Origins and Ecology of the Sierran Alpine Flora and Vegetation

• Published in: Ecological Monographs
• Main Authors: Chabot, Brian F., Billings, W. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1972
• Subjects: Ecology, Evolution, Behavior and Systematics; Arctic
• Online Access: http://dx.doi.org/10.2307/1942262; http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1942262; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1942262; https://onlinelibrary.wiley.com/doi/pdf/10.2307/1942262; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1942262

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 ...