Metcalfe R.J.,University of Victoria |
Nault J.,Pacific Forestry Center |
Hawkins B.J.,University of Victoria
Canadian Journal of Forest Research | Year: 2011
There are few examinations of the relative availability and plant uptake of inorganic N and amino acid N in temperate forest regions. We determined the availability of amino acid N and inorganic N in soils under two shrub species (Vaccinium ovalifolium Sm. versus Rubus spectabilis Pursh) on three sites near Jordan River, British Columbia, over a growing season. We compared biomass production of the two shrubs and two conifers (Picea sitchensis (Bong.) Carr. and Pseudotsuga menziesii (Mirb.) Franco var. menziesii) when given inorganic N (20:80 or 80:20 NH 4 +-NO 3 -) or organic N (glycine and glutamic acid) and assessed short-term uptake (24 h) of 15N-labelled NH 4 +, NO 3 -, glycine, or glutamic acid by the four species. Water-extracted soil concentrations of NH 4 + were up to 1.5 times greater than NO3- averaged across sites. Concentrations of amino acid N and inorganic N were similar on soils under Rubus, but the amino acid N to inorganic N ratio was up to 2.4:1 in soils under Vaccinium. Soils dominated by Rubus had up to twice the NO 3 --N and two thirds the amino acid N concentrations of soils dominated by Vaccinium, averaged across sites and Rubus had relatively high shortterm 15NO 3 - uptake. The dry biomass of conifers was approximately four times greater when supplied mainly with NH 4 + compared with NO 3 -, but biomass of the two shrub species was similar in both inorganic N treatments. All plants had comparable rates of short-term 15N uptake from amino acids and inorganic N, suggesting that amino acids could contribute to the N nutrition of these temperate species; however, dry biomass of all four species grown with amino acids was less than one half that of plants grown with inorganic N.
Niquidet K.,Pacific Forestry Center |
Niquidet K.,University of Victoria |
Tang J.,Pacific Forestry Center
Canadian Journal of Forest Research | Year: 2013
Over the past decade, Chinese demand for forest products has increased substantially. While domestic production has risen, this increased demand has been met mostly by imports. The boom has been a welcome benefit to large forest products exporting countries such as Canada, especially in light of the weakened demand that occurred in the United States (US) following the financial crisis. While estimates of demand parameters for the US are vast, little is known about Canada's other two leading markets: China and Japan. Furthermore, many existing trade models assume that logs and lumber are homogenous, perfectly substitutable regardless of their origin. In this note, we apply a source-differentiated Almost Ideal Demand System (AIDS) model to Chinese and Japanese log and lumber imports, with an emphasis on imports originating from Canada. Results indicate that the price elasticity of demand for Canadian lumber and logs in China is elastic. In contrast, in Japan, the price elasticity of demand for Canadian lumber is inelastic, but like China, demand for Canadian log imports is elastic. Expenditure elasticities suggest that Canadian wood products are expected to be favoured relative to other countries as demand in China grows; this finding may be attributed to marketing programs.
Moreira X.,Research Center Forestal Of Lourizan |
Alfaro R.I.,Pacific Forestry Center |
King J.N.,British Columbia Ministry of forests
Forestry | Year: 2012
Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by resin canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the resin canals or sclereid cells for each cross. © 2012 Institute of Chartered Foresters. All rights reserved.
McRoberts R.E.,U.S. Department of Agriculture |
Magnussen S.,Pacific Forestry Center |
Tomppo E.O.,Finnish Forest Research Institute |
Chirici G.,University of Molise
Remote Sensing of Environment | Year: 2011
Nearest neighbors techniques have been shown to be useful for estimating forest attributes, particularly when used with forest inventory and satellite image data. Published reports of positive results have been truly international in scope. However, for these techniques to be more useful, they must be able to contribute to scientific inference which, for sample-based methods, requires estimates of uncertainty in the form of variances or standard errors. Several parametric approaches to estimating uncertainty for nearest neighbors techniques have been proposed, but they are complex and computationally intensive. For this study, two resampling estimators, the bootstrap and the jackknife, were investigated and compared to a parametric estimator for estimating uncertainty using the k-Nearest Neighbors (k-NN) technique with forest inventory and Landsat data from Finland, Italy, and the USA. The technical objectives of the study were threefold: (1) to evaluate the assumptions underlying a parametric approach to estimating k-NN variances; (2) to assess the utility of the bootstrap and jackknife methods with respect to the quality of variance estimates, ease of implementation, and computational intensity; and (3) to investigate adaptation of resampling methods to accommodate cluster sampling. The general conclusions were that support was provided for the assumptions underlying the parametric approach, the parametric and resampling estimators produced comparable variance estimates, care must be taken to ensure that bootstrap resampling mimics the original sampling, and the bootstrap procedure is a viable approach to variance estimation for nearest neighbor techniques that use very small numbers of neighbors to calculate predictions. © 2011.
Barclay H.J.,Pacific Forestry Center |
Vreysen M.J.B.,International Atomic Energy Agency
Population Ecology | Year: 2011
A spatial model of tsetse (Glossina palpalis ssp. and G. pallidipes) life cycle was created in FORTRAN, and four control measures [aerial spraying of non-residual insecticides, traps and targets, insecticide-treated livestock (ITL) and the sterile insect technique] were programmed into the model to assess how much of each of various combinations of these control tactics would be necessary to eradicate the population. The model included density-independent and -dependent mortality rates, temperature-dependent mortality, an age-dependent mortality, two mechanisms of dispersal and a component of aggregation. Sensitivity analyses assessed the importance of various life history features and indicated that female fertility and factors affecting survivorship had the greatest impact on the equilibrium of the female population. The female equilibrium was likewise reduced when dispersal and aggregation were acting together. Sensitivity analyses showed that basic female survivorship, age-dependent and temperature-dependent survivorship of adults, teneral-specific survivorship, daily female fertility, and mean temperature had the greatest effect on the four applied control measures. Time to eradication was reduced by initial knockdown of the population and due to the synergism of certain combinations of methods [e. g., traps-targets and sterile insect technique (SIT); ITL and SIT]. Competitive ability of the sterile males was an important parameter when sterile to wild male overflooding ratios were small. An aggregated wild population reduced the efficiency of the SIT, but increased it with increased dispersal. The model can be used interactively to facilitate decision making during the planning and implementation of operational area-wide integrated pest management programs against tsetse. © 2010 The Society of Population Ecology and Springer.
Barclay H.J.,Pacific Forestry Center |
Vreysen M.J.B.,International Atomic Energy Agency
Population Ecology | Year: 2011
The critique by Hargrove et al. (Popul Ecol, 2011) of our recently published paper on a tsetse population model (Barclay and Vreysen in Popul Ecol 53:89-110, 2011) has made some good points but has also misinterpreted the intent of some of our results as we presented them. Hargrove et al. rightly say that there is a mismatch between the size of the unit cells in the model (1 ha) and the iteration rate of the model (every 5 days), yielding too low a dispersal rate to simulate reality. However, they have misconstrued several of our results that we presented as examples to imply that those results were a necessary condition for control of tsetse, especially using traps and targets. © 2011 The Society of Population Ecology and Springer.
Barclay H.J.,Pacific Forestry Center |
Hendrichs J.,International Atomic Energy Agency
Annals of the Entomological Society of America | Year: 2014
Models were presented that describe the attraction and killing at toxic baits or traps of adult males and females of an insect pest species. These models were used to test the effects of the following factors on ease of control: female monogamy versus polygamy, attraction of only males versus both sexes, initiating mating before versus after responding to baits/traps, the ability of males to mate many times each day versus only once per day, and the existence of a time lag of several days before females can mate versus mating immediately after emergence. The models indicated that mating before trapping or the ability of males to mate many times each day will probably render this control method ineffective. The other factors tested (mating habit and specifics of attraction) had little effect on the efficiency of trapping males as a control method. We then included age structure and a refractory period for virgin females before they can mate. The models were then made specific to Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) by using parameter values derived from the literature. The results of the models imply that the attraction and killing of large numbers of males is rather ineffective to suppress populations. However, the combination of attracting both males and females can be more effective than attracting either sex alone. The increased attraction of females to methyl eugenol baits that has been observed with the declining presence of males during Male Annihilation Technique campaigns may explain the reported effectiveness against invasive Bactrocera pest species. © 2014 Entomological Society of America.
Moore T.R.,McGill University |
Trofymow J.A.,Pacific Forestry Center |
Prescott C.E.,University of British Columbia |
Titus B.D.,Pacific Forestry Center
Plant and Soil | Year: 2011
We measured changes in carbon (C), nitrogen (N) and phosphorus (P) concentrations and mass of 10 foliar litters decomposing over 12 years at 21 sites across Canada, ranging from subarctic to temperate, to evaluate the influence of litter quality (nature) and forest floor (nurture) on N and P dynamics. Most litters lost P faster than N, relative to C, except in one litter which had a high initial C:P quotient (2,122). Net N loss occurred at mass C:N quotients of between 33 and 68, positively correlated with the C:N quotient in the original litter, and net P loss likely occurred at C:P quotients between 800 and 1,200. Forest floor properties also influenced N and P dynamics: the higher the C:N or C:P quotient in the surface soil organic matter, the smaller the proportion of initial N or P left in the decomposing litter, relative to C. There was a convergence of C:N and C:P quotients as the litters decomposed, with an overall mass ratio of 427:17:1 when the litters reached 20% original C remaining. These results, covering a wide range of sites and litters and thus decomposition rates, showed that the C:N:P quotients followed similar trajectories and converged as the litters decomposed. The relative loss of N and P was affected by both the initial litter nutrient concentration and the chemistry of the site forest floor, with the former being more important than the latter, resulting in spatial variations in nutrient content of the forest floor. © 2010 Springer Science+Business Media B.V.
Niquidet K.,Pacific Forestry Center
Canadian Journal of Forest Research | Year: 2010
Financial capital is very mobile and the failure to earn the cost of capital can result in capital flight and a considerably altered forest industry. This article seeks to assess the cost of equity capital for the forest sector from a modern finance perspective and test to what extent it has earned the cost of this capital over the period spanning from December 2003 to December 2008. To do so, using time series and cross-sectional methods, the capital asset pricing model and the Fama-French three-factor model were applied to the weekly returns of 45 publicly traded forest sector securities that are listed on North American stock exchanges. The time series results for both the capital asset pricing and Fama-French three-factor models yielded several negative pricing errors, suggesting ex post that many firms in the sector have failed to earn the cost of equity. Furthermore, cross-sectional results show that riskier firms tended to have lower returns. Such findings are unlikely to hold in the long run and could be one of the primary factors driving significant change in the forest sector in the future.
Osono T.,Kyoto University |
Trofymow J.A.,Pacific Forestry Center
Ecological Research | Year: 2012
Species richness and species composition of microfungi associated with Oregon beaked moss (Kindbergia oregana) were studied at two forest chronosequences on southeast Vancouver Island, British Columbia, Canada. The purposes were to investigate the effects of clear-cutting and the transformation of old-growth forests into secondary forests on microfungi and the succession of microfungi in relation to long-term stand development. Green and brown parts of moss were collected from the forest floor of Douglas-fir (Pseudotsuga menziesii) stands of four age classes: post-harvest regeneration (13-14 years), immature (50-51 years), and mature (85-101 years) stands, and a control old-growth (296-324 years) stand, and used for the isolation of microfungi. A total of 49 microfungal species were recorded. Study site, stand age, and moss parts significantly affected the species richness and species composition of microfungi. The species richness of microfungi was significantly greater on brown than on green moss parts and lower in post-harvest regenerations than in forest stands of the other age classes. The species composition of major microfungal species changed gradually along the seral stages. Possible environmental and biological factors that could account for the succession of microfungi were discussed. © 2011 The Ecological Society of Japan.