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NCSU Inside Wood project; Reproduction of The American Woods: exhibited by actual specimens and with copious explanatory text by Romeyn B. Hough; US Forest Products Laboratory, "Characteristics and Availability of Commercially Important Wood" from the Wood Handbook Archived 2021-01-18 at the Wayback Machine PDF 916K; International Wood ...
The hardest hardwoods are much harder than any softwood, [4] but in both groups there is enormous variation with the range of wood hardness of the two groups overlapping. For example, balsa wood, which is a hardwood, is softer than most softwoods, whereas the longleaf pine, Douglas fir, and yew softwoods are much harder than several hardwoods.
Hardwood from deciduous species, such as oak, normally shows annual growth rings, but these may be absent in some tropical hardwoods. [3] Hardwoods have a more complex structure than softwoods and are often much slower growing as a result. The dominant feature separating "hardwoods" from softwoods is the presence of pores, or vessels. [4]
It is common to classify wood as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from dicotyledons (usually broad-leaved trees, e.g. oak) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft.
In North America, market practices for dimensional lumber made from hardwoods [a] varies significantly from the regularized standardized 'dimension lumber' sizes used for sales and specification of softwoods – hardwood boards are often sold totally rough cut, [b] or machine planed only on the two (broader) face sides. When hardwood boards are ...
The term just refers to wood that comes from gymnosperms or conifers. Some hardwood trees are even softer than specific softwood tree species. [8] Softwoods are used in wood manufacturing as well, and are sometimes preferred over hardwoods depending on the product being constructed.
Native ash species, including white ash (pictured), have been declining rapidly this century due to predation by the emerald ash borer. [1]Silvics of North America (1991), [2] [3] a forest inventory compiled and published by the United States Forest Service, includes many hardwood trees.
Softwoods exhibit a simpler basic wood structure, characterized by only two cell types and limited variation within these categories. In contrast, hardwoods display increased structural complexity owing to a higher number of fundamental cell types and a considerable degree of variability within these cell types.