Regional variation in wood specific gravity of planted loblolly pine in the United States
نویسندگان
چکیده
Loblolly pine (Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with increasing age and varies significantly among physiographic regions. The South Atlantic and Gulf regions had the highest ring SGs, while the Hilly and Piedmont regions had the lowest. Based on ring SG, the juvenile period averages 4.3 years, followed by 8.6 years of transition wood, with mature wood produced by year 13. Whole-core mean SG was significantly higher in the South Atlantic (0.486) compared with the other regions (mean = 0.455), which were not statistically different from each other. Trees from the South Atlantic have significantly higher whole-core SG because they contain significantly more latewood (40.1%) compared with trees growing in other regions (33.8%). Maps indicate that stands in the South Atlantic and Gulf regions have the highest SG at a given age. Stands growing on the northern and western fringe of the natural range of loblolly pine have the lowest whole-core SG. Résumé : Le pin à encens (Pinus taeda L.) est la plus importante espèce plantée dans le sud-est des États-Unis d’Amérique et la densité est la plus importante caractéristique de la qualité du bois chez cette essence. L’analyse de la densité des cernes annuels dans des carottes prélevées à hauteur de poitrine (1,37 m) sur 3957 arbres provenant de 147 plantations établies partout dans l’aire naturelle de répartition de l’espèce montre que la densité des cernes annuels augmente avec l’âge et varie significativement entre les régions physiographiques. Les cernes annuels des régions de l’Atlantique Sud et du Golfe ont les densités les plus élevées tandis que ceux des régions de Hilly et du Piedmont ont les plus faibles. Sur la base de la densité des cernes annuels, la période juvénile dure en moyenne 4,3 ans, suivie d’une période de transition de 8,6 ans et du bois mature vers l’âge de 13 ans. La densité moyenne de l’ensemble de la carotte est significativement plus élevée dans la région de l’Atlantique Sud (0,486) que dans les autres régions (moyenne = 0,455) qui ne sont pas statistiquement différentes les unes des autres. Les carottes des arbres de la région de l’Atlantique Sud ont une densité significativement plus élevée parce qu’ils contiennent significativement plus de bois final (40,1 %) que les arbres qui croissent dans les autres régions (33,8 %). Pour un âge donné, les cartes indiquent que les peuplements des régions de l’Atlantique Sud et du Golfe ont la densité la plus élevée. Les carottes provenant des peuplements qui croissent aux limites nord et ouest de l’aire naturelle de répartition du pin à encens ont les plus faibles densités. [Traduit par la Rédaction]
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