Late Quaternary Changes in Pinyon and Juniper Distributions in the White Mountain Region of California and Nevada

Abstract

Data from packrat middens are used to reconstruct the migration of singleleaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma) in the White Mountain region of California and Nevada for the last 20,000 years. Today this region is characterized by arid conditions with dry summers. Pinyon woodlands, which are favored by dry summer conditions, are dominant at middle elevations of the White Mountains. The midden record indicates that during the late Pleistocene and early Holocene, juniper was dominant at elevations now occupied by desert shrubs. A late Pleistocene-early Holocene record of desert shrubs was found only in the double rainshadow of the Sierra Nevada and the White Mountains. Pinyon entered the area during the Holocene (ca. 9000 yr B.P.) and subsequently became more important than juniper. During the late Holocene, desert shrubs became established at the lower elevation sites that they now occupy. The late Pleistocene-early Holocene record indicates that there may have been a more zonal upper-level wind flow and associated penetration of Pacific moisture, as indicated by the occurrence of desert shrubs downwind of the north-south-trending mountain ranges. Zonal flow probably became less important during the early Holocene based on the increasing amount of pinyon. The increase in pinyon also may indicate a change from an even seasonal distribution of precipitation to the dry summer conditions presently found in the region. [

The ecology, history, ecohydrology, and management of pinyon and juniper woodlands in the Great Basin and Northern Colorado Plateau of the western United States

“…Anderson et al 2000;Spaulding 1985Spaulding , 1990; USDA-NRCS plant guide). During the Glacial Maximum, the midden record indicates Utah juniper woodlands were the dominant vegetation type at elevations now occupied by desert shrubs (Jennings 1988(Jennings , 1995. This is about 2,000 feet lower than where pinyon and juniper woodlands are found today (Jennings and Elliot-Fisk 1993).…”

“…But elevations occupied by pinyon and juniper woodlands vary with latitude and, at local scales, with aspect. In the White Mountains just east of Bishop, California, woodlands grow between 6,500-9,500 feet (Jennings 1995;St. Andre et al 1965).…”

“…By 9,000 years ago, singleleaf pinyon entered the area of the White Mountains but remained a minor component of the tree canopy, which was dominated by Utah juniper ( fig. 3-10; Jennings 1988Jennings , 1995. Today pinyon is the dominant woodland tree.…”

From middens to molecules: phylogeography of the piñon pine, Pinus edulis

“…, 2003). The distributional patterns of several species as well as temporal changes in communities have been constructed from packrat midden data (Betancourt & Davis, 1984; Jennings, 1995; Anderson et al. , 2000).…”