Maturity Selection versus Improvement Selection: Lessons from a Mid-20th Century Controversy in the Silviculture of Ponderosa Pine

Abstract

Abstract Two rival silvicultural systems for promoting multiaged ponderosa pine stands emerged in the 1930s and 1940s. Maturity selection was developed to move the vast ponderosa pine (Pinus ponderosa) acreage in eastern Oregon and Washington into regulation to limit bark beetle losses. In the Southwest, improvement selection was designed to improve residual growing stock by making stands less susceptible to wind, lightening, and dwarf mistletoe. The primary difference between the systems was the treatment of undesirable smaller trees. Maturity selection tended to ignore them whereas improvement selection removed them. Improvement selection appeared to place a greater emphasis on the future whereas maturity selection focused more on current economic values. The controversy subsided by 1960 because of increased interest in even-aged systems. Although these systems have largely been forgotten, they provide interesting insights to the current trend of increased use of multiaged systems. Both systems involved greater volume removals at longer cutting cycles than current systems.