Graduate Abstract

Rekha Saxena
Winter 2005

Relationship between soil characteristics and occurrence of Arctomecon california: Is A. californica restricted to gypsum soils?

by

Rekha Saxena

M.S. Environmental Science
University of Lucknow, Lucknow
1997

Bachelor of Science
University of Lucknow, Lucknow
1994

A thesis submitted in partial fulfillment
of the requirements for the

Master of Science Degree in Environmental Science

Department of Environmental Studies
Greenspun College of Urban Affairs

Graduate College
University of Nevada, Las Vegas
Winter 2005

Dr. Patrick Drohan, Examination Committee Chair
Professor of Geoscience
University of Nevada, Las Vegas

ABSTRACT

Many authors have reported endemism of few vascular plants to gypsum soils of arid environments. However not much has been found about the factors which restrict their occurrence on such habitats. Arctomecon californica, commonly known as Las Vegas Bearpoppy, is a gypsophile which is believed to be endemic to gypsiferous substrates derived from the Moenkopi and Horse springs geological formations in southeastern Nevada and northwestern Arizona. (Mistretta et al.1996). It is commonly found in association with desert washes where cryptogamic crusts have developed (Mistretta et al. 1996). A. californica tends to tolerate disturbed soil surfaces relatively well (Mistretta et al.1996). From the past few decades, population of A. californica has been declining mostly around the rapidly developing urban areas in the Las Vegas Valley and on public lands on the outskirts of the valley.

The objective of this research was to access relationship between A. californica and the soils inhabited by it. Soils at study sites were analyzed by studying the physical, chemical and the mineralogical properties within and outside the species habitat, to provide researchers with a better understanding of habitat requirements for A. californica. Results show that surficial characteristics play an important role in the establishment of A. californica. A significant difference was found in surface roughness, percent rock fragments and penetrometer data between A. californica populated and unpopulated sites. Populated sites were found to have rougher surface and higher percent rock fragments cover as compared to the unpopulated sites which probably aids catching of A. californica seeds and prevent them from blown away by winds. The sub surface horizons on populated sites were found to have lower bulk densities as compared to unpopulated sites. The penetrometer data also showed similar results. A. californica populated sites were less compact and showed less mechanical resistance to penetrometer as compared to unpopulated site, which suggest that loose soils allow better root penetration and therefore better availability of water and nutrients to the plant. Results also show that there was no significant difference found in sulfur or sulfate levels on A. californica populated and unpopulated sites, suggesting that A. californica is not restricted to gypsum soils and can habitat wide variety of soil and/or parent material. I believe results from this research will help in sustaining healthy populations of A. californica in its natural habitat and on habitats with similar soil characteristics.