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Nemec A.F.L.,International Statistics and Research Corporation | Parish R.,1540 Ash Road | Goudie J.W.,British Columbia Ministry of forests
Canadian Journal of Forest Research | Year: 2012

A compound, nonhomogeneous Poisson process was used to model the number, vertical distribution, and size of branches on four coniferous tree species: 134 western hemlock (Tsuga heterophylla (Raf.) Sarg.) on six sites, 45 amabilis fir (Abies amabilis Douglas ex J. Forbes) (three sites), 60 lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) (six sites), and 60 white spruce (Picea glauca (Moench) Voss) trees (five sites) and two varieties: 66 coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) (five sites) and 50 interior Douglas-fir (Pseudotsuga menziesii var. glauca (Mayr) Franco) (four sites). Branches of these species are typically more or less clustered and have a characteristic, nonuniform vertical distribution along annual shoots. Total number and relative positions of clusters varied with shoot age. Clustering patterns in three of four species and two varieties appeared to scale proportionally with shoot length. However, in lodgepole pine, which has fewer clusters per metre and more branches per cluster, the vertical distribution of clusters along shoots ≤5 years old was consistent with a gamma-Poisson model but converged to a nonhomogeneous Poisson process model in shoots >5 years old. Separate mixed-effect regression models were developed for each species relating length and diameter of live branches to tree (crown), shoot, and branch (cluster) predictor variables. Source

Cruickshank M.G.,Natural Resources Canada | Jaquish B.,British Columbia Ministry of forests | Nemec A.F.L.,International Statistics and Research Corporation
Canadian Journal of Forest Research | Year: 2010

The objectives of this study were to (i) develop a methodology for screening conifer seedlings for resistance to Armillaria ostoyae (Romagn.) Herink and (ii) screen a population of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Biessn.) Franco) population for resistance to A. ostoyae. Eighteen potted seedlings from each of 86 half-sib interior Douglas-fir families were challenged with inoculum in a 3-year greenhouse trial. The seed originated from four geographically distinct tree breeding zones that represent physically and biologically different environments in southeastern British Columbia. Mortality and the final percent survival of inoculated trees showed differences among the families (survival range 0%-61.1%) and breeding zones (survival range 6.6%-25.3%). Maximum heritability index (0.19) occurred at 28 months. Survival analyses revealed that most of the differences in survival could be explained by the zone from which the family originated. The less susceptible seedlings originated from the drier and warmer zones and limited the spread of the fungus in the root system. Moderate levels of family variation in resistance to A. ostoyae and low-moderate heritability suggest that, in interior Douglas-fir, gains in resistance can be achieved through breeding. Source

Nemec J.M.,Camosun College | Nemec J.M.,International Statistics and Research Corporation | Cohen J.G.,California Institute of Technology | Ripepi V.,National institute for astrophysics | And 6 more authors.
Astrophysical Journal | Year: 2013

Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude δ Sct star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which sixteen exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from -2.54 ± 0.13 (NR Lyr) to -0.05 ± 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al. the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be metal-rich. Five of the non-Blazhko RRab stars are found to be more metal-rich than [Fe/H] ∼-0.9 dex while all of the 16 Blazhko stars are more metal-poor than this value. New P - [Fe/H] relationships are derived based on ∼970 days of quasi-continuous high-precision Q0-Q11 long- and short-cadence Kepler photometry. With the exception of some Blazhko stars, the spectroscopic and photometric [Fe/H] values are in good agreement. Several stars with unique photometric characteristics are identified, including a Blazhko variable with the smallest known amplitude and frequency modulations (V838 Cyg). © 2013. The American Astronomical Society. All rights reserved. Source

Nemec A.F.L.,International Statistics and Research Corporation | Goudie J.W.,British Columbia Ministry of forests | Parish R.,British Columbia Ministry of forests
Canadian Journal of Forest Research | Year: 2010

The aim of this work was to model the vertical location and number of branch primordia (buds) on the leader of lodgepole pine (Pinus contorta Doug, ex Loud.) trees in central British Columbia. For species such as lodgepole pine, where branches occur in clusters rather than individually, the Gamma-Poisson model provides a natural framework for describing and simulating the distribution of buds on the annual shoot. Parameters in the model are identifiable with measurable attributes, that is, the average number of clusters per unit length of the annual shoot and the average number of buds per cluster, and can be related to explanatory variables via a log link. Applicability of the Gamma-Poisson model was demonstrated for a sample of 58 lodgepole pine trees ranging in age from 29 to 103 years old. The agreement between observed and expected cluster counts and spacing, cluster sizes, and total number of branches was good. Height to crown base and length of the annual shoot were selected as the best predictors of the number of clusters and number of buds per cluster, respectively, although other single variables were also identified as having significant predictive value. Source

Boateng J.O.,British Columbia Ministry of forests | Heineman J.L.,J. Heineman Forestry Consulting | Bedford L.,British Columbia Ministry of forests | Nemec A.F.L.,International Statistics and Research Corporation
Scandinavian Journal of Forest Research | Year: 2010

This study examined mechanical site preparation and windrow burning effects on soil properties and lodgepole pine (Pinus contorta var. latifolia) foliar nutrients on a sub-boreal site in northcentral British Columbia, Canada. After two decades, there were no adverse long-term effects on soil bulk density. Rather, bulk densities to 20 cm depth declined continuously in all treatments including the control. Coarse mixing was associated with lasting increases in organic matter-related properties [total carbon (C) and nitrogen (N), ammonium-N, C/N] compared with the control, whereas plow-inverting, disk trenching, fine mixing and windrow burning had no lasting effects on these attributes. In contrast, windrow burning caused persistent increases in pH and related properties (cation exchange capacity, exchangeable calcium and potassium) relative to the control. Mechanical treatments had more short-lived effects on these properties, with the exception that coarse mixing caused significant 20-year reductions in pH relative to the control. There were slight deficiencies of foliar N, sulfur (S) and boron according to published thresholds. None of the treatments affected foliar N, and the effects on total S and sulfate-S were highly variable and not statistically significant. Boron deficiency in the control and mechanical treatments worsened between years 10 and 20, whereas levels on burned windrows were continuously high. © 2010 Taylor & Francis. Source

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