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.        

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.     

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.     

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 ).        

Relative and seasonal abundance of three bark beetle predators (Coleoptera: Trogositidae, Cleridae) across an elevation gradient in ponderosa pine forests of north central Arizona

We examined abundance and flight periodicity of 3 predators of bark beetles (Coleoptera: Curculionidae, Scolytinae), Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), Enoclerus sphegeus (Fabricius) (Coleoptera: Cleridae), and E. lecontei (Wolcott) (Coleoptera: Cleridae), across an elevational gradient of ponderosa pine ( Pinus ponderosa Lawson) forests in north central Arizona. Predator populations were estimated at 10 sites in each of 3 elevation bands (low: 1600–1736 m; mid: 2058–2230 m; high: 2505–2651 m) for 3 years (2004–2006) using pheromone-baited funnel traps targeting 3 primary bark beetle species. We also investigated how predator abundance and flight seasonality related to those of 5 bark beetle species: Ips pini (Say), I. lecontei Swaine, Dendroctonus frontalis Zimmermann, D. brevicomis LeConte, and D. adjunctus Blandford. Temnochila chlorodia was most abundant in the low- and mid-elevation bands, whereas E. sphegeus was most abundant in the high-elevation band. Enoclerus lecontei showed no consistent elevational trend in abundance. Within each elevation band, changes in annual abundance of pooled predator species tracked shifts in abundance of pooled bark beetle species. In general, predator flight initiation coincided with or closely followed bark beetle flight initiation in the spring, but predator flight terminated before flight activity ended for most bark beetle species in the fall. In addition, the ratio of prey to predators was lowest in the summer and highest in the fall. This suggests that all bark beetle species examined may be provided temporal escape from their predators in the fall. For all 3 predator species, the pheromone-baited trap targeting D. brevicomis was less attractive than the pheromone-baited traps targeting I. pini and I. lecontei.     

Bristlecone pine and Clark's Nutcracker: probable interaction in the White Mountains, California

Many bristlecone pines in the White Mountains, California, are members of multistem clumps. We propose that these clumps have arisen by multiple germinations from seed caches of Clark’s Nutcracker, as occurs in several other pine species. The commonness of nutcrackers and their caching of singleleaf pinyon seeds in the study area provide supporting evidence. Other vertebrates appear unlikely to be responsible for the stem clumps. Seed burial may be required to establish regeneration on these adverse sites where bristlecone pine attains great longevity.        

A mountain cercocarpus population-revisited

A mountain cercocarpus ( Cercocarpus montanus Raf.) population was analyzed first in 1965 and again in 1975 to gain insight into the growth and reproduction of this species. The basis for comparison was plant height and number of basal stems. Growth (measured by height) was slow during the 10 - year period, with plants on the northeast - facing slope having an average increase of 37 cm and those on the southwest - facing slope maintaining relatively the same average height. There was an overall decrease in average number of base stems for plants positioned on both slopes.        

Selection of dwarf mistletoe-infected ponderosa pines by Ips species (Coleoptera, Scolytidae) in northern Arizona

Following an Ips bark beetle outbreak in 2002, mortality of ponderosa pine ( Pinus ponderosa Douglas ex C. Lawson) was evaluated in 2 study areas infested with southwestern dwarf mistletoe ( Arceuthobium vaginatum [Willd.] Presl subsp. cryptopodum [Engelm.] Hawksw. & Wiens) in the Coconino and Tonto National Forests, Arizona. A pairwise comparison of dwarf mistletoe ratings for live and dead ponderosa pines was conducted to determine whether dead ponderosa pines had higher dwarf mistletoe ratings than pines that were not attacked. In both study areas, dead ponderosa pines had significantly higher dwarf mistletoe ratings, indicating an association between the severity of dwarf mistletoe infection and susceptibility to attack by Ips spp. We suggest that the probability of ponderosa pine mortality is greater in stands severely infested with southwestern dwarf mistletoe in northern Arizona.     

High rates of photosynthesis in the desert shrub Chrysothamnus nauseosus ssp. albicaulis

  Basic aspects of photosynthesis were investigated in white rubber rabbitbrush ( Chrysothamnus nauseosus (Pallas) Britt. ssp. albicaulis ), a common C 3 deciduous shrub native to arid regions of the western U.S. Under favorable field conditions, net photosynthesis (P n ) ranged from 36 to 73 mgCO 2 · dm – 2 · hr – 1 , which is relatively high for a woody species. The leaves from the actively growing flowering shoots exhibited higher P n than those on the vegetative shoots. P n also varied according to the age of the leaves and the location of the plants. P n did not light saturate even at quantum flux densities (QFD) equivalent to full sunlight. The light compensation point was relatively high (ca 100 μ mol · m – 2 · S – 1 ), perhaps due to the presence of a tomentose vestiture on the leaf surface. At high QFD's, the stomatal conductance was high (ca 520 mmol · m – 2 · s – 1 ) for a woody species. RUBP - carboxylase content of the leaves ranged from 20 to 22 mg per gram F.W., which is similar to that found in most C 3 crop species. These results suggest that rabbitbrush is able to maintain high rates of P n , at least under nonstressed conditions.           

Survivorship and cause-specific mortality in five populations of mule deer

We used retrospective analyses to investigate cause-specific mortality and survivorship among 5 populations of mule deer ( N = 168 telemetered animals) wintering in the western Great Basin during 1986-1994. These populations existed under similar environmental conditions, but survivorship functions differed among them. Monthly survival ranged from 0.964 to 0.990, and annual survival ranged from 0.643 to 0.884. The proportion of deaths attributed to predation and malnutrition or anthropogenic causes did not differ among the 5 populations. Predation was the leading cause of mortality; mountain lions were responsible for approximately 90% of the deer killed by predators. No difference existed among these populations in the proportion of telemetered deer that were killed by mountain lions, but proportionally more females than males were killed by these large fields. Predation by mountain lions is the primary source of mortality and a widespread phenomenon among the populations of mule deer we investigated.     

Late quaternary plant zonation and climate in southeastern Utah

Plant macrofossils from packrat middens in two southeastern Utah caves outline development of modern plant zonation from the late Wisconsin. Allen Canyon Cave (2195 m) and Fishmouth Cave (1585 m) are located along a continuous gradient of outcropping Navajo Sandstone that extends from the Abajo Mountains south to the San Juan River. By holding the site constant, changes in the floral composition for a plot of less than one hectare can be observed, even if sporadically, over tens of millennia. At Allen Canyon Cave, Engelmann spruce-alpine fir forest was replaced by the present vegetation consisting of pinyon-juniper woodland on exposed ridgetops and cliffside stands of Douglas fir, ponderosa pine, and aspen. Xerophytic woodland plants such as pinyon, plains prickly pear, and narrowleaf yucca arrived sometime in the middle Holocene between 7200 and 3400 B.P. At Fishmouth Cave, Utah juniper in Holocene middens replaced blue spruce, limber pine, Douglas fir, and dwarf and Rocky Mountain junipers in late Wisconsin samples. Disharmonious associations for the late Wisconsin occur only at the lower site with the xerophytes Mormon tea, plains prickly pear, and narrowleaf yucca growing alongside subalpine conifers. One possible explanation involves the late Wisconsin absence of ponderosa and pinyon pines from the Colorado Plateaus. Released from competition at their lower limits, subalpine conifers were able to expand into lower elevations and mix with xerophytic plants found today in understories of pinyon-juniper and ponderosa pine woodlands. Quantitative climatic estimates are derived for the late Wisconsin by applying vertical gradients for temperature and precipitation to the amount of vegetation depression. The Fishmouth Cave sequence indicates a minimum lowering of 850 m for blue spruce, limber pine, and dwarf juniper. A depression of at least 700 m for Engelmann spruce and alpine fir is suggested for the Allen Canyon locality. Use of conservatively low gradients for stations below 2080 m yields a 3–4 C cooling from present mean annual temperature and 35 to 60 percent more rainfall than today. Steeper gradients associated with more mountainous terrain suggest a 5 C lowering in temperature and up to 120 percent increase over modern precipitation.        

Effects of Douglas-fir beetle (Coleoptera: Scolytidae) infestations on forest overstory and understory conditions in western Wyoming

Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) infestations frequently result from disturbance events that create large volumes of weakened Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco. Previous research has focused on determining susceptibility of forest stands to Douglas-fir beetle and predicting the amount of tree mortality from Douglas-fir beetle infestations following disturbance events. Little work has been done on consequent changes in the forest overstory and understory. In the early 1990s, populations of Douglas-fir beetle increased in fire-scorched trees, subsequently infesting undamaged neighboring stands in the Rocky Mountains of western Wyoming, USA. In 1999 transect sampling and 25 pairs of previously infested and uninfested plots were used to quantify changes in forest stand conditions and ensuing responses in the understory caused by Douglas-fir beetle infestations. Significant effects of the Douglas-fir beetle infestation comprised 3 general categories: (1) overstory effects: basal area was reduced by 40%-70%, average tree diameter decreased by 8%-40%, and the Douglas-fir component of the overstory decreased by more than 12%; (2) regeneration effects: conifer seedling regeneration increased nearly fourfold in infested plots and 90% of the regeneration was Douglas-fir; (3) understory effects: understory vegetation (forbs, grass, and shrubs) had a threefold increase in infested compared with uninfested plots. In addition, basal area of Douglas-fir killed by the Douglas-fir beetle was significantly correlated with initial Douglas-fir basal area and percentage of Douglas-fir, but not with stand density index, tree diameter, or trees per hectare. Significant inverse relationships also were found between post-infestation basal area and abundance of forbs, grass, and shrubs, and understory height. Thus, we found that Douglas-fir beetle infestations cause significant short-term effects in both the overstory and understory and contribute to an altered mosaic in forest structure.     

Mycorrhization of ponderosa pine in a second-growth Sierra Nevada forest

Ectomycorrhizal colonization and rooting characteristics were quantified in a mature ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) stand in the western Sierra Nevada. Root length totaled 3835.9 m · m –2 of forest floor surface area, with 96% consisting of the fine-root fraction. Total root dry weight and volume were 2230.4 g · m –2 and 5807.4 cm 3 · m –2 of forest floor area, respectively, with 69% of the former and 75% of the latter accounted for by the coarse fraction. Fine roots were most prevalent in the upper 15 cm of the mineral soil profile, and their abundance declined with increasing depth. Coarse roots were most abundant at a depth of 15–30 cm. Ectomycorrhizal counts totaled 26,814 · m –2 of forest floor area, and an overwhelming preponderance was associated with the fine-root fraction. More than three-quarters of mychorrhizae resided in the upper 15 cm of mineral soil, with an overall trend of declining numbers with increasing depth. Roots and mycorrhizae were exceedingly scarce at a depth of 45–60 cm, and neither was found in the organic soil layer above the mineral profile. A necessary step in understanding the ecophysiological role of mycorrhizae in mature forests is to quantify their abundance in such settings, and the results of this study contribute such information for ponderosa pine.     

A new combination and a new variety in Artemisia tridentata

The combination Artemisia tridentata Nutt. ssp. spiciformis (Osterhout) Goodrich & McArthur comb. nov. is made. This high elevation taxon was originally described at the species level and more recently has generally been treated as a form of A. tridentata ssp. vaseyana . The subspecies designation is supported by its parallel nature to the other A. tridentata  subspecies and by its relatively widespread and locally abundant populations. Also, a new variety of A. tridentata ssp. vaseyana is proposed.         

Patterns of macroinvertebrate colonization in an intermittent Rocky Mountain stream in Utah

Colonization of macroinvertebrates in a headwater mountain stream was monitored using basket and Surber samplers. Taxa showed differences in colonization ability based both on dispersal ability and feeding strategy. Collector - gatherer feeding groups that could actively enter the water, i.e., Baetis mayflies, were the first organisms to colonize bare or new substrate. The slowest colonizers were heptageniid mayflies that colonized primarily from upstream migration. All organisms examined increased drifting behavior in response to decreases in discharge.         

Microhabitat affinities of Gambel oak seedlings

Previous work suggested that Gambel oak seedlings are rare in the northern parts of its range in Utah where summer rainfall is relatively low but should be abundant in southern parts of the range where summer rainfall is usually high. Gambel oak grades from a relatively minor component of a ponderosa pine/mixed conifer assemblage in the south to a virtually monotypic formation in the north, where it exists as long-lived clones.   Quadrat analysis in Arizona and New Mexico, within the oak zone, revealed a seedling density ranging from 120 to 1320 per hectare. We found a significant tendency of seedlings to be located on the NE (cool, shady) side of sheltering objects in the environment. Mature ponderosa pine ranged in density from ca 40 to 500 stems per hectare, whereas mature Gambel oak ranged from ca 10 to 20 genets per hectare with ca 1 to 7 ramets per clone. These results support our previous conclusion that Gambel oak in northern Utah probably became established as a minor component of a mixed pine/oak woodland at a time in mid-Holocene when summer rainfall was much higher than today.     

Multiple ectopic limbs in a wild population of Hyla regilla

A wild population of Pacific tree frogs ( Hyla regilla ) in Idaho exhibited a high incidence (22%) of hind limb abnormalities. This situation is discussed with reference to similar occurrences reported for isolated populations of the species in the Pacific Northwest.         

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.     

Helminth parasites of the white-tailed jackrabbit, Lepus townsendi, from northwestern Colorado and southern Wyoming

Helminth parasites of white - tailed jackrabbits, Lepus townsendi , were surveyed from southern Wyoming and northwestern Colorado. A total of eight helminth species were identified, including two species of adult cestodes, Mosgovoyia pectinata and M. varabilis ; three species of larval cestodes, Multiceps serialis , Taenia pisiformis , and Taenis sp. ; and three species of nematodes, Dermatoxys veliger , Passalurus ambiguus , and a filariid, Micipsella brevicauda . In addition, eggs of an unidentified species of Nematodirus were found in pooled fecal samples. The cysticercus larva of Taenia sp. is a species new to science and will be reported elsewhere. Mosgovoyia varabilis and Micipsella brevicauda are new records for the white - tailed jackrabbit.         

Three new records for diatoms from the Great Basin, USA

Three diatom species recently collected from Great Basin localities represent new records of these taxa from this region of western North America. Cocconeis scutellum   Ehr. and Melosira dubia   Kuetz. were collected from a thermal spring in Tooele County, Utah. Nitzschia hustedtiana   Salah was collected from newly flooded marshes at the south end of the Great Salt Lake, Tooele Countv, Utah.