Pines
Clad in evergreen needles and decorated with handsome woody cones, pine trees (Pinus spp.) are among the most recognizable trees in the world. In addition to their aesthetic charm, pine trees provide a variety of resources to the ecosystems in which they grow. This not only includes the sustenance and shelter prized by wildlife, but the raw materials humans have used to build everything from homes to fences to furniture.
Meet the Family
The term “pine tree” applies to all members of the genus Pinus. Different authorities recognize different levels of diversity within the genus, although most works report between 130 and 170 living species. Within the genus, pines exhibit considerable variation in life history and physical traits.
For example, Siberian dwarf pines (Pinus pumila) — one of the smallest species in the genus – are essentially shrubs that rarely exceed 10 feet in height. Conversely, ponderosa pines (Pinus ponderosa) are one of the largest members of the genus, and they may exceed 200 feet in height; the tallest documented specimen is approximately 270 feet high.
The living pines are grouped into several subgenera, each of which contains a collection of closely related species. The subgenus Pinus includes a number of two- or three-needled species with hard, yellow wood, while the subgenus Ducampopinus is comprised solely of the pinyon pines. The white pines (subgenus Strobus) have soft wood and needles bundled in groups of five.
Bundled Needles and Seed-Bearing Cones
Most pines are instantly recognizable by noting their bundled needles (the bundles are often called fascicles), which bear a deciduous sheath around the base. Most species produce needles in bundles of two to five, although there are exceptions, such as the single-leaved pinyon pine (Pinus monophylla), which produces single needles. The leaves are evergreen and vary in size from one species to the next. For example, whitebark pine needles (Pinus albicaulis) may measure slightly more than 1 inch, while longleaf pines (Pinus palustris) of the southeastern coastal plain may produce needles measuring up to 18-inches in length.
While they are similar to those of many other conifers, pinecones are also iconic characteristics of pines. Comprised of numerous rows of woody scales, pinecones remain tightly closed when they are young. When they open, the seeds are released to the forest floor below. A few varieties retain their seeds until birds separate the scales and remove the seeds manually. The seeds then pass through the digestive tracts of the birds, and germinate where they are deposited.
Other pine species rely on fire to help disperse their seeds, as the seeds remain inside serotinous (resinous) cones that remain tightly closed until the high temperatures of a forest fire melt the resin and allow the cones to open. At this point, the seeds may fall onto the recently burned earth, where they will grow rapidly, courtesy of the abundant sunshine and lack of competitors.
Ecology and Adaptability
Although Sumatran pines (Pinus merkusii) slightly encroach into the Southern Hemisphere, pines are largely restricted to the Northern Hemisphere. Nevertheless, pines inhabit a variety of habits throughout much of North America, Europe and Asia. As a group, pines exhibit a number of adaptations to these varied habitats that allow them to survive.
For example, while most pines prefer well-drained soils, lodgepole pines (Pinus contorta) grow readily in damp earth. Whereas Great Basin bristlecone pines (Pinus longaeva) are exposed to high winds, which lead them to grow in twisted, contorted manners, forest-grown sugar pines (Pinus lambertiana) grow tall and straight. .
Commercial Importance
Pine trees are some of the most commercially important trees in the world. Early European settlers, for example, harvested broad swaths of white pine (Pinus strobus) growing throughout east-coast forests to make their houses and other items. In addition to their considerable timber value, the seeds of many pines are edible and delicious – especially those from Korean pines (Pinus koraiensis), which are intensively managed in China.
Pines also make excellent ornamental trees, and because they live in a wide range of habitats and geographic regions, most property owners can find a species suitable for the site. This is especially true of California-based property owners, as 19 species are native to the state and many others are suitable for the region’s climate and geology.
