"Curing" of Nicotiana attenuata leaves by small mammals does not decrease nicotine contents

Basal leaves of Nicotiana attenuata are frequently found neatly excised at the petiole and piled on rocks or soil in the sun until dry, after which they disappear, sometimes to be found again in the nests of Neotoma lepida . In response to herbivore attack, N. attenuata increases the concentration of nicotine in its leaves, where it functions as an induced defense. Since excision of leaves at the petiole allows for leaf removal without substantially activating this induced defense, and air-drying at high temperatures can volatilize nicotine, we examined the hypothesis that the observed leaf ""curing"" behavior decreased nicotine contents. In a natural population, replicate bundles of excised leaves were allowed to dry in the sun for up to 96 hours and harvested in 10 intervals. Even though surface temperatures reached 63° C during drying, no significant loss of nicotine was observed. In the laboratory, significant losses of nicotine were not observed until leaves were dried at 100° C. Nicotine contents of naturally ""cured"" leaf piles at 4 populations were found to be marginally higher than those of neighboring intact plants from which the leaves were likely harvested. We conclude that mammalian ""curing"" behavior does not reduce nicotine contents and may allow the leaves to be used for insect repellant purposes.     

Exotic plants in early and late seral vegetation of fifteen northern Rocky Mountain environments (HTs)

We determined the capacity of exotic plants to invade major environmental types of the northern Rocky Mountains. We did this by observing their presence on disturbed and undisturbed sites in relatively well inoculated locations--corridors adjacent to highways--on transects across the mountains in Glacier National Park and Grand Teton National Park and on low-altitude sites between them. We draw 3 primary conclusions. First, of 29 exotics commonly found, the most dominant are intentionally introduced grasses ( Agrostis, Bromus, Dactylis , and especially Phleum pratense and Poa pratensis ) and legumes ( Melilotus, Medicago , and Trifolium ) rather than the forbs more often listed as noxious. Second, in the environmental types studied, disturbed sites are invasible, except in the alpine. Third, invasion of undisturbed sites declines from grasslands and open forests to alpine to moist forests. This gradient probably represents a decline in resource (light, water, nutrients) availability for herbs, except in the alpine, where a physical limitation is suggested by the poor performance of exotics on noncompetitive disturbed sites.     

Site and stand characteristics related to white pine blister rust in high-elevation forests of southern Idaho and western Wyoming

Successful infection of white pine species by white pine blister rust (WPBR) is contingent upon environmental conditions that are favorable to the spread and development of Cronartium ribicola . Site and stand factors related to this process have been studied elsewhere within the distribution of the disease, but few studies have concentrated on the high-elevation white pine forests of southern Idaho and western Wyoming. We found that mean summer precipitation, average tree diameter, and elevation were the most important variables in 3 logistic regression models of WPBR presence and intensity. The models were tested on a randomly chosen portion of our data set. The model with 9 variables correctly predicted categories of low-, moderate-, and high-disease incidence in 79% of cases. The 2 models with fewer variables had lower predictive efficiencies but were more parsimonious and generally easy to measure. The ability to use easily measured or remotely sensed site and stand characteristics to predict WPBR spread or intensification could be an important asset to land managers who need to decide where to focus disease mitigation efforts and predict disease effects on water quality, wildlife habitat, recreation potential, and other land-management activities.     

Demographic and environmental relations of two rare Astragalus species endemic to Washington County, Utah: Astragalus holmgreniorum and A. ampullarioides

Two endemic locoweeds of Washington County, Utah, Astragalus holmgreniorum and A. ampullarioides , were recently listed as federally endangered plant species (Federal Register 2001). They both occur in few, small populations surrounded by increasing human activity in the St. George, Utah, area. Demographic and habitat studies have been ongoing since 1992 and results of those studies are presented here. Astragalus holmgreniorum (Holmgren locoweed) is presently limited to 1 larger population and 2 smaller, isolated populations on the eastern and western edges of its range. It is a short-lived perennial that grows primarily on the Virgin limestone member of the Moenkopi Formation. Density of A. holmgreniorum over the 10-year study averaged about 2 plants per m 2 . The number of living plants of this species perhaps never exceeds 10,000. In drought years A. holmgreniorum populations are as much as 95% smaller than in years with adequate water, and few plants produce flowers that successfully contribute to the seed bank. Astragalus ampullarioides (Shivwits locoweed) occurs in 4 populations where plant density fluctuated between 0.5 and 4.8 per m 2 during our study period (average = 2.6). This locoweed is restricted to clay soils of the Chinle Formation. Direct threats to both Astragalus species include widespread urbanization, road construction, population fragmentation, and off-highway vehicle use. Indirect threats include competition from aggressive, introduced annual species such as Bromus rubens, B. tectorum, Malcolmia africana , and Erodium cicutarium . Our data show that 3 of 4 species most closely associated with these Astragalus species are introduced. Studies of seed banks and reproduction biology, as well as continued monitoring of these Astragalus species, are critically needed. Studies of the consequences of competition from alien and native species on seedling establishment of these locoweeds are especially needed.     

Functional characteristics of wilderness streams twenty years following wildfire

We compared functional attributes of streams draining catchments burned by wildfire 20 years previously to those of streams in unburned catchments. Long-term analyses of channel profiles indicated most channel change occurred within the first 10 years after fire with little subsequent change the following 10 years. Much of the standing dead timber had fallen, and its effect on stream morphology was directly related to stream size, with important ramifications for future years as decay progresses. The volume of wood in the active channel was 5X higher in a 3rdorder burn stream than in other burn or reference streams, but > 80% of this wood was still bridging the stream. Retention of leaves was strongly associated with channel morphology and location of debris dams. Sediment respiration was significantly greater (1.7X) in streams of burned catchments, resulting from greater amounts of loosely attached organic matter in the sediments of these streams. In concordance with respiration results, coefficients of exchange (k ex ) were almost 5X higher in burn streams than in reference streams, although estimates of transient storage were similar between stream types. We expect the input of large woody debris to increase in the next 10 years in fire-impacted streams as bridging trees collapse into the stream, thereby enhancing channel complexity and habitat heterogeneity, instream metabolism and retention, and consequently stream function. The results emphasize the importance of landscape history, such as large-scale wildfires, on present patterns and processes in stream ecosystems.     

Birds of northern Black Mesa, Navajo County, Arizona

Two hundred forty-one species of birds have been identified from northern Black Mesa, Arizona. This region's avifauna was poorly known until the late 1970s when large-scale coal mining began. Vegetation of the region is predominantly Great Basin desert scrub, pinyon-juniper woodland, and mixed-conifer woodland. The latter vegetation supports an assemblage of isolated montane bird species unique to the region. Numerous environmental changes have recently affected the bird life of Black Mesa. These include large-scale type conversions (pinyon-juniper clearing and surface mining), pond construction, and establishment of exotic vegetation.     

Pigment granules in choroidal melanophores of the albino goldfish.

Pigment granules in choroidal melanophores of the albino goldfish contained fine particulate materials which were in various degrees aggregated in clumps. Tyrosinase was considered to be present in an inhibited state in these pigment granules.     

HCO-3-ATPase activity distribution in rat liver cell fractions prepared by zonal centrifugation.

Plasma membrane sheets prepared by zonal centrifugation of a premicrosomal pellet obtained from a rat liver homogenate are devoid of HCO-3-ATPase activity. Since the microsomal fraction is also lacking in this ATPase activity, it can be concluded that the HCO-3-ATPase is not involved in the secretion of HCO-3 into bile.     

Neutral proteases in the guinea-pig lymphocytes.

Partial purification of neutral proteolytic enzymes in guinea-pig lymphocytes yielded 2 enzymes. Both enzymes were heat-labile and inhibited by thiol reagents. The molecular weights were more than 200,000 and 150,000-200,000, and optimal pH around 9 and 8, respectively.     

Toxicity of Phytophthora infestans and Alternaria solani to chick embryos

None of the extracts and culture filtrates from growth of 9 races of Phytophthora infestans on living potato tissue and potato dextrose broth are toxic to chick embryos. Chloroform extracts of 4 out of 10 isolates of Alternaria solani grown on potato dextrose broth showed some toxicity to chick embryos.