bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparaison de divers adsorbants naturels pour la récupération du plomb lors de la décontamination de chaux usées d'incinérateur de déchets municipaux
Authors: Blais J F , Salvano E , Hammy F , Mercier Guy
Published: October 2002

The objective of this research was to compare the efficiency of different natural adsorbents for lead recovery from basic leachate produced during municipal incinerator used lime decontamination. Shake flasks adsorption tests have shown that cedar barks, pine barks, cocoa shells, and peat moss are efficient and cheap adsorbents for lead removal from this type of leachate. Peanut skins are less efficient than other tested natural materials. The use of a hot-acid treatment (H2SO4 0.75 M) allows to slightly increase lead removal performance of the adsorbents. However, this gain does not justify, from an economical point of view, the utilization of the chemical treatment. Tests done with different cedar and pine bark concentrations (230 g/L) have revealed that heavily lead-contaminated (approximately 130140 mg/L) used lime leachate can be efficiently treated by addition of a small adsorbent concentration (e.g. 2 g/L). Finally, elution tests (HCl 0.5 M) with reuse of adsorbents have demonstrated that some natural materials, like cedar barks and cocoa shells, can be used for many adsorptionelution cycles without loss of lead removal efficiency. Key words: lead, adsorption, used lime, leaching, peat, bark.[Journal translation]
Trihalomethane formation in drinking water and production within a polyvinyl chloride pipe environment
Authors: Chan K C.W , Mavinic D S , Brereton J A
Published: October 2002

This project used pipe-incubated water samples collected from a pilot plant in North Vancouver, B.C., and the material-specific simulated distribution system (MS-SDS) test (Brereton 1998) to investigate the interaction between chlorine residuals in drinking water and the interior surface of polyvinyl chloride (PVC) distribution system pipes. Seasonal differences and residence time were important factors in trihalomethane (THM) production, and surface biofilm had a more significant impact on chloroform formation in bulk water than the treatment process. Biofilm adsorption has been identified as one surface mechanism responsible for the removal of THM precursors from the bulk water phase. This study observed that compounds previously adsorbed and extracellular materials from biofilm bacteria (including protoplasm from lysed cells) could participate in the aqueous chloroform formation in the absence of available precursor. Under chlorination conditions typical to the Greater Vancouver Regional District (GVRD) utilities, additional precursors were masked by the chlorine-limited condition; however, experiments confirmed that the practice of rechlorination would increase THM production beyond its bulk water capacity. Heterotrophic plate counts (HPCs), measured from biofilm scrapings, revealed that higher chloroform production was accompanied by bacterial regrowth. A proposed model summarizes the major mechanisms interacting in a PVC pipe environment. Key words: biofilm, chloroform, distribution system, drinking water, material specific simulated distribution system (MS-SDS), PVC pipe, regrowth, trihalomethane (THM) formation.
Seismic passive resistance in soils for negative wall friction
Authors: Choudhury Deepankar , Rao K S. Subba
Published: October 2002

In the presence of pseudo-static seismic forces, passive earth pressure coefficients behind retaining walls were generated using the limit equilibrium method of analysis for the negative wall friction angle case (i.e., the wall moves upwards relative to the backfill) with logarithmic spirals as rupture surfaces. Individual density, surcharge, and cohesion components were computed to obtain the total minimum seismic passive resistance in soils by adding together the individual minimum components. The effect of variation in wall batter angle, ground slope, wall friction angle, soil friction angle, and horizontal and vertical seismic accelerations on seismic passive earth pressures are considered in the analysis. The seismic passive earth pressure coefficients are found to be highly sensitive to the seismic acceleration coefficients both in the horizontal and the vertical directions. The results are presented in graphical and tabular formats.Key words: seismic passive resistance, limit equilibrium, pseudo-static.
Comportement physico-chimique de mélanges à base de poussières de four de cimenterie et de cendres volantes
Authors: Bellaloui Achour , Tagnit-Hamou Arezki , Ballivy Gérard
Published: October 2002

Enhancing the value of the cement kiln dust so as to use it as an environmental barrier requires, amongst other things, the addition of fly ashes in order to improve the different properties needed to insure a better placing and a long term efficiency. Taking advantage of different experimental techniques, particular attention was devoted to the physicochemical behaviour of different kiln dusts associated with the fly ashes. Depending on the nature of the added compound, a different behaviour may condition the evolution of the mixtures with an effect on their stability. Indeed, this study has confirmed the improvement of the physicochemical properties of the dusts interacting with the fly ashes rich in silica and poor in lime, which argues well for their use as an environmental barrier. Moreover, the follow up has led to a better understanding of certain mechanisms generated by the systems dealt with. Hence, after hydration and different chemical transformations, some expansive phases as the ettringite, gypsum, syngenite, and portlandite develop in the paste, and therefore condition the behaviour of the mixtures worked out.Key words: cement kiln dusts, fly ashes, stabilization, physicochemistry, environmental barrier, lixiviation.[Journal translation]
Slope stability thresholds for vegetated hillslopes: a composite model
Authors: Ekanayake Jagath C , Phillips Christopher J
Published: October 2002

Location of the critical shear plane (CSP) plays a major role in determining landslide-initiation thresholds. Depth to the CSP increases as the soil shear strength increases. Tree roots provide a significant strength contribution to soil shear strength. Our objective is to understand how vegetation can be used to increase landslide-initiation thresholds by changing the location of the CSP. This will enable us to select and compare combinations of plant species and densities to suit any given situation to increase landslide-initiation thresholds and improve slope stability. The CSP location is estimated incorporating available root cross-sectional area  root depth data in the stability analysis in terms of energy. The energy approach has been developed to take into account the contribution of the roots to soil strength. Generalization of the original energy approach is required to enable its use outside our study areas. Once depth to the CSP is found, the time for the wetting front to reach it is found using a soil-water infiltration model. The composite model described may be used as a simple tool to choose the most appropriate plant density to maximize the stability of a given hillslope. A worked example of the model demonstrates how the approximate thresholds for different hillslopes with known plant densities under different climatic conditions are estimated.Key words: slope stability, safety factor, roots, energy, threshold.
Dynamic simulation of the motion of fragmenting rock avalanches
Authors: Davies T R , McSaveney M J
Published: October 2002

A mass-referenced continuum model for dynamic analysis of rapid mass movement (DAN) is verified by laboratory and field data. Increased earth pressure coefficients are used in this model to represent the dispersive pressures caused by fragmentation within a translating rock avalanche. The numerical model demonstrates that increased runout in large rock avalanches can occur with normal friction coefficients if higher than normal internal pressures, such as those believed to be generated by fragmentation, are present. The extent of the Falling Mountain rock-avalanche deposit in New Zealand is reproduced in the model with normal friction and high earth pressure coefficients to represent by analogy the additional internal pressures due to fragmentation. It appears that if internal friction is changed by fragmentation, it is only by a small amount and may increase rather than decrease. To test this, and to move beyond the present analogue model, requires a better understanding of the rheology of fragmenting rock.Key words: rock avalanches, long runout, fragmentation, simulation model, dispersive stresses, earth pressure coefficients, Falling Mountain.
Population biology ofAureobasidium pullulanson apple leaf surfaces
Authors: Andrews John H , Spear Russell N , Nordheim Erik V
Published: October 2002

Colonization of apple leaves by the yeast-like fungus Aureobasidium pullulans was studied in the field on eight dates over 2 years. Population densities from adaxial leaf surfaces were approximately log100.52.6 U higher when enumerated directly along line transects as microscopic counts of A. pullulans cells specifically identified by fluorescence in situ hybridization (FISH) than indirectly as CFU obtained by plating leaf washings from comparable surfaces onto nutrient media. Site-specific mapping of the leaf landscape colonized by A. pullulans was facilitated by use of geographic information system (GIS) software. Colonization was plotted and analyzed both qualitatively (as occupancy) and quantitatively (as density). Overall, when expressed as mean occupancy per date, 2242% of the microscope fields (each 0.196 mm2) contained [Formula: see text]1 A. pullulans cell. Occupancy on a microscope field basis was greater over the midvein (4789%) or smaller veins (4965%) than over interveinal regions (1121%). Intensity of colonization, whether expressed as percentage of total A. pullulans cells associated with a particular leaf feature or as cell density per unit area, was also significantly greater (P < 0.05) over the veinal areas compared with the interveinal areas. The primary fungal morphotypes involved in colonization were blastospores, swollen cells, and chlamydospores; only infrequently were hyphae or pseudohyphae seen. Numbers of microcolonies ([Formula: see text]10 clustered cells) and percentage of total A. pullulans cells that occurred as microcolonies increased over the growing season and were significantly greater (P < 0.05) over veinal regions compared with interveinal regions. Locally high concentrations of A. pullulans were associated with naturally occurring micro-wounds in interveinal areas. We conclude that A. pullulans colonizes the phylloplane predominantly as single cells and groups thereof in a highly heterogeneous fashion and that sites exist that are relatively conducive (veins; wounds) or nonconducive (unwounded interveinal areas) for epiphytic fungal growth.Key words: phylloplane, yeast, phyllosphere, Aureobasidium, colonization.
Prevalence ofGiardiaandCryptosporidiumand characterization ofCryptosporidiumspp. isolated from wildlife, human, and agricultural sources in the North Saskatchewan River Basin in Alberta, Canada
Authors: Heitman T L , Frederick L M , Viste J R , Guselle N J , Morgan U M , Thompson R C.A , Olson M E
Published: October 2002

The environmental distribution of Giardia spp. and Cryptosporidium spp. is dependent upon human, agricultural, and wildlife sources. The significance of each source with regard to the presence of parasites in the environment is unknown. This 2-year study examined parasite prevalence in human sewage influent, wildlife, and agricultural sources associated with the North Saskatchewan River Basin in Alberta, Canada. Fecal samples were collected from cowcalf, dairy, and hog operations in the watershed area. Sewage-treatment facilities were sampled bimonthly during the 2-year study, and wildlife scat was collected at locations along tributaries of the North Saskatchewan River. All samples were analyzed for the presence of Giardia and Cryptosporidium, using sucrose-gradient separation followed by immunofluorescent microscopy. Giardia and Cryptosporidium were detected in all three sources. The lowest prevalence of both Giardia (3.28%) and Cryptosporidium (0.94%) was found in wildlife, with 6 of 19 species testing positive. Sewage influent had the highest prevalence of Giardia (48.80%) and Cryptosporidium parvum-like oocysts (5.42%); however, the concentration of both parasites was minimal compared with the concentration detected in cattle feces. Cowcalf sources contained the highest concentration of Giardia (mean 5800/g feces, P < 0.01), and dairy sources contained the highest concentration of C. parvum-like oocysts (mean 295/g feces, P < 0.01). Although prevalence and concentration are higher in cattle feces than in sewage, the Giardia and Cryptosporidium in animal manure do not have direct access to water draining into the North Saskatchewan River. PCR-based characterization of rDNA from isolates ofCryptosporidium collected from Alberta human, pig, calf, mature steer, dog, cat, and beaver hosts revealed distinct genetic differences that may reflect host specificity.Key words: Giardia , Cryptosporidium, cattle, pigs, PCR, diagnostics, waterborne parasites.
Carbon balance of the taiga forest within Alaska: present and future
Authors: Yarie John , Billings Sharon
Published: October 2002

Forest biomass, rates of production, and carbon dynamics are a function of climate, plant species present, and the structure of the soil organic and mineral layers. Inventory data from the U.S. Forest Service (USFS) Inventory Analysis Unit was used to develop estimates of the land area represented by the major overstory species at various age-classes. The CENTURY model was then used to develop an estimate of carbon dynamics throughout the age sequence of forest development for the major ecosystem types. The estimated boreal forest area in Alaska, based on USFS inventory data is 17 244 098 ha. The total aboveground biomass within the Alaska boreal forest was estimated to be 815 330 000 Mg. The CENTURY model estimated maximum net ecosystem production (NEP) at 137, 88, 152, 99, and 65 g·m2·year1 for quaking aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), balsam poplar (Populus balsamifera L.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) BSP) forest stands, respectively. These values were predicted at stand ages of 80, 60, 41, 68, and 100 years, respectively. The minimum values of NEP for aspen, paper birch, balsam poplar, white spruce, and black spruce were 171, 166, 240, 300, and 61 g·m2·year1 at the ages of 1, 1, 1, 1, and 12, respectively. NEP became positive at the ages of 14, 19, 16, 13, and 34 for aspen, birch, balsam poplar, white spruce, and black spruce ecosystems, respectively. A 5°C increase in mean annual temperature resulted in a higher amount of predicted production and decomposition in all ecosystems, resulting in an increase of NEP. We estimate that the current vegetation absorbs approximately 9.65 Tg of carbon per year within the boreal forest of the state. If there is a 5°C increase in the mean annual temperature with no change in precipitation we estimated that NEP for the boreal forest in Alaska would increase to 16.95 Tg of carbon per year.
Coarse woody debris in forest regions of Russia
Authors: Krankina Olga N , Harmon Mark E , Kukuev Yuri A , Treyfeld Rudolf F , Kashpor Nikolai N , Kresnov Vladimir G , Skudin Viktor M , Protasov Nikolai A , Yatskov Mikhail , Spycher Gody , Povarov Ewgeni D
Published: October 2002

To assess regional stores of coarse woody debris (CWD) in seven major forest regions of Russia, we combined data collected as part of the routine forest inventory with measurements in 1044 sample plots and the results of density sampling of 922 dead trees. The stores of CWD in the western part of Russia (St. Petersburg, Central, Khanty-Mansi, and Novosibirsk regions) were on average lower (1420 m3/ha or 4.05.8 Mg/ha) than in the East Siberian and Far Eastern regions (4051 m3/ha or 11.014.4 Mg/ha). The difference in CWD stores was particularly large between young forests in two western regions (2.4 Mg/ha in St. Petersburg and 3.4 Mg/ha in the Central region) and in the east (20.424.4 Mg/ha). This difference is associated with the prevailing disturbance type: clear-cut harvest in western Russia and natural disturbances in the east. Analysis of variance in CWD stores indicates that region, dominant species, forest age group, productivity class, and interactions of these factors explain 8788% of the total variance and the strongest effects are for age group and region. Lower stores of CWD within the intensively managed forest regions suggest that further expansion of forest use in many regions of Russia may reduce regional stores of CWD and carbon.
Estimates of soil organic carbon stocks in central Canada using three different approaches
Authors: Bhatti J S , Apps M J , Tarnocai C
Published: October 2002

This study compared three estimates of carbon (C) contained both in the surface layer (030 cm) and the total soil pools at polygon and regional scales and the spatial distribution in the three prairie provinces of western Canada (Alberta, Saskatchewan, and Manitoba). The soil C estimates were based on data from (i) analysis of pedon data from both the Boreal Forest Transect Case Study (BFTCS) area and from a national-scale soil profile database; (ii) the Canadian Soil Organic Carbon Database (CSOCD), which uses expert estimation based on soil characteristics; and (iii) model simulations with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2). At the polygon scale, good agreement was found between the CSOCD and pedon (the first method) total soil carbon values. Slightly higher total soil carbon values obtained from BFTCS averaged pedon data (the first method), as indicated by the slope of the regression line, may be related to micro- and meso-scale geomorphic and microclimate influences that are not accounted for in the CSOCD. Regional estimates of organic C from these three approaches for upland forest soils ranged from 1.4 to 7.7 kg C·m2 for the surface layer and 6.2 to 27.4 kg C·m2 for the total soil. In general, the CBM-CFS2 simulated higher soil C content compared with the field observed and CSOCD soil C estimates, but showed similar patterns in the total soil C content for the different regions. The higher soil C content simulated with CBM-CFS2 arises in part because the modelled results include forest floor detritus pool components (such as coarse woody debris, which account for 412% of the total soil pool in the region) that are not included in the other estimates. The comparison between the simulated values (the third method) and the values obtained from the two empirical approaches (the first two methods) provided an independent test of CBM-CFS2 soil simulations for upland forests soils. The CSOCD yielded significantly higher C content for peatland soils than for upland soils, ranging from 14.6 to 28 kg C·m2 for the surface layer and 60 to 181 kg C·m2 for the total peat soil depth. All three approaches indicated higher soil carbon content in the boreal zone than in other regions (subarctic, grassland).
Estimated rates of deforestation in two boreal landscapes in central Saskatchewan, Canada
Authors: Fitzsimmons Michael
Published: October 2002

No national long-term monitoring system exists to estimate temporal changes in the area of forests within Canada. Changes in wooded area, defined as land at least 35% covered by trees or shrubs with a minimum height of 2 m, were estimated for two study areas in central Saskatchewan, Canada. Sequential editions of 1 : 50 000 topographic maps were digitized and analyzed with a geographic information system to quantify changes in wooded area over approximately three decades for the Waskesiu Hills landscape (53°45' N, 106°15' W) and the Red Deer River landscape (52°45' N, 103°00' W). Both study areas were located within the Boreal Plain Ecozone, which was predominantly boreal forest prior to the past century of agricultural land clearing. In the 4570km2 Waskesiu Hills landscape, wooded area decreased by 164 km2 between 1963 and 1990. In the 4692km2 Red Deer River landscape, wooded area decreased by 371 km2 in between 1957 and 1990. Estimated mean annual rates of change in wooded area were 0.19%·year1 and 0.43%·year1 for the former and latter landscapes, respectively. Losses of wooded area were not proportional across three land-use classes. Rates of change for wooded area were small in parks (0.10%·year1 and1.02%·year1) and commercial forests (0.10%·year1 and 0.22%·year1), and larger in predominantly agricultural zones (1.27%·year1 and 1.21%·year1 for the Waskesiu Hills landscape and Red Deer River landscape, respectively). These measured declines in wooded area do not account for losses due to roads, transmission lines, buildings, and other features not represented on topographic maps in an area-proportional manner, but this error is estimated to be very small. The total length of roads increased by 95 km (0.27%·year1 between 1963 and 1990) in the Waskesiu Hills landscape and by 507 km (0.74%·year1 between 1957 and 1990) in the Red Deer River landscape. Expanding infrastructure networks were contrasted by negative rates of change for human population (0.89%·year1 between 1961 and 1991 for the Waskesiu Hills region and 1.19%·year1 between 1956 and 1991 for the Red Deer River region). Within the two study areas, wooded lands that are unprotected by legislation remain vulnerable to future deforestation. Continued clearing of extant forests could jeopardize potential carbon gains from afforestation and reforestation initiatives presently being considered for marginal agricultural lands in western Canada.
The growing season carbon balance of a sub-boreal clearcut 5 years after harvesting using two independent approaches to measure ecosystem CO2 flux
Authors: Pypker Thomas G , Fredeen Arthur L
Published: October 2002

From 27 June to 3 September 1999, CO2 fluxes from a 5-year-old, 84.15-ha vegetated clearcut in sub-boreal British Columbia were measured using a Bowen ratio energy balance (BREB) system and a second approach (the component model) that was based on scaled up CO2-flux measurements from belowground and plants (spruce seedlings and representative deciduous species). Over the 69-day study period both methods estimated the site to be a small sink for CO2 (22.4 and 85 g C·m2, respectively). Differences between the sink size of the two approaches largely resulted from a divergence in the data after 7 August when the BREB data indicated a switch from sink to source approximately 14 days in advance of the same change from sink to source seen in the component model data. The main components of the CO2 flux within the clearcut were belowground respiration (338 g C·m2) and deciduous plant photosynthesis (375 g C·m2). The conifer seedlings were only a minor component in overall CO2 flux over the growing season (48 g C·m2). The small overall sink estimated for the site for the approximately 2.5-month growing period would likely have been surmounted by the belowground respiration if the yearly CO2 fluxes had been taken into account. For example, an additional 68 g C·m2 was added to the atmosphere from 3 to 23 September (based on belowground respiration data only), after deciduous plants senesced. This source alone was enough to push the site from a sink to a source for CO2.
Effects of silvicultural practices on carbon stores in Douglas-fir  western hemlock forests in the Pacific Northwest, U.S.A.: results from a simulation model
Authors: Harmon Mark E , Marks Barbara
Published: October 2002

We used a new model, STANDCARB, to examine effects of various treatments on carbon (C) pools in the Pacific Northwest forest sector. Simulation experiments, with five replicates of each treatment, were used to investigate the effects of initial conditions, tree establishment rates, rotation length, tree utilization level, and slash burning on ecosystem and forest products C stores. The forest examined was typical of the Cascades of Oregon and dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg). Simulations were run until a C steady state was reached at the landscape level, and results were rescaled relative to the potential maximum C stored in a landscape. Simulation experiments indicated agricultural fields stored the least (15% of the maximum) and forests protected from fire stored the greatest amount (93% of the maximum) of landscape-level C. Conversion of old-growth forests to any other management or disturbance regime resulted in a net loss of C, whereas conversion of agricultural systems to forest systems had the opposite effect. The three factors, in order of increasing importance, most crucial in developing an optimum C storage system were (i) rotation length, (ii) amount of live mass harvested, and (iii) amount of detritus removed by slash burning. Carbon stores increased as rotation length increased but decreased as fraction of trees harvested and detritus removed increased. Simulations indicate partial harvest and minimal fire use may provide as many forest products as the traditional clearcut  broadcast-burn system while increasing C stores. Therefore, an adequate supply of wood products may not be incompatible with a system that increases C stores.
Possible causes of slow growth of nitrate-suppliedPinus pinaster
Authors: Warren Charles R , Adams Mark A
Published: October 2002

We investigated possible causes of slower growth of Pinus pinaster Ait. supplied with nitrate, as compared with ammonium or with ammonium nitrate mixtures. Six-month-old mycorrhizal seedlings of P. pinaster were grown in sand culture for 4 months at four concentrations of N (0.125, 0.5, 2.0, or 8.0 mM) as nitrate or ammonium or with an ammoniumnitrate mixture at 0.125 or 2.0 mM. After 4 months of nutrient addition, we measured light-saturated rates of photosynthesis (Amax), rates of ammonium and nitrate uptake, growth, macro- and micro-elements, and patterns of N allocation in needles. Dry mass was unaffected by N form at 0.125 or 0.5 mM N. In contrast, dry mass of seedlings supplied with ammonium or ammonium nitrate at 2.0 and 8.0 mM N, was approximately threefold greater than seedlings supplied with nitrate alone. Concentrations of N in foliage and Amaxwere unaffected by the form or concentration of N supplied. Furthermore, concentrations of amino acid N were greater in seedlings supplied with nitrate, suggesting rates of uptake were not limiting growth. Foliage concentrations of zinc were low with nitrate supplied at a concentration of 0.5 mM or greater, and seedlings displayed symptoms typical of zinc deficiency when nitrate was supplied at 2.0 or 8.0 mM. Slower growth with nitrate could not be explained solely by either slower root uptake of nitrate N or lesser Amax. Instead, aspects of N metabolism postuptake coupled with other factors such as nutrient deficiencies may limit growth with nitrate as the sole N source.
Problems and options in modelling fine-root biomass of single mature Norway spruce trees at given points from stand data
Authors: Ammer Christian , Wagner Sven
Published: October 2002

In a 75-year-old Norway spruce (Picea abies (L.) Karst.) stand, three different single-tree models were tested to predict the fine-root biomass of root samples. This approach is based on the assumption that the fine-root biomass at a given point determines the availability of belowground resources as, for example, soil water. All models assume a monotonously decreasing function describing the distribution of the fine-root biomass of a subject tree depending on the distance to the trunk of the tree. To the contrary, the models differ in the maximum distance from the stem where roots can be found. There were high correlations between the observed and the predicted fine-root biomasses for all models in a part of the stand where the trees are distributed less uniformly and where root biomasses are most heterogeneous. In a section with medium stand density, the model of diameter at breast height dependent root spread yields higher correlation coefficients compared with the fixed-distance approach of the two other models. Significant correlations between model predictions of root distributions and measured soil water potential supported the validity of the models. The results of the model estimations imply differences in the maximum distance of lateral root spread dependent on stand density.
Single-tree versus group selection in hemlock-hardwood forests: are smaller openings less productive?
Authors: Webster Christopher R , Lorimer Craig G
Published: October 2002

The influence of opening size on gap cohort biomass was examined in uneven-aged hemlock-hardwood forests in northeastern Wisconsin by sampling 36 canopy gaps ranging from 5 to 800 m2 in area and from 3 to 55 years of age. The standing crop of whole-tree aboveground biomass per hectare was greater in multiple-tree gaps than single-tree gaps of similar age. However, biomass production approached an asymptote at fairly small opening sizes, and 400800 m2 group selection openings did not have significantly more biomass per unit area than small multiple-tree gaps (80100 m2). Similarly, mean tree dimensions, recent height growth increments, and basal area increments for most species of gap trees approached an asymptote at an opening size of approximately 100 m2. As opening size increased, yellow birch (Betula alleghaniensis Britton) superseded eastern hemlock (Tsuga canadensis (L.) Carrière) as the species with greatest relative biomass. The selection system appears to be a viable alternative to the even-aged shelterwood system in hemlock forests where browsing pressure is not excessive, but use of group selection may require additional treatments to ensure that some gaps >100 m2 are captured by hemlock.
Forest harvesting impacts on soil properties and vegetation communities in the Northwest Territories
Authors: Bock Michael D , Van Rees Ken CJ
Published: October 2002

Management of boreal mixedwood forests in Canada has traditionally relied almost exclusively on the clear-cut silvicultural system. In recent years, greater utilization of the hardwood component of boreal mixedwoods and increased societal concerns over maintenance of the integrity and sustainability of these ecosystems has provided impetus for forest managers to consider alternative silvicultural practices in boreal mixedwood forests. Little is currently known, however, concerning the response of soils and vegetation to forest harvesting systems in the mixedwood forests of the Liard River valley, Northwest Territories (NWT). Therefore, the objective of this study was to quantify the effects of patch clear-cut, strip clear-cut, and clear-cut harvesting systems on soil properties and understory vegetation composition and structure. Treatment sites with 3 or 4 years of recovery since harvesting and adjacent uncut forest sites were sampled using transect methodology. Soil samples were collected and understory vegetation community species composition and percent crown cover were assessed in 1-m2 quadrats. Compared with the range of conditions present in the uncut forest, increases in mineral soil bulk density (2%), exchangeable calcium (7%), LFH horizon thickness (13%), pH (0.2 units), and total organic carbon (5%) and decreases in LFH horizon total nitrogen (6%) and exchangeable potassium (22%) were observed following harvesting. Harvesting resulted in the reduction in crown cover of feathermoss species and increased abundance of shrub and herb species and minimal changes to species composition. Multivariate analysis of the data indicated that the method of harvesting did not result in significant differences in species composition and structure of the understory vegetation community. Overall, winter harvesting of these boreal mixedwood sites did not have a major impact on the majority of soil properties evaluated or on the species composition of the understory vegetation community.
Vertical fine root distributions of western redcedar, western hemlock, and salal in old-growth cedarhemlock forests on northern Vancouver Island
Authors: Bennett Jennifer N , Andrew Ben , Prescott Cindy E
Published: October 2002

The vertical distributions of fine roots of western hemlock (Tsuga heterophylla (Raf.) Sarg.) western redcedar (Thuja plicata Donn ex D. Don), and salal (Gaultheria shallon Pursh) were characterized in old-growth cedarhemlock forests on northern Vancouver Island. Total biomasses of cedar, hemlock, and salal roots in the forest floor and upper mineral soil were 817, 620, and 187 g·m2, respectively. Hemlock and salal fine roots were concentrated in the upper forest floor, while cedar fine roots were evenly distributed through the profile. Salal and hemlock fine root densities (g·m3) in the forest floor and mineral soil were positively correlated, as were salal and cedar root biomass distributions (g·m2). Only salal and hemlock root densities were significantly correlated with N concentrations. Hemlock root densities were negatively correlated with total N, and salal root densities were negatively correlated with total N and soluble organic N. Based on fine root densities, hemlock and salal probably compete for resources in the upper forest floor, whereas cedar accesses resources in the lower organic and mineral soil horizons. The differences in the vertical distributions of cedar, hemlock, and salal fine roots may partly explain the co-occurrence and different productivities of the three species in cedar-hemlock forests.
A practical modification of horizontal line sampling for snag and cavity tree inventory
Authors: Ducey M J , Jordan G J , Gove J H , Valentine H T
Published: October 2002

Snags and cavity trees are important structural features in forests, but they are often sparsely distributed, making efficient inventories problematic. We present a straightforward modification of horizontal line sampling designed to facilitate inventory of these features while remaining compatible with commonly employed sampling methods for the living overstory. The method is simpler in its implementation than traditional horizontal line sampling. We develop unbiased estimators and present methods for dealing with special cases, including boundary overlap. A field test of the method shows it to have time efficiency comparable with or better than ordinary prism cruising, and it requires far fewer sample locations to achieve similar confidence limits. The method may also be useful for inventorying other rare or unusual trees.
Density and rectangularity of planting influence 20-year growth and development of red alder
Authors: DeBell Dean S , Harrington Constance A
Published: October 2002

Red alder (Alnus rubra Bong.) seedlings were planted in northwestern Oregon, U.S.A., at five initial spacings: 0.6 × 1.2 m, 1.2 × 1.2 m, 1.2 × 1.8 m, 1.8 × 1.8 m, and 2.5 × 2.5 m. Up to about age 10, tree and stand characteristics were correlated primarily with initial planting density in the expected manner; through age 20, however, tree growth and stand development in plots planted at rectangular spacings were substantially more rapid than in the two closest square spacings. Mean stand diameter ranged from 19.2 cm in the widest spacing to 14.0 cm in the closest square (1.2 × 1.2 m) spacing; mean tree height decreased from nearly 24 m in the widest (2.5 × 2.5 m) spacing to about 18 m in the closest square spacing. Diameterdensity relationships in the widest spacing were consistent with existing density management guidelines, but very dense spacings and rectangular plantings began to experience substantial mortality at smaller diameters than assumed in the guidelines. We suggest that rectangular planting of red alder at dense spacing enhanced stand differentiation, accelerated competition-related mortality, and thus led to improved growth of surviving trees.
Predicting stump sprouting and competitive success of five oak species in southern Indiana
Authors: Weigel Dale R , Peng Chao-Ying Joanne
Published: October 2002

We measured 2188 oak trees (Quercus spp.) on the Hoosier National Forest in southern Indiana before and 1, 5, and 10 years after clear-cutting to determine the influence of parent tree age, diameter breast height, and site index on the probability that there was one or more living sprouts per stump: (i) 1 year after clear-cutting (sprouting probability) or (ii) that were competitively successful 5 or 10 years after clear-cutting (competitive success probability). We used logistic regression to develop predictive models for five species in each of the three measurement years. Two species were in the white oak group: white oak (Quercus alba L.) and chestnut oak (Qurcus prinus L.). Three species were in the red oak group: black oak (Quercus velutina Lam.), scarlet oak (Quercus coccinea Muenchh.), and northern red oak (Quercus rubra L.). Black oak site index ranged from 15 to 25 m at an index age of 50 years on the study sites. Parent tree age and diameter at breast height were significant predictors in all models. Sprouting and competitive success probabilities decreased with increasing parent tree age and diameter at breast height. Increasing site index was a significant contributor of increasing sprouting probabilities for year 1 and competitive success probabilities for year 5. By year 10, site index was negatively related to competitive success for the white oaks but was not a significant predictor for the red oaks. The models have practical value for predicting the stump sprouting potential of oak stands in southern Indiana and possibly in ecologically similar regions.
Interaction among deer browsing, hunting, and tree regeneration
Authors: Martin Jean-Louis , Baltzinger Christophe
Published: October 2002

The intentional removal or addition of species or specific human impacts on ecosystems trigger changes that can help us understand species interactions. In many temperate forests, deer populations are increasing and so is the need to understand how they influence ecosystems. We took advantage of the introduction of Sitka black-tailed deer (Odocoileus hemionus sitchensis Merriam) to the Queen Charlotte Islands (Haida Gwaii), British Columbia, Canada, to study how hunting pressure affects the impact of deer on tree regeneration after logging. We show that although the regeneration of western redcedar (Thuja plicata Donn ex D. Don) is drastically reduced in presence of deer, regeneration is better and browsing stress lower, in areas where deer are more exposed to hunting. Similar effects of accessibility for hunters are observed on browsing stress of Sitka spruce (Picea sitchensis (Bong.) Carrière). Western hemlock (Tsuga heterophylla (Raf.) Sarg.) is not significantly affected, and its regeneration is not correlated to hunting. We suggest that the effect of hunting on tree regeneration could be explained by the incidence of hunting on deer behaviour rather than by the actual number of deer killed by hunters. These results suggest that the future occurrence of redcedar stands in second-growth forests on this archipelago may depend on the amount and distribution of deer hunting.
Croissance juvénile comparée de deux générations successives de semis d'épinette noire issus de graines après feu en forêt boréale, Québec
Authors: Fantin Natalie , Morin Hubert
Published: October 2002

The objective of this study was to compare juvenile (012 years) height growth pattern of dominant mature trees from two virgin black spruce (Picea mariana (Mill.) BSP) forests established during the 19th century (1870) to that of young dominant black spruce seedlings newly regenerated following a 1983 fire on the same sites. The pattern was reconstructed by measuring the distance between terminal bud scars on young seedlings, and by precise counting of growth rings by cross-dating from the collar, which was identified by anatomical features, for mature trees. New seedlings growth was significantly higher than that of mature trees. Seedlings were almost twice as high as mature trees after 12 years of juvenile growth. Assuming that mature trees were dominant during their juvenile growth phase, we put forward the hypothesis that juvenile height growth of mature trees would have been affected by the combined action of spruce budworm (Choristoneura fumiferana (Clem)) and colder climatic conditions than those presently observed. Also, young seedlings juvenile height growth may have been favored by nitrogen soil enrichment along with more favourable climatic conditions.
Spatial simulation of historical landscape patterns in coastal forests of the Pacific Northwest
Authors: Wimberly Michael C
Published: October 2002

Concerns about the fragmentation of Pacific Northwest forests are based on the assumption that these landscapes historically contained large, contiguous patches of old growth. However, this supposition appears to conflict with disturbance history research, which shows that wildfire was an important component of pre-settlement forest ecosystems. To better quantify historical forest patterns, a spatial simulation model of wildfire and forest succession was used to simulate pre-settlement landscape dynamics in the Oregon Coast Range, U.S.A. The model was parameterized to simulate fire regimes over 1000 years prior to Euro-American settlement using data from paleoecological, dendro ecological, and historical sources. A simple fire-spread algorithm produced mosaics of variable fire severity and allowed simulated fires to be calibrated to match the shapes of real fires. The simulated landscape was spatially heterogeneous and highly dynamic. Old growth was the dominant patch type occupying a median of 42% of the total area. The relatively long fire return intervals, highly skewed fire size distributions, and mixed severities characteristic of the historical fire regime generated a landscape mosaic with large (> 100 000 ha) patches of old-growth forest, although smaller patches (<100 ha) were the most numerically abundant. Both small and large patches of old forest have important ecological roles in a dynamic ecosystem, and future landscape management efforts should consider the implications of altering these historical patterns.
Effects of chronic N fertilization on foliar membranes, cold tolerance, and carbon storage in montane red spruce
Authors: Schaberg Paul G , DeHayes Donald H , Hawley Gary J , Murakami Paula F , Strimbeck G Richard , McNulty Steven G
Published: October 2002

We evaluated the influence of protracted low-level nitrogen (N) fertilization on foliar membrane-associated calcium (mCa), sugar and starch concentrations, membrane stability, winter cold tolerance, and freezing injury of red spruce (Picea rubens Sarg.) trees growing in six experimental plots on Mount Ascutney, Vermont. For 12 consecutive years before this evaluation, each plot received one of three treatments: 0, 15.7, or 31.4 kg N·ha1·year1supplied as NH4Cl. In comparison with trees from control plots, the current-year foliage of trees from N-addition plots had lower mCa concentrations, higher levels of electrolyte leakage, reduced cold tolerance, and greater freezing injury. Levels of mCa, membrane stability, and cold tolerance did not differ between N treatments, but trees in high-N treated plots experienced greater freezing injury. Although no differences in carbohydrate nutrition were detected in September, foliar sugar and starch concentrations from trees in N-treated plots were higher than control plot trees in January. We propose that foliar mCa deficiencies reduced cell membrane stability, decreased cold tolerance, and increased freezing injury for trees in N addition plots relative to controls. Declines in mCa may also help account for increases in respiration previously measured. Because soil, root, and mycorryhizal conditions were not evaluated, it is unknown how treatment-induced changes in these compartments may have influenced the alterations in foliar mCa and physiological parameters measured in this study.
Aboveground and belowground biomass and sapwood area allometric equations for six boreal tree species of northern Manitoba
Authors: Bond-Lamberty B , Wang C , Gower S T
Published: October 2002

Allometric equations were developed relating aboveground biomass, coarse root biomass, and sapwood area to stem diameter at 17 study sites located in the boreal forests near Thompson, Man. The six species studied were trembling aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), tamarack (Larix laricina (Du Roi) Koch.), and willow (Salix spp.). Stands ranged in age from 4 to 130 years and were categorized as well or poorly drained. Stem diameter ranged from 0.1 to 23.7 cm. Stem diameter was measured at both the soil surface (D0) and breast height (DBH). The relationship between biomass and diameter, fitted on a loglog scale, changed significantly at ~3 cm DBH, suggesting that allometry differed between saplings and older trees. To eliminate this nonlinearity, a model of form log10Y = a + b(log10D) + c(AGE) + d(log10D × AGE) was used, where D is stem diameter, AGE is stand age, and the cross product is the interaction between diameter and age. Most aboveground biomass equations (N = 326) exhibited excellent fits (R2> 0.95). Coarse root biomass equations (N = 205) exhibited good fits (R2> 0.90). Both D0and DBH were excellent (R2> 0.95) sapwood area predictors (N = 413). Faster growing species had significantly higher ratios of sapwood area to stem area than did slower growing species. Nonlinear aspects of some of the pooled biomass equations serve as a caution against extrapolating allometric equations beyond the original sample diameter range.
Mechanical site preparation impacts on soil properties and vegetation communities in the Northwest Territories
Authors: Bock Michael D , Van Rees Ken CJ
Published: October 2002

Greater utilization of hardwood species and societal concerns over maintenance of ecological integrity have provided impetus for forest managers to consider alternative silvicultural practices in boreal mixedwood forests. The objective of this study was to quantify the effects of five mechanical site preparation (MSP) treatments on soil properties and understory vegetation of mixedwood stands in the Northwest Territories (NWT). Soil and understory vegetation conditions in treatments (3 years post-MSP treatment) and adjacent uncut forest controls were sampled. Significant Shearblade  Grizz R-ex and Shearblade treatment soil property effects were consistently found. Increases in bulk density (307%) and decreases for total organic carbon (92%); total nitrogen (86%); cation exchange capacity (74%); and exchangeable calcium (72%), magnesium (67%), and potassium (75%) in the soil surface (012.8 cm) were observed. Increases in mineral soil pH (1.0 units), total organic carbon (94%), cation exchange capacity (20%), and exchangeable calcium (35%) and magnesium (56%) were also found. Dissimilarity of the understory community with that of the uncut forest increased as follows: uncut forest < harvested only < MeriCrusher = Grizz R-ex < Shearblade  Meri-Crusher < Shearblade  Grizz R-ex < Shearblade. This research suggests that winter shearblading should be utilized only where it is necessary to achieve specific management objectives.
Fire growth using minimum travel time methods
Authors: Finney Mark A
Published: October 2002

Fire-growth modeling on complex landscapes can be approached as a search for the minimum time for fire to travel among nodes in a two-dimensional network. The paths producing minimum travel time between nodes are then interpolated to reveal the fire perimeter positions at an instant in time. These fire perimeters and their fire behavior characteristics (e.g., spread rate, fireline intensity) are essentially identical to the products of perimeter expansion techniques. Travel time methods offer potential advantages for some kinds of modeling applications, because they are more readily parallelized for computation than methods for expanding fire fronts and require no correction for crossed fronts or merging separate fires.