Dendrology

The American Woods
Wood sections of 350 North American trees from the 14-volume book The American Woods, published between 1888 and 1910 by Romeyn Beck Hough.
http://www.lib.ncsu.edu/specialcollections/forestry/hough/

The Ancient Bristlecone Pine
Dedicated to the oldest-known living tree, growing in the White Mountains in east central California. Information about the location, dendrochronology, photo gallery, and bibliography.
http://www.sonic.net/bristlecone/

Dendrochronology
Information from Wikipedia on tree-ring dating which is a scientific method of dating based on the analysis of tree-ring growth patterns.
http://en.wikipedia.org/wiki/Dendrochronology

Dendrology
Information from Wikipedia on the study of woody plants including trees, shrubs and lianas.
http://en.wikipedia.org/wiki/Dendrology

Forest Biology and Dendrology at Virginia Tech
Information about courses, trees, and forest biology. Includes fact sheets on over 450 species of trees.
http://www.cnr.vt.edu/dendro/wwwmain.html

International Dendrological Research Institute
Nonprofit organization dedicated to documenting the woody flora worldwide.
http://www.interdendr.org/

Silvics of North America
Compendium of research papers describing the characteristics and distribution of important broadleaf and coniferous forest trees of the United States and Canada, plus many of the native and naturalized trees of Mexico, the Caribbean Islands, and Hawaii. Compiled over several decades by USDA Forest Service scientists.
http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm

Tree Matters
Site for The Dendrologist, a quarterly magazine. Also contains tree tips and a record of the dates of upcoming dendrology events in the UK.
http://www.treematters.freeserve.co.uk/

Tree Root Architecture, Root Dynamics and Rhizosphere Processes
Information on research into tree root architecture, tree root growth and tree stability.
http://www.agrsci.unibo.it/dicabo/stelloncini/TREE_ROOT.htm