Foliage age as a factor in food utilization by the western spruce budworm, Choristoneura occidentalis

The influence of current year foliage age on food consumption and utilization by the western spruce budworm, Choristoneura occidentalis (Lepidoptera:Tortricidae), was examined. Larvae were fed immature foliage of Douglas-fir ( Pseudotsuga menziesii var. glauca ), Engelmann spruce ( Picea engelmannii ), and corkbark fir ( Abies lasiocarpa var. arizonica ) in June and August of 1981 and Douglas fir in June and July of 1982. All larvae feeding on early season (June) foliage reached maturity. Larvae feeding on middle (July) and late (August) season foliage died before reaching pupation. Relative growth rate and efficiency of conversion of ingested food decreased with foliage age in both the 1981 and 1982 experiments. Relative consumption rate increased with foliage age in the 1981 and decreased in the 1982 experiment.     

Douglas-fir beetle ( Dendroctonus pseudotsugae Hopkins, Coleoptera: Scolytidae) brood production on Douglas-fir defoliated by western spruce budworm ( Choristoneura occidentalis Freeman, Lepidoptera: Tortricidae) in Logan Canyon, Utah

Douglas-fir beetle brood production was studied on Douglas-fir ( Pseudotsuga menziesii [Mirb. ] Franco)trees defoliated by the western spruce budworm between 1983 and 1985. Tallies were made of the number of attacks, total length and number of egg galleries, number of eggs deposited, number of larval tunnels, number of pupal chambers, and number of emerging beetles (per female and per unit area). Data analysis showed no significant differences among the three years studied. The number of emerging beetles per female parent was 0.59, and emergence per 90 cm 2 was 2.32 beetles. Egg, larval, and pupal survivals were 47.5%, 30.0%, and 15.5%, respectively.     

Observations on natural enemies of western spruce budworm ( Choristoneura occidentalis Freeman)(Lepidoptera, Tortricidae) in the Rocky Mountain area

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Three species of predators and parasites were found associated with western spruce budworm ( Choristoneura occidentalis Freeman) (Lepidoptera, Tortricidae) in Larimer Co., Colorado. These were: Ancistrocerus antilope (Panzer) (Hymenoptera, Vespidae), Goniozus gracilicornis (Kieffer) (Hymenoptera, Bethylidae), and Ceromasia auricaudata Townsend (Diptera, Tachinidae). The first two species stored caterpillars in wooden trap nests, while the third was reared from final instar budworms.     

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.     

Effects of dwarf mistletoe on growth and mortality of Douglas-fir in the Southwest

The effects of dwarf mistletoe ( Arceuthobium douglasii ) on growth and mortality of Douglas-fir ( Pseudotsuga menziesii ) were studied on 387 plots in mixed-conifer stands in three national forests in New Mexico and two in Arizona. Analyses of 8,570 trees showed that low infection ratings (dwarf mistletoe classes 1 or 2) had no significant effect on tree growth, but that losses increased markedly as infection severity increased. Average volume growth losses for trees over 10 inches in diameter were: dwarf mistletoe class 3, 10%; class 4, 25%; class 5, 45%; and class 6, 65%. Mortality of Douglas-fir in stands severely infested with dwarf mistletoe was three to four times that of healthy stands. These high losses confirm the need for silvicultural control of Douglas-fir dwarf mistletoe in the Southwest.     

Effects of dwarf mistletoe on spruce in the White Mountains, Arizona

Mortality of spruce in mixed conifer stands moderately to heavily infested with western spruce dwarf mistletoe was two to five times greater than in healthy stands in the White Mountains, Arizona. Ten-year volume growth loss for heavily infected spruce trees ranged from 25% to 40%. Estimates of growth loss for spruce on a stand basis ranged from 10% to 20% in heavily infested stands. Because western spruce dwarf mistletoe is prevalent in the White Mountains and causes increased mortality and reduced growth, its control should be included in management of mixed conifer stands there.     

Effects of prairie dog rodenticides on deer mice in western South Dakota

Mortality of nontarget small mammals was determined after application of three black-tailed prairie dog ( Cynomys ludovicianus ) rodenticide treatments (prebaited zinc phosphide, prebaited strychnine, and strychnine alone) in western South Dakota. Immediate (September 1983) and long-term (September 1983 through August 1984) impacts on deer mouse ( Peromyscus maniculatus ) relative densities were evaluated and the three rodenticide treatments were compared for efficacy. The three treatments had no significant (α < .10) immediate impacts on deer mouse relative densities, although zinc phosphide did lower them; that impact was not, however, long term. Long-term impacts of the two strychnine treatments were variable, with an increase in deer mouse densities with the strychnine only treatment. Overall, comparisons among the three treatments indicated that zinc phosphide was more effective than either strychnine treatment in reducing deer mouse densities.     

Effects of 2,4-D on a Populus tremuloides community in the western United States-22 years after treatment

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Quaking aspen ( Populus tremuloides Michx.) stands were accidentally sprayed with 2,4-D in a sagebrush control program in western Wyoming in 1958. We visited the site during the summer of 1981 to evaluate the long-term effect on the aspen trees and the associated vegetation. Initially, some observers believed that the aspen had been &ldquo;destroyed.&rdquo; Subsequent data indicate just the opposite&mdash;aspen stocking appeared to have been improved by the treatment. On two of the sampled clones, 22 years after spraying, there were approximately 17,000 more suckers/ha on the sprayed than on the unsprayed plots. These are adequate numbers to restock the site to pretreatment densities. Although undergrowth vegetation appeared to be changed as a result of the treatment, this cannot be attributed solely to the herbicide because heavy grazing, mostly by domestic livestock, has occurred on the grazing allotment. A similarity index was calculated between sprayed and unsprayed portions of the same aspen clones. Forbs were still less on the sprayed areas, whereas grasses were similar on the sprayed and unsprayed areas. Spraying apparently does not have as adverse an effect on aspen communities as some conservationists originally thought. &nbsp;&nbsp;     

Influence of precipitation and temperature on ring, annual branch increment, and needle growth of White Fir and Douglas-fir in central Utah

The study evaluates growth variations in mixed stands of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) and White Fir ( Abies concolor Hoopes) from the Bighorn Ranch in northern Sanpete County, Utah. The study area lies 26 km southwest of Thistle, Utah. Tree-ring width, annual branch growth and needle length for the period 1970&ndash;1976 were obtained from Douglas-Fir and White Fir individuals distributed along an altitudinal and moisture gradient. Elevation ranged from 2257 m to 2500 m above sea level. Temperature and precipitation are shown to exert a significant influence on needle and annual branch growth and width of the annual rings. It was found that multiple correlation coefficients were always larger than the simple correlation coefficients. This suggests that the trees are responding to both temperature and precipitation. Annual branch growth is shown to be positively correlated with ring width and needle length. The influence of precipitation on growth is synchronized with 1 October&ndash;1 June precipitation. Best growth occurs in cool, moist years and at lower elevations.     

Depletion of soil moisture by two cold-desert bunchgrasses and effects on photoshythetic performance

This study compared the abilities of two cool-season bunchgrasses to extract moisture from a drying soil and compared photosynthetic and stomatal responses of the two species as soil moisture supplies were depleted. When grown in 49-L pots in a greenhouse, Leymus cinereus extracted more water from the soil and maintained higher gas exchange rates to lower absolute amounts of soil water than did Agropyron desertorum . The soil water content at the lower limit of extraction was 10.3% for L. cinereus and 13.3% for A. desertorum . When soil moisture was expressed as extractable soil water, there was little difference between the species in pattern of water use. Both species maintained high stomatal conductances (g w ) and photosynthetic rates (A) until extractable soil moisture was reduced to about 15%. For field-grown plants under severe water stress, A was higher in L. cinereus than in A. desertorum at comparable leaf water potentials. The relationship between A and g w was similar for the two species; higher A in L. cinereus was a consequence of higher g w . Thus, higher A in L. cinereus is achieved through some sacrifice of water-use efficiency.     

Seasonal abundance and life cycle of Archaeomysis articulata (Crustacea: Mysidacea) on a sandy beach of western Hokkaido,Japan

Abundance and life cycle of the sandy beach mysid Archaeomysis articulata Hanamura were investigated based on seasonal collections over 2 years in the surf-swept intertidal zone of an open sandy beach in Ishikari Bay, western Hokkaido, Japan. The number of mysids in the intertidal zone increased from winter to spring, reaching its maximum in summer to autumn (average >2500 ind. m^-2), and decreased considerably towards the end of the year. The abundance was maintained at a minimal level (<200 ind. m^-2) throughout the winter. The breeding season was March to November, during which the liberation of young was most intensive from late April to mid-October. Three alternate generations, including overwintering, spring and summer generations, were suggested from field observations. Archaeomysis articulata is primarily iteroparous; only a restricted number of breeding females could produce more than two broods. The life span was estimated to be 7–9 months for the overwintering generation and 2.5–3.5 months for the spring–summer generations. The sex ratio fluctuated at samplings, with a tendency toward female dominance (overall mean=54%). The number of embryos carried by a single female ranged from 16 to 94, tending to increase with increasing size of females. The size of egg-like embryos varied seasonally from 0.45 to 0.54mm, being largest in spring and smallest in summer, with no correlation to the length of females; water temperature is considered an important factor in regulating the size of eggs. The embryonic development time was estimated to be 1.5 months for the spring generation (water temperature 5–10°C), and much shorter than this for the summer and overwintering generations. The mortality rate during embryonic development was estimated to be 7–18%.     

Effects of long-term livestock grazing and habitat on understory vegetation

The herbaceous understory stratum contains most of the plant diversity in ponderosa pine ( Pinus ponderosa P. & C. Lawson var. scopulorum Engelm.) forests of the American Southwest and provides critical food and habitat for many wildlife species. During the last century, this stratum has been affected by livestock grazing and by increased dominance of overstory trees. We sampled a unique grazing exclosure to examine the relative importance of long-term livestock grazing (grazed or ungrazed) and habitat (park or tree) on the understory community. We sampled 3 plots of 192 contiguous quadrats (each quadrat 0.5 m 2 ) in each of the 4 treatment combinations, for a total of 2304 quadrats. Species-area curves were generated by aggregating quadrats into nonoverlapping areas at grain sizes of 0.5 to 576 m 2 . The effects of habitat and grazing on species density were evident at very different scales. Species density was higher in park than tree plots at scales &le;32 m 2 but did not differ between habitats at larger scales. Species density differed minimally between grazed and ungrazed treatments at small grains, but grazed plots contained more species than ungrazed plots at larger grains. Grazing treatments differed at smaller grains (to 4&ndash;8 m 2 ) than did habitats (to 32 m 2 ), with respect to density of native species and graminoids. Grazed plots had more exotic species than ungrazed plots at all grain sizes, though few exotics were present. Twenty-two species were identified as indicator species associated with habitats and/or grazing treatments. Evaluations of plant community response to treatments would be improved by accounting for the grain at which data have been collected and analyzed and by identifying indicator species associated with various treatments. These data would enable more-informed conservation and management decisions.     

Larval release rhythms of four species (family Grapsidae and Ocypodidae) of intertidal crabs on a coastal flat in western central Taiwan

Larval release rhythms of four crab species, Parasesarma tripectinis (Shen, 1940), Perisesarma bidens (De Haan, 1835), Hemigrapsus penicillatus (De Haan, 1835) and Baruna sinensis Tan and Huang, 1995, were studied in two different intertidal zones on a coastal flat. Of these, P. bidens is the only species that migrates between high and lower intertidal zones. In general, larval release patterns of these intertidal crabs are not too different from those of intertidal crabs living in other geographical regions, which often release larvae around new or full moons and nocturnal high tides. However, differences were apparent when compared with previous studies in that: (1) peak larval release periods of P. bidens occurred during submaximum tidal amplitudes, (2) a good portion of B. sinensis released their larvae during neap tides, (3) all four species released their larvae during both daytime and nighttime high tides although the percentage varied among these species, (4) three species released their larvae within 1 h after the time of high slack tide, but larval release of B. sinensis peaked between 1 and 2h after the time of maximum tidal height. Larval release pattern of Perisesarma bidens suggests that locomotory behaviour of high intertidal crabs may influence their larval release rhythms. Antipredatory adaptation may explain larval release rhythms of the four species examined in the present study. Larvae of Parasesarma tripectinis, P. bidens and Hemigrapsus penicillatus are more vulnerable to planktivorous fish predation and tend to release their larvae at nocturnal high tides during maximum tidal amplitudes. On the other hand, larvae of Baruna sinensis may be better adapted against planktivorous fish predation by having yellow-green colour. The timing of larval release of this species occurred throughout the lunar cycle and often at daytime 1-2 h after the time of high slack tide.     

Effects of burning and clipping on five bunchgrasses in eastern Oregon

Response of five perennial bunchgrasses following clipping and burning was evaluated in eastern Oregon. Burned plants were compared with clipped plants on several dates from spring to fall with respect to mortality and change in basal area. Basal area was generally reduced for one year but did not change the second year after defoliation. Treatments rarely affected yield. Burning in May was most detrimental, reducing basal area of all species. Fall clipping was least harmful, producing little or no change in basal area. Plant mortality was significant only for burned Thurber needlegrass ( Stipa thurberiana ).     

Effects of logging on habitat quality and feeding patterns of Abert squirrels

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} In 1973 a timber harvest of ponderosa pine ( Pinus ponderosa ) was conducted in an area southeast of Monticello, Utah, that is inhabited by Abert squirrels ( Sciurus aberti ). Abert squirrel dietary habits, foraging patterns, and population densities were compared in the timber harvest area and in an adjacent nonharvested area. Squirrel feeding patterns and preferences were visually determined by physical evidence of past feeding. Live-trapping and field-marking of animals were used to determine population density and trends in the two areas. Squirrels fed in only 26.3% of sampled plots on the timber harvest areas, while 42.7% of the uncut area plots showed use (P 50 acres) by clear-cut methods commonly employed by management agencies.     

Effects of convict cichlids on growth and recruitment of White River springfish

Observations of changes in population density of native White River springfish ( Crenichthys baileyi ) in Pahranagat Valley led to the following hypothesis: introduced convict cichlids ( Cichlasoma nigrofasciatum ) cause reduced growth and recruitment; cover reduces the magnitude of the effect. The hypothesis was tested by establishing sympatric and allopatric groups of the two species in experimental aquaria with and without cover. Change in volume (= mass) and length of the two species over a three-month period in spring 1986 and 1987 was measured and analyzed using 2 × 2 factorial analyses. Convict cichlids caused reduced growth and eliminated recruitment of springfish under the experimental conditions. Cover did not influence growth but positively affected recruitment of springfish in allopatry. It is likely that a portion of the reduced springfish population densities in nature can be attributed to adverse effects from introduced cichlids.     

Coexistence of two species of sucker, Catostomus , in Sagehen Creek, California, and notes on their status in the western Lahontan Basin

The observed distribution and relative abundance of two morphologically similar species of sucker, Catostomus , have shifted dramatically over the past four decades in Sagehen Creek and nearby streams in eastern California. The mountain sucker, C. platyrhynchus , formerly abundant and more numerous than the Tahoe sucker, C. tahoensis , has become relatively rare and during this study was consistently less abundant than the Tahoe sucker at all eastern California sites in 1983. Similar shifts in abundance were not seen at the three Nevada sites. Behavioral observations and data on spatial and temporal patterns of habitat use, collected in Sagehen Creek between May and September 1982 and 1983 using a snorkel survey method, indicate nearly complete overlap between mountain and Tahoe sucker habitat use and an absence of any agonistic behavioral interaction between species. The decline of the mountain sucker in these areas is likely the result of an interaction of loss of habitat due to reservoir construction and destructive management practices. These changes may have led to the elimination of isolating mechanisms between the two species and may be increasing the opportunity for introgressive hybridization.