Plant Species of San Jacinto Mountain:
Distribution of Jeffrey pine, Pinus jeffreyi and ponderosa pine, P. ponderosa
Distribution of Jeffrey pine, Pinus jeffreyi and ponderosa pine, P. ponderosa
This page discusses the distribution at San Jacinto Mountain for these species. See also a discussion of how to identify them, and a map of their distribution on the Ernie Maxwell and Devils Slide Trails.
So far, I have only found ponderosa pine near the town of Idyllwild on the west side of San Jacinto Mountain. The distribution I have found is consistent with the much-lower resolution map shown in Minnich and Everett, Conifer Tree Distributions in Southern California, published in Madroño 48: 177-197, 2001.
In fact, surprisingly, despite the small areal coverage of my surveys, the Minnich and Everett map seems to contain only one additional area containing ponderosa pine, in the vicinity of Pine Cove. (I can't place their locations precisely on my map since the entire area shown in my map is only 2-3 mm long in their printed map, which shows all of southern California.) Of course, there are more ponderosa pines surrounding each of the areas shown in my map; my map is incomplete in the extent of ponderosa pine distribution in each of the plotted areas.
That my map nearly shows all the major areas containing ponderosa pine is almost too hard to believe, due to my low sampling of the area. However, since the Minnich and Everett map was made from aerial photography of the entire area, their map should show the complete distribution of these pines.
The following maps shown every location where I have found ponderosa pine, with an identically-sized map giving locations for Jeffrey pine:
| Jeffrey pine | ponderosa pine |
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The green line is the approximate boundary of the pine belt as shown in Hall 1902. Many roads and most trails are shown with black lines, as are a few of the major creeks. The black outline area just above the lower right corner is a chaparral belt inside the pine forest noted by Hall. The red line at the upper left corner outlines Hall Canyon.
Most areas without a location for either species have not been mapped, although some of them in fact do not contain either species. Locations are GPS points along the Ernie Maxwell, Devils Slide, South Ridge and Deer Springs Trails, and along SR243 at Mountain Center. Locations on other trails were derived from observations, without specific locations, made for the plant guides for those trails. These points are generally simply regularly spaced along those trails in locations where each of those species was found.
The following plots show the locations of the two species on the same map, but without the topo map, on the left; a plot of elevation versus longitude is on the right:
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For GPS points, the elevations are from GPS measurements in the field and could be off by up to 100 feet. The elevations of points placed from field observations without GPS points were derived automatically from National Geographic Topo Software, and could also be off by up to 100 feet.
The distribution of these two species is not a simple pattern in geographic area nor in elevation, except that only Jeffreys are found above ~6800 feet. The two species are mixed at lower elevations. Only Jeffreys have been found on ridges so far. Ponderosas seem to be found in flatter areas and on east-facing slopes.
The large-scale distribution of Jeffrey pines is shown in the following map:
Jeffreys are found continuously from Mountain Center down to Garner Valley, throughout Garner Valley along SR74, to the eastern limit of my survey just east of SR371. All points along SR74 are GPS points from a survey where I stopped every 1-4 miles to verify the species. It is likely Jeffreys are found continuously between each of those GPS points, with the exception that no pines appear along SR74 in the vicinity of Lake Hemet.
These observations seem to imply that the Jeffrey pines in Garner Valley do not appear preferentially in Garner Valley for any reason other than there is enough water to support their growth. I.e., they do not just appear in the coldest parts of Garner Valley, so low temperatures do not appear to be the major factor in their distribution.