hardwoods or the structural complexity of their trees' canopy and boles, historic timber inventories can yield insights to the range of unharvested forests conditions. A 1929 data set derived from timber stands stratified into 20-thousand board feet per acre redwood classes on Caspar Lumber Company lands reveals an inverse J-shaped size frequency distribution based on diameter at breast height (DBH). Across the stand conditions, redwood comprised 67 to 96 percent of the tree density (31 to 51 trees per ac) and 73 to 97 percent of the basal area (116 to 537 ft2/ac); the DBH50 (diameter at which half of the trees were smaller) ranged from 17 to 30 inches DBH; while the DBH90 ranged from 42 to 70 inches. The largest size classes measured were 126+ inches, 78 to 82 inches, and 42 to 46 inches for redwood, Douglas-fir, and grand fir, respectively.