Treesearch

Perennial forage kochia (Kochia prostrata) is a halfshrub valuable for reclamation, fire breaks, and livestock and wildlife forage on semiarid and saline rangelands. Interest is mounting about this species, but some are concerned that it will become an invader of perennial communities. Only one cultivar (Immigrant) has been released in the United States. Eighty-one forage kochia plantings (mainly Immigrant) were evaluated to document forage kochia’s adaptation and spread. Ecological descriptions were taken for each site and multiple regression analyses were done to determine prediction...

The objectives of this study were to determine tebuthiuron’s (1) effectiveness at low application rates in thinning dense, high elevation stands of mountain big sagebrush, (2) impact on understory herbaceous plants and soil microflora, and (3) movement and stability in soil. Four study sites were established in the Fish Lake National Forest and adjacent Bureau of Land Management holdings. Tebuthiuron pellets were applied at one site in 1994, a second site in 1995, and two sites in 1996 at rates ranging from 0.2 to 0.7 pounds of active ingredient (AI) per acre (0.18 to 0.63 kg AI per ha)....

Cheatgrass (Bromus tectorum) has recently displaced salt desert shrubland in many areas of the Great Basin. We studied the dynamics of cheatgrass invasion into an intact shadscale-gray molly community in Dugway Valley, Utah, by adding seeds and manipulating disturbance regime and resource availability. Shrub clipping or cryptobiotic crust trampling on large plots increased cheatgrass recruitment and biomass production slightly in a favorable moisture year (1997 to 1998), whereas in a less favorable moisture year (1998 to 1999) these disturbance treatments had a significant negative effect....

The Plant Materials Center at Aberdeen, Idaho, is operated by the United States Department of Agriculture, Natural Resources Conservation Service. The purpose of the Plant Materials Center is to evaluate and release plant materials for conservation use and to develop and transfer new technology for the establishment and management of plants. The Center serves portions of Nevada, Utah, California, Oregon and Idaho. ‘Rush’ intermediate wheatgrass was released in 1994 and was chosen for superior seedling emergence, high forage production and drought tolerance. In 1995, two selected ecotypes...

Eolian dust (windblown silt and clay) and biological soil crusts are both important to ecosystem functioning of arid lands. Dust furnishes essential nutrients, influences hydrology, contributes to soil formation, and renders surfaces vulnerable to erosion. Biological soil crusts contribute directly to soil fertility by fixing carbon and nitrogen, and indirectly by trapping newly-deposited dust and stabilizing already-present soil. Results from crust-stabilized, unconsolidated sandy sediments on prominent rock exposures and grasslands show dust inputs have significantly increased all...

From January 1997 through October 1998, research was conducted at Canyonlands National Park to investigate soil traits responsible for distinct spatial patterns of cheatgrass (Bromus tectorum) occurrence. Field experiments were conducted at sites representing a broad range of soil conditions and cheatgrass abundances. Standard physicochemical soil measures in combination with innovative ion-exchange resin capsules and bags were used to describe spatial and seasonal soil variations. Cheatgrass performance varied along a complex, multivariate soil gradient, with the strongest cheatgrass-soil...

The topography, climatic pattern, location, and origin of islands generate unique patterns of species distribution. The equilibrium theory of island biogeography creates a general framework in which the study of taxon distribution and broad island trends may be conducted. Critical components of the equilibrium theory include the species-area relationship, island-mainland relationship, dispersal mechanisms, and species turnover. Because of the theoretical similarities between islands and fragmented mainland landscapes, reserve conservation efforts have attempted to apply the theory of...

Reciprocal transplant studies in the big sagebrush hybrid zone at Salt Creek Canyon, Utah, showed that hybrids between basin (Artemisia tridentata ssp. tridentata) and mountain big sagebrush (A. t. ssp. vaseyana) are more fit than either parental taxon, but only when raised in the hybrid zone. Hybrids are less fit than the native parent when raised in the parental environments. Why this is the case remains an open question. Our earlier work has shown that the hybrid zone occurs in an ecotone where the soil, vegetation, and herbivorous insect community all differ markedly from that found in...

Previous studies conducted at our research site on the shortgrass steppe in Colorado showed that phenotypic sex ratios of tetraploid fourwing saltbush (Atriplex canescens Pursh [Nutt]) shrubs were less female biased in grazed pastures than in adjacent exclosures. The potential effects of cattle browsing on shrub sex ratios were studied both in the field and in a greenhouse. In the field study, winter or late summer grazing resulted in higher utilization of female shrubs relative to males. In early spring, when shrubs were browsed the least, utilization of male and female shrubs was not...

Plant species with limited dispersal ability, narrow geographical and physiological tolerance ranges, as well as with specific habitat and ecological requirements are likely to be rare. Small and isolated populations and species contain low levels of within-population genetic variation in many plant species. The gene pool of plants is a product of phenotype-environment interaction. The effects of inbreeding mating systems, geographical ecotypes, phenotypic plasticity, microhabitat differentiation, and stochasticity on genetic variability in locally rare plants are considered. The emphasis...