bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of methods for edge-bias compensation
Authors: Radtke Philip J , Burkhart Harold E
Published: April 2011

Ignoring the effects of off-plot trees on variables measured within a plot boundary may result in the under estimation problem known as edge bias. A number of edge bias compensation techniques have been proposed in the literature. Four of these were compared with the alternative of ignoring off-plot trees to determine their relative adequacy in modeling crown closure from individual tree crown measurements. Data from a spacing trial of loblolly pine (Pinus taeda L.) were used to make the comparisons. By shrinking the effective size of experimental plots, measurements of "off-plot" data were made available to compare with the results of edge-bias compensation models. Three edge-bias compensation algorithms were found to perform equivalently well: translation; reflection via a reflecting line through the edge trees; and a random arrangement of interior trees around the plot. The ability of the models to compensate for edge bias declined with stand age. Furthermore,the variability of compensation values increased with age and as plot size was reduced.
Variability of wood extractives among Quercus robur and Quercus petraea trees from mixed stands and their relation to wood anatomy and leaf morphology
Authors: Mosedale J R , Feuillat F , Baumes R , Dupouey J -L , Puech J -L
Published: April 2011

Heartwood ellagitannins and volatile extractives were studied by high-pressure liquid chromatography and gas chromatography - mass spectrometry after extraction of wood samples taken from 54 mature trees of pedunculate oak (Quercus robur L.) and sessile oak (Quercus petraea (Matt.) Liebl.) from 14 mixed stands located in the forest of Cîteaux (Bourgogne). These same trees had been previously subject to detailed study of leaf morphology and wood anatomy. Over 50 compounds, of diverse chemical types, were identified in the wood extracts and over 30 of these compounds were quantified. No species-specific extractives were identified, but the amounts of ellagitannins and a small number of volatile compounds, including cis- and trans-β-methyl-γ-octalactone isomers, were found to vary significantly between the two species. Multivariate analyses of these extractives allowed the classification of samples according to species, although less distinctly than similar analyses using leaf morphological characteristics. No strong intraspecific correlations between chemical constituents and anatomical or morphological characteristics were found that were common for both species. Nonetheless, sessile oaks displaying atypical wood anatomy were also less morphologically and chemically representative of their species. Trees possessing the lowest levels of cis- and trans-β-methyl-γ-octalactone are found to be those with a morphology the least distinct of either species.
Salt-wind induced wave regeneration in coastal pine forests in New Zealand
Authors: Campbell D J
Published: April 2011

Strong onshore winds and airborne sea salt can gradually defoliate trees at the exposed margin of temperate pine stands in New Zealand and induce a slowly moving front of dieback and regeneration. Overcrowded mature stands are vulnerable to crown abrasion: abrasion affects trees 20 m ahead of the dieback front; suppressed trees 12 m ahead die before the front reaches them. At the stand margin, trees die from abrasion and salt wind induced dieback. The dieback zone lets sunlight enter the stand; light-demanding pine seedlings establish, but a gradient of increasing litter depth from the dieback front and summer dryness restrict successful seedling establishment to a narrow zone that moves parallel with the dieback front and 11-13 m ahead of it. Further seedlings establish for 4-10 years before the juveniles form a closed canopy; competing vegetation is partly suppressed by infrequent cattle browsing. Regenerating juvenile maritime pine (Pinus pinaster Ait.), show a strict age-related gradation from the dieback front and indicate that wind and salt deposition have been constant for 30 years. Stands further from the sea, with lower stocking rates and other pine species, did not have a clear-cut regeneration zone, because there were no strong gradients of litter depth and light intensity.
Comparison of rolling front and discrete generation breeding strategies for trees
Authors: Borralho Nuno MG , Dutkowski Gregory W
Published: April 2011

Discrete generation and rolling front breeding strategies are compared in terms of gain and inbreeding over a period of 40 years using stochastic simulation. In the rolling front strategy, crosses are made between the best available trees in each year, and new progeny trials are established using the crosses done in the previous year, rather than waiting for all crosses in that generation to be completed. For a given amount of resources, the rolling front strategy resulted in 25-35% greater gains per year, mainly due to a shorter generation interval. Inbreeding was also higher in the rolling front, although gains per unit of inbreeding were consistently greater than with the discrete generation strategy. Despite the smaller size of trials and greater imbalance between trials in rolling front, the results suggest that breeding value estimation using mixed-model BLUP is robust enough to ensure accurate prediction of breeding values and maintain the advantage of the rolling front strategy.
Managing riparian zone vegetation to sustain streamflow: results of paired catchment experiments in South Africa
Authors: Scott David F
Published: April 2011

The reductions in streamflow associated with timber plantations are of particular concern in South Africa and, as a means of sustaining flows, permits granted by the state for the establishment of plantations have required that plantings should be no closer than 20-50 m from streams and other waterbodies. This paper presents the results of three catchment experiments, analysed by the paired catchment method, that aimed to provide a quantitative evaluation of the water yield savings attributable to this practice. These experiments show conclusively that, for South African conditions, riparian vegetation is a more liberal user of water than vegetation in other parts of a catchment and that the clearing of indigenous forest or exotic trees in the riparian zone of the catchment will result in disproportionately greater gains in water yield than would result from clearing similar vegetation elsewhere in the catchment. First year flow increases from clearing of tall woody vegetation in the riparian zone ranged from 55 to 110 mm (9-44%) per 10% of catchment cleared. In the same catchments, clearing of similar vegetation in upslope (nonriparian positions) led to flow increases ranging from 27 to 35 mm (2.5-14%) per 10% of catchment cleared.
Effects of root wrenching on the growth and water relations of Prunus avium and Castanea sativa seedlings in nursery beds and after outplanting
Authors: Hipps N A , Higgs K H , Collard L G
Published: April 2011

The roots of wild cherry (Prunus avium L.) and sweet chestnut (Castanea sativa Mill.) seedlings grown in a nursery bed at the same density (110 plants/m2) were cut by passing a wedge-shaped blade horizontally through the soil (wrenched) at 20 cm depth on 10 July (early) or 12 August (late) or on both dates. Shoot growth was reduced, and this coincided with lower final leaf areas for both species. Leaf water potential (ψ) and leaf conductance to water vapour (gl) of each were reduced immediately after the root wrenching treatments, but recovered within 1 month. Prunus avium seedlings that were late root wrenched suffered more severe drought stress than C. sativa seedlings wrenched at the same time. This was indicated by a larger reduction in ψ and shedding of leaves. Seedlings of P. avium that were wrenched early suffered less drought stress when wrenched a second time (late). Late root wrenching caused greater stress in P. avium than C. sativa, which is ascribed to the smaller quantity of their roots above the depth of wrenching. Early wrenching increased the total shoot growth of both species in the first 2 years after outplanting.
Determining the "optimum" slash pine seedling size for use with four levels of vegetation management on a flatwoods site in Georgia, U.S.A.
Authors: South David B , Mitchell Robert J
Published: April 2011

A slash pine (Pinus elliottii Engelm. var elliottii) study was established to determine the "optimum" seedling size for use on a flatwoods site in the Coastal Plain physiographic province of Georgia, U.S.A. The optimum seedling is defined as the ideotype that will minimize overall reforestation costs while achieving established goals for initial survival and growth. Initial survival and fourth-year performance were examined in relation to (i) method of site preparation, (ii) herbicide application, and (iii) seedling class (based on root-collar diameter) and to associated establishment costs. Seedling class greatly influenced survival with large-diameter classes (8.5-11.5 mm) exhibiting the best survival (87-99%). Seedlings with 4.5-mm diameters averaged 75% survival. A second bedding pass (double bedding) reduced grasses and woody shrubs, and the herbicide imazapyr reduced grasses and herbaceous broadleaf weeds. Neither treatment improved pine survival. Use of 9.5 to 11.5-mm seedlings (without double bedding) produced larger trees 4 years after planting than 4.5-mm seedlings with double bedding. A simple cost analysis indicated the optimum seedling would be considerably larger (9.5-11.5 mm) in diameter than the "target" seedling (4.5 mm) typically produced at slash pine nurseries. For each dollar invested in establishment, planting the optimum pine seedling on this site resulted in greater gains in early survival and growth than either double bedding or use of imazapyr.
Projected gains in rotation-age volume and value from fusiform rust resistant slash and loblolly pines
Authors: Brawner Jeremy T , Carter Douglas R , Huber Dudley A , White Timothy L
Published: April 2011

Midrotation data from large block plots of resistant and susceptible slash (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) were used in combination with the Georgia pine plantation simulator growth model to provide projected gains per hectare in volume and value generated by resistance to fusiform rust (Cronartium quercum (Berk.) Miyabe ex Shirai f.sp. fusiforme). The difference in the projected volume production between the resistant and susceptible planting stock of slash pine was larger than the difference between resistance levels in loblolly pine. The increases in projected volume and the reductions in percent infection of the resistant stock led to large differences in the value of the resistant and susceptible planting stock. At a 6% real discount rate, plantations of resistant slash pine were on average worth between 40.2 and 89.8% more than plantations of susceptible slash pine. Plantations of resistant loblolly were on average worth between 6.1 and 40.3% more than plantations of susceptible loblolly pine. However, the marginal value of rust resistance in loblolly was not significantly different from zero under the assumption that economic differences are only due to volume losses and not losses due to product degrade.
A method for integrated planning of timber production and biodiversity: a case study
Authors: Carlsson Mattias
Published: April 2011

A stepwise planning method is presented that supports decision making on a long-term basis by forest managers with both timber production and biodiversity objectives. An information set was generated that provides a range of solutions, which were illustrated by production possibility frontiers and future landscape development. Steps involved in generating such an information set included clarification of objectives, derivation of indicators related to the objectives, formulation of a linear program, construction of a stand projection model, generation of alternatives, and repeated generation of solutions using the linear program. An example is provided in which the method is applied to a forest management area to illustrate its function. The forest management area covered 18 000 ha. Based on forest conditions at the time it was decided to establish reserve networks, maintain the area of old forest, and increase the area of broad-leaved forest, and also use these criteria as indicators of biodiversity. The method should meet some of the demands involved in the complex problem of integrating timber production and biodiversity objectives. Principles to realize decision-makers values are discussed to exemplify how the method can be used in conjunction with such principles.
Inoculation methods for selecting Populus tremuloides resistant to Hypoxylon canker
Authors: Enebak S A , Ostry M E , Anderson N A
Published: April 2011

Canker expansion and the amount of callus tissue formed were measured monthly on 60 ramets from each of five trembling aspen (Populus tremuloides Michx.) clones that had been inoculated in wounds with Entoleuca mammata (= Hypoxylon mammatum (Wahl.) Mill.) over a 12-month period. At the clone level, the prevalence of nonlethal cankers within clones prior to the study had no correlation with canker expansion with three of the five clones. Greenhouse inoculation of ramets derived from the same five clones resulted in the same resistance rankings as main-stem inoculations in the field. One isolate, Hm-27, produced longer cankers, and less callus developed on all clones compared with trees inoculated with the less aggressive strain, Hm-24. Cankers developed only on clones that were inoculated during the months of April through July with April inoculations resulting in the largest cankers. These results indicate that there is a limited time frame when wounds on aspen are susceptible to infection by artificial inoculation with the pathogen as many wound inoculations neither produced cankers nor wound callus. Comparing inoculation methods, either main-stem inoculations in the field or greenhouse inoculations coupled with the natural canker prevalence could be used to include or exclude clones for use in an aspen breeding program.
Loblolly pine growth response to herbaceous vegetation control at different planting densities
Authors: Quicke Harold , Glover Glenn , Meldahl Ralph S
Published: April 2011

Growth of Pinus taeda L., with and without control of competing herbaceous vegetation, was evaluated over 15 years at planting densities ranging from 747 to 2990 trees/ha. A height response to vegetation control of 0.9 m at age 5 decreased to 0.3 m at age 15. Convergence in the cumulative height between treated and untreated stands did not translate into converging basal area and volume yield. For 1500 and 2200 trees/ha, volume response to early vegetation control increased to age 15. For 800 trees/ha volume gains increased to age 12 and were stable between ages 12 and 15. Higher densities apparently captured more of the site resources made available through vegetation control. Age-15 volume gains for 2200, 1500, and 800 trees/ha were 71 (23%), 48 (17%), and 19 m3·ha-1 (8%), respectively. A separate adjustment term in height and basal-area models captured the short-term positive effect of vegetation control on height growth and longer term basal-area responses. Previously published height and basal-area models were modified to account for planting-density effects.
Functional ecology of advance regeneration in relation to light in boreal forests
Authors: Messier Christian , Doucet René , Ruel Jean-Claude , Claveau Yves , Kelly Colin , Lechowicz Martin J
Published: April 2011

This paper reviews aspects of the functional ecology of naturally established tree seedlings in the boreal forests of North America with an emphasis on the relationship between light availability and the growth and survival of shade tolerant conifers up to pole size. Shade tolerant conifer species such as firs and spruces tend to have a lower specific leaf mass, photosynthetic rate at saturation, live crown ratio, STAR (shoot silhouette area to total needle surface area ratio), and root to shoot ratio than the shade intolerant pines. The inability of intolerant species such as the pines and aspen to survive in shade appears to be mainly the result of characteristics at the shoot, crown, and whole-tree levels and not at the leaf level. Although firs and spruces frequently coexist in shaded understories, they do not have identical growth patterns and crown architectures. We propose a simple framework based on the maximum height that different tree species can sustain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneration is important to the understanding of boreal forest dynamics and can be useful to forest managers seeking to develop or assess novel silvicultural systems.
Floristic diversity, stand structure, and composition 11 years after herbicide site preparation
Authors: Miller James H , Boyd Robert S , Edwards M Boyd
Published: April 2011

This study tested for effects of site preparation herbicides applied at high labeled rates 11 years earlier on plant species richness, diversity, and stand structure and composition. Four study sites in three physiographic provinces were established in central Georgia in 1984. Six herbicide treatments were included on each site: hexazinone liquid, hexazinone pellets, glyphosate, triclopyr, picloram, and a mixture of dicamba and 2,4-dichlorophenoxyacetic acid (2,4-D). Herbicide and untreated plots were prescribed-burned and planted to loblolly pine (Pinus taeda L.). Eleven years after treatment, 177 total species were identified in these dense pine plantations; 99 species were forbs and grasses-grasslikes. Treated and check plots did not differ in species richness or diversity. Structurally, the total basal area of the tree canopy was not significantly altered, but the proportion of pine to hardwoods and shrub stem density were influenced by treatment. Latent effects were detected in the abundance and frequency of Pinus taeda, Prunus serotina Ehrh., Quercus stellata Wangenh., Diospyros virginiana L., Vaccinium stamineum L., Vitis rotundifolia Michx., and Lespedeza bicolor Turcz. Most are potential mast producers for wildlife. Herbicide site preparation had little influence on total species numbers or their diversity 11 years after treatment but affected composition by altering perennial species abundance.
Comparison of photosynthetically active radiation and cover estimation for measuring the effects of interspecific competition on jack pine seedlings
Authors: Ter-Mikaelian Michael T , Wagner Robert G , Bell F Wayne , Shropshire Christy
Published: April 2011

Using an additive-density study with 10 woody and herbaceous plant species of the boreal forest, we compared equations predicting the biomass growth of jack pine(Pinus banksiana Lamb.)seedlings using measurements of photosynthetically active radiation (PAR) transmission and visual estimates of vegetation cover. Nonlinear regression equations accounted for between 77 and 83% of the variation in the annual biomass increment of jack pine when all competing species were combined. Our objective was to determine whether measuring PAR provided any advantage over cover estimation for predicting the effects of interspecific competition. We found no difference in the predictive ability of visual cover estimates and either a single PAR measurement at the point of maximum canopy development or repeated PAR measurements throughout the growing season. Results were consistent among experimental plots that contained a variety of competing plant species with different growth forms. Measurements of PAR transmission once during the growing season performed as well as PAR measurements taken throughout the growing season. Although the precision of plant cover estimates in vegetation sampling has been a concern for some time, high variation in PAR measurements can be created by sensor location sensitivity, narrow sampling windows, and the need for sensor calibration.
Effects of seven forestry management herbicides on Myriophyllum sibiricum, as compared with other nontarget aquatic organisms
Authors: Roshon Roxana D , McCann Janet H , Thompson Dean G , Stephenson Gerald R
Published: April 2011

Historically, studies on the nontarget aquatic effects of forest-use herbicides focused largely on fish and invertebrates despite the ecological importance of aquatic plants. Regulatory requirements and the aquatic phytotoxicity database need to be improved to reflect the importance of aquatic plants. Based on a review of the scientific literature and results from laboratory testing with the submersed macrophyte Myriophyllum sibiricum Komarov, the effects of 2,4 dichlorophenoxyacetic acid (2,4-D), glyphosate, hexazinone, imazapyr, metsulfuron methyl, sulfometuron methyl, and triclopyr on nontarget aquatic organisms were compared. Laboratory results indicate that M. sibiricum is sensitive to herbicide effects, especially those that impact root growth. For most herbicides, the inhibitory concentrations 25 and 50 (IC25 and IC50, concentrations that inhibit an endpoint parameter by 25 and 50%, respectively) for shoot and root growth were below the expected environmental concentrations (EEC). For example, the IC50 values for root dry mass were 0.000 12 and 0.000 22 mg active ingredient/L for sulfometuron methyl and metsulfuron methyl, respectively, concentrations that were approximately 3100 and 1700 times below the EEC for these compounds. Interspecies comparisons, conducted during this study, demonstrated that M. sibiricum was generally equally or more sensitive to these herbicides than other aquatic plant species (i.e., floating macrophytes and algae) and, in some cases, more sensitive than fish, zooplankton, and other invertebrates. For example, available data demonstrated that 2,4-D, imazapyr, and the sulfonylureas investigated were more toxic to rooted and floating macrophytes than to other aquatic organisms, including algae. Because of the high sensitivity and ecological significance of aquatic macrophytes, a greater emphasis should be placed on evaluating aquatic phytotoxicity in future ecotoxicological research.
Relationships between loblolly pine yield and woody plant diversity in Virginia Piedmont plantations
Authors: Schabenberger Lisa E , Zedaker Shepard M
Published: April 2011

This study was established to determine the effects of competition control on loblolly pine (Pinus taeda L.) yield and woody plant diversity in Virginia Piedmont plantations 12-14 years of age. In a factorial experiment, loblolly pine and competing woody vegetation were analyzed at eight levels of competition control: total, two-thirds, one-third, or no woody stem control in combination with either total or no herbaceous vegetation control. Pine yield increased linearly with increasing levels of woody control intensity. As woody control increased, noncrop woody plant basal area and woody plant diversity (Shannon index (H')) in the canopy decreased. Woody plant species richness in the canopy was reduced by herbaceous control and by total woody control. Percent woody cover, H', and species richness in the understory were not affected at any level of competition control. Regression analysis was used to examine relationships between loblolly pine yield, noncrop woody dominance and canopy plant diversity (H'). Pine yield was negatively correlated (R2 = 0.74) with the percentage of noncrop woody basal area (PNCW BA) in the canopy, while canopy diversity was proportional to PNCW BA (R2 = 0.97). Canopy diversity was inversely related to pine yield (R2 = 0.77), with a high trade-off in diversity at low yield levels, but with decreasing sensitivity as pine yield increased.
Identification en forêt de chênes sessiles (Quercus petraea) présentant un angle du fil du bois intrinsèquement faible
Authors: Guilley E , Loubère M , Nepveu G
Published: April 2011

Grain angle on bark (angle between the general direction of bark fissures and the axis of the trunk) was assessed at the four cardinal points at breast height (1.3 m) on 82 standing sessile oaks (Quercus petraea Liebl.). After felling, wood spiral grain was measured at breast height from cambium to pith along two diametrically opposite radii. A mixed-effect model that links the tangent of grain angle to radial position (age and distance from the pith) allows to estimate two individual parameters of grain angle. In the field, nondestructive measurements of grain angle (subcortical spiral grain or spiral grain on bark) on an individual tree combined with information on the tree stand allow to estimate one of the two parameters that describes the change in grain angle for a given radial increment. This parameter is independent of mean ring width, tree age and circumference, and site characteristics; it should allow a more accurate identification and selection of standing trees with low wood spiral grain.
Economics of fossil fuel substitution and wood product sinks when trees are planted to sequester carbon on agricultural lands in western Canada
Authors: van Kooten G Cornelis , Krcmar-Nozic Emina , Stennes Brad , van Gorkom Ruud
Published: April 2011

To meet its international commitment to reduce CO2 output by 7% from the 1990 level by 2012, Canada will rely to some extent on terrestrial carbon uptake, particularly afforestation of marginal agricultural land. The economics of afforestation is examined for northeastern British Columbia and all of Alberta, with harvested wood used either as a replacement for coal in energy production or as a wood-product sink. Some 7 × 106 ha of marginal agricultural land are identified, but very little could reasonably be afforested if wood is used as a substitute for coal. If C is stored in wood products, nearly one third of the land might reasonably be planted to trees; if similar results hold for the rest of Canada, afforestation can be included in the policy arsenal. Before that can be done, however, some serious issues need to be resolved, including problems associated with the mechanism used to transfer land out of agriculture into plantation forest.
Predicting branch diameters on second-growth Douglas-fir from tree-level descriptors
Authors: Maguire Douglas A , Johnston Stuart R , Cahill James
Published: April 2011

The quality of lumber and veneer recovered from logs of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is directly influenced by the maximum limb size attained on the crop tree. Because limb sizes are influenced by stand-density regimes, a need has arisen for quantitative tools that link a wide array of silvicultural regimes to wood-product quality by accounting for silvicultural effects on crown development. An equation for estimating maximum branch size at a given level within the live crown was developed from data collected on 96 felled sample trees in the Coast Ranges and Cascade foothills of Oregon and Washington. Height and basal diameter of the largest branch within each live whorl were measured on each felled tree, and a predictive equation was developed by various regression techniques. The final mixed-effects nonlinear model estimates maximum branch size as a function of depth into crown and tree diameter at breast height, height, and live crown length.
Genetic variation in response to shade in coastal Douglas-fir
Authors: St. Clair J Bradley , Sniezko Richard A
Published: April 2011

Tree improvement programs have generally relied on testing families in open light environments. With increased interest in multiaged silvicultural systems, some people have questioned whether families selected in the open are appropriate for planting in the shade. We grew Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) families from two climatically distinct seed sources for 2 years under four levels of shade. The response to shade differed for several traits between the two populations and among families within populations. The magnitude of variation associated with the interaction, however, was small compared with the overall effects of genetic selection or of shade. Families selected based on performance in an open light environment resulted in nearly the same response to selection when grown under shade as families selected based on performance in the shade. We conclude that seedlings from families selected in an open light environment are appropriate for use in the low-light environments of alternative silvicultural systems and that use of such genetically selected stock may compensate for the less favorable growing conditions. Genetic selection may contribute importantly to meeting multiple objectives, including the production of significant amounts of wood as well as the efficient and timely creation of large stand structures needed for other forest values.
Factors affecting natural regeneration of Abies lasiocarpa and Picea engelmannii in a subalpine silvicultural systems trial
Authors: Eastham Andrea M , Jull Michael J
Published: April 2011

An experiment was established in 1991-1992 in northern British Columbia to investigate factors influencing natural regeneration rates of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in three stand structures created by harvesting. Harvest treatments were a 32-ha clearcut, 0.2-ha patch cuts, and single-tree selection. Cone crop periodicity was independent of harvesting system. Natural seedfall was higher in the selection treatment and small patch cut than the clearcut treatment every year. Five years after harvest, the selection and patch cut treatments had 7 times as many spruce germinants and 10 times as many subalpine fir germinants as the clearcut treatment. Seed availability appears to be the primary limiting factor for establishment of both subalpine fir and spruce in the clearcut treatment. For spruce establishment in the selection and small patch cut treatments, availability of both seed and mineral soil seedbeds were limiting factors, while for subalpine fir, germinant establishment appears primarily limited by availability of disturbed forest floor seedbeds. Foresters could increase opportunities for natural regeneration in these subalpine forests by (i) modifying harvest patterns to enhance conifer seed distribution over harvested areas and (ii) applying seedbed preparation treatments prior to anticipated heavy seedfalls.
Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska
Authors: Yarie John
Published: April 2011

The Spatial Alaskan Forest Ecosystem Dynamics (SAFED) model was validated across four of the most common vegetation types found in interior Alaska. The vegetation types were an alder (Alnus spp.) - balsam poplar (Populus balsamifera L.) site (FP2), an old-growth balsam poplar and white spruce (Picea glauca (Moench) Voss) site (FP3), a mixed deciduous (primarily birch (Betula papyrifera Marsh.) and aspen (Populus tremuloides Michx.)) and white spruce site (UP2), and a mature white spruce site (UP3). The FP site types are common on the floodplain along the Tanana River and the UP site types are common in the uplands in interior Alaska. SAFED is based on nitrogen productivity for vegetation growth, litter fall quantity and quality, and microbial efficiency for forest floor decomposition. The state factors (climate, topography, and disturbance) are used to describe a broad-scale classification of the landscape to define basic limitations for the driving variables. Climate and ecosystem-level disturbances are handled as restricted stochastic processes. The model has been programed in a spatial framework as an ARC/INFO AML within the GRID package. The current version of the model has been validated as functional from an individual tree basis (1-m2 cell size) in a number of forest types found in interior Alaska. The growth, litter fall, and forest floor decomposition were compared with data from the sites. An estimate of yearly carbon balance for the four sites was calculated.
Early cohort development following even-aged reproduction method cuttings in New York northern hardwoods
Authors: Nyland Ralph D , Ray David G , Yanai Ruth D , Briggs Russell D , Zhang Lianjun , Cymbala Robert J , Twery Mark J
Published: April 2011

We described a general pattern of cohort development following two types of even-aged reproduction methods in northern hardwoods. Three clearcut sites initially had divergent numbers of stems, because of variable amounts of advance regeneration. By 10 years, total stem densities became quite similar across sites. Three sites treated by shelterwood seed cutting lacked advance regeneration. Compared with the clearcuts, seedlings became established at much higher stem densities there, and even early cohort development followed a consistent pattern. By 20-25 years, both the clearcut and shelterwood sites supported 7600-8900 total stems/ha. Stems >=2.54 cm diameter at breast height peaked at about 6000, but by age 15 following clear-cutting, and not until age 20 after shelterwood seed cutting. The time lag likely reflects initial differences in advance regeneration, and possibly other factors between sites. Basal area at the clearcut sites reached 26 m2/ha within about 25 years. At the shelterwood sites it reached 22 m2/ha by age 25. The quadratic stand diameter increased consistently across sites and treatments. Regression models describe changes in numbers of total stems, numbers of saplings, stand basal area, and quadratic stand diameter for each treatment.
Growth, nutrient dynamics, and ectomycorrhizal development of container-grownPicea marianaseedlings in response to exponential nutrient loading
Authors: Quoreshi M , Timmer V R
Published: April 2011

Containerized black spruce (Picea mariana (Mill.) BSP) seedlings fertilized conventionally (12.5 mg N/plant) or exponentially (12.5, 25, or 50 mg N/plant) and inoculated with Hebeloma crustuliniforme (Bull. Ex St-Amans) Quel. or Laccaria bicolor (R. Mre.) Orton were periodically monitored for a 20-week greenhouse rotation to assess growth dynamics, steady-state N and P nutrition, and ectomycorrhizal development. Growth and nutrient accumulation increased exponentially for the exponential regimes and more linearly for the conventional regime, although final biomass was similar except for the low-dose exponential addition. Shoot/root biomass ratios were relatively stable for most of the growing season, characterizing steady-state nutrient supply that benefits seedling outplanting performance and mycorrhizal colonization. Exponential fertilization also stimulated mycorrhiza formation even at high loading (25 or 50 mg N) rates that build up nutrient reserves in the seedlings without affecting seedling size. Plant nutrient uptake was more efficient under exponential fertilization and (or) fungal colonization, although efficiency dropped off at high loading levels. Vector nutrient diagnosis revealed marked nutrient dilution under conventional fertilization, but steady-state nutrition under exponential fertilization that coincided with satisfactory mycorrhiza development on seedlings. Dilution-free nutrient conditions for seedlings may provide stable carbohydrates for symbiosis and may develop enhanced tolerance to high fertilizer inputs.
Genetic variability in sexually dimorphic and monomorphic populations of Populus euphratica (Salicaceae)
Authors: Rottenberg Aaron , Nevo Eviatar , Zohary Daniel
Published: April 2011

The genetic polymorphism of three populations of the dioecious riparian tree Populus euphratica Oliv. in Israel was examined with isozyme tests. Twelve enzyme systems revealed 20 putative loci, of which 13 were polymorphic. A centrally located population (comprising both females and males) was sampled, as well as two small peripheral and isolated stands: one comprised of only females and one containing males only. Genetic diversity values in P. euphratica were usually lower than those reported in other poplars and other species with similar life-history traits. The highest genetic diversity was found in the central, sexually dimorphic population; however, the sexually monomorphic (unisexual) marginal populations also manifested some genetic diversity, with the lowest values in the male population. Each of the unisexual populations could have originated from very few founder individuals of the same gender. The genetic variability detected in the unisexual populations may reflect somatic mutations accumulated in a vegetatively reproducing lineage over a long time span.
Height growth of planted black spruce seedlings in response to interspecific vegetation competition: a comparison of four competition measures at two measuring positions
Authors: Wang G G , Su J , Wang J R
Published: April 2011

Four simple measures of interspecific competition (percent cover visually estimated in the field, percent cover derived from hemispherical photographs, percent full sunlight measured by a ceptometer, and gap light index derived from hemispherical photographs) obtained at two reference positions (the top and the middle of crop seedlings) were evaluated in relation to two growth variables (relative height growth rates in 1998 and during 1996 to 1998) of black spruce (Picea mariana (Mill.) BSP) seedlings planted on boreal mixedwood sites in southeastern Manitoba. The four competition measures assessed at the two measuring positions explained 57.2-68.0% of the total variation in black spruce height growth rate. Significant relationships were found among the four measures, and between the two measuring positions for each measure. The measuring position was not critical for all competition measures except the percent full sunlight measured by the ceptometer, for which the middle position was much better. When assessed at their preferred positions, the four competition measures ranked as follows: (i) percent cover derived from hemispherical photographs or percent full sunlight measured by the ceptometer; (ii) gap light index derived from hemispherical photographs; and (iii) visually estimated percent cover of vegetation.
Effects of partial cutting in winter on white-tailed deer
Authors: St-Louis Antoine , Ouellet Jean-Pierre , Crête Michel , Maltais Jean , Huot Jean
Published: April 2011

We documented how commercial logging influenced the spatial behavior and nutritional ecology of northern white-tailed deer (Odocoileus virginianus). Using periodic browse surveys, we estimated the additional biomass of twigs available from felled trees to deer in the Pohénégamook wintering area (25 km2) at 55 kg/ha in a 43-ha cut conducted in 1995-1996 that aimed to favor conifers by removing overtopping deciduous trees. Over the entire winter, deer used 54% of the browse made available by the felling residues. The use of the cutover, estimated by pellet group census, was five times greater than the average recorded over the entire wintering area. Felled trees provided approximately 35% of the food intake of the animals that have used the cutover. Of 30 deer fitted with radio collars, the cutover attracted only those whose range neighbored the logging area (<2 km). In preference tests carried out in the winter of 1996-1997, deer showed no preference for twigs from newly cut trees over those from trees cut earlier in the winter, nor for twigs from treetops (browse made accessible during the logging operation) over twigs from saplings (browse usually accessible in winter). If commercial logging is conducted in winter as a means of providing emergency food during snowy winters to enhance deer survival, our results suggest that partial cutting may be ineffective because felling residues were used only by deer found near the cutover and because of the difficulties of logging in deep snow.
Enhancement of hippocampal cholinergic neurotransmission through 5-HT1A receptor-mediated pathways by repeated lithium treatment in rats
Authors: Fujii Takeshi , Nakai Katsuhiko , Nakajima Yasuo , Kawashima Koichiro
Published: April 2011

Hippocampal cholinergic neuronal activity is reported to be regulated, at least partly, through serotonin1A (5-HT1A) receptors. Chronic lithium treatment has been shown to alter both behavioral and neurochemical responses mediated by postsynaptic 5-HT1A receptors. We investigated whether long-term lithium treatment affects central cholinergic neurotransmission through 5-HT1A receptor-mediated pathways. Changes in acetylcholine (ACh) release induced by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, in the rat hippocampus were measured using a microdialysis technique and a radioimmunoassay for ACh. Administration of lithium for 21 days resulted in a serum lithium concentration of 1.03 mM and caused little change in density or affinity of [3H]8-OH-DPAT binding sites in the hippocampus. The local application of 8-OH-DPAT into the hippocampus of lithium treated rats increased the ACh efflux in both the absence and the presence of physostigmine, a cholinesterase (ChE) inhibitor, in the perfusion fluid. The basal ACh efflux of lithium treated rats was not different from that of the control rats under normal conditions, but was significantly higher than that of the controls when ChE was inhibited. These results demonstrate that chronic lithium treatment increases spontaneous ACh release in the hippocampus under conditions of ChE inhibition, but not under normal conditions, and enhances cholinergic neurotransmission through 5-HT1A receptor-mediated pathways, and suggest that activation of 5-HT1A receptor function by lithium is related to the enhancement of hippocampal cholinergic neurotransmission.

Key words: Acetylcholine (ACh), hippocampus, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), lithium, serotonin1A (5-HT1A) receptor.
Predictors of Torsades de Pointes in rabbit ventricles perfused with sedating and nonsedating histamine H1-receptor antagonists
Authors: Gilbert Jeremy D , Cahill Sean A , McCartney Douglas G , Lukas Anton , Gross Gil J
Published: April 2011

Several nonsedating histamine H1-receptor antagonists are associated with torsades de pointes ventricular tachycardia. The objectives of this study were to: (i) compare electrocardiographic, monophasic action potential, and arrhythmogenic effects of sedating and nonsedating H1-receptor antagonists, and (ii) identify correlates of drug-induced torsades de pointes in an isolated ventricle model. Isolated, electrically paced (1-3 Hz) rabbit ventricles were Langendorff-perfused with either drug-free Tyrode's solution or one of the following: (i) the sedating H1-receptor antagonist hydroxyzine (0.1-30 µM), (ii) cetirizine, a nonsedating metabolite of hydroxyzine (1-300 µM), and (iii) the nonsedating, putatively arrhythmogenic H1-receptor antagonist astemizole (0.1-30 µM). Volume conducted electrocardiographic signals and monophasic action potentials from the periapical left ventricular endocardium and epicardium were recorded. There were no apparent changes in control (n = 15) or hydroxyzine-perfused (n = 7) hearts. Cetirizine (n = 13) produced a mild biphasic electrocardiographic QT interval prolongation and was associated with early afterdepolarizations, but not with torsades de pointes. Astemizole (n = 11) lengthened QT intervals, and at high concentration (30 µM) induced torsades de pointes in 10 of 11 hearts (P < 0.001 vs. all other groups). These findings are consistent with previously reported repolarizing current inhibition by cetirizine, but may additionally indicate "compensatory" inhibition of inward currents at higher concentrations. By contrast, astemizole-induced changes are consistent with unopposed repolarizing current inhibition.

Key words: Langendorff preparation, rabbit ventricle, H1-receptor antagonists, QT interval, ventricular arrhythmias.
Short-term exposure to homocysteine depresses rat aortic contractility by an endothelium-dependent mechanism
Authors: Wang S , Wright G , Harrah J , Touchon R , McCumbee W , Geng W , Fultz M E , Abdul-Jalil M N , Wright G L
Published: April 2011

The effect of short-term exposure to homocysteine (Hcy) on the contractile characteristics of rat aortic tissue was assessed both in vitro and in vivo. The contractile response of Hcy-treated aortic rings in culture for 1 or 4 days was unchanged from control responses. By comparison, aortic rings from animals injected with Hcy showed marked attenuation of response compared with controls injected with saline, cysteine or methionine. The contractile response to K+was decreased within 24 hours of Hcy injection, whereas the response to both K+(-27%) and noradrenaline (-56%) was significantly decreased by 4 days. In contrast, the contractile response to phorbol-12,13-dibutyrate was not different between Hcy and control groups. Intimal rubbing completely restored the responsiveness of Hcy-treated tissue to K+and noradrenaline. By comparison, L-NAME only partially restored contractile responsiveness, while the cyclooxygenase inhibitor indomethacin had no effect on contractile attenuation induced by Hcy. Western blot analysis showed a 2-fold increase of endothelial nitric oxide synthase (eNOS) and a 3-fold increase in inducible nitric oxide synthase (iNOS) protein expression in the aortic endothelial cells from Hcy-injected rats. The results indicate an early detectable effect of Hcy on the in vivo contractile properties of vascular smooth muscle. The effect is endothelium-mediated and may vary depending on the agonist studied. The mechanism is uncertain but appears to involve increased nitric oxide (NO) production. Finally, the data suggest that attenuation of contraction may not be due to a direct effect of Hcy but that the compound is modified or acts indirectly in vivo.Key words: nitric oxide, nitric oxide synthase, in vivo, smooth muscle.
Vasodilator responses to ATP and UTP are not dependent on nitric oxide release, K+ATP channel activation, or the release of vasodilator prostaglandins in the hindlimb vascular bed of the cat
Authors: Champion Hunter C , Kadowitz Philip J
Published: April 2011

The effects of the purinergic agonists, ATP, ATPγS, UTP, and 2-Met-Thio AP, were investigated in the hindlimb vascular bed of the cat. Under constant-flow conditions, injections of the purinergic agonists into the perfusion circuit elicited dose-related decreases in perfusion pressure. The order of potency was 2-Met-Thio ATP > ATPγS > ATP > UTP. In contrast, injections of GTPγS, cAMP, UDP, and UMP had no effect. Vasodilator responses to ATP, ATPγS, UTP, and 2-Met-Thio ATP were increased in duration by the cAMP phosphodiesterase inhibitor rolipram, whereas the cGMP phosphodiesterase inhibitor zaprinast had no effect. Responses to the purinergic agonists were not altered by nitric oxide synthase inhibitors, K+ATP channel antagonists, cyclooxygenase inhibitors, or agents that interfere with the actions of the adrenergic nervous system. These data suggest that ATP, ATPγS, UTP, and 2-Met-Thio ATP dilate the hindlimb vascular bed by a direct cAMP-dependent mechanism, and that the release of nitric oxide, vasodilator prostaglandins, K+ATP channel opening, or an inhibitory effect on the adrenergic nervous system play little, if any, role in mediating or modulating responses to the purinergic agonists in the hindlimb circulation of the cat.Key words: purinergic agonists, P2 purinergic receptors, cAMP-dependent vasodilator activity, adrenergic system, nitric oxide prostaglandins.