alpine vegetation of the keyhole plateau, sierra nevada, california
TRANSCRIPT
Alpine vegetation of the Keyhole Plateau, Sierra Nevada, California
Dean W. Taylor, October 2008
This unglaciated surface on the alpine crest of the Sierra Nevada [Fresno and Inyo Counties, California [37.21141/‐
118.67874, Figure 1] is entirely underlain by granitic rocks and is located in the southern SN Jepson Manual bioregion.
Jurisdictionally, the site is in Kings Canyon National Park, and on both the Inyo and Sierra National Forests. The plateau
is about 35 ha in size, and is inclined gently westward. Elevations range between 3930 m to nearly 4000 m.
Alpine vegetation was characterized on 9 July 1997 using releve sampling. Braun‐Blanquet cover classes for all vascular
plants were estimated visually (cover was estimated by cover classes). A total of 41 vascular plants were documented
on the site. The limits of the unglaciated surface visited is show in the Google Earth image (Fig 2. below) outlined.
The overall character of this unglaciated surface is one that was largely barren of vegetation: lying at nearly 4000 meters
(Figure 3), the cover of vascular plant vegetation in 1977 was exceedingly low (perhaps no more than ±5‐10%. Although
the ocular cover estimates I recorded are subject to uncertainty, they with the photograph shown demonstrate a
landscape that is largely barren of vascular plant cover. This assessment should be repeated in the future to ascertain
changes attributed to global warming. Theory would predict that both cover and diversity should increase markedly as a
site such as this is influenced by amelioration of the extreme climate.
One releve was taken in a seepage area just below the rim of the plateau (dominated by Carex vernacula), and this
releve should be disregarded in assessment of future estimates of vegetation change on the dry sites.
Of the 6 dry site releves sampled (see table below), vegetation cover estimates ranged from about 6% to 18% cover, and
this low cover can be seen in the photograph (Fig. 3). Cover averaged over the 6 releves was about 8%.
Only one voucher specimen was obtained on the Keyhole Plateau, Carex incurviformis (JEPS101113). This sedge is
known only from the highest unglaciated landform surfaces in the Sierra Nevada (see below).
Floristically, the vegetation composition of the Keyhole Plateau is similar to that described for many high, dry alpine sites
in the central Sierra (Major and Taylor 1977): the vegetation is most similar to the Eriogonum incanum‐Raillardella
argentea community ( based on data of Pemble 1970).
Of the 38 vascular plants documented on the Keyhole Plateau, 26 of these are in common with the florula of Mono
Mesa (Howell 1947a), an analogous 3700 m elevation unglaciated plateau about 30 km to the north (Howell 1947b): the
two sites have a moderately similar flora (Sorenson Coefficient = 0.45), with the Mono Mesa being a larger florula (76
species) perhaps being a function of the lower elevation of that plateau. The vascular flora of the larger Dana Plateau
near Tioga Pass, Mono County [ca. 250 ha, ca. 3400 m elevation], is on the order of 130 vascular plants, by comparison.
Ungiaciated surfaces in the Sierra Nevada such as the Keyhole Plateau merit further study. There are perhaps 100 or so
such surfaces that are at least 2 ha in size or more (discounting unglaciated peaks and arêtes) scattered from Yosemite
National Park southward to south of Mount Whitney.
Figure 1. Topographic map – Keyhole Plateau (UGSG Mount Darwin quadrangle, 1994 edition)
Figure 2. The Keyhole Plateau as it appears on Google Earth imagery (accessed 2008). The imagery is marked to show
the approximate outline of the unglaciated plateau surface (red line). Note that in this image dense vegetation
associated with seepage occurs only on the westerly flank of the plateau. Sky High lake is in the lower right portion of
the view.
Figure 3. Photograph of the Keyhole Plateau, view to the south with Mount Lamarck in the background. Note the rounded shapes of the
granitic rocks, their orientation parallel to the ground surface, and the gruss soils between the boulders. Vegetation cover, as can be seen in this
view is very low (Calphotos 0000 0000 1008 1414)
RELEVE TABLE – Keyhole Plateau (nomenclature follows either Jepson Manual (1993) except where superseded by
published volumes of FNA as of 2008)
Elev. (meters) 3980 3983 3970 3998 3773 3925 3820
Slope (degrees) 1 1 2 1 40 10 12
Exposure (aspect) 340 290 210 220 80 250 FREQ. Cover 345
Moisture (class) dry dry dry dry dry dry wet
Phlox condensata 2.0 1.0 0.1 0.2 0.50 0.83 0.6
Draba oligosperma var. oligosperma 1.5 0.2 0.1 0.2 0.67 0.3
Erigeron pygmaeus 0.2 0.2 0.33 0.1
Potentilla pseudosericea 0.1 0.17 0.0
Carex incurviformis var. danaensis 0.1 0.5 1.0 3.0 0.67 0.8
Festuca brachyphylla var. breviculmis 0.1 0.1 3.00 0.50 0.5
Calyptridium umbellatum var. caudiciferum 0.1 0.1 0.33 0.0
Selaginella watsonii 0.1 1.0 0.50 0.50 0.3
Eriogonum ovalifolium var. nivale 2.0 0.5 0.50 0.50 0.4
Polemonium exemium 0.2 0.17 0.0
Ivesia lycopodioides var. lycopodides 3.0 5.0 1.0 0.50 1.5
Lewisia sierrae 0.1 0.1 0.2 0.50 0.0
Carex exserta 1.0 0.17 0.2
Luzula spicata 0.5 1.0 0.50 0.50 0.3 0.5
Danthonia unispicata 0.5 0.5 0.50 0.50 0.3 0.5
Antennaria pulchella 1.0 0.1 0.33 0.2
Lewisia pygmaea 0.1 0.17 0.0
Draba lemmonii 0.1 0.17 0.0 3.0
Carex leporinella 0.1 1.0 0.33 0.2
Calamagrostis muiriana 0.5 0.17 0.1
Erigeron vagus 0.1 0.17 0.0
Packera wernearifolius 0.1 0.50 0.33 0.1
Rhodiola rosea ssp. integrifolia 0.1 0.17 0.0
Carex helleri 5.0 0.17 0.8 3.0
Boechera lyallii 0.1 0.17 0.0
Eriogonum incanum 0.1 0.17 0.0
Penstemon davidsonii 0.1 0.17 0.0
Phacelia hastata ssp. comacta 0.1 0.17 0.0
Senecio fremontii var. occidentalis 0.1 0.17 0.0
Carex nigricans 3.00 0.17 0.5 3.00
Carex vernacula 3.00 0.17 0.5 30.0
Antennaria alpina 0.50 0.17 0.1 0.50
Sibbaldia procumbens 0.50 0.17 0.1 2.00
Carex capitata ssp. arctogena 3.00 0.17 0.5
Erigeron algidus 0.50 0.17 0.1
Bochera lemmonii 0.50 0.17 0.1
Juncus mertensianus 0.50 0.17 0.1
Salix petrophylla 0.50 0.17 0.1
ESTIMATED TOTAL COVER 6.40 6.20 9.60 7.80 5.50 18.0 8.92 42.5
Carex incurviformis var. danaensis
The distribution of Carex incurviformis var. danaensis is restricted to highest elevation peaks of the Sierra Nevada and
White Mountains. The Keyhole Plateau site is in the central portion of the known distribution. Given its restriction to
highest peaks in the Sierra, Carex incurviformis var. danaensis can be expected to be particularly vulnerable to climate
change effects.
Figure 4. Map showing known distribution of Carex incurviformis in California.
References:
Howell, J.T. 1947a. Mono Mesa, Sierra sky island. Sierra Club Bulletin 32(5):15‐18
Howell, J. T. 1947b. The florula of Mono Mesa. Wassmann J. Biol. 7:16‐21
Major, J. and D.W. Taylor. 1977. Alpine, Chapter 18 in: Terrestrial Vegetation of California, pp. 603‐675 in: M.G. Barbour
& J. Major [Eds.]. John Wiley, New York.
Pemble, R.H. 1970. Alpine vegetation of the Sierra Nevada as lithosequences and in relation to local site factors. Ph.D.
Dissertation, University of California, Davis.
References