|What's wrong with this picture? (Laramie, Wyoming; click on image to view).|
Deciduous trees toss their leaves each fall but then must produce a new set in the spring. This seems wasteful and costly.
|Every fall, quaking aspen (Populus tremuloides) kills it leaves by starving them, a pretty but brutal process.|
|Western red cedar, an evergreen conifer, keeps its beautiful needles year round.|
What would you do if you were a tree? Here are a couple of tools to help you decide, produced by botanists in collaboration with Mother Nature. First, a table of terms and definitions:
|*Gymnosperms and angiosperms are two evolutionary branches within seed-producing plants (spermatophyes).|
In a sense, the ideal place to live is where it never freezes and there’s always adequate moisture, for example the tropics. In these places a tree can grow year-round, so it’s not surprising that most tropical trees are evergreen. Furthermore, they’re broadleaved. It’s worth investing in large thin leaves that maximize sunlight and carbon dioxide uptake. Highly-productive leaves mean faster growth to compete for sunshine. Evergreen leaves do die and fall off but not all at once. There’s always plenty to feed the tree.
Left, Shorea sp., a canopy species of tropical forests in Borneo, from Landmark Trees.
Of course evergreen broad leaves would be a poor choice where the climate is seasonal. They aren’t hardy enough. Deciduous is a better strategy -- drought-deciduous in deserts, cold-deciduous where winters are harsh.
The cold-deciduous weeping birch (Betula pendula, right) produces a new set of thin highly-productive leaves for the growing season, tosses them in the fall, then goes dormant and rests over the winter.
|Limber pine (Pinus flexilis) in the Laramie Mountains, Wyoming.|
Juniper scales and berry-like seed cones (source).
So evergreen or deciduous, broad leaves or needles ... which would you choose? I would be an evergreen conifer so I wouldn’t have to go do the intensive-growth-thing. Summers are too short ... I want as much leisure time as possible!
|Tree impersonation, a popular plant-geek pastime.|
Sources (in addition to links in post)
Havranek, WM and Tranquillini, W. 1995. Physiological processes during winter dormancy. in Smith, WK and Hinckley, TM, eds. Ecophysiology of coniferous forests. Academic Press.
Thomas, P. 2000. Trees: their natural history. Cambridge University Press.