Treesearch

Expansion of diploid creosote shrubs (Larrea tridentata (Sessé & Moc. ex DC.) Coville)) into grassland sites occurs exclusively through seed production. We compared the reproductive biology of Larrea shrubs located in a Chihuahuan desert shrubland with isolated shrubs well-dispersed into the semiarid grasslands at the Sevilleta National Wildlife Refuge. Specifically, we examined (1) reproductive success on open-pollinated branches, (2) the potential of individual shrubs to self-pollinate, and (3) bee pollinator guild composition at shrubland and grassland sites. Sampling of the bee guild...

Rapid and substantial reductions in the local density of invasive rubber rabbitbrush (Chrysothamnus nauseosus) have been achieved on a shrub-infested meadow complex solely by manipulating grazing so as to benefit the native meadow vole, Microtus montanus. The key adjustment has been a shift from spring-summer to late season grazing, thereby allowing sufficient growth of herbaceous vegetation to offer suitable vole habitat. We hypothesize that voles were instrumental in defending many historic western meadowlands against woody shrub encroachment, but have now been widely displaced by...

In the springs of 2004, 2005, and 2006, surveys were conducted on the Nevada Test Site (NTS) to characterize vegetation resources and climatic components of the environment that contribute to wildland fires. The NTS includes both Great Basin Desert and Mojave Desert ecosystems and a transitional zone between these two deserts. The field surveys assessed 211 sites along major NTS corridors for the abundance of native perennial and annual species and invasive weeds. The abundance of fine‑textured (grasses and herbs) and coarse‑textured (woody) biomass was visually estimated on numerical...

Cheatgrass (Bromus tectorum) is an exotic winter annual grass weed that has invaded millions of hectares in the Intermountain West. Restoration of cheatgrass-invaded wildlands is generally impractical without some form of cheatgrass control. We are investigating the possibility of manipulating indigenous fungal pathogens that already occur on cheatgrass for short-term biocontrol in conjunction with restoration seedings. Three potential biocontrol organisms have been identified. The head smut pathogen (Ustilago bullata) and the chestnut bunt pathogen (Tilletia fusca) infect at the seedling...

This case study documents temporal and spatial squarrose knapweed (Centaurea virgata Lam. spp. squarrosa (Willd.) Gugler) seed dispersal from study sites in central Utah. Felt seed traps were placed along transects extending from sites occupied by squarrose knapweed into adjacent plant communities. Seed dispersal from knapweed plants occurred over an 8-month period. By 1 November 1999, 50 and 53 percent of dispersed seed had been recovered at the Knight and Cherry Creek locations respectively. By May, nearly all seed has dispersed from the producing plant. Most seed was deposited and...

Mule deer (Odocoileus hemionus) populations have gradually declined in recent decades, while elk (Cervus elaphus) have often increased throughout their common ranges. The cause is uncertain and a source of debate. Increasing elk numbers on these ungulate winter ranges may be causing competition for resources. We contrast winter diets of mule deer and elk and relate them to population trends of both species on the Mount Haggin Wildlife Management Area in southwest Montana. Elk increased from an observed number of 172 in 1978 to 700 in 1996 and slightly declined in 1997. Likewise, mule deer...

To better understand why medusahead (Taeniatherum caput-medusae) is invasive, we quantified soil N availability and characterized soil microbial communities between native and invasive populations. No consistent differences in soil N mineralization potentials were noted between native medusahead sites in Spain, Turkey, France, and Greece and two invaded sites on the volcanic tablelands of northeastern, California, U.S.A. The proportional makeup of the microbial community, as quantified by phospholipid fatty acid analysis (PLFA), did not differ appreciably between a native site in southern...

Squarrose knapweed (Centaurea virgata var. squarrosa), herein referred to simply as knapweed, is a noxious weed that invades both disturbed and healthy sagebrush communities. Fire, grazing, mining, recreation, and farming have all played a large part in the establishment of knapweed in Tintic Valley, Utah. This study was designed to look at the effect of fire on the establishment of knapweed in four community types, namely cheatgrass, crested wheatgrass, degraded sagebrush, and healthy sagebrush. Plots were either burned or left unburned after which subplots were seeded with knapweed....

A steady decline of perennial bunch grasses in arid rangelands has resulted in losses of productivity and germplasm. Remediation is costly and rarely successful. Cryptic symbiotic fungi, structurally integrated with cells and organs of native plants cannot be separated from host plant tissue. However, they were successfully transferred from cell cultures of native plants to other native grasses and tomato. Fungi in recipient plants were heritable and substantially enhanced vigor, biomass and reproductive potential. The transfer of novel fungal symbionts to other native or crop plants may...

Obligate fungal endophytes form cryptic communities in vascular plants that can defy detection and isolation by microscopic examination of reproductive structures. Molecular detection by PCR amplification of fungal DNA sequences alone is insufficient, since target endophyte sequences are unknown and difficult to distinguish from sequences already characterized as plant DNA. We have successfully separated fungal and plant ribosomal DNA sequences by amplifying plant-extracted DNA with polymerase chain reaction, and separating sequences with denaturing gradient gel electrophoresis (DGGE). The...