Little, Elbert L., Jr. U.S. Department of Agriculture, Washington DC.
Last reviewed:August 2019
- Related Primary Literature
- Additional Reading
Any of the deciduous shrubs and trees of the genus Alnus in the birch family (Betulaceae). There are approximately 30 species of alder, with 10 in the United States. Alders are widespread in cool north temperate regions and are also found southward in the Andes of South America. They have a smooth gray bark; elliptical or ovate saw-toothed leaves in three rows; male flowers in long catkins, mostly in early spring; and clusters of several dry, hard, ellipsoid blackish fruits that are 0.5–1 in. (1.25–2.5 cm) in length. The fruits are conelike and present throughout the year. Alders are common in wet soils, such as stream borders. They often form thickets even beyond treelines and are pioneers on bare areas (including landslides and roadsides) and after fire or logging. As in legumes, the roots bear swellings or nodules containing nitrogen-fixing bacteria, which enrich the soil. See also: Fagales; Nitrogen fixation; Nitrogen-fixing trees
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information