bluuebunny/crossref_metadata_2025 huggingface dataset:
Organotin compounds and their interactions with microoganisms
Authors: White Jane S , Tobin John M , Cooney Joseph J
Published: April 2011

Organotin compounds are ubiquitous in the environment. The general order of toxicity to microorganisms increases with the number and chain length of organic groups bonded to the tin atom. Tetraorganotins and inorganic tin have little toxicity. Because of their lipophilicity, organotins are regarded as membrane active. There is evidence that the site of action of organotins may be both at the cytoplasmic membrane and intracellular level. Consequently, it is not known whether cell surface adsorption or accumulation within the cell, or both is a prerequisite for toxicity. Biosorption studies on a fungus, cyanobacteria, and microalgae indicates that cell surface binding alone occurred in these organisms, while studies on the effects of TBT (tributyltin) on certain microbial enzymes indicated that in some bacteria TBT can interact with cytosolic enzymes. Microorganism-organotin interactions are influenced by environmental conditions. In aquatic systems, both pH and salinity can determine organotin speciation and therefore reactivity. These environmental factors may also alter selectivity for resistant microorganisms in polluted systems. Tin-resistant microorganisms have been identified, and resistance can be either plasmid or chromosomally mediated. In one TBT-resistant organism, an Altermonas sp., an efflux system was suggested as the resistance mechanism. Biotransformation of organotin compounds by debutylation or methylation has been observed. These reactions may influence the toxicity, mobility, and environmental fate of organotin compounds.Key words: inorganic tin, organotins, microorganisms, organotin resistance, biosorption, biotransformation.
Assessing genetic variability among Brazilian strains ofXanthomonas axonopodispv.manihotisthrough restriction fragment length polymorphism and amplified fragment length polymorphism analyses
Authors: Restrepo S , Valle T L , Duque M C , Verdier V
Published: April 2011

Xanthomonas axonopodis pv.manihotis (Xam) causes bacterial blight, a major disease of cassava, which is a starchy root crop that feeds about 500 million people throughout the world. To better select resistant cassava germplasm, we examined the population structure of Xam in Brazil, Latin America's largest producer of cassava, and a major center of diversity for the crop. The 79 strains collected between 1941 and 1996 from three edaphoclimatic zones were analyzed by restriction fragment length polymorphism (RFLP), using a probe linked to a Xam pathogenicity gene (pthB). Thirty-eight haplotypes were identified, and geographical differentiation for the Xam strains was demonstrated. Strains from subtropical zone (ECZ 6) showed high genetic diversity in most of the sites from which they were collected. They also showed migration from site to site. RFLP and amplified fragment length polymorphism (AFLP) analyses were carried out on 37 Xam strains and compared; the AFLP assays were performed using eight primer combinations. A multiple correspondence analysis, used to assess genetic relatedness among strains and estimate genetic diversity, indicated that the Brazilian Xam population showed high diversity. No correlation was found between AFLP and RFLP data, but the two techniques provided complementary information on the genetic diversity of Xam. Most strains were highly aggressive on a susceptible cultivar. The genetic analysis presented here contributes to a better understanding of the Xam population structure in Brazil and will help select strains of the pathogen for screening cassava germplasm resistant to the disease.Key words: cassava bacterial blight, resistance, genetic diversity, molecular characterization.
Poor efficacy of residual chlorine disinfectant in drinking water to inactivate waterborne pathogens in distribution systems
Authors: Payment Pierre
Published: April 2011

To evaluate the inactivating power of residual chlorine in a distribution system, test microorganisms (Escherichia coli, Clostridium perfringens, bacteriophage phi-X 170, and poliovirus type 1) were added to drinking water samples obtained from two water treatment plants and their distribution system. Except for Escherichia coli, microorganisms remained relatively unaffected in water from the distribution systems tested. When sewage was added to the water samples, indigenous thermotolerant coliforms were inactivated only when water was obtained from sites very close to the treatment plant and containing a high residual chlorine concentration. Clostridium perfringens was barely inactivated, suggesting that the most resistant pathogens such as Giardia lamblia, Cryptosporidium parvum, and human enteric viruses would not be inactivated. Our results suggest that the maintenance of a free residual concentration in a distribution system does not provide a significant inactivation of pathogens, could even mask events of contamination of the distribution, and thus would provide only a false sense of safety with little active protection of public health. Recent epidemiological studies that have suggested a significant waterborne level of endemic gastrointestinal illness could then be explained by undetected intrusions in the distribution system, intrusions resulting in the infection of a small number of individuals without eliciting an outbreak situation.Key words: drinking water, chlorine, disinfection, pathogens, distribution system.
Use of spectrophotometric reading for in vitro antifungal susceptibility testing ofAspergillusspp.
Authors: Dannaoui Eric , Persat Florence , Monier Marie-France , Borel Elisabeth , Piens Marie-Antoinette , Picot Stéphane
Published: April 2011

A comparative study of visual and spectrophotometric MIC endpoint determinations for antifungal susceptibility testing of Aspergillus species was performed. A broth microdilution method adapted from the National Committee for Clinical Laboratory Standards (NCCLS) was used for susceptibility testing of 180 clinical isolates of Aspergillus species against amphotericin B and itraconazole. MICs were determined visually and spectrophotometrically at 490 nm after 24, 48, and 72h of incubation, and MIC pairs were compared. The agreement between the two methods was 99% for amphotericin B and ranged from 95 to 98% for itraconazole. It is concluded that spectrophotometric MIC endpoint determination is a valuable alternative to the visual reference method for susceptibility testing of Aspergillus species.Key words: antifungal, susceptibility testing, Aspergillus, spectrophotometric reading.
Transfer RNA genes and their significance to codon usage in thePseudomonas aeruginosalamboid bacteriophage D3
Authors: Kropinski Andrew M , Sibbald Mary Jo
Published: April 2011

Using tRNAscan-SE and FAStRNA we have identified four tRNA genes in the delayed early region of the bacteriophage D3 genome (GenBank accession No. AF077308). These are specific for methionine (AUG), glycine (GGA), asparagine (AAC), and threonine (ACA). The D3 Thr- and Gly-tRNAs recognize codons, which are rarely used in Pseudomonas aeruginosa and presumably, influence the rate of translation of phage proteins. BLASTN searches revealed that the D3 tRNA genes have homology to tRNA genes from Gram-positive bacteria. Analysis of codon usage in the 91 ORFs discovered in D3 indicates patterns of codon usage reminiscent of Escherichia coli or P. aeruginosa.Key words: bacteriophage, Pseudomonas, D3, tRNA, codon usage.
Extracellular hydrolytic enzymes in the fungal genus Verticillium: adaptations for pathogenesis
Authors: Bidochka Michael J , Burke Susan , Ng Luna
Published: April 2011

The insect and plant pathogens within the fungal genus Verticillium showed enzymatic adaptation (production and regulation) directed to the degradation of some of the polymers found in the integument of their respective hosts. For example, the facultative plant pathogens (V. albo-atrum and V. dahliae) produced greater levels of cellulase and xylanase than the facultative insect pathogen (V. lecanii). Verticillium lecanii produced extracellular subtilisin-like protease when grown in insect cuticle medium but not in plant cell wall medium, while the plant pathogen V. albo-atrum showed a diminished regulatory component in the production of this enzyme. The opportunistic pathogens (V. fungicola and V. coccosporum) and the saprobic species (V. rexianum) were less specific in the production and regulation of several proteases as well as cellulases and xylanases. A dendrogram based on cluster analysis compiled from fungal API-ZYM profiles showed commonalties in a broad array of extracellular enzymes within a host-pathogen group (i.e. insect or plant pathogen). The opportunistic pathogens were dispersed throughout the dendrogram, suggestive of the diversity in type and expression of extracellular enzymes.Key words: extracellular enzymes, pathogenic fungi.
Arginine biosynthesis inCampylobacter jejuniTGH9011: determination of theargCOBDcluster
Authors: Hani Eric Kurt , Ng David , Chan Voon-Loong
Published: April 2011

Arginine biosynthetic genes from Campylobacter jejuni TGH9011 were cloned by functional complementation of the respective Escherichia coli arginine biosynthetic mutants. Complementation of argA, argB, argC, argD, argE, argF, and argH auxotrophs was accomplished using a pBR322-based C. jejuni TGH9011 plasmid library. By cross-complementation analyses, the first four steps of arginine biosynthesis were shown to be closely linked on the genome. Two additional clones complementing the first (ArgA) and fifth (ArgE) steps in arginine biosynthesis were obtained. Neither recombinant showed linkage to the arg cluster, to each other, nor to other arginine biosynthetic functions by cross-complementation. Genes argF and argH were not linked to other arginine biosynthetic genes by cross-complementation analysis. Restriction enzyme patterns of recombinant plasmids fell into five groups. Group I contained the arg(ABCD) complementing locus. Group II and Group III were the two genetic loci corresponding to the argA and argE complementing genes. Group II contains the hipO gene encoding N-benzoylglycine-amino-acid amidohydrolase, also known as hippurate hydrolase. Group III contains the hipO homolog of C. jejuni. Group IV represents the argF gene. GroupV is the argH gene. Functional complementation of mutations in the first four steps of the arginine biosynthetic pathway was obtained on recombinant plasmid pARGC2. The predicted order of gene complementation was argCargA(argBargD). The sequence of the insert in plasmid pARGC2 revealed direct homologs for argC, argB, and argD. However, sequence analysis of the gene complementing ArgA function in two separate E. coli argA mutants determined that the C. jejuni gene was not a canonical argA gene. The gene complementing the argA defect, which we call argO, showed limited homology to the streptothricin acetyltransferase gene (sat) of Escherichia coli. The flanking open reading frames in pARGC2 showed no homologies to arginine biosynthetic genes. The structure of the argCOBD gene arrangement is discussed with reference to the presence and location of other arginine biosynthetic genes on the genome of C. jejuni and other bacterial organisms.Key words: arginine synthesis, Campylobacter jejuni, arginine biosynthetic genes, gene sequence, gene arrangement.
Biochemical interactions of conifer seedling roots with Fusarium spp.
Authors: Asiegbu F O , Kacprzak M , Daniel G , Johansson M , Stenlid J , Mañka M
Published: April 2011

The importance of root and spore surface molecules in the interactions of Fusarium spp. with conifer roots, and cellular localization of proteins presumed to be involved in host defence, were investigated. For adhesion studies, using a combination of fluorescein isothiocyanate (FITC) labelled lectins and high perfomance liquid chromatography (HPLC), several sugars (pinitol, xylitol, galactose, mannose, and glucose) were detected in root surface mucilage. Both artificial substrata and detached living roots were used to evaluate the significance of selective removal of root or spore surface components on the adhesion process. The spores or roots were pretreated with either periodic acid, pronase E, potassium hydroxide or diethyl ether. Pretreatment of the spores with diethyl ether reduced significantly the level of spore adhesion, which suggests that the adhesive component is either a lipid, or is bound to lipid. Since oxidation of carbohydrate reactive sites with periodic acid on the root surface almost completely abolished the development of germ tubes by adherent spores, it was presumed that some of these periodate-sensitive substances serve as a nutrient source for the fungus. On inoculated roots, F. avenaceum and F. culmorum were significantly pathogenic to both Norway spruce and Scots pine seedlings. Cytochemical labelling of sites of accumulation of host defence molecules within infected root tissues using anti-peroxidase demonstrated increased peroxidase activity in host cell walls. With anti-chitinase and anti-glucanase, gold labelling was found mainly on pathogen hyphal walls.Key words: conifer seedlings, adhesion, Fusarium spp., PR proteins, immunolocalization, lectins.
Antigenic and genetic characterization of a putative hybrid transferrin-binding protein B fromNeisseria meningitidis
Authors: Menéndez Tamara , Pérez Mairet , Alvarez Anabel
Published: April 2011

The transferrin-binding protein Bs (TbpBs) from the bacterium Neisseria meningitidis have been divided into two families according to genetic and antigenic features. TbpB from meningococcal strain B385 showed a molecular mass similar to that exhibited by TbpBs belonging to the high molecular mass family of TbpBs. TbpB was recognized by immunoassay using a specific serum directed against the TbpB of the reference strain for this family (strain M982). It was also recognized by a serum elicited against the TbpB of the reference strain for the low molecular mass family (strain B16B6). The tbpB gene from strain B385 was cloned and sequenced. The highest degree of sequence homology was found to be with the TbpBs belonging to the high molecular mass family, although a region of 14 amino acids that is only present in the TbpB from strain B16B6 was also found. This report illustrates a TbpB that shows hybrid antigenic and genetic behaviour.Key words: Neisseria meningitidis, transferrin-binding proteins, TbpB families.
Characterization of a major envelope protein from the rumen anaerobeSelenomonas ruminantiumOB268
Authors: Kalmokoff M L , Austin J W , Whitford M F , Teather R M
Published: April 2011

Cell envelopes from the Gram-negative staining but phylogenetically Gram-positive rumen anaerobe Selenomonas ruminantium OB268 contained a major 42 kDa heat modifiable protein. A similarly sized protein was present in the envelopes of Selenomonas ruminantium D1 and Selenomonas infelix. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of Triton X-100 extracted cell envelopes from S. ruminantium OB268 showed that they consisted primarily of the 42 kDa protein. Polyclonal antisera produced against these envelopes cross-reacted only with the 42 kDa major envelope proteins in both S. ruminantium D1 and S. infelix, indicating a conservation of antigenic structure among each of the major envelope proteins. The N-terminus of the 42 kDa S. ruminantium OB268 envelope protein shared significant homology with the S-layer (surface) protein from Thermus thermophilus, as well as additional envelope proteins containing the cell surface binding region known as a surface layer-like homologous (SLH) domain. Thin section analysis of Triton X-100 extracted envelopes demonstrated the presence of an outer bilayer overlaying the cell wall, and a regularly ordered array was visible following freeze-fracture etching through this bilayer. These findings suggest that the regularly ordered array may be composed of the 42 kDa major envelope protein. The 42 kDa protein has similarities with regularly ordered outer membrane proteins (rOMP) reported in certain Gram-negative and ancient eubacteria.Key words: Selenomonas envelope surface SLH domain.
Eight-year responses of light interception, effective leaf area index, and stemwood production in fertilized stands of interior Douglas-fir (Pseudotsuga menziesii var. glauca)
Authors: Balster Nick J , Marshall John D
Published: April 2011

Data from 72 Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) plots across the Interior Northwest were used to determine whether (i) increased intercepted photosynthetically active radiation (%IPAR), effective leaf area index (LAIe), and stemwood volume production (cubic metres stemwood per hectare per year) could still be detected 7 or 8 years after nitrogen fertilization and (ii) fertilization would increase the efficiency by which light is converted into stemwood volume. Projected LAIe varied from 1.82 to 6.07 m2·m-2 on the control plots. The fertilized plots intercepted 9-11% more light than the control plots (P < 0.001); they also had 22-25% higher LAIe than the control plots (P < 0.001). Stemwood volume production increased by 25-29% relative to the control (P < 0.001) and increased exponentially with %IPAR across all study plots (R2 = 0.57). Stemwood growth efficiency averaged 12.0 ± 0.4 (mean ± SE), 13.5 ± 0.4, and 13.7 ± 0.4 m3·ha-1·a-1 per IPAR for the control, low fertilization, and high fertilization plots, respectively (P < 0.01). Fertilization thus induced increases in both light interception and the efficiency with which intercepted light was converted to stemwood across the region.
Relative competitiveness of nine early-successional boreal forest species associated with planted jack pine and black spruce seedlings
Authors: Bell F Wayne , Ter-Mikaelian Michael T , Wagner Robert G
Published: April 2011

Differences in yield-density models derived from an additive experimental design were used to compare the relative competitiveness of nine early-successional boreal forest plants (aster, grass, fireweed, fern, raspberry, willow, alder, birch, and aspen) on jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) BSP). A randomized complete block split-split-plot design with three replications blocked on soil type was used. Initial density gradients were 0-4 plants/m2 for woody and 0-8 plants/m2 for herbaceous species. An a priori analytical approach that compared a full model (using linear regression analysis of 4th-year stem diameter of conifers under increasing cover and height of competitors) to various reduced models was used to assess competition. Increasing cover and (or) height of all competitors (except fern) significantly (P < 0.05) decreased conifer stem diameter. The final regression model (based on visual estimates of cover and differences in initial conifer size) accounted for 89% of the variation in stem diameter. During the years studied, both conifers responded similarly to competition, and herbaceous species were on average 28.9% more competitive than woody species. Under different growing conditions (e.g., a natural forest) the relative competitiveness of herbaceous and woody species may vary from these results.
Seedling inoculation distinguishes lodgepole pine families most and least susceptible to gall rust
Authors: White E E , Allen E A , Ying C C , Foord B M
Published: April 2011

Resistance of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was compared between 21-year field infection trials and inoculation of 2-month-old seedlings. The seedlings were produced from seed stored since the original field plantings. Virtually all of the seedlings from families identified as susceptible in the field produced galls in the inoculation trial, only 1% of seedlings from these families did not develop galls. Nearly half the seedlings in families classed as resistant in the field trials did not form galls 13 months after inoculation. Only one of these seedlings developed galls in the following 2 years. Seedling inoculation provides a simple early test to assess field resistance to gall rust of lodgepole pine seedlots, and an efficient way to cull at least the most susceptible ones.
Storability and root freezing tolerance of Norway spruce (Picea abies) seedlings
Authors: Stattin Eva , Hellqvist Claes , Lindström Anders
Published: April 2011

The objective of the study was to evaluate if root freezing tolerance and post-storage survival of Norway spruce (Picea abies (L.) Karst.) seedlings can be improved by cool storage prior to frozen storage. Four-year-old bare-root seedlings were lifted and put into cool or frozen storage at 2-week intervals from mid-September to mid-December. Length of cool (5.5°C) storage prior to frozen (-4.6°C) storage was 0, 2, 4, 6, 8, 10, or 12 weeks. Root freezing tolerance, determined directly by freezing-induced electrolyte leakage and indirectly by shoot and root dry matter content, were assessed at lifting and biweekly during cool storage. At these occasions, seedlings were also transferred from cool storage to frozen storage. Survival of the seedlings was assessed in a cultivation test in April. Root freezing tolerance increased for seedlings put into cool storage before November, whereas seedlings put into cool storage from November onwards did not increase in root freezing tolerance. Electrolyte leakage after root freezing to -5°C at the time of transfer to frozen storage correlated to post-storage survival of seedlings pretreated up to 6 weeks. Lifting for successful overwinter storage could be done up to 1 month earlier if seedlings were pretreated in cool storage 6 weeks before transfer to frozen storage.
Selected biological and chemical properties of forest floors across bedrock types on the north coast of British Columbia
Authors: Kranabetter J M , Banner A
Published: April 2011

We examined some of the factors related to nutrient availability of forest floors developed over saprolitic and colluvial mineral soils of four bedrock types (granodiorite, gneissic diorite, schist, and limestone) on the outer northern coast of British Columbia. All sites were relatively well drained with old-growth coniferous forests. Forest floor morphology was quite similar across sites, with friable, moderately aggregated horizons dominating the profile. There were significant differences in concentrations of total nitrogen, available phosphorus, total sulphur, and condensed tannins across bedrock types. We found detritivores such as sowbugs, millipedes, and potworms across all sites. We could not detect differences in turnover rates (via laboratory respiration) of organic matter between bedrock types. Turnover rates instead were negatively correlated with forest floor carbon and total canopy cover. Overall, forest floor properties were quite similar across the range in parent materials because of the strong influence of climate and vegetation on soil development.
Age and diameter structure of a managed uneven-aged oak forest
Authors: Loewenstein Edward F , Johnson Paul S , Garrett Harold E
Published: April 2011

We studied the age and diameter structure on one section (259 ha) of a 63 000-ha privately owned forest in the Ozark Highlands of Missouri. The forest has been managed using a partial cutting strategy since 1954. Because a majority of the trees predate current management practices, the existing stand structure is a function of not only the current silvicultural system and the dynamics of this ecosystem but also the initial stand conditions. To determine age structure and evaluate the relationship of diameter and age, a random sample of 600 oaks [Formula: see text]4 cm DBH were collected from ten 0.4-ha plots. Based on the test of a binomial proportion, the oak populations on 7 of the 10 plots were deemed uneven aged, two were deemed two aged, and one was even aged. DBH accounted for 40 (red oaks) to 62% (white oaks) of the variation in tree age. Although the overall diameter frequency distribution of oaks formed a reverse-J shape, the age-frequency distribution approximated a normal (bell-shaped) distribution. We show how this apparent inconsistency between diameter and age distributions can be an artifact of a minimum sampling diameter. Such a truncation of the sampled population reduces the observed frequency of trees in the younger age-classes, which in turn results in a bell-shaped rather than a reverse-J-shaped age-frequency distribution. Thus, the lack of a reverse- J-shaped age distribution should not be interpreted as a failure to sustain regeneration in an uneven-aged stand.
Carbon and nitrogen distribution and accumulation in a New Zealand scrubland ecosystem
Authors: Scott Neal A , White Joseph D , Townsend Jackie A , Whitehead David , Leathwick John R , Hall Graeme MJ , Marden Michael , Rogers Graeme ND , Watson Alex J , Whaley Patrick T
Published: April 2011

Reversion of agricultural land to native woody vegetation can sequester carbon (C), influencing regional and global C budgets. We examined whole-ecosystem differences in C and nitrogen (N) storage and distribution, and sapwood - leaf area relationships in a scrubland vegetation chronosequence in New Zealand dominated by manuka (Leptospermum scoparium J.R. et G. Forst) and kanuka (Kunzea ericoides var. ericoides (A. Rich.) J. Thompson). At 25 years, manuka dominated, and vegetation C was 6.5 kg C·m-2. In the 55-year-old stand, stem density was similar for the two species, and vegetation C storage was 15.1 kg C·m-2, similar to the 35-year-old stand (p = 0.9). Foliar biomass comprised 3-5% of vegetation C stock but contained 26%-37% of vegetation N. Root biomass was 10-15% of total and varied little with stand age. The sapwood - leaf area relationship differed significantly for the two species (p < 0.05). Mineral soil C and N (to 0.30 m) did not vary with stand age, but forest floor C and N were highest in the 55-year-old stand (2 kg C·m-2; p < 0.01). Soil and forest floor C/N ratios were significantly higher in the 35-year-old stand (p < 0.04), possibly because of high interspecific competition for N. While the sampling intensity was too limited to allow spatial extrapolation, our results suggest that carbon accumulation in this scrubland is rapid and similar to plantation forests, suggesting that land abandonment could significantly impact New Zealand's C budget.
Allocation of current photosynthate and changes in tissue dry weight within northern red oak seedlings: individual leaf and flush carbon contribution during episodic growth
Authors: Dickson Richard E , Tomlinson Patricia T , Isebrands J G
Published: April 2011

Relatively little is known about the changing carbon allocation patterns in species with episodic growth cycles such as northern red oak (Quercus rubra L.). To examine such changing allocation and growth patterns, northern red oak plants were grown from seed in controlled environment chambers through four cycles of growth. 14CO2 was supplied to leaves of the first, second, or third flushes at different Quercus morphological index growth stages within each flush, and the distribution of 14C within the plant was analyzed. Carbon allocation from source leaves of the first and second flush was primarily upward during the subsequent cycle of shoot growth and downward during lag and bud growth stages. All leaves within a flush did not respond the same. Upper leaves allocated most 14C-photosynthate upward during leaf and shoot growth while lower leaves supplied more 14C to lower stem and roots. During the third and fourth flushes, differential allocation from leaves within a flush resulted in essentially equal upward and downward carbon allocation. Growth and allometric relationships reflected these changes in carbon allocation.
Optimal timber harvest scheduling with spatially defined sediment objectives
Authors: Hof John , Bevers Michael
Published: April 2011

This note presents a simple model formulation that focuses on the spatial relationships over time between timber harvesting and sediment levels in water runoff courses throughout the watershed being managed. A hypothetical example is developed to demonstrate the formulation and show how sediment objectives can be spatially defined anywhere in the watershed. Spatial sensitivity in the example is shown, indicating that, at least in some cases, tracking sediment levels below a watershed may be inadequate for achieving sediment objectives within the watershed itself.
Throughfall and fog deposition of nitrogen and sulfur at an N-limited and N-saturated site in the San Bernardino Mountains, southern California
Authors: Fenn Mark E , Poth Mark A , Schilling Susan L , Grainger David B
Published: April 2011

Inorganic nitrogen (N) and sulfur (S) deposition in bulk throughfall and fog were determined at two sites located at opposite ends (42 km apart) of a pollution gradient in the San Bernardino Mountains. Plot-level averages for total annual N and S deposition in throughfall in 1996 were 18.8 and 2.9 kg·ha-1, respectively, at Camp Paivika (CP) and 2.9 and 0.4 kg·ha-1, respectively, at Barton Flats (BF). Deposition of N in throughfall in the four transects at CP ranged from 12.1 to 31.7 kg·ha-1·year-1. Spatial variability was high because of heterogenous canopy cover and varying exposure to air pollution. Annual estimated stand-level deposition of N and S in fog were 10.9 and 1.9 kg·ha-1, respectively, at CP, and 0.6 and 0.2 kg·ha-1, respectively, at BF. We estimated that N deposition in fog contributed 35% of the total annual N deposition at CP and 13% at BF. Analogous values for S were 39% at CP and 26% at BF. Ammonium deposition in throughfall and fog at CP were 72 and 122% as high as NO3- deposition because of elevated NH3 emissions from dairy farms in the Chino-Norco area 34 km southwest of CP.
An economic assessment of using the allowable cut effect for enhanced forest management policies: an Alberta case study
Authors: Hegan R L , Luckert M K
Published: April 2011

In Canada, forest policymakers are considering the allowable cut effect (ACE) as a potential mechanism to provide tenure holders with incentives to practice enhanced forest management. To investigate the incentives created by the ACE, this paper estimates returns to ACE investments for a trembling aspen (Populus tremuloides Michx.) - white spruce (Picea glauca (Moench) Voss) mixedwood forest in Alberta. A timber supply model is used to optimize harvesting schedules to maximize net present values over a 200-year planning horizon. A number of scenarios are investigated with variations in intensity of silvicultural investments, beginning age-class distributions, levels of flexibility around the allowable annual cut (AAC), calculations of AACs based on coniferous and mixedwood volumes, and green-up constraints. In our simulations, it was difficult to find positive returns to the ACE. Positive returns only occurred when operating under harvesting constraints with a mature starting forest and AAC calculations that ignored deciduous volumes. In those limited cases where there were positive returns to the ACE, returns were higher for extensive, rather than intensive investments. Combining these results with other potential impediments to the ACE, previously identified in the literature, the probability of tenure holders having incentives to undertake ACE investments is low.
Creating continuous areas of old forest in long-term forest planning
Authors: Öhman Karin
Published: April 2011

Harvest activities tend often to create landscapes where the old forest is fragmented into isolated patches that provide marginal conditions for species that inhabit forest interiors. This paper presents a long-range planning model designed to maximize the net present value and to create continuous patches of old forest. In this model, the spatial structure of old forest is controlled by core area and edge habitats. Core area is defined as the area of old forest that is free of edge effects from surrounding habitats. The core area requirement is set to a fixed value for each of a number of time periods, whereas the area of edge habitats, which should be as small as possible, is weighted against the net present value. The model is applied in a case study to an actual landscape consisting of 755 stands of forest in northern Sweden and solved using simulated annealing. The results show that distinct continuous patches of old forest are created when both a core area requirement and consideration of the amount of edge habitats are included in the problem formulation. The cost of creating continuous areas of old forest was found to be significant.
Genetic selection for cold hardiness in coastal Douglas-fir seedlings and saplings
Authors: O'Neill Gregory A , Aitken Sally N , Adams W Thomas
Published: April 2011

Genetic control of cold hardiness in two-year-old seedlings was compared with that in 7-year-old saplings of 40 open-pollinated families in each of two breeding populations (Coast and Cascade) of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) from western Oregon. In addition, the efficacy of bud phenology traits as predictors of cold hardiness at the two stages was explored. Fall and spring cold hardiness were assessed using artificial freeze testing. Similar genetic control of cold hardiness in seedlings and saplings is suggested by strong type-B genetic correlations (rB) between the two ages for fall and spring cold injury traits (rB[Formula: see text] 0.78) and by similar trends in individual tree heritability estimates (hi2), e.g., hi2was greater in spring (hi2= 0.73) than in fall (hi2= 0.36) and greater in the Coast population (hi2= 0.69) than in the Cascade population (hi2= 0.40) at both ages. Strong responses to direct selection are expected for spring cold hardiness at both ages and for fall cold hardiness in seedlings, even under mild selection intensities. Similar heritabilities in seedlings and saplings, and strong genetic correlations between ages for cold-hardiness traits, ensure that selection at one age will produce similar gains at the other age. Type-A genetic correlations (rA) between fall and spring cold hardiness were near zero in the Cascade population (rA= 0.08 and -0.14 at ages 2 and 7, respectively) but were moderate and negative in the Coast population (rA= -0.54 and -0.36, respectively). Bud-burst timing appears to be a suitable surrogate to artificial freeze testing for assessing spring cold hardiness in both seedlings and saplings, as is bud set timing for assessing fall cold hardiness in seedlings, but bud set timing is a poor predictor of fall cold hardiness in saplings.
Structure and developmental process of aQuercus mongolicavar.grosseserrataforest in theFagetea crenataeregion in Japan
Authors: Fujita Kazumi , Sano Junji
Published: April 2011

Structure and developmental processes were studied in a Quercus mongolica Fisch. var. grosseserrata (Bl.) Rehd. et Wils. forest in the Fagetea crenatae Bl. region in Japan. The Quercus forest was classified into three stand types: stands dominated by Quercus with many species (type Q-MIX), Quercus-Fagus (type Q-F), and Quercus (type Q). In Q-MIX, Alnus hirsuta Turcz. had a bell-shaped DBH-class distribution. Most Quercus trees were single stemmed. The establishment of Quercus trees occurred continuously from the 1900s. The percentage of growth change (%GC) exhibited negative values from the 1940s. In Q-F and Q, Quercus trees had bell-shaped DBH-class distributions, and multiple-stemmed trees showed broad distributions. In Q-F, tree establishment peak was in the 1870s. %GC exhibited large fluctuations. In Q, tree establishment peak was in the 1850s. %GC exhibited negative values for 60 years. In conclusion, type Q-MIX, Q-F, and Q developed mainly by seedling regeneration following major cutting in the 1900s, sprout and seedling regeneration following intermittent cuttings mainly in the 1870s, and sprout and seedling regeneration following successive cuttings mainly in the 1850s, respectively. Cutting disturbance can be a major factor in developmental processes in Quercus forest; the frequency and intensity of cuttings affect the stand structure and the dominance of Quercus in the Fagetea crenatae region.
Financial feasibility of marker-aided selection in Douglas-fir
Authors: Johnson G R , Wheeler N C , Strauss S H
Published: April 2011

The land area required for a marker-aided selection (MAS) program to break-even (i.e., have equal costs and benefits) was estimated using computer simulation for coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in the Pacific Northwestern United States. We compared the selection efficiency obtained when using an index that included the phenotype and marker score with that obtained using only the phenotype. It was assumed that MAS was restricted to within-family selection, that the rotation age was 50 years, and that growth rate (h2= 0.25), tree form (h2= 0.25), and (or) wood density (h2= 0.45) were the objects of improvement. Several population quantitative trait loci (QTL) models, selection population sizes, and interest rates were considered. When large selection population sizes were employed (500 trees per family) MAS gave considerable increases in efficiency of within-family selection; however, results showed that the combination of small selection population sizes (100 trees per family) and many QTL of moderate effect could lead to losses in gain from MAS compared with phenotypic selection. For many reasonable selection scenarios and the simplified assumptions in our model, the land base required for breeding programs to break-even is smaller or near to the limit of those in place under operational breeding programs in the region. Considerably more research is needed to reasonably predict whether MAS would be cost-effective in practice. However, before some of the basic research needed to implement MAS can be done, organizations need to establish large blocks of full-sib families to allow for QTL identification.
Landscape influence on the spatial and temporal distribution of the Kirtland's warbler at the Bald Hill burn, northern Lower Michigan, U.S.A.
Authors: Kashian Daniel M , Barnes Burton V
Published: April 2011

The Kirtland's warbler (Dendroica kirtlandii Baird) is an endangered songbird that nests in northern Lower Michigan in ecosystems dominated by young jack pine (Pinus banksiana Lamb.). We used the landscape ecosystem approach to identify two adjacent landform-level ecosystems located at different elevations within the area burned by the 1975 Bald Hill fire in Crawford County, Michigan. Eighty-five percent of the warblers occupied the high-elevation landform from 1982 to 1987 compared with only 25% from 1992 to 1997, indicating a shift in warbler occupancy of the burn from the high- to the low-elevation landform by 1991. Although similar in soil, the landforms have significantly different microclimates as mediated by physiography. Because of a warmer microclimate, jack pines in the high-elevation landform exhibited faster growth and were colonized first by the warbler; the trees in the cooler low-elevation landform grew more slowly and were colonized later. We suggest that the presence of two adjacent landform-level ecosystems within a single burned area prolonged the warbler occupancy of the burn. Thus, a broad-scale ecosystem approach that considers physical site factors as well as vegetative characteristics is useful for understanding the complex interactions that affect spatial and temporal species distributions across the landscape. Such an approach may benefit the management of particular endangered species, especially when the size of management areas is considered to be a crucial element of species preservation.
Genetic diversity and disease resistance: some considerations for research, breeding, and deployment
Authors: Burdon Rowland D
Published: April 2011

Fungal pathogens present a complex challenge for genetic management of forest trees. The need is for disease resistance that withstands mutations and genetic shifts in pathogens. Also desirable are defences against new and dangerous pathogens. An understanding of how hosts and pathogens can continue to coexist should help. Experience from agriculture has allowed modelling of pathosystems, the genetic variations within hosts and pathogens that permit coexistence. While it is impractical to construct a comprehensive model, two phenomena seem generally conducive to stability: a cost of "virulence" in pathogen fitness and a multiplicity of host resistance mechanisms. However, other factors, notably indirect costs of resistance, are very difficult to model. Overall, the diversity of behaviour of models, of the nature of resistance and virulence genes, and of biology of both hosts and pathogens precludes any unique formula for stability. For current crops, genetic diversity offers risk spread for susceptibility to a new and serious pathogen or pathotype. For longer-term breeding, relatively rare resistance may be useful, but pedigreed breeding populations typically entail very finite population sizes. Providing for selecting within improved production populations may therefore be needed. This would give breeders technical challenges, and give forest managers opportunity costs and major logistical challenges.
Effects of selective cutting on the epidemiology of armillaria root disease in the southern interior of British Columbia
Authors: Morrison D J , Pellow K W , Nemec A FL , Norris D J , Semenoff P
Published: April 2011

In selectively cut and undisturbed parts of four mature stands, five 0.04-ha plots were established, and trees were measured, mapped, and examined for aboveground symptoms of armillaria root disease. Trees were felled, and stumps and their root systems were removed by an excavator and were measured and examined for Armillaria lesions. Isolates from root lesions, rhizomorphs associated with lesions, and basidiomes collected in or adjacent to plots were of Armillaria ostoyae (Romagn.) Herink. All trees were assigned to one of five tree condition classes based on the location of lesions and host response. The merchantable volume in each class was calculated. In undisturbed plots, incidence of trees with A. ostoyae lesions on roots was about 10% in the dry climatic region compared with about 75% in the moist region and 35% in the wet region. In plots in the selectively cut parts of the stands, 50-100% of stumps were colonized by A. ostoyae. Results of a logistic regression analysis showed that selective cutting was associated with a statistically significant increase in the probability of a tree having A. ostoyae lesions, where the magnitude of the increase depended on tree diameter. The increase in the probability of a tree being diseased was accompanied by an increase in the proportion of primary roots with lesions and the average number of lesions per diseased tree; however, the increases in disease intensity were statistically significant at only two (one dry and one moist) of the four sites. The percentage of merchantable volume threatened or killed by A. ostoyae was usually higher in cutover than undisturbed plots.
Responses of quaking aspen (Populus tremuloides) seedlings to solution calcium
Authors: Lu Erh-Yang , Sucoff Edward I
Published: April 2011

Quaking aspen (Populus tremuloides Michx.) seedlings were grown in nutrient solutions to investigate their responses to a range of solution Ca levels (10-1000 µM) similar to those found in aspen stands of upper Lakes States. Growth increased significantly with increasing level of solution Ca. The level of solution Ca associated with 90% of maximum elongation (critical level) was 61 µM for shoots and 88 µM for roots. Critical Ca levels for biomass probably were lower. Concentrations of Ca in leaves and roots increased significantly with increasing solution Ca. Elongation of shoots and roots was also strongly and positively related to Ca concentrations in leaves and roots. Critical Ca concentrations (oven-dry mass) for shoot elongation were 0.46% in leaf tissue and 0.12% in root tissue, while critical Ca concentrations for root elongation were 0.54% in leaf tissue and 0.13% in root tissue. Solution Ca may have induced deficiencies of other elements, but direct Ca deficiency was the primary cause of growth reduction. These critical Ca levels in solutions or tissues cannot be used to diagnose Ca deficiency in aspen forests until it is known how other soil and plant factors affect the Ca requirement of aspen.
A cautionary note on the minimum crown cover criterion in forest definitions
Authors: Kleinn Christoph
Published: April 2011

Forest area and its changes are understood as an important and, supposedly, easily measurable indicator for sustainable management of natural resources in larger areas. The observation and estimation of forest area must be based upon a clear definition. The minimum crown cover percentage is, in many forest definitions, a central element. This paper illustrates that any definition of a minimum cover percentage must be complemented by a definition of the sampling unit, which is used as a reference area on which the percent cover is to be determined. Otherwise, the results are not unique. A simple theoretical example and an aerial photograph are analyzed to illustrate these relations. The examples underline that, for the same minimum crown cover, the forest cover estimates vary considerably when the size of the sampling unit is changed. In general, for small values of the minimum crown cover as they are commonly used in forest definitions (0.1 to 0.3, say), the expected value of the cover estimate increases consistently with increasing size of the sampling unit on which the cover measurement is done. This effect is the more pronounced the more fragmented the forest cover and the more open the forest formations are.
Early-age and later-age thinning affects growth, dominance, and intraspecific competition in Eucalyptus nitens plantations
Authors: Medhurst J L , Beadle C L , Neilsen W A
Published: April 2011

High-intensity thinning treatments were applied to young Eucalyptus nitens (Deane and Maiden) Maiden plantations aged 6 (early-age thinning), 8, and 9 years (later-age thinning). Thinning treatments were an unthinned control plus final density levels that ranged from 100 to 600 trees/ha, representing between 14 and 72% of pretreatment stand basal area. Initial planting densities were between 1143 and 1430 trees/ha. Cumulative basal area increment was significantly reduced after both early- and later-age thinning if more than 50% of the standing basal area was removed. When select groups of trees in the thinning treatments were compared with the equivalent groups of trees in the unthinned control, there was a significant response to early-age thinning in the best 100-400 trees/ha and to later-age thinning for the best 100-600 trees/ha. Height increment was not affected by thinning. However, mean live crown ratio increased with time in thinned treatments. Dominant and codominant trees showed the greatest growth response to thinning. From the data presented in this study, a final density in the range of 200-300 trees/ha is recommended. This density would improve the growth of individual trees during a rotation length of 20 to 25 years without seriously under utilizing site resources.