Analysis of the Number of Plants on the Heller's Bend Trail, Fallbrook, North San Diego County

The figure below plots the percentage of native taxa as a function of the mean elevation of each trail. The plants on this trail are represented by the pink solid rectangle in the plots below.

For its elevation, the percentage of native taxa is among the lowest compared to the other trails in my database.

The low percentage of native taxa is probably because this is a small parcel surrounded by agriculture or development on all sides, disturbed by a road which runs through it with a former orchard in the middle.

It is also possible that the low percentage of native taxa is simply due to the incompleteness of the trail list so far, especially the lack of springtime observations to catch annual non-native species. However, the trail at Monserate Mountain has also not been surveyed in spring, and it has among the highest percentage of native plants of all of our trails.

Note that this trail contains a significantly higher percentage of native plants than the Los Jilgueros Preserve, which has very little undisturbed habitat. Aside from the grove and road, the rest of this parcel is relatively undisturbed.

It is interesting to note that the percentage of native taxa, adjusted for elevation, is still significantly higher than two low-elevation portions of the San Gabriel Mountains, the Brown Mountain Fire Road and the Sunset Ridge Trail.

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 my more complete trail guides in 2002.)

The number of native taxa is somewhat lower than many of the other trails with plant guides. It is most likely that this simply reflects the incompleteness of this guide so far.

The following figure shows the number of non-native taxa as a function of unique trail distance.

Again, the number of non-native taxa is fairly high compared to other trails.

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Copyright © 2004 by Tom Chester.
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Comments and feedback: Tom Chester
Updated 27 February 2004.