• Horticultural Survivors of a Southwestern Arizona Ghost Town

      Robinson, D. Lowell; Dobrenz, Albert K.; Agronomy and Plant Genetics Department, University of Minnesota; Plant Sciences Department, University of Arizona (University of Arizona (Tucson, AZ), 1994-06)
    • Phenology and Stand Composition of Woody Riparian Plants in the Southwestern United States

      Brock, John H.; School of Agribusiness and Environmental Resources, Arizona State University (University of Arizona (Tucson, AZ), 1994-06)
      Knowledge of phenology is important for understanding the autecology of a species. Information concerning flowering dates, leaf development, seed/fruit dispersal, and aberrant weather effects on phenological status of a species should be well utilized by persons interested in the ecology, management and restoration of riparian communities. The phenology and stand composition of key woody species from selected riparian areas of the southwestern United States was studied. Eight riparian tree species were observed monthly (bimonthly in summer) at six sites in eastern Arizona and New Mexico. Phenological events were placed into eight categories for data collection. Stand composition data was collected from four randomly located macroplots at each site in the summer of 1983. Weather data for the period of study was summarized for the region. Four general phenology groups were identified: 1) spring flowering and fruit dispersal as characterized by Fremont cottonwood (Populus fremontii) and Goodding willow (Salix gooddingii), 2) Spring flowering/autumn-winter fruit dispersal characterized by box elder (Acer negundo var. interius), netleaf hackberry (Celtis reticulata), Arizona sycamore (Plantanus wrightii), and velvet ash (Fraxinuspennsylvanica ssp. velutina), 3) Spring flowering and late summer fruit dispersal demonstrated by Arizona walnut (Juglans major), and 4) Multidate flowering and fruit dispersal displayed by velvet mesquite (Prosopis velutina). Fremont cottonwood and Goodding willow dominated the sites, while netleaf hackberry, box elder, velvet ash and Arizona walnut were minor components of the stands. Variation in phenology of the tree species reflected individual species adaptations to the particular environment.
    • The Ecology of Selerocactus polyancistrus (Cactaceae) in California and Nevada

      May, Richard W. (University of Arizona (Tucson, AZ), 1994-06)
      Several key aspects of the ecology of Sclerocactus polyancistrus (Cactaceae) are described based on a 15 year study by the author. Highlights of the study, funded in part by grants from the Cactus and Succulent Society of America and the United States Navy (China Lake Naval Weapons Center), include a record of growth rates and the impact of predation and infestation. The study also includes the analysis of the carcass remains, identification of predators, the benefits and offsetting effects of predation, and the resulting morphological abnormalities. Using microhystological analyses to determine the relative density of discerned fragments of scats found within the carcasses, Neotoma lepida was found to be the chief predator of this species at elevations below 1500 m (5000 ft). At higher elevations, infestation primarily by the cerambycid beetle Moneilema semipunctatum, is the dominant cause of mortality. Returning each spring over a 15 year period (1976-1991) to six study sites in the Mojave Desert, the author recorded apical growth measurements of over 350 stems and correlated these growth rates to rainfall and other key climatological factors. The results show that microhabitat is a major factor in this species growth rate and that the oldest plants within a given population are in excess of 50 years in age. As expected, there is a direct correlation between seasonal rainfall and the growth rate and number of flowers produced. When surveying eastern Nevada and the Canyonlands National Park areas of Utah, the author has found similar predation and infestation in S. parviflorus and S. spinosior, which indicates that some of the data collected in this study may also be applicable to other small stem cacti of the southwestern deserts, particularly within the same genus.
    • Desert Plants, Volume 11, Number 1 (June 1994)

      University of Arizona (Tucson, AZ), 1994-06
    • Editorial - Status of Desert Plants

      University of Arizona (Tucson, AZ), 1994-06