Trästammar

Trästammar is the plural term for tree trunks, the main above-ground axis of a tree that supports the crown and links roots with the branches. The trunk consists of outer bark, inner bark (phloem), cambium, and wood (xylem). The xylem is divided into sapwood, which conducts water and minerals and remains living for a period, and heartwood, which is typically denser and provides structural support but is less active in transport. Growth rings in the xylem reflect annual growth in temperate climates; in tropical species rings may be indistinct or absent.

Anatomy and morphology influence function and appearance. The trunk provides structural stability to withstand gravity and weather, and serves as the main conduit for nutrient transport from roots to shoots and leaves, as well as for sugars produced by photosynthesis from the leaves back down to storage tissues. Bark protects underlying tissues from physical injury, pathogens, and desiccation. Trunk form varies widely among species, with some showing straight, tall trunks; others feature buttresses at the base or curved, leaning shapes.

In forestry and arboriculture, trunk diameter is a key metric, often measured as diameter at breast height (DBH). The trunk’s quality affects timber value; defects such as knots, cracks, or cankers reduce usefulness. Silvicultural practices—pruning, thinning, and selective harvesting—aim to optimize trunk form for timber or for ecosystem services.

Ecologically, large trunks store carbon, influence microhabitats, and provide nesting and foraging sites for numerous organisms. Humans utilize trunks primarily for timber, plywood, paper, and other wood products, making the study of trunk growth and condition important for resource management and conservation.