Ice-Age Vegetation of Kings Canyon, Sierra Nevada
Principal Investigator:
Kenneth L. Cole, USGS FRESC Colorado Plateau Research Station
Abstract:
A series of packrat middens were collected between 1000 and 1300 m elevation on a marble roof pendant in the Kings River Gorge just west of Kings Canyon National Park. Plant macrofossils from these middens include the first Late Wisconsin macrofossil records of giant sequoia (Sequoiadendron giganteum), and the California ponderosa pine/Jeffrey pine complex (Pinus ponderosa/jeffreyi) (picture of macrofossils). Other important macrofossil records include: western juniper (Juniperus occidentalis), incense-cedar (Calocedrus decurrens), red fir (Abies magnifica), and California torreya (Torreya California). The Pleistocene vegetation recorded between 45,000 and 12,500 year B.P. is a mixture of Sierran montane species typical of elevations about 1000 m above the site today, such as giant sequoia, ponderosa pine, and red fir, and more xerophytic species such as western juniper, single needle pinyon (Pinus monophylla), and mountain mahogany (Cercocarpus intricatus) which are found today on xeric substrates like this marble and on the eastern side of the range.
By 8400 year B.P. the Pleistocene plant communities had been replaced by an oak woodland. The macrofossils from this midden are surprising as they suggest a plant assemblage quite unlike any others yet found. Oak acorns represent a minimum age on the Holocene arrival of this now dominant species. However, the midden also contains macrofossils of western juniper (Juniperus occidentalis) and incense-cedar (Calocedrus decurrens) both of which now occupy much higher slopes. These species may have persisted at lower elevations in the western Sierra throughout the early Holocene
Needles of single needle pinyon, which grows on the marble outcrop today, are present throughout the sequence, beginning at >45,000 yr B.P. An l9,250 yr B.P. AMS radiocarbon date on one pinyon needle is in agreement with other dates from that midden. The disjunct stand of this Great Basin dominant was previously thought to have spread to this locality during the warm climate of the middle Holocene around 6000 years ago. Instead, it is actually an example of an edaphically assisted disjunct population that has persisted on its favored substrate despite radical shifts in climate over at least the last 45,000 years.
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Ice age packrat middens were preserved in inaccessible caves within marble outcrops in the Kings River Canyon. (Click for larger image) |
Publications:
Cole, K. L. 1983. Late Pleistocene vegetation of Kings Canyon, California. Quaternary Research 19:117-129.
Ken
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