“Questions About Trees”, 2020-09-04 (; similar):
[Series of simulations exploring explanations for the “paradox of the plankton”: why, in apparently homogenous environments, such as open sea water, are there countless thousands of species of plankton all doing the same task of photosynthesis & competing for the same resources? Why isn’t there just a few, or one, species which is optimal in that niche and outcompetes all the others rapidly? Similarly, in a forest: why is there such a dense mix of tree species, rather than relatively continuous stands of species as local conditions vary?
The initial simulations demonstrate that even a tiny fitness difference will result in a loss of diversion; in fact, with no difference, simple random fluctuations, ‘drift’, will eventually irreversibly drive species to extinction (even assuming occasional ‘immigrants’). This can be fended off by assuming a specialty, like metabolizing a particular chemical well, but can this really explain forest stands with 200+ species? More plausible is predatory-prey dynamics like the Lotka-Volterra model: a species which becomes too common gets preyed on by diseases and parasites and predators, stopping it from spreading further. The dynamics of it are chaotic, but preserve diversity. To some extent, probably all of these explanations are true.]