Status of white pine blister rust in the Intermountain West

During 1995-1997 we conducted a white pine blister rust (WPBR) disease survey in white pines of the Intermountain West. Incidence of WPBR in white pines was 59% overall, 73% in the northern Rocky Mountains, 55% in the middle Rocky Mountains, and 67% in the Sierra Nevada sample stands. Intensity within infected stands averaged 35% and ranged from 2% to 100%. Southward spread of the disease along the western slopes of the Rocky Mountains appears to have slowed or stopped, and the disease was found at the northern and western edges of, but not within, the Great Basin region. Smaller-diameter trees infected with WPBR sustained more severe damage than larger-diameter trees. Mortality and top kill caused by WPBR were very low across the entire study area, but incidence and intensity of the disease appear to have increased substantially in the northern and middle Rocky Mountains since the 1960s.     

Forest health impacts of bark beetles, dwarf mistletoe, and blister rust in a Lake Tahoe Basin mixed conifer stand

Interactions between forest health variables and mensurational characteristics in an uneven-aged eastern Sierra Nevada mixed conifer stand were examined. The stand was located in the Lake Tahoe Basin on a site featuring a coarsely textured granitic soil and numerous rock outcrops. Its composition was dominated by California white fir ( Abies concolor var. lowiana [Gord.] Lemm.), with Jeffrey pine ( Pinus jeffreyi Grev. & Balf.) and sugar pine ( Pinus lambertiana Dougl.) less prominent and incense-cedar ( Libocedrus decurrens Torr.) and mountain alder ( Alnus tenuifolia Nutt.) the most minor constituents. The majority of saplings and seedlings were white fir. The stand exhibited no evidence that its development had been influenced by fire and, overall, it consisted of numerous small trees accruing little radial growth. Nearly one-quarter of all standing stems pole size or larger were dead, with mortality concentrated in white fir. Forestfloor fuel accumulations were excessive, and coarse debris was especially prominent. A fir engraver beetle ( Scolytus ventralis LeConte) epidemic in white fir contrasted against apparent endemic population levels of the Jeffrey pine ( Dendroctonus jeffreyi Hopkins) and red turpentine ( Dendroctonus valens LeConte) beetles in Jeffrey pine and of the mountain pine beetle ( Dendroctonus ponderosae Hopkins) in sugar pine. The severity of fir engraver attack on white fir was weakly related to overall tree size and to the proportion of composition consisting of this host species, while in Jeffrey pine and sugar pine, bark beetle attacks were strongly correlated with the individual proportions of these 2 hosts. Across all species, basal area explained a substantial proportion of the variation in overall attack severity. We found light infestations of true fir dwarf mistletoe ( Arceuthobium abietinum Engelm. ex Munz f. sp. concoloris ) in white fir and western dwarf mistletoe ( Arceuthobium campylopodum Engelm.) in Jeffrey pine, plus an early stage of infection by the white pine blister rust ( Cronartium ribicola J.C. Fischer) in sugar pine. Collectively, this case study characterized and quantified many of the conditions, symptoms, and causative agents inherent in a decadent mixed conifer stand in the eastern Sierra Nevada.     

Effectiveness of the seed wing of Pinus flexilis in wind dispersal

Limber pine ( Pinus flexilis James) seeds are usually wingless but occasionally have short, stubby wings. To determine the effectiveness of these wings in slowing seed descent, rates of fall were determined before and after wing removal. A similar experiment was conducted with seeds of Himalayan blue pine ( P. griffithii McClelland), a white pine with typically long seed wings. The short wings of limber pine seeds were found to influence rate of seed fall far less than the wings of Himalayan blue pine. This is consistent with evidence suggesting that limber pine seeds are not effectively dispersed by wind but are dependent for dispersal on Clark's Nutcracker ( Nucifraga columbiana ).        

Effects of exotic species on Yellowstone's grizzly bears

Humans have affected grizzly bears ( Ursus arctos horribilis ) by direct mortality, competition for space and resources, and introduction of exotic species. Exotic organisms that have affected grizzly bears in the Greater Yellowstone Area include common dandelion ( Taraxacum officinale ), nonnative clovers ( Trifolium spp.), domesticated livestock, bovine brucellosis ( Brucella abortus ), lake trout ( Salvelinus namaycush ), and white pine blister rust ( Cronartium ribicola ). Some bears consume substantial amounts of dandelion and clover. However, these exotic foods provide little digested energy compared to higher-quality bear foods. Domestic livestock are of greater energetic value, but use of this food by bears often leads to conflicts with humans and subsequent increases in bear mortality. Lake trout, blister rust, and brucellosis diminish grizzly bears foods. Lake trout prey on native cutthroat trout ( Oncorhynchus clarkii ) in Yellowstone Lake; white pine blister rust has the potential to destroy native whitebark pine ( Pinus albicaulis ) stands; and management response to bovine brucellosis, a disease found in the Yellowstone bison ( Bison bison ) and elk ( Cervus elaphus ), could reduce populations of these 2 species. Exotic species will likely cause more harm than good for Yellowstone grizzly bears. Managers have few options to mitigate or contain the impacts of exotics on Yellowstones grizzly bears. Moreover, their potential negative impacts have only begun to unfold. Exotic species may lead to the loss of substantial highquality grizzly bear foods, including much of the bison, trout, and pine seeds that Yellowstone grizzly bears currently depend upon.     

Condition models for wintering Northern Pintails in the Southern High Plains

Three condition models for wintering Northern Pintails ( Anas acuta ) were tested for their ability to predict fat mass, logarithm of fat mass, or a condition index (CI) incorporating fat mass. Equations generated to predict fat mass and the logarithm of fat mass accounted for more than 69% of the variation in these dependent variables. Log transformations of body mass, wing length, and total length explained at least 60% of the variation in CI. All models performed better on an independent data set. Mean prediction error was minimal (≤8% of measured variables) and negative for all models. Regression models apply to live and dead pintails and thus represent tools that have utility in a wide variety of studies on pintail condition.     

Vegetal responses and big game values after thinning regenerating lodgepole pine

Understory vegetal response was found to significantly increase with the degree of thinning in an early regenerating, dense stand of lodgepole pine ( Pinus contorta ). The value of the increased vegetation for deer and elk was determined to be important through comparisons with known dietary and habitat preferences.     

Seed and cone insects associated with Pinus monophylla in the Raft River Mountains, Utah

Yearly variation in numbers of cones produced by western white pine was found to affect the population level of the mountain pine cone beetle. In years when cone production is moderate to heavy, beetle populations increase. Increasing beetle populations are ultimately limited by poor cone crops, which increase competition for nutrients and oviposition sites. Variability in western white pine cone production is regarded as the most important factor regulating populations of the mountain pine cone beetle.        

Effect of western white pine cone production variability on mountain pine cone beetle population levels

Yearly variation in numbers of cones produced by western white pine was found to affect the population level of the mountain pine cone beetle. In years when cone production is moderate to heavy, beetle populations increase. Increasing beetle populations are ultimately limited by poor cone crops, which increase competition for nutrients and oviposition sites. Variability in western white pine cone production is regarded as the most important factor regulating populations of the mountain pine cone beetle.        

A disjunct ponderosa pine stand in southeastern Oregon

An isolated stand of ponderosa pine ( Pinus ponderosa ) is surviving on an extremely harsh site in southeastern Oregon. Seed production is low because of insects, primarily pine coneworm ( Dioryctria auranticella ), feeding in developing cones. Seedling establishment is infrequent and difficult because of drought and coarse, rocky soils. A rock-mulch soil surface probably reduces interspecific competition. Because stand size is small (     

Breeding birds of an ancient bristlecone pine stand in east central Nevada

This paper describes features of the breeding bird population of a Great Basin ancient bristlecone pine stand on Wheeler Peak in White Pine County, east central Nevada. The bird population was determined by spot-mapping methods on a 20-ha plot during June and July 1981. The density of breeding birds was 82 pairs per 40 ha. Fourteen species were territorial. The most abundant species were the Dark-eyed Junco, Mountain Chickadee, Mountain Bluebird, and Townsend’s Solitaire. Other common breeding species included the Cassin’s Finch, Yellow-rumped Warbler, Pine Siskin, and Dusky Flycatcher. There were 410 individual breeding birds per km 2 . When expressed as standing crop biomass, the Townsend’s Solitaire was the predominant species, followed by the Dark-eyed Junco, American Robin, Mountain Bluebird, and Northern Flicker. Total standing crop biomass was 95 g/ha. None of the breeding birds were restricted to the bristlecone pine stand. The structure of the breeding bird community in the bristlecone pine forest compared best to those of the Rocky Mountain and Northern Boreal forest regions.     

Winter habitat selection patterns of Merriam's turkeys in the southern Black Hills, South Dakota

In northern areas of their expanded range, information on Merriam's turkeys ( Meleagris gallopavo merriami ) is lacking, specifically pertaining to wintering behavior and factors associated with winter habitat selection. Forest managers need detailed quantification of the effects of logging and other management practices on wintering habitats needed by Wild Turkeys and other wildlife. Therefore, we examined winter habitat selection patterns within ponderosa pine ( Pinus ponderosa ) forests and determined factors associated with use of farmsteads by Merriam's turkeys in the southern Black Hills, South Dakota. We radio-marked 86 female Merriam's turkeys (70 adults and 16 yearlings) and monitored them during winter (1 December–31 March), 2001–2004. Female Wild Turkeys used recently burned pine forest less than expected but selected farmsteads and stands of mature ponderosa pine ( 22.9 cm diameter at breast height [DBH] trees) for foraging sites. Within forests, female Wild Turkeys selected foraging sites with less understory vegetation and visual obstruction, and larger-diameter ponderosa pine. Ponderosa pine seed abundance varied among years, and pine seeds were most abundant in stands of 30–35 cm DBH with basal area of 22–28 m2 ? ha–1. Abundance of pine seeds may have influenced use of farmsteads by Wild Turkeys, more so than ambient temperatures or snow depth. In the southern Black Hills, management should emphasize open- to mid-canopy and mature-structural-stage pine stands, where seed production was greatest. During winters when mast from pine is unavailable, farmsteads likely provide nutritional supplementation and may be important for maintaining Merriam's turkey populations.     

Comparison of regression methods for predicting singleleaf pinyon phytomass

Succession, nutrient cycling, production, and competition studies in plant communities require estimation of plant biomass. This is often accomplished by relating weight to easily measured plant dimensions via allometric equations. Dimensions of basal area and crown volume were used to predict phytomass of singleleaf pinyon ( Pinus monophylla Torr. & Frem.). Two regression methods for fitting the allometric equation to data for phytomass prediction were tested. These methods were the more commonly used logarithmic transformation of both data variables followed by linear regression analysis and an iterative nonlinear analysis without data transformation. The first was consistently less effective for predicting both individual tree and total plot phytomass for pinyon. Basal area was a better predictor of phytomass on a site than was crown volume. Prediction equations were highly site specific. Age of the trees in the stand used to derive the equations significantly affected the phytomass estimates. Other site and stand factors also appear to affect the phytomass-allometric parameter relationship.     

Pilfering of stored seeds and the relative costs of scatter-hoarding versus larder-hoarding in yellow pine chipmunks

Yellow pine chipmunks ( Tamias amoenus ) scatter-hoard food during summer and autumn but must form a larder as a winter food source before winter begins. Yellow pine chipmunks do not larder-hoard large quantities of food during the summer, apparently because a summer larder could not be defended from pilferers. We tested the assumption that the rate of pilferage from an unguarded larder would be significantly greater than the rate of pilferage from surface caches (which are also unguarded by yellow pine chipmunks) during the summer and autumn. Buried plastic buckets were used as artificial nests containing larders of 1000 sunflower seeds or 200 Jeffrey pine ( Pinus jeffreyi ) seeds. The pilferage of larder contents was monitored daily and compared to pilferage of surface caches. Animals (yellow pine chipmunks and deer mice, Peromyscus maniculatus ) removed sunflower seeds from caches much faster than from larders, but caches of Jeffrey pine seeds disappeared much more slowly than pine seeds in larders. Further, animals removed pine seeds from larders more quickly than they did sunflower seeds from larders. The difference between seed species was probably because sunflower seeds have much stronger odors, which rodents readily detect, and because chipmunks prefer pine seeds over sunflower seeds. Yellow pine chipmunks must spend a considerable portion of their time foraging for seeds and may not be able to defend a large larder during summer.     

Estimation procedures for understory biomass and fuel loads in sagebrush steppe invaded by woodlands

Regression equations were developed to predict biomass for 9 shrubs, 9 grasses, and 10 forbs that generally dominate sagebrush ecosystems in central Nevada. Independent variables included percent cover, average height, and plant volume. We explored 2 ellipsoid volumes: one with maximum plant height and 2 crown diameters and another with live crown height and 2 crown diameters. Dependent variables were total, live, leaf, and dead biomass. Simple, multiple, linear, and power equations were investigated. Models were chosen based on scatter plots, residual plots, and R 2 and SEE values. In general, simple power equations provided the best-fit regressions. For shrubs, the ellipsoid volume computed with maximum plant height best predicted total plant weight, and the ellipsoid volume computed with the live crown height best predicted shrub foliage weight. In addition to regression equations for biomass, ratios for division of that biomass into 1-, 10-, 100-, and 1000-hour fuels were derived for common large shrubs. Regression equations were also derived to relate litter mat sizes of major shrub species to litter weights. The equations in this paper could be used to predict biomass in other areas of the Great Basin if training data were taken to validate or adjust these models.     

Attributes associated with probability of infestation by the pi?on ips, Ips confusus (Coleoptera: Scolytidae), in pi?on pine, Pinus edulis

We examined attributes of pi?on pine ( Pinus edulis ) associated with the probability of infestation by pi?on ips ( Ips confuses ) in an outbreak in the Coconino National Forest, Arizona. We used data collected from 87 plots, 59 infested and 28 uninfested, and a logistic regression approach to estimate the probability of infestation based on plot and tree-level attributes. Pi?on pine stand density index was a good predictor of the likelihood of infestation by pi?on ips at the plot level, and a cross-validation analysis confirmed that the model correctly classified 82% of the cases. Diameter at root collar and pi?on dwarf mistletoe infestation level were good predictors of individual tree infestation, and a cross-validation analysis indicated that the model correctly classified 72% of the cases. Results suggest that the occurrence of pi?on ips infestations may be related to stress factors associated with increased stocking and pi?on dwarf mistletoe infestations.     

Fire frequency and the vegetative mosaic of a spruce-fir forest in northern Utah

Fire scar and vegetative analysis were used to construct a fire history for the Engelmann spruce/subalpine fir ( Picea engelmannii/Abies lasciocarpa ) vegetation type of Utah State University (USU) T. W. Daniel Experimental Forest. Three distinct periods of fire frequency were established-presettlement (1700-1855), settlement (1856-1909), and suppression (1910-1990). Mean fire interval (MFI) decreased during the settlement period and greatly increased during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of nearby Cache Valley, located 40 km to the west. Logging and livestock grazing appear to have led to the reduced MFI, which in turn worked as a factor to create the vegetative mosaic now observed on the study area. The increase in MFI during the suppression ear permitted the advancement of shade-tolerant species in the understory of the shade-intolerant lodgepole pine ( Pinus contorta var. latifolia ) and quaking aspen ( Populus tremuloides ). Continued suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experience the lowest MFI during the settlement period, to be further invaded by shade-intolerant species, decreasing spatial stand diversity and increasing the risk of more intense fires.     

Phalacropsis dispar (Coleoptera: Phalacridae), an element in the natural control of native pine stem rust fungi in the western United States

Larvae of the phalacrid beetle Phalacropsis dispar (LeConte) consumed aeciospores and the underlying sporogenous mycelium, thereby destroying the aecia of all native western pine stem rust fungi studied. Aecia of the introduced white pine blister rust fungus ( Cronartium ribicola ) were not found to be infested by the beetle. A close, if not obligate, biosis of the beetle apparently exists with the native rust fungi, and their geographic distributions closely coincide. Laboratory tests and field observations indicate that the beetle completes its life cycle in 30 to 40 days and apparently overwinters as an adult. Quantitative data on aeciospore inoculum destruction were beyond the means of this study; however, observations over a 12 - year period evidenced widespread and extensive destruction of aeciospores. The beetle may be an effective element in the natural control of native pine stem rust fungi. Natural control by secondary organisms could significantly reduce the selective pressure for high host resistance in a naturally evolving host - parasite population.     

Scatter-hoarding behavior of deer mice ( Peromyscus maniculatus )

Deer mice ( Peromyscus maniculatus ) are known to larder hoard food, but their scatter-hoarding behavior is poorly documented. Eleven deer mice were each presented with 150 Jeffrey pine ( Pinus jeffreyi ) seeds in 10 γ 10- m enclosures in Jeffrey pine forests on the east slope of the Sierra Nevada. Subjects made a mean ± 1 s of 31.2 ± 30.0 caches per trial. Caches were shallow (most 2-12 mm deep) and usually contained only 1 or 2 seeds. Most caches were made at the edge of antelope bitterbrush ( Purshia tridentata ) shrubs in mineral soil or in thin layers of plant litter. These results suggest that deer mice might make a significant contribution to the dispersal of Jeffrey pine.     

Impacts of nonnative plant species on production and diversity in the front range of Colorado

Nonnative plant species are considered one of the greatest threats to biodiversity, yet we still are unable to predict how production and diversity of a community will change once a species has invaded. Ponderosa pine woodlands in the Front Range of Colorado are ideal for studying the impacts of nonnative plants on production and species richness. We selected 5 sites along the northern Front Range with varying proportions of nonnative and native species and compared understory production and species richness along the gradient of nonnative species dominance. Total species production was positively and significantly related to total species richness, and total species production increased significantly with increasing nonnative species richness. There was a negative relationship between native and nonnative species production, and there was no relationship between nonnative species richness and native species richness. This study demonstrates the complex nature of species richness and productivity relationships and should serve as a starting point for future research in which a variety of other variables are considered.     

Relationship between environmental conditions and host-seeking activity of Ochlerotatus albifasciatus (Diptera: Culicidae) in an agroecosystem and in an urban area in Chubut,Central Patagonia,Argentina

Ochlerotatus albifasciatus is associated with aquatic environments that are frequently flooded. Awareness of blood hematophagic activity of female mosquitoes is particularly important in species which are vectors of human disease and domestic animals. The study of host-seeking activity allows us to infer the risk of transmission of these parasites. The objective of this work was to study in an agro-ecosystem and urban area of central Argentine Patagonia the relationship between the circadian rhythm of activity of host-seeking of Oc. albifasciatus, and environmental variables. During January 2003, 99 human bait catches were carried out, of which 77.8% registered at least one individual of Oc. albifasciatus. Generalised linear models were used to evaluate the relationship between Oc. albifasciatus biting activity rate and capture time, environmental humidity, air temperature, sunshine degree, wind speed, habitat type and proximity of larval habitat. The model that best explained the variation in biting activity rate included the capture time, environmental humidity, air temperature, sunshine degree and wind speed as predictor variables. Host-seeking activity was higher in the evening than in the morning or afternoon, and it was positively related to mean air temperature and environmental relative humidity (RH), but negatively to sunshine degree and wind speed. The combination of these characteristics (wind speed less than 20 km/h, environmental temperature greater than 26°C, sunshine less than 40% and (RH) greater than 50%) would provide favourable conditions to allow seeking activity and to feed on the host. The dispersion of this mosquito could be among environmental patches that present these characteristics.