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  • Articles  (10,551)
  • 2005-2009  (10,551)
  • 1980-1984
  • 1930-1934
  • 2006  (10,551)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (10,551)
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  • Articles  (10,551)
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  • 2005-2009  (10,551)
  • 1980-1984
  • 1930-1934
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  • 1
    Electronic Resource
    Electronic Resource
    Strategic Labeling and Trade of GMOs (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art1 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: The emergence of agricultural biotechnology and the subsequent introduction of genetically modified organisms (GMOs) into the food system have been among the most controversial issues surrounding the increasingly scrutinized agri-food system. They have received considerable attention in the economics literature with the main focus being on the optimal regulatory response to products of biotechnology. This paper builds on the literature on the regulation of products of biotechnology by placing the analysis of labeling decisions in a multi-country context. Specifically, the objective of this study is to examine the effect of the strategic interdependence between countries on their regulatory responses to products of biotechnology. The paper analyzes the strategic effects of national regulatory decisions on labeling of GM products and identifies the determinants of the non-cooperative Nash equilibrium labeling regimes in a small number of producing countries that supply the world market of an agricultural product. Analytical results show that the Nash equilibrium configuration of labeling regimes in countries that have adopted the GM technology depends on (i) the distribution of consumer preferences and the level of consumer aversion to GM products; (ii) the size of the segregation and labeling costs in these countries; (iii) the relative productive efficiency and the cost effectiveness of the GM technology; (iv) the market power of the life science companies; and (v) the strength of intellectual property rights in these countries.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art1
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  • 2
    Electronic Resource
    Electronic Resource
    Less Choice is Better, Sometimes (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art3 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: Psychological experiments have revealed that more choice does not always make one better off. For example, consumers are sometimes more likely to purchase a product from a small variety than a large variety. Some have suggested that this excessive-choice effect may have implications for how well markets serve society. This paper constructs an economic model where the excessive-choice effect results from search costs. The model shows that it is possible for markets to produce too much variety, but there are also incentives inducing markets to provide an optimal variety. Advertising, retailer market power, and slotting fees are not just signs of imperfect competition, but mechanisms of ensuring consumers are presented with an ideal choice set.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art3
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  • 3
    Electronic Resource
    Electronic Resource
    Choices of Marketing Outlets by Organic Producers: Accounting for Selectivity Effects (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art4 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: Organic farmers have traditionally relied on a variety of marketing channels, suggesting that earned organic income will depend on the farmer's experience in producing and selling organic products and their comparative advantage in bargaining and marketing skills. A discrete choice model of the choice of marketing channels is developed which accounts for the role of selectivity bias. Farmers who are most likely to sell through a diversified set of outlets or to use a single outlet have increased earnings relative to farmers who overlook these marketing options. Producers with less experience gravitate toward use of a single marketing outlet while more experienced producers tend to diversify and market through all three channels. Constraints in selling organic products tends tend to have a negative effect on farm income.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art4
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  • 4
    Electronic Resource
    Electronic Resource
    Ensuring a Safe Food Supply: The Importance of Heterogeneity (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art2 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: In this paper we develop a model of food safety regulation that considers the employment of a differentiated food market with two types of government certified quality standards: a minimum standard and a higher one. Individuals, heterogeneous in their susceptibility to food-related health risks, choose which safety-grade of food to consume based on price and their vulnerability. The model is then extended to the case where consumers misperceive their susceptibility to health risks associated with food consumption. The theoretical presentation is followed by an application of the model to examine campylobacteriosis and salmonellosis caused by consumption of beef, pork, and chicken. The paper demonstrates that the benefits from multiple quality standards hinges fundamentally on the distribution of vulnerabilities across the population and the associated distribution of population health risks for a given level of food quality. Uniform standards are generally preferred to differentiated ones under either stringent or lax regulations on population health risk. If the population distribution of vulnerabilities is unimodal and consumers misperceive their vulnerability, the value of a differentiated policy will depend on which quality standard is attracting the majority of consumers. The empirical results confirm the importance of the population distribution of vulnerability on the relative desirability of single versus multiple quality standards.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art2
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  • 5
    Electronic Resource
    Electronic Resource
    Imperfect Competition and Strategic Trade Theory: Evidence for International Food and Agricultural Markets (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art6 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: Strategic trade theory offers a way of conceptualizing and testing for strategic government interventions in imperfectly competitive international markets. This survey critically assesses recent empirical evidence, with a focus on food and agricultural markets. One finding is that while many international markets are characterized by oligopoly, price-cost markups tend to be small, and the potential gains from intervention are modest at best. In turn, empirical work has turned up few examples in which government intervention has been optimal in a strategic trade sense. Nonetheless, governments are found to frequently intervene on behalf of domestic firms and play a major role in shaping the nature of international competition. Suggestions for future research are made.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art6
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  • 6
    Electronic Resource
    Electronic Resource
    Market Segmentation Analysis of Preferences for GM Derived Animal Foods in the UK (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art8 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: This paper undertakes a detailed market segmentation analysis of the demand for GM derived animal foods in the UK with the aim of illustrating how this analysis can provide distinct information that can assists in evaluating the welfare impacts of proposed changes to the EU's GM labelling policy. The specific modelling approach employed was the latent segment (LS) model which allows for the simultaneous determination and explanation of both segment membership and product choice. Based on psychometric and demographic variables as well as choice data, the LS model was able to identify three distinct and behaviourally consistent consumer segments. Further, the LS model was found to outperform alternative econometric approaches for accounting for preference heterogeneity. Finally, our analysis shows how it can yield distinct information over the segmented nature of the food market that can uniquely assist both European policy makers in designing GM labelling regimes and public awareness campaigns as well as the agricultural and food industry in developing pricing, marketing and new product development strategies.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art8
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of Sales on Brand Loyalty (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art5 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: Although many theoretical industrial organization models are based on the existence of a critical mass of exogenously "brand loyal" consumers, we find little empirical evidence supporting these assumptions in the orange juice retail market. There are very few loyal consumers. More importantly, the frequency with which stores conduct sales affects the share of loyal types so that loyalty is endogenous rather than exogenous. Households' demographics have statistically significant but economically minor effects on switching behavior. Switching across frozen and refrigerated states is very common, leading to more complicated substitution patterns and less loyalty than one observes looking at each state separately.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art5
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  • 8
    Electronic Resource
    Electronic Resource
    Market Power and European Competition in the Swedish Food Industry (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art7 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: This paper investigates the existence of market power in the Swedish food and beverage industry and how market power has been affected by European competition (the Single Market and Swedish EU membership). The study makes use of a census of some 500 firms for the period 1990-2002. The results show that firms in the Swedish food and beverage industry do enjoy some market power, the degree of which varies significantly across the sectors of the food and beverage industry. Increased foreign competition has contributed to reducing market power in sectors that were protected by tariff and non-tariff barriers to trade prior to Swedish EU membership.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art7
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  • 9
    Electronic Resource
    Electronic Resource
    Proving Anti-Competitive Conduct in the U.S. Courtroom: Economic Issues with the Courts' Opinions in Pickett v. Tyson Fresh Meats, Inc. (2006)
    Lincoln, Neb. : Berkeley Electronic Press (now: De Gruyter)
    Journal of agricultural & food industrial organization 4.2006, 1, art9 
    Details
    ISSN: 1542-0485
    Source: Berkeley Electronic Press Academic Journals
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Notes: Four articles have been published in this Journal about the historic cattle trial, Pickett v Tyson Fresh Meats, Inc., in which Plaintiff cattlemen alleged that Tyson/IBP--the buyer--used captive (contracted) supplies of cattle to manipulate the cash market in violation of the 1921 Packers & Stockyards Act (PSA). The first article gave a Trial's eye view by David Domina who served as co-lead counsel representing Plaintiff cattlemen. Domina's article led to a published comment by Thomas Green who was the lead attorney representing Tyson during the Trial phase of lengthy legal proceedings. Green alleged that Domina's article was "littered with rank speculation and baseless opinion." Domina countered that "proof is not litter, and evidence is not rank speculation" and that Green's commentary was "abusive." The adversarial exchange between Domina and Green was followed by another advocacy article in which William Rosales maintained that Pickett "represents an opportunity for the judiciary to reform the meatpacking industry (and) awaken the (PSA's) intended power to dethrone the economic kings of the meatpacking industry."After a five week Trial in Federal Court, the Jury found Tyson/IBP guilty on all counts and assessed actual damages of $1.28 billion over 2/1994 -10/2002. Justice for Plaintiff cattlemen was short, as the Trial Judge set aside the Jury's verdict--a rare but not unprecedented legal action--and entered summary judgment for Tyson. The Eleventh Appellate Court subsequently sided with the Trial Judge. On March 24, 2006, the United States Supreme Court denied without comment Plaintiff's Petition to rehear the case, thus ending legal activities in Pickett v Tyson and effectively killing similar legal action pending against two other major beef packers, Excel (Cargill) and Swift (ConAgra).This article emphasizes three significant and troubling legal and economic issues from the historic litigation: (1) the Courts' narrow and extreme interpretation of the antitrust rule-of-reason; (2) the Courts' endorsement of a "meeting the competition" defense, and (3) whether the Courts inserted themselves above the Jury as fact-finders in the case, contrary to the 7th Amendment to the U.S. Constitution that establishes the Jury as the only fact-finder in civil litigation.In essence Pickett was filed under the Packers and Stockyards Act, tried under Sherman and Clayton antitrust law, and overturned, in part, under the Robinson-Patman Act.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/jafio/vol4/iss1/art9
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  • 10
    Electronic Resource
    Electronic Resource
    Anaerobic Bioremediation of Groundwater Containing a Mixture of 1,1,2,2-Tetrachloroethane and Chloroethenes (2006)
    Springer
    Biodegradation 17 (2006), S. 193-206 
    Details
    ISSN: 1572-9729
    Keywords: bioremediation ; Dehalococcoides ; dechlorination ; microcosm ; tetrachloroethane ; trichloroethene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study investigated the biotransformation pathways of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) in the presence of chloroethenes (i.e. tetrachloroethene, PCE; trichloroethene, TCE) in anaerobic microcosms constructed with subsurface soil and groundwater from a contaminated site. When amended with yeast extract, lactate, butyrate, or H2 and acetate, 1,1,2,2-TeCA was initially dechlorinated via both hydrogenolysis to 1,1,2-trichloroethane (1,1,2-TCA) (major pathway) and dichloroelimination to dichloroethenes (DCEs) (minor pathway), with both reactions occurring under sulfidogenic conditions. In the presence of only H2, the hydrogenolysis of 1,1,2,2-TeCA to 1,1,2-TCA apparently required the presence of acetate to occur. Once formed, 1,1,2-TCA was degraded predominantly via dichloroelimination to vinyl chloride (VC). Ultimately, chloroethanes were converted to chloroethenes (mainly VC and DCEs) which persisted in the microcosms for very long periods along with PCE and TCE originally present in the groundwater. Hydrogenolysis of chloroethenes occurred only after highly reducing methanogenic conditions were established. However, substantial conversion to ethene (ETH) was observed only in microcosms amended with yeast extract (200 mg/l), suggesting that groundwater lacked some nutritional factors which were likely provided to dechlorinating microorganisms by this complex organic substrate. Bioaugmentation with an H2-utilizing PCE-dechlorinating Dehalococcoides spp. -containing culture resulted in the conversion of 1,1,2,2-TeCA, PCE and TCE to ETH and VC. No chloroethanes accumulated during degradation suggesting that 1,1,2,2-TeCA was degraded through initial dichloroelimination into DCEs and then typical hydrogenolysis into ETH and VC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-4218-7
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  • 11
    Electronic Resource
    Electronic Resource
    Impacts of Bioremediation Schemes on Bacterial Population in Naphthalene-Contaminated Marine Sediments (2006)
    Springer
    Biodegradation 17 (2006), S. 227-235 
    Details
    ISSN: 1572-9729
    Keywords: community fingerprint ; polycyclic aromatic hydrocarbon ; 16S rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microcosm experiments were conduced in which the surface of marine sediment was contaminated with naphthalene and subjected to either of three different bioremediation schemes, i.e., biostimulation (BS) by supplementing with slow-release nitrogen and phosphorus fertilizers, bioaugmentation (BA) by inoculating with Cycloclasticus sp. E2, an aromatics-degrading bacterium identified to play an important role for aromatic-hydrocarbon degradation in marine environments and combination (CB) of BS and BA. These three schemes were found to be similarly effective for removing naphthalene, while naphthalene disappearance in sediment without any treatment (WT) was slower than those in the treated sediments. Shifts in bacterial populations during and after bioremediation were analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments. It was found that the Cycloclasticus rRNA type occurred as the strongest bands in the course of naphthalene degradation. Clustering analysis of DGGE profiles showed that bacterial populations in the WT, BS and CB sediments differed consistently from those in the uncontaminated control, while the profile for the BA sediment was finally included in the cluster for uncontaminated control sediments after a 150-day treatment. The results suggest that bioaugmentation with ecologically competent pollutant-degrading bacteria is an ecologically promising bioremediation scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-5018-9
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  • 12
    Electronic Resource
    Electronic Resource
    Isolation of Fenitrothion-degrading Strain Burkholderia sp. FDS-1 and Cloning of mpd Gene (2006)
    Springer
    Biodegradation 17 (2006), S. 275-283 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; Burkholderia ; fenitrothion ; mpd gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A short rod shaped, gram-negative bacterium strain Burkholderia sp. FDS-1 was isolated from the sludge of the wastewater treating system of an organophosphorus pesticides manufacturer. The isolate was capable of using fenitrothion as the sole carbon source for its growth. FDS-1 first hydrolyzed fenitrothion to 3-methyl-4-nitrophenol, which was further metabolized to nitrite and methylhydroquinone. The addition of other carbon source and omitting phosphorus source had little effect on the hydrolysis of fenitrothion. The gene encoding the organophosphorus hydrolytic enzyme was cloned and sequenced. The sequence was similar to mpd, a gene previously shown to encode a parathion-methyl-hydrolyzing enzyme in Plesiomonas sp. M6. The inoculation of strain FDS-1 (106 cells g−1) to soil treated with 100 mg fenitrothion emulsion kg−1 resulted in a higher degradation rate than in noninoculated soils regardless of the soil sterilized or nonsterilized. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-7130-2
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  • 13
    Electronic Resource
    Electronic Resource
    2,4-Dichlorophenoxyacetic Acid (2,4-D) Utilization by Delftia acidovorans MC1 at Alkaline pH and in the Presence of Dichlorprop is Improved by Introduction of the tfdK Gene (2006)
    Springer
    Biodegradation 17 (2006), S. 263-273 
    Details
    ISSN: 1572-9729
    Keywords: Delftia acidovorans MC1 ; 2,4-dichlorophenoxyacetic acid (2,4-D) ; 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) ; effect of tfdK gene ; simultaneous utilization of 2,4-D and 2,4-DP ; uptake characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth of Delftia acidovorans MC1 on 2,4-dichlorophenoxyacetic acid (2,4-D) and on racemic 2-(2,4-dichlorophenoxy)propanoic acid ((RS)-2,4-DP) was studied in the perspective of an extension of the strain’s degradation capacity at alkaline pH. At pH 6.8 the strain grew on 2,4-D at a maximum rate (μmax) of 0.158 h−1. The half-maximum rate-associated substrate concentration (Ks) was 45 μM. At pH 8.5 μmax was only 0.05 h−1 and the substrate affinity was mucher lower than at pH 6.8. The initial attack of 2,4-D was not the limiting step at pH 8.5 as was seen from high dioxygenase activity in cells grown at this pH. High stationary 2,4-D concentrations and the fact that μmax with dichlorprop was around 0.2 h−1 at both pHs rather pointed at limited 2,4-D uptake at pH 8.5. Introduction of tfdK from D. acidovorans P4a by conjugation, coding for a 2,4-D-specific transporter resulted in improved growth on 2,4-D at pH 8.5 with μmax of 0.147 h−1 and Ks of 267 μM. Experiments with labeled substrates showed significantly enhanced 2,4-D uptake by the transconjugant TK62. This is taken as an indication of expression of the tfdK gene and proper function of the transporter. The uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) reduced the influx of 2,4-D. At a concentration of 195 μM 2,4-D, the effect amounted to 90% and 50%, respectively, with TK62 and MC1. Cloning of tfdK also improved the utilization of 2,4-D in the presence of (RS)−2,4-DP. Simultaneous and almost complete degradation of both compounds occurred in TK62 up to D = 0.23 h−1 at pH 6.8 and up to D = 0.2 h−1 at pH 8.5. In contrast, MC1 left 2,4-D largely unutilized even at low dilution rates when growing on herbicide mixtures at pH 8.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-6894-8
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  • 14
    Electronic Resource
    Electronic Resource
    Efforts to Explain and Control the Prolonged Thermophilic Period in Two-phase Olive Oil Mill Sludge Composting (2006)
    Springer
    Biodegradation 17 (2006), S. 285-292 
    Details
    ISSN: 1572-9729
    Keywords: composting ; crude oil ; olive mill wastewater ; olive oil mills ; olive tree branches ; olive tree leaves ; sludge ; woodchips
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aim of this paper was to evaluate the use of different bulking agents in different ratios as a means to control, optimise and eventually reduce the duration of the thermophilic period in two-phase olive oil mill sludge (OOMS) composting. The bulking agents used were: (i) olive tree leaves (OTL), (ii) olive tree shredded branches (OTB) and (iii) woodchips (WDC). The selection of these materials was based on their abundance and availability on the island of Crete, the southernmost point of Greece. The ratios studied were: Pile 1, OOMS:OTL in 1:1 v/v; Pile 2, OOMS:WDC in 1:1.5 v/v; Pile 3, OOMS:OTL in 1:2 v/v; Pile 4, OOMS:OTL:OTB in 1:1:1 v/v; and Pile 5, OOMS:OTL:OTB in 1:1:2 v/v. The composting system used was that of windrows with the volume of each pile approximately 20–25 m3. The experiments took place over two consecutive years. A composting turner was used and turnings were performed at one and two week intervals. In each pile a variety of physiochemical parameters were monitored. Temperature remained high in all five trials. Piles 1, 2, 3, 4 and 5 temperatures recorded values of above 50 °C for 106, 158, 160, 175 and 183 days, respectively. Volumes were reduced by approximately 67%, 62%, 63%, 80% and 84%, respectively. Temperature remained high, mainly due to the presence in large amounts of oily substances which during their complete oxidation release important amounts of energy and aid the cometabolism of more stable molecules such as lignin. This process is better described as the slow “burning” of a “fuel” mixture in an “engine” than composting. This approach is based on the extensive similarities of this process to that of crude oil sludge or similar waste composting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-7566-4
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  • 15
    Electronic Resource
    Electronic Resource
    The Impact of Bioaugmentation on Metal Cyanide Degradation and Soil Bacteria Community Structure (2006)
    Springer
    Biodegradation 17 (2006), S. 207-217 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; DGGE ; K2Ni(CN)4 soil bacterial populations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Metal cyanides are significant contaminants of many soils found at the site of former industrial activity. In this study we isolated bacteria capable of degrading ferric ferrocyanide and K2Ni(CN)4. One of these bacteria a Rhodococcus spp. was subsequently used to bioaugment a minimal medium broth, spiked with K2Ni(CN)4, containing 1 g of either an uncontaminated topsoil or a former coke works site soil. Degradation of the K2Ni(CN)4 was observed in both soils, however, bioaugmentation did not significantly impact the rate or degree of K2Ni(CN)4 removal. Statistical analysis of denaturing gradient gel electrophoresis profiles showed that the topsoil bacterial community had a higher biodiversity, and its structure was not significantly affected by either K2Ni(CN)4 or bioaugmentation. In contrast, profiles from the coke works site indicated significant changes in the bacterial community in response to these additions. Moreover, in both soils although bioaugmentation did not affect rates of biodegradation the Rhodococcus spp. did become established in the communities in broths containing both top and coke works soil. We conclude that bacterial communities from contaminated soils with low biodiversity are much more readily perturbed through interventions such as contamination events or bioaugmentation treatments and discuss the implications of these findings for bioremediation studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-4219-6
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  • 16
    Electronic Resource
    Electronic Resource
    Isolation and Characterization of a Pseudomonas Oleovorans Degrading the Chloroacetamide Herbicide Acetochlor (2006)
    Springer
    Biodegradation 17 (2006), S. 219-225 
    Details
    ISSN: 1572-9729
    Keywords: acetochlor ; degradation ; isolation ; Pseudomonas oleovorans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To date, no pure bacterial cultures that could degrade acetochlor have been described. In this study, one strain of microorganism capable of degrading acetochlor, designated as LCa2, was isolated from acetochlor-contaminated soil. The strain LCa2 is Pseudomonas oleovorans according to the criteria of Bergey’s manual of determinative bacteriology and sequence analysis of the partial 16S rRNA gene. Optimum growth temperature and pH were 35 °C and 8.0, respectively. The strain could degrade 98.03% of acetochlor treated at a concentration of 7.6 mg l−1 after 7 days of incubation and could tolerate 200 mg l−1 of acetochlor. When the acetochlor concentration became higher, the degradation cycle became longer. The acetochlor biodegradation products were identified by GC–MS based on mass spectral data and fragmentation patterns. The main plausible degradative pathways involved dechlorination, hydroxylation, N-dealkylation, C-dealkylation and dehydrogenation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-4220-0
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  • 17
    Electronic Resource
    Electronic Resource
    Bioremediation by Composting of Heavy Oil Refinery Sludge in Semiarid Conditions (2006)
    Springer
    Biodegradation 17 (2006), S. 251-261 
    Details
    ISSN: 1572-9729
    Keywords: bioremediation ; composting ; ecotoxicity ; oil sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The present work attempts to ascertain the efficacy of low cost technology (in our case, composting) as a bioremediation technique for reducing the hydrocarbon content of oil refinery sludge with a large total hydrocarbon content (250–300 g kg−1), in semiarid conditions. The oil sludge was produced in a refinery sited in SE Spain The composting system designed, which involved open air piles turned periodically over a period of 3 months, proved to be inexpensive and reliable. The influence on hydrocarbon biodegradation of adding a bulking agent (wood shavings) and inoculation of the composting piles with pig slurry (a liquid organic fertiliser which adds nutrients and microbial biomass to the pile) was also studied. The most difficult part during the composting process was maintaining a suitable level of humidity in the piles. The most effective treatment was the one in which the bulking agent was added, where the initial hydrocarbon content was reduced by 60% in 3 months, compared with the 32% reduction achieved without the bulking agent. The introduction of the organic fertiliser did not significantly improve the degree of hydrocarbon degradation (56% hydrocarbon degraded). The composting process undoubtedly led to the biodegradation of toxic compounds, as was demonstrated by ecotoxicity tests using luminescent bacteria and tests on plants in Petri dishes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-5020-2
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    Electronic Resource
    Electronic Resource
    The ACCEL Model for Accelerating the Detoxification Kinetics of Hydrocarbons Requiring Initial Monooxygenation Reactions (2006)
    Springer
    Biodegradation 17 (2006), S. 237-250 
    Details
    ISSN: 1572-9729
    Keywords: activated sludge ; dichlorophenol ; monooxygenation ; nicotinamide adenine dinucleotide ; phenolics ; specific growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The two-tank accelerator/aerator modification of activated sludge significantly increases the biodegradation of hydrocarbons requiring initial monooxygenation reactions, such as phenol and 2,4-dichlorophenol (DCP). The small accelerator tank has a controlled low dissolved oxygen (DO) concentration that can enrich the biomass in NADH + H+. It also has a very high specific growth rate (μacc) that up-regulates the biomass’s content of the monooxygenase enzyme. Here, we develop and test the ACCEL model, which quantifies all key phenomena taking place when the accelerator/aerator system is used to enhance biodegradation of hydrocarbons requiring initial monooxygenations. Monooxygenation kinetics follow a multiplicative relationship in which the organic substrates (phenol or DCP) and DO have separate Monod terms, while the biomass’s content of NADH + H+ has a first-order term. The monooxygenase enzyme has different affinities (K values) for phenol and DCP. The biomass’s NADH + H+ content is based on a proportioning of NAD(H) according to the relative rates of NADH + H+ sources and sinks. Biomass synthesis occurs simultaneously through utilization of acetate, phenol, and DCP, but each has its own true yield. The ACCEL model accurately simulates all trends for one-tank and two-tank experiments in which acetate, phenol, and DCP are biodegraded together. In particular, DCP removal is affected most by DOacc and the retention-time ratio, Θacc/Θtotal. Adding an accelerator tank dramatically increases DCP removal, and the best DCP removal occurs for 0.2 〈 DOacc  〈 0.5 mg/l and 0.08 〈 Θacc/Θtotal 〈 0.2. The rates of phenol and DCP utilization follow the multiplicative relationship with a maximum specific rate coefficient proportional to μacc. Finally, μacc increases rapidly for Θacc/Θtotal 〈 0.25, acetate removal in the accelerator fuels the high μacc, and the biomass’s NADH + H+ content increases very dramatically for DOacc 〈 0.25 mg/l.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10532-005-5019-8
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    Twenty years of community dynamics in a mixed conifer broad-leaved forest under a selection system in northern Japan (2006)
    Canadian Science Publishing
    Details
    Publication Date: 2006-06-01
    Description: Single-tree selection has been employed widely in northern Japanese mixed forests, but management-induced changes in forests are not well understood. This study examined demographic parameters of major tree species during a 20-year study of a 68 ha stand in which single-tree selection has been conducted since 1971. Results showed that growth and survival of conifers (mostly Abies sachalinensis (Fr. Schm.) Masters) was the most strongly positively affected by the treatment. Nevertheless, recruitment of conifers was not sufficiently improved, suggesting their decreased dominance over the longer term. Instead, shade-intolerant broad-leaved species (mainly Betula ermanii Cham.) will gradually increase because of their higher recruitment rates after the treatment. Shade-tolerant broad-leaved species (mainly Acer mono Maxim. and Tilia japonica (Miq.) Simonkai) appeared to experience the most distinct negative effects, especially on survival. These trends differed markedly from those reported in previous papers concerning partial harvesting systems, which predicted an increase in dominance of shade-tolerant species. The results shown here should be generalized carefully because we have investigated only one stand without repetition of the control area. Nevertheless, trends described in this large-scale, long-term study could provide a basis for simulating stand dynamics. We discussed possible reasons for the observed patterns and provided implications for sustainable management in the region.
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    Age-independent difference equations for modelling tree and stand growth (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: Modelling growth of trees or stands when age is not available is often necessary. This is the case in national forest inventories or when age is not a main determinant of growth (e.g., trees growing in uneven-aged stands). Even if age is not known, functions used to model growth should follow the required pattern, with a maximum and a slow decline after the maximum is attained. There are some empirical functions with these properties; however, direct modelling with difference equations derived from the so-called theoretical growth functions has not been used for this purpose, as they are age dependent. This paper presents a methodology to formulate growth functions as age-independent difference equations. These can be used when age is not available or is not relevant. The proposed equations have the advantage of allowing the direct modelling of yield instead of growth. If the parameters are expressed as a function of site variables, the equations are invariant for projection length and therefore can be used when data is not equally spaced in time, as is the case of most data sets. The methodology is applied to the Lundqvist and Richards growth functions, the most commonly used in growth and yield modelling. The use of the age-independent growth functions is illustrated by using two case studies in Portugal: dominant height growth of eucalyptus (Eucalyptus globulus Labill.) plantations and individual tree growth in diameter at breast height in sparse cork oak (Quercus suber L.) stands.
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    Determining optimal road class and road deactivation strategies using dynamic programming (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: Forest managers are faced with complicated road construction and deactivation decisions. When construction, upgrading, and deactivation strategies must be determined simultaneously over broad spatial and temporal scales, the problem becomes very complex and decision support systems are needed. In this paper, we report the development and application of an optimal road class and deactivation model using dynamic programming. We tested our model on projected road networks on Hardwicke Island, British Columbia. Sensitivity of inputs such as construction costs, upgrade costs, hauling and maintenance costs, deactivation costs, length of time horizon, discount rate, and haul volume were tested within and between two road networks. Comparison of road networks revealed that haul volume concentration, average haul distance, and total road length are the most important variables that affect road class decisions and total network costs. Within our case study, the road network with the lowest average hauling distance resulted in the lowest total cost (CAN$0.24/m3 less), because hauling costs are the largest component (46%) of total transportation costs. The dynamic programming model can be used to assess numerous road construction and maintenance assumptions under various silviculture and harvest systems.
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    Spatial analysis enhances modelling of a wide variety of traits in forest genetic trials (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: Spatial analysis of progeny trial data improved predicted genetic responses by more than 10% for around 20 of the 216 variables tested, although, in general, the gains were more modest. The spatial method partitions the residual variance into an independent component and a two-dimensional spatially autocorrelated component and is fitted using REML. The largest improvements in likelihood were for height. Traits that exhibit little spatial structure (stem counts, form, and branching) did not respond as often. The spatial component represented up to 50% of the total residual variance, usually subsuming design-based blocking effects. The autocorrelation tended to be high for growth, indicating a smooth environmental surface, it tended to be small for measures of health, indicating patchiness, and otherwise the autocorrelation was intermediate. Negative autocorrelations, indicating competition, were present in only 10% of diameter measurements for the largest diameter square planted trials, and between nearest trees with rectangular planting at smaller diameters. Bimodal likelihood surfaces indicate that competition may be present, but not dominant, in other cases. Modelling of extraneous effects yielded extra genetic gain only in a few trials with severely asymmetric autocorrelations. Block analysis of resolvable incomplete-block or row–column designs was better than randomized complete-block analysis, but spatial analysis was even better.
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    Empirical models of forest fire initial attack success probabilities: the effects of fuels, anthropogenic linear features, fire weather, and management (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: Canadian fire managers seek to contain fires below some target size (here 3 ha) by initial attack (IA). Suppression failures occur when fire size at IA exceeds this target (a response failure) or if an initially small fire cannot be contained below it (a containment failure). We examined the effects of cause, season, forest fuels, anthropogenic linear features, weather, and fire management (response time, size at IA) on the probability of these two types of suppression failures, using multiple logistic regression on 1196 fires that occurred within the boreal mixedwood forest of northeastern Alberta during 1995–2002. The frequencies of containment (7%) and response failures (10%) were similar, but the latter accounted for 85% of the area burned. Response failure probability was greater for fires caused by lightning than those caused by humans and increased with longer response times, local abundance of black spruce in summer, and pine fuel under severe fire weather. We found no effect of linear features or other fuel types. Containment failure probability was related to size at IA and fire weather conditions. Our models suggest that a reduction in area burned might be possible if additional fire-specific factors affecting response failure probability could be incorporated into operational decisions.
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    Comparison of canonical correlation and regression based focal point seed zones of white spruce (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: The focal point seed zone methodology determines spatially explicit areas of adaptive similarity for any selected geographic point and is used to match seed sources and planting sites. A total of 127 seed sources (provenances) of white spruce (Picea glauca (Moench) Voss) from Ontario and western Quebec were established at a greenhouse and in six field trials throughout Ontario. Growth and phenological variables were measured over three growing seasons. Two focal point seed zone methodologies were employed: (i) using models derived from principal components analysis (PCA) of biological response variables followed by multiple linear regression against climate variables and (ii) using models derived from canonical correlation analysis (CANCOR). While both approaches use climate data to model adaptive variation, CANCOR reduces the number of steps in the analysis by simultaneously finding the relationships of biological and climatic variables that maximize the covariance between the two data sets. Although more of the variation in adaptive biological traits was actually described by climate variables using the PCAregression approach, this method produced intuitively less realistic patterns. Both methods showed similar overall geographic trends, but the CANCOR method had a finer resolution, especially in southern Ontario, presumably due to statistical efficiency; growth was modeled by all climate variables.
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    Silviculture that sustains: the nexus between silviculture, frequent prescribed fire, and conservation of biodiversity in longleaf pine forests of the southeastern United States (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: The longleaf pine (Pinus palustris Mill.) forest ecosystems of the US southeastern Coastal Plain, among the most biologically diverse ecosystems in North America, originally covered over 24 × 106 ha but now occupy less than 5% of their original extent. The key factor for sustaining their high levels of diversity is the frequent application of prescribed fire uninterrupted in time and space. Pine fuels, critical to application of fire and regulated by canopy distribution, provide the nexus between silviculture and fire management in this system. Typical silvicultural approaches for this type were, in large part, developed to maximize the establishment and growth of regeneration as well as growth and yield of timber, with much less regard to how those practices might influence the ability to sustain prescribed burning regimes or the associated biodiversity. However, many landholdings in the region now include conservation of biodiversity as a primary objective with sustained timber yield as an important but secondary goal. This review synthesizes the literature related to controls of biodiversity for longleaf pine ecosystems, and silvicultural approaches are compared in their ability to sustain natural disturbance such as fire and how closely they mimic the variation, patterns, and processes of natural disturbance regimes while allowing for regeneration.
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    Vegetation dynamics in declining eastern hemlock stands: 9 years of forest response to hemlock woolly adelgid infestation (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carrière) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area. This is the first study to use pre-adelgid disturbance data, annual monitoring of infestation severity, and annual records of hemlock health to assess forest response to HWA infestation. In 2003, 25% of monitored hemlock trees were either dead or in severe decline. Measures of hemlock decline (crown vigor, transparency, density, and dieback) were correlated with HWA infestation severity and changes in light availability over the study period. Average percent total transmitted radiation more than doubled at these sites from 5.0% in 1994 to 11.7% in 2003. The total percent cover of vascular plants increased from 3.1% in 1994 to 11.3% in 2003. Species richness increased significantly, and more species were gained (53) than lost (19) from both ravine floras over the 9-year study period. Though exotic invasive plants were absent from these ravines in 1994, our 2003 resurvey found invasive plants in 35% of the permanent vegetation plots.
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    Measuring the decay resistance of Scots pine heartwood indirectly by the Folin-Ciocalteu assay (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: To exploit the variation in the natural durability of heartwood timber, screening of a large number of trees or timber is necessary. We suggest that the concentration of total phenolics, measured by the Folin–Ciocalteu (FC) assay, can be used to supplement or even replace in vitro decay tests for screening the variation in the resistance of Scots pine (Pinus sylvestris L.) heartwood timber against the brown-rot fungus Coniophora puteana (Schum. ex Fr.). We screened the juvenile heartwood of 520 Scots pine trees with the FC assay. Samples from 40 trees, with total phenolics concentrations ranging from 1.9 to 21.7 mg tannic acid equivalents (TAE)/g of heartwood, were subjected to an in vitro decay test. The correlation (r) between the total phenolics concentration and mass loss was –0.82 (p 
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    Ten-year effect of dolomitic lime on the nutrition, crown vigor, and growth of sugar maple (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: In a base-poor northern hardwood stand in Quebec, subjected to high acid deposition, sugar maple (Acer saccharum Marsh.) nutrition, growth, and crown vigor were evaluated 10 years after application of 0–50 t·ha–1 of CaMg(CO3)2 in 1994. One decade after treatment, foliar calcium and magnesium concentrations of sugar maple were still higher for treated than for control trees. The analysis of foliar nutrient indices showed that liming improved the nutrition of nitrogen and calcium, but caused imbalance of phosphorus, potassium, and magnesium. In 2004, crown dieback was much lower for limed trees (0.5%–4.5%) as compared to unlimed trees (23.7%). When compared with crown dieback before treatment, dieback of limed trees generally had decreased by 2004, while dieback of untreated maple trees increased over the 1994–2004 period. In 2004, basal area increment for limed trees was nearly double that of unlimed trees. However, no difference was detectable among trees limed at different rates. Midterm efficacy of liming in this study was demonstrated by the improvement of sugar maple calcium nutrition, crown vigor, and stem growth 10 years following treatment. This confirms the potential of liming to limit damage caused by acid deposition in base-poor and declining northern hardwood stands.
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    Bayesian belief networks: applications in ecology and natural resource management (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: In this introduction to the following series of papers on Bayesian belief networks (BBNs) we briefly summarize BBNs, review their application in ecology and natural resource management, and provide an overview of the papers in this section. We suggest that BBNs are useful tools for representing expert knowledge of an ecosystem, evaluating potential effects of alternative management decisions, and communicating with nonexperts about making natural resource management decisions. BBNs can be used effectively to represent uncertainty in understanding and variability in ecosystem response, and the influence of uncertainty and variability on costs and benefits assigned to model outcomes or decisions associated with natural resource management. BBN tools also lend themselves well to an adaptive-management framework by posing testable management hypotheses and incorporating new knowledge to evaluate existing management guidelines.
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    Five-year growth responses of Douglas-fir, western hemlock, and western redcedar seedlings to manipulated levels of overstory and understory competition (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don) seedlings were planted in March 2001 within three clearcut-harvested, shelterwood, or thinned stands of mature Douglas-fir near Olympia, Washington. From 2002 to 2005, areas of vegetation control of 0, 4.5, or 9 m2 were maintained with herbicides around a total 162 seedlings per species. Photosynthetically active radiation (PAR) was 34%, 62%, and 100% of full sunlight in thinned stands, shelterwoods, and clearcuts, respectively. Effects of overstory level and vegetation control on seedling growth and resource availability generally were additive. Seedling stem volume index in clearcuts averaged four to eight times that observed in thinned stands, and with vegetation control, it averaged two to four times that observed without it. In thinned stands, relative growth rate of seedling stem volume index had a positive linear relationship with PAR (R2 = 0.38). Foliar nitrogen content of Douglas-fir explained 71% of the variation in relative growth rate. Factors explaining the most variation in foliar nitrogen content differed between thinned stands (PAR, R2 = 0.34) and clearcuts or shelterwoods (midday water potential, R2 = 0.63), suggesting that light and root competition, respectively, were the primary growth-limiting factors for these overstory levels.
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    Soil resources and the growth and nutrition of tree seedlings near harvest gap – forest edges in interior cedar–hemlock forests of British Columbia (2006)
    Canadian Science Publishing
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    Publication Date: 2006-01-01
    Description: Observations of tree seedlings with chlorotic foliage and stunted growth near harvest gap – forest edges in interior cedar–hemlock forests inspired a study addressing the following questions: (1) Do seedling foliar chemistry, foliar nitrogen (N) versus growth relationships, and fertilizer responses suggest N-limited seedling growth? (2) Are patterns in soil characteristics consistent with N limitation, and can interrelationships among these characteristics infer causality? Our results suggest that seedling growth near gap–forest edges was colimited by N and light availability. Soil mineral N and dissolved organic N (DON) concentrations, in situ net N mineralization, and water generally increased from forest to gap, whereas N mineralization from a laboratory incubation and total N and carbon did not vary with gap–forest position. Interrelations among variables and path analysis suggest that soil water and total soil N positively affect DON concentration and N mineralization, and proximity to mature gap–forest edge trees negatively impacts mineral N concentration and water. Collectively, our results suggest that soil N levels which limit seedling growth near gap edges can be partially explained by the direct negative impacts of gap–forest edge trees on mineral N concentrations and their indirect impacts on N cycling via soil water, and not via effects on substrate chemistry.
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    Past, current, and future fire frequencies in Quebec's commercial forests: implications for the cumulative effects of harvesting and fire on age-class structure and natural disturbance-based management (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: The past decade has seen an increasing interest in forest management based on historical or natural disturbance dynamics. The rationale is that management that favours landscape compositions and stand structures similar to those found historically should also maintain biodiversity and essential ecological functions. In fire-dominated landscapes, this approach is feasible only if current and future fire frequencies are sufficiently low compared with the preindustrial fire frequency, so a substitution of fire by forest management can occur without elevating the overall frequency of disturbance. We address this question by comparing current and simulated future fire frequency based on 2 × CO2 and 3 × CO2 scenarios to historical reconstructions of fire frequency in the commercial forests of Quebec. For most regions, current and simulated future fire frequencies are lower than the historical fire frequency, suggesting that forest management could potentially be used to maintain or recreate the age-class distribution of fire-dominated preindustrial landscapes. Current even-aged management, however, tends to reduce forest variability by, for example, truncating the natural age-class distribution and eliminating mature and old-growth forests from the landscape. Therefore, in the context of sustainable forest management, silvicultural techniques that retain a spectrum of forest compositions and structures at different scales are necessary to maintain this variability and thereby allow a substitution of fire by harvesting.
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    Decomposition and nutrient release from fresh and dried pine roots under two fertilizer regimes (2006)
    Canadian Science Publishing
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    Publication Date: 2006-01-01
    Description: Root decomposition and nutrient release are typically estimated from dried root tissues; however, it is unlikely that roots dehydrate prior to decomposing. Soil fertility and root diameter may also affect the rate of decomposition. This study monitored mass loss and nutrient concentrations of dried and fresh roots of two size classes (
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    The ecology of forest insect invasions and advances in their management (2006)
    Canadian Science Publishing
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    Publication Date: 2006-02-01
    Description: Invasions by nonindigenous forest insects can have spectacular effects on the biodiversity, ecology, and economy of affected areas. This introduction explores several critical issues that are generally relevant to invasions by forest insects to provide an extended background for this special issue of the Canadian Journal of Forest Research and highlights the key findings of the papers included in the issue. The topics covered address new information about (1) the role of cargo shipments as invasion pathways for the arrival of insects such as wood borers and bark beetles, (2) biogeographical effects that can influence the ecological and economic impact of insects feeding on exotic tree species, (3) the influence of biodiversity on impacts of forest insects and on the invasibility of ecosystem, and (4) recent advances in the detection, monitoring, and management of invasive species and native pests, including DNA barcoding for identification, the use of pheromones for monitoring and mating disruption, and biological control. These findings are likely to become even more important with elevated prevalence of invasions as a result of increasing global trade and international travel. Avenues of international communication and cooperation among scientists should be encouraged to enhance the sharing of information about biological invasions and to find solutions to this alarming problem.
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    Ectomycorrhizal fungal communities of black spruce differ between wetland and upland forests (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Ectomycorrhizal (ECM) communities of black spruce (Picea mariana (Mill.) BSP) seedlings were characterized from three habitats spanning a moisture gradient in central British Columbia: black spruce dominated wetlands, black spruce tamarack wetlands, and black spruce lodgepole pine uplands. Morphological and molecular (PCR-RFLP) analyses indicated a diverse community of root-associated ECM fungi consisting of 33 morphotypes and 65 genotypes. ECM abundance varied significantly between habitats for six morphotypes. Although many occurred in all three habitats, some occurred in only one or two, and some genotypes had distributions that suggested habitat specificity across the moisture gradient. Intraspecific variation (defined as genotype variation within morphotypes) ranged from one to seven genotypes, depending on ECM morphotype. Both morphological and molecular analyses showed that ECM diversity was greater in upland than in wetland habitats and greater in black spruce tamarack wetlands than in black spruce dominated wetlands (α ≤ 0.05). Morphological assessment captured contributions to diversity by both abundant and less abundant ECM morphotypes, whereas molecular analysis revealed patterns of genetic variation and habitat distribution at a finer resolution. The study presents the first comprehensive information on black spruce ECM and suggests that ECM community composition and richness varies across the moisture gradient in response to soil heterogeneity and alternate hosts (tamarack and lodgepole pine).
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    Snag dynamics in partially harvested and unmanaged northern hardwood forests (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: We used data from hardwood-dominated permanent sample plots in Ontario to estimate the probability of a tree falling during the 5 year period in which it dies ("tree fall"), and likewise the 5 year probability of snag fall. Tree fall probabilities ranged from 5% to 31% across species, with smaller dead trees more likely to be downed than larger ones. Expected half-lives (median time from death to fall) for 25 cm diameter snags varied from 5 to 13 years among species. Fall rates were higher for 10 cm diameter snags but relatively constant for 20–60 cm diameter snags. Recent harvesting substantially increased the probabilities of both tree fall and snag fall, with the former effect most pronounced for small individuals. We used these estimated fall rates to simulate snag dynamics in uneven-aged sugar maple (Acer saccharum Marsh.) stands. Mean snag densities were 32 and 50 snags/ha in selection-management and old-growth scenarios, respectively. Fifty-four percent of this difference was attributable to the lower density of live trees in the selection-management scenario, while 31% was attributable to losses of snags during harvesting. Silvicultural practices that strategically increase tree mortality rates, together with snag retention, as far as safety permits, during harvesting, could represent an effective approach to snag management under the selection system.
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    Comparing methods of reconstructing fire history using fire scars in a southwestern United States ponderosa pine forest (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Fire scars have been used to understand the historical role of fire in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) ecosystems, but sampling methods and interpretation of results have been criticized for being statistically invalid and biased and for leading to exaggerated estimates of fire frequency. We compared "targeted" sampling, random sampling, and grid-based sampling to a census of all 1479 fire-scarred trees in a 1 km2 study site in northern Arizona. Of these trees, 1246 were sufficiently intact to collect cross-sections; of these, 648 had fire scars that could be cross-dated to the year of occurrence in the 200-year analysis period. Given a sufficient sample size (approximately n ≥ 50), we concluded that all tested sampling methods resulted in accurate estimates of the census fire frequency, with mean fire intervals within 1 year of the census mean. We also assessed three analytical techniques: (1) fire intervals from individual trees, (2) the interval between the tree origin and the first scar, and (3) proportional filtering. "Bracketing" fire regime statistics to account for purported uncertainty associated with targeted sampling was not useful. Quantifying differences in sampling approaches cannot resolve all the limitations of fire-scar methods, but does strengthen interpretation of these data.
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    Clear-fell harvest impacts on biodiversity: past research and the search for harvest size thresholds (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Clear-fell harvesting has large aesthetic impacts and significantly alters ecosystem attributes at multiple spatial scales. Known abiotic changes include increased microclimatic variability, changes in regional water balance, and modified hydrological patterns that influence erosion processes. Biotic changes include increased species richness immediately post-clear-felling due to shifts in species composition resulting from changes in individual species abundance and colonization by disturbance-adapted or open-habitat species. Given the large ecological changes caused by clear-fell harvesting and the negative public perception of clear-felling, it is surprising that few studies have investigated whether reducing clear-fell harvest area may be a viable strategy to mitigate ecological change within individual clearcuts. Clear-fell size studies conducted to date rarely exceed a maximum harvest area of 10 ha, and biotic communities measured exhibit mixed responses with respect to species richness and other biodiversity attributes with increasing clear-fell size. Some postharvest ecological responses are nonlinear with respect to harvest area and suggest possible threshold sizes beyond which clear-fell impacts increase disproportionately to their size. Conceptual models of potential ecological thresholds in clear-fell harvest impacts are discussed, as is the need for rigorous empirical testing to ensure a solid foundation exists for forest harvesting guidelines.
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    Nitrogen availability in soil and forest floor of contrasting types of boreal mixedwood forests (2006)
    Canadian Science Publishing
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    Publication Date: 2006-01-01
    Description: Boreal mixedwood forests with varying proportions of coniferous and deciduous species are found throughout the North American continent. Maintenance of a deciduous component within boreal forests is currently favoured, as deciduous species are believed to promote faster nutrient turnover and higher nutrient availability. Results of comparisons of deciduous and coniferous forests are, however, inconsistent in supporting this generalization. We compared indices of soil nitrogen (N) availability in the forest floor and mineral soil of deciduous, mixed, and coniferous stands of boreal mixedwood forest in northwestern Alberta. Deciduous stands had higher N availability, reflected by higher pools of NH4-N and inorganic N in the forest floor. Forest floors of deciduous stands also tended to have higher concentrations of microbial N but did not have higher levels of NO3-N or higher rates of net nitrification. Mixed stands showed the highest rates of net N mineralization. Soil N availability was more closely related to litter N content than to litter decomposition rate. The variation among the forest types is likely attributable to vegetation, as topography is fairly uniform, stands do not differ in soil texture, and N-availability indices correlated directly with the proportion of deciduous trees.
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    How to shift unproductive Kalmia angustifolia – Rhododendron groenlandicum heath to productive conifer plantation (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: Conifer-regeneration failure is often observed on sites invaded by ericaceous shrubs. In northeastern Quebec, Canada, these sites are frequently characterized by dense Kalmia angustifolia L. – Rhododendron groenlandicum (Oeder) K.A. Kron & Judd cover. Such failures are potential consequences of nutrient limitation, allelopathy, or low soil temperatures. Conversion of productive forests into heaths poses a threat to the maintenance of forest productivity and biodiversity. We evaluated scarification, spot fertilization, and increased seedling foliar N concentration as treatments to promote planted black spruce (Picea mariana (Mill.) BSP) seedling survival and growth. We measured seedling, vegetation, and soil responses to the treatments for 5 years following planting. Scarification had positive impacts on seedling growth: the differences between scarified and unscarified plots increased over time, and double-pass scarification proved slightly more effective than a single-pass treatment. Responses to scarification were enhanced when seedlings were fertilized. A slow-release fertilizer with micronutrients proved slightly more effective than the 26N–12P–6K formulation; the latter also induced higher mortality than the former or no fertilizer. Gains due to increased N concentrations based on nursery practices were significant but short-lived. Our results demonstrate how silviculture and nursery practices can be used for resetting the secondary succession where ecosystem retrogression is observed following K. angustifolia – R. groenlandicum invasion.
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    Relations between red alder composition and understory vegetation in young mixed forests of southeast Alaska (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: Interest in mixed red alder (Alnus rubra Bong.) conifer young-growth stands has grown in southeast Alaska, USA, because they appear to provide much more productive understory vegetation and wildlife habitat than do similar-aged pure conifer stands. We studied understory vegetation in nine even-aged young-growth stands (3842 years old) comprising a gradient of red alder conifer overstory composition, with red alder ranging from 0% to 86% of stand basal area. Conifers were Sitka spruce (Picea sitchensis (Bong.) Carr.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don). We measured understory biomass and net production (current annual growth) in each stand by species and plant part and estimated carrying capacity for black-tailed deer (Odocoileus hemionus sitkensis Cowan) with a food-based habitat model. Highly significant positive relations (P 〈 0.002) were found between red alder basal area and all of the following: total understory biomass (r2 = 0.743), net production of shrubs (r2 = 0.758) and herbs (r2 = 0.855), and summer carrying capacity for deer (r2 = 0.846). The high correlation between red alder and herbaceous production is especially important, because herbs are least abundant and most difficult to maintain in young-growth conifer forests of this region. Red alder offers prospects for increasing understory vegetation biomass and its food value for deer and other wildlife when included as a hardwood overstory species in mixed hardwoodconifer young-growth forests.
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    Compatible taper function for Scots pine plantations in northwestern Spain (2006)
    Canadian Science Publishing
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    Publication Date: 2006-05-01
    Description: A compatible system for estimation of individual tree volume was developed for Scots pine (Pinus sylvestris L.) in northwestern Spain. The system comprises a merchantable volume equation, a total volume equation, and a taper function. The use of the volume equation allows rapid estimation of tree volume, and stand volume by summing individual tree volumes, which is equal to the volume obtained by integrating the taper equation. The volume equation is very easy to use and is therefore preferred when classification of the products by merchantable sizes is not required. Data from 228 destructively sampled trees were used for model development. Fourteen compatible volume equations were evaluated, 13 of these equations were taken from the available literature, and the other was developed in the present study. A modified second-order continuous autoregressive error structure was used to correct the autocorrelation of the hierarchical data used. The model developed by Fang et al. (Z. Fang, B.E. Borders, and R.L. Bailey. 2000. For. Sci. 46: 112) best described the data. There model is therefore recommended for the estimation of diameter at a specific height, merchantable volume, and total volume of Scots pine stems in the area of study.
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    Critical period of interspecific competition for four northern conifers: 10-year growth response and associated vegetation dynamics (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: The influence of the timing and duration of interspecific competition on planted jack pine (Pinus banksiana Lamb.), red pine (Pinus resinosa Ait.), eastern white pine (Pinus strobus L.), and black spruce (Picea mariana (Mill.) BSP) was assessed using 10-year growth responses in a northern Ontario experiment. Stand volume was 117%, 208%, 224%, and 343% higher for jack pine, red pine, white pine, and black spruce, respectively, with 5 years of vegetation control than with no vegetation control. Stand volume increased linearly with number of years of vegetation control, and the slope of the relationship varied among conifer species. Change-point regression analysis was used to derive segmented weed-free and weed-infested curves, and to simultaneously estimate key critical-period parameters. Weed-free and weed-infested curves in the 10th year were similar to those derived in year 5, indicating that the patterns established during the first few years after planting were relatively robust for the first decade. The critical-period was 2 and 3 years after planting for jack pine and red pine, respectively, and occupied most of the 5-year period for white pine and black spruce. Principal components analysis of the vegetation community indicated that repeated herbicide applications caused differential shifts in the relative abundance of shrub, fern, and moss species through the 10th year. Species richness, however, was not substantially different between the untreated control and the most intensive treatments. Difference modeling was used to quantify how annual volume increment during the first decade varied with time, conifer species, cover of woody and herbaceous vegetation, and stage of development.
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    Microbial community responses in forest mineral soil to compaction, organic matter removal, and vegetation control (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: We tested three disturbance hypotheses in young conifer plantations: H1: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity; and H3: community responses are strongly modified by regional climate. Microbial biomass, respiration, carbon utilization, and phospholipid fatty acids were compared at two subtropical installations and one Mediterranean-type climate installation of the North American Long-Term Soil Productivity study. Treatments included combinations of compaction (none vs. severe), organic matter removal (none vs. complete), and weed control (none vs. complete), plus an uncut reference stand. Weed control resulted in the only consistent decline or shift in microbial indices at the subtropical sites. At the Mediterranean-type climate site, overstory harvesting resulted in declines in microbial biomass, respiration, and fungal phospholipid fatty acids that far outweighed the effects of the soil disturbance treatments. Severe compaction had no effect on community size or activity at any site. Microbial communities were generally tolerant of postharvest soil disturbance, leading to a rejection of the experimental hypotheses, with the exception of a link between microorganisms and recovery of plant diversity (H2) at the subtropical sites.
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    Overstory influences on light attenuation patterns and understory plant community diversity and composition in southern boreal forests of Quebec (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: We have characterized overstory light transmission, understory light levels, and plant communities in mixed wood boreal forests of northwestern Quebec with the objective of understanding how overstory light transmission interacts with composition and time since disturbance to influence the diversity and composition of understory vegetation, and, in turn, the further attenuation of light to the forest floor by the understory. Overstory light transmission differed among three forest types (aspen, mixed deciduous–conifer, and old cedar-dominated), with old forests having higher proportions of high light levels than aspen and mixed forests, which were characterized by intermediate light levels. The composition of the understory plant communities in old forests showed the weakest correlation to overstory light transmission, although those forests had the largest range of light transmission. The strongest correlation between characteristics of overstory light transmission and understory communities was found in aspen forests. Species diversity indices were consistently higher in aspen forests but showed weak relationships with overstory light transmission. Light attenuation by the understory vegetation and total height of the understory vegetation were strongly and positively related to overstory light transmission but not forest type. Therefore, light transmission through the overstory influenced the structure and function of understory plants more than their diversity and composition. This is likely due to the strong effect of the upper understory layers, which tend to homogenize light levels at the forest floor regardless of forest type. The understory plant community acts as a filter, thereby reducing light levels at the forest floor to uniformly low levels.
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    Multinomial logit estimation of a matrix growth model for tropical dry forests of eastern Bolivia (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: Multinomial logistic (MNL) regression was employed to estimate the transition probabilities of a matrix growth model for dry forests of the eastern Bolivian lowlands. Probabilities of mortality, stability, and upgrowth of a size and species group were estimated as a function of tree and stand attributes influencing growth and mortality. Data for model estimation were drawn from logged and undisturbed permanent sample plots (PSPs) measured over 6 and 7 years in Chiquitania forests south of Concepción, Santa Cruz, Bolivia. The estimated transition probabilities of the MNL models are not significantly different from those derived from PSP data by the conventional approach of employing simple mean proportions of observed movements per guild and size class. MNL estimation is advantageous in that it generates a smoother distribution of transition probabilities across size classes, correcting for variance in the data and model estimation errors imposed by limited samples. Moreover, the MNL approach allows deterministic, stochastic, and dynamic prediction of forest evolution, while preserving the simple linear form of matrix models that facilitates their integration into economic optimization studies.
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    Boreal mixedwood tree growth on contrasting soils and disturbance types (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Mixedwood forests are an ecologically and economically important ecosystem in the boreal forest of northern Canada. The objectives of this study were to (i) compare the ageheight relationships for dominant tree species growing on two contrasting soil types and originating from different disturbances (logging versus wildfire), and (ii) determine the influence of competition on tree growth. Eight stands were selected that encompassed two age-classes replicated on two soil types (clay loam and sand) in a split-plot design. Four of the eight stands originated from logging (2126 years old), and the four others originated from wildfires (80 years old). Nonlinear ageheight analyses were used to compare annual height and radial increment growth of black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), and trembling aspen (Populus tremuloides Michx.). Species, soil type, and size class explained significant amounts of the measured variation in the ageheight models. Aspen, black spruce, and jack pine were 16%, 27%, and 19% taller, respectively, on clay soils than on sandy soils at the burned stand. Tree heights did not differ significantly among species or between soil types in logged stands. Diameter growth decreased as competition increased for black spruce and jack pine in the burned stands. The results for these three important boreal tree species are discussed in the context of sustainable forestry for boreal mixedwood forests.
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    Response of soil microbial biomass, activities, and community structure at a pine stand in northeastern Germany 5 years after thinning (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: A thinned and an unthinned treatment were compared in a 62-year-old pine stand located in northeastern Germany (Brandenburg, Ost-Prignitz, Revier Beerenbusch) (year of thinning: 1999, degree of canopy opening: 0.4). Samples of the organic layer (O) and the mineral horizon (Aeh) of an acid brown earth were collected along a transect at each treatment in November 2003 and April 2004. Substrate induced respiration, basal respiration, and a suite of enzymes involved in the degradation of lignocellulose (endocellulase, exocellulase, β-glucosidase, endoxylanase, exoxylanase, phenoloxidase, peroxidase) were assayed. Microbial community structure and relative biomass of bacteria, actinomycetes, and fungi were assayed by phospholipid fatty acid analysis. Five years after thinning, microbial biomass, basal respiration, and enzyme activities in both soil layers did not differ significantly between thinned and unthinned treatments. However, the analysis of soil microbial community structure revealed a significant difference between the thinned and unthinned treatment at both sampling dates. Thus, it was concluded that thinning had not yet resulted in any response in soil microbial activities at the site under study, but since early evidence of change in the microbial community was detected, long-term monitoring and additional studies on mineralization activities are required.
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    Evaluation of a large-scale forest scenario model in heterogeneous forests: a case study for Switzerland (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: Large-scale forest scenario models are widely used to simulate the development of forests and to compare the carbon balance estimates of different countries. However, as site variability in the application area often exceeds the variability in the calibration area, model validation is important. The aim of this study was to evaluate the European Forest Information Scenario model (EFISCEN). As Switzerland exhibits high spatial and climatic diversity, it was taken as a case study. The model output was compared to measured data in terms of initialization, estimation of growing stock, stand age, increment, management, and natural mortality. Comparisons were done at the country level, but also for regions and site classes. The results showed that the initialization procedure of EFISCEN works well for Switzerland. Moreover, EFISCEN accurately estimated the observed growing stock at the country level. On a regional level, major differences occurred. In particular, distribution of the harvesting amounts, mortality, and age-class distribution deviated considerably from empirical values. For future model applications, we therefore propose to define the required harvesting level not per country, but to specify it for smaller regions. Moreover, the EFISCEN simulations should be improved by refining the mortality function and by incorporating more flexibility in forest management practices.
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    Incorporating genetic parameters into a loblolly pine growth-and-yield model (2006)
    Canadian Science Publishing
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    Publication Date: 2006-08-01
    Description: Differences in survival, diameter, height (site index), and stem profile among eight North Carolina half-sib families and one Mississippi–Alabama commercial check of loblolly pine (Pinus taeda L.) at three spacings over 17 years were evaluated for effects on a growth-and-yield model. Actual stand volume at age 17 was determined from a 100% measurement of all trees. This volume was compared with predicted volumes from age nine measurements using (i) the unmodified model and (ii) the model after modifications for family differences. Modifications to the model included family-specific site indices for height differences and family-specific regression functions for each of the other traits. The unmodified model resulted in an underestimate of actual stand volume by 31%. Adjustments for family differences in dominant height (site index), survival, or profile had little effect on this bias. Insertion of family-specific regressions for stem profile and site index in combination with survival-diameter density effects greatly reduced the bias and provided the best estimates of future stand volumes.
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    Changes in bird communities throughout succession following fire and harvest in boreal forests of western North America: literature review and meta-analyses (2006)
    Canadian Science Publishing
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    Publication Date: 2006-05-01
    Description: Within boreal forests of western North America, the dominant large-scale natural disturbance is wildfire. Thus, harvesting that is as similar as possible to fire is expected to best maintain natural bird communities. We reviewed studies of birds (mainly grouse, woodpeckers, and songbirds) from boreal forests of western North America and conducted meta-analyses to compare the similarity of bird communities occurring postfire versus postharvest. We compared the bird communities at five seral stages and also summarized the effects of retaining large live trees at harvest. Bird communities immediately postharvest differed greatly from those postfire. Differences between disturbance types disappeared as the forest regenerated, and both disturbance types became dominated by relatively few bird species in 31- to 75-year-old forests. During the period 76125 years postdisturbance, old-forest birds became present and bird species richness increased. However, the trajectory of forest succession during this period influenced bird communities; old aspen (Populus tremuloides Michx.), old mixedwood, and old white spruce (Picea glauca Moench (Voss)) forests all had different bird communities. Retention of large live trees in cutblocks resulted in their use by many old-forest birds, but results were not consistent among studies. Although most bird species had clear peaks in abundance in a specific forest type, no species with more than five detections was limited to a single forest type.
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    Simulations of the influence of clear-cutting on the risk of wind damage on a regional scale over a 20-year period (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: The aim of this study was to integrate component models for tree growth, wind damage, and airflow to assess the consequences of alternative forest-management options on the long-term risk of wind damage on a regional scale. This work could help forest managers to identify possible vulnerable edges and determine the probability of risk for alternative management plans. This new, integrated system was applied to assessing the risk of wind damage over a 20-year period on three alternative management choices. The risk was compared for the current forest edges without creating new edges (case study I) and situations where new edges were created through different clear-cut options (case studies II and III). Case study II represented more intensive cuttings compared with case study III (over four times more timber was cut). It was found that despite intensive cuttings in case study II, only 15% and 7% fewer vulnerable edges were found on average (risk probability class ≥0.1%) in case studies I and III, respectively. Therefore, forest managers must consider the possible risk of wind damage when harvesting timber.
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    Mapping stand-level forest biophysical variables for a mixedwood boreal forest using lidar: an examination of scanning density (2006)
    Canadian Science Publishing
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    Publication Date: 2006-01-01
    Description: Light detection and ranging (lidar) is becoming an increasingly popular technology among scientists for the development of predictive models of forest biophysical variables. However, before this technology can be adopted with confidence for long-term monitoring applications in Canada, robust models must be developed that can be applied and validated over large and complex forested areas. This will require "scaling-up" from current models developed from high-density lidar data to low-density data collected at higher altitudes. This paper investigates the effect of lowering the average point spacing of discrete lidar returns on models of forest biophysical variables. Validation of results revealed that high-density models are well correlated with mean dominant height, basal area, crown closure, and average aboveground biomass (R2 = 0.84, 0.89, 0.60, and 0.91, respectively). Low-density models could not accurately predict crown closure (R2 = 0.36). However, they did provide slightly improved estimates for mean dominant height, basal area, and average aboveground biomass (R2 = 0.90, 0.91, and 0.92, respectively). Maps were generated and validated for the entire study area from the low-density models. The ability of low-density models to accurately map key biophysical variables is a positive indicator for the utility of lidar data for monitoring large forested areas.
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    Correlation between clonal means and open-pollinated seedling progeny means and its implications for radiata pine breeding strategy (2006)
    Canadian Science Publishing
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    Publication Date: 2006-08-01
    Description: Open-pollinated (OP) offspring of individual genotypes are commonly used for estimating their breeding values in recurrent selection programmes. Alternatively, vegetative propagules of individual genotypes could also be used to evaluate their relative performance. However, the mean for the vegetative propagules of a genotype represents an estimate of its total genotypic value, and it may or may not be closely related to the general combining ability. The main objective of this study was to correlate the performance of a number of clones, propagated by fascicle cuttings in a clonal test, with the performance of their OP offspring, planted in a progeny test. The empirical correlations between performance of a genotype, given as the mean of its ramets, and performance of the genotypes's offspring, given as the mean of its OP progeny, were 0.56, 0.63, 0.81, and 0.09 for stem diameter, stem straightness scores, branch cluster frequency scores, and malformation scores, respectively. The theoretical expectations of these correlations were 0.55, 0.69, 0.81, and 0.24, respectively. The size of the correlation largely depended on the genetic control of the trait concerned. Implications of these results on the radiata pine (Pinus radiata D. Don) breeding strategy were discussed.
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    Influence of climate on tree rings and vessel features in red oak and white oak growing near their northern distribution limit, southwestern Quebec, Canada (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: Little is known about environmental controls on vessel features in ring-porous tree species. Our objectives were to assess (i) the association between tree-ring descriptors (vessels and width) and climate in two oak species, white oak, Quercus alba L., and red oak, Quercus rubra L., and (ii) the utility of vessel series in climate reconstruction. The study was conducted in southern Quebec and 10 trees of each species were analyzed. For each species, 11 chronologies (vessel and ring width) were developed and compared. Few differences were observed between the oak species. All vessel chronologies were associated with those of ring dimension and none revealed a unique climate signal. Current growing season conditions were mainly associated with latewood features, whereas those of the year prior to ring formation were mainly associated with earlywood features. The best climate variable to reconstruct was the July Canadian Drought Code and the best reconstruction model was derived from earlywood, latewood, and ring-width chronologies. We conclude that vessel chronologies for Q. alba and Q. rubra have limited use in dendroclimatology. Vessel features are best used to identify event years recorded during the life of a tree. Vessel series could prove useful, however, in calibrating physiologically based models of tree growth.
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    QTL analysis of growth and wood chemical content traits in an interspecific backcross family of white poplar (Populus tomentosa × P. bolleana) × P. tomentosa (2006)
    Canadian Science Publishing
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    Publication Date: 2006-08-01
    Description: The genetic control of tree growth and wood chemical content traits was studied using interspecific backcross progeny between clone TB01 (Populus tomentosa × Populus bolleana) and clone LM50 (P. tomentosa). In total, 247 and 146 amplified fragment length polymorphism (AFLP) markers from genetic maps previously constructed for backcross parents LM50 and TB01 were used for the analyses of quantitative trait loci (QTL). These markers were distributed among 19 linkage groups and covered 3265 and 1992 cM in the backcross parents, respectively. A total of 32 putative QTLs, associated with five growth and chemical content traits, sylleptic branch number, sylleptic branch angle, stem volume, wood cellulose content, and wood lignin content, were detected. These QTLs were dispersed among 16 linkage groups in parent LM50 and 10 groups in parent TB01. The phenotypic variance explained by each QTL ranged from 7.0% to 14.6%. QTLs controlling sylleptic branch number and stem volume were colocalized in two linkage groups, TLG6 and TLG8, respectively. The favorable alleles were mostly from P. tomentosa, which is phenotypically superior to P. bolleana for sylleptic branch angle, stem volume, and wood chemical content traits. The favorable alleles for sylleptic branch number were from P.bolleana. These AFLP markers that were associated with the QTLs have potential use in P. tomentosa breeding programs.
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    Are mineral soils exposed by severe wildfire better seedbeds for conifer regeneration? (2006)
    Canadian Science Publishing
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    Publication Date: 2006-08-01
    Description: We examined jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) seed germination and seedling recruitment in aspen (Populus tremuloides Michx.) and conifer mixedwood stands following the 1999 Black River fire in southeastern Manitoba, Canada. Three postfire seedbed types were tested: scorched (surface litter only partially consumed), lightly burned (surface litter consumed with little or no duff consumption), and severely burned (complete consumption of litter and duff exposing mineral soil). Seeds were sown in 1999, 2000, and 2001, and each cohort was monitored for 3 years. In 1999, severely burned seedbeds had poor germination, while scorched seedbeds had the highest germination. The reverse was true in 2001. After the first growing season, continued survival of seedlings was greater on severely burned seedbeds for all three cohorts. However, better survival on severely burned seedbeds was not sufficient to overcome poor germination in 1999 and 2000. When using artificial seeding to promote conifer regeneration, we recommend a delay of one full year after a severe spring fire for jack pine and two full years for black spruce and white spruce on boreal aspen and conifer mixedwood sites.
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    Estimating canopy fuel characteristics in five conifer stands in the western United States using tree and stand measurements (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: Assessment of crown fire potential requires quantification of canopy fuels. In this study, canopy fuels were measured destructively on plots in five Interior West conifer stands. Observed canopy bulk density, canopy fuel load, and vertical profiles of canopy fuels are compared with those estimated from stand data using several computational techniques. An allometric approach to estimating these canopy fuel characteristics was useful, but, for accuracy, estimates of vertical biomass distribution and site-adjustment factors were required. Available crown fuel was estimated separately for each tree according to species, diameter, and crown class. The vertical distribution of this fuel was then modeled within each tree crown on the basis of tree height and crown base height. Summing across trees within the stand at every height yielded an estimated vertical profile of canopy fuel that approximated the observed distribution.
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    Restoration of floral diversity through plantations on abandoned agricultural land (2006)
    Canadian Science Publishing
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    Publication Date: 2006-05-01
    Description: Plantations have been claimed to be "monocultures", or "biological deserts". We investigated these claims in the context of a long-term study on plant diversity within plantations with different indigenous tree species, spacings, and soil types that were compared with 410 native stands. Soil type had no influence on plantation species diversity or abundance, and wider spacing resulted in higher richness, lower woody plant abundance, slightly higher cover of herbaceous plants, and large increases in cryptogam cover. We also found a canopy species × spacing interaction effect, where the impact of increased spacing on understory vegetation was more pronounced in spruce than in pine plantations. The dynamic community interactions among species of feathermoss appear to be in response to the physical impediment from varying amounts of needle rain from the different tree species. High light interception and needle fall were negatively correlated with understory plant diversity, as was lack of structural diversity. This study indicates that through afforestation efforts agricultural lands can be restored to productive forests that can harbour nearly one-half of the plant species found in equivalent natural forests within the same geographic region in as little as 50 years. We recommend applying afforestation using indigenous conifer species as a first step towards rehabilitating conifer forests that have been converted to agriculture and subsequently abandoned.
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    Development of a basal area growth system for maritime pine in northwestern Spain using the generalized algebraic difference approach (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: A basal area growth system for single-species, even-aged maritime pine (Pinus pinaster Ait.) stands in Galicia (northwestern Spain) was developed from data of 212 plots measured between one and four times. Six dynamic equations were considered for analysis, and both numerical and graphical methods were used to compare alternative models. The double cross-validation approach was used to assess the predictive ability of the models. The data were best described by a dynamic equation derived from the Korf growth function using the generalized algebraic difference approach (GADA) by considering two parameters to be site specific. The equation was fitted in one stage using the base-age-invariant dummy variables method. In addition, the system incorporates a function for predicting initial stand basal area, in which the site-related variable was expressed as a power function of site index. This function can be used to establish the starting point for the projection equation when no inventory data are available. The two equations are compatible. The effect of thinning on basal area growth was examined; the results showed that there was no need to use a different equation to reliably predict postthinning basal area development. The nonlinear extra sum of squares method indicated differences in the model parameters for the two ecoregions (coastal and interior) defined for this species in the area of study.
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    Beneficial influence of plant neighbours on tree growth in drained forested peatlands: a case study (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: In boreal forest, drainage can be successfully used to lower the water-table level of postharvest forested peatland stands suffering from watering-up. The later vegetation revival and growth is suspected to gradually create a water-table drawdown described in this study as biological drainage. Its effect on the annual stump diameter increment of planted eastern larch (Larix laricina (Du Roi) K. Koch) and naturally regenerated black spruce (Picea mariana (Mill.) BSP) was studied on a postharvested and drained forested peatland located in eastern part of the Canadian boreal forest. A factor describing the neighbourhood occupancy of every subject tree was used to illustrate biological drainage in a retrospective growth analysis. Results showed the dual effect of the neighbourhood occupancy factor: competing situations close to the ditch and growth-favouring situations farther from it. In the latter case, the studied trees demonstrated better growth with moderately increasing neighbourhood occupancy. This was interpreted as evidence of the beneficial effect of biological drainage on tree growth. The presence of speckled alder (Alnus incana subsp.rugosa (Du Roi) J. Clausen) in the neighbourhood of selected trees corresponded to improved growth for both studied species.
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    Effects of forest roads on the growth of adjacent lodgepole pine trees (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: The effects of roads on growth of adjacent lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) trees were studied in an area near Williams Lake, British Columbia. Plots were established in a range of stand ages, site qualities, stand densities (stems/ha), stand basal areas (m2/ha), edge aspects, and adjacent road widths. Plots were divided into five zones beginning at the road edge: 0–5 m (zone 1), 5–10 m, 10–20 m, 20–30 m, and 30–40 m (zone 5) from the edge. When the 5 years prior to road establishment were used to scale growth rates, relative tree basal growth rates for zone 1 differed significantly from those for the other zones, with zone 1 rates being 32.1% higher, on average, for 3 to 15 years after the road opening was established. Fewer dead standing trees were found nearest the road edge. Tree bole shapes at breast height were not significantly different among zones, and no significant increases in average basal area per tree or in average height were found. On average, zone 1 had a 31.3% greater stand basal area than zone 5. For a 23.4 m wide road, the increased stand basal area translates to 3.13 m (2 × 31.3% × 5 m for zone 1), or 13.4% recovery of timber losses, if both sides of the road were similarly impacted. This estimate can be improved by using stand basal area to reduce variability.
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    Comparing productivity of pure and mixed Douglas-fir and western hemlock plantations in the Pacific Northwest (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: We studied pure and 50/50 mixtures of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) plantations to compare attained total yields between mixed-species stands as opposed to monocultures of equal densities. Whether overall stand density influences this outcome has not been adequately investigated, and to address this we included three density levels (494, 1111, and 1729 trees/ha) in the analysis. At age 12, as components of the mixed stands, Douglas-fir exhibited greater height, diameter, and individual-tree volume than western hemlock at all densities. At 494 and 1111 trees/ha the monocultures had a higher volume per hectare than the mixed stand, but at 1729 trees/ha the mixed stand appeared to be just as productive as the pure stands. The increase in productivity by the mixture at high densities seems to have resulted from the partial stratification observed and most likely also from better use of the site resources. Because of this, less interspecific competition was probably experienced in the mixed stand than intraspecific competition in the pure stands. This study shows the important role density plays in the productivity of mixed stands and thus in comparing mixed and pure stands.
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    Influence of long-term nutrient optimization on biomass, carbon, and nitrogen acquisition and allocation in Norway spruce (2006)
    Canadian Science Publishing
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    Publication Date: 2006-06-01
    Description: We examined the effects of a long-term nutrient-optimization treatment on the acquisition and allocation of biomass, carbon (C), and nitrogen (N) in young Norway spruce (Picea abies (L.) Karst.) growing in northern Sweden. After 12 years of fertilization the absolute biomass of stem, needles, living branches, and stump and coarse roots was more than doubled by nutrient optimization (irrigation liquid fertilization treatment, IL), but the standing biomass of fine and small roots was unaffected compared with that of control trees. Biomass allocation among aboveground organs was not plastic to nutrient optimization and only the relative proportion of dead branches was reduced by nutrient optimization. Within the crown, biomass allocation to living branches was shifted towards the apex in IL trees. The N content in IL trees was substantially higher than in control trees. Most of the total N was allocated to needles and most of the needle N was found in the middle stratum of the living crown in both treatments, although the N concentration of current-year and older needles increased towards the apex in IL trees but not in control trees. The C concentration in the biomass components was not affected by the optimized fertilization. The results clearly show that there is a large potential to increase biomass production of Norway spruce (C sequestration) in the Nordic countries. This would secure the supply of raw material for the forest industry at the same time as the demand for biofuel from forest biomass is increasing.
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    Scale and spatial structure effects on tree size distributions: implications for growth and yield modelling (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: Diameter and other size distributions are extensively used in growth modelling. These are usually obtained from sample plot data and assumed to apply both at the stand level, of interest for production planning, and at the forest patch level, the level relevant for tree growth interactions. However, spatial correlation can cause distribution parameters and their estimates to vary with the extent of ground considered. Using mapped tree data from four forest stands in central Canada, it is shown that differences in DBH variance with plot size can be substantial. In addition, size correlations between neighbouring trees were positive, rather than negative as implied by current distance-dependent growth models. Biases in mean DBH are also found. It is proved that plot totals and frequencies are unbiased estimates of stand parameters, but variances and some other statistics are not. The expected variance is expressed in terms of plot size and shape and of second-order stand spatial structure properties. Some possible approaches for reducing bias in stand-level variance estimates are discussed, and the desirability of modelling microsite or genetic spatial correlations in individual-tree simulators is pointed out.
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    Can forest management based on natural disturbances maintain ecological resilience? (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance.
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    Effects of organic matter removal, soil compaction, and vegetation control on 5-year seedling performance: a regional comparison of Long-Term Soil Productivity sites (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: We examined fifth-year seedling response to soil disturbance and vegetation control at 42 experimental locations representing 25 replicated studies within the North American Long-Term Soil Productivity (LTSP) program. These studies share a common experimental design while encompassing a wide range of climate, site conditions, and forest types. Whole-tree harvest had limited effects on planted seedling performance compared with the effects of stem-only harvest (the control); slight increases in survival were usually offset by decreases in growth. Forest-floor removal improved seedling survival and increased growth in Mediterranean climates, but reduced growth on productive, nutrient-limited, warmhumid sites. Soil compaction with intact forest floors usually benefited conifer survival and growth, regardless of climate or species. Compaction combined with forest-floor removal generally increased survival, had limited effects on individual tree growth, and increased stand growth in Mediterranean climates. Vegetation control benefited seedling growth in all treatments, particularly on more productive sites, but did not affect survival or alter the relative impact of organic matter removal and compaction on growth. Organic matter removal increased aspen coppice densities and, as with compaction, reduced aspen growth.
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    The role of epiphytes in rainfall interception by forests in the Pacific Northwest. I. Laboratory measurements of water storage (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests frequently contain large populations of epiphytic lichens and bryophytes. To determine the effect these epiphytes have on canopy hydrology we measured the maximum water fraction (f(x)max; maximum mass of internal and external water stored by an epiphyte divided by its tissue dry mass) of common lichens, bryophytes, and dead branches in the laboratory and the water storage and interception efficiency (pi) (the rainfall stored on a branch divided by the rainfall intercepted by the branch) of whole epiphyte-laden branches under a rainfall simulator at three intensities (11.3, 16.1, and 39.8 mm·h1). The f(x)max values for epiphytic fruticose lichens, foliose lichens, and bryophytes were 2.2 ± 0.4, 3.4 ± 0.6, and 10.0 ± 0.5, respectively. The water stored by an epiphyte-laden branch during and after exposure to simulated rainfall could be predicted if the biomass of epiphytic lichens and bryophytes on the branch was known (R2 = 0.8, p value 〈 0.0001). For all three rainfall intensities, the branches required 〉6 mm of rainfall to saturate. Values of pi averaged between 0.5 and 0.7 after 2 mm of rainfall and did not differ among the three intensities (all p values 〉 0.05). We conclude that epiphytes increase the canopy water storage of a typical old growth Douglas-fir forest by 〉1.3 mm.
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    A note on fire frequency concepts and definitions (2006)
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    Publication Date: 2006-07-01
    Description: The concepts of hazard of burning, fire interval, and fire cycle are considered. It is claimed that the current notion of fire cycle is poorly defined, since the time required to burn a specified area is a random variable. It is shown that the expected time to burn an area equal in size to the study area normally exceeds the fire interval (the average time between fires at any location). In view of this, it is recommended that the notion of fire cycle in its current form be abandoned.
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    Welfare effects of forestry best management practices in the United States (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: State forestry best management practice (BMP) programs have been widely developed and implemented to prevent nonpoint source water pollution in the past three decades. The unanswered question is how forestry BMPs have affected the welfare positions of consumers, mills, loggers, and forest landowners. A Muth-type equilibrium displacement model was constructed to examine welfare changes of these stakeholders. The model considered a two-stage vertical production system with variable proportion production technology and imperfect market structure. Industrial mills experienced little welfare loss from forestry BMP regulation. Consumers had the largest absolute welfare loss, and loggers had the largest relative welfare loss in the base scenario. The supply elasticity of harvesting services had the greatest impact on the relative incidence of welfare losses between landowners and loggers, and in the long run their welfare losses were comparable. These results may help to improve future state forestry BMP guidelines and design incentive systems for increasing implementation rates.
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    Twelfth-year response of Douglas-fir to area of weed control and herbaceous versus woody weed control treatments (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: Coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) response to eight weed control treatments was measured 12 years after planting at two Oregon sites. Treatments included four areas of weed control around individual trees (0.375, 1.49, 3.35, and 5.95 m2), no weed control (check), total vegetation control, control of herbaceous competition only, or control of woody competition only. Douglas-fir growth and woody-species invasion differed between the Coast Range site (Summit) and the Cascade Range foothills site (Marcola). Woody species reinvasion was more intense at Summit, with Douglas-fir cumulative mortality in the check treatment reaching 23% in year 12. Woody-only control improved Douglas-fir growth at Summit but had no significant effect on growth at Marcola. Total vegetation control had a profound effect on stem volume growth 12 years after planting. At Summit, total vegetation control resulted in a 355% increase in volume per hectare relative to the check. At Marcola the increase was only 63%. At Summit, growth increased with each increase in area of weed control, whereas at Marcola growth increased with increasing area of weed control up to 3.35 m2 of control. Results suggest that much of the gain in volume growth attributable to weed control may be lost if weed-control treatments are not highly efficacious. The differential response to woody control indicates that its benefit at a given site is strongly related to the abundance of competitive hardwood species, which may be predicted from the preharvest stand structure and vegetation community.
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    Economic analysis of health effects from forest fires (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: Epidemiological studies have shown that high levels of fine particulate matter (PM) are correlated with adverse human health effects. Approximately one-third of PM emissions in Canada originate from forest fires. However, air quality concerns are not typically included in resource allocation decisions in fire management. In this paper we examine the economic magnitude of these health concerns and compare them to other costs of forest fires using the 2001 fire in Chisholm, Alberta, as a case study. We construct an empirical air dispersion model to estimate the concentration of PM arising from the fire. Benefit transfer methods were used to determine the health impacts associated with elevated PM from the fire and to value these impacts. The economic impacts appear to be substantial, second only to timber losses. The approaches used in this case study can be extended to construct a map that identifies the values at risk from health effects. The use of monetary values of these impacts helps in comparison and aggregation of the values at risk.
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    Geographic and seasonal variation in cold hardiness of whitebark pine (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: Artificial freeze-testing utilizing the electrolyte-leakage method was used to test the cold hardiness of 2-year-old whitebark pine (Pinus albicaulis Engelm.) seedlings growing in a common garden. Testing across all seasons was used to determine the annual pattern of cold hardiness, and more intensive sampling in the fall and spring was used to assess genetic variation in cold injury among geographic regions spanning the range of the species. Mean hardiness varied widely from –9 °C in early summer to below –70 °C in the winter. Trees from interior and northern regions were the most hardy in the fall, while trees from California were the least hardy. Geographic patterns of hardiness in the spring were reversed. Significant differences in cold injury among regions were detected on all dates except during the winter. Heritability was low to moderate for both the spring (h2 = 0.18) and the fall (h2 = 0.28), and genetic correlation was weak (rA = 0.18). Only spring cold injury was genetically correlated with date of needle flush (rA = 0.34). Mean cold injury in the fall was most closely correlated with mean temperature of the coldest month in the parental environment (r = 0.81). Whitebark pine is well adapted to the low temperatures of the harsh environments where it is found; however, regional variation indicates that moving seed for restoration purposes from areas with higher winter temperatures to colder environments may increase the chance of fall cold injury.
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    Native American influences on the forest composition of the Allegheny Plateau, northwest Pennsylvania (2006)
    Canadian Science Publishing
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    Publication Date: 2006-05-01
    Description: We integrate witness tree distribution, Native American archaeological sites, and geological and topographic variables to investigate the relationships between Native American populations and pre-European settlement forest types on the Allegheny Plateau, northwest Pennsylvania. Detrended correspondence analysis of witness tree data separated the presettlement forests into oakhickorychestnut and beechhemlockmaple communities. Oak, hickory, and chestnut forests were centered on Native American village sites. Using archaeological data, an index of Native American influence (NAI) was derived to reflect the intensity of Native American land use across the landscape. In a comparison among species, mean NAI value of oak, hickory, and chestnut trees was significantly higher than that of beech, maple, and hemlock. Logistic regression demonstrated that among geology type, landform, elevation, aspect, slope, and NAI, NAI was by far the most significant predictor of oak, hickory, and chestnut distribution. Although cause and effect of this relationship cannot be tested, we suggest that long-term Native American activity selected for the disturbance-adapted oak, hickory, and chestnut. We contend that Native American agriculture, burning, and resource extraction could have converted maplebeechhemlock to oakhickorychestnut, or at least reinforced the dominance of this forest type.
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    Nonconstituent species in soil seed banks as indicators of anthropogenic disturbance in forest fragments (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: Forest fragmentation is prevalent in regions with high human population density, but also with high biological diversity, such as southwestern China. Predicting potential changes in species composition in native forest ecosystems resulting from forest fragmentation is an important approach in assessing forest ecosystems and sustainable management of forests. The term nonconstituent species is proposed for plant species that occur in a natural landscape but are not native to it. We hypothesized that fragmentation of continuous forests significantly increases both the richness and the size of soil seed banks of nonconstituent species. To test our hypothesis we compared soil seed banks in three small fragments and one large tract of subtropical evergreen broad-leaved forest in Yunnan Province, southwestern China. In total, 249 species were identified in all soil samples from the four sites. Nonconstituent species represented 36.4%–61.5% of the total taxa and 33.8%–59.6% of total germinants from soil samples in the three forest fragments, but only 3.7%–7.9% of total taxa and 7.5%–9.4% of total germinants from soil samples in the continuous forest tract. Both richness and size of soil seed banks of nonconstituent species were greater under forest fragments than under continuous forest. A majority of nonconstituent species were native weeds and annual herbs with wind-dispersed seeds; most were present in soil seed banks but not in aboveground vegetation. We suggest that nonconstituent species in soil seed banks could be used as an indicator species group for assessing human disturbance. If so, the richness and size of soil seed banks of nonconstituent species could play an important role in quantifying disturbance in forests.
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    Genetic variation of leaf traits related to productivity in a Populus deltoides × Populus nigra family (2006)
    Canadian Science Publishing
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    Publication Date: 2006-02-01
    Description: In breeding and selection, two of the main goals of hybridization are to combine favourable traits from different species and to obtain high hybrid vigor (or heterosis). The objectives of our study were (1) to determine which leaf traits are most closely linked to growth in a cross between Populus deltoides Bartr. ex Marsh. and Populus nigra L. and (2) to estimate the relevance of this cross for selection of highly productive genotypes. To achieve these objectives, 26 poplar F1 hybrids and their parents were studied during their second growing season in central France. Tree growth (i.e., growth rates of stem height, circumference, and volume) was monitored during 1 month, and leaf traits (i.e., increases in number of leaves, maximum individual leaf area, specific leaf area, petiole length, and dry mass, leaf carbon and nitrogen contents, and internode length) were estimated at the end of the 1-month period. Growth traits were tightly correlated to most of the leaf traits. More precisely, it appeared that stem volume growth rate can be decomposed into two single leaf characteristics: maximum individual leaf area and leaf increment rate. All traits showed moderate values of broad-sense heritability. Heterosis as well as coefficients of genetic variation were also modest.
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    Towards a nationwide growth and yield model for radiata pine plantations in New Zealand (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: A study was designed to evaluate a forest stand modelling approach for management use that can be applied across a wide range of site types and climatic regions. Radiata pine (Pinus radiata D. Don) plantations dominate New Zealand's forestry sector; thus, this species was the subject of the study. A major goal of the study was to compare different modelling approaches, which combine simplicity and site sensitivity. Therefore, two general modelling approaches were investigated: a site-stratified and a physiological hybrid approach. Both approaches were implemented by using difference equations. The investigation revealed more consistently improved fits of stratified models, although the fitting process showed potential bias of parameter estimates. On the other hand, the hybrid approach resulted in promising results, especially for stand basal area. The introduction of climate and site variables showed less improvement for mean top height than for basal area. The application of the model on regional scales resulted in an improved prediction in a region with plenty of growth limitations, but less precise results in a region where growth was limited primarily by light and temperature. In the whole, results of the hybrid approach will encourage further studies that incorporate more sophisticated approaches for depicting physiological processes.
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    The economics of site preparation and the impacts of current forest policy: evidence from central British Columbia (2006)
    Canadian Science Publishing
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    Publication Date: 2006-02-01
    Description: A trend in forestry is to move away from intensive stand establishment practices in favor of prescriptions that are lighter on the land. This study examined the condition and projected yields of nine different site preparation treatments on two high-elevation sites in central British Columbia. Treatments included the following: raw planting (i.e., no site preparation); scalping; mounding; chemical site preparation; chemical brushing; and combinations of mounding and chemical treatments. All treatments were manually planted with 2+1 bare-root interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) seedlings. By age 15, trees growing on prepared sites had significantly greater survival, larger stem diameters, and taller tree heights than did trees that were raw planted as seedlings. Moreover, site preparation generally led to earlier and less costly compliance with mandatory reforestation requirements. Growth and yield simulations predicted raw-planted timber volumes that were just 33%51% of the volumes in the most productive treatments. Financial returns varied as well. Site preparation typically resulted in larger land expectation values than that resulting from raw planting; however, the results were sensitive to rotation length and discount rate. Collectively, these results suggest that moderate investments in site preparation may lead to a more profitable allocation of regeneration resources and a greater future timber supply.
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    DNA barcodes for insect pest identification: a test case with tussock moths (Lepidoptera: Lymantriidae) (2006)
    Canadian Science Publishing
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    Publication Date: 2006-02-01
    Description: Reliable and rapid identification of exotic pest species is critical to biosecurity. However, identification of morphologically indistinct specimens, such as immature life stages, that are frequently intercepted at borders is often impossible. Several DNA-based methods have been used for species identification; however, a more universal and anticipatory identification system is needed. Consequently, we tested the ability of DNA "barcodes" to identify species of tussock moths (Lymantriidae), a family containing several important pest species. We sequenced a 617 base pair fragment of the mitochondrial gene cytochrome c oxidase 1 for 20 lymantriid species. We used these, together with other Noctuoidea species sequences from GenBank and the Barcoding of Life Database to create a "profile" or reference sequence data set. We then tested the ability of this profile to provide correct species identifications for 93 additional lymantriid specimens from a data set of mock unknowns. Of the unknowns, 100% were correctly identified by the cytochrome c oxidase 1 profile. Mean interspecific sequence (Kimura 2-parameter) divergence was an order of magnitude greater (14%) than mean intraspecific divergence (
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    Effects of precommercial thinning on tree growth and lumber quality in a jack pine stand in New Brunswick, Canada (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: A naturally regenerated jack pine (Pinus banksiana Lamb.) trial established in 1966 in New Brunswick was studied to determine how three precommercial thinning intensities (1.22 m × 1.22 m, 1.52 m × 1.52 m, and 2.13 m × 2.13 m) and a control (154 trees in total) affected tree growth and lumber quality. Mild (thinned to 1.22 m) and moderate (1.52 m) thinning had a modest impact on tree growth after 34 years (stand age 59). However, intensive thinning (2.13 m, or 2212 stems/ha) increased tree height by 13.1% compared with the control, whereas tree diameter and merchantable stem volume per tree increased by 〉20% and 〉75%, respectively. Yields of No. 2 and Better increased slightly with increasing thinning intensity, but lumber bending properties decreased with increasing thinning intensity. There was, respectively, 〉20% and 〉15% difference in lumber strength (modulus of rupture) and stiffness (modulus of elasticity) between the mild (1.22 m) and intensive (2.13 m) thinnings. Intensive precommercial thinning (2.13 m) is recommended for increased volume growth, but rotation age (〉59 years) should not be reduced if lumber bending properties are of concern.
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    Wildfire mitigation strategies affect soil enzyme activity and soil organic carbon in loblolly pine (Pinus taeda) forests (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: We quantified the effects of three wildfire hazard reduction treatments (prescribed fire, thinning from below, and the combination of fire and thinning), and passive management (control) on mineral soil organic C, and enzyme activity in loblolly pine (Pinus taeda L.) forests on the Piedmont of South Carolina. Soil organic C was reduced by thinning, either alone or with prescribed fire, and this effect persisted through the fourth post-treatment year. Fire also resulted in reduced soil organic C, but not until several years after treatment. Soil C/N ratio initially increased after fire, either alone or with thinning, but this difference did not persist. The activities of three soil enzymes (acid phosphatase, chitinase, and phenol oxidase) in the upper mineral soil were quantified as measures of microbial activity. During the fourth post-treatment year we observed significant stimulation of all three enzyme systems as a result of thinning or thinning and burning. Although the patterns of variation in acid phosphatase and chitinase activity among treatments were similar during the first and fourth post-treatment years, the first-year treatment effects were not statistically significant. Given the management objective of utilizing these stands for timber production, the increased potential for rapid nutrient turnover offered by thinning gives this approach advantages over prescribed fire; however, management for maximum long-term storage of soil C may be better facilitated by prescribed fire.
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    Immediate tree uprooting after retention-felling in a coniferous boreal forest in Fennoscandia (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: We studied the immediate effects of retention-felling on the occurrence of tree uprooting in two different types of boreal spruce forest in Finland to determine whether susceptibility to uprooting is dependent on the biotope. During the first post-treatment year, 7.1% of the trees in the paludified forest type and 1.8% in the upland forest type were uprooted. During the 2 following post-treatment years, uprooting percentages increased considerably (39.3% in the paludified type and 11.5% in the upland type in year 2; 48.3% in the paludified type and 15.2% in the upland type in year 3). Norway spruce (Picea abies (L.) Karst.), the dominant species in both forest types, was the species most susceptible to uprooting. The high uprooting rate in the paludified groups was probably caused by an interaction between the rocky ground and moist overlying peat layer with the shallow root system of P. abies. As paludified forest biotopes are generally recognized to have high biodiversity, the use of green-tree retention in these biotypes may enhance the continuum and survival of sensitive species. Moreover, because of the high level of uprooting, green-tree retention in paludified forest types can quickly and more naturally help restore levels of coarse woody debris.
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    Calibration and testing of a generalized process-based model for use in Portuguese eucalyptus plantations (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: The work described in this paper aimed to establish a single set of parameter values for a process-based model (3-PG), applicable to Eucalyptus globulus Labill. in Portugal. Initial testing was done with parameter values from Australia using climate, biometric, and soils data from an irrigation and fertilization trial and a spacing trial. The model provided good estimates for stem mass and basal area, poor estimates for leaf mass, and reasonable estimates for volume. The fit between simulated and observed values was then improved by tuning parameter values to produce a final set. The calibrated model was tested, and performed well, against data from permanent sample plots (PSPs) at different locations across Portugal. Volume and basal area predictions made by 3-PG for PSPs were then compared with predictions made by the empirical model in use for E. globulus plantations in Portugal. Differences were negligible. Model outputs with the Australian parameter set and the optimum set for Portugal indicated that partitioning of carbohydrates (net primary productivity) was very different in E. globulus grown in Portugal and Australia. The study has confirmed the potential of this process-based model as a practical tool to support forest management decision-making.
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    Quantity and decay stages of coarse woody debris in old-growth subalpine spruce forests of the western Carpathians, Poland (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: The amount and decay stages of dead wood and the residence time of logs was studied in old-growth spruce-dominated stands in the Tatra and Babia Góra in the western Carpathian Mountains in Central Europe. The DBH of living trees and snags as well as the dimensions of logs (with a minimum diameter of 10 cm) were measured on nine sample plots with a pooled area of 4.3 ha. For the logs, the decay stage was identified according to an eight-level decay classification. Dendrochronological cross-dating was applied to 107 wood samples of logs to determine the time since death. The average volume of living trees was 454 m3/ha and the volume of coarse woody debris (CWD) averaged 191 m3/ha. The noted volume of CWD was higher than volumes reported from previous studies in the Carpathian Mountains. On average, CWD made up 30% of the total volume (living plus dead) and varied between 49% and 21% for the stands. The average age of logs for decay class 1 was 13 years and 24, 28, 38, 45, 38, and 60 years for decay classes 2–7, respectively. Considerable variation of time since death between decay classes was probably due to a variable time while dead trees remained standing as snags.
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    Pathogenicity of Leptographium longiclavatum associated with Dendroctonus ponderosae to Pinus contorta (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: We assessed the pathogenicity of Leptographium longiclavatum sp. nov., a recently reported fungal associate of the mountain pine beetle, Dendroctonus ponderosae (Hopkins, 1902). In September 2003, 30 lodgepole pines (Pinus contorta Dougl. ex Loud. var latifolia Engelm. ex S. Wats) between 98 and 130 years old were inoculated with L. longiclavatum, the known pathogen Ophiostoma clavigerum, or an agar control. Inoculation densities consisted of 200 and 800 points/m2 in a 60 cm wide band at breast height. The inoculated trees were examined in July 2004, 9 months after inoculation. Five of six trees inoculated with L. longiclavatum at high density (800 points/m2) developed yellow crowns, while the foliage of all trees inoculated at low density (200 points/m2) remained green. Both O. clavigerum and L. longiclavatum generated significantly longer necrotic lesions in the phloem and more occlusions in the sapwood than in the agar controls. In addition, the sapwood colonized by both fungi had a reduced moisture content compared with controls. These results suggest that L. longiclavatum is pathogenic and may contribute to the mortality of mountain pine beetle infested pines.
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    Exotic earthworm invasion increases soil carbon and nitrogen in an old-growth forest in southern Quebec (2006)
    Canadian Science Publishing
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    Publication Date: 2006-04-01
    Description: To test whether invasion of exotic earthworms affects soil carbon (C) and nitrogen (N), we sampled the litter and upper mineral soil (to 30 cm) at a series of sites varying in their earthworm populations in an old-growth beechmaple forest at Mont St. Hilaire, southern Quebec. We measured earthworm abundance and biomass using hand-sorting and chemical extraction (allyl isothiocyanate) methods. They gave similar results, though there was evidence of size and species-specific biases. Abundance and biomass of the earthworms ranged from 100 earthworms·m2 and from 10 earthworms·m2 showed significantly (p 〈 0.05) greater concentrations and masses of both C and N than did sites with
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    Guidelines for developing and updating Bayesian belief networks applied to ecological modeling and conservation (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: Bayesian belief networks (BBNs) are useful tools for modeling ecological predictions and aiding resource-management decision-making. We provide practical guidelines for developing, testing, and revising BBNs. Primary steps in this process include creating influence diagrams of the hypothesized "causal web" of key factors affecting a species or ecological outcome of interest; developing a first, alpha-level BBN model from the influence diagram; revising the model after expert review; testing and calibrating the model with case files to create a beta-level model; and updating the model structure and conditional probabilities with new validation data, creating the final-application gamma-level model. We illustrate and discuss these steps with an empirically based BBN model of factors influencing probability of capture of northern flying squirrels (Glaucomys sabrinus (Shaw)). Testing and updating BBNs, especially with peer review and calibration, are essential to ensure their credibility and reduce bias. Our guidelines provide modelers with insights that allow them to avoid potentially spurious or unreliable models.
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    Protists in soil ecology and forest nutrient cycling (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: Recent progress in protistology has shown that these organisms (protists) are far more diverse than traditionally assumed by soil ecologists. Most studies have grouped these into motility groups, as amoebae, flagellates, and ciliates. Unfortunately, these do not represent functionally useful groups and do not have any ecological relevance to food web processes and community structure. Typically, abundance values have relied on the most probable number estimate based on bacterivore cultures. In fact, there are many functional groups of protists besides the bacterivores. These other functional groups are very much part of the forest soil decomposition food web, but they remain unaccounted for in models. Modelling studies have shown repeatedly that protozoan bacterivores are responsible for much of the nutrient turnover and flux through the soil food web, as they are in the aquatic microbial loop. The contribution of other protist functional groups to this nutrient cycling remains to be quantified. To this end, new sampling strategies are required, and functional diversity needs to be considered in future studies. We consider both temporal and spatial stratification as contributing factors, to explain the apparent redundancy of function. Finally, drawing on data from agricultural fields, we consider new ideas on rates of recovery after disturbance.
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    Population structure and parentage analysis of black poplar along the Morava River (2006)
    Canadian Science Publishing
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    Publication Date: 2006-05-01
    Description: Twelve nuclear microsatellite markers were used to assess the population genetic structure of the riparian pioneer tree species Populus nigra L. along the Morava River in the Czech Republic. Parentage analysis of 30 seedlings was performed to examine the extent of hybridization between P. nigra and introduced hybrid poplars and to determine the distances of pollen and seed movement. Additionally, spatial genetic structure was analysed and gene dispersal was estimated indirectly. In spite of the limited size of our studied population (65 adult trees), the apparent overall genetic diversity was high (expected heterozygosity He = 0.82) and comparable to the known diversity of P. nigra in southern Europe, where its glacial refugia were located. Introgression of Populus deltoides Bartr. ex Marsh. genes to P. nigra was confirmed, since 13% of tested seedlings descended from a Populus ×canadensis Moench female. The results of parentage analysis showed that a low percentage (20%) of offspring originated from parents located outside the study site. Dispersal distances for pollen and seeds movement ranged from 10 to 230 m and from 163 to 370 m, respectively. The study revealed significant spatial genetic structure (regression slope 0.0158), which was probably caused by limited gene flow.
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    Scale-dependent environmental controls over species composition in Alaskan black spruce communities (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: The boreal forest is the second largest terrestrial biome, and the black spruce (Picea mariana (Mill.) BSP) forest type occupies a large extent of boreal North America. Black spruce communities occur in a variety of environmental conditions and are especially important in the context of climate change because of underlain permafrost in much of the northern black spruce forests, as well as their adaptation to fire disturbance. We used a classification and ordination approach to describe and name Alaskan black spruce communities and relate them to key environmental variables. We analyzed the relationship of species richness with topographic position and with soil pH using both univariate and multivariate analyses of variance. We also explored the variability in structural, physical, and soil characteristics. We described three black spruce community types and five subtypes based purely on floristic composition. Paludification and topography were the most important gradients explaining species composition for the Fairbanks region (61% variance explained). However, at the scale of interior Alaska, pH, drainage, and productivity were the strongest environmental gradients (81% variance explained). We conclude that species composition of mature black spruce forests in interior Alaska results from the complex interaction of landscape and fire history, soil pH, paludification, permafrost, and topographic position.
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    Unusual disturbance: forest change following a catastrophic debris flow in the Canadian Rocky Mountains (2006)
    Canadian Science Publishing
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    Publication Date: 2006-09-01
    Description: Trees are often well adapted to periodic physical disturbances such as fires or floods. However, I investigated forest response to an extremely unusual disturbance event. Following heavy rain in June 1995 a catastrophic debris flow from Vimy Peak in the Canadian Rocky Mountains terminated as an alluvial debris fan that plowed through a trembling aspen (Populus tremuloides Michx.) grove. I analyzed the site over a decade to monitor forest response and determine whether there would be recolonization to the prior forest type. In contrast to my expectation, aspen recolonization did not occur; instead, black cottonwoods (Populus trichocarpa Torr. & Gray) colonized the site. These originated from seedlings and not through clonal propagation, and by 2004, black cottonwoods composed 99% of the saplings and were typically 0.61.4 m tall with a density of about 1/m2. The debris fan dramatically changed the physical environment, which partly resembled a floodplain depositional zone and was colonized by the regionally dominant riparian tree. I propose the concept of foreign disturbance to recognize an unusual disturbance that an organism would very rarely experience and thus to which it is unlikely to be adapted. In this example the disturbance produced an abrupt transition to an alternative forest type and this response may provide insight into forest response to other unusual disturbances, such as extreme weather events, that might increase with climate change.
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    Long-Term Soil Productivity: genesis of the concept and principles behind the program (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: The capacity of a forest site to capture carbon and convert it into biomass defines fundamental site productivity. In the United States, the National Forest Management Act (NFMA) of 1976 mandates that this capacity must be protected on federally managed lands. Responding to NFMA, the USDA Forest Service began a soil-based monitoring program for its managed forests. Lacking an extensive research base, soil-based standards were predicated largely on professional judgment. To provide a stronger foundation, a national program of Long-Term Soil Productivity (LTSP) research was established. The LTSP program addresses both short- and long-term consequences of site and soil disturbance on fundamental forest productivity. Research centers on two key properties affecting a site's long-term productive capacity, site organic matter and soil porosity, each of which is readily influenced by management. A coordinated research network of more than 100 field installations in the United States and Canada is examining how pulse changes in these properties affect soil processes supporting vegetative growth and potential productivity. Results from installations with ≥5 years of response were presented on the 10th anniversary of LTSP, and the latest findings are assembled here. This paper describes the evolution of the study and the characteristics of the oldest field installations.
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    Production structure and input substitution in Canadian sawmill and wood preservation industry (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: We use a translog cost function to analyze the sawmill and wood-preservation industry in Canada from 1958 to 2003. The estimated cost function is homothetic and Hicks neutral. Allen elasticities of substitution indicate that significant substitution possibilities exist. According to Morishima elasticities of substitution, substitution of labour by other inputs is easier than the substitution of other inputs by labour, and substitution of other inputs by materials is easier than the substitution of materials by other inputs. The demand for production labour, nonproduction labour, and electric power inputs is elastic. In contrast to the previous findings of zero or negative rate of technical change, we find technical progress at the rate of 0.57% per annum and a total factor productivity growth rate of 0.54% per annum in the Canadian sawmill and wood preservation industry.
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    Using Bayesian belief networks in adaptive management (2006)
    Canadian Science Publishing
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    Publication Date: 2006-12-01
    Description: Bayesian belief and decision networks are modelling techniques that are well suited to adaptive-management applications, but they appear not to have been widely used in adaptive management to date. Bayesian belief networks (BBNs) can serve many purposes, from illustrating a conceptual understanding of system relations to calculating joint probabilities for decision options and predicting outcomes of management policies. We describe the nature and capabilities of BBNs, discuss their applications to the adaptive-management process, and present a case example of adaptive management of forests and terrestrial lichens in north-central British Columbia. We recommend that those unfamiliar with BBNs should begin by first developing influence diagrams with relatively simple structures that represent the system under management. Such basic models can then be elaborated to include more variables, the mathematical relations among them, and features that allow assessment of the utility of alternative management actions or strategies. Users of BBNs should be aware of several important limitations, including problems in representing feedback and time–dynamic functions. Nevertheless, when properly used, Bayesian networks can benefit most adaptive-management teams by promoting a shared understanding of the system being managed and encouraging the rigorous examination of alternative management policies.
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    On the analysis of cubic smoothing spline-based stem curve prediction for forest harvesters (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: In the cut-to-length (CTL) harvesting system the felling, delimbing, and bucking processes take place at the harvesting site. The optimal cutting points along the stem can be determined if the whole stem curve is known. In practice, however, it is not economically feasible to measure the whole stem first before crosscutting, and hence the first cutting decisions are usually made when only a short part of the stem is known. Predictions are used to determine the cutting pattern to compensate for the unknown part of the stem. In this paper our interest focuses on stem curve prediction in a harvesting situation and we study a modified version of a cubic smoothing spline-based prediction method devised by Nummi and Mottonen (T. Nummi and J. Mottonen. 2004. J. Appl. Stat. 31: 105–114). The method's performance was assessed in five different final felling stands of spruce and pine, collected by harvesters in southern Finland. The results for the spline approach are very promising and show the superiority of the method over the linear mixed-model-based approach of Liski and Nummi (E. Liski and T. Nummi. 1995. Scand. J. Stat. 22: 255–269) and also over the approach based on the variable-exponent taper equation of Kozak (A. Kozak. 1988. Can. J. For. Res. 18: 1363–1368).
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  • 96
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    Poisson mixture models for regression analysisof stand-level mortality (2006)
    Canadian Science Publishing
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    Publication Date: 2006-11-01
    Description: Periodic stand-level mortality data from permanent plots tend to be highly variable, skewed, and frequently contain many zero observations. Such data have commonly been modeled using nonlinear mortality functions fitted by least squares, and more recently by a two stage approach incorporating a logistic regression step. This study describes a set of nonlinear regression models that structure stochastic variation about a mortality function according to basic probability distributions appropriate for non-negative count data, including the Poisson, negative binomial (NB), and generalized Poisson (GP). Also considered are zero-inflated and hurdle modifications of these basic models. The models are developed and fit to mortality data from a loblolly pine (Pinus taeda L.) spacing trial with a conspicuous mode at 0. The sample data exhibit more variability than can be accommodated by a Poisson or modified Poisson model; the NB and GP models incorporate the extra-Poisson dispersion and offer an improved fit. A hurdle NB model best describes this sample, but, like the zero-inflated models and two-stage approach, modifies the interpretation of the mean structure and raises the question of overfitting. Considering both data-model agreement and the biological relevance of these models' components, the analysis suggests that the NB model offers a more compelling and credible inferential basis for fitting stand-level mortality functions.
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    The spatial influence of Pseudotsuga menziesii retention trees on ectomycorrhiza diversity (2006)
    Canadian Science Publishing
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    Publication Date: 2006-10-01
    Description: Living retention trees are being used in managed forests to promote a variety of values, including the maintenance of biological diversity. Federal forest plans for the northwestern USA include guidelines that require the retention of a minimum of 15% basal area in harvest units, with the goal of facilitating the development of late-seral stand structure, which is an important habitat element for old-growth forest-dependent species. However, effective levels and patterns of green-tree retention are unknown. We present results of a treatment consisting of 15% basal area, evenly dispersed retention (15%D). We quantified changes in the ectomycorrhiza (EM) community after the 15%D treatment, both near and away from retention trees. Pretreatment samples were obtained between 1 and 24 months before tree harvest. Post-treatment samples were collected within 14–25 months of harvest. In areas 8–25 m from retention trees, there was a 50% decline in the number of EM types per soil core from before to after treatment. Soil cores taken 〉5 m from retention trees exhibited a shift in EM community structure. EM-type richness was positively correlated with fine-root-tip density. We demonstrate the potential for retention trees to act as refugia for recolonization of newly established seedlings by ectomycorrhizal fungi.
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    Planting black walnut in southern Ontario: midrotation assessment of growth, yield, and silvicultural treatments (2006)
    Canadian Science Publishing
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    Publication Date: 2006-02-01
    Description: We established 480 remeasurement plots in plantations originally laid out by F.W. von Althen in the 1970s and 1980s for his pioneering work on hardwood planting in southern Ontario. We used 110 of these plots to summarize the growth and yield of black walnut (Juglans nigra L.) plantations in southern Ontario. Overall, walnut growth averaged only 2.3 m3·ha1·year1, reflecting the less than optimal soil conditions at the majority of sites. However, good growth rates (i.e., 〉5 m3·ha1·year1) were recorded at sites with well-drained loamy soils, particularly when walnut was interplanted with other tree species. We also carried out a detailed analysis of four of the original experiments of F.W. von Althen to examine the long-term impacts of silvicultural treatments applied at an early stage in plantation development. Briefly, these analyses found (i) a significant long-term effect of controlling herbaceous competition at an early point in plantation development, although there is a suggestion that lower herbicide concentrations may be adequate in the long run, (ii) that fertilization effects, which were marginal at the time of application, were not apparent at age 32, (iii) generally better walnut growth when interplanted with other woody species, but autumn olive (Elaeagnus umbellata Thunb.), the species that stimulated the best walnut growth, grew invasively throughout the study area, thus ruling it out as a nurse species, and (iv) weak evidence that an initial spacing of 3 m × 3 m is optimal for walnut development in the absence of thinning up to age 30. This study provides rare insight into black walnut growth rates and best management practices in southern Ontario, although we recognize that the scope of these findings is limited by less than optimal soil conditions at many of the study sites.
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  • 99
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    Soil physical property changes at the North American Long-Term Soil Productivity study sites: 1 and 5 years after compaction (2006)
    Canadian Science Publishing
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    Publication Date: 2006-03-01
    Description: The impact of forest management operations on soil physical properties is important to understand, since management can significantly change site productivity by altering root growth potential, water infiltration and soil erosion, and water and nutrient availability. We studied soil bulk density and strength changes as indicators of soil compaction before harvesting and 1 and 5 years after harvest and site treatment on 12 of the North American Long-Term Soil Productivity sites. Severe soil compaction treatments approached root-limiting bulk densities for each soil texture, while moderate compaction levels were between severe and preharvest values. Immediately after harvesting, soil bulk density on the severely compacted plots ranged from 1% less than to 58% higher than preharvest levels across all sites. Soil compaction increases were noticeable to a depth of 30 cm. After 5 years, bulk density recovery on coarse-textured soils was evident in the surface (010 cm) soil, but recovery was less in the subsoil (1030 cm depth); fine-textured soils exhibited little recovery. When measured as a percentage, initial bulk density increases were greater on fine-textured soils than on coarser-textured soils and were mainly due to higher initial bulk density values in coarse-textured soils. Development of soil monitoring methods applicable to all soil types may not be appropriate, and more site-specific techniques may be needed for soil monitoring after disturbance.
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    Anchorage of coniferous trees in relation to species, soil type, and rooting depth (2006)
    Canadian Science Publishing
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    Publication Date: 2006-07-01
    Description: A database was constructed of tree-anchorage measurements from almost 2000 trees from 12 conifer species that were mechanically overturned on 34 sites in the United Kingdom between 1960 and 2000. Anchorage was compared among species, soil groups (freely-draining mineral, gleyed mineral, peaty mineral, and deep peat) and root depth classes (shallow, 80 cm) using regressions of critical turning moment against stem mass. Sitka spruce (Picea sitchensis (Bong.) Carr.) was used as a benchmark because it formed the largest part of the database and was the only species with all soil-group and depth-class combinations. Anchorage of Sitka spruce was strongest on peat and poorest on gleyed mineral soils. Deep rooting increased critical turning moments by 10%–15% compared with trees of equivalent mass with shallower roots. Significantly better anchorage than Sitka spruce was found for grand fir (Abies grandis (Dougl. ex D. Don) Lindl.), with various rooting depths on freely draining and gleyed mineral soils and for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) on medium-depth mineral soil. Lodgepole pine (Pinus contorta Dougl. ex Loud.) had poorer anchorage than Sitka spruce over a range of soil groups and root depth classes. Norway spruce (Picea abies (L.) Karst.) on shallow gleyed mineral soil, and Corsican pine (Pinus nigra subsp. laricio (Poir.) Maire) on medium depth mineral soil, also had poorer anchorage. Other combinations had similar anchorage to the equivalent Sitka spruce. These results are discussed with respect to the development of forest wind-risk models.
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