Analysis of the Number of Species on the Bayside Trail, Cabrillo National Monument, San Diego

The trail analyzed here is the Bayside Trail, and is represented by the pink solid rectangle in the plots below. Not too much attention should be given to this analysis, since the trail guide is probably still quite incomplete due to a lack of a survey in a normal rainfall year.

For its elevation, the percentage of native taxa is surprisingly high compared to the other trails in our database. This is most likely due to one for more of the following: the relative pristineness of this area, an intensive effort by the U.S. Park Service to eliminate non-native plants or the low, and the almost desert-like rainfall here. However, the incompleteness of this trail guide so far could also be a factor. The subnormal rainfall in the years I've surveyed this trail might not have germinated all the non-native annuals.

The following figure plots the number of native taxa as a function of unique trail distance. High altitude trails, with a mean elevation above 4000 feet, now are marked with a blue cross inside their filled blue diamond. The yellow curve shows the usual power law increase of the number of species with area. (See Number Of Taxa Vs. Trail Length For Trails In Our Master Database; the curve plotted here is the same one fitted to our more complete trail guides in 2002.)

The number of native taxa is well below that expected from our other trails. This is most likely due to my lack of surveying the trail during a normal rainfall year. For comparison, see the similar plots for two Torrey Pines Trails, which both have about the number of native species expected for their trail lengths.

The following figure shows the number of non-native taxa as a function of unique trail distance. The number of non-native taxa is remarkably low. Many of the points with fewer non-native taxa are from higher altitude trails (see the first plot above).

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Copyright © 2004 by Tom Chester.
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Updated 12 February 2004.