When I was much younger I discovered a series of books called the Golden Guides. The first I ever acquired was for insects and over the years I wore out several copies. Several years later I picked up a copy of their guide to trees and this became one of my favorites, along with volumes on birds, reptiles and amphibians, wildflowers, stars and seashores. There were many more, but these especially excited me and help set me on an unlikely career path that through a whole lot of twists and turns eventually resulted in my becoming a professor of entomology. Trees still fascinated me though, as did other botanical areas. One of my office mates at the University of Arizona, the venerable Dr. Joseph Becquaert (who was retired from the Harvard Museum of Comparative Zoology), often said that no entomologist worth their salt was ignorant of botany and I took that to heart, especially for trees. My major professor, Dr. Walter Miller, was also interested in these large woody plants and could always find trees to examine no matter where he went, even if he could find no land snails (his specialty.)
I grew up and went to college through my Masters degree in the deserts of Arizona, so most of our trees were not like huge sequoias, but they were always interesting and I found them to be sources of numerous arthropods. Of course the mountains, especially the sky island mountain ranges of Southeast Arizona, had larger trees in real forests, so I could get to these. When I moved to Florida a whole new world of subtropical and swamp trees were to be found. Finally I settled in New Mexico and some familiar species along with new ones were evident. After 32 years in southern New Mexico I found myself transplanted again to Puget Sound in Washington state and getting acquainted with trees I had never seen, plus a few old friends such as Douglas fir.
Trees are by their nature somewhat subjective in definition because some species that are normally “trees” can be “shrubs” and vice-versa. But then nature does not have to follow our classification systems. Some plant families (for example the Solanaceae or nightshade family) are normally herbaceous (potatoes, tomatoes, eggplant, tobacco, petunias, nightshade and sacred datura), but also contain a few tree species (the so-called potato tree of the American tropics.) Others that are usually trees (the Fagaceae or beech family) have shrubby members, such as shinnery oak. However, as one who spent a lot of time in shinnery oak “forests” I can testify that even a few of these can reach tree status, dwarfing their nearby conspecifics.
The very tallest trees — the redwoods, Australian gum trees, Douglas fir and others — reach over 300 feet in height, or close to and above 100 meters! A shrub is usually defined as a woody plant shorter than 20 feet, or 6 meters, although this gets a bit tricky at the high end. Botanists puzzled for years as to the mechanism trees used to transport water and nutrients to their upper trunks and branches against the pull of gravity, but this seems to have been solved (See: www.scientificamerican.com/....)
Trees in the desert are, as I mentioned, not usually very tall. Some, such as saguaro and cardon cacti are not very similar to what one usually thinks of as a tree, being without true leaves and being actually composed of photosynthetic stems covered with spines (the remains of leaves and related structures).
Other desert trees are not especially succulent, but may or may not have photosynthetic stems (palo verdes have such stems, palo blanco trees lack them), but may have varying amounts of spines and reduces or absent leaves. Both palo verde and palo blanco belong to the Faberaceae or pea family.
Another pea family member, the smoke tree, is almost white with bluish flowers (hence the name) and lacks leaves during drought periods.
Other desert or desert canyon trees include desert willow (really a catalpa), Texas madrone, and elephant trees.
Many trees live for long time, with several species measuring their life span in several thousand years (redwoods and others). Some trees, while they not be as long-lived as individuals, are “living fossils,” having survived from the age of dinosaurs. Ginkos and the Araucaria species are examples of these.
Palm trees are not exactly trees except by size. The trunk is fibrous and they are monocots so they do not lay down growth rings. They are, however, a potent symbol of the tropics and subtropics and I have always liked them.
Trees, of course, make up forests and while cactus forests are the ones I spent much of my early life around, I eventually got to explore other more typical forests. Mountain forests are, other than the Florida and Georgia cypress swamp and pine and hardwood forests, the ones I know the best, having grown up in Arizona and lived for 32 years in New Mexico, and spent several years in Florida. I was especially fond of the pine, spruce, Douglas fir and fir forest in the Sacramento Mountains near Cloudcroft, New Mexico, and the Sierra Madrean forests of the Sky Islands of Southeast Arizona.
Forests are important carbon dioxide sinks and producers of oxygen, ranking up with marine algae, including diatoms. There are many good reasons for wanting to protect forests and for planting trees, including watershed protection, erosion control, wildlife habitat, tourism, as well as for carbon sinks and oxygen production. The Tongass National Forest is one such gem and its protection is much more important then just for love of trees.
However, I have to admit a strong connection to trees that is not entirely scientific. When the problems with my parents became too much for me when I was living in Florida, I would, rain or shine, find my way to a very large live oak in the hardwood hammock (forest) surrounding Lake Kanapaha and climb on the one of its massive lower limbs. For some reason being in touch with the tree and its associated epiphytes (Spanish moss, resurrection fern, etc.) above the forest floor revived me. I felt a kinship with nature that I could not achieve with my relatives. I guess I am a tree-hugging dirt-worshiper after all!
There are many books on trees and I can’t give a complete bibliography. Perhaps the most interesting are the two books on North American tree natural history (split into western and eastern trees) by Donald Culross Peattie.
As usual all photos (including those taken many years ago with a rather primitive box camera) are by me.