bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Block to Mouse Mammary Tumor Virus Infection of Lymphocytes in B10.BR Mice
Authors: Okeoma Chioma M. , Shen Ming , Ross Susan R.
Published: November 2007

Classic studies on C57BL-derived mouse strains showed that they were resistant to mouse mammary tumor virus (MMTV) infection. Although one form of resistance mapped to the major histocompatibility complex (MHC) locus, at least one other, unknown gene was implicated in this resistance. We show here that B10.BR mice, which are derived from C57BL mice but have the same MHC locus (H-2k) as susceptible C3H/HeN mice, are resistant to MMTV, and show a lack of virus spread in their lymphoid compartments but not their mammary epithelial cells. Although in vivo virus superantigen (Sag)-mediated activation of T cells was similar in C3H/HeN and B10.BR mice, T cell-dependent B-cell and dendritic cell activation was diminished in the latter. Ex vivo, B10.BR T cells showed a diminished capacity to proliferate in response to the MMTV Sag. The genetic segregation of the resistance phenotype indicated that it maps to a single allele. These data highlight the role of Sag-dependent T-cell responses in MMTV infection and point to a novel mechanism for the resistance of mice to retroviral infection that could lead to a better understanding of the interplay between hosts and pathogens.
The Spike Glycoprotein of Murine Coronavirus MHV-JHM Mediates Receptor-Independent Infection and Spread in the Central Nervous Systems ofCeacam1a−/−Mice
Authors: Miura Tanya A. , Travanty Emily A. , Oko Lauren , Bielefeldt-Ohmann Helle , Weiss Susan R. , Beauchemin Nicole , Holmes Kathryn V.
Published: November 2007

The MHV-JHM strain of the murine coronavirus mouse hepatitis virus is much more neurovirulent than the MHV-A59 strain, although both strains use murine CEACAM1a (mCEACAM1a) as the receptor to infect murine cells. We previously showed thatCeacam1a−/−mice are completely resistant to MHV-A59 infection (E. Hemmila et al., J. Virol. 78:10156-10165, 2004). In vitro, MHV-JHM, but not MHV-A59, can spread from infected murine cells to cells that lack mCEACAM1a, a phenomenon called receptor-independent spread. To determine whether MHV-JHM could infect and spread in the brain independent of mCEACAM1a, we inoculatedCeacam1a−/−mice. AlthoughCeacam1a−/−mice were completely resistant to i.c. inoculation with 106PFU of recombinant wild-type MHV-A59 (RA59) virus, these mice were killed by recombinant MHV-JHM (RJHM) and a chimeric virus containing the spike of MHV-JHM in the MHV-A59 genome (SJHM/RA59). Immunohistochemistry showed that RJHM and SJHM/RA59 infected all neural cell types and induced severe microgliosis in bothCeacam1a−/−and wild-type mice. For RJHM, the 50% lethal dose (LD50) is <101.3in wild-type mice and 103.1inCeacam1a−/−mice. For SJHM/RA59, the LD50is <101.3in wild-type mice and 103.6inCeacam1a−/−mice. This study shows that infection and spread of MHV-JHM in the brain are dependent upon the viral spike glycoprotein. RJHM can initiate infection in the brains ofCeacam1a−/−mice, but expression of mCEACAM1a increases susceptibility to infection. The spread of infection in the brain is mCEACAM1a independent. Thus, the ability of the MHV-JHM spike to mediate mCEACAM1a-independent spread in the brain is likely an important factor in the severe neurovirulence of MHV-JHM in wild-type mice.
A Conserved Motif in Region V of the Large Polymerase Proteins of Nonsegmented Negative-Sense RNA Viruses That Is Essential for mRNA Capping
Authors: Li Jianrong , Rahmeh Amal , Morelli Marco , Whelan Sean P. J.
Published: November 2007

Nonsegmented negative-sense (NNS) RNA viruses cap their mRNA by an unconventional mechanism. Specifically, 5′ monophosphate mRNA is transferred to GDP derived from GTP through a reaction that involves a covalent intermediate between the large polymerase protein L and mRNA. This polyribonucleotidyltransferase activity contrasts with all other capping reactions, which are catalyzed by an RNA triphosphatase and guanylyltransferase. In these reactions, a 5′ diphosphate mRNA is capped by transfer of GMP via a covalent enzyme-GMP intermediate. RNA guanylyltransferases typically have a KxDG motif in which the lysine forms this covalent intermediate. Consistent with the distinct mechanism of capping employed by NNS RNA viruses, such a motif is absent from L. To determine the residues of L protein required for capping, we reconstituted the capping reaction of the prototype NNS RNA virus, vesicular stomatitis virus, from highly purified components. Using a panel of L proteins with single-amino-acid substitutions to residues universally conserved among NNS RNA virus L proteins, we define a new motif, GxxT[n]HR, present within conserved region V of L protein that is essential for this unconventional mechanism of mRNA cap formation.
Autofluorescent and ultraviolet-absorbing components in cell walls and papillae of barley coleoptiles and their relationship to disease resistance
Authors: Aist James R. , Israel Herbert W.
Published: November 2007

Earlier studies showed that normal-size papillae induced in barley coleoptile epidermal cells by Erysiphe graminis f. sp. hordei were less effective in resisting fungal penetration attempts than were oversize papillae. To determine if a differential content of phenolic derivatives could account for this difference in resistance, we analyzed normal papillae and oversize papillae by histochemical, epifluorimetric, and ultraviolet-microspectrophotometric methods. Whereas the histochemical tests revealed phenolic derivatives only in oversize papillae, the autofluorescence and ultraviolet-absorption properties indicated that both types of papillae contain phenolics. Ultraviolet-absorption spectra indicated that the phenolics were primarily phenylpropanoid groups. Phenolics in papillae were distinct from both those in the secondary wall thickenings of coleoptile xylem vessel elements and those in the periclinal walls of coleoptile epidermal cells. The deposition of phenolics in oversize papillae long before they were challenged by the fungus, the presence of certain phenolics that, tentatively, were detected histochemically only in the oversize papillae, or both could have rendered them resistant to penetration by the fungus.
Environmental pH influences growth and tissue chemistry of the submersed macrophyte Vallisneria americana
Authors: Grisé David , Titus John E. , Wagner Daniel J.
Published: November 2007

Wild celery (Vallisneria americana, Hydrocharitaceae) is a common submersed freshwater macrophyte rarely reported from lakes with pH below 6. Plants grown in a greenhouse on a uniform sediment within pH-controlled tanks all survived 60 days at pH 5 but showed reduced dry matter accumulation (by 76%), leaf area (by 79%), and rosette and winter bud production (by 44 and 63%, respectively) compared with plants grown at pH 7.5. The sensitivity of this plant to only moderate acidity did not differ for plants in water acidified to pH 5 by a combination of H2SO4 and HNO3 or by HCl, indicating that the former acids exerted no fertilizing effects to counter the detrimental influence of acidification. Tissue nitrogen and phosphorus levels were well above the critical concentrations previously reported for this species. Tissue calcium and manganese concentrations showed no clear relationship to treatment pH. Both aluminum and iron levels in tissues were twofold to threefold higher for the smaller plants grown at pH 5 (means of 1970 and 3090 μg/g, respectively), suggesting that metal toxicity may have caused growth reduction at low pH.
Monoclonal antibodies to isolate-, species-, and genus-specific components on the surface of zoospores and cysts of the fungus Phytophthora cinnamomi
Authors: Hardham A. R. , Suzaki E. , Perkin J. L.
Published: November 2007

Monoclonal antibodies have been raised to components on the surface of glutaraldehyde-fixed zoospores and cysts of an isolate of the pathogenic fungus Phytophthora cinnamomi. Hybridoma supernatants were screened using an immunofluorescence assay, and of 35 cell lines producing antibodies that reacted with the P. cinnamomi cells, 10 have been selected and their specificities examined in detail. The monoclonal antibodies were found to possess a valuable spectrum of taxonomic specificities, and have revealed, for the first time, the presence of isolate-specific antigens on the surface of P. cinnamomi cells. The monoclonal antibodies were tested against six isolates of P. cinnamomi, six species of Phytophthora, and three species of Pythium. In addition to the isolate-specific monoclonal antibodies, species-specific and genus-specific markers which are unambiguous in tests conducted so far have been obtained. The monoclonal antibodies have also revealed the presence of spatially restricted antigens on the surface of the zoospores. Some of these segregated antigens are species-specific and others are more general, occurring in all Phytophthora and Pythium species examined. All of the monoclonal antibodies promise to be of great assistance in investigations of the biology and taxonomy of P. cinnamomi. The methods described should be readily applicable to studies of other fungal pathogens.
Wave and nonwave regeneration processes in a subalpine Abies balsamea forest
Authors: Moloney Kirk A.
Published: November 2007

An investigation was conducted on Whiteface Mountain, New York, to determine if the dynamics of the dominant tree species, Abies balsamea, were similar among two wave areas and one nonwave area of subalpine fir forest. Associated understory populations of vascular and bryophyte species were also studied to determine their response to changes in the organization of the Abies balsamea canopy. The regeneration cycles of the wave and nonwave areas exhibited strong parallels. However, some differences were noted, particularly with respect to the transition between generations of trees. Changes in understory populations were associated with changes in the organization of the Abies balsamea population, but to differing degrees dependent upon location. It is suggested that fir wave formation is the result of the interaction between an underlying demographic process common to both wave and nonwave regions (the Abies balsamea regeneration cycle) and a directional stress imposed on the canopy by prevailing winds. This implies that wave formation does not result from a major reorganization of the demographic structure of the Abies balsamea population, but from a reorganization of the spatial distribution of regeneration stages.
Genetic evidence for a single functional deficiency in isolates of Nectria haematococca unable to demethylate pisatin
Authors: Cowling W. A. , VanEtten H. D.
Published: November 2007

Previous evidence suggests that pisatin-demethylating ability (PDA+) is necessary for tolerance of pisatin and for high virulence of Nectria haematococca on pea and that positive alleles at any one of at least three loci can give a PDA+ phenotype. A number of naturally occurring isolates of this fungus lack the ability to demethylate pisatin, but it is not known whether the PDA− phenotype is always due to the presence of negative alleles at all three of the previously studied genes. We have attempted to identify other functional classes of pda genes by searching for PDA+ recombinants among the ascospore progeny of crosses between PDA− isolates. A method was developed to detect rare PDA+ recombinants in a mixed culture containing a large number of PDA− progeny. No PDA+ recombinants were detected from 99 crosses of PDA− isolates when analysed by this method, nor were any detected among 171 ascospore progeny assayed individually. Complementary heterokaryons for the PDA+ phenotype were not formed from mixtures of 37 PDA− isolates when they were grown together on a pisatin-amended medium that was inhibitory to the PDA− isolates. No evidence was found to suggest that the PDA− phenotype can be caused by genes with different functions in N. haematococca.
An overview of the hydrologic concerns related to wetlands in the United States
Authors: Carter Virginia
Published: November 2007

There is a tremendous diversity in wetland types and wetland vegetation in the United States, caused primarily by regional, geologic, topographic, and climatic differences. Wetland hydrology, a primary driving force influencing wetland ecology, development, and persistence, is as yet poorly understood. The interaction between groundwater and surface water and the discharge–recharge relationships in wetlands affect water quality and nutrient budgets as well as vegetative composition. Hydrologic considerations necessary for an improved understanding of wetland ecology include detailed water budgets, water chemistry, water regime, and boundary conditions. Wetland values are often based on perceived wetland functions. These hydrologic functions include (i) flood storage and flood-peak desynchronization, (ii) recharge and discharge, (iii) base flow and estuarine water balance, and (iv) water-quality regulation. Expanded research and basic data collection focussed on wetland hydrology and its relation to wetland ecology are needed to identify and quantify the hydrologic functions of wetlands.
Hydrology, development, and biogeochemistry of ombrogenous peat bogs with special reference to nutrient relocation in a western Newfoundland bog
Authors: Damman Antoni W. H.
Published: November 2007

Ombrogenous bogs differ fundamentally from other peatlands in their hydrology, and this affects peat accumulation and bog development as well as the elemental concentrations in peat and water. In oceanic and northern parts of the raised bog zone, the surface of the bog center remains below the critical profile of the water mound because factors other than moisture supply limit its maximum height. In the surface peat, Na and K decrease with depth, whereas other elements increase to a greater or smaller extent. Most elements occur in surprisingly low concentrations below the anaerobic level. In an ombrotrophic bog in western Newfoundland, Na, Mg, and Ca concentrations of bog water were 5, 4–5, and 0.5 times higher, respectively, than in precipitation. K and Mg increased downslope, especially in spring, but not during the vegetation season. In July and August, 20–30% of the Mg, 75–80% of the K, and 93% of the Ca are removed from the precipitation while the water seeps over the bog. Uptake by vegetation is primarily responsible, but Ca is mostly adsorbed on the peat. Increased water flow, rather than higher nutrient concentration, appears to account for the occurrence of more nutrient-demanding species, such as Nymphaea odorata and Utricularia vulgaris, in the pools of the lower slope.
Some aspects of Sphagnum ecology
Authors: Andrus Richard E.
Published: November 2007

Sphagnum species are ecologically prominent wetland plants with xerophytic adaptations and succession-directing acidification capabilities. Species are organized along environmental gradients of pH, cation concentrations, hummock and hollow, wet versus dry, shade versus sun, coastal versus inland, and cold versus warm. The known factors responsible for this organization include cation-exchange capacity, desiccation tolerance, desiccation resistance, water-holding capacity, drying rates, and photosynthetic response at differing water contents. Small-scale distribution of Sphagnum species can be better explained for ombrotrophic sites than for minerotrophic sites.
How endemic injuries affect early growth of aspen suckers
Authors: Perala Donald A.
Published: November 2007

The number and stem position of three endemic disease- and insect-caused injuries, shoot dieback, galls, and lesions, were monitored during the first 7 years of development of aspen (Populustremuloides Michx.) sucker stands on both a good and an excellent site. Injury frequency was significantly higher on the good site compared with the excellent site. Only shoot dieback clearly had a negative effect on height growth and tree class differentiation. Galls and lesions were related directly to bole area but not tree class. These injuries healed rapidly and most were undetectable within a few years. The apparently high incidence of insect- and disease-induced injury is normal in aspen sucker stands. Tree mortality was caused by intraspecific suppression and was not enhanced by any of these injuries. Although growth is undoubtedly diminished owing to injury, productivity of these stands should meet or exceed historical expectations. The effect of site quality, stocking density, and other stand variables on the influence of insect- and disease-induced injury needs controlled experimentation to assess their roles in affecting aspen productivity.
Organic matter and nitrogen content of the forest floor in even-aged northern hardwoods
Authors: Federer C. Anthony
Published: November 2007

Organic content of the forest floor decreases for several years after clear-cutting, and then slowly recovers. Thickness, bulk density, organic matter, and nitrogen content of forest floors were measured for 13 northern hardwood stands in the White Mountains of New Hampshire. Stands ranged from 1 to about 100 years in age. Forest-floor thickness varied significantly with stand age, but bulk density, organic fraction, and nitrogen fraction were independent of age. Total organic content of the forest floor agreed very well with data from Covington's (W. W. Covington 1981. Ecology, 62: 41–48) study of the same area. Both studies indicated that mature forest floors have about 80 Mg organic matter•ha−1 and 1.9 Mg nitrogen•ha−1. Within 10 or 15 years after cutting, the organic matter content of the floor decreases to 50 Mg•ha−1, and its nitrogen content to 1.1 Mg•ha−1. The question whether the decrease is rapid and the minimum broad and flat, or if the decrease is gradual and the minimum sharp, cannot be answered. The subsequent increase to levels reached in mature forest requires about 50 years. Some of the initial decrease in organic matter and nitrogen content of the forest floor may be caused by organic decomposition and nitrogen leaching, but mechanical and chemical mixing of floor into mineral soil, during and after the harvest operation, may also be important. The difference is vital with respect to maintenance of long-term productivity.
Survival and early growth of white ash provenances and progenies in 19 plantations
Authors: Clausen Knud E.
Published: November 2007

White ash from many geographic origins was planted in 19 locations throughout the natural range of the species. Each plantation contained 36–52 families and 16–27 provenances from portions of the range near its geographic location. Survival after 5 years ranged from 97 to 46% and differed among provenances in 12 plantations. Provenances accounted for up to 55% of the variation in survival, and the variance component for provenances was greater than the family component in 14 plantations. Average tree height after 5 years ranged from 53 cm in northern Wisconsin to 373 cm in Alabama, and differed among provenances in 12 plantations. Provenance variation was generally larger than family variation and provenances accounted for up to 75% of the variation in height. Neither survival nor height was closely correlated with latitude of seed origin except in plantations near the southern and northern extremes of the natural range. In some plantations the family variance component was much greater than the provenance component, and in others the family component increased from the 3rd to the 5th year. This suggests that gains are also possible through family selection once suitable provenances have been identified.
A simple production function model for variable density growth and yield modeling
Authors: Chang Sun Joseph
Published: November 2007

This paper proposes a logarithmic–reciprocal yield function that improves upon the function proposed by Nautiyal and Couto (J. C. Nautiyal and L. Couto. 1982. Can. J. For. Res. 12: 452–458) by allowing forest crops starting with different stocking levels to eventually approach the same volume and peaking of the current annual increment (CAI) at different ages of the stands. The function is then used to fit yield data generated from Smalley and Bailey's study (Smalley, G. W., and R. L. Bailey. 1974. U.S. For. Serv. Res. Pap. SO–96) that shows wobbles in CAI and changes in yield as a result of changes in planting density. The basic model is then expanded by incorporating site index to account for local differences in productivity. Finally, compatible growth functions that can be estimated with log differences in yield instead of instantaneous growth are also derived.
Nutrient fluxes in litterfall and decomposition in four forests along a gradient of soil fertility in southern Ohio
Authors: Boerner Ralph E. J.
Published: November 2007

To determine how soil nutrient availability influences nutrient cycling, fluxes of nutrients through litterfall and decomposition were determined for four forest stands similar in all respects except soil nutrient availability and microclimate, within Neotoma Valley, a small watershed in southern Ohio, U.S.A. Litterfall varied from 10 to 60% among sites while nutrient concentrations and masses in new leaf litter varied as a function of extractable soil nutrient levels. Mass loss from litterbags was significantly higher in more fertile sites. Stepwise regression indicated that initial litter nitrogen and phosphorus concentrations were strongly correlated with relative decomposition rate while lignin concentration and microclimate variables were only correlated weakly. Thus, both litterfall nutrient transfers and decomposition rates were under the control of soil nutrient levels. Nitrogen was immobilized in litter at all sites during the 1st year of decay; litter from more fertile sites mineralized nitrogen during the 2nd year, while that from less fertile sites continued to immobilize nitrogen. Phosphorus and calcium mineralization rates were strongly correlated with the availability of these elements in the soil. Magnesium and potassium were leached rapidly from litter; amounts mineralized were correlated with amounts in litterfall. Interrelations among soil fertility, litterfall, and nutrient mineralization, as well as litter redistribution, are discussed as processes important in the development and maintenance of the soil fertility gradient in this watershed.
Electrical resistance and capacitance measurements on young, spaced and unspaced, defoliated and protected, balsam fir trees
Authors: Piene H. , Fensom D. S. , McIsaac J. E. , Thompson R. G. , Alexander K. G.
Published: November 2007

Electrical resistance and capacitance were measured in 1981 and 1982 on 25- to 30-year-old spaced and unspaced, defoliated and protected balsam fir (Abiesbalsamea (L.) Mill.) trees on the Cape Breton Highlands, Nova Scotia. Significantly higher average electrical resistance readings were observed for the spaced and unspaced, defoliated trees than for the comparable protected trees. With one exception, the average capacitance was significantly lower in defoliated compared with protected trees. In general, for both the defoliated and protected trees, decreases in average electrical resistance were associated with increases in foliar biomass. Caution has to be taken when monitoring electrical properties in the field because of seasonal cyclic patterns, and aberrations in tissues of dying or dead trees.
Variance estimation for volume when D2H is the covariate in regression
Authors: Schreuder H. T. , Anderson Jana
Published: November 2007

For two realistic (but not real) populations of loblolly pine, variance estimators for weighed regression estimates of total volume are compared. The traditional variance estimators and two robust variance estimators proposed by Royall and Cumberland (R. M. Royall and W. G. Cumberland. 1981. JASA, J. Am. Stat. Assoc. 76: 924–930) are found to be quite unreliable. In contrast, the jackknife variance estimate and confidence intervals based on it are found to be much more reliable.
Juvenile–mature relationships and heritability estimates of several traits in loblolly pine (Pinustaeda)
Authors: Loo Judy A. , Tauer C. G. , Buijtenen J. P. van
Published: November 2007

Heritability estimates for wood specific gravity of loblolly pine (Pinustaeda L.) in east Texas were high and relatively constant for all ages of wood sampled, but tracheid length was found to have low heritability at all ages. Heritability estimates for tracheid length declined with age after age 4 years. Coefficients of genetic prediction indicated that specific gravity of age 2 wood is a reliable predictor of wood specific gravity at age 25. Genetic covariances between juvenile and mature tracheid length were approximately zero. Coefficients of genetic prediction and genetic correlations between specific gravity and height and diameter at age 20 years indicated a strong negative relationship.
Relative control of air temperature and water status on seasonal transpiration of Pinuscontorta
Authors: Graham Jeff S. , Running Steven W.
Published: November 2007

Leaf conductance was measured periodically from early spring until October for three Pinuscontorta Dougl. saplings in Western Montana on a harsh site exhibiting low temperatures, high absolute humidity deficits, and substantial soil moisture depletion. Springtime maximum daily leaf conductance was correlated with previous night minimum air temperature and a seasonal temperature summation (R2 = 0.93). Summer leaf conductance was correlated with predawn leaf water potential and absolute humidity deficit (R2 = 0.87). To assess the significance of these leaf conductance controls to the seasonal water balance of a forest stand on this site, regression equations relating leaf conductance to environmental parameters were incorporated into a stand hydrologic model. Removing spring air temperature controls of leaf conductance was estimated to increase transpiration in May and June by 47%; however, overall seasonal transpiration was increased by only 8%. Summer humidity and predawn water potential controls were found necessary to prevent lethal water stress.
Availability of carbon-bonded sulfur for mineralization in forest soils
Authors: Fitzgerald J. W. , Andrew T. L. , Swank W. T.
Published: November 2007

The capacities of soil from hardwood, clear-cut, and pine forests of the Coweeta basin to mineralize, adsorb; and incorporate into Organic matter carbon-bonded sulfur in the form of L-methionine was investigated. These soils adsorbed and incorporated between 40 and 66% of this amino acid within a 0.5-h incubation period, but much of the immobilized sulfur was mineralized after 48 h incubation. Ah additional hardwood forest (watershed 18) was chosen for further study of the incorporation process in both litter and mineral horizons. The O2 forest floor layer exhibited the highest levels of activity in samples taken along a transect of this watershed. Incorporation of methionine into the organic matter of these samples was complete within about 12 h of incubation and was inhibited by pretreatment of the samples with sodium azide; a general inhibitor of cell respiration. The capacities for methionine incorporation determined invitro complement observations of the high levels of carbon bonded sulfur found insitu in forest litter and soil.
Gibberellic acid induced growth acceleration in Populus hybrids
Authors: Rood S. B. , Daicos G. , Blake T. J.
Published: November 2007

Weekly applications of 0.4 mg gibberellic acid (GA) in 8 μL 95% ethanol micropipetted onto shoots of rooted cuttings increased Populuseuramericana (Dode) Guinier height growth by 54% and shoot dry weight by 25% after 21 days. Total leaf area increased by 21% as a result of more rapid leaf production and slightly larger leaf sizes. Root growth was unaffected by GA treatment. The observed GA-induced acceleration resulted from an increase in relative growth rate while mean net assimilation rate was unaffected. Owing to a substantial increase in the number and size of leaves, the leaf area ratio, representing the ratio of photosynthesizing to respiring material, increased. While direct micropipette application of GA promoted height growth and primary shoot dry weight accumulation, GA application through either foliar spray or soil drench also promoted the growth of secondary shoots. Application of GA to shoots was more effective in promoting shoot growth than application through the roots. Direct GA application also promoted the growth of P. alba L. × P. grandidentata Michx. and P. × canescens (Ait.) Smith × P. alba × P. grandidentata. Thus, GA can be used for hastening early growth of these trees under winter greenhouse conditions.
Soil nitrogen concentration and Juglansnigra growth in mixed plots with nitrogen-fixing Alnus, Elaeagnus, Lespedeza, and Robinia species
Authors: Friedrich John M. , Dawson Jeffrey O.
Published: November 2007

Soil samples and black walnut (Juglansnigra L.) measurements were taken in plots of a 14-year-old plantation combining two walnut spacings with four interplanted nitrogen-fixing species and a control, lnterplantings of walnut with black locust (Robiniapseudoacacia L.) and autumn-olive (Elaeagnusumbellata Thunb.) had the highest total soil nitrogen concentrations in the top 30 cm of soil, followed by European alder (Alnusglutinosa L. [Gaertn.]), lespedeza clover (Lespedezastriata [Thunb.] Hook & Arn.), and control plots. Soil nitrogen concentrations were greatest in the surficial 6 cm of soil. At the closer, 3.7- by 4.9-m spacing in autumn-olive plots where walnut growth and competition were greatest, and at both spacings in plots with girdled black locust, nitrogen concentrations in the soil were especially high. This is consistent with speculation that recent stress on autumn-olive from walnut competition and stress on locust from past stem girdling resulted in increased inputs of nitrogen into soil. Walnut size was greatest by far in autumn-olive plots, where the spreading form of the shrub afforded soil shading and weed control. Walnut size was generally greater in mixed plots at the wider 3.7 m by 9.8 m spacing, where walnut competition with itself was least. However, walnut basal area was not strongly correlated with mean total soil nitrogen concentration of the top 30 cm of soil in a plot (r2 = 0.32 at closer walnut spacings), suggesting that the net accretion of nitrogen in soil accounted only in part for measured differences in walnut growth in mixed plantings with nitrogen-fixing plants.
Multistage sampling with partial replacement
Authors: Omule Stephen A. Y.
Published: November 2007

Multistage sampling is a cost-effective technique for obtaining samples in large-scale sampling situations. If the sampling is repeated over time, the application of successive sampling with partial replacement (SPR) is advantageous. In this paper, some theory of SPR when the sampling design is multistage, is considered. Estimators of the population mean and the change in the mean over successive occasions, together with their respective variances, are derived without the restrictive assumptions of equal sample sizes and (or) equal variances at each stage of the multistage design on the successive occasions. The derivation is restricted to a two-stage design on two successive occasions, although sufficient background is presented to enable the reader to extend the theory to other than the two-stage design.
Effects of thinning and urea fertilization on the distribution of area increment along the boles of Douglas-fir at Shawnigan Lake, British Columbia
Authors: Thomson A. J. , Barclay H. J.
Published: November 2007

The effects of fertilization and thinning of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) on the distribution of area increment along the bole were assessed using radial growth measurements 6 and 9 years after treatment. Within treatments, the average area increment per tree was linearly related to diameter at breast height, and this relationship was used to evaluate the effects of treatment on growth rate. Fertilization had the greatest effect on average area increment, and for a particular fertilization regime, thinning increased the response. Thinning modified the distribution of growth over the bole of all trees and increased butt flare, especially in smaller trees. The effect declined from the 4- to 6-year measurement period to the 7-to 9-year measurement period. Fertilization had no consistent effect on growth distribution. The regression methods used in this study provided a more sensitive measure of form changes than previous methods, were independent of size distribution, and facilitated extrapolations and evaluation of temporal trend.
Effects of ectomycorrhizae and solution pH on [15N]nitrate uptake by coniferous seedlings
Authors: Rygiewicz Paul T. , Bledsoe Caroline S. , Zasoski Robert J.
Published: November 2007

The interacting effects of mycorrhizae and pH on nitrate uptake by three native Northwest coniferous species were examined. Seedlings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), Sitka spruce (Piceasitchensis (Bong.) Carr.), and western hemlock (Tsugaheterophylla (Raf.) Sarg.) were grown for several months, and then half of the seedlings were inoculated with the ectomycorrhizal fungus Hebelomacrustuliniforme (Bull, ex St. Amans) Quél. In a series of experiments, pH was continuously maintained at set levels and fluxes of nitrate, potassium, calcium, and hydroxide ions were measured. While both coniferous species and mycorrhizae did affect nitrate uptake rates, the major effect on nitrate uptake rates was due to solution pH. Nitrate uptake rates generally increased with increasing pH from pH 2.5 to 7.5, as did calcium flux rates, which changed from efflux at low pH to uptake at higher pH levels. Potassium was released from the roots at all pH levels. Hydroxide ion release rates decreased with increasing pH, resulting in hydrogen ion release above pH 5.5. Mycorrhizal roots often released fewer hydroxide ions per nitrate ion taken up than did nonmycorrhizal roots, leading to the suggestion that mycorrhizae may act as rhizosphere buffers. Among the three coniferous species, Douglas-fir roots released more hydroxide ions per nitrate taken up than did western hemlock; Sitka spruce values were intermediate. These apparent species effects may be related to the less acidic mineral soil environment where Douglas-fir roots are often found, and to the more acidic forest floor environment where western hemlock roots primarily grow.
Conifers and broadleaf species: stomatal sensitivity differs in western Oregon
Authors: Marshall J. D. , Waring R. H.
Published: November 2007

Increasing stomatal closure was exhibited by two conifer and six broadleaf species as vapor pressure deficit increased. Conifers were more sensitive to high vapor pressure deficit than were the broadleaved species. One shrub, snowbrush (Ceanothusvelutinus Dougl. ex Hook.), exhibited no stomatal closure as vapor pressure deficit increased. These traits, when interpreted in terms of known soil moisture depletion patterns, help explain why broadleaved species initially colonize disturbed areas in western Oregon, but are later replaced by long-lived conifers.
Comparative carbon dioxide exchange for two Populus clones grown in growth room, greenhouse, and field environments
Authors: Nelson Neil D. , Ehlers Paul
Published: November 2007

Light-saturated net photosynthetic rates per unit leaf area were 1.6–2.1 times greater for the photosynthetically mature leaves of plants of two hybrid Populus clones (NC-5260, 'Tristis No.1' (Populustristis Fisch. × P. balsamifera L.); NC-5326, 'eugenei' (P. deltoides Bartr. ex Marsh. × P. nigra L.)) grown in pots in the field than in comparable plants from a controlled environment growth room and a winter greenhouse. Stomatal resistances to CO2 in the field trees were only 0.4–0.6 of those in growth room and greenhouse trees. Mesophyll (residual) resistances to CO2 in field trees were 0.4–0.8 of those in growth room and greenhouse trees. Field plants had specific leaf weights 1.5–1.8 times higher than growth room and greenhouse plants, likely primarily owing to the greater average photosynthetic photon flux density in the field (835, 225, and 142 μE m−2 s−1 for field, growth room, and greenhouse conditions, respectively). When net photosynthetic rates (Ps) were corrected for the differences in specific leaf weights to derive net photosynthetic rate per unit leaf dry weight, the values were similar for plants from the three environments (Ps in field trees was 0.9–1.2 times Ps in growth room and greenhouse trees); gross photosynthetic rates per unit leaf weight were even more similar. Internal leaf CO2 concentrations, and photorespiration and dark respiration rates per unit leaf area were not related to growth environment. However, photorespiration rate as a percentage of net photosynthetic rate was lower in the field trees (12–16% in field trees, 19–24% in growth room trees, and 23–39% in greenhouse trees). Net photosynthetic rate was shown to be under strong genetic control in these clones. The effects of growth environment on variables of carbon exchange are sensitive to the basis of expression of those variables.
Conducting sapwood area, foliage area, and permeability in mature trees of Piceasitchensis and Pinuscontorta
Authors: Whitehead D. , Edwards W. R. N. , Jarvis P. G.
Published: November 2007

The relationships between foliage area and sapwood area between trees and within the crowns of 20 Piceasitchensis (Bong.) Carr., provenance Queen Charlotte Island, British Columbia (10 in a control plot and 10 in a plot fertilized with potassium and phosphorus 8 years before harvest) and 10 Pinuscontorta Dougl., provenance Ladysmith trees were examined using a physiological analysis based on Darcy's law. Foliage area index on the fertilized P. sitchensis plot was higher than on the control. The variation of foliage area density with depth in the canopies followed a normal distribution. Relationships between foliage area and sapwood basal area were linear but the slopes were different for the two species. There was no significant difference between the control and fertilized P. sitchensis trees. The relationship between foliage area and the product of sapwood area and permeability was linear and data from the three plots fell on the same line. Sapwood area, permeability, and their product decreased with depth through the crowns of the trees. Within the crowns, relationships between cumulative foliage area and sapwood area, and between cumulative foliage area and the product of sapwood area × permeability were different with species and treatment. A single linear relationship resulted when the product of cumulative foliage area above an internode × the internode length was plotted against sapwood area × permeability for the internode. This suggests that it is the drop in potential across a node and internode rather than the gradient of potential across the internode that is related to the flux of water through tree crowns. The data support the hypothesis that the relationship between foliage area and sapwood area depends on permeability of the sapwood and the local climate through its influence on transpiration rate, particularly via average water vapour pressure deficit of the air and stomatal conductance.
Seasonal and diurnal patterns in leaf gas exchange of Eucalyptusglobulus trees growing in Portugal
Authors: Pereira J. S. , Tenhunen J. D. , Lange O. L. , Beyschlag W. , Meyer A. , David M. M.
Published: November 2007

Gas exchange of adult leaves of Eucalyptusglobulus Labill. trees growing in Portugal was monitored during weekly periods between September 1982 and August 1983. Photosynthetic carbon assimilation rates and leaf water use efficiency were highest (maximum instantaneous values, ca. 12 μmol CO2 m−2 s−1 and ca. 7 mmol CO2 mol H2O−1, respectively) in the spring, somewhat reduced in the winter, and strongly depressed by the middle of the summer, when severe drought conditions prevailed. Diurnal patterns of variation in stomatal conductance and net photosynthesis rates showed a marked seasonal variation. With the transition from winter to spring and summer, as the environmental conditions became warmer and drier, there was an increasing tendency for a midday depression in gas exchange rates as well as a decreasing capacity in the afternoon for recovery to the same net photosynthesis rates measured in the morning. Midday depression in gas exchange and stomatal conductance occurred in leaves positioned both vertically and horizontally inside the measurement cuvettes. Leaf dark respiratory rates also changed with the season; the temperature necessary to evoke similar rates increased with the transition from winter to summer.
Influence of shoot age on growth and nutrient uptake patterns in a willow plantation
Authors: Nilsson Lars Owe , Ericsson Tom
Published: November 2007

The seasonal patterns of growth and nutrient uptake of a short-rotation Salixviminalis L. plantation located along the southeastern coast of Sweden were investigated during 1981. One-year-old shoots of clone 683 yielded 9.6 t dry weight ha−1 of stems and 4.2 t dry weight ha−1 of leaves; whereas the same cultural treatment during the 2nd year after coppicing yielded 13.3 and 8.2 t dry weight ha−1, respectively. Maximums in foliage dry weight occurred between early August and early September in the older shoots (6.3 t ha−1) and in late September in the younger shoots (3.5 t ha−1). Foliage and stem growth early in the season were markedly higher in the 2-year-old shoots than in the 1-year-old shoots. N uptake increased rapidly shortly after the first fertilizer application in all three investigated plots. Aboveground N uptake ranged from 140 to 191 kg ha−1 year−1. From the onset of liquid fertilization until the end of the growing season the aboveground N uptake ranged from 92 to 98 kg N ha−1; the total N fertilization during this period was 120 kg N ha−1. Nitrogen productivity varied between clones and was higher for 2- than for 1-year-old shoots. Greater relative amounts of biomass and N were allocated to leaves on the 2-year-old shoots. The amount of N allocated to stems for producing 11 of stem biomass decreased from 4.3 to 2.5 kg during the 2nd year after coppicing.
Stream bed configuration and stability following gabion weir placement to enhance salmonid production in a logged watershed subject to debris torrents
Authors: Klassen H. D. , Northcote T. G.
Published: November 2007

Tandem V-shaped gabion weirs for improving spawning habitat for salmon (Oncorhynchus spp.) were installed to replace large organic debris at three sites below the terminus of a debris torrent in Sachs Creek, Queen Charlotte Islands. Stream conditions were compared between gabion and nearby control sites. The stability of added and entrapped gravel at all gabion sites was poor over the first winter and excessive scour threatened the integrity of the upstream steeper (3%) slope gabion site. However, the two gabion sites at a lower (1%) slope successfully stabilized spawning gravel in the 2nd year after installation, probably through a reduction in the local slope gradient and self-armouring of the high flow channels. Higher summer densities of juvenile coho salmon (Oncorhynchuskisutch (Walbaum)) and steelhead trout (Salmogairdneri Richardson) were recorded at the gabion sites (means, 1.2 and 0.33/m2, respectively) compared with the control sites (means, 0.89 and 0.10/m2). Underyearling coho fry were also significantly larger (p < 0.05) at gabion sites (mean, 50 mm) than at control sites (mean, 45 mm). Improved rearing habitat was created for coho juveniles by the gabions, a result of increased pool area and cover.
Patterns of starch reserves in healthy and diseased American elms
Authors: Shigo A. L. , Gregory G. F. , Campana R. J. , Dudzik K. R. , Zimel D. M.
Published: November 2007

Healthy American elms stored starch all year in 12–18 growth rings. Starch reserves in healthy elms were lowest at the time of leaf expansion, which was also the time of spring vessel formation and the time of highest susceptibility to Ceratocystisulmi. Nonconductive barrier zones separated infected wood from wood that normally stored starch. The new wood cells that formed after the barrier zone was completed did not store starch until the end of the growth period. When additional infections occurred the same growth period or the next growth period, the tree had only a single functioning growth ring to maintain starch reserves. Trees inoculated with C. ulmi in June had significantly less starch reserves than controls in August of the same year. All trees in one study that died during the end of 1984 had trace amounts of starch at the end of 1983, while trees that were still alive at the end of 1984 had high amounts of starch at the end of 1983. The data suggest that depletion in trunk starch reserves is a manifestation of the host–pathogen interaction that is correlated with tree death.
Interaction between gibberellin A4/7 and root-pruning on the reproductive and vegetative processes in Douglas-fir. IV. Effects on lateral bud development
Authors: Owens J. N. , Webber J. E. , Ross S. D. , Pharis R. P.
Published: November 2007

The anatomy, mitotic frequency, size, and total insoluble carbohydrate histochemistry was studied in axillary apices from 9- and 10-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees after cone induction treatments of root-pruning and (or) stem injections of a gibberellin A4 and A7 (GA4/7) mixture. Axillary buds were initiated at the time of root-pruning, but root-pruning treatment had no effect on axillary bud initiation. Axillary apices from control and gibberellin-treated trees were similar and followed the normal sequence of bud-scale initiation, differentiation, and leaf initiation (described previously) and no cone buds differentiated. Early development of axillary apices from root-pruned and root-pruned, gibberellin-treated trees was normal, but development became retarded near the time of vegetative bud flush. Retarded apices were small with low mitotic frequency and developed many features characteristics of latent apices. Retardation of axillary apices continued until mid-July when normal development resumed and apices differentiated into reproductive buds or vegetative buds, or became latent. The trees in which the greatest retardation of apical development occurred during lateral shoot elongation produced the most cone buds. These results are discussed in relation to hypotheses proposed to explain how cultural and gibberellin treatments affect cone induction in the Pinaceae.
Growth decline of wind-exposed red spruce and balsam fir in the White Mountains
Authors: Harrington T. C.
Published: November 2007

Overstory red spruce (Picearubens Sarg.) and balsam fir (Abiesbalsamea (L.) Mill.) trees suddenly exposed to strong, turbulent winds along a ski trail cut in 1962 in New Hampshire showed growth (increment of basal area) reductions during 1974 through 1983 of 82 and 63%, respectively, compared with growth during 1954 through 1963. Growth of comparable trees on the upwind side of the ski trail did not decline during this period. Mechanical damage to crowns and roots during tree sway is proposed as the primary cause of the growth decline. Six downwind fir trees had smaller living crowns, fewer living fine roots, more abrasion wounds on woody roots, and more discoloration of root wood than did the six fir trees on the upwind side of the trail. Six downwind spruce trees had smaller living crowns and more root discoloration than did the six upwind spruce trees. Regression analyses were made using the 24 trees along the ski trail and 29 trees from two other poorly stocked and declining stands in the White Mountains. Of the site, stand, and tree parameters tested, only root and crown damage parameters significantly correlated with reductions in growth rate. For fir, percent root discoloration and percent roots abraded explained 82% of the variation in growth decline. For spruce, crown loss explained 70% of the variation. The symptomatology of these wind-stressed trees was consistent with that described for spruce–fir decline. Although acid deposition or some other anthropogenic stress has been proposed as the primary cause of spruce–fir decline, wind appears to be an overlooked but significant natural stress factor that could explain at least some of the growth decline and mortality of spruce and fir at high elevations in the northern Appalachian Mountains.