Flora of Mountain Springs Grade area, Imperial / San Diego County
Fig. 1. Google Earth View of the upper part of the Mountain Springs Grade area. The bottom of the Grade is on the desert floor near Ocotillo, CA. Click on the picture for a larger version showing more area.
Introduction
Voucher Summary
Checklist Summary
Checklist
Introduction
Mountain Springs Grade is a visually-stunning area where the mountains in the southeast corner of San Diego County abruptly descend to the desert floor in Imperial County. The descent is so steep that the two traffic directions of Interstate 8 are routed down two separate canyons as the freeway descends 4000 feet in 11 miles. Probably because of the steep slopes, with low rainfall that often comes in large quantities from thunderstorms, the area features what has been called a magnificent arrangement of huge boulders. The boulders appear quite naked, with little plant life evident. See photographs at the following links: US 80 Photo Gallery; Mountain Springs History; and Off-Road Trip to Mountain Spring.
But plant life there is, and it is fascinating!
There are a number of plant species found here that are not found in the rest of Anza Borrego Desert State Park, or San Diego County, some of which are the northernmost locations of species found in Baja California such as Deinandra floribunda, Hulsea mexicana, Ipomopsis tenuifolia and Linanthus bellus.
There are also a number of interesting plant species that are supposedly vouchered from here, but which apparently are actually not found here, since no one else has ever seen them here, and they appear to be very out of range from the rest of their distribution. Examples are Cryptantha similis, Cynoglossum grande, Lepidium fremontii, Salvia dorrii var. pilosa, Scutellaria mexicana, Syntrichopappus fremontii, and Xylorhiza tortifolia. At least one other interesting species is mentioned as being in this area in Beauchamp's 1986 Flora of San Diego County, such as Herissantia crispa, but there are no vouchers of this species from here.
I had always wanted to work in the field on a flora of this area to try to figure out what species are actually here, and what species are not. However, as I was compiling vouchers for this area, it soon became apparent that nearly all of the curious plant species are from a single collector, Charles Russell Orcutt, from what appears to be a single collection event in April 1917. See below for more information about the Orcutt vouchers.
Field observations have been made by three groups of people:
- Jon Rebman led a CNPS field trip to Mountain Springs some years ago, and posted a checklist from that trip with 58 species.
- Mike Crouse made a one hour stop at the exit of I-8 on 13 February 2013, and compiled a list of 56 species which he kindly sent me.
- On 11/17/14, a bad time of year in a very dry year, Tom Chester, Keir Morse, Mike Crouse, Adrienne Ballwey, Jim Roberts, Jeff Field, and Bill Sullivan surveyed a 3.5 mile loop south of the section of Old Highway 80 at the Mountain Spring exit of I-8. This survey found 82 species that could be confidently identified, and another 8 species with identifications that could only be surmised based on the voucher list. Their observed minimum # of plants is now given in the checklist, with the uncertain identifications marked.
- On 3/20/15, when the area was in peak bloom, Tom Chester, Mike Crouse, and Karyn Sauber surveyed 2.4 miles circling peak 2513 that is 1.7 mile east of the Mountain Springs exit of I-8, and 1.3 miles west of Myer Valley. The route went through two culverts of the freeway for Myer Creek, up Boulder Creek to a minor drainage from the east, and then northwest along a flattish sandy valley that is just west of Myer Valley.
- Karyn Sauber made three separate additional trips on 3/13, 3/17 and 3/22/15.
The surveys in March 2015 found a total of 156 taxa.
Voucher Summary
Vouchers were searched on 13 and 14 November 2014 at Consortium of California Herbaria. A geographic coordinate search, for vouchers with coordinates, was made for the region of 32.65 to 32.70° north latitude and -116.13 to -116.06° east longitude. The search was augmented by a separate locality search for "Mountain Spring" for vouchers without coordinates from San Diego or Imperial County. I later found 12 additional vouchers from this area that had coordinates but had been georeferenced just outside this area.
The localities of all vouchers were reviewed, and ones with localities that were clearly outside this area were tossed.
After compiling the list of species from vouchers, I sorted that list by the number of observations in my database, and began to examine the species that I had either never seen, or had just a few records of in my database. For each of those species, I checked the geographic distribution given in the Jepson Manual second edition, and that given by maps of voucher locations. When I found species that seemed unlikely to actually be here, I checked the voucher record that placed them here.
In this analysis, it soon became apparent that nearly all of the curious plant species are from a single collector, Charles Russell Orcutt, from what appears to be a single collection event in April 1917. I then examined the total geographic range in vouchers for every species from his set of ~62 vouchers, and quickly realized that most of the Orcutt vouchers were not actually from the Mountain Springs area.
The problem is that in April 1917 Orcutt clearly collected vouchers from a very large area, probably from the Mojave Desert to Mountain Springs Grade to the coast of San Diego County, and called the entire collection his Mountain Springs Collection. Most of those vouchers have no further locality information, perhaps because Orcutt was primarily interested in collecting living and fossil animal shells at that time, and/or perhaps because Orcutt was said to be a librarian's nightmare, somewhat careless in his work, and careless in his collecting methods.
It flouts common sense that vouchers from the Mountain Springs Collection would not actually be from the Mountain Springs area, but that appears to be the case.
For example, the voucher label for this specimen has the typed information of Mountain Springs Grade; Orcutt Collection, but a hand-written locality of near Sweetwater River, Jacumba. The Sweetwater River is 33 miles west of Mountain Spring, and Jacumba is six miles southwest of Mountain Spring as well as six miles west of the head of Mountain Spring Grade as measured along the current route of I-8.
And this is one of his better localities! Off all 721 vouchers collected by Orcutt that are in the Consortium of California Herbaria, 65% do not even have a collection number assigned; 20% have a locality of just San Diego; 15% have a locality of just Colorado Desert or sw Colorado Desert; 10% do not even have a COUNTY assigned; and 10% have no locality information at all.
His specimen numbering appears to have started anew with his April 1917 Mountain Springs Grade collection trip, with those online vouchers numbered from 155 to 307, after his collection number had reached 2555 in 1890. There are few online collections from him between 1890 and 1917.
Of the vouchers collected in 1917 in the Mountain Springs Grade collection, at least 15 of the species are coastal or montane San Diego County species whose eastern limit is reached at a significant distance to the west of the actual location of Mountain Springs Grade. Two of those species, Pseudognaphalium ramosissimum and Ceanothus verrucosus, are found only very near the coast of San Diego County, 40 to 50 miles west of Mountain Springs Grade. An additional 11 of the species from this set have Mountain Spring significantly out of their actual range. One of those species, Cryptantha similis, is endemic to an area on the north side of the San Gabriel and San Bernardino Mountains. Another species, Cynoglossum grande, is not even found in southern California. His voucher has a note in it Found in this group possibly out of range, indicating that he possibly had accidentally included a voucher from another trip with this collection.
Since the Orcutt locality of Mountain Springs Grade is clearly meaningless, I went through all of his vouchers and tossed 37 species that had no other indication that they could actually be found here. I kept 48 species that had other vouchers within about ten miles, since they possibly might be found here. Of those 48 species, 25 have other vouchers from this area and thus probably are actually found here. The other 23 species are the only ones possibly documenting those species here. Since there is obviously a big uncertainty as to whether those 23 species are actually found here, I put a ? in the voucher column below for those species. I'll eventually toss all such vouchers if they aren't confirmed by future field work or vouchers. Since many other people have collected from this area on many other occasions, it is possible that none of these 23 questionable species are actually found here.
In summary, of 85 species in Orcutt's Mountain Springs Grade collection, 37 of them (44%) almost surely were not actually collected here, 25 of them (29%) might have been collected here, and 23 of them (27%) likely have a low probability that they were collected here.
The above process yielded a total of 1535 accepted vouchers. A large number of different collectors, including many famous names, were responsible for this wonderful list. Table 1 lists the dominant collectors, where I have combined all collector groups containing the dominant collector under that collector's name. (For example, Jon Rebman has vouchers with 24 different combinations of collector names; all combinations were subsumed under Jon P. Rebman et al.)
Thanks to a communication with Duncan Bell Potentilla rimicola was subsequently removed from the voucher flora. Thanks to Aaron Schusteff, Rebecca Peters, and Barbara Ertter, it turned out that this voucher, DS39086, was actually Potentilla rivalis, and the apparent misdetermination was a databasing error. It isn't clear where exactly the locality was for this voucher since it just says Mountain Springs, so it may or may not be in the area considered here. I'll add it to the next iteration of the flora, since it might be found in this area.
Table 1. Dominant Collectors for the Mountain Springs Grade Area
| #V | Collector |
|---|---|
| 126 | Jon P. Rebman et al |
| 94 | Joni Ward et al |
| 72 | Duncan S. Bell et al |
| 70 | Edgar A. Mearns |
| 59 | Roxana S. Ferris |
| 56 | A. C. Sanders et al |
| 56 | Mary F. Spencer |
| 48 | Frank F. Gander |
| 48 | F. W. Peirson |
These collectors were responsible for 629 of the 1535 accepted vouchers, 41% of the total. Other notable collectors include Alice Eastwood, Lyman Benson, W. L. Jepson, Marcus E. Jones, S. B. Parish and C.B. Wolf. This area has obviously been a favorite stop for botanists!
Checklist Summary
The voucher list resulted in a list of 340 species from vouchers other than from Orcutt, plus an additional 23 species with only an Orcutt voucher that may or may not document them being here. The total voucher list contains 363 taxa.
It is possible that some of the 340 species in the following checklist from collectors other than Orcutt are not actually in the Mountain Springs Grade area, since Orcutt was not alone in having somewhat vague localities, especially among the earlier collectors.
The checklist below contains 185 observed species, from the union of the Rebman list, the Crouse list, and the field surveys.
The total checklist contains 388 taxa.
The checklist does not contain Herissantia crispa, which was reported as being in this area in Beauchamp's 1986 Flora of San Diego County. If anyone has any information as to the source of this report in Beauchamp, please let me know.
Checklist
The column #V gives the number of vouchers for this area, with a maximum value of 9. If a species was only vouchered by Orcutt, the column contains ? unless it was also in Rebman's or Crouse's checklists. Note that these species marked with a ? may not actually be present here!
The column #Pls gives the minimum number of plants, up to a maximum of 99 plants, for each species observed in the surveys of the two different areas. The area surveyed one mile east of the Mountain Springs Exit on I-8 is in the column with header East. The area surveyed near the Mountain Springs Exit on 11/17/14 is in the column with header MS. An O in the column for Mountain Springs indicate a species not observed in the survey, but which was was in Rebman's Checklist for Mountain Springs, or was observed by Mike Crouse on 2/13/13.
One species, ironwood, Olneya tesota, has a pl? in this column to indicate it may have been planted. It is near the old cabin in an alcove just south of I-8.
Some species in each surveyed area need further work to be certain of their determination; these species are marked with the usual qualifiers in the #Pls columns.
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