. Growth and mortality of ponderosa pine poles thinned to various densities in the Blue Mountains of Oregon. Ponderosa pine, Thinning, Blue Mountains (Or. and Wash. ); Ponderosa pine, Blue Mountains (Or. and Wash. ), Growth; Mountain pine beetle, Blue Mountains (Or. and Wash. ); Forest health, Blue Mountains (Or. and Wash. ). Treatments and Design Six growing stock levels (GSLs) are being tested at this location. Originally, these GSLs were 30, 60, 80, 100, 120, and 140 square feet of basal area per acre where the Dq is 10 inches or more after thinning. Where Dq was less than 10 inches, the pr
. Growth and mortality of ponderosa pine poles thinned to various densities in the Blue Mountains of Oregon. Ponderosa pine, Thinning, Blue Mountains (Or. and Wash. ); Ponderosa pine, Blue Mountains (Or. and Wash. ), Growth; Mountain pine beetle, Blue Mountains (Or. and Wash. ); Forest health, Blue Mountains (Or. and Wash. ). Treatments and Design Six growing stock levels (GSLs) are being tested at this location. Originally, these GSLs were 30, 60, 80, 100, 120, and 140 square feet of basal area per acre where the Dq is 10 inches or more after thinning. Where Dq was less than 10 inches, the prescribed basal areas (PBA) for each GSL and Dq are tabulated in the study plan (Myers 1967). The relation of PBAs to GSLs and Dqs where Dq is less than 10 inches is, PBA = (GSL)(Dq2)Exp( Dq). (1) Equation (1) was determined by fitting the equation, logePBA = bo+biloge(GSL) + b2(GSL) + D3loge(Dq) + b4(Dq) , (2) to the tabulated values in Meyers (1967) by using step wise linear regression tech- niques. The coefficient for the (GSL) term was not significant (p < ). Plots and buffer strips were thinned to the prescribed levels initially (fall 1967) and after the second (fall 1977) and fourth periods (fall 1986) (figs. 1 and 2). After the fourth remeasurement (fall 1986), GSLs were changed to stand density index (SDI) values of 55, 110, 147, 183, 220, and 257. These SDI values are equivalent to the original GSLs when Dq is 10 inches. A wide range in Dqs had developed both within and between treatments by the end of the fourth period. The change in defining den- sities was necessary because the GSLs defined by equation (1) have no relation to any biological limit and cannot be interpreted as a constant relative level of competi- tion across a range of stand diameters. The SDI values for ponderosa pine were determined by using, SDI = (N)(Dq/10)1'77 , (3) where N is live trees per acre and Dq is the quadratic mean diameter (DeMars and Barrett 1987). An exponent of
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