bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep sampling and testing in soft stratified clay
Authors: Cummings Simon James , Sivakumar Vinayagamoorthy , Doran Isaac Gregg , Graham Jim
Published: May 2003

A 37-m thick layer of stratified clay encountered during a site investigation at Swann's Bridge, near the sea-coast at Limavady, Northern Ireland, is one of the deepest and thickest layers of this type of material recorded in Ireland. A study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline, the clay was deposited in a fresh-water glacial lake formed approximately 13 000 BP. The 37-m layer of clay can be divided into two separate zones. The lower zone was deposited as a series of laminated layers of sand, silt, and clay, whereas the upper zone was deposited as a largely homogeneous mixture. A comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit. The results obtained from these tests were complex and confusing, particularly the results of tests done on samples from the lower zone. The results of one-dimensional compression tests, unconsolidated undrained triaxial tests, and consolidated undrained triaxial compression tests showed that despite careful sampling, all of the specimens from the lower zone exhibited behaviour similar to that of reconstituted clays. It was immediately clear that the results needed explanation. This paper studies possible causes of the results from tests carried out on the lower Limavady clay. It suggests a possible mechanism based on anisotropic elasticity, yielding, and destructuring that provides an understanding of the observed behaviour.Key words: clay, laminations, disturbance, yielding, destructuring, reconstituted.
Application of electrical resistivity imaging to the development of a geologic model for a proposed Edmonton landfill site
Authors: Meads Lindsay N , Bentley Laurence R , Mendoza Carl A
Published: May 2003

Electrical resistivity imaging (ERI) was used to further characterize the geologic setting at the proposed Aurum solid-waste landfill site near Edmonton, Alberta. Two bedrock channel aquifers, the east and south channels, exist in or near the site. Previous studies at the proposed site used borehole and pumping test data to determine that the two aquifers are separate and hydraulically disconnected by a sheet of ice thrust bedrock. The three objectives of the ERI were to resolve the sand channels and terrace sands, resolve the top of the thrust bedrock, and resolve the sand channels beneath the thrust bedrock. The ERI survey, in combination with the borehole data, presented a more detailed representation of the site's complex geology than borehole data alone. The south channel has a long and even bottom, steeply sloping sides, and two levels. The thrust bedrock occurs as irregular massive blocks throughout the site, and the aquifers are hydraulically confined by the glacial till. The bedrock surface is highly variable where it has been modified by glacial ice thrusting and relatively uniform elsewhere. Electrical resistivity imaging was found to be useful for the prompt and accurate development of a geologic model for the proposed Aurum landfill site.Key words: electrical resistivity imaging, thrust bedrock, site characterization.
Evaluation of an HDPE geomembrane after 14 years as a leachate lagoon liner
Authors: Rowe R Kerry , Sangam Henri P , Lake Craig B
Published: May 2003

A geomembrane  compacted clay composite liner system used to contain municipal solid waste (MSW) landfill leachate for 14 years is evaluated. Field observations of the geomembrane revealed many defects, including holes, patches, and cracks. Physical, chemical, and mechanical tests conducted on samples collected from five different locations of the liner suggest that samples continuously exposed to sunlight and high temperatures experienced more degradation compared to samples that were covered by leachate or soil. Sorption and diffusion tests revealed that the permeation coefficients of volatile organic compounds were in the range of 4 × 1012 to 6 × 1011 m2/s and that, with respect to these parameters, there was no significant difference between samples with different exposure levels. However, the permeation coefficients were between four and five times lower than values obtained for unaged HDPE geomembranes typical of present day production. Contaminant modelling of the entire lagoon liner suggests that the geomembrane liner most likely stopped being effective as a contaminant barrier to ionic species sometime between 0 and 4 years after the installation.Key words: liquid containment, composite liner, diffusion, HDPE geomembrane, performance.
The 2001 R.M. Hardy Lecture: The limits of limit equilibrium analyses
Authors: Krahn John
Published: May 2003

Limit equilibrium types of analysis have been in use in geotechnical engineering for a long time and are now used routinely in geotechnical engineering practice. Modern graphical software tools have made it possible to gain a much better understanding of the inner numerical details of the method. A closer look at the details reveals that the limit equilibrium method of slices has some serious limitations. The fundamental shortcoming of limit equilibrium methods, which only satisfy equations of statics, is that they do not consider strain and displacement compatibility. This limitation can be overcome by using finite element computed stresses inside a conventional limit equilibrium framework. From the finite element stresses both the total shear resistance and the total mobilized shear stress on a slip surface can be computed and used to determine the factor of safety. Software tools that make this feasible and practical are now available, and they hold great promise for advancing the technology of analyzing the stability of earth structures.Key words: limit equilibrium, stability, factor of safety, finite element, ground stresses, slip surface.
Landscape patterns of change in coarse woody debris accumulation in an old-growth deciduous forest on the Cumberland Plateau, southeastern Kentucky
Authors: Muller Robert N
Published: May 2003

Forest disturbance was evaluated in an old-growth forest on the Cumberland Plateau in southeastern Kentucky using a 10-year history of coarse woody debris (CWD) accumulation. CWD averaged 21.8 Mg/ha in 1989 and 29.6 Mg/ha (36% increase) in 1999. In both years, Quercus montana Willd. and Fagus grandifolia Ehrh. were the two dominant components of CWD; however, over the 10-year interval, Tilia heterophylla Vent., Carya glabra (Mill.) Sweet, and Acer saccharum Marsh. increased significantly, while Quercus alba L. declined. CWD occurrence had a highly skewed frequency, which is consistent with the idea that gap dynamics dominate the disturbance patterns of temperate old-growth forests. However, CWD composition bore limited relationship to overstory species composition or to the dynamics of gap creation. Further, while CWD showed no relationship to forest community (i.e., landscape position) in 1989, it was strongly related to community in 1999. The increase in CWD mass and changing importance of landscape position appear to have occurred in the absence of extrinsic disturbance factors. Thus, in old-growth deciduous forests of the temperate region, autogenic disturbance appears to occur at two scales: (i) the patch dynamics of individual tree mortality and (ii) landscape-scale patterns of mortality that are determined by species composition and differing patterns of mortality among species.
Potential effects of ozone, climate, and spruce budworm on Douglas-fir growth in the Wasatch Mountains
Authors: Wager David J , Baker F A
Published: May 2003

This study assessed the potential for ozone injury to vegetation in the central Wasatch Mountains of Utah by determining if Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) experienced reduced growth since the onset of high ozone concentrations. Dendrochronological techniques were used to model Douglas-fir growth in six central Wasatch Mountain stands, where ozone concentrations suggest the possibility of injury to vegetation, and in four Bear River stands, where ozone concentrations are lower than injury thresholds. Previous-year growth, temperature, and Palmer's Z index variables explained 5370% of the variance in annual growth. Reduced Douglas-fir growth, not explained by the model or insect and disease records, occurred after 1970 in the central Wasatch Mountains but not in the Bear River Mountains. Douglas-fir growth in the central Wasatch Mountains was slightly negatively correlated with the previous-year ozone concentrations in nearby Salt Lake valley. Between 1962 and 1973, a fluctuating budworm population due to varying spring precipitation was suggested to have replaced precipitation as the factor limiting tree growth, causing an anomalous negative relationship between precipitation and Douglas-fir growth. Because of a suite of possible factors (e.g., undetected climatic variables, fungal pathogens, competitive interactions) influencing Douglas-fir growth, ozone may be one factor in a larger stressor complex reducing growth.
Spatial patterns of lightning strikes in interior Alaska and their relations to elevation and vegetation
Authors: Dissing Dorte , Verbyla David L
Published: May 2003

The relationship between lightning strike density, vegetation, and elevation was investigated at three different spatial scales: (i) interior Alaska (~630 000 km2), (ii) six longitudinal transects (~100 000 km2), and (iii) 17 individual physiographic subregions (~50 000 km2) within Alaska. The data consisted of 14 years (19861999) of observations by the Alaska Fire Service lightning strike detection network. The best explanation for the variation in lightning strike density was provided by a combination of the areal coverage of boreal forest and elevation. Each of these factors has the potential to influence the convective activity. Our study suggests that in a region that is climatically favorable for air-mass thunderstorms, surface properties may enhance local lightning storm development in the boreal forest. Lightning strikes were found to occur frequently both in mountainous areas and at river flats, which is contrary to results from previous Alaskan studies.
Effects of dispersal, shrubs, and density-dependent mortality on seed and seedling distributions in temperate forests
Authors: Lambers Janneke Hille Ris , Clark James S
Published: May 2003

Processes limiting recruitment of trees may have large impacts on forest dynamics. In this paper, we determined the effects of dispersal, shrubs (Rhododendron maximum), and density-dependent mortality on seed and seedling distributions of Southern Appalachian trees. We quantified the spatial distribution of seed rain, seed bank densities, first-year seedlings, and older than first-year seedlings in five vegetation plots. We fit models to these data assuming effects of limited dispersal, R. maximum (an understory shrub), and (or) density-dependent mortality (as well as a null model with none of these effects) and used best-fitting models to indicate which processes affected a particular species. We found that all factors examined limit species distributions, and thus, affect seedling dynamics. Seedling densities are higher near parent trees long after dispersal occurs. This pattern is less frequently observed for animal-dispersed species than for wind-dispersed species, presumably due to secondary dispersal of seeds by animals. Seedling densities of five species are decreased beneath R. maximum. Shade tolerance does not explain which species are affected, suggesting that factors other than low light are responsible for increased seedling mortality under this shrub. Our results suggest that density-dependent mortality affects four species, decreasing seedling densities close to parent trees. Dispersal, density-dependent mortality, and R. maximum all act in ways that may promote or limit diversity, illustrating that multiple factors are likely to control species diversity.
Response to clear-cut logging by northern waterthrushes
Authors: Warkentin Ian G , Fisher Allison L , Flemming Stephen P , Roberts Shawn E
Published: May 2003

We examined the distribution and foraging behaviour of northern waterthrushes (Seiurus noveboracensis) in recently harvested and intact landscapes of Newfoundland. Data were collected along six 1-km segments of stream and adjoining upland habitat resulting in four treatments (harvested or intact, upland or stream) with three replicates each. Although known as a riparian specialist, we found waterthrush territories equally distributed across intact upland and riparian habitats. However, few waterthrushes occupied harvested uplands, while large numbers packed into riparian buffer strips adjacent to these 5- to 10-year-old postharvest clearcuts. Arthropod abundance and biomass were highly variable between years and across the four treatments, generating significant year × treatment interaction effects. Riparian habitat (in both intact and harvested areas) had consistently greater numbers of arthropod prey and more biomass than either upland habitat type. Northern waterthrushes foraging in riparian habitat adjacent to harvested uplands had lower attack rates and more frequent long flights than waterthrushes foraging in the intact treatment types. Prolonged packing of individuals into riparian buffer strips, and apparent adverse affects on waterthrush foraging efficiency, raise concerns about the effectiveness of buffer strips for sustaining viable populations of terrestrial riparian habitat specialists.
Grizzly bear selection of managed and unmanaged forests in the Selkirk Mountains
Authors: Wielgus Robert B , Vernier Pierre R
Published: May 2003

We tested the commonly held hypotheses that grizzly bears (Ursus arctos) select against clearcuts and young forests and select for natural openings and old forests in the Selkirk Mountains from 1986 to 1991. We compared use versus availability using χ2 goodness-of-fit for 11 bears (five females, six males) in a south study area containing both open roads (public use allowed) and closed roads (no public use allowed) and 11 bears (seven females, four males) in a north study area containing restricted roads (forestry use only). Zero of 11 females and 1 of 11 males (1/22 bears) selected against (P < 0.05) clearcuts. Five of 11 females and 2 of 11 males (7/22 bears) selected against (P < 0.05) young forests. The apparent selection against young forests appeared to be due to selection against associated open roads, not against young forests themselves. Forestry activities alone (managed forests and restricted roads) appeared to have no negative impact on grizzly bear habitat use. Because of small sample sizes, pooling of seasonal data, and lack of experimental replication, our results should not be extrapolated until similar studies are conducted elsewhere.
Effects of harvesting on fine root biomass and decomposition in an Engelmann spruce  subalpine fir forest
Authors: Welke Sylvia E , Hope Graeme D , Hunt Gary A
Published: May 2003

The effect of timber harvesting on the biomass, nutrient standing crop, and decomposition of fine roots (<2 mm) was studied in a high elevation, Engelmann spruce (Picea engelmannii Parry ex Engelm.)  subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forest. Root dynamics were compared in openings of different sizes. The sequential core method was used to collect fine root samples over 4 years. Differences in fine root biomass between opening sizes were most significant for the active fine root portion and were most pronounced in the fall compared with the spring. Active fine root biomass was significantly lower in the 10-ha clearcuts (164 kg/ha) compared with control plots (275 kg/ha). Furthermore, active fine root biomass was often lower in the 1.0-ha opening than in the 0.1-ha and control plots. A similar trend was established for inactive fine root biomass, although this was not consistent over sampling years. Nutrient concentrations of K, but no other elements, were higher in control plots. Nutrient standing crops, however, followed trends observed in fine root biomass. In the 10-ha clearcuts, the largest changes in fine root biomass occurred at the edge of the opening. The findings suggest that small (<10 ha) cutblocks may maintain greater fine root longevity.
Assessing site suitability for Scots pine using airborne and terrestrial gamma-ray measurements in Finnish Lapland
Authors: Hyvönen Eija , Pänttäjä Markku , Sutinen Marja-Liisa , Sutinen Raimo
Published: May 2003

Low-altitude airborne gamma-ray (AGR) data, obtained with the aircraft-mounted 25-l NaJ(Tl) gamma spectrometer and interpolated into a 50 × 50 m pixel size, over 1200 km2 of glaciated terrain in Finnish Lapland, were applied to classify and interpret site suitability for Scots pine (Pinus sylvestris L.). The selection of the training and validation sets for the classification of AGR data was based on the forest management history and soil moisture content (θv) determined by dielectric (ε) measurements. The ground calibration measurements showed a significant negative correlation between the soil ε (i.e., θv) and terrestrial gamma-ray flux (TGR-γ) from potassium (γK) and thorium decay series (γTh), suggesting that the attenuation of gamma flux is due to soil θv. Both ground and airborne surveys indicated that γK was significantly higher in drift of Scots pine stands than in drift of Norway spruce (Picea abies (L.) Karst.) stands. Out of four tested combinations of the AGR channels, i.e., (i) potassium (K), (ii) K and thorium (Th)/K, (iii) K, Th, and Th/K, and (iv) K and Th, K alone resulted in the best overall accuracy of 80.44% (Kappa coefficient, κ = 0.609) to classify drift materials suitable for Scots pine. The present study demonstrates that the TGR-γK and AGR-γK measurements provide a basis to delineate soil θv patterns within the site and landscape level, thus having a significant implication for the forest management planning to assess sites suitable for Scots pine.
Short-term impacts of partial cutting on lichen retention and canopy microclimate in an Engelmann spruce  subalpine fir forest in north-central British Columbia
Authors: Coxson Darwyn , Stevenson Susan , Campbell Jocelyn
Published: May 2003

The retention of canopy lichens (Alectoria, Bryoria, and foliose) in group selection (GS) and single-tree selection (STS) partial cuts (30% removal) was studied within a subalpine sprucefir forest (Picea englemannii Parry ex Engelm.  Abies lasiocarpa (Hook.) Nutt.) in north-central British Columbia. Baseline canopy lichen loading (preharvest and immediate postharvest) was compared with lichen loading 2 years after harvesting, using both ground- and canopy-based sampling techniques. Additionally, canopy microclimate was compared between GS and adjacent stand areas with no harvest treatment (NT). Partial cutting did not have a significant effect on lichen loading in residual trees, although a trend of declining lichen abundance was observed in each of the GS, STS, and NT areas. Partitioning of lichen abundance data showed significant postharvest declines for upper canopy STS Bryoria and smaller, but significant, changes in foliose lichen abundance in the NT and STS areas. No significant changes in canopy microclimate were observed between treatments, with the exception of south-facing aspects in GS trees, which showed reduced duration of lichen hydration. Taken together, these factors suggest that although the placement of Bryoria in residual trees may shift towards lower canopy exposures, partial-cut harvest treatments can maintain short-term lichen loading and associated ecosystem values (e.g., caribou forage) in subalpine sprucefir stands.
Ethanol in ponderosa pine as an indicator of physiological injury from fire and its relationship to secondary beetles
Authors: Kelsey Rick G , Joseph Gladwin
Published: May 2003

Sixteen days after a September wildfire, ethanol and water were measured in phloem and sapwood at breast height and the base of Pinus ponderosa Dougl. ex P. & C. Laws. with zero (control), moderate, heavy, and severe crown scorch. The quantity of ethanol increased with each level of injury, resulting in trees with severe scorch containing 15 and 53 times more phloem and sapwood ethanol, respectively, than controls. Ethanol concentrations in the sapwood and adjacent phloem were related, probably as a result of diffusion. Upward movement in xylem sap was most likely responsible for the relationship between sapwood ethanol concentrations at breast height and the stem base. As trees recovered from their heat injuries, the ethanol concentrations declined. In contrast, ethanol accumulated in dead trees that lost their entire crowns in the fire. Various bark and xylophagous beetles landed in greater numbers on fire-damaged trees than on controls the following spring and summer, suggesting that ethanol was being released to the atmosphere and influencing beetle behavior. Beetle landing was more strongly related to sapwood ethanol concentrations the previous September than in May. Sapwood ethanol measured 16 days after the fire was the best predictor of second-year mortality for trees with heavy and severe crown scorch.
Indirect effects of beech bark disease on sugar maple seedling survival
Authors: Hane Elizabeth N
Published: May 2003

To investigate the mechanisms of indirect effects of the increased presence of American beech (Fagus grandifolia Ehrh.) saplings on sugar maple (Acer saccharum Marsh.) seedling survival, I conducted several experiments in the area of the Hubbard Brook Experimental Forest in central New Hampshire, U.S.A. To investigate the effects of competition from beech saplings on sugar maple seedlings, a removal experiment was conducted. Sugar maple seedling survival was monitored in five replicate plots of each of the two treatments for 6 years. Survivorship in plots in which beech saplings had been removed was significantly higher (33%) than in control plots (1%). A shading experiment demonstrated that a large proportion of the mortality of sugar maple seedlings results from the effects of shading. Cutting and shade cloth treatments were done in a two-factor factorial block design, and results showed a strong negative effect of shading in the plot. A third experiment investigated the role of soil moisture. Plots that had higher soil moisture and also had beech removed had the highest survival (76%), while control plots in a dry area had the lowest (22%). Overall, the experiments showed that beech bark disease and the associated increase in beech saplings had a negative indirect effect on sugar maple seedling survival. Sugar maple regeneration failure appeared to be, at least in part, due to the indirect effects of beech bark disease.
Factors limiting the early survivorship ofThuja plicataon northern Vancouver Island, British Columbia
Authors: Weber Adrian , Gilbert Benjamin , Kimmins JP (Hamish) , Prescott C E
Published: May 2003

Western redcedar (Thuja plicata Donn ex D. Don), a late successional species on northern Vancouver Island, has a low seedling survival in mature hemlock (Tsuga heterophylla (Raf.) Sarg.)  amabilis fir (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes) (HA) stands. Shade, moss competition, and substrate were tested as causes of low cedar establishment. Cedar seeds were sown on reference and local soils isolated from surrounding soil, on nonisolated local soil, and on forest floor with moss removed. Western hemlock, amabilis fir, and cedar seeded on forest floor acted as controls. Treatments were implemented in the HA interior and the HAclearcut edge, with soil treatments also implemented in clearcuts. Germinants and very young seedlings of cedar have a low leaf area of needle-like primary foliage. Cedar development of secondary foliage (the scale foliage normally associated with this species) was correlated with greater vigour and growth. Secondary foliage developed in the rankings forest edge and clearcut > forest interior, and reference isolated soil > local isolated soil > nonisolated local soil. Seedling survival rankings were edge > interior, and amabilis fir > hemlock > cedar on soil and with moss removed > cedar on forest floor. Cedar and amabilis fir showed a smaller growth response to light than hemlock. The results indicate that cedar, normally considered a late successional species, needs disturbance for early seedling establishment and survival and thus has some characteristics of an early seral species.
Combined effects of site preparation, soil properties, and sowing date on the establishment of Pinus sylvestris and Picea abies from seeds
Authors: Chantal Michelle de , Leinonen Kari , Ilvesniemi Hannu , Westman Carl Johan
Published: May 2003

The aim of this study is to determine the effect of site preparation on soil properties and, in turn, the emergence, mortality, and establishment of Pinus sylvestris L. (Scots pine) and Picea abies (L.) Karst. (Norway spruce) seedlings sown in spring and summer along a slope with variation in soil texture and moisture. Three site preparation treatments of varying intensities were studied: exposed C horizon, mound (broken LFHAeB horizons piled over undisturbed ground), and exposed AeB horizons. Seedling emergence was higher in the moist growing season than in the dry one. During a dry growing season, mounds and exposed C horizon had negative effects on soil moisture that increased mortality. Moreover, frost heaving was an important cause of winter mortality on mounds and exposed C horizon, whereas frost heaving was low on exposed AeB horizons, even though soil moisture and the content of fine soil particles (<0.06 mm) were high. Frost heaving mortality was higher for summer-sown than for spring-sown seedlings and for P. abies than for P. sylvestris. Growing season mortality was high following a winter with frost heaving, suggesting that roots were damaged, thereby making seedlings more susceptible to desiccation.
Contribution to the fine anatomy and histochemistry of birdseye sugar maple
Authors: Rioux D , Yamada T , Simard M , Lessard G , Rheault F J , Blouin D
Published: May 2003

Light and transmission electron microscope observations of birdseye tissues in sugar maple revealed the following features in the xylem: inclined axial elements, vessels smaller and shorter than the ones found in adjacent normal xylem, occasional gaps between xylem cells, abnormal thickenings of vessel secondary walls, and absence of multi seriate rays. Histochemical and cytochemical tests also indicated that birdseye xylem was less lignified than adjacent normal xylem. When this figure appeared in more than five consecutive growth rings, collapsed and hypertrophied cells were observed at the beginning of rings. These abnormal cells seemed to show that cambial initials were injured at the start of the growing season. The injury apparently occurred following a pressure exerted on a group of fibres present in the inner bark, very close to the cambium. After forming these unusual cells, the cambium resumed production of more typical elements. In birdseye tissues, the phloem layer was reduced and rays showed many anomalies. These anatomical changes may have induced poor translocation of nutrients to the cambium, eventually leading to abnormal differentiation of xylem derivatives. High levels of ethylene may have stimulated phellogen activities that could have generated a pressure toward the cambium. Future studies on birdseye formation are also suggested.
High-resolution forest fire weather index computations using satellite remote sensing
Authors: Han Kyung-Soo , Viau Alain A , Anctil François
Published: May 2003

Wildfires are important in regions dominated by forest, such as found in large parts of Canada. The principal objective of this study was to provide homogeneously distributed indices for the Canadian Fire Weather Index (FWI) System. The FWI was calculated using four sets of input variables: meteorological station measurements (OBS); weather forecast model output (SIM); meteorological station measurements and remote sensing estimations combined (SAT1); and weather forecast model output and remote sensing estimations combined (SAT2). Remote sensing parameterization of air temperature and relative humidity was performed. The air temperature and relative humidity reproduced showed good agreement with ground-based measurements (R2 = 0.77 and SE = 1.48°C; R2 = 0.73 and SE = 5%, respectively). For the FWI regionalized using this requirement, category SAT1 showed the best fit. Category SAT2 produced more precise results (0.09 to 2.19% of the normalized root mean square error) versus SIM.
Effects of chronic ammonium sulfate treatment on basal area increment in red spruce and sugar maple at the Bear Brook Watershed in Maine
Authors: Elvir Jose Alexander , Wiersma G Bruce , White Alan S , Fernandez Ivan J
Published: May 2003

Responses in basal area increment (BAI) of sugar maple (Acer saccharum Marsh.) and red spruce (Picea rubens Sarg.) to chronic ammonium sulfate ((NH4)2SO4) treatment were examined at the Bear Brook Watershed in Maine. The Bear Brook Watershed is a pair-watershed forest ecosystem study with West Bear watershed treated with (NH4)2SO4at a rate of 1800 equiv.·ha1·year1since 1989, while East Bear watershed serves as a reference. Following 10 years of treatment, BAI was significantly higher for sugar maple trees growing in the treated watershed, with yearly increases relative to the reference watershed ranging from 13% in 1999 to 104% in 1996. The increase in sugar maple radial growth was attributed to a fertilization effect from the (NH4)2SO4treatment. A reduction in BAI in sugar maple growing in the treated watershed observed in 1998 and 1999 was attributed to internal stresses and growth allocation to crown recovery after the severe 1998 ice storm. Red spruce showed no BAI growth responses to the treatment. Lower foliar Mg and Ca concentrations in red spruce in the treated watershed and lower soil responses to N enrichment in treated softwood stands compared with treated hardwood stands could explain the lack of BAI response in red spruce.
Nitrogen uptake and utilization by slow- and fast-growing families of interior spruce under contrasting fertility regimes
Authors: Miller B D , Hawkins B J
Published: May 2003

Six full-sib families of interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) of contrasting growth rates (three fast-growing, three slow-growing families) were grown from seed in a greenhouse under three fertility regimes (25, 75, and 125 mg nitrogen/seedling over 175 days). The use of vector analysis showed that the lowest fertility regime was nitrogen-limited while the highest indicated luxury consumption. After 175 days, fast-growing families were larger than slow-growing at all fertility levels. At the lowest fertility level, fast-growing families exhibited greater nitrogen productivity and utilization of internal nitrogen. At higher fertility levels, fast-growing families took up nitrogen more quickly and efficiently thus accumulating greater nitrogen reserves. Fast-growing families also exhibited a greater plasticity in dry mass allocation between shoots and roots with different fertility levels.
Assessing inter- and intra-specific variation in trunk carbon concentration for 32 neotropical tree species
Authors: Elias Marlène , Potvin Catherine
Published: May 2003

Trunk carbon (C) concentrations were assessed for 32 species of tropical trees to understand sources of variation. The main effect of species accounted for 38% of the total variance in C concentration (p < 0.0001). Tectona grandis demonstrated the greatest C concentration (49.4%), while Ormosia macrocalyx displayed the lowest C concentration (44.4%). We also observed significant differences among the sampling sites (F = 2.2, p < 0.02). For three of the species sampled in both plantations and natural forests, the natural forest individuals had significantly higher C concentrations (Dipteryx panamensis: F = 6.10, p = 0.06; Hura crepitans: F = 5.53, p = 0.06; and Miconia argentea: F = 8.92, p = 0.02). C concentration was highly correlated with wood specific gravity (r2 = 0.86). A canonical correspondence analysis was performed to identify the environmental and (or) growth factors explaining variation in trunk C concentration. The two factors with the highest loading values on the first canonical axis are site and diameter at breast height (DBH), while DBH and density load on axis 2. The biplot shows that species respond differently to environmental factors. Our results suggest that a better consideration of interspecific variation in C concentration could reduce the error associated with estimates of C sequestration by up to 10%.
Growth rate predicts mortality of Abies concolor in both burned and unburned stands
Authors: Mantgem Phillip J. van , Stephenson Nathan L , Mutch Linda S , Johnson Veronica G , Esperanza Annie M , Parsons David J
Published: May 2003

Tree mortality is often the result of both long-term and short-term stress. Growth rate, an indicator of long-term stress, is often used to estimate probability of death in unburned stands. In contrast, probability of death in burned stands is modeled as a function of short-term disturbance severity. We sought to narrow this conceptual gap by determining (i) whether growth rate, in addition to crown scorch, is a predictor of mortality in burned stands and (ii) whether a single, simple model could predict tree death in both burned and unburned stands. Observations of 2622 unburned and 688 burned Abies concolor (Gord. & Glend.) Lindl. (white fir) in the Sierra Nevada of California, U.S.A., indicated that growth rate was a significant predictor of mortality in the unburned stands, while both crown scorch and radial growth were significant predictors of mortality in the burned stands. Applying the burned stand model to unburned stands resulted in an overestimation of the unburned stand mortality rate. While failing to create a general model of tree death for A. concolor, our findings underscore the idea that similar processes may affect mortality in disturbed and undisturbed stands.
Substitution between floor constructions in wood and natural stone: comparison of energy consumption, greenhouse gas emissions, and costs over the life cycle
Authors: Petersen Ann Kristin , Solberg Birger
Published: May 2003

This paper compares two floor constructions used at the new airport outside Oslo, one made of solid oak and one made of natural stone, to (i) make an inventory of energy consumption and greenhouse gas (GHG) emissions over the life cycle of the two constructions, (ii) calculate the differences regarding GHG emissions and cost, and (iii) determine which factors have the strongest influence on the results. Manufacturing the wood floor required 1.6 times more energy and produced one-third of the GHG emissions compared with the natural stone floor. Over the life cycle, net GHG emissions can be avoided only if the wood is used as a biofuel after the replacement or demolition of the floor. The wooden floor must be competitive on price to be a cost-efficient action against global warming. Per cubic metre of wood floor, emissions of up to 1.263 t of CO2 equivalents can be avoided by a substitution between the two floor constructions. The factors that have the most influence on the result are carbon fixation on forest land, waste handling of wood, and discount rate, the latter reflecting the relative importance over time given to a unit of GHG emissions.
Altered growth and fine root chemistry of Betula papyrifera and Acer saccharum under elevated CO2
Authors: Parsons William FJ , Kopper Brian J , Lindroth Richard L
Published: May 2003

We investigated the effects of CO2 enrichment on fine root chemical composition of two tree species common to northern hardwood forests. Two-year-old Betula papyrifera and 3-year-old Acer saccharum saplings were grown under ambient (400 µmol·mol1) and elevated (700 µmol·mol1) CO2 in a glasshouse experiment. In both species, root/shoot ratios and fine root percentages (of total biomass) were unaltered by CO2 enrichment. Tissue nitrogen concentrations decreased in the fine roots, and consequently, C/N ratios increased with elevated CO2. In birch, only condensed tannins increased with CO2 enrichment, while root starch levels were conserved. In maple, neither condensed tannins nor hydrolysable tannins were positively influenced by elevated CO2. Both fine root biomass and chemistry responses of the tree saplings may be related to their successional status.
Does cross validation provide additional information in the evaluation of regression models?
Authors: Kozak Antal , Kozak Robert
Published: May 2003

A detailed study using seven data sets, two standing tree volume estimating models, and a heightdiameter model showed that fit statistics and lack of fit statistics calculated directly from a regression model can be well estimated using simulations of cross validation or double cross validation. These results suggest that cross validation by data splitting and double cross validation provide little, if any, additional information in the process of evaluating regression models.
Relationships between dwarf mistletoe and the canopy structure of an old-growth lodgepole pine forest in central Oregon
Authors: Godfree R C , Tinnin R O , Forbes R B
Published: May 2003

The relationships between abundance of dwarf mistletoe (Arceuthobium americanum Nutt.) and the canopy structure of stands of lodgepole pine (Pinus contorta var. murrayana (Grev. & Balf.) Engelm.) were investigated in the central Oregon pumice zone. Foliage height profiles were generated for stands containing light, moderate, and heavy infestations of A. americanum, and the vertical distribution of P. contorta foliage was modeled using the Weibull distribution. Stand-level changes in the Weibull parameters σ (scale parameter) and c (shape parameter) as well as other canopy indices were related to the abundance of A. americanum, the density of competing tree species, and stand-level abiotic factors. Foliage intercept diagrams showed that heavily infested stands had more foliage in the lower canopy and less in the upper canopy than lightly infested stands, but that total canopy height and canopy volume were similar regardless of infestation level. We also found that dwarf mistletoe abundance was strongly related to σ (r = 0.74, p < 0.001) and c (r = 0.54, p < 0.0001). Since heavily infested stands contained fewer large but many more small P. contorta than lightly infested stands, we conclude that A. americanum causes the canopy of infested stands to change, in part, by inducing demographic changes in populations of the host tree. These results illustrate the significant effects that dwarf mistletoes can have on the structural diversity of conifer forest communities and have important consequences for the conservation and management of these systems.
A tree-ring reconstruction of western spruce budworm outbreaks in the San Juan Mountains, Colorado, U.S.A.
Authors: Ryerson Daniel E , Swetnam Thomas W , Lynch Ann M
Published: May 2003

Tree-ring records were used to reconstruct spatial and temporal patterns of western spruce budworm (Choristoneura occidentalis Freeman) outbreaks in mixed conifer forests of southern Colorado. Reconstructions in 11 host stands showed a regionally synchronous pattern of at least 14 outbreaks during the past 350 years. Intervals between outbreaks were highly variable within stands, but at the regional scale outbreak intervals were more consistent. Spectral analyses of regional outbreak time series confirmed periodicities at about 25, 37, and 83 years. Comparison with an independent drought reconstruction indicated that outbreaks typically corresponded to increased moisture, while relatively little budworm activity occurred during dry periods. In contrast to other published reconstructions in Colorado and New Mexico, reconstructions from this study area did not exhibit significant 20th-century changes in the frequency of outbreak occurrence or magnitude of growth reduction. Sharply reduced growth during outbreaks was not clearly visible on the increment core samples, and budworm-induced reductions in tree-ring growth were usually detectable only after comparison with nonhost tree-ring series. This finding emphasizes that defoliation effects on ring growth can be highly relativistic. Hence, caution should be exercised in reconstructing insect outbreak histories based only on visual detection approaches, or without comparison with nonhost or nondefoliated tree-ring control series.
Patterns of canopy interception and throughfall along a topographic sequence for black spruce dominated forest ecosystems in northwestern Ontario
Authors: Morris Dave M , Gordon Alan G , Gordon Andrew M
Published: May 2003

A 3-year (19931995) study was conducted to describe both the spatial (within- and between-site) and temporal (monthly) patterns associated with canopy interception, throughfall, and net forest water along a black spruce (Picea mariana (Mill.) BSP) topo-sequence situated in northwestern Ontario. This site array included (1) an upland, well-drained, mineral soil site; (2) a poorly drained, midslope, wet mineral site; and (3) a treed wetland on organic (peat) soil. Bulk precipitation (BP) and throughfall (TF) were collected, on an event basis (63 events, over 4800 samples analyzed), using standard collecting devices and analyzed for total Kjeldahl nitrogen (TKN), ammonium (NH4+), nitrate (NO3), total phosphorus (TP), potassium (K), calcium (Ca), and magnesium (Mg). Comparison of BP and TF data suggested that an enrichment of K (190%), Mg (115%), and Ca (70%) occurred during canopy interactions. On the other hand, inorganic nitrogen (NH4+: 73%; NO3: 47%), and to a lesser extent TP (35%), rates declined. TKN, however, remained the same, suggesting that inorganic N reductions were offset by organic N inputs. Downward shifts in pH were also detected for TF (4.454.48), as compared with the pH of BP (4.524.80). Although all study sites received similar rainfall amounts, the more productive sites (i.e., carrying greater foliar mass, higher leaf area index) had lower TF volumes (i.e., higher interception rates) but higher macronutrient returns to the forest floor. This increase in macronutrient deposition was directly related to substantial increases in nutrient concentrations, which, in turn, suggested a greater degree of canopy interaction and (or) leaching on these sites. Throughfall pH, however, was not significantly different across the three study sites. With respect to temporal patterns, the major cations (K+, Ca2+, Mg2+) demonstrated an increasing trend in concentration levels in TF as the season progressed to a maximum in October. TKN and TP concentrations, on the other hand, maintained relatively stable levels throughout the summer, peaking in September, but dropping substantially in October as metabolic processes slowed and the supply of these nutrients to the foliage was reduced. Even with the increase in base cation concentration, throughfall pH shifted downward to 4.3 or below by late fall.
Phytotoxicity of American beech leaf leachate to sugar maple seedlings in a greenhouse experiment
Authors: Hane Elizabeth N , Hamburg Steven P , Barber Adelia L , Plaut Jennifer A
Published: May 2003

In an effort to reexamine the factors that affect codominance of American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marsh.), a greenhouse experiment was conducted to test the potential phytotoxic effects of American beech leaf leachate on sugar maple seedlings. We utilized an experimental protocol that addressed phytotoxic, nutrient, and pH effects by watering seedlings with seven treatment solutions: simulated throughfall water, average and dilute concentrations of beech leachate, average and dilute concentrations of maple leachate, and average and dilute concentrations of nutrient solutions. Sugar maple leachate had no effect on sugar maple seedling development, chemistry, or physiology. However, sugar maple seedlings exposed to average levels of beech leachate had significantly lower leaf area, fewer nodes, lower biomass, higher carbon assimilation rates, and higher stomatal conductance than seedlings exposed to the control solution. Results suggest that secondary compounds in beech leaf leachate are suppressing sugar maple seedling development and that field experiments are needed to explore the potential allelopathic relationship between these species.
Nest predation and breeding activity of songbirds in riparian and nonriparian black spruce strips of central Quebec
Authors: Boulet Marylène , Darveau Marcel , Bélanger Louis
Published: May 2003

The black spruce (Picea mariana (Mill.) BSP) forests of Quebec are often harvested according to a single-pass system where clearcuts are separated by 20- to 60-m-wide forest strips. Little is known about the suitability of these strips as habitats for breeding birds. We selected five nonriparian strips, five riparian strips, and five forest control sites located in a forested area of central Quebec. During 19971998, we monitored the predation of artificial bird nests baited with a common quail (Coturnix coturnix L.) egg and a plasticine egg and the breeding activity of adult songbirds in strips and controls. Artificial nest predation was high in all sites (72%). The most common predators were specialists of mature coniferous forests: gray jays (Perisoreus canadensis L.) and red squirrels (Tamiasciurus hudsonicus Erxleben). In forest-dwelling bird species, the number of breeding pairs was lower in strips than in controls. We conclude that the small number of forest-dwelling breeding birds observed in strips is not related to an increase in predation pressure following harvest of adjacent forests and that forest strips are not suitable breeding habitats for these species.
Dendrochronology-based fire history of Jeffrey pine - mixed conifer forests in the Sierra San Pedro Martir, Mexico
Authors: Stephens Scott L , Skinner Carl N , Gill Samantha J
Published: May 2003

Conifer forests in northwestern Mexico have not experienced systematic fire suppression or logging, making them unique in western North America. Fire regimes of Pinus jeffreyi Grev. & Balf. mixed conifer forests in the Sierra San Pedro Martir, Baja California, Mexico, were determined by identifying 105 fire dates from 1034 fire scars in 105 specimens. Fires were recorded between 1521 and 1980 and median fire return intervals were less than 15 years at all compositing scales. Significant differences in mean fire return intervals were detected from 1700 to 1800, 1800 to 1900, and 1900 to 1997, most often at intermediate spatial compositing scales, and the proportion of trees scarred in the fires of the 1700s was significantly different from the fires of either the 1800s, the 1900s, or the combined post-1800 period. Superposed epoch analysis determined that moderate and large spatial scale fires occurred on significantly dry years during the length of the record, but before 1800, these fires were preceded by significantly higher precipitation 1 year before the fire. The dominance of earlywood fires in the Sierra San Pedro Martir is similar to the seasonality found in the southwest United States and is different from the western slope of the Sierra Nevada and Klamath Mountains of California.