Analysis of the Number of Species on Two Torrey Pines Trails, San Diego County

The two trails analyzed here are the Guy Fleming Trail, represented by the pink solid rectangle in the plots below, and the Beach Trail / Broken Hill Trail Loop, represented by the yellow solid triangle, both at Torrey Pines State Reserve.

For their elevation, the percentage of native taxa on both trails is very high compared to the other trails in our database. This is most likely due to either the relative pristineness of this area or the low, 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, adjusted for trail length, is similar for both trails, and consistent with that of many of our other trails.

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 8 February 2004.