Plant Species of San Jacinto Mountain: Overview of Geographic Distribution Maps for Species of Tamarack, Round and Long Valleys and Higher Elevations


Introduction
Species Diversity
Examples of Variation in the Geographic Distribution of Individual Species
Groups of Species with Somewhat-Similar Distributions


Introduction

For an introduction to this area, see the Flora of Tamarack, Round and Long Valleys and the Flora of San Jacinto Peak Area.

The latest combined flora of those areas is here; see also a sort of the flora in descending order of maximum elevation, and a sort in descending order of the number of GPS points recorded for each species.

As of 30 July 2017, we have finally digitized all of our 2,856 species GPS points from 40 full-day surveys in Round, Tamarack and Long Valleys, and above 10,000 feet in the San Jacinto / Jean Peak area, in 2007, 2008, 2010, 2012, 2013 and 2017. This page presents an overview of geographic distribution maps and histograms of elevations using those points.

A species GPS point is a single GPS point associated with a single plant species. There may be several plant species recorded at a single GPS point. If ten species were recorded at that single GPS point, that would produce ten species GPS points.

Our general procedure in surveys was to record the location of just the first plant of each species. Since our surveys were typically broken into sections of one to four miles in length, each species would only have one location in that distance. In order to create denser maps for common species, in many places we also did spot surveys spaced every 0.1 to 0.5 mile in which we recorded all the species found within about 100 feet of each spot.

Fig. 1 shows two maps of all the species GPS points, one showing the individual points (with many on top of each other), and another showing the number of points grouped into "clusters" as determined by the clustering algorithm of the Berkeley Mapper to show the number of species GPS points in a given area.

Fig. 1. Geographic distribution maps for all species GPS points. Top: map showing the individual GPS points (many are plotted on top of other points). Bottom: map giving the count of the number of individual species GPS points grouped into clusters. A cluster of 8 points could result from 8 species being recorded at a single GPS point, or 8 species each recorded at different, but very nearby, GPS points.

The top map in Fig. 1 shows clearly the main trails in this area as dense lines of points, since those trails provide the easiest, and sometimes only feasible way, to survey this area. For example, the trail from Wellman Divide to Miller Peak traverses a steep slope, much of which is covered by nearly-impenetrable chinquapin mats. There are essentially no off-trail survey points there. In contrast, we surveyed a number of off-trail areas in other places, such as along ridgelines, drainages, and the flatter areas. Sometimes we could take advantage of any use trail or deer trail we could find, but mostly the exploration was cross-country.

Still, it is quite obvious there are large areas that we weren't able to cover in our six years of surveys here, and there almost surely are species found in those areas not present in our flora. What might be found in those areas is an exercise left to the reader. (:-)

Fig. 2 breaks down the GPS points by elevation.

Fig. 2. Geographic distribution maps for all species GPS points separated by elevation in feet.

Fig. 3 shows a histogram of the elevations for the species GPS points.

Fig. 3. Histogram of the elevations for all species GPS points.

The overall shape of the histogram, with more points at lower elevations and few points at higher elevations, reflects both the larger area at lower elevations and the higher species diversity there. The dip at the very lowermost elevations, at 8200 to 8300 feet, is because in the area here only a small portion of lowermost Long Valley Creek has those elevations.

The dip from 8700 to 8900 feet is mainly due to those elevations having steep slopes separating Long Valley from Round and Tamarack Valleys. Those steep slopes present less area to survey, and since they are difficult to survey, little of those slopes was surveyed.

The peak at 9000 to 9100 feet is due to a large number of species GPS points from Round Valley Meadow.

The steep drop in the number of species GPS points above 9300 feet is created by the same factors creating the dip from 8700 to 8900 feet, as well as the low diversity of species at higher elevations.

The rest of this page gives an overview of the botanical structure of the geographic distribution maps of individual species. We first group the species into those with similar distributions to show how dramatically different those groups are in geography, and then show examples of how individual species can vary in their geographic distribution.

Species Diversity

The spot surveys in which we recorded all the species found within about 100 feet of each spot can be used to map the species diversity in those areas that contain spot surveys.

A total of 122 spot surveys were done on six days from 20 July to 23 August 2017. The most frequent number of species in those surveys was six, which reflects the low diversity of the pine forest in most of the area of Tamarack, Round and Long Valleys that contain steep slopes. Higher species counts were found along ridgelines, flattish areas, and riparian areas. Spot surveys in areas along Long Valley Creek had 14 to 28 species.

A simplified map of the species diversity is shown in Fig. 4. See also a more detailed graphic of the species diversity.

Fig. 4. Map of the species diversity from our 122 spot surveys. The vast majority of the point surveys contain 3 to 9 species. Areas circled in green contain 10 to 20 species, and include ridgelines, flattish areas such as Tamarack Valley, and moist areas outside of creeks. Long Valley Creek, circled in red, had spot surveys with 14 to 28 species. No spot surveys were done in Round Valley Meadow, Tamarack Meadow, lower Tamarack Creek and Round Valley Creek. If those areas had been spot surveyed, they undoubtedly would have been circled in red.

A histogram of the # of species found in the spot surveys is given in Fig. 5.

Fig. 5. Histogram of the species counts for all the spot surveys. The dry slopes of the pine forest are quite depauperate, with just 3 to 9 species found in the spot surveys. Ridgelines are more diverse, with members of the cliff formation (see below) and different aspects, having typically 10 to 13 species in the spot surveys. Flattish areas, such as Tamarack Valley, hold more moisture and have typically 10 to 20 species in the spot surveys. Riparian areas with abundant water, such as Long Valley Creek, have a number of locations with 23 to 28 species in the spot surveys.

Groups of Species with Somewhat-Similar Distributions

There are three main groups of species in this area that each have a somewhat-similar geographic distribution:

Of course, we have the usual number of species that are found only in a single location, or a small number of locations, that can't be placed in any group having a similar geographic distribution.

Species that are widespread throughout the area growing in dry areas. This area is part of the pine belt of San Jacinto Mountain, so trees are a perfect example of the widespread species growing in dry areas. Fig. 6 shows the geographic distribution of all the species GPS points for trees.

Fig. 6. Geographic distribution map for all species GPS points for trees.

The points are much less dense in Fig. 6 than in Fig. 1, since Fig. 1 includes points from the many other species whose first occurrence was not at the beginning of each survey. This map would have much-sparser points if it were not for the spot surveys, which can be seen clearly in this map from the regularly-spaced points along many survey routes.

Since this map shows the spot surveys well, as well as the first point of the other surveys, this is the best map to use for comparison to maps of other species to see where those species were not found. For example, comparing the maps in Fig. 11 to the map in Fig. 6 clearly reveals that those species shown in Fig. 11 are not present in many places of the higher elevations on the west side of Round and Tamarack Valleys since they were not found in the spot surveys there.

Species that are mostly confined to rock cliffs. Hall, in his 1902 Flora of the Pine Belt of San Jacinto Mountain, defined the crest formation as

that assemblage of plants, other than trees, found growing on the peaks and ridges above 7000 feet altitude.... The shrubby vegetation is most abundant among the rocks, often springing from fissures in their sides... Cercocarpus ledifolius...Holodiscus discolor var. microphyllus (Holodiscus discolor dumosa)...Philadelphus microphyllus (Philadelphus serpyllifolius)...Ericameria cuneata.

Fig. 7 shows the geographic distribution of all the species GPS points for species of the crest formation.

Fig. 7. Geographic distribution map for all species GPS points for species of the crest formation.

The distribution of species GPS points in fig. 7 is quite different from those in Fig. 6. Most of the points in the interior of the valleys have disappeared, leaving the points highly concentrated to the ridgelines. The points remaining in the interior of the valleys are in rock outcrops scattered throughout the interior, with many of the latter points in the steeper areas where rocks are more likely to be exposed by erosion.

Species that grow only in moist or wet areas. The geographic distribution of all the species GPS points for these species are shown in Fig. 8. These have the most-dramatically-different distribution since they are confined to the meadows and wet drainages, and show very clearly where those moist areas are. The points in Fig. 8 are mostly the opposite of the points in Fig. 7, present in the low areas instead of the ridgetops.

One exception where there are points in both maps is the lowermost section of Long Valley Creek which has steep rock walls where the Creek begins to descend precipitously, and the moist-area species grow in close proximity to the crest-formation species.

Fig. 8. Geographic distribution map for all species GPS points for species that grow only in moist or wet areas. Round Valley Meadow is the dense collection of points in a round area just below the middle of the map, with Tamarack Meadow the linear collection of almost-north-south points just north of Round Valley Meadow.

Examples of Variation in the Geographic Distribution of Individual Species

Pinus contorta and P. flexilis. The geographic distribution of these two species is shown in Fig. 9, and a histogram of the elevations for them is shown in Fig. 10.

Pinus contorta
Pinus flexilis
Fig. 9. Geographic distribution maps for Pinus contorta (top) and P. flexilis (bottom).

Fig. 10. Histogram of the elevations for Pinus contorta and P. flexilis

These two pine tree species are the highest-elevation species at San Jacinto Mountain, are very often found together, and span the same elevation range in this area. Ridgetops and peaks often have just P. flexilis at their very tops, but usually P. contorta is lurking just 20 feet or so in elevation below the tops. The main difference in their distribution is that P. contorta is the more abundant of the two species at elevations of 8200 to 9000 feet.

Abies concolor, Pinus jeffreyi and P. lambertiana. The geographic distribution of these two species is shown in Fig. 11, and a histogram of the elevations for them is shown in Fig. 12.

Abies concolor
Pinus jeffreyi
Pinus lambertiana
Fig. 11. Geographic distribution maps for Abies concolor (top), Pinus jeffreyi (middle), and P. lambertiana (bottom).

Fig. 12. Histogram of the elevations for Abies concolor, Pinus jeffreyi and P. lambertiana

Note the very different distribution of these three species from that of P. contorta and P. flexilis shown previously. Abies concolor, Pinus jeffreyi and P. lambertiana essentially drop out above 9300 feet elevation, and are absent above 10,000 feet elevation. They are most abundant at the lowest elevations here.

Although Pinus jeffreyi and P. lambertiana have a similar elevation distribution, P. lambertiana is almost entirely confined to Long Valley, whereas P. jeffreyi is fairly widespread in Round and Tamarack Valleys as well as Long Valley.

Abies concolor is more abundant at elevations of 8800 to 9400 feet than the other two, and there are a number of places here where the forest consists almost entirely of it.

Cercocarpus ledifolius, Quercus chrysolepis and Salix scouleriana. The geographic distribution of these two species is shown in Fig. 13.

Cercocarpus ledifolius
Quercus chrysolepis
Salix scouleriana
Fig. 13. Geographic distribution maps for Cercocarpus ledifolius (top), Quercus chrysolepis (middle), and Salix scouleriana (bottom).

Cercocarpus ledifolius, Quercus chrysolepis and Salix scouleriana are each strikingly different in their geographic distribution. Cercocarpus ledifolius is a member of Hall's crest formation, preferring to live on ridgetops and peaks. Salix scouleriana is a wet-area species, living in the drainages.

Quercus chrysolepis occupies a very different habitat here than it does on the west mountain slopes of San Jacinto Mountain. Its common name is canyon live oak, since it loves to live in canyons on the west side, as well as on the slopes themselves. Here it appears mostly as a member of the crest formation! You have to wonder whether this really is the same species as the plants on the west mountain slopes.


We thank the following people for their assistance: Eric Baecht (11 trips), Bruce Watts (4 trips), Wayne Armstrong (3 trips), Bill Bulger (2 trips), Michael Charters (2 trips), Brendan Crill (2 trips), Bob Hepburn (2 trips), Anne Kelly (2 trips), Joseph Migliori (2 trips), Tarja Sagar (2 trips), Krista Adamek (1 trip), Adrienne Ballwey (1 trip), Beth Cobb (1 trip), Mike Crouse (1 trip), Aaron Fellows (1 trip), Walt Fidler (1 trip), Cliff McLean (1 trip), Gabi McLean (1 trip), Keir Morse (1 trip), Pam Pallette (1 trip), Jim Roberts (1 trip), and Pat Sutter (1 trip).


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Copyright © 2017 by Tom Chester (41 trips), Dave Stith (26 trips), James Dillane (10 trips), and Nancy Accola (6 trips).
Commercial rights reserved. Permission is granted to reproduce any or all of this page for individual or non-profit institutional internal use as long as credit is given to us at this source:
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Comments and feedback: Tom Chester
Updated 19 September 2017.