Relative Abundance of 1,175 Plant Species within a Borneo Plot

relative abundance graph

THE MATHEMATICAL FORMULA associated with a radical theory of ecology exactly predicts both the diversity and abundance of the species that make up a community. The data above (black symbols) illustrate a census of every plant more than one centimeter in diameter at breast height within a 50 hectare rainforest plot in Lambir Hills National Park, Sarawak, Malaysia. Surveyors counted 324,592 individual trees and shrubs, and sorted them by species--ranking these in turn according to their abundance The above graph shows relative abundance on a logarithmic scale and arrayed from commonest to rarest. The blue curve shows what the formula predicts when its two effectively "free" parameters are optimized for this census (the parameters reflect hard-to-measure quantities, such as the rate at which new species are born). The dashed line shows the abundance relationship that the formula predicts within the larger region the censused species and others inhabit. The blue bars show the formula's prediction of the likely range within which data should fall in a census of the same number of plants in any other plot in the same region. The demographics within a plot reflect a random sample of the region as a whole, the theory says.

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