Populus sect. Populus

Some of the species in the section are: • Populus adenopoda – Chinese aspen (China, south of P. tremula) • Populus alba – white poplar (northwest Africa, southern Europe, east to central Asia) • Populus davidiana – Korean aspen (Korea) • Populus grandidentata – bigtooth aspen (eastern North America, south of P. tremuloides) • Populus koreana – Korean poplar (Japan) • Populus simonii – Simon's poplar (China) • Populus tremula – Eurasian aspen (northern Europe and Asia) • Populus tremuloides – American aspen (northern and western North America) • Populus wulianensis Natural hybrids between species in the section include: • Populus × canescens: grey poplar, P. alba × P. tremula • Populus × hopeiensis: P. davidiana × P. tomentosa • Populus × pseudotomentosa: P. adenopoda × P. tomentosa ==Ecology==

Aspens do not thrive very well in the shade, and it is difficult for aspen seedlings to grow in an already mature aspen stand. Fire indirectly benefits aspen trees, since it allows the saplings to flourish in open sunlight in the burned landscape. Lately, aspens have an increased popularity in forestry, mostly because of their fast growth rate and ability to regenerate from sprouts, making the reforestation after harvesting much cheaper, since no planting or sowing is required. In contrast with many trees, aspen bark is base-rich, meaning that aspens are important hosts for bryophytes and act as food plants for the larvae of butterfly (Lepidoptera) species—see List of Lepidoptera that feed on poplars. Young aspen bark is an important seasonal forage for the european hare and other animals in early spring. Aspen is also a tree of choice of the european beaver. ==Uses==

Aspen wood is white and soft, but fairly strong, and has low flammability. It has a number of uses, notably for making matches and paper where its low flammability makes it safer to use than most other woods. Shredded aspen wood is used for packing and stuffing, sometimes called excelsior (wood wool). It is also a popular animal bedding, since it lacks the phenols associated with pine and juniper, which are thought to cause respiratory system ailments in some animals. Heat-treated aspen is a popular material for the interiors of a sauna. While standing trees sometimes tend to rot from the heart outward, the dry timber weathers very well, becoming silvery-grey and resistant to rotting and warping, and has traditionally been used for rural construction in the northwestern regions of Russia (especially for roofing, in the form of thin slats). The Ojibwe used the inner bark of the trunk as a poultice, and the Cree ate the inner bark in the spring as a mild purgative. ==References==