Effect of competition on genetically improved ponderosa pine seedlings

Abstract

In northern California, ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) height and diameter growth were analyzed to determine if genetically improved seedlings were more competitive than other vegetation and if they outgrew nursery stock in the field. Analysis of growth during the third through sixth growing seasons (1992-1995), indicated no statistical differences for pine height or diameter among genetic classes (control pollinated, wind pollinated, nursery run) when grown with competing vegetation. In 1995, mean height of seedlings grown with competition was 2.4 m for control-pollinated seedlings, 2.3 m for wind-pollinated seedlings, and 2.2 m for nursery-run seedlings. For seedlings grown essentially without competition, control-pollinated seedlings significantly outgrew nursery-run seedlings in height each year for the first six growing seasons. In 1995, the values were 3.0 versus 2.6 m, respectively. The competition consisted of a vigorous stand of shrubs, hardwood sprouts, forbs, and grasses. Within each genetic class, mean height and diameter of pines were significantly larger without competition.