Flora of San Jacinto Mountain: Voucher Coverage for the San Jacinto Mountain area

This page shows my best current understanding of what areas of the San Jacinto Mountains have been vouchered. Large areas have apparently not yet been surveyed, although the final word on this awaits further digitization of herbarium records.

This work would not have been possible without the work of all the botanists who have vouchered species and deposited them in herbaria, as well the considerable efforts of the major herbaria in California to digitize their collections and georeference the localities on the labels. This digitization is a huge task, which is still ongoing. I and many other botanists are deeply grateful for the immense amount of work done on this task.

I searched the Consortium of California Herbaria for records in Riverside County with the word Jacinto in the Geographic Locality field. This finds most of the vouchers from the San Jacinto Mountains, but also finds vouchers from the San Jacinto River, San Jacinto Valley, and a few other locations such as Jacinto Road.

The results were as follows:

Herbarium# Vouchers# Vouchers
With Coordinates
# Vouchers
With Elevations
# Vouchers With
Elevations Above
6500 feet
All others121097702129

The number of vouchers with coordinates in the above table is slightly fewer than the number reported from the Consortium results page since I have tossed out some records with typos in their positions and those clearly outside of the area of the San Jacinto Mountains. I reported the records with typos to the appropriate herbarium.

The above table is in general not complete for every herbarium. My understanding is that the UC and UCR herbaria have been completely databased, and the RSA/POM is about 50% databased. The UCR collection has been nearly entirely georeferenced for Riverside County, but the southern California portion of the UC and RSA/POM databases have not yet been georeferenced for the bulk of the data. In particular, only one of the 950 Hall vouchers has coordinates.

With the above incompleteness in mind, the following plot shows the coverage of the almost 5,000 georeferenced vouchers for the SnJt area:

The map above gives the major roads in the area, and labels some of the denser concentrations of vouchers away from roads. Hall Canyon is the site of the UC James Reserve, which has a vouchered flora.

Apache Peak, on the Pacific Crest Trail along the Desert Divide, is labeled; the lack of vouchers along the PCT is somewhat surprising.

The flattish high country of the San Jacinto Mountains is shown as a light blue line. That line approximately maps where the gentle slopes of the high country abruptly meet the steep sides of the Mountain. That line corresponds roughly to a contour level of ~8000 feet on all sides except the north slope, where that line is at ~9000 - 10,000 feet. Several locations within that contour are labeled.

Note that many of the vouchers have the same location, and hence plot on top of each other. Thus although there are nearly 5,000 vouchers plotted above, there are far fewer than 5,000 unique locations.

This interesting map shows the following:

I intend to georeference the Hall vouchers, and will digitize some of the major trails, and update this map when I have done so.

Vouchers are much more complete for elevations, and it turns out that they can answer the question about how well the high country has been covered. The following histogram shows the coverage:

The histogram shows two big peaks in the number of vouchers, one at elevations of 1000-2000 feet, and one at elevations of 4000-6000 feet.

The vouchers at 1000-2000 feet comes mostly from two areas: the San Jacinto River on the west side of the range, as well as all on the desert side of the range, in locations easily accessed from the Palm Springs / Coachella Valley area. (I haven't discarded all the San Jacinto River vouchers just to the west of the range yet.)

The vouchers at 4000-6000 feet are nearly all along SR74 and SR243; most of those roads are at those elevations. The highest elevation along SR74 is 4913 feet; the highest elevation along SR243 is ~6220 feet.

Thus the histogram of elevations verifies the conclusion from the georeferenced vouchers - nearly all vouchers are taken alongside roads.

However, note that the coverage of the elevations above the highest road elevation is much better in the RSA and UC vouchers than in the UCR vouchers, and as expected, the biggest collector is Hall. But not by much; Munz is close on his heels!

The following histogram gives the dominant collectors from each Herbarium above an elevation of 6500 feet, along with the total vouchers at each Herbarium above that elevation:

HerbariumVouchers Above 6500 feet
# Vouchers Total# Vouchers
by Dominant Collector
Dominant Collector
All others12935Hoffman (SBBG)

Of the 950 Hall vouchers, 780 (82%) of them have elevations, and 170 do not. Most of the ones without elevations appear to be at elevations lower than 6500 feet, and hence the above numbers might be fairly complete for coverage of the highest elevations.

There are a total of 1,370 vouchers with recorded elevations above 6500 feet, compared to a total of 10,979 vouchers with recorded elevations between 4000 and 6000 feet; a ratio of 12%. How does this compare with the areas for each elevation range?

The area above 6500 feet is roughly an ellipse with major axis of ~9 miles and a minor axis of ~6.5 miles, giving an area of ~45 square km. The area above 4000 feet is roughly a rectangle with sides of 28 and 12 miles, giving an area of ~340 square miles. The ratio of the areas is 13%, almost exactly the same as the voucher ratios for those areas.

Thus surprisingly, thanks primarily to Hall and Munz, the highest elevations in the San Jacinto Mountains have been sampled as well as the areas along roads at lower elevations!

I strongly suspect that this high elevation area is anomalous, since it has been of high interest to many botanists, and other areas away from roads will prove to be poorly sampled even after all the other vouchers are geolocated.

I thank Andy Sanders for correcting an error in the voucher location map for Bautista Canyon Road.

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Copyright © 2006 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Updated 6 November 2006.