Origins and Ecology of the Sierran Alpine Flora and Vegetation

Abstract

The alpine flora of the Sierra Nevada has developed relatively recently and largely in situ from western American sources. The Sierra thus provides a good site for an attempt to answer the question: "How does an alpine flora originate?" The primary study area was a transect from the desert near Bishop, California (1,400 m), to Piute Pass in the Sierra Nevada (3,540 m). Upward along the transect the vegetational gradient is Ephedra nevadensis—Tetradymia spinosa desert shrub, Pinus monophylla—Artemisia tridentata open woodland, Pinus jeffreyi open forest, Pinus murrayana forest, Pinus albicaulis—subalpine herbaceous vegetation, and scattered alpine communities. Only 19% of the alpine species at Piute Pass occur in the Arctic, whereas 38% are held in common with the Rocky Mountains. Species endemic to the Sierra (17%) are in genera predominantly from the Californian or Great Basin floras of lower elevations. A number of species have populations in the desert and also at high elevations near the alpine zone. Most of the alpine flora consists of perennials, but several annual species are also present. Annuals are rare in other arctic and alpine floras. Environmental monitoring stations were maintained at several locations along the transect during two summers. Air temperature at 5 cm above the ground decreased with increasing elevation at a rate of 0.74°C/100 m. Summer precipitation increased nonlinearly with elevation at a rate of 0.16—0.82 cm/100 m. Long—term annual average precipitation for Bishop is 14.6 cm; the annual precipitation for Piute Pass estimated from this study is greater than 78 cm with a strong winter maximum in the form of snow. Soil moisture during the summer is low for all sites. Strong vegetation patterning occurs in both alpine and desert areas along drainageways from snowbanks or perennial streams. Solar, sky, and net radiation at 1 m above the soil are greater for alpine than for desert areas. Air and plant—tissue temperatures near the surface of the alpine soil are higher than those in most other alpine areas. Laboratory experiments showed several physiological responses to be characteristic of Sierran alpine populations. These may be important in plant evolution and migration into an alpine habitat. (1) Germination of seeds from alpine plants occurred maximally between 20° and 30°C. Constitutive dormancy is a minor factor; the low winter temperatures of the alpine zone appear to operate as an exogenous dormancy control. Desert and low—elevation species of this area are predominantly winter—germinators and have maximum germination at low temperatures. (2) Mature alpine plants have strong dormancy control by short photoperiod; dormancy in lower elevation populations may be induced by either short or long photoperiods. (3) Temperatures of the upper photosynthetic compensation point and maximum net photosynthesis are lower in plants of alpine species. (4) Low temperature regimes cause plants to shift dark respiration higher rates when compared with plants of the same species from high temperature...

The hot and the cold: unravelling the variable response of plant respiration to temperature

“…1, where exposure of a warm-grown plant to the cold for several days results in an increase in the rate of R at a common measurement temperature (Rook 1969;Chabot and Billings 1972;Pisek et al 1973;Larigauderie and Körner 1995;Körner 1999;Atkin et al 2000b;Covey-Crump et al 2002;Zha et al 2002Zha et al , 2005Bolstad et al 2003). Conversely, exposure to high temperatures results in a decrease in the rate of R at a common temperature (Fig.…”

“…Differences in the rate of R at standard measurement temperatures are also commonly exhibited by plants that grew and developed under contrasting temperature regimes (either in the laboratory or in the field) (e.g. Figs 1, 3; Billings and Mooney 1968;Chabot and Billings 1972;Körner and Larcher 1988;Collier and Cummins 1990;Semikhatova et al 1992;Collier 1996;Goldstein et al 1996;Arnone and Körner 1997;Zha et al 2002). In some cases, acclimation is associated with a change in the rate of R primarily at moderate to high measuring temperatures, with little or no change in R at low measuring temperatures (i.e.…”

“…4). Type I acclimation R can occur within a 1-2-d period following a change in ambient temperature (Rook 1969;Billings et al 1971;Chabot and Billings 1972;Atkin et al 2000b;Covey-Crump et al 2002;Bolstad et al 2003), raising the possibility that plant R may dynamically acclimate to changes in thermal environment with an onset of the acclimation processes within perhaps hours. Changes in gene expression may also occur, but are not essential for the overall change in respiratory flux (Fig.…”

Patterns of Morphological, Biochemical, and Molecular Evolution in the Oeneis chryxus Complex (Lepidoptera: Satyridae): A Test of Historical Biogeographical Hypotheses

“…Sierran alpine organisms may have dispersed from the east, across the Great Basin, or from the Cascade Range located north of the Sierra Nevada. Alternatively, Sierran alpine organisms may have evolved in situ from low-elevation forms (Billings, 1978;Chabot and Billings, 1971;Major and Bamberg, 1967;Major and Taylor, 1990;Stebbins, 1982;Taylor, 1977 Specimens were captured and maintained alive until frozen in either a Ϫ80°C freezer or in a liquid nitrogen thermos in the field. Those frozen in liquid nitrogen were later transferred to a Ϫ80°C freezer.…”

Growth and Population Dynamics of Espeletia (Compositae) in the Venezuelan Andes

“…Each station had a white, double-roofed, louvered, instrument shelter (Chabot and Billings, 1972) placed at ground level. Each shelter contained a Taylor maximum-minimum thermometer.…”