bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil exploitation strategies of fine roots in different tree species of the southern boreal forest of eastern Canada
Authors: Bauhus Jürgen , Messier Christian
Published: April 2011

This study compared the ability of conifers (Abies balsamea (L.) Mill., Picea glauca (Moench) Voss) and deciduous trees (Populus tremuloides Michx., Betula papyrifera Marsh.) and shrubs and herbs to exploit soils in a southern boreal forest. Root samples were collected from undisturbed soil and ingrowth cores (disturbed soil) of aspen- and conifer-dominated plots. Total fine-root biomass was similar in aspen and conifer plots but length density was higher under aspen. The low root length density (0.7 cm·cm-3) of conifers suggests a dependency on mycorrhizal associations for effective nutrient uptake. Coniferous fine roots were thicker than in the other species. Root tip and internode lengths in deciduous trees showed little differences between undisturbed and disturbed soil, whereas these parameters increased substantially in conifers in disturbed soil. Root growth and architecture in disturbed soil indicated that conifers follow a conservative strategy of optimizing soil exploitation efficiency through the relatively slow development of coarse fine-root systems. In contrast, deciduous trees and understorey shrubs and herbs colonized favourable soil environments to a larger extent maintaining highly ramified thin fine roots to optimize the exploited soil volume. The different soil exploitation strategies may be as important as those differences reported for aboveground growth to explain the coexistence of these species.
Allozyme diversity and gene flow in the bark beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae)
Authors: Six Diana L , Paine T D , Hare J Daniel
Published: April 2011

Genetic variation within and among 10 California populations of the Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, was assessed using allozymes. Of 21 loci assayed, 6 were polymorphic in at least one population. Average heterozygosity across all populations and loci was 4%. Genetic distance among the populations ranged from 0.001 to 0.060. The two most southern populations were the most differentiated. At two loci, alleles were present in the southern populations that were not present in any northern populations. The southern populations were also lacking an allele at one locus that was present in all northern populations. Geographic isolation is apparently responsible for allowing the divergence of the southern populations. A dendrogram estimating the relationships among the 10 populations was developed using restricted maximum likelihood. Evidence of inbreeding was found, which in these beetles may be closely tied to population size and dispersal behavior.
Allozyme diversity and gene flow in Ophiostoma clavigerum (Ophiostomatales: Ophiostomataceae), the mycangial fungus of the Jeffrey pine beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae)
Authors: Six Diana L , Paine T D
Published: April 2011

Genetic variation within and among 10 California populations of Ophiostoma clavigerum (Robinson-Jeffrey & Davidson) Harrington associated with the mycangia of Dendroctonus jeffreyi Hopkins was assessed using allozymes. Gene diversity was uniformly low across all populations, averaging 1.4%. Only 2 of 19 gene loci assayed were polymorphic. The three most southerly populations (two from the San Bernardino Mountains in southern California and one from the southern tip of the Sierra Nevada Mountains) were the most differentiated; however, all populations exhibited very low genetic distance. Several factors alone, or in combination could be responsible for the low genetic diversity observed in these populations including (i) a rarity of sexual recombination, (ii) a history involving genetic bottlenecks, and (iii) selection for a mutualistic association with the host beetle.
Changes in soil sulfur constituents in a forested watershed 8 years after whole-tree harvesting
Authors: Zhang Yimin , Mitchell M J , Driscoll C T , Likens G E
Published: April 2011

Soil S constituents were evaluated before and after the whole-tree harvesting of Watershed 5 (W5) at the Hubbard Brook Experimental Forest, New Hampshire. Soil solution and stream water concentrations of SO42-, NO3-, and H+ were compared between W5 and W6 (reference watershed). Whole-tree harvesting increased phosphate-extractable SO42- (PSO4) in the E horizon, from 2 mg S·kg-1 soil in pre-harvest to 9 and 10 mg S·kg-1 soil 3 and 8 years post-harvest, respectively. Harvesting increased PSO4 in the Bh horizon from 11 mg S·kg-1 soil prior to harvesting to 20 and 25 mg S·kg-1 soil 3 and 8 years after harvesting, respectively. Temporal patterns in soil chemistry were also reflected in stream SO42-, NO3-, and H+ concentrations. Eight years after harvesting, PSO4 concentrations in the mineral soil increased with elevation. This elevational pattern was likely due to the higher concentrations of SO42- and H+ in soil solutions that enhanced SO42- adsorption at the higher elevations. The high H+ concentrations were attributed to enhanced nitrification and differences in vegetation at upper elevations. The importance of these factors were discussed with respect to the effects of forest harvesting and changes in atmospheric S deposition.
Microsatellite DNA as shared genetic markers among conifer species
Authors: Echt C S , Vendramin G G , Nelson C D , Marquardt P
Published: April 2011

Polymerase chain reaction (PCR) primer pairs for 21 simple sequence repeat (SSR) loci in Pinus strobus L. and 6 in Pinus radiata D. Don. were evaluated to determine whether SSR marker amplification could be achieved in 10 other conifer species. Eighty percent of SSR primer pairs for (AC)n loci that were polymorphic in P. strobus also amplified SSR loci in two other soft pines of the subgenus Strobus but not in seven hard pines of the subgenus Pinus, nor in Picea glauca (Moench) Voss or Pseudotsuga menziesii (Mirb.) Franco. The six P. strobus SSR primer pairs that did amplify loci from conifers other than soft pines were those that were specific to loci monomorphic within P. strobus. These six loci were also monomorphic within seven other species tested, but four of the loci were polymorphic among species. A comparison of allelic variation among the three soft pine species found only 25 shared alleles among a total of 122 alleles at eight loci. Primer pairs for dinucleotide SSR loci that were polymorphic in Pinus radiata also specifically amplified loci from various other hard pines but not from the soft pines or from the other conifers tested.
Effect of landscape position on N mineralization and nitrification in a forested watershed in the Adirondack Mountains of New York
Authors: Ohrui Kiyokazu , Mitchell Myron J , Bischoff Joseph M
Published: April 2011

Within a forest ecosystem in the Adirondack Mountains of New York, net N mineralization and nitrification rates were measured at different landscape positions (zones). Net N mineralization rates (0-15 cm depth) were less (39 kg N·ha-1 per year) within a wetland without alder and with a coniferous overstory than an upland conifer zone (82 kg N·ha-1 per year) and an upland hardwood zone (107 kg N·ha-1 per year). Net N mineralization rates (39 to 82 kg N·ha-1 per year) and the forest floor N concentrations (2.3 to 2.5%) were higher than values reported (1.2-29 kg N·ha-1 and 1.1-2.12%, respectively) for other spruce forests. The net nitrification rates were higher at the upland hardwood zone (29 kg N·ha-1 per year) than the upland conifer zone (2 kg N·ha-1 per year). The wetland conifer zone without alders had an intermediate rate of net nitrification (13 kg N·ha-1 per year) compared with the upland zones. The presence of white alder (Alnus incana (L.) Moench) in the wetland increased the NO3- content and net nitrification rate of the soil.
Vector competition analysis of black spruce seedling responses to nutrient loading and vegetation control
Authors: Imo Moses , Timmer Victor R
Published: April 2011

Impacts of methods to overcome competing vegetation (fertilization, herbicide application, and shading) on conventional and nutrient-loaded black spruce (Picea mariana (Mill.) BSP) seedlings were examined on six forest site types in northeastern Ontario using vector competition analysis. Four sites (Alnus; hardwood; mixedwood, herb rich; and mixedwood, herb poor) were selected to represent high competition, and two sites (feathermoss and Vaccinium) to represent low-competition forest sites. Although similar in biomass before planting, loaded seedlings had greater N, P, and K content than nonloaded seedlings. After planting, loaded seedlings outperformed growth of nonloaded seedlings under all vegetation-control treatments on all sites. Herbicide application eliminated noncrop vegetation but resulted in significantly higher seedling biomass only on the high-competition Alnus site. Field fertilization stimulated weed growth resulting in seedling suppression on the high-competition sites, while nutrient loading countered weed competition on most sites. Interpretation of these results by vector competition analysis revealed that, without fertilization, competition for nutrients was the primary factor limiting seedling growth, while competition for light and (or) moisture was greater after fertilizer addition on weed-prone sites. Similar interpretation revealed no seedling-weed interactions in the less competitive sites.
Strength properties of wind- and snow-damaged stems of Picea sitchensis and Pinus sylvestris in comparison with undamaged trees
Authors: Cameron A D , Dunham R A
Published: April 2011

This study compared the strength properties of wood taken from Sitka spruce (Picea sitchensis (Bong.) Carr.) and Scots pine (Pinus sylvestris L.) trees damaged as a result of wind and snow. The spruce trees were located in triplets of stems of similar diameter that had snapped, overturned (i.e., uprooted), or remained undamaged as a result of wind and snow. The pine trees were located in pairs of similar-sized stems that had snapped or remained undamaged. None of the pine trees overturned. Clear wood (wood without knots and sloping grain) from the outer part of the stem of snapped Sitka spruce and Scots pine trees was less stiff (lower modulus of elasticity (MOE)) than wood taken from the same location from overturned (spruce only) or standing trees. Modulus of rupture and density were unaffected. Damaged trees of both species were found to have significantly more compression wood within the test samples in comparison with undamaged trees. These findings suggest that trees that either overturn or snap are bending more than undamaged trees (because of their low MOE) thereby introducing a greater component of crown weight to the overall forces acting on the stem, and that this may be associated with compression wood.
Future alternatives to the use of herbicides in British forestry
Authors: Willoughby Ian
Published: April 2011

Weed control is often crucial for successful tree establishment in British forestry. Herbicides currently offer the most cost-effective means available for achieving this, but research into alternatives is required. Recent experiments have been conducted by the Great Britain Forestry Commission investigating the use of 19 alternative ground cover and silvicultural treatments for newly planted ash (Fraxinus excelsior L.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) established on fertile lowland ex-agricultural sites. Most ground cover treatments proved difficult to establish and were more competitive to trees than naturally occurring vegetation. White clover (Trifolium repens L.) showed some potential for suppressing weed vegetation without reducing tree growth. Closer initial tree planting densities appeared to offer a practical means of reducing herbicide inputs, whilst still permitting good rates of growth. It is concluded that a comprehensive review of other alternative methods of weed control is now required to set a framework for future Great Britain Forestry Commission research in this field.
Spatial patterns of tree height variations in a series of Douglas-fir progeny trials: implications for genetic testing
Authors: Fu Yong-Bi , Yanchuk Alvin D , Namkoong Gene
Published: April 2011

Spatial variation patterns of tree heights at ages from 6 to 12 years in a series of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) progeny trials that were conducted on 66 test sites over southern coastal British Columbia were examined with conventional statistics and geostatistical techniques. It was found that there were large variations in tree height over the years within and among the 66 test sites. The estimated proportions of the within-site variance explained by family, row, column, patchiness, and within-plot were on average 11, 7, 5, 12, and 47%, respectively, plus 7% due to unknown factors, and the applied blocking removed about 5% of the within-site variance. Significant gradients in row and column directions were observed in more than 44 test sites, and the estimated slopes ranged in average from 0.33 to 1.52 cm/plot. Patch sizes varied greatly over the test sites and ranged in average from 5.21 to 6.47 (plots), indicating that the average patch size for these trials was 18 m across. Temporal variations were large for family variance but not much for those variance proportions explained by row, column, patchiness, and within-plot. More gradients and larger patch sizes were found with older trees. Implications of these results are discussed for forest genetic testing.
Effect of competition on genetically improved ponderosa pine seedlings
Authors: McDonald P M , Mori S R , Fiddler G O
Published: April 2011

In northern California, ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) height and diameter growth were analyzed to determine if genetically improved seedlings were more competitive than other vegetation and if they outgrew nursery stock in the field. Analysis of growth during the third through sixth growing seasons (1992-1995), indicated no statistical differences for pine height or diameter among genetic classes (control pollinated, wind pollinated, nursery run) when grown with competing vegetation. In 1995, mean height of seedlings grown with competition was 2.4 m for control-pollinated seedlings, 2.3 m for wind-pollinated seedlings, and 2.2 m for nursery-run seedlings. For seedlings grown essentially without competition, control-pollinated seedlings significantly outgrew nursery-run seedlings in height each year for the first six growing seasons. In 1995, the values were 3.0 versus 2.6 m, respectively. The competition consisted of a vigorous stand of shrubs, hardwood sprouts, forbs, and grasses. Within each genetic class, mean height and diameter of pines were significantly larger without competition.
Nitrogen and phosphorus cycling following prescribed burning in natural and managed Aleppo pine forests
Authors: Gillon D , Houssard C , Valette J C , Rigolot E
Published: April 2011

Two prescribed burnings (downhill and uphill fires) were conducted in two stands of Aleppo pine (Pinus halepensis Mill.): a natural stand and a managed stand that was subject to thinning, pruning, and shrub removal. The concentrations of nitrogen (N) and phosphorus (P) in the pine needles and regrowth of the main shrub species, Quercus coccifera L., and the quantities of N and P in the needle fall and in the forest floor were measured during the 6 months following the fires. The concentrations of N and P in the pine needles and leaves of Q. coccifera increased compared with the unburned control after both fires in the natural stand, where there was only a slight reduction in fuel during prescribed burnings and where there was an abundant fall of scorched needles. In contrast, the chemical composition of the foliage was unchanged after the fires in the managed stand, where there was a greater reduction in fuel, and where only small quantities of scorched needles fell. This study showed that first opening prescribed burnings (natural stand) were less severe in terms of nutrient balance than maintenance prescribed burnings (managed stand) and that the forest floor reduction was a good indicator of fire severity.
Seed lot, nursery, and bud dormancy effects on root electrolyte leakage of Douglas-fir (Pseudotsuga menziesii) seedlings
Authors: Folk Raymund S , Grossnickle Steven C , Axelrood Paige , Trotter Dave
Published: April 2011

The effects of seed lot, nursery culture, and seedling bud dormancy status on root electrolyte leakage (REL) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were assessed to determine if these factors should be considered when interpreting REL for seedling quality. The relationships of REL to survival, net photosynthesis (Pn), stomatal conductance (gwv), mid-day shoot water potential (Ψmid), root growth capacity (RGC), and relative height growth were determined for each factor. Nursery culture had no effect on the relationship between REL and all other measured attributes. Seed lot affected the relationship between REL and Pn, Ψmid, and survival. However, critical REL (i.e., lowest value associated with detectable root damage) and PS80 REL (i.e., level associated with an 80% probability for survival) were similar between seed lots. Bud dormancy status affected the relationship between REL and survival, RGC, and relative height growth. Control levels of REL, critical REL, and PS80 REL decreased as the number of days required for 50% terminal bud break declined. Thus, terminal bud dormancy status must be known before REL can be used to assess seedling quality. If the bud dormancy status of Douglas-fir populations is known, then critical and PS80 REL levels may be useful as indices of root damage.
Effects of alternative conifer release treatments on terrestrial gastropods in regenerating spruce plantations
Authors: Prezio John R , Lankester Murray W , Lautenschlager R A , Bell F W
Published: April 2011

This study examined changes in terrestrial gastropod density and species composition in the second and third years after the application of conifer release treatments in regenerating spruce plantations. Data were collected monthly from June to September during the summers of 1995 and 1996 from four conifer release treatments (herbicides (Vision® and Release®); motor-manual clearing (brushsaw); and mechanical clearing (Silvana Selective or Ford Versatile)) and an untreated control on each of four replicate blocks. A total of 15 083 terrestrial gastropods, comprising 18 genera and 21 species, was collected using cardboard sheets over the 2 years. Gastropod densities in untreated control areas were 50-60% greater than those in treated areas, in 1995 and 1996 (p = 0.033 and p = 0.0007, respectively). The greatest differences in densities among individual treatments were evident in the third summer following treatments (1996; p = 0.004). Declines may be attributable to decreased litter deposition and changed near-ground microclimate on the treated sites. Gastropod densities in nonchemical, cutting treatments started to recover more quickly than those in herbicide-treated sites.
Forest landscape change in the northwestern Wisconsin Pine Barrens from pre-European settlement to the present
Authors: Radeloff Volker C , Mladenoff David J , He Hong S , Boyce Mark S
Published: April 2011

Natural disturbance patterns can provide useful information for ecosystem management. Our objective was to provide a detailed spatial picture of the pre-European settlement vegetation cover for the northwestern Wisconsin Pine Barrens and to compare it with the present vegetation cover. We analyzed the presettlement conditions using an extensive data set comprised of U.S. General Land Office surveyor records from the mid-19th century and related it to the vegetation cover in 1987 as depicted in a Landsat satellite forest classification. Changes were quantified by calculating differences in abundance and relative importance of tree species at presettlement time and today. Our results revealed a strong decline of jack, red, and white pine (Pinus banksiana Lamb., Pinus resinosa Ait., and Pinus strobus L., respectively), accompanied by an increase of oak (Quercus spp.), trembling aspen (Populus tremuloides Michx.), and other hardwood species. Certain vegetation types, e.g., red pine and oak savannas, were removed from the landscape. The forest density gradient of the presettlement landscape with open savannas and woodlands in the South and denser forests in the North disappeared. These changes, especially the increase in forest cover, are ecologically significant because numerous species are adapted to open habitat, which was previously created by fire, and their populations are declining.
Species richness of ectomycorrhizal fungi in cutblocks of different sizes in the Interior Cedar-Hemlock forests of northwestern British Columbia: sporocarps and ectomycorrhizae
Authors: Durall D M , Jones Melanie D , Wright Elaine F , Kroeger Paul , Coates K Dave
Published: April 2011

We investigated the species richness of ectomycorrhizal fungi based on epigeous sporocarps in an Interior Cedar-Hemlock forest in northwestern British Columbia in gap sizes of 49-4526 m2, 3-4 years following harvest. We also determined ectomycorrhizal diversity on Pinus contorta var. latifolia Engelm. and Tsuga heterophylla (Raf.) Sarg. seedlings 2 years after outplanting. Ectomycorrhizal fungal richness, based on epigeous sporocarps, decreased exponentially as gap size increased. There were sporocarps of 15 species along 475 m of transect in gaps larger than 900 m2, which was approximately 13% of the number of species present in neighboring forests (115 species along 300 m of transect). These data have implications for foresters who would be interested in managing forests for both timber and edible mushroom harvesting. Ectomycorrhizal richness on seedlings decreased slightly at increasing distances from the edge of the intact forest. The maximum richness was found at 7 m or less from the forest edge for both tree species. The decrease in richness with distance from the forest was associated with an increase in the proportion of Thelephora mycorrhizae in the samples. The number of types of ectomycorrhizae on root systems and the number of species producing epigeous sporocarps were not correlated. These results confirm the importance of sampling both sporocarps and root tips to achieve an accurate estimate of the ectomycorrhizal fungal community in forest ecosystems.
Forest productivity and land ownership in the U.S. Lake States
Authors: Stier Jeffrey C , Kim Kwang-Koo , Marcouiller David W
Published: April 2011

The characteristics of forest growing stock and its rate of growth are important determinants of current stand value, silvicultural practice, and future productivity. The level of silvicultural practice, or management intensity, affects the productive potential of timber yield. Among forest ownership groups, the conventional wisdom holds that the forest-products industry manages lands of relatively higher productivity and applies more intensive silvicultural practices to maximize timber production. This appears to be the case throughout the United States, except in the North Central Region. We analyzed forest inventory data to test whether there are differences in potential timber productivity across ownerships and examined the relationships between land ownership and the level of growing stock productivity and net annual growth for 101 counties in the U.S. Lake States of Minnesota, Wisconsin, and Michigan. Results suggest that, in contrast with the rest of the United States, industrial private forest owners of the Lake States operate on sites of inferior quality relative to other forest owners. The most productive sites in the region are in the national forests, which also carry average levels of growing stock that are higher than those of other landowners. Constraints on timber supply from the national forests could limit the potential of regional forest products led economic growth in the Lake States.
Effect of aluminum on the growth and nutrition of tulip-poplar seedlings
Authors: Lux Heidi B , Cumming Jonathan R
Published: April 2011

Atmospheric deposition of nitrogen and sulfate is acidifying some ecosystems, potentially increasing the availability of aluminum in the soil solution. The effects of Al on tulip-poplar (Liriodendron tulipifera L.) were investigated with seedlings grown in sand culture. Seedlings were exposed to Al at four concentrations ranging from 0 to 800 µM. Reductions of 77% in shoot biomass and 71% in root biomass were observed at 200 µM Al. Aluminum reduced the concentrations of multivalent cations in leaves and roots. The Ca concentration of leaves was reduced at 400 µM Al, and the Mg concentration of roots was significantly reduced at 200 µM Al. Relationships between tissue Ca, Mg, and Al indicated that Al alters the translocation of Ca and Mg to the shoots and the accumulation of Mg in the roots. If mature trees respond in a similar fashion as seedlings noted here, then tulip-poplar has a low threshold for A1 toxicity, which may lead to declines in the health of tulip-poplar populations in ecosystems exposed to elevated levels of acidic deposition.
Effect of fertilizer on wood properties of Eucalyptus globulus
Authors: Raymond C A , Muneri A
Published: April 2011

The effects of N and P fertilizers applied to Eucalyptus globulus Labill. at plantation establishment on basic density, fibre length, fibre coarseness, predicted pulp yield, and N and P concentration in the wood were examined by sampling four fertilizer factorial trials: three in Victoria and one in Western Australia. Treatments sampled were control, maximum levels of N and P by themselves and combined. Growth responses varied across sites with significant growth responses at the Victorian sites but no response at the Western Australian site. An interaction was suggested between rainfall and the effects of the fertilizer; wood properties at the drier sites were detrimentally affected by fertilizer but there was little effect at the wetter sites. On the two drier sites, application of both N and P, alone or in combination, resulted in changes in density, shorter fibres, and slightly lower predicted pulp yield. Addition of both N and P increased the levels of these nutrients in the wood at the three Victorian sites. Changes occurred in wood properties in the absence of growth responses to the applied fertilizer indicating that these changes were not induced by changing tree growth rate.
Initial rates and limit values for decomposition of Scots pine and Norway spruce needle litter: a synthesis for N-fertilized forest stands
Authors: Berg Björn
Published: April 2011

Nitrogen fertilization increased concentrations of N, P, S, and K in Scots pine (Pinus sylvestris L.) needle litter, and in those of N, S, and Ca in Norway spruce (Picea abies (L.) Karst.). Lignin concentrations increased for both species. Initial rates and limit values for decomposition were estimated using a simple equation. For Scots pine litter, initial rates ranged between 0.0618 and 0.2986%/day with P, K, N, and Mg being positively related, but lignin and Ca negatively related. For Norway spruce, initial rates were low (0.0455-0.1007%/day) and positively related with initial concentrations of water solubles, K, and P but negatively with N, Ca, and lignin. Limit values for Scots pine litter ranged from 53.1 to 94.3% decomposition in fertilized plots and from 71.5 to 93.2% in controls. They were negatively related to N concentrations and positively to Mn and Ca. Limit values for Norway spruce litter ranged from 53.8 to 74.3% in controls and from 48 to 71.3% in fertilized plots and were positively correlated to Mn and Ca but not to N. The paper concludes that N fertilization will increase the fraction of Scots pine litter that accumulates as humus but not for Norway spruce.
Predicting tree mortality from diameter growth: a comparison of maximum likelihood and Bayesian approaches
Authors: Wyckoff Peter H , Clark James S
Published: April 2011

Ecologists and foresters have long noted a link between tree growth rate and mortality, and recent work suggests that interspecific differences in low growth tolerance is a key force shaping forest structure. Little information is available, however, on the growth-mortality relationship for most species. We present three methods for estimating growth-mortality functions from readily obtainable field data. All use annual mortality rates and the recent growth rates of living and dead individuals. Annual mortality rates are estimated using both survival analysis and a Bayesian approach. Growth rates are obtained from increment cores. Growth-mortality functions are fitted using two parametric approaches and a nonparametric approach. The three methods are compared using bootstrapped confidence intervals and likelihood ratio tests. For two example species, Acer rubrum L. and Cornus florida L., growth-mortality functions indicate a substantial difference in the two species' abilities to withstand slow growth. Both survival analysis and Bayesian estimates of mortality rates lead to similar growth-mortality functions, with the Bayesian approach providing a means to overcome the absence of long-term census data. In fitting growth-mortality functions, the nonparametric approach reveals that inflexibility in parametric methods can lead to errors in estimating mortality risk at low growth. We thus suggest that nonparametric fits be used as a tool for assessing parametric models.
Effects of elevated CO2, N-fertilization, and season on survival of ponderosa pine fine roots
Authors: Johnson M G , Phillips D L , Tingey D T , Storm M J
Published: April 2011

We used minirhizotrons to assess the effects of elevated CO2, N, and season on the life-span of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) fine roots. CO2 levels were ambient air (A), ambient air + 175 µmol·mol-1 (A + 175) and ambient air + 350 µmol·mol-1 (A + 350). N treatments were 0, 100, and 200 kg N·ha-1 per year (N0, N100, and N200, respectively). Fine root survival was strongly influenced by season and seemed to be most strongly linked to soil temperature. Roots born in the fall and winter had longer median root life-span (MRLs) than those born during the spring and summer. Elevated CO2 increased root life-span, but N fertilization decreased it. Under A, MRL was 74 ± 12 days (mean ± SE) and was significantly different from the MRL for the A + 350 treatment (102 ± 14 days). MRL under A + 175 averaged 92 ± 10 days. MRL was 116 ± 13 days for the N0 treatment and was significantly greater than MRL for the N100 (70 ± 10 days) and N200 (62 ± 14 days) treatments. Assuming that longer lived fine roots continue their resource acquisition functions, then elevated CO2 may have the effect of extending the resource acquisition period. In contrast, fine roots in N-rich environments have shorter life-spans than fine roots in N-poor environments.
Epicormic sprouting of pruned western larch
Authors: O'Hara Kevin L , Valappil Narayanan I
Published: April 2011

Western larch (Larix occidentalis Nutt.) trees in western Montana, U.S.A., were monitored for 6 years following pruning to assess incidence of epicormic sprouting. Trees were pruned to either 2.4 or 5.5 m. Epicormic sprouts were more prevalent in smaller diameter trees and in trees pruned to shorter live crown lengths than larger or longer crowned trees. Number of sprouts declined since pruning, but over 30% of trees still had epicormic sprouts 6 years after pruning. Sprouts that did not extend from the bole were prone to becoming dormant or dying over time. Extended sprouts were more persistent and will probably form wood-quality defects that remain outside the defect core. Pruning of western larch may still be successful for enhancing clearwood production if trees are pruned to retain at least a 50% live crown ratio and if pruning is delayed until trees reach about 16 cm diameter at breast height for a short pruning lift (2.4 m) or 22 cm for a higher pruning lift (5.5 m).
Armillaria species in Newfoundland
Authors: Bérubé Jean A
Published: April 2011

Crosses with standard testers were used to identify 96 haploid Armillaria isolates from 34 collections made in Newfoundland. Isoenzyme patterns were also used to identify 36 diploid and 3 haploid Armillaria isolates from 39 other collections. Diagnostic electromorphs at Rf 0.70 for esterases, Rf 0.32 for succinate dehydrogenase, and Rf 0.31 for 6-phosphogluconate dehydrogenase permitted positive identification of Armillaria ostoyae (Romagn.) Herink for all isolates tested by electrophoresis, and the method worked with haploid and diploid isolates. Crosses of the 96 haploid isolates collected on hardwoods and conifers were all positive for A. ostoyae, except for eight isolates. These eight isolates from three collections made on or near an American mountain-ash (Sorbus americana Marsh.) in a St. John's city park, where numerous exotic tree species are present, were found to be Armillaria sinapina Bérubé & Dessureault. These isolated collections in an area of limited natural hardwood presence may be the result of an introduction from the mainland; thus, A. ostoyae appears to be the only Armillaria species found in natural habitats in Newfoundland.
Action of pyridine-2-aldoxime methochloride (PAM) on neuromuscular transmission in vitro and in vivo
Authors: Goyer G. Robert
Published: April 2011

The action of pyridine-2-aldoxime methochloride (PAM) was evaluated on nerve–muscle preparations in vitro and in situ. On the isolated diaphragm of the rat, PAM shows a d-tubocurarine-like effect at concentrations higher than 6 mM. No facilitating effects were observed with lower concentrations, even when the acetylcholinesterases were inhibited to an important extent. However, the biphasic actions of PAM could be demonstrated with nerve–muscle preparations of the rat and rabbit in situ: lower concentrations produced fasciculations and twitch potentiation whereas a depressing d-tubocurarine-like effect was obtained with higher doses. The decrease in the amplitude of contraction appears to be related to an action at the myoneural junction rather than a direct toxic action on the muscle fibers themselves.
Restoration of adrenal-regeneration hypertension in corticosterone-blocked rats by ACTH
Authors: Hall C. E. , Hall O.
Published: April 2011

Adrenal-regeneration hypertension developed uniformly in uninephroadrenalectomized, contralaterally adrenal-enucleated rats, but not in uninephroadrenalectomized controls, maintained on a high salt intake. Adrenal regeneration and the accompanying hypertension were both blocked by daily administration of 1 mg of corticosterone. One unit of ACTH gel given daily had no effect on either the blood pressure or the adrenal weight of rats with uncomplicated adrenal-regeneration hypertension or those in which blood pressure elevation was blocked with corticosterone. There were no significant differences in thymus weight between any of the foregoing groups. The daily administration of 4 units of ACTH permitted only slight enlargement of the adrenals of corticosterone-blocked, adrenal-enucleated rats, or of the hypertrophying adrenals of unilaterally adrenalectomized rats. Hypertension was fully restored to the former, but was not developed in the latter. Both groups displayed a degree of thymus involution. It would appear that full morphologic regeneration is not a prerequisite of adrenal-regeneration hypertension, but that adequate steroidogenesis to support the change can be elicited from an atrophied adrenal gland by adequate ACTH stimulation. The thymolytic effect of ACTH is analyzed for its possible relevance in respect to the secretory profile of adrenosteroids.
The fat-free dry matter of epididymal adipose tissue in relation to metabolic activity
Authors: Trahan Luc , Pagé Edouard
Published: April 2011

In rats exposed to cold over a 5-week period there occurs a rise and then a partial return to initial values of the fat-free dry matter content of epididymal adipose tissue. The fat-free dry matter is also slightly higher in the right fat pad. Under such circumstances there may be some advantage in expressing metabolic activity in terms of fat-free dry matter rather than on a wet weight basis. Both methods are equally satisfactory in control rats.
The calibration of bicycle ergometers
Authors: Cumming Gordon R. , Alexander W. D.
Published: April 2011

A mechanical dynamometer was constructed to calibrate two electronic and four mechanically braked bicycle ergometers. The work required to operate an electronic ergometer may differ as much as 20% from the factory calibration. The compensation for various cycling speeds may be over 10% in error. The calibration of the mechanically braked ergometer with a weighted pendulum calibrates the braking force on the wheel, but does not take into account the frictional resistance of the chain drive, which is as low as 20 kilopond meters (kpm) at low loads, and as high as 175 kpm at high loads. The mechanical dynamometer for calibration also had a significant error of ± 20 kpm.
The source of choline for acetylcholine synthesis in a sympathetic ganglion
Authors: Collier B. , MacIntosh F. C.
Published: April 2011

Choline (Ch) and acetylcholine (ACh) uptake and release were measured by a combination of tracer and bioassay techniques in perfused superior cervical ganglia of the cat during rest and repetitive preganglionic stimulation. The uptake of labelled ACh as such was small; but when Ch (methyl-3H labelled) was present at physiological concentration (1.5 μg/ml) in the perfusion fluid, its incorporation into the ACh and free Ch pools of the ganglion proceeded linearly in the absence of stimulation, was accelerated by stimulation, and was inhibited by hemicholinium but not by hexamethonium. Up to 85% of ganglionic ACh could be replaced by labelled ACh during a 1-h stimulation period. On subsequent perfusion with fluid containing unlabelled Ch, labelled Ch was lost but labelled ACh was retained and could be released by stimulation, either as ACh in the presence or as Ch in the absence of eserine. The output of label during stimulation was approximately doubled by eserine but was unaffected by hemicholinium, which, however, prevented the formation and release of newly synthesized ACh. It appears that about half the Ch formed from released ACh is immediately recaptured and resynthesized into ACh. Newly synthesized ACh rapidly gains access to the releasable transmitter pool and may be preferentially released.
The effect of chicken and hog calcitonin on some parameters of Ca, P, and Mg metabolism in dogs
Authors: Cramer C. F. , Parkes C. O. , Copp D. H.
Published: April 2011

Partially purified calcitonin extracted from both chickens and hogs was injected intravenously into young dogs. The effects of each extract were essentially similar in causing immediate depression of both plasma Ca and P but not Mg. The preparations caused hyperphosphaturia and decreased urinary excretion of magnesium. Gut transport of Ca, P, or Mg in either direction was unaffected by the extracts.
Effects of aldosterone on blood pressure and glucose-6-phosphate dehydrogenase activity of heart muscle
Authors: Liew C. C. , Gornall A. G.
Published: April 2011

A study was made of the effects of aldosterone on the activity of heart muscle glucose-6-phosphate dehydrogenase (G6PDH) in relation to the pathogenesis of experimental hypertension. In a 17-day experiment, with rats given daily 1-μg doses of aldosterone/100 g body weight, no change in systolic pressure occurred and the specific activity (s.a.) of heart muscle G6PDH declined. Rats receiving daily 100 μg of aldosterone, or 500 μg of desoxycorticosterone acetate (DOCA) per 100 g body weight, showed a significant elevation of systolic pressure by the 17th day. This effect was accompanied by increases in the s.a. of heart muscle G6PDH, apparently preceding the development of hypertension. Evidence for a homeostatic role for aldosterone was revealed by the ability of low doses to prevent a decline in s.a. of cardiac G6PDH during fasting, and to reverse the increase produced by DOCA.
The cardiovascular and metabolic effects of epinephrine in man and their modification by beta adrenergic blocking agents
Authors: Mahon W. A. , Campbell D. J.
Published: April 2011

Normal adult patients were infused with epinephrine in a dose of 0.15 μg/kg per minute given intravenously before and after beta adrenergic blockade with propranolol, 0.1 mg/kg and butoxamine 1 mg/kg. Epinephrine produced a significant rise of heart rate, cardiac output, and blood pressure and an elevation of free fatty acids and glucose. The beta adrenergic blocking agents reversed all these effects with the exception that a rise in systolic blood pressure occurred. These findings are consistent with the hypothesis that a rise in free fatty acid is mediated by beta adrenergic stimulation whereas the rise in blood glucose produced by epinephrine is probably due to alpha adrenergic stimulation. In man, the beta adrenergic effects of butoxamine include a reversal of most of the cardiovascular as well as the metabolic effects produced by epinephrine infusion.
The effect of muscle activity factor (MAF) on cardiac contractility and sugar transport
Authors: Frederickson R. C. A. , Bihler I. , Dresel P. E.
Published: April 2011

A material has been isolated from the incubation medium of both resting and stimulated rat hemidiaphragms and tested for cardiac inotropic activity as well as for ability to enhance sugar uptake by skeletal muscle. It appears that a factor which increases glucose uptake is released from contracting muscle only, whereas a factor which increases the force of contraction of isolated failed atria is released both by contracting muscle and by muscle at rest.
The effect of erythropoietin on survival in irradiated polycythemic mice
Authors: Vittorio P. V. , Watkins E. A. , Dziubalo-Blehm S.
Published: April 2011

In mice in which polycythemia was induced by transfusion, stem cell activity was almost completely suppressed, and this was accompanied by increased resistance to radiation since survival studies showed the polycythemic mouse to be more resistant to radiation than the normal mouse. The stimulation of stem cell activity in the polycythemic mouse with the humoral factor erythropoietin produced an increase in radiation sensitivity, as measured by survival studies. This was then followed by a more radioresistant phase as stem cell activity slowed down. Thus, in the polycythemic mouse, changes in radiation sensitivity can be brought about by a change in the state of the stem cell compartment at the time of irradiation.
Location of epicardial pacemaker electrodes and myocardial contractility
Authors: Tremblay G. M. , Nahas M.
Published: April 2011

Effects of pacing from different epicardial sites on cardiac contractility were studied in the isolated perfused rat heart. An indwelling balloon containing a known volume of saline was used to record intracavitary pressure (LVP), force, and maximum dp/dt during isovolumic paced contraction. Coronary flow was kept constant, and the adequacy of oxygenation was verified by lactate extraction. Forty male Sprague–Dawley rats weighing 250–300 g were divided into two groups, according to the rate of pacing, and stimulated. Pacing from four different epicardial sites failed to show any statistically significant difference in LVP, force, or maximum dp/dt at either different heart rate or calcium concentration. The present study suggests that myocardial contractility in the isolated perfused rat heart is not affected by the pacing site of the epicardial pacemaker.
Noradrenergic innervation of the arrectores pilorum muscles of the ox (Bos taurus)
Authors: Thompson G. E. , Robertshaw D. , Findlay J. D.
Published: April 2011

The nerve supply to the arrectores pilorum muscles of the ox shows formaldehyde-induced fluorescence for primary catecholamines. These nerves disappear after cutaneous sympathectomy.
Intravascular transport of selenium by chick serum proteins
Authors: Jenkins K. J. , Hidiroglou M. , Ryan J. F.
Published: April 2011

The distribution of 75Se among various electrophoretic serum protein fractions was studied at different time intervals after the administration of the isotope to chicks. Within the first 2 h after crop intubation with H275SeO3, 33%–44% and 20%–24% of the serum protein radioactivity was located in the α2 and α3 globulins respectively. The percentage of serum protein radioactivity bound to the γ globulin increased at a rapid rate during the first 24 h. During the subsequent 24- to 173-h interval, 52%–70% of the 75Se was carried by the α2 and γ globulin fractions. The development of pectoral myopathy, as the result of a concomitant dietary deficiency of selenium, vitamin E, and cystine, had no effect on the time distribution of 75Se among the various serum protein fractions. Elevation of the dose carrier level of selenium from 2.1 μg to 300 μg caused a high proportion of the 75Se activity to become bound to the albumin during the first 28 h. When the serum proteins were doubly labeled with 75Se and 14C, the α2 and α3 globulins turned over 75Se more rapidly than the 14C label during the first 12 h after dosage. The data indicate that initially selenium is labile-bound to the α2 and α3 globulins and to albumin if the selenium dose level is high. Later, the 75Se complexed with the globulins is turned over at a slower rate than the 14C label as a preponderance of a more stable complex of protein-bound selenium develops. At this later time most of the 75Se activity is carried by the γ and α2 globulins.
Use of the Programma 101 desk-top computer in radioimmunoassay and liquid scintillation calculations
Authors: Manns J. G. , MacKenzie E. P.
Published: April 2011

Computer programs for calculating hormonal concentrations from standard radioimmunological procedures and for obtaining disintegrations per minute from liquid scintillation counting data are described. The procedures are accurate, convenient, and easily adapted to methods used in many laboratories.
Vitamin B12 absorption in dogs with chronic isolated intestinal loops
Authors: Taylor R. M. , Hildes J. A. , Lind J. F.
Published: April 2011

The absorption of physiological amounts of vitamin B12 is thought to occur only from the ileum, but the nature of the mechanism involved has not been established. A method utilizing the detection of radioactive vitamin B12 in plasma was used to investigate the mechanism of vitamin B12 absorption in dogs with isolated Thiry–Vella loops of small intestine, either ileum or jejunum. An animal with a Thiry–Vella loop of the entire ileum failed to absorb orally administered vitamin B12, but did absorb the vitamin from the isolated ileal loop when it was given with intrinsic factor, but not when given without. Attempts to restore absorption of orally administered vitamin B12 by the administration of ileal juice (either resting or stimulated), by the administration of an extract of ileal mucosa, or by the simultaneous absorption of non-radioactive vitamin B12 from the ioslated loop, all failed. In contrast, the animal with a jejunal Thiry–Vella loop absorbed vitamin B12 given orally but not when administered into the isolated jejunum alone, in combination with intrinsic factor, or with intrinsic factor and ileal juice. Under the conditions of these experiments the results confirm that vitamin B12 absorption is limited to the ileum, but fail to provide support for the hypothesis that the ileum liberates, either locally or systemically, a vitamin B12 absorption factor. Thus the hypothesis that ileal mucosa contains a special cellular mechanism for vitamin B12 absorption gains indirect support from these results.