The next day, Saturday, a student had some questions about an article on an English reading comprehension test he had taken. The article was called "What Is a Community?" and began thus:
The Black Hills forest, the prairie riparian forest, and other forests of the western United States can be separated by the distinctly different combinations of species they comprise. It is easy to distinguish between prairie riparian forest and Black Hills forest -- one is a broad-leaved forest of ash and cottonwood trees, the other is a coniferous forest of ponderosa pine and spruce trees.
Not only is that an example of diversity in forests, it is specifically the beta diversity I focused on in my post -- that is, one forest differing from another in terms of its species composition (as opposed to alpha diversity among trees within a single forest).
Incidentally, Kevin McCall (who, unlike me, is a trained mathematician) has taken up the quest for a formula interrelating the various types of diversity. Check out his "Summary and discussion of ecological formulas" if you're interested.
1 comment:
Interesting synchronicity.
When I went back over to revise what I had written, I realized I had made a mistake in deriving the beta formula, so it is only an inequality. But interestingly enough, it shows that the β = γ - α formula which we can rewrite as γ = α + β was incorrect, but on the right track. It correctly expresses as α and β increase, γ also increases. The inequality then helps us understand their relationships more precisely.
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