Thirty-five-year growth of thinned and unthinned ponderosa pine in the Methow Valley of northern Washington.

Abstract

It is commonly expected that self-thinning will maintain small-diameter stands at near-normal densities and allow dominant trees to grow reasonably well. Such self-thinning did not occur in the unthinned plots in a thinning study in the Methow Valley of northern Washington, even though there was some suppression-caused mortality. A shift from suppression-caused mortality to insect-caused mortality took place when quadratic mean diameters (QMDs) reached 7 inches. Thinning to spacings wider than 9.3 feet reduced growth of both basal area and cubic volume per acre but greatly in-creased growth of board-foot volume per acre, and diameter and height growth. Periodic annual increments of cubic volume and QMD are curvilinearly related to stand density index. Growth of the largest 62 trees per acre was clearly reduced by the presence of smaller trees in the stand. Density management is necessary to produce reasonable growth rates of even the largest trees in the stand and to speed the development of mid-seral conditions.

Citation

Cochran, P.H.; Barrett, James W. 1998. Thirty-five-year growth of thinned and unthinned ponderosa pine in the Methow Valley of northern Washington. Res. Pap. PNW-RP-502. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.