Plants of Southern California: Analysis Pages: Our Master List

The following plots give a quick look at how our master list has grown with time.

This plot shows that we continue to add new trails at about the same rate with time, despite also repeating a number of trails to sample their flora at different times (also see below).

This plot shows the that the total number of taxa seen on all trails grows only very slowly with the number of trails, and at a declining rate as the number of trails increases. The first fact is quite surprising to many, and results from the fact that rare plants are common; common plants are rare. I.e., there are only a very small number of taxa that are found on many trails, and most taxa are restricted to a very small number of trails.

The declining rate of growth is a simple consequence of the fact that the number of taxa in Southern California is a fixed number. Eventually, the curve will hit the total number of taxa, and then stop increasing at all.

This is the same plot as the previous one, but now for the lists (digitized floras), and shows the same features.

This shows numerically how common rare plants are: 39% of all taxa in our digitized floras, and 39% of all taxa in our trails, are found in only a single flora or trail, respectively. Thus to see 39% of all the taxa in our trail guides, you would have to hike essentially every single one of our trail guides.

The number was higher initially, due simply to the fact that in the first trail or list, 100% of the plants were found on only one list. It took a while to stabilize on the true value.

The jump in the floras in April 2003 was due to the addition of floras from San Diego County, which had not been well-represented before. As more of those floras were added, the percentage quickly came down to the same percentage as found before the addition of that new area.

The jump in the trail guides in June 2003 was due to the same reason, the addition of trails in the Laguna and Palomar Mountains.

This plot shows that 23 of our 65 trails, 35%, have been visited just once, with 10 trails having 5 or more visits so far. The two most sampled trails are both from the Santa Rosa Plateau: the Granite Loop Trail (15 visits for the plant trail guide) and the Vernal Pool Trail (26 visits).

This plot shows that our trail guides began on 5/31/01, which was for the Big Horn Mine Trail, San Gabriel Mountains, and that we got serious about trail lists in mid-December 2001, just in time for the severe drought of that year. Interestingly, it shows no marked season where we were not able to work on a trail for its plant list. Of course, the heaviest workload is in the Spring and Summer, when there are more species blooming and hence more work needs to be done then to identify the species.

This plot shows that since 12/15/01, we have usually updated a trail guide every 1 to 4 days. The longest interval between updates, 24 days, was 4-28 November 2002. The second-longest interval was when we took a 20 day vacation from trail lists in 3-23 July 2003.

Number of taxa vs. time:

Date# on all trails# only on one trail% only on one trail# in all plant lists (doesn't include our trails)# only on one list%# in all plant lists plus our trailstotal number db entries%

The following plots shows, for each trail separately, a histogram of the number of trails in our database which contained each species found on that trail. Thus, for example, on the Dawson Saddle Trail, 39% of the species found on that trail were found only on that trail out of the 21 trails in our database at the time the histogram was made. Only 2.5% of those species were found on 12 trails (11 trails other than the Dawson Saddle Trail).

This plot should be interpreted with considerable caution, since the number of unique species on a given trail depends strongly on how many nearby trails are in our database. For example, if we did not have two neighboring trails of the Baden-Powell Trail, its percentage of unique species would be much higher. Thus any tentative conclusions drawn from this plot need to be supported with detailed follow-up analysis.

Go to Native and Introduced Plants of Southern California

Copyright © 2002 by Tom Chester and Jane Strong
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
Comments and feedback: Tom Chester | Jane Strong
Last update: 31 August 2003