. Vingt ans de croissance des jeunes plants de pin ponderosa éclaircis à espacements cinq dans le centre de l'Oregon. Le pin de l'Oregon ; l'éclaircie de la forêt de l'Oregon. La figure 1-pin ponderosa mature avec un peuplement dense, supprimé 40- à 70 ans, sous-étage des gaules avant l'éclaircie à diverses densités. Des expériences dans la gestion des jeunes, sup- pression se trouve dans le nord-ouest du Pacifique ont changé au cours des 40 dernières années. Les premières expériences participent habituellement deux parcelles, l'une éclaircis à un 5b- tion de l'espacement de 6 ou 9 pieds, l'autre gauche (non éclaircis Mowat, 1953). Plus tard, son expérience de l'éclaircie des arbres ont été créées (Barr

• Contributeur: The Book Worm / Alamy Banque D'Images
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. Twenty-year growth of ponderosa pine saplings thinned to five spacings in central Oregon. Ponderosa pine Oregon; Forest thinning Oregon. Figure 1—Mature ponderosa pine stand with a dense, suppressed 40- to 70-year-old sapling understory before thinning to various densities. Experiments in managing young, sup- pressed stands in the Pacific Northwest have changed over the past 40 years. The first experiments usually involved two plots, one thinned to a conserva- tive spacing of 6 or 9 feet, the other left unthinned (Mowat 1953). Later, experi- ments in crop-tree thinning were established (Barrett 1969). All studies showed that suppressed, understory trees are capable of substantial response to thinning. The full potential for diameter growth of second-growth ponderosa pine was not visualized until a study of free- growing trees was reported by Dahms and Silen in 1956.' They observed young trees free from competition growing at the rate of 6 to 7 inches per decade. They also found that heavy competition from brush reduced the growth rate to about 3 inches per decade. Thus, a tentative rate for maximum diameter growth was sug- gested and the importance of brushy understory competition was estab- lished. This work by Dahms and Silen suggested that the next thinning study should sample a wide range of spac- ings and should attempt to quantify the effect of brush competition on tree growth. The Methow study, established about 4 years later, tested spacings of 9.3, 13.2, 18.7, and 26.4 feet as well as growth in unthinned plots (Barrett 1981). It showed that dense, sup- pressed ponderosa pine responded to increased space with more diameter and height growth. This study also showed that wider spacings produced large diameter trees in 20 years after thinning but that very wide spacings (26.4 feet) where the understory is predominantly pine grass can sacrifice substantial yields of wood fiber during the early part of a rotation. This paper presents 20-year results from a sp

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