The expansion of pinyon-juniper woodland and the appearance of peromyscus truel in the Toiyabe range of central Nevada

In the early twentieth century field biologists from the University of California Museum of Vertebrate Zoology conducted vertebrate faunal surveys throughout the Great Basin region. Over the past several years we have been conducting resurveys of many of the localities visited by MVZ scientists. Our resurvey of the Toiyabe Range of central Nevada revealed the presence of the Pinyon mouse, Peromyscus truei. This species was not recorded in the Toiyabes during the original survey of 1930-31, but in our recent survey the species was widespread and abundant. The appearance of P. truei is correlated with the expansion of the pinyon-juniper woodland plant community, which is its primary habitat. The regional expansion of single-leaf pinyon, Pinus monophylla, is very evident through comparisons of landscape photographs taken by the original surveyors in 1930 and photographs taken from the recent surveys. Our aim is to understand the nature of the pinyon expansion over the past 80 years through dendrochronology techniques using tree cores obtained from pinyon in the area. The correlation of tree ring patterns with climate data reveal the conditions favorable to recruitment and growth of trees and allow us to assess the relative importance of climate warming as a factor behind pinyon expansion. Understanding the causes behind such dramatic habitat shifts and the associated changes in small mammal assemblages has important implications for conservation and management of biotic communities in the Great Basin.