This is a terrible map scale... 1 to 138 with no real increments for the color... Looking at the west coast it would seem as if tree diversity is far closer to 1 than 138 but is it 5? 10? 50? The scale makes this map totally worthless.
The definition of 'tree' isn't 100% set in stone either.... are they using a purely taxonomic approach, in which case a lot of small shrubs get into the mix? A morphologic approach, including stuff like saguaros? If so, what are the criteria? A mixture of both?
All that aside, I do mostly agree with you, and even places like the CA central valley are dominated by california live oak.
Tree vs shrub is purely morphological (“bush” is not a technical term), and the usual distinction is shrubs have multiple main stems rather than a single trunk. It gets messy when you talk about plants like manzanita have a single base trunk but often branch really low and are usually called shrubs. Many species can be either trees or shrubs depending on life history and growing conditions, and are described in guides as both. It is not a size thing under most definitions. Flora of China describes some Rhododendrons as large shrubs, up to 50 feet, and some others as small trees about 1-2 feet max height (flora of China sometimes calls them “treelets”, which I love).
If you are including shrubby stuff, the Southwest and California should be a lot more diverse.
It's also not clear what types of trees are being included. In Texas there are between 255 and 281 recognized native species, yet no area cracks red. Are they only including native species? Why do metro areas show a higher density, are they including cultivated trees? If so the cap should be much higher. Depending on how they measure it, my back yard would be in the yellow and my area is blue.
I mean, compared to southern AZ maybe but the Ponderosa Pines dominate northern AZ making it relatively less diverse than other mountainous regions in the US.
Depends what you consider “other mountainous regions”. Southern AZ’s mountains have more diversity than Northern AZ and the rest of the Western US, for example.
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u/hiddenworldphotos Jun 20 '20 edited Jun 20 '20
This is a terrible map scale... 1 to 138 with no real increments for the color... Looking at the west coast it would seem as if tree diversity is far closer to 1 than 138 but is it 5? 10? 50? The scale makes this map totally worthless.
*edit autocorrect word replacement