Seed fall of three conifers in west central Oregon

Seed fall of Douglas-fir, western hemlock, and western redcedar was measuredwith seed traps on clearcut areas in western Oregon from 1954 to 1965. During the 12 years,crops of filled seed per acre showed the following ranges: Douglas-fir 300 to 168,800, hemlock1,000 to 178,900, and redcedar 0 to 367,400. The percentage of seed that was filled showed adirect relation to size of the annual crop for Douglas-fir and redcedar, but not for hemlock.Percentage of seed that was filled averaged 15 for Douglas-fir compared with 21 for hemlock,and 27 for redcedar. Seed fall began in late August or early September; by December, itreached 70 percent for Douglas-fir and 60 percent for hemlock and redcedar, and was vir-tually complete for all three species by April. Percentage of the species composition in theadjacent forest and of the total seed fall was: Douglas-fir 80 and 26, hemlock 10 and 40, andredcedar 10 and 34. Distribution of seed of the three species showed similar gradients intothe clearcuts. Seed fall declined roughly in the ratio of 7 to 2 to 1 at 75, 225, and 375 feetfrom the timber edge.
Additional key words. Pseudotsuga mehziesii, Dug,: eterophyll•, Thuja plicata, seed dis-tribution.