Analysis of the Number of Plants on the Monserate Mountain 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 surprisingly high compared to the other trails in our database.

I would have expected a higher number of non-native taxa because this is a small parcel surrounded by agriculture or development on all sides, disturbed by a road which runs through the middle of it and the placement of a water tank on top of it. However, aside from the road and water tank, this parcel is undisturbed, which may have prevented many non-native taxa from gaining a foothold here.

It is also possible that the high 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 the Los Jilgueros Preserve has also not been surveyed in spring, and it has the second-lowest percentage of native plants of all of our trails. (Los Jilgueros Preserve was farmed and hence highly disturbed.) So perhaps this high percentage of native taxa is truly a feature of this parcel.

If we ever get enough rain to germinate the annuals here, we should know the answer this spring.

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 lower than many of our other trails. 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.

The number of non-native taxa is remarkably low, but again this might be due to the incompleteness of the guide so far.

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Copyright © 2004 by Tom Chester.
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Comments and feedback: Tom Chester
Updated 1 February 2004.