. Economics of thinning stagnated ponderosa pine sapling stands in the pine-grass areas of central Washington. Forest thinning; Ponderosa pine Washington (State) Thinning; Forest management Economic aspects. During the 10 years of observation on this study, thinning has stimulated diameter growth to produce a usable product (fig. 2) within a reasonable time. Trees at the widest spacing have added 3 inches to their diameter during the past decade, and trees spaced and feet have grown and inches, re- spectively (fig. 3). Comparable trees in unthinned plots continue to grow at o
. Economics of thinning stagnated ponderosa pine sapling stands in the pine-grass areas of central Washington. Forest thinning; Ponderosa pine Washington (State) Thinning; Forest management Economic aspects. During the 10 years of observation on this study, thinning has stimulated diameter growth to produce a usable product (fig. 2) within a reasonable time. Trees at the widest spacing have added 3 inches to their diameter during the past decade, and trees spaced and feet have grown and inches, re- spectively (fig. 3). Comparable trees in unthinned plots continue to grow at only a half or a third of those Figure 2.—Cross section cut from a released ponderosa pine. Thinned-^ Unthinned J 250 125 * * 62 * Trees per acre and spacing (feet) Figure 3.—Average annual diameter increment per tree in the thinned stand and average growth on a comparable number of trees in the unthinned stand during the 10 years fol- lowing thinning. During the 10 years, none of the thinned stands have produced as much wood fiber as the unthinned stand (fig. 4). However, there has been an increase in fiber production in thinned stands from the first 5-year period to the second; the growing-stock base is increasing so net cubic growth will probably equal or ex- ceed unthinned stand production in the next decade or so. And most important, in the thinned stand, wood is being added to trees that will grow to usable sizes. In contrast, much of the wood growth in the unthinned stand will be added to trees that will either die or never reach mer- chantability. GROUND COVER The understory in these thickets of ponderosa pine is a sparse stand of spindly shrubs and scattered forbs and grasses (fig. 5). Total air-dry herbage production on the unthinned portion of the study area was about 117 pounds per 55 _ 50 45 = 40 S 35 30 E 25 20 - 15 10 1958-63 1963-68 No 250 125 62 thinning * * * Trees per acre and spacing (fee
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