Sample records for process hemlock semiconductor
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-04-10
... Status, Hemlock Semiconductor Corporation, (Polysilicon), Hemlock, Michigan Pursuant to its authority... polysilicon manufacturing facility of Hemlock Semiconductor Corporation, located in Hemlock, Michigan (FTZ... manufacturing of polysilicon at the facility of Hemlock Semiconductor Corporation, located in Hemlock, Michigan...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-12
... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [Docket 61-2011] Foreign-Trade Zone 140--Flint, Michigan; Application for Subzone; Hemlock Semiconductor Corporation (Polysilicon); Hemlock, MI An... Hemlock Semiconductor Corporation (HSC), located in Hemlock, Michigan. The application was submitted...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-09
... 140 and 78; Applications for Subzone Authority; Dow Corning Corporation, Hemlock Semiconductor Corporation and Hemlock Semiconductor, L.L.C.; Extension of Comment Periods The comment periods for the...- 63283, October 12, 2011), at the Hemlock Semiconductor Corporation facility in Hemlock, Michigan (76 FR...
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-05-23
... 140 and 78, Applications for Subzone Authority, Dow Corning Corporation, Hemlock Semiconductor Corporation, and Hemlock Semiconductor, L.L.C.; Reopening of Comment Periods The comment periods for the...- 63283, 10/12/2011), at the Hemlock Semiconductor Corporation facility in Hemlock, Michigan (76 FR 63282...
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-04-09
... 140 and 78, Applications for Subzone Authority Dow Corning Corporation, Hemlock Semiconductor Corporation, and Hemlock Semiconductor, L.L.C.; Reopening of Rebuttal Periods The rebuttal periods for the...- 63283, 10/12/2011), at the Hemlock Semiconductor Corporation facility in Hemlock, Michigan (76 FR 63282...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-28
...-Trade Zones 140 and 78 Applications for Subzone Authority Dow Corning Corporation, Hemlock Semiconductor Corporation and Hemlock Semiconductor, L.L.C.; Notice of Public Hearing and Extension of Comment Period A... facility in Midland, Michigan (76 FR 63282-63283, 10/12/2011), the Hemlock Semiconductor Corporation...
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-15
... identified by name by the International Trade Commission as a member of a domestic industry in an... date 82,509 Hemlock Semiconductor Corporation, Hemlock, MI......... February 27, 2012. Dow Corning Corporation, Adecco, Qualified Staffing, SimplexGrennell LP. 82,509A Hemlock Semiconductor LLC, Dow...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-12
... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [Docket 62-2011] Foreign-Trade Zone 78--Nashville, TN, Application for Subzone, Hemlock Semiconductor, L.L.C. (Polysilicon); Clarksville, TN An... polysilicon manufacturing facility of [[Page 63282
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Economics of polysilicon processes
NASA Technical Reports Server (NTRS)
Yaws, C. L.; Li, K. Y.; Chou, S. M.
1986-01-01
Techniques are being developed to provide lower cost polysilicon material for solar cells. Existing technology which normally provides semiconductor industry polysilicon material is undergoing changes and also being used to provide polysilicon material for solar cells. Economics of new and existing technologies are presented for producing polysilicon. The economics are primarily based on the preliminary process design of a plant producing 1,000 metric tons/year of silicon. The polysilicon processes include: Siemen's process (hydrogen reduction of trichlorosilane); Union Carbide process (silane decomposition); and Hemlock Semiconductor process (hydrogen reduction of dichlorosilane). The economics include cost estimates of capital investment and product cost to produce polysilicon via the technology. Sensitivity analysis results are also presented to disclose the effect of major paramentes such as utilities, labor, raw materials and capital investment.
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A review of the silicon material task
NASA Technical Reports Server (NTRS)
Lutwack, R.
1984-01-01
The Silicon Material Task of the Flat-Plate Solar Array Project was assigned the objective of developing the technology for low-cost processes for producing polysilicon suitable for terrestrial solar-cell applications. The Task program comprised sections for process developments for semiconductor-grade and solar-cell-grade products. To provide information for deciding upon process designs, extensive investigations of the effects of impurities on material properties and the performance of cells were conducted. The silane process of the Union Carbide Corporation was carried through several stages of technical and engineering development; a pilot plant was the culmination of this effort. The work to establish silane fluidized-bed technology for a low-cost process is continuing. The advantages of the use of dichlorosilane is a siemens-type were shown by Hemlock Semiconductor Corporation. The development of other processes is described.
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A review of the silicon material task
NASA Astrophysics Data System (ADS)
Lutwack, R.
1984-02-01
The Silicon Material Task of the Flat-Plate Solar Array Project was assigned the objective of developing the technology for low-cost processes for producing polysilicon suitable for terrestrial solar-cell applications. The Task program comprised sections for process developments for semiconductor-grade and solar-cell-grade products. To provide information for deciding upon process designs, extensive investigations of the effects of impurities on material properties and the performance of cells were conducted. The silane process of the Union Carbide Corporation was carried through several stages of technical and engineering development; a pilot plant was the culmination of this effort. The work to establish silane fluidized-bed technology for a low-cost process is continuing. The advantages of the use of dichlorosilane is a siemens-type were shown by Hemlock Semiconductor Corporation. The development of other processes is described.
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Silicon production process evaluations
NASA Technical Reports Server (NTRS)
1981-01-01
Chemical engineering analysis of the HSC process (Hemlock Semiconductor Corporation) for producing silicon from dichlorosilane in a 1,000 MT/yr plant was continued. Progress and status for the chemical engineering analysis of the HSC process are reported for the primary process design engineering activities: base case conditions (85%), reaction chemistry (85%), process flow diagram (60%), material balance (60%), energy balance (30%), property data (30%), equipment design (20%) and major equipment list (10%). Engineering design of the initial distillation column (D-01, stripper column) in the process was initiated. The function of the distillation column is to remove volatile gases (such as hydrogen and nitrogen) which are dissolved in liquid chlorosilanes. Initial specifications and results for the distillation column design are reported including the variation of tray requirements (equilibrium stages) with reflux ratio for the distillation.
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Effects of hemlock mortality on streams in the southern Appalachian mountains
J.R. Webster; K. Morkeski; C.A. Wojculewski; B.R. Niederlehner; E.F. Benfield; K.J. Elliott
2012-01-01
The death of eastern hemlock (Tsuga canadensis) trees in response to infestation by the introduced hemlock woolly adelgid (Adelges tsugae)may affect ecosystem processes and structure of streams. Prior to hemlock mortality,we documented the condition so feight small streams and their associated riparian forests within the...
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Chelcy R. Ford; James M. Vose
2007-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr.) is one of the principal riparian and cove canopy species in the southern Appalachian Mountains. Throughout its range, eastern hemlock is facing potential widespread mortality from the hemlock woolly adelgid (HWA). If HWA-induced eastern hemlock mortality alters hydrologic function, land managers...
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-04-09
... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [Order No. 1895] Grant of Authority for Subzone... foreign commerce, and for other purposes,'' and authorizes the Foreign-Trade Zones Board to grant to..., and when the activity results in a significant public benefit and is in the public interest; Whereas...
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Natural regeneration of eastern hemlock: a review
Daniel L. Goerlich; Ralph D. Nyland
2000-01-01
Successful regeneration of eastern hemlock involves a complex biophysical process that commonly spans many years. Critical factors include a reliable source of seed, a suitable seedbed, a partially shaded environment, and several years of favorable moisture. Surface scarification appears critical as a means of site preparation. Even then, young hemlocks grow slowly,...
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Vegetation and invertebrate community response to eastern hemlock decline in southern new England
Laura L. Ingwell; Mailea Miller-Pierce; R. Talbot Trotter; Evan L. Preisser
2012-01-01
The introduction of Adelges tsugae (Hemlock Woolly Adelgid [HWA]) to the eastern United States has had a devastating impact on Tsuga canadensis (Eastern Hemlock). Although much research has been done to assess HWA impacts on ecosystem processes and vegetation structure, few researchers have examined community-level changes in...
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Eccentricity and fluting in young–growth western hemlock in Oregon.
Ryan Singleton; Dean S. DeBell; David D. Marshall; Barbara L. Gartner
2004-01-01
Stem irregularities can influence estimates of tree and stand attributes, efficiency of manufacturing processes, and quality of wood products. Eccentricity and fluting were characterized in young, managed western hemlock stands in the Oregon Coast Range. Sixty-one trees were selected from pure western hemlock stands across a range of age, site, and densities. The trees...
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Spatial pulses of water inputs in deciduous and hemlock forest stands
NASA Astrophysics Data System (ADS)
Guswa, A. J.; Mussehl, M.; Pecht, A.; Spence, C.
2010-12-01
Trees intercept and redistribute precipitation in time and space. While spatial patterns of throughfall are challenging to link to plant and canopy characteristics, many studies have shown that the spatial patterns persist through time. This persistence leads to wet and dry spots under the trees, creating spatial pulses of moisture that can affect infiltration, transpiration, and biogeochemical processes. In the northeast, the invasive hemlock woolly adelgid poses a significant threat to eastern hemlock (Tsuga canadensis), and replacement of hemlock forests by other species, such as birch, maple, and oak, has the potential to alter throughfall patterns and hydrologic processes. During the summers of 2009 and 2010, we measured throughfall in both hemlock and deciduous plots to assess its spatial distribution and temporal persistence. From 3 June to 25 July 2009, we measured throughfall in one hemlock and one deciduous plot over fourteen events with rainfall totaling 311 mm. From 8 June through 28 July 2010, we measured throughfall in the same two plots plus an additional hemlock stand and a young black birch stand, and rainfall totaled 148 mm over eight events. Averaged over space and time, throughfall was 81% of open precipitation in the hemlock stands, 88% in the mixed deciduous stand, and 100% in the young black birch stand. On an event basis, spatial coefficients of variation are similar among the stands and range from 11% to 49% for rain events greater than 5 mm. With the exception of very light events, coefficients of variation are insensitive to precipitation amount. Spatial patterns of throughfall persist through time, and seasonal coefficients of variation range from 13% to 33%. All stands indicate localized concentrations of water inputs, and there were individual collectors in the deciduous stands that regularly received more than twice the stand-average throughfall.
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Brantley, Steven; Ford, Chelcy R; Vose, James M
2013-06-01
Infestation of eastern hemlock (Tsuga canadensis (L.) Carr.) with hemlock woolly adelgid (HWA, Adelges tsugae) has caused widespread mortality of this key canopy species throughout much of the southern Appalachian Mountains in the past decade. Because eastern hemlock is heavily concentrated in riparian habitats, maintains a dense canopy, and has an evergreen leaf habit, its loss is expected to have a major impact on forest processes, including transpiration (E(t)). Our goal was to estimate changes in stand-level E(t) since HWA infestation, and predict future effects of forest regeneration on forest E(t) in declining eastern hemlock stands where hemlock represented 50-60% of forest basal area. We used a combination of community surveys, sap flux measurements, and empirical models relating sap flux-scaled leaf-level transpiration (E(L)) to climate to estimate the change in E(t) after hemlock mortality and forecast how forest E(t) will change in the future in response to eastern hemlock loss. From 2004 to 2011, eastern hemlock mortality reduced annual forest E(t) by 22% and reduced winter E(t) by 74%. As hemlock mortality increased, growth of deciduous tree species--especially sweet birch (Betula lenta L.), red maple (Acer rubrum L.), yellow poplar (Liriodendron tulipifera L.), and the evergreen understory shrub rosebay rhododendron (Rhododendron maximum L.)--also increased, and these species will probably dominate post-hemlock riparian forests. All of these species have higher daytime E(L) rates than hemlock, and replacement of hemlock with species that have less conservative transpiration rates will result in rapid recovery of annual stand E(t). Further, we predict that annual stand E(t) will eventually surpass E(t) levels observed before hemlock was infested with HWA. This long-term increase in forest E(t) may eventually reduce stream discharge, especially during the growing season. However, the dominance of deciduous species in the canopy will result in a permanent reduction in winter E(t) and possible increase in winter stream discharge. The effects of hemlock die-off and replacement with deciduous species will have a significant impact on the hydrologic flux of forest transpiration, especially in winter. These results highlight the impact that invasive species can have on landscape-level ecosystem fluxes.
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Hydraulic responses to environmental perturbations in Tsuga canadensis and Betula lenta.
Daley, Michael J; Phillips, Nathan G; Pettijohn, Justin C; Hadley, Julian
2008-09-01
Eastern hemlock (Tsuga canadensis (L). Carr.) is a late-successional species found across the northeastern United States of America that is currently threatened by the exotic pest, hemlock woolly adelgid (Adelges tsugae Annand). Because whole-tree physiological characteristics may scale to influence ecosystem processes, we considered whole-tree hydraulic controls in eastern hemlock and the replacement species black birch (Betula lenta L.). Through a series of misting perturbations, whole-tree resistances (R), capacitances (C) and time constants (tau) were determined from time series sap flux data in eastern hemlock and black birch. Black birch trees responded more rapidly to environmental perturbations than eastern hemlock. Utilizing the step function after applied treatments, whole-tree tau ranged between 9.4 and 24.8 min in eastern hemlock trees compared with 5.9 to 10.5 min in black birch. Species was not a significant predictor of R or C when controlling for tree size. In both species, R decreased with sapwood area and C increased. Our tau results indicate that the loss and replacement of eastern hemlock by black birch will decrease the lag between transpiration and absorption of water from the soil and potentially alter the diurnal pattern of carbon and water uptake.
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Silicon production process evaluations
NASA Technical Reports Server (NTRS)
1982-01-01
Chemical engineering analysis was continued for the HSC process (Hemlock Semiconductor Corporation) in which solar cell silicon is produced in a 1,000 MT/yr plant. Progress and status are reported for the primary engineering activities involved in the preliminary process engineering design of the plant base case conditions (96%), reaction chemistry (96%), process flow diagram (85%), material balance (85%), energy balance (60%), property data (60%), equipment design (40%), major equipment list (30%) and labor requirements (10%). Engineering design of the second distillation column (D-02, TCS column) in the process was completed. The design is based on a 97% recovery of the light key (TCS, trichlorosilane) in the distillate and a 97% recovery of the heavy key (TET, silicon tetrachloride) in the bottoms. At a reflux ratio of 2, the specified recovery of TCS and TET is achieved with 20 trays (equilibrium stages, N=20). Respective feed tray locations are 9, 12 and 15 (NF sub 1 = 9, NF sub 2 = 12,, and NF sub 3 = 15). A total condenser is used for the distillation which is conducted at a pressure of 90 psia.
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Mary Ann Fajvan; Petra Bohall Wood
2010-01-01
Eastern hemlock (Tsuga canadensis [L.]) is the most shade-tolerant and long-lived tree species in eastern North America. The hemlock woolly adelgid (Adelges tsugae) (HWA), is a nonnative invasive insect that feeds on eastern hemlock and Carolina hemlock (Tsuga caroliniana Engelm.). HWA currently is established in...
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Early regeneration following the presalvage cutting of hemlock from hemlock-dominated stands
Robert T. Brooks
2004-01-01
Live overstory hemlock were cut from three hemlock hardwood stands on the watershed of the Barkhamsted Reservoir in northwestern Connecticut. The presalvage cuttings occurred during a hemlock looper outbreak and in anticipation of hemlock woolly adelgid (HWA) infestation. All merchantable and accessible hemlock trees were cut, as were a smaller quantity of other...
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William C. Fischer
1981-01-01
Four series of color photographs show different levels of downed woody material resulting from natural processes in four forest cover types in Montana. Each photo is supplemented by fuel inventory data and potential fire behavior ratings.
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Tuula Kantola; Päivi Lyytikäinen-Saarenmaa; Robert N. Coulson; Sheryl Strauch; Maria D. Tchakerian; Markus Holopainen; Hannu Saarenmaa; Douglas A. Streett
2014-01-01
Hemlock woolly adelgid (Adelges tsugae Annand, HWA) outbreaks are posing a major threat to eastern hemlock (Tsuga canadensis L. Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) forest landscapes in the eastern USA. As foundation species, hemlocks play a variety of functional roles in forest landscapes....
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Biology and control of hemlock woolly adelgid
Nathan P. Havill; Ligia C. Vieira; Scott M. Salom
2014-01-01
This publication is a substantial revision of FHTET 2001-03, Hemlock Woolly Adelgid, which was published in 2001. This publication contains information on the native range of hemlock and range of hemlock woolly adelgid, the importance of hemlocks in eastern forest ecosystems, and on hosts, life cycle, control, and population trends of the hemlock woolly adelgid.
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Katherine L. Martin; P. Charles Goebel
2011-01-01
Hemlock woolly adelgid (HWA) is an invasive insect causing widespread mortality in eastern hemlock (Tsuga canadensis [L.] Carr; hereafter "hemlock") throughout eastern forests. Hemlock is a foundation species, regulating ecosystem structure and function (e.g., microclimate, nutrient cycling). Across the central and southern Appalachians,...
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Assessment of landscape correlates of eastern hemlock decline due to hemlock woolly adelgid
John Young; Craig Snyder; James Akerson; Gary Hunt
2000-01-01
Eastern hemlock (Tsuga canadensis) is in decline throughout its range in the eastern US due to infestation by an exotic insect pest, the hemlock woolly adelgid (Adelges tsugae). In Shenandoah National Park, the hemlock woolly adelgid (HWA) rapidly killed many stands of hemlock after first appearing in the late-1980's, while...
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Characterization of wood strands from young, small-diameter Douglas-fir and western hemlock trees
Vikram Yadama; Eini C. Lowell; Christopher E. Langum
2012-01-01
Tensile properties of strands processed from small-diameter Douglas-fir and western hemlock trees grown on the Washington coast were analyzed and effects of location within the tree on properties was examined. Reduction factors for strand properties relative to small, clear solid wood specimen properties were determined by correlating strand properties to previously...
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Fajvan, Mary Ann; Wood, Petra Bohall
2010-01-01
Eastern hemlock (Tsuga canadensis [L.]) is the most shade-tolerant and long-lived tree species in eastern North America. The hemlock woolly adelgid (Adelges tsugae) (HWA), is a nonnative invasive insect that feeds on eastern hemlock and Carolina hemlock (Tsuga caroliniana Engelm.). HWA currently is established in 17 eastern states and is causing tree decline and wide-ranging tree mortality. Our data from West Virginia and Pennsylvania suggest that hemlock crown vigor (a ranking of amount of live crown) relates to a predictable pattern of hemlock vulnerability at light and moderate levels of HWA infestation. We found that crown variables, such as live crown ratio and crown density and transparency, are accurate predictors of hemlock decline; more vigorous trees appear to be less vulnerable to HWA. Thus, silvicultural thinning treatments may be a means for reducing stand densities and increasing crown vigor in colder areas where climate may slow HWA spread.
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Sarah Z. Jonas; Weimin Xi; John D. Waldron; Robert N. Coulson
2012-01-01
We present a synthesis of current knowledge and information of hemlock woolly adelgid (HWA, Adelges tsugae Annand) impact on hemlock forests and conceptual framework of restoring damaged hemlock stands by HWA infestation. Native to Asia, HWA has been thriving in the eastern United States since the early 1950s and has become a serious pathological agent of both eastern...
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Ross, R.M.; Bennett, R.M.; Snyder, C.D.; Young, J.A.; Smith, D.R.; Lemarie, D.P.
2003-01-01
Hemlock (Tsuga canadensis) forest of the eastern U.S. are in decline due to invasion by the exotic insect hemlock woolly adelgid (Adelges tsugae). Aquatic biodiversity in hemlock ecosystems has not been documented; thus the true impact of the infestation cannot be assessed. We compared ichthyofaunal assemblages and trophic structure of streams draining hemlock and hardwood forests by sampling first- and second-order streams draining 14 paired hemlock and hardwood stands during base flows in July 1997 at the Delaware Water Gap National Recreation Area of Pennsylvania and New Jersey. Over 1400 fish of 15 species and 7 families were collected, but hemlock and hardwood streams individually harbored only one to four species. Brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) were two to three times as prevalent in hemlock than hardwood streams. Insectivorous fishes occurred in significantly higher proportion in streams of hardwood (0.90) than hemlock (0.46) stands, while piscivores occurred more often in hemlock (0.85) than hardwood (0.54) stands. Functional (trophic) diversity of fishes in hemlock and second-order streams was numerically greater than that of hardwood and first-order streams. Species composition also differed by stream order and terrain type. Biodiversity is threatened at several levels within hemlock ecosystems at risk to the hemlock woolly adelgid in eastern U.S. forests.
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Hemlock Woolly Adelgid (Pest Alert)
USDA Forest Service
2005-01-01
Native to Asia, the hemlock woolly adelgid (Adelges tsugae) is a small, aphidlike insect that threatens the health and sustainability of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) in the Eastern United States. Hemlock woolly adelgid was fi rst reported in the Eastern United...
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April E. Nuckolls; Nina Wurzburger; Chelcy R. Ford; Ronald L. Hendrick; James M. Vose; Brian D. Kloeppel
2008-01-01
The recent infestation of southern Appalachian eastern hemlock stands by hemlock woolly adelgid (HWA) is expected to have dramatic and lasting effects on forest structure and function. We studied the short-term changes to the carbon cycle in a mixed stand of hemlock and hardwoods, where hemlock was declining due to either girdling or HWA infestation. We expected that...
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Hadley, Julian L; Kuzeja, Paul S; Daley, Michael J; Phillips, Nathan G; Mulcahy, Thomas; Singh, Safina
2008-04-01
Water use and carbon exchange of a red oak-dominated (Quercus rubra L.) forest and an eastern hemlock-dominated (Tsuga canadensis L.) forest, each located within the Harvard Forest in north-central Massachusetts, were measured for 2 years by the eddy flux method. Water use by the red oak forest reached 4 mm day(-1), compared to a maximum of 2 mm day(-1) by the eastern hemlock forest. Maximal carbon (C) uptake rate was also higher in the red oak forest than in the eastern hemlock forest (about 25 versus 15 micromol m(-2) s(-1)). Sap flux measurements indicated that transpiration of red oak, and also of black birch (Betula lenta L.), which frequently replaces eastern hemlock killed by hemlock woolly adelgid (Adelges tsugae Annand.), were almost twice that of eastern hemlock. Despite the difference between species in maximum summertime C assimilation rate, annual C storage of the eastern hemlock forest almost equaled that of the red oak forest because of net C uptake by eastern hemlock during unusually warm fall and spring weather, and a near-zero C balance during the winter. Thus, the effect on C storage of replacing eastern hemlock forest with a forest dominated by deciduous species is unclear. Carbon storage by eastern hemlock forests during fall, winter and spring is likely to increase in the event of climate warming, although this may be offset by C loss during hotter summers. Our results indicate that, although forest water use will decrease immediately following eastern hemlock mortality due to the hemlock woolly adelgid, the replacement of eastern hemlock by deciduous species such as red oak will likely increase summertime water use over current rates in areas where hemlock is a major forest species.
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Post release recovery of hemlock woolly adelgid predators in the North Georgia mountains.
C.E. Jones; Nathan P. Havill; James Hanula; S.K. Braman
2014-01-01
Eastern hemlock, Tsuga Canadensis (L.) Carriere, and Carolina hemlock, Tsuga caroliniana Engelmann, provide unique habitat that is threatended by the invasive hemlock woolly adelgid, Adelges tsugae Annand, which arrived in Georgia in 2003. In an attempt to conserve a portion of the mature hemlocks in north...
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Andrew G. Birt; Yu Zeng; Maria D. Tchakerian; Robert N. Coulson; Charles W. Lafon; David M. Cairns; John Waldron; Weimin Xi; Szu-Hung Chen; Douglas Streett
2014-01-01
Eastern hemlock (Tsuga canadensis Carriére) and the Carolina hemlock (Tsuga caroliniana Engelmann) are ecologically important tree species in eastern North America forests that are currently threatened by the hemlock woolly adelgid (HWA, Adelges tsugae Annand, Hemiptera: Adelgidae). HWA has spread rapidly from...
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The effect of hemlock woolly adelgid infestation on water relations of Carolina and eastern hemlock
Laura Rivera; JC Domec; John Frampton; Fred Hain; John King; Ben Smith
2012-01-01
In North America, hemlock woolly adelgid (HWA; Adelges tsugae) is an exotic insect pest from Asia that is causing rapid decline of native eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) populations. The exact physiological mechanisms that cause tree decline and...
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James Rentch; Mary Ann Fajvan; Richard Evans; Brad Onken
2008-01-01
This study examined the relationship between eastern hemlock (Tsuga canadensis (L.) Carr.) crown condition and changes in radial growth associated with infestation by hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae). Tree-ring chronologies of eastern hemlock were used to develop a binomial decline index based on...
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Vegetation composition and structure in two hemlock stands threatened by the hemlock woolly adelgid
John J. Battles; Natalie Cleavitt; Timothy J. Fahey; Richard A. Evans
2000-01-01
We quantified the vegetation composition and structure of two hemlock (Tsuga canadensis) ravines in the Delaware Water Gap National Recreation Area threatened by the hemlock woolly adelgid (Adelges tsugae). Hemlock accounted for more than 50% of the canopy basal area (ravine mean = 52.3 m² ha-1) and...
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Robert M. Jetton; Albert E. Mayfield; Zaidee L. Powers
2014-01-01
The hemlock woolly adelgid Adelges tsugae Annand (Hemiptera: Adelgidae), is a non-native invasive pest that has caused widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr. (Pinales: Pinaceae)) and Carolina hemlock (T. caroliniana Engelm.) in the eastern United States. Our preliminary...
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Kimberly F. Wallin; Tanya M. Latty; Darrell W. Ross
2011-01-01
We studied the adult ambulatory response of the predator, Laricobius nigrinus Fender (Coleoptera: Derodontidae), to odors from its prey, Adelges tsugae Annand, the hemlock woolly adelgid, and foliage of hemlock woolly adelgid, host hemlocks (Tsuga spp.), and other conifers. Both the predator and hemlock woolly...
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Mark McClure
2002-01-01
The elongate hemlock scale, Fiorinia externa Ferris, native to Japan, is a pest of eastern hemlock, Tsuga canadensis, and Carolina hemlock, T. caroliniana, in the Eastern United States. It has been found in the District of Columbia and in nine states from Virginia to southern New England and west to Ohio. F. externa attacks the lower surface of the hemlock needle,...
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Zaidee Powers; Albert Mayfield; John Frampton; Robert Jetton
2015-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive forest pest in eastern North America that has caused significant decline and mortality in populations of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.). The breeding of adelgid-resistant genotypes for...
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Seasonality and partitioning of root allocation to rhizosphere soils in a midlatitude forest
Abramoff, Rose Z.; Finzi, Adrien C.
2016-11-09
Root growth, respiration, and exudation are important components of biogeochemical cycles, yet data on the timing and partitioning of C to these processes are rare. As a result, it is unclear how the seasonal timing, or phenology, of root C allocation is affected by the phenology of its component processes: growth of root tissue, respiration, mycorrhizal allocation, and exudation of labile C. The objective of this study was to estimate the phenology and partitioning of C belowground across the growing season in a midlatitude forest located in central Massachusetts. Fine and coarse root production, respiration, and exudation were summed tomore » estimate a monthly total belowground C flux (TBCF) in two hardwood stands dominated by Quercus rubra and Fraxinus americana, respectively, and one conifer stand dominated by Tsuga canadensis. We observed significant stand-level differences in belowground C flux and the partitioning of C to root growth, mycorrhizal fungi, exudation, and respiration. The deciduous hardwood stands allocated C belowground earlier in the season compared to the conifer-dominated stand. The deciduous stands also allocated a greater proportion of TBCF to root growth compared to the conifer-dominated hemlock (T. canadensis) stand. Of the three stands, red oak partitioned the greatest proportion of TBCF (~50%) to root growth, and hemlock the least. Low root growth rates in hemlock may be related to the arrival and spread of the invasive pest, hemlock wooly adelgid (Adelges tsugae), during the study period. Ongoing research in the eastern hemlock stand may yet determine how whole tree allocation and partitioning change as a result of this infestation.« less
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Seasonality and partitioning of root allocation to rhizosphere soils in a midlatitude forest
DOE Office of Scientific and Technical Information (OSTI.GOV)
Abramoff, Rose Z.; Finzi, Adrien C.
Root growth, respiration, and exudation are important components of biogeochemical cycles, yet data on the timing and partitioning of C to these processes are rare. As a result, it is unclear how the seasonal timing, or phenology, of root C allocation is affected by the phenology of its component processes: growth of root tissue, respiration, mycorrhizal allocation, and exudation of labile C. The objective of this study was to estimate the phenology and partitioning of C belowground across the growing season in a midlatitude forest located in central Massachusetts. Fine and coarse root production, respiration, and exudation were summed tomore » estimate a monthly total belowground C flux (TBCF) in two hardwood stands dominated by Quercus rubra and Fraxinus americana, respectively, and one conifer stand dominated by Tsuga canadensis. We observed significant stand-level differences in belowground C flux and the partitioning of C to root growth, mycorrhizal fungi, exudation, and respiration. The deciduous hardwood stands allocated C belowground earlier in the season compared to the conifer-dominated stand. The deciduous stands also allocated a greater proportion of TBCF to root growth compared to the conifer-dominated hemlock (T. canadensis) stand. Of the three stands, red oak partitioned the greatest proportion of TBCF (~50%) to root growth, and hemlock the least. Low root growth rates in hemlock may be related to the arrival and spread of the invasive pest, hemlock wooly adelgid (Adelges tsugae), during the study period. Ongoing research in the eastern hemlock stand may yet determine how whole tree allocation and partitioning change as a result of this infestation.« less
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Monitoring hemlock crown health in Delaware Water Gap National Recreation Area
Michael E. Montgomery; Bradley Onken; Richard A. Evans; Richard A. Evans
2005-01-01
Decline of the health of hemlocks in Delaware Water Gap National Recreation Area was noticeable in the southern areas of the park by 1992. The following year, a series of plots were established to monitor hemlock health and the abundance of hemlock woolly adelgid. This poster examines only the health rating of the hemlocks in the monitoring plots.
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R. Talbot Trotter; Randall S. Morin; Sonja N. Oswalt; Andrew. Liebhold
2013-01-01
Since its introduction, the non-native hemlock woolly adelgid (Adelges tsugae) has spread to infest hemlock (Tsuga spp.) in at least 18 states in the eastern USA. Previous studies have documented highly variable rates of hemlock mortality among infested stands making it difficult to estimate regional impacts. Here data from the US...
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Jennifer Pontius; Richard Hallett; Mary Martin; Lucie Plourde
2010-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) (HWA) is an invasive insect pest that is causing widespread mortality of eastern hemlock (Tsuga canadensis (L.) Carr.). However, some stands remain living more than a decade after infestation. The ability to target management efforts in locations where hemlock is most likely to...
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Kathryn B. Piatek; Mary Ann Fajvan; Richard M. Turcotte
2017-01-01
Stand thinning is being tested as a means to limit the impacts of the invasive hemlock woolly adelgid (HWA; Adelges tsugae Annand) on eastern hemlock (Tsuga canadensis (L.) Carriere). The efficacy of this strategy may be reduced if thinning increases hemlock foliar nutrients because HWA densities are correlated with foliar...
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Hemlock infestation and mortality: impacts on nutrient pools and cycling in Appalachian forests
Jennifer D. Knoepp; James M. Vose; Barry Clinton; Nark D. Hunter
2011-01-01
Eastern hemlock [Tsuga canadensis (L.) Carrière] trees serve an important ecological role in riparian ecosystems in the southern Appalachians. Significant hemlock mortality is occurring due to infestation by the hemlock woolly adelgid (HWA) (Adelges tsugae Annand), a non-native invasive pest. Our objective was to quantify the impacts of HWA and hemlock mortality on...
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John M. Hastings; Kevin M. Potter; Frank H. Koch; Mark Megalos; Robert M. Jetton
2017-01-01
Hemlock woolly adelgid (Adelges tsugae Annand) (HWA) is an invasive forest insect sweeping across the native range of eastern (Tsuga canadensis [L.] Carr.) and Carolina (Tsuga caroliniana Engelm.) hemlocks, threatening to severely reduce eastern hemlock extent and to push Carolina hemlock to extirpation. HWA poses a significant threat to these eastern US natives, now...
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Incorporating hemlock woolly adelgid impacts into the Forest Vegetation Simulator model
R. Talbot III Trotter; Anthony W. Courter; Richard M. Turcotte; Brad. Onken
2008-01-01
The hemlock woolly adelgid (HWA), Adelges tsugae, is a small aphid-like insect that feeds on the xylem ray parenchyma cells near the base of hemlock needles. This insect, a native of Asia and western North America, was first noted in eastern North America in 1951 and has now spread to infest hemlock in at least 17 states. The increased hemlock...
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Elizabeth Butin; Joseph Elkinton; Nathan Havill; Michael Montgomery
2003-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) is an introduced pest thought to be native to Asia. Damage to eastern hemlock and Carolina hemlock can be serious (Salom et al. 1996), but western and Asian hemlocks are seldom damaged. Potential biological control agents have been observed in Japan and China (Sasaji and McClure 1997, Yu et al. 2000...
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James M. Vose; David N. Wear; Albert E. Mayfield; C. Dana Nelson
2013-01-01
Hemlock woolly adelgid (Adelges tsugae Annad; or HWA) is a non-native invasive pest that attacks and kills eastern hemlock (Tsuga canadensis (L.) Carrière) and Carolina hemlock (Tsuga caroliniana Engelm.). Hemlock is a ââfoundation speciesââ due to its strong influence on ecosystem structure and function,...
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Ross, R.M.; Redell, L.A.; Bennett, R.M.; Young, J.A.
2004-01-01
Avian biodiversity may be at risk in eastern parks and forests due to continued expansion of the hemlock woolly adelgid (Adelges tsugae), an exotic homopteran insect native to East Asia. To assess avian biodiversity, mesohabitat relations, and the risk of species loss with declining hemlock forests in Appalachian park lands, 80 randomly distributed fixed-radius plots were established in which territories of breeding birds were estimated on four forest-terrain types (hemlock and hardwood benches and ravines) in the Delaware Water Gap National Recreation Area. Both species richness and number of territories were higher in hardwood than hemlock forest types and in bench than ravine terrain types. Four insectivorous species, Acadian flycatcher (Empidonax virescens), blue-headed vireo (Vireo solitarius), black-throated green warbler (Dendroica virens), and Blackburnian warbler (Dendroica fusca), showed high affinity for hemlock forest type and exhibited significantly greater numbers of territories in hemlock than hardwood sites. These species are hemlock-associated species at risk from continued hemlock decline in the Delaware River valley and similar forests of the mid-Atlantic east slope. Two of these species, the blue-headed vireo and Blackburnian warbler, appeared to specialize on ravine mesohabitats of hemlock stands, the vireo a low-to-mid canopy species, the warbler a mid-to-upper canopy forager. Unchecked expansion of the exotic adelgid and subsequent hemlock decline could negatively impact 3,600 pairs from the park and several million pairs from northeastern United States hemlock forests due to elimination of preferred habitat.
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Snyder, C.D.; Young, J.A.; Lemarie, D.P.; Smith, D.R.
2002-01-01
We conducted a comparative study in the Delaware Water Gap National Recreation Area to determine the potential long-term impacts of hemlock forest decline on stream benthic macroinvertebrate assemblages. Hemlock forests throughout eastern North America have been declining because of the hemlock woolly adelgid, an exotic insect pest. We found aquatic invertebrate community structure to be strongly correlated with forest composition. Streams draining hemlock forests supported significantly more total taxa than streams draining mixed hardwood forests, and over 8% of the taxa were strongly associated with hemlock. In addition, invertebrate taxa were more evenly distributed (i.e., higher Simpson's evenness values) in hemlock-drained streams. In contrast, the number of rare species and total densities were significantly lower in streams draining hemlock, suggesting that diversity differences observed between forest types were not related to stochastic factors associated with sampling and that streams draining mixed hardwood forests may be more productive. Analysis of stream habitat data indicated that streams draining hemlock forests had more stable thermal and hydrologic regimes. Our findings suggest that hemlock decline may result in long-term changes in headwater ecosystems leading to reductions in both within-stream (i.e., alpha) and park-wide (i.e., gamma) benthic community diversity.
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Resistance of hemlock species and hybrids to hemlock woolly adelgid
S.E. Bentz; Michael E. Montgomery; Richard T. Olsen
2008-01-01
The eastern North American native hemlock species, T. canadensis [L.] Carriere and T. caroliniana Engelm., are highly susceptible to injury from the hemlock woolly adelgid (HWA), Adelges tsugae, while the Asian species, T. chinensis (Franch.) E. Pritz, T. diversifolia (Maxim...
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Impacts of hemlock woolly adelgid - the effects on tree health and mortality probability
J. J. Colbert; Bradley Onken
2000-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) (HWA) was first found on the eastern hemlock (Tsuga canadensis (L.) Carriere) in the early 1950s and has been recognized as a significant pest of eastern hemlock since the mid-1980s.
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Hemlock woolly adelgid and its hemlock hosts: A global perspective
Nathan P. Havill; Michael E. Montgomery; Melody. Keena
2011-01-01
The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hempitera: Adelgidae), threatens the health and sustainability of the native eastern North American hemlocks, Tsuga canadensis (L.) Carriere and T. caroliniana Engelman. The lineage of HWA that was introduced to the eastern United States came from Japan...
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Isolation and characterization of microsatellite markers for carolina hemlock (Tsuga caroliniana)
S.A. Josserand; K.M. Potter; C.S. Echt; C.D. Nelson
2008-01-01
We describe the isolation and characterization of 31 polymorphic di- and trinucleotide microsatellite marker loci for Carolina hemlock (Tsuga caroliniana Englem.). In addition, primer pairs for 16 loci amplified scoreable alleles in six other Euga species. In eastern North America, both Carolina hemlock and eastern hemlock (Tsuga canadensis...
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Elizabeth Butin; Evan Preisser; Joseph Elkinton
2007-01-01
We assessed the importance of several factors potentially affecting the settlement rate of the invasive hemlock woolly adelgid, Adelges tsugae, on uninfested foliage of the eastern hemlock, Tsuga canadensis. We conducted our experiments in Massachusetts (USA) with overwintering sistens adelgids, and applied standard densities of...
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USDA Forest Service
2000-01-01
The hemlock borer, Melanophila fulvoguttata (Harris), is a pest of eastern hemlock, Tsuga canadensis (L.) Carr., throughout its natural range. Although normally considered a secondary pest and seldom abundant, the borer can develop to outbreak conditions following wind-throw, drought, excessive stand openings, or attacks by other primary pests such as the hemlock...
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Eastern hemlock: a market perspective
Theodore Howard; Paul Sendak; Claudia Codrescu
2000-01-01
Although it is an important component of the northern forest, eastern hemlock (Tsuga canadensis (L.) Carr.) is a secondary species in its regions' markets. In this paper, we examine the markets for hemlock, analyze price trends for stumpage, and suggest implications of market forces for management of forests containing hemlock. The...
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W.A. Whittier; A.E. Mayfield III; R.M. Jetton
2017-01-01
The ecologically foundational species eastern hemlock, Tsuga canadensis, is being functionally eliminated from southern Appalachian forests by the hemlock woolly adelgid (HWA, Adelges tsugae). The management of HWA has focused on chemical and biological control, conservation of hemlock genetic resources, and host resistance...
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Predicting long-term forest development following hemlock mortality
Jennifer C. Jenkins; Charles D. Canham; Paul K. Barten
2000-01-01
The hemlock woolly adelgid (Adelges tsugae Annand.), an introduced pest specializing on eastern hemlock (Tsuga canadensis (L.) Carr.), threatens to cause widespread hemlock mortality in New England forests. In this study, we used a stem-based model of forest dynamics (SORTIE) to predict forest development in a northeastern forest...
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Hemlock Dwarf Mistletoe (FIDL)
Paul E. Hennon; Jerome S. Beatty; Diane Hildebrand
2001-01-01
Hemlock dwarf mistletoe, Arceuthobium tsugense (Rosendahl) G.N. Jones, causes a serious disease of western hemlock and several other tree species along the Pacific Coast of North America. This small, seed-bearing plant lives exclusively as a parasite on living trees. Throughout its range, hemlock dwarf mistletoe occurs in patch-like patterns in the forests. Some...
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Property value impacts of hemlock woolly adelgid in residential forests
Thomas P. Holmes; Elizabeth A. Murphy; Kathleen P. Bell; Denise D. Royle
2010-01-01
This study estimates the economic losses attributable to a nonindigenous forest insect, the hemlock woolly adelgid (Adelges tsuga), using cross-sectional and difference-in-difference hedonic price models. The data span a decade of residential property value transactions in West Milford, New Jersey. Hemlock health in naturally regenerated hemlock stands was measured...
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Allozyme Variation in Hemlock Woolly Adelgid (Hemiptera: Adelgidae) from the United States and China
V. S& #225; nchez; M.A. Keena; M.A. Keena
2009-01-01
The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is a major introduced pest of eastern hemlock, Tsuga canadensis (L.) Carriere. Hemlock woolly adelgid in the United States is anholocyclic and an obligate parthenogen, because no suitable primary host (on which sexual reproduction occurs in Asia) is...
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Michael E. Montgomery; S.E. Bentz; Richard T. Olsen
2009-01-01
Hemlock (Tsuga) species and hybrids were evaluated for resistance to the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae). The adelgid was accidentally introduced from Asia to the eastern United States, where it is causing widespread mortality of the native hemlocks, Tsuga canadensis (L.)...
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Use of water by eastern hemlock: implications for systemic insecticide application
Chelcy R. Ford; James M. Vose; Michael Daley; Nathan Phillips
2007-01-01
The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is causing widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr.) throughout most of the range of eastern hemlock. Stem injection of insecticide is widely used as a chemical control measure, but the effectiveness of this method depends on the...
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Association of ring shake in eastern hemlock with tree attributes
John P. Brown; Paul E. Sendak
2006-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr.) is a major or minor associate in many forest types in northeastern North America. There has never been the high level of demand for eastern hemlock lumber that characterizes competing softwoods like white pine and spruce. Nevertheless, periodically interest in greater utilization of eastern hemlock for...
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Production of wood pellets from Alaska-grown white spruce and hemlock
Allen M. Brackley; Daniel J. Parrent
2011-01-01
An extensive literature review failed to locate any information relative to the pelleting characteristics of hemlock speciesâwestern hemlock (Tsuga heterophylla (Raf.) Sarg.) and mountain hemlock (Tsuga mertensiana (Bong.) Carr. )âthat grow in Alaska. To determine more about the pelletizing properties of the species,...
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Influences of eastern hemlock mortality on nutrient cycling
Thad E. Yorks; Jennifer C. Jenkins; Donald J. Leopold; Dudley J. Raynal; David A. Orwig
2000-01-01
Mortality of eastern hemlock (Tsuga canadensis (L.) Carriere) may be caused by a variety of agents, but hemlock trees of all sizes over a large geographic area are currently threatened by an outbreak of the hemlock woolly adelgid (HWA: Adelges tsugae Annand) in the eastern United States. In this paper, we review what is currently...
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K.L.F. Oten; A.C. Cohen; F.P. Hain
2012-01-01
The hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae), is an invasive forest pest that threatens the existence of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.) in the eastern United States. It is a small, aphid like insect with piercing-sucking...
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Web orientation and prey resources for web-building spiders in eastern hemlock.
Mallis, Rachael E; Rieske, Lynne K
2010-10-01
We examined the arthropod community on eastern hemlock, Tsuga canadensis (L.) Carr, in the context of its role in providing potential prey items for hemlock-associated web-weaving spiders. Using sticky traps simulating spider webs, we evaluated what prey items are available to web-weaving spiders in eastern hemlock based on web orientation (horizontal versus vertical) and cardinal direction. We found that the overwhelming majority (>70%) of prey items available to spiders in hemlock canopies were Diptera. Psocoptera, Hymenoptera, and Hemiptera comprised most of the remaining potential prey. A significant direction × orientation interaction, and greater trap capture in some direction-orientation combinations, suggests that spiders might locate their webs in eastern hemlock canopies for thermoregulatory purposes, ultimately optimizing prey capture. We also evaluated these findings in the context of hemlock infestation by the invasive hemlock woolly adelgid, Adelges tsugae Annand. The adelgid is a sedentary insect with a mobile crawler stage that provides a readily available, easily obtained food source for predators in hemlock canopies. However, an abundance of alternative prey will affect within canopy spider distribution and the potential intensity with which spiders consume these prey. Understanding the response of spiders to potential prey availability is essential to understanding the trophic interactions involving these predators and their potential for influencing herbivore populations.
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The effects of shade, fertilizer, and pruning on eastern hemlock trees and hemlock woolly adelgid
Thomas McAvoy; Ryan Mays; Nels Johnson; Scott Salom
2017-01-01
Hemlock woolly adelgid (HWA), Adelges tsugae Annand, an invasive insect native to the Pacific Northwest and Asia, is responsible for widespread health decline and mortality of native hemlocks (Tsuga spp.) in the eastern United States. Shading and fertilizer has been found to affect the survival and health of both HWA and...
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Eastern hemlock decline in riparian areas from Maine to Alabama
Daniel Evans; Michael Aust; C. Dolloff; Ben Templeton; John Peterson
2011-01-01
Eastern hemlock (Tsuga canadensis) in the Appalachian mountain range is threatened by the introduced hemlock woolly adelgid (Adelges tsugae). Potential impacts on riparian systems are great because of eastern hemlockâs role as a foundation species that influences site soil, vegetation, and stream characteristics. We installed permanent research sites at 49 locations in...
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Melissa Churchel; James Hanula; C. Wayne Berisford; James Vose; Mark Dalusky
2011-01-01
Imidacloprid, a systemic insecticide that acts on the nervous system, is currently being used to control hemlock woolly adelgid (Adelges tsugae Annand), which is damaging hemlock trees. The objective of this study was to determine whether soil injection with imidacloprid for hemlock woolly adelgid control near streams adversely affects aquatic invertebrates. Eastern...
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Eastern Hemlock Forests: Guidelines to Minimize the Impacts of Hemlock Woolly Adelgid
Jeffrey S. Ward; Michael E. Montgomery; Carole A.S.-J. Cheah; Brad P. Onken; Richard S. Cowles
2004-01-01
Eastern hemlock (Tsuga canadensis) is the most shade-tolerant and long-lived tree species in Eastern North America. Its unsurpassed ability to tolerate low light enables it to form dense canopies and stands that provide a unique habitat for many plant and wildlife species. Carolina hemlock (Tsuga caroliniana) is a relic species...
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Steven Brantley; Chelcy R. Ford; James M. Vose
2013-01-01
Infestation of eastern hemlock (Tsuga canadensis (L.) Carr.) with hemlock woolly adelgid (HWA, Adelges tsugae) has caused widespread mortality of this key canopy species throughout much of the southern Appalachian Mountains in the past decade. Because eastern hemlock is heavily concentrated in riparian habitats, maintains a dense...
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Management of eastern hemlock for deer wintering areas
Russell S. Reay
2000-01-01
Hemlock stands provide superior winter cover for white-tailed deer. When a site is suitable for the support of a hemlock community, a decision to undertake active management is appropriate, however the difficulty of securing adequate hemlock regeneration must guide and govern the timber management plan. The need to maintain deer wintering areas creates some limitations...
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Classification and spatial analysis of eastern hemlock health using remote sensing and GIS
Laurent R. Bonneau; Kathleen S. Shields; Daniel L. Civco; David R. Mikus
2000-01-01
Over the past decade hemlock stands in southern Connecticut have undergone significant decline coincident with the arrival in 1985 of an exotic insect pest, the hemlock woolly adelgid (Adelges tsugae Annand). The objective of this study was to evaluate image enhancement techniques for rating the health of hemlocks at the landscape level using...
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Composition, structure, and sustainability of hemlock ecosystems in eastern North America
William H. McWilliams; Thomas L. Schmidt
2000-01-01
Across its natural range in North America, eastern hemlock (Tsuga Canadensis (L.) Carriere) is an important resource for people and wildlife, but it is seriously threatened by the hemlock woolly adelgid (HWA) (Adelges tsugae Annand). From 10 to 20 percent of the hemlock resource is found in the Canadian provinces of New Brunswick,...
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Growth and stocking of eastern hemlock (Tsuga canadensis) in New England
Dale S. Solomon; William B. Leak
2000-01-01
Summarization of the limited growth information in mixed-species stands in New England indicates that eastern hemlock (Tsuga canadensis) may be one of the fastest growing species in diameter, second only to white pine. However, on some sites hemlock diameter growth is about equal to that of associated hardwoods. Hemlock grows slowly in height and...
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K. M. Potter; W. S. Dvorak; B. S. Crane; V. D. Hipkins; R. M. Jetton; W. A. Whittier; R. Rhea
2008-01-01
Eastern hemlock (Tsuga canadensis [L.] Carr.) is a widespread and ecologically important conifer species of eastern North America that is threatened by the hemlock woolly adelgid (Adelges tsugae Annand), a pest introduced into the United States from Asia in the 1920s. Information about the genetic composition of eastern hemlock is...
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Distribution and Abundance of Adelges tsugae (Hemiptera: Adelgidae) Within Hemlock Trees
S.V. Joseph; J.L. Hanula; S.K. Braman
2011-01-01
We studied the distribution of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), within hemlock trees for three summer (progrediens) and two winter (sistens) generations in northern Georgia. Eastern hemlock, Tsuga canadensis (L.) Carrie` re, trees were treated with 0, 10, or 25% of 1.5 g of imidacloprid per 2.5 cm of tree diameter at breast height...
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Mary Ann Fajvan
2008-01-01
In order to increase hemlock survivability in stands threatened by hemlock woolly adelgid (HWA), a new study is developing silvicultural thinning guidelines to reduce stand densities, reallocate resources, and increase hemlock vigor across a range of stand types and structures before HWA invasion. The 7 study areas are all geographically similar in that they regularly...
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Robert T. Brooks
2001-01-01
Eastern hemlock (Tsuga canadensis) is a common conifer throughout northeastern North America. The species is threatened by the exotic hemlock woolly adelgid (HWA), Adelges tsugae; infestation by this forest pest can result in high levels of mortality of overstory trees with a resultant change in understory vegetation composition and structure. Pre-salvage harvesting of...
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Thad E. Yorks; Donald J. Leopold; Dudley J. Raynal
2000-01-01
We examined propagule banks in six eastern hemlock (Tsuga canadensis (L.) Carriere) stands in the Catskill Mountains of New York. These stands are at risk of mortality due to the hemlock woolly adelgid (Adelges tsugae Annand), but potential effects of mortality on species composition are uncertain.
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Utilization options for decadent eastern hemlock timber
Matthew F. Winn; Philip A. Araman
2007-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) is a non-native pest that is decimating the eastern hemlock (Tsuga canadensis L.) population in the forests of the eastern United States. Nearly one third of the area inhabited by native hemlocks in the Central Hardwoods region is infested with the insect. Once a tree is heavily infected, it is estimated that tree...
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Jeffrey Krebs; Jennifer Pontius; Paul G. Schaberg
2017-01-01
To better understand the potential impact of the invasive hemlock woolly adelgid (HWA, Adelges tsugae Annand) and presalvage activities on carbon (C) dynamics in northern stands of eastern hemlock (Tsuga canadensis (L.) Carr.), we used the Forest Vegetation Simulator and Forest Inventory and Analysis data to model C storage and...
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Albert E. Mayfield; Barbara C. Reynolds; Carla I. Coots; Nathan P. Havill; Cavell Brownie; Andrew R. Tait; James L. Hanula; Shimat V. Joseph; Ashley B. Galloway
2014-01-01
An integrated management approach is needed to maintain eastern hemlock (Tsuga canadensis (L.) Carrière) in eastern North America and to minimize tree damage and mortality caused by the invasive hemlock woolly adelgid (Adelges tsugae Annand). This study examined the hypothesis that chemical control with low rates of insecticide...
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The effects of site factors on the rate of hemlock decline: a case study in New Jersey
Denise Royle; Richard Lathrop
2000-01-01
The rate of decline of hemlock (Tsuga canadensis) trees infested with hemlock woolly adelgid (Adelges tsugae) appears to be highly variable and site dependent. Rates of hemlock forest decline have not been quantified at the landscape scale and reasons for observed variations in the rate of decline remain unknown. Others have...
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Barbara S. Burns; Henry, Jr. Trial
2000-01-01
Following an outbreak of spring hemlock looper in 1991, ten hemlocks in each of fifteen study plots were monitored annually through 1999. Although some mortality occurred within two years after defoliation, and additional mortality occurred in plots which were subsequently disturbed by logging, most defoliated trees recovered. Twenty-four percent of the trees with 90%...
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Restoration of southern Appalachian riparian forest affected by eastern hemlock mortality
Katherine Elliott; Chelcy F. Miniat; Jennifer Knoepp; Michael A. Crump; C. Rhett Jackson
2016-01-01
Widespread mortality of eastern hemlock (Tsuga canadensis) through hemlock woolly adelgid (HWA) infestation has altered riparian forest structure and function throughout the southern Appalachians. Eastern hemlock and Rhododendron maximum often co-occur in these riparian forests, where the latter species is highly shade tolerant, forms a dense shrub layer that strongly ...
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Gouyue Yu; Michael E. Montgomery; Defu Yao
2000-01-01
Fifty-four species of lady beetles were collected from three Chinese hemlock species, Tsuga dumosa (D. Don) Eichler, T. forrestii Downie and T. chinensis (Franchet) Pritzel, in Yunnan, Sichuan and Shaanxi provinces of China as part of a search for natural enemies of the hemlock woolly adelgid, Adelges tsugae Annand. Twenty new species are described: Clitostethus...
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An exotic pest threat to eastern hemlock: an initiative for management of hemlock woolly adelgid
J. Robert Bridges; Kathleen S. Shields
2003-01-01
Hemlock woolly adelgid (HWA) is the greatest threat to the health and sustainability of hemlock in eastern North America. The potential ecological impacts of this exotic insect pest can be compared to those of gypsy moth, Dutch elm disease, and chestnut blight. The USDA Forest Service, with the support and cooperation of the National Association of State Foresters and...
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Chelcy F. Miniat; David Zeitlow; Steven T. Brantley; Albert (Bud) Mayfield; Rusty Rhea; Robert Jetton; Paul. Arnold
2016-01-01
The rapid loss of eastern hemlock (Tsuga canadensis) from riparian zones in the southern Appalachian Mountains due to Hemlock Woolly Adelgid (Adelgis tsugae, HWA) infestation has resulted in changes to watershed structure and function. Several restoration strategies have been proposed, including silvicultural treatments that increase incident light in forest...
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Wildlife habitat associations in eastern hemlock - birds, smaller mammals, and forest carnivores
Mariko Yamasaki; Richard M. DeGraaf; John W. Lanier
2000-01-01
Ninety-six bird and forty-seven mammal species are associated with the hemlock type in the northeastern United States. Of these species eight bird and ten mammal species are strongly associated with the hemlock type though none of these species are limited to it. Hemlock species richness appears to be lower than in other conifer or hardwood types. Avian habitat...
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T. R. Horton; R. Molina; K. Hood
2005-01-01
We investigated ectomycorrhizal (EM) fungi in forest stands containing both early successional Douglas-fir and late successional western hemlock at two points in the typical stand development by identifying EM fungi from roots of Douglas-fir and western hemlock in mixed stands. Tn an early seral stage forest, EM roots of western hemlock seedlings and intermingling 40-...
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Spatial tools for managing hemlock woolly adelgid in the southern Appalachians
NASA Astrophysics Data System (ADS)
Koch, Frank Henry, Jr.
The hemlock woolly adelgid (Adelges tsugae) has recently spread into the southern Appalachians. This insect attacks both native hemlock species (Tsuga canadensis and T. caroliniana ), has no natural enemies, and can kill hemlocks within four years. Biological control displays promise for combating the pest, but counter-measures are impeded because adelgid and hemlock distribution patterns have been detailed poorly. We developed a spatial management system to better target control efforts, with two components: (1) a protocol for mapping hemlock stands, and (2) a technique to map areas at risk of imminent infestation. To construct a hemlock classifier, we used topographically normalized satellite images from Great Smoky Mountains National Park. Employing a decision tree approach that supplemented image spectral data with several environmental variables, we generated rules distinguishing hemlock areas from other forest types. We then implemented these rules in a geographic information system and generated hemlock distribution maps. Assessment yielded an overall thematic accuracy of 90% for one study area, and 75% accuracy in capturing hemlocks in a second study area. To map areas at risk, we combined first-year infestation locations from Great Smoky Mountains National Park and the Blue Ridge Parkway with points from uninfested hemlock stands, recording a suite of environmental variables for each point. We applied four different multivariate classification techniques to generate models from this sample predicting locations with high infestation risk, and used the resulting models to generate risk maps for the study region. All techniques performed well, accurately capturing 70--90% of training and validation samples, with the logistic regression model best balancing accuracy and regional applicability. Areas close to trails, roads, and streams appear to have the highest initial risk, perhaps due to bird- or human-mediated dispersal. Both components of our management system are general enough for use throughout the southern Appalachians. Overlay of derived maps will allow forest managers to reduce the area where they must focus their control efforts and thus allocate resources more efficiently.
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Ryan P. Hanavan; Jennifer Pontius; Richard Hallett
2015-01-01
The hemlock woolly adelgid is a serious pest of Eastern and Carolina hemlock in the eastern United States. Successfully managing the hemlock resource in the region depends on careful monitoring of the spread of this invasive pest and the targeted application of management options such as biological control, chemical, or silvicultural treatments. To inform these...
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Heather L. Spaulding; Lynne K. Rieske
2010-01-01
As the highly invasive hemlock woolly adelgid, Adelges tsugae, continues to expand its distribution in eastern North America, affected forests will incur drastic changes in composition and structure. While these changes have been well-studied in dense hemlock forests in the Northeast, relatively little work is known about the effects of the adelgid at the western edge...
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Intravenous Poison Hemlock Injection Resulting in Prolonged Respiratory Failure and Encephalopathy.
Brtalik, Douglas; Stopyra, Jason; Hannum, Jennifer
2017-06-01
Poison hemlock (Conium maculatum) is a common plant with a significant toxicity. Data on this toxicity is sparse as there have been few case reports and never a documented poisoning after intravenous injection. We present a case of intravenous poison hemlock injection encountered in the emergency department. We describe a 30-year-old male who presented to the emergency department after a brief cardiac arrest after injecting poison hemlock. The patient had return of spontaneous circulation in the emergency department but had prolonged muscular weakness and encephalopathy later requiring tracheostomy. Intravenous injection of poison hemlock alkaloids can result in significant toxicity, including cardiopulmonary arrest, prolonged weakness, and encephalopathy.
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Letheren, Amanda; Hill, Stephanie; Salie, Jeanmarie; Parkman, James; Chen, Jiangang
2017-01-01
Hemlock woolly adelgid (Adelges tsugae Annand, HWA) remains the single greatest threat to the health and sustainability of hemlock in the eastern USA. The loss of hemlock trees leads to further negative impacts on the diversity and stability of ecosystems in the eastern part of North America. It is, therefore, urgent to develop effective control measures to reduce HWA populations and promote overall hemlock health. Currently available individual and integrated approaches should continue to be evaluated in the laboratory and in the field along with the development of other new and innovative methods. PMID:28422072
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Hemlock woolly adelgid biological control research
Michael Montgomery; Nathan Havill; Carole Cheah; Mark McClure; Gabriella Zilahi-Balogh; Ashley Lamb; Scott Salom
2003-01-01
The hemlock woolly adelgid (HWA), Adelges tsugae Annand, is an introduced pest that causes mortality of hemlock in the eastern U. S. Three laboratories have imported and are evaluating predacious beetles for biological control of the adelgid.
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David D. Morton; John A. Young; Nissa M. Thomsen
2000-01-01
Hemlock woolly adelgid (HWA) was first observed in Shenandoah National Park (SNP) in the mid-1980s. Since then, this exotic insect has expanded its range throughout the park. Most stands were heavily defoliated within several years of infestation. However, several hemlock stands appear to be not affected or only moderately affected to the present date. To investigate...
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Young, J.A.; Smith, D.R.; Snyder, C.D.; Lemarie, D.P.
2002-01-01
Biodiversity surveys are often hampered by the inability to control extraneous sources of variability introduced into comparisons of populations across a heterogenous landscape. If not specifically accounted for a priori, this noise can weaken comparisons between sites, and can make it difficult to draw inferences about specific ecological processes. We developed a terrain-based, paired-site sampling design to analyze differences in aquatic biodiversity between streams draining eastern hemlock (Tsuga canadensis) forests, and those draining mixed hardwood forests in Delaware Water Gap National Recreation Area (USA). The goal of this design was to minimize variance due to terrain influences on stream communities, while representing the range of hemlock dominated stream environments present in the park. We used geographic information systems (GIS) and cluster analysis to define and partition hemlock dominated streams into terrain types based on topographic variables and stream order. We computed similarity of forest stands within terrain types and used this information to pair hemlock-dominated streams with hardwood counterparts prior to sampling. We evaluated the effectiveness of the design through power analysis and found that power to detect differences in aquatic invertebrate taxa richness was highest when sites were paired and terrain type was included as a factor in the analysis. Precision of the estimated difference in mean richness was nearly doubled using the terrain-based, paired site design in comparison to other evaluated designs. Use of this method allowed us to sample stream communities representative of park-wide forest conditions while effectively controlling for landscape variability.
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Saroj Sivaramakrishnan; Graeme P. Berlyn
2000-01-01
Both greenhouse and field studies have shown that it is the combined stress of drought and infestation by the hemlock woolly adelgid that causes death in eastern hemlocks. In three separate greenhouse studies it was found that the presence of adelgids alone did not cause the death of the plants over a period of 1, 2 or 5 years respectively, if they were well watered...
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Willis R. Littke; John E. Browning
1989-01-01
Heterobasidion annosum infects western hemlock (Tsuga heterophylla) and causes a root and butt-rot disease. A disease survey was initiated in thinned Southwestern Washington hemlock stands to determine current disease incidence caused by H. annosum.
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NASA Astrophysics Data System (ADS)
Zukswert, J. M.; Rhodes, A. L.; Dwyer, C. H.; Sweezy, T.
2012-12-01
Removal of foundation species as a result of disturbance events such as exotic species invasions can alter community composition and ecosystem function. The current hemlock woolly adelgid (Adelges tsugae) infestation in eastern North America that threatens the eastern hemlock (Tsuga canadensis), a foundation species, has motivated salvage logging efforts. Ecological succession resulting from salvage logging of hemlock would eventually produce a deciduous hardwood forest. The chemistry of throughfall beneath a mature hemlock forest canopy is expected to be more acidic than throughfall from a mature deciduous forest canopy because hemlock foliage releases more organic acids and fewer base cations. The chemical composition of throughfall during the early successional transition from hemlock to deciduous is less understood. We hypothesize that throughfall chemistry in a deciduous forest consisting primarily of juvenile trees may be more similar to direct precipitation because leaf area index is smaller. Differences between hemlock throughfall and direct precipitation may be larger due to the denser canopy of these mature trees. We compared the chemical composition of precipitation, hemlock throughfall, and black birch throughfall for 26 precipitation events from 4 March to 30 July 2012. The black birch (Betula lenta) forest patch resulted from salvage logging of hemlocks twenty years ago at the MacLeish Field Station in Whately, MA. From the three plots we measured the volume of water collected and pH, acid neutralizing capacity, dissolved organic carbon (DOC), and concentrations of cations (Ca2+, K+, Na+, Mg2+, NH4+), anions (Cl-, NO3-, SO42-), and dissolved silica. Precipitation totaled 405 mm during the course of the study. Throughfall totaled 347 mm in the black birch plot and 315 mm in the hemlock plot. The proportion of precipitation passing through the forest canopy was smaller in hemlock throughfall than black birch throughfall during small precipitation events (depth < 10 mm), but appeared comparable in larger events. Before leaf emergence, differences between base cation and DOC deposition were not significant (p>0.05, n = 5) for throughfall and direct precipitation. After leaf emergence, base cation and DOC deposition was significantly (p<0.05, n = 21) greater in throughfall than direct precipitation. Additionally, K+, Mg2+, and DOC deposition were significantly greater in hemlock throughfall than black birch throughfall. Black birch throughfall had significantly less H+ deposition than direct precipitation, which suggests that the black birch canopy appears to neutralize the acidity of the precipitation. H+ deposition in hemlock throughfall, however, was not significantly different than precipitation, which could be due to its higher DOC. These results suggest that the successional stage of a deciduous forest canopy has an effect on throughfall chemistry. Lower deposition of base cations prior to and during this juvenile stage could affect soil chemistry by increasing soil acidity and lowering base saturation.
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Regenerating eastern hemlock in the Lake States
Richard M. Godman
1992-01-01
The eastern hemlock type is declining in area faster than any other. Growing-stock volume, for example, declined 71 percent in only 20 years in Michigan, and has declined similarly in Wisconsin. Many land management agencies have stopped cutting hemlock until satisfactory regeneration can be assured.
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Breeding for resistance to adelgids in Abies fraseri, Tsuga canadensis, and T. caroliniana
Ben Smith; Fred Hain; John Frampton
2012-01-01
The balsam woolly adelgid (BWA; Adelges piceae) and hemlock woolly adelgid (HWA; Adelges tsugae) have had a tremendous impact on native ecosystems with Fraser fir (Abies fraseri (Pursh) Poir), eastern hemlock (Tsuga canadensis (L.) Carrière), and Carolina hemlock (T....
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Tsuga chinensis as a source of host resistance to the hemlock woolly adelgid
S. E. Bentz; Robert J. Griesbach; Margaret R. Pooler; A. M. Townsend
2007-01-01
The eastern North American native hemlock species, T. canadensis [L.] Carriere and T. caroliniana Engelm., are highly susceptible to injury from the hemlock woolly adelgid (HWA), while the Asian species, T. chinensis (Franch.) E. Pritz., T. diversifolia (Maxim.) Mast., and T. sieboldii...
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David C. Shaw; Jiquan Chen; Elizabeth A. Freeman; David M. Braun
2005-01-01
We investigated the distribution and severity of trees infected with western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones subsp. tsugense) in an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) - western hemlock (Tsuga heterophylla (Raf.) Sarg.)...
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Evaluation of aestival diapause in hemlock woolly adelgid
Scott M. Salom; Warren T. Mays; John Neal; Alexei Sharov
2000-01-01
Hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), has two generations/year that feed and reproduce on hemlock, Tsugae spp. The spring generation, present from March to June, is called progrediens. The next generation, present from June until the following March, is called sistens (McClure 1987, Gray and Salom...
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Dynamics in late-successional hemlock-hardwood forests over three decades
Kerry D. Woods
2000-01-01
Permanent plots in old-growth hemlock-northern hardwood forests of Michigan's upper peninsula have been remeasured over periods of 16-32 yr. A gradient from hemlock (Tsuga canadensis) to sugar maple (Acer saccharum) dominance is associated with increasing soil pH and calcium. Secondary species include yellow birch (...
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Effects of fertilizer and low rates of Imidacloprid on Adelges tsugae (Hemiptera: Adelgidae).
S. V. Joseph; James Hanula; S. K. Braman; F. J. Byrne
2011-01-01
Healthy hemlock trees, Tsuga canadensis (L.) Carriere, and hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), populations should favor retention and population growth of adelgid predators such as Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Sasajiscymnus tsugae (Sasaji&McClure) (Coleoptera: Coccinellidae). Eastern hemlock trees...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-20
... conditions. Existing HWA management options include chemical control and silvicultural control, which, in...] Availability of an Environmental Assessment for a Biological Control Agent for Hemlock Woolly Adelgid AGENCY... environmental assessment relative to the control of hemlock woolly adelgid (Adelges tsugae). The environmental...
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Dennis R. Souto; Kathleen S. Shields
2000-01-01
Although many insects and diseases are associated with hemlock, we will, ironically, draw our first conclusion, that hemlocks are very sensitive to the stress of insect defoliation, from a tale of gypsy moth defoliation. The unprecedented gypsy moth (Lymantria dispar L.) outbreak of 1981, when nearly 13 million acres were defoliated in the Northeast...
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Kelly L.F. Oten; Allen C. Cohen; Fred P. Hain
2014-01-01
The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is a pest of eastern and Carolina hemlocks (Tsuga canadensis (L.) Carriere and Tsuga caroliniana Engelmann, respectively) in the eastern United States and has already caused catastrophic changes to eastern forests. As one of the significant...
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Radville, Laura; Chaves, Arielle; Preisser, Evan L
2011-06-01
Herbivores can trigger a wide array of morphological and chemical changes in their host plants. Feeding by some insects induces a defensive hypersensitive response, a defense mechanism consisting of elevated H(2)O(2) levels and tissue death at the site of herbivore feeding. The invasive hemlock woolly adelgid Adelges tsugae ('HWA') and elongate hemlock scale Fiorinia externa ('EHS') feed on eastern hemlocks; although both are sessile sap feeders, HWA causes more damage than EHS. The rapid rate of tree death following HWA infestation has led to the suggestion that feeding induces a hypersensitive response in hemlock trees. We assessed the potential for an herbivore-induced hypersensitive response in eastern hemlocks by measuring H(2)O(2) levels in foliage from HWA-infested, EHS-infested, and uninfested trees. Needles with settled HWA or EHS had higher H(2)O(2) levels than control needles, suggesting a localized hypersensitive plant response. Needles with no direct contact to settled HWA also had high H(2)O(2) levels, suggesting that HWA infestation may induce a systemic defense response in eastern hemlocks. There was no similar systemic defensive response in the EHS treatment. Our results showed that two herbivores in the same feeding guild had dramatically different outcomes on the health of their shared host.
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Impact of an Invasive Insect and Plant Defense on a Native Forest Defoliator
Wilson, Claire M.; Vendettuoli, Justin F.; Orwig, David A.; Preisser, Evan L.
2016-01-01
Eastern hemlock (Tsuga canadensis [L.] Carriére) in the United States is threatened by the invasive hemlock woolly adelgid (Adelges tsugae Annand). The native hemlock looper (Lambdina fiscellaria Guenée) also appears to have played a role in previous population declines of this conifer. Although these two insects co-occur in much of the adelgid’s invaded range, their interactions remain unstudied. We assessed looper performance and preference on both uninfested and adelgid-infested foliage from adelgid-susceptible hemlocks, as well as on uninfested foliage from an eastern hemlock that is naturally adelgid-resistant. Larvae reared on uninfested foliage from adelgid-susceptible hemlocks experienced 60% mortality within the first two weeks of the experiment, and pupated at a lower weight than larvae fed adelgid-infested foliage. Despite differences in foliage source, this first look and strong pattern suggests that the hemlock looper performs better (pupates earlier, weighs more) on adelgid-infested foliage. In addition, trends suggested that larvae reared on foliage from the adelgid-resistant tree survived better, pupated earlier, and weighed more than in the other treatments. Larvae preferred adelgid-resistant over adelgid-susceptible foliage. Our results suggest that looper perform slightly better on adelgid-infested foliage and that plant resistance to xylem-feeding adelgid may increase susceptibility to foliar-feeding looper larvae. PMID:27649247
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NASA Astrophysics Data System (ADS)
Fraterrigo, J.; Ream, K.; Knoepp, J.
2017-12-01
Forest insects and pathogens (FIPs) can cause uncertain changes in forest carbon balance, potentially influencing global atmospheric carbon dioxide (CO2) concentrations. We quantified the effects of hemlock (Tsuga canadensis L. Carr.) mortality on soil carbon fluxes and pools for a decade following either girdling or natural infestation by hemlock woolly adelgid (HWA; Adelges tsugae) to improve mechanistic understanding of soil carbon cycling response to FIPs. Although soil respiration (Rsoil) was similar among reference plots and plots with hemlock mortality, both girdled and HWA-infested plots had greater activities of β-glucosidase, a cellulose-hydrolyzing extracellular enzyme, and decreased O-horizon mass and fine root biomass from 2005 to 2013. During this period, total mineral soil carbon accumulated at a higher rate in disturbed plots than in reference plots in both the surface (0-10 cm) and subsurface (10-30 cm); increases were predominantly in the mineral-associated fraction of the soil organic matter. In contrast, particulate organic matter carbon accrued slowly in surface soils and declined in the subsurface of girdled plots. δ13C values of this fraction demonstrate that particulate organic matter carbon in the surface soil has become more microbially processed over time, suggesting enhanced decomposition of organic matter in this pool. Together, these findings indicate that hemlock mortality and subsequent forest regrowth has led to enhanced soil carbon stabilization in southern Appalachian forests through the translocation of carbon from detritus and particulate soil organic matter pools to the mineral-associated organic matter pool. These findings have implications for ecosystem management and modeling, demonstrating that forests may tolerate moderate disturbance without diminishing soil carbon storage when there is a compensatory growth response by non-host trees.
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USDA Forest Service Northern Area State & Private Forestry and Region 8
1992-01-01
The hemlock looper Lambdina fiscellaria is a defoliating insect native to North America. It occurs in the eastern United States from Maine to Georgia and west to Wisconsin. The larvae can be extremely destructive to hemlock, balsam fir, and white spruce. During an outbreak it will also feed on many other species including: larch, red and black spruce, cedar, jack pine...
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Exotic forest insects and residential property values
Thomas P. Holmes; Elizabeth A. Murphy; Kathleen P. Bell
2006-01-01
This paper presents a case study of the economic damages to homeowners in a northern New Jersey community due to an exotic forest insect-the hemlock woolly adelgid. Hedonic property value methods are used to estimate the effect of hemlock health on property values. A statistically significant relationship between hemlock health and residential property values is...
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Hemlock woolly adelgid impact assessment survey
Jim Colbert; Matthew Seese; Bradley Onken
2002-01-01
The impact of hemlock woolly adelgid has been varied among the sites followed in this study of the mid-Atlantic region. It appears that in some sites, the insect has not yet had an impact while in others it has killed or put the hemlock in such a state of severe decline that death is imminent.
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David A. Orwig; David R. Foster
2000-01-01
Hemlock woolly adelgid (HWA) (Adelges tsugae), an introduced aphid-like insect from Asia, is expanding across the northeastern United States through the range of eastern hemlock (Tsuga canadensis (L.) Carr.) and has the potential to severely reduce or eliminate this important late-successional species. While infestation and...
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Hemlock woolly adelgid initiative: progress and future direction
Brad Onken; Melody Keena
2008-01-01
In 2001, the USDA Forest Service in cooperation with the National Association of State Foresters and the National Plant Board proposed a five-year program that would accelerate development and implementation of management options to reduce the spread and impact of hemlock woolly adelgid. From 2003-2007, this "Hemlock Woolly Adelgid Initiative" has involved...
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William P. Shepherd; Brian T. Sullivan; Albert (Bud) Mayfield; Richard C. McDonald
2016-01-01
Laricobius nigrinus Fender (Coleoptera: Derodontidae) is a specialist predator of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), native to the Pacific Northwest. It has been introduced into the eastern United States for biological control of exotic hemlock woolly adelgid populations that threaten...
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Hemlock woolly adelgid (Homoptera: Adelgidae): stylet bundle insertion and feeding sites
Rebecca F. Young; Kathleen S. Shields; Graeme P. Berlyn
1995-01-01
Stylet bundle insertion site, path traveled, and feeding site were examined for the hemlock woolly adelgid, Adelges tsugae Annand, on needles from current and previous years of eastern hemlock, Tsuga canadensis Carriere. The stylet bundle is composed of 4 individual stylets--2 outer mandibular stylets and 2 inner maxillary stylets...
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Sprinkling to prevent decay in decked western hemlock logs.
Ernest Wright; A.C. Knauss; R.M. Lindgren
1959-01-01
Decay developing in decked western hemlock (Tsuga heterophylla) has caused considerable loss in pulp yields in the Pacific Northwest. The Oregon Pulp and Paper Co., which commonly decks hemlock logs through one summer and occasionally through two summers, cooperated with the Pacific Northwest Forest and Range Experiment Station in a study to...
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David L. Mausel; Scott M. Salom; Loke T. Kok
2007-01-01
Studies are being conducted to determine optimal release procedures for establishment and sampling methodology of Laricobius nigrinus Fender (Coleoptera: Derodontidae), a predator of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae) on eastern hemlock, Tsuga canadensis (L.) Carriere, trees...
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Early effect of two successive thinnings in western hemlock.
George R. Staebler
1957-01-01
The Hemlock Experimental Forest near Grays Harbor in western Washington was established in 1949 in cooperation with the St. Regis Paper Company. A major effort in this cooperative research program is a study of commercial thinning in a stand of nearly pure, well stocked, even-aged western hemlock that originated in 1903, after logging.
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Hemlock woolly adelgid: a threat to eastern forests
Nathan P. Havill; Ligia C. Vieira; Scott M. Salom
2014-01-01
The hemlock woolly adelgid (HWA) (Adelges tsugae Annand) is a destructive, non-native pest of forest and ornamental hemlock trees in eastern North America. It was first collected in the eastern United States in 1951 in Richmond, Virginia, arriving sometime earlier directly from southern Japan, probably on live plant material. Other than its new...
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Basal area growth impacts of dwarf misletoe on western hemlock in an old-growth forest
David C. Shaw; Huso Manuela; Howard Bruner
2008-01-01
We investigated the effect of western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosend.) G.N. Jones ssp. tsugense) on the 13-year basal area growth of large (>45.7 cm diameter at breast height) western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees in an old-growth forest in southwestern Washington...
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Low temperature in the hemlock woolly adelgid system
Scott D. Costa; R. Talbot Trotter; Michael Montgomery; Michael Fortney
2008-01-01
Hemlock woolly adelgid (HWA) vary in their susceptibility to temperatures considerably below freezing. Many individuals may die by -20°C (-4°F), but more cold-tolerant individuals will allow populations to persist. Managers wanting to gauge temperature impacts on future adelgid pressure to hemlock forests may benefit from using available daily records...
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Monitoring hemlock vitality using ground-based digital imaging
Neil A. Clark; Sang-Mook Lee
2005-01-01
The vitality of hemlock (Tsuga spp.) trees needs to be assessed in order to evaluate the effectiveness of treatments that combat hemlock woolly adelgid (HWA), Adelges tsugae Annand 1 (Homoptera: Adelgidae). Ground-based photomonitoring can be used to assess canopy dynamics, which serves as a visual indicator of tree vitality. Here we propose a...
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Gouyue Yu; Michael E. Montgomery
2008-01-01
More than 63 species of lady beetles (Coleoptera: Coccinellidae) have been collected in China from hemlock infested with hemlock woolly adelgid, Adelges tsugae. The lady beetle species that seem most useful for biological control are in the genus/subgenus Scymnus (Neopullus), namely S. camptodromus, S....
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Weed, Aaron S; Elkinton, Joseph S; Lany, Nina K
2016-12-01
Insect populations are affected by density-dependent and density-independent factors, and knowing how these factors affect long-term population growth is critical to pest management. In this study, we experimentally manipulated densities of the hemlock woolly adelgid on eastern and western hemlock trees in the western USA to evaluate the effects of density and host species on hemlock woolly adelgid crawler colonization. We then followed development of hemlock woolly adelgid on each hemlock species. Settlement of crawlers was strongly density-dependent and consistent between host species. In addition, a period of hot days that coincided with the settlement of hemlock woolly adelgid crawlers put our experimental and naturally occurring populations into diapause during April. Diapause resulted in one generation that yr in our experimental population. Analyses of long-term air temperature records indicated that diapause-inducing temperatures in April similar to those observed in our experiment have occurred rarely since 1909 and the frequency of these events has not changed over time. Prior work suggests that hemlock woolly adelgid completes two generations per yr in the western USA with a diapause occurring in the summer. This typical life history reflects the long-term influence of regional average seasonal temperature patterns on development and the timing of diapause-inducing temperatures. However, the timing of unseasonal weather, such as the hot days observed in our experiment, occasionally changes life history trajectories from this normal pattern. Our results show that density-dependent and density-independent factors have strong effects on generational mortality and life history of hemlock woolly adelgid that are important to its population dynamics and management. Published by Oxford University Press on behalf of Entomological Society of America 2016. This work is written by US Government employees and is in the public domain in the US.
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Chelcy R. Ford; Barbara C. Reynolds; James Vose
2010-01-01
The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is causing widespread decline and mortality of eastern hemlock trees (Tsuga Canadensis (L.) Carr.). Stem injection of insecticide is widely used as a control measure, but its effectiveness depends on individual tree hydraulic characteristics. Recent work has shown that eastern...
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Chelcy R. Ford; James M. Vose
2006-01-01
Eastern hemlock, a principal riparian and cove canopy species in the southern Appalachian mountains, is facing potential widespread mortality due to the hemlock adelgid (HWA). To estimate the impact that the loss of this species will have on forest transpiration (E1) we quantified whole-tree (Ec) and leaf-level (E
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S. A. Vasiliauskas; L. W. Aarssen
2000-01-01
Casual observations have suggested that intermediate size and age gaps may exist in the eastern hemlock (Tsuga canadensis (L.)Carr.) populations of Algonquin Provincial Park, Ontario. This was confirmed in vegetation surveys reported here. Several hypotheses, involving mortality risks at different points in the life cycle of hemlock, are proposed to...
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Michael E. Montgomery; Anthony F. Lagalante
2008-01-01
The terpenoid profiles in the needles of the hemlock species were found to be related to geographic distribution of the species and their presumed ancestry. Although a definitive association of individual terpenoids with resistance to the hemlock woolly adelgid (HWA), Adelges tsugae Annand, was not identified, isobornyl acetate and α-...
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Management Strategies for Annosus Root Disease in Pacific Northwest Coastal Western Hemlock
Kenelm W. Russell
1989-01-01
Actual loss from annosus root disease infections in hemlock stands is difficult to determine. As political trends move toward protecting old-growth timber, greater market demand will be placed on second growth western hemlock. These stands must be kept healthy for maximum productivity. The paper compares the following 70-year rotation timber management scenarios: The...
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Glenn A. Christensen; Kent R. Julin; Robert J. Ross; Susan. Willits
2002-01-01
Wood volume recovery, lumber grade yield, and mechanical properties of young-growth Sitka spruce (Picea sitchensis (Bong.) Carr.) and western hemlock (Tsuga heterophyla (Raf.) Sarg.)were examined. The sample included trees from commercially thinned and unthinned stands and fluted western hemlock logs obtained from a sort yard....
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Phenology of the Hemlock Woolly Adelgid (Hemiptera: Adelgidae) in Northern Georgia
Shimar V. Joseph; Albert E. Mayfield; Mark J. Dalusky; Christopher Asaro; C. Wayne. Berisford
2011-01-01
Understanding the seasonal phenology of an insect pest in a specific geographic region is essential for optimizing the timing of management actions or research activities. We examined the phenology of hemlock woolly adelgid, Adelges tsugae Annand, near the southern limit of the range of eastern hemlock, Tsuga canadensis (L.) Carriere, in the Appalachians of northern...
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Scott M. Salom; Loke T. Kok; David L. Mausel; Theresa A. Dellinger; Brian M. Eisenback; Robbie W. Flowers
2007-01-01
Laricobius nigrinus is a natural predator of hemlock woolly adelgid (HWA), native to the western hemlock forests of North America. Research over the past 8 years at Virginia Tech has shown that this prey-specific predator is highly adapted to HWA. Several ongoing studies were reported on and will briefly be mentioned here.
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Joseph S. Elkinton; Robert T. Trotter; Ann F. Paradis
2011-01-01
The hemlock woolly adelgid (Adelges tsugae) is a small invasive Hemipteran herbivore that threatens the continued presence and abundance of hemlock in eastern North America. Efforts to control the adelgid have focused on the introduction of classical biological control agents. These biological controls include six different species of predatory...
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John A. Muir; Paul E. Hennon
2007-01-01
Hemlock dwarf mistletoe (Arceuthobium tsugense [Rosendahl] G.N. Jones) is a small, inconspicuous parasite that has significant effects on tree growth and stand structure in coastal forest ecosystems of western North America. Most previous research focused on the effects of hemlock dwarf mistletoe on timber production. Previous clearcut harvesting...
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Kevin M. Potter; Lia Campbell; Sedley A. Josserand; C. Dana Nelson; Robert M. Jetton
2017-01-01
Carolina hemlock (Tsuga caroliniana) is a rare conifer species that grows in small, isolated populations in the southern Appalachian Mountains of Virginia, North Carolina, South Carolina, Tennessee, and Georgia. The species is additionally imperiled by the hemlock woolly adelgid (Adelges tsugae), an invasive insect that can...
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Water hemlock poisoning in cattle: Ingestion of immature Cicuta maculata seed as the probable cause
USDA-ARS?s Scientific Manuscript database
Immature water hemlock seed heads caused the death of 9 cows in a herd of 81 in central Utah. This is the first documented case of poisoning and death in cattle from ingesting immature water hemlock seed. Field investigation of the poisoning and follow up diagnostic, chemical and toxicological eva...
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G. Narayanaraj; P.V. Bolstad; K.J. Elliott; J.M. Vose
2010-01-01
We examined the relationships between hemlock distribution and abundance and terrain attributes for the Coweeta Basin in the southern Appalachian Mountains. Field measurements were combined with GIS mapping methods to develop predictive models of abundance and distribution of Tsuga canadensis (L.) Carriere (eastern hemlock) and evaluate the co-...
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Use of satellite image data to identify changes in hemlock health over space and time
Laurent R. Bonneau; Kathleen S. Shields; Daniel L. Civco; David R. Mikus
2000-01-01
Eastern hemlock (Tsuga canadensis (L.) Carriere), is an important component of ecosystems in the northeastern United States and is the primary coniferous species in southern Connecticut. Hemlocks play a unique role in the region by providing spatial and structural habitat diversity that supports many wildlife and fish populations. Widespread damage...
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Hemlock woolly adelgid phenology and predacious beetle community on Japanese hemlocks
Shigehiko Shiyake; Yorio Miyatake; Michael Montgomery; Ashley Lamb
2008-01-01
Monthly samples of the hemlock woolly adelgid (HWA), Adelges tsugae, and predatory beetles were taken from Tsuga sieboldii near the border of Osaka and Kyoto prefectures. The beetles were collected by sweeping the canopy up to 5 meters height with nets. The phenology of HWA life stages were monitored by collecting branches and...
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Nathan P. Havill; Shigehiko Shiyake; Ashley Lamb Galloway; Robert G. Foottit; Guoyue Yu; Annie Paradis; Joseph Elkinton; Michael E. Montgomery; Masakazu Sano; Adalgisa Caccone
2016-01-01
Hemlock woolly adelgid, Adelges tsugae, is an invasive pest of hemlock trees (Tsuga) in eastern North America. We used 14 microsatellites and mitochondrial COI sequences to assess its worldwide genetic structure and reconstruct its colonization history. The resulting information about its life cycle, biogeography and host...
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Corinne E. Block; Jennifer D. Knoepp; Katherine J. Elliott; Jennifer M. Fraterrigo
2012-01-01
The impacts of exotic insects and pathogens on forest ecosystems are increasingly recognized, yet the factors influencing the magnitude of effects remain poorly understood. Eastern hemlock (Tsuga canadensis) exerts strong control on nitrogen (N) dynamics, and its loss due to infestation by the hemlock woolly adelgid (Adelges tsugae...
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Jennifer D. Knoepp; James M. Vose; Jerry L. Michael; Barbara C. Reynolds
2012-01-01
Imidacloprid is a systemic insecticide effective in controlling the exotic pest Adelges tsugae (hemlock woolly adelgid) in eastern hemlock (Tsuga canadensis) trees. Concerns over imidacloprid impacts on nontarget species have limited its application in southern Appalachian ecosystems. We quantified the movement and adsorption of imidacloprid in forest soils after soil...
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AmeriFlux US-Ha2 Harvard Forest Hemlock Site
Munger, William [Harvard University
2016-01-01
This is the AmeriFlux version of the carbon flux data for the site US-Ha2 Harvard Forest Hemlock Site. Site Description - The forest surrounding the Hemlock site has remained pristine with two exceptions. In the early to mid-1700s, European settlers cleared the majority of the forest for agricultural purposes. Selective harvesting of hemlock and chestnut trees occurred up until the early 1900s, when the chestnut blight killed all of the chestnut trees. In the current forest, about 83% of the total basal area of trees is hemlock. The remainder is equally divided between eastern white pine (Pinus strobus L.) and deciduous species, including red maple (Acer rubrum), red oak (Quercus rubra) and black birch (Betula lenta). A very thick organic layer (10-20 cm or more) covers the soil surface, and highly decayed coarse woody debris is abundant.
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Successful transplantation of donor organs from a hemlock poisoning victim.
Foster, Preston F; McFadden, Robert; Trevino, Raul; Galliardt, Scott; Kopczewski, Lea Ann; Gugliuzza, Kristene; Gonzalez, Zulma; Wright, Francis
2003-09-15
The poison hemlock plant (Conium maculatum) has been a known poison since early in human history, most notably as the agent used for the execution/suicide of Socrates in ancient Greece. No experience has been reported regarding the suitability of a hemlock victim's organs for transplantation. This report documents successful transplantation of the liver, kidney, and pancreas from a 14-year-old girl who died of anoxic encephalopathy from asphyxia after the accidental ingestion of fresh hemlock while on a nature hike. Predonation laboratory values were not remarkable, and liver and kidney biopsy results were normal. All organs in the three recipients had immediate function, and no recipient had any clinical evidence of transmitted toxin. All recipients are well, with functioning transplants at greater than 6 months after transplantation. Poison hemlock intoxication does not seem to be a contraindication to organ donation.
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Shimat V. Joseph; S. Kristine Braman; Jim Quick; James L. Hanula
2011-01-01
Hemlock woolly adelgid (HWA), Adelges tsugae Annand is a serious pest of eastern and Carolina hemlock in the eastern United States. A series of experiments compared commercially available and experimental insecticides, rates, application methods and timing for HWA control in Georgia and North Carolina. Safari 20 SG (dinotefuran) provided an average of 79 to 87%...
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Winter water relations at the upper elevational limits of hemlock on Mt. Ascutney, Vermont
Chandra B. Vostral; Richard L. Boyce
2000-01-01
Winter water relations have been monitored in hemlock (Tsuga canadensis (L.) Carr.) at their upper elevational limits for three winters, 1997, 1998, and 1999, on Mt. Ascutney, Vermont. Hemlock and white pine trees (Pinus strobus L.) reach their elevational limit on Mt. Ascutney at 640 m (2100?), while the summit has an elevation of...
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Effects of the removal of overstory hemlock on redback salamanders and other forest-floor fauna
Robert T. Brooks
2000-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr.) is the second most abundant conifer species in the northeastern United States. It occurs both in almost pure stands and in stands where it is mixed with hardwoods and white pine (Pinus strobus L.). Recently, hemlock in the middle-Atlantic and southern New England states has become...
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R. Talbot, III Trotter; Kathleen S. Shields
2009-01-01
The hemlock woolly adelgid (Adelges tsugae Annand) is a small, aphid-like insect native to East Asia and western North America. First documented in the eastern United States in Richmond, VA, in 1951, it has spread to at least 17 states, where it causes increased mortality among both eastern and Carolina hemlocks (Tsuga canadensis...
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Potential social and economic impacts of the hemlock woolly adelgid in southern New England
Xiaoshu Li; Evan L. Preisser; Kevin J. Boyle; Thomas P. Holmes; Andrew Liebhold; David. Orwig
2014-01-01
Adelges tsugae (Hemlock Woolly Adelgid; HWA) is a non-native forest insect that causes defoliation and mortality of hemlock in the eastern US. We quantified the extent to which people are potentially affected by the spread of HWA infestation where they live and where they recreate. We also considered how these impacts might change through time...
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Using AVIRIS to assess hemlock abundance and early decline in the Catskills, New York
Jennifer Pontius; Richard Hallett; Mary Martin
2005-01-01
In order to aid land managers in monitoring and controlling the ongoing hemlock woolly adelgid outbreak, more accurate landscape scale tools are required to locate the hemlock resource, identify infestation and spot early decline. To this end, NASA's Airborne Visible Infra-red Imaging Spectrometer was flown over the infestation front in the Catskills region of New...
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Hemlock resources at risk in the Great Smoky Mountains National Park
Kristine D. Johnson; Fred P. Hain; Katherine S. Johnson; Felton Hastings
2000-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr) is the dominant species in a variety of sites in Great Smoky Mountains National Park. Hemlock covers approximately 3820 acres (1528 hectares) or one percent of the Park, which at 524,856 acres is the largest area managed as wilderness in the eastern United States. Since timber was never harvested in about...
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Adaptation during northern range expansion in the elongate hemlock scale Fiorinia externa
Evan Preisser; Alexandra Lodge; David Orwig; Joseph Elkinton
2007-01-01
The elongate hemlock scale Fiorinia externa, (EHS) an invasive pest from Japan, was first found in the eastern United States in 1908. It feeds on a variety of plants, most notably the eastern hemlock Tsuga canadensis, and has been spreading slowly into southern New England. In order to examine the northern spread of EHS and the...
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S.V. Joseph; James Hanula
2011-01-01
Understanding how fertilization affects host resistance to hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera:Adelgidae), is important because fertilizers are often used to grow resistant selections to a suitable size for testing. We evaluated four hemlock species (Tsuga) under three different fertilizer regimes to assess whether fertility affected resistance to...
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Kevin M. Potter; Robert M. Jetton; William S. Dvorak; Valerie D. Hipkins; Rusty Rhea; W. Andrew Whittier
2012-01-01
Eastern hemlock (Tsuga canadensis [L.] Carr.) is an ecologically important tree species experiencing severe mortality across much of its eastern North American distribution, caused by infestation of the exotic hemlock woolly adelgid (Adelges tsugae Annand). To guide gene conservation strategies for this imperiled conifer, we conducted a range-wide genetic variation...
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The role of arboreta in studying the evolution of host resistance to the hemlock woolly adelgid
Nathan P. Havill; Michael E. Montgomery
2008-01-01
The hemlock woolly adelgid, Adelges tsugae, is an introduced pest of hemlock which is, unfortunately, all too familiar to many readers of Arnoldia. Adelgids are a small family of sucking insects, related to aphids, which feed only on conifers. Because they are so small and typically not very common, most adelgids usually go...
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Hemlock (Conium Maculatum) Poisoning In A Child.
Konca, Capan; Kahramaner, Zelal; Bosnak, Mehmet; Kocamaz, Halil
2014-03-01
Poison hemlock (Conium maculatum) is a plant that is poisonous for humans and animals. Accidental ingestion of the plant may result in central nervous system depression, respiratory failure, acute rhabdomyolysis, acute renal failure and even death. The main treatment of hemlock poisoning is supportive care. The case of a 6-year-old girl who was admitted to the emergency department with complaints of burning sensation in mouth, hypersalivation, tremor in hands and ataxia after ingestion of poison hemlock is presented here with clinical and laboratory features. In this case, we aim to report that accidental ingestion of plants resembling vegetables that are consumed daily can lead to serious complications and even death.
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Potential feeding deterrents found in hemlock woolly adelgid, Adelges tsugae
NASA Astrophysics Data System (ADS)
Jones, Anne C.; Mullins, Donald E.; Jones, Tappey H.; Salom, Scott M.
2012-07-01
The nonnative hemlock woolly adelgid ( Adelges tsugae Annand, Hemiptera: Sternorrhyncha: Adelgidae) has been a significant mortality agent of eastern hemlock ( Tsuga canadensis Carriere) throughout a large portion of its geographic range. During a study investigating adelgid vigor in relation to host health, it was noted that adelgid extracts ranged from a yellow to a deep red color. Analysis by GC-MS identified the presence of the anthraquinone, chrysophanol and its anthrone precursor, chrysarobin in the extract. These compounds are predator deterrents in several other insects, including chrysomelid beetles. It is hypothesized that these compounds serve a similar purpose in the hemlock woolly adelgid.
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Roger D. Ottmar; Colin C. Hardy; Robert E. Vihnanek
1990-01-01
A series of stereo photographs displays a range of residue loadings for harvested units in the Douglas-fir-western hemlock cover type common to the Willamette National Forest. Postburn residue levels are also represented for the Douglas-fir-western hemlock types. Information with each photo includes measured quadratic means and weights for various size classes, woody...
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John C. Brissette; Laura S. Kenefic
2000-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr.) is an important tree species in the mixed-species conifer forests of northern New England and adjacent Canada. Hemlock is very tolerant of understory conditions; consequently, it responds differently to various silvicultural treatments. In a long-term study at the Penobscot Experimental Forest in east-...
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Michael E. Montgomery; Defu Yao; Hongbin Wang
2000-01-01
The hemlock woolly adelgid, Adelges tsugae Annand, is generally believed to be native to Asia and is known to occur in India, Japan, and China. In China, there are approximately four species of hemlock that grow in 14 provinces. We explored regions of the Southwestern Plateau in Yunnan, Sichuan, and Shaanxi Provinces for the adelgid and its natural...
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J.M. Hastings; K.M. Potter; F.H. Koch; M.A. Megalos; R.M. Jetton
2017-01-01
Hemlock woolly adelgid (HWA, Adelges tsugae) is an invasive forest insect that has caused mortality of eastern (Tsuga canadensis) and Carolina hemlock (T. caroliniana) at an alarming rate. Now infesting 19 states and over 400 counties of the eastern United States, HWA poses a significant threat to native host species. The current biological and chemical methods for...
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P.E. Hennon; E.M. Loopstra
1991-01-01
Dead western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex. D. Don) trees were examined 38 years after intentional girdling (cuts made into wood around the bole) at Cat Island, Alaska, to describe their condition as wildlife habitat. All but 1 of 42 hemlock had boles broken at or below 30...
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Michael Montgomery; Carole A. S-J. Cheah; Christopher Asaro
2007-01-01
Biological control has been a major focus of efforts to reduce the impact of hemlock woolly adelgid (HWA) on hemlocks in the eastern United States. The lady beetle Scymnus sinuanodulus Yu et Yao, one of the most abundant predators of HWA in China, was first imported in 1996. Subsequently its biology and host range were evaluated in quarantine and...
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A. M. Zobel; K. Glowniak; J. E. Lynch; S. Dudka; A. Alliota
2000-01-01
Several species of higher plants and mushrooms have been surveyed growing under the canopy of old stands of hemlock surrounding Clear Lake near Minden, Ontario. Some of the hemlock seedlings growing on fallen trunks together with debris in which they were growing were brought to a greenhouse in pots, and some of them were transferred into sandy soil. The conditions of...
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Hakeem, A; Grant, J F; Lambdin, P L; Hale, F A; Rhea, J R; Wiggins, G J; Coots, C
2018-05-08
Hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is an exotic pest of eastern hemlock, Tsuga canadensis (L.) Carrière (Pinales: Pinaceae), in the eastern United States. Two commonly used insecticides to manage adelgid are imidacloprid, a systemic neonicotinoid insecticide, and horticultural oil, a refined petroleum oil foliar spray. We have investigated the influence of imidacloprid and horticultural oil on spider abundance at different canopy strata in eastern hemlock. In total, 2,084 spiders representing 11 families were collected from the canopies of eastern hemlock. In beat-sheet and direct observation samples, the families Theridiidae, Araneidae, Salticidae, and Anyphaenidae were the most abundant. Significantly higher numbers of spiders were recorded on untreated control trees compared with trees treated with imidacloprid using soil drench and soil injection applications. Spider abundance in trees injected with imidacloprid and horticultural oil applications did not significantly differ from control trees. Spider abundance was significantly greater in the top and middle strata of the canopy than in the bottom stratum, where imidacloprid concentrations were the highest. Regression analysis showed that spider abundance was inversely associated with imidacloprid concentration. This research demonstrates that imidacloprid, when applied with selected methods, has the potential to result in reductions of spider densities at different strata. However, slight reductions in spider abundance may be an acceptable short-term ecological impact compared with the loss of an untreated hemlock and all the associated ecological benefits that it provides. Future studies should include investigations of long-term impact of imidacloprid on spiders associated with eastern hemlock.
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Hanavan, Ryan P; Pontius, Jennifer; Hallett, Richard
2015-02-01
The hemlock woolly adelgid is a serious pest of Eastern and Carolina hemlock in the eastern United States. Successfully managing the hemlock resource in the region depends on careful monitoring of the spread of this invasive pest and the targeted application of management options such as biological control, chemical, or silvicultural treatments. To inform these management activities and test the applicability of a landscape-scale remote sensing effort to monitor hemlock condition, hyperspectral collections, and concurrent ground-truthing in 2001 and 2012 of hemlock condition were compared with field metrics spanning a 10-yr survey in the Catskills region of New York. Fine twig dieback significantly increased from 9 to 15% and live crown ratio significantly decreased from 67 to 56% in 2001 and 2012, respectively. We found a significant shift from 59% "healthy" hemlock in 2001 to only 16% in 2012. However, this shift from healthy to declining classifications was mostly a shift to decline class 2 "early decline". These results indicate that while there has been significant increase in decline symptoms as measured in both field and remote sensing assessments, a majority of the declining areas identified in the resulting spatial coverages remain in the "early decline" category and widespread mortality has not yet occurred. While this slow decline across the region stands in contrast to many reports of mortality within 10 yr, the results from this work are in line with other long-term monitoring studies and indicate that armed with the spatial information provided here, continued management strategies can be focused on particular areas to help control the further decline of hemlock in the region. Published by Oxford University Press on behalf of Entomological Society of America 2015. This work is written by US Government employees and is in the public domain in the US.
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Robert H. Ruth; Carl M. Berntsen
1955-01-01
Four years' measurement of seed fall in the spruce-hemlock type on the Cascade Head Experimental Forest indicates that an ample supply of seed is distributed over clear-cut areas under staggered-setting cutting. The largest tract sampled was 81 acres; in spite of a seed crop failure in 1950, it received an average of 243,000 viable spruce and hemlock seeds per...
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Nathan P. Havill; Michael E. Montgomery; Guoyue Yu; Shigehiko Shiyake; Adalgisa Caccone; Adalgisa Caccone
2006-01-01
The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is an introduced pest of unknown origin that is causing severe mortality to hemlocks (Tsuga spp.) in eastern North America. Adelgids also occur on other Tsuga species in western North America and East Asia, but these trees are not significantly damaged. The purpose of this study is to use...
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Anthony Lagalante; Frank Calvosa; Michael Mirzabeigi; Vikram Iyengar; Michael Montgomery; Kathleen Shields
2007-01-01
A previously developed single-needle, SPME/GC/MS technique was used to measure the terpenoid content of T. canadensis growing in a hemlock forest at Lake Scranton, PA (Lagalante and Montgomery 2003). The volatile terpenoid composition was measured over a 1-year period from June 2003 to May 2004 to follow the annual cycle of foliage development from...
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Conium maculatum (poison hemlock) toxicosis in a flock of range turkeys.
Frank, A A; Reed, W M
1987-01-01
Five 20-week-old tom turkeys from a flock of range turkeys were presented for examination; the flock had a history of salivation, tremors, paralysis, and increased mortality. Necropsy revealed numerous seeds identified as seeds from Conium maculatum (poison hemlock) within the crop, proventriculus, and gizzard. Histopathologic alterations were limited to catarrhal enteritis. Clinical signs of Conium maculatum toxicosis abated after the turkeys were removed from their range, which was infested with poison hemlock.
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Characterization of terpenoid volatiles from cultivars of eastern hemlock (Tsuga canadensis).
Lagalante, Anthony F; Montgomery, Michael E; Calvosa, Frank C; Mirzabeigi, Michael N
2007-12-26
The volatile terpenoid fraction from needles in 13 cultivars of Tsuga canadensis L. (Carriere) was analyzed by gas chromatography with mass spectrometry (GC-MS). The results of this study are considered along with previously reported results for foliar terpenoid levels of the Asian (T. sieboldii, T. chinensis, T. diversifolia), western North American (T. mertensiana, T. heterophylla), and eastern North American species (T. canadensis, T. caroliniana) of hemlock to draw conclusions about the potential of cultivar host resistance to the hemlock woolly adelgid (Adelges tsugae Annand). It is suggested that hemlocks in eastern North America have adapted their terpenoid chemistry for protection against endemic defoliators and that this has made them vulnerable to non-native, sucking pests such as adelgids and scales. Some cultivars of T. canadensis have a terpenoid profile that resembles that of the resistant noneastern North American species and are candidates for biological screening for resistance. Among the cultivars, the variation in terpenoid chemistry did not absolutely correspond with the considerable differences in morphological characters observed, indicating that the terpenoid chemistry is not definitively coupled with hemlock morphology.
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Intraspecific variation in Tsuga canadensis foliar chemistry
Laura Ingwell; Joseph Brady; Matthew Fitzpatrick; Brian Maynard; Richard Casagrande; Evan Preisser
2009-01-01
Three groups of eastern hemlock (Tsuga canadensis Carr.) trees were analyzed to compare their chemical composition and the potential for naturally occurring resistance to hemlock woolly adelgid (Adelges tsguae...
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1980-06-01
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NASA Astrophysics Data System (ADS)
Hadley, J. L.; Kuzeja, P.; Mulcahy, T.; Singh, S.
2008-12-01
Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S. Julian Hadley, Paul Kuzeja, Safina Singh and Thomas Mulcahy Transfers of water vapor from terrestrial ecosystems to the atmosphere affect regional hydrology, weather and climate over short time scales, and forest-atmosphere CO2 exchange affects global climate over long timescales. To better understand these effects for forests dominated by two very different tree species, we measured forest-atmosphere water vapor and CO2 transfers by the eddy flux technique to at two sites in central Massachusetts USA for three years. Average annual evapotranspiration (ET) for a young deciduous forest dominated by red oak (Quercus rubra L., the most abundant tree species in the area), was about 430 mm or 25 percent greater than for a coniferous forest dominated by 100 to 230 year old eastern hemlock (Tsuga canadensis L.). The difference in ET was most pronounced in July and August when the deciduous forest lost about 50 percent more water by ET in the average year (192 mm for oak forest versus 130 mm for hemlock). These data indicate that if deciduous trees with similar physiology to red oak replace hemlocks, summertime ET will increase while summer streamflow, soil water content and the extent of year- round wetlands will decrease. Increased summertime ET should also lead to slightly higher regional atmospheric humidity and precipitation. Hemlock-to-deciduous forest conversion has occurred from North Carolina to southern New England and is continuing northward as a lethal insect pest, the hemlock woolly adelgid (Adelges tsugae Annand) continues to kill hemlocks. Average annual carbon storage for the old hemlock forest in our study was about 3.3 Mg C/ha, nearly equal to the average for the deciduous forest, 3.5 Mg C/ha. This calls into question ecological theory that predicts large declines in the rate of carbon uptake for old forests, and indicates that annual carbon storage will not necessarily increase over the long term after hemlock trees are killed by the hemlock woolly adelgid and replaced by deciduous species. Maximum monthly carbon storage in the hemlock forest occurred in spring (April and May) and was enhanced by early soil thawing and cessation of nighttime frost. This pattern is probably common to many evergreen conifers in the northeastern U.S., so climate warming that includes an earlier end to freezing temperatures in spring should increase C storage by conifer forests in the northeastern U.S. - unless this effect is canceled out by reduced C uptake or enhanced C loss due to changes in summer and fall climate.
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Timber productivity of seven forest ecosystems in southeastern Alaska.
Willem W.S. van Hees
1988-01-01
Observations of growth on Alaska-cedar (Chamaecyparis nootkatensis), mountain hemlock (Tsuga mertensiana), Sitka spruce (Picea sitchensis), western hemlock (Tsuga heterophylla), and western redcedar (Thuja plicata) on seven forest ecosystems in southeastern Alaska...
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Panter, K E; Bunch, T D; Keeler, R F; Sisson, D V
1988-01-01
Fetal movement in pregnant ewes gavaged with Conium maculatum (poison-hemlock) was reduced significantly, but temporarily. Fetal movement was observed by radio ultrasound at 45, 54 and 60 days of gestation in control ewes and on days 45, 54, and 60 of gestation immediately before and 1 hour following poison-hemlock feeding in treated ewes. Fetal movement was significantly reduced (P less than 0.01) 1 hour after poison-hemlock administration, but returned to normal within 18 hours post treatment. At parturition seven of eleven lambs born to seven treated ewes had varying degrees of front limb abnormalities. Modest to moderate flexure of the carpal joints, some lateral deviation in the front limbs at the pastern joint and kinked tails were observed. These malformations were transient and resolved spontaneously by 8 weeks after lambing.
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Toxicoses in livestock from the hemlocks (Conium and Cicuta spp.).
Panter, K E; Keeler, R F; Baker, D C
1988-09-01
The hemlocks, Conium maculatum (poison-hemlock) and Cicuta spp. (waterhemlock), are poisonous plants that cause sizeable losss to the livestock industry. Clinical signs of poisonhemlock toxicosis are similar in all species of livestock and include muscular weakness, incordination, trembling, initial central nervous system stimulation, depression and death from respiratory paralysis. Poison-hemlock also causes skeletal defects in the offspring of cattle, pigs and sheep and cleft palate in pigs when ingested during specific periods of gestation. The primary toxicants in poison-hemlock are coniine and gamma-coniceine. Coniine predominates in mature plants and seed, whereas gamma-coniceine predominates in early growth of the plant. Waterhemlock is the most violently toxic poisonous plant known. The toxicant is cicutoxin, which acts on the central nervous system, causing violent convulsions and death. Clinical signs of poisoning appear within 15 min after ingestion of a lethal dose and include excessive salivation, nervousness, tremors, muscular weakness and convulsive seizures interspersed by intermittent periods of relaxation and a final paralytic seizure resulting in anoxia and death. Elevated activities of lactic dehydrogenase, aspartate aminotransferase and creatine kinase in blood are observed, indicative of muscular damage. Toxicoses from poisonhemlock and waterhemlock generally occur in early spring when both plants emerge before other, more palatable plants begin to grow. All parts of the poison-hemlock plant are toxic. The root or tubers of waterhemlock are toxic; however, experimental evidence concerning the toxicity of other plant parts is inconclusive.
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Johnson, Jeremy S; Gaddis, Keith D; Cairns, David M; Konganti, Kranti; Krutovsky, Konstantin V
2017-03-01
Untangling alternative historic dispersal pathways in long-lived tree species is critical to better understand how temperate tree species may respond to climatic change. However, disentangling these alternative pathways is often difficult. Emerging genomic technologies and landscape genetics techniques improve our ability to assess these pathways in natural systems. We address the question to what degree have microrefugial patches and long-distance dispersal been responsible for the colonization of mountain hemlock ( Tsuga mertensiana ) on the Alaskan Kenai Peninsula. We used double-digest restriction-associated DNA sequencing (ddRADseq) to identify genetic variants across eight mountain hemlock sample sites on the Kenai Peninsula, Alaska. We assessed genetic diversity and linkage disequilibrium using landscape and population genetics approaches. Alternative historic dispersal pathways were assessed using discriminant analysis of principle components and electrical circuit theory. A combination of decreasing diversity, high gene flow, and landscape connectivity indicates that mountain hemlock colonization on the Kenai Peninsula is the result of long-distance dispersal. We found that contemporary climate best explained gene flow patterns and that isolation by resistance was a better model explaining genetic variation than isolation by distance. Our findings support the conclusion that mountain hemlock colonization is the result of several long-distance dispersal events following Pleistocene glaciation. The high dispersal capability suggests that mountain hemlock may be able to respond to future climate change and expand its range as new habitat opens along its northern distribution. © 2017 Botanical Society of America.
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NASA Astrophysics Data System (ADS)
Appleton, S.; St George, S.
2014-12-01
This study investigates the climate sensitivity of mountain hemlock (Tsuga mertensiana (Bong.) Carr.) near the southern limit of its range, tests the stability of its climate-tree relations over the last few decades, and explores its potential as a hydroclimatic proxy for Crater Lake National Park. We collected tree cores at seven locations around the caldera rim, focusing on hemlock growing at higher elevations (2000-2400 masl). The median length of all ring-width series is 283 years, and the oldest hemlock sample extends back to C.E. 1450. Several types of anatomical anomalies, including frost rings, traumatic resin ducts, false rings, and light late-wood bands were observed within the specimens, the most common feature being a false ring in C.E. 1810. Each set of standardized ring-width measurements has a strong common signal, with between-tree correlations (r-bar) ranging from 0.31 to 0.49. Preliminary analysis suggests hemlock growth across the park is strongly and inversely related to total cool-season precipitation, and is also influenced positively (albeit more weakly) by mean summer temperature. Most sites are significantly and negatively correlated with total December-to-February precipitation (r = -0.41) and total precipitation from December to August (r = -0.48). Compared to other ring-width records exhibiting similar negative responses to winter precipitation, these hemlocks appear to track that specific signal quite clearly and, as a result, these data may be suitable to reconstruct past changes in cool-season moisture in Crater Lake National Park and across the broader southern Cascades.
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Mapping forest risk associated with the hemlock woolly adelgid
Andrew M. Liebhold; Randall S. Morin; Andrew Lister; Kurt W. Gottschalk; Eugene Luzader; Daniel Twardus
2003-01-01
The hemlock woolly adelgid, Adelges tsugae, is native to Asia and was first introduced to North America in British Columbia in the 1920s and was later discovered in the Shenandoah Mountains of Virginia in the 1950s.
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Scott Costa; Karen Felton; Bradley Onken; Richard Reardon; Rusty. Rhea
2011-01-01
Forest populations of hemlock woolly adelgid (HWA) were reduced using an operational formulation of the insect-killing fungus Lecanicillium muscarium when it was supported by microfactory formulation technology.
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NASA Astrophysics Data System (ADS)
Munger, J. W.; David, O.; Barker Plotkin, A.; Schaaf, C.
2017-12-01
Hemlock Woolly Adelgid (HWA) is an invasive insect pest infesting eastern hemlock. Affected hemlock trees typically die within 4-10 years. Black birch seedlings thrive as a thinning canopy allows additional light to reach the forest floor. HWA invasion is a unique disturbance where decline and recovery are occuring simultaneously over an extended period. Although the overall vegetation dynamics associated with HWA disturbance have been well studied, the instantaneous carbon balance at the ecosystem scale has not been closely observed. At the Harvard Forest in central MA we have measured CO2, water and energy eddy flux since 2004. HWA has been present at Harvard Forest since 2002, but defoliation was insignificant prior to 2010. Since 2010 defoliation among trees near the Hemlock tower has increased dramatically and tree mortality is increasing. The pace of HWA attack has been monitored by periodic surveys and stand structure has been observed by 3-d lidar scans. In order to quantify changes in ecosystem metabolism without biasing the results from data filling we evaluate mean ecosystem function derived from a simple model that relates CO2 flux to temperature and light response. The mean carbon uptake efficiency during summer growing season has declined about 13% from before 2010 (pre-HWA) to after 2010 (post-HWA). Ecosystem respiration averaged over these intervals has not changed noticeably over this period. However, annual mean Reco in the summer peaks in 2014 and then declines over subsequent years. Mean uptake coefficients declined from 26 to 14 μmol-C m-2s-1 per μmol-photon m-2s-1 between 2010 and 2015, with some recovery in 2016. Taken together, results show that despite an accelerating forest mortality, ecosystem carbon stock in this infested hemlock stand has not been destabilized and that rates of carbon metabolism are changing more slowly than the decline in hemlock biomass. The ecosystem can partially compensate for loss of foliage as more light reaches previously shaded needles and new seedlings emerge in open gaps. However, we anticipate a shift in carbon uptake phenology as the fraction of deciduous vegetation increases. Ongoing mortality will add to the large carbon stock in the forest floor, but as yet there has not been a detectable change in rates of whole-ecosystem respiration.
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Samita Limbu; Melody A. Keena; David Long; Nancy Ostiguy; Kelli Hoover
2015-01-01
Development time and prey consumption of Scymnus (Neopullus) camptodromus Yu and Liu (Coleoptera: Coccinellidae) larvae by instar, strain, and temperature were evaluated. S. camptodromus, a specialist predator of hemlock woolly adelgid Adelges tsugae (Annand) (Hemiptera:...
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NASA Astrophysics Data System (ADS)
Chaisson, W. P.; Arnold, M. R.; Cottrell, R. D.
2002-05-01
Between 1900 and 1930 CE when the NAO index showed large amplitude positive excursions, but the AO index varied at very small amplitudes, drought conditions frequently prevailed in western New York state according the Palmer Drought Index (PDI). Since 1970, when both the NAO and the AO indices show large and progressively increasing positive excursions, the PDI has been generally positive, indicating moisture surpluses in the region. Magnetic properties, including coercivity of remanence, have been measured and the diatoms have been enumerated in sediments from two gravity cores collected from Hemlock and Conesus Lakes. The sediments date from ~1875 CE in the Hemlock core and ~1923 CE in the Conesus core. Variations in magnetic grain-size are interpreted from the coercivity of remanence, with lower coercivity of remanence associated with large grain size. The primary productivity of lakes is interpreted from the Lake Trophic Status Index (LTSI), which is calculated based on known ecologies of several diatom species. In both lakes we find that larger magnetic grain size is associated with greater productivity in the lakes. In the Hemlock core, through the interval corresponding to 1913-1943 coercivity of remanence values declined to 281-259 Oersteds, from late 19th century values that were >350 Oersteds. The bottom of the Conesus core (1923-1938 CE) has the lowest coercivity of remanance values in the record (309-317 Oersteds). LTSI values in the Hemlock samples increase as remanence of coercivity values decline between 1888 and 1920 CE. This reflects an increase in the abundance of the mesoeutrophic Tabellaria fenestrata during this interval. In the Conesus samples the agreement between coercivity of remanence and LTSI is quite close. The range of variation in both LTSI and magnetic grain size is smaller in Conesus than in Hemlock Lake. The diatom assemblage is also quite different in Conesus, dominated by eutrophic Aulacosiera granulata, which are rare or absent at Hemlock Lake. The Hemlock basin is much steeper than than that of Conesus and its water level fluctuates more extremely because it is the reservoir for the city of Rochester. Hemlock Lake is oligotrophic and its drainage basin is heavily forested and lightly populated. Conesus Lake is eutrophic, its shores lined with cottages and the basin is heavily agricultural. In spite of these differences in both natural conditions and anthropogenic factors, the LTSI and magnetic measurements of the two lakes share variance, ostensibly forced by regional climate change. Initial results suggest that the shared component of variance in these proxy indicators can predict variations in regional drought intensity. Regional drought intensity, in turn, seems associated with an uncoupling of AO and NAO variation.
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Samita Limbu; Katie Cassidy; Melody Keena; Patrick Tobin; Kelli Hoover
2015-01-01
Scymnus (Neopullus) camptodromus Yu and Liu (Coleoptera: Coccinellidae) was brought to the United States from China as a potential biological control agent for hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae). Scymnus camptodromus phenology is...
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Eastern hemlock decline in riparian areas from Maine to Alabama
D.E. Evans; W.M. Aust; C.A. Dolloff; B.S. Templeton
2010-01-01
Eastern hemlock (Tsuga canadensis) is an integral component of Appalachian forest ecosystems and is valued for its ecological functions and aesthetic qualities. It is a foundation tree species in riparian systems and is known to moderate steam temperatures and base flow.
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Western hemlock as a veneer resource.
Thomas D. Fahey; Jr. Woodfin
1982-01-01
Presents recovery of veneer grade and volume from western hemlock from Oregon and Washington. Veneer grade recovery varied by grade and size of logs. Veneer volume recovered was about 45 percent of the cubic volume of the log and varied somewhat with log diameter.
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-08-03
... eastern hemlock (Tsuga canadensis), where it causes needle loss, abortion of buds, and the eventual death..., S. coniferarum, is a small lady beetle about 2 millimeters long and covered in fine, short hairs. In...
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Cost and productivity of new technology for harvesting and in-woods processing small-diameter trees.
Michael B Lambert; James O. Howard
1990-01-01
A study was conducted on the productivity and cost of an integrated harvesting and processing system operating in small-diameter timber (western hemlock-type) on the Olympic Peninsula of western Washington. The system uses a new steep-slope fellerbuncher, a clam-bunk grapple-skidder (forwarder), a prototype chain-flail debarker delimber, a chipper, a conveyor system,...
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Role of acid and aluminum-rich media in the growth and nutrition of Pacific Northwest conifers
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ryan, P.J.
1983-01-01
Forest soils of coastal Washington and Oregon tend to be very acidic with large accumulations of organic matter. Yet the productivity of forest species on these sites can attain record levels. The effect of acid and aluminum-rich media on the growth and nutrition of Pacific Northwest conifer species was investigated for western hemlock, Douglas-fir, western redcedar, and Sitka spruce. The four different types of growth media utilized were solution cultures, sand cultures, mineral soils, and forest floor organic matter. Hydroponic nutrient solutions and sand cultures were used in experiments designed to differentiate the effect of aluminum ions from the hydrogenmore » ions generated by hydrolysis of Al/sup 3 +/. Relative to agronomic plants, all the conifers were found tolerant of the acid solutions and high levels of aluminum. Species differed in their relative tolerance to H/sup +/ and Al/sup 3/ ions. Western hemlock seedling growth was superior to Douglas-fir in the acidified soils and forest floor media, while Ca(OH)/sub 2/ amendment favored Douglas-fir. The marginal increase in western hemlock growth in N + P treated soils was highest in acidified soils. Western hemlock exhibited an ability to absorb nutrients in the presence of excess solution H/sup +/ ions, maintain growth with low tissue requirements of Ca and Mg, and accumulate high levels of aluminum in its roots and foliage without major adverse effect. These attributes are considered to make western hemlock the most acid and Al-tolerant of the four Pacific Northwest forest species studied. Western redcedar was second in acid tolerance to western hemlock. This species' ability to accumulate Ca minimized Al absorption and H/sup +/ damage to its roots.« less
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E. Gaige; D.B. Dail; D.Y. Hollinger; E.A. Davidson; I.J. Fernandez; H. Sievering; A. White; W. Halteman
2007-01-01
Most experimental additions of nitrogen to forest ecosystems apply the N to the forest floor, bypassing important processes taking place in the canopy, including canopy retention of N and/or conversion of N from one form to another. To quantify these processes, we carried out a large-scale experiment and determined the fate of nitrogen applied directly to a mature...
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Charles E. Williams; William J. Moriarity
2000-01-01
We assessed the species composition and structure of three riparian forest stands of differing ages (old-growth, late-successional, mid-successional), dominated by eastern hemlock (Tsuga canadensis Carr.), in the Allegheny National Forest of northwestern Pennsylvania.
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Mountain hemlock: a bibliography with abstracts.
Jerry F. Franklin
1962-01-01
This bibliography lists references pertaining to mountain hemlock (Tsuga mertensiana (Bong.) Carr.) found in North American and European literature for individuals interested in this species. The author has attempted to include all references which might conceivably provide useful information on this species; abstracts are provided for those...
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NASA Technical Reports Server (NTRS)
Salas, W. A.; Ranson, K. J.; Rock, B. N.; Moss, D. M.
1991-01-01
The diurnal characteristics of microwave dielectric properties and water potential of two conifer species were investigated in July and September, 1990. P-band and C-band radial dielectric profiles of hemlock and red spruce, as well as hemlock diurnal water potential and dielectric profiles, are presented. The resulting radial dielectric profiles matched the regions of the functional sapwood (water transport component of the active xylem) in both species such that the sapwood was characterized by a higher dielectric than the bark and heartwood tissues. This is probably due to characteristic differences in the water content of each tissue. As the hemlocks progressed through their diurnal water potential pattern, the dielectric profile remained static until mid-afternoon. As the tension in the water column relaxed (2 to 3 bars) the dielectric constant decreased by 30 to 40 percent. There are several possible explanations for this phenomenon, and these may relate to the dependency of the dielectric measurements on temperature, salinity, and volumetric water content.
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NASA Astrophysics Data System (ADS)
Dunckel, Kathleen Lois
Introduced invasive pests and climate change are perhaps the most important and persistent catalyst for changes in forest composition. Infestation and outbreak of the hemlock woolly adelgid (HWA, Adelges tsugae) along the eastern coast of the USA, has led to widespread loss of hemlock (Tsuga canadensis (L.) Carr.), and a shift in tree species composition towards hardwood stands. Maine's forest dominated landscape and position at the leading edge of the HWA invasion provides an excellent opportunity to inform sustainable forest management (SFM) practices by using spatially explicit models to predict current tree species distribution, future range shifts, and solicit broad based feedback from Maine residents about forest management goals and preferences. This paper describes an interdisciplinary study of the ecological and social implications of changes in mixed northern hardwood forests due to disturbance. A two stage mapping approach was used where presence/absence of eastern hemlock is predicted with an overall accuracy of 85% and the continuous distribution (% basal area) was predicted with an accuracy of 83%. Given the importance of climate variables in predicting eastern hemlock, forecasts of future range shifts are possible using data generated through climate scenarios. The NASA Earth Exchange (NEX) Downscaled Climate Projections (NEX-DCP30) dataset was used to model future shifts in the geographic range of eastern hemlock throughout the state of Maine. The results clearly describe a significant shift in eastern hemlock range with gains in total geographic area that is suitable habitat. Sustaining forest systems across the landscape requires not only ecological knowledge, but also the integration of multiple socio-economic criteria as well, including data obtained through broad-based public participation approaches. Here, 3000 Maine residents were surveyed and asked how they: (1) value local forests; (2) view forest management goals and threats to forest ecosystems; and (3) evaluate alternative treatment options for the control of invasive species - in this case, HWA. Results suggest that despite Maine's historic dependence on forest products, resident values regarding forests are complex and display agreement with both psycho-spiritual and anthropocentric motivations.
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Renninger, Heidi J; Meinzer, Frederick C; Gartner, Barbara L
2007-01-01
We compared hydraulic architecture, photosynthesis and growth in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a shade-intolerant species, and western hemlock (Tsuga heterophylla (Raf.) Sarg.), a shade-tolerant species, to study the temporal pattern of release from suppressive shade. In particular, we sought to determine whether hydraulic architecture or photosynthetic capacity is most important in constraining release. The study was conducted at two sites with mixed stands of 10- to 20-year-old Douglas-fir and western hemlock. At one site, the stand had been thinned allowing release of the understory trees, whereas at the other site, the stand remained unthinned. Douglas-fir had lower height growth (from 1998-2003) and lower relative height growth (height growth from 1998 to 2003/height in 1998) than western hemlock. However, relative height growth of released versus suppressed trees was higher in Douglas-fir (130%) than in western hemlock (65%), indicating that, although absolute height growth was less, Douglas-fir did release from suppression. Release seemed to be constrained initially by a limited photosynthetic capacity in both species. Five years after release, Douglas-fir trees had 14 times the leaf area and 1.5 times the leaf nitrogen concentration (N (area)) of suppressed trees. Needles of released western hemlock trees had about twice the maximum assimilation rate (A (max)) at ambient [CO(2)] as needles of suppressed trees and exhibited no photoinhibition at the highest irradiances. After release, trees increased in leaf area, leaf N concentration and overall photosynthetic capacity. Subsequently, hydraulic architecture appeared to constrain release in Douglas-fir and, to a lesser extent, in western hemlock. Released trees had significantly less negative foliar delta(13)C values than suppressed trees and showed a positive relationship between leaf area:sapwood area ratio (A (L)/A (S)) and delta(13)C, suggesting that trees with more leaf area for a given sapwood area experienced a stomatal limitation on carbon gain. Nonetheless, these changes had no significant effects on leaf specific conductivities of suppressed versus released trees of either species, but leaf specific root conductance was significantly lower in released Douglas-fir.
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Aerially released spray penetration of a tall coniferous canopy
USDA-ARS?s Scientific Manuscript database
An aerial spray deposition project was designed to evaluate aerial application to an Eastern Hemlock (Tsuga canadensis) canopy to combat Hemlock Woolly Adelgid (Adelges tsugae). This adelgid offers a difficult target residing in the forest canopy at the nodes of branchlets. The study collected 1680 ...
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Spatial and Temporal Distribution of Imidacloprid Within the Crown of Eastern Hemlock
Turcotte, Richard M.; Lagalante, Anthony; Jones, Jonathan; Cook, Frank; Elliott, Thomas; Billings, Anthony A.
2017-01-01
Systemic imidacloprid is the most widely used insecticide to control the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), an exotic pest of eastern hemlock, Tsuga canadensis (L.) Carriére in the United States. This study was conducted to 1) determine the effect of treatment timing (spring vs. fall) and application method (trunk injection vs. soil injection) on the spatial and temporal distribution of imidacloprid within the crown of A. tsugae-free eastern hemlock using a competitive enzyme-linked immunosorbent assay (ELISA), 2) compare ELISA to gas chromatography-mass spectrometry (GC/MS) for the detection of imidacloprid in xylem fluid, and 3) determine the concentration of imidacloprid in leaf tissue using high performance liquid chromatography with tandem mass spectrometric (LC/MS/MS) detection methods. Xylem fluid concentrations of imidacloprid were found to be significantly higher for spring applications than for fall applications and for trunk injections than soil injections in the first year posttreatment. A total of 69% of samples analyzed by ELISA gave 1.8 times higher concentrations of imidacloprid than those found by GC/MS, leading to evidence of a matrix effect and overestimation of imidacloprid in xylem fluid by ELISA. A comparison of the presence of imidacloprid with xylem fluid and in leaf tissue on the same branch showed significant differences, suggesting that imidacloprid moved intermittently within the crown of eastern hemlock. PMID:28130463
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John D. Waldron; Robert N. Coulson; David M. Cairns; Charles W. Lafon; Maria D. Tchakerian; Weimin Xi; Kier Klepzig; Andrew Birt
2010-01-01
The southern pine beetle, Dendroctonus frontalis (Zimmerman) (Coleoptera: Curculionidae: Scolytinae) (SPB), is an indigenous invasive species that infests and causes mortality to pines (Pinus spp.) throughout the Southern United States. The hemlock woolly adelgid, Adelges tsugae (Annand) (Homoptera:...
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Management of western Hemlock-sitka spruce forests for timber production.
Robert H. Ruth; A.S. Harris
1979-01-01
Ecological and management information for the coastal western hemlock-Sitka spruce forests is summarized in this report. Areas of emphasis include logging methods, silvicultural systems, natural and artificial regeneration, residue disposal, weed control, thinning, growth and yield, and forest protection. Consideration is given site protection and nontimber values as...
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Forest dynamics following eastern hemlock mortality in the southern Appalachians
Chelcy R. Ford; Katherine J. Elliott; Barton D. Clinton; Brian D. Kloeppel; James M. Vose
2011-01-01
Understanding changes in community composition caused by invasive species is critical for predicting effects on ecosystem function, particularly when the invasive threatens a foundation species. Here we focus on dynamics of forest structure, composition and microclimate, and how these interact in southern Appalachian riparian forests following invasion by hemlock...
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Growth response of suppressed true fir and mountain hemlock after release.
K.W. Seidel
1985-01-01
The diameter and height growth of advance reproduction of suppressed true fir (Abies spp.) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) was measured in south-central Oregon after release by overstory removal in clearcuttings, shelterwood units, and uncut stands. Postrelease growth was greatest in clearcuttings,...
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Recognizing all-aged hemlock forests
Orie L. Loucks; James Nighswander
2000-01-01
Eastern hemlock (Tsuga canadensis (L.) Carr.) occurs in old-growth stands sometimes over 400 years old, throughout its principal range from Nova Scotia to Wisconsin. Studies based on aging as well as diameter distributions indicate a stand structure often dominated by an initial multi-decade post-disturbance pulse of seedling establishment, followed...
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Sarah M. Grubin; Darrell W. Ross; Kimberly F. Wallin
2011-01-01
Leucopis spp. (Diptera: Chamaemyiidae) from the Pacific Northwest previously were identified as potential biological control agents for the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in the eastern United States. We collected Leucopis spp. larvae from A. tsugae...
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USDA-ARS?s Scientific Manuscript database
Characteristics of the plant surface significantly affect host-plant selection by phytophagous insects. Surface morphology of six hemlock species (Tsuga spp.) and a hybrid was investigated using low-temperature scanning electron microscopy. Observations focused on trichome presence and placement a...
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Cherry Creek Research Natural Area: guidebook supplement 41
Reid Schuller; Jennie Sperling; Tim Rodenkirk
2011-01-01
This guidebook describes Cherry Creek Research Natural Area, a 239-ha (590-ac) area that supports old-growth Douglas-fir-western hemlock (Pseudotsuga menziesii- Tsuga heterophylla) forest occurring on sedimentary materials in the southern Oregon Coast Range. Major plant associations present within the area include the western hemlock/Oregon oxalis...
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Potential concerns for tree response from stem injection
Kevin T. Smith; Phillip A. Lewis
2005-01-01
Stem injection of imidacloprid is an available component of management strategies for hemlock woolly adelgid. Preliminary observations of similar treatments of maple and ash show that the injury sustained by injection warrants investigation of the wound response in eastern hemlock. Such investigations need adequate experimental controls to identify the role of...
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Downed wood as seedbed: measurement and management guidelines
Mark J. Ducey; Jeffrey H. Gove
2000-01-01
Eastern hemlock has exacting germination requirements, and availability of suitable microsites for germination can limit the development of hemlock regeneration. A major contributor to those microsites is coarse woody debris. New methods for quantifying coarse woody debris have recently been developed that are complementary to strategies typically used in timber...
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Is Pseudoscymnus tsugae the solution to the hemlock woolly adelgid problem?: An early perspective
Mark S. McClure; Carole A. S-J. Cheah; Timothy C. Tigner
2000-01-01
Hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae) is native to Japan where it is an innocuous inhabitant of Tsuga diversifolia Masters and T. sieboldii Carriere. Native populations of this insect are regulated by host resistance and natural enemies. However, introduced populations in eastern...
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Developing Biomass Equations for Western Hemlock and Red Alder Trees in Western Oregon Forests
Krishna Poudel; Hailemariam Temesgen
2016-01-01
Biomass estimates are required for reporting carbon, assessing feedstock availability, and assessing forest fire threat. We developed diameter- and height-based biomass equations for Western hemlock (Tsuga heterophylla (Raf.) Sarg.) and red alder (Alnus rubra Bong.) trees in Western Oregon. A system of component biomass...
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Processing mill scale study data on a type 650 electronic machine.
Floyd A. Johnson
1956-01-01
During April 1956, about 20,000 boards from 210 white fir and 290 western hemlock logs were measured at a lumber mill in western Washington. A magnetic drum, data-processing machine (type 650) was then used to calculate board-feet volumes by lumber grade for each log, and average board-foot volumes by lumber grade for each log diameter-class within log grades and...
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Arielle L. Arsenault; Nathan P. Havill; Albert E. Mayfield; Kimberly F. Wallin
2015-01-01
The predatory species Laricobius nigrinus (Fender) and Laricobius osakensis (Shiyake and Montgomery) (Coleoptera: Derodontidae) have been released for biological control of hemlock woolly adelgid (Adelges tsugae; Hemiptera: Adelgidae) in eastern North America. L. osakensis is native to Japan, whereas
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Chapter 16: Inland Habitat Associations of Marbled Murrelets in British Columbia
Alan E. Burger
1995-01-01
Most Marbled Murrelets (Brachyramphus marmoratus) in British Columbia nest in the Coastal Western Hemlock biogeoclimatic zone. In this zone, detection frequencies were highest in the moister ecosections and in low elevation forests. Nests and moderately high levels of activity were also found in some forest patches in the subalpine Mountain Hemlock...
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Genotype x shade effects for western hemlock.
G.R. Johnson; C. Cartwright
2005-01-01
Western hemlock (Tsuga heterophylla (Raf.) Sarg.) families were grown under different levels of shade for 2 or 3 years at two nursery sites to determine whether families performed differently relative to one another in the different shade environments. Differences were found both for levels of shade and families, but no family x shade interaction...
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Stand-density study of spruce-hemlock stands in southeastern Alaska.
Donald J. DeMars
2000-01-01
The lack of growth and yield information for young even-aged western hemlock (Tsuga heterophylla(Raf.) Sarg.)-Sitka spruce (Picea sitchensis (Bong.) Carr.) stands in southeastern Alaska served as the impetus for a long-term stand-density study begun in 1974. The study has followed permanent growth plots in managed stands under...
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Western hemlock seedlings were grown in nutrient solutions with ammonium, nitrate or ammonium plus nitrate as nitrogen sources. he objectives were to examine (1) possible selectivity for ammonium or nitrate as an N source, (2) the maintenance of charge balance during ammonium and...
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H.J. Renninger; B.L. Gartner; F.C. Meinzer
2006-01-01
We assessed differences in growth-ring width, specific conductivity (Ks), tracheid dimensions, moisture content, and wood density in suppressed Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees and trees released from suppression. Growth-ring width was 370 percent...
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Wenhua Lu; Michael E. Montgomery
2000-01-01
Scymnus (Neopullus) sinuanodulus Yu et Yao, S. (N.) camptodromusYu et Liu, and Scymnus (Neopullus) n. sp. (in press) were collected in the People's Republic of China from hemlocks infested with the hemlock woolly adelgid, Adelges tsugae Annand. To date, 3 of the 14 provinces in China where...
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Richard McDonald; David Mausel; Scott Salom; Loke Kok; Michael Montgomery; Gina Luker; Stan Steury; Gene Spears; Stewart Skeate; James Graham; Byron Hamstead.
2008-01-01
Three species of predatory beetles have been released to combat infestations of the hemlock woolly adelgid in the High Country region of northwestern North Carolina. They are the spring/summer predators Sasajiscymnus tsugae Sasaji (St), Scymnus sinuanodulus Yu and Yao (Ss), and the winter/fall...
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Silvical characteristics of eastern hemlock (Tsuga canadensis)
Ashbel F. Hough
1960-01-01
The eastern hemlock (Tsuga canadensis (L.) Carr.), as its common and scientific names imply, is a native of the eastern United States and adjacent Canada. It is one of the four North American species of this genus. The genus name means "yew-leaved" and is of Japanese origin. In 1763 the species was named Pinus canadensis...
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Laricobius osakensis, a hemlock wooly adelgid predator from Japan
Ashley Lamb; Michael E. Montgomery; Ligia Cota Viera; Shigehiko Shiyake; Scott Salom
2011-01-01
The approach for the biological control of hemlock woolly adelgid (HWA), Adelges tsugae Annand, has been to release multiple species of host-specific predators in order to reduce HWA populations below damaging thresholds. Beetles in the genus Laricobius prey excusively on adelgids and have life histories matched closely to that of...
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Spatial and temporal distribution of imidacloprid in eastern hemlock
Richard M. Turcotte
2007-01-01
Enzyme-linked immunosorbent assay (ELISA) and gas chromatography/mass spectrometry (GC/MS) techniques were used to measure imidacloprid and metabolite concentrations in xylem fluid extracted from eastern hemlock (Tsuga canadensis) trees treated in the spring or fall with soil or trunk applications of the systemic insecticides Merit® 2F and...
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Natural regeneration following timber harvest in interior cedar-hemlock-white pine forests
Dennis E. Ferguson
1994-01-01
Natural regeneration of interior cedar-hemlock-white pine forests is usually prompt and abundant. These productive sites support up to 10 commercial timber species. Retrospective examination of cutover forest stands allowed determination of variables that are important predictors of regeneration. This report discusses variables such as habitat type, slope, aspect,...
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Initial survey of predacious diptera on hemlocks in Japan
Hisashi Ohishi; Shigehiko Shiyake; Yorio Miyatake; Ashley Lamb; Michael E. Montgomery
2011-01-01
Some species of Coleoptera and Diptera are specialist predators of adelgids. Previously, we reported our survey of predacious Coleoptera on hemlocks in Japan (Shiyake et al. 2008). Two of these beetles, Sasajiscymnus tsugae and Laricobius sp. nov., have been exported to the U.S. for biological control. Here, we provide the first...
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Emergence of Laricobius nigrinus (Fender) (Coleoptera: Derodontidae) in the North Georgia mountains.
C.E. Jones; James Hanula; S.K. Braman
2014-01-01
Hemlock woolly adelgid, Adelges tsugae Annand, is currently found throughout most of the range of eastern hemlock, Tsuga Canadensis (L.) Carriere. Biological control agents have been released in attempts to control this pest, but how different climates influence the efficacy and survival of these agents has not been studied.
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A new species and introgression in eastern Asian hemlocks (Pinaceae: Tusga)
Garth Holman; Peter Del Tredici; Nathan Havill; Nam Sook Lee; Richard Cronn; Sarah Mathews; Linda Raubeson; Christopher S. Campbell
2017-01-01
Species delimitation in Pinaceae is often challenged by limited morphological differentiation and introgression. In Tsuga (hemlocks), species delimitation has been most challenging among northeastern Asian taxa, where the species are weakly marked morphologically and range in number from three to five in previous studies. Two low-copy nuclear four-...
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Matthew J. Kelty
2000-01-01
In the early part of this century, considerable interest existed in the silviculture of hemlock (Tsuga canadensis (L.) Carr.) in the southern New England region, where it occurs in mixture with oak (Quercus spp.), white pine (Pinus strobus L.), birches (Betula spp.), and maples (Acer...
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Dynamics of Connecticut hemlock stands
Jeffrey S. Ward; David M. Smith
2000-01-01
The stand dynamics and production of two one-acre plots of eastern hemlock (Tsuga canadensis L) in Connecticut have been followed for more than six decades. Data were recorded for all individual trees. One plot (Saltonstall) was established in 1924 after the removal of a hardwood overstory. This stand had a nearly pure, almost fully closed understory...
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F.H. Koch; H.M. Cheshire; H.A. Devine
2006-01-01
After causing substantial mortality in the northeastern and mid-Atlantic United States, the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), has recently invaded the southern Appalachian region. Although general estimates of regional spread exist, the landscape level dynamics of A. tsugae invasion are poorly...
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Taper tables for western hemlock.
Floyd A. Johnson; Wilbur Engstrom
1949-01-01
In 1947 the West Coast Forestry procedures Committee recommended several mensuration projects, one of which called for the construction of taper tables for Western hemlock. In response the present tables were prepared. Basic data for these tables consist of measurements of 912 trees taken a number of years ago by members of the Pacific Northwest Forest & Range...
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Development of Sirococcus shoot blight following thinning in western hemlock regeneration.
Charles G. Shaw; Thomas H. Laurent; Spencer Israelson
1981-01-01
Shoot mortality from Sirococcus strobilinus Preuss. and other causes was recorded by crown position from April 1978 through October 1979 in younggrowth western hemlock (Tsuga heterophylla (Raf.) Sarg.) crop trees released in a 1977 thinning at Thomas Bay, Alaska. All study trees contained some infected shoots, but no terminal...
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Changes to southern Appalachian water yield and stormflow after loss of a foundation species
Steven T. Brantley; Chelcy Ford Miniat; Katherine J. Elliott; Stephanie H. Laseter; James M. Vose
2014-01-01
Few studies have examined how insect outbreaks affect landscape-level hydrologic processes. We report the hydrologic effects of the invasive, exotic hemlock woolly adelgid (HWA) in a headwater catchment in the southern Appalachian Mountains. The study watershed experienced complete mortality of an evergreen tree species, Tsuga canadensis (L.) Carr. (...
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Chip Debarking of Several Western Species
William A. Hillstrom
1974-01-01
Discusses processing and conditioning treatments before and aftger compression debarking of western hemlock, Douglas fir, red alder, and bigleaf maple. Bark removal and wood recovery from red alder far exceeded the other species tested. Approximately 90 percent of the wood fiber input was recovered at a residual bark content of less than 2 percent by weight.
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Tara M. Barrett; Greg Latta; Paul E. Hennon; Bianca N.I. Eskelson; Hailemariam. Temesgen
2012-01-01
Dwarf mistletoes (Arceuthobium species) influence many processes within forested ecosystems, but few studies have examined their distribution in relation to climate. An analysis of 1549 forested plots within a 14.5 million ha region of southeast Alaska provided strong indications that climate currently limits hemlock dwarf mistletoe (...
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Multi-decadal establishment for single-cohort Douglas-fir forests
James A. Freund; Jerry F. Franklin; Andrew J. Larson; James A. Lutz
2014-01-01
The rate at which trees regenerate following stand-replacing wildfire is an important but poorly understood process in the multi-century development of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests. Temporal patterns of Douglas-fir establishment reconstructed from old-growth forests (>450 year) have...
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Murray, Bryan D.; Holmes, Stacie A.; Webster, Christopher R.; Witt, Jill C.
2012-01-01
Opportunities to directly study infrequent forest disturbance events often lead to valuable information about vegetation dynamics. In mesic temperate forests of North America, stand-replacing crown fire occurs infrequently, with a return interval of 2000–3000 years. Rare chance events, however, may have profound impacts on the developmental trajectories of forest ecosystems. For example, it has been postulated that stand-replacing fire may have been an important factor in the establishment of eastern hemlock (Tsuga canadensis) stands in the northern Great Lakes region. Nevertheless, experimental evidence linking hemlock regeneration to non-anthropogenic fire is limited. To clarify this potential relationship, we monitored vegetation dynamics following a rare lightning-origin crown fire in a Wisconsin hemlock-hardwood forest. We also studied vegetation in bulldozer-created fire breaks and adjacent undisturbed forest. Our results indicate that hemlock establishment was rare in the burned area but moderately common in the scarified bulldozer lines compared to the reference area. Early-successional, non-arboreal species including Rubus spp., Vaccinium angustifolium, sedges (Carex spp.), grasses, Epilobium ciliatum, and Pteridium aquilinium were the most abundant post-fire species. Collectively, our results suggest that competing vegetation and moisture stress resulting from drought may reduce the efficacy of scarification treatments as well as the usefulness of fire for preparing a suitable seedbed for hemlock. The increasing prevalence of growing-season drought suggests that silvicultural strategies based on historic disturbance regimes may need to be reevaluated for mesic species. PMID:22928044
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Benton, E P; Grant, J F; Webster, R J; Nichols, R J; Cowles, R S; Lagalante, A F; Coots, C I
2015-12-01
Widespread decline and mortality of eastern hemlock, Tsuga canadensis (L.) Carrière, have been caused by hemlock woolly adelgid, Adelges tsugae (Annand) (HWA) (Hemiptera: Adelgidae). The current study is a retrospective analysis conducted in collaboration with Great Smoky Mountains National Park (GRSM) to determine longevity of imidacloprid and its insecticidal metabolites (imidacloprid olefin, 5-hydroxy, and dihydroxy) in GRSM's HWA integrated pest management (IPM) program. Foliage samples were collected from three canopy strata of hemlocks that were given imidacloprid basal drench treatments 4-7 yr prior to sampling. Foliage was analyzed to assess concentrations in parts per billion (ppb) of imidacloprid and its metabolites. Imidacloprid and its olefin metabolite were present in most, 95 and 65%, respectively, branchlets 4-7 yr post-treatment, but the 5-hydroxy and dihydroxy metabolites were present in only 1.3 and 11.7%, respectively, of the branchlets. Imidacloprid and olefin concentrations significantly decreased between 4 and 7 yr post-treatment. Concentrations of both imidacloprid and olefin were below the LC50 for HWA 5-7 yr post-treatment. Knowledge of the longevity of imidacloprid treatments and its metabolite olefin can help maximize the use of imidacloprid in HWA IPM programs. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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NASA Astrophysics Data System (ADS)
Hadley, J. L.; Urbanski, S. P.
2002-12-01
Carbon storage in forests of the northeastern U.S. and adjacent Canada may be a significant carbon sink, as forests and soils in this region have recovered after agricultural abandonment in the 19th century. Data collected during the 1990's showed that an area of 70 to 100 year old deciduous forest on abandoned farmland in central Massachusetts stored an average of 2.0 Mg C/ha/yr in trees and soil. During 2001 we measured carbon exchange and environmental parameters (above-canopy air temperature, atmospheric humidity, photosynthetically active radiation (PAR) and soil temperature) in both the 70-100 year old deciduous forest and in a nearby eastern hemlock (Tsuga canadensis L.)-dominated forest with trees up to 220 years old that was never cleared for agricultural use. The deciduous forest stored more than 4 Mg C/ ha in 2001, far higher than in any previous year since measurements started in 1991. Highest monthly deciduous forest carbon storage (1.8 - 1.9 Mg ha-1 month-1) occurred in July and August. The hemlock forest stored about 3 Mg C/ha, with peak storage in April and May (0.8 - 0.9Mg C ha-1 month-1), and little or no C storage during August. The differences in carbon storage between the two forests were related to differences in quantum use efficiency. Quantum efficiency of ecosystem carbon storage in the foliated deciduous forest averaged about 0.16 g C /mol PAR and was insensitive to temperature after leaf maturation. In contrast, the average hemlock forest quantum efficiency declined from about 0.10 g C /mol PAR at daily average above-canopy air temperature (T{a}{v}{g}) = 5 oC to zero quantum efficiency (no net carbon storage) at T{a}{v}{g} = 23 oC. Optimum temperatures for carbon storage in the hemlock forest occurred in April. Differences between the two forests are likely due primarily to a higher maximum photosynthetic rate and a more positive temperature response of leaf-level photosynthesis in red oak (the dominant deciduous species) as compared with eastern hemlock. Maintenance of high soil respiration in the hemlock forest during warm dry summer weather may also contribute to declining quantum efficiency of carbon storage in the hemlock forest during the summer.
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Melissa J. Fischer; Carlyle C. Brewster; Nathan P. Havill; Scott M. Salom; Loke T. Kok
2015-01-01
In 2003, Laricobius nigrinus Fender was introduced into the eastern United States as a biological control agent of the hemlock woolly adelgid (Adelges tsugae Annand). Following its release, it was discovered that L. nigrinus was hybridising and producing viable progeny with Laricobius rubidus...
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Impact of Precommercial Thinning on Development of Heterobasidion annosum in Western Hemlock
Robert L. Edmonds; David C. Shaw; Tom Hsiang; Charles H. Driver
1989-01-01
The impact of precommercial thinning of western hemlock (Tsuga heterophylla) on the development of Annosus root and butt rot (caused by Heterobasidion annosum) in coastal Washington has been followed for more than 20 years. Infection of stumps and wounds was high following thinning and there was a high probability of residual tree...
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Hemlock woolly adelgid and its natural enemies in Sichuan Province, China, 2005
Jianhua Zhou; Yinbo Xiao; Yugui Xiao; Wenhua Lu; Michael Montgomery; Roy Van Driesche; Scott Salom
2007-01-01
A partnership of Chinese and American institutions was formed in 2005 to obtain natural enemies for biological control of Adelges tsugae Annand, the hemlock woolly adelgid (HWA), in the eastern United States. We report here the first 6 months (June-November) of studies done at three sites in Kangding and Baoxing Counties in Sichuan Province.
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Forest Health Monitoring in Connecticut, 1996-1999
Northeastern Research Station
2002-01-01
Connecticut has mature forests dominated by hardwoods. Most trees are healthy with full crowns (low transparency and high density), little dieback and little damage. The exception is eastern hemlock, which was in poor condition, with thin crowns, more dieback and more damage, especially broken tops. These conditions are likely the result of attack by the hemlock woolly...
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M.A. Radwan; Dean S. DeBell
1980-01-01
Twelve different nitrogen (N) fertilizer treatments were tested on potted western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings. Fertilizers affected soil N and pH, and growth and foliar chemical composition of seedlings. Urea plus N-Serve and sulfur-coated urea appear more promising for promoting growth than other fertilizers tested. Results...
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Influence of family and nitrogen fertilizer on growth and nutrition of western hemlock seedlings.
M.A. Radwan; D.S. DeBell; J.E. Wilcox
1990-01-01
Effects of genotype and nitrogen fertilizer on growth and shoot nutrients of western hemlock seedlings were determined by using 11 open-pollinated families from coastal Oregon and Washington. The families differed significantly in growth, initially and after one growing season after treatment. All seedlings responded well to fertilizer, and fertilization significantly...
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An attribute-based approach to contingent valuation of forest protection programs
Christopher C. Moore; Thomas P. Holmes; Kathleen P. Bell
2011-01-01
The hemlock woolly adelgid is an invasive insect that is damaging hemlock forests in the eastern United States. Several control methods are available but forest managers are constrained by cost, availability, and environmental concerns. As a result forest managers must decide how to allocate limited conservation resources over heterogeneous landscapes. We develop an...
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Annosus Root disease of Western Conifers (FIDL)
Craig L. Schmitt; John R. Parmeter; John T. Kliejunas
2000-01-01
Annosus root disease is found on all western conifer species but is of most concern on true firs, hemlocks, and pines. Incense cedar, coast redwood and sequoia are sometimes infected in California. Western juniper is infected throughout its range. Annosus is common and causes extensive decay in old-growth western and mountain hemlock stands. Many mixed conifer stands...
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The effects of climate, geography, and time on hemlock woolly adelgid and its natural enemies
R. Talbot, III Trotter
2007-01-01
Although the hemlock woolly adelgid (HWA) has been documented in the western United States since the 1920s, it has not expressed outbreak dynamics, and has not behaved as a pest species. In the eastern United States however, the spatial and temporal dynamics of the HWA have been quite different.
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Susan Ernst; Marlin E. Plank; Donald J. Fahey
1986-01-01
The suitability of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) beach logs in southeast Alaska for lumber, pulp, and energy was determined. Logs were sawn at a cant mill in southeast Alaska and at a dimension mill in northern Washington. Volume and value recovery was...
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Genetic variation in rootability of cuttings from one-year-old western hemlock seedlings.
Frank C. Sorensen; Robert K. Campbell
1980-01-01
One-year-old western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings from three open-pollination families from eight locations in the Washington and Oregon Coast Ranges were cultured under accelerated growth conditions in a glasshouse. Forty cuttings from each of five seedlings (open-pollination siblings) per family were then placed in a...
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Growth and yield of sitka spruce and western hemlock at Cascade Head Experimental Forest, Oregon.
Stephen H. Smith; John F. Bell; Francis R. Herman; Thomas See
1984-01-01
A study established in 83-year-old, even-aged stands of Sitka spruce (Picea sitchensis (Bong.) Carr.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) at Cascade Head Experimental Forest in the Siuslaw National Forest on the Oregon coast traces their development for 33 years. Statistical data collected from 12 permanent...
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The white pine - hemlock forests of the anthracite region
C. F. Burnham; M. J. Ferree; F. E. Cunningham
1947-01-01
The white pine - hemlock forests are found chiefly on well drained slopes and along the sides of ravines. Though the area occupied by this type is less than 8 percent of the forest land in the region, it accounts for a quarter of the saw-timber area and 29 percent of the volume in saw-timber stands.
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Management of Westside Washington Conifer Stands Infected with Heterobasidion annosum
Elvira Young
1989-01-01
Timber stands in western Washington are managed for many purposes. Such stands yield commodity and noncommodity outputs, such as recreation, wildlife, visual resources, or watershed benefits, and often from the same stands. Annosus root disease is widespread in many mixed conifer stands within the western hemlock, mountain hemlock, and Pacific silver fir zones west of...
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True fir-hemlock spacing trials: design and first results.
Robert O. Curtis; Gary W. Clendenen; Jan A. Henderson
2000-01-01
A series of 18 precommercial thinning trials was established in true fir-hemlock stands in the Olympic Mountains and along the west side of the Cascade Range in Washington and Oregon from 1987 through 1994. This paper documents establishment of these installations and presents some preliminary observations and results. Substantial differences in growth rates in height...
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Moisture distributions in western hemlock lumber from trees harvested near Sitka, Alaska.
David L. Nicholls; Allen M. Brackley; Travis. Allen
2003-01-01
Western hemlock (Tsuga heterophylla) can be characterized by localized regions of high-moisture-content wood, often referred to as wet pockets, and uneven drying conditions may occur when lumber of higher and lower moisture content is mixed together in a dry kiln. The primary objective of this preliminary study was to characterize the frequency and...
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Vegetation of forested uplands in the Massabesic Experimental Forest
Alison C. Dibble; Catherine A. Rees; Paul E. Sendak; John C. Brissette
2004-01-01
A summary of an inventory of vascular plants in the 3,700-acre Massabesic Experimental Forest in York County, Maine. We identified about 500 species and subspecies. The most common overstory trees were eastern white pine, eastern hemlock, northern red oak, and red maple. Hemlock was the most abundant tree seedling. Shrub density was greatest for beaked hazlenut,...
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The forest ecosystem of southeast Alaska: 2. Forest insects.
John S. Hard
1974-01-01
Southeast Alaska's remaining virgin forests have few insect pests. The black-headed budworm and the hemlock sawfly, both western hemlock defoliators, are the most important species. They kill some trees, kill tops in others, and cause growth loss, but stands survive their attacks. Extensive conversion of virgin stands to second growth may result in an increase in...
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Paul A. Weston; Richard W. Harper
2007-01-01
Several species of Tsuga from the western United States and Asia are under evaluation as potential replacements for T. canadensis being destroyed by hemlock woolly adelgid (Adelges tsugae Annand). Test plots were established in Katonah, NY in October, 2003, and trees were inoculated with adelgid egg masses in...
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Treatment of understory hemlock in the western white pine type
I. T. Haig
1933-01-01
Silvicultural practice for the national forests in the mixed western white pine stands of northern Idaho has long been complicated by the economic problems arising from the presence of aggressive, tolerant, low-value species, such as western hemlock (Tsuga heterophylla) and lowland white fir (Abies grandis), in association with the less tolerant, faster-growing, high-...
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Evaluation of blown down Alaska spruce and hemlock trees for pulp.
Donald J. Fahey; James M. Cahill
1983-01-01
Chips from Alaska hemlock and spruce trees blown down more than 10 years produced usable grades of viscose pulp. Yields of pulp from both species were about 2 percent lower for blowdown material than for control trees. Ash content was slightly higher in the pulp manufactured from blowdown timber than in pulp from control trees.
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Predicting regeneration in the grand fir-cedar-hemlock ecosystem of the northern Rocky Mountains
Dennis E. Ferguson; Albert R. Stage; Raymond J. Boyd
1986-01-01
Conifer establishment following regeneration treatments can be predicted in the grand fir-cedar-hemlock ecosystem of the northern Rocky Mountains. Alternative treatments can be evaluated by a model that represents regeneration establishment and early development. This model is designed to be used with the Intermountain Forest and Range Experiment Station's...
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Relationships between environmental factors and hemlock distribution at Mt. Ascutney, Vermont
Richard L. Boyce
2000-01-01
In order to quantify relationships between environmental factors and the distribution of eastern hemlock (Tsuga canadensis (L.) Carr.) and other tree species, sites were established every 100 m along four contour lines, lying at 455 m (1500'), 610 m (2000'), 760 m (2500') and 915 m (3000') on Mt. Ascutney, a monadnock in the...
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Plant association and management guide for the western hemlock zone.
Christopher Topik; Nancy M. Halverson; Dale G. Brockway
1986-01-01
This guide presents the plant association classification for the western hemlock zone of the Gifford Pinchot National Forest. The bulk of the forest below about 3000 feet in elevation is included in this zone, comprising about one half of the entire landbase. Much of this area is blanketed with productive stands of Douglas-fir.
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Legault, Simon; Hébert, Christian; Blais, Julie; Berthiaume, Richard; Bauce, Eric; Brodeur, Jacques
2012-12-01
We describe seasonal patterns of parasitism by Telenomus coloradensis Crawford, Telenomus droozi Muesebeck, Telenomus flavotibiae Pelletier (Hymenoptera: Scelionidae), and Trichogramma spp. (Hymenoptera: Trichogrammatidae), egg parasitoids of the hemlock looper, Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), after a 3-yr survey of defoliated stands in the lower St. Lawrence region (Quebec, Canada). Results from sentinel trap sampling indicate that T. coloradensis and T. droozi are the most common species, whereas parasitism by T. flavotibiae and Trichogramma spp. is rare. Telenomus coloradensis and T. droozi show similar seasonal periods of parasitism, both species being active in early spring (late April) at temperatures as low as 4°C. Using thermal threshold (T(0)) and thermal constant (K) for immature development of T. coloradensis males and females from egg to adult emergence, we estimated that the spring progeny emerges in the middle of the summer while hemlock looper eggs are absent from the forest environment. Parasitoid females would then mate and remain in the environment to 1) exploit alternate host species, 2) enter into quiescence and later parasitize eggs laid by hemlock looper females in the fall, 3) enter into a reproductive diapause and parasitize hemlock looper eggs only the next spring, or all of these. Although previous studies have shown that T. coloradensis can overwinter in its immature form within the host egg, our field and laboratory results indicate that in the lower St. Lawrence region, this species principally enters diapause as fertilized females, with a mean supercooling point of -30.6°C in the fall.
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Lupines, poison-hemlock and Nicotiana spp: toxicity and teratogenicity in livestock.
Panter, K E; James, L F; Gardner, D R
1999-02-01
Many species of lupines contain quinolizidine or piperidine alkaloids known to be toxic or teratogenic to livestock. Poison-hemlock (Conium maculatum) and Nicotiana spp. including N. tabacum and N. glauca contain toxic and teratogenic piperidine alkaloids. The toxic and teratogenic effects from these plant species have distinct similarities including maternal muscular weakness and ataxia and fetal contracture-type skeletal defects and cleft palate. It is believed that the mechanism of action of the piperidine and quinolizidine alkaloid-induced teratogenesis is the same; however, there are some differences in incidence, susceptible gestational periods, and severity between livestock species. Wildlife species have also been poisoned after eating poison-hemlock but no terata have been reported. The most widespread problem for livestock producers in recent times has been lupine-induced "crooked calf disease." Crooked calf disease is characterized as skeletal contracture-type malformations and occasional cleft palate in calves after maternal ingestion of lupines containing the quinolizidine alkaloid anagyrine during gestation days 40-100. Similar malformations have been induced in cattle and goats with lupines containing the piperidine alkaloids ammodendrine, N-methyl ammodendrine, and N-acetyl hystrine and in cattle, sheep, goats, and pigs with poison-hemlock containing predominantly coniine or gamma-coniceine and N. glauca containing anabasine. Toxic and teratogenic effects have been linked to structural aspects of these alkaloids, and the mechanism of action is believed to be associated with an alkaloid-induced inhibition of fetal movement during specific gestational periods. This review presents a historical perspective, description and distribution of lupines, poison-hemlock and Nicotiana spp., toxic and teratogenic effects and management information to reduce losses.
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Joseph, S V; Braman, S K; Hanula, J L
2011-02-01
Understanding how fertilization affects host resistance to hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is important because fertilizers are often used to grow resistant selections to a suitable size for testing. We evaluated four hemlock species (Tsuga) under three different fertilizer regimes to assess whether fertility affected resistance to the adelgid and to determine whether it affected feeding preferences of the adelgid predators Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji & McClure). Treatments were long-term fertilization (from June 2008 to June 2009), short-term fertilization (from March to June 2009), and no fertilizer. Fertilizer was applied biweekly with 240 ppm N by using water-soluble fertilizer (N-P-K, 20:20:20). Plants (>1 yr old) were artificially infested with adelgids on 31 March 2009. Among unfertilized hemlocks (n=10 per species), foliar N was highest in Tsuga mertensiana (Bong.) CarriBre and lowest in T. chinensis (Franch.) E. Pritz. Significantly more progredien ovisacs or sisten eggs were present on T. mertensiana than on the other hemlock species with none on unfertilized T. chinensis. A. tsugae adults on T. heterophylla (Raf.) Sarg. were unaffected by fertility, but densities of developing A. tsugae nymphs were higher on unfertilized T. heterophylla plants than on fertilized T. heterophylla plants regardless of fertilizer treatment. Both L. nigrinus and S. tsugae consumed more adelgid eggs that developed on fertilized T. canadensis than from unfertilized plants. The predators did not exhibit this preference for adelgid eggs from females that developed on T. heterophylla or T. mertensiana.
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Spatial and Temporal Distribution of Imidacloprid Within the Crown of Eastern Hemlock.
Turcotte, Richard M; Lagalante, Anthony; Jones, Jonathan; Cook, Frank; Elliott, Thomas; Billings, Anthony A; Park, Yong-Lak
2017-01-01
Systemic imidacloprid is the most widely used insecticide to control the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), an exotic pest of eastern hemlock, Tsuga canadensis (L.) Carriére in the United States. This study was conducted to 1) determine the effect of treatment timing (spring vs. fall) and application method (trunk injection vs. soil injection) on the spatial and temporal distribution of imidacloprid within the crown of A. tsugae-free eastern hemlock using a competitive enzyme-linked immunosorbent assay (ELISA), 2) compare ELISA to gas chromatography-mass spectrometry (GC/MS) for the detection of imidacloprid in xylem fluid, and 3) determine the concentration of imidacloprid in leaf tissue using high performance liquid chromatography with tandem mass spectrometric (LC/MS/MS) detection methods. Xylem fluid concentrations of imidacloprid were found to be significantly higher for spring applications than for fall applications and for trunk injections than soil injections in the first year posttreatment. A total of 69% of samples analyzed by ELISA gave 1.8 times higher concentrations of imidacloprid than those found by GC/MS, leading to evidence of a matrix effect and overestimation of imidacloprid in xylem fluid by ELISA. A comparison of the presence of imidacloprid with xylem fluid and in leaf tissue on the same branch showed significant differences, suggesting that imidacloprid moved intermittently within the crown of eastern hemlock. Published by Oxford University Press on behalf of the Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.
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Seasonal variation in effects of herbivory on foliar nitrogen of a threatened conifer.
Schaeffer, Robert N; Soltis, Nicole E; Martin, Jennifer L; Brown, Aden L; Gómez, Sara; Preisser, Evan L; Orians, Colin M
2017-03-01
Invasive herbivores can dramatically impact the nitrogen (N) economy of native hosts. In deciduous species, most N is stored in stem tissues, while in evergreen conifer species N is stored in needles, making them potentially more vulnerable to herbivory. In eastern forests of the USA, the long-lived, foundational conifer eastern hemlock ( Tsuga canadensis ) is under the threat of extirpation by the invasive hemlock woolly adelgid (HWA: Adelges tsugae ). We assessed the impact of HWA infestation on the patterns of seasonal foliar N availability in hemlock planted in a deciduous forest understory. Over the course of a year, we sampled needles and twigs and measured N, carbon (C), C:N ratio, and total protein concentrations. Tissue sampling events were timed to coincide with key life-history transitions for HWA to determine the association between HWA development and feeding with these foliar nutrients. In uninfested trees, needle and twig N concentrations fluctuated across seasons, indicating the potential importance of N storage and remobilization for the N economy of eastern hemlock. Although N levels in HWA-infested trees also cycled annually, the degree to which N concentrations fluctuated seasonally in tissues was significantly affected by HWA feeding. These fluctuations exceeded N levels observed in control trees and coincided with HWA feeding. HWA feeding generally increased N concentrations but did not affect protein levels, suggesting that changes in N do not occur via adelgid-induced protein breakdown. Herbivore-induced mobilization of N to feeding sites and its rapid depletion may be a significant contributor to eastern hemlock mortality in US forests.
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Seasonal variation in effects of herbivory on foliar nitrogen of a threatened conifer
Soltis, Nicole E.; Martin, Jennifer L.; Brown, Aden L.; Gómez, Sara; Preisser, Evan L.; Orians, Colin M.
2017-01-01
Abstract Invasive herbivores can dramatically impact the nitrogen (N) economy of native hosts. In deciduous species, most N is stored in stem tissues, while in evergreen conifer species N is stored in needles, making them potentially more vulnerable to herbivory. In eastern forests of the USA, the long-lived, foundational conifer eastern hemlock (Tsuga canadensis) is under the threat of extirpation by the invasive hemlock woolly adelgid (HWA: Adelges tsugae). We assessed the impact of HWA infestation on the patterns of seasonal foliar N availability in hemlock planted in a deciduous forest understory. Over the course of a year, we sampled needles and twigs and measured N, carbon (C), C:N ratio, and total protein concentrations. Tissue sampling events were timed to coincide with key life-history transitions for HWA to determine the association between HWA development and feeding with these foliar nutrients. In uninfested trees, needle and twig N concentrations fluctuated across seasons, indicating the potential importance of N storage and remobilization for the N economy of eastern hemlock. Although N levels in HWA-infested trees also cycled annually, the degree to which N concentrations fluctuated seasonally in tissues was significantly affected by HWA feeding. These fluctuations exceeded N levels observed in control trees and coincided with HWA feeding. HWA feeding generally increased N concentrations but did not affect protein levels, suggesting that changes in N do not occur via adelgid-induced protein breakdown. Herbivore-induced mobilization of N to feeding sites and its rapid depletion may be a significant contributor to eastern hemlock mortality in US forests. PMID:28439394
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Grading options for western hemlock "pulpwood" logs from southeastern Alaska.
David W. Green; Kent A. McDonald; John Dramm; Kenneth Kilborn
Properties and grade yield are estimated for structural lumber produced from No. 3, No. 4, and low-end No. 2 grade western hemlock logs of the type previously used primarily for the production of pulp chips. Estimates are given for production in the Structural Framing, Machine Stress Rating, and Laminating Stock grading systems. The information shows that significant...
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Crown profile equations for stand-grown western hemlock trees in northwestern Oregon.
David D. Marshall; Gregory P. Johnson; David W. Hann
2003-01-01
Crown profile equations were developed for stand-grown western hemlock(Tsuga heterophylla (Raf.) Sarg.) in northwest Oregon. The profile model uses a segmented approach, dividing the crown into an upper and lower portion at the point of the largest crown width (LCW). The model explains about 86% of the variation in crown width when LCW is known but...
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Melissa J. Fischer; Nathan P. Havill; Carrie S. Jubb; Sean W. Prosser; Brent D. Opell; Scott M. Salom; Loke T. Kok
2014-01-01
Laricobius osakensis (Coleoptera: Derodontidae) was imported from Japan to the United States in 2006 for study in quarantine facilities as a potential biological control of Hemlock Woolly Adelgid. Laricobius osakensis was released from quarantine in 2010, but it was soon discovered that the colony also contained a cryptic species...
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Mike Montgomery; Roy Van Driesche; Scott Salom; Wenhua Lu; Guoyue Yu; Jianhua Zhou; Li Li; Shigehiko Shiyake
2007-01-01
The objectives of this newly funded Forest Service activity are to promote the biological control of hemlock woolly adelgid (Adelges tsugae Annand) by (1) hiring an entomologist to work in Asia; (2) revisit known collecting sites and find promising new ones; (3) study the life history and phenology of HWA and its predators; (4) establish protocols...
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L.C. Viera; S.M. Salom; M.E. Montgomery; L.T. Kok
2013-01-01
The hemlock woolly adelgid, Adelges tsugae Annand, is a serious, non-native pest of hemlock in eastern North America. Laricobius osakensis Montgomery and Shiyake was identified as a key predator in Japan, where A. tsugae is native. Performance of adult and immature stages of L. osakensis was...
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Feasibility of producing value-added wood products from reclaimed hemlock lumber
John J. Janowiak; Robert H. Falk; Jeffery D. Kimmel
2007-01-01
This study evaluated the feasibility of producing value-added wood products from hemlock lumber salvaged from building deconstruction. About 6,000 board feet of lumber, ranging in size from 3 in. by 8 in. to 3 in. by 12 in., was remilled into four products including log cabin siding, V-groove paneling, beadboard (wainscoting), and tongue and groove flooring. The...
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Betsy Lyons; Nalini M. Nadkarni; Malcolm P. North
2000-01-01
We examined the distribution and abundance of nonvascular epiphytes on western hemlock trees in an oldgrowth coniferous forest focusing on patterns of epiphyte distribution at different spatial scales, epiphyte abundance amongst trees differing in size, and crown structures associated with epiphyte abundance. Total epiphyte cover was greatest in four canopy...
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Susan M. Tait; Charles G. III Shaw; Andris Eglitis
1985-01-01
Insects and diseases were surveyed in 16 even-aged, young-growth stands of Sitka spruce (Picea sitchensis (Bong.) Carr.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) in southeastern Alaska. Stand ages ranged from 17 to 27 years in nine thinned stands and from 12 to 22 years in seven unthinned stands. All stands...
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The Tionesta Scenic and Research Natural Areas
John C. Bjorkbom; Rodney G. Larson
1977-01-01
Hemlock-beech forests once covered 6 million acres of the Allegheny Plateau in Pennsylvania and New York. To preserve a remnant of this forest, the Federal Government purchased the last remaining uncut hemlock-beech forest in 1936. Four years later, half of this area was set aside in the Tionesta Scenic Area, primarily for public enjoyment; the other half was set...
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Leslie Chandler Brodie; Dean S. DeBell
2013-01-01
In recent years, interest has increased in silvicultural systems and harvest cuts that retain partial overstories, but there are few data available on the growth of the understory trees in such stands. We studied the response of overstory trees and underplanted seedlings, Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga...
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M.A. Radwan; J.S. Shumway; D.S. Debell; J.M. Kraft
1991-01-01
Three experiments were conducted to determine effects of N and P fertilizers on growth and levels of plant-tissue nutrients of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Both pole-size trees in closed-canopy stands and potted seedlings were use d . Soil series were...
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Uneven-aged silviculture in cedar-hemlock-grand fir ecosystems of the northern Rocky Mountains
Russell T. Graham; Theresa B. Jain; Jonalea R. Tonn
1999-01-01
Uneven-aged silviculture is used infrequently in the Northern Rocky Mountains. Because of wildlife, watershed, or scenic issues it is often preferred for managing many stands. While it has been applied in the ponderosa pine (Pinus ponderosa) forests it has had limited application in the grand fir (Abies grandis)-westem redcedar (Thuja plicate)-westem hemlock (Tsuga...
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Indirect effects of an invasive exotic species on a long-distance migratory songbird
Kirk W. Stodola; Eric T. Linder; Robert J. Cooper
2013-01-01
The loss of foundational tree species to non-native pests can have far reaching consequences for forest composition and function, yet little is known about the impacts on other ecosystem components such as wildlife. We had the opportunity to observe how the loss of eastern hemlock (Tsuga canadensis), due to the invasive hemlock woolly adelgid (Adelges tsugae...
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Turker Dundar; Xiping Wang; Robert J. Ross
2013-01-01
The objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25- x
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Hemlock woolly adelgid and its natural enemies in Yunnan Province, China: first-year (2005) results
Li Li; Wenhua Lu; Michael Montgomery; Roy Van Driesche; Scott Salom
2007-01-01
Chinese and American institutions formed a partnership in 2005 for the purpose of studying and obtaining natural enemies for biological control of Adelges tsugae Annand, the hemlock woolly adelgid (HWA), in the eastern United States. We report here the first 6 months (June-November) of studies conducted in Yulong (Lijiang) County in Yunnan Province....
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Artemis Roehrig; Joseph. Elkinton
2011-01-01
The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), is an introduced species first reported in the eastern United States in 1951. The infestation has since spread in all directions from its initial sighting in Virginia, to its current range from northern Georgia, to southern Maine, and westward into Tennessee, causing...
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Sarah K. Poznanovic; Erik A. Lilleskov; Christopher R. Webster
2015-01-01
Coarse woody debris (CWD) is an important nursery environment for many tree species. Understanding the communities of ectomycorrhizal fungi (ECMF) and the effect of ECMF species on tree seedling condition in CWD will elucidate the potential for ECMF-mediated effects on seedling dynamics. In hemlock-dominated stands, we characterized ECMF communities associated with...
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Molecular ecology of hemlock woolly adelgid, its hosts, and its natural enemies
Nathan P. Havill; Michael E. Montgomery; Robert Foottit
2008-01-01
Molecular analyses show that the hemlock woolly adelgid (HWA) has distinct native lineages in western North America, Japan, China, and Taiwan, while in eastern North America, HWA is not native and was introduced from Japan some time before 1951 (Havill et al. 2006 and 2007). The typical holocyclic lifecycle in the family Adelgidae involves primary hosts in the genus...
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Jingjing Liang; Joseph Buonglorno; Robert A. Monserud
2005-01-01
A density-dependent matrix model was developed for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) -- western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest stands in the Pacific Northwest of the United States. The model predicted the number and volume of trees for 4 species groups and 19 diameter classes. The parameters...
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A comparison of conifers planted on the Hemlock Experimental Forest.
Norman P. Worthington
1955-01-01
Test plantings have been made on the Hemlock Experimental Forest in cooperation with the St. Regis Paper Company to test suitability of several native conifers for planting on heavy bracken and brush-covered Site II areas typical of the western Olympic Peninsula. In the spring of 1950, 2,500 Douglas-fir seedlings from the Forest Industries Tree Nursery at Nisqually...
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Ring Shake in Eastern Hemlock: Frequency and Relationship to Tree Attributes
John E. Baumgras; Paul E. Sendak; David L. Sonderman; David L. Sonderman
2000-01-01
Ring shake is a barrier to improved utilization of eastern hemlock, an important component of the total softwood timber resource in the Eastern United States and Canada. Ring shake is the lengthwise separation of wood that occurs between and parallel to growth rings, diminishing lumber yields and values. Evaluating the potential for ring shake is essential to improving...
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Ring shake in eastern hemlock: frequency and relationship to tree attributes
John E. Baumgras; Paul E. Sendak; David L. Sonderman
2000-01-01
Ring shake is a barrier to improved utilization of eastern hemlock, an important component of the total softwood timber resource in the Eastern United States and Canada. Ring shake is the lengthwise separation of wood that occurs between and parallel to growth rings, diminishing lumber yields and values. Evaluating the potential for ring shake is essential to improving...
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A.J. Tepley; F.J. Swanson; T.A. Spies
2013-01-01
Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation. Despite the attention to their old-growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand-replacing (SR...
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Effects of incising on treatability and leachability of CCA-C-treated eastern hemlock
S. Nami Kartal
2002-01-01
Incising is used to increase exposed wood surface and improve uptake and penetration of preservative during pressure treatment of refractory species. However, incising may also cause increased leaching of preservative when the wood is placed in service. This study compared the rate of leaching from unincised eastern hemlock to that of wood that had been incised to two...
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Seedling distribution on a spruce-hemlock clearcut.
Carl M. Berntsen
1955-01-01
A better job of regeneration on cutover areas can be done if foresters know what areas are difficult to regenerate and what sort of practices are best for the difficult areas. A study recently completed at Cascade Head Experimental Forest has supplied that sort of information for a typical spruce-hemlock clearcut. Nearly a fifth of the area was still unstocked 6 years...
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T.P. Holmes; E.A. Murphy; D.D. Royle
2005-01-01
In this paper, we provide preliminary estimates of the impacts of the hemlock woolly adelgid on residential property values in Sparta, New Jersey, using the hedonic property value method. The literature on the aesthetic perceptions of forest landscapes is briefly reviewed to provide guidance in formulating economic hypotheses based on the assumption of an informative...
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Effect of prestain on the release rate of copper, chromium, and arsenic from western hemlock
Stan T. Lebow; James W. Evans
1999-01-01
To enhance appearance, stains are often sprayed onto western hemlock (Tsuga heterophylla (Raf.) Sarg.) lumber prior to treatment with chromated copper arsenate (CCA-C). Recently, concerns have increased that prestaining may affect the rate of leaching of CCA-C components from the treated wood and that leaching data generated with prestained material may not reflect...
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Paul B. Alaback
1984-01-01
Preliminary information on general landscape patterns in southeast Alaska suggests that two major, compositionally distinct vegetation zones can be defined for the closed-forest type: western hemlock-Sitka spruce/Alaska huckleberry/bunchberry on the uplands, and Sitka spruce/devils club-salmonberry on alluvial flats and terraces.Recent clearcuts (0 to 30...
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Product Recovery From Hemlock "Pulpwood" From Alaska.
Thomas D. Fahey
1983-01-01
A total of 363 western hemlock (Tsuga heterophylla (Raf.) Sarg.) logs from Alaska were sawn to compare recovery at a stud mill and at a dimension mill. Recovery at both mills varied by log diameters and by log scaling system. Lumber grade recovery was primarily in Stud grade at the stud mill and in Standard and Construction grade at the dimension...
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Arielle L. Arsenault; Nathan P. Havill; Albert E. Mayfield; Kimberly F. Wallin
2015-01-01
The predatory species Laricobius nigrinus (Fender) and Laricobius osakensis (Shiyake and Montgomery) (Coleoptera: Derodontidae) have been released for biological control of hemlock woolly adelgid (Adelges tsugae; Hemiptera: Adelgidae) in eastern North America. L. osakensis is native to Japan, whereas L. nigrinus is endemic to the Pacific Northwest of the United States...
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Seasoning and surfacing degrade in kiln-drying western hemlock in western Oregon.
A.C. Knauss; E.H. Clarke
1961-01-01
This report presents the results of a study to determine the degrade (loss in volume and value) of western hemlock lumber cut, kiln-dried, and surfaced in accordance with commercial practice in western Oregon. The study measured (1) loss in volume due to culling and trimming surfaced dry lumber because of sawing, seasoning, and surfacing defects; (2) reduction in grade...
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Renninger H.J.; Meinzer F.C.; B.L. Gartner
2006-01-01
We compared hydraulic architecture, photosynthesis, and growth in Douglas-fir with that of a shade-tolerant western hemlock. The study was conducted in a site that had been thinned to release suppressed trees, and one that remained unthinned. Release seemed to be constrained initially by photosynthetic capacity in both species. After released trees increased their...
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Dean S. DeBell; Ryan Singleton; Barbara L. Gartner; David D. Marshall
2004-01-01
Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. Growth and wood density traits of individual rings were measured via X-ray densitometry, and relationships of ring density and its components to age...
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S. A. Vasiliauskas; L. W. Aarssen
2000-01-01
The effects of moose on eastern hemlock (Tsuga canadensis) natural seedling establishment in Algonquin Provincial Park, Ontario, were examined. Two thousand seedlings were tagged on 56 sites in 1992 and monitored for six years. Initial data collected included seedling height, browsing history and percent crown closure. At the end of the growing...
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Anthony F. Lagalante; Nyssa Lewis; Michael E. Montgomery; Kathleen S. Shields
2006-01-01
The terpenoid content of eastern hemlock (Tsuga canadensis) foliage was measured over an annual cycle of development from bud opening, shoot elongation, shoot maturation, to bud-break at the start of the next growing season. The objective was to determine if variation in terpenoid composition is linked with spatial and temporal feeding preferences of...
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Nathan J. Poage
2008-01-01
To better understand the long-term basal area and diameter growth response of young, well-stocked, even-aged, mixed-species stands of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) to a range of thinning intensities (heavy, moderate, light, and unthinned), 20 years of...
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R. A. Reid; K. M. Somers; J. E. Nighswander; A. M. Zobel
2000-01-01
Clear Lake is located in the centre of the 1300 ha Clear Lake Conservation Reserve in Haliburton County, Ontario, Canada. In 1988, the reserve was designated as a protected area representing undisturbed, old-growth ecosystems. The reserve includes several headwater lakes and their associated catchments which support old-growth hemlock stands that are estimated to be up...
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Publications - GMC 430 | Alaska Division of Geological & Geophysical
: Formation hardness of Hemlock Formation cores after immersion in water and oil based fracturing fluids; and mechanics: Formation hardness of Hemlock Formation cores after immersion in water and oil based fracturing Surveys Skip to content State of Alaska myAlaska My Government Resident Business in Alaska
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Estimating the weight of crown segments for old-growth Douglas-fir and western hemlock.
J.A. Kendall Snell; Timothy A. Max
1985-01-01
The purpose of this study was to develop and validate estimators to predict total crown weight and weight of any segment of crown for old-growth felled and bucked Douglas-fir and western hemlock trees. Equations were developed for predicting weight of continuous live crown, total live crown, dead crown, any segment of live crown, and individual branches for old-growth...
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Kevin M. Potter; Angelia Rose Campbell; Sedley A. Josserand; C. Dana Nelson; Robert M. Jetton
2017-01-01
Carolina hemlock (Tsuga caroliniana Engelm.) is a rare conifer species that exists in small, isolated populations within a limited area of the Southern Appalachian Mountains of the USA. As such, it represents an opportunity to assess whether population size and isolation can affect the genetic diversity and differentiation of a species capable of longdistance gene flow...
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Michael C. Feller; Stefanie L. Pollock
2006-01-01
Surface and crown fuels were measured in 186 stands ranging in age from 0 years after clearcutting to old-growth forests > 300 years old in Douglas-fir (Pseudotsuga menziesii) â western hemlock (Tsuga heterophylla) â western redcedar (Thuja plicata) â dominated forests in southwestern British Columbia. Indexes...
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Growth of site trees and stand structure in mixed stands of Pacific silver fir and western hemlock.
Marshall D. Murray; Peggy C. Leonard
1990-01-01
Height and diameter growth of Pacific silver fir (Abies amabilis Dougl. ex Forbes) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) site trees, as well as overall stand structure on 0.15-acre plots, were analyzed in mixed stands 43 to 57 years old in breast height age at six locations in western Washington. These mixed...
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Gerald E. Hoyer; Jon D. Swanzy
1986-01-01
Growth, stand development, and yield were studied for young, thinned western hemlock (Tsuga heterophylla Raf. [Sarg.]). Two similar studies were located at Cascade Head Experimental Forest in the Siuslaw National Forest, western Oregon, and near Clallam Bay on the Olympic Peninsula in Washington. At the latter, first thinnings were made at two ages...
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Anthony Lagalante; Peter Greenbacker; Jonathan Jones; Richard Turcotte; Bradley Onken
2007-01-01
Imidacloprid is a nonvolatile insecticide and its direct quantification is not possible by gas chromatography. In order to ascertain imidacloprid levels in soil and trunk injection treated trees, a sensitive and selective method has been developed using GC/MS to measure the imidacloprid levels in xylem fluid exudates. In May 2005, a stand of hemlock trees in West...
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Gabriella Zilahi-Balogh; Scott M. Salom; L. T. Kok
2000-01-01
Laricobius nigrinus (Coleoptera: Derodontidae) is being evaluated as a potential biological control agent of hemlock woolly adelgid (HWA), Adelges tsugae (Homoptera: Adelgidae) Annand in eastern North America. HWA is not considered a pest on western species of hemlock (McClure et al. 1996). A combination of natural enemies and host...
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Patrick C. Tobin; Richard M. Turcotte; Laura M. Blackburn; John A. Juracko; Brian T. Simpson
2017-01-01
The ability to survive winter temperatures is a key determinant of insect distributional ranges and population dynamics in temperate ecosystems. Although many insects overwinter in a state of diapause, the hemlock woolly adelgid [Adelges tsugae (Annand)] is an exception and instead develops during winter. We studied a low density population of
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Nathan P. Havill; Stephen D. Gaimari; Adalgisa. Caccone
2018-01-01
Exploring genetic diversity within species of biological control agents can expose previously overlooked beneficial genotypes. This may be the case for two species of silver flies, Leucopis argenticollis and L. piniperda, predators of the hemlock woolly adelgid (Adelges tsugae) in the Pacific Northwest of...
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Anantha M. Prasad; Kevin M. Potter
2017-01-01
Eastern hemlock (Tsuga canadensis) occupies a large swath of eastern North America and has historically undergone range expansion and contraction resulting in several genetically separate lineages. This conifer is currently experiencing mortality across most of its range following infestation of a non-native insect. With the goal of better...
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Growth patterns of Tsuga canadensis in managed uneven-aged northern conifer stands
Laura S. Kenefic; Robert S. Seymour
2000-01-01
This study reports patterns of regeneration and growth for 100 eastern hemlock (Tsuga canadensis (L.) Carr.) up to 20 inches (50 cm) dbh in two mixed-species selection stands on the Penobscot Experimental Forest in east-central Maine. The study stands are part of a U.S.D.A. Forest Service experiment in which eastern hemlock has remained stable over a...
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Louise S.Y. Levy; Robert L. Deal; John C. Tappeiner
2010-01-01
This studyâs objective was to document and describe the current seedling bank of Sitka spruce (Picea sitchensis (Bong.) Carr.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) stands in southeast Alaska that were partially cut between 1900 and 1984. We investigated the following: (1) What are seedling bank densities? (2)...
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R.S. Cowles; M.E. Montgomery; C.A.S.-J. Cheah
2006-01-01
We studied imidacloprid application methods and timing to control the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in forests. The methods compared were 1) soil injection near the trunk; 2) soil injection dispersed throughout the area under the canopy; 3) soil drench near the base of the trunk; and trunk injection with the 4...
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Robert M. Northington; Jackson R. Webster; Ernest F. Benfield; Beth M. Cheever; Barbara R. Niederlehner
2013-01-01
Forested ecosystems in the southeastern United States are currently undergoing an invasion by the hemlock woolly adelgid (HWA). Previous studies in this area have shown changes to forest structure, decreases in canopy cover, increases in organic matter, and changes to nutrient cycling on the forest floor and soil. Here, we were interested in how the effects of canopy...
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Chronic impacts of invasive herbivores on a foundational forest species: a whole-tree perspective.
Wilson, Claire M; Schaeffer, Robert N; Hickin, Mauri L; Rigsby, Chad M; Sommi, Amanda F; Thornber, Carol S; Orians, Colin M; Preisser, Evan L
2018-05-05
Forests make up a large portion of terrestrial plant biomass, and the long-lived woody plants that dominate them possess an array of traits that deter consumption by forest pests. Although often extremely effective against native consumers, invasive species that avoid or overcome these defenses can wreak havoc on trees and surrounding ecosystems. This is especially true when multiple invasive species co-occur, since interactions between invasive herbivores may yield non-additive effects on the host. While the threat posed by invasive forest pests is well known, long-term field experiments are necessary to explore these consumer-host interactions at appropriate spatial and temporal scales. Moreover, it is important to measure multiple variables to get a 'whole-plant' picture of their combined impact. We report the results of a four-year field experiment addressing the individual and combined impacts of two invasive herbivores, the hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa), on native eastern hemlock (Tsuga canadensis) in southern New England. In 2011, we planted 200 hemlock saplings into a temperate forest understory and experimentally manipulated the presence/absence of both herbivore species; in 2015, we harvested the 88 remaining saplings and assessed plant physiology, growth, and resource allocation. Adelgids strongly affected hemlock growth: infested saplings had lower above/belowground biomass ratios, more needle loss, and produced fewer new needles than control saplings. Hemlock scale did not alter plant biomass allocation or growth, and its co-occurrence did not alter the impact of adelgid. While both adelgid and scale impacted the concentrations of primary metabolites, adelgid effects were more pronounced. Adelgid feeding simultaneously increased free amino acids local to feeding sites and a ~30% reduction in starch. The cumulative impact of adelgid-induced needle loss, manipulation of nitrogen pools, and the loss of stored resources likely accelerates host decline through disruption of homeostatic source-sink dynamics occurring at the whole-plant level. Our research stresses the importance of considering long-term impacts to predict how plants will cope with contemporary pressures experienced in disturbed forests. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Western hemlock lumber recovery at a western Washington sawmill.
E.E. Matson
1957-01-01
During April 1956, a study was made at a western Washington sawmill to determine lumber grades that my be expected from old-growth western hemlock timber. Lumber cut at this mill is not seasoned and most of it is sold surfaced-green. It is the practice at this plant to use the band headrig for producing side-cut lumber and to send the large cantsthe full...
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R. Talbot Trotter III
2011-01-01
The hemlock woolly adelgid (HWA) is a small, aphid-like piercing-sucking insect native to Asia and northwestern North America (Havill et al. 2006, 2007). First documented in 1951 in the eastern United States near Richmond, VA, the HWA has spread to infest at least 17 states along the Appalachian Mountains from Georgia to southern Maine, where infestations have been...
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Thomas A. Hanley; Cathy L. Rose
1987-01-01
Snow depth and density were measured in 33 stands of western hemlock-Sitka spruce (Tsuga heterophylla [Rat] Sarg.-Picea sitchensis [Bong.] Carr.) over a 3-year period. The stands, near Juneau, Alaska, provided broad ranges of species composition, age, over-story canopy coverage, tree density, and wood volume. Stepwise multiple regression analyses indicated that both...
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Partial cutting of western hemlock and sitka spruce in southeast Alaska.
Wilbur A. Farr; A.S. Harris
1971-01-01
This study of response to partial cutting over a 17-year period in a 96-year-old stand of western hemlock-Sitka spruce at Karta Bay, Alaska, showed that crop trees left after partial cutting were able to increase or maintain &out the same rate of diameter growth as before thinning, but growth in diameter of trees in an unthinned stand followed the norma2 pattern of...
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T.B. Harrington
2006-01-01
Douglas-fir, western hemlock, and western redcedar seedlings were planted in 2001 within clearcuts, shelterwoods, or thinned stands of second-growth Douglas-fir. Understory vegetation was left untreated or removed to provide areas of vegetation control (AVC) of 0, 50, or 100 percent of seedling growing space. Third-year stem volume of seedlings growing in clearcuts...
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Darrell W. Ross; Glenn R. Kohler; Kimberly F. Wallin
2017-01-01
As part of a comprehensive study to survey predators associated with hemlock woolly adelgid, Adelges tsugae Annand, 1928 in the Pacific Northwest (PNW), U.S.A. (Kohler et al. 2008), predators of balsam woolly adelgid, Adelges piceae (Ratzeburg, 1844) and Cooley spruce gall adelgid, Adelges cooleyi (Gillette...
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Joseph S. Elkinton; Jeffrey A. Lombardo; Artemis D. Roehrig; Thomas J. McAvoy; Albert Mayfield; Mark Whitmore
2017-01-01
As a measure of cold hardiness, we tested the supercooling points or freezing temperatures of individual hemlock woolly adelgids (Adelges tsugae Annand) collected from 15 locations across the north to south range of the adelgid in eastern North America at different times during two winters. Adelgids from the northern interior locations with USDA hardiness zones of 5Bâ...
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A. M. Zobel; R. A. Reid; K. Cybulski; K. Glowniak; O. Loucks; J. E. Nighswander
2000-01-01
Since 1969 Trent University researchers have been investigating the chemistry and biotic part of a small undisturbed lake near Minden, Ontario. Clear Lake is surrounded by old growth hemlock stands, some 400 years old. The research was later joined by personnel of the Ontario Ministry of the Environment, and the educational program in the Frost Centre. We are going to...
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Taylor, A.H.
1995-08-01
The relationship between climate change and the dynamics of ecotonal populations of mountain hemlock (Tsuga mertensiana [Bong.] Carr.) was determined by comparing climate and the age structure of trees from 24 plots and seedlings from 13 plots in the subalpine zone of Lassen Volcanic National Park, California. Tree establishment was greatest during periods with above normal annual and summer temperatures, and normal or above normal precipitation. Seedling establishment was positively correlated with above normal annual and summer temperatures and negatively correlated with April snowpack depth. The different responses of trees and seedlings to precipitation variation is probably related to sitemore » soil moisture conditions. Mountain hemlock populations began to expand in 1842 and establishment increased dramatically after 1880 and peaked during a warm mesic period between 1895 and 1910. The onset of forest expansion coincides with warming that began at the end of the Little Ice Age (1850-1880). These data indicate that stability of the mountain hemlock ecotone is strongly influenced by climate. If warming induced by greenhouse gases does occur as climate models predict, then the structure and dynamics of near timberline forests in the Pacific Northwest will change. 52 refs., 8 figs., 3 tabs.« less
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Oviposition traps to survey eggs of Lambdina fiscellaria (Lepidoptera: Geometridae).
Hébert, Christian; Jobin, Luc; Auger, Michel; Dupont, Alain
2003-06-01
Outbreaks of the hemlock looper, Lambdina fiscellaria (Gueneé), are characterized by rapid increase and patchy distribution over widespread areas, which make it difficult to detect impending outbreaks. This is a major problem with this insect. Population forecasting is based on tedious and expensive egg surveys in which eggs are extracted from 1-m branches; careful observation is needed to avoid counting old unhatched eggs of previous year populations. The efficacy of artificial substrates as oviposition traps to sample hemlock looper eggs was tested as a means of improving outbreak detection and population forecasting. A white polyurethane foam substrate (1,095 lb/ft3) used with the Luminoc insect trap, a portable light trap, was highly efficient in sampling eggs of the hemlock looper. Foam strips placed on tree trunks at breast height were less efficient but easier and less expensive to use for the establishment of extensive survey networks. Estimates based on oviposition traps were highly correlated with those obtained from the 1-m branch extraction method. The oviposition trap is a standard, inexpensive, easy, and robust method that can be used by nonspecialists. This technique makes it possible to sample higher numbers of plots in widespread monitoring networks, which is crucial for improving the management of hemlock looper populations.
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Controls on Nitrogen Retention and Loss in Urban and Rural Forest Ecosystems.
NASA Astrophysics Data System (ADS)
Templer, P. H.
2011-12-01
Human activities, such as the burning of fossil fuels and production of fertilizer, have increased the amount of nitrogen deposited onto terrestrial ecosystems. In addition to changes in atmospheric deposition of nitrogen, other human-induced disturbances have led to dramatic shifts in forest composition of the United States over the last 100 years. Tree species composition of many forests is changing in response to introduced pests and pathogens, competition with introduced plant species and changes in climate. Understanding the combined effects of increased nitrogen inputs and changes in plant species composition on forest nitrogen cycling is critical to our understanding of forest biogeochemistry and nutrient budgets. Despite several decades of research on the effects of atmospheric nitrogen deposition, there is still significant uncertainty about the factors that regulate nitrogen retention and loss in forest ecosystems. The use of natural abundance stable isotopes of nitrogen and oxygen has proven to be a powerful tool for tracing the sources of nitrate in water, from inputs to leaching, as it moves through an ecosystem. The evaluation of natural abundance nitrogen values in atmospheric deposition has been used to partition sources of nitrogen, such as coal-fired power plants vs. tailpipe exhaust, since each of their isotopic signatures is distinct. Similarly, natural abundance oxygen values of nitrate in atmospheric inputs and soil leachate have been used as a tool to partition sources of nitrate between precipitation and nitrate produced microbially during nitrification. We measured the natural abundance isotopic composition of nitrate to quantify rates of nitrogen inputs to the forest and to determine rates of nitrogen losses from healthy, declining and preemptively cut eastern hemlock (Tsuga canadensis) stands in both an urban forest at the Arnold Arboretum in Boston, MA, and a rural forest at Harvard Forest in Petersham, MA. The hemlock woolly adelgid (Adelges tsugae Annand), an introduced aphid-like insect from Japan, threatens hemlock stands throughout the eastern United States. The hemlock woolly adelgid was first reported in forests of the eastern United States in the early 1950s and is currently leading to mortality of eastern hemlock trees from Georgia to Massachusetts. We found that rates of nitrogen inputs to the forest floor were 4-5 times greater, and rates of nitrogen losses via leachate were more than ten times greater, at the Arnold Arboretum compared to Harvard Forest. Our results also show that current management regimes used to control the hemlock woolly adelgid, such as salvage cutting, may be reducing nitrogen losses in urban areas due to rapid regrowth of vegetation and the associated uptake of nitrogen by those plants. In contrast, cutting of trees in rural areas may be leading to proportionately greater losses of nitrogen in those sites, though the total magnitude of nitrogen lost is still smaller than in urban sites. Results of this study suggest that the combination of the hemlock woolly adelgid, atmospheric nitrogen inputs and management practices lead to changes in the nitrogen cycle within eastern hemlock forest ecosystems.
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Jingjing Liang; Joseph Buongiorno; Robert A. Monserud
2006-01-01
WestProPlus is an add-in program developed to work with Microsoft Excel to simulate the growth and management of all-aged Douglas-firâwestern hemlock (Pseudotsuga menziesii (Mirb.) FrancoâTsuga heterophylla (Raf.) Sarg.) stands in Oregon and Washington. Its built-in growth model was calibrated from 2,706 permanent plots in the...
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Lance Craighead; Baden Cross
2007-01-01
To identify the remaining areas of the Interior Cedar- Hemlock Forest of North America and prioritize them for conservation planning, the Craighead Environmental Research Institute has developed a 2-scale method for mapping critical habitat utilizing 1) a broad-scale model to identify important regional locations as the basis for a Conservation Area Design (CAD), and 2...
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[Child poisoning after ingestion of a wild apiaceae: a case report].
Durand, M-F; Pommier, P; Chazalette, A; de Haro, L
2008-02-01
Apiaceae family (formerly Umbelliferae) contains several highly toxic species, including Poison Hemlock (Conium maculatum), Water Hemlock (Cicuta virosa) and Hemlock Water Dropwort (Oenanthe crocata) which are the three main poisonous Apiaceae species growing in France. Thinking he was identifying wild carrots, an 11-year-old boy without previous history ingested the root from a wild Apiaceae. One hour later, he was confused, had drowsiness, headache as well as abdominal pain, vomiting and diarrhoea. Upon hospital admission, myosis, ophtalmoplegia and a moderate rhabdomyolysis were noted. The patient recovered after 24 h of symptomatic treatments. In this case, the description of the ingested plant allowed to identify the Apiaceae family but not the species involved. The geographical location (Southern France in a humid area), the clinical features and the aspect of the ingested root, with an orange secretion led to implicate Oenanthe crocata as the origin of this unusual poisoning.
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Panter, K E; Keeler, R F; Buck, W B
1985-10-01
Skeletal malformations were induced in newborn pigs from gilts fed Conium maculatum seed or plant during gestation days 43 through 53 and 51 through 61. The teratogenic effects in groups dosed during gestation days 43 through 53 were more severe than those in groups dosed during the later period, with many newborn pigs showing arthrogryposis and twisted and malaligned bones in the limbs and with 1 pig showing scoliosis and deformity of the thoracic cage. The pigs born to gilts given C maculatum during gestation days 51 through 61 had excessive flexure primarily in the carpal joints, without scoliosis or bone malalignment in the limbs. The teratogenicity of poison hemlock depends on the alkaloid concentration and content. Based on the data presented, we speculate that gamma-coniceine is the teratogenic alkaloid in the poison hemlock fed to the gilts.
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David Bryan Dail; David Y. Hollinger; Eric A. Davidson; Ivan Fernandez; Herman C. Sievering; Neal A. Scott; Elizabeth Gaige
2009-01-01
In N-limited ecosystems, fertilization by N deposition may enhance plant growth and thus impact C sequestration. In many N deposition-C sequestration experiments, N is added directly to the soil, bypassing canopy processes and potentially favoring N immobilization by the soil. To understand the impact of enhanced N deposition on a low fertility unmanaged forest and...
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Diagenesis of conifer needles in a coastal marine environment
NASA Astrophysics Data System (ADS)
Hedges, John I.; Weliky, K.
1989-10-01
Physically intact fir, hemlock and cedar needles were isolated from different horizons of a sediment core from a coastal marine bay (Dabob Bay, Washington State, U.S.A.) and from nearby trees and forest litter. Green fir, hemlock and cedar needles were all characterized by glucose-rich aldose mixtures (~30% of tissue carbon), the production of vanillyl and cinnamyl CuO-derived phenols (~8% of tissue carbon) and the presence of both pinitol and myo-inositol (1-2% of tissue carbon). Needles from forest litter were enriched in lignin phenols and non-glucose aldoses and depleted in glucose and cyclitols. The sediment core contained an average of 10 mg/1 of physically intact fir, hemlock and cedar needles, which occurred in similar relative abundances and accounted for less than 1% of the total nonwoody gymnosperm tissue. Compared to the green and litter counterparts, all sedimentary needles were greatly depleted in cyclitols, glucose and p-coumaric acid and enriched in vanillyl phenol precursors. The degree of elevation of vanillyl phenol yield from the degraded needles was used to estimate minimal carbon losses from the samples, which ranged from near 40% for needle litter to almost 70% for the deepest (~100 years old) sedimentary fir/hemlock samples. Although downcore increases in carbon loss and refractory organic components indicated in situ diagenesis, the bulk of overall degradation occurred either on land or during the first 10-20 years after deposition. Atomic C/N ratios of degraded needles were lower than for green counterparts, but nitrogen was lost overall. These relative changes indicate the following stability series: vanillyl phenols > N > ferulic acid, p-hydroxy phenols, most aldoses and bulk tissue > glucose and p-coumaric acid > cyclitols (near 100% loss). Vanillic acid to vanillin ratios, (Ad/Al)v, of the green fir and hemlock needles were unusually high (0.36-0.38) and decreased downcore. Diagenesis also decreased the cinnamyl/vanillyl phenol ratio (C/V) of the deepest sedimentary fir/hemlock needles to 20% of the original value and almost tripled the carbon-normalized yield of total vanillyl plus cinnamyl phenols (Λ). The net result of these compositional variations was to make the lignin component of the buried conifer needles resemble lignin in gymnosperm wood, thereby leading to underestimates of needle input and mass.
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Functional response of ungulate browsers in disturbed eastern hemlock forests
DeStefano, Stephen
2015-01-01
Ungulate browsing in predator depleted North American landscapes is believed to be causing widespread tree recruitment failures. However, canopy disturbances and variations in ungulate densities are sources of heterogeneity that can buffer ecosystems against herbivory. Relatively little is known about the functional response (the rate of consumption in relation to food availability) of ungulates in eastern temperate forests, and therefore how “top down” control of vegetation may vary with disturbance type, intensity, and timing. This knowledge gap is relevant in the Northeastern United States today with the recent arrival of hemlock woolly adelgid (HWA; Adelges tsugae) that is killing eastern hemlocks (Tsuga canadensis) and initiating salvage logging as a management response. We used an existing experiment in central New England begun in 2005, which simulated severe adelgid infestation and intensive logging of intact hemlock forest, to examine the functional response of combined moose (Alces americanus) and white-tailed deer (Odocoileus virginianus) foraging in two different time periods after disturbance (3 and 7 years). We predicted that browsing impacts would be linear or accelerating (Type I or Type III response) in year 3 when regenerating stem densities were relatively low and decelerating (Type II response) in year 7 when stem densities increased. We sampled and compared woody regeneration and browsing among logged and simulated insect attack treatments and two intact controls (hemlock and hardwood forest) in 2008 and again in 2012. We then used AIC model selection to compare the three major functional response models (Types I, II, and III) of ungulate browsing in relation to forage density. We also examined relative use of the different stand types by comparing pellet group density and remote camera images. In 2008, total and proportional browse consumption increased with stem density, and peaked in logged plots, revealing a Type I response. In 2012, stem densities were greatest in girdled plots, but proportional browse consumption was highest at intermediate stem densities in logged plots, exhibiting a Type III (rather than a Type II) functional response. Our results revealed shifting top–down control by herbivores at different stages of stand recovery after disturbance and in different understory conditions resulting from logging vs. simulated adelgid attack. If forest managers wish to promote tree regeneration in hemlock stands that is more resistant to ungulate browsers, leaving HWA-infested stands unmanaged may be a better option than preemptively logging them.
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A Long Term View of Forest Response to Environmental Change: 25 Years of Studying Harvard Forest
NASA Astrophysics Data System (ADS)
Munger, J. W.; Wofsy, S. C.; Lindaas, J.; David, F.; David, O.
2014-12-01
Forests influence the budgets of greenhouse gases, and understanding how they will respond to environmental change is critical to accurately predicting future GHG trends. The time scale for climate change is long and forest growth is slow, thus very long measurement periods are required to observe meaningful forest response. We established an eddy flux tower within a mixed forest stand dominated by red oak and red maple at the Harvard Forest LTER site in 1989 where CO2, H2O and energy fluxes together with meteorological observations have been measured continuously. An array of plots for biometric measurements was established in 1993. Flux measurement at an adjacent hemlock stand began in 2000. Records of land use and disturbance and vegetation plot data extend back to 1907. The combined suite of measurements merges observations of instantaneous ecosystem responses to environmental forcing with details of vegetation dynamics and forest growth that represent the emergent properties relevant to long-term ecosystem change. Both the deciduous stand and hemlock stand are accumulating biomass. Each has added over 20 Mg-C ha-1 as woody biomass in trees >10cm dbh since 1990, even though the hemlock stand is older. Net carbon exchange shows enhanced uptake in early spring and late fall months in response to warmer temperatures and likely an increase in evergreen foliage at the deciduous site. Net carbon uptake efficiency at the deciduous stand has increased over time as well as indicated by peak NEE under optimum light conditions. The trend is only partly explained by variation in mean leaf area index and cannot be directly attributed to climate response. The combination of longer growing season and increased uptake efficiency yields a general trend of increasing annual NEE (Fig. 1). However, significant excursions in the trend highlight the sensitivity of forest carbon stocks. The pulse of high annual carbon uptake (peak 6 Mg-C ha-1y-1 in 2008) from 2000-2008 is only partially matched by carbon stored in woody biomass, leaving a large fraction of carbon to have accumulated in litter and fine roots in the forest floor, which has as much carbon as the above-ground woody biomass, but shorter turnover time. Invasion by Hemlock wooly adelgid, an insect that kills hemlock trees portends a major shift in NEE for the hemlock stand in the next decade.
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Harold A. Rapraeger
1952-01-01
In the Pacific Northwest logs are often scaled in lengths which average about 32 feet to facilitate logging. Although several excellent Western hemlock, Sitka spruce and Douglas-fir volume tables based on a 32-foot scaling length have been available for some time, they provide for a larger top diameter than is now used in actual practice. Other tables specify a...
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Grubin, Sarah M; Ross, Darrell W; Wallin, Kimberly F
2011-12-01
Leucopis spp. (Diptera: Chamaemyiidae) from the Pacific Northwest previously were identified as potential biological control agents for the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in the eastern United States. We collected Leucopis spp. larvae from A. tsugae infested western hemlocks in Oregon and Washington and reared them on an unidentified Pineus spp., Pineus strobi (Hartig), Adelges cooleyi (Gillette), Adelges piceae (Ratzeburg), and A. tsugae in three no-choice tests. Leucopis spp. survival on A. tsugae was significantly higher than on A. piceae during the 2010 progrediens generation test and significantly higher than on P. strobi and A. cooleyi during the 2010 sistens generation test. However, across all three tests, some larvae completed development to adult on all four of the alternative adelgid species. Larvae that survived to the adult stage were identified as Leucopis argenticollis Zetterstedt and Leucopis piniperda Malloch. These results suggest that populations of L. argenticollis and L. piniperda in the Pacific Northwest may not be specific to A. tsugae. We also studied the phenology of Leucopis spp. on fourteen A. tsugae infested western hemlock trees in Oregon and Washington over a period of 14 mo. Leucopis spp. larvae were collected year-round, but highest densities coincided with the presence of progrediens and sistens eggs and adults of A. tsugae. There was a positive correlation between Leucopis spp. and A. tsugae abundance.
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Theresa Jain
2001-01-01
During the past 50 years the moist forests of northern Idaho changed from being dominated by western white pine (Pinus monticola), an early sera! species, to ones dominated by late serial species, grand fir (Abies grandis) and western hemlock (Tsuga heterophylla). Variable fire regimes, successional processes and endemic insects and pathogens worked in concert to...
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David V. SANDBERG; Franklin R. Ward
1981-01-01
This publication presents tables on the behavior of fire and the resistance of fuels to control. The information is to be used with the photos in the publication, "Photo Series for Quantifying Forest Residues in the Coastal Douglas-firâHemlock Type, Coastal Douglas-firâHardwood Type" (Maxwell, Wayne G.; Ward, Franklin R. 1976. Gen. Tech. Rep. PNW-GTR-051....
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Eastern hemlock found in Macon County, Alabama
David B. South; Brian Via; Henri D. Grissino-Mayer; Richard Martin; Richard Shelby; Sandie McCall
2016-01-01
Alabama is currently the southern limit of the range of eastern hemlock [Tsuga canadensis (L.) Carriere]. In 2012, several well preserved stumps were excavated from a farm located in Notasulga, Alabama (32 º 33â 6â N; 85º 40â 22â W). Even though they were buried in a saturated soil for approximately 1,500 years, the stumps were remarkably well preserved. The low-...
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Polyketide synthases from poison hemlock (Conium maculatum L.).
Hotti, Hannu; Seppänen-Laakso, Tuulikki; Arvas, Mikko; Teeri, Teemu H; Rischer, Heiko
2015-11-01
Coniine is a toxic alkaloid, the biosynthesis of which is not well understood. A possible route, supported by evidence from labelling experiments, involves a polyketide formed by the condensation of one acetyl-CoA and three malonyl-CoAs catalysed by a polyketide synthase (PKS). We isolated PKS genes or their fragments from poison hemlock (Conium maculatum L.) by using random amplification of cDNA ends (RACE) and transcriptome analysis, and characterized three full-length enzymes by feeding different starter-CoAs in vitro. On the basis of our in vitro experiments, two of the three characterized PKS genes in poison hemlock encode chalcone synthases (CPKS1 and CPKS2), and one encodes a novel type of PKS (CPKS5). We show that CPKS5 kinetically favours butyryl-CoA as a starter-CoA in vitro. Our results suggest that CPKS5 is responsible for the initiation of coniine biosynthesis by catalysing the synthesis of the carbon backbone from one butyryl-CoA and two malonyl-CoAs. © 2015 FEBS.
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NASA Astrophysics Data System (ADS)
Hawthorne, S. N.; Miniat, C.; Elliott, K.
2017-12-01
Forest disturbance that alters vegetation species composition can affect ecosystem productivity and function. The loss of eastern hemlock (Tsuga canadensis) to hemlock woolly adelgid infestations in southern Appalachian Mountains has resulted in more than a two-fold increase in growth of co-occurring rhododendron (Rhododendron maximum) understory, evergreen shrubs. In contrast, the growth of hardwood species increased by 1.2 fold during the same 5 year period following infestation. This study examines the effects of mechanically removing the rhododendron shrub layer on water use and growth of hardwood species. The treatment—hypothesized to speed ecosystem recovery of structure and function—involved cutting, spreading and burning rhododendron stems to remove both rhododendron and soil O-horizon. Sap flow, soil moisture and micro-climate (humidity, temperature) were measured in a pair of reference and treated plots. Preliminary results from the relatively dry summer/fall 2016 have shown that the mean daily transpiration (Et) of the treated plot was 24% greater than the mean daily Et of hardwood trees in the reference plot (t-test, p < 0.05). Light incident onto the forest floor doubled in the treatment plots compared to the reference plots. This suggests that the removal of the shrub layer reduced competition for resources for the canopy and seedling trees, which may increase tree growth and recruitment. Thus, in the wake of hemlock loss, recovery of riparian forest structure and function may be aided with shrub layer removal.
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Geology of the Lake Mary quadrangle, Iron County, Michigan
Bayley, Richard W.
1959-01-01
The Lake Mary quadrangle is in eastern Iron County, in the west part of the Upper Peninsula of Michigan. The quadrangle is underlain by Lower and Middle Precambrian rocks, formerly designated Archean and Algonkian rocks, and is extensively covered by Pleistocene glacial deposits. A few Upper Precambrian (Keweenawan) diabase dikes and two remnants of sandstone and dolomite of early Paleozoic age are also found in the area. The major structural feature is the Holmes Lake anticline, the axis of which strikes northwest through the northeast part of the quadrangle. Most of the quadrangle, therefore, is underlain by rock of the west limb of the anticline. To the northwest along the fold axis, the Holmes Lake anticline is separated from the Amasa oval by a saddle of transverse folds in the vicinity of Michigamme Mountain in the Kiernan quadrangle. The Lower Precambrian rocks are represented by the Dickinson group and by porphyritic red granite whose relation to the Dickinson group is uncertain, but which may be older. The rocks of the Dickinson group are chiefly green to black metavolcanic schist and red felsite, some of the latter metarhyolite. The dark schist is commonly magnetic. The Dickinson group underlies the core area of the Holmes Lake anticline, which is flanked by steeply dipping Middle Precambrian formations of the Animikie series. A major unconformity separates the Lower Precambrian rocks from the overlying Middle Precambrian rocks. In ascending order the formations of the Middle Precambrian are the Randville dolomite, the Hemlock formation, which includes the Mansfield iron-bearing slate member, and the Michigamme slate. An unconformity occurs between the Hemlock formation and Michigamme slate. The post-Hemlock unconformity is thought to be represented in the Lake Mary quadrangle by the absence of iron-formation of the Amasa formation, which is known to lie between the Hemlock and the Michigamme to the northwest of the Lake Mary quadrangle in the Crystal Falls quadrangle. Post-Hemlock erosion may account also for the absence of iron-formation of the Fence River formation on the east limb of the Holmes Lake anticline within the Lake Mary quadrangle. The Randville dolomite is not exposed and is known only from diamond drilling in the northeast part of the area where it occurs in the east and west limbs of the Holmes Lake anticline. The formation has a maximum thickness of about 2,100 feet; this includes a lower arkosic phase, some of which is quartz pebble conglomerate, a medial dolomitic phase, and an upper slate phase. The triad is gradational. Included within the formation are a few beds of chloritic schist thought to be of volcanic origin. An unconformity between the Randville and the succeeding Hemlock is not indicated in the quadrangle, but is probably present. The Hemlock formation is best exposed in the northwest and south-central parts of the area. The apparent thickness of the formation is 10,000- 17,000 feet. It is composed mainly of mafic metavolcanic rocks and intercalated slate and iron-formation. In the north part of the quadrangle the volcanic rocks are greenstone, which includes altered basaltic flow rocks, volcanic breccia, tuff, and slate. Pillow structures are common in the metabasalt. It is not certain if any Hemlock rocks are present in the east limb of the Holmes Lake anticline. In the south part of the quadrangle, the rocks of the Hemlock are chiefly chlorite and hornblende schist and hornfels. Pyroxene hornfels is sparingly present. At least two sedimentary slate belts are included in the Hemlock formation. One of these, the Mansfield iron-bearing slate member, includes in its upper part an altered chert-siderite iron-formation 30 to over 150 feet thick from which iron ore has been mined at the Mansfield location. The position of the iron-bearing rocks has been determined magnetically, and past explorations for iron ore are discussed. Though probably; unconformable, the contact between the Hemlock and the Michigamme formations appears conformable. The Michigamme slate consists of at least 4,000 feet of interbedded mica schist and granulite, the altered equivalents of the slate and graywacke characteristic of the Michigamme in adjacent areas. The Michigamme rocks are best exposed in the south part of the quadrangle in the vicinity of Peavy Pond. Two periods of regional metamorphism have resulted in the alteration of almost all of the rocks of the quadrangle. The Lower Precambrian rocks underwent at least one period of metamorphism, uplift, and erosion before the deposition of the Randville dolomite. After the deposition of the Michigamme slate, a post-Middle Precambrian period of regional metamorphism occurred with attending deformation and igneous intrusion. The grade of metamorphism rises toward the south in the area. The rocks in the northern two-thirds of the quadrangle are representative of greenschist facies of regional metamorphism, whereas the rocks in the southern onethird of the quadrangle are representative of the albite-epidote-amphibolite, the amphibolite, and the pyroxene hornfels facies, the metamorphic node centering about the intrusive Peavy Pond complex in the Peavy Pond area. The Precambrian sedimentary and volcanic rocks are cut by intrusive igneous rocks of different types and several different ages. Gabbroic sills and dikes invaded the Hemlock rocks at some time after the Hemlock was deposited and before the post-Middle Precambrian orogeny and metamorphism. Some contact metamorphism attended the intrusion of the major sills. One of the sills, the West Kiernan sill, is well differentiated. A syntectonic igneous body, composed of gabbro and minor ultramafic parts and fringed with intermediate and felsic differentiates and hybrids, the Peavy; Pond complex, was intruded into the Hemlock and Michigamme formations during the post-Middle Precambrian orogeny. The complex is situated in the Peavy Pond area at the crest of the regional metamorphic node. Contact-altered sedimentary and volcanic rocks margin the complex. The effects of regional metamorphism have been superposed on the contact metamorphic rocks peripheral to the complex and on the igneous rocks of the complex as well. The mafic augite-bearing rocks of the complex emplaced early in the orogeny were deformed by granulation at the peak of the deformation and subsequently metamorphosed to hornblende rocks. Some of the intermediate and felsic rocks of the complex were foliated by the deformation, while the more fluid, felsic parts of the complex were intruded under orogenic stress and crystallized after the peak of deformation. The deformation culminated in major faulting during which the formations were dislocated, and some of the granite of the complex was extremely brecciated. A few diabase dikes, probably of Keweenawan age, have intruded the deformed and altered Animikie rocks. The only known metallic resource is iron ore. The Mansfield mine produced 1¥2 million tons of high-grade iron ore between the years 1890 and 1913. Sporadic exploration since 1913 has failed to reveal other ore deposits of economic importance.
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Maternal and fetal toxicity of poison hemlock (Conium maculatum) in sheep.
Panter, K E; Bunch, T D; Keeler, R F
1988-02-01
Poison hemlock (Conium maculatum) was toxic to pregnant ewes and their fetuses when fed during gestation days 30 through 60. Maternal effects included trembling, muscular weakness in the neck initially, then progressing to the limbs, ataxia, frequent urination and defecation, and death. Convulsive seizures were not observed. Fetotoxic effects included excessive flexure of the carpal joints with lateral deviation in the front limbs and kinked tails. At term, 7 of 11 lambs had varying degrees of the limb abnormalities, but all lambs appeared clinically normal at 8 weeks after parturition.
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Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process
Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato
2001-01-01
A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.
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Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process
Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato
2001-01-01
A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.
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NASA Astrophysics Data System (ADS)
Pontius, J.; Duncan, J.
2017-12-01
Land managers are often faced with balancing management activities to accomplish a diversity of management objectives, in systems faced with many stress agents. Advances in ecosystem modeling provide a rich source of information to inform management. Coupled with advances in decision support techniques and computing capabilities, interactive tools are now accessible for a broad audience of stakeholders. Here we present one such tool designed to capture information on how climate change may impact forested ecosystems, and how that impact varies spatially across the landscape. This tool integrates empirical models of current and future forest structure and function in a structured decision framework that allows users to customize weights for multiple management objectives and visualize suitability outcomes across the landscape. Combined with climate projections, the resulting products allow stakeholders to compare the relative success of various management objectives on a pixel by pixel basis and identify locations where management outcomes are most likely to be met. Here we demonstrate this approach with the integration of several of the preliminary models developed to map species distributions, sugar maple health, forest fragmentation risk and hemlock vulnerability to hemlock woolly adelgid under current and future climate scenarios. We compare three use case studies with objective weightings designed to: 1) Identify key parcels for sugarbush conservation and management, 2) Target state lands that may serve as hemlock refugia from hemlock woolly adelgid induced mortality, and 3) Examine how climate change may alter the success of managing for both sugarbush and hemlock across privately owned lands. This tool highlights the value of flexible models that can be easily run with customized weightings in a dynamic, integrated assessment that allows users to hone in on their potentially complex management objectives, and to visualize and prioritize locations across the landscape. It also demonstrates the importance of including climate considerations for long-term management. This merging of scientific knowledge with the diversity of stakeholder needs is an important step towards using science to inform management and policy decisions.
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Cristel C. Kern; Peter B. Reich; Rebecca A. Montgomery; Terry F. Strong
2012-01-01
Innovative forestry practices that use natural disturbance and stand developmental processes as models to increase forest complexity are now being considered as a way to conserve biodiversity while managing for a range of objectives.We evaluated the influence of harvest-created gap size (6, 10, 20, 30, and 46 m diameter gaps and uncut references) over 12 growing...
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Keena, Melody A; Trotter, R Talbot; Cheah, Carole; Montgomery, Michael E
2012-12-01
Three sequential studies were conducted on the interacting effects of exposure to low (5°C) temperature for 0, 7, 28, 56, or 84 d followed by incubation at 10, 15, or 20°C on the egg diapause of Scymnus (Neopullus) camptodromus Yu and Liu (Coleoptera: Coccinellidae). This beetle was imported from China as a potential biological control agent for hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae). Very few eggs laid and held at a constant 15 or 20°C showed any indication of development. Only eggs exposed to temperature combinations of 5 and 10°C had >50% hatch. Highest percent hatch and fastest development occurred when eggs were held at 5°C for 56 or 84 d followed by holding at 10°C. A model estimated the lower threshold for postdiapause development to be 2°C. The effect of temperature on egg hatch was similar at photoperiods of 12:12 and 16:8 (L:D) h, suggesting egg development is not governed by photoperiod or light exposure. Collectively these data indicate that S. camptodromus eggs laid in the spring and summer go through an aestivo-hibernal diapause that is maintained by warm temperatures and that development resumes when temperatures drop, in parallel with the development of hemlock woolly adelgid. This concurrent development allows S. camptodromus eggs to hatch while hemlock woolly adelgid is laying eggs. This synchrony between the development of S. camptodromus eggs and the overwintering adelgid suggest this beetle may be a good candidate for the biological control of the hemlock woolly adelgid.
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Poison hemlock (Conium maculatum L.).
Vetter, J
2004-09-01
One of the most poisonous species amongst higher plants is Conium maculatum. It is a very common nitrophile weed species, belonging to the Apiaceae (formerly Umbelliferae) family. It contains some piperidine alkaloids (coniine, N-methyl-coniine, conhydrine, pseudoconhydrine, gamma-coniceine), which are formed by the cyclisation of an eight-carbon chain derived from four acetate units. gamma-Coniceine is the precursor of the other hemlock alkaloids. All vegetative organs, flowers and fruits contain alkaloids. The concentrations (both absolute and relative) of the different alkaloids depend on plant varieties, on ecological conditions and on the age of the plant. The characteristic biological effects of the plants are summarised on cattle, sheep, goat, swine, rabbit, elk, birds and insects and the symptoms of the human toxicosis (some cases of poisonings) are discussed according to the literature data. The general symptoms of hemlock poisoning are effects on nervous system (stimulation followed by paralysis of motor nerve endings and CNS stimulation and later depression), vomiting, trembling, problems in movement, slow and weak later rapid pulse, rapid respiration, salivation, urination, nausea, convulsions, coma and death.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Woodward, A.; Silsbee, D.G.; Schreiner, E.G.
1995-08-01
Noticeable changes in vegetation distribution have occurred in the Pacific Northwest during the last century as trees have established in some subalpine meadows. To study the relationship of this process to climate, recently established trees were aged in six subalpine meadows in the Olympic Mountains, Washington. The sites represent three points along a steep precipitation gradient. Subalpine fir (Abies lasiocarpa) has been establishing at the dry end of the gradient, mountain hemlock (Tsuga mertensiana) at the wet end, and both species in the center. Establishment patterns were compared with deviations from the century-long average for these weather variables: winter precipitation,more » Palmer Drought Severity Index, and winter, October and May temperatures. Results show that establishment occurred in dry areas when weather conditions were wetter than average, and in wet areas under drier than average conditions. Establishment at central sites did not show consistent relationships with climate. If future climatic conditions continue to warm, establishment of subalpine fir in subalpine meadows in dry areas may cease and mountain hemlock may resume in wet areas. 34 refs., 5 figs., 3 tabs.« less
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Galey, F D; Holstege, D M; Fisher, E G
1992-01-01
Cattle in two herds developed signs of bloating, increased salivation and lacrimation, depression, respiratory distress, ataxia, and death after ingestion of hay that contained large amounts of poison hemlock (Conium maculatum). Twenty of 30 Angus cows and calves were affected in the first herd (2 died). In the second herd, 5 of 30 Holstein heifers were affected (1 died). The Conium alkaloids, coniine and gamma-coniceine, were quantified in the hay, the plants from the responsible hayfield, and the urine of affected animals.
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Hemlock Alkaloids in Aloes. Occurrence and Distribution of gamma-Coniceine.
Dring, J V; Nash, R J; Roberts, M F; Reynolds, T
1984-10-01
The hemlock alkaloid gamma-coniceine was identified in a number of ALOE species, namely A. GILLILANDII, Reynolds A. BALLYI Reynolds, A. RUSPOLIANA Baker, A. IBITIENSIS Perrier and A. DELTOIDEODONTA Baker. Coniine was identified in A. VIGUIERI Perrier. The levels of gamma-coniceine are higher than those found in CONIUM MACULATUM L. Some species also contained trace amounts of conhydrinone and pseudoconhydrin. Three of the species are Madagascan endemics, one is restricted to Arabia, while the rest are remote from each other in East Africa. Some of the species are loosely related but there is no overall taxonomic affinity between them.
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Ravindran, Anita; Yang, Shang-Shyng
2015-08-01
Microbial biomass plays an important role in nutrient transformation and conservation of forest and grassland ecosystems. The objective of this study was to determine the microbial biomass among three vegetation types in subalpine mountain forest soils of Taiwan. Tatachia is a typical high-altitude subalpine temperate forest ecosystem in Taiwan with an elevation of 1800-3952 m and consists of three vegetation types: spruce, hemlock, and grassland. Three plots were selected in each vegetation type. Soil samples were collected from the organic layer, topsoil, and subsoil. Microbial biomass carbon (Cmic) was determined by the chloroform fumigation-extraction method, and microbial biomass nitrogen (Nmic) was determined from the total nitrogen (Ntot) released during fumigation-extraction. Bacteria, actinomycetes, fungi, cellulolytic microbes, phosphate-solubilizing microbes, and nitrogen-fixing microbes were also counted. The Cmic and Nmic were highest in the surface soil and declined with the soil depth. These were also highest in spruce soils, followed by in hemlock soils, and were lowest in grassland soils. Cmic and Nmic had the highest values in the spring season and the lowest values in the winter season. Cmic and Nmic had significantly positive correlations with total organic carbon (Corg) and Ntot. Contributions of Cmic and Nmic, respectively, to Corg and Ntot indicated that the microbial biomass was immobilized more in spruce and hemlock soils than in grassland soils. Microbial populations of the tested vegetation types decreased with increasing soil depth. Cmic and Nmic were high in the organic layer and decreased with the depth of layers. These values were higher for spruce and hemlock soils than for grassland soils. Positive correlations were observed between Cmic and Nmic and between Corg and Ntot. Copyright © 2014. Published by Elsevier B.V.
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Associations between regional moisture gradient, tree species dominance, and downed wood abundance
NASA Astrophysics Data System (ADS)
Johnson, A. C.; Mills, J.
2007-12-01
Downed wood functions as a source of nurse logs, physical structure in streams, food, and carbon. Because downed wood is important in upland and aquatic habitats, an understanding of wood recruitment along a continuum from wet to dry landscapes is critical for both preservation of biodiversity and restoration of natural ecosystem structure and function. We assessed downed wood in public and private forests of Washington and Oregon by using a subset of the Forest Inventory and Analysis (FIA) database including 15,842 sampled conditions. Multivariate regression trees, ANOVA, and t-tests were used to discern environmental conditions most closely associated with abundance of woody debris. Of the 16 parameters included in the analysis, rainfall, forest ownership, number of damaged standing trees, and forest elevation were most indicative of woody debris abundance. The Hemlock/spruce Group, including hemlock, spruce, cedar, and white pine, most associated with wetter soils, had significantly more downed wood than 12 other forest groups. The Ponderosa Pine Group, indicative of drier sites with higher fire frequencies, included ponderosa pine, sugar pine, and incense cedar, and had significantly less downed wood volume. Overall, the amount of woody debris in either the Spruce/hemlock Group or the Ponderosa Pine Group did not change significantly as tree age increased from 5 to 350 years. Plots within the Hemlock/spruce with greater standing tree volume also had significantly greater downed wood volume. In contrast, greater downed wood volume was not associated with greater standing tree volume in the Ponderosa Pine Group. Knowledge of linkages among environmental variables and stand characteristics are useful in development of regional forest models aimed at understanding the effects of climate change and disturbance on forest succession.
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Darr, M N; McAvoy, T J; Brewster, C C; Salom, S M
2016-12-01
The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive pest of eastern (Tsuga canadensis (L.) Carrière) and Carolina hemlock (Tsuga caroliniana Engelmann) forests in the eastern United States. Scymnus (Pullus) coniferarum Crotch (Coleoptera: Coccinellidae) is a lady beetle that preys on A. tsugae in the western United States, where A. tsugae infestations on western hemlocks are not lethal. It is thought that S. coniferarum could be an important predator that helps keep A. tsugae populations from reaching damaging levels in this region. This study assesses the potential of this predator as a biological control agent for A. tsugae in the eastern United States. S. coniferarum predation, reproductive potential, and survival were evaluated in field-cages on adelgid-infested T. canadensis at two sites in southwestern Virginia. Sampling was conducted between December 2012 and June 2014 to evaluate the impact of S. coniferarum on both generations of A. tsuage (sistens and progrediens). Adult S. coniferarum fed on both generations and all life stages of A. tsugae during both field trials at rates comparable to other adelgid-specific predators. Evidence of S. coniferarum oviposition was minimal, and may be attributed to low temperatures and prey availability. S. coniferarum mortality was greatest when exposed to winter temperatures at the higher elevation site in 2013, and least throughout the 2014 spring sample period. S. coniferarum demonstrated a high predation rate on A. tsugae and survived for extended periods of time at sites in southwest Virginia, indicating that this species could be an effective predator of hemlock woolly adelgid in similar climates. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Method for depositing high-quality microcrystalline semiconductor materials
Guha, Subhendu [Bloomfield Hills, MI; Yang, Chi C [Troy, MI; Yan, Baojie [Rochester Hills, MI
2011-03-08
A process for the plasma deposition of a layer of a microcrystalline semiconductor material is carried out by energizing a process gas which includes a precursor of the semiconductor material and a diluent with electromagnetic energy so as to create a plasma therefrom. The plasma deposits a layer of the microcrystalline semiconductor material onto the substrate. The concentration of the diluent in the process gas is varied as a function of the thickness of the layer of microcrystalline semiconductor material which has been deposited. Also disclosed is the use of the process for the preparation of an N-I-P type photovoltaic device.
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Poison hemlock-induced respiratory failure in a toddler.
West, Patrick L; Horowitz, B Zane; Montanaro, Marc T; Lindsay, James N
2009-11-01
The ingestion of poison hemlock, or Conium maculatum, is described in a 2-year-old boy. He had the onset of abdominal pain and weakness after being fed C. maculatum picked by his sister from the roadside 2 hours earlier. He had a rapidly progressive muscular weakness and was intubated for respiratory failure. His symptoms completely resolved within 24 hours of the ingestion. Conium maculatum is a common weed that causes toxicity by its primary toxin, coniine, which stimulates nicotinic receptors and causes a syndrome of rapidly progressive muscle weakness and paralysis. We describe the course of a benign-appearing plant ingestion resulting in respiratory failure.
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NASA Astrophysics Data System (ADS)
Marsicek, Jeremiah P.; Shuman, Bryan; Brewer, Simon; Foster, David R.; Oswald, W. Wyatt
2013-11-01
A decline of hemlock (Tsuga) populations at ca 5.5 ka (thousands of calibrated radiocarbon years before 1950 AD) stands out as the most abrupt vegetation change of the Holocene in North America, but remains poorly understood after decades of study. Recent analyses of fossil pollen have revealed a concurrent, abrupt oak (Quercus) decline and increases in the abundance of beech (Fagus) and pine (Pinus) on Cape Cod in eastern Massachusetts, but the replacement of drought-tolerant oaks by moisture-sensitive beeches appears inconsistent with low lake levels in the region at the same time. The oak and beech changes are also limited to coastal areas, and the coastal-inland differences require an explanation. Here, we develop a new lake-level reconstruction from Deep Pond, Cape Cod by using a transect of sediment cores and ground-penetrating radar (GPR) profiles to constrain the past elevations of the sandy, littoral zone of the pond. The reconstruction shows that a series of multi-century episodes of low water coincide with the abrupt hemlock and oak declines, and interrupt subsequent phases of hemlock recovery. The lake-level variations equal precipitation deficits of ˜100 mm superimposed on a Holocene long moisture increase of >400 mm. However, because moisture deficits do not easily explain the oak and beech changes, we also evaluate how the climate preferences of the regional vegetation changed over time by matching the fossil pollen assemblages from Deep Pond with their modern equivalents. Reconstructions of the precipitation requirements of the vegetation correlate well even in detail with the lake-level record (r = 0.88 at Deep Pond), and indicate close tracking of effective moisture (precipitation minus evapotranspiration) by the vegetation despite the abrupt species declines, which could have decoupled climate and vegetation trends. Reconstructions of the temperature preferences of the vegetation indicate that coastal sites may have cooled by 0.5-2.5 °C after ca 5.5 ka, while inland sites warmed by 0.5-1 °C. The change in coastal temperature preferences agrees with sea surface cooling in the western Atlantic Ocean of >1 °C. Consequently, the persistence of low hemlock abundance after 5.5 ka in the northeast U.S. may have resulted from oceanic changes that produced multi-century droughts and thus delayed the post-decline recovery of hemlock populations.
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Semiconductor structure and recess formation etch technique
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lu, Bin; Sun, Min; Palacios, Tomas Apostol
2017-02-14
A semiconductor structure has a first layer that includes a first semiconductor material and a second layer that includes a second semiconductor material. The first semiconductor material is selectively etchable over the second semiconductor material using a first etching process. The first layer is disposed over the second layer. A recess is disposed at least in the first layer. Also described is a method of forming a semiconductor structure that includes a recess. The method includes etching a region in a first layer using a first etching process. The first layer includes a first semiconductor material. The first etching processmore » stops at a second layer beneath the first layer. The second layer includes a second semiconductor material.« less
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Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA
2008-01-01
A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) an affinity molecule linked to the semiconductor nanocrystal. The semiconductor nanocrystal is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Exposure of the semiconductor nanocrystal to excitation energy will excite the semiconductor nanocrystal causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.
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Thermoelectric generator and method for the fabrication thereof
Benson, David K.; Tracy, C. Edwin
1987-01-01
A thermoelectric generator using semiconductor elements for responding to a temperature gradient to produce electrical energy with all of the semiconductor elements being of the same type is disclosed. A continuous process for forming substrates on which the semiconductor elements and superstrates are deposited and a process for forming the semiconductor elements on the substrates are also disclosed. The substrates with the semiconductor elements thereon are combined with superstrates to form modules for use thermoelectric generators.
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Thermoelectric generator and method for the fabrication thereof
Benson, D.K.; Tracy, C.E.
1984-08-01
A thermoelectric generator using semiconductor elements for responding to a temperature gradient to produce electrical energy with all of the semiconductor elements being of the same type is disclosed. A continuous process for forming substrates on which the semiconductor elements and superstrates are deposited and a process for forming the semiconductor elements on the substrates are also disclosed. The substrates with the semiconductor elements thereon are combined with superstrates to form modules for use as thermoelectric generators.
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A stable solution-processed polymer semiconductor with record high-mobility for printed transistors
Li, Jun; Zhao, Yan; Tan, Huei Shuan; Guo, Yunlong; Di, Chong-An; Yu, Gui; Liu, Yunqi; Lin, Ming; Lim, Suo Hon; Zhou, Yuhua; Su, Haibin; Ong, Beng S.
2012-01-01
Microelectronic circuits/arrays produced via high-speed printing instead of traditional photolithographic processes offer an appealing approach to creating the long-sought after, low-cost, large-area flexible electronics. Foremost among critical enablers to propel this paradigm shift in manufacturing is a stable, solution-processable, high-performance semiconductor for printing functionally capable thin-film transistors — fundamental building blocks of microelectronics. We report herein the processing and optimisation of solution-processable polymer semiconductors for thin-film transistors, demonstrating very high field-effect mobility, high on/off ratio, and excellent shelf-life and operating stabilities under ambient conditions. Exceptionally high-gain inverters and functional ring oscillator devices on flexible substrates have been demonstrated. This optimised polymer semiconductor represents a significant progress in semiconductor development, dispelling prevalent skepticism surrounding practical usability of organic semiconductors for high-performance microelectronic devices, opening up application opportunities hitherto functionally or economically inaccessible with silicon technologies, and providing an excellent structural framework for fundamental studies of charge transport in organic systems. PMID:23082244
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Generic process for preparing a crystalline oxide upon a group IV semiconductor substrate
McKee, Rodney A.; Walker, Frederick J.; Chisholm, Matthew F.
2000-01-01
A process for growing a crystalline oxide epitaxially upon the surface of a Group IV semiconductor, as well as a structure constructed by the process, is described. The semiconductor can be germanium or silicon, and the crystalline oxide can generally be represented by the formula (AO).sub.n (A'BO.sub.3).sub.m in which "n" and "m" are non-negative integer repeats of planes of the alkaline earth oxides or the alkaline earth-containing perovskite oxides. With atomic level control of interfacial thermodynamics in a multicomponent semiconductor/oxide system, a highly perfect interface between a semiconductor and a crystalline oxide can be obtained.
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The killer of Socrates: Coniine and Related Alkaloids in the Plant Kingdom.
Hotti, Hannu; Rischer, Heiko
2017-11-14
Coniine, a polyketide-derived alkaloid, is poisonous to humans and animals. It is a nicotinic acetylcholine receptor antagonist, which leads to inhibition of the nervous system, eventually causing death by suffocation in mammals. Coniine's most famous victim is Socrates who was sentenced to death by poison chalice containing poison hemlock in 399 BC. In chemistry, coniine holds two historical records: It is the first alkaloid the chemical structure of which was established (in 1881), and that was chemically synthesized (in 1886). In plants, coniine and twelve closely related alkaloids are known from poison hemlock ( Conium maculatum L.), and several Sarracenia and Aloe species. Recent work confirmed its biosynthetic polyketide origin. Biosynthesis commences by carbon backbone formation from butyryl-CoA and two malonyl-CoA building blocks catalyzed by polyketide synthase. A transamination reaction incorporates nitrogen from l-alanine and non-enzymatic cyclization leads to γ-coniceine, the first hemlock alkaloid in the pathway. Ultimately, reduction of γ-coniceine to coniine is facilitated by NADPH-dependent γ-coniceine reductase. Although coniine is notorious for its toxicity, there is no consensus on its ecological roles, especially in the carnivorous pitcher plants where it occurs. Lately there has been renewed interest in coniine's medical uses particularly for pain relief without an addictive side effect.
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Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska
Ager, T.A.; Carrara, P.E.; Smith, Jane L.; Anne, V.; Johnson, J.
2010-01-01
An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ∼12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (∼12,900 cal yr BP) was pine woodland (Pinus contorta) with alder (Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ∼12,240 cal yr BP, Sitka spruce (Picea sitchensis) began to colonize the island while pine woodland declined. By ∼11,200 cal yr BP, mountain hemlock (Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ∼10,180 cal yr BP, when western hemlock (Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ∼7100 cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars (Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.
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Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska
NASA Astrophysics Data System (ADS)
Ager, Thomas A.; Carrara, Paul E.; Smith, Jane L.; Anne, Victoria; Johnson, Joni
2010-03-01
An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ˜12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (˜12,900 cal yr BP) was pine woodland ( Pinus contorta) with alder ( Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ˜12,240 cal yr BP, Sitka spruce ( Picea sitchensis) began to colonize the island while pine woodland declined. By ˜11,200 cal yr BP, mountain hemlock ( Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ˜10,180 cal yr BP, when western hemlock ( Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ˜7100 cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars ( Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.
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Stable surface passivation process for compound semiconductors
Ashby, Carol I. H.
2001-01-01
A passivation process for a previously sulfided, selenided or tellurated III-V compound semiconductor surface. The concentration of undesired mid-gap surface states on a compound semiconductor surface is reduced by the formation of a near-monolayer of metal-(sulfur and/or selenium and/or tellurium)-semiconductor that is effective for long term passivation of the underlying semiconductor surface. Starting with the III-V compound semiconductor surface, any oxidation present thereon is substantially removed and the surface is then treated with sulfur, selenium or tellurium to form a near-monolayer of chalcogen-semiconductor of the surface in an oxygen-free atmosphere. This chalcogenated surface is then contacted with a solution of a metal that will form a low solubility chalcogenide to form a near-monolayer of metal-chalcogen-semiconductor. The resulting passivating layer provides long term protection for the underlying surface at or above the level achieved by a freshly chalcogenated compound semiconductor surface in an oxygen free atmosphere.
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Plasma Processing of Metallic and Semiconductor Thin Films in the Fisk Plasma Source
NASA Technical Reports Server (NTRS)
Lampkin, Gregory; Thomas, Edward, Jr.; Watson, Michael; Wallace, Kent; Chen, Henry; Burger, Arnold
1998-01-01
The use of plasmas to process materials has become widespread throughout the semiconductor industry. Plasmas are used to modify the morphology and chemistry of surfaces. We report on initial plasma processing experiments using the Fisk Plasma Source. Metallic and semiconductor thin films deposited on a silicon substrate have been exposed to argon plasmas. Results of microscopy and chemical analyses of processed materials are presented.
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Preparation of a semiconductor thin film
Pehnt, Martin; Schulz, Douglas L.; Curtis, Calvin J.; Ginley, David S.
1998-01-01
A process for the preparation of a semiconductor film. The process comprises depositing nanoparticles of a semiconductor material onto a substrate whose surface temperature during nanoparticle deposition thereon is sufficient to cause substantially simultaneous fusion of the nanoparticles to thereby coalesce with each other and effectuate film growth.
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Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul
2006-09-05
A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.
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Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA
2004-03-02
A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe, causing the emission of electromagnetic radiation. Further described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.
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Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul
2005-08-09
A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.
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Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul
2002-01-01
A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in he probe, causing the emission of electromagnetic radiation. Further described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.
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Weiss, Shimon; Bruchez, Marcel; Alivisatos, Paul
2014-01-28
A semiconductor nanocrystal compound and probe are described. The compound is capable of linking to one or more affinity molecules. The compound comprises (1) one or more semiconductor nanocrystals capable of, in response to exposure to a first energy, providing a second energy, and (2) one or more linking agents, having a first portion linked to the one or more semiconductor nanocrystals and a second portion capable of linking to one or more affinity molecules. One or more semiconductor nanocrystal compounds are linked to one or more affinity molecules to form a semiconductor nanocrystal probe capable of bonding with one or more detectable substances in a material being analyzed, and capable of, in response to exposure to a first energy, providing a second energy. Also described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and treating materials with the probe.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Weiss, Shimon; Bruchez, Marcel; Alivisatos, Paul A.
2016-12-27
A semiconductor nanocrystal compound and probe are described. The compound is capable of linking to one or more affinity molecules. The compound comprises (1) one or more semiconductor nanocrystals capable of, in response to exposure to a first energy, providing a second energy, and (2) one or more linking agents, having a first portion linked to the one or more semiconductor nanocrystals and a second portion capable of linking to one or more affinity molecules. One or more semiconductor nanocrystal compounds are linked to one or more affinity molecules to form a semiconductor nanocrystal probe capable of bonding with onemore » or more detectable substances in a material being analyzed, and capable of, in response to exposure to a first energy, providing a second energy. Also described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and treating materials with the probe.« less
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Preparation of a semiconductor thin film
Pehnt, M.; Schulz, D.L.; Curtis, C.J.; Ginley, D.S.
1998-01-27
A process is disclosed for the preparation of a semiconductor film. The process comprises depositing nanoparticles of a semiconductor material onto a substrate whose surface temperature during nanoparticle deposition thereon is sufficient to cause substantially simultaneous fusion of the nanoparticles to thereby coalesce with each other and effectuate film growth.
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Context-based automated defect classification system using multiple morphological masks
Gleason, Shaun S.; Hunt, Martin A.; Sari-Sarraf, Hamed
2002-01-01
Automatic detection of defects during the fabrication of semiconductor wafers is largely automated, but the classification of those defects is still performed manually by technicians. This invention includes novel digital image analysis techniques that generate unique feature vector descriptions of semiconductor defects as well as classifiers that use these descriptions to automatically categorize the defects into one of a set of pre-defined classes. Feature extraction techniques based on multiple-focus images, multiple-defect mask images, and segmented semiconductor wafer images are used to create unique feature-based descriptions of the semiconductor defects. These feature-based defect descriptions are subsequently classified by a defect classifier into categories that depend on defect characteristics and defect contextual information, that is, the semiconductor process layer(s) with which the defect comes in contact. At the heart of the system is a knowledge database that stores and distributes historical semiconductor wafer and defect data to guide the feature extraction and classification processes. In summary, this invention takes as its input a set of images containing semiconductor defect information, and generates as its output a classification for the defect that describes not only the defect itself, but also the location of that defect with respect to the semiconductor process layers.
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Tree species and soil nutrient profiles in old-growth forests of the Oregon Coast Range
Cross, Alison; Perakis, Steven S.
2011-01-01
Old-growth forests of the Pacific Northwest provide a unique opportunity to examine tree species – soil relationships in ecosystems that have developed without significant human disturbance. We characterized foliage, forest floor, and mineral soil nutrients associated with four canopy tree species (Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and bigleaf maple (Acer macrophyllum Pursh)) in eight old-growth forests of the Oregon Coast Range. The greatest forest floor accumulations of C, N, P, Ca, Mg, and K occurred under Douglas-fir, primarily due to greater forest floor mass. In mineral soil, western hemlock exhibited significantly lower Ca concentration and sum of cations (Ca + Mg + K) than bigleaf maple, with intermediate values for Douglas-fir and western redcedar. Bigleaf maple explained most species-based differences in foliar nutrients, displaying high concentrations of N, P, Ca, Mg, and K. Foliar P and N:P variations largely reflected soil P variation across sites. The four tree species that we examined exhibited a number of individualistic effects on soil nutrient levels that contribute to biogeochemical heterogeneity in these ecosystems. Where fire suppression and long-term succession favor dominance by highly shade-tolerant western hemlock, our results suggest a potential for declines in both soil Ca availability and soil biogeochemical heterogeneity in old-growth forests.
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Emission factors of air toxics from semiconductor manufacturing in Korea.
Eom, Yun-Sung; Hong, Ji-Hyung; Lee, Suk-Jo; Lee, Eun-Jung; Cha, Jun-Seok; Lee, Dae-Gyun; Bang, Sun-Ae
2006-11-01
The development of local, accurate emission factors is very important for the estimation of reliable national emissions and air quality management. For that, this study is performed for pollutants released to the atmosphere with source-specific emission tests from the semiconductor manufacturing industry. The semiconductor manufacturing industry is one of the major sources of air toxics or hazardous air pollutants (HAPs); thus, understanding the emission characteristics of the emission source is a very important factor in the development of a control strategy. However, in Korea, there is a general lack of information available on air emissions from the semiconductor industry. The major emission sources of air toxics examined from the semiconductor manufacturing industry were wet chemical stations, coating applications, gaseous operations, photolithography, and miscellaneous devices in the wafer fabrication and semiconductor packaging processes. In this study, analyses of emission characteristics, and the estimations of emission data and factors for air toxics, such as acids, bases, heavy metals, and volatile organic compounds from the semiconductor manufacturing process have been performed. The concentration of hydrogen chloride from the packaging process was the highest among all of the processes. In addition, the emission factor of total volatile organic compounds (TVOCs) for the packaging process was higher than that of the wafer fabrication process. Emission factors estimated in this study were compared with those of Taiwan for evaluation, and they were found to be of similar level in the case of TVOCs and fluorine compounds.
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Optical processing for semiconductor device fabrication
NASA Technical Reports Server (NTRS)
Sopori, Bhushan L.
1994-01-01
A new technique for semiconductor device processing is described that uses optical energy to produce local heating/melting in the vicinity of a preselected interface of the device. This process, called optical processing, invokes assistance of photons to enhance interface reactions such as diffusion and melting, as compared to the use of thermal heating alone. Optical processing is performed in a 'cold wall' furnace, and requires considerably lower energies than furnace or rapid thermal annealing. This technique can produce some device structures with unique properties that cannot be produced by conventional thermal processing. Some applications of optical processing involving semiconductor-metal interfaces are described.
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Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.
2016-01-01
Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V−1s−1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315
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Method of physical vapor deposition of metal oxides on semiconductors
Norton, David P.
2001-01-01
A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.
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Semiconductor photoelectrochemistry
NASA Technical Reports Server (NTRS)
Buoncristiani, A. M.; Byvik, C. E.
1983-01-01
Semiconductor photoelectrochemical reactions are investigated. A model of the charge transport processes in the semiconductor, based on semiconductor device theory, is presented. It incorporates the nonlinear processes characterizing the diffusion and reaction of charge carriers in the semiconductor. The model is used to study conditions limiting useful energy conversion, specifically the saturation of current flow due to high light intensity. Numerical results describing charge distributions in the semiconductor and its effects on the electrolyte are obtained. Experimental results include: an estimate rate at which a semiconductor photoelectrode is capable of converting electromagnetic energy into chemical energy; the effect of cell temperature on the efficiency; a method for determining the point of zero zeta potential for macroscopic semiconductor samples; a technique using platinized titanium dioxide powders and ultraviolet radiation to produce chlorine, bromine, and iodine from solutions containing their respective ions; the photoelectrochemical properties of a class of layered compounds called transition metal thiophosphates; and a technique used to produce high conversion efficiency from laser radiation to chemical energy.
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Unitary lens semiconductor device
Lear, Kevin L.
1997-01-01
A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.
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Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul
1999-01-01
A luminescent semiconductor nanocrystal compound is described which is capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation (luminescing) in a narrow wavelength band and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source (of narrow or broad bandwidth) or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The luminescent semiconductor nanocrystal compound is linked to an affinity molecule to form an organo luminescent semiconductor nanocrystal probe capable of bonding with a detectable substance in a material being analyzed, and capable of emitting electromagnetic radiation in a narrow wavelength band and/or absorbing, scattering, or diffracting energy when excited by an electromagnetic radiation source (of narrow or broad bandwidth) or a particle beam. The probe is stable to repeated exposure to light in the presence of oxygen and/or other radicals. Further described is a process for making the luminescent semiconductor nanocrystal compound and for making the organo luminescent semiconductor nanocrystal probe comprising the luminescent semiconductor nanocrystal compound linked to an affinity molecule capable of bonding to a detectable substance. A process is also described for using the probe to determine the presence of a detectable substance in a material.
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Suppressing molecular vibrations in organic semiconductors by inducing strain
Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun
2016-01-01
Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm2 V−1 s−1 by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices. PMID:27040501
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Suppressing molecular vibrations in organic semiconductors by inducing strain.
Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun
2016-04-04
Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm(2) V(-1) s(-1) by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices.
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40 CFR 63.7182 - What parts of my facility does this subpart cover?
Code of Federal Regulations, 2011 CFR
2011-07-01
... CATEGORIES (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Semiconductor... manufactures semiconductors. (b) An affected source subject to this subpart is the collection of all semiconductor manufacturing process units used to manufacture p-type and n-type semiconductors and active solid...
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Unitary lens semiconductor device
Lear, K.L.
1997-05-27
A unitary lens semiconductor device and method are disclosed. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors. 9 figs.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Dahal, Rajendra P.; Bhat, Ishwara B.; Chow, Tat-Sing
Methods for facilitating fabricating semiconductor structures are provided which include: providing a multilayer structure including a semiconductor layer, the semiconductor layer including a dopant and having an increased conductivity; selectively increasing, using electrochemical processing, porosity of the semiconductor layer, at least in part, the selectively increasing porosity utilizing the increased conductivity of the semiconductor layer; and removing, at least in part, the semiconductor layer with the selectively increased porosity from the multilayer structure. By way of example, the selectively increasing porosity may include selectively, anodically oxidizing, at least in part, the semiconductor layer of the multilayer structure.
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The relationship between spontaneous abortion and female workers in the semiconductor industry.
Kim, Heechan; Kwon, Ho-Jang; Rhie, Jeongbae; Lim, Sinye; Kang, Yun-Dan; Eom, Sang-Yong; Lim, Hyungryul; Myong, Jun-Pyo; Roh, Sangchul
2017-01-01
This study investigated the relationship between job type and the risk for spontaneous abortion to assess the reproductive toxicity of female workers in the semiconductor industry. A questionnaire survey was administered to current female workers of two semiconductor manufacturing plants in Korea. We included female workers who became pregnant at least 6 months after the start of their employment with the company. The pregnancy outcomes of 2,242 female workers who experienced 4,037 pregnancies were investigated. Personnel records were used to assign the subjects to one of three groups: fabrication process workers, packaging process workers, and clerical workers. To adjust for within-person correlations between pregnancies, a generalized estimating equation was used. The logistic regression analysis was limited to the first pregnancy after joining the company to satisfy the assumption of independence among pregnancies. Moreover, we stratified the analysis by time period (pregnancy in the years prior to 2008 vs. after 2009) to reflect differences in occupational exposure based on semiconductor production periods. The risk for spontaneous abortion in female semiconductor workers was not significantly higher for fabrication and packaging process workers than for clerical workers. However, when we stratified by time period, the odds ratio for spontaneous abortion was significantly higher for packaging process workers who became pregnant prior to 2008 when compared with clerical workers (odds ratio: 2.21; 95% confidence interval: 1.01-4.81). When examining the pregnancies of female semiconductor workers that occurred prior to 2008, packaging process workers showed a significantly higher risk for spontaneous abortions than did clerical workers. The two semiconductor production periods in our study (prior to 2008 vs. after 2009) had different automated processes, chemical exposure levels, and working environments. Thus, the conditions prior to 2008 may have increased the risk for spontaneous abortions in packaging process workers in the semiconductor industry.
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Surface passivation process of compound semiconductor material using UV photosulfidation
Ashby, Carol I. H.
1995-01-01
A method for passivating compound semiconductor surfaces by photolytically disrupting molecular sulfur vapor with ultraviolet radiation to form reactive sulfur which then reacts with and passivates the surface of compound semiconductors.
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Risk assessment of imidacloprid use in forest settings on the aquatic macroinvertebrate community.
Benton, Elizabeth P; Grant, Jerome F; Nichols, Rebecca J; Webster, R Jesse; Schwartz, John S; Bailey, Joseph K
2017-11-01
The isolated effects of a single insecticide can be difficult to assess in natural settings because of the presence of numerous pollutants in many watersheds. Imidacloprid use for suppressing hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae), in forests offers a rare opportunity to assess potential impacts on aquatic macroinvertebrates in relatively pristine landscapes. Aquatic macroinvertebrate communities were assessed in 9 streams in Great Smoky Mountains National Park (southern Appalachian Mountains, USA). The streams flow through hemlock conservation areas where imidacloprid soil drench treatments were applied for hemlock woolly adelgid suppression. Sites were located upstream and downstream of the imidacloprid treatments. Baseline species presence data (pre-imidacloprid treatment) were available from previous sample collections at downstream sites. Downstream and upstream sites did not vary in numerous community measures. Although comparisons of paired upstream and downstream sites showed differences in diversity in 7 streams, higher diversity was found more often in downstream sites. Macroinvertebrate functional feeding groups and life habits were similar between downstream and upstream sites. Downstream and baseline stream samples were similar. While some functional feeding group and life habit species richness categories varied, variations did not indicate poorer quality downstream communities. Imidacloprid treatments applied according to US Environmental Protection Agency federal restrictions did not result in negative effects to aquatic macroinvertebrate communities, which indicates that risks of imidacloprid use in forest settings are low. Environ Toxicol Chem 2017;36:3108-3119. © 2017 SETAC. © 2017 SETAC.
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1988-01-01
usually be traced to a combination of new semiconductors one on top of the other, then concepts, materials, and device principles, the process is called...example, growth techniques. New combinations of compound semiconductors such as GaAs have an materials called heterostructures can be made intrinsically...of combinations of metals, have direct energy band gaps that facilitate semiconductor, and insulators. Quantum the efficient recombination of
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Photo-Spectrometer Realized In A Standard Cmos Ic Process
Simpson, Michael L.; Ericson, M. Nance; Dress, William B.; Jellison, Gerald E.; Sitter, Jr., David N.; Wintenberg, Alan L.
1999-10-12
A spectrometer, comprises: a semiconductor having a silicon substrate, the substrate having integrally formed thereon a plurality of layers forming photo diodes, each of the photo diodes having an independent spectral response to an input spectra within a spectral range of the semiconductor and each of the photo diodes formed only from at least one of the plurality of layers of the semiconductor above the substrate; and, a signal processing circuit for modifying signals from the photo diodes with respective weights, the weighted signals being representative of a specific spectral response. The photo diodes have different junction depths and different polycrystalline silicon and oxide coverings. The signal processing circuit applies the respective weights and sums the weighted signals. In a corresponding method, a spectrometer is manufactured by manipulating only the standard masks, materials and fabrication steps of standard semiconductor processing, and integrating the spectrometer with a signal processing circuit.
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NASA Technical Reports Server (NTRS)
Fiegl, George (Inventor); Torbet, Walter (Inventor)
1981-01-01
A replenishment crucible is mounted adjacent the usual drawing crucible, from which a monocrystalline boule is drawn according to the Czochralski method. A siphon tube for molten semiconductor transfer extends from the replenishment crucible to the drawing crucible. Each crucible is enclosed within its own hermetic shell and is provided with its own heater. The siphon tube is initially filled with molten semiconductor by raising the inert atmospheric pressure in the shell surrounding the replenishment crucible above that surrounding the drawing crucible. Thereafter, adjustment of the level of molten semiconductor in the drawing crucible may be achieved by adjusting the level in either crucible, since the siphon tube will establish the same level in both crucibles. For continuous processing, solid semiconductor may be added to and melted in the replenishment crucible during the process of drawing crystals from the drawing crucible. A constant liquid level of melted semiconductor is maintained in the system by an optical monitoring device and any of several electromechanical controls of the rate of replenishment or crucible height.
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Sensors for process control Focus Team report
NASA Astrophysics Data System (ADS)
At the Semiconductor Technology Workshop, held in November 1992, the Semiconductor Industry Association (SIA) convened 179 semiconductor technology experts to assess the 15-year outlook for the semiconductor manufacturing industry. The output of the Workshop, a document entitled 'Semiconductor Technology: Workshop Working Group Reports,' contained an overall roadmap for the technology characteristics envisioned in integrated circuits (IC's) for the period 1992-2007. In addition, the document contained individual roadmaps for numerous key areas in IC manufacturing, such as film deposition, thermal processing, manufacturing systems, exposure technology, etc. The SIA Report did not contain a separate roadmap for contamination free manufacturing (CFM). A key component of CFM for the next 15 years is the use of sensors for (1) defect reduction, (2) improved product quality, (3) improved yield, (4) improved tool utilization through contamination reduction, and (5) real time process control in semiconductor fabrication. The objective of this Focus Team is to generate a Sensors for Process Control Roadmap. Implicit in this objective is the identification of gaps in current sensor technology so that research and development activity in the sensor industry can be stimulated to develop sensor systems capable of meeting the projected roadmap needs. Sensor performance features of interest include detection limit, specificity, sensitivity, ease of installation and maintenance, range, response time, accuracy, precision, ease and frequency of calibration, degree of automation, and adaptability to in-line process control applications.
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A compact semiconductor digital interferometer and its applications
NASA Astrophysics Data System (ADS)
Britsky, Oleksander I.; Gorbov, Ivan V.; Petrov, Viacheslav V.; Balagura, Iryna V.
2015-05-01
The possibility of using semiconductor laser interferometers to measure displacements at the nanometer scale was demonstrated. The creation principles of miniature digital Michelson interferometers based on semiconductor lasers were proposed. The advanced processing algorithm for the interferometer quadrature signals was designed. It enabled to reduce restrictions on speed of measured movements. A miniature semiconductor digital Michelson interferometer was developed. Designing of the precision temperature stability system for miniature low-cost semiconductor laser with 0.01ºС accuracy enabled to use it for creation of compact interferometer rather than a helium-neon one. Proper firmware and software was designed for the interferometer signals real-time processing and conversion in to respective shifts. In the result the relative displacement between 0-500 mm was measured with a resolution of better than 1 nm. Advantages and disadvantages of practical use of the compact semiconductor digital interferometer in seismometers for the measurement of shifts were shown.
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Solid-state-based analog of optomechanics
Naumann, Nicolas L.; Droenner, Leon; Carmele, Alexander; ...
2016-09-01
In this study, we investigate a semiconductor quantum dot as a microscopic analog of a basic optomechanical setup. We show that optomechanical features can be reproduced by the solid-state platform, arising from parallels of the underlying interaction processes, which in the optomechanical case is the radiation pressure coupling and in the semiconductor case the electron–phonon coupling. We discuss bistabilities, lasing, and phonon damping, and recover the same qualitative behaviors for the semiconductor and the optomechanical cases expected for low driving strengths. However, in contrast to the optomechanical case, distinct signatures of higher order processes arise in the semiconductor model.
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Electroless silver plating of the surface of organic semiconductors.
Campione, Marcello; Parravicini, Matteo; Moret, Massimo; Papagni, Antonio; Schröter, Bernd; Fritz, Torsten
2011-10-04
The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor. © 2011 American Chemical Society
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Kwon, Guhyun; Kim, Keetae; Choi, Byung Doo; Roh, Jeongkyun; Lee, Changhee; Noh, Yong-Young; Seo, SungYong; Kim, Myung-Gil; Kim, Choongik
2017-06-01
The stabilization and control of the electrical properties in solution-processed amorphous-oxide semiconductors (AOSs) is crucial for the realization of cost-effective, high-performance, large-area electronics. In particular, impurity diffusion, electrical instability, and the lack of a general substitutional doping strategy for the active layer hinder the industrial implementation of copper electrodes and the fine tuning of the electrical parameters of AOS-based thin-film transistors (TFTs). In this study, the authors employ a multifunctional organic-semiconductor (OSC) interlayer as a solution-processed thin-film passivation layer and a charge-transfer dopant. As an electrically active impurity blocking layer, the OSC interlayer enhances the electrical stability of AOS TFTs by suppressing the adsorption of environmental gas species and copper-ion diffusion. Moreover, charge transfer between the organic interlayer and the AOS allows the fine tuning of the electrical properties and the passivation of the electrical defects in the AOS TFTs. The development of a multifunctional solution-processed organic interlayer enables the production of low-cost, high-performance oxide semiconductor-based circuits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Fabrication of Metallic Hollow Nanoparticles
NASA Technical Reports Server (NTRS)
Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)
2016-01-01
Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.
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Kang, Minji; Hwang, Hansu; Park, Won-Tae; Khim, Dongyoon; Yeo, Jun-Seok; Kim, Yunseul; Kim, Yeon-Ju; Noh, Yong-Young; Kim, Dong-Yu
2017-01-25
We report on the fabrication of an organic thin-film semiconductor formed using a blend solution of soluble ambipolar small molecules and an insulating polymer binder that exhibits vertical phase separation and uniform film formation. The semiconductor thin films are produced in a single step from a mixture containing a small molecular semiconductor, namely, quinoidal biselenophene (QBS), and a binder polymer, namely, poly(2-vinylnaphthalene) (PVN). Organic field-effect transistors (OFETs) based on QBS/PVN blend semiconductor are then assembled using top-gate/bottom-contact device configuration, which achieve almost four times higher mobility than the neat QBS semiconductor. Depth profile via secondary ion mass spectrometry and atomic force microscopy images indicate that the QBS domains in the films made from the blend are evenly distributed with a smooth morphology at the bottom of the PVN layer. Bias stress test and variable-temperature measurements on QBS-based OFETs reveal that the QBS/PVN blend semiconductor remarkably reduces the number of trap sites at the gate dielectric/semiconductor interface and the activation energy in the transistor channel. This work provides a one-step solution processing technique, which makes use of soluble ambipolar small molecules to form a thin-film semiconductor for application in high-performance OFETs.
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Origin of poor doping efficiency in solution processed organic semiconductors.
Jha, Ajay; Duan, Hong-Guang; Tiwari, Vandana; Thorwart, Michael; Miller, R J Dwayne
2018-05-21
Doping is an extremely important process where intentional insertion of impurities in semiconductors controls their electronic properties. In organic semiconductors, one of the convenient, but inefficient, ways of doping is the spin casting of a precursor mixture of components in solution, followed by solvent evaporation. Active control over this process holds the key to significant improvements over current poor doping efficiencies. Yet, an optimized control can only come from a detailed understanding of electronic interactions responsible for the low doping efficiencies. Here, we use two-dimensional nonlinear optical spectroscopy to examine these interactions in the course of the doping process by probing the solution mixture of doped organic semiconductors. A dopant accepts an electron from the semiconductor and the two ions form a duplex of interacting charges known as ion-pair complexes. Well-resolved off-diagonal peaks in the two-dimensional spectra clearly demonstrate the electronic connectivity among the ions in solution. This electronic interaction represents a well resolved electrostatically bound state, as opposed to a random distribution of ions. We developed a theoretical model to recover the experimental data, which reveals an unexpectedly strong electronic coupling of ∼250 cm -1 with an intermolecular distance of ∼4.5 Å between ions in solution, which is approximately the expected distance in processed films. The fact that this relationship persists from solution to the processed film gives direct evidence that Coulomb interactions are retained from the precursor solution to the processed films. This memory effect renders the charge carriers equally bound also in the film and, hence, results in poor doping efficiencies. This new insight will help pave the way towards rational tailoring of the electronic interactions to improve doping efficiencies in processed organic semiconductor thin films.
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Process waste assessment: Petroleum jelly removal from semiconductor die using trichloroethylene
DOE Office of Scientific and Technical Information (OSTI.GOV)
Curtin, D.P.
The process analyzed involves non-production, laboratory environment use of trichloroethylene for the cleaning of semiconductor devices. The option selection centered on the replacement of the trichloroethylene with a non-hazardous material. This process waste assessment was performed as part of a pilot project.
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Campos, Antonio; Riera-Galindo, Sergi; Puigdollers, Joaquim; Mas-Torrent, Marta
2018-05-09
Solution-processed n-type organic field-effect transistors (OFETs) are essential elements for developing large-area, low-cost, and all organic logic/complementary circuits. Nonetheless, the development of air-stable n-type organic semiconductors (OSCs) lags behind their p-type counterparts. The trapping of electrons at the semiconductor-dielectric interface leads to a lower performance and operational stability. Herein, we report printed small-molecule n-type OFETs based on a blend with a binder polymer, which enhances the device stability due to the improvement of the semiconductor-dielectric interface quality and a self-encapsulation. Both combined effects prevent the fast deterioration of the OSC. Additionally, a complementary metal-oxide semiconductor-like inverter is fabricated depositing p-type and n-type OSCs simultaneously.
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Publications - GMC 332 | Alaska Division of Geological & Geophysical
DGGS GMC 332 Publication Details Title: X-Ray Diffraction analysis and flow testing of Hemlock information. Quadrangle(s): Alaska Statewide Bibliographic Reference BJ Services Company , 2006, X-Ray
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Attempt to induce lightwood in eastern hemlock by treating with paraquat
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kiatgrajai, P.; Rowe, J.W.; Conner, A.H.
1976-01-01
Treatment of eastern hemlock (Tsuga canadensis (L.) Carr.) with the herbicide paraquat did not induce formation of lightwood. However, a dead zone of phloem extended above the paraquat-treatment site. Traumatic resin ducts were observed in the wood immediately adjacent to this dead zone. Although some of these ducts were filled with resin, most were empty. A very small amount of resin soaking was observed at the edges of the dead phloem. Although there was an increase in the extractives content of the wood behind the dead phloem, this did not reach levels with commercial potential. The increase in turpentine levelmore » was mostly due to slightly volatile waxes. The nonvolatile ether extractives were predominately acids other than the fatty and resin acids typical of pines. Electron microscopy revealed fungal hyphae in the wood behind the dead phloem, and several species of fungi were cultured from the wood.« less
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Anti-Pseudomonas aeruginosa activity of hemlock (Conium maculatum, Apiaceae) essential oil.
Di Napoli, Michela; Varcamonti, Mario; Basile, Adriana; Bruno, Maurizio; Maggi, Filippo; Zanfardino, Anna
2018-05-21
Conium maculatum is a nitrophilous weed belonging to the Apiaceae family and occurring in hedgerows, pastures, waste ground, along rivers and roadsides. Little is known on the chemistry and bioactivity of other secondary metabolites occurring in the plant. In the present work, we have analysed the chemical composition and antimicrobial activity of the essential oils hydrodistilled from leaves and inflorescenes of C. maculatum growing in Sicily, Italy. The composition of essential oils was achieved by gas chromatography-mass spectrometry (GC-MS) analysis, whereas the inhibitory effects on the growth of two Gram negative strains, namely Escherichia coli and Pseudomonas aeruginosa were assessed by two different analysis. The essential oils exhibited different chemical profiles (1-butylpiperidine and myrcene in the inflorescenes), (mostly (E)-caryophyllene in the leaves). The latter oil was particularly active in inhibiting the growth of P. aeruginosa. These results shed light on the possible application of hemlock essential oils as antimicrobial agents.
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Frank, A A; Reed, W M
1990-01-01
Coniine, an alkaloid of Conium maculatum (poison hemlock), was administered by gavage to immature chickens, quails, and turkeys at 0, 25, 50, and 100 mg/kg body weight. At 25 mg coniine/kg body weight, clinical signs were observed only in quails (2/10) and consisted of excitement, depression, hypermetria, seizures, opisthotonos, and flaccid paralysis. Chickens (9/10) and quails (8/10) dosed at 50 mg/kg body weight were affected, and several birds of each species died (2/10 and 5/10, respectively). Turkeys (7/10) were affected only when dosed at 100 mg/kg body weight, and quails (6/10), turkeys (4/10), and chickens (10/10) died at this dose. There were no gross or microscopic lesions. Coniine was detected in skeletal muscle and liver of birds dying after ingestion and was present in some survivors 7 days post-treatment.
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NASA Technical Reports Server (NTRS)
Cohen, Warren B.; Spies, Thomas A.
1992-01-01
Relationships between spectral and texture variables derived from SPOT HRV 10 m panchromatic and Landsat TM 30 m multispectral data and 16 forest stand structural attributes is evaluated to determine the utility of satellite data for analysis of hemlock forests west of the Cascade Mountains crest in Oregon and Washington, USA. Texture of the HRV data was found to be strongly related to many of the stand attributes evaluated, whereas TM texture was weakly related to all attributes. Data analysis based on regression models indicates that both TM and HRV imagery should yield equally accurate estimates of forest age class and stand structure. It is concluded that the satellite data are a valuable source for estimation of the standard deviation of tree sizes, mean size and density of trees in the upper canopy layers, a structural complexity index, and stand age.
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Radar modeling of a boreal forest
NASA Technical Reports Server (NTRS)
Chauhan, Narinder S.; Lang, Roger H.; Ranson, K. J.
1991-01-01
Microwave modeling, ground truth, and SAR data are used to investigate the characteristics of forest stands. A mixed coniferous forest stand has been modeled at P, L, and C bands. Extensive measurements of ground truth and canopy geometry parameters were performed in a 200-m-square hemlock-dominated forest plot. About 10 percent of the trees were sampled to determine a distribution of diameter at breast height (DBH). Hemlock trees in the forest are modeled by characterizing tree trunks, branches, and needles as randomly oriented lossy dielectric cylinders whose area and orientation distributions are prescribed. The distorted Born approximation is used to compute the backscatter at P, L, and C bands. The theoretical results are found to be lower than the calibrated ground-truth data. The experiment and model results agree quite closely, however, when the ratios of VV to HH and HV to HH are compared.
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REDUCTION OF ARSENIC WASTES IN THE SEMICONDUCTOR INDUSTRY
The research described in this report was aimed at initiating and developing processes and process modifications that could be incorporated into semiconductor manufacturing operations to accomplish pollution prevention, especially to accomplish significant reduction in the quanti...
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Real time quantitative imaging for semiconductor crystal growth, control and characterization
NASA Technical Reports Server (NTRS)
Wargo, Michael J.
1991-01-01
A quantitative real time image processing system has been developed which can be software-reconfigured for semiconductor processing and characterization tasks. In thermal imager mode, 2D temperature distributions of semiconductor melt surfaces (900-1600 C) can be obtained with temperature and spatial resolutions better than 0.5 C and 0.5 mm, respectively, as demonstrated by analysis of melt surface thermal distributions. Temporal and spatial image processing techniques and multitasking computational capabilities convert such thermal imaging into a multimode sensor for crystal growth control. A second configuration of the image processing engine in conjunction with bright and dark field transmission optics is used to nonintrusively determine the microdistribution of free charge carriers and submicron sized crystalline defects in semiconductors. The IR absorption characteristics of wafers are determined with 10-micron spatial resolution and, after calibration, are converted into charge carrier density.
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Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers
NASA Astrophysics Data System (ADS)
Pierścińska, D.
2018-01-01
This review focuses on theoretical foundations, experimental implementation and an overview of experimental results of the thermoreflectance spectroscopy as a powerful technique for temperature monitoring and analysis of thermal processes in semiconductor lasers. This is an optical, non-contact, high spatial resolution technique providing high temperature resolution and mapping capabilities. Thermoreflectance is a thermometric technique based on measuring of relative change of reflectivity of the surface of laser facet, which provides thermal images useful in hot spot detection and reliability studies. In this paper, principles and experimental implementation of the technique as a thermography tool is discussed. Some exemplary applications of TR to various types of lasers are presented, proving that thermoreflectance technique provides new insight into heat management problems in semiconductor lasers and in particular, that it allows studying thermal degradation processes occurring at laser facets. Additionally, thermal processes and basic mechanisms of degradation of the semiconductor laser are discussed.
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Methods of Measurement for Semiconductor Materials, Process Control, and Devices
NASA Technical Reports Server (NTRS)
Bullis, W. M. (Editor)
1973-01-01
The development of methods of measurement for semiconductor materials, process control, and devices is reported. Significant accomplishments include: (1) Completion of an initial identification of the more important problems in process control for integrated circuit fabrication and assembly; (2) preparations for making silicon bulk resistivity wafer standards available to the industry; and (3) establishment of the relationship between carrier mobility and impurity density in silicon. Work is continuing on measurement of resistivity of semiconductor crystals; characterization of generation-recombination-trapping centers, including gold, in silicon; evaluation of wire bonds and die attachment; study of scanning electron microscopy for wafer inspection and test; measurement of thermal properties of semiconductor devices; determination of S-parameters and delay time in junction devices; and characterization of noise and conversion loss of microwave detector diodes.
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SEMICONDUCTOR TECHNOLOGY Supercritical carbon dioxide process for releasing stuck cantilever beams
NASA Astrophysics Data System (ADS)
Yu, Hui; Chaoqun, Gao; Lei, Wang; Yupeng, Jing
2010-10-01
The multi-SCCO2 (supercritical carbon dioxide) release and dry process based on our specialized SCCO2 semiconductor process equipment is investigated and the releasing mechanism is discussed. The experiment results show that stuck cantilever beams were held up again under SCCO2 high pressure treatment and the repeatability of this process is nearly 100%.
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Plasma Processes for Semiconductor Fabrication
NASA Astrophysics Data System (ADS)
Hitchon, W. N. G.
1999-01-01
Plasma processing is a central technique in the fabrication of semiconductor devices. This self-contained book provides an up-to-date description of plasma etching and deposition in semiconductor fabrication. It presents the basic physics and chemistry of these processes, and shows how they can be accurately modeled. The author begins with an overview of plasma reactors and discusses the various models for understanding plasma processes. He then covers plasma chemistry, addressing the effects of different chemicals on the features being etched. Having presented the relevant background material, he then describes in detail the modeling of complex plasma systems, with reference to experimental results. The book closes with a useful glossary of technical terms. No prior knowledge of plasma physics is assumed in the book. It contains many homework exercises and serves as an ideal introduction to plasma processing and technology for graduate students of electrical engineering and materials science. It will also be a useful reference for practicing engineers in the semiconductor industry.
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Limbu, Samita; Cassidy, Katie; Keena, Melody; Tobin, Patrick; Hoover, Kelli
2016-02-01
Scymnus (Neopullus) camptodromus Yu and Liu (Coleoptera: Coccinellidae) was brought to the United States from China as a potential biological control agent for hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae). Scymnus camptodromus phenology is closely synchronized with that of A. tsugae and has several characteristics of a promising biological control agent. As a prerequisite to field release, S. camptodromus was evaluated for potential nontarget impacts. In host range studies, the predator was given the choice of sympatric adelgid and nonadelgid prey items. Nontarget testing showed that S. camptodromus will feed to some degree on other adelgid species, but highly prefers A. tsugae. We also evaluated larval development of S. camptodromus on pine bark adelgid (Pineus strobi (Hartig)) (Hemiptera: Adelgidae) and larch adelgid (Adelges laricis Vallot) (Hemiptera: Adelgidae); a small proportion of predator larvae was able to develop to adulthood on P. strobi or A. laricis alone. Scymnus camptodromus showed no interest in feeding on woolly alder aphid (Paraprociphilus tessellatus Fitch) (Hemiptera: Aphididae) or woolly apple aphid (Eriosoma lanigerum (Hausmann)) (Hemiptera: Aphididae), and minimal interest in cotton aphid (Aphis gossypii Glover) (Hemiptera: Aphididae) in choice and no-choice experiments. Scymnus camptodromus females did not oviposit on any host material other than A. tsugae-infested hemlock. Under the circumstances of the study, S. camptodromus appears to be a specific predator of A. tsugae, with minimal risk to nontarget species. Although the predator can develop on P. strobi, the likelihood that S. camptodromus would oviposit on pine hosts of this adelgid is small.
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Optimum germination temperatures
Richard M. Godman; Gilbert A. Mattson
1992-01-01
Why is sugar maple abundant under nearly all stand conditions, and why do hemlock and yellow birch, although differing in tolerance, occur together as a type? At least part of the answer may have to do with the optimum germinating temperatures for their seeds.
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Responses of southeast Alaska understory species to variation in light and soil environments
Thomas A. Hanley; Bernard T. Bormann; Jeffrey C. Barnard; S. Mark Nay
2014-01-01
Aboveground growth rates of seedlings of bunchberry (Cornus canadensis L.), oval-leaf blueberry (Vaccinium ovalifolium Sm.), salmonberry (Rubus spectabilis Pursh), devilsclub (Oplopanax horridus (Sm.) Miq.), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) were...
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Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication
Ashby, C.I.H.; Myers, D.R.; Vook, F.L.
1988-06-16
An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.
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Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication
Ashby, Carol I. H.; Myers, David R.; Vook, Frederick L.
1989-01-01
An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.
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Intelligent monitoring and control of semiconductor manufacturing equipment
NASA Technical Reports Server (NTRS)
Murdock, Janet L.; Hayes-Roth, Barbara
1991-01-01
The use of AI methods to monitor and control semiconductor fabrication in a state-of-the-art manufacturing environment called the Rapid Thermal Multiprocessor is described. Semiconductor fabrication involves many complex processing steps with limited opportunities to measure process and product properties. By applying additional process and product knowledge to that limited data, AI methods augment classical control methods by detecting abnormalities and trends, predicting failures, diagnosing, planning corrective action sequences, explaining diagnoses or predictions, and reacting to anomalous conditions that classical control systems typically would not correct. Research methodology and issues are discussed, and two diagnosis scenarios are examined.
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Submillimeter Spectroscopic Diagnostics in Semiconductor Processing Plasmas
NASA Astrophysics Data System (ADS)
Helal, Yaser H.; Neese, Christopher F.; De Lucia, Frank C.; Ewing, Paul R.; Stout, Phillip J.; Walker, Quentin; Armacost, Michael D.
2014-06-01
Submillimeter absorption spectroscopy was used to study semiconductor processing plasmas. Abundances and temperatures of molecules, radicals, and ions can be determined without altering any of the properties of the plasma. The behavior of these measurements provides useful applications in monitoring process steps. A summary of such applications will be presented, including etching and cleaning endpoint detection.
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Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers
Norman, Andrew
2016-08-23
A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.
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Roadmap on semiconductor-cell biointerfaces
NASA Astrophysics Data System (ADS)
Tian, Bozhi; Xu, Shuai; Rogers, John A.; Cestellos-Blanco, Stefano; Yang, Peidong; Carvalho-de-Souza, João L.; Bezanilla, Francisco; Liu, Jia; Bao, Zhenan; Hjort, Martin; Cao, Yuhong; Melosh, Nicholas; Lanzani, Guglielmo; Benfenati, Fabio; Galli, Giulia; Gygi, Francois; Kautz, Rylan; Gorodetsky, Alon A.; Kim, Samuel S.; Lu, Timothy K.; Anikeeva, Polina; Cifra, Michal; Krivosudský, Ondrej; Havelka, Daniel; Jiang, Yuanwen
2018-05-01
This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world.
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Methods for enhancing P-type doping in III-V semiconductor films
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Feng; Stringfellow, Gerald; Zhu, Junyi
2017-08-01
Methods of doping a semiconductor film are provided. The methods comprise epitaxially growing the III-V semiconductor film in the presence of a dopant, a surfactant capable of acting as an electron reservoir, and hydrogen, under conditions that promote the formation of a III-V semiconductor film doped with the p-type dopant. In some embodiments of the methods, the epitaxial growth of the doped III-V semiconductor film is initiated at a first hydrogen partial pressure which is increased to a second hydrogen partial pressure during the epitaxial growth process.
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Temperature control of power semiconductor devices in traction applications
NASA Astrophysics Data System (ADS)
Pugachev, A. A.; Strekalov, N. N.
2017-02-01
The peculiarity of thermal management of traction frequency converters of a railway rolling stock is highlighted. The topology and the operation principle of the automatic temperature control system of power semiconductor modules of the traction frequency converter are designed and discussed. The features of semiconductors as an object of temperature control are considered; the equivalent circuit of thermal processes in the semiconductors is suggested, the power losses in the two-level voltage source inverters are evaluated and analyzed. The dynamic properties and characteristics of the cooling fan induction motor electric drive with the scalar control are presented. The results of simulation in Matlab are shown for the steady state of thermal processes.
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Adoption of engineered wood products in Alaska
Joseph A. Roos; Indroneil Ganguly; Allen Brackley
2009-01-01
Based on an in-grade testing program, the Ketchikan Wood Technology Center has registered three proprietary grademarks for Alaska species of hemlock (Tsuga heterophylla (Raf.) Sarg.), yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach), and spruce (combined Sitka spruce [Picea sitchensis (Bong.) Carr...
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Fall versus spring transplanting of container seedlings: A comparison of seedling morphology
David Steinfeld; David Davis; Steve Feigner; Karen House
2002-01-01
Containerized seedlings of Engelmann spruce (Picea engelmannii), sugar pine (Pinus lambertiana), Douglas-fir (Pseudotsuga menziesii), western redcedar (Thuja plicata), and western hemlock (Tsuga heterphylla) transplanted in the early fall and later in the early spring were...
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Producing Silicon Carbide for Semiconductor Devices
NASA Technical Reports Server (NTRS)
Hsu, G. C.; Rohatgi, N. K.
1986-01-01
Processes proposed for production of SiC crystals for use in semiconductors operating at temperatures as high as 900 degrees C. Combination of new processes produce silicon carbide chips containing epitaxial layers. Chips of SiC first grown on porous carbon matrices, then placed in fluidized bed, where additional layer of SiC grows. Processes combined to yield complete process. Liquid crystallization process used to make SiC particles or chips for fluidized-bed process.
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Controlling Molecular Doping in Organic Semiconductors.
Jacobs, Ian E; Moulé, Adam J
2017-11-01
The field of organic electronics thrives on the hope of enabling low-cost, solution-processed electronic devices with mechanical, optoelectronic, and chemical properties not available from inorganic semiconductors. A key to the success of these aspirations is the ability to controllably dope organic semiconductors with high spatial resolution. Here, recent progress in molecular doping of organic semiconductors is summarized, with an emphasis on solution-processed p-type doped polymeric semiconductors. Highlighted topics include how solution-processing techniques can control the distribution, diffusion, and density of dopants within the organic semiconductor, and, in turn, affect the electronic properties of the material. Research in these areas has recently intensified, thanks to advances in chemical synthesis, improved understanding of charged states in organic materials, and a focus on relating fabrication techniques to morphology. Significant disorder in these systems, along with complex interactions between doping and film morphology, is often responsible for charge trapping and low doping efficiency. However, the strong coupling between doping, solubility, and morphology can be harnessed to control crystallinity, create doping gradients, and pattern polymers. These breakthroughs suggest a role for molecular doping not only in device function but also in fabrication-applications beyond those directly analogous to inorganic doping. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Wang, Li; Zhang, Xiaojie; Tian, Hongkun; Lu, Yunfeng; Geng, Yanhou; Wang, Fosong
2013-12-14
A cyano-terminated dimer of dithienyldiketopyrrolopyrrole (TDPP), DPP2-CN, is a solution processable ambipolar semiconductor with field-effect hole and electron mobilities of 0.066 and 0.033 cm(2) V(-1) s(-1), respectively, under ambient conditions.
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A hybrid life cycle inventory of nano-scale semiconductor manufacturing.
Krishnan, Nikhil; Boyd, Sarah; Somani, Ajay; Raoux, Sebastien; Clark, Daniel; Dornfeld, David
2008-04-15
The manufacturing of modern semiconductor devices involves a complex set of nanoscale fabrication processes that are energy and resource intensive, and generate significant waste. It is important to understand and reduce the environmental impacts of semiconductor manufacturing because these devices are ubiquitous components in electronics. Furthermore, the fabrication processes used in the semiconductor industry are finding increasing application in other products, such as microelectromechanical systems (MEMS), flat panel displays, and photovoltaics. In this work we develop a library of typical gate-to-gate materials and energy requirements, as well as emissions associated with a complete set of fabrication process models used in manufacturing a modern microprocessor. In addition, we evaluate upstream energy requirements associated with chemicals and materials using both existing process life cycle assessment (LCA) databases and an economic input-output (EIO) model. The result is a comprehensive data set and methodology that may be used to estimate and improve the environmental performance of a broad range of electronics and other emerging applications that involve nano and micro fabrication.
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NASA Technical Reports Server (NTRS)
Bouldin, D. L.; Eastes, R. W.; Feltner, W. R.; Hollis, B. R.; Routh, D. E.
1979-01-01
The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.
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NASA Technical Reports Server (NTRS)
Stirn, R. J.; Yeh, Y.-C. M.
1975-01-01
A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.
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Support apparatus for semiconductor wafer processing
Griffiths, Stewart K.; Nilson, Robert H.; Torres, Kenneth J.
2003-06-10
A support apparatus for minimizing gravitational stress in semiconductor wafers, and particularly silicon wafers, during thermal processing. The support apparatus comprises two concentric circular support structures disposed on a common support fixture. The two concentric circular support structures, located generally at between 10 and 70% and 70 and 100% and preferably at 35 and 82.3% of the semiconductor wafer radius, can be either solid rings or a plurality of spaced support points spaced apart from each other in a substantially uniform manner. Further, the support structures can have segments removed to facilitate wafer loading and unloading. In order to withstand the elevated temperatures encountered during semiconductor wafer processing, the support apparatus, including the concentric circular support structures and support fixture can be fabricated from refractory materials, such as silicon carbide, quartz and graphite. The claimed wafer support apparatus can be readily adapted for use in either batch or single-wafer processors.
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The dynamics of rainfall interception by a seasonal temperate rainforest.
Timothy E. Link; Mike Unsworth; Danny Marks
2004-01-01
Net canopy interception (Inet) during rainfall in an old-growth Douglas-fir-western hemlock ecosystem was 22.8 and 25.0% of the gross rainfall (PG) for 1999 and 2000, respectively. The average direct throughfall proportion (p) and canopy storage capacity (
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Jerome F. Grant; James Rusty Rhea; Paris Lambdin; Greg Wiggins; Abdul Hakeem
2009-01-01
While commonly used approaches (petri dishes, small arenas, growth chambers, greenhouse studies, sleeve cages, etc.) for evaluation of natural enemies provide important information, does the small size of these arenas limit their...
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Strip clearcutting to regenerate northern hardwoods.
Frederick T. Metzger
1980-01-01
Describes results of strip clearcutting trials in mature northern hardwood and hemlock-hardwood stands in the Lake States. Two strip width and orientations were tested, with and without herbicide treatment of the advance regeneration. Establishment, growth, and species composition of the regeneration were assessed.
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Cancer mortality among US workers employed in semiconductor wafer fabrication.
Boice, John D; Marano, Donald E; Munro, Heather M; Chadda, Bandana K; Signorello, Lisa B; Tarone, Robert E; Blot, William J; McLaughlin, Joseph K
2010-11-01
To evaluate potential cancer risks in the US semiconductor wafer fabrication industry. A cohort of 100,081 semiconductor workers employed between 1968 and 2002 was studied. Standardized mortality ratios and relative risks (RRs) were estimated. Standardized mortality ratios were similar and significantly low among fabrication and nonfabrication workers for all causes (0.54 and 0.54) and all cancers (0.74 and 0.72). Internal comparisons also showed similar overall cancer risks among fabrication workers (RR = 0.98), including process equipment operators and process equipment service technicians (OP/EST) employed in cleanrooms (RR = 0.97), compared with nonfabrication workers. Nonsignificantly elevated RRs were observed for a few cancer sites among OP/EST workers, but the numbers of deaths were small and there were no trends of increasing risk with duration of employment. Work in the US semiconductor industry, including semiconductor wafer fabrication in cleanrooms, was not associated with increased cancer mortality overall or mortality from any specific form of cancer. However, due to the young average age of this cohort and its associated relatively low numbers of deaths, regular mortality updates of this semiconductor worker cohort are warranted.
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Screenable contact structure and method for semiconductor devices
Ross, Bernd
1980-08-26
An ink composition for deposition upon the surface of a semiconductor device to provide a contact area for connection to external circuitry is disclosed, the composition comprising an ink system containing a metal powder, a binder and vehicle, and a metal frit. The ink is screened onto the semiconductor surface in the desired pattern and is heated to a temperature sufficient to cause the metal frit to become liquid. The metal frit dissolves some of the metal powder and densifies the structure by transporting the dissolved metal powder in a liquid sintering process. The sintering process typically may be carried out in any type of atmosphere. A small amount of dopant or semiconductor material may be added to the ink systems to achieve particular results if desired.
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Windthrow and salvage logging in an old-growth hemlock-northern hardwoods forest
Lang, K.D.; Schulte, L.A.; Guntenspergen, G.R.
2009-01-01
Although the initial response to salvage (also known as, post-disturbance or sanitary) logging is known to vary among system components, little is known about longer term forest recovery. We examine forest overstory, understory, soil, and microtopographic response 25 years after a 1977 severe wind disturbance on the Flambeau River State Forest in Wisconsin, USA, a portion of which was salvage logged. Within this former old-growth hemlock-northern hardwoods forest, tree dominance has shifted from Eastern hemlock (Tsuga canadensis) to broad-leaf deciduous species (Ulmus americana, Acer saccharum, Tilia americana, Populus tremuloides, and Betula alleghaniensis) in both the salvaged and unsalvaged areas. While the biological legacies of pre-disturbance seedlings, saplings, and mature trees were initially more abundant in the unsalvaged area, regeneration through root suckers and stump sprouts was common in both areas. After 25 years, tree basal area, sapling density, shrub layer density, and seedling cover had converged between unsalvaged and salvaged areas. In contrast, understory herb communities differed between salvaged and unsalvaged forest, with salvaged forest containing significantly higher understory herb richness and cover, and greater dominance of species benefiting from disturbance, especially Solidago species. Soil bulk density, pH, organic carbon content, and organic nitrogen content were also significantly higher in the salvaged area. The structural legacy of tip-up microtopography remains more pronounced in the unsalvaged area, with significantly taller tip-up mounds and deeper pits. Mosses and some forest herbs, including Athyrium filix-femina and Hydrophyllum virginianum, showed strong positive responses to this tip-up microrelief, highlighting the importance of these structural legacies for understory biodiversity. In sum, although the pathways of recovery differed, this forest appeared to be as resilient to the compound disturbances of windthrow plus salvage logging as to wind disturbance alone, by most vegetative measures.
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Knoepp, Jennifer D; Vose, James M; Michael, Jerry L; Reynolds, Barbara C
2012-01-01
Imidacloprid is a systemic insecticide effective in controlling the exotic pest (hemlock woolly adelgid) in eastern hemlock () trees. Concerns over imidacloprid impacts on nontarget species have limited its application in southern Appalachian ecosystems. We quantified the movement and adsorption of imidacloprid in forest soils after soil injection in two sites at Coweeta Hydrologic Laboratory in western North Carolina. Soils differed in profile depth, total carbon and nitrogen content, and effective cation exchange capacity. We injected imidacloprid 5 cm into mineral soil, 1.5 m from infested trees, using a Kioritz soil injector. We tracked the horizontal and vertical movement of imidacloprid by collecting soil solution and soil samples at 1 m, 2 m, and at the drip line from each tree periodically for 1 yr. Soil solution was collected 20 cm below the surface and just above the saprolite, and acetonitrile-extractable imidacloprid was determined through the profile. Soil solution and extractable imidacloprid concentrations were determined by high-performance liquid chromatography. Soil solution and extractable imidacloprid concentrations were greater in the site with greater soil organic matter. Imidacloprid moved vertically and horizontally in both sites; concentrations generally declined downward in the soil profile, but preferential flow paths allowed rapid vertical movement. Horizontal movement was limited, and imidacloprid did not move to the tree drip line. We found a negative relationship between adsorbed imidacloprid concentrations and soil microarthropod populations largely in the low-organic-matter site; however, population counts were similar to other studies at Coweeta. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
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Quantum theory of the electronic and optical properties of low-dimensional semiconductor systems
NASA Astrophysics Data System (ADS)
Lau, Wayne Heung
This thesis examines the electronic and optical properties of low-dimensional semiconductor systems. A theory is developed to study the electron-hole generation-recombination process of type-II semimetallic semiconductor heterojunctions based on a 3 x 3 k·p matrix Hamiltonian (three-band model) and an 8 x 8 k·p matrix Hamiltonian (eight-band model). A novel electron-hole generation and recombination process, which is called activationless generation-recombination process, is predicted. It is demonstrated that the current through the type-II semimetallic semiconductor heterojunctions is governed by the activationless electron-hole generation-recombination process at the heterointerfaces, and that the current-voltage characteristics are essentially linear. A qualitative agreement between theory and experiments is observed. The numerical results of the eight-band model are compared with those of the threeband model. Based on a lattice gas model, a theory is developed to study the influence of a random potential on the ionization equilibrium conditions for bound electron-hole pairs (excitons) in III--V semiconductor heterostructures. It is demonstrated that ionization equilibrium conditions for bound electron-hole pairs change drastically in the presence of strong disorder. It is predicted that strong disorder promotes dissociation of excitons in III--V semiconductor heterostructures. A theory of polariton (photon dressed by phonon) spontaneous emission in a III--V semiconductor doped with semiconductor quantum dots (QDs) or quantum wells (QWs) is developed. For the first time, superradiant and subradiant polariton spontaneous emission phenomena in a polariton-QD (QW) coupled system are predicted when the resonance energies of the two identical QDs (QWs) lie outside the polaritonic energy gap. It is also predicted that when the resonance energies of the two identical QDs (QWs) lie inside the polaritonic energy gap, spontaneous emission of polariton in the polariton-QD (QW) coupled system is inhibited and polariton bound states are formed within the polaritonic energy gap. A theory is also developed to study the polariton eigenenergy spectrum, polariton effective mass, and polariton spectral density of N identical semiconductor QDs (QWs) or a superlattice (SL) placed inside a III--V semiconductor. A polariton-impurity band lying within the polaritonic energy gap of the III--V semiconductor is predicted when the resonance energies of the QDs (QWs) lie inside the polaritonic energy gap. Hole-like polariton effective mass of the polariton-impurity band is predicted. It is also predicted that the spectral density of the polariton has a Lorentzian shape if the resonance energies of the QDs (QWs) lie outside the polaritonic gap.
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NASA Astrophysics Data System (ADS)
De Biasio, M.; Kraft, M.; Schultz, M.; Goller, B.; Sternig, D.; Esteve, R.; Roesner, M.
2017-05-01
Silicon carbide (SiC) is a wide band-gap semi-conductor material that is used increasingly for high voltage power devices, since it has a higher breakdown field strength and better thermal conductivity than silicon. However, in particular its hardness makes wafer processing difficult and many standard semi-conductor processes have to be specially adapted. We measure the effects of (i) mechanical processing (i.e. grinding of the backside) and (ii) chemical and thermal processing (i.e. doping and annealing), using confocal microscopy to measure the surface roughness of ground wafers and micro-Raman spectroscopy to measure the stresses induced in the wafers by grinding. 4H-SiC wafers with different dopings were studied before and after annealing, using depth-resolved micro-Raman spectroscopy to observe how doping and annealing affect: i.) the damage and stresses induced on the crystalline structure of the samples and ii.) the concentration of free electrical carriers. Our results show that mechanical, chemical and thermal processing techniques have effects on this semiconductor material that can be observed and characterized using confocal microscopy and high resolution micro Raman spectroscopy.
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Electron-phonon interaction, transport and ultrafast processes in semiconductor microstructures
NASA Astrophysics Data System (ADS)
Sarma, Sankar D.
1992-08-01
We have fulfilled our contract obligations completely by doing theoretical research on electron-phonon interaction and transport properties in submicron semiconductor structures with the emphasis on ultrafast processes and many-body effects. Fifty-five papers have been published based on our research during the contract period.
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Jin Lee, Su; Kim, Yong-Jae; Young Yeo, So; Lee, Eunji; Sun Lim, Ho; Kim, Min; Song, Yong-Won; Cho, Jinhan; Ah Lim, Jung
2015-01-01
Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step. PMID:26359068
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Lee, Su Jin; Kim, Yong-Jae; Yeo, So Young; Lee, Eunji; Lim, Ho Sun; Kim, Min; Song, Yong-Won; Cho, Jinhan; Lim, Jung Ah
2015-09-11
Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step.
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Preliminary test of two stump surface protectants against Fomes annosus.
E.E. Nelson; C.Y. Li
1980-01-01
Two materials, monolaurin (at two concentrations) and an unidentified species of the genus Streptomyces, were tested along with borax for ability to protect freshly cut stump surfaces of western hemlock (Tsuga heterophylla (Raf.) Sarg.) from colonization by Fomes annosus. Protectants were significantly (P...
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Steroselective Potencies and Relative Toxicities of Coniine Enantiomers
USDA-ARS?s Scientific Manuscript database
Coniine, one of the major toxic alkaloids present in poison hemlock (Conium maculatum), occurs in two optically active forms. A comparison of the relative potencies of (+)- and (-)-coniine enantiomers has not been previously reported. In this study, we separated the enantiomers of coniine and dete...
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Michael L. McManus; Andrew M. Liebhold
2009-01-01
Over the last 50 years, North American forests have been inundated by a multitude of alien pest invasions. Among these, noteworthy invaders include the hemlock woolly adelgid (Adelges tsugae), emerald ash borer (Agrilus planipennis), chestnut blight and Dutch elm disease. These species have greatly altered both the ecological and...
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Percent crown cover tables for applying the shelterwood system in New England
W. B. Leak; C. H. Tubbs
1983-01-01
Provides tables for estimating residual percent crown cover, using a 10-factor prism, of three species groups: (1) sugar and red maples, yellow and paper birches; (2) white ash, white pine, red spruce, balsam fir, and hemlock; and (3) beech.
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Stereoselective potencies and relative toxicities of y-Coniceine and N-Methylconiine enantiomers
USDA-ARS?s Scientific Manuscript database
'-Coniceine, coniine, and N-methylconiine are toxic alkaloids present in poison hemlock (Conium maculatum). We previously reported the comparison of the relative potencies of (+)- and (-)-coniine enantiomers. In this study, we synthesized '-coniceine and the enantiomers of N-methylconiine and dete...
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Examples of fire restoration in Glacier National Park
Laurie Kurth
1996-01-01
Covering just over 1 million acres, Glacier National Park straddles the Continental Divide in northwestern Montana. Diverse vegetation communities include moist western cedar- western hemlock (Thuja plicata - Tsuga heterophylla) old growth forests similar to those of the Pacific Coast, dry western grasslands and prairies, dense...
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Energy values for whole trees and crowns of selected species.
James O. Howard
1988-01-01
Energy values, BTU's (British thermal units) per ovendry pound, were determined for whole-tree and crown materials from western hemlock (Tsuga heterophylla (Raf.) Sarg.), coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), and western redcedar (Thuja plicata Donn ex D. Don)....
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Spahn, Olga B.; Lear, Kevin L.
1998-01-01
A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.
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Wang, Lei; Yan, Danhua; Shaffer, David W.; ...
2017-12-27
Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. In this study, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm 2 photocurrents atmore » the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ~1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation layers. Further enhanced PEC performances were realized by improving the bottom ohmic contact to the organic semiconductor, achieving ~60 μA/cm 2 water oxidation photocurrent at the equilibrium potential, the highest values reported for organic semiconductor thin films to our knowledge. The improved stability and performance of passivated organic photoelectrodes and discovered design rationales provide useful guidelines for realizing the stable visible solar PEC water splitting based on organic semiconductor thin films.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, Lei; Yan, Danhua; Shaffer, David W.
Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. In this study, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm 2 photocurrents atmore » the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ~1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation layers. Further enhanced PEC performances were realized by improving the bottom ohmic contact to the organic semiconductor, achieving ~60 μA/cm 2 water oxidation photocurrent at the equilibrium potential, the highest values reported for organic semiconductor thin films to our knowledge. The improved stability and performance of passivated organic photoelectrodes and discovered design rationales provide useful guidelines for realizing the stable visible solar PEC water splitting based on organic semiconductor thin films.« less
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Rapid Thermal Processing (RTP) of semiconductors in space
NASA Technical Reports Server (NTRS)
Anderson, T. J.; Jones, K. S.
1993-01-01
The progress achieved on the project entitled 'Rapid Thermal Processing of Semiconductors in Space' for a 12 month period of activity ending March 31, 1993 is summarized. The activity of this group is being performed under the direct auspices of the ROMPS program. The main objective of this program is to develop and demonstrate the use of advanced robotics in space with rapid thermal process (RTP) of semiconductors providing the test technology. Rapid thermal processing is an ideal processing step for demonstration purposes since it encompasses many of the characteristics of other processes used in solid state device manufacturing. Furthermore, a low thermal budget is becoming more important in existing manufacturing practice, while a low thermal budget is critical to successful processing in space. A secondary objective of this project is to determine the influence of microgravity on the rapid thermal process for a variety of operating modes. In many instances, this involves one or more fluid phases. The advancement of microgravity processing science is an important ancillary objective.
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Low temperature junction growth using hot-wire chemical vapor deposition
Wang, Qi; Page, Matthew; Iwaniczko, Eugene; Wang, Tihu; Yan, Yanfa
2014-02-04
A system and a process for forming a semi-conductor device, and solar cells (10) formed thereby. The process includes preparing a substrate (12) for deposition of a junction layer (14); forming the junction layer (14) on the substrate (12) using hot wire chemical vapor deposition; and, finishing the semi-conductor device.
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Semiconductors: In Situ Processing of Photovoltaic Devices
NASA Technical Reports Server (NTRS)
Curreri, Peter A.
1998-01-01
The possible processing of semiconductor photovoltaic devices is discussed. The requirements for lunar PV cells is reviewed, and the key challenges involved in their manufacturing are investigated. A schematic diagram of a passivated emitter and rear cell (PERC) is presented. The possible fabrication of large photovoltaic arrays in space from lunar materials is also discussed.
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Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors
Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; ...
2015-07-22
The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe 2 monolayer crystals with SiO 2, and the exposed locations are selectively and totally converted to MoS 2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe 2/MoS 2 heterojunctions in predefinedmore » patterns. The junctions and conversion process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.« less
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Tan, Shih-Wei; Lai, Shih-Wen
2012-01-01
Characterization and modeling of metal-semiconductor-metal (MSM) GaAs diodes using to evaporate SiO2 and Pd simultaneously as a mixture electrode (called M-MSM diodes) compared with similar to evaporate Pd as the electrode (called Pd-MSM diodes) were reported. The barrier height (φ b) and the Richardson constant (A*) were carried out for the thermionic-emission process to describe well the current transport for Pd-MSM diodes in the consideration of the carrier over the metal-semiconductor barrier. In addition, in the consideration of the carrier over both the metal-semiconductor barrier and the insulator-semiconductor barrier simultaneously, thus the thermionic-emission process can be used to describe well the current transport for M-MSM diodes. Furthermore, in the higher applied voltage, the carrier recombination will be taken into discussion. Besides, a composite-current (CC) model is developed to evidence the concepts. Our calculated results are in good agreement with the experimental ones. PMID:23226352
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NASA Technical Reports Server (NTRS)
1983-01-01
The process technology for the manufacture of semiconductor-grade silicon in a large commercial plant by 1986, at a price less than $14 per kilogram of silicon based on 1975 dollars is discussed. The engineering design, installation, checkout, and operation of an Experimental Process System Development unit was discussed. Quality control of scaling-up the process and an economic analysis of product and production costs are discussed.
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Mohawk Research Natural Area: guidebook supplement 45
Reid Schuller; Cheshire Mayrsohn
2013-01-01
This guidebook describes major biological and physical attributes of the 119-ha (293-ac) Mohawk Research Natural Area. The area supports old-growth Douglas-fir (Pseudotsuga menziesii) forest characterized by plant associations representative of the western Cascade foothills. These include the western hemlock/Oregon grape-salal (Tsuga...
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RELATING FINE ROOT BIOMASS TO SOIL AND CLIMATE CONDITIONS IN THE PACIFIC NORTHWEST
The additive contribution of fine root biomass for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) to the stand average fine root biomass were estimated for eight conifer stands in the Pacific Northwest. Base...
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Changes in Landscape Greenness: Anthropogenic or Natural: Proof of Concept, Selected Study Areas
We selected four National Forest areas that span east to west of USA to conduct the study over the 25-year period from 1989 through 2013: GWJ (Virginia), Chatt-O (Georgia), Kisatchie (Louisiana), Hemlock Restoration (California). The Normalized Difference Vegetation Index (NDV...
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High performance printed oxide field-effect transistors processed using photonic curing.
Garlapati, Suresh Kumar; Marques, Gabriel Cadilha; Gebauer, Julia Susanne; Dehm, Simone; Bruns, Michael; Winterer, Markus; Tahoori, Mehdi Baradaran; Aghassi-Hagmann, Jasmin; Hahn, Horst; Dasgupta, Subho
2018-06-08
Oxide semiconductors are highly promising candidates for the most awaited, next-generation electronics, namely, printed electronics. As a fabrication route for the solution-processed/printed oxide semiconductors, photonic curing is becoming increasingly popular, as compared to the conventional thermal curing method; the former offers numerous advantages over the latter, such as low process temperatures and short exposure time and thereby, high throughput compatibility. Here, using dissimilar photonic curing concepts (UV-visible light and UV-laser), we demonstrate facile fabrication of high performance In 2 O 3 field-effect transistors (FETs). Beside the processing related issues (temperature, time etc.), the other known limitation of oxide electronics is the lack of high performance p-type semiconductors, which can be bypassed using unipolar logics from high mobility n-type semiconductors alone. Interestingly, here we have found that our chosen distinct photonic curing methods can offer a large variation in threshold voltage, when they are fabricated from the same precursor ink. Consequently, both depletion and enhancement-mode devices have been achieved which can be used as the pull-up and pull-down transistors in unipolar inverters. The present device fabrication recipe demonstrates fast processing of low operation voltage, high performance FETs with large threshold voltage tunability.
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High performance printed oxide field-effect transistors processed using photonic curing
NASA Astrophysics Data System (ADS)
Garlapati, Suresh Kumar; Cadilha Marques, Gabriel; Gebauer, Julia Susanne; Dehm, Simone; Bruns, Michael; Winterer, Markus; Baradaran Tahoori, Mehdi; Aghassi-Hagmann, Jasmin; Hahn, Horst; Dasgupta, Subho
2018-06-01
Oxide semiconductors are highly promising candidates for the most awaited, next-generation electronics, namely, printed electronics. As a fabrication route for the solution-processed/printed oxide semiconductors, photonic curing is becoming increasingly popular, as compared to the conventional thermal curing method; the former offers numerous advantages over the latter, such as low process temperatures and short exposure time and thereby, high throughput compatibility. Here, using dissimilar photonic curing concepts (UV–visible light and UV-laser), we demonstrate facile fabrication of high performance In2O3 field-effect transistors (FETs). Beside the processing related issues (temperature, time etc.), the other known limitation of oxide electronics is the lack of high performance p-type semiconductors, which can be bypassed using unipolar logics from high mobility n-type semiconductors alone. Interestingly, here we have found that our chosen distinct photonic curing methods can offer a large variation in threshold voltage, when they are fabricated from the same precursor ink. Consequently, both depletion and enhancement-mode devices have been achieved which can be used as the pull-up and pull-down transistors in unipolar inverters. The present device fabrication recipe demonstrates fast processing of low operation voltage, high performance FETs with large threshold voltage tunability.
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Concept Maps as Expressions of Teachers' Meaning-Making While Beginning to Teach Semiconductors
ERIC Educational Resources Information Center
Rollnick, Marissa; Mundalamo, Fhatuwani; Booth, Shirley
2013-01-01
The challenge of teaching new subject matter is a familiar one for most teachers. This paper investigates the content knowledge gains made by seven teachers as they learn to teach the topic of semiconductors through a process of self-study. "Semiconductors" is a new topic in the curriculum which looks at the sub-microscopic properties of…
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Timm, Rainer; Head, Ashley R; Yngman, Sofie; Knutsson, Johan V; Hjort, Martin; McKibbin, Sarah R; Troian, Andrea; Persson, Olof; Urpelainen, Samuli; Knudsen, Jan; Schnadt, Joachim; Mikkelsen, Anders
2018-04-12
Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor-oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.
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Process for making photovoltaic devices and resultant product
Foote, James B.; Kaake, Steven A. F.; Meyers, Peter V.; Nolan, James F.
1996-07-16
A process and apparatus (70) for making a large area photovoltaic device (22) that is capable of generating low cost electrical power. The apparatus (70) for performing the process includes an enclosure (126) providing a controlled environment in which an oven (156) is located. At least one and preferably a plurality of deposition stations (74,76,78) provide heated vapors of semiconductor material within the oven (156) for continuous elevated temperature deposition of semiconductor material on a sheet substrate (24) including a glass sheet (26) conveyed within the oven. The sheet substrate (24) is conveyed on a roller conveyor (184) within the oven (156) and the semiconductor material whose main layer (82) is cadmium telluride is deposited on an upwardly facing surface (28) of the substrate by each deposition station from a location within the oven above the roller conveyor. A cooling station (86) rapidly cools the substrate (24) after deposition of the semiconductor material thereon to strengthen the glass sheet of the substrate.
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Process for making photovoltaic devices and resultant product
Foote, James B.; Kaake, Steven A. F.; Meyers, Peter V.; Nolan, James F.
1995-11-28
A process and apparatus (70) for making a large area photovoltaic device (22) that is capable of generating low cost electrical power. The apparatus (70) for performing the process includes an enclosure (126) providing a controlled environment in which an oven (156) is located. At least one and preferably a plurality of deposition stations (74,76,78) provide heated vapors of semiconductor material within the oven (156) for continuous elevated temperature deposition of semiconductor material on a sheet substrate (24) including a glass sheet (26) conveyed within the oven. The sheet substrate (24) is conveyed on a roller conveyor (184) within the oven (156) and the semiconductor material whose main layer (82) is cadmium telluride is deposited on an upwardly facing surface (28) of the substrate by each deposition station from a location within the oven above the roller conveyor. A cooling station (86) rapidly cools the substrate (24) after deposition of the semiconductor material thereon to strengthen the glass sheet of the substrate.