Patch size estimates and stem density of large trees (>76.2cm d.b.h.) in old-growth mixed-conifer forests of California and Oregon

Density and spatial patterns of large trees were analyzed within seven study sites in old-growth mixed-conifer forests of California and Oregon.  The study sites ranged in size from 16 – 100 ha, and were mapped using a GPS/laser rangefinder/digital compass system with a known sub-meter error. Three general aggregated patch sizes existed at roughly one, three and eight hectares when all species, study sites and size classes are considered together.  When considered independently, the smallest size class (76.2 – 99.9 cm d.b.h.) also had the smallest mean patch size of roughly 1/5^th hectare, while the largest size class (>125 cm d.b.h.) had the largest aggregated patch sizes of almost fifteen hectares.  Large Jeffrey pine trees are clumped at roughly one, four and nine hectares; ponderosa pine is at one-half, two, five and ten hectares; sugar pine at one-quarter, one, five and nine hectares; incense cedar at one fiftieth (1/50^th), four and twelve hectares; and white fir at one and a half, four and sixteen hectares, on average.  Sugar pine was the only species to contain any evidence of uniform patterning in the large tree distributions, and this occurred at the scale of roughly thirteen hectares.  When all species were considered simultaneously, the actual mean large tree density between the study sites was from 8.7 – 27.3 stems/ha, in.  Large trees in Yosemite National Park, California, had the highest overall density of large trees (27.3 stems/ha), and had a density range by species of 2.4 stems/ha for sugar pine to 14.8 stems/ha for ponderosa pine.  Density of individual species peaked at 14.9 stems/ha for ponderosa pine, 11.3 stems/ha for Jeffrey pine, 8.2 stems/ha for incense cedar, 6.3 stems/ha for sugar pine, and 4.5 stems/ha for white fir.